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To Promote the production and application of ductile iron castings Issue 3 1998

Ductile Iron News Reaches Out Globally by Joining the Internet

...The Ductile Iron Society is proud to announce the decision to begin publishing the DuctileIron News on the Internet as a link from the Ductile Iron Society home page.

FEATURES

•Cover StoryDuctile Iron News Reaches Out Globally by Joining the Internet

• Prioritizing GreenSand Testing

•Keough of Applied ProcesWins Dual Recognitionfor Industry Services

• Ductile IronBomb Bodies

• Experiences in DuctileIron Production

•The Effect of Metallic ChaMelt History on NucleationPotential in Ductile Cast Ir

• FEF College IndustryConference

• Record Ductile Iron Castin

DEPARTMENTS

• News Briefs

• Back Issues

• Advertisers

• DIS Home page

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COVER STORYDuctile Iron News Reaches Out Globally by Joining the Internet The Ductile Iron Society is proud to announce the decision to begin publishing the DuctileIron News on the Internet as a link from the Ductile Iron Society home page. There will bemany advantages to this new electronic format.

Beginning in 1999, the articles that we receive, the associate and foundry member profiles,news briefs, and our very important member advertisements will be readily available toprofessionals and students around the world. Articles from the Ductile Iron News pages canbe easily printed for future reference or for distribution to interested parties. We appreciateyour continued contribution of articles as in the past. Currently the Ductile Iron Society web site is averaging 350 visits per day. Our advertisers will get similar exposure as peoplebrowse the site and read the timely articles. Please visit the site at the usual magazine publishing times of January, June and September to view an exciting new version of theDuctile Iron News.

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PRIORITIZING GREEN SAND TESTINGPrioritizing Green Sand Testing By George DiSylvestro Green Sand Molding Specialist

Introduction Green sand molding is one of the oldest and most economical casting methods that hassurvived time and represents the highest tonnage produced in the metal-casting industry.Those committed to using this process may wish to review and audit their method ofcontrolling their green sand system. Most growth and profit-oriented foundries are interestedin improvements in economy, problem solving, decision making and or casting quality.

Our studies of many production metal casting centers, has confirmed that there is very littleuniformity or standardization in green sand testing and assigned priorities of tests for qualitymold production. Of paramount importance to improve mold production and produceexceptional casting quality, is the consistency of the prepared molding sand.

Many tests are being performed and may not be completely understood. In order to make the information obtained moremeaningful, the following is a summary of previous studies that can assist in qualifying and prioritizing the objectives of sandtesting.

The Testing of the SandMolding sand is tested to control the green sand process in order to produce consistently high quality castings. This includes theability to reproduce casting dimensions.

As the casting cycle is continuous in high production foundries, using automatic molding systems, an important objective is tomonitor and exercise vigilance to the extent of any changes that occur. Success can be rated based on the ability to maintainmaximum consistency of the return sand. Different bentonites do not perform the same. There is a synergy effect when they areblended at different ratios. Prediction of sand properties is also made difficult by: pouring temperature inconsistencies, amount oforganics added, funneling in storage, hang ups, blend inconsistencies, processing of shakeout sand and changes in casting weightsand sizes. Clay activation can vary widely when more than one molding line is fed with the same prepared sand if they run atdifferent speeds and product mix. We can add to these variables the efficiency of fine removal, core sand dilution and new sandadditions. We can easily see why the molding sand can be in a constant state of flux. Foundries that can precisely measure themost important properties and interpret them accurately and promptly can achieve molding sand consistency.

The question is, what tests should be run and what are their importance and value. The frequency of testing is determined by theamount of meaningful important changes that occur during the complete cycle of the sand system. It has been determined that withan average sand storage volume, it takes approximately 25 cycles, of average product mix castings, to complete a major change inthe sand composition. The previously stated information has to be considered in order to focus on and categorize the tests. Theycan be separated into what I will call primary and secondary tests.

Primary TestsA. Sieve Analysis and size frequency of washed molding sand before and after use. Sand is 90% of the mold.

B. Active Clay Content in percent, using the methylene blue method, when using bentonite with water as the major bond.Sometimes called effective clay, it produces the adhesive to bond the sand grains.

C. Moisture Content in percent taken from the prepared sand at the point of entering the mold. (Plasticizes clay)

C-1. Percent Compactibility - to determine the level of resistance to compaction based on the clay / water ratio and other factors tocontrol the sand moldability. (Rel. wetness)

D. Percent of Combustibles - or also known as total loss on ignition. Relates to the total organics in the sand.

D-1. Percent of Volatile Organics @ 1200F - Relates to that portion of the organics that will produce a reducing atmosphere in themold and prevent wetting by the metal.

The primary tests, listed above in order of importance, virtually affect most other properties and are the primary contributors to moldproduction, casting finish and integrity. Most metal casters rely on these tests for controlling the molding sand and make decisions

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based on their results. When the primary tests indicate a value above or below the set limits they have an effect on moldproduction, shakeout, casting cleaning and ultimately casting quality. These tests should be performed on representative samplesand it should be recorded when and where they were taken and if necessary the temperature of the sand sampled. An accuratehistory of these tests will become necessary when addressing a casting problem.

Some foundries have automatic processing and testing equipment that can manage the variations and they are indeed fortunate.Also important in the controlling of the sand properties is the employment of cooling equipment by most.

To determine, predict and maintain the correct ranges for all the above test results, will demand the coordination of management tointegrate the casting product mix with sand processing. It is necessary to operate the molding sand department with the samedegree of technical discipline as would be used in the melting and metallurgical departments.

Secondary TestsE. Compacted Density of a standard AFS test specimen - the actual weight in grams of the sand required to produce the specimento be used in other tests determines mold density. F. Permeability Number - measures the ability of the steam and gas from burning organics to escape from the mold and reduceback pressure. It affects the venting ability of the mold. G. Dry Compression Strength - in psi it measures the strength developed by the clay/water ratio of a specimen dried to zeromoisture. H. Green Compression Strength - in psi it measures the load that the sand can carry and maintain the pattern dimensions whenpouring the mold. I. All Other Specialized Tests - to include tensile properties, splitting, tensile, green deformation, friability, mold hardness etc., whichare used to supply information needed for a special molding method or casting design. To even begin to obtain control of molding sand systems, it seems that logical steps in the proper sequence should be established.It is recommended that -

1. Only one person should be responsible and accountable for a foundry’s molding sand system. The size of the foundry willdetermine whether that person will be able to handle other duties or need help in his primary responsibility for sand control.Provide a job description.

2. This person, preferably a sand technician, must gain and maintain intimate knowledge of the total molding sand system,from storage through preparation, delivery to the mold station, shakeout and return to storage.

3. The technician must be conscious of all sources of base sands and additives and their quality.4. The technician must question if new sand additions are being made to maintain the level of the system or to purge

contaminants. New sand additions will require compensating additive additions. All storage hoppers should be kept full.5. The technician must give strict attention to the condition of the sand preparation and sand cooling equipment and all test

equipment that is used to determine sand properties. Also, monitor the dust collecting equipment.6. Closely monitor sand results from different shifts and if different, determine the cause. He should be responsible for any

composition changes.7. Graphing of all sand test results is mandatory in order to predict needed changes before major problems occur. Certification

is necessary as personnel change and equipment must be standardized. They should be continuously trained in newtechnology

Control Basics for the Dimensional Reproducibility of Casting

Fineness and grain distribution of the base sand.Amount and type of bentonite used.Mulling and transport of the molding sand.Sand flowability in filling the mold.Degree and uniformity of mold compaction.Core restraint that resists normal contraction.Maintenance of molding machines, flasks and mold handling equipment.Tooling - gating, risering and venting.Personnel training for all personnel.

Sand Related Defects That Can Occur

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Sand inclusions.Blow holes and/or gas porosity.Cracked molds and veining.Expansion defects (rat tails, buckles, scabs).Surface roughness (penetration, burn in, burn on)Erosion related (cuts and washes)Contraction problems (cracks and hot tears).Molding problems (drops).Mold lifts and runouts.Incorrect casting dimensionsShrinkage

ConclusionsThe important conclusions of this abbreviated article which can help get the most out of sand testing for the green sand moldingprocess are as follows:

1. The four primary tests (A through D) recommended can directly change the consistency and casting performance of themolding sand. They directly affect mold making and can contribute greatly to casting dimensional stability. They affect allother properties separately or in combination.

2. Any changes that occur in any of the primary tests will affect most all of the secondary test properties. Therefore, exercisinga major effort in controlling the primary test properties will contribute to the consistency of the secondary test results.

3. In the event of equipment breakdowns, material inventory changes, or the introduction of cost reduction programs, theseeventualities can be managed by knowing exactly what is happening in the way of physical properties of the prepared sand.

4. The control of minor or major changes in casting production can be achieved by obtaining meaningful test results in a timelymanner and then the changes needed in the sand can be made with confidence.

5. The combination of the primary and or secondary tests, if the budget allows, are absolutely necessary to control the processof producing castings of consistent quality at the lowest cost with minimum casting losses.

DialogueAn example would be - Should you want to make a stronger mold, you cannot add green compression strength only. If you want toimprove mold rigidity, you must change one or more of the primary tests, such as - increase active clay bond, moisture or changegrain size frequency. The same would hold true with permeability. Mold permeability can be the result of all the primary tests tosome degree. A review of the time, frequency and technical labor required to perform daily and weekly testing, including the cost ofthe equipment, should be analyzed. Consistency in the sand composition, sand preparation, maintenance of equipment, physical sand properties and constantpersonnel education are paramount in the production of high quality castings at the lowest cost. Constant training sessions for sand control technicians will ensure that they are working with the latest technology and this in turnwill promote company profitability and growth. "Prioritizing Sand Testing" will ensure the achievement of these objectives. References

1. Ductile Iron Production Training Seminars - Part 4. "Raw Materials & Molding Sand Control" (Video by George DiSylvestro)2. Standard Test Procedures - Compendium of testing raw materials and molding & core sands. 1981 American Colloid

Company.3. Molding and Core Testing Handbook, AFS4. Foundry Sand Practice - C. A. Sanders, American Colloid Company.5. Gold Medal Series of Videos by George DiSylvestro -

"Critical Molding Factors""Experiences in Defect Diagnosis""Penetration""Shrinkage""Inclusions""Gas Related Defects""Pouring Technology""Core Related Defects:

6. AFS Casting Defect Handbook7. High-Density Handbook 3rd Edition - Chapter 4 "Molding Sand" - AFS Publication

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8. "Does the Squeaking Wheel Control Your Sand System? - AFS Regional Presentation by Dave Boyd of Grede Foundries

DECISION MAKING GUIDELINES TO ASSIST IN IMPROVING CASTING QUALITY

TEST WHEN COURSE WHEN FINE

A. SIEVE ANALYSIS ANDSIZE FREQUENCY (Primary)

Poor casting finish, lower clay/water required, sticking onpatterns, mechanical penetration.

Improved casting finish, higher clay/water required, blows, pinholes,boils, expansion defects, increased gas pressure and cope lifts.

WHEN LOW WHEN HIGH

B. PERCENT ACTIVE CLAYCONTENT BY METHYLENEBLUE TEST (Primary)

Broken molds, cuts and washes, erosion, poor draws, lowermoisture required, burned on sand and poor castingdimensions. Narrow moisture range

Improved casting dimension, poor shakeout, reduced expansion defects,clay balling and resistance to compaction required for larger heavycastings.

C. PERCENT MOISTURECONTENT (Primary)

Loose sand, cuts and washed, inclusions, drops, brokenmolds, friable mold edges, improved shakeout, goodflowability and increased mold density.

Apparent shrinkage, poor casting dimensional control, blows, sticking onpattern, penetration, boils, increased expansion defects, resistance tocompaction.

C-1. PERCENTCOMPACTIBILITY

Friable mold edges, crushes, inclusions, hard to lift pockets,cuts and washes, cope drops, good flowability, increasedmold density and improved casting dimensions.

Mechanical penetration, apparent shrinkage, oversize castings, roughsurfaces, difficult mold compaction, poor flowability and casting knots.

D. PERCENTCOMBUSTIBLES OR LOSSON IGNITION OF ORGANICS(Primary)

Poor casting peel, poor shakeout, lower moisture and clayrequired and oxidizing mold atmosphere.

Higher clay and moisture required, low mold density, high smoke, lowerhot strength, blows, erosion, lower expansion defects.

E. COMPACTED DENSITY INGRAMS PER 2" SPECIMEN(Secondary)

Penetration, poor casting dimensional tolerance, run outs,cuts, washed, apparent shrinkage and low mold hardness.

Expansion defects, hard molds, penetration, high mold hardness, higherdry and hot strength and poor shakeout.

F. PERMEABILITY NUMBER(Secondary)

Blows, pinholes, mold lifts, run outs, metal boils, improvedfinish, expansion defects, increased venting required formolds and cores.

Mechanical penetration, rough surfaces, reduced gas pressure andfaster allowable pouring rate.

G. DRY COMPRESSIONSTRENGTH IN PSI

Good shake out, erosion and sand inclusions, indicator offriable sand and poor mold edges, best indicator of westernbentonite level in composition.

Direct correlation with baked sand lumps at shake out, hot strength canbe controlled with composition using additives, good for making heavycastings. Adds to mold rigidity during casting cycle.

H. GREEN COMPRESSIONSTRENGTH IN PSI(Secondary)

Poor draws, broken molds, erosion defects based on moldhardness, good sand flowability, lower dry strength, dry moldedges with high mold compaction.

Good for automatic molding at lower water/clay ratio, higher moldcompaction can be tolerated. Contributes to more uniformity of moldhardness and improved casting dimensions.

SPLITTING, TENSILE FRIABILITY, MOLD HARDNESS, pH VALUE, GREEN TENSILE ETC. Specialized tests can be developed, monitored and compared. Controlling the primary tests will be the key to adjusting these teststo meet the physical characteristics desired to achieve excellence and maintain profitability.

Mold hardness consistently over 90-92 (B-scale) creates many undesirable results that nullify the primary test results from thelaboratory.

Inconsistent hot sand surges of molding sand delivered at the molding station can negate most all control endeavors.

Don’t Be Left Behind Invest in your metal casting technical and operating staff. They participate daily in important operationaldecisions that contribute to your profitability in casting ductile iron. Make them part of your team, by makingavailable up-to-date technical knowledge via video tape.

People are your greatest assets, invest in them. A Gold Medal Series of video training programs are available. They include subjects enhancing the green sand molding processand controls. They include "Defect Diagnosis," covering all major defects and also programs which exhibit "Reduction of CastingLosses." Extensive casting production experience is available. Contact "The Green Sand Molding Specialist," George DiSylvestro at DiSylvestro Videography Service (847) 825-5620 or fax (847) 825-2512.

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KEOUGH OF APPLIED PROCESS

Keough of Applied Process Wins Dual Recognition for Industry Services

John R. (Chip) Keough, PE, President/CEO of Applied Process, Inc., has been awarded two metal industryhonors. First, the American Foundrymen’s Society has granted him its Wm. J. Grede Award "for majorcontributions in the field of management, marketing and education, which have resulted in expanding theeffective use of metal castings." In Keough’s second award, the ASM International (a metals and materials society) has made him a Fellow ofthe organization for his contribution to the commercialization of the Austempered Ductile Iron Process. Mr. Keough has a two-award tradition; he was graduated from the University of Michigan in 1977 withBachelors Degrees in both Mechanical and Materials/Metallurgical Engineering. He is a RegisteredProfessional Engineer who has authored numerous papers, co-authored one book, written and editedchapters in many more and given scores of technical presentations in classes on foundry and heat treating

related subjects. He holds six heat treating or foundry-related patents. Mr. Keough’s company Applied Process Inc., specializes in a high-tech heat-treating process known as Austempering. Thecompany has operations in Livonia, Michigan; Oshkosh, Wisconsin; and Elizabethtown, Kentucky; as well as licensees in Australiaand England.



Ductile Iron Bomb Bodies

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DUCTILE IRON BOMB BODIES

Ductile Iron (DI) castings are finding increasing applications for military hardware. The ability to produce complicated shapes,minimizing machining, yet providing performance characteristics equivalent to wrought steel components, are the drivers. As a plus,there is often considerable cost savings. These applications are in vehicles and armament hardware, and now, new opportunitieshave been identified by the DOD for DI applications in projectiles and bomb bodies. The latter offers potential for significant addingof tonnage to the ductile iron industry. Five hundred pound, 1000 pound and eventually 2000 pound conventional explosive typebombs are needed by the Navy and the Air Force. Current DOD forecasts estimated requirements between 23,000 and 60,000 peryear between 1999 and at least 2005. Here is the development story and technical achievements. Figure 1. Casting vs. Forging

Casting Multiple sourcesNear net shapeMachine featuresInstall lug inserts

ForgingSingle SourceForge pipe & lugsCut & weld pipeMachine features Current SituationToday, bomb bodies are single sourced in steel. The steel bodies are produced by beginning with cut-to-length steel pipe,swedging to the desired profile, followed by machining and welding on aircraft suspension lugs. Steel aft end guidance wings (fins)are subsequently attached. The welded forging is heat treated. High cost, distortion and other quality problems make DI castings anattractive replacement as illustrated below. CDIB Requirements As-cast ductile iron bombs (CDIB) were first evaluated over ten years ago, but failed to meet a fragmentation requirement whendetonated. In short, it did not duplicate the requirement for large, uniform fragments, a capability of the heat treated steel. Aprogram initiated four years ago at the Naval Air Warfare Center (NAWC) identified the excellent potential of DI for meeting allrequirements, if the castings have good graphite morphology and were in the fully annealed condition. This structure produces thedesired walnut or marble size fragmentation; plus, provides the structural strength and fracture toughness necessary for handling,transport and airborne dynamic load forces. Table I below provides the desired property requirement for the heat treated castings. Table 1 Properties, Annealed CDIB



TS(KSI)

YS(KSI)

Elong (%) Charpy V-Notch (ft-lbs) Nod. (%) Pearlite (%)

TT(oF) -20oF RT

Target >60 >40 22 -40 7-8 15 >95 5 max

Minimum 60 40 18 -20 6 HP 90 ---

TT = Ductile to brittle transition temperature (F).HP = Highest practical (11-12 verified).

High casting soundness is necessary for meeting the elongation and impact requirements. The target is ASTM severity level 2 orless radiographic soundness throughout all sections. No gross shrinkage can be tolerated. This unsoundness is restricted toscattered microporosity that might occur in the matrix structure cell boundaries or at the mid center of any section. Otherrequirements are good as-cast surface finish and freedom from other types of casting defects. Surface finish is important becausethe only machining that is required is for the nose cone insert, threading for aircraft suspension lugs and an aft V-groove where theflight guidance steel wings are attached during final bomb casing assembly. The balance of the OD and the ID remain with as-castfinishes. The production 500 pound CDIB body is illustrated below.

Figure 2. Production Unit

Sizes of the various CDIB bodies are:

BombSize

Length OD Wall,min.

Wt. Cstg Only*

500 60" 12" .50" 270

1000 72" 14" .60" 490

2000 97" 18.1 .75" 950

*After 25 lbs machining removal.

Development Program Using an outside contractor, Tolo, Inc., the NAWC at China Lake, California, divided development into three phases for the 500pound bomb. Phase I: Computer modeling of casting design, solidification, gating, mold rigging and projected mechanical properties. Phase II: Metal process development and prototype manufacture using test blocks and 30 CDIB bodies. Phase III: Process verification and a 75 unit production of prototype bodies meeting all requirements for flight and missionperformance testing. Figure 3 illustrates the final mold design developed in Phase I. Sample castings had been produced in a iterative processthroughout Phase I and tested, leading to best possible mold design to meet all final casting requirements, The work determined that:



• Casting is best in the vertical position in no-bake resin silica sand split molds, to minimize distortion and provide required surfacefinish. • The long center core, supported only at each end, must be metal arbor reinforced and top vented. Chaplets may not be used toprevent local defects. • A large top ring riser and blind side risers are needed to feed heavier sections. • Zircon sand is necessary in the heavier suspension lug area (where side risers are located). • Two CDIB’s on were the most efficient mold design. • With this design, mold yields around 30-35% are obtained. (In commercial production, this might be improved.) The total down sprue on the 500 pounder is over 7.5 feet tall, necessitating metal fill speed trap. Molds are clamped in a pouringjacket and poured vertically. Two Keel blocks are incorporated in each mold for subsequent determination of tensile, Charpyimpact, chemical and microstructural properties. All properties need to be met after the final anneal heat treatment, so test barsmust be heat treated in the same furnace load as the castings. During mold design work in Phase I, a long run of casting Keel blocks was used to determine metal properties and make processchanges to meet target metal properties. Experimentation looked at different silicon levels, carbon equivalents, alloying with nickel, treatments, inoculants, and pouringtemperatures to optimize practices. All tests were of sufficient scope to forecast expected 6 sigma control ranges for commercialmanufacture. The bottom line is meeting a 3 sigma lower statistical scatter limit. Keel blocks will be required when production iscommercialized. During Phase II, three-fourths of the bomb bodies were destructed to gain additional statistical property and casting integrity data,check out dimensional control and develop machining and heat treatment practices. Included were tests from heavy and lightsections, top and bottom, and lug areas.

Figure 3. Production Mold Design The plan followed was: Produce thirty 500 pound bomb bodies with... • 24 bodies for property testing.

Non-Destructive Tests Destructive Tests-Dimensional-Visual

-Tensile properties-Impact properties



-Mag particle-Radiographic-Lug area load-Hydrostatically

-Ductile to brittle transition curves-Chemical analyses-Hardness-Metallographic

• Simultaneously cast Keel blocks from poured molds. - Tensile, impact and chemical properties. • Six CDIB for arena fragmentation and structural tests at the Naval Air Warfare Center, China Lake, California. Simulated Bomb Material TestsThroughout Phases I and II, parallel projects were contracted to two government development foundries and two commercial ductileiron foundries. Each produced 30" long, 12-14" OD simple right cylinders with wall thicknesses similar to the 0.50-0.60" minimalwalls in 500 and 1000 pound bombs. The majority of these and Keel blocks cast simultaneously were destruct tested after annealheat treatment for tensile, impact chemical and metallographic properties. The purpose was to verify if expectations of finalproperties are realistic and can be met by any well controlled commercial producer. Some cylinders were also fragmentation testedat the NAWC, at China Lake, as shown in Figure 4.

Figure 4. Cylinder Fragmentation Test These results are then verified in actual CDIB fragmentation tests shown in an arena testing in Figure 5.

Figure 5. Bomb Test in Arena In the arena, explosive charges fragment the DI castings, Fragments are captured in Celitex and wood screening for size, weightand distribution analyses. Fragment velocities, distance, impact forces, etc., are either measured or calculated. Results need toduplicate the acceptable patterns of existing commercial steel bodies. These analyses show annealed CDIB bodies do the job. Awalnut to marble size appears desirable. Metallurgical ConsiderationsDuctile iron bomb bodies must provide equivalent properties and performance as any steel assembly. Some importantcharacteristics and reasons are:

Requirement Property

Flight temp to -65oF Low transition temperature (TT)



Handling-Drop 40 ft. to carrier hold-Drop on flight deck or ground- Roll alive overboard-Flights return with bombx

Highest ductility and impact energy value

Extreme G forces during flight maneuvering Good tensile properties and low notch sensitivity

High in flight static and fatigue loading in lugattachment areas and forces on bomb aft wings area

High tensile and yield strength

Pressure tightness No shrink or porosity

Salt spray corrosion and stress corrosion resistance Improved over steel due to Si+Ni content and ferrite

Fragmentation requirements Optimized combination of all properties

During Phases I and II, a series of composition and processing variations were evaluated. Target being identifying the best potentialcombination of all mechanical properties. That is highest possible yield strength coupled with highest possible ductility and lowestachievable impact transition temperature, with minimum trade-offs. The following was identified: • All elements except Si, C and Ni need to be as low as practical. Actual limits were set. • Optimum CE and Si should be 4.4 and 2.2 ± 0. 1%. A 1-1.5% Ni level is required at this low Si level to meet yield strength. Si isa ferrite strengthener and contributes to annealability. Ni has one-third the effect of Si on yield strength. Without the Ni, the verycritical 40 KSI yield strength is not met, simultaneously with the highest ductility, following full ferritization annealing.

• Additional tests indicate nickel additions can be eliminated if final Si is raised to 2.5%. However, the higher silicon raises thenotched bar impact transition temperature. The trade-off study is needed.

• Full ferritizing annealing results in the highest ductility and best impact properties. While subcritical annealing produced equal orslightly higher tensile properties at the sacrifice of ductility and impact. Therefore, current requirement is for full annealing. Thereason is full annealing provides increased homogenization of the final matrix structure, reducing the "notching effect" ofsegregation and cell boundary constituents. • Nodularity approaching 100% and an optimum nodule count of 100-15ON/MM 2 provides best overall properties. Good nucleationin the melt was achieved by use of crystalline graphite and silicon carbide additions during melting and multiple ferrosiliconinoculation steps. Inoculation is enhanced when using a combination of MgFeSi alloy for treatment followed by ladle transfer postinoculation with FeSi or proprietary ladle inoculation plus late stream or mold inoculation at the casting station. With all these siliconadditions, a well managed operation is needed to avoid exceeding maximum target final iron silicon levels. Smallest practicaladditions are necessary at each step. The multiple inoculations also prevent carbides, which affect annealing cycles and haveresidual property effects. • Complete mold cooling is needed to minimize casting distortion. • Residual Cu and P are particularly detrimental to final ductility and impact properties. These are minimized by careful selection ofsteel scrap in the charge (slitter steel preferred). A significant charge component of sorel pig iron was also found necessary tomaintain low Cu and P levels, manage Mn content to a target of 0.30%, and hold furnace Si low to meet maximum final Sianalyses. Cu and P max levels of 0.06 and 0.015 are desirable. The balance of the charge can be returns, but should be only"bomb quality" metal returns. • The minimum properties listed in Table 1 are easily met in Keel blocks poured and heat treated with the castings. Test bars takenfrom actual castings, although having equivalent tensile and yield strength, had lower ductility and inferior Charpy properties. Thistended to occur in all cases and is assignable to isolated centerline microporosity, and perhaps, to micro segregation which isenhanced by the slow solidification in large mass castings. Since these properties necessarily represent n-midsections, and mostimportant strain resisting forces are at the OD, this may not be a significant factor. This is however in no way an acceptance of lowradiographic soundness. Keel blocks provide best representation of the true material properties. What’s Next?The Navy has completed most of the development work on the 500 lb CDIB and is ready to solicit commercial foundries forproduction contracts. We are told that all development information will be shared with industry. This does not mean the DOD will



write prescriptions for production. They are only interested in suppliers meeting the final product properties and quality levelspecifications. There are of course opportunities for commercial foundries to improve on properties, material costs and processes,such as utilizing cost-saving subcritical annealing, casting mold yield reduction and use of alternative production raw materials andcommercial processes. The production of 75 castings in Phase III is underway. These will be furnished for not only use in process verification, but actualflight testing, practice drops and other mission evaluations. Commercial production solicitation could begin by 1999. A very similar program as Phases IV through VI has also been initiated for the 1000 pound bomb. This program should beconsiderably shorter, having mastered the basics in the 500 pound study. And, we have just learned that the Air Force is nowexamining the potential for a 2000 pound bomb. There will be a number of opportunities for commercial foundries interested in these types and sizes of castings, Additionalinformation is available from Mr. Joe Etoch, 473320D, NAWC, China Lake, California, 93555-6001. Naval Air Warfare Center - Weapons Division



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EXPERIENCES IN DUCTILE IRON PRODUCTION

Experiences in Ductile Iron Production Greenfield Start-up Cupola vs. Coreless Electric MeltingDuctile Iron Society 1998 Annual Meeting, June 17-19, 1998By Joel W. Yates, Briggs & Stratton Corporation

AbstractThis paper will be discussing two different topics that are similar in context. Both are based on the start-up of an electric meltingductile iron facility. The first topic will discuss the greenfield start-up and the second will compare this foundry to another foundry inthe same company. Keep in mind that both foundries are identical in every way except for the melting process. This is veryimportant to some of the conclusions being made. Also, the paper is based on metallurgical aspects of a start-up situation. 1. Greenfield Start-up of a Ductile Iron FoundryThe start-up of a greenfield operation involves many different areas of normal foundry practices. Well over 95% of the effort isplaced on the physical construction of the facility. The rest involves the training of new people and designing the overall process ofmelting, molding and finishing the castings. The topic of this paper is to focus on the metallurgical aspects of starting a new facility. MeltingThe foundry being discussed does all melting using three (3) line frequency, 20 metric ton coreless electric furnaces. These offerapproximately 21 tons per hour of melting capacity. All charge materials are pre-weighed and preheated by natural gas direct flame.This is done due to the nature of the furnaces being used. The melting practice used is what is referred to as "heel melting." Of the40,000 pounds of metal in the furnace, 4500 pounds is tapped and 4500 charged for melting. The entire process of tapping,charging, sampling and melting takes approximately 20 minutes. There are only three charge materials being used, pig iron, fragmentized black steel scrap and returns from operations. Cleanlinessand size are very critical due to slag amounts and density respectively. Since the furnaces do not have a back-tilt option forslagging, all slag must be removed manually using steel "spoons." Therefore, the amount of generated slag becomes an importantfactor. Also, this is why as much sand is removed from returns as possible using a media drum. The size of the charge materialsare monitored closely for density so that the entire charge of 4500 pounds will fit easily into the charging bucket followingpreheating operations. There are just two alloying materials used in the melting operation . The first is graphite, which serves as both a carbon additiveand as a nucleator of the base iron. The second is silicon carbide. This serves both as a silicon additive and also as a deoxidizerof the base iron. Both of these alloys are added to the furnace after tapping and before charging. In a heel melting operation, theaddition of these materials before charging allows for a larger recovery rate of the alloys due to its submersion in the bath by thecharge. The amounts of each alloy needed in each heat is dependent on the carbon and silicon thermal analysis results obtainedfrom the furnace on the previous heat. In a start-up situation, it will need to be determined how much iron should be tapped. This will depend on the most evencombination between the needs of the molding department and the capabilities/efficiencies, of the melting department. This will bedifferent in every facility. Also, it is best to start with the highest quality of charge materials and alloys possible. This is one variableof quality that you do not want to have to worry about when operations are starting. After a benchmark is set, experimentation intoother materials can safely be done. Treatment MethodThe equipment chosen for ductile treatment are "modified" tundish ladles. Basically, they are 5000 lb. capacity double-spoutedteapot ladles with an alloy pocket wall designed in. The purpose of this ladle is to prevent the initial molten iron from contacting thealloy until enough iron has entered the ladle as to maximize magnesium recoveries. Since magnesium is mostly lost due tooxidation, it is in our best interest to submerge the alloy under the molten bath for as long as possible. Since different grades of iron will be produced, it was necessary to devise a way of making copper and ferro-manganese additions.What we came up with was a semi-computerized way to make such additions. Since there are two molding lines, it was necessaryto be able to alloy for both. At the initial treatment stage, the ladle operator will alloy up to the lower alloy grade of the two lines.The metal delivered to the molding lines, therefore, is ready for one of the lines, but needs to be alloyed up for the second grade.The computers are used by showing base iron chemistry data to the ladle operator and letting them determine the pounds of alloyneeded. The final chemistry targets for each job being run are shown to the operator and a conversion chart is also provided. Anexample of the computer screen the operator sees and the conversion chart are provided in figure 1 and figure 2.

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Click here for figure 1 Click here for figure 2 As you can see, by taking the base iron copper and manganese levels and the corresponding targets from the screen, the operatorcan determine the alloy needed, in pounds, on the conversion chart on the right. This chart is used at the treatment vessel where4500 lbs. is being treated. A similar chart is used at the molding lines and is based on either 2250 lbs., half a full heat, or 1500 lbs.,a third of a heat. Either may be necessary depending on the iron needs of each line. Also, the same type of conversion chart isused for ferro-manganese additions. This method of adding alloy was extremely helpful in the start-up due to the fact that the work force was completely green. In otherwords, they had no foundry experience at all. The next step in this process would be to have the computer automatically figure outthe pounds needed on its own. All the operator would have to do would be to tell the computer which furnace they were going totap from. This can be very important, especially on Monday morning after a furnace reline when the chemistries in each furnaceare different. MoldingThe pouring method used is an unheated "bottom pour" ladle. The stopper rod is operated by an automatic laser guided pouringsystem. Alloys used for inoculation include 75% ferro-silicon and some instream inoculant. The ferro-silicon is added to the ladleupon receipt of iron and the instream is blown into the stream as the molds are being poured. Determining the frequency of nodularity and chemistry sampling will be important when considering the type of parts beingproduced in the future. It may be a good idea to go ahead and sample every heat from all molding lines. This will be a goodpractice to be in use, even though it can be costly, especially if you plan on making "safety critical" parts in the future. Historically, nodularity was determined using a rating chart that had examples of different percentage levels of nodularity, pearliteand carbides. A good example of this is the "Ductile Iron Microstructures Rating Chart" that AFS publishes. This can be seen in justabout every ductile iron foundry in the Midwest. When going through a greenfield start-up, this can pose a rather large problem.Since there is no experience in reading nodularity to draw from and the fact that everyone reads a visual chart differently, it is toone’s advantage to look into imaging software. This software will allow for a totally subjective recording of nodularity, allowing noroom for interpretation of results. This will be helpful when going through a start-up and experiencing the "growing pains" oflearning the process’ capabilities. Figure 3 and figure 4 are examples of such software and what it can do. % Nodularity TestingAs you can see, it is able to measure nodularity and pearlite by measuring contrast in light. Carbide percentage is determinedusing the same method. The data obtained from this analysis can then be used to predict how long it takes before the iron has faded to the point of beingunusable. Using this type of unpressurized ladle, the magnesium fades fairly quickly depending on time, temperature and surfacecontact area of the iron with the ambient air. To do a prediction such as this, and it is highly recommended that a new facility does,it will be necessary to compile historical time study data comparing the nodularity at different time intervals. This data can then beanalyzed through a regression software to predict, historically, what the length of time it will take before the iron is at or below 80%nodularity. An example of such a regression is shown in figure 5 and figure 6 (below) along with the data used. Even though, by examining the data, you know the iron can go longer than the predicted time, on average it cannot. This ispossibly a result of how fast the ladle was emptied. The longer the ladle can stay full, the slower the iron will "fade." This is a resultof the amount of surface area in contact with the air. LaboratoryWhen setting up the laboratory, make sure the testing equipment is user friendly. It will be probable that the people hired will nothave any experience running a tensile machine or spectrometer and will not have an in-depth knowledge of personal computers.Research this carefully before expending large amounts of resources. It is a good idea to monitor results of mechanical properties testing using some form of statistical software. A new facility may see alot of interest from its customers regarding their capabilities in meeting physical property specifications. Remember, the customerhas never purchased castings from you before and will be cautious at first. Following on the next page are some examples of howthese physical properties can be monitored. The "R Squared" value represents the correlation of the regression between the two results being compared. The closer this

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number is to 1, the more consistent the equipment and the iron is. Also, it allows the customer to be able to predict the physicalproperties just as we did for the nodularity predicting mentioned in figure 6. Figure 6

Time (min.) %Nod.

PredictedTime(min.)

9.50 93.9 9.15 92.5

13.35 86.7 7.50 89.4

11.60 90.1 11.50 87.8 12.30 87.0 9.60 91.5

10.50 91.5 7.20 95.3 7.50 94.4

10.15 91.7 10.26 91.0 8.30 93.3

11.00 91.0 12.50 91.1 14.00 89.2 11.20 89.6 9.50 92.5

13.00 85.7 80.0 12.889

2. Cupola vs. Coreless Electric MeltingThe comparisons that will be discussed in this section are based on two foundries that are identical in every way except for themelting equipment. This is interesting and unique because all other factors do not come into play due to total similarity. This allowsfor a completely subjective comparison of base metal costs and fuel consumption.

Raw Material Selection, Cost and ConsumptionThe main difference between the raw materials used in the two foundries is the cost and quality needed. The materials used in theelectric melting shop are more expensive, but are able to be used in a more efficient way. The electric shop is able to use morereturns than the cupola shop. This is due to the yield difference. The cupola shop has a larger yield and therefore has a smallerquantity of available returns for charging. Even so, the charge material cost per ton for the electric melted iron was less than thatof the cupola. It must be mentioned that some of the coke and silicon carbide briquettes were taken out of the charge costs for thecupola melted iron due to the fact that a certain percentage of the two act as fuel. Then, this fuel has been added in along withnatural gas and electric to determine a total cost per ton. The electric usage was added in to the electric melted iron cost for equalcomparison. Still, the electric shop does have a lower cost per ton. This goes against industry-wide thoughts about melting costs ofcupola and electric melted irons. The largest reason probably being the difference in the amounts of returns being used. Chemistry FlexibilityDue to the nature of the melting practices, more success in chemistry control has been achieved in the electric melting foundry.This is due to the fact that a chemistry sample is taken on every heat out of the furnace before it is tapped. In the cupola, a sampleis taken out of the holding furnaces at specified time intervals. The variance in the cupola is due to the fact that it is running intothe holding furnaces constantly. Therefore, the chemistry may change from heat to heat in between samples. With the electric

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melting, no new iron is introduced in between samples. Another factor is the need for desulphurization out of the cupola. This does allow for some variance in sulphur levels. This is due tothe raw materials being used and the consistency of the desulphurizing vessel. Finally, the raw material used in the cupola is less expensive, but along with that comes a wider variance in chemistry. The moreexpensive materials used in the electric shop do not vary nearly as much. Oxygen LevelsThe soluble oxygen levels out of the cupola are much lower than that of the electric furnaces. The cupola is, by nature, a reducingenvironment, whereas, the electric furnace, by way of its rolling action, actually draws in oxygen. This is probably why the cupolashop mentioned in this paper adds almost 20% less magnesium alloy than the electric shop. This is a large contributing factor tomaterial costs. It is important to note that the more sand that can be left on the returns, the lower the oxygen levels should be. The sand behavesmuch like the silicon carbide by way of deoxidizing the bath. Unfortunately, electric furnaces are not self slagging and the extrasand may inhibit productivity. Availability of MetalThe advantage in the area of metal availability is by far in the cupola’s favor. The electric furnaces are limited by iron that is not totemperature. In other words, it is still melting in. The cupola foundry, however, has the advantage that in case power to the cupolais lost, the iron in the holding furnaces may still be tapped. Only the iron in the electric melting furnaces that were up totemperature may be tapped. ConclusionThe ideas that were discussed in this paper are to try and show some of the things a metallurgist and/or foundry manager shouldbe looking at when starting a greenfield ductile foundry and deciding what type of melting equipment to purchase. Again, all of theconclusions made are based on the analysis of two specific foundries that are identical except for the melting practices. Hopefully,this can provide some insight into the different aspects of going through a start-up situation.

Additional Figures

Figure 7. Brinell Hardness vs. % Elongation

Figure 8. % Elongation vs. Tensile Strength

Figure 9. Charge Cost Sheet Cupola Melting

Figure 10. Charge Cost sheet Coreless Melting



Figure 1

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Furnace Chemistries (Base)Briggs & Stratton

Time Heat Furn Cu Si S Mn P Cr Al 5/13/98 09:11:09

09:05 26 1 0.279 1.78 0.010 0.25 0.012 0.040 0.004 Plates Scheduled &Suggested Additives:

09:03 25 3 0.269 1.77 0.011 0.25 0.012 0.043 0.004

08:51 24 2 0.285 1.73 0.010 0.25 0.012 0.042 0.005 Plate #: Cu Si MN

08:44 23 1 0.289 1.74 0.010 0.26 0.013 0.042 0.005 BRE587 0.60 6 0.30

08:32 22 3 0.278 1.79 0.011 0.25 0.013 0.043 0.004 RBA547 0.57 6 0.27

08:29 21 2 0.286 1.75 0.010 0.25 0.012 0.042 0.005 RBA700 0.60 6 0.30

08:16 20 1 0.285 1.68 0.009 0.26 0.012 0.043 0.005 RSA301 1.10 7 0.43

08:02 17 2 0.291 1.80 0.010 0.25 0.011 0.042 0.005 RSA308 0.35 11 0.27

07:57 18 3 0.281 1.77 0.010 0.25 0.011 0.044 0.005 RSB218 0.45 9 0.27

07:45 16 1 0.286 1.66 0.008 0.26 0.011 0.044 0.005 SRD377 0.65 6 0.30

07:35 15 3 0.276 1.75 0.010 0.25 0.011 0.044 0.005 Number of Plates: 707:23 14 2 0.289 1.81 0.010 0.25 0.011 0.043 0.004

07:20 13 1 0.291 1.75 0.010 0.26 0.012 0.044 0.005

07:10 12 3 0.289 1.73 0.011 0.25 0.013 0.046 0.005

07:08 11 2 0.295 1.79 0.010 0.25 0.012 0.042 0.005

06:58 10 1 0.297 1.78 0.011 0.25 0.013 0.043 0.004

06:55 9 3 0.280 1.72 0.009 0.24 0.011 0.045 0.004

06:38 8 2 0.304 1.70 0.012 0.24 0.013 0.043 0.004

06:33 7 1 0.302 1.78 0.012 0.26 0.013 0.044 0.004

05:31 3 3 0.280 1.74 0.011 0.25 0.014 0.046 0.003

05:28 2 2 0.305 1.77 0.012 0.25 0.014 0.045 0.003

05:26 1 1 0.304 1.80 0.012 0.27 0.013 0.046 0.003Quit

Number of records: 22 General Info

Figure 1 Back to Experiences in Ductile Iron

Figure 2

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Final Copper Target 4500 Lbs.

BaseLevel

0.30 0.35 0.45 0.50 0.55 0.60 0.65 0.90 1.00 1.10

0.25 2.5 4.5 9.0 11.5 13.5 16.0 18.0 29.5 34.0 38.5

0.26 1.8 4.1 8.6 10.8 13.1 15.3 17.6 28.8 33.3 38.8

0.27 1.4 3.6 8.1 10.4 12.6 14.9 17.1 28.4 32.9 38.4

0.28 0.9 3.2 7.7 9.9 12.2 14.4 16.7 27.9 32.4 37.9

0.29 0.5 2.7 7.2 9.5 11.7 14.0 16.2 27.5 32.0 37.5

0.30 0.0 2.3 6.8 9.0 11.3 13.5 15.8 27.0 31.5 37.0

0.31 0.0 1.8 6.3 8.6 10.8 13.1 15.3 26.6 31.1 36.6

0.32 0.0 1.4 5.9 8.1 10.4 12.6 14.9 26.1 30.6 36.1

0.33 0.0 0.9 5.4 7.7 9.9 12.2 14.4 25.7 30.2 35.7

0.34 0.0 0.4 5.0 7.2 9.5 11.7 14.0 25.2 29.7 35.2

0.35 0.0 0.0 4.5 6.8 9.0 11.3 13.5 24.8 29.3 34.8

0.36 0.0 0.0 4.1 6.3 8.6 10.8 13.1 24.3 28.8 34.3

0.37 0.0 0.0 3.6 5.9 8.1 10.4 12.6 23.9 28.4 33.9

0.38 0.0 0.0 3.2 5.4 7.7 9.9 12.2 23.4 27.9 33.4

0.39 0.0 0.0 2.7 5.0 7.2 9.5 11.7 23.0 27.5 33.0

0.40 0.0 0.0 2.3 4.5 6.8 9.0 11.3 22.5 27.0 32.5

0.41 0.0 0.0 1.8 4.1 6.3 8.6 10.8 22.1 26.6 32.1

0.42 0.0 0.0 1.4 3.6 5.9 8.1 10.4 21.6 26.1 31.6

0.43 0.0 0.0 0.9 3.2 5.4 7.7 9.9 21.2 25.7 31.2

0.44 0.0 0.0 0.4 2.7 5.0 7.2 9.5 20.7 25.2 30.7

0.45 0.0 0.0 0.0 2.3 4.5 6.8 9.0 20.3 24.8 30.3

0.46 0.0 0.0 0.0 1.8 4.1 6.3 8.6 19.8 24.3 29.8

0.47 0.0 0.0 0.0 1.4 3.6 5.9 8.1 19.4 23.9 29.4

0.48 0.0 0.0 0.0 0.9 3.2 5.4 7.7 18.9 23.4 28.9

0.49 0.0 0.0 0.0 0.4 2.7 5.0 7.2 18.5 23.0 28.5

0.50 0.0 0.0 0.0 0.0 2.3 4.5 6.8 18.0 22.5 28.0

Figure 3

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Figure 4



Figure 5


Back to Experiences in Ductile Iron

Figure 5 - % Nodularity Regression Results

Regression Coefficients% Nod. vs. Time (min.)

Coefficient Std. Error Std. Coeff. t-Value P-Value

Intercept 94.543 1.297 94.543 72.900 <.0001

Time (min.) -.432 .127 -.348 -3.398 .0010

Figure 7



Figure 7 - Brinell Hardness vs. % ElongationRegression Summary

Brinell vs. % Elongation

Count 122

Num. Missing 0

R .955

R Squared .912

Adjusted R Squared .910

RMS Residual 8.487

Figure 8



Figure 8 - % Elongation vs. Tensile StrengthRegression Summary

% Elongation vs. Tensile Strength

Count 122

Num. Missing 0

R .973

R Squared .948

Adjusted R Squared .946

RMS Residual .800

Figure 9



Figure 10



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THE EFFECT OF METALLIC CHARGE

The Effect of Metallic Charge/Melt History on Nucleation Potential in Ductile Cast Irons A paper presented at the Ductile Iron Society meeting, June 1998.By James D. Mullins & Eugene C. Muratore;Rio Tinto Iron & Titanium, Inc. The melt history, including the type of charge material, chemistry and molten metal processing of a cast iron melt has a pronouncedand measurable effect on the final structure and properties of the castings poured. The assessment of the nucleation potential of agraphitic cast iron before treatment and/or inoculation has been practiced at some level or degree for a long time. CHILL WEDGESSee Figure1 Chill wedge testing of base cupola iron gave the operating foundryman a qualitativemeasurement of the graphitizing (nucleating) potential of that iron. See figure 1. An iron that hasa large chill value (tendency to form carbides upon solidification) means that it possesses a lownucleating potential. So by measuring the width of the chilled (carbidic) portion of the wedge,changes to the charge amount or type of material could be made. Pouring another wedge afterthe inoculation step could assess the effectiveness of the inoculant. Before the advent ofaffordable and timely chemical analysis, and certainly before the development of computerizedcooling curve analysis, the dependency upon wedge testing for the assessment of suitability ofan iron for pouring was mandatory. Melters soon realized that changes to the charge and/orthermodynamic changes within the cupola manifested dramatic changes in the chill wedge values of cast iron. For example, when pig iron was introduced into the charge, the chill value typically decreased. As the steel portion of the chargewas increased, the chill value increased. As the melt conditions moved to more oxidizing conditions, the chill value increased.Cupola well depths and iron dam heights were carefully measured and controlled in order to maximize the nucleating effect of thecoke. All of these changes to the nucleation potential were seen even though the chemistry most often did not change. With the increasing popularity of induction melting furnaces as primary melters, the utilization of the wedge test has fallen out offavor. Since the chemical analysis could be much more closely controlled, it was incorrectly assumed that the nucleation potentialwas also being more closely controlled.

DUCTILE IRON FINAL WEDGESee Figure 2 Ductile Iron foundrymen oftentimes saw nothing other than white iron (100% carbidic) fractures intheir base iron wedges, typically because of the lower content of silicon and sulfur, and also inthe final wedges. So they too abandoned the use of chill wedge testing for evaluation of thenucleation potential. There are a number of factors that affect the nucleation potential and metallurgical quality of castirons. They are: the metallic charge, the type of melting equipment employed, melting andholding temperatures, dwell time (holding time), chemical composition, and inoculation. Each ofthese factors will now be explored further. As I mentioned earlier with cupola melted irons, the metallic components of the charge exert a large effect on the nucleationpotential of the melt. The reason for this effect is the steel component of the charge contributes very little in the way of nuclei forthe growth of graphite. Likewise, the Ductile Iron returns portion of the charge, being quite deoxidized during treatment andinoculation, also contribute little nucleation. EFFECT OF REMELTINGSee Figure 3 As an example, when returns are repeatedly remelted, even just two times, the solidifying ironcan become all carbidic. To reduce this effect and renucleate, additions of some pig irons,

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graphite, silicon carbide, and other ferrosilicon alloys are made to liquid melts. In order to produce a cast iron melt that responds well to inoculation and exhibits the lowestpotential for carbide formation during solidification, the returns should be limited to no more than50%, the steel component should be limited to 40% maximum, and consideration should begiven to utilizing some pig iron in the charge. Figure 4. Effect of rusty scrap on chill in inductionmelted 4.1% C.E. gray cast iron with no inoculation EFFECT OF RUST ON CHILL VALUESee Figure 4 The cleanliness of the charge material also plays a role in determining the chill value. If thecharge material is heavily oxidized, the resulting iron will exhibit a much higher chill value. Wehave seen the opposite to also be a problem. Several foundries have shot blasted all of theircharge materials to remove rust and sand. They found very high chilling tendency in this iron andas a result more shrinkage defects. So having a small amount of oxygen in the base melt isnecessary. The type of melting equipment can play a role in iron nucleation. Iron melted in a cupola isconditioned by the nucleating effect of the intimate contact between molten iron and the coke inthe cupola well and a relatively short time at high melt temperatures. Cupola melted irons usually exhibit a lower chill value andgenerally require less inoculation in order to produce carbide free microstructures. Further the presence of adequate oxides andsulfides as nucleation sites renders cupola melted iron as one with a high metallurgical quality. As more experience was gained throughout the 1950's and 1960's with melting gray irons and ductile base irons in induction andarc furnaces, note was made that these irons exhibited higher chill and more shrinkage tendency even while having identicalchemical compositions as cupola melted irons. The reasons for this are several: In electric furnaces there is no coke contact aswell as more stagnant bath conditions, higher melting temperatures are used to dissolve carbon, and longer holding times and oftentimes there are lower oxide contents. This leads to higher base iron chill (low nucleation values) . For these reasons, electricfurnace melted irons generally require different charge ratios and additional amounts and often times more potent inoculants. I have already mentioned something about temperature, but there is more. In the case of cast iron melting in electric arc furnaces,the temperatures attained near the arc tip may exceed 5000oF. Irons thusly treated are called "fried" irons, because all the nucleihave been cooked out, leaving an iron that will not have a low chill value. EFFECT OF SUPERHEATING See Figure 5As the temperature of any melt is increased above the normal melt temperature (highsuperheat), the nucleation is reduced. This loss of nucleation or reduction in metallurgical qualityis manifested with virtually no change in chemical analysis. The measured chill depth maychange from an acceptable level to all white wedge over a 200oF temperature range or less.This reduction in metallurgical quality requires the use of greater amounts of inoculant(s) in orderto produce acceptable final microstructures. It may not be possible to correct this iron. It istherefore advisable to melt and hold iron at as low temperatures as practical. The effect of long dwell or holding times on the nucleation potential of cast irons is similar to theeffect of high melting (superheating) temperature. The longer the hold times, at any temperature, the greater the loss of nucleation.The higher the temperature during this holding period, the worse is the loss. The most prevalent instance of this phenomenon isknown in the trade as "Monday morning iron". It has long been recognized that irons held over a weekend exhibit very differentsolidification behavior than normal. These irons exhibit higher shrinkage tendency and have more carbide due to this loss ofnucleation. Irons that have not been renucleated by the addition of "fresh" iron or nucleating agents exhibit a much higher chilllevel. This issue is so important, that the AFS Molten Metal Processing Committee has begun a research project to show foundriesthis holding effect on iron properties/defects and what can be done to reduce or eliminate this problem. The chemical composition can alter the nucleating (graphitizing) tendency of cast irons to a certain extent. As the carbonequivalent is lowered the tendency to solidify with a more carbidic microstructure increases. As the level of carbide stabilizingelements is increased, the same effect is seen. Even at the same carbon equivalent and residual element levels, changes incarbon/silicon ratio can alter the metallurgical quality and physical properties. Generally speaking increasing carbon content reducesshrinkage tendency in cast irons and increasing silicon content reduces carbide formation, but these effects are lost due to the loss

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of nucleation. Ductile Irons treated with magnesium ferrosilicon alloys often begin as base irons of very low silicon (often times less than 1.2%)content. These low silicon base irons may exhibit an all white chill unless an adequately large wedge test core is used. Of course,a low nucleation level may also contribute to an all white chill value. So using the correct size wedge (see ASTM A367) isimportant, as is a good sampling procedure in order to achieve the correct result. Done properly, the chill test can be very helpful toassess ductile iron base metal to see that is has been well processed and has a low chill value. MAGNESIUM vs. MODULUS In magnesium treated irons, high magnesium content acts to promote carbidic microstructuresand increase shrinkage. The magnesium level must be controlled carefully to the cooling rate ofthe casting to avoid increased chilling tendency. This cooling rate is described as the modulus,which is a ratio of casting volume to cooling surface area. Thus modulus is a more accurate wayto describe the cooling of a casting section than just measuring the section(s) size. See figure 6.

Of course, all of the carbide stabilizing elements should be kept to relatively low levels tominimize their effect on chill (carbide) promotion. Doing this will then allow more of the availablecarbon to transform to graphite. Many foundries have reinstituted melt assessment through chill wedge testing and /or thermal (cooling curve) analysis programsbecause they are simple and inexpensive. The wedge test can be used to verify the results of the cooling curve. Magnesium concentration effect on shrinkage Inoculation is the final and the most important step in molten metal processing. Although not all of the problems addressed abovecan be compensated for with inoculants, several facts stand out. Foundries that pour thin-section castings, tapped at elevatedtemperatures, may be able to produce acceptable castings with very good inoculation. Without it, this would not be possible. Thecorrect use of inoculants and preconditioning agents can also allow for the utilization of irons held over weekends and holidayperiods, if the iron has not deteriorated badly. Despite the rigid control of residual elements in many foundries, some percentage of deleterious elements is usually alwayspresent. The employment of adequate amounts of and effective inoculants enables the seasoned foundrymen to produceacceptable castings from these irons. ELEMENT SEGREGATION TENDENCY The production of heavy section castings also requires adequate nucleation and inoculation inorder to shorten the intercellular spacing so that strong segregation of carbide stabilizingelements is avoided. Even at low concentration levels, these elements are known to segregate tothe last to freeze areas and contribute to grain boundary carbides and deteriorate themechanical properties, as well as machinability. When we look at the tendency to segregate; elements with numbers greater than 1 tend tosegregate into the intercellular regions and those elements with numbers less than 1 tend toincrease their concentration around the graphite nodules. As an example, from the slide, themolybdenum concentration can be up to 25 times more in the intercellular region than it is in the rest of the iron. Conversely theconcentration of copper around the nodule will be higher than the concentration of silicon and neither one will have much of apresence in the intercellular regions See figure 7. Element Segregation Factor Mo..........................25.3 Ti..........................25.0 V..........................13.2 Cr..........................11.6 Mn..........................1.7 - 3.5 P..........................2.0 Si..........................0.7 Co..........................0.4 Ni..........................0.3 Cu..........................0.1

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Supporting Work The metallurgical quality or nucleation state of the iron has been studied and published by many authors. Vern Patterson who wroteFoote Foundry Facts - devoted several issues to the importance of measuring chill wedge values and the effects of processingvariables on the nucleation level of cast irons. The benefits of an established and practiced wedge control program are a recurrenttheme throughout the issues.

See Figure 8. Preconditioning Effect on BHN Hardness

See Figure 9. Preconditioning Effect of Elongation

SeeFigure 10. B.C. Godsell, in his AFS Transactions paper, "Preconditioning of Ductile Iron" describes one foundry's method to adjust the basenucleation state of ductile base iron before treatment. Before utilizing a preconditioning program, the foundry was unable toproduce castings to an acceptable hardness or elongation range. After the institution of a preconditioning program, whichnormalized the nucleation state of the iron before treatment, ductile iron castings could be produced as cast with propertiesconsistent to those of heat-treated castings. J.M. Frost and D.M. Stefanescu in their paper "Melt Quality Assessment of SG Iron ThroughComputer Aided Cooling Curve Analysis" ran a designed experiment where it was shown thatseveral processing variables had pronounced effects on nodule count and chill depth. As the percentage of pig iron is increased and the superheat and pouring temperatures aredecreased the nodule count is increased. As the superheat time or temperature is decreased, the nodule count is increased and the chilldepth decreased. See figure 11. Further, decreasing superheat temperature and increasing pig iron content had the effect ofreducing the chill depth, while reducing the pouring temperature had little effect. See figure 12. In conclusion, the metallic charge and melting history of cast iron melts have a significant effecton the final metallurgical structures obtained. These structures affect mechanical properties,shrinkage behavior and machinability in these castings. A base iron that has a low chill value oris preconditioned to have a high nucleation state will tend to have less magnesium andinoculation fading. This usually means that shrinkage problems will be reduced. Assessment of

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this nucleation condition is important to producing consistently high quality castings.? References

1. Ductile Iron Production, Vol I QIT Fer et Titane, (1993).2. Cupola Handbook, American Foundrymen's Society (1975).3. Foote Foundry Facts, Foote Mineral Company.4. Ductile Iron Handbook, American Foundrymen's Society (1992).5. B.C. Godsell, "Preconditioning of Ductile Iron" AFS Transactions, vol 86, pp 273-276 (1978).6. J.M.Frost, D.M. Stefanescu, "Melt Quality Assessment of SG Iron Through Computer Aided Cooling Curve Analysis, AFS

Transactions, vol 100, pp 189-199 (1992).



Figure 1

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file:///C|/WEBSHARE/062013/magazine/1998_3/fef.htm[6/18/2013 2:44:47 PM]

FEF COLLEGE INDUSTRY CONFERENCE

The FEF College Industry Conference, Opportunities in Metal Casting, was held at the Drake Hotel in Chicago, November 5-7,1998. Two hundred seventy-one industry and university people attended, along with 131 student delegates from all of FEF’s 30schools. This unique conference brought together top industry executives, FEF Board Members, Key Professors, university officialsand top student delegates, all interested in metal casting. Preceding the conference was a Strategic Planning meeting and Board of Trustees meeting. The Board of Trustees accepted therecommendation of the Accreditation Team to add Kettering University in Flint, Michigan as the 30th FEF affiliated school. TheTrustees also accepted the recommendation of the FEF Key Professor at Eric Community College to drop this school from the FEFprogram. The FEF Annual Banquet was held Thursday night prior to the official beginning of the conference on Friday. Due to the generous"special contributions" of several companies and individuals (see back page), this year’s banquet was held at the Shedd Aquariumin Chicago. FEF’s highest award, the E.J. Walsh Award, went to Charter Lifetime Patron, Burleigh Jacobs. Special recognitionwas given to four contributors who have assisted FEF in its mission and goals this past year. Foundry recognition went to GredeFoundries, represented by Burleigh Jacobs and GM Powertrain represented by Ron Cafferty and Rick Sutton; Supplier recognitionwent to Porter Warner Industries represented by Doug Warner; and Society/Industry recognition went to the NADCA IndianaChapter 25 represented by Chapter Chairman, Mike Cox. During the banquet it was announced that the University of Missouri-Rolla was announcing the creation of the Robert V. Wolf Endowed Professorship in the field of metals casting. The EndowedProfessorship will be held by a faculty member in the Department of Metallurgical Engineering who, whenever possible, will be theFEF Key Professor. The professorship will assure the continued excellence of the foundry program at UMR. Phil Duke, this year’sVice Chairman, was the Master of Ceremonies. At the same time, the students were enjoying an exciting evening in downtown Chicago at a local restaurant, followed by free timearound the city. With them were the Student Hospitality Chairman, Tim Hajduk (a former FEF student), his wife, Jodi; Jerry Clancey,his wife, Wendy; and Lee White. Chuck Fowler was the conference chairman this year, assisted by a committee made up of professors, former FEF students, andFEF Board Members. The Keynote address was given by Jim Bushman, President, Cast-Fab Technologies. The three panelistswere Kelley Kerns, Manager of Technical Services, Fairmount Minerals, an FEF scholar from the University of Northern Iowa; SidTankersley, President, American Foam Cast, Inc., an FEF scholar from the University of Alabama; and Paul Mikkola, ExecutiveVice President of Operations at Hitchiner Manufacturing and FEF Past President. The Edward C. Hoenicke Memorial Luncheon address was given by Jack Pohlman, Vice President of Taylor-Pohlman, Inc. EachFEF affiliated school and Key Professor was highlighted through a computer presentation compiled by FEF Secretary, Paul Carey. The Industry Information Session offered students an up-close and personal look at the industry. It also gave the 52 participatingcompanies the most cost-effective way to see over 130 of the top metal casting students in the country all in one place. The Awards and Recognition Breakfast speaker was the President of the University of Windsor, Ross Paul. Following hiscomments, 20 sponsored scholarships were awarded to the student delegates who had submitted applications for these awards(see next page). A special AFS Director’s Award was again given through FEF to one of the Key Professors. Russ Rosmait fromPittsburgh State University was the recipient of this award. Bill Sorensen, FEF’s Executive Director, announced next year’s College Industry Conference, in Chicago on November 4-6, 1999.More information on this conference, or any of the FEF activities, can be obtained from the FEF office at 484 E. NorthwestHighway, Des Plaines, IL 60016, Phone 847/299-1776, Fax 847/299-1789, E-Mall Pam@)FEFOffice.org, Web Pagehttp://www.fefoffice.org. 1998 FEF COLLEGE INDUSTRY CONFERENCE CIC Breakfast Awards, November 7, 1998

Keith D. Millis Scholarship Jennifer Michigan Tech

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Lilly

Keith D. Millis Scholarship JasonZuelke

Wisconsin-Platteville

Keith D. Millis Scholarship RobynJohnson Michigan Tech

Ron Ruddle MemorialScholarship

JamesYurko

Mass. Inst. ofTech.

CISA Scholarship StevenBurkholder Tri-State Univ.

AFS Southwestern OhioScholarship

MatthewHachman

Purdue-Indianapolis

Richard M. FrazierScholarship

RichardVoss Missouri-Rolla

William M. Grimes Schol.-Gartland Foundry

JasonBurnette

Purdue-Indianapolis

Jacobs- Geo. W. Mathews Jr.Endowment

MarkSalzman

Wisconsin-Madison

Sims-Geo. W. Mathews Jr.Endowment

AlanDemmons

Cal Poly-SanLuis Obispo

Walsh-Geo. W. Mathews Jr.Endowment Shelly Dutler Univ. of Northern

Iowa

James P. KeatingScholarship

JuliePaterson Univ. of Windsor

Ron & Glenn Birtwistle Mem.Scholarship

MarkSweany Michigan Tech

Ron & Glenn Birtwistle Mem.Scholarship Brad Jud Michigan Tech

Tony & Elda DorfmuellerScholarship

MichaelZeno Kent State

Wm. E. Conway Schol.-Fairmount Minerals

MeganMcDonough Missouri-Rolla

Deere Scholarship-Environmental David Purvis Penn State

Edward C. HoenickeEndowment

MatthewDurr Pittsburgh State

AFS Detroit - George Booth GabrielleChifor Univ. of Windsor

Robert W. Reesman Mem.Scholarship Kevin Cook Univ. of Alabama

FEF 50th AnniversaryScholarship

ClintonWarnick Penn State

Donald G. BrunnerScholarship (NEW)

MattSchlinkert

Wisconsin-Madison

George Isaac Scholarship(NEW)

JasonReimer

Univ. of NorthernIowa

Modern Casting PartnersScholarship (NEW)

HarlanMeischen Southwest Texas

AFS Director’s Award Russ Pittsburgh State

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Rosmait Univ.

Special Mention

Thompson Scholarship Richard Voss Missouri-Rolla

David LaineScholarship

Justin Heimsch Wisconsin-MadisonBrad Jud Michigan TechRichard Miller Ohio State

The following three students were selected from the delegates to attend the Department of Energy Office of Industrial Technologies"3rd Industrial Energy Efficiency Symposium and Exposition" in Washington, DC, February 7-9, 1999: Brian Floyd - University of AlabamaJames Meudt - Wisconsin-MadisonAllison Vrieze - Missouri-Rolla Companies and individuals contributing special gifts for the Annual Banquet at the Shedd Aquarium: Dale BongaPhil DukeDoug WarnerJohn WelchAhlbeck & CompanyFairmount MineralsFord Motor-CanadaFoseco,lnc.Superior Aluminum



Ductile Iron News

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RECORD SETTING CASTING

Siempelkamp Pours World Record Ductile Iron Casting

Siempelkamp, of Krefeld, Germany has announced the pouring of a press base for their sistercompany Siempelkamp Press Systems. Two similar beds were cast in 1998, each with a weightof 255 metric tons. Photo #1 shows the pouring of one of the castings using five large ladles and

photo #2 shows one of the finished castings.



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NEWS BRIEFS

Meetings The 1999 annual meeting of the Ductile Iron Society is scheduled for May 19-21, 1999, and will be held at the Holiday Inn CityCentre in South Bend, IN.

Business Automotive component supplier Intermet Corporation has gone on-line to a highly secure "virtual private network" in order toenhance the exchange of vital design and engineering data with Honda R&D Americas, Inc. The electronic communication system,or extranet, is being utilized by Honda and other automobile manufacturers to more efficiently transfer design information to theirNorth American suppliers. Intermet is the first foundry company and one of the leading suppliers overall to establish this type ofconnection with Honda R&D. Specifically, the collaboration provides for the confidential transfer of component engineering data such as solid models that arecreated with product design software platforms common to both Intermet and Honda. Foseco Inc. has named Milchap Products, of Milwaukee, WI, a distributor of Foseco Foundry Products in Wisconsin, Minnesotaand northern Illinois. The addition of Milchap Products will facilitate delivery of Foseco products and services to this region of theUnited States. AMCOL International Corp. through its minerals operation, Volclay International, has acquired the assets of Tae KwangBentonite Co. located near Kyungju, Korea. Terms of the acquisition were not disclosed. The company, now called Volclay Korea, will be headed by S.W. Kant, the new managing director.

PeopleJerry Wurtsmith

Jerry Wurtsmith has been named Plant Manager of the Applied Process, Inc. production facility in Livonia, MI.He comes to the position with 27 years of experience in manufacturing and human resources in the metalsprocessing industry. Mr. Wurtsmith holds a BS in Education and an MS in Industrial Relations from Wayne StateUniversity.

Kathy Hayrynen The Technical Director of Applied Process, Inc., Kathy Hayrynen, has been inducted into the PresidentialCouncil of Alumnae (PCA) of the Michigan Technological University in Houghton, MI. The Metallurgical andMaterials Engineering Department of the University nominated Dr. Hayrynen for the honor "because of herprofessionalism, service to community, family-related accomplishments, education and service" to MichiganTech. As a member of the Council, Dr. Hayrynen is committed to three years of support to enhance theorganization’s mission. The University’s announcement of her appointment notes that she will act as an advisorto the President of the University and to the institution’s Educational Opportunity Department, and "will work toadvance women students and alumnae by helping to develop their leadership and professional skills."

Dr. Hayrynen is a 1993 graduate of Michigan Tech and now resides in Northville, MI.

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Joseph A. Mentz Intermet Corporation announced today that Joseph A. Mentz has been named general manager of the Intermet Machining plantlocated in Columbus, Georgia. Mentz will be responsible for the operation of the machining plant. Mentz comes to Intermet with over 20 years of managementexperience, most recently as director of operations for Statesboro, Georgia-based Fisher-Rosemount Petroleum, a division ofEmerson Electric and a leading manufacturer of precision flow measurement meters and valves for the petroleum industry. Prior tothat Mentz was vice president of operations at Milford Fastening Systems, located in Milford, Connecticut. Mentz holds a BS degree in administrative science from Central Connecticut State University and an MBA from the University ofConnecticut.

Michael S. Becker Intermet Corporation announces the appointment of Michael S. Becker to director of foundry purchasing, effective October 19,1998. He will be based at the Troy, Michigan corporate office. Becker comes to Intermet from Arthur Anderson & Co., LLP, Auburn Hills, MI, where he was a senior auditor. Prior to that, Beckerheld the position of materials manager with Webesto Sunroofs, Inc.,Rochester Hills, MI. In his new role, Becker will have direct responsibility for purchasing and materials for Intermet’s North American foundry group. Becker holds a BS degree in aviation technology from Western Michigan University and an MBA in operations from Michigan StateUniversity.

Alicia Leal Alicia Leal has joined Superior Graphite as its new Director of Human Resources. In her new role, Leal will oversee all of the company’s human resources functions, from employee relations and hiring to theadministration of company benefits. Leal, who started in August, holds a master’s degree in industrial relations. Before joining Superior, she was the Director of HumanResources at RG Ray Corporation, a global manufacturer.

James F. Mason John Doddridge, chairman and CEO of Intermet Corp., announced today that James F. Mason has been promoted to group vicepresident of Intermet. In this newly created position, Mason will be located at the corporate office in Troy, MI and will assumeresponsibility for a number of Intermet’s operating units. Mason most recently served as president of Wagner Castings Co., which came to Intermet in January 1997 as a result of theSudbury acquisition. He has been with Wagner in Decatur, IL since 1984 serving in several positions before becoming president in1988. Prior to joining Wagner, Mason was president of Mason Steel Fabricating, and earlier in his career, was employed byGeneral Motors’ Central Foundry Division.

Mel Ostrander Applied Process Inc. is pleased to announce that Mel Ostrander has been named president and plant managerof their new, affiliated facility, AP Southridge, Inc. in Elizabethtown, KY. Mr. Ostrander has 17 years of experience with Applied Process, the last 12 of which have been as plantmanager of the company’s main production facility.

George B. Freer Intermet Corporation announced today that George B. Freer has been named general manager of Frisby P.M.C. Inc., an Intermet

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precision machining company located in Elk Grove Village, Illinois. Freer brings a wealth of operations experience to Intermet, having most recently served as president and general manager of SasibPackaging North American, an Illinois-based company. Prior to this, he was executive vice president of Thiele EngineeringCompany in Minneapolis, Minnesota. Freer received a degree in physics from Syracuse University. He also served in the U.S. Navy as a nuclear weaponscommissioned officer.

Chad Gallentine Superior Graphite Co. has hired Chad Gallentine as U.S. Sales Manager for its Industrial Products Division, company officialsannounced today. In his new position, Gallentine, 29, oversees national sales of Superior’s industrial products, which include natural and syntheticgraphite, as well as other components used for heavy machinery and in the automotive and battery industries. Gallentine, a Chicago area native, was a regional sales manager with Superior from 1995 to 1997 before working one year at ametal-producing company.

Gary Morrison American Colloid Co., a specialty minerals operation of AMCOL International Corp., has promoted Gary Morrison to the newlycreated position of executive vice president. Morrison, 42, joined American Colloid in 1981 as a sales representative for the company’s petroleum products group. He waspromoted to manager of the metalcasting products group in 1988, and to vice president in 1994, during which time he helped leadAmerican Colloid’s market share growth and profit improvement. Prior to joining American Colloid, he held various field engineeringand laboratory technician positions for Baroid Corp., Odessa, Texas. Morrison has a bachelor’s degree in chemistry and biology from Abilene Christian University, Abilene, Texas, as well as severalhours of graduate credit.

Alan J. Miller Intermet Corporation has named Alan J. Miller to the position of corporate general counsel for Intermet. In this position, Miller willbe responsible for Intermet’s legal activities, including the coordination of all external legal counsel. Miller joins Intermet from Toledo, Ohio-based Libbey-Owens-Ford Company, where he was vice president, general counsel andsecretary. At L-O-F, Miller was also responsible for establishing the in-house legal function for the company. Prior to this, heserved as staff attorney with Aeroquip-Vickers, Inc. and had been in private practice with a leading Ohio-based law firm.

ObituaryNeil H. Mingledorff, 76, retired chairman of the board for Ductile Iron Co. of America, passed away on September 26, 1998.Mingledorff attended Auburn University and was an officer and a pilot with the Army Air Corps with service in World War II. He waspast president of United Foundry & Metal Co., the Ductile Iron Company of America and Isle of Hope Marine and R.G. Industries. Mingledorff served as AFS director class of 1970. He was past president of the Ductile Iron Society and was a director of theFoundry Educational Foundation. He also served on the executive committee of the Boy Scouts of America and organized theSavannah Sport Fishing Club and served as its first president. Memorial contributions may be made to Hospice Savannah, 1352 Eisenhower Drive, Savannah, GA 31406 or St. John’s EpiscopalChurch, 1 W. Macon St., Savannah, GA 31401



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