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Intensiive' QuenchingEvery heat. treater knows that the

greater the pan cooling rate duringquenching, the better the part perform-anee.However, the conventional wis-dom with heat treated parts. is thatquenching a part too quickly wilJ resultin harmiu] tensile and residual stresses,greater dislOmon and the possibility of"part cracking, But engineers andresearchers at. IQ Tecllrn.ol.ogies Inc.(IQT) of" Akron, OH,are out to provethat. comrolled, rapid cooling througlJ. themartensite range can actually result inhigher quality hardened steel. with bene-ficia] compressive residual surfacestresses ona througlJ hardened part.

IQT's IntensiQuencbsM process hasbeen used successfully to quenchsplined shafts, sprockets and other steelparts, such as coil springs, torsion bars~mples. bearing products and gearblanks. It cam also be applied to gears,says [QT President Joe Powell, butsome applications may require specialmodification of the quenching equip-ment. Results of the process have beenvalidated in hundreds of laboratory andfield experiments, which demonstrateimprovements in mechanical proper-ties, microstructure. compressive resid-ual stress and part lifetime when corn-pared with parts quenched in oil usingtraditional methods.

During conventional quenching.martensite forms first in the thinner sec-tions of a part, since those sections coolmore rapidly than the thicker sections.The difference in cooling rate results indistortion and possible cracking, The !IntensiQuench process uses a highly agio !tated quenchant (usually water) to cool .1

the part rapidly but uniformly •.according

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to Powell. Moreover, the processque-nches parts three to, six times faster

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than other methods, without the usualdistortion,he says.

The unique, 6,OOO-gaUo[Jj quenchtank is equipped with four I8-inchimpellers rotated by lO-hp variable speed

Inlelllive quencbinll cln be, i'illt4l1ed in-li!!e will! !lny bllt $Qgr~,.Sbow!ll!!l!oy!! !!f!! qgeg~1! t!!!!b 'used willi ,b.\cb 'fllflllCl_

Welcome to Revolutions, the col-.umn that brings 'OU the IBtestmost up-to-date and eas,-to-leldinformlt;onlboul the peopleBnd technology of the gearindustry. Revolutions w•.lcomesyour submissions. Plelse sendthem to Gear Technology, 1'.0'.Box '426, Elk ,Grove Jlil/llge, IL60009, fiX (841) 431-6618 Dr e-mlilpeo.ple@geanechnologY'.com. If,ou~dlike mOle information aboutIny of the ,dicles that appeal,please circle the appropriB,e,,,um-ber on the Reider Service Card.

motors to keep the water or sah/watersolution moving overthe part. In addi-tion, the quench tank is equipped with atemperature and concentration controlsystem to ensure 'the proper conditions ofthe cooling medium.

Those controls are essential,because one of the keys to theInte[lsiQuellch process is to interruptthe cooling of the part at the criticaltemperature when compressive stresseson the surface are at their maximum.The part is then held at that tempera-ture. allowing the continued, even for-mation of martensite, resulting in high-er uniform surface compression andincr-eased strength in the part .

Depending on the application, thebeneficial surface compressive stressescreated through the process can some-times take the place of carburiaation orshot peening, Powell says. He adds thatIheability to increase the amount ofmartensite Formed in a given steel allowsthe part designer to use a less expensivesteel or one with lower alloy content andstill achieve the same hardness.

The rntellsiQuench process reliesheavily on sophi ticated computer mod-eling, Powell says. By performing fin:iteelement analysis and a eries of calcula-tions.nre process software can determine

..........ao ...ertrensmieston.com .... ww_gssrtschnology_com ' G,EAR TECHNOLOGY·' MARCH/APRIL 2001 91

a part's thermal and stress profiles. Thatallows the process to accurately predictthe critical holding temperature and toachieve the optimum hardened depthwith compressive stresses.

The quenching process can be usedwith induction, atmosphere, salt, vacuumor any other type of heat treatmentand ithas been used successfuUy with mostcommon steels, Powell says,

Cin:le300

REVOLUTIONS

INDTPrecess finds 'Crac~ksBy Shakli:ng Parts

An .infrared NDT process bas beendeveloped that detects closed cracks byforcing their two sides to rub together,then photographing the resulting heat-all in less than a second.

Suitable for qualily control, the non-destructive testing technique was devel-

ON

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The Thenno'Soni~ lest stal.ionl finlh closed cracks j'npal'b. by using ultr,asoniG energy '101"orea !he ,cracg'sides to rub together, which 0",8181, heal, and imagingl!hal infrared. energywilh '11Mltation,'s camer.'.

oped at Wayne State University inDetroit. A commercially available ver-sion of that technology is theThermoSoniX test station, manufacturedby Indigo Systems Corp. of SantaBarbara, CA.

The test station Co':Ln be used in gearmanafacturiog to supplement or replaceether inspection methods, like dye pene-trant, Magnaflux, and visual inspectionusing a microscope.

To detect cracks, the station directs apulse of high-frequency sound at a partsurface. The pulse lasts 50-200 millisec-onds and has a frequency of 20 kHz.

The sound makes the part vibrate. Ifthere's a crack. even a dosed crock, itstwo sides will vibrate as welL But, theywon't vibrate in unison. They'll. rub, cre-ating heat. Tile station's infrared cameradetects that heat, showing the crack'slocation on the part surface.

The station can detect temperaturechanges as small as 0.02°C.The NDTprocess raises a crack's temperature afew degrees Celsius. Con equently, thecracks look like "explosions," processdeveloper Bob Thomas says.

Also, the process can detect cracksvertical to a part surface-without beingperpendicular to them, Vertical crackscan be hard to detect. Proces developer"Skip" Favro says looking at a verticalcrack is like looking at a knife's cuttingedge-"There's not much to see."

Consequently, inspection devices canbetter detect a crack when they're per-pendicalar to the crack, so it looks like asheet, not a line. The ThermoSoniX teststation can detect cracks regardless oftheir orientation to a part surface.

According to Thomas, the NDTprocess can beautomared for high-vel-

"0 MARCH/APRI L .2001 • GEAR TECHNOLOGY' www.geart6chnotogy.com • www.powerlransmisslon.com

REVOLIUTID:NIS !!I _

ume inspection. However, AustinRichards, Indigo Systems' project man-ager forthe test. station, explains that thestation is mainly intended for handinspection of low-volume, high-costparts. The station can be automated toinspectup to 30 parts per second.

The NDT process can inspect metals,like steel. and iron, ceramics and com-posites. "It can do basically any olid,"Thomas says.

Richard, who holds a doctorate inphysics, estimatesthe station can detect

cracks 4 or 5 millimeters beneath a pan'surface and likel.y can inspect parts weigh-ing up to 100 kilograms. The station itself

weighs 150 pounds and fils on a 3-foot-by-5-foot surface. like a desktop.

For the process to work. a part mustbe solid and be a good emitter ofiIlfraredenergy with wavelengths of 3-5microns. Richards describes that wave-length range as: "A great waveband ifyou want to see tiny bits of changes insurface temperature."

The station provides real-time dis-plays of cracks. Also, it uses no consum-ables, as with dye penetrant andMagnaflux, and no radiation. as with X-ray processes.

Also, X-ray imaging can't effectivelydetect some types of cracks, like compres-sion cracks. During manufacture, a. partcan crack at high temperature, but thatcrack can clese as the pan cools, becom-ing 3ncarly invisible oompression crack.

The deeper the compression crack is,the more th.c crack weakens the pan. Ahallow era k may not weaken a part too

much, but any crack: can be dangerousbecause it cam grow as Ille part is used.

Asa drawback, the test station can bequite loud. "II's a good idea to wear bear-ing protection, '"Richard says.

Also. he describeathe station-withits computer. software and camera-casmore complicated to set lip initially mandye penetrant or MagllafllilX is.

"But," he says, "once it's up'. it's easy(0. use."

The station costs about $85,000 andconsists of a part platform, a piezoelec-trie converter that provides ultrasonicenergy, a hard metal probe that transmits

the energy to the part, a pneumatic actu-ator that holds the converter, an infraredcamera, a mechanical structure U'al.holds the camera, and a computer thatcontrols the station.

"Most of that cost is the infrared cam-era," Richards says.

A major part of the camera is thedetector. That part detects infrared heat.But, it can't do 0. if it's generating healitself. Consequently, the detector is

cooled by a.miniature, closed-cycle heli.-urn refrigerator to the temperature of hq-uid nitrogen=-about -350°F.

The camera records a part's image andtransmits the 12-bit digital image data toa digital framegrabber, which allows forrecording and storing of images in acomputer's memory.

As for thecost to operate the station,Ri.chards says: "There's no consumables,you're just buying electricity."

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• ---.. 'R'EVOLUTIONS,

The NDT process was developed by materials are cracks perpendicular, orphysics professors Favro and Thomas, vertical, to a part surface,with electrical engineering professor To detect vertical cracks, Favro andXiaoyan Han and then- students at Wayne Thomas developed another NDT tech-State University. Favro and Thomas aremembers of the university's Institute ofManufacturing Re earch,

Favro and Thomas bad performednondestructive testing with infrared cam-eras for years, They had been using flashlamps to warm a part, then detectingdefects as the part cooled, The defectswere broken glue joints, corrosion, anddeIaminations-the popped-apart hori-zontal layers of a composite material.

Also, that old method detected thosedefects only if they included air gaps. Adefect's gap would reflect heat to the partsurface above the defect, making thatsurface area wanner than the surround-.jng surface.

"All the kinds of defects we were see-ing were parallel to the surface, not per-pendicular," says Thomas, explainingthat most cracks which people look for in

nique and experimented withit in sum-mer 1999, Favro recalls the verticalcracks "lit up like a Christmas tree" usingthe new process.

They filed for a patent that September."It happened very fast," Favro says,

Indigo Systems obtained a license tomanufacture products based on Favroand Thomas's technique and developedthe ThermoSoniX test station from it.

eirel.!! 301

Vintage' Machines StillProducing

Some technologies are worth preserv-ing, says Bennie R. Boxx, president ofB&R Machine & Gear in Sharon, TN.

B&R is home to one of America's fewremaining model 77GP Gleason Planers,a versatile machine capable of cuttingbevel gears up to 8'0 inches in diameter.

The machine was built in ]917. Sincethen, the technology for cutting bevelgears has been updated many times. Still,B&R's machine has recently Come backinto demand, Boxx says,

Much of that demand comes from thesteel mill indus tty, which often requireslarge bevel gears with pitches as coarseas 0.4 DP, Boxx says that most modembevel gear machines aren't capable ofcutting gears, in that pitch range.

B&R uses near-net-shaped forgedgear blanks in specialty alloy steels forits large bevel gears, The blanks aremachined on the Gleason planers and

AI KHngelnberg, the pointprecision is to help youyour gear manufacturingcess and improve gearwith measuring systemsare benchmarks for:

R:EVO:LUTIONS •• _ ••••••••••• _

then heat treated,However. running rna hines that use

technology which has been largely for-gotten bas challenges of its own, Ballsays. One challenge is finding the toolingto make the machines operate. TheGleason planers use top and bottom for-mers, which are templates used tognidethe blades thai. cut the gear profile. Thetooling was originally manufacmred byGleason ill standard ]4.5- and 2:O-degJreepressure angles.

However. steel mills often requirebevel gears with 2-5-or 27.S-degree pres-sure angles, Boxxsays. When B&R

accuracyreHabilitymaintainabilityflexibilityperformanceand life cycle cost,

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received an order for such gears in 1999.Sou discovered that the tooling wouldhave to be custorn-rnanufactured,

B&R turned to Trogetec Inc. ofRiverton, WY. for help. According tooompany president Sandor l Baranyi,Trogetec had never worked with Gleasonplaners before, but the project was intrigu.ing, "We bad the feeling that we could fil]the order based on our preliminary designstudy," Baranyi says. He determined thatTrogetec would be able to modify itsEZGearPl.ot version 3.0 software so that itcould create the patterns. for the fanners.

The first tLme Trogetec created theformers, the process had to becreated onthe fly .."We didn't have the software yet,"Baranyi says, "but we were able to piece-mea] it together."

Since that. time, Trogetec has releasedE21GearPlot-"GP version 2.0, which, inadditionto its gear design functions, isable to. create CAD tiles for manufactur-ing the formers for Gleason gear planermodeJ's .54, 77, .144 and 1.92. The user

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enters the gear set's, design parametersand the model of the gear planer. "Wepl.ug in the data and it goes like a cinch,"Baranyi says.

Once the CAD files for the formersare created, the tooling is, manufacturedfrom O.SO-inch thick cold-rolled plateusing CNC abrasive waterjet cuttingtechnology ..

The result is that .B&R's Gleasonplaner is back in business. "Since westarted getting the formers made. thismachine runs 24 hours a day." Bou says.

Cin:l'e 301

If you found this column of interest endIoruseful, pleau cln:M _

If you did not care for this column cInIIe_If you would like to respond to this or anyother article in this edition of Ge., Tech-nology. plelse fex your response to theIlUantion of Randy Stott. managing editor. at847-437-8818 or sand en a-mail message toP'OpleOg'Brtechnology.com.

Til' Us W'Mt YOIIl'IIIIIIt ...