Foundry Sand Reclamation

An Overview of Foundry

Mold Ma kin a ODera tions

and a Review of Sand

Reclamation Methods

Including Emerging

Electrotechnologies

Prepared by July 1990

John M. Svoboda Center for Materials Productions Foundry Office

CUP Report No. 90-6

. 1 1 8 ,

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I I I I 1 I I I I I I I I I ! I I

FOUNDRY SAND RECLAMATION

CMP Report Number 90-6

J u l y 1 9 9 0

Prepared by &I &r+

John M. Svoboda * ? 0 8 - d ~ ~ - ~ 0 ' Q o CMP Foundry Office

Prepared f o r

C e n t e r f o r Materials Product ion Carnegie Mellon Research I n s t i t u t e

4400 F i f t h Avenue P i t t s b u r g h , PA 15213-2683

Joseph E. Goodwil l CMJ? Direc to r

. . . , * .

CME' PERSPECTIVE

BACKGROUND

Because of current environmental regulations, the disposal of waste foundry sand which may contain hazardous chemicals and/or metals has become difficult and expensive. One alternative to the dumping of waste sand is the sand reclamation process which llcleans" the sand to a degree sufficient to allow its re-use in the foundry operation. Several different reclamation processes exist which creates some confusion as to which system or combination of systems provide optimum results.

OBJECTIVE

As foundries represent a significant load to many utilities, this report has been prepared to present the basic principles of foundry molding and coremaking processes and the reclamation of these sands. The objective of this report is to provide the utility engineer with an overview of mold making operations and sand reclamation to assist in communications with his foundry customers and to enable him to discuss the use of electric fired sand reclaimers with the industry. Although there are few electric thermal sand reclaimers in use-worldwide, these units do offer some unique advantages.

APPROACH

This report is based on a review of existing foundry literature and discussions with prominent foundry sand reclamation experts.

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RESULTS

The report covers current molding and coremaking processes, both clay-bonded and chemically-bonded, describing the advantages, disadvantages, and unique characteristics of each. The report also covers the three principal methods of sand reclamation, mechanical, thermal, and wet, presenting the advantages and disadvantages of each. The report also covers recent advances in this technology and discusses the programs CMP is working on to develop and demonstrate electric fired reclaimers.

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ABSTRACT

Current environmental regulations have created a situation where the disposal of waste foundry sand has become difficult and expensive. One solution to this problem is the use of a sand reclamation system which "cleans" the sand to a sufficient degree to allow re-use of the sand in the foundry sand system. A large number of sand binder systems are in use for various reasons of cost and performance characteristics. There are also three main methods of sand reclamation and combinations of these. A basic understanding of these technologies will allow a utility engineer to communicate better with his foundry customers.

The principal binder system used in foundries is bentonite clay. When properly mixed with sand and water, the clay forms an adhesive film around the individual sand grains allowing compaction to form a rigid mass. After pouring with molten metal, the sand is easily removed in a mechanical "shake-out" procedure. The main advantages of this system, known as "green sand molding" are high production capabilities and low cost.

Chemically-bonded, or "no-bake", sands use chemical binders that cure to form rigid molds by the use of heat and/or a chemical catalyst. These systems generally provide more precise dimensional tolerances and better surface finish; however, production rates are lower and costs higher.

Sand can be reclaimed by thermal, mechanical, or wet scrubbing processes. Thermal systems alone are adequate for the reclamation of chemically-bonded sands. Most thermal systems in the U.S. are gas fired; however, electrically fired thermal systems are in use in Canada and Europe. CMP is endeavoring to initiate a project to demonstrate an electric resistance sand reclaimer in a domestic foundry to introduce the technology to the American foundry industry.

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3 i Q! I P I I I I f t I I I I

Clay bonded sands r e q u i r e t h e combina ion of mechanical and h i g h temperature thermal reclamation f o r greatest e f f i c i e n c y . -.

A high temperature, i n f r a r e d system i s be ing developed w i t h

t h e h e l p of EPRI/CMP f o r u s e i n t h i s a p p l i c a t i o n .

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TABLE OF CONTENTS

Section Paqe

SUMMARY

1 INTRODUCTION

2 SAND RECLAMATION

Introduction

Sand and Binders

Definitions

Functions of Sand Reclamation

Sat is factory Performance

Need for Sand Reclamation

Justification for Sand Reclamation

Potential Benefits for Sand Reclamation

Potential Liabilities for Sand Reclamation

Reclamation Processes

Thermal Reclamation

Electric vs Gas Reclaimers

Dry Reclamation

Wet Reclamation

Applications

Clay Bonded Sand

Organically Bonded Sand

Sodium Silicate Bonded Sands

Phenolic Ester Bonded Sands

Quality Considerations

Trends in Reclamation

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It I 3 a c I I I I I I I t I I I I I c

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MOLDING MD COREMAKING PROCESSES

Overview

Green Sand Binders

Organic No-Bake Binders

S h e l l Process

Hot Box Binders

W a r m Box Binders

Core O i l Processes

Cold Box Processes

Caut ionary Note

REFERENCES

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Sect ion 1

SUMMARY

Many d i f f e r e n t sand b inder s y s t e m s are i n use i n t h e foundry

i n d u s t r y w i t h each having i t s own unique set o f c o s t /

performance/qual i ty c h a r a c t e r i s t i c s . The v a s t major i ty o f sand molds a r e made w i t h clay-bonded, o r "green" sand. Clay and water, and o f t e n o t h e r a d d i t i v e s , a r e mixed w i t h t h e

sand, and mechanically o r pneumatically compacted t o form a r i g i d mold. Green sand molding provides high production rates and acceptable dimensional and s u r f a c e q u a l i t y performance.

No-bake sand sys t ems u s e chemical b inders t h a t a r e cured e i ther by t h e add i t ion of a c a t a l y s t o r t h e a p p l i c a t i o n of heat. These s y s t e m s gene ra l ly f e a t u r e lower production rates, w i t h e x c e l l e n t s u r f a c e f i n i s h and dimensional t o l e r a n c e c a p a b i l i t i e s . A very large number of d i f f e r e n t systems a r e on t h e market, each f e a t u r i n g d i f f e r e n t b inder / c a t a l y s t chemistries; however, t h e b a s i c p r i n c i p l e of chemical cu r ing i s s i m i l a r f o r a l l .

Some of t h e organic sys t ems can pose environmental problems and c a r e f u l s e l e c t i o n and use i s requi red . Binder chemistry is a r a p i d l y advancing f ie ld , and t h e r eade r is advised t o fo l low t h e t r a d e l i t e r a t u r e o r ca l l t h e CMP foundry o f f i c e fo r up-to-date information.

I n recent yea r s it has become i n c r e a s i n g l y d i f f i c u l t and c o s t l y f o r t he ope ra t ing foundryman t o d ispose of foundry waste sands, p a r t i c u l a r l y i f t h e y con ta in hazardous chemicals and/or metals . A number of sand reclamation p rocesses have been developed t o minimize t h e amount o f sand t h a t r e q u i r e s d i sposa l . The goa l of a l l of t he processes i s t o "clean" t h e waste sand t o a s u f f i c i e n t degree t o al low re-use back i n t o t h e foundry molding and coremaking

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I I I I I I I I I I I

processes. Three primary types of reclamation systems are in general use:

- Dry Reclamation - Wet Reclamation - Thermal Reclamation

Dry reclamation systems utilize the mechanical attrition or scrubbing principle to remove clay and organic coatings. They can be used with all common types of sand; however, they do not achieve the degree of cleanliness attained with other systems.

The wet systems rely on a wet scrubbing action to clean the sand. While effective in cleaning, maintenance is high and

water discharge is an environmental problem. These considerations have limited their application in recent years to sands employing water soluble sodium silicate as a binder.

Thermal reclamation systems heat the sand to temperatures

high enough to burn off the organic binders. Thermal systems used in the 'U.S. are generally gas-fired, although electric thermal reclaimers suitable for processing chemically bonded sand are in use in Canada and Europe. Thermal systems are particularly appropriate for organically bonded sands, but the higher temperature gas fired varieties may also be used for clay bonded sands. Consensus among industry sand reclamation authorities is that a combination thermal/mechanical system will provide the best results overall.

EPRI/CMP is participating in the development of a high temperature infrared system for application with clay-bonded sands. In addition, CMP is working with the foundry industry in a endeavor to initiate a project to demonstrate

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an electric resistance sand reclaimer f o r processing chemically bonded sands.

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Section 1

INTRODUCTION

Due t o environmental regu la t ions , the disposal o f waste

foundry sand has become one o f the most pressing problems f o r

the foundry indus t ry i n recent years because o f the high

d isposal costs encountered and d i f f i c u l t y i n f i n d i n g disposal

s i t e s . These considerat ions have been the d r i v i n g fo rce f o r

t he development o f a number o f technologies f o r the

reclamat ion and reuse o f waste foundry sand. Considerable

research work continues, and the technology i s f l u i d a t the

present t ime.

Because some o f the reclamat ion technologies are based on

e l e c t r i c heat ing, and because foundr ies represent a

s i g n i f i c a n t load t o many u t i l i t i e s , t h i s repor t has been

prepared t o present the bas ic p r i n c i p l e s o f foundry molding

and coremaking processes and the reclamation o f these sands.

While n o t intended t o make a foundry engineer ou t o f the

u t i l i t y engineer, the repo r t should provide s u f f i c i e n t

fundamentals t o a l low i n t e r a c t i o n w i t h the foundry customer.

The r e p o r t begins by reviewing cu r ren t sand reclamation

technologies. I ndus t r y consensus i s t h a t a combination

thermal/mechanical system w i l l p rov ide optimum performance.

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I A t t he present t ime, thermal u n i t s i n operat ion i n the U.S.

are gas f i r e d . However, e l e c t r i c f i r e d sand reclaimers a re i n use i n Canada and Europe fo r processing chemical ly bonded

sands. The EPRI Center f o r Mater ia ls Production i s cu r ren t l y i

arranging a demonstration of t h i s technology a t a se lected

U.S. foundry.

The reclamat ion o f clay-bonded sands (green sand) requ i res

h igher t reatment temperatures, up t o 1600O F. CMP i s

p resent ly working w i th an innovat ive i n d u s t r i a l o rgan iza t ion

t o develop a h igh - in tens i t y i n f r a r e d reclamat ion u n i t .

I n i t i a l research work looks v e r y promising, and arrangements

are being made t o i n s t a l l a prototype u n i t i n a product ion

foundry.

Also inc luded i n the repo r t a re .desc r ip t i ons o f the most

common molding and coremaking processes and a shor t

b ib l i og raphy f o r the reader ’s reference.

A s mentioned above, sand reclamat ion i s a r a p i d l y advancing

area o f foundry technology, and the reader i s advised t o

r e f e r t o the foundry t rade magazines f o r the most recent

s t a t u s o f t he process o r contact the CMP Foundry O f f i c e .

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Section 2

SAND RECLAMATION

I I n t roduc t i on

D The conventional meta lcast ing process, i n which molten metal

i s poured i n t o sand molds, exposes the bonded sand t o h igh

temperatures which burn ou t the binder and leave a residue

which i s det r imenta l t o the reuse o f the sand f o r making

add i t i ona l molds. I n the past , t h i s used sand was simply

discarded. However, economic and environmental concerns now

I t I

make i t des i rab le t o process the sand i n a manner which makes

i t s u i t a b l e f o r reuse i n the foundry. I I

Sands and Binders

Although many types o f b inders and sands are used i n the

foun'dry indus t ry , , the vas t m a j o r i t y of molds and cores are

made us ing e i t h e r the "Green Sand" process o r the "Organic

No-Bake" process.

The "Green Sand" process uses c lay and water as the binder

system. General ly the sand used i s s i l i c a , and carbonaceous

add i t i ons such as seacoal are o f t e n added t o promote good

sur face f i n i s h . This i s the type o f sand/binder p rac t i ce

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t used i n h igh product ion operations such as automotive

foundr ies.

The "Organic No-Bake" process uses chemical ly s e t t i n g organic s

binders such as furan and phenol ic compounds. Again, the most

commonly used sand i s s i l i c a , although spec ia l t y sands such

as z i rcon and chromite are f requent ly used to promote good

surface q u a l i t y and accurate dimensions i n the cast ings. This

fam i l y o f b inder systems i s used i n jobbing foundr ies

producing smal ler numbers o f cast ings from an ind i v idua l

pa t te rn o r design.

D e f i n i t i o n s

Sand reclamat ion i s the phys ica l , chemical o r thermal

treatment o f foundry sands so t h a t they can be sa fe l y re-used

i n place o f new sand i n molding and coremaking mixes.

True reclamat ion t r e a t s and cleans a l l the i nd i v idua l g ra ins

w i t h i n the sand mass, whereas recond i t ion ing , as p rac t i ced

when regenerat ing green system sands, t r e a t s and p a r t i a l l y

cleans the mass as a whole. Some forms o f reclamat ion such as

dry mechanical a t t r i t i o n are more l i k e recond i t ion ing than

t r u e reclamat ion as l i t t l e work and c leaning i s performed on

the i n d i v i d u a l sand gra ins.

Funct ion of Sand Reclamation

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-- Reduce a l l lumps t o sand g ra in s ize. The sand

g ra in s i ze d i s t r i b u t i o n o f the reclaimed sand

should be the same as t h a t o f the new sand as

purchased.

-- Remove a l l tramp mater ia ls such as metal

p a r t i c l e s , slag, re f rac to ry p a r t i c l e s , e t c .

-- Remove a l l b inder coat ings, e i t h e r i n e r t o r

ac t i ve , from the grains.

-- Remove f i n e s t o a acceptable l e v e l .

Sa t i s fac to ry Pe rformance

-- Reclaimed sand must be dry and a t an acceptable

temperature.

-- Reclaimed sand must bond as we l l as, and have

s i m i l a r molding and coremaking proper t ies , as the

new sand.

-- Reclaimed sand must produce cast ings w i t h q u a l i t y

equal t o those produced w i t h new sand.

I d e a l l y , a sand reclamat ion system would process s a n d a t a

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d

maximum y i e l d and re tu rn the sand i n such cond i t i on t h a t i t

would be s u i t a b l e f o r re-use w i th any b inder .whi le producing

cast ings w i t h no defects -- and do a l l o f t h i s a t low cos t !

Th is i s d i f f i c u l t and expensive t o achieve, and i n p rac t i ce

compromises are made. F o r the m a j o r i t y o f app l i ca t ions , a

small amount o f res idual bond and small amounts o f impur i t i es

can be to le ra ted . I t i s no t poss ib le fo r any one s i n g l e

reclamat ion system t o handle a l l the binder systems and

rec la im them w e l l enough f o r re-use i n a l l o ther systems. A

combination o f two or more reclamat ion systems may be

requ i red when mu l t i p le binders are used. General ly, the purer

and cleaner the reclaimed sand, the higher i s i t s u t i l i z a t i o n

i n mixes and the lower the requirement f o r new sand

add i t i ons (2).

-- Need f o r Reclamation

A number o f f ac to rs have combined t o generate a growing need

f o r sand reclamat ion -

-- The increas ing cos t o f new sand and the need t o

conserve ava i l ab le sources o f h igh q u a l i t y sand.

-- The increas ing cos t o f used sand disposal . Dump

s i t e s are becoming fewer, f u r the r from the

foundr ies and increas ing ly cos t l y . I t was repor ted

a t a recent i n te rna t i ona l conference on rec la-

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mation and reuse o f foundry sands t h a t one h a l f o f

a l l l a n d f i l l s i n the USA w i l l c lose by 1992.

-- S t r i c t e r environmental con t ro l s which make

disposal o f foundry waste more d i f f i c u l t and

expensive.

-- High consumption o f new sand w i t h the use o f

chemical ly bonded sands. Without reclamation these

systems can consume 2-5 tons o f new sand per ton

o f cas t i ngs produced.

J u s t i f i c a t i o n - f o r Reclamation

The d r i v i n g fo rce f o r cons ider ing sand reclamation has always

been the economics o f saving on the cos t o f new sand. I n

recent years, the h igh cos t o f d isposal has entered

s i g n i f i c a n t l y i n t o the equation. Sand reclamation i s usua l ly

j u s t i f i e d when -

-- Large q u a n t i t i e s o f new sand are used i n the

foundry.

-- New sand costs are higher than average due t o

sh ipp ing charges.

-- Dumping o f waste i s d i f f i c u l t and/or expensive.

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-- One base sand and a single binder system are used

throughout the foundry. When several binders and

sands are utilized, the used sand has a complex

composition and generally does not respond to a

si ng le recl amati on processes.

Potential Benefits of Reclamation

-- Savings from reduced purchases o f new sand.

-- Savings in sand dumping charges.

-- Possible cost savings due to reduced binder

1 eve1 s.

_- Possible cost savings due to the reduction o f in-

plant storage of both old and new sand.

Potential Liabilities of Reclamation

-- Capital cost o f reclamation plant,

-- Cost o f maintenance, repair and replacement o f

equipment.

-- Operational costs o f reclamation plant.

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-- Sand losses dur ing reclamation, $ .e. , y i e l d

Reclamation Processes

Three methods o f sand reclamat ion are commonly used:

Thermal Reclamation

Burns away and removes a l l organic b inders and m a t e r i a l s i n

the sand. Inorgan ic b inders a re n o t removed, and a c t u a l l y may

become fused on the sand gra ins. Thermal rec lamat ion u n i t s

may be e i t h e r e l e c t r i c a l l y heated o r gas f i r e d (F igure 1 ) .

F igure 1 - Schematic Drawing o f E l e c t r i c

Thermal Sand Reclamation System

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Thermal reclamation removes a l l o f the organic and

carbonaceous mater ia ls i n the sand. Compared w i t h mechanical

a t t r i t i o n , i t i s an expensive process because, i n add i t i on t o

the usual pre-crushing and metal removal t reatment, the sand

i s heated to approximately 500-8OO0C (932-1475OF) and then

cooled f o r re-use. Various types of equipment are used f o r

thermal reclamation such as ro ta ry k i l n s , f l u i d i z e d beds and

s h a f t furnaces. F lu id i zed bed systems are now very popular as

there are no moving pa r t s , processing i s e f f i c i e n t and some

coo l i ng can be achieved.

The q u a l i t y o f the reclaimed sand i s equal t o t h a t o f the new

sand provided t h a t no inorganic mater ia l such as c lay o r i r o n

ox ide i s present. Treatment a t the h igher temperatures l i s t e d

above could cause fus ion o f these ma te r ia l s t o the sand

gra ins thus lowering the re f rac to r iness o f the sand.

I n thermal systems, e f f i c i e n c y i s achieved by opera t ing

twenty fou r hours a day-seven days a week. Under these

opera t ing condi t ions, even a small u n i t processing one

ton/hour w i l l produce 8,000 tons/year o f reclaimed sand.

E l e c t r i c vs. Gas Reclaimers

Thermal reclaimers using e l e c t r i c power o f f e r some unique

advantages over gas f i r e d un i t s . The u n i t s do no t requ i re

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la rge quan t i t i es o f a i r t o support combustion, and s ince f u e l

i s not burned i n the reclaimer, contamination o f the sand

w i th products o f combustion i s no t possible. Complete

reclamation i s achieved a t lower temperatures (500O ) ,

minimizing thermal shock cracking and reducing heat loss.

Further, lower temperature operat ion avoids the unwanted

s i l i c a phase change from Quartz t o C r i s t o b a l i t e . Add i t i ona l l y

the reclamation process can be programed t o i n teg ra te w i th

p l a n t power demands t o g i v e optimum load f a c t o r and l i m i t

peak power.

O F

A disadvantage of operat ing a t the lower temperature,

however, i s t h a t some o f the v o l a t i l e organic compounds

dr iven o f f the sand may no t be f u l l y burned i n the

reclamation u n i t proper. I n these cases an a f te rburner may be

requi red t o meet l oca l a i r q u a l i t y standards.

Dl”y Rec 1 amat i on

D r y reclamat ion processes f i r s t crush the lumps t o g ra in

s ize . Mechanical abrasion then removes p a r t o f the binder

from around the sand grains. Released f i n e s are separated and

removes by dry c l a s s i f i c a t i o n .

With dry pneumatic systems, r e l a t i v e l y dry sand ( l ess than

1% moisture) i s prepared by crushing the sand t o i nd i v idua l

g ra in s i ze and removing metal p a r t i c l e s . The used sand i s

then prope l led by a i r and b las ted against a metal t a r g e t

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p l a t e (F igu re 2 ) . The impact of t h e sand scrubs o f f t h e c l a y

c o a t i n g f rom t h e sur face o f the sand g ra in , and the r e s u l t i n g

f i n e s a re removed t o a dus t c o l l e c t o r , A t y p i c a l rec lamat ion

i

t

p l a n t c o n s i s t s o f severa l scrubbing c e l l s arranged

s e q u e n t i a l l y (F igure 2 ) and the degree o f c lean ing i s

regu la ted by t h e feed r a t e through the rec la imer .

- - 5 ti-*, - .llL c- -- *<

a

7 ::

\

L 4 I -

'd. =?;

-u F- -.-a.

F i g u r e 2 - Schematic Drawing o f I n d i v i d u a l

C e l l o f Dry Pneumatic System

e-" F igu re 3 - Schematic Drawing o f D r y

Pneumatic Reclamation System

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only partial cleaning of the sand occurs, even with long

scrubbing cycles. The minimum clay content is about 2.0%

which is quite suitable for a new sand addition replacement

in green system sand or a clay bonded facing sand mix . It i s

not sufficiently clean, however, to be used alone in core or

chemically-bonded mixes. Because o f the mechanical nature of

the scrubbing process, yield of reclaimed sand is only 75-90%

and the large volumes o f dust generated require

collecting, handling and disposal.

- Wet Rec 1 amat i on

Scrubbing in water washes or dissolves binders from the sand.

Loose clay is readily suspended in water and a vigorous

scrubbing action releases the clay coatings from the sand

grains. Released binder and fines are separated and removed

by washing or classification. The cleaned sand is dewatered

and dried as shown in Figure 4.

Wet reclamation cleans clay bonded sands very efficiently and

the reclaimed sand is almost equivalent in purity and

cleanliness to new Sand. It can, therefore, be used in place

o f new sand in molding and some core mixes.

High water requirements (2000 gal/ton of sand) and the need

to treat and clarify the water before recirculation and

disposal are major operating problems with wet reclamation

systems. In addition, capital cost of the equipment is high

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and a large amount o f floor space is required.

I

Figure 4 - Schematic Drawing of Wet Reclamation System

Amlications

Clay Bonded Sand

Reclamation o f clay bonded sand (green sand), which is used

by 70-80% o f all foundries, i s usually limited to that

portion o f the sand that would normally be discarded

(Approximately 10%). The remaining sand, approximately go%,

contains appreciable amounts of active bentonite (clay) and

other green sand additives such as cereal, cellulose or

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lJll I carbonaceous mater ia ls . I t i s desirable t o “save” these

add i t i ves . This bulk o f the sand i s therefore simply recyc les

as the “sand” o f the sand system, thereby u t i l i z i n g these

remaining binders and add i t i ves .

The discarded sand i s genera l ly reclaimed by the dry

pneumatic process. The reclamation systems used t y p i c a l l y

break down agglomerates, remove ca lc ined c lay and ad jus t

moisture and temperature. D r y reclamation i s idea l when the

reclaimed sand i s t o be recycled as described i n the l a s t

paragraph s ince the ca lc ined c lay i s removed whi le

appreciable amounts o f ac t i ve c lay remain.

Wet reclamat ion i s also sometimes used f o r c lay bonded sands

r e s u l t i n g i n pure and c lean reclaimed sand. However, such

c leanl iness i n no t normally necessary f o r a green system

sand, and the h igh cos t and problems associated w i th wet

reclamation g rea t l y reduce the f e a s i b i l i t y o f t h i s approach.

. .

Organica l ly Bonded Sands

Chemically-bonded sands u t i l i z i n g organic b inder systems

comprise the bu lk o f molding and coremaking sands used i n the

jobbing sector o f the foundry indus t ry . These sands genera l ly

lend themselves t o reclamat ion because the b inder plus

c a t a l y s t content o f the sand i s lower, genera l ly not

exceeding 2%, there fore there i s less binder t o be removed.

b t R

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sands i n t o the United States has produced a new se t of

requirements f o r sand reclamation processes. Because o f t he

h igh a l k a l i n i t y of the binders, the importance o f c o n t r o l l i n g

the res idual a l k a l i content o f t he reclaimed sand i s of

utmost importance. Recent work i n the United States has shown

t h a t a l l types o f reclamation processes have a favorable

e f f e c t on sand q u a l i t y , although a thermal/mechanical process

d i d no t produce the same favorable e f f e c t rea l i zed w i t h

sodium s i l i c a t e systems. I n f a c t , heat ing t o 260oC (500OF)

appeared t o lower rebonding s t rength. A s i n the case o f

sodium s i l i c a t e sand reclamation, add i t i ona l research work i s

requi red.

Qua l i t y Considerations ( 4 )

Reclaimed sand should be evaluated i n the same manner t h a t a

sand from a new source would be evaluated. The screen

ana lys i s o f t h e reclainled sand should be close t o the new

sand used i n the process. With a very angular sand, the

reclamat ion process w i l l produce a more rounded g ra in and the

g r a i n s i ze d i s t r i b u t i o n w i l l be somewhat f i n e r . Unless the

f i nes are con t ro l l ed , the sand the sand w i l l have a f i n e r

o v e r a l l g ra in s i ze . A s the f ineness o f the reclaimed sand

changes, the b inder requirements change.

Loss-on-Igni t ion (LOI) i s an important t e s t i n o rgan ica l l y -

bonded sands. Standard AFS (American Foundrymen’s Society)

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i I I I I I I I

procedures should be used. A number o f impor tant fac to rs

should be considered when running the LO1 t e s t . The sample

should be d r i e d f i r s t t o make sure t h a t no mois ture i s d r i v e n

of f and read as LOI. I n sands t h a t con ta in l a rge amounts of

a c t i v e c lay , t he burning o f the LO1 sample w i l l d r i v e o f f

chemically-bonded water from t h e c l a y and t h i s w i l l be read

as L O I , when i n r e a l i t y , i t i s n o t an organic loss. The

m e t a l l i c content should be kept t o a minimum s ince small

m e t a l l i c p a r t i c l e s w i l l o x i d i z e and gain weight, r e s u l t i n g i n

a f a l s e LO1 reading.

The content o f a c t i v e and dead c l a y i s another important

cons idera t ion i n reclaimed sand. Both types o f c l a y w i l l

lower pe rmeab i l i t y o f t he reclaimed sand and may r e a c t w i t h

c a t a l y s t s and acce le ra to rs i n chemically-bonded systems.

Standard AFS procedures should be employed.

M e t a l l i c con ten t i s impor tant i n any a c i d cured chemical ly-

bonded system. I f the m e t a l l i c content i s h igh, t h e ac id

c a t a l y s t w i l l reac t w i t h t h e meta l , r e s u l t i n g i n i n s u f f i c i e n t

C a t a l y s t t o cure the sand proper ly .

Depending o f t h e binder system employed, o the r t e s t s used i n

rec lamat ion system eva lua t i on a re low-power microscopic

examination, rebonding t e s t s , gas evo lu t i on , s u l f u r content

and n i t r o g e n content.

2-17

.

I n the f i n a l analysis, the u l t ima te t e s t i s t o pour cast ings

w i t h the reclaimed sand core o r mold and evaluate the

resu l t s . The cast ing surface should be as good as t h a t

produced w i t h new sand, and the reclaimed sand must n o t

r e s u l t i n a higher scrap ra te .

Trends in Reclamation ( 5 )

Current t rends i n sand reclamation f a l l i n t o three

categor ies:

-- Green sand back i n t o green sand systems.

-- Chemically-bonded sands back i n t o chemically-

bonded systems.

-- To ta l sand reclamat ion - reclaimed sand t h a t can be

re-used w i th any binder system.

More foundr ies are beginning t o look a t t he p o s s i b i l i t y o f

us ing sand reclamat ion t o mainta in t h e i r green sand system a t

a h igh q u a l i t y l eve l . By running a p o r t i o n o f t h e i r green

sand through a scrubber and re tu rn ing the scrubbed sand t o

the system, they can mainta in a higher q u a l i t y s ing le system

sand. I n some s tee l foundr ies, the sand t h a t i s scrubbed i n

t h i s manner i s used t o make fac ing sand u t i l i z i n g the

re ta ined a c t i v e c lay f o r more economical operat ion.

2-18

Jobbing foundries are looking a t rec la iming chemically-bonded

sands fo r re-use i n chemically-bonded systems. Higher f r e i g h t

and disposal costs are making reclamation i n smal ler

foundries more economically f eas ib le . Reasonably p r i ced

reclamation systems are now ava i l ab le o f f -he s h e l f from

several manufacturers.

One o f the most i n t r i g u i n g recent t rends i s t he concept o f

using thermal u n i t s t o ca lc ine refuse sand from the foundry.

The ca l c in ing u n i t must be backed-up w i t h some type o f pos t

scrubbing u n i t t o remove the dead c lay . The sand g ra in

surface under the res idua l binder i s s t i l l i n good shape - only the coat ing must be removed. I n most cases add i t i ona l

separat ion steps are required because used sand i s o f t e n

mixed w i t h other foundry refuse such as furnace dust and

re f rac to r ies , I n most foundr ies, the amount o f discarded sand

i s subs tan t i a l , cons i s t i ng o f t y p i c a l l y 30-40% core sand and

60-70% molding sand. ,If t h i s sand i s no t reclaimed i t must be

replaced w i t h cos t l y new sand add i t ions .

One f i n a l po ten t i a l t rend i s t he concept o f cen t ra l i zed Sand

reclamat ion p lan ts serv ing i n d u s t r i a l centers w i t h several

foundries. One la rge reclaimer, operated by some cen t ra l

agency o r au tho r i t y , could process the sands from a l l o f the

foundr ies i n the area. While problems e x i s t w i t h d i f f e r e n t

b inder systems, g ra in finenesses and the separation o f

spec ia l t y sands, the concept has considerable mer i t .

2-19

Sect ion 3

MOLDING AND COREMAKING PROCESSES

ove r v i ew

A s descr ibed e a r l i e r , most cas t ings are produced i n sand

molds p r i m a r i l y because t h i s i s the lowest-cost method

a v a i l a b l e . There i s , however, a wide range o f sand molding

and coremaking systems a v a i l a b l e t h a t o f f e r d i f f e r e n t

c h a r a c t e r i s t i c s . Se lec t i on o f a molding o r coremaking system

depends p r i m a r i l y on t h e metal being poured, t he type o f

c a s t i n g being made, t h e a v a i l a b i l i t y o f molding aggregates,

t he mold and core making equipment owned by the foundry, and

the q u a l i t y requirements o f t he customer (€5). An

understanding o f the bas i c c h a r a c t e r i s t i c s w i l l enable t h e

reader t o b e t t e r eva lua te the var ious systems a v a i l a b l e and

understand t h e i r r e l a t i o n s h i p t o the o v e r a l l opera t ion of a

p a r t i c u l a r foundry.

Molding and coremaking systems may be c l a s s i f i e d , f o r .

convenience, i n t o the f o l l o w i n g categor ies:

I - Green Sand - Hot BOX

- Organic No-Bake - Warm B o x

- S h e l l - Cold BOX c

Because most foundr ies use severa l b inder systems i n the

normal course o f t h e i r product ion, i t i s d i f f i c u l t t o

I I I I I I I I I I

INVESTMENT 10.0%

8.0%- NO-BAKE 24.0%

accura te ly determine the percentage o f cas t i ngs made i n any

g iven process. However, a rough est imate can be obta ined f rom

e a r l i e r pub l i shed work (a ) and in te rv iews w i t h i n d u s t r y

personnel. A s i l l u s t r a t e d i n Figure 5 , almost h a l f o f t h e

cas t i ngs manufactured are produced i n t h e green sand process.

These processes w i l l be discussed i n d i v i d u a l l y below:

GREEN SAND 48.w.

c02 Hoc0 4.0Z

OTHER 6.0%

Figure 5

Major Molding and Coremaking

Processes

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I I I I I I 1 r r

Green Sand Binders

Western Bentoni te - Western bentoni te i s t he t y p e of c lay

t h a t i s p re fe r red fo r use i n cast ing the higher temperature

metals, p a r t i c u l a r l y s t e e l . It i s bas i ca l l y a mont-

m o r i l l o n i t e , o r hydrated aluminum s i l i c a t e c lay i n which some

o f the aluminum atoms are replaced by sodium atoms. Thus i t

i s f requent ly re fe r red t o as "sodium bentoni te" . Western

bentoni te imparts h igh l eve l s o f green and dry s t rength to

the sand mold, and develops a h igh degree o f p l a s t i c i t y ,

toughness and deformabil i t y when proper ly "mu1 led" (mixed)

w i t h water. Western bentoni te a lso swe l ls when "mulled" w i t h

water, thus ac t i ng as a cushion between sand gra ins and

reducing sand expansion defects such a scabs and buckles. I t

a lso i s "durable" , t h a t i s i t can be reused many t imes i n a

system sand w i t h a minimum o f new add i t i ons required.

Southern Bentoni te - Southern bentoni te d i f f e r s from western

bentoni te i n a number of ways. I t a lso i s a hydrated aluminum

s i l i c a t e c lay , however some o f t he aluminum atoms have been

replaced w i t h calcium ra the r than sodium atoms. It i s

f requen t l y c a l l e d "calc ium bentoni te" . Southern bentoni te

develops h igher green s t reng th bu t lower ho t and dry

s t rengths than western bentoni te. Sands bonded w i t h southern

bentoni te are more f lowable and can be compacted t o h igher

dens i t i es . Southern benton i te i s a l so l ess durable, and i s

genera l ly used w i th lower me l t i ng p o i n t metals such as cas t

r

r II r

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i r o n . I t i s common p rac t i ce t o blend mixtures of both

bentoni tes t o achieve the desired proper t ies.

Addi t ives - Most green sand molds are made w i t h s i l i c a sand

and, whi le s i l i c a i s inexpensive, has some shortcomings w i t h

regard t o cas t ing surface f i n i s h . To minimize problems i n

t h i s area, and number o f add i t i ves are normally used i n the

process. These can be c l a s s i f i e d as fo l lows:

- Carbonaceous

- Cel lu lose

- Cereal

Carbonaceous add i t i ves are p r i m a r i l y used i n cas t i r o n

product ion t o provide a reducing atmosphere a t the mold-metal

i n t e r f a c e which minimizes ox ida t i on o f the metal and

the burn-on defect . Mater ia ls commonly used are seacoal ( a

f i n e l y ground bituminous coa l ) , G l l son i te (na tu ra l asphal t )

and p rop r ie ta ry petroleum based products.

Ce l lu lose i s added t o cont ro l sand expansion defects and

broaden the l a t i t u d e o f moisture con t ro l . Cel lu lose a l so

lowers ho t s t rength and improves shakeout p roper t ies , I t i s

normal ly added as wood f l o u r , ground nu t she l l s , o r ground

cerea l husks.

3- 4

> 4

Cereal a d d i t i v e s are adhesive when wetted and a c t as a

b inder . They are f requent ly used t o improve the a b i l i t y t o

"draw" o r p u l l out deep pockets. Because cerea ls v o l a t i l i z e

when heated, they can cause gas defects i n the cast ings.

Cereals a re normal ly added as corn f l o u r , d e x t r i n , and o t h e r

starches

Orqanic No-Bake Binders (3,

-- furan Acid Catalyzed No-Bake - The bas ic component o f f u r a n

no-bake b inders i s f u r f u r y l a lcoho l . These b inders can be

mod i f ied w i t h urea, formaldehyde, phenol, and o ther

a d d i t i v e s t o improve p roper t i es . The speed o f c u r i n g i s

ad justed by va ry ing t h e amount and/or type o f a c i d c a t a l y s t

used. Furan b inders p rov ide a h igh degree o f dimensional

accuracy and res is tance t o mold-metal i n t e r f a c e defects . They

a l s o impar t e x c e l l e n t t e n s i l e and h o t s t reng th making them

use fu l f o r f l a s k l e s s molding app l i ca t i ons .

Phenol ic Ac id Catalyzed No-Bake - Phenol ic no-bake r e s i n s

a re phenol ic/ formaldehyde r e s i n s w i t h a molar r a t i o o f less

than 1 : l . These res ins can a l s o be mod i f ied t o improve

p r o p e r t i e s . The p r o p e r t i e s a t t a i n e d are s i m i l a r , though

s l i g h t l y lower, than those o f t h e f u r a n r e s i n systems . Cost

i s u s u a l l y somewhat l e s s . Resins o f t h i s type con ta in f r e e I

I phenol and f r e e formaldehyde, and can cause odor problems I

du r ing the m ix ing opera t ion . Adequate v e n t i l a t i o n i s

I I I

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r equ i red.

Ester-Cured A l k a l i n e Phenol ic No-Bake - This system i s a

two-part system c o n s i s t i n g o f a water-soluble a l k a l i n e

pheno l ic r e s i n and l i q u i d e s t e r co-reactants. Phys ica l

s t reng ths achieved are n o t as h igh as w i t h the ac id -ca ta lyzed

systems, however, d i s t i n c t advantages are achieved i n t h e

reduc t i on o f ve in ing de fec ts i n gray i r o n cas t ings and i n

e x c e l l e n t res i s tance t o e ros ion . The r a t e o f gas e v o l u t i o n i s

low thus min imiz ing gas de fec ts . Since both t h e r e s i n and co-

reac tan ts a re water so lub le , clean-up i s s i m p l i f i e d .

S i l i c a t e / E s t e r Catalyzed No-Bake - Th is system c o n s i s t s o f a

sodium s i l i c a t e b inder and a l i q u i d organic e s t e r hardening

agent. High r a t i o b inders w i t h a S i 0 2 / N a 2 O conten ts o f 2.5-

3 .2 /1 are used. The e s t e r s a re m a t e r i a l s such as g l y c e r o l

d i a c e t a t e o r t r i a c e t a t e or e th lyene g l y c o l d iace ta te . Cur ing

takes severa l hours. P roper t i es e x h i b i t e d are moderate

s t reng th , low r a t e o f gas evo lu t i on , e x c e l l e n t degree o f

p l a s t i c i t y and good e ros ion res is tance. L i t t l e o r no smoke or

fume i s evolved du r ing pour ing.

- O i l Urethane No-Bake - These b inders , a l s o known as o i l -

urethane, alkyd-urethane, alkyd-oi l -urethane, o r po l yes te r -

urethane, a r e t h r e e component systems e x h i b i t i n g a unique

two-step c u r i n g mechanism. The th ree p a r t s a re an a l k y d o i l

t ype r e s i n , a l i q u i d amine/meta l l ic c a t a l y s t , and a

3-6

polymeric methyl di- isocyanate. The f i r s t cu r ing step

produces a urethane coat ing on the sand t h a t al lows s t r i p p i n g

of the mold and handling; the second step provides a f u l l

cure t o wi thstand the condi t ions imposed by the molten metal.

This unique two-step cur ing process r e s u l t s i n unmatched

s t r i p p i n g cha rac te r i s t i cs and provides a good method f o r

producing la rge cores and molds t h a t requ i re long work and

s t r i p t imes.

Phenolic Urethane No-Bake - This binder cons is ts o f three

pa r t s , a phenol formaldehyde r e s i n d isso lved i n a solvent, a

polymeric type isocyanate a l so d isso lved i n a solvent, and an

amine c a t a l y s t . The type and amount o f c a t a l y s t determine the

set-up t ime. The reac t ion i s a one-step reac t i on r e s u l t i n g i n

a urethane bond throughout the sand mass. Proper t ies inc lude

moderate s t rength , good eros ion res is tance, and good

f l o w a b i l i t y . This binder can sometimes r e s u l t i n p inhole gas

defects i n fe r rous cast ings, and i r o n oxide add i t ions are

made t o minimize t h i s problem.

Polyol-Isocyanate System - The polyol- isocyanate system i s

s i m i l a r t o the phenol ic urethane system prev ious ly described

except t h a t the ingred ien ts are s p e c i a l l y se lected and

blended t o a l low decomposition a t lower temperatures. This

a’llows successful use i n the produc t ion o f aluminum and

magnesium cast ings where the pour ing temperatures are too low

t o a l low the use o f t he prev ious ly described systems. For the

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I I I I I I I I I I I I !

same reasons t h a t make t h i s system good f o r t h e low

temperature a l l o y s , i t i s no t recommended f o r f e r r o u s a l l o y s .

She l l Drocess

The s h e l l process, a l so known as the Croning process, uses

sands coated w i t h pheno l ic novolac r e s i n s and hexamethylene-

te t ram ine ( "hexa" ) . The sands may be "warm" coated us ing

l i q u i d o r d isso lved res ins , o r "ho t " coated us ing s o l i d

r e s i n s . Hot coated sands are genera l l y more f lowab le . When

the coated sands are p laced i n contac t w i t h t h e heated

p a t t e r n i n t h e s h e l l machine, a thermoset t ing bond forms. The

th i ckness o f t he s h e l l developed i s a f u n c t i o n o f t h e p a t t e r n

temperature and dwel l t ime. The excess sand i s then dumped.

The s h e l l process o f f e r s super io r dimensional reproduc t ion

c a p a b i l i t i e s and the f l o w a b i l i t y o f t h e sand a l lows i n t r i c a t e

cores t o be produced. Various a d d i t i v e s can be used t o

f u r t h e r improve performance. I n a d d i t i o n , t h e bench l i f e o f

t he coated sand i s i n f i n i t e thus e l i m i n a t i n g sand removal and

clean-up a t t h e end o f each s h i f t .

-- Hot Box Process

The h o t box process u t i l i z e s a l i q u i d thermoset t ing b inder

and a l a t e n t a c i d c a t a l y s t . These components are mixed w i th

t h e sand and blown i n t o a core box. The heat from t h e core

box causes t h e c a t a l y s t t o re lease a c i d which r e s u l t s i n a

3- 8

. . very r a p i d cure; i n t h e order o f 10 t o 30 seconds. There are

two main types o f h o t box b inders; f u r a n types con ta in ing

f u r f u r y l a l coho l , and pheno l ic types con ta in ing phenol. Both

types a l s o con ta in urea and formaldehyde. Because of t he

r a p i d cure r a t e , these b inders are e x t e n s i v e l y used i n the

automotive i ndus t r y f o r producing i n t r i c a t e cores and molds

t h a t r e q u i r e good t e n s i l e s t reng ths f o r low c o s t gray i r o n

c a s t i ngs.

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-- Warm Box Process

The warm box b inders a re s i m i l a r t o t h e h o t box b inders

except t h a t t h e c a t a l y s t m a t e r i a l s a re d i f f e r e n t and a l l o w

t h e cure t o take p lace a t a lower temperature. Copper s a l t s

are genera l l y used as c a t a l y s t s r a t h e r than t h e n i t r a t e s or

c h l o r i d e s used i n the h o t box process. Th is chemist ry

d i f f e r e n c e a l l ows p roduc t i on o f cores g i v i n g good dimensional

accuracy and e x c e l l e n t ' e r o s i o n res is tance.

-- Core Oil Processes

Core o i l b inde rs a re used i n combinat ion w i t h water a c t i v a t e d

ce rea l t o p rov ide a smal l amount o f green s t reng th . Th is

a l l ows t h e sand mix t o be blown o r rammed i n t o t h e core box

and removed. The core i s then oven-baked t o develop t e n s i l e

s t r e n g t h . Several t ypes of o i l can be used i n c l u d i n g l i n s e e d

o i l , vegetable o i l , urea formaldehyde and r e s o l e phenol ic . A

3- 9

8 . ,. 1-

, I small amount o f western o r southern ben ton i te i s o f t e n added

t o prov ide a d d i t i o n a l green s t rength .

The long baking cyc le tends t o make these b inders q u i t e

i n e f f i c i e n t from an energy s tandpoint which has re legated

these b inders t o the category o f " o l d fashioned". However,

t h e h igh q u a l i t y cores t h a t are produced, and t h e f l e x i b i l i t y

o f the process f o r making small q u a n t i t i e s o f cores, have

r e s u l t e d i n the continued use o f s i z a b l e q u a n t i t i e s o f these

b inders ( F i g . 5 ) .

-- Cold Box Processes

Cold box processes, by d e f i n i t i o n , f ea tu re a c u r i n g mechanism

t h a t occurs a t room temperature. The sand-binder mix i s blown

i n t o a core box and cured by passing a gas o r vapor c a t a l y s t

through the sand mass. The severa l d i f f e r e n t b inde r -ca ta l ys t

systems i n general usage w i l l be descr ibed below:

Phenol ic Urethane Cold Box - The phenol ic urethane c o l d box

system i s a th ree p a r t system c o n s i s t i n g o f a pheno l ic r e s i n ,

a po lymer ic isocyanate, and a t e r t i a r y amine vapor c a t a l y s t .

Sand t h a t has been coated w i t h t h e f i r s t two p a r t s i s blown

i n t o a core box a t room temperature. The amine vapor i s then

passed through the core box fo l l owed by an a i r purge t o

remove a l l t r aces of amine. The exhaust should be scrubbed

chemical ly t o remove the amine. Th is i s an e x c e l l e n t h igh

3-10

product ion system p rov id ing e x c e l l e n t sur face f i n i s h on t h e

cast ings.

Process (Furan/SOz 1 - This process can be described as a

rap id-cur ing, gas-act ivated, furan no-bake. F u r f u r y l a lcoho l

base r e s i n s mixed w i t h organic hydroperoxides and methanol

d i l u t e d s i l a n e form the binders. Af ter blowing i n t o t h e core

box, t he i n t r o d u c t i o n o f SO2 r e s u l t s i n the format ion o f

complex ac ids which cure the r e s i n . These sands e x h i b i t

e x c e l l e n t f l o w a b i l i t y and cores can be produced w i t h

s u b s t a n t i a l l y lower blow pressures. The r e s u l t i n g cores are

h i g h l y accurate and can be produced i n very complex,

i n t r i c a t e shapes.

Free Radical Cure ( F R C ) Process - This i s a c t u a l l y a f a m i l y

o f processes t h a t inc ludes a l l a c r y l i c and acry l ic -epoxy

b inders. The b inders a re cured w i t h an organic hydroperoxide

and s u l f u r d iox ide. Proper t ies can be var ied considerably by

s e l e c t i n g d i f f e r e n t b inder compositions. The most b e n e f i c i a l

p r o p e r t i e s r e a l i z e d w i t h these systems are good an t i - ve in ing

c h a r a c t e r i s t i c s and a minimum o f p inho le gas de fec t problems.

Phenol ic E s t e r Cold Box - Th is system cons is t s o f two pa r t s :

a water-soluble a l k a l i n e pheno l ic reso le r e s i n and a v o l a t i l e

e s t e r vapor co-reactant. Sand i s coated w i t h t h e r e s i n and

blown i n t o t h e core box. The l i q u i d es te r i s vaporized and

i n j e c t e d as a gas through t h e sand m i x . Most o f the e s t e r i s

3-11

. F

. ‘ consumed by the cu r ing react ion, min imiz ing t h e amount o f a i r

purge requ i red . Castings made w i t h t h i s system e x h i b i t good

sur face f i n i s h , and minimum amounts o f eros ion and ve in ing .

Coatings are requ i red t o prevent penet ra t ion defects ,

however, a d d i t i v e s such as i r o n o x i d e and sugar a re n o t

requ i red t o c o n t r o l ve in ing and n i t rogen defects ,

Sodium Sil icate/COz Process - This system u t i l i z e s sodium

s i l i c a t e as the b inder which i s cured w i t h carbon d i o x i d e

gas which makes i t an inorganic system. S i l i c a t e b inders a re

odor less, non-flammable, s u i t a b l e f o r a17 types o f work,

usable w i t h a l l types o f molding aggregates, and are

env i ronmenta l ly acceptable i n t h a t they produce no harmful

emissions upon pour ing o r shakeout. The main d i f f i c u l t y w i t h

t h e i r use has been w i t h problems w i t h ho t t e a r i n g and

d i f f i c u l t shakeout due t o t h e . h i g h re ta ined s t reng th

developed. The favorab le environmental c h a r a c t e r i s t i c s of

these b inders w i l l i nsu re expanded use i n the f u t u r e .

Caut ionary no te

AS can e a s i l y be seen from t h e above discussion, t h e s u b j e c t

Of mold and core b inders i s q u i t e complex and should be

approached accord ing ly . Hans Heine, Technical E d i t o r , Foundry

Management and Technology s t a t e s the f o l l o w i n g ( 5 ) : “ A number

Of f a c t o r s combine t o regu7ate a r e s i n sand’s coat ing

c a p a b i l i t y , usable l i f e of the coated sand, r a t e and

ef fect iveness o f cure, bonded sand st rength, and

3-12

" c a s t i b i l i t y . "

foundryman, o r

apprec ia te t h e I

Only an a s t u t e , experienced no-bake

one who has been p r o p e r l y t r a i n e d , can

dramatic in f luences t h a t t i m e , humid i ty ,

equipment v a r i a t i o n s , and e s p e c i a l l y temperature have on t h e

I o p e r a t i o n ' s success o r f a i l u r e . "

.I

I I -.--

3-13

t

1 .

2.

3.

4 .

5 .

6.

7 .

Sect ion 4

REFERENCES

P. R . Brawler and M. F. B u r d i t t "Is t he P r o f i t L ine t h e

Bottom Line i n Sand Reclamation?" Modern Casting, Vol .

78 , No. 5 , May 1988, p. 2 7 .

Sand Reclamation, SCRATA Technical B u l l e t i n No. 28.

S. Raja I y e r and C. K. Johnson "Reclamation o f Phenol ic

Es ter Cured No-Bake Sands" Transact ions. 1988.

M. J. Granlund "Sand Reclamation-Update" SFSA T&O

Conference PaDer , 1988.

M. J. Granlund, "Eros ion & Expansion Type Stee l Cast ing

S tee l Cast ing Defects", and d . M. Svoboda, "Adhering

Sand Defects" , Troubleshoot ing t h e Steel Cast ing

Process, J. M. Svoboda and B. Linskey, E d i t o r s , SFSA,

1987.

P.R. Carey, e t al, "Updating Resin Binder Processes - P a r t I - I X , Foundry Management and Technoloav, Feb.

1986.

H. J. Heine, "Chemical ly Bonded Sand Systems f o r Steel

Cast ings - Current S ta tus" , 1988 SFSA T&O Conference

PaDer, S tee l Founders' Soc ie ty o f America, 1988.

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