ductile iron: 2002 Issue 2

7/27/2019 ductile iron: 2002 Issue 2

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To Promote the production and application of ductile iron cast

Ductile Iron Society Visits

At the 116th Meeting


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To Promote the production and application of ductile iron castin

PMI Answers Questions on Investment C

PMI Answers the Ten Most Asked Questions About Investmen

Since ductile iron was developed in the 1940s, this remarkableproved its value in tens of thousands of engineering and castinapplications. Ductile iron is created by an alloying process whthe crack-promoting graphite flakes of gray iron into nodules. microstructural transformation, the metal acquires superior ducelongation characteristics, and machinability. The ductile ironthe design engineer a unique combination of strength, wear res


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casting from PMI on the right providedthe customer with better quality, near netshape, improved surface finish,elimination of most costly machining,

reduction in rejected parts and significant cost savings. 0.1471size of both parts together is 4.25".

PMI Answers the Ten Most Asked Questions About Investmen

ViewDuctile Iron RelatedPublications

Located in Strongsville, O

15400 Pearl Road, Suite 2

Billing Address: 2802 Fis

Phone (440) 665-3686; Fa

il j d@d til
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To Promote the production and application of ductile iron casting

Ten Most Asked Ques

About Investment Ca

1. What is an "Invest

An investment castingmade by the "lost waxcast-in detail, tight tolesurface finish. The termthe ceramic materials thollow shell into whic


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Generally, most ferrous and non-ferrousalloys can be cast. Among ferrous metals, the are carbon, tool, and alloy steel, along with the

17-4 PH stainless steels. Of the non-ferrous mcopper-based are the most common alloys use

In addition, there are super alloys used primarindustry to produce blades and vanes. These acomposed of nickel and cobalt with a variety oadded to achieve specific strength, corrosion, a

properties. Often, a vacuum process is used in

i f fi i h d A l


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requirements for your finished part. As a resulthe as cast part should require minimal or no m

Linear Tolerance

Dimensions

up to 1"

up to 2"

up to 3"

up to 4"from 5" to 10"

maximum variation

Minimum Wall Thicknes

Alloy Small Area (.25 x .25)

Beryllium Copper 030"i i h l 020 030 fi i h d


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investment cast with only .020 - .030 finished

Again, communication between you and the cthe process is crucial to determining what canvs. what should be achieved through after cast

7. How many pieces do I need to purchase tcasting practical?

The bulk of investment castings that are produ10,000 annual piece requirement range. Howereasonable, investment casting might be a pracsmaller quantities. For example, in the machininvestment castings are often specified on 25 psubsequent orders being for only a piece or twof the spectrum, companies that provide invesautomotive users might produce 100,000 parts

d ti d


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produc-tion orders.

To make lead times more livable in a businessJust-In-Time ordering, many companies offer determining your projected use of a part over (such as a year), by communicating this need committing to purchase the projected quantity shortcut the normal lead time. Advance planni

enable your investment casting supplier to havyou need them.

In summary, investment casting can offer youwith cast-in detail, tight tolerances, and excellBecause PMI and other investment casting commuch of what you need into the actual castingmachining, welding, assembly, and other secona part is designed as an investment casting or


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Shrinkages in Iron Castings

Some facts and hypotheses related to thermal analysis with AT

Author: Rudolf SillnTechnical Director, NovaCast AB

Shrinkages are one of the most common casting defects. The mshrinkage cavities is the fact that all commercial alloys contraccasting cools from the pouring temperature to solidus. The conusually between 1-5 % depending on the type of alloy and the

t t f 50 C ill i th d f f d t


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temperature of 50 C will increase the need for feed metaWhen pouring castings with small modulus in ductile iro

pouring temperature might decrease shrinkage tendency hard moulds. The reason is a better temperature distributmould and less fast initial cooling.

2. Insufficient amount of feed metal available at early stagesolidification. Normally no feeder is needed for castingsmodulus (less than 0.4 cm). Feed metal can be supplied

pouring cup through the gating system. However, if the mthe ingate is too small then feed metal might be lacking.3. Deformation (expansion) of the casting cavity. This mig

green sand moulds and cause mould wall movement, whthe casting cavity.

4. Too high liquidus temperature. A liquidus temperature hwhat the system has been designed for will cause the surform earlier and thereby increase the risk for outer sunks

5 Too high amount of primary austenite (S1) cause by too


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The important fact is that ATAS allows the foundry man to enout of 8 variables are within the specification.

A5 - How can out sunks (pull downs) be avoided?The pouring temperature must be chosen individually for the ccastings with small modulus and/or long flow length must use

pouring temperature and/or be poured very fast to avoid castinsuch as cold shuts. Castings with a high modulus and/or short

can be poured with a low temperature. To minimize the volumin liquid state, the general advice is to use as low a pouring tem

possible without getting any casting defect. The feeding systemdesigned and dimensioned once the optimal pouring temperatuestablished for a casting. Mould hardness must also be considedimensioning the feeding system. It should be as high as possi

Feeding from the gating system is normally sufficient if the ca

2 F di th l d t l iti f f d M


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2. Feeding path closed too early - wrong position of feeder. Mothan usual at an early stage (CLF factor in NovaSolid). Too lowcarbon equivalent (ACEL=the true carbon equivalent measuredATAS). For ductile iron, ACEL should be eutectic and carbon3.6%.

3. Mould hardness during solidification. Soft moulds which favwall movement. A green sand mould, hard at room temp can bsolidification due to the high water level in the condensation z

4. Mould weighting or clamping insufficient to stand the presssolidification. Eutectic pressures up 50 kg/cm2 has been claim

5. Higher liquidus temperature (TL) than normal. In hypoeutecmeans too much primary austenite and more difficult feeding. Ihypereutectic it means more primary graphite which reduces theutectic graphite.

a stenite is appro imatel 6 9 g/cm3 at temperat res aro nd 1


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austenite is approximately 6.9 g/cm3 at temperatures around 1density of graphite about 2.3 g/cm3).

Another reason especially in gray iron is too high levels of nitrductile iron this is less likely as the high CEL-level reduces sonitrogen. High nitrogen levels cause an increased solubility of During the end of solidification a dispersed type of shrinkage uoccurs in almost all of the casting. The cavities look like a "coare often referred to as "comma" cavities or sometimes commaAdding about 0.02% titanium usually helps. Another alternativzirconium especially with ductile iron.

The other mechanism is that due to the composition of the ironone or more phases that solidify at a lower temperature than thgraphite eutectic. The most well-known case is the formation o

phosphide (Fe3P) in gray iron if the phosphorus level is higherThe Fe3P phase segregates to cell boundaries where it continu C4 Whi h i bl b it d b ATAS?


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C4 - Which variables can be monitored by ATAS?The mechanism behind micro shrinkages is dependent on the mstatus of the melt, which can not be measured by chemical anaATAS thermal analysis method is therefore a powerful tool forand verifying that a melt is within acceptable metallurgical thrvalues. ATAS can also be used to study the result of changes iand treatment variables and alloying materials, whereby the malloying materials as well as melting and treatment processes c

established. ATAS factors 10, 11, 12,13 and14 as mentioned inprevious chapter are good indicators for micro shrinkages.

C5 - How can micro shrinkages be avoided?The first condition is to have a hard mould - ideally chemicallysand moulds. A green sand mould is compressible, however hatemperature, because of the formation of a condensation zone.condensation zone, which travels from the surface of the caviti d th i t t t b t 3 ti hi h th (which does not expand)


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(which does not expand).

These metallurgical factors can be influenced by selection of cmaterials, charging sequence, the melting cycle (temp/time stetype and amount of alloying materials, inoculants and FeSiMgit is possible to find the optimal melting and treatment practicethe likelihood for shrinkages. Such an optimization can NOT btraditional chemical analysis alone. The behavior of a melt deponly on the percentage of each element but also on formed comas oxides, silicates, sulphides, nitrates and their interaction dursolidification. The total behavior can however be revealed by mATAS thermal analysis. A quantitative analysis of the solidificalso be made which allows the user to study the precipitation oand the associated volume changes in details. ATAS shows the

precipitated graphite during the different phases of solidificatiothe need for feed metal.

3 Too high amount of phases which exhibits solidus below


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3. Too high amount of phases which exhibits solidus belowE.g. Fe3P.

4. Too high levels of Nb, V etc.

C4 - Which variables can be monitored by ATAS?As the mechanism behind porosities is more dependent on soliminute phases with a temperature below the normal solidus it not detectable by thermal analysis. Some guidance might be avstudying TS and the last part of the first derivative curve.

C5 - How can porosities be avoided?The phosphorous content should be less than 0.12 % in unalloy(But minimum 0.08% in order to avoid expansion penetration!content can also influence this type of defect. Metallurgically iimportant to avoid all phases, which have a solidus temperaturmain solidus temperature. In gray iron the phosphorous level snormally be less than 0 12 % If molybdenum or chromium is p

1200 C Due to the low pouring temperature the pouring


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1200 C. Due to the low pouring temperature, the pouringbe short, to avoid defects. Two other conditions must alsfulfilled. First the modulus of the casting must be at leasThis will ensure that the solidification time is slow enouthe eutectic reaction to occur slowly in order to precipitaeutectic graphite as possible. In order to avoid mould wadue to the forces during solidification the moulds must hsufficient strength. Chemically bonded moulds using binfuran or cement must be used. The moulds should be fir(instead of using weights).

Illustrations from ATAS Screens:


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Pic. 3. This screen shows how the expert system has interprete


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Machinabili

Submitted by Jim Mullins, Technical Director

This is an excerpt (with DIS comments) from work done by UnAlabama, Birmingham, for the American Foundry Society (AFseveral foundry companies with support from the US DepartmEnergy. The original report was presented by Dr. Charles BateConvention, 2002 and is copyrighted by AFS. This is paper # 0those who would like to review the entire paper, which is availAFS.

the faster speed which can accelerate tool wear


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the faster speed, which can accelerate tool wear.2. Higher tool wear rates were seen in irons with a higher B

hardness.3. Lower wear rates were seen in the irons with higher silic

but the data was limited and the silicon content was on tat 2.4% max. Note that at higher silicon levels of > 2.6%machinability is generally reduced.

4. Higher wear rates were seen in irons with a higher combcontents.

5. Higher wear rates were seen in irons with higher copperconcentrations. Note, it appeared that in irons of the samthat had both copper and tin, strengthening of the iron bycopper gave higher tool wear rates than strengthening w

6. Higher tool wear was seen in irons with less rounded nothese irons also had higher hardness, so it is difficult to gcomparison.

7 Irons with the highest volume of pearlite lowest pearlite


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DIS FAQ's

Submitted by Jim Mullins, Technical Director

Questions

1. What is good melting practice for gray and ductile iron?2. How do I know what chemistry to aim for in ductile iron3. Describe controls for good ductile iron treatment practic4. What are the basics for inoculation of cast iron?5. What sulfur and manganese do I need in gray iron?
http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


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evenly and get it dissolved uniformly in the metal This is usua


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evenly and get it dissolved uniformly in the metal. This is usuathe pouring ladle (with ductile, after the treatment step). It canon a reduced scale (never more than 0.2%) in the pouring box

All inoculant effects fade with time after addition. Usually 20 the maximum time to insure any residual effect. For this reasofoundries do some inoculation in the ladle and some in the mocontrol the time of the ladle on the floor. Un-inoculated irons awith faded inoculation behave much differently and can have u

graphite structures, carbides, and changes to the matrix structucan also be affected.

Inoculants must be carefully weighed and be kept dry as they some moisture. Water in inoculants will produce large carbidemetal.

Back to top

Magnesium Must be kept as low as possible and while still p
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Magnesium - Must be kept as low as possible and while still pgood graphite shape. In sections of to 1" a final Mg of 0.03okay. Mg levels will increase slightly until at about 2" sectionabout 0.045%.

Sulfur - Level in base ductile iron should be 0.010- 0.015%. Tpromote carbides in the final structure, also because Mg can bmuch requires a larger Mg addition and the possibility of redu

nodularity.

Metallurgy of ductile iron - Nodularity checks

All separate ladles of ductile iron should be checked for nodulof the approved methods from the end of the pouring ladle. Ththen polished sufficiently to reveal the graphite structure. The should be > 85% in the test sample. Also examination of the n

d l t i f t d 1" t t b i h ld l h


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Nitrogen in Ductile Iron 2002

By George D. Haley

Corporate MetallurgistHICKMAN, WILLIAMS & COMPANY

presented at The 2002 Ductile Iron Society Annual MeetingPioneer Resort & Marina; Oshkosh, WisconsinJune 13, 2002

ABSTRACT

C l "B" d d b t l f 82 it ith


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Cupola "B" produced a base metal of 82 ppm nitrogen with a s0.07-0.08%. The nitrogen content in the holder further droppm. The metal was treated with 5% magnesium wire to desunodulize. This was an excessive use of wire . The final nitroge52 ppm. When electric induction melted base iron with a 0.015and a nitrogen of 56 ppm was treated with 5% wire the nitrogethe treated metal was 58 ppm. The amount of wire consumedhalf that consumed by the cupola foundry.

Five foundries that melted base iron in medium frequency furnaces reported nitrogen contents in the 41-56 ppm range waverage in the mid to high 40's. After treatment with 5% MgFenitrogen contents were about the same or slightly higher, averlow 50's. The treatment was done in either open or tundish ladfoundry treated in an open ladle with 3% alloy and the nitrogefrom 48 ppm to 44 ppm. This was a very quiet reaction.

insoluble nitrogen are nearly constant at 50 to 60 ppm some


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insoluble nitrogen are nearly constant at 50 to 60 ppm , somethan the Evans number. This is verified in the data presented fmedium frequency electric furnace induction melted iron.

The reported nitrogen content ofgray iron is probably mostly nitrogen as it is known that if certain levels are exceeded in thetitanium and zirconium, porosity will be present in the castings

Ductile iron, however, is usually produced with about 50% ret

magnesium in the returns can form MgSiN2 nitrides as reporteWada and R.D. Pehlke. The tendency to react with nitrogen is magnesium than it is for titanium, aluminum or boron. This mafor the softening of flake graphite irons when ductile iron returincluded in the charge. Nitrogen is an important alloying agenThe increase in graphitic carbon could also be a factor.

In "The Physical Metallurgy of Cast Iron", I. Minkoff reports


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Inoculation

Do you inoculate your iron?

You probably do, since it is an essential part of most foundry oAside from reducing chill, inoculation promotes the uniformity

properties throughout varying section sizes, as well as improvemachineability and strength. Calcium bearing 75% Ferrosilicocommon inoculant. In addition, there are several proprietary inthe market.


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College Industry Conference

FOR IMMEDIATE RELEASEJUNE, 2002

College Industry Conference

email [email protected];b htt // f f ffi
mailto:[email protected]:[email protected]:[email protected]


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email [email protected];web page http://www.fefoffice.org.Registrations can be taken now;Drake Hotel reservations can be made at 312/787-2200.

A detailed CIC brochure will be sent out in August.

ViewDuctile Iron RelatedPublications

Located in Strongsville, O

15400 Pearl Road, Suite 2

Billing Address: 2802 Fis

Phone (440) 665-3686; Fa

email:[email protected]
mailto:[email protected]:[email protected]://c%7C/WEBSHARE/062013/books.htmhttp://c%7C/WEBSHARE/062013/books.htmhttp://c%7C/WEBSHARE/062013/books.htmmailto:[email protected]:[email protected]://c%7C/WEBSHARE/062013/books.htmhttp://c%7C/WEBSHARE/062013/books.htmhttp://c%7C/WEBSHARE/062013/books.htm


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Monday Morning Iron - Phase I

Restoring Techniques for Monday Morning Iron - Phase I

Submitted by: Jim Mullins Technical Director

The primary work was done by M. Popescu from Materials TeLaboratory (CANMET), Ottawa, Ontario, Canada and the resuto the public at the AFS Convention in Kansas City, May 2002report is available from AFS and is copyrighted by them.

The project was commissioned by the AFS 5L committee on M

3. Examination of final microstructures of test samples witcarbon equivalents indicated the holding time at lower te


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3. o o c os uc u es o es s p es wcarbon equivalents indicated the holding time at lower te(2456 & 2565) increased the nodule counts (some had tradditions), while holding at high temperature (2709) didhave any effect on the nodule count.

4. While the holding time did not seem to affect the matrixsamples, the microstructural study indicated that holdingtemperatures encouraged more ferrite formation in 6 & 9diameter samples. However these also had higher nodule

5. The 5 % MgFeSi plus 1% TRE used for treatment and thused for inoculation had strong nucleation effect, which make the ductile iron less susceptible to the holding timecompared to grey irons.

DIS comments about this topic and conclusions are:

1 Holding temperature was relatively low for two out of th


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can cause core breakage, especially to many of today's thin andcores such as water jacket cores (Figure 6)


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Figure 6

g , p y y ycores such as water jacket cores (Figure 6).

The stress is better simulated because rarely arecores pulled apart as dog bones are in the tensile test.When thin, problematic cores break, the stresscausing the core breakage is usually more similar tothe stress applied in the disc transverse test. Anotheradvantage to

this test arises from the fact that the discspecimen is thin. As Boenisch pointed ocore is first prepared, when it leaves thethe strength gradient will resemble Figuexterior will have the highest strength wcore was in contact with the core box wwhile the interior will have slightly less
http://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand07.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand06.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand10.jpg


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Figure 10

Figure 1

bentonite, however, these organic condehinder the movement of the water moleout from between the clay platelettes asFigure 10. This produces a

waterproofing effect that deteriorates the propertiesof the molding sand. The wet tensile test, Figure 11,

is sensitive to this type of deterioration. In this test,as illustrated in Figure 12, a specimen is formed inthe specimen tube and the specimen has a taper onthe one end which fits into a lift off ring. During thetest, the end of the specimen with the ring is

subjected to a heat, and theheat drives the moisture in the sand bac

B 36 No

C 30 No
http://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand12.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand11.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand10.jpg


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C 30 No

D 9,5 No

E 32 No

F 25 No

G 195 Yes

H 107 Yes

I 81 Yes

J 83 Yes

K 61 YesL 73 Yes

Figure 16

whether or not nitrogen fissure defects were being experiencedexception of the first system which went through both good pebad periods the remaining systems fell into two categories bas

lustrous carbon is almost like a lubricant. Negative effects on rdifficult to detect with the conventional tests such as green co


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Figure 2

gdifficult to detect with the conventional tests, such as green coThe most sensitive tests to detect these effects include the friaband the cone jolt toughness test.

Figure 20 shows the friability test. In this test, twostandard test specimens are rotated in a screen forone minute, and the weight percent of sand thatabrades from the surface is measured. Molding

sands that have a high friability are prone toproducing erosion and inclusion type defects.Generally, under 10% friability is considered good.Molding sands that run over 10% friability aregenerally prone to erosion and inclusion typedefects, because the molding sand cannot withstand the erosivmolten metal.
http://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand20.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand23.jpg


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Figure 2

consistently.

Figure 24 shows typicalvalues for Southern

bentonites. Note that by observing leachcalcium, one can distinguish between Sbentonite from Alabama versus Souther

values that were calculated from the base values and the prebleformulation. The next row of data shows the actual data obtain


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pformulation. The next row of data shows the actual data obtaintesting Bond #1. Since the theoretical values matched extremelthe actual values, this proved that the preblend was properly praccording to its formulation, and there was not more Southern the preblend as suspected. Examining the values for Bond #9, last row, indicates that there was a difference between Bond ##9. Bond #9 apparently contained a low magnesium Western bgeneral, low magnesium Western bentonites have higher hot st

important to point out that this does not suggest that high magnWestern bentonites are inferior. Many foundries use high magnWestern bentonites quite successfully, and even prefer them dushakeout. The point here is that these tests can be used to checformulations and raw bentonites for consistency as an incomintest.


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Figure 36 Figure 37 Figure 3

improve surface finish. The foundry then also decided to applyinstrument in their no-bake area as part of a continuing quality
http://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand41.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand40.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand39.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand38.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand37.jpghttp://c%7C/WEBSHARE/062013/magazine/2002_2/images/sand36.jpg


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Figure 44

st u e t t e o ba e a ea as pa t o a co t u g qua tyimprovement program.

Figure 46 shows another area in whichadvancements are being made in the arecontrol. Sieving has been the conventiocontrolling sand fineness, but it is widesieve analysis results are variable from

sieve stack, from technician to technicialaboratory to laboratory. This presents m

problems, especially when applied as anmaterial check between supplier and foToday, new technology utilizing photo-

particle size measurement is being introfoundry sand testing and control (Figurtechnology measures the particle diame


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News Briefs

MEETINGS

The World ADI Conference will be held on September 25-27at the Galt Hotel in Louisville, Kentucky.

The June 2003 meeting has not been scheduled yet.

There will be a Keith Millis Symposium on October 20-23, 2the Crowne Plaza Resort in Hilton Head Island South Carolina industry," said Jim White, director, Safety, Health, and EnviroGrede Foundries. "Undertaking the ISO 14001 process ac


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g pcountry demonstrates Grede's commitment to environstandards and to being good neighbors in the communities whoperate. "

ISO 14001 is an international standard that defines threquirements of an Environmental Management System, incluEnvironmental Policy, setting environmental objectives, ope

controls, management review, corrective action procedurecontinuous improvement.

Grede Foundries is an industry leader in developing wbeneficially reuse foundry byproducts, which avoids landfill dand conserves natural resources. The Company's byproduactively being used as construction fill and in materials asphalt and concrete most widely applied filters in North American iron fouCorning and Foseco will continue to refine product and app


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g p pptechnologies to further expand their use and the value delivour customers."

Steven P. Suttle, Vice President and General Manager, CEnvironmental Technologies, said, "We are extremely pleasedcan continue delivering a full range of premium-qualit

performance filters to customers in co-operation with our lon

North American distribution partner, Foseco."

Foseco Metallurgical Inc. of Cleveland Ohio is a memberworldwide group of Foseco companies that has provided innsolutions to foundries for the past 70 years.

Established in 1851, Corning Incorporated (www.cornincreates leading-edge technologies for the fastest-growing mar
http://www.corning.com/http://www.corning.com/


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ductile iron: 2002 Issue 2

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