DUCTILE IRON CASTINGS - SCOPE FOR ENGINEERING KNOWLEDGE. By C. R. STOFFBERG. """" """" l'"'" '"'''' '''''' "" """".vv-,,,"""" """" ro-.."",,',...

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1 DUCTILE IRON CASTINGS - SCOPE FOR ENGINEERING KNOWLEDGE By C. R. STOFFBERG Mineral-Ly C C - POBx 6285 Marshalltwn 217 Transvaal Abstract It was revealed at a series f "DesignEngineer Sympsia" that many Engineers in industry are prly infrmed abut the prperties and attributes f varius ferrus engineering materials nw available, especially f. In particular, Ductile irn are underutilised in Suth Africa cmpared with ther cuntries. The versatility f Ductile irn is shwn by its mechanical prperties and sme ptential sugar industry applicatins are mentined. The paper als describes a survey undertaken in the sugar industry and makes recmmendatins fr engineering material usage plicy. Intrductin Since its inventin in 1948, the versatile newclass f cast irn has been variusly knwn as Spheridal Graphite irn r SG irn, Ndular irn r Ductile irn. In this paper, the newlyrecmmended universal descriptin, Ductile irn, will be used. During the last 7 years, 26 Design Engineers' Sympsia have been arranged by Mineral-Ly C C. These were presented t Engineers respnsible fr material selectin in the Mtr Mining, SugarMilling and General Engineering sectrs f the ecnmy. The reasn behind the presentatin f these meetings, at which the physical and mechanical prpertiesand attributesf variusengineering materials are discussed, was the bservatin that manycmpnents prduced by the SuthAfrican Ferrus Fundry Industry were cast in materials r grades f materials nt best suitedecnmically r functinally fr the intended applicatin. It was als nticed that industry in general made use f welding and frging in prducing cmpnents that were mre suitable fr prductin in Ductile irn. Ductile irn, ne f the fastest grwing and ne f the mst widely used engineering materials, are nt receiving the same attentin in Suth Africa that they are in ther parts f the wrld. Meaningful cmparisns are difficult t btain but as an indicatin f the statement that Ductile irn is nt being usedt full ptential, the fllwing chart was prduced frm statistics btained frm the American Fundryman's Sciety as published in "Mdem Castings".' The tnnage f Ductile irn prduced per I tn f steel is shwn in Figure I. Ductileirn was nlydiscvered in the late 194's, almst simultaneusly by the British Cast Irn Research Assciatin and the Internatinal Nickel Cmpany. Since then the material has shwn phenmenal grwth as an engineering United Kingdm United States France W, Germany Japan Australia Taiwan Suth Africa Krea Mexic ","",..."r\.'''"".","" "",''J "'","'",",'l\.",'" '\."''\.'\.' '"""''\.'."'"" '\.l ""'" "''''.,,"",, :\.",'\.'\.'\.,",,,,,,, 1\."",,,, '"""'",'\.'\.,,, """'" '"'''''' :\.,,'" "'"'''"'''''' """" I:\.""'I,,"'"''\... L",",",'\...,""""."'\.J I",","'\.."'"'-,"\ N """" """" l'"'" '"'''' '''''' "" """".vv-,,,"""" """" r-.."",,',... Tns,5 1, 1,5 2, 2,5 3, 3,5 4, 4,5 5, Tnnage f Ductile Irn Castings prduced per I Tn f steel, FIGURE 1 The rati f Ductile Irn Casting Prductin vs Steel Casting Prductin in Varius Cuntries, 94

2 material. It is estimated that the current wrld prductin is in excess f eight millin tns per annum. Apprximately half f this prductin is accunted fr by the Ductile Irn Centrifugally Cast Pipe prducers. Of the balance, apprximately 35 %finds its way int the autmtive industry and the rest int a multitude f engineering industries which include mining, agriculture, paper making, cement manufacture, earth mving and sugar milling. The reasn fr this rapid grwth and wide acceptance f Ductile irn can nly be ascribed t functinal suit- 14, 12, 1, 8, ir: f- 1,6 :l..j 1,4 1,2 f= U ::J c 1, p::..,8,6,4, YEAR Ferrus Castings Ductile Irn (Excluding Pipe) Cast Steel U.K. Ductile Irn (Exc!. Pipe) FIGURE 2 Prductin f ferrus in Eurpe ability and f curse, ecnmics. It has cmpeted successfully against fabricatins, frgings, steel and malleable irn in sme f the mst cmpetitive industries in the wrld. The use f Ductile irn cmpared with ther cast materials in Eurpe is shwn in Figure 2. 2 The versatility f Ductile irn The ability t be easily cast int cmplex shapes and varying sectin sizes within anyne cmpnent can be said t be ne f the biggest assets f Ductile irn. The functin f several cmpnents can be cmbined int ne cmpnent due t the castability f the material. Ductile irn affrds the Designer maximum freedm f design and the ability t distribute evenly the stresses encuntered during service. Table I cmpares sme prperties f Ductile irn with thse f ther ferrus engineering materials:- The prperties f Standard Ductile and Grey irn, unlike all the ther materials in Table I, can be btained in the as-cast cnditin. In ther wrds n heat treatment is necessary. The five mst ppularly specified grades f Ductile irn can be prduced either unallyed r thrugh allying with small amunts f cpper. Fr all practical purpses, Ductile irn can be described as steel with graphite spherids dispersed thrughut. It is largely this graphite that accunts fr the superir castability and machinability that Ductile irn enjys when cmpared with steel. Ductile irn can seldm cmpete with steel when welding is required. Ductile irn can vary in size frm a few grams t the present wrld recrd f 2 tns. Why is Ductile irn apparently nt being used t its full ptential in Suth Africa? In rder t try t answer this questin, it was decided t persnally cnduct a number f surveys in varius industries. The sugar milling industry was selected first and the survey cnducted at chief engineer level r abve n the use f varius engineering materials. Findings frm the survey The general preferences f respndents are shwn in Figure 3. Table 1 Prperties f sme Ferrus Engineering Materials Irn Steel Ductile Grey Malleable Cast Frged ASTM Specificatin A.DJ. Standard - A536 A48 A2 A27 A29,A-D Ultimate Tensile Strength (MPa) Yield Strength (MPa) % Elngatin Hardness (HBN)

3 ... '" 9 7 c: 6 CIJ " c c. 5 CIJ... '" 4?f _-:2nd CHOICE-_ Steel Grey irn Mild steel Ductile fabricatins irn Brnze FIGURE 3 Preferred material fr prductin f parts and cmpnents, Brnze Ductile Grey irn Steel Mild 'steel irn frgings The degree t which respndents were cnversant with the prperties f the different materials is depicted in Figure 4. Respndents were asked:- Based n yur experience with and/r perceptins f steel fabricatins, rank it in terms f the fllwing cnsideratins: Mechanical prperties; Physical prperties; Chemical prperties; Machinability; Weldability; Familiarity; Weight f part; Cnfidence in meeting specificatins; Cst. Their replies are depicted in Figure 5. In answer t the same questin, but asking fr the rankings in respect f Ductile irn, 73 % failed t cmplete the questin due t lack f knwledge f the material. The materials used at present fr nine cmmn sugar mill items are shwn in Table 2. Other ptential large scale applicatins are chain links, casings, gears, cnveyr slats and wear pads. Varius grades fductile irn culd perhaps prvidethe mst cst effective material fr sme f these applicatins, if engineers were mre cnversant with its prperties. This unfamiliarity is nt unique t the sugar milling industry. With the exceptin f a survey in the autmtive industry, it is strngly suspected that all ur surveys will shw a similar picture. Again this is nt unique t Suth -",=".".,,= _ f/l... c Q) " cc. f/l _-_NO FAMILIARITY:"'-_- FIGURE 4 Steel Brnze Grey irn Steel Mild fabricatins frgings steel 96 Ductile Allyed irn steel Ceramics AD!.

4 FIGURE 5 Cnfidence Cst Mechanical Weldabil- in meeing Familiarity prperties ity specificatin Machinability Physical prperties Chemical prperties Weight f part Africa: a survey cnducted in the United States in all industries excluding autmtive and pipe manufacture, shwed a very similar respnse frm design engineers.. Table 2 Sme materials currently used in the Sugar Milling Industry Shredder Hammers Mill Pinins Cupling Bx Millrll Shell Trash Plates Scrapers % % % % Steel Grey Ductile Spec. Unknwn Recmmendatins All existing specificatins shuld be examined by a materials engineer and recmmendatins shuld be made as t their suitability fr the functin t be perfrmed. Specificatins shuld be drawn up fr thse cmpnents that d nt have a specificatin. The industry, the grups r the individual mills shuld cnsider either in-huse r externally appinted quality cntrl inspectrs wh visit the fundries and ensure adherence t the specificatins. Nn destructive examinatin (NDE) techniques shuld be cnsidered fr applicatin n certain. The grups r individual mills shuld establish "An apprved suppliers list" with the assistance f a suitably qualified Engineer. Life cycle csting shuld be intrduced. This is an ecnmic assessment f cmpeting alternatives taking int accunt all significant csts ver the ecnmic life feach alternative as illustrated in Figure 6. Cane Knife Palm Grate Bars Grate Shes 12,5 5 37,5 62, What is t be dne? Design Engineers' Sympsia will cntinue t be run and staff fthe fundries will be encuraged t make mre cntact with engineers than they have dne in the past. A bklet is being prduced fr the sugar mill engineer. The bklet will cver principles f irn casting design, specificatins, physical and mechanical prperties f varius grades firns which can be cmpared with ther cast r frged ferrus materials ' 14 a: Mild steel system - a{ 4,a needs rfpracement R87.1 Mild steel IR55.35J- R Savings start ere..1.': ""R"7J.82 IR58.84J IR a{ 4,a Stainless steel R95,4 6 R6276 IR95,41 Purchase date year years years years years NB: Figures in brackets shw net present value (ie. R value at time f purchase] FIGURE 6 97

5 Prceedings fthe Suth African Sugar Technlgists' Assciatin - June 1987 When designing a new cmpnent r switching frm ne material t anther fr an existing cmpnent, the designer shuld invlve the technical department fa fundry n the apprved list f suppliers. These recmmendatins, if fllwed, will resultin the use f the mst apprpriate and cst effective material fr each applicatin. This in turn will result in savings in time and mney. Acknwledgements The authr wuld like t thank the QIT-Fer et Titane Technical Team fr all the assistance received in cnducting the Designers Sympsia and fr the knwledge gained ver the years. REfERENCES I. MdemCastings, December Page Wrld casting tnnages. 2. BritishCast Irn Research Assciatin Cnference entitled,ductile Ir>n - The Next 4 Years: KJ Smith and J Mrrisn, Tayfrth Fundnes Limited, Cst effective substitutin f steel cmpnents by Ductile irn. 98