Scholars' Mine Masters Theses Student Theses and Dissertations 1964 Investigation of inoculant effect on cast iron Darrell W. Donis Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Metallurgy Commons Department: Recommended Citation Donis, Darrell W., "Investigation of inoculant effect on cast iron" (1964). Masters Theses. 6974. https://scholarsmine.mst.edu/masters_theses/6974 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. INVESTIGATION OF INOCULANT EFFECT ON CAST IRON BY DARRELL W. DONIS A THESIS submitted to the faculty of the UNIVERSITY OF MISSOURI AT ROLLA in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE IN METALLURGICAL ENGINEERING Rolla, Missouri 1964 Approved by ·. : ii ABSTRACT An assumption was made that extensive holding time of an inoculated g r ay iron melt would result in a loss of physical pr operties of castings poured from this melt. This theory was examined in both a literature search and by testing and conclusions drawn from these findings are presented and discussed. Although there is a great deal of data available which discusses inoculan ts and their effects, very little me n­ tion is made of the effect of holding time in any of thts material. The results i ndicate that holding time is of considerable importance when dealing with inoculated iron, and that calcium silicon inocul ant is a very effective inoculant when used properly. It was also shown that the size of the inoculant used has a great deal to do with obtaining desired results in ~ray iron castings . iii_ ACKNOWLEDGEMENT The author wishes to express his appreciation to Carondelet Foundry Company of St. Louis and Mr. John Lodenkamper, Metallurgist at Carondelet, for their assistance and guidance in choosing a subject for this thesis and in aiding in the accumulation of data used in the thesis. Thanks also go to the production crew at Carondelet for their assistance in pouring iron samples. The au.thor also wishes to thank Professor R. 'V. Wolf for his able advice and assistance. iv TABLE OF CONTENTS PAGE List of Figure.s • • • v List of Tables • • • • vii r. Introduction l II. Review of Literature • 2 A. Discussion of Inoculation Theories 2 B. Conside ration of Fl ake Structure • • • 5 c. S olidifica tion o f the Melt • • 9 D. Cooling Rates and Undercooling . 10 E. Cell Sizes 13 F . Inoculation Classification • • • • • 19 G. Fade Effect • 24 I II. Experimental Procedure and Results • 27 Teat Series l • 28 Test Series 2 • • • • • • • 34 Test Serie s 3 • • • 41 Test Series 4 • • 47 Teat Seri es 5 • • • • • • • • • • • • • 55 I V. Discussion of Results • • • • • • • • • 65 v. Conclusions • • • • • • • • • • 67 Bibliography • • • • • • • • • • • • • 68 Vita • • • • • • • • • • • • • • • • • • • • • 70 v LIST OF FIGURES FIGURE PAGE 1. Type A Graphite Flakes • . • • 6 2 . Type B Graphite Flakes • . • • • • • • • • • • 6 3· Type C Graphite Flakes • • • • • • • • • • • • • 7 4. Type D Graphite Flakes •• • • • • • • • • • • • • • 7 5· Type E Graphit e Flakes ••••••• • • • • • • • • 7 6. Low, Moderate, and High Cooling Rates • • • • • • • 12 7 • Physical Transformations and Graphite Flake Formation • . 12 8. Flake Sizes Resulting From Different Cooling Rates • 12 9. Eutectic Cells vs. %Carbon Eouivalence For Inoc- ulated and Uninoculated Samples •••• • • 18 10. Tensile Strength vs. Carbon Equivalence For Inoc- ulatea and Uninoculated Samples • • . • • • . • 18 11. Dimensions of Keel Block Casting . • . 33 12. Microstructure of Sample 2-Center • • • • • • . 35 13. Microstructure of Sample 5-Center • . • • • . • • • 35 14. Microstructure of Sample 26-Center • • • • • • • • • ·39 15. Microstructure of Sample 26-Edge • . • • . • • • • . ·39 16. Microstructure of Sample 28-Center . • • • • .40 17. Microstructure of Sample 28-Edge . • • • • • • • • • .40 18. ~icrostructure of Sample 30-Center . • . • . • • • • .48 U-9. Micrdstru cture of :S a,mple 30-Edge • • • • • • • • .48 vi FIGURE PAG E 20. Microstru cture of Sample 31- Cent er . 49 2l. Micros tructure of Sample 31-Edge . 49 22 . Microstructure of Sample 32-Center . • . 50 23. Mi cros tructure of Sample ? 2-Edge . • . 50 24. Micros tructure of Sample oo-Center . 53 25 . Mic rostructure of Sample 90-Edge . • • • . 53 26. Mic r ostructure of Sample 92-Center . 54 27. Microstructure of Sample 92-Edge . 54 28 . Tensil e Strength vs. Holding Time , Series 40 . 60 29. Tensile Strength vs . Holding Time , Series 50 . 60 30. Microstructure of Sample 40-Center • . 61 31. Microstructure of Sample 41-Center . 61 32. Microstructure of Sample 42- Center • • • • . • • . 62 3.3 . Microstructure of Sample 43-Center- . • . • • . • • 62 34. Mi crostructure of Sampl e ')2- Center . • • • • • • • . 63 35. Microstructure of Sample 53-Center . • • • • • . 63 vii LIST OF 'I'ABLES TABLE PAGE I. Experimental Data, Inoculant Addit i on and Cell Size • • 15 !I. Experimental Da t a , Comparison of Calcium Sil icon and Ferrosilicon • . .. .22 III . Experimental Resul ts, Evaluation of Inoculants • .25 IV. Experimental Results, Test Series l ••••• • •••• 29 V. Evaluations Concerning Test Series l • • • • • • • • • • 32 VI. Experimental Resul ts, Test Series 2 • • • • . 37 VII. Experimental Result s , Test S eries 3 . • • • • . 43 VIII.Experiment a l Results , Tes t Series 4 . • • • . • . • 52 IX. Experimental Results, Test Series 5 • . • • • • . • . 57 1 I . IN ~ RODU CTIO N The original pro j ect outline was t o eval uate Cla ss 2 4 ~ray iron with r e s pect to microstructure after i noc ulation with c alcium s ilicon, 8 5% ferrosilicon, or silicon- manganese- zirconium ~ o mm er cia l inoculant . The inoculants we re to be added s i n~ly and the eff e cts of f ade time were to be studied clos ely . There a r e many theories a s sociat ed with i noculatio n procedure and r esulting phenomena. A brief discussi on mip·ht he lp t o expla i n s ome o f thes e theorie s as we ll as the a dvis ability of using, to best adv ~ ntage, certain i noc ulante . As a result o f this prelimi nary work , the outlinin ~ of plans f or a ctua l sampl e pourin~ wa s mu c h simplified . The f ollo wing section c ont ains inf ormation on i noculation t e chniques . This section i s the n f o llowed by a c ompl e t e d iscussion ana evaluation of experimenta l work. 2 II . REVI EW OF LITERATURE A. Discussion o f Inocul ation Theories: A good definition o f i noc ulation , as presented by R. A. Clark , is: "A ~roce ss i n which an addition is made to mol t en cast iron for the purpose o f a lter i ng or modifying the microstructure o f the iron and thereby i mproving the mechanica l and physical properties to a degree not explainable on the basis of a change in c omposition . 111 The me chanicAl and physical properti es men tioned i n the definition i nc lude t he f o ll ow in~ list of pos s i bilities f or i mprove­ ment: a ) r e duction in chi lling tendencies on edges of thin c asting sections in s o ft gray iron , b ) con trolling chill on hi~h er strength l ow carbon e quivalen t iron, c) ov oro om i n~ variations i n melting practice t o produce a mo re uni f o r m produc t , and d ) imp rovement o f t ensile stren~th and the ha rdness to tensile strength ratio. Le t u s t hen loo ~ at several of the i noculation theorie s t hat a r e mo st wi del y accepted. Sil icate- S lime Theory: The addition o f silicon produc es clouds o f nucl e i of sili ca 3 or silicates which nucleate solidificat~on to produce Type A 2 graphite. Gas Theory: Since silicon and other elements contained in the, inoculation alloys are deoxidizing agents, it is argued that the reduction -of the oxygen content produced by the addition effects the change in microstructure. Evidence is found that nitrogen and hydrogen are 2 also involved in graphite distribution. Undercooling Theory: Type D and Type E graphite irons, called abnormal irons, are a result of undercooling during solidification, and nucleation resulting from late additions prevents this undercooling and pro~ 2 duces desireable Type A graphite. Graphite Nuclei Theory: Particles act· as nuclei to begin graphitization. To form Type A graphite, flakes must form on nuc:lei distributed through the melt. When Type A or Type C graphite forms it is usually in the upper temper~ture regions. However, Type D and Type E graphite form because the iron solidified by passing through the temperature region of Type A without formation of Type A flakes and so graphite 4 forms in the lower temperature regions. This theory is substantiated by the fact that late additions of graphite to normally Type D o r Type E iron changes graphite 2 structure to Type A. Carbide Stability Theory: Changes in carbide stability affect the availability of carbon during flake formation and thereby influence flake size and shape . This theory is supported by the fact that inoculation is accompanied 2 by reduction in chilling tendency. Surface Tension or Surface Energy Theory: The inoculating agent influences size and shape of graphite particles by supplying or removing adsorbed substances from graph­ 2 ite- metal interfaces. Degasification Theory: Reactions of degasification may produce inoculation by 1) elim­ i nation of chill-forming gases and 2) formation of inclusions in the melt which act as effective nuclei formers.3 None of the foregoing can explain all observations which have been recorded, but most are reasonable and merit consideration.