Solidification Structures and Continuous Casting of Steel Revisited D. J. Hurtuk and A. A. Tzavaras
SUMMARY
Extensive investigations into the solidification structures of continuously cast steel demonstrate strong compositional effects, particularly by carbon and nickel. The columnar grain size first decreases with increasing carbon content, up to 0.10 C, then increases to a maximum at about 0.60% C, and then decreases again. Internal defects and surface characteristics change markedly also with carbon content and are affected by such operational variables as degree of superheat and electromagnetic stirring. The fundamental cause of the effect of carbon is the peritectic solidification; this is supported by very similar dependence of solidification structures on nickel content in iron-nickel alloys, where peritectic solidification also occurs. INTRODUCTION Recently, the large influence of solidification structures on the quality and properties of cast steel has been recognized but not fully understood. This influence is further complicated since solidification structures are rarely homogeneous in any kind of casting- small or large, ingot or continuously cast. The reasons for this inhomogeneity are themselves not well understood. In ingot casting, inhomogeneous solidification structures are somewhat controlled and overcome by inherently low cooling rates during solidificatioI]., large section sizes, and massive reductions which significantly reduce the anisotropy. In continuous casting, inhomogeneous solidification structures are more ofa challenge because of inherently high cooling rates, small section sizes, and small reductions. And, it is highly desirable to further decrease the amount of . reduction of continuously cast products for reasons of yield, energy, and capital cost benefits. Yet to accomplish this, the operative mechanisms causing the formation of inhomogeneous structures need to be understood and controlled. A well-known technique for controlling columnar dendritic growth and associated inhomogeneous problems has involved casting at low temperatures. Although this technique is frequently used out of necessity, it is unpopular with operating personnel since it restricts operating flexibility. And it can adversely affect other quality aspects especially in casting processes where fluid flow affects cleanliness and structures like continuous casting. Certain grades of steel appear to have a congenital problem in growing large columnar grains, 1 and efforts have been made by some to take special precautions when casting these grades if they cannot be avoided altogether. Yet, this is not a practical approach for a large integrated steel plant to take. The importance of at least knowing the particular type of behavior exhibited by the various grades of steel relative to dendritic growth need not be further justified. Of at least equal importance are methods by which the columnar dendritic structure can be controlled. An attempt will be made to describe the origins and point to the therapy of some problems related to the apparently innate large or small columnar dendritic zones in cast steel. Both internal and surface quality problems will be addressed. Due to present day interest, the emphasis of applying these basic results will be placed in the area of continuous casting where the need is greater, the application is easier, and the consequences may be larger than in ingot casting. It must be 40
stated, though, that the principles of solidification discussed in this paper relate f:)qually as well to ingot casting and are equally as valid. LITERATURE Dendrites have been observed since 1868,2 but it was B. Chalmers and his associates that have established the basic principles ofthe theory for dendritic growth,3,4 the concept of constitutional supercooling,5 and the well-known criterion for the transition from cellular to cellular dendritic solidification structures6
where G is thermal gradient in the liquid, R is the growth rate of the solid, Co is the solute content, ko is the equilibrium distribution coefficient, and A is a constant. The available literature, dealing with the transition from cellular dendritic to equiaxed solidification structure, suggests a strong dependence of this transition on the growth rate of solid (R) and the temperature gradient in the liquid (G). However, no widely accepted criterion exists for this transition, even though some very interesting mechanisms have been proposed by Burden and Hunt 7 which explain the abrupt changes in structures observed in castings. This transition is important because the inhomogeneity encountered in continuous casting stems from the formation of large columnar dendrites which sometimes grow all the way to the center of billets. In other words, the transition to equiaxed structure is either delayed or cancelled altogether. Many research efforts have been made in the past to increase homogeneity in castings by grain refinement,8 but continuous casting is not particularly suitable for application of conventional techniques such as ultrasonics or grain refiners 52r-----r-~_,r----,----_,----_.----_,
e e
0.4
0.8
1.2
1.6
2.0
2.4
CARBON, % Figure 1. Plots of laboratory data of columnar zone length against carbon concentration for 193 ingots of 8620 type steel.
JOURNAL OF METALS· February 1982
(AI or Ti). Electromagnetic stirring has been suggested to grain refine in continuous casting, that is to break the columnar dendrites and increase the size of the equiaxed zone. 9 This technique, although it has been shown to be very effective in breaking dendrites, is not free of problems stemming mostly from the fact that our fundamental knowledge on the effects of flow on growing solidification structures is very ljmited. lO These problems may become particularly annoying with some grades of steel that normally tend to produce large columnar dendrites,1 the refinement of which may require exceptionally intense stirring. Indeed, after it was established that most casting defects in continuously cast steel are related to large columnar dendritic zones,1 a specific effort was made to understand the reasons for this unusual behavior of steel and alloy steel. More specifically, an attempt was made to understand why increasing the concentration ofcarbon between 0.10 and 0.60% in iron base alloys increases rather than decreases (as one would expect on the basis ofthe concept of constitutional superco01ing) the size of the columnar grain growth. The unusual behavior ofthese alloys has been reported, incidentally, in the literature by other investigators.u However, it was never attempted to delineate fully or explain the observed phenomena.
46
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CARBON, % Figure 2. Plot of laboratory data of columnar zone length against carbon concentration tor Ingots of Fe-C alloys.
SOME BASIC FACTS AND THEIR SIGNIFICANCE IN CONTINUOUS CASTING Using an experimental apparatus described elsewhere, 1 a very extensive investigation was made on the relationship between the chemistry and the solidification structure in steels. After it was established that the ingots produced in the laboratory had solidification structures exhibiting similar characteristics and morphology to those produced in continuous casting, a large number of ingots were solidified under controlled conditions. Extensive measurements of pertinent parameters, such as columnar growth size, dendrite arm spacing, local solidification time, growth rate, temperature gradient, etc., were made on those ingots. The results of these measurements were. analyzed by various techniques, the detailed description of which is beyond the scope of this paper, intended to convey only some very useful basic facts and information. One of the most important facts established so far in this investigation is that steel, both plain and carbon, shows a very peculiar solidification behavior. This behavior is described in Figure 1 (data in Table I) which indicates that for steels that have an otherwise (except for the carbon content) 8620 composition there are a local minimum (at 0.10% C) and a local maximum (at 0.60% C) in the columnar growth size measurements when plotted as a function of carbon content. In other words, if the carbon content in an alloy steel with typical 8620 composition (0.55% Ni, 0.50% Cr, 0.20% Mo, .28% Si, 0.80% Mn, 0.04% P, and 0.03% S) varies between zero and 1.2% C, the columnar zone size first decreases (up to 0.10% C) then increases with at least two different rates along the way (up to 0.60% C), and finally it decreases again. It ia understood that this is so with all the other pertinent variables held constant. These changes are substantial, as the maximum columnar zone size appearing for approximately 0.60% C is more than 100% larger than the minimum, which occurs at 0.10% C, for all superheats. As expected, the size of the columnar growth is directly related to the superheat, but the shape of the curve remains the same at least within the tested area, that is between nco (20FO) and 67CO (120FO) (Figure 1). Similar behavior has been established for plain binary iron-carbon alloys as shown in Figure 2 (data in Tables II and III), except the observed effect (changes of columnar growth as a function of carbon content) has been found to be somewhat less intense (as expressed by the difference between the maximum and minimum sizes of the columnar growth). This means that the observed effect is likely to show up and have an effect on the properties of the casting to a substantially JOURNAL OF METALS· February 1982
Table I: Columnar Zone Length Measurements for Laboratory Ingots of 8~20 Type Steel with Various Carbon Contents·
Columnar Zone Length(mm) (Superheat) % Carbon
(20 FO)
(50 Fa)
0.05 0.06 0.10 0.16 0.20 0.22 0.30 0.50 0.57 0.70 0.90 1.2
16.1 17.2 12.4 16.3 18.4 17.0 16.7 15.0 21.8 22.9 21.8 18.5
18.4 20.7 15.1 22.2 24.5 21.1 23.7 22.8 30.9 29.5 27.4 23.7
(SO Fa)
20.7 24.3 17.7 28.1 30.6 29.2 30.7 ,30.5 40.0 36.3 33.0 28.9
(120 Fa)
23.9 29.1 21.3 36.0 38.5 37.2 40.1 40.7 52.0 45.1 40.4 35.9
• Approximately 15·20 ingots were cast at each carbon content.
Table II: Columnar Zone Measurements For Laboratory Ingots of Various Fe-C Alloys·
Columnar Zone Length (mm) (Superhe/lt) %C
(20 Fa)
(50 Fa)
(SO Fa)
(120 Fa)
0.05 0.10 0.20 0.30 0.40 0.51 0.60 0.70 0.80 1.0
18.1 16.3 18.6 17.2 18.3 21.8 22.4 22.5 19.6 16.0
21.5 19.0 21.9 21.8 23.7 26.8 27.5 27.0 24.3 21.0
24.9 21.7 25.2 26:3 29.0 31.7 32.8 31.5 28.9 25.9
29.5 25.3 29.5 32.4 36.2 38.3 39.8 37.6 35.0 32.4
• Approximately 15.20 ingots were cast at each carbon content.
41
greater extent in alloy steels, as compared to plain carbon steels. However, it should be emphasized that even in plain carbon steels, this effect is important enough to warrant the attention of people concerned with casting plain carbon steels.
Table III: Columnar Zone Measurements for Laboratory Ingots of Various Fe-C Alloys'
Liquidus Temperature, %C 0.02 0.03 0.04 0.06 0.08 0.10 0.15 0.17 0.22 0.25 0.30 0.35 0.56 0.59 0.60 0.60 0.70 0.90
of
2795 2794 2792 2787 2784 2782 2778 2775 2767 2762 275&2750 2720 2716 2715 2715 2704 2680
Casting Temperature,
Superheat,
2872 2868 2861 2869 2880 2866 2862 2856 2845 2842 2839 2814 2788 2786 2795 2790 2778 2763
77 74 69 82 96 84 84 81 78 80 83 64 68 70 80 75 74 83
of
FO
Columnar Length, mm 30 28 27 26 24 21 26 24 26 27 27 28 35 38 41 36 30 29
*These ingots were cast at approximately 80°F (44"C) superheat in addition to those listed in Table II.
Table IV: Columnar Zone Measurements for Laboratory Ingots of Various Fe-Ni Alloys
liquidus Temperature,
Superheat
%Ni
OF
Casting Temperature,
Columnar Length, 10m
0.2 0.5 0.5 1.0 1.5 2.0 2.0 3.0 3.0 3.0 3.4 34 4.0 4.0 4.0 4.0 4.5 4.7 4.7 4.7 4.7 4.7
2796 2794 2794 2792 2788 2782 2782 2777 2777 2777 2775 2775 2771 2771 2771 2771 2769 2767 2767 2767 2767 2767
2895 2870 2865 2863 2858 2840 2826 2848 2829 2827 2852 2845 2840 2838 2836 2836 2832 2861 3860 2859 2842 2839
99 76
45 43 39 31 37 35 30 34 34 32 32 22 34 27 30 29 30 38 32 34 33 32
42
of
FO
71 71
70 58 44 71 52 50 77 70 69 67 65 65 63 94 93 92 75 72
The peculiar behavior of iron base alloys mentioned above appears to be strongly related to the peritectic reaction in the iron-carbon alloys (even though there is ample evidence to show that other iron base alloys containing no carbon exhibit the same peculiar behavior as long as there is a peritectic reaction involved in their solidification). Indeed, as Figure 3 shows, the observed minimum in the columnar growth size versus carbon content coincides with the beginning of the peritectic reaction, whereas the observed maximum in columnar growth occurs at the end of the peritectic reaction. As stated before, this is not mere coincidence, as similar correlations have been found in other alloy systems. 12 Indeed, the iron-nickel system, as shown in Figure 4 (data in Table IV), exhibits similar columnar zone size behavior as that of the iron~carbon system except in a more intense fashion, since the maximum in columnar zone size in the Fe-Ni system is nearly 400% larger than the minimum. The implication is quite obvious: Ni-containing stainless steels are not immune and should be expected to present problems similar to those of plain and alloy steels when cast continuously if a peritectic reaction is involved. The basic effect in this peritectic reaction, as far as solidification of steels is concerned, is the 0 to 'Y transformation which is well known to be associated with substantial shrinkage since the 'Y phase is significantly more dense than the 0 phase. 13 ,14 The liquid phase in the peritectic reaction plays a very minor role, as far as final shrinkage, because the liquid phase can accommodate volume changes as long as feeding can be secured. On the contrary, the 0 - 'Y transformation affects substantially the final solid structures as it may introduce not only elastic but plastic deformations as well. To verify and support the data mentioned earlier in Figures 1, 2 and 3, pertinent heat flux measurements were made and compared with published data of other investigators.1 5 A sample from this comparison is shown in Figure 5. It is evident from this figure that there is very good agreement between the two sets of data. This view is further supported by other comparisons including dendrite spacings mentioned elsewhere. 12 Finally, on the basis ofthe information discussed above, it is evident that the morphology and size of the mushy zone developed during solidification of various grades of steel should change according to the carbon and other alloying element content of steel. This, in turn, must have a very significant effect both on the properties of the final product as well as the solidification behavior of these steels. Indeed, it has been known to at least some continuous casting operators that &teels with more than 0.40% C content can sometimes present severe internal quality problems when cast continuously, like ghost lines, pipe, segregation, etc. Low carbon steels, on the other hand, present mostly surface problems. Another very important deduction from this observation is that the refinement through the multiplication mechanism should operate with various degrees of efficiency for the different grades of steel. This is extremely important in the application of EMS (electromagnetic stirring) in continuous casting (which is very popular outside the U.S.A., witnessed by the numerous reports published in the last two years in the Transactions of the Iron and Steel Institute of Japantoo many in fact to be referenced individually). It is quite evident that the velocity of the liquid, which has been shown to be one of the major factors influencing refinement with EMS, should be adjusted according to carbon content if the efficiency of stirring is to be maintained anywhere close to constant.
SOME WELL-BASED AND SOME NOT-SO-WELL-BASED OPINIONS To summarize the previous discussion, steel grades in general can be placed in three categories. The first category includes grades with 0.08-.12% C content. These grades solidJOURNAL OF METALS· February 1982
ify with a rather short columnar zone, show no major internal problems, but exhibit an as-cast surface characterized by roughness and high-temperature oxidation. The second category includes grades containing approximately 0.50% C or slightly more. These grades produce long columnar zones (more than 100% larger than that in the first category), are usually associated with internal problems (segregation, pipe, ghost lines, rhomboidity), but exhibit a rather smooth surface, oxidized but not as much as the first category. Grades with carbon content between 0.12 and 0.50% C, without being totally free of internal or external defects, are normally the easiest to cast continuously. It is understood that this being a general statement, there may be some exceptions which do not change the general picture. It is also understood that resulfurized grades or grades with special additives are not included in this classification and general statement about it. It is the opinion ofthese authors that this behavior is the resulLof an interplay between the o--''Y solid state transformation on one hand, and the peritectic reaction 0 + L-+- 'Yon the other, during solidification. Other investigators have suggested 15 ,16 that at 0.10% C a minimum occurs in heat flow from strand to mold, because at this composition, the air gap between the mold and the strand is maximum. This maximum occurs at this composition because the 0 - . 'Y transformation for this composition occurs at the maximum possible temperature. Therefore, the deformations caused by the 0--' 'Y reaction tend to be plastic rather than elastic (as the case would be for nearly pure iron, for instance). Thus, the first skin of the strand to form wrinkles in the most severe fashion for this composition, the air gap becomes largest, and the heat flow is minimized. This explanation is well based on facts and theory, and it justifies the observed surface roughness of steel grades with 0.10% C contents. The rather undesirable sequence of events described above can hardly be changed if some degree of solidification is to take place in a physical mold (even though a high conductivity low melting slag may reduce the air gap and thus the surface roughness). The only medicine the steelmaking engineer can use is to avoid the 0.10% C composition if this surface problem becomes unacceptable. Fortunately, the above mentioned minimum for heat flow (maximum air gap and deformation) occurs over an extremely narrow range of compositions around 0.10% C and thus shifting to 0.08% or 0.12% C may reduce the problem substantially. Caution is to be added here, however, as the beginning of the peritectic reaction is not dependent on carbon content only; therefore, the overall composition of the charge has to be taken into account in deciding the amount and direction of the shifting that should be attempted in each case. Experience, of course, is always invaluable in these situations. For grades of steel with more than 0.12% but less than 0.50% C content, the problem of shrinkage (and the ensuing casting defects) becomes less objectionable as the concentration of carbon increases. Indeed, simple lever rule considerations would indicate that the amount of /) phase transforming to austenite decreases as the carbon content increases, and there(ore, the deformation associated with this solid phase changes, tt:ecreases accordingly. The more liquid transforms directly to ,,/, the less warping of the skin of the strand is to be expected as long as the liquid can feed the shrinkage (which is no problem at this early stage offreezing the strand). As more and more 'Y forms directly from the liquid and the air gap diminishes, (and the surface problem takes care of itself), another problem starts to appear, that is, an internal problem this time. Indeed a good surface, small air gap and, therefore, less inhibited heat flow help to increase the size of columnar growth. In fact, when the 0 phase ceases to be a factor in the solidification process, i.e., when all or nearly all liquid transforms directly to austenite, the rate controlling process is not heat flow through the air gap any more. Thus, the type of solid growth that occurs depends on superheat and the carbon content. Superheat has been known to proJOURNAL OF METALS· February 1982
CARBON ATOMIC % 2
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NICKEL, % Figure 4a. Plot of laboratory data of columnar zone length against nickel concentration tor 55 ingots of Fe-Ni alloys. NICKEL ATOMIC, % 0
5
10
20
15
2800 1520 L
1500 1480
2700
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NICKEL, WT % Figure 4b. Fe-Ni equilibrium phase diagram.
mote columnar growth, but at these rather high levels of carbon, segregation and centerline shrinkage caused by excessive columnar growth (sometimes all the way to the center of the casting) can make the casting unacceptable, as they are usually associated with other defects such as rhomboidity, internal cracks, etc. Caster operators are familiar with the internal problems associated with steel grades containing 0.50% carbon or more. Now, however, it is evident that these problems are related to the large columnar growth that is innate in these grades (Figure 1), and also that the worst problems are associated with a rather narrow composition spectrum approximately 0.60% to 0.80% carbon (not as narrow a spectrum as around
43
the 0.10% C mentioned earlier). Similar problems are to be expected for iron-nickel alloys with 5-7% nickel content as Figure 4 would indicate. For the above mentioned problematic grades of steel there are a few remedies the operator may try ifhe has to cast them continuously. Lowering the superheat is a well-known road, but as discussed earlier, at times these are undesirable side effects. Decreasing the cooling rate (spray water) particularly at the early stages of solidification (that is, before the solid shell is one inch thic\<.) may help cure some of the symptoms, but not the disease. (It goes without debate that strand alignment is an absolute must with these grades.) As explained earlier, the rate controlling process for solid growth morphology (in continuous casting) of these grades appears to occur at the solid-liquid interface. Therefore, if a remedy is to be applied, it has to be applied at the solid-liquid interface to be effective. This means that the growth conditions at the solid-liquid interface have to be changed significantly. There is only one method to change drastically and effectively the growth conditions at the solid-liquid interface in continuous casting: EMS. Application of EMS (electromagnetic stirring) has been shown to help in a variety of problems in continuous casting; however, its application in continuous casting of these grades appears to be most appropriate, because the high amount of carbon content induces severe microsegregation and macrosegregation problems-in addition to the problems of large columnar dendrites. It is true that EMS can cause the so-called "picture frame" effect,IO which appears more intense with these grades; however, this problem can be handled if the appropriate type of stirring is applied,I7 as it stems mostly from discontinuities in the flow patterns rather than the flow itself. The above thesis is equally applicable for stainless steel containing 5-7% nickel which also exhibits a peritectic reaction for these nickel compositions. This thesis is not the only one in the literature regarding these aspects ofthe solidification ofsteel. Recently an attempt has been made to show that phosphorus content and phosphorus microsegregation, or rather the absence of it, is the villain for the reduced heat flow and warped surface of steel grades containing 0.10% carbon. 18 After computing the phosphorus concentration in the liquid (CPL ) at the last or nearly last liquid to solidify, it was pointed out that CPL had a minimum at 0.10% C which was related somehow to a minimum in the solidus temperature for this alloy (Figure 6). On the
160 ....----r----.----r----,.----,----,
'"~ ~ 1201---+----+----+---+----1-----1 :IE 'SINGH a BLAZEK :::> CONTINUOUS CASTING DATA
....ID
basis of these computations, it is suggested that steels containing 0.10% C carbon solidify with difficult to deform skin which once deformed by shrinkage stay deformed thus increating the air gap and reducing the heat flow. On the other hand, steels with 0.20% C content form a skin which, even if it is deformed by the O~ 'Y transformation, can be easily pushed back by the ferrostatic pressure, thus, the air gap reduces in size and the heat flow is restored. Although it is difficult to understand why P can do all these things that the above mentioned computations accuse it of doing (when it is well known that carbon is a stronger solidus temperature depressant than phosphorus), a simple test of this thesis is the examination of the solidification behavior of an iron base peritectic alloy system containing no phosphorus. Such a system is the Fe-Ni system, and its solidification behavior has been investigated as shown in Figure 4. These data clearly indicate that phosphorus is not a necessary ingredient (for the peritectic reaction of iron base alloys) in order to show a minimum in heat flow at the beginning of the peritectic range and a maximum at the end of it. Needless to say, plain Fe-C alloys containing no phosphorus also follow the same pattern. 12 One can hardly avoid thinking once more that computer results may not be trusted without a test as they are as good as the data fed into the computer, at best.
CLOSING REMARKS The direct control of the solidification process, at the solidliquid interface, for many years appeared to be beyond the human reach. There are signs now that this can be done with the use of Lorentz forces and the relevant electronic hardware. When this is accomplished, the quality of the castings produced will increase greatly. Continuous casting appears the most likely candidate for application of such modern technology. Indeed, the advent of continuous casting made available a large number of possible controls for the solidification of steels that were not available before. However, so far, we have learned to use very few of them effectively as we are missing a lot of essential information regarding the fashion with which the different grades of steel solidify. There is reason to believe that it is worth trying to master this knowledge as the dividends appear to be very large. Unfortunately, the process of acquiring this knowledge is closely related to
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TI ME AFTER TEEM, SEC
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C - CONTENT (WT %) Figure 5. Heat transfer data against time after teeming for experimental Ingots of 8620 type steel with 0.10% C from the present Investigation and for continuously cast steel with 0.10% C from Singh and Blazek.ls
44
Figure 6. Influence of C-content on a) calculated P-concentration, CPL, at f.=0.99, and b) temperature difference between Fe-C equilibrium solidus, Ta, due to P-segregation (Co=0.040 wt. % P, t= 1.0 s) (From Wolf and Kurz I8).
JOURNAL OF METALS· February 1982
long and tedious experiments, but we have no other alternative. The name of the new game is quality.
ABOUT THE AUTHORS
References 1. D. J. Hurtuk, A. A. Tzavaras, "Aberrations Observed in the Relationship of Dendrite
Size·AlIoying Elements for Low Alloy Steel ," in Solidification alld Casting of Metals. Metals Society, London, 1979, p. 21. 2. C. S. Smith, "History of Metallography," University of Chicago Press 11960 1. 3. F. Weinberg, B. Chalmers, "Dendritic Growth in Lead," Canadian Journal of Phys· ics, 29 (1951), p. 382. 4. Ibid., 30, (1952), p. 488. 5. J. W. Rutter, B. Chalmers, "A Prismatic Substructure Formed During Solidification of Metals," Canadian Journal of Physics, 31, 119531, p. 15. 6. E. Holmes,J. W. Rutter, W. C. Winegard. "Growth Conditions for Stabilityofa Cellular Solid.Liquid Interface," Canadian Journal of Physics, 35, 119571, p. 1223. 7. M. H. Burden, J. D. Hunt, "A Mechanism for the Columnar to Equiaxed Transi tion in Castings or Ingots," Met. Trans., 66, (1975), p. 240. 8. J. P. Wallace, "Grain Refinement - A General Review ," Journal of Metals, 15 151. May 1963, p. 372. 9. W. Poppmeier, B. Tarmann, O. Schraber, "Alternating Electromagnetic Fields in the Continuous Casting of Steel," Journal of Metals, 18 (10), October 1966, p. 1109. 10. D. J. Hurtuk, A. A. Tzavaras, "Some Effects of Controlled Fluid Flow on Macrosegregation in Continuously Cast Steel," Met. Trans., 8, 11977), p. 243. 11. H. Fredriksson, L. Hellner, "The Influence of Carbon on the Segregation of Chromium in Steel," Scandinavian Journal of Metallurgy, 3, 119741. p. 61. 12. D. J. Hurtuk, "Factors Influencing Steel Solidification Structures." PhD Thesis. Case Western Reserve University, January 1981. 13. P. J. Wray, "Volume Change Accompanying Solidification." Met. Trans., 5, I19741. p. 2602. 14. A. A. Vertman, E. S. Filipov, A. M. Samarin. "Density of Iron Alloys With Carbon in Solid and Liquid States," Izv. Chern. Metal, 7, 119641. p. 19. 15. S. N. Singh, K. E. Blazek, "Heat Transfer and Skin Formation in a Continuous Casting Mold as a Function of Steel Carbon Content." Journal of Metals, 26. I 101. October 1974, p. 17. 16. A. Grill, J. K. Brimacombe, "Influence of Carbon Content on the Rate of Heat Extrac· tion in the Mold of a Continuous Casting Machine," Ironmaking and Steelmaking, 140. 11976), p. 76. 17. A. A. Tzavaras, R. E. Ryan, "Apparatus for Application of Limited Induction Stirring in a Continuous Casting Machine," U.s. Patent 3995678. 18. M. Wolf, W. Kurz, "The Effect of Carbon on Solidification of Steel in the Continuous Casting Mold," Met. Trans., 12B, (j9811, p. 85.
Donald J. Hurtuk, Section Chief, Solidification Research, Republic Steel Corporation, Research Center, 6801 Brecksville Road, P.O. Box 7806, Independence, Ohio 44131. Dr. Hurtuk received a BS, MS, and PhD in metallurgy from Case Western Reserve University. He has been with Republic Steel Research for over eight years, where he is presently co-chairman, Corporate Mold Committee as well as section chief, Solidification Research . He is author of numerous technical papers. Alexander A. Tzavaras, Professor, Aristotelian University, Salonika, Greece. Dr. Tzavaras received his diploma from Athens Technical University in 1959, MS in metallurgy from Massachusetts Institute of Technology in 1963, and PhD in metallurgy from Case Western Reserve University in 1970. He worked for 10 years in the steel industry, at the Republic Steel Research Center, prior to taking his present position as professor of Physical Metallurgy at Aristotelian University.
(Continued from page 29) August 1-7,1982: XVII Convention of the Pan American Federation of Engineering Associations; San Juan, Puerto Rico. Contact Mrs. Pelsi Zachmann, ASCE, 345 East 47th Street, New York,New York 10017; telephone (212) 644-2193. August 9-12,1982: International Conference on Martensitic Transformations: Leuven, Belgium. Topics will include fundamental studies of martensitic and bainitic transformations in metallic and non-metallic materials; physical and mechanical properties relevant to the understanding of martensitic transformation; and application. Contact 1;. Lelaey, Departement Metaalkunde, Katholieke Universiteit Leuven, de Croylaan 2, B-3030 Heverlee, Belgium. August 16-20, 1982: 6th International Conference on the Strength of Metals and Alloys; Melbourne, Australia. The meeting will focus on advances in understanding the mechanical properties of metals and alloys. Contact R. Hobbs, Conference Secretary, c/o Australasian Institute of Metals, 191 Royal Parade, Parkville, Vic. 3052, Australia. August 29 - September 1,1982: 21st Annual Conference of the Metallurgical Society of CIM and the 12th Annual Hydrometallurgical Meeting; Toronto, Canada; Royal York Hotel. JOURNAL OF METALS· February 1982
Contact The Canadian Institute of Mining and Metallurgy, Suite 400, 1130 Sherbrook St. West, Montreal, Canada H3A 2M8; telephone (514) 842-3461. September 22-24,1982: The 4th European Fracture Conference; Leoben, Austria; Montanuniversitat. Contact K. Maurer, Montanuniversitat, Institut fur Metallkunde und Werkstofij:lImung, Leoben, Austria, telephone (03842) 42555-431. September 29-0ctober 2,1982: Materials in Nuclear Energy; Huntsville, Ontario, Canada, Hidden Valley Inn. Contact D.O. Northwood, Dept. of Engineering Materials, University of Windsor, Windsor, Ontario, Canada N9B 3P4, telephone (519) 253-4232, ext. 343/486; or George J. Field, Nuclear System Department, Ontario Hydro, 700 University Avenue, Toronto, Ontario, Canada, telephone (416) 592-5925. October 4-6, 1982: High Temperature Alloys for Gas Turbines 1982; Liege, Belgium. Conference is organized by Centre de Recherches Metallurgiques, under the auspices of COST-SO, A European Collaborative Programme on Materials for Gas Turbines. Recent progress in the development of high-temperature alloys with particular emphasis on the results of the European Collaborative Progamme will be explored. Contact D. Coutsouradis, Centre de Recher-
ches Metallurgiques, Abbaye du Val-Benoh, 11, Rue E. Solvay, B-4000 Liege, Belgium. October 17-23, 1982: International Mineral Processing Congress; Toronto, Ontario, Canada; Sheraton Centre Hotel. Contact L.J. Vincze, Publicity ChairmanXIV IMPC, c/o CE Lummus-Minerals Division, 251 Consumers Road, Willowdale, Ontario M2V 4H4 Canada. October 17-23,1982: XIV International Minerai Processing Congress; Toronto, Canada; The Sheraton Centre Hotel. The program will cover floatation; comminution; modeling and simulation; plant design; precious metals recovery; energy minerals recovery; industrial minerals recovery; materials processing; mineralogy applied to ore dressing. Contact The Canadian Institute of Mining and Metallurgy, Suite 400,1130 Sherbrooke St., West, Montreal, Canada H3A 2M8; telephone (514) 842-3461. October 27-29, 1982: Nineteenth Annual Meeting of the Society of Engineering Science; University of Missouri-Rolla, Rolla, Missouri. Contact H. P. Leighly, Department of Metallurgical and Nuclear Engineering, Fulton Hall, University of Missouri-Rolla, Rolla, Missouri 65401; telephone (314) 3414711.
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