In a disdussion of the foregoing work, the desulphurization product by manganese was assumed to be probably Mn-sulphide (Tetsu-to-Hagane Vol. 43, 1957, pp. 517-535). However, it seemed doubtful in lower manganese range especially at higher temperature. This paper describes the experimental results of the relations between the composition of desulphuriza-tion product and the Mn-S equilibrium in C-saturated iron melts. The desulphurization product was a sulphide slag which was produced by mixing the liquid FeS and Fe-C-Mn melts at that temperature and brought into equilibrium with C-saturated iron melts. The results were as follows: 1) The main components of the slag were Mn, Fe and S, and the manganese content in the slag increased with the manganese in the metal and attained constant at above 3% Mn in the metal. 2) From the Norelco X ray analysis, it was assumed that the slags were solutions of FeS or Fe-FeS dissolved into MnS. 3) Considering the manganese in the slag was entirely combined with sulphur, the MnS pct in the slag was found to be constant above 3% Mn in the metal. This value was about 94%. MnS. 4) Regarding the slag as FeS-MnS solution and referring to the FeS-MnS diagram, the activity of MnS might be equal to concentration, which was expressed in terms of mol frac-tion NMnS. The authors could write the equilibrium constant K=NMnS/aS·aMn=0·428 at 1500°C From this value the apparent equilibrium constant K″=[Mn%]·[S%] in lower manganese range was discussed.
In the 2nd and 3rd Reports (Tetsu-to-Hagane, 1958, No. 8, p. 872-880, and No. 11, p. 1259-1265) the authors made some observations and experiments with the large ingots which revealed several phenomena concerning the vertical segregation occurred in the melt of ingot core. Combining these new findings with some of the known primary causes for segregation, an unified and systematic explanation for the mechanism of formation of the three major segregations, i. e. inverse V, V and negative segregation, can be derived. Assuming that the convection and chemical changes in the melt of solidifying, core, Soreteffect at the liquid-solid interface, dilution (diffusion) of concentrated elements into the mother-liquor, etc. have no first-order effect upon the formation of macrosegregation, then the concentrating action at the liquid-solid interface and upward transfer in the solidifying melt play a leading role in the course of forming macrosegregations, as follows: i) Inverse-V segregation: Nearly horizontal concentration and upward movement of segregating elements give a resultant direction to the inverse-V strings. A key point of difference from the older concept lies in the manner that the enriched segregates move upwards without convection. (cf. 2nd & 3rd Reports). ii) V and negative segregations: The forming mechanism of both segregations is essentially identical. The difference in the balance between the upward concentration and upward movement in the melt merely produces V or inverse segregation. (Figs. 3 & 4) iii) Unified mechanism of formation for the three segregations: From i) & ii), the three segregations are formed as the liquid-solid interface advances inwards. (Fig. 5)
In the first report, entitled "Forgeability of Transformation-free Alloy Ingots (I)" the authors reported the relationship between the forgeability and as-cast structures, which are a granular structure and columnar one, For the purpose of the auxiliary experiments of the first report, by both impact and static tensile tests and bending tests at high temper-ature the relationship between tensionability, bendability of as-cast structures of Timken 16-25-6 were studied. The direction of the tensile stress was parallel to the long axial direction of a columnar (longitudinal), and vertical to it (transversal). Bending directions of the columnar structure were bending stress applies to bend the columnar axis (longitudinal) and applies to does not bend the columnar axis (transversal). Both experiments were performed dynamic and static. The results were as follows: (1) The best elongation is obtained in the case of stress is applied to the longitudinal dire-ction and next, the granular structure, the least elongation is obtained when the stress is applied to transversal, in the tensile test. In the bending test, the best elongation is obtained in the transversal direction, and next, the granular structure, the least elongation is obtained in the longitudinal. The easy crack forming case is stresses that applied to seperate the boundaries of columnar. The static test shows better elongation than dynamic one, in the both experiments. (3) Working energies until specimens broken, are most in the granular structure, next,
Hot workability of rolled steel depends on many factors, i.e., refining molten steel, heating ingots, condition of the rolling mill, impure elements in material, etc. Especially, in the case of the special-shape steel rolling, such as sash bars for building and rims and side rings for wheels, high level material for hot workability is demanded, because of necessity to make seamless skin and accurate size. The problem of material, principally the influence of impure elements, is one of the most important theme among many factors in workability of steel. In this report, studies are made on the influences of Cu, Sn, and other factors on the hot workability. Methods to measure the workability are special hot-rolling test, hot-torsion test, hot bending test, hot up-set test, hot rotary-hammering test, sensibility test for over-heating, sulfur-print test, and microstructure test, In general, the material which shows low workability in these tests, also causes many seams and small cracks on the surface of shaped steel, and is not available for rolling production. The special hot-rolling test and other tests for determining the workability show that either of Cu or Sn as impure elements makes workability of steel lower. Increasing the content of Cu (or Sn), Cu (or Sn) concentrating phenomena re found in the matrix metal just under scale after heating (surface oxidation), through a microscope. Cu (or Sn)-concentrating phase seems to be related to degree of seams and hair cracks on shape steel surface during rolling.
The effect of nitrogen on nichrome and Nimonic alloys were investigated. These alloys were prepared in the following manners by using raw metals of high purity by melting rapidly in a Tammann furnace: (a) melted in air, (b) melted in air and added nitrogen in the form of nitrided chromium. The nitrogen content of all alloys melted in air was in the range of 0.03-0.04%N. Che-mical analyses of these alloys showed large amount of "soluble" nitrogen (soluble in hydro-chloric acid: water=1:1) in nichrome and of "insoluble" nitrogen (insoluble in hydrochloric acid but soluble in fuming sulphuric acid) in Nimonic alloys. Hence, nitrogen in the former was presumed to be contained as solid solution, and that in the latter as both aluminium nitride and titanium nitride. Small amount of nitrogen in Nichrome modified various properties a little: it strengthened the material without decreasing the ductility so much, increased the electrical resistance, decreased a temperature coefficient and increased the expansion
Age hardening characteristics of nickel-base heat-resisting alloys were studied comparing with carbide precipitation type heat-resisting alloys. Age-hardening of nickel-base heatresisting alloys is much faster and more remarkable than carbide-precipitation-type alloys. Hardness after aging is above B.H.N. 300 within 10 hours at 750°C, though solution-treated hardness is below B.H.N. 230. Maximum aging hardness is attained at 750°C, and above this aging temperature the coaguration of precipitates becomes remarkable and aging hardness falls down. As the amount of Ti, Al and Nb increases, hardness after aging or solution-treatment increases. Addition of Mo increases aging-hardness of Ni-Cr-Co alloys, though it does not affect to Ni-Cr alloys. Co, also, does not affect the hardness after aging or solution-treatment.
The authors studied other factors controlling the graphitization of high carbon steel at subcritical temperature in sequence of the first report (Tetsu-to-Hagane Vol. 44, No. 10 p 1180). The results obtained were as follow: (1) Cold deformation had an accelerating effect on graphitization and compressive forces were as effective as the tensile strength in promoting graphite formation. (2) The heating at 870°C and furnace cooling after cold drawing inhibited markedly the graphitization on subsequent heating at 650°C. (3) Hydrogen, when used as annealing atmosphere at 650°C, had a stabilizing effect on the carbide and inhibited graphite formation. Nitrogen atmosphere and vacuum had no effect of stabilizing carbide. Cast iron chips used as packing material caused a less graphitization than nitrogen atmosphere or vacuum.