The solubility of hydrogen in liquid iron, liquid nickel and liquid iron alloys has been studied by SIEVERTS' method at the temperature range of 1450-1670°C and under the atmospheric pressure of hydrogen. The carbon, silicon and phosphorus decrease the solubility of hydrogen in alloys, while nickel increases it. The iron-silicon alloy has the minimum solubility of hydrogen at the concentration of 31-34%Si. The results obtained are summarized as follows: 1. Solubility of hydrogen in liquid iron log KFe-H(=[%H]/√PH2)=-1900/T-1.577 2. Solubility of hydrogen in liquid nickel log KNi-H(=[%H]/√PH2)=-939/T-1.869 3. Interaction parameter in iron alloys ∂ log f(C)H/∂[%C]=417/T-0.204……<2%C ∂ log f(Si)H/∂[%Si]=0.031……<2%Si ∂ log f(P)H/∂[%P]=0.015……<6%P ∂ log f(Ni)H/∂[%Ni]=10.4/T+0.0040……<50%Ni
The behaviour of oxygen in melt, when deoxidizer was added into molten steel, was studied. Both macroscopic and microscopic oxide inclusions in solid steel, which was enriched with oxygen and contained silicon or aluminum, were disposed iniide interdendritic spaces. The result shows that all of inclusions found in solid steel are precipitated from melt during solidification of the steel, and that there are no suspended deoxidation products in melt. It was observed that deoxidation products were precipitated on the inner surface of crucible during holding in melt. In some cases, the deoxidation products were dendritic. From above experimental results, the following conclusions were introduced. (1) When deoxidant was added in molten steel enriched with oxygen, dissolved oxygen and deoxidant react rapidly to produce an oxide dissolved in monomolecule state, but not to be grown to oxide particles. (2) Dissolved monomolecular oxides in steel diffuse through diffusion layer on the boundary between melt and crucible, and form oxide phase only on the inner surface of crucible. Consequently oxygen content in steel is decreased slowly. Rate of oxygen drop after addition of silicon in iron melt enriched with oxygen was measured. The experimental results were consistent with theoretical result introduced by the above model of deoxidation reaction. When a deoxidant is added into the melt containing a great amount of oxygen, then deoxidation occurs according to different reaction mechanism from the above mentionedi The reaction comes rapidly to an end. It is observed that some calcium can dissolve in molten steel.
On the cost down of manufacturing bearing steel tubes, Hikari Works has adapted the continuously cast process and then studied the soaking process. The studies were mainly made with continuously cast blooms which have 260 mm square section and 180 mm octagonal section. A 350mm square section conventional cast ingot was also examined for comparison. Soaking was the necessary process to dissolve massive carbides in bearing steels. Without this process these coarbides were decomposed by hot working but composed again in the annealing process.(Photo.2, Fig.6) The massive carbides appeared much at center parts of cross section of blooms or ingots, and size of the carbides was larger in larger cross section.(Fig.2, Fig.3) It seems that these massive carbides formed as the eutectics at the grain boundary segregate parts in non equilibrium solidification. The massive carbides were dissolved by soaking. Experiments of soaking showed that the process was diffusional (Fig.7). The soaking time became shorter at higher soaking temperature to 1260°C. Above this temperature the steel would be overheated. The dissolution conditions depended on amount and size of the massive carbides.(Fig.8) The carbides were analyzed as (Fe, Cr) 3C. In these constituents Cr is most difficult to diffuse. Therefore the dissolution conditions of the massive carbides were considered to be determined by diffusion of Cr. Single Cr sphere which had same size as maximum size of the massive carbides in blooms or ingots, was watched. During the soaking process Cr concentration of the sphere would be decreased to same concentration in matrix. These considerations gave eq.(4). From this equation and experimental roults, the diffusion constants of the massive carbides in bearing steels were shown in table 2 and the activity energy to diffuse was 1.63-1.79×105 Cal/g atom. Obtained diffusion constants were slightly lower and activity energy was slightly higher as compared to the case of diffusion of Cr in pure austenite. Therefore in the dissolution of the massive carbides was considered that the constituent atoms of the carbides separated out of molecular bond of cementite and diffused in segregate parts of the steels. From es:(4), the relation of the diffusion constant and the activity energy eq.(5) and the experimental results, the dissolution conditions were derived as eq.(7). This equation showed that the conditions were determined by maximum size of the massive carbides in blooms or ingots. Calculation examples are shown in Fig.7. Finally, we approved that experimental results were able to apply the process of mass production of bearing steel.
Occurrence of cracks in tube-making, particularly in piercing tube blanks, constitutes one of the important problems, and has been studied on its various aspects since many years; research efforts have also been made to find an effective method for determining the optimum working temperature, however, without any satisfactory result. It was seemed that the hot twisting test was a valid method for advancing these studies, but because the deformining mechanism in the course of twisting was not as yet clarified, the extent and scope of this validity were not considered to be sufficiently established. For this reason, the author developed a device capable of easily measuring not only the torque and the number of revolutions at fracture, but also the secondary stress in gauge direction caused by twists, and examined the twisting deformation patterns and importance of the secondary stress in determining the hot workability. In this way, the following conclusions were obtained. (1) The secondary stress occurring in the course of twisting is the phenomenon accompanying shearing, and acts as tension at a temperature higher than the recrystallization temperature. (2) There exists a certain relationship between the shearing strain (ε') and the absolute temperature (TK) at which the secondary tensile stress appears within the range of austenite temperature examined._??_ It seem to us that there is a close relationship between this fact and the recrystallization of material. (3) The intensity of secondary tensile stress (σt) is determined by strain (ε), strain rate (ε) and absolute temperature (TK); and these correlation can be expressed in the equation._??_ where m, n and A are the constants incidental to a particular material; n indicates the sensitivity to speed, A represents that to temperature. (4) The patterns of deformation in hot working of steel can be generally classified into three types, in relation to the stress, the strain and the fracturing shape. (5) The relation of the coefficient of hot torsional working (ΔR) and the critical deformation (δ) in piercing can be expressed in following common equation._??_ where k and δa are the constants incidental to a particular material.