(1) A study was carried out on the reduction equilibrium of chromium between molten pig iron (Fe-C at·-Cr[1%]) and molten slag of blast furnace type (CaO-SiO2-Al2O3-(CrO), at the temperature range of 1350-1500°C and the slag basicity CaO/SiO2 ranging from O·6 to 1·4, under one atomospheric pressure of carbon monoxide. (2) From the fact that the rate of reduction of chromium from slags to pigiron was relatively rapid, the partial equilibrium concerning chromium seemed to have been obtained between two phases. (3) The chromium oxides in slags was presumably mainly present in the formof CrO, judging from their coloured blue-black. The apparent partition ratio of chromium %(CrO)/%Cr between pig iron and slags was appreciably decreased as increasing the basicity upto CaO/SiO2≈1, in other words the activity coefficients of (CrO) should be much affected by the slag compositions. (4) The relation between log %(CrO)/%Cr and 1/T( T:°K) was linear and parallel for each slags, the basicity of which ranged from 0·6 to 1·0. (5) The Cr-O equilibrium relation in pig iron was introduced utilizing theabove results and some other thermodynamical data, and we emphasized that the favorable conditions to eliminate chromium should be reduced to two main factors of 1) more acidicslags and 2) lower temperatures.
When aluminum, silicon and nitrogen are contained in steel, nitrides of these elements are formed according to the degree of stability, of these nitrides. The free energy equations of the formation of nitrides in steel are derived from the data already reported and by a rough calculating method of using equilibrium diagrams. The equilibrium relations of the forma- tion of aluminum-, silicon- and iron-nitrides are calculated by these equations ranging from the state of solid at room temperature to that of liquid, by assumption that the content of these elements is as follows: According to the results of calculation, both aluminum- and silicon-nitrides are estimated to be effective as grain-growth inhibitors, although the latter may be less effective than the former. Some considerations are made about nonmetallic inclusions which act as grain-growth inhibitors.
This paper treats the result of studying the effect of shot of shot size, hardness and speed on the coverage, peening intensity or surface roughness of the work. Results obtained are as follows: 1) The size of indentation marked on the surface increases as the wheel speed goes up and is practically proportional to the shot diameter. 2) Peening intensity increases as the shot size, velocity, or hardness increases. 3) Surface roughness increases as the shot size, speed, or hardness increases. When the surface has the initial roughness, this may, in some case, be lowered by peening. 4) Intensity by soft, heat-treated steel or iron shot is high enoughand does not roughen the surface of work to be peened. 5) Broken shot loweres the peening intensity but does not affect theroughness.
In sequence to the report No. 1, the authors studied the influences of copper content on the properties at the ordinary temperature of Si-Mn spring steel with the same samples, and the results were as follows: 1) No change was occurred on the non-metallic inclusions. 2) The hardenability measured by Jominy method increased with the Cu addition. 3) At normalized states, the tensile strength, yield point and hardness increased, but the elongation and reduction of area decreased a little with the Cu content. 4) Resistance to the tempering increased with Cu, specially at the range of 400-450°C. 5) Endurance limits of the spring leaves tended to decrease slightly.
The inner rings of the ball bearing, which had been known the life time in life test, was studied in order to look for the relation between some metallurgical factors and life. As some factors the chemical composition, non-metallic inclusions, hardness, compressive load of inner rings, cementite content, grain size and forging degree were tested. The results obtained by our investigation were summarized as follows. (1) Generally speaking, the chemical composition had no direct relation to life of ball bearing. By our results carbon content of our home-made ball bearing steels was controlled in a higher range of the standard, but it must be controlled in a lower range to avoid the segregation and coarse carbide. Chromium content must be controlled in 1•40-1•50 per cent. (2) Nitrogen content had no dlear relation to life of bal1 bearing steels. But some group of the nitrogen had relation to cementite content, while the other group had no relation to cementite content. (3) The higher hardness of after heat-treatment, the longer was life of ball bearing. Hardness of inner ring increased mostly after life test. It is due to transformation of the retained austenite. Hardness of after 1ife test has no relation to the life. (4) The compressive load of inner ring had no direct relation to life of ball bearing. (5) Non-metallic inclusions had scarcely relation to life of ball bearing according to our investigation. (6) In the forging ratio our home-made ball bearing steels were considerably lower. It must be raised by using the bigger ingot. (7) Cementite content retained after heat-treatment had clear relation to life of ball bearing. Maximum life was in about 6-8 percent of cementite content (8) Grain Size had no distinct relation to life of ball bearing. But some group of it had relation to life, and the other group had no relation to life.
The effects of 0•003 and 0•006% B on the transformation, hardenability, quenched and tempered hardness and mechanical properties etc. of Mn-Cr and Mn-Cr-Mo high tensile steels were investigated. The results obtained were as follows. The Ac1 points were not affected by addition B, But Ac3 points were raised while Ar points were lowered. 0•003% B was more effective to increase the hardenability than 0•006% B and as compared with no adding B the hardenability increased remarkably by addition of B. The quenched and tempered hardness was not affected by addition of B above 300°C of tempering temperature. The yielding point tensile strength and impact value increased a little by addition of B, but elongation and reduction of area were not affected. As one of the practical making processes of B steel, 400kg ingot was made by addition of B in the ingot mould while pouring the molten steel from ladle. The properties of this 400kg ingot were uniform and the effect of B on the ingot was the same as that of B on the small ingot which was made experimentally by a small furnace.
Niobium was effective to increase ductility of the short-time tensile test at 700°C in the age-hardened, or "hot cold worked" state. In creep rupture testing above 650°C, Nb was effective to increase ductility, and rupture life. Effect of Nb is distinct at longer time or higher temperature of testing and at "hot cold working" rather than in age-hardened state. The higher the working temperature of "hot cold working" the lower the strength on short time tensile test, and the shorter the creep rupture time, the more increased ductility in both testing. Reduction of working at "hot cold working" had little effects on the result of the short-time tensile tests, but by increasing the reduction of working, creep rupture time was shortened. Tensile and yield strength increased by "hot cold working" beyond 700°C and creep rupture test at 600, 650, 700°C, beyond 100h. of testing time were studied in age-hardened state. At 650°C, 100h creep rupture strength was somewhat 13kg/mmmm2 lower than in "hot cold worked" condition, but its difference was reduced in proportion to testing time.