軸受鋼材に現わるゝ粗大炭化物について : 軸受鋼の研究第 1 報

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The authors observed often huge carbides which could not be considered to appear in simple alloy steel such as the ball-bearing steel (C≒1.0, Cr≒1.5%), refering to the equilibrium diagram, generally at the cores of the steel billets. These carbides appeared at the phosphorus-rich parts in the segregation strip bands in the longitudinal section of the billets. Their appearances were almost same as the elongated slags of the manganese-sulphide series and in many cases they coexisted with these slages too. By many microscopic examinations of the production billets, they were closely connected with the segregating degree of the impurities which were apt to segregate, such as carbon or phosphorus, and the solidifying conditions of the molten steel in the ingot-cases had the decisive influences. After the solidification, it was difficult to eliminate them by the ordinary hotworkings or heat-treatments. By refering the results of microscopic examinations of the longitudinal sections of the many test-ingots which contained various amounts of carbon and phosphorus respectively and the results of examinations of the structures just after solidification of these samples, to the equilibrium diagrams of Fe-C-P and Fe-C-Cr series, it seemed that these huge carbides separated out as the eutectics at the places where the grain boundary segregations of carbon, phosphorus, etc. increased over the definite degree, or that they were the coagulations of the carbide θ which separated out by the solubility limit while cooling after solidification at the segregation parts, such as above described. Now these huge carbides dissolved at about 1060℃ which was much higher than the solubility temperature in the equilibrium diagram, and in many cases the colonies of the fine particles rest undissolved at the places where the huge carbides were situated. These particles seemed to be the phosphide series, and, at about 1160℃, all of them dissolved too. Next the authors measured the hardness differences by the micro-hardness tester, not only at the huge carbides, but also at the segregation parts after heat-treatment. For example, the huge carbides had the hardness about 1300 kg/mm^2. Then the authors studied the influences of the added elements ; when carbon increased near to the upper limit, though in the specification range, and when phosphorus to about 0.04∿0.05%, the huge carbides became to appear very much. Sulphur accelerated their appearances considerably, aluminium and titanium, added as the deoxidizing materials, suppressed a little, vanadium suppressed also a little, but tungsten and molybdenum accelerated on the contrary. Based on these results the authors considered the device to decrease appearance of the huge carbides.
1952-06-25

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出口喜勇爾
日本特殊鋼

軸受鋼材に現わるゝ粗大炭化物について : 軸受鋼の研究第 1 報

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