<報文>軸受鋼の偏析と其の改善に就いて
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It is said that carbide segregation in bearing steels together with non-metallic inclusions cause the roughness of the polished truck of the race which lowers the life of a bearing ; such segregated steel can not be improved by simple heat treatment to a desirable uniform structure. It may be considered that there are two types of segregation, namely, carbide segregation in banded form and precipitated carbide along granular crystals. The former can be improved by comparatively lower temperature homogenizing or proper annealing, but the latter can be improved by high temperature homogenizing only. The author investigated the cause of carbide segregation by metallurgical and statistical method and e succeeded to a certain extent to make sure the true nature of the segregation and preventing it. The results of these experiment are summarized as follows. 1. Insufficient boiling and killing are the primary causes of the segregation, especially, it may be promoted by forced deoxidation by aluminium, high casting temperature and a large-sized ingot. 2. The carbides of the filling mass are enriched in carbon and chrome, but the matrix of it may be rather rare of them and containing much sulphur and phosphor. 3. The filling mass of the banding shows abnormal structure, so the grain size of this part is smaller than dendritic skelton part, and give rise to the soft spot by normal quenching temperature. 4. It may be put to practical use by homogenizing of banding carbides and which is achieved by annealing at 960℃ or rolling (rolling ratio beyond 7), especially forging is most effective to diffuse it. 5. I suppose the precipitated carbides are the η compound (Cr_7C_3 containing sulphur, phosphor and iron less than 55%) which crystallized out by ternally eutectic reaction at the temperature of 1,130℃, accordingly it can he diffused with difficulty by homogenizing beyond the temperature of this reaction, but it may be decomposed in certain extent by forging.
- 東北大学の論文
- 1951-10-03
著者
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