特殊鑄鋼の研究(XII)

特殊鑄鋼の燒入,燒戻性

抄録

The author studied on the relationship with the quench-hardening and grain size of some special cast steels which were made to add Ni, Mn, Cr, Al, Al alloys and Ca-Si in Cr-Mo cast steels. It was found that the larger the grain size was the more remarkable the quench-hardening effect become. Futher the quench-hardening effect was affected by the irreversibility of steels such as element Ni, Mn, Cr, which made decreased the transformation point of steel. It was presumed that the low carbon steel rapidly increased in quench-hardening with the addition of Ni. If the C content was large, however, the hardenability was not so marked as that of the low C steels. On the other hand, the addition of Mn and Cr had a pronounced effect than Ni.
The author also investigated the relationship of such alloy steels with nonmetallic inclusions and quench-hardening. Though the quench-hardening increased with increase of Ni, Mn or Cr content, the number of inclusions was rather small and the size of it became larger. The number of inclusions increased with the addition of Fe-Si or Ca-Si, while the size of it became finer.
The impact resistance decreased considerably with elevation of tempering temperature, and reached a minimum value at 300°-400°C (that is a first temper brittleness), while it markedly increased as tempering temperature were more elevated. In the present report the author also investigated the effect of various elements on the temper-brittleness of Cr-Mo or Cr-Mn-Si cast steels.