16-15-6型合金の熱冷加工ならびに曲げクリープ特性

耐熱材料における合金元素としての窒素の作用について-III

抄録

This study covers the hardening accompanied by hot-cold working and bending creep property of low Ni Timken 16Cr-15Ni-6Mo(-7.5Mn) type alloys. Main results obtained were as follows:
(1) For this type alloys, in general, the hardness became considerably higher by hot-cold working than by cold working, and the trend became significant with increasing content of N and C. From the above results, it was concluded that the precipitation of nitrides or carbides probably occurred duringthe hot-cold working of the alloys and the hardening accompanied by the precipitation superimposed on the work hardening.
(2) The hot-cold worked specimens maintained the higher hardness than the solution treated one even after the aging at 700°C for 500h. The working, however, seemed to be effective only when the alloys were used at temperatures below 700°C, since it accelerated the aging and resulted in rapid softening at 700°C.
(3) In the hot-cold rolled state, the hardness distribution of the specimens became heterogeneous and the hardness in the outer layer was considerably higher than that in inner one, and this trends maintained still after aging at 700°C for 500h.
(4) Bending creep property at 700°C of the alloys subjected to 20% hot-cold working by rolling was improved remarkably with the content of N added. In the range of Ni content from 13 to 17%, the alloy containing 15% Ni was superior in the property, though the effect of Ni content was not remarkably, while addition of carbon reduced the toughness of the alloys rupturing in comparatively short testing time. In the range of the present experiment, the 16-15-6 type alloy was considerably superior to the standard Timken 16-25-6 alloy, and the hot-cold working of each alloy improved the bending creep property significantly.