Cr-Mo強靱鋼の低温焼戻状態における衝撃遷移特性に及ぼすAl, Ti及びB添加の影響

抄録

Both the low tempering temperature embrittlement and the transition characteristics of high strength steel are in close connection with the quality of steel, and the effect of Al, Ti and B addition upon them is thought to be very important from the industrial point of view, as it is related to the deoxidation, nitrogen-fixation and austenite grain size of steel.
The authors, therefore, have investigated the effect of Al, Ti and B addition on the low tempering temperature embrittlement of high strength Cr-Mo steel from the view point of impact transition characteristics.
Results obtained were summarized as follows:
(1) The Al, AI-Ti or AI-Ti-B treatment improved the impact values at the tempering temperature ranging from 100 to 450°C. Especially in the case of the Al-Ti-B treatment, the impact value in the range of embrittlement was markedly improved.
(2) The tempering embrittlement temperature was not changed by the Al treatment, and the embrittlement occurred at about 300°C. But the A1-Ti or A1-Ti B treatment raised its temperature to about 350°C.
(3) In each treatment, the transition temperature varied apparently with the tempering termperature: the tempering within the range of embrittlement at 300 to 350°C and at about 100°C causes a higher transition temperature, whereas the tempering at about 200°C(the impact value was maximum at this state) and at about 400-450°C resulted in a lower transition temperature.
(4) The Al, Al-Ti or-Al-Ti-B treatment lowered the transition temperature, especially the Al-Ti and Al-Ti-B treatments markedly lowered it in the range of embrittlement of tempering at 300 to 350°C.
Therefore, by the proper treatment with such elements, actual finished products were presumed to be given more security against the brittle failure.