鋼の再熱割れ感受性におよぼすクロムとモリブデンの影響 Ｃｒ‐Ｍｏ鋼の再熱割れに関する研究 ＩＩ

Abstract

Influences of chromium and molybdenum on the reheat cracking sensitivity of the high strength steels and Cr-Mo heat resisting steels were investigated using 20 synthetic Cr-Mo steels melted in our laboratory. These steels contained 0 to 5 wt%Cr and 0.25 to 1.5 wt%Mo. Cracking sensitivity were evaluated in terms of the criticl restraint stress obtained by the modified implant method for the reheat cracking. The results are summarized as follows. 1) When the chromium content was smaller than about 1 wt%, the cracking sensitivity increased with the increase of chromium content, but when it exceeded about 1 wt%, the cracking sensitivity decreased conversely. 2) The harmful effect of molybdenum was maximum when the chromium content was about 1 wt%. 3) The combined influence of chromium and molybdenum was shown by means of the contour lines of the critical restraint stress in the Cr-Mo contents diagram.