REHEAT CRACKING TEST ON HIGH STRENGTH STEELS BY A MODIFIED IMPLANT TEST. (STUDY OF REHEAT CRACKING OF Cr-Mo STEELS, REPORT 1).

Reheat cracking has occasionally occurred in the welded zone of 80 kgf/mm**2 high strength steels. It was confirmed from test results of commercial high strength steels that the reheat cracking sensitivity could be compared in terms of the critical value of the initial restraint stress obtained by the implant test. T-1 type high strength steel which contained both chromium and molybdenum was much more sensitive to cracking than chromium free, Mo steel. The reheat cracking sensitivity of synthetic Ni-Cr-Mo and Cr-Mo steels, in which nickel and chromium contents were varied, was also examined. Nickel increased the sensitivity only when its content exceeded 1. 5%. The chromium addition up to about 1% together with molybdenum remarkably increased the sensitivity.