Effect of Restraint Stress on Crack-initiating Temperature of Reheat Cracking of Cr-Mo Steels (Study of Reheat Cracking of Cr-Mo Steels, Report 6)

概要

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The temperature initiating the reheat cracking was examined on three Cr-Ma steels by the implant test of constant-strain type. The cracking test was stopped optionally in a certain period in the course of raising and keeping the temperature. The crack-initialing temperature of each steel is constant regardless of the stress value when the stress at the moment of crack initiation is larger than 300 N/mm^2. Those temperatures are 820, 780 and 810 K for 1/2Mo, 1Gr-1/2Mo and 2 1/4Cr-lMo steels, respectively. It rises, however, with a decreasing stress; the crack initiates after several hours at 873 K when the stress is slightly larger than the critical stress for producing the reheat cracking. The crack-initiating temperatures obtained by constant-load test were generally higher than those by constant-strain test. Such a difference in the temperatures comes from an excess stress experienced prior to crack initiation in the latter test. The excess stress will promote the crack initiation by the effect that it increases the phosphorus concentration in prior-austenite grain boundary and makes it brittle.
社団法人溶接学会の論文
1986-10-01