This article describes the procedure and results of investigation of the main thermal strain indices that determine the probability of cold cracking in welding of low- and medium-alloyed steels. The relationship has been established between the process of intensive relaxation of temporary stresses during structural transformations and initiation of microcracks in cooling under the conditions of welding thermal strain cycle. Parameter M{sub r} has been suggested for estimation of steel susceptibility to cold crack formation. Effect of hydrogen on cold cracking is analyzed.

Thermal strain dependencies characterizing susceptibility of steels to cold cracking

A weld thermal-restraint stress and strain-cycles simulator, briefly "Thermal Restraint Simulator; Thermorestor", which enables us to simulate various phenomena caused by welding, and to analyze separately the effects of each factor such as thermal cycles, restraint stress cycles, strain cycles and atmosphere upon materials, has been developed.It is confirmed that this apparatus can be applied to making clear weld cracking phenomena, to evaluation of weldability of base metal, to selection of welding materials, to establishment of welding procedure and so on.Examples of standard programs and their application tests for investigation of welding phenomena with this apparatus are as follows:1) The program of a rigid restraint control during synthetic weld thermal cycles can make clear the weld hot crack sensitivity in the heat-affected zone of base metals.2) By the program of enforced strain control during synthetic weld thermal cycles they can investigate the hot crack sensitivity and the propagation characteristics of micro-cracks of base metlas or weld metals, and me program is useful for selection of base metals or welding materials.3) The program of a constant strain control during cooling of a notched specimen charged with hydrogen at a high temperature can make cleur the phenomena of delayed cracking due to hydrogen, and is very useful for the evaluation of cold crack sensitivity during welding and dealyed cracking characteristic during operation.4) The programs of various controlled strain or stress during weld post-heat treatment can make clear stress relaxation and anneal cracking phenomena, and are used for decision of the conditions of stress relief heat treatment and the evaluation of anneal crack sensitivity of base metals.

小管信吾

Papers

溶接部熱・拘束応力・ひずみサイクル試験装置の開発とその応用例について

小管 信吾

Papers

溶接部熱・拘束応力・ひずみサイクル試験装置の開発とその応用例について

小管信吾