Study of Algorism for Avoiding Weld Cold Cracking

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This paper firstly deals with a parameter dominating cold cracking arising in the heat affected zone (HAZ). From experimental data of Implant and TRC tests, it is clear that stress-parameter is more useful for cold cracking than strain-parameter. However, Stress-parameter was not useful for data of Takken test which is considered to be a typical joint used in welding field. This cause is due to a phase transformation which affects the stress in HAZ. Then, a study of transformation versus cooling time of weld thermal cycle will be important.Second, for decreasing the hardness and the hydrogen concentration in HAZ, cooling times was studied. Cooling time t85, which means time needed cooling down from 800^ﾟC to 500^ﾟC of weld metal, is related to hardness. Cooling time t150, which means time from solidification temperature to 150^ﾟC of weld metal, is connected with hydrogen concentration after weld thermal cycle. For avoiding cold cracking, software based on algorism predicting cooling time from informations of welding and constructing conditions is made. Experiments were carried out for checking whether software is applicable or not. It is shown that software is applicable for avoiding cold cracking.