Study of Algorism for Avoiding Weld Cold Cracking

本文首先讨论了热影响区产生冷裂的一个主要参数。从植入和TRC试验数据可以看出，应力参数比应变参数对冷裂的影响更大。然而，应力参数对Takken试验数据并不适用，Takken试验被认为是焊接领域的典型接头。这是由于相变对热影响区应力的影响。因此，研究焊接热循环的相变与冷却时间的关系将具有重要意义。其次，为了降低热影响区硬度和氢浓度，研究了冷却次数。冷却时间t85，这意味着从焊接金属的800^ C冷却到500^ C所需的时间，与硬度有关。冷却时间t150，即从凝固温度到焊缝金属150^ C的时间，与焊缝热循环后的氢浓度有关。为了避免冷裂，根据焊接和施工条件信息，开发了基于算法的冷却时间预测软件。通过实验验证软件是否适用。结果表明，该软件在防止冷裂方面是可行的。

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.