Cold Cracking and its Prevention in Steel Welding

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Test procedures, cause of cracking and combined effects of hydrogen, chemical composition and restraint on crack imitiation are discussed together with the pertinent preventive measures and precautions against such cold cracking as root cracking of a single or multipass weld, or microcracking in multipass weld metal. By means of Fujii's new nomogram, values of the critical hydrogen concentration in the heat-affected zone at the root of weld at the instant of root crack initiation were estimated from the author's and others' cracking test data. It was found that the critical hydrogen concentration can be satisfactorily correlated with a combined parameter of Ito-Bessyo's P_cm (%) and intensity of restraint RF (kg/mm・mm). A new cracking parameter P_H=P_cm+0.065 log H_D+R_F/40, 000, where H_D (ml/100 g) is the diffusible hydrogen content, was introduced by the author in order to improve the drawback of Ito-Bessyo's cracking parameter P_w. The new parameter covers the whole range of hydrogen contents and is shown to correlate values of critical preheating temperatures more satisfactorily than Ito-Bessyo's P_w. Critical preheating temperatures and intensities of deleterious effects of various factors on cold cracking are compared in a table. The P_cm ranges of current Japanese steels and the hydrogen level of low hydrogen electrodes are shown with the recommended preheating temperatures. WT62CF, a new crack free steel of NSC, is also introduced.
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Cold Cracking and its Prevention in Steel Welding

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