Prevention of Welding Crack by A Process for Local Heating at Constant Maximum Temperature
1971 Volume 40 Issue 11 Pages 1098-1103
Details
1971 Volume 40 Issue 11 Pages 1098-1103
Under the condition that the base metal to be welded is easily distorted, cracking seldom occurs. As to welding crack in high tensile steel plates, a lot of researchers have studied and presented the results of their studies, in which not a few researchers have done the restraint cracking test, such as U-type or slant Y-type.
In this research, a restraint cracking test was done as follows, first of all, special butt welding of high tensile steel plates (Fig. 2) was made by manual arc welding process with coated electrode, NOW process or submerged arc welding process, secondly the profile of butt groove, which seemed to be most suitable, was chosen for each process, and thirdly for heating, "A Process for Local Heating at Constant Maximum Temperature with Gas Flames" published before was used. In these tests, the following investigations were made, such as prevention of welding crack at welded parts of high tensile steel and the relation between welding cracks and preheating or post heating.
According to the results of experiments, the authors recognized the following facts:
1. In case of butt welding of high tensile steel plates, Wel-Ten 80C, a crack rarely occurs. But if the. butt welding is made in central part of Fig. 2, crackings are likely to occur.
2. In these tests, welding was done after preheating by the above mentioned process. There are instances where cloy preheating at 120°C could prevent cracking at the welded part. But when the temperature of preheating was 120°C and the interlayer temperature was kept at 200°C, in any method of welding, cracking was fully prevented.
3. After welding by the various processes, post heating at 700°C was done by this heating method. By this post heating, the welded part with single-layer was softened and therefore cracking was prevented. But a small crack in crater was recognized in case of submerged arc welding process. Besides in case of multi-layer welding, if the interlayer temperature was kept at 200°C and post heating was done only after deposition of final weld, there was.no danger of cracking at all.
