2018 年 36 巻 1 号 p. 86-93
Cold cracking is a serious concern in the welding of large-scale steel structures. And, diffusible hydrogen is a major factor affecting to it. Several general techniques are known for preventing cold cracking, however there are no examples of approach in the past from welding apparatus side. The new welding process was developed to reduce diffusible hydrogen content in the weld metal with special welding torch in GMAW and FCAW. Furthermore, the factors were researched that affecting the effectiveness of the new welding process. The special welding torch was designed by calculation results of wire temperature distribution and analysis results of hydrogen source behavior during welding. It slightly sucks the gas around the wire through the suction nozzle. The effectiveness of developed process was showed by comparative experiment with conventional process, namely confirmed the correctness of the structural design. Meanwhile, it was revealed that wire structure (i.e. seamed or seamless) affects strongly the effectiveness of the process. This process was very effective with seamed flux cored wire.