Yuichi Komizo

Cold cracking susceptibility of girth welding for arctic grade line pipe

High strength line pipe steels require not only good low temperature toughness but also excellent weldability. The use of cellulose welding electrodes has introduced the possibility of cold cracking due to the introduction of hydrogen. This report deals with the cracking susceptibility of line pipe steels. Test results make it possible to establish a diagram to predict and determine the welding conditions for crackfree girth welds. This diagram contains an emperical parameter, Pw, which includes the alloying composition of the steel, the effective hydrogen concentration at the root of the weld, and the restraining stress. When Pw is plotted against the cooling time (the time to cool from the weld condition to 100 °C), a distinct separation is seen between cracked and crack-free weld joints. Thus, the Pw parameter has utility.It is found that crackfree girth welds can be made in line pipe steels if the equivalent carbon parameter is sufficiently low. References are given to pertinent literature from the International Institute of Welding (ILW).

Effect of Ni content on weld hot cracking susceptibility of fully austenitic Fe-Cr-Ni alloy - investigation on weld hot cracking susceptibility of fully austenitic fe-cr-ni alloy (report 1)

The generally acknowledged reduction in hot cracking susceptibility using the p ferritic phase cannot be achieved for fully austenitic (hereinafter inscribed as fully y) stainless steel such as SUS310S and fully y group alloys with a high Ni content, such as high Ni heat and corrosion resisting alloys; there is a tendency for hot weld cracking susceptibility to increase. Consequently, there are many cases where the initiation of hot cracking during the welding procedure becomes a problem. Possible countermeasures involve the use of materials, so numerous investigations have been carried out, including the study of the effects of impurity elements (P, S etc.) upon hot cracking susceptibility; many investigations have been limited to within the scope of restricted major constituents (for example, under the category ofSUS310S group, high Ni group heat resisting alloys). However, where the major constituent group varies, the effects of the alloying elements upon hot cracking susceptibility are thought to be not necessarily similar. In other words, the effects of the alloying elements upon hot cracking susceptibility in different major constituent groups and the information which can generally explain the effect mechanisms are not necessarily established. This study aims to clarify the effects of alloying elements upon hot cracking susceptibility and the effect mechanisms for a wide range of Ni content of fully y Fe-Cr-Ni alloys. Consequently, the effects of Ni content upon hot cracking susceptibility were evaluated by means of a Trans-Varestráint test and the hot ductility test; hot cracking regions and fracture surfaces were observed; the solidification temperature range and the residual liquid phase content were investigated using Thermo-Calc (Version L, SSOL data base) and the weld solidification process using the liquid tin quenching system was examined.