This study investigates various factors that influence the cold-cracking ratio (CCR) of flux-cored arc welds through Y- and y-groove tests. Factors affecting the CCR include the alloy component, diffusible hydrogen content, microstructure, hardness, and groove shape. In weld metals (WMs; WM375-R and WM375-B) of a low-strength grade, the diffusible hydrogen content has a more significant effect on the CCR than the carbon equivalent (Ceq) and microstructure. However, the combined effects of the microstructure and diffusible hydrogen content on the CCR are important in high-strength-grade WM. The CCR of the WM increased upon increasing Ceq and the strength grade because hard martensite and bainite microstructures were formed. Moreover, y-groove testing of the 500 MPa grade WM revealed a more significant CCR than that of the 375 MPa grade WM. Therefore, in high-strength-grade WMs, it is necessary to select the groove shape based on the morphology in the real welds.

Tungsten Inert Gas (TIG) welding process is mostly applied to high alloy steel pipes including stainless steels because of superior welding quality and gap bridge-ability than other welding processes. However, it has poor productivity due to low welding speed and deposition rate. In order to improve TIG welding productivity, high performance TIG welding with higher arc temperature, automation and high deposition rate system including hot wire have been developed. Higher arc temperature and longer welding time damage tungsten electrodes of TIG welding. It causes welding defect such as tungsten inclusion and short replacement cycle of tungsten electrodes. Various types of tungsten electrodes containing rare earth metal oxides (thorium, lanthanum, cerium, etc) were introduced to improve electrode erosion resistance and arc stability. In this study, their operation characteristics, arc starting performance, tip development, and electrode consumption were reviewed.