GTAW-SMAW와 SAW를 이용한 고장력강관의 용접에 대한 연구

A Study on the Welding Process of High Strength Steel Pipe in GTAW-SMAW and SAW

This study is to compare the welding quality of API 5L-X65 Steel- pipe's for natural gas transmission piping applied by SAW at shop and by GTAW-SMAW at site. The results can be summarized as follows; 1) Tensile strength of the welded zone by SAW(611.5 MPa) and by GTAW-SMAW(608.6 MPa) was maintained greater than that of the base metal(583.5 MPa). 2) Hardness of the welded zone and HAZ by SAW(Hv 194.8) & GTAW-SMAW (Hv 196.1) was slightly increased above that of the base metal (Hv 168.8), but less than the maximum allowable hardness(Hv 248). 3) Impact value of the welded zone by SAW(126.8 J) & GTAW-SMAW(88 J) became lower than that of the base metal(282.5 J), but was above the requirement of API 5L(68J). 4) Microscopic structure of the welded zone and HAZ by both SAW & GTAW-SMAW became fine-grained.