In some overseas offshore oil and gas field development projects

the girth welds of submarine pipelines subjected to sour servive condition is mandatory to use welding process for root pass without copper shoes to ensure that the welds will not have sulfide stress crack (SSC) during the service process of hydrogen sulfide (H2S) acid corrosion. In order to solve the problem that copper atoms of copper shoes are diffused into the weld metal and have a destructive effect on its performance during the root pass welding

a full-automatic GMAW welding process without backing for pipeline S-lay and mechanical tests were developed by using surface tension transfer (STT) for root pass and gas metal arc welding (GMAW) for fill and cap passes .The test results of mechanical properties meet the requirments of the project welding specification and DNV OS F101 (2013) standard. All welded joint samples have passed the sulfur-induced stress cracking test under NACE 0177 standard

and can be applied to the welding construction of X65 carbon steel subsea pipe in acidic environment containing H

2

S; STT surface tension transfer for root pass welding is a single-sided welding and double-sided forming technology

with small welding heat input

little spatter

and good weld formation. It is a reliable choice for backing less back cover welding technology.