The 6 core process modules of the Yamal LNG project is the core part of the largest LNG project in polar regions, and also the first LNG core process module exported by China. The project has great difficulty in construction and strict requirements of precision, and has to be delivered in short time; the project shall withstand the harsh environment at -50 centigrade, and it may be called the project with the strictness requirement of welding of LNG modules completed in China.