20G seamless steel pipe is a kind of high pressure boiler steel pipe, which is a high quality carbon structural steel with carbon content of 0.2%. It is mainly applicable to the main steam pipe of medium pressure and sub high pressure power plant boiler whose wall temperature is not greater than 450℃. The national standard of 20G seamless steel pipe is GB5310-2017 seamless steel pipe for high pressure boiler. Considering the direct relationship between service life under high temperature conditions, the standard has made clear provisions on the delivery heat treatment of 20G seamless steel pipe, and normalizing at 880℃- 940℃ C is required.
The chemical composition directly affects the weldability of 20G seamless steel pipe. Generally speaking, carbon content is the main factor affecting the weldability of 20G seamless steel pipe. The more carbon content is, the worse the weldability of 20G seamless steel pipe is.
Secondly, the content of alloy elements also has certain impact on the weldability of 20G seamless steel pipe. The more alloy elements are, the worse the weldability of steel is. In addition, according to the carbon equivalent formula of International Welding Association, CE is 0.23-0.34.
Therefore, 20G seamless steel pipe has excellent weldability, and its welding joint is not easy to produce slag inclusion pores, cracks and other defects. The chemical composition directly affects the weldability of 20G seamless steel pipe.
