20g steel pipe is the steel grade in the old national standard gb53 10 (foreign counterparts: German st45.8, Japanese STB42, American SA 106B), and it is the most commonly used steel for boiler steel pipes, and its chemical composition and mechanical properties are basically the same as those of 20 plates. The steel has certain strength at room temperature and medium and high temperature, low carbon content, good plasticity and toughness, and good cold and hot forming and welding properties.

"G" stands for "pot", that is, the steel used for the pressure vessel of No.20 boiler.

This steel grade has been changed to Q245R in the 2008 standard.