Carbon Steel Classification

10 # 20 # A3 Q235A 20g 20G 16Mn ASTM A234 ASTM A105 ASTM A403, etc
Seamless tees DN15 to DN800 generally comply with the standards of GB/T12459-2005 in China.
The larger one belongs to the welded tee with seams, and the execution standard is GB/T13401-2005