According to the GB / T 707 - 1998 hot-rolled steel GB, No. 20 channel is divided into: 20A; 20b two.20A: height: 200 mm width: 73 mm thickness: 7 mm weight: 22.637 kg / m theory.20b: height: 200 mm width: 75 mm thickness: 9 mm weight: 25.777 kg / m theory.(Note: the theoretical weight calculation of steel hot-rolled steel according to the density of 7.85 g / cm3)
Can check the hot-rolled ordinary channel GB707-88
