Q275ASS490SS540碳素/低合金结构钢专用结构钢牌号等级化学成分，%脱氧方法CMnSiSP不大于SS330―0.06~0.120.25~0.500.300.0500.045F、b、ZSS330A0.09~0.150.25~0.550.300.0500.045F、b、ZB0.045SS400A0.14~0.220.30~0.650.300.0500.045F、b、ZB0.12~0.200.30~0.700.045C≤0.180.35~0.800.0400.040ZD≤0.170.0350.035T、ZSS490―0.28~0.380.50~0.800.350.0500.045b、Z)