法兰毛坯 q235分a、b、c、d四级(gb/t 700-2006)
q23级含 c 0.14-0.22% mn 0.30-0.65% si ≤0.30% s ≤0.050 p ≤0.045
q235b级含 c 0.12-0.20% mn 0.30-0.70% si ≤0.30% s ≤0.045 p ≤0.045（经需方同意，碳含量可不大于0.22%）
q235c级含 c ≤0.18% mn 0.35-0.80% si ≤0.30% s ≤0.040 p ≤0.040
q235d级含 c ≤0.17% mn 0.35-0.80% si ≤0.30% s ≤0.035 p ≤0.035