Q235B or Q355B: Grade Selection Is Really Just Arithmetic

Higher grade isn't automatically better. Q355 is 33% stronger — but in the wrong place it just wastes money.

Q235B and Q355B yield at 235MPa and 355MPa — 33% apart. But grade selection isn't “buy the strongest”; it's arithmetic:

Primary members (frames, crane girders): in high-stress zones Q355 can slim plates by 8–15%, and the steel saved usually outweighs the price premium — worthwhile on most projects.

Secondary members (purlins, girts, knee braces): their sections are governed by stability and detailing, not strength — Q355 adds nothing there but cost.

Connections and gussets: match the grade of the connected members; mixing grades complicates welding.

For export projects under Eurocode: Q355B corresponds to S355JR, but confirm the impact-test temperature (grade B = +20°C) against site climate — cold regions need grade C or D. Xionglan quotes always include grade recommendations and cost comparisons for primary vs secondary steel.