ASTM A36 is a common structural steel in the US. It contains carbon in the range of 0.26 - 0.29%, which contributes to its strength. Manganese is present at 0.80 - 1.20%, enhancing hardenability and strength. Phosphorus and sulfur are restricted to 0.04% each to maintain ductility and prevent brittleness.
Q235B, widely used in China, has a lower carbon content, typically 0.12 - 0.20%. This lower carbon makes it more weldable compared to A36. Manganese ranges from 0.3 - 0.7%, still playing a role in strengthening the steel. Sulfur and phosphorus are limited to 0.045% each. These chemical differences result in Q235B having a slightly lower yield strength (235 MPa for Q235B vs 250 MPa for A36), but better weldability, which is crucial in Chinese construction practices where welding is a common joining method.