Q235B is a carbon structural steel defined by Chinese standard GB/T 700-2006. It has a minimum yield strength of 235 MPa for thicknesses up to 16 mm, and a tensile strength range of 370–500 MPa. The “B” indicates a guaranteed Charpy impact test at 20°C with a minimum of 27 J. This makes Q235B suitable for general structural purposes such as buildings, bridges, and machinery frames. When cross-referencing Q235B to international standards, several equivalents are commonly used, but careful attention must be paid to impact properties and chemical composition.
The closest European equivalent is S235JR according to EN 10025-2. Both have the same yield strength and require 27 J at 20°C. The chemical limits are very similar, with S235JR typically having a slightly lower maximum carbon content for thicker plates. For most non-critical welding applications, S235JR can directly replace Q235B. However, the European grade S235J0 (0°C impact) or S235J2 (-20°C impact) are not direct substitutes because they have different impact temperature requirements.
The American equivalent is ASTM A36. While A36 has a slightly higher yield strength (250 MPa minimum) and tensile strength (400–550 MPa), it does not mandate impact testing unless specified by the purchaser. Therefore, if the application requires the 20°C impact property of Q235B, one must order A36 with supplementary Charpy test requirements. Also, A36 allows a higher carbon content (up to 0.26% for plates), which may affect weldability in very thick sections.
The Japanese equivalent is Ss400 from JIS G3101. SS400 has the same yield strength of 235 MPa and tensile strength of 400–510 MPa. However, the standard does not require any impact test. For indoor or warm environments this may be acceptable, but for structures subject to impact or low temperatures, SS400 is not a direct replacement unless additional testing is agreed. Other equivalents include Fe360B (old ISO 630) and Indian grade E250A (which has 250 MPa yield, higher than Q235B). In Russia, St3sp (GOST 380) is often used. When cross-referencing, always compare the thickness-specific mechanical properties and ensure the material certificate confirms compliance with the required impact test. For welded structures, all these equivalents have good weldability, but preheating may be needed for plates above 30 mm.
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