Q235 is a widely used carbon structural steel in China, specified by the national standard GB/T 700-2006. The designation “Q” stands for yield strength, and “235” refers to its minimum yield strength of 235 MPa (for thickness ≤ 16 mm). It is also known as mild steel or common steel plate, with excellent weld ability, form ability, and cost-effectiveness, making it the most common material in construction, machinery, and general engineering. It is equivalent to ASTM A36 (USA) and S235JR (Europe) in international standards.

1. Grade Classification (Quality Grades)

Q235 is divided into four quality grades based on chemical composition and impact performance, with increasing purity and toughness from A to D:

• Q235A: No impact test required; highest S content; suitable for non-critical static structures.
• Q235B: Impact test at 20°C (≥27 J); most widely used for general structural applications.
• Q235C: Impact test at 0°C (≥27 J); lower S/P content; for cold environments.
• Q235D: Impact test at -20°C (≥27 J); lowest S/P content; for extreme cold and critical structures.

2. Core Characteristics

• Chemical Composition: Low carbon (≤22%), moderate Mn, low S/P; good weldability and machinability.
• Mechanical Properties: Balanced strength and ductility; yield strength decreases with increasing thickness.
• Physical Properties: High density, standard elastic modulus, and good thermal conductivity.
• Processing: Easy to cut, bend, weld, and machine; suitable for hot rolling and cold forming.

3. Main Applications

• Construction: Steel frames, beams, columns, scaffolding, bridge components.
• Machinery: General parts, chassis, brackets, gears, and pressure vessels.
• Transportation: Vehicle frames, ship hulls, and railway components.
• Other: Pipes, storage tanks, and general engineering structures.

Chemical Composition (Mass Fraction, ≤%)

Physical Properties (Typical Values)

Dimensions (Common Range)