GB/T 700 — Carbon structural steels
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Scope
Technical delivery conditions for Chinese hot-rolled carbon structural steel in the Q195, Q215, Q235 and Q275 strength classes, each divided into quality grades A to D by impact test temperature. Covers plate, strip, sections, bar and profiles. Specifies chemical composition, yield by thickness, tensile range, elongation and Charpy requirements. The higher-strength low-alloy grades, including Q355, are in GB/T 1591 instead.
Grades covered by GB/T 700
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Nearest equivalents |
|---|---|---|---|---|---|---|
| Q235 | — | Carbon structural steel (Chinese national standard) | 0.12 – 0.2 | 235 | 370–500 | s235jr, s235j0, a36 |
Revision history and superseded standards
| Year | Change |
|---|---|
| 1979 | GB 700 issued; grades named A3, A3F and similar |
| 1988 | Q-designation introduced with deoxidation suffixes F, b, Z and TZ |
| 2006 | Current edition; deoxidation suffix dropped from the grade name, quality grades A to D retained |
Supersedes: GB/T 700-1988; GB 700-1979.
Where to buy the standard
The full text is copyrighted by SAC (Standardization Administration of China) and is not reproduced here. Purchase the current edition from Standardization Administration of China (SAC) or your national standards body. The values on this site are the normative limits as published; the standard's own tables, notes and test methods govern.
Related standards
Q is the yield point, the letter is the impact test
GB/T 700 is the Chinese carbon structural steel standard and its designation reads directly: Q for the yield point, then that yield in MPa. Q235 guarantees 235 MPa up to 16 mm with a 370–500 MPa tensile band.
The letter after it — A, B, C or D — grades the Charpy test and nothing else. A has no impact requirement, B is tested at +20 °C, C at 0 °C and D at −20 °C, each to 27 J. Strength is identical across all four, exactly as JR, J0 and J2 work in the European system, and a certificate that says only "Q235" has not named a quality class.
The carbon minimum that catches welders out
Q235B specifies carbon as a range, 0.12–0.20 %, where European structural grades only set a ceiling. That is a genuine difference and not a rounding detail: a conforming Q235B plate must contain carbon, while a conforming S235JR plate may run near 0.10 %.
In a thick restrained joint that shows up as a harder heat-affected zone. A welding procedure qualified on European S235JR is therefore not automatically valid on Q235B material, and the declared analysis rather than the grade name is what the procedure should be checked against.