Quick Answer
Quick Answer
GB/T 700 is China's national standard for carbon structural steel, covering grades Q195, Q215, Q235, and Q275. The "Q" prefix denotes 屈服强度 (yield strength) in MPa; the letter suffix (A, B, C, D) defines the quality grade — primarily the impact test temperature requirement. Q235B is the most widely used structural steel in China and is broadly equivalent to ASTM A36 and EN S235JR.
GB/T 700 (most recent revision: 2006, confirmed 2017) is the foundational Chinese standard for ordinary carbon structural steel supplied as plates, sections, bars, and other hot-rolled products. It is issued by the Standardization Administration of China (SAC) and administered by the National Technical Committee on Steel (SAC/TC183). The standard governs four base grades — Q195, Q215, Q235, Q275 — each subdivided into quality grades that determine impact test requirements and sulphur/phosphorus limits.
The "Q" in the grade designation stands for 屈服强度 (qūfú qiángdù, yield strength). The number is the guaranteed minimum yield strength in MPa for material ≤ 16 mm thick. Quality grade letters A through D indicate progressively tighter chemistry limits and lower impact test temperatures, with A requiring no Charpy impact test and D requiring testing at −20 °C.
Scope and Applicability
GB/T 700 applies to hot-rolled carbon structural steel products intended for:
- General structural fabrication (bridges, buildings, towers, frames)
- Manufacturing of machinery and general engineering components
- Welded, bolted, and riveted connections
- Applications not subject to pressure vessel or cryogenic service
The standard does not cover:
- High-strength low-alloy (HSLA) steels — see GB/T 1591
- Boiler and pressure vessel plate — see GB 713
- Reinforcing bars for concrete — see GB 1499.2
- Cold-formed sections (which reference GB/T 700 grades but have separate product standards)
Delivery condition is hot-rolled (as-rolled) unless normalizing is specified on the purchase order.
Grade Coverage
| Grade | Quality Grades Available | Impact Test Requirement |
|---|---|---|
| Q195 | — (single quality) | None |
| Q215 | A, B | A: none; B: +20 °C |
| Q235 | A, B, C, D | A: none; B: +20 °C; C: 0 °C; D: −20 °C |
| Q275 | A, B, C, D | A: none; B: +20 °C; C: 0 °C; D: −20 °C |
Q195 and Q215 are lower-strength grades used in lightly loaded structural applications, stampings, and general fabrication. Q235 is the most widely specified general-purpose structural grade. Q275 offers higher strength and is used where Q235 yield strength is insufficient but HSLA grades are not yet required.
Chemical Composition Requirements
Chemical composition is determined by ladle analysis (heat analysis). Product analysis tolerances are permitted per Annex A of GB/T 700. All values are mass fraction (wt%).
| Grade | Quality | C max | Mn | Si max | S max | P max |
|---|---|---|---|---|---|---|
| Q195 | — | 0.12 | 0.25–0.50 | 0.30 | 0.040 | 0.035 |
| Q215 | A | 0.15 | 0.25–0.55 | 0.30 | 0.045 | 0.045 |
| Q215 | B | 0.15 | 0.25–0.55 | 0.30 | 0.045 | 0.045 |
| Q235 | A | 0.22 | — | 0.35 | 0.050 | 0.045 |
| Q235 | B | 0.20 | 0.30–0.70 | 0.35 | 0.045 | 0.045 |
| Q235 | C | 0.17 | 0.35–0.80 | 0.35 | 0.040 | 0.040 |
| Q235 | D | 0.17 | 0.35–0.80 | 0.35 | 0.035 | 0.035 |
| Q275 | A | 0.24 | — | 0.35 | 0.050 | 0.045 |
| Q275 | B | 0.22 | 0.50–1.00 | 0.35 | 0.045 | 0.045 |
| Q275 | C | 0.20 | 0.50–1.00 | 0.35 | 0.040 | 0.040 |
| Q275 | D | 0.20 | 0.50–1.00 | 0.35 | 0.035 | 0.035 |
Notes:
- Q235 Grade A with carbon ≤ 0.22% may be supplied without Mn range control.
- For Q235A and Q275A, Mn is not prescribed as a range; only the maximum C applies.
- Al (acid-soluble): not less than 0.020% for Grade C and D (deoxidation requirement).
- For Q235B/C/D: if Si ≤ 0.07%, the steel shall contain Mn ≥ 0.60%.
Mechanical Properties
Tensile properties are determined on longitudinal test specimens per GB/T 228.1. Yield strength values below are minimum values (ReH); UTS (Rm) is a range. Elongation (A) is minimum % on 80 mm gauge length for plate/flat bar.
Yield Strength (ReH, MPa minimum) by Thickness
| Grade | ≤16 mm | >16–40 mm | >40–60 mm | >60–100 mm | >100–150 mm |
|---|---|---|---|---|---|
| Q195 | 195 | 185 | — | — | — |
| Q215 | 215 | 205 | — | — | — |
| Q235 | 235 | 225 | 215 | 215 | 195 |
| Q275 | 275 | 265 | 255 | 245 | 225 |
Tensile Strength (Rm, MPa) and Elongation (A, %)
| Grade | Rm (MPa) | A min % (t ≤ 40 mm) | A min % (t >40–60 mm) | A min % (t >60–100 mm) |
|---|---|---|---|---|
| Q195 | 315–430 | 33 | — | — |
| Q215 | 335–450 | 31 | 30 | — |
| Q235 | 370–500 | 26 | 25 | 24 |
| Q275 | 490–630 | 20 | 19 | 18 |
Note: For sections (angles, channels, beams), the thickness used for grade/property assignment is the flange or web thickness as applicable.
Impact Test Requirements
Charpy V-notch impact tests apply to Quality Grades B, C, and D only. Grade A is exempt. Tests are performed on longitudinal specimens (10 × 10 × 55 mm) per GB/T 229.
| Quality Grade | Test Temperature | Minimum Average Impact Energy (KV₂) |
|---|---|---|
| A | Not required | — |
| B | +20 °C | 27 J |
| C | 0 °C | 27 J |
| D | −20 °C | 27 J |
- Three specimens tested per heat/lot; individual minimum = 70% of average (i.e., ≥ 19 J).
- If one value falls below 19 J or below 27 J average, re-test per GB/T 700 Clause 6.
Quality Grades / Delivery Condition
| Quality Grade | Impact Test | Deoxidation Method | Typical Use |
|---|---|---|---|
| A | None | Rimmed (Z), semi-killed (b), or killed (镇静钢) | General fabrication, non-welded |
| B | +20 °C | Semi-killed or killed | Welded structures, mild climates |
| C | 0 °C | Killed | Welded structures, temperate climates |
| D | −20 °C | Killed + fine-grain (Al ≥ 0.020%) | Cold-weather welded structures |
Delivery is as-rolled (热轧状态). Normalizing may be ordered but is not standard. Surface condition: hot-rolled scale acceptable; surface defects shall not exceed limits in GB/T 700 Table 4.
Cross-Standard Equivalents
The following equivalencies are approximate. Chemical compositions do not align perfectly; verify before substitution.
| GB/T 700 Grade | ASTM Equivalent | EN 10025 Equivalent | IS Equivalent | JIS Equivalent |
|---|---|---|---|---|
| Q195 | — | S185 (EN 10025-2) | — | SS330 (JIS G3101) |
| Q215 | — | S235 (partial) | — | SS330 (JIS G3101) |
| Q235A | A36 (partial) | S235JR | E250 (IS 2062 Gr A) | SS400 (JIS G3101) |
| Q235B | A36 | S235JR | E250A (IS 2062) | SS400 |
| Q235C | A36 (with CVN) | S235J0 | E250B | SS400 |
| Q235D | A36 (with CVN −20) | S235J2 | E250C | — |
| Q275A | A572 Gr 42 (partial) | S275JR | E300 (IS 2062) | SS490 (JIS G3101) |
| Q275B | A572 Gr 42 | S275JR | E300A | SS490 |
| Q275C | A572 Gr 42 | S275J0 | E300B | — |
| Q275D | A572 Gr 42 | S275J2 | E300C | — |
Key differences from A36: Q235B has a lower carbon maximum (0.20%) and requires a positive Mn range (0.30–0.70%), while A36 permits up to 0.26% C (for shapes) and does not mandate impact testing. Yield strength requirements are nearly identical.
MTC Verification Checklist
A Chinese 质量证明书 (zhìliàng zhèngmíngshū, quality certificate / mill test certificate) for GB/T 700 material must include:
- Standard number: GB/T 700 (and year of edition, e.g., GB/T 700-2006)
- Grade and quality designation (e.g., Q235B)
- Heat (炉号 lú hào) and batch number (批号 pī hào)
- Product dimensions (thickness × width × length or section profile)
- Ladle chemical analysis: C, Mn, Si, S, P (all within limits above)
- Mechanical test results: ReH (yield), Rm (tensile), A (elongation)
- Impact test result (if B/C/D quality): temperature, individual values, average (≥ 27 J)
- Delivery condition: hot-rolled (热轧) or normalized (正火)
- Mill signature, stamp, and inspector name
- Compliance statement: "符合 GB/T 700-2006 标准要求"
Common MTC errors to flag:
- Impact values reported at wrong temperature (e.g., +20 °C reported for Grade C ordered at 0 °C)
- Carbon exceeds 0.17% for Q235C/D
- Missing Mn range for Q235B (must be 0.30–0.70%)
- Grade A supplied where Grade B or above was specified
Frequently Asked Questions
What does 'Q' stand for in Q235 and Q275?
The letter Q stands for 屈服强度 (qūfú qiángdù), which means yield strength in Mandarin. The number that follows is the minimum guaranteed yield strength in MPa for material up to 16 mm thick. So Q235 guarantees at least 235 MPa yield for thicknesses ≤ 16 mm, dropping to 225 MPa for 16–40 mm, and so on.
Is Q235B the same as ASTM A36?
They are broadly equivalent in yield strength (235 MPa vs. 250 MPa for A36), but not identical. Q235B has a lower carbon maximum (0.20 wt%) than A36 (up to 0.26 wt% for shapes), making it slightly more weldable. Q235B also requires a Charpy impact test at +20 °C (27 J min), whereas A36 does not mandate impact testing. For most structural substitution purposes they are interchangeable, but confirm with the design engineer.
What is the difference between Q235A and Q235B?
Both have the same yield and tensile strength requirements. The difference is in quality controls: Q235A has a higher permitted carbon (0.22% vs. 0.20%) and no Mn range requirement, and it does not require any Charpy impact testing. Q235B has tighter carbon and Mn controls and requires impact testing at +20 °C (27 J minimum). Q235B is the standard choice for welded structural applications.
Can Q235 be used for pressure vessels?
No. GB/T 700 Q235 is a structural steel standard and is not listed in the Chinese pressure vessel material catalogue (GB 150.2). For boiler and pressure vessel plate in China, use GB 713 grades (e.g., Q245R, Q345R). Substituting Q235 for pressure vessel use would not comply with TSG 21 (Safety Technical Supervision Regulations for Stationary Pressure Vessels).
How do I read a GB/T 700 mill test certificate issued in Chinese?
Key fields to locate: 牌号 (pái hào) = grade designation; 炉号 (lú hào) = heat number; 化学成分 (huàxué chénfèn) = chemical composition; 力学性能 (lìxué xìngnéng) = mechanical properties; 冲击试验 (chōngjī shìyàn) = impact test; 屈服强度 (qūfú qiángdù) = yield strength; 抗拉强度 (kànglā qiángdù) = tensile strength; 断后伸长率 (duàn hòu shēn cháng lǜ) = elongation after fracture. TestCert can parse and validate these fields automatically against the GB/T 700 limits.
What quality grade should I specify for welded offshore or cold-weather structures?
For structures exposed to temperatures down to 0 °C, specify Q235C (impact at 0 °C, 27 J min). For temperatures down to −20 °C, specify Q235D. For higher-strength applications in cold environments, consider GB/T 1591 Q345D or Q345E. Note that for offshore or seismic applications, GB/T 700 grades are generally considered too low in strength and toughness — GB/T 1591 HSLA grades are preferred.
Ready to automate your certificate workflow?
Try TestCert free