When sourcing structural steel from Chinese mills, two standards dominate purchase specifications: GB/T 700 and GB/T 1591. While both cover carbon structural steel, they serve fundamentally different purposes. GB/T 700 defines general-purpose structural steel — the Chinese equivalent of EN 10025 S235/S275. GB/T 1591 covers high-strength low-alloy (HSLA) structural steel with elevated yield strengths up to 460 MPa.
This guide explains the scope, grades, chemical requirements, mechanical properties, and practical procurement implications of each standard — so you can specify the right one with confidence.
Standard Scope: What Each Covers
| Aspect | GB/T 700-2006 | GB/T 1591-2018 |
|---|---|---|
| Full Name | Carbon Structural Steels | High Strength Low Alloy Structural Steels |
| Grade Range | Q195, Q215, Q235, Q275 | Q345, Q355, Q390, Q420, Q460 |
| Min Yield (MPa) | 195-275 | 345-460 |
| Microalloying | None (plain carbon) | Nb, V, Ti, Al (optional) |
| Typical Delivery | As-rolled | As-rolled, normalized, TMCP |
| Weldability | Excellent (low CEV) | Good (CEV 0.35-0.47) |
| European Equivalent | EN 10025-2 S235/S275 | EN 10025-2 S355 / EN 10025-3 S420/S460 |
GB/T 700 Grade Breakdown
| Grade | Yield (MPa) ≤16mm | Tensile (MPa) | Elongation (%) | C% max | Mn% max | Typical Use |
|---|---|---|---|---|---|---|
| Q195 | 195 | 315-430 | 33 | 0.12 | 0.50 | Wire rod, light profiles |
| Q215A/B | 215 | 335-450 | 31 | 0.15 | 1.20 | Light structural sections |
| Q235A/B/C/D | 235 | 370-500 | 26 | 0.20 (A), 0.17 (B/C/D) | 1.40 | General structures |
| Q275A/B/C/D | 275 | 410-540 | 22 | 0.21 (A), 0.20 (B/C/D) | 1.50 | Higher strength structures |
Key: The letter suffix (A, B, C, D) indicates increasing quality levels with tighter chemistry, lower sulfur/phosphorus limits, and — for B, C, D — guaranteed impact properties at progressively lower temperatures:
- A: No impact test required (+20°C)
- B: Impact at +20°C, min 27J
- C: Impact at 0°C, min 27J
- D: Impact at -20°C, min 27J
GB/T 1591 Grade Breakdown
| Grade | Yield (MPa) ≤16mm | Tensile (MPa) | Elongation (%) | CEV max | EN Equivalent |
|---|---|---|---|---|---|
| Q345B/C/D/E | 345 | 470-630 | 21-22 | 0.45 | S355JR/J0/J2/K2 |
| Q355B/C/D/E | 355 | 470-630 | 22 | 0.45 | S355JR/J0/J2/K2 |
| Q390B/C/D/E | 390 | 490-650 | 20 | 0.47 | S420N/NL |
| Q420B/C/D/E | 420 | 520-680 | 19 | 0.47 | S420N/NL / S420M/ML |
| Q460C/D/E | 460 | 550-720 | 17 | 0.47 | S460N/NL / S460M/ML |
Important update (2018 revision): GB/T 1591-2018 introduced Q355 as the replacement for Q345. While Q345 remains in common usage and most Chinese mills can still produce to it, new projects should specify Q355. The chemical and mechanical properties are nearly identical — the change primarily reflects harmonization with international standards that use 355 MPa as the base HSLA yield strength.
Impact Test Requirements Comparison
| Standard | Grade Suffix | Test Temp | Min Energy | Notes |
|---|---|---|---|---|
| GB/T 700 | A | N/A | N/A | No impact test |
| GB/T 700 | B | +20°C | 27J | Room temperature only |
| GB/T 700 | C | 0°C | 27J | |
| GB/T 700 | D | -20°C | 27J | Highest GB/T 700 quality level |
| GB/T 1591 | B | +20°C | 34J | |
| GB/T 1591 | C | 0°C | 34J | |
| GB/T 1591 | D | -20°C | 34J | Minimum for structural applications |
| GB/T 1591 | E | -40°C | 34J | Offshore, arctic applications |
Key difference: GB/T 1591 requires a minimum impact energy of 34J, while GB/T 700 requires only 27J. This reflects the higher criticality of HSLA steel applications.
Practical Procurement: How to Specify Chinese Steel
When buying GB/T 700 or GB/T 1591 steel from Chinese mills, include these elements in your purchase order:
- Standard + year: “GB/T 1591-2018” (not just “GB/T 1591” — the 2018 revision introduced Q355)
- Grade + quality suffix: “Q355D” (not just “Q355” — D suffix guarantees -20°C impact)
- Delivery condition: As-rolled (AR), normalized (N), or TMCP (M) if required
- Dimensions and tolerances: Reference the applicable dimensional standard (GB/T 709 for plate, GB/T 706 for sections)
- MTC type: EN 10204 3.1 or 3.2 (3.2 requires third-party witness)
- Surface condition: As-rolled, shot blasted, or primed (specify primer type)
International Equivalents for Common GB/T Grades
| GB/T Grade | EN 10025 | ASTM | JIS | IS (India) |
|---|---|---|---|---|
| Q235B | S235JR | A36, A283 Gr.C | SS400 | E250BR |
| Q235D | S235J2 | A36 mod | SS400 | E250C |
| Q275C | S275J0 | A572 Gr.42 | SS490 | E275C |
| Q345B | S355JR | A572 Gr.50 | SM490A | E350BR |
| Q355D | S355J2 | A572 Gr.50 Type 1 | SM490B | E350C |
| Q355E | S355K2/NL | A572 Gr.50 mod | SM490C | E350E |
| Q420D | S420NL | A572 Gr.60 | SM520B | E410C |
| Q460E | S460NL/ML | A572 Gr.65 | SM570 | E460E |
Important caveat: These are “approximate equivalents” based on yield strength and typical chemistry. They are NOT identical and should not be used for direct substitution without engineering review. Always verify the full mechanical and chemical requirements of the target standard against the proposed substitute grade.
FAQ
Can I use Q235B as a direct substitute for ASTM A36?
For most general structural applications, Q235B is functionally equivalent to ASTM A36. Both have minimum yield strength of 235-250 MPa and similar tensile ranges. However, Q235B may have slightly lower manganese (1.40% max vs. no explicit max for A36) and different tolerancing. For critical or code-governed structures, verify that the governing specification (AISC, EN 1993, etc.) accepts Q235B as a listed substitute for A36. When in doubt, request dual-certified material (Q235B/A36) from the mill.
Why did GB/T 1591 replace Q345 with Q355?
The 2018 revision of GB/T 1591 harmonized Chinese structural steel grades with international norms. The EN 10025 and ISO 630 standards use 355 MPa as the base HSLA yield strength. The 10 MPa increase from 345 to 355 MPa required only minor chemistry adjustments — primarily a slight increase in manganese and/or microalloy content. Most Chinese mills can produce Q355 with the same production cost as Q345. The change simplifies international procurement by eliminating the confusing “345 vs. 355” discrepancy.
What delivery conditions are available for GB/T 1591 steel?
GB/T 1591-2018 defines four delivery conditions: AR (as-rolled), N (normalized), M (TMCP/thermomechanical rolling), and QT (quenched and tempered). For common structural grades Q355-Q420, AR and N are most typical. M delivery (TMCP) is increasingly common for plate products where low CEV for weldability is critical. QT delivery is primarily for Q460 and above. The delivery condition must be specified on the purchase order — it is not automatically selected by the standard.
Can GB/T 700 Q235 steel be galvanized?
Yes, Q235 (both A and B quality levels) is routinely hot-dip galvanized for structural applications. The silicon content of Q235 (≤0.35% for A, ≤0.35% for B) falls within the Sandelin range (0.04-0.14% Si) where galvanized coating thickness can be variable. For consistent HDG coating, specify Q235 with silicon outside the Sandelin range (≤0.03% or 0.15-0.25%) in the purchase order. This is a mill-controlled parameter and must be requested at the time of order.
Do Chinese mills issue EN 10204 3.1 certificates for GB/T steel?
Most major Chinese mills (Baosteel, Ansteel, Shougang, WISCO, Shagang) routinely issue EN 10204 Type 3.1 mill test certificates for GB/T 700 and GB/T 1591 products destined for export. The 3.1 certificate includes full chemical composition (ladle analysis), mechanical properties (yield, tensile, elongation), impact test results (if specified by quality suffix), and any supplementary testing (ultrasonic, Z-direction) ordered. Always request 3.1 certification specifically — do not assume it is included by default.
Conclusion
GB/T 700 and GB/T 1591 are the two pillars of Chinese structural steel procurement. GB/T 700 covers general-purpose carbon steel (Q195-Q275) — choose this for standard fabrication where yield strength of 235-275 MPa is sufficient. GB/T 1591 covers HSLA structural steel (Q345-Q460) — choose this for load-bearing structures, bridges, offshore platforms, and applications requiring guaranteed low-temperature toughness. The key to successful procurement is specifying the full grade designation with quality suffix (e.g., Q355D) and delivery condition on every purchase order.
Need GB/T 700 or GB/T 1591 carbon steel from certified Chinese mills? Contact Huaxia-Steel for factory-direct pricing, EN 10204 3.1 certification, full range of grades Q195 through Q460, and global shipping with third-party inspection available.
