29 9 月, 2026
Q235B vs A36 vs S235JR: Chinese Steel Grade Equivalents Explained
If you are sourcing structural steel from China, the single most common question is: “Is Q235B the same as A36?” The short answer is close, but not identical — and the differences matter at the drawing-review stage, not after the steel is on the water. This guide sets out the Chinese grade system, how it maps to ASTM, EN and JIS grades, and where substitution is safe.
What Q235B actually means
Q235B is a Chinese carbon structural steel defined by GB/T 700. Reading the designation:
- Q — qufu (“yield”), indicating a yield-strength grade.
- 235 — minimum yield strength of 235 MPa at 16 mm and under.
- B — quality class B, which controls impact toughness and sulphur/phosphorus limits.
It is the workhorse grade of the Chinese market: fully weldable, widely stocked, and the cheapest structural option that still meets mainstream engineering requirements. The workhorse structural grade in China. Fully weldable, excellent cost-performance, the closest Chinese equivalent to ASTM A36 / EN S235JR.
Grade equivalence table: GB / ASTM / EN / JIS
The table below is the reference most useful at the quoting stage. Values are drawn from our own verified grade database (39 grades), which we use for every technical enquiry.
| Chinese grade | ASTM | EN | JIS |
|---|---|---|---|
| Q195 GB/T 700 |
A36 (approx.) | S185 (EN 10025-2) | SS330 (JIS G3101) |
| Q235B GB/T 700 |
A36 / A283 Gr.C | S235JR (EN 10025-2) | SS400 (JIS G3101) |
| Q355B GB/T 1591 |
A572 Gr.50 / A992 | S355JR (EN 10025-2) | SM490 (JIS G3106) |
| SS400 (JIS) JIS G3101 |
A36 | S235JR | SS400 |
How to read this: “equivalent” here means similar mechanical role, not an interchangeable certificate. A mill test certificate for Q235B is not a certificate for A36, and a buyer’s inspector is entitled to reject a substitution on that basis alone.
Q235B technical data
Chemical composition (ladle analysis, %)
| Element | Limit |
|---|---|
| C | ≤0.20 |
| Si | ≤0.35 |
| Mn | ≤1.40 |
| P | ≤0.045 |
| S | ≤0.045 |
Source: GB/T 700
Mechanical properties
| Property | Value |
|---|---|
| Yield strength (ReL) | ≥235 MPa |
| Tensile strength (Rm) | 370–500 MPa |
| Elongation (A) | ≥26% |
| Impact energy | +20 °C, ≥27 J |
Where the substitution is safe — and where it is not
| Application | Q235B → A36 | Reason |
|---|---|---|
| General structural framing, non-certified | Typically acceptable | Yield requirements overlap; both are weldable carbon steels |
| Projects specified to ASTM | Requires written approval | Certificate must match the specified standard |
| Low-temperature service (below 0 °C) | Usually not acceptable | Impact-toughness class must be verified for the design temperature |
| Pressure-retaining or safety-critical | Not acceptable | Different standard, different inspection regime |
What to put in your enquiry
To get an accurate quotation and a compliant certificate, specify the following four items. Missing any one of them is the most common cause of a shipment being held at destination.
- Standard and grade — e.g. “ASTM A36” or “GB/T 700 Q235B”, not just “Q235”.
- Product form and dimensions — plate thickness, section size, or pipe OD × wall.
- Tolerance basis — actual thickness or theoretical weight; this changes the price.
- Documentation — mill test certificate to EN 10204 3.1, third-party inspection, or both.
Frequently asked questions
Is Q235B stronger than A36?
Their minimum yield strengths are very close (Q235B at 235 MPa, A36 at 250 MPa). The practical difference is in the certification and tolerance framework, not in raw strength.
Can I get Q235B with an EN 10204 3.1 mill test certificate?
Yes. For export orders we supply a 3.1 certificate issued by the producing mill. If your project requires 3.2 (with an independent inspection body), that must be arranged before rolling — tell us at enquiry stage.
Which grade should I choose for a welded structure?
Q235B is the standard choice for general welded structures in China. Where a design specifies an EN or ASTM grade, we normally quote against that standard directly rather than proposing a substitution, so the certificate matches your drawings.
Who supplies Q235B structural steel from China?
We do — as a trading company, we source from multiple accredited mills rather than a single plant, which means we can hold a delivery schedule when one mill is fully booked. See our steel product catalogue, our quality and inspection process, or request a quotation with your specification. For more grade guidance, see our steel knowledge base.