Q235 steel: properties, composition, equivalents
Q235 is the Chinese carbon structural steel of GB/T 700: 235 MPa yield, 370–500 MPa tensile, in four quality classes A–D separated by the impact test.
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What is Q235?
Q235 is the workhorse structural steel of Chinese production, and the grade most often seen on a mill certificate arriving from Asia. The designation is literal: Q is *qufu diandian*, the yield point, and 235 is that yield in MPa up to 16 mm. It is defined in GB/T 700, the Chinese carbon structural steel standard.
What confuses buyers is the letter that follows. Q235A, Q235B, Q235C and Q235D are not strength classes — the strength is identical — they are quality classes defined by the impact test, exactly as JR, J0 and J2 are in the European system. Q235A is tested not at all, Q235B at +20 °C, Q235C at 0 °C and Q235D at −20 °C, each to 27 J.
In practice Q235B is what the market means by Q235: it is the stock grade, the one rolled into sections and coil, and the one that maps directly onto S235JR. A and D are order grades.
The equivalence to S235JR is close but not an identity. Q235B's tensile band is 370–500 MPa against 360–510, and — the detail that matters on a welding procedure — Q235B specifies a *minimum* carbon of 0.12 %, where S235JR only sets a ceiling. A European welding procedure qualified on low-carbon S235JR is not automatically valid on material that has to contain carbon.
Q235 chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | 0.12 – 0.2 | Q235B; Q235A allows 0.14–0.22 %, Q235C and D cap at 0.17 % with no minimum |
| Si | ≤ 0.35 | |
| Mn | ≤ 1.4 | |
| P | ≤ 0.045 | 0.040 % for Q235C, 0.035 % for Q235D |
| S | ≤ 0.045 | 0.040 % for Q235C, 0.035 % for Q235D |
GB/T 700-2006 ladle analysis. The quality letter changes the chemistry as well as the test: A and B carry a carbon minimum, C and D do not and are supplied killed or special killed. A carbon minimum is the structural difference from the European S235 family, which only caps carbon.
Q235 mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| ≤ 16 mm | 235 (34.1) | 370–500 (53.7–72.5) | 26 | ≈ 110–145 HB (typical) |
| > 16 ≤ 40 mm | 225 (32.6) | 370–500 (53.7–72.5) | 26 | — |
| > 40 ≤ 60 mm | 215 (31.2) | 370–500 (53.7–72.5) | 25 | — |
| > 60 ≤ 100 mm | 215 (31.2) | 370–500 (53.7–72.5) | 24 | — |
| > 100 ≤ 150 mm | 195 (28.3) | 370–500 (53.7–72.5) | 22 | — |
| > 150 ≤ 200 mm | 185 (26.8) | 370–500 (53.7–72.5) | 21 | — |
The tensile floor is 370 MPa against 360 MPa for S235JR, and the ceiling is 500 against 510 — a narrower band sitting slightly higher. Yield steps down with thickness on the same pattern as the European grade.
Impact toughness
Q235 requires a minimum Charpy V-notch energy of 27 J at 20 °C (Q235B; longitudinal). The quality letter is the impact test. Q235A has none, Q235B is tested at +20 °C, Q235C at 0 °C and Q235D at −20 °C, all to 27 J. The ladder maps one to one onto S235JR, S235J0 and S235J2.
Q235 equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| A36 | ASTM / ASME | Near | A36 yield is 250 MPa with no impact requirement; close on strength, different on quality class. |
| S235JR | EN (European) | Near | Q235B is the direct counterpart: same 235 MPa yield, same 27 J at +20 °C. Tensile floor is 10 MPa higher and Q235B carries a carbon minimum that S235JR does not. |
| s235j0 | EN (European) | Near | Q235C matches it — 27 J at 0 °C with tightened phosphorus and sulphur. |
| St3sp | GOST (Russia/CIS) | Near | Q235B: 235 MPa yield, 370–500 MPa tensile, carbon minimum present in both. The two grades occupy the same position in their national systems. |
| E250 | IS (India) | Near | Q235B is 235 MPa yield and 370–500 MPa tensile; E250 sits one small step above it on both counts, with a carbon equivalent limit that Q235 does not carry. |
| SS400 | JIS (Japan) | Near | JIS G3101 SS400: 245 MPa yield to 16 mm, 400–510 MPa tensile, no impact test — the Japanese commodity structural grade of the same tier. |
| Q355 | GB/T (China) | Functional | The grade below in the Chinese system: 235 MPa yield under GB/T 700. Q235 to Q355 is the Chinese equivalent of the S235 to S355 step. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for Q235 →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| A3 / A3F | GB 700-1979 (withdrawn) | The pre-1988 Chinese designation; still heard in workshops and occasionally seen on old drawings. |
| Q235-A·F | GB/T 700-1988 | The suffix marked the deoxidation practice: F rimmed, b semi-killed, Z killed, TZ special killed. The 2006 edition dropped the suffix from the grade name. |
Product forms and tolerance standards
Product forms: hot-rolled plate and coil, sections: H beam, channel, angle, flat bar, welded and seamless tube (often certified to GB/T 3091 or GB/T 8162), merchant bar and round bar, cold-formed hollow sections.
Dimensional tolerances: plate: GB/T 709; sections: GB/T 706 (channel and angle), GB/T 11263 (H beam); hot-rolled coil: GB/T 709; round bar: GB/T 702.
Key property values
Q235 yield strength
235 MPa minimum up to 16 mm, stepping to 225 MPa at 16–40 mm, 215 MPa at 40–100 mm, 195 MPa at 100–150 mm and 185 MPa above that. The steps and the values follow the same pattern as the European S235 family, which is what makes the substitution workable.
Q235A, B, C and D
The letters grade the impact test, not the strength. A: no Charpy requirement, carbon up to 0.22 %. B: 27 J at +20 °C, carbon 0.12–0.20 %. C: 27 J at 0 °C, carbon ≤ 0.17 %, P and S to 0.040 %. D: 27 J at −20 °C, carbon ≤ 0.17 %, P and S to 0.035 %, special killed. Q235B is the commercial default.
Q235 chemical composition
For Q235B: C 0.12–0.20 %, Si ≤ 0.35 %, Mn ≤ 1.40 %, P ≤ 0.045 %, S ≤ 0.045 %. The carbon *minimum* is the feature to notice — European structural grades cap carbon without requiring any, so a Q235B plate can be harder and less forgiving in a restrained weld than an S235JR plate of the same nominal grade.
Q235 and Q355
Q355 is the grade above, and it replaced Q345 when GB/T 1591 was revised in 2018. Q235 to Q355 is the Chinese equivalent of the S235 to S355 step: same standard family, same product forms, roughly 50 % more yield. A drawing that still says Q345 is working from the pre-2018 edition.
Accepting Q235 against an S235JR specification
Technically the substitution works and is made daily. Three things should be checked rather than assumed: that the certificate names the quality letter and not just 'Q235'; that the impact test appears on it if the design needs one; and that the welding procedure covers the carbon range actually declared, not the European ceiling.
Weldability
Q235B is readily weldable by all arc processes without preheat in normal thicknesses, and the carbon equivalent is comparable to S235JR. The caution is the carbon minimum: material at the top of the 0.12–0.20 % band behaves differently from a typical European S235JR heat running near 0.10 %, and in thick restrained joints that shows up as a harder heat-affected zone. Use E43xx / ER70S-class consumables. Q235A may be supplied rimmed or semi-killed under older practice, which is a further reason it is not the grade to weld in critical work — specify B as a minimum, and C or D where toughness matters.
Machining, forming and heat treatment
Machinability is good in the as-rolled condition and comparable to other low-carbon structural steels. Cold forming behaviour is acceptable but less predictable than a forming grade, since the standard sets no yield ceiling: a plate at the top of the strength band springs back further. For bending and roll forming from Chinese supply, the forming grades in GB/T 912 or GB/T 3274 are the better specification than the structural one.
Typical applications
- General building steelwork: columns, beams, bracing and purlins in Chinese and export construction
- Welded frames, platforms, ladders and stairs
- Structural hollow sections and fabricated tube structures
- Machine bases, guards and non-critical load-bearing weldments
- Plate for tanks, hoppers and chutes with no pressure duty
- Export sections and coil sold against an S235JR requirement
Q235 compared with related grades
Frequently asked questions
What is Q235 steel?
Q235 is the Chinese carbon structural steel of GB/T 700, with a 235 MPa minimum yield up to 16 mm and a 370–500 MPa tensile band. The Q stands for yield point and 235 is that yield in MPa; it is the most widely rolled structural grade in Chinese production.
What is the difference between Q235A, Q235B, Q235C and Q235D?
The impact test and the chemistry that supports it, not the strength. A has no Charpy requirement, B is tested at +20 °C, C at 0 °C and D at −20 °C, all to 27 J; C and D also tighten phosphorus, sulphur and carbon and are supplied killed.
Is Q235 the same as S235JR?
Q235B is the close counterpart — same yield, same 27 J at +20 °C — but they are not identical. Q235B's tensile band is 370–500 MPa against 360–510, and Q235B specifies a minimum carbon of 0.12 % where S235JR only caps it, which can matter for a welding procedure.
What is the ASTM equivalent of Q235?
A36 is the usual match, with a higher 250 MPa yield and no impact requirement. It is an equivalence of class rather than of specification: a project that calls for A36 with a mill test report will accept Q235B in most commercial work but not where a code names the standard explicitly.
Can Q235 be welded?
Yes, by all arc processes without preheat at normal thicknesses. Specify Q235B as a minimum for welded work — Q235A may be supplied rimmed or semi-killed — and qualify the procedure against the carbon actually declared rather than against a European ceiling.
What replaced Q345?
Q355, in the 2018 revision of GB/T 1591. It is the grade above Q235 in the Chinese system, equivalent in role to S355 in the European one. Drawings still calling for Q345 are working from the pre-2018 edition of the standard.
Is Q235 good quality steel?
For its class, yes — it is a commodity structural steel with a national standard behind it, and the quality letter tells you exactly what was tested. The risk in importing it is not the grade but the certificate: material sold simply as 'Q235' with no letter has no defined impact class.
Related grades
Verified against GB/T 700-2006; GB/T 700-2006 Tables 1 and 2; GB/T 1591-2018 (the Q355 family above it). Last checked: November 2026.