30 9 月, 2026
Q355B vs S355JR vs Q235B vs S235JR: Chinese and EN Grade Equivalents
The two pairs line up as Q235B with S235JR and Q355B with S355JR. In both cases the number is the minimum yield strength in MPa and the letter denotes the quality class that controls impact toughness. They are close equivalents, but “equivalent” is not the same as interchangeable: the certificate must reference the standard your drawing names.
Grade equivalence from our database
| Chinese grade | ASTM | EN | JIS |
|---|---|---|---|
| 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 |
| Q195 GB/T 700 |
A36 (approx.) | S185 (EN 10025-2) | SS330 (JIS G3101) |
Q355B technical data
Chemical composition
| Element | Limit |
|---|---|
| C | ≤0.24 |
| Si | ≤0.55 |
| Mn | ≤1.60 |
| P | ≤0.035 |
| S | ≤0.035 |
| Ceq | ≤0.45 |
Mechanical properties
| Property | Value |
|---|---|
| Yield strength (ReL) | ≥355 MPa (≤16 mm) |
| Tensile strength (Rm) | 470–630 MPa |
| Elongation (A) | ≥22% |
| Impact energy | +20 °C, ≥27 J |
How to read the designations
Q stands for qufu (yield). The number is the minimum yield strength in MPa. The trailing letter is the quality class: for the B class, impact toughness is verified at +20 °C. The EN grades read the same way — S355JR is a 355 MPa structural steel with a JR toughness class — which is why the two systems map so closely.
Where substitution is safe and where it is not
| Situation | Substitution |
|---|---|
| General non-certified structural work | Usually acceptable if the section and yield requirement are met |
| A project specified to EN | Requires written approval; the certificate must reference the EN standard |
| Low-temperature service | Not without verifying the impact class for the design temperature |
| Pressure or safety-critical | Not acceptable without the specified standard and inspection regime |
Related reading
Frequently asked questions
Is Q355B the same as S355JR?
They are close equivalents: both are 355 MPa minimum yield structural steels with a toughness class verified at +20 C. They are not interchangeable certificates, so a project specified to EN requires the EN standard on the certificate.
Is Q235B the same as S235JR?
They are close equivalents, both with a 235 MPa minimum yield and a toughness class verified at +20 C. As with Q355B and S355JR, the certificate must name the standard your project requires.
What does the letter B mean in Q235B or Q355B?
The letter is the quality class. Class B means the impact toughness is verified at +20 C; higher classes are verified at lower temperatures.
Tell us the standard, grade, form and size you need and we will quote against it. See our steel product catalogue, how we inspect and certify each order, or request a quotation.