The direct Chinese equivalent of S355J0 (EN 10025-2) is Q355B according to GB/T 1591-2018.
However, this equivalency requires important clarification regarding the impact toughness test temperature, which is a key point of difference between the standards.
1. Direct Grade Equivalent
| European Grade (EN) | Chinese Equivalent (GB/T) | Standard |
|---|---|---|
| S355J0 | Q355B | GB/T 1591-2018 (High strength low alloy structural steels) |
Decoding the Chinese Grade Q355B:
Q: "Qu" (屈) for Yield Strength.
355: Minimum Yield Strength in MPa (thickness ≤ 16mm).
B: Quality Grade, indicating impact testing at room temperature (20°C).
2. Critical Difference: Impact Test Temperature
This is the most important technical discrepancy between the two "equivalent" grades.
S355J0 (EN): Mandatory Charpy V-notch impact test at 0°C. Minimum energy: 27 J.
Q355B (GB): Mandatory Charpy V-notch impact test at +20°C (Room Temperature). Minimum energy: ≥ 34 J for thickness ≤ 40mm.
The Issue: Q355B is not required by the standard to be tested at 0°C. Therefore, while it matches the strength, it does not automatically guarantee the same low-temperature (0°C) toughness as S355J0.
3. How to Specify a True "S355J0 Equivalent" in China
To get a material that matches both the strength and the 0°C impact toughness of S355J0, you have several options:
Option 1: Specify Q355B with Supplemental 0°C Impact Requirement
This is the most common and practical method. On the purchase order, specify:
Material: Q355B according to GB/T 1591-2018.
Supplementary Requirement: Charpy V-notch impact test at 0°C shall be conducted. Minimum average impact energy shall be 27 Joules (longitudinal).
Option 2: Use a Higher Chinese Quality Grade
Q355C: Tested at 0°C (Min. energy: ≥ 34 J). This is the closest standardized match. It actually has a higher energy requirement (34J vs 27J) at 0°C, making it technically superior.
Q355D: Tested at -20°C.
Q355E: Tested at -40°C.
Option 3: Reference the Old GB Standard (Still Recognized)
The old standard GB/T 1591-2008 had a grade Q345B, which was tested at +20°C, and Q345C, which was tested at 0°C. Many mills and fabricators are still familiar with this designation.
Q345C (GB/T 1591-2008) is a historic direct match for S355J0.
4. Comparison Table for Clarity
| Property | S355J0 (EN 10025-2) | Q355B (GB/T 1591-2018) | Q355C (GB/T 1591-2018) |
|---|---|---|---|
| Min. Yield Str. | 355 MPa (t≤16mm) | 355 MPa (t≤16mm) | 355 MPa (t≤16mm) |
| Tensile Str. | 470-630 MPa | 470-630 MPa | 470-630 MPa |
| Impact Test Temp. | 0°C | +20°C | 0°C |
| Min. Impact Energy | 27 J | ≥ 34 J (at +20°C) | ≥ 34 J (at 0°C) |
| True Equivalence | Benchmark | Not Equivalent (wrong test temp) | Superior Equivalent (same temp, higher energy) |
5. Practical Recommendation for Procurement
To avoid mistakes and ensure you get the correct material:
For drawings/specs in China: Use Q355C if you need the guaranteed 0°C toughness of S355J0. It is a safer, standardized choice.
When communicating with a Chinese mill/supplier: Always state clearly:
*"We require material equivalent to European grade S355J0, with Charpy impact test at 0°C minimum 27J. Please supply Q355C per GB/T 1591 or equivalent with mill certificate showing 0°C impact test results."*
Always require the Mill Test Certificate (MTC): Verify it lists the actual chemical composition and mechanical properties, including the impact test results at the specified temperature.
Summary
The nominal Chinese equivalent of S355J0 is Q355B, but this does not guarantee the same low-temperature toughness. To get a true technical equivalent, you should specify Q355C (which is actually tougher), or explicitly add a supplemental 0°C impact test requirement to a Q355B order. Always clarify the impact test requirement to prevent receiving a material that is only suitable for ambient temperature applications.