Q235A is a very common carbon structural steel grade under the Chinese standard GB/T 700. The "Q" denotes the yield strength, "235" indicates the minimum yield strength of 235 MPa at a thickness of <=16mm, and "A" represents the quality grade (A being the lowest, with the least stringent impact toughness requirements).
Pipes made from Q235A are primarily used for conveying fluids at low pressures and for general structural applications where high toughness is not critical, such as in water and gas pipelines, fencing, scaffolding, and support structures.
Easy to machine, bend, and weld.
One of the most economical steel grades available.
Not suitable for low-temperature environments or dynamic loading conditions.
Non-Pressure Critical: Generally not recommended for high-pressure applications.
Chemical Composition (GB/T 700)
The chemical composition is a key factor defining the grade. The maximum percentages by weight are:
| <= 0.22 | <= 0.35 | <= 1.40 | 0.045 | 0.050 |
Note: The "A" grade is primarily distinguished by its higher permissible limits for Phosphorus and Sulfur compared to B, C, and D grades.
Mechanical Properties (GB/T 700)
The mechanical properties are typically tested on the base material, not the finished pipe. Properties can vary slightly based on the pipe manufacturing process (seamless vs. welded).
| >= 235 MPa | 370 - 500 MPa | >= 26% |
These values are typically for materials with a thickness or diameter of <= 16mm. Yield strength decreases as thickness increases.
The "A" quality grade does not require Charpy V-notch impact testing at any temperature.
Common Q235A Steel Pipe Specifications & Dimensions
Q235A is produced as both seamless (GB/T 8162, GB/T 8163) and welded (GB/T 3091) pipes. The most common standard for welded structural pipes is GB/T 3091.
GB/T 3091 - Welded Steel Pipes for Low-Pressure Fluid Conveyance
| (WT=3.0mm) | (WT=3.5mm) | (WT=4.0mm) | |||
| 15 | 21.3 | 2.5 - 4.0 | 1.39 | 1.53 | 1.71 |
| 25 | 33.7 | 2.5 - 4.5 | 2.35 | 2.59 | 2.93 |
| 40 | 48.3 | 2.5 - 4.5 | 3.42 | 3.87 | 4.37 |
| 50 | 60.3 | 2.5 - 5.0 | 4.24 | 4.90 | 5.55 |
| 65 | 76.1 | 2.5 - 5.5 | 5.41 | 6.26 | 7.11 |
| 80 | 88.9 | 2.5 - 6.0 | 6.36 | 7.38 | 8.38 |
| 100 | 114.3 | 2.5 - 6.5 | 8.23 | 9.56 | 10.88 |
| 150 | 168.3 | 3.0 - 8.0 | 12.23 | 14.21 | 16.21 |
| 200 | 219.1 | 4.0 - 10.0 | 21.21 | 24.60 | 28.57 |
Weight (kg/m)=(OD - WT) * WT * 0.02466
Typically 6 meters or 12 meters per piece.
Q235A is to any single international grade due to differences in standard requirements. However, it is often compared to these grades for reference:
| ASTM A36 | A36 | A36 has a specified tensile strength range and mandatory Charpy impact requirements for structural shapes, which Q235A lacks. |
| EN 10025-2 | S235JR | S235JR has a mandatory Charpy impact test at +20℃ (27J min). In practice, S235JR is much closer to Q235B. |
| JIS G3101 | SS400 | SS400 is a special grade with a specified tensile strength requirement, not a yield strength. |
These comparisons are approximate. For critical applications, the specific chemical and mechanical properties of the actual material should be reviewed against project specifications.
Water and air conveyance systems.
Structural frameworks, fencing, and scaffolding.
Handrails, furniture, and agricultural equipment.
Low-stress mechanical parts.
