Ever seen “Q355” or “Q460” in a spec sheet but weren’t sure what it means for seamless steel pipes?
GB/T 1591-2018 is the Chinese national standard for low alloy high-strength structural steels. While it’s often associated with plates and beams, its grades also apply to billets used in cold drawn seamless pipes.
At Yige Steel, we specialize in manufacturing cold drawn seamless steel pipes using Q355, Q460, and other GB/T 1591-compliant materials. Here’s how to understand the standard and how it relates to what you’re sourcing.
What is GB/T 1591?
GB/T 1591-2018 defines technical specifications for low alloy high strength structural steels—often referred to as “Q” series steel.
Key features:
- High yield strength (Q355 = 355 MPa, Q460 = 460 MPa)
- Low carbon and good weldability (CEV < 0.45)
- Impact toughness classified as B, C, D, E grades
- Grades applicable for structural plates, sections, and billets (→ seamless pipes)
Yige Steel uses Q355D, Q460C, and Q460D billets for cold drawn seamless pipes, delivering mechanical performance equivalent to high-end structural steels.
GB/T 1591 Steel Grades Used for Pipes
| Grade | Yield Strength (MPa) | Impact Temp | Common Use |
|---|---|---|---|
| Q355B | ≥355 | Room temp | General mechanical |
| Q355D | ≥345 | -20°C | Structural in cold regions |
| Q460C | ≥460 | 0°C | Load-bearing pipe |
| Q460D | ≥440 | -20°C | Precision machinery tubing |
Why Use Cold Drawn Seamless Pipes with GB/T 1591 Grades?
Cold drawn pipe offers more than just roundness—it brings real performance benefits.
At Yige Steel, we combine GB/T 1591-compliant steel billets with precision cold drawing and heat treatment, resulting in:
- Tight dimensional tolerances (OD ±0.1 mm, WT ±0.15 mm)
- Smooth surface finish (ideal for coatings, welding)
- Improved mechanical uniformity
- Flexibility for small batch custom production
Whether you’re building frames, cylinders, or agricultural equipment, these tubes are lightweight, strong, and ready to perform.
Key Differences Between Q355 and Q460 in Pipes
| Feature | Q355 | Q460 |
|---|---|---|
| Strength | Moderate (most applications) | High (heavy load, lighter structure) |
| Elongation | Better | Slightly lower |
| Cost | Lower | Higher |
| Use case | General structural/mechanical | Machinery, load-bearing parts |
| Impact Resistance | Q355D: -20°C | Q460D: -20°C |
Want help deciding? Contact our team and we’ll recommend the best fit.
What Buyers Should Know When Ordering GB/T 1591 Tubes
It’s not just about the grade—spec details matter.
Before ordering, always confirm:
- Which delivery condition you need (+A, +N)
- Whether impact testing at low temperatures is required
- Full MTC with mechanical and chemical results
- Dimensional tolerances (especially for welding or hydraulic applications)
Yige Steel provides cold drawn seamless tubes with full documentation and supports small-batch orders, starting from just 2 tons.
Conclusion
GB/T 1591 isn’t just a plate standard—it’s a comprehensive framework for structural steel selection, including cold drawn seamless tubes.
At Yige Steel, we use this standard to deliver reliable, weldable, and high-strength seamless pipes tailored to your project needs.
