API 5L Grade B vs API 5L X42
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
API 5L Grade B
Pipe & Tube Steel
API 5L Grade B is the entry grade of the pipeline specification — the most common line-pipe steel worldwide for low and medium-pressure oil, gas and water transmission. The letter B grade anchors the bottom of the X-grade strength ladder.
Standards: DIN L245 (EN 10208, near) · AISI API 5L B (PSL2) · GB L245 (GB/T 9711)
API 5L X42
Pipe & Tube Steel
API 5L X42 is the first of the X grades — 42 ksi minimum yield — used for moderate-pressure oil and gas pipelines. In the Chinese GB/T 9711 system the identical strength level is designated L290.
Standards: DIN L290 (near) · AISI API 5L X42 (PSL2) · GB L290 (GB/T 9711)
Chemical composition compared (%)
| Element | API 5L Grade B | API 5L X42 |
|---|---|---|
| C | ≤0.24 (PSL2) | ≤0.24 (PSL2) |
| Si | ≤0.40 | ≤0.45 |
| Mn | ≤1.20 (PSL2) | ≤1.30 (PSL2) |
| P | ≤0.025 | ≤0.025 |
| S | ≤0.015 | ≤0.015 |
Properties compared
| Property | API 5L Grade B | API 5L X42 |
|---|---|---|
| Yield strength | ≥245 MPa (35,500 psi) | ≥290 MPa (42,000 psi) |
| Tensile strength | 415–655 MPa (PSL2) | 415–655 MPa (PSL2) |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: API 5L Grade B · API 5L X42. Substitution decisions for certified parts stay with the design authority.