1. Equivalence of domestic standards
GB/T 3639-2000: Early national standards approximated DIN 2391, but did not fully cover the provisions of quality class C. Additional requirements had to be negotiated.
GB/T 3639-2009: After revision, it is changed to adopt EN 10305-1 (European standard), and the correlation with DIN 2391 is weakened.
2. Material composition equivalence
St35 (DIN 2391) and 20-gauge steel (GB/T 8163):
Chemical composition: Both have similar carbon (C: 0.17-0.23%) and manganese (Mn: 0.35-0.65%) contents, and are low carbon steels.
Mechanical properties: St35 yield strength ≥ 235 MPa, tensile strength of 360-510 MPa; 20 steel yield strength ≥ 245 MPa, tensile strength of 410-550 MPa, performance is similar but 20 steel strength is slightly higher.
Applicability: It can be used in mechanical structure, hydraulic system and other scenarios, but the impurity control of St35 is more stringent, and it is recommended to give priority to the original standard material in high-precision scenarios.
3. International standards
EN 10305-1: The corresponding version of the current European standard DIN 2391, which covers the high-precision requirements for cold-drawn seamless steel tubes.
ASTM A519: Similar materials (e.g. 1020 carbon steel) in the American standard can be partially replaced, but the dimensional tolerance and surface finish should be verified with specific applications.
4. Special scenario differences
High precision requirements: DIN 2391 outer diameter tolerance (±0.05 mm), surface roughness (Ra ≤ 0.8 μm) requirements are higher than DIN 1630 and some of the national standards, you need to give preference to the original standard or EN 10305-1 materials.
Corrosion resistance: For acid resistance, St35 needs to be upgraded to St35 N by normalising, while 20-gauge steel requires additional surface treatment or acid-resistant alloy steel.
