1. Chemical Composition

Carbon steel pipes primarily consist of iron (Fe) and carbon (C), with low levels of other elements. Typical compositions (using ASTM standards as an example) are as follows:

Element Typical Range (Weight Percentage) Remarks

Carbon (C) 0.06%–0.35% Low-carbon steels (e.g., ASTM A53) typically ≤0.30%; high-carbon steels offer higher strength but poorer weldability.

Manganese (Mn) 0.29%–1.06% Enhances strength and hardenability; ASTM A106 Grade B allows 0.29–1.06%.

Silicon (Si) 0.10%–0.35% Improves deoxidation and increases strength.

Sulfur (S) ≤0.035% Impurity; excessive amounts cause hot brittleness.

Phosphorus (P) ≤0.035%–0.05% Impurity; excessive amounts reduce toughness.

Others Traces (e.g., Cu≤0.40%, Ni≤0.40%, etc.) Varies by standard requirements.

Example Grades:

ASTM A53 Grade B: C≤0.30%, Mn≤1.2%, S≤0.045%, P≤0.05%.

GB/T 8163 20# Steel: C 0.17%–0.24%, Mn 0.35%–0.65%, Si 0.17%–0.37%.

2. Mechanical Properties

Mechanical properties depend on composition, heat treatment (e.g., normalizing, annealing), and processing:

Property Typical Range (ASTM Standards) Example (ASTM A106 Grade B)

Tensile Strength 415–655 MPa ≥415 MPa

Yield Strength 240–450 MPa ≥240 MPa

Elongation ≥20%–30% (50mm gauge length) ≥30% (wall thickness ≤22mm)

Hardness ≤197 HB (Brinell) or ≤90 HRB Controlled via heat treatment.

Comparison with Other Standards:

GB/T 8163 20# Steel: Tensile strength ≥410 MPa, yield strength ≥245 MPa, elongation ≥25%.

API 5L Gr.B: Tensile strength ≥414 MPa, yield strength ≥241 MPa.