Carbon steel welded pipe chemical composition

Element

Function

Typical Content Range

Carbon (C)

Enhances strength and hardness; higher levels reduce ductility.

0.06% – 0.30% (low to medium carbon steel)

Manganese (Mn)

Improves strength, toughness, and hardenability.

0.25% – 1.65%

Silicon (Si)

Slightly increases strength and improves corrosion resistance.

0.10% – 0.35%

Phosphorus (P)

Enhances machinability in low amounts; excess lowers ductility.

≤ 0.035%

Sulfur (S)

Aids machinability but reduces toughness and weldability.

≤ 0.035%

Copper (Cu)

Improves atmospheric corrosion resistance (used in certain grades).

≤ 0.40% (optional)

Grade

C (max)

Mn

P (max)

S (max)

Si

Grade A

0.25%

0.95% max

0.05%

0.045%

Not specified

Grade B

0.30%

1.20% max

0.05%

0.045%

Not specified

C (max)

Mn (max)

P (max)

S (max)

Other Elements

0.26%

1.20%

0.030%

0.030%

Cu, Ni, Cr, Mo ≤ 1.0% combined

Type

Carbon Content

Properties

Application Examples

Low Carbon Steel

≤ 0.25%

Good weldability, ductility, and formability

Water/gas transport, structural parts

Medium Carbon Steel

0.25% – 0.60%

Higher strength, lower weldability

Pressure piping, automotive systems

High Carbon Steel

≥ 0.60%

Very high strength, limited weldability

Rarely used for welded pipes