ASTM A106 Grade B and Grade C are both specifications for seamless carbon steel pipe suitable for high-temperature service. However, there are key differences between them in terms of their mechanical properties and chemical composition. Here's a detailed comparison:

ASTM A106 Grade B

Chemical Composition:

Carbon (C): 0.30% max

Manganese (Mn): 0.29-1.06%

Phosphorus (P): 0.035% max

Sulfur (S): 0.035% max

Silicon (Si): 0.10% min

Mechanical Properties:

Tensile Strength: 415 MPa (60,000 psi) min

Yield Strength: 240 MPa (35,000 psi) min

Elongation: Varies with wall thickness, generally around 30-22% in 2 inches (50.8 mm) depending on the wall thickness and diameter.

Applications:

Grade B is commonly used in applications that require moderate strength and good welding properties. It is widely used in the oil and gas industry, for steam lines, and in high-temperature applications.

ASTM A106 Grade C

Chemical Composition:

Carbon (C): 0.35% max

Manganese (Mn): 0.29-1.06%

Phosphorus (P): 0.035% max

Sulfur (S): 0.035% max

Silicon (Si): 0.10% min

Mechanical Properties:

Tensile Strength: 485 MPa (70,000 psi) min

Yield Strength: 275 MPa (40,000 psi) min

Elongation: Varies with wall thickness, generally around 20-22% in 2 inches (50.8 mm) depending on the wall thickness and diameter.

Applications:

Grade C is used when higher mechanical properties are required, such as in high-pressure applications and in situations where the pipe may be subjected to high stress.

Key Differences

Mechanical Properties:

Tensile Strength: Grade C has higher tensile strength (485 MPa vs. 415 MPa).

Yield Strength: Grade C has higher yield strength (275 MPa vs. 240 MPa).

Carbon Content:

Grade C has a higher maximum carbon content (0.35% vs. 0.30%).

Applications:

Grade B is suitable for moderate conditions and widely used in general applications.

Grade C is suitable for more demanding conditions where higher strength and durability are required.

Summary

A106 Grade B: Suitable for general high-temperature service with moderate strength requirements.

A106 Grade C: Suitable for more demanding applications requiring higher strength.

Choosing between Grade B and Grade C depends on the specific mechanical requirements and the conditions under which the pipe will be used.