ASTM A106 is a standard specification for seamless carbon steel pipe used for high-temperature service. The specification includes three grades: A, B, and C. The primary differences between A106 Grade B and Grade C lie in their chemical composition and mechanical properties. Here's a breakdown:

1. Chemical Composition:

The main difference in the chemical composition between A106 Grade B and Grade C is the carbon content:

Grade B:

Carbon (C): Max 0.30%

Manganese (Mn): 0.29–1.06%

Phosphorus (P): Max 0.035%

Sulfur (S): Max 0.035%

Silicon (Si): Min 0.10%

Grade C:

Carbon (C): Max 0.35%

Manganese (Mn): 0.29–1.06%

Phosphorus (P): Max 0.035%

Sulfur (S): Max 0.035%

Silicon (Si): Min 0.10%

Note: The carbon content is slightly higher in Grade C, which generally contributes to higher strength.

2. Mechanical Properties:

The mechanical properties of the two grades differ due to the varying carbon content:

Grade B:

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

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

Grade C:

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

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

Grade C has higher tensile and yield strengths than Grade B, making it stronger and more suitable for higher-stress applications.

3. Applications:

Grade B: Typically used in lower stress applications like general piping, structural piping, and boiler tubing.

Grade C: Used in higher-stress applications due to its higher strength, such as in more demanding service conditions, including higher pressure and temperature environments.

Summary:

A106 Grade B has lower carbon content and lower mechanical strength than A106 Grade C.

A106 Grade C is stronger and more suitable for higher-stress applications due to its higher carbon content and resulting mechanical properties.