ASTM A106 is a standard specification for seamless carbon steel pipes used in high-temperature services. The specification covers three different grades: A, B, and C, which differ mainly in their chemical composition and mechanical properties.

1. Chemical Composition:

Grade A has the lowest carbon content, followed by Grade B and then Grade C, which has the highest carbon content.

Grade A: ≤ 0.25% Carbon

Grade B: ≤ 0.30% Carbon

Grade C: ≤ 0.35% Carbon

2. Mechanical Properties:

Tensile Strength (Ultimate strength):

Grade A: 48,000 psi (330 MPa)

Grade B: 60,000 psi (415 MPa)

Grade C: 70,000 psi (485 MPa)

Yield Strength (The stress at which material begins to deform permanently):

Grade A: 30,000 psi (205 MPa)

Grade B: 35,000 psi (240 MPa)

Grade C: 40,000 psi (275 MPa)

3. Applications:

Grade A: Used where lower strength is acceptable, such as low-pressure piping.

Grade B: The most commonly used grade, suitable for higher pressure and temperature.

Grade C: Used for even higher pressure and temperature applications due to its higher strength.

In summary, Grade A has the lowest strength, while Grade C has the highest strength. Grade B is the most widely used due to its balance of strength and cost.