ASTM A533 Grades B and C are manganese-molybdenum (and Mn-Mo-Ni) alloy steel plates for pressure vessels, differing mainly in their required tensile/yield strength and impact toughness, with Grade C generally offering higher strength than Grade B, both used in quenched and tempered conditions for demanding applications like low-temperature storage or nuclear reactors, but Grade C (Type C) specifies Mn-Mo-Ni alloy for enhanced properties compared to Grade B (Type B).
ASTM A533 Standard
Purpose: Specification for alloy steel plates used in welded pressure vessels and boilers, known for strength and low-temperature toughness.
Composition: Primarily Manganese-Molybdenum (Mn-Mo) steel, with some types (like C) also containing Nickel (Ni) for better properties.
Classes: Available in five types (A, B, C, D, E) and three strength classes (Class 1, 2, 3).
Chemical composition of ASTM A533 Grades B
Grade | C % | Mn %(<40mm) | P% | S% | Si% | Mo% | Ni% |
A533 Grades B | 0.25 | 1.07-1.82 | 0.035 | 0.035 | 0.13-0.45 | 0.41-0.84 | 0.37-0.73 |
Chemical composition of ASTM A533 Grades C
Grade | C % | Mn %(<40mm) | P% | S% | Si% | Mo% | Ni% |
A533 Grades C | 0.25 | 1.07-1.82 | 0.035 | 0.035 | 0.13-0.45 | 0.41-0.84 | 0.67-1.03 |
Mechanical Property of ASTM A533 Grades B
Grade | Min Yield | Tensile | Thicknesss | Elongation |
A533 Grades B | 485 Mpa | 620-795Mpa | <50MM | 16% |
Mechanical Property of ASTM A533 Grades C
Grade | Min Yield | Tensile | Thicknesss | Elongation |
A533 Grades C | 345 Mpa | 550-690Mpa | <50MM | 18% |
Grade B vs. Grade C (Types)
Type B (Mn-Mo): A common grade offering good strength and impact properties, often used in general pressure vessel construction.
Type C (Mn-Mo-Ni): Contains nickel, providing improved toughness and strength, especially at lower temperatures, making it suitable for more critical applications.
Key Differences (General Trends)
Strength: Grade C usually provides higher tensile and yield strengths compared to Grade B within the same class (e.g., Class 2).
Toughness: The addition of nickel in Type C enhances its resistance to brittle fracture, a crucial factor for cryogenic or severe service.
Application: While both are for pressure vessels, Type C's superior properties lend it to even more demanding environments, such as certain nuclear reactor components or extremely cold LNG storage.
