What Is ASTM A387 Grade 11
ASTM A387 Grade 11, identical to ASME SA387 Grade 11 per the ASME Boiler and Pressure Vessel Code, is a 1.25Cr-0.5Mo chromium-molybdenum low-alloy heat-resistant steel plate engineered for elevated-temperature welded pressure vessels and industrial boilers. Chromium provides oxidation and corrosion resistance, while molybdenum enhances high-temperature creep strength, allowing the material to maintain integrity under sustained stress at temperatures exceeding 500 degrees C. The grade is specified in Class 1 and Class 2 strength levels sharing identical chemical composition.
Class Differences
Class 1 has standard mechanical properties with yield strength of 240 MPa minimum and tensile strength of 415 to 585 MPa, supplied normalized or annealed. Class 2 has enhanced mechanical properties with yield strength of 310 MPa minimum and tensile strength of 515 to 690 MPa, supplied normalized and tempered at a minimum of 620 degrees C.
Equivalent Grades
The closest European equivalent is EN 10028-2 13CrMo4-5 with material number 1.7335; the former German DIN 17155 grade is 13CrMo44; and the Chinese equivalent commonly used for engineering reference is GB/T 713.2-2023 14Cr1MoR. These engineering equivalents may not be suitable for direct substitution without verification of composition, mechanical properties, heat treatment, and design code requirements.
Composition Comparison
A387 Gr.11 has carbon of 0.05 to 0.17 percent, silicon of 0.50 to 0.80 percent, manganese of 0.40 to 0.65 percent, chromium of 1.00 to 1.50 percent, and molybdenum of 0.45 to 0.65 percent. The EN and DIN equivalents have chromium of 0.70 to 1.15 percent with tighter sulfur limits; the Chinese 14Cr1MoR has chromium of 1.15 to 1.50 percent with very tight phosphorus and sulfur limits.
Key Features
The optimized 1.25Cr-0.5Mo chemistry gives superior oxidation resistance, creep strength, and elevated-temperature tensile strength compared with carbon steel plates. Class 2 provides a reliable balance of strength and ductility for welded pressure vessel fabrication. The controlled carbon content minimizes weld cracking susceptibility, and the material is compatible with plate rolling, cold forming, beveling, and submerged arc welding.
Applications
A387 Gr.11 is used for hydrogenation reactors, fractionating columns, heat exchangers, high-temperature piping, shift converters, gasifier shells, boiler drums, superheater headers, high-pressure feedwater heaters, and high-temperature high-pressure separators.
Frequently Asked Questions
Q: What is the equivalent of ASTM A387 Gr.11?
A: EN 10028-2 13CrMo4-5 (1.7335), DIN 17155 13CrMo44, and GB/T 713.2 14Cr1MoR for engineering reference.
Q: Is ASME SA387 Gr.11 the same as ASTM A387 Gr.11?
A: Yes, ASME adopts the ASTM specification with SA designation for pressure vessel code use.
Q: What is the difference between Class 1 and Class 2?
A: Class 2 has higher strength of 310 MPa minimum yield through normalizing and tempering, versus 240 MPa for Class 1.
Q: Can 13CrMo4-5 replace A387 Gr.11?
A: Yes, both are 1.25Cr-0.5Mo steels, but verification per design code is required.
Q: Which grade has better weldability, Gr.11 or Gr.22?
A: Gr.11, with a lower carbon equivalent and hardness, making it less susceptible to cracking.
Q: What is the typical thickness range?
A: 5 to 150 mm with widths of 1000 to 4500 mm and lengths to 18000 mm.
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