What Is A387 Grade 12
ASTM A387 Grade 12 Class 2 is a chromium-molybdenum alloy steel plate, about 1 percent chromium and 0.5 percent molybdenum, ideal for elevated-temperature service with excellent anti-corrosion characteristics. It is used in welded pressure vessels and boilers where the 1Cr-0.5Mo composition balances elevated-temperature strength and fabrication ease.
Equivalents
Engineering equivalents include the EN grade 13CrMo4-5, the former German DIN 13CrMo44, and the British BS 620B. Equivalents share the 1Cr-0.5Mo family composition; the applicable standard governs for design.
Mechanical Properties
Class 2 plates have a tensile strength of 450 to 585 MPa, a minimum yield strength of 275 MPa, a minimum elongation of 19 percent in 200 mm and 22 percent in 50 mm.
Chemical Composition
Heat analysis limits are carbon 0.05 to 0.17 percent, manganese 0.40 to 0.65 percent, phosphorus and sulfur 0.035 percent, silicon 0.15 to 0.40 percent, chromium 0.80 to 1.15 percent, and molybdenum 0.45 to 0.60 percent.
Applications
Pressure vessels and storage tanks for high-temperature processes; boiler and heat exchanger components in steam systems; high-temperature piping, ducting, and pipe supports; sour-service equipment in refineries and petrochemical plants; and power generation components including thermal stations and turbine parts.
Frequently Asked Questions
Q: What is the difference between Class 1 and Class 2?
A: Class 2 has significantly higher tensile and yield strength through heat treatment.
Q: What is the chromium content?
A: About 1 percent.
Q: What is the EN equivalent?
A: 13CrMo4-5 is the common engineering reference.
Q: What is the tensile strength of Class 2?
A: 450 to 585 MPa.
Q: Where is it used?
A: Pressure vessels, boilers, heat exchangers, and power components.
Q: What is the yield strength?
A: 275 MPa minimum.
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