What Is A387 Grade 5 Class 2
ASTM A387 Grade 5 Class 2 is a chromium-molybdenum alloy steel plate specifically designed for weldable pressure vessels and industrial boilers operating at elevated temperatures. The nominal composition is about 5 percent chromium and 0.5 percent molybdenum, and Class 2 is supplied in the normalized and tempered condition with higher strength than Class 1.
Chemical Composition
Heat analysis limits are carbon 0.15 percent maximum, manganese 0.30 to 0.60 percent, phosphorus 0.035 percent, sulfur 0.030 percent, silicon 0.50 percent maximum, chromium 4.00 to 6.00 percent, and molybdenum 0.45 to 0.65 percent, with slightly wider product analysis ranges.
Mechanical Properties
Class 2 plates have a tensile strength of 515 to 690 MPa, a minimum yield strength of 310 MPa at 0.2 percent offset, a minimum elongation of 18 percent in 50 mm, and a reduction of area of 45 percent on round specimens and 40 percent on flat specimens.
Heat Treatment and Properties
Class 2 requires normalizing and tempering, or quenching and tempering, with a minimum tempering temperature, refining the microstructure for higher strength and toughness. The 5Cr composition provides superior oxidation and sulfidation resistance at elevated temperatures compared with lower-chromium grades.
Applications
Oil and gas: refinery towers, catalytic crackers, and gas processing equipment. Petrochemical: high-pressure vessels, separators, and heat exchangers. Power generation: boilers, steam components, and heat recovery steam generators. Fertilizer: ammonia and urea synthesis towers. Chemical and pulp and paper: reactors and processing equipment under cyclic thermal load.
Frequently Asked Questions
Q: What is the difference between Class 1 and Class 2?
A: Class 2 receives stricter normalization and tempering with higher tensile, yield, and toughness.
Q: What is the yield strength of Class 2?
A: 310 MPa minimum.
Q: What industries use Gr.5 Cl2?
A: Oil and gas, petrochemical, power generation, and fertilizer.
Q: What is the nominal chromium content?
A: About 5 percent.
Q: What is the tempering requirement?
A> Normalized and tempered or quenched and tempered with a minimum tempering temperature.
Q: Is it suitable for sour service?
A: Yes, with good resistance to wet H2S in many refinery services.
For A387 Grade 5 Class 2 plate quotations with certification, contact our sales team.