What Is P275NH
P275NH is a non-alloy pressure vessel steel specified in EN 10028-2, a weldable fine-grain structural steel mainly used for pressure-bearing equipment operating at moderate temperatures. The designation indicates a minimum yield strength of 275 MPa and an N heat treatment condition with impact testing at minus 20 degrees C.
Delivery Condition
The mandatory delivery condition is normalized: heating to 890 to 950 degrees C, sufficient holding, and air cooling. This refines the grain structure, improves toughness, and ensures stable mechanical properties, laying the foundation for high-temperature and pressure-resistant service.
Composition and Mechanical Properties
Chemical composition limits are carbon 0.16 percent, silicon 0.40 percent, manganese 0.50 to 1.40 percent, phosphorus 0.030 percent, sulfur 0.020 percent, and nitrogen 0.02 percent, with chromium, copper, molybdenum, niobium, nickel, titanium, and vanadium in controlled small amounts. The minimum yield strength is 275 MPa for thicknesses up to 35 mm, 265 MPa for 35 to 50 mm, 255 MPa for 50 to 70 mm, and 235 MPa for 70 to 150 mm, with tensile strengths of 390 to 510 MPa decreasing with thickness and a minimum impact energy of 47 J at minus 20 degrees C.
Equivalent Grades
Engineering equivalents include the German WSt E285, British BS 1501 224 Gr. 430, and ASTM A516 Grade 60. Equivalent comparisons are for reference only; the applicable standard governs.
Processing Characteristics
The material has excellent formability with low forming force for cold forming and hot forming at 700 to 1050 degrees C, and superior weldability by SMAW, GMAW, and GTAW with preheating of 80 to 150 degrees C and post-weld heat treatment of 550 to 650 degrees C as required. The carbon equivalent is 0.42 percent maximum, and ultrasonic inspection per EN 10028-3 is applied.
Applications
P275NH serves boiler drums, steam headers, heat exchangers, high-pressure storage tanks, and reactor shells in thermal power, chemical, and metallurgical industries; refinery separators and desulfurization towers; and pressure components in marine, food sterilization, and structural service, with long-term operation from minus 20 to 400 degrees C.
Frequently Asked Questions
Q: What is the delivery condition of P275NH?
A: Normalized, heating to 890 to 950 degrees C followed by air cooling.
Q: What is the yield strength?
A: 275 MPa minimum for thicknesses up to 35 mm.
Q: What is the difference between P275NH and P275NL2?
A: Impact test temperature, minus 20 degrees C versus minus 50 degrees C.
Q: What is the maximum carbon equivalent?
A: 0.42 percent.
Q: Is P275NH suitable for boiler drums?
A: Yes, for moderate temperatures and pressures.
Q: What certificates are supplied?
A: EN 10204 3.1 or 3.2 with composition, mechanical, and heat treatment results.
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