P355GH and S355J2 steel plates both belong to the family of fine-grained steels with a nominal minimum yield strength of 355 MPa, but they are governed by different European standards and are intended for different service conditions. P355GH is a pressure vessel steel defined in EN 10028-2 for boilers and elevated temperature equipment, while S355J2 is a structural steel defined in EN 10025-2 for general engineering structures. This article compares the designations, chemical composition, mechanical properties, and applications of the two grades so that the correct material can be selected for a given project.
Designations and Standards
In P355GH, P identifies pressure vessel application, 355 is the minimum yield strength in MPa for the thinnest thickness group, G indicates fine-grain steel, and H indicates suitability for elevated temperatures. The material is covered by EN 10028-2 for flat products made of steels for pressure purposes. In S355J2, S identifies a structural steel, 355 is the minimum yield strength in MPa, and J2 is the impact testing designation requiring a minimum Charpy V-notch energy of 27 J at -20 C. S355J2 is covered by EN 10025-2 for hot rolled structural steel products. P355GH plates are normally delivered in the normalized condition, while S355J2 is commonly supplied in the normalized or as-rolled condition depending on thickness and producer practice.
Chemical Composition Comparison
P355GH has carbon 0.10 to 0.22%, silicon maximum 0.60%, manganese 1.10 to 1.70%, phosphorus maximum 0.025%, and sulfur maximum 0.015%, with total aluminum minimum 0.020%, nitrogen maximum 0.012%, and limits on chromium 0.30%, copper 0.30%, molybdenum 0.08%, niobium 0.040%, nickel 0.30%, titanium 0.03%, and vanadium 0.02%. S355J2 has carbon maximum 0.24%, silicon maximum 0.60%, manganese maximum 1.70%, phosphorus maximum 0.035%, and sulfur maximum 0.035%, with chromium, copper, molybdenum, niobium, and nickel restricted to about 0.30% each and vanadium up to 0.60%. The tighter phosphorus and sulfur limits of P355GH provide better toughness and weldability for pressure service, while the higher allowable carbon of S355J2 reflects its structural role where through-thickness properties are less critical.
Mechanical Properties Comparison
For P355GH, the minimum yield strength ranges from 355 MPa for plates up to 16 mm down to 280 MPa for plates from 150 to 250 mm, with tensile strength of 510 to 650 MPa and a minimum elongation of 20%. For S355J2, the minimum yield strength is 355 MPa for plates up to 16 mm and 295 MPa for plates from 150 to 250 mm, with tensile strength of 510 to 680 MPa for plates up to 16 mm, 450 to 600 MPa for thicker plates, and elongation of 22% for thin plates reducing to 17% for thicker sections. Both grades require a minimum impact energy of 27 J at -20 C. The key difference is that P355GH maintains tighter strength and toughness control across the full thickness range and retains usable strength at elevated temperature, which is the basis for its use in pressure equipment.
Applications
P355GH is used for boilers and boiler drums including shells, water walls, superheater tubes, and economizer tubes; heat exchangers and steam generators such as shell-and-tube exchangers and waste heat recovery systems; high-pressure storage tanks for petroleum, gas, and LPG; chemical and petrochemical processing equipment including reactors, distillation columns, and fractionators; and power generation components such as feedwater heaters, condensers, and steam generators. S355J2 is used for general structural engineering including bridges, buildings, halls, and industrial frames, as well as machinery frames, vehicle structures, and components subject to static and dynamic loads in construction and transportation. When a component must resist pressure and elevated temperature, P355GH is the appropriate choice; when the requirement is load-bearing structural strength at ambient temperature, S355J2 is the economical option.
Frequently Asked Questions
What is P355GH material?
P355GH is a pressure vessel steel that gives optimum performance for pressurized products that must support a creep limit greater than 180 N/mm2 at 400 C. It is characterized by good weldability and is used for boilers, pressure vessels, and pipes transporting hot liquids.
What is EN 10028 P355GH equivalent to?
P355GH pressure vessel steel is approximately equivalent to ASTM A516 Grade 70 and ASME SA516 Grade 70 in strength level, although the specifications differ in chemical limits and testing rules.
What is the difference between P355GH and P355NH?
P355GH is designed for high-temperature applications and is characterized by high strength at temperatures up to about 500 C. P355NH is designed for low-temperature applications and is characterized by high toughness at low temperatures.
What is P235GH pipe equivalent ASTM material?
P235GH is a European standard grade under EN 10028-2. Its approximate ASTM equivalent is ASTM A285 or A285M carbon steel plate.
What is the yield strength of P355GH?
Carbon steels such as P355GH can bear significant pressure at both high and low temperatures. The yield strength ranges between 315 and 355 MPa depending on thickness, and the tensile strength goes from 510 to 650 MPa.
Which standard covers S355J2 steel?
S355J2 is specified in EN 10025-2, which covers hot rolled products of structural steels, and requires a minimum Charpy V-notch impact energy of 27 J at -20 C.