ASTM A203 Gr.D | 3.5%Ni Steel Plates

Characteristics & Applications

The ASTM A203 Grade D plate, which is the same as ASME SA-203 Grade D, is a typical nickel alloy steel pressure vessel plate. Since Grade D steel of ASTM A203 has the nominal nickel content of 3.5%, it is also called “3.5% nickel steel” or “3.5-Ni steel”. Nickel is a ferrite strengthener. Because nickel does not form any carbide compounds in steel, it remains in solution in the ferrite, thus strengthening and toughening the ferrite phase. The 3.5% nickel steels are easily heat treated because nickel lowers the critical cooling rate. It exhibits greater fracture toughness,  greater fatigue resistance and greater hardenability than can be achieved in carbon steels. These characteristics makes it an ideal steel for low- and cryogenic-temperature services.

The ASTM A203 Gr.D plates are primarily intended for low-temperature pressure vessels in petrochemical and coal chemical industry. It can be used for the construction of pressure vessels and equipment operating at low temperatures such as methanol scrubber columns, carbon dioxide absorbing columns, H₂S evaporation columns, ethylene distillation facilities, storage tanks for liquefied propane gas (LPG), and spherical tanks for ethane. In engineering practices, ASTM A203 Gr.D plates are also used as structural steel for the construction of cross-sea bridges in both tropical and arctic regions.

Design Minimum Temperature

The design minimum temperature for ASTM A203 plate, which is the lowest component temperature expected in service, is determined by the thickness of plate according to ASME B31.3 – Process Piping. For plate thickness no greater than 51 mm, the design minimum temperature is -101°C [-150°F]; for plate thickness over 51 mm but no greater than 76 mm, the design minimum temperature is -87°C [-125°F]; for plate thickness over 76 mm, the design minimum temperature is -29°C [-20°F].

Chemical Composition Requirements

Mechanical Properties

Manufacture & Heat Treatment

The main manufacturing processes of ASTM A203 Gr.D plates include: electric furnace melting, ladle furnace refining, vacuum refining, continuous casting, blooming, hot rolling, sandblasting, heat treatment, cutting, sampling, inspection & test, packing & storage. All plates made of ASTM A203 Grade D steel shall be normalized, or cooled at a cooling rate faster than air cooling for improvement of the toughness and subsequently tempered  at not less than 1100°F [595°C] for not less than 0.5 hours.