Alloy-steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other Special Purpose Applications

Heat Treatment: All austenitic stainless steels shall receive a carbide solution treatment (with special requirements for each grade).
Class 1D shall be applied only to bar and wire, and to finished fasteners directly manufactured from Class 1D bar or wire without any subsequent hot or cold working. Class 1D steel—Grade B8 bar that is hot rolled or forged shall be rapidly cooled immediately after hot working, while the temperature is above 1759°F (955°C), to retain the intergranular carbides in solution. Class 1D should be limited to use at temperatures below 850°F (455°C).

Material Summary: 304 is a typical low-carbon austenitic stainless steel. This grade is derived from 302 with a further reduction in carbon content, possessing good process formability and oxidation resistance. It exhibits strong corrosion resistance to oxidizing acids (such as nitric acid) and has certain corrosion resistance to alkaline solutions and most organic and inorganic acids. Its resistance to intergranular corrosion is superior to 302, which has a higher carbon content, but it still has a tendency toward intergranular corrosion when working long-term in water and steam. This steel has good welding performance. Austenitic stainless steel cannot be strengthened by heat treatment and can only be strengthened by work hardening.

Chemical Properties: 304 exhibits stable oxidation resistance in hot air below 900°C and has good corrosion resistance to nitric acid, sulfuric acid, acetic acid, oxalic acid, and phosphoric acid. When components work long-term in corrosive media, water, or steam media, intergranular corrosion failure may occur. In the solution-annealed state, a U-bend constant strain specimen failed due to intergranular corrosion after 31 hours in a boiling 42% magnesium chloride solution.

Scope of This Standard:
① This standard covers alloy steel and stainless steel bolting materials and bolting for pressure vessels, valves, flanges, and fittings or other special purpose applications for high-temperature or high-pressure service. The definition of bolting is detailed in standard ASTM A962/A962M. Bar and wire shall be hot rolled, and this material may be further processed by centerless grinding or cold drawing. Austenitic stainless steels may be supplied as carbide solution treated or carbide solution treated plus strain hardened. When ordering strain-hardened austenitic steel, the purchaser should pay special attention to ensure full understanding of the contents of Annex X1.
② This standard includes several grades of ferritic steel and austenitic stainless steel designated B5, B8, etc. The selection of steel is determined by design, service conditions, mechanical properties, and high-temperature performance.