Grade Of Precipitation-Hardened Stainless Steel

　　1. 0Cr17Ni4Cu4Nb steel

　　The steel is martensitic precipitation hardening stainless steel, Ms point about 150℃, Mf point below 30℃. Whether the martensitic transformation is complete or not is affected by the composition and cooling method. The copper in the steel is dispersed on the matrix in a very fine and dispersed ε phase to increase the strength. When treated with H900. σb=1310MPa, σ0.2=1170MPa, δ5=10%, ψ=40%. The steel has good corrosion resistance, corrosion resistance is better than the general martensitic stainless steel, and similar to the general austenitic stainless steel. It has good cutting properties, can be welded without preheating and can be welded without local annealing. It is mainly used in the manufacture of corrosion-resistant and high-strength components such as jet engine compressor casings and large turbine final stage blades.

　　2. 0Cr17Ni7Al steel

　　This grade is semi-austenitic precipitation-hardened stainless steel. It is a steel that is hardened by adding aluminum to 0Cr17Ni7. an unstable austenitic steel, and then undergoing martensitic transformation and precipitation of NiAl compounds. After RH950 treatment, σb=1580MPa, σ0.2=1470MPa, δ5=6%. The steel has good corrosion resistance in oxidizing acids and poor corrosion resistance in non-oxidizing acids such as sulfuric acid and hydrochloric acid. Acid resistance is best when treated with A or A1750. The acid resistance was worse after TH, RH and CH treatment. The steel can be welded using the same welding process as austenitic stainless steel. If the welding rod with the same composition as the base metal is used, there will be a large amount of δ ferrite in the weld, resulting in a decrease in weld toughness, so the welding rod can be appropriately reduced chromium or nickel. Inert gas protection should be used during welding to prevent oxidation of aluminum in the electrode. In order to obtain good welding efficiency, it is best to carry out solution treatment after solution annealing, and then adjust and age treatment. This kind of steel is mainly used in the manufacture of aircraft shells, structural parts, pressure vessels and components of missiles, jet engine parts, springs, diaphragms, bellows, antennas, fasteners, measuring instruments and so on.

　　3. 0Cr15Ni25Ti2MoVB steel

　　The steel is austenitic precipitation-hardened stainless steel, that is, an iron-nickel based superalloy. The steel has stable austenitic structure not only in the solution state but also in the aging state. - Generally by the formation of intermetallic compounds in steel to achieve increased strength and improve high temperature performance. In the aging state σb=1035MPa, σ0.2=690MPa, δ=25%, ψ=40%. The high temperature strength of the steel is good, and the use temperature can reach 600 ~ 700℃. The yield strength below 650℃ is similar to room temperature. It has good toughness at low temperature, but has some disadvantages such as low strength at room temperature and poor welding performance.