The result of heat treatment on 17-4PH
With the aerospace industry, marine industry and the modern chemical industry, the continuous development of new technologies, with the requirement of corrosion resistance, strength of austenitic stainless steel and martensitic stainless steel for strength precipitation hardening stainless steel 17-4PH (equivalent to domestic Cr17Ni4Cu4Nb), in the field of domestic demand for steel is increasing. As our study of precipitation hardening stainless steel in comparison with foreign countries, there are still some gaps, and thus ,17-4PH steel, this single treatment type of martensitic precipitation hardening stainless steel, metallurgical materials in domestic workers has aroused great attention . The performance of 17-4PH steel is mainly through the formation of martensite at this stage, the analysis of copper-rich ε phase out of atoms tend to gather in groups, they maintained a continuous parent phase coherent link. Occurred when the maximum lattice distortion, resulting in the greatest strengthening effect, the phase transition with a lot of steel, like,17-4PH precipitation hardening steel is determined by temperature and time.
The result of heat treatment on 17-4PH precipitation hardening martensitic stainless steel mechanical properties shows on four points.
1. In order to take the strength and toughness into account, the temperature solution treatment on 17-4PH steel should not be too high, nor too low, the general controlled temperature should be between 1020 ~ 1060 ℃. For this homogeneous steel,austenite content is less.
2. The aging temperature of 17-4PH steels shows that as aging temperature increases, the strength and hardness gradually decreases , while the plasticity increases.
3. The aging time on the 17-4PH Steels shows that, σb maximum value of 3h after aging, with the aging time increased to 4h, 5h, its value decreases; and after aging σ0.2 the highest value in the 4h, 3h, 5h, follows after aging. For δ and ψ, its value as the prolongation of aging time increases slightly.
4. At the temperature between 700 ~ 816 ℃ treatment, with the aging temperature, the magnitude of the ultimate strength σb will be lower than the smaller. This means that, if using at higher temperatures, and requiring a good toughness, the better to use the additional intermediate processing of the heat treatment system, it can be better strength and toughness.
(need rectification )
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