Effect Of Heat Treatment Processes On Microstructure And Mechanical Properties Of Low Carbon Martensite Stainless Steel ZG06Cr13Ni₄Mo

Low carbon Fe-13Cr-4Ni marthensitic stainless steels are wildly used in hydraulic turbines, valve bodies and high-pressure pipes in power generation due to their excellent hardenability, high strength, superior low temperature ductility, good toughness and corrosion resistance. The good properties of the steels are on account of its carbon content, austenite-stabilizing elements, and heat treatment conditions. But many factors, such as inappropriate chemistries compositions, cooling rate, or even casting processes, will induce delta ferrite, a controversial phase.By different heat-treatment processes, we gained two kinds ofδ-ferrite in the steel, the steel A contents noδ-ferrite, and the content of 8-ferrite in steel B was about 1%. The influence of the content ofδ-ferrite to the microstructure and mechanical properties was studied. The results show that,δ-ferrite was enrich of Cr and lack of Ni, a low amount ofδ-ferrite will increase the strength and decrease the toughness, and 8-ferrite will trigger cleavage fracture.The effect of cooling rate and tempering time to the microstructure and mechanical properties was also studies. The results show that, a faster cooling rate or longer tempering time does harm to the strength and increase the toughness. Under the same cooling rate, a longer tempering time involves more amount of reversed ausenite, increases the strength and decreases the toughness. Under the same tempering time, a lower cooling rate increases the strength of the material.This article trended to eliminateδ-ferrite in the steel. The research shows that, the heat-treatment temperature under 1030℃can't removeδ-ferrite from the steel. The effect of heat-treatment process to the mechanical properties of the steel containing 1%δ-ferrite is similar to that of noδ-ferrite.