Z12CN不锈钢热处理工艺研究

Heat Treatment Process for Z12CN Stainless Steel

Z12CN钢为铸造马氏体不锈钢,常用于制作水泵零件。为确定Z12CN钢的最佳热处理工艺,制作了ϕ30 mm×300 mm的Z12CN钢试块,并对其进行了1020℃保温1.5 h空冷正火和660℃、720℃和760℃回火3 h空冷及760℃回火5 h和7 h空冷。经上述工艺热处理后检测了试块的硬度、强度和冲击韧度以及经最佳工艺热处理后的显微组织。结果表明:随着回火温度的提高,正火后的Z12CN钢强度和硬度降低,冲击韧度提高;回火温度相同,随着回火时间的延长,钢的强度和硬度降低,冲击韧度提高;Z12CN钢的最佳热处理工艺为1020℃保温1.5 h空冷正火+760℃回火3~5 h空冷,经此工艺热处理的30 mm厚Z12CN试块力学性能满足设计要求,显微组织为正常的回火索氏体。

Z12CN steel is a cast martensitic stainless steel,used commonly to manufacture water pump components.To determine the most applicable heat treating processes for the Z12CN steel,the test blocks 30 mm in diameter by 300 mm long were prepared from Z12CN steel,and were normalized by heating at 1020℃for 1.5 h followed by air cooling,and tempered at 660℃,720℃and 760℃for 3 h then air cooled,and tempered at 760℃for 5 h and for 7 h then air cooled.The test blocks were tested for hardness,strengths and impact toughness after being heat treated by the foregoing procedures,as well as for microstructure after being heat treated by the most applicable procedures.The results showed that(a)after normalizing,as tempering temperature increased,the Z12CN steel exhibited decreased strength and hardness and increased impact toughness;(b)when the tempering temperature was the same,as the tempering time prolonged,the steel decreased in strength and hardness and increased in impact toughness;and(c)the most applicable heat treating processes for Z12CN steel were as follows:normalizing consisting of heating at 1020℃for 1.5 h followed by air cooling,tempering at 760℃for 3 to 5 h followed by air cooling,and after being heat treated by such processes the 30-mm-thick test block of Z12CN steel gave the mechanical properties conforming with the design specifications,and the microstructure consisting of normal tempered sorbite.