循环加热和淬火对20MnCrNiMo钢组织及性能的影响

Effect of Cyclic Heating and Quenching on Microstructure and Mechanical Properties of 20MnCrNiMo Steel

对从40 mm厚板坯上切取尺寸为20 mm×40 mm×200 mm的20MnCrNiMo钢试样,分别进行了860℃水淬,860℃水淬再860℃水淬二次淬火,900℃水淬再860℃水淬二次淬火,以及900℃水淬、860℃水淬再860℃水淬三次淬火。经1~3次淬火的试样均于620℃回火。随后,采用光学显微镜、扫描电镜等设备研究了试样的显微组织、断口形貌和力学性能。结果表明,多次淬火可细化钢的晶粒,改善钢的力学性能;三次淬火对组织细化及性能改善的效果好于两次淬火;对于这种钢的两次淬火工艺,初次淬火温度为860℃的工艺能使钢的晶粒更细小,力学性能更优。

20MnCrNiMo steel samples 20 mm thick by 40 mm wide by 200 mm long, cut from a 40 mm thick slab, were subjected to water- quenching from 860℃, two separate water- quenching treatments from 860 ℃, two separate water-quenching treatments from 900℃ and 860 ℃, and three separate water-quenching treatments from 900℃, 860℃ and 860℃, respectively. All the samples were tempered at 620℃ after single or multiple quenching. Subsequently, the samples were subjected to microstructural surveying, fracture observation and mechanical property measurements by means of OM, SEM and so on. The results showed that the multiple quenching practice could cause the steel to exhibit finer grains and better mechanical properties, and that the triple quenching practice was more favorable to structure refining and improvement in properties than the double quenching practice. As to the double quenching practice for the steel, the first quenching from 860℃ was preferable to from 900℃ in terms of the finer grains and better mechanical properties.