回火温度对25SiMnNi2CrMo钢组织和性能的影响

为提高钎具产品的性能和使用寿命，采用OM、TEM、冲击和拉伸试验，研究了正火后不同回火温度对25SiMnNi2CrMo钢组织与力学性能的影响．结果表明，25SiMnNi2CrMo钢920℃正火后不同温度回火，随着回火温度的提高，材料的硬度和抗拉强度呈逐渐下降的趋势，冲击韧度值呈先升高后降低、复又升高的变化趋势，300℃回火后冲击韧度出现峰值，450℃回火出现回火脆性．试验材料在300℃回火后，具有最佳的强韧性配合，具体性能为：抗拉强度σb1391MPa、硬度HRC40、冲击韧性AKV72．5 J．300℃以下回火的组织为回火马氏体＋贝氏体＋残余奥氏体；超过350℃回火，残余奥氏体开始发生分解，组织中有碳化物析出，随回火温度提高，碳化物有聚集和球化趋势．提出了25SiMnNi2CrMo钢最佳回火热处理工艺．

Influence of Tempering Temperature on the Microstructure and Properties of 25SiMnNi2CrMo Steel

In order to improve the mechanical properties and quality of drill products, the influence of different tempering temperatures on the microstructure and mechanical properties of 25SiMnNi2CrMo steel are studied by using of OM, TEM, impact test and tensile test. The results show that, with tempering temperature increasing after normalizing at 920℃, the tensile strength and hardness of the tested material reduce gradually, that the toughness falls after rising, then rises again, and reaches mximum value after tempering at 300℃, and that the temper brittleness appears after tempering at 450℃. The experimental material has better matching of strength and toughness after tempering at 300℃. The mechanical properties are as follows： tensile strength σb 1391MPa, hardness HRC 40 and impact strength Axv 72. 5 J. The microstructure of 25SiMnNi2CrMo steel consists of tempering martensite, bainite and retained austenite after tempering at below 300℃. When the tempering temperature exceeds 350℃, the retained austenite is decomposed and carbide precipitated, the precipitated carbide has the tendency of gathering and glomeration with the tempering temperature increasing. The best tempering process of 25SiMnNi2CrMo steel is put forward.