等温淬火温度对ADI组织和力学性能的影响

Influence of Isothermally Quenching Temperature on ADI Microstructure and Mechanical Properties

分析了含Ni-Cu-Mo低合金的ADI在不同温度下盐浴等温淬火时的组织和力学性能,试验结果表明:(1)淬火温度从400℃降到340℃,针状铁素体和高C奥氏体不断细化,针状铁素体体积分数越来越高,高C奥氏体量越来越低;(2)随着等温淬火温度降低,抗拉强度和伸长率不断升高,均在360℃时达到最高,分别为1 071.3 MPa和8.14%,达到了抗拉强度>1 000 MPa、伸长率>8%的2个性能要求;(3)石墨球的不均匀分布是造成材料伸长率波动的主要原因,石墨球分布均匀,基体组织呈韧性断裂,材料的伸长率高;而石墨分布不均匀,基体组织则呈脆性断裂,材料伸长率就低。

The microstructure and mechanical properties of Ni,Cu-Mo-containing low-alloyed ADI isothermally quenched at different temperatures in Salt-bath was analyzed. The test results showed： （1）When quenching temperature decreased from 400 ℃to 340℃ ,the acicular ferrite and high-C austenite continually became finer,the volume fraction of the acieular ferrite became more and more higher,the quantity of the high-C austenite became less and less. （2）Along with decreasing of the is- othermally quenching temperature the tensile strength and elongation continually increasing,arid both of them reached the highest values at 360 ℃ of 1 071.3 MPa 8.14% respectively which met the requirements of tensile strength 〉1 000 MPa and elongation 〉8%. （3）Spherical graphites （S.G） distributing not uniformly was the main reason causing elongation fluctuation of materials. When S.G distributing uniformly ,the fracture of the matrix structure would be of nodular fracture, and the elongation would be high. When S.G distributing not uniformly, the fracture of matrix structure would be of brittle type and the elongation would be low.