气缸套用灰铸铁等温淬火后的组织与性能

Microstructures and Mechanical Properties of Gray Cast Iron for Cylinder Liner after Austempering Heat Treatment

采用扫描电镜、电子拉伸试验机、布氏硬度等实验方法研究了气缸套用灰铸铁等温淬火前、后的组织特性及力学性能。研究结果表明:灰铸铁在880℃奥氏体化30 min+330℃等温淬火30 min后,基体组织为针状贝氏体,抗拉强度和布氏硬度分别由铸态时的275 MPa、205HB增至处理后的400 MPa、307HB,同时灰铸铁的摩擦磨损性能也得到显著改善;灰铸铁拉伸断口均呈现典型的脆性断裂特征,但是随着等温淬火温度的升高,断口呈现出不同程度的韧性断裂特征。

The microstructures and mechanical properties of gray cast iron for cylinder liner,before and after austempering heat treatment,were investigated by using scanning electron microscopy,tensile tests and Brinell hardness tester.The results show that after austempering heat treatment the matrix microstructures of gray iron change from lamellar pearlite to acicular bainite structure at the austenitizing temperature of 880 ℃ for 30 min and at austempering temperature of 330 ℃ for 30 min.Ultimate tensile strength(UTS) and Brinell hardness value increase from 275 MPa and 205HB(as cast condition) to 400 MPa and 307HB(after austempering heat treatment) respectively,and desirable frictional wear property is also exhibited.The tensile fracture of gray iron is typical brittle cleavage fracture.But with the increase of austempering temperature,the fracture appears some ductile fracture.