RE与Mg残留量对厚壁蠕铁组织和性能的影响

Influence of Residual RE and Mg Contents on Structure and Properties of Thick-wall Vermicular Graphite Iron

研究了铁液中RE残留量和Mg残留量对厚壁蠕墨铸铁气缸套组织和性能的影响,分析了厚壁断面组织与性能的均匀性。试验结果表明:(1)铁液中的RE残余量和Mg残余量分别为0.010%和0.009%时,气缸套厚壁处的石墨形态为片状石墨和少量蠕虫状石墨;当RE残余量由0.010%提高至0.022%时,厚壁处的石墨形态为蠕虫状石墨,外层和内层的蠕化率为93%,而中间层的蠕化率为85%。(2)气缸套的基体组织存在晶界碳化物,是由于碳化物形成元素偏析于最后凝固铁液中,增加了铁液的白口倾向,促进晶界碳化物的形成。(3)蠕墨铸铁气缸套的抗拉强度、伸长率和硬度分别为368~390 MPa、0.40%~0.41%和255~266 HBW,试样的拉伸断口形貌由解理面和撕裂棱组成,呈典型的脆性断裂。

The influence of residual RE and Mg contents in iron liquid on the structure and properties of heavy section vermicular graphite iron cylinder liner was investigated,the uniformity of structure and properties were analyzed.The test results showed:(1)When the residual RE and Mg contents in iron liquid were of 0.010%and 0.009%respectively,the morphology in thick wall of cylinder liner was flake graphite+little amount of vermicular graphite,when the residual RE content was increased from 0.010%to 0.020%,the graphite morphology in thick section was of vermicular,the vermicularity of outer and inner layers was of 93%,and the vermicularity of middle layer was of 85%.(2)The existence of crystal boundary carbide in the matrix structure of the cylinder liner was caused due to the precipitation of carbide forming elements in the final solidification of iron liquid,which increased the white tendency of iron liquid and promotes the formation of crystal boundary carbide.(3)The tensile strength,elongation and hardness were of 368~390 MPa,0.40%~0.41%and 255~266 HB respectively,the fracture morphology of specimen was consisted of cleavage surface and tearing edge which was a typical brittle fracture.