Cr系汽车发动机连杆用钢LG40Cr的疲劳性能

莱钢特钢事业部生产的连杆用钢LG40Cr(/%:0.40C、0.24Si、0.72Mn、0.016P、0.005S、0.98Cr、0.036Al)的工艺流程为50 t电弧炉-60 t LF-VD-260 mm×300 mm连铸-连轧Φ70 mm棒材。用30支LG40Cr钢试样进行旋转弯曲疲劳试验,试验前试样经860℃油淬+570℃回火处理,其屈服、抗拉强度、伸长率和断面收缩率分别为835～840 MPa,1 030～1 040 MPa,14%～15%和48%～49%。钢中非金属夹杂为0～1.0级。圆柱形试样在400～600 MPa 9个应力下采用4点加力的方式进行试验,测试其S-N曲线,计算疲劳极限,并分析420 MPa、500MPa两应力下的疲劳断121形貌。试验结果表明,材料具有良好的强塑性匹配,内部质量良好,洁净度较高,对应于1.0×10⁷疲劳寿命,LG40Cr钢试样的疲劳极限可达427 MPa。

Fatigue Property of Cr Series Steel LG40Cr for Connecting Rod of Auto Engine

The steel LG40Cr for connecting rod (/% : 0. 40C, 0. 24Si, 0. 72Mn, 0. 016P, 0. 005S, 0. 98Cr, 0. 036Al) is produced by 50 t EAF-60 t LF-VD-260 mm x 300 mm bloom concasting- continuous rolling Φ70 mm round bar process flow sheet at Laiwu Special Steel Division. 30 samples of steel LG40Cr are used to carry out rotating bending fatigue test, and before test the samples are heat-treated by oil quenched at 860 ℃ + tempered at 570 ℃ , and their yield and tensile strength, elongation and reduction of area are respectively 835 〜840 MPa and 1 030 ~ 1 040 MPa, and 14% ~ 15% and 48% -49% . The ratings of nonmetallic inclusion in steel are 0 - 1. 0. The test of cylindrical specimen is carried out at 9 stress (400 ~ 600 MPa) by 4 loading point, the S-N curve and the fatigue limit are measured and calculated and the morphology of fatigue fracture of samples at both stress 420 MPa and 500 MPa is analyzed. Test results show that the test material has nice combination of strength and plasticity, good interior metallurgy quality and higher cleanliness, and corresponding to 1. 0 x 10⁷ fatigue life the fatigue limit of the steel LG40Cr samples is up to 427 MPa.