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 lim

it 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 10

7

fatigue life the fatigue limit of the steel LG40Cr samples is up to 427 MPa.