The main reason of low fatigue life of steel 60Si2MnA for auto stabilizing rod (/% : 0.56C

1.74Si

0.74Mn

0.011P

0.007S

0.04Cr) is analyzed by using optical microscope

scanning electron microscope and energy dispersive spectrometer

i. e. the decarburized layer is deeper

there are cracks at surface of steel rod and the quenched structure has a lot of ferrite. With the process measures including adding 0.22% Cr in steel

adding procedure of grinding on while surface of billet and decreasing heating temperature of 150 mm x 150 mm casting billet from original 1130~1150 ℃ to 1080~1100℃

the ferrite content in quenched steel decreases obviously

there is no crack defect on surface of steel bar and the total decarburized layer depth of φ18 mm bar decreases from original 128 μm to 87.5 μm

as a results the fatigue life of the steel increases form 6 x 10

4

~10 x 10

4

to 20 x

10

4

~25 X 10

4

to meet the requirement of design.