After quenching and tempering

straightening and grinding

the surface cracks are found on the polished rod surface of steel 40Crl0Si2Mo 6. 5 mm wire rod. Through the simulation test of quenching and tempering of steel 40Crl0Si2Mo

it is obtained that the reason for the surface crack of steel 40Crl0Si2Mo wire rod is the short cooling time after hot rolling

the cooling speed is fast

and there is a large residual stress on the surface of the hot rolled wire rod leading to form the surface crack. The production process of steel 40Crl0Si2Mo is optimized and improved

including prolonging Stelmo roller slow cooling time

adjusting the finishing rolling temperature and lay-off temperature from 900 ~ 950 °C and 850 〜900 °C to 800 〜850 °C

and within 24 hours after rolling to anneal the wire

the surface crack of steel 40Crl0Si2Mo product has been avoided.