The examination and analysis on thickness

structure and composition of surface residual oxide scale of Φ14mm and Φ16mm coii of spring steel (/%：0.58C

1.66Si

0.78Mn

0.006P

0.004S) have been carried out by using optical microscope and scanning electron microscope. Results show that with eutectoid reaction of Si in spring steel and FeO to form fayalite (2FeO·SiO

2

) produced pinning effect on oxide scale and higher cooling speed of coil after rolling and thicker decarburization layer of coil lead to difficultly remove the oxide scale by picking process. With decreasing heating furnace soaking temperature to 1050℃;from original 1150℃

heating time no more than 2h

controlling residual oxygen content in furnace ≤2%

decreasing finishing r

olling temperature from original 920℃ to 870℃ and end rolling temperature from 880°C to 840°C to avoid occurring full decarburization layer to lighten and avoid to form fayalite ( 2FeO·SiO

2

)

descaling water pressure ≥14MPa and decreasing average cooling speed from 1.9°C/s to 1.6°C/s to make partial FeO transformation

expanding and cracking

the picking effect markedly improves. Results show that after process improvement the picking defect ratio of oxide scale decreases from original 2.91%~3.58% to 0.69%~1.65%.