Production practice at steel works shows that the surface quality of hot-rolled strip with thickness less than 9mm is better but the surface iron scale of hot-rolled strip with thickness more than 9mm is thick easily to come off during uncoiling process and press-in surface led to dent defect

and its structure is loose easily to absorb moisture from air led to rust spot and mottled spot defects. The oxidation process

forming mechanism in process and forced condition in uncoiling of iron scale are analyzed

and the control technology of iron scale thickness and structure is put forward. The results pilot production of 9.5mm hot-rolled strip coil of steel SPHC (/%: 0.02〜0.06C

≤0.10Si

0.20~0.50Mn

≤0.035P

≤0.035S

≤0.01Alt) show that with the process measures including decreasing heating temperature from 1200℃ to 1180 °C

increasing outlet temperature and rolling speed of finishing rolling respectively from 860°C and 5.0 m/s to 880°C and 6.5 m/s

decreasing coiling temperature from 600℃ to 520℃

and single-stocking of coil

the scale thickness of steel strip decreases from original 10.093~18.94μm to 6.613μm

the iron scale come off phenomenon is no-occurrence at production situ and the surface dent defects of strip after pickling decreases markedly.