Patent ID: 7815757

Claim:
A water-cooling method for water cooling a heated steel material, said water-cooling method for a steel material characterized by controlling the thickness of the oxide film formed on the steel material surface by the following equation: d H20 +d o2 =7.98×10 −4 ( T i −T o ) dD o +{5.50×10 −3 ( T i 2 −T o 2 )−6.51( T i −T o )}/ C R where, d H20 : thickness of oxide film formed using steam as oxidizing source (nm) d H2O ={5.50×10 −3 ( T i 2 −T o 2 )−6.51( T i −T o )}/ C R where, T o ≧573K d o2 : thickness of oxide film formed using solute oxygen as oxidizing source (nm) d o2 =7.98×10 −4 ( T i −T o ) dD o , where, T o 24 573K T i : water-cooling start temperature (K) T o : water-cooling end temperature (K) d: steel material thickness (mm) D o : concentration of solute oxygen in cooling water (mgL − ) C R : cooling rate (Ks −1 ).