| 摘要 |
A cold-rolled low carbon steel strip is continuously annealed by rapidly heating the steel strip with a gaseous combustion product which has been prepared at a combustion air ratio of 0.8 or more but less than 1.0 in a direct fired furnace to a temperature of 500 DEG C. to an Ac3 point of the steel strip at an average heating rate of 30 DEG to 100 DEG C./sec to cause the thickness of a layer of oxides produced on the peripheral surface of the steel strip not to exceed 1,000 angstroms; by maintaining the temperature of the rapidly heated steel strip in a range of from 700 DEG C. to the Ac3 point, in a reducing atmosphere comprising 4% or more of hydrogen and the balance nitrogen, for at least 10 seconds, to reduce the oxide layer; by cooling the steel strip from at least 600 DEG C. to a desired temperature, at an average cooling rate of 10 DEG to 300 DEG C./sec by using a cooling medium comprising a gas and a liquid; and by eliminating an oxide layer formed on the peripheral surface of the steel strip during the cooling procedure. |
