Process for continuously annealing a cold-rolled low carbon stee

Details Process for continuously annealing a cold-rolled low carbon stee Process for continuously annealing a cold-rolled low carbon stee

1982-01-13

1984-03-20

Sheehan, John P.

Metal treatment

Compositions

Heat treating

148 121, 148151, C21D 148

Patent

active

044379056

ABSTRACT:
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.degree. C. to an Ac.sub.3 point of the steel strip at an average heating rate of 30.degree. to 100.degree. 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.degree. C. to the Ac.sub.3 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.degree. C. to a desired temperature, at an average cooling rate of 10.degree. to 300.degree. 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.

REFERENCES:
patent: 1144884 (1915-06-01), White
patent: 2287467 (1942-06-01), Carpenter et al.
patent: 2529689 (1950-11-01), Hess
patent: 3320085 (1967-05-01), Turner
patent: 3939013 (1976-02-01), Gardner et al.
patent: 4140552 (1979-02-01), Arnold et al.

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