Purge method for annealing of low-carbon cold-roll steel sheets

Abstract

The invention discloses a purge method for annealing of low-carbon cold-roll steel sheets and belongs to the technical field of metallurgical production. The invention provides the low-carbon cold-roll steel sheet annealing specialized purge method which can be adopted to realize reduction protection of strip steel during the annealing process and avoid element precipitation defects of strip steel during the annealing process. According to the purge method, primary deoxygenation nitrogen purging is firstly carried out for at least one hour until the content of oxygen in an annealing furnace is less than 1%; denitrogen hydrogen purging is carried out for at least 50 minutes to discharge nitrogen in the annealing furnace; protective hydrogen purging is carried out during the heating process until steel coil temperature reaches 650 DEG C while guaranteeing that the purging time for the protective hydrogen purging lasts at least 8 hours from the protective hydrogen purging; reducing hydrogen purging is carried out during the thermal insulation process so as to discharge oxidizing gases which have been reduced in steel coil from the annealing furnace; and finally, filling hydrogen purging is carried out during the annealing process until the steel coil temperature in the annealing furnace drops to 400 DEG C.

Description

technical field [0001] The invention relates to a purging method, in particular to a purging method for annealing low-carbon cold-rolled steel plates, and belongs to the technical field of metallurgical production. Background technique [0002] The bell annealing furnace is used for recrystallization annealing of cold-rolled strip steel to eliminate the residual stress of the strip steel and improve the stamping and drawing properties of the material. Bell annealing furnaces in the prior art are further divided into full-hydrogen bell annealing furnaces and nitrogen-hydrogen bell annealing furnaces. Compared with nitrogen-hydrogen bell annealing furnaces, full-hydrogen bell annealing furnaces have high heat transfer efficiency, It has the advantages of strong purging ability, good surface quality and low energy consumption. [0003] The production process of bell annealing furnace includes three stages of heating, heat preservation and cooling. The heat of gas combustion i...

AI Technical Summary

Problems solved by technology

[0004] The traditional hydrogen blowing mode uses the hydrogen blowing time and hydrogen blowing flow rate to realize gas replacement and reduction protection in the annealing furnace. The disadvantage is that it is difficult to control the hydrogen blowing time

If the hydrogen blowing time is too short, the reduction protection and impurity volatilization of the strip cannot be realized, and light yellow or light blue oxidation color defects will appear; if the hydrogen blowing time is too long, it is easy to cause the precipitation of Si, Mn, Al and other elements to form gray-white oxidation. color defects while increasing hydrogen consumption