Hot rolled strip steel pickling-free hot galvanizing method based on scale reduction

Abstract

The invention discloses a hot rolled strip steel pickling-free hot galvanizing method based on scale reduction, belonging to the technical field of metallurgy. The method comprises the following steps: (1) heating the hot rolled strip steel to 600-900 DEG C in a heating furnace, and performing reduction annealing; then performing heat-preservation reduction in a 10-100% hydrogen atmosphere by volume; (2) cooling the hot rolled strip steel after the heat-preservation reduction to 450-460 DEG C at a speed of 5-20 DEG C per second; (3) performing hot galvanizing in zinc liquid for 3-5 seconds to obtain a zinc coating on the surface of the hot rolled strip steel. According to the method disclosed by the invention, the scale on the surface of the hot rolled strip steel is removed through hydrogen reduction, the discharge of waste acid is reduced by 20kg per ton of steel, the environmental problem caused by pickling is eliminated, and the transformation of the existing production equipment is avoided; the defects of a hot galvanized plate such as skip plating and the like often occurring in a conventional technology can be eliminated, and the scale which is waste before is effectively utilized.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, in particular to a pickling-free hot-dip galvanizing method for hot-rolled strip steel based on scale reduction. Background technique [0002] Since the steel plate is in a high-temperature environment during hot forming, it is inevitable that it will be oxidized in contact with oxygen in the air, and a layer of oxide scale will be formed on the surface of the steel plate. The existence of this layer of oxide will affect the downstream cold rolling and other processes. In the conventional process, the oxide scale on the surface of the hot-rolled steel plate is removed by pickling. Pickling can obtain a good surface quality of the steel plate, but it also brings a series of negative effects; the pickling process and the equipment itself increase the production cost, and at the same time The acid mist generated during pickling corrodes the equipment and also deteriorates the working environment,...

AI Technical Summary

Problems solved by technology

For example, the patent application of Chinese application number 200610086831.0 "Technical method and production device for acid-free descaling of cold-rolled strip steel" provides a process method and production device for acid-free descaling of cold-rolled strip steel. The tooth descaling machine breaks the oxide scale on the surface of the strip steel, and the remaining scale skin is removed by the steel brush machine, and then the strip steel is washed with wet sand with a water content of 5% by high-pressure water in the descaling box. After descaling, use Rinse with clean water; the surface roughness of the steel strip after cleaning by this method is relatively high, and at the same time, a series of cost increases due to mechanical descaling equipment

[0004] The Korean POSCO application number is US 6258186B1 "Method for manufacturing hot rolled galvanized steel sheet at high speed, with pickling skipped" patent application provides a hydrogen reduction hot-dip galvanizing process for hot-rolled Si-containing carbon steel. The invention mainly controls the structure of the hot-rolled iron oxide scale in the hot rolling cooling and coiling process, so that the FeO content in the iron oxide scale exceeds 20%, and then reduces the iron oxide scale on the surface of the strip to pure iron in more than 20% hydrogen, and then Hot-dip galvanizing; this method can realize non-pickling descaling and continuous hot-dip galvanizing; but controlling the oxide scale structure in the hot rolling cooling and coiling sections requires a faster cooling rate and a lower coiling temperature, which is important for The equipment capacity of the cooling and coiling section has high requirements

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