A method for reducing iron scale of hot-rolled strip steel based on reduction pretreatment process

Abstract

The invention discloses a reduction method based on a reduction pretreatment process and used for the iron oxide scale of hot-rolled strip steel. The reduction method comprises the following steps: rapidly heating the hot-rolled strip steel to 400-550 DEG C at a speed of 80-150 DEG C / s; carrying out isothermal reduction for 30-600s, wherein the reduction product is multigap sponge iron; after intermediate cooling, heating to 700-1100 DEG C at a speed of 80-150 DEG C / s; and carrying out isothermal reduction for 30-600s, wherein iron particles in the multigap sponge iron are mutually bound, thecrystal grains grow, the gaps, air holes and crystal boundaries in the reduction product are gradually reduced through material transfer, the total volume is reduced, a compact multi-crystal pure ironlayer with a microstructure is formed, and reduction for the iron oxide scale is completed. The reduction method is capable of remarkably increasing the reduction efficiency for the iron oxide scaleof the hot-rolled strip steel in a continuous annealing furnace, and capable of obtaining lots of reduced pure iron in a short reduction time, so that the influence of the residual of the iron oxide scale on the formability and adhesivity of the subsequent plated layer is avoided, and then the industrial promotion of a pickling-free reduction annealing hot-galvanizing prototype technology is ensured.

Description

Technical field: [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for reducing iron scale of hot-rolled strip steel based on a reduction pretreatment process. Background technique: [0002] At present, the method of removing iron scale in major iron and steel enterprises at home and abroad is generally pickling with hydrochloric acid or sulfuric acid. Pickling technology can provide an ideal metal surface. However, long-term and intensive use of acid can easily cause air pollution and groundwater pollution. Great harm to the ecological environment. In view of the requirements of environmental protection, domestic and foreign enterprises and scientific research institutes have carried out extensive research on the technology of descaling without pickling, and proposed the gas (H 2 , CO) reduction instead of pickling to remove the new method of scale removal on the surface of hot-rolled steel products, that is, the pickl...

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Problems solved by technology

[0016] The purpose of the present invention is to aim at the prior art, in the pickling-free reduction annealing hot-dip galvanizing technology, the reduction efficiency of the iron scale on the surface of the hot-rolled strip steel in the continuous annealing furnace is low, and the amount of residual iron scale is too much to affect the need for galvanized sheet forming Performance problem, provide a method based on the reduction pretreatment process of hot-rolled steel oxide scale reduction, using the multi-grain boundary eutectoid structure in the oxide scale in the H 2 In order to improve the reduction characteristics in the high-temperature reduction section, a reduction pretreatment section with rapid heating is added before the high-temperature reduction section, and a pickling-free hot-dip galvanized sheet with high surface quality and good formability is prepared, which provides a new idea for industrial promotion and application, making the hot-dip galvanized sheet The iron oxide scale on the surface of the rolled strip can be reduced to a dense pure iron layer at a faster rate, which improves the adhesion and formability of the hot-dip galvanized sheet while reducing the investment cost of the continuous annealing furnace

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