Method for producing color-coated plate for structure with yield strength of more than or equal to 550 MPa

Abstract

The invention relates to a method for producing color-coated steel sheet for a structure. The method comprises the following steps of: smelting, namely desulfurizing by molten iron, smelting by a converter, casting continuously to form a blank and performing hot rolling; performing acid washing; performing cold milling; annealing continuously; performing hot dipping on aluminum and zinc; and polishing, straightening, performing color coating and packaging for later use. In the method, the yield strength RP 0.2 (or ReH) is between 550 and 600 MPa; the tensile strength Rm is between 560 and 610MPa; and the percentage elongation after break A80 mm is more than or equal to 6 percent. A neutral salt mist test is performed for 1,200 hours, a coating does not have bubbling and corrosion phenomena. At present, the annealed color-coated plate of which the metallographic structure is ferrite and pearlite or the ferrite and free cementite or the ferrite and the pearlite and less free cementite cannot achieve the effect, and the production cost can be reduced by 10 to 15 percent. By the method, special occasions which have high-yield strength and are used for cooling chambers of automobiles,arch coverings and the like can be met, and a process is simple and easy to implement.

Description

technical field [0001] The invention relates to the technical field of alloy steel production, and belongs to a production method of structural color-coated sheet steel, in particular to a production method of structural color-coated steel with a yield strength ≥ 550 MPa. Background technique [0002] my country's color-coated panels are mainly used in the construction field, and the proportion of sandwich panels and corrugated panels accounts for about 85% of the color-coated panels used in construction, and require high strength, good toughness and excellent corrosion resistance. Many domestic users (especially those in the construction industry) need color-coated panels for structures to improve the strength of structural parts, reduce weight and reduce costs. [0003] By searching the literature resources at home and abroad, it is found that the Chinese patent application number is CN99810709.3, "A Manufacture of Cold Rolled Strip" invented by B. Engel, K. D. Horn and K....

AI Technical Summary

Problems solved by technology

[0004] With the development of color-coated sheet technology, it is gradually considered to apply the economical structural aluminum-zinc alloy sheet as the substrate to the color-coated sheet, but there are still shortcomings: in order to ensure the high strength of the structural color-coated substrate, usually More alloying elements are added to the steel, but after adding more alloying elements to the steel, on the one hand, the production cost of color-coated plates for structural use is increased; on the other hand, the added high-strength pre-coated steel Among the alloying elements (such as Mn, Si, Al, Cr, P, Ti, Nb, Mo, etc.), some elements (such as Mn, Si, Ti, Nb, Al, etc.) During the process, it is easy to enrich on the surface, forming a thin layer of oxide film, which reduces the adhesion of the galvanized layer, resulting in a decrease in the corrosion resistance of the color-coated plate

[0005] In the prior art, the temperature for annealing in a continuous annealing furnace is generally 680°C and above, and the highest reaches 780°C. The disadvantage is that after continuous annealing, the metallographic structure of the steel plate is ferrite+ Pearlite or ferrite + free cementite, or ferrite + pearlite + a small amount of free cementite

This type of metallographic structure will cause its yield strength to be less than 550MPa and above, so it cannot be used in special occasions that require high yield strength, such as car freezers and arched roofs.

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