A kind of hot-dip galvanized high-strength steel with excellent fe-al alloy layer characteristics and its manufacturing method

Abstract

A hot-dip galvanized high-strength steel having the characteristics of an excellent Fe-Al alloy layer and a manufacturing method thereof, the hot-dip galvanized high-strength steel sequentially comprises a substrate, an Fe-Al alloy layer and a galvanized layer, and the chemical composition of the substrate is weight percent are: C: 0.15-0.25wt%, Si: 1.00-2.00wt%, Mn: 1.50-3.00wt%, P≤0.015wt%, S≤0.012wt%, Al: 0.03-0.06wt%, the rest are Fe and Impurities are unavoidable; the missing area of ​​the Fe-Al alloy layer is less than 5%, the Fe-Al alloy layer is uniform, complete, and has consistent appearance characteristics, and the hot-dip galvanized steel sheet obtained after hot-dip galvanizing has good appearance quality, no leakage plating, Defects such as pitting and chromatic aberration are suitable for automotive structural parts and outer panels that have high requirements on surface quality and formability.

Description

technical field [0001] The invention belongs to the technical field of hot-dip galvanized steel sheets, and in particular relates to a hot-dip galvanized high-strength steel with the characteristics of an excellent Fe-Al alloy layer and a manufacturing method thereof. Background technique [0002] When the steel plate is hot-dipped with pure zinc (without adding aluminum), the alloy layer formed by the Fe-Zn reaction is thick and brittle, resulting in poor workability, and the zinc layer is prone to fall off during bending deformation. In order to inhibit the growth of Fe-Zn alloy layer in modern continuous hot-dip galvanizing production lines, a small amount of aluminum (about 0.2%) is added to the zinc solution. Since the chemical affinity of aluminum to iron is higher than that of zinc to iron, A selective reaction occurs on the surface of the steel sheet, and a thin Fe-Al alloy layer is first formed, thereby inhibiting the diffusion of zinc. [0003] At present, the dem...

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Problems solved by technology

In order to improve the strength and toughness of the substrate, alloying elements such as Si, Mn, Cr, and Al are often added to the substrate. Although these alloying elements can make the substrate obtain good mechanical properties, these alloying elements often It is enriched in the form of oxides on the surface of the steel plate, resulting in uneven composition and state of the substrate surface, thus affecting the formation and characteristics of the Fe-Al alloy layer during hot-dip galvanizing. Uniformity, the shape of the alloy layer is different, etc., and the characteristics of the alloy layer directly affect the product characteristics such as the surface quality of the galvanized layer and the adhesion of the galvanized layer

[0004] Chinese patent CN103805840A discloses a high-formability hot-dip galvanized ultra-high-strength steel plate. By optimizing the heating section and heat preservation section process and dew point atmosphere, the platability is improved and hot-dip galvanized products are obtained, but the actual surface quality of hot-dip galvanized products will be lower. Fluctuation occurs, which is greatly affected by the microscopic changes of the surface state of the incoming material, and the on-site production is difficult. Problems such as missing plating, pitting, and color difference often occur. The root cause is that the Fe-Al alloy layer between the coating and the substrate is missing or Discontinuous

At the same time, it discloses that if the direct pre-plating of Fe requires a thicker pre-coating layer (greater than 800nm), the enrichment of oxides on the surface of the steel plate can be suppressed, and the Fe coating is not suitable for reducing the enrichment of Mn oxides

This patent uses a two-layer pre-plating process, which not only increases the cost, but also does not match well with the hot-dip galvanizing process, and it is difficult to realize two-layer pre-plating and hot-dip galvanizing in the same unit at the same time, so the actual production is more difficult. Big

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