Hot galvanized high-strength steel with excellent Fe-Al alloy layer characteristics and manufacturing method thereof

Abstract

The invention relates to a hot galvanized high-strength steel with excellent Fe-Al alloy layer characteristics and a manufacturing method thereof. The hot galvanized high-strength steel comprises a substrate, a Fe-Al alloy layer and a galvanized layer in sequence, the substrate comprises the following chemical components of, in percentage by weight, 0.15-0.25 wt% of C, 1.00-2.00 wt% of Si, 1.50-3.00 wt% of Mn, less than or equal to 0.015 wt% of P, less than or equal to 0.012 wt% of S, 0.03-0.06 wt% of Al and the balance Fe and inevitable impurities. The loss area of the Fe-Al alloy layer is less than 5%, the Fe-Al alloy layer is uniform, complete and uniform in appearance, the hot galvanized steel plate obtained after hot galvanizing is good in appearance quality, the defects such as leakage plating, hemp spots, chromatic aberration and the like are avoided, and the hot galvanized high-strength steel is suitable for automobile structural parts and outer plates with higher requirementson 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 excellent Fe-Al alloy layer characteristics and a manufacturing method thereof. Background technique [0002] When the steel plate is hot-dip pure zinc (without adding aluminum), the alloy layer formed by the Fe-Zn reaction is thick and brittle, resulting in poor processability, and the zinc layer is prone to fall off during bending deformation. In order to suppress the growth of Fe-Zn alloy layer in the modern continuous hot-dip galvanizing production line, 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, in A selective reaction occurs on the surface of the steel plate to form a thin Fe-Al alloy layer first, thereby inhibiting the diffusion of zinc. [0003] At present, the demand for lightwe...

AI Technical Summary

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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