阅读说明：本技术 一种具有高表面质量和优良耐蚀性的热镀锌高强度钢板及其制造方法 (Hot-dip galvanized high-strength steel plate with high surface quality and excellent corrosion resistance and manufacturing method thereof ) 是由 谭宁 魏军胜 钟勇 唐成龙 于 2018-07-27 设计创作，主要内容包括：一种具有高表面质量和优良耐蚀性的热镀锌高强度钢板及其制造方法,所述热镀锌高强度钢板自下往上依次包括：基板、预镀金属层、Fe-Al阻挡层、镀锌层；其中,基板化学成分重量百分比为：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％,其余为Fe及不可避免杂质；所述预镀金属层为金属Ni层。本发明所述热镀锌钢板表面质量好,镀层均匀完整,较常规热镀锌产品具有更好的耐蚀性,其屈服强度在600～900MPa,抗拉强度在980MPa以上,延伸率在15％～22％,表面质量和耐蚀性能较常规热镀锌高强钢优越,适用于对表面质量、耐蚀性和成形性都有较高要求的汽车结构件和外板。(A hot-dip galvanized high-strength steel sheet having high surface quality and excellent corrosion resistance, comprising, in order from bottom to top: the device comprises a substrate, a pre-plated metal layer, a Fe-Al barrier layer and a zinc coating; the substrate comprises the following chemical components in percentage by weight: c: 0.15 to 0.25 wt%, Si: 1.00-2.00 wt%, Mn: 1.50-3.00 wt%, P is less than or equal to 0.015 wt%, S is less than or equal to 0.012 wt%, Al: 0.03-0.06 wt%, the balance being Fe and unavoidable impurities; the pre-plated metal layer is a metal Ni layer. The hot-dip galvanized steel sheet disclosed by the invention is good in surface quality, uniform and complete in coating, better in corrosion resistance compared with a conventional hot-dip galvanized product, and superior to a conventional hot-dip galvanized high-strength steel in yield strength of 600-900 MPa, tensile strength of 980MPa or above and elongation of 15-22%, and surface quality and corrosion resistance, and is suitable for automobile structural parts and outer plates with higher requirements on surface quality, corrosion resistance and formability.)

1. A hot-dip galvanized high-strength steel sheet having high surface quality and excellent corrosion resistance, characterized by comprising, in order from bottom to top: the device comprises a substrate, a pre-plated metal layer, a Fe-Al barrier layer and a zinc coating; the substrate comprises the following chemical components in percentage by weight: c: 0.15 to 0.25 wt%, Si: 1.00-2.00 wt%, Mn: 1.50-3.00 wt%, P is less than or equal to 0.015 wt%, S is less than or equal to 0.012 wt%, Al: 0.03-0.06 wt%, the balance being Fe and unavoidable impurities; the pre-plated metal layer is a metal Ni layer.

2. The hot-dip galvanized high-strength steel sheet according to claim 1, characterized in that the steel sheet component contains 0.18 to 0.22% by weight of C.

3. The hot-dip galvanized high-strength steel sheet according to claim 1, characterized in that the steel sheet composition contains 1.4 to 1.8% by weight of Si.

4. The hot-dip galvanized high-strength steel sheet according to claim 1, characterized in that the steel sheet has a Mn content of 1.8 to 2.3% by weight.

5. The hot-dip galvanized high-strength steel sheet according to claim 1, wherein the steel sheet has a composition comprising, in terms of weight percent, P ≦ 0.012% and S ≦ 0.008%.

6. The hot-dip galvanized high-strength steel sheet according to claim 1, wherein silicon oxide, manganese oxide, or silicon-manganese oxide is present on the substrate or the pre-plating metal layer, and the silicon oxide, manganese oxide, or silicon-manganese oxide is discontinuously distributed.

7. The hot-dip galvanized high-strength steel sheet according to claim 1 or 6, wherein the thickness of the pre-plated metal layer is 5nm to 500 nm.

8. The hot-dip galvanized high-strength steel sheet according to claim 1, characterized in that the yield strength of the hot-dip galvanized high-strength steel sheet is 600 to 900MPa, the tensile strength is 980MPa or more, and the elongation is 15% to 22%.

9. The method for producing a hot-dip galvanized high-strength steel sheet according to any one of claims 1 to 8, comprising the steps of:

1) pre-plating treatment

Pre-plating Ni on the substrate, and forming a metal Ni layer on the surface of the substrate after the pre-plating Ni;

2) annealing treatment

Preheating the substrate to 600-650 ℃; keeping the temperature at 780-820 ℃ for 40-80 s, and H in an annealing furnace₂The content is 3-7.5%; cooling to 700-800 ℃ at the speed of 3-10 ℃/s, then cooling to 230-340 ℃ at the speed of more than or equal to 50 ℃/s, and then heating to 455-465 ℃;

3) and (4) hot-dip galvanizing.

10. The method for producing a hot-dip galvanized high-strength steel sheet according to claim 9, characterized in that the preliminary plating treatment is electrochemical plating, chemical plating, or vacuum plating.

11. The method of producing a hot-dip galvanized high-strength steel sheet according to claim 9, wherein in step 3), the hot-dip galvanized molten zinc is Zn, Zn-Al-Mg, or Zn-Al-Mg + X, and X includes at least one of Si, Ca, Sr, Ba, and a rare earth element.

12. The method for producing a hot-dip galvanized high-strength steel sheet according to claim 9, characterized in that the yield strength of the hot-dip galvanized high-strength steel sheet is 600 to 900MPa, the tensile strength is 980MPa or more, and the elongation is 15% to 22%.

Technical Field

The invention relates to the technical field of hot-dip galvanized steel sheets, in particular to a hot-dip galvanized high-strength steel sheet with high surface quality and excellent corrosion resistance and a manufacturing method thereof.

Background

At present, the demand for light weight of automobiles is more and more intense, and the competitive pressure of materials such as aluminum, magnesium, plastics and the like forces the steel for automobiles to develop towards high strength and high toughness. In order to improve the strength and toughness of the substrate, alloy elements such as Si, Mn, Cr, Al, etc. are often added to the substrate, and in recent years, new-generation high-strength steel products with higher strength and better toughness, represented by QP steel, TRIP steel, TWIP steel, etc., have been developed, and the content of Mn in TWIP steel is even more than 20 wt.%, although the addition of these alloy elements is favorable for obtaining good mechanical properties at a lower cost, however, the high alloy elements bring troubles to the production and manufacturing links, the existence of the high alloy elements causes the pickling difficulty to be increased, the oxide skin residue is easy to be caused, before the hot galvanizing of the annealing section, the alloy elements can be enriched on the surface of the steel plate in the form of oxides, and the residual oxide skin and the oxide enrichment can cause the strip steel to be subjected to the hot galvanizing process, the problems of plating leakage, pockmarking, color difference, coating dezincification and the like on the surface of the steel plate, thereby influencing the surface quality of products and further influencing the corrosion resistance of the hot-dip galvanized high-strength steel plate. Therefore, it is required to develop a hot dip galvanized high strength steel sheet having high surface quality and good corrosion resistance.

Chinese patent CN103805840B discloses a high-formability hot-dip galvanized ultrahigh-strength steel sheet and a manufacturing method thereof, the chemical components of which comprise C: 0.15 to 0.25 wt%, Si: 1.0-2.00 wt%, Mn: 1.5-3.00%, P is less than or equal to 0.015 wt%, S is less than or equal to 0.012 wt%, Al: 0.03-0.06 wt%, N is less than or equal to 0.008 wt%, yield strength is 600-900 MPa, tensile strength is 980-1200 MPa, and elongation is 15-22%. The surface quality of a steel plate is improved and the platability is improved by optimizing the processes of the heating section and the heat preservation section and the dew point atmosphere, so that a hot-dip galvanized product is obtained, but the surface quality of the actual hot-dip galvanized product fluctuates, is greatly influenced by the microscopic change of the surface state of an incoming material, and often causes the problems of plating leakage, pocking marks, color difference and the like.

Chinese patent CN105112914A discloses a device and a method for carrying out hot galvanizing after PVD vacuum nickel plating, which do not relate to specific product performance and do not know the effect of vacuum nickel plating.

Chinese patent 201480008243.8 discloses a coated steel substrate for hot dip galvanizing, which contains 0.01-1% of C, 0.15-15% of Mn, 0.005-3.5% of Si, 0.01-2% of Al and 0.01-2% of Cr, and two layers of preplating treatment are carried out before hot dip galvanizing, wherein the first preplating layer takes Cu as a main component, and the second preplating layer takes Fe as a main component; however, due to the mismatch of the two-layer pre-plating process and the hot galvanizing process, it is difficult to simultaneously realize the two-layer pre-plating and the hot galvanizing in the same unit, so that the actual product production difficulty is high.

Chinese patent CN101225518A discloses a hot-dip galvanizing method after chemical nickel plating of silicon-containing steel, wherein the nickel plating process adopts a chemical nickel plating method, the plating thickness is long, the thickness of the nickel plating layer is 3-4 microns, and the significance of the actual hot galvanizing continuous production is not great.

Chinese patent CN101160416B discloses a hot galvanizing method without plating leakage defect, which mainly aims at the base material with the Si content below 0.2%, does not relate to other alloy elements such as Mn, Al and the like, has lower strength and toughness of a steel plate, mainly solves the problem of plating leakage and does not relate to other product performances.

Disclosure of Invention

The invention aims to provide a hot-dip galvanized high-strength steel plate with high surface quality and excellent corrosion resistance and a manufacturing method thereof, the hot-dip galvanized steel plate has good surface quality, uniform and complete coating, better corrosion resistance than a conventional hot-dip galvanized product, yield strength of 600-900 MPa, tensile strength of 980MPa or above, elongation of 15-22%, superior surface quality and corrosion resistance compared with the conventional hot-dip galvanized high-strength steel, and is suitable for automobile structural parts and outer plates with higher requirements on surface quality, corrosion resistance and formability.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a hot-dip galvanized high-strength steel sheet having high surface quality and excellent corrosion resistance, which comprises, in order from bottom to top: the device comprises a substrate, a pre-plated metal layer, a Fe-Al barrier layer and a zinc coating; the substrate comprises the following chemical components in percentage by weight: c: 0.15 to 0.25 wt%, Si: 1.00-2.00 wt%, Mn: 1.50-3.00 wt%, P is less than or equal to 0.015 wt%, S is less than or equal to 0.012 wt%, Al: 0.03-0.06 wt%, the balance being Fe and unavoidable impurities; the pre-plated metal layer is a metal Ni layer.

Further, silicon oxide, manganese oxide or silicon-manganese oxide exists on the substrate or the pre-plating metal layer, and the silicon oxide, the manganese oxide or the silicon-manganese oxide are distributed discontinuously.

Preferably, the thickness of the pre-plated metal layer is 5nm to 500 nm.

Preferably, the content of C in the steel plate component is 0.18-0.22% by weight.

Preferably, the content of Si in the steel plate component is 1.4-1.8% in percentage by weight.

Preferably, the steel plate component contains 1.8-2.3% of Mn by weight percentage.

Preferably, the steel plate composition contains P less than or equal to 0.012 percent and S less than or equal to 0.008 percent in percentage by weight.

The yield strength of the hot-dip galvanized high-strength steel plate is 600-900 MPa, the tensile strength is over 980MPa, and the elongation is 15-22%.

The method for manufacturing the hot-dip galvanized high-strength steel sheet comprises the following steps:

1) pre-plating treatment

Pre-plating Ni on the substrate, and forming a metal Ni layer on the surface of the substrate after the pre-plating Ni;

2) annealing treatment

Preheating the substrate to 600-650 ℃; keeping the temperature at 780-820 ℃ for 40-80 s, and H in an annealing furnace₂The content is 3-7.5%; cooling to 700-800 ℃ at the speed of 3-10 ℃/s,then cooling to 230-340 ℃ at the speed of more than or equal to 50 ℃/s, and then heating to 455-465 ℃;

3) and (4) hot-dip galvanizing.

Further, the pre-plating treatment may be chemical, electrochemical, or vacuum plating.

The zinc liquid of the hot dip galvanizing can be Zn, Zn-Al-Mg or Zn-Al-Mg + X, wherein the X comprises Si, Ca, Sr, Ba, rare earth elements and other metals.

The prior manufacturing method of hot-dip galvanized high-strength steel mainly adopts optimized heating and annealing section process parameters to selectively oxidize Si, Mn and other alloy elements or oxidize firstly and then reduce the alloy elements, a heating section pre-oxidizes Si, Mn and Fe firstly, an annealing section reduces Fe oxide secondly, thereby realizing hot-dip galvanizing of high-strength steel products.

Before annealing and hot galvanizing, the high-strength steel is pre-plated with a layer of metal, and then is annealed and hot galvanized. The method has the advantages that no matter how the incoming material is, after the pre-plating is carried out, the influence of microscopic difference of the incoming material surface state on the surface quality of the final hot-dip galvanized product can be greatly reduced, meanwhile, the window of a heating and annealing process can be widened, the manufacturability is improved, in addition, the existence of the pre-plating layer is helpful for the corrosion resistance of the final product, and the corrosion resistance is better compared with the conventional hot-dip galvanized high-strength steel product.

The invention has the beneficial effects that:

the invention can improve the contact between the substrate and the zinc liquid by adding the pre-plated Ni layer and controlling the annealing process, and simultaneously optimize the thickness of the metal Ni layer and the annealing process, thereby maximizing the effects of the two means of the metal Ni layer and the annealing process, which is difficult to achieve by independently controlling the annealing process.

The pre-coating can inhibit the diffusion of alloy elements Si and Mn to the surface in the annealing process, and increase the diffusion distance of Si and Mn to the surface, thereby inhibiting the enrichment of oxides of Si and Mn and the like on the surface, at least preventing the oxides from being continuously distributed on the surface, reducing the effective contact of the substrate and zinc liquid in the hot galvanizing process, increasing the wettability of strip steel and the zinc liquid, improving the surface quality of the coating, and reducing the problems of plating leakage, pit and the like.

The pre-plating layer is equivalent to the priming pretreatment of the incoming material of the base plate, so that the surface uniformity of the base plate is greatly improved, and the continuity and integrity of the Fe-Al barrier layer are improved, thereby improving the uniformity of the zinc plating layer and reducing the problems of color difference, plating leakage and the like caused by the microscopic difference of the incoming material.

In the hot galvanizing product, the pre-plating metal layer is Ni, and compared with zinc and substrate iron, the Ni has higher electrode potential and can further delay the corrosion of the substrate, so that the hot galvanizing product containing the pre-plating Ni has better corrosion resistance than the conventional hot galvanizing product.

The hot-dip galvanized steel sheet has the characteristics of high strength and high toughness, and has good application prospect in automobile structural members and outer plate members with higher requirements on surface quality, corrosion resistance and formability.

Drawings

FIG. 1 is a scanning electron microscope image of the surface of a hot-dip galvanized substrate prepared in comparative example 1.

FIG. 2 is a scanning electron microscope image of the surface of a substrate before hot dip galvanizing prepared in example 1 of the present invention.

FIG. 3 is an appearance view of a hot-dip galvanized steel sheet produced in comparative example 1 and example 1 of the present invention.

FIG. 4 is a scanning electron microscope image of a cross section of a hot dip galvanized steel sheet prepared in example 1 of the present invention.

FIG. 5 is a depth distribution diagram of elements of a hot dip galvanized steel sheet prepared in example 1 of the present invention.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

The components of the hot-dip galvanized steel sheet according to the present invention are shown in table 1.

The performances of the hot-dip galvanized steel sheet after the pre-plating, annealing and hot-dip galvanizing are shown in tables 2 and 3.

TABLE 1 main Components of Hot-dip galvanized Steel sheets according to the invention

	C	Si	Mn	P	S	Al
							Example 1	0.22	1.8	1.9	0.006	0.008	0.04
Example 2	0.15	2.0	1.7	0.014	0.007	0.05
							Example 3	0.19	1.5	2.9	0.008	0.006	0.03
Example 4	0.23	1.2	2.2	0.009	0.008	0.05
							Comparative example 1	0.22	1.8	1.9	0.006	0.008	0.04

Table 2 annealing process according to the invention

TABLE 3 Properties of the products according to the invention

Referring to fig. 1 and 3, scanning electron micrographs and external views of the surface of comparative example 1 without pre-plating treatment and direct annealing hot dip galvanizing are shown.

Referring to FIGS. 2 and 3, there are shown scanning electron micrographs of the surface and the appearance of a galvanized sheet after Ni pre-plating treatment in example 1 of the present invention.

The upper and lower portions of the steel sheet shown in FIG. 3 are galvanized sheets which are not subjected to the pre-Ni plating treatment and are subjected to the pre-Ni plating treatment, respectively.

The comparison shows that the surface of the substrate after nickel plating has no obvious oxide enrichment, the surface is uniform and consistent, the surface quality after zinc plating is better, and the surface of the steel plate without the pre-plating layer has obvious plating missing points.

FIG. 4 is the cross-sectional feature of the plated layer of the hot-dip galvanized sheet after pre-plating Ni, wherein a Ni layer is present on the surface of the substrate, a complete Fe-Al barrier layer is present above the Ni layer, and a complete galvanized layer is present above the Ni layer.

FIG. 5 is a GDS picture of a hot-galvanized Ni-plated sheet with metallic Ni and Fe-Al barrier layers at the interface of the substrate and the zinc layer.