CN113528950B

CN113528950B - Preparation method of hot-dip galvanized high-strength steel with good welding performance

Info

Publication number: CN113528950B
Application number: CN202110693552.5A
Authority: CN
Inventors: 刘华赛; 王崇学; 李维; 林志峰; 张永强; 韩赟; 白雪; 邱木生; 滕华湘; 朱国森; 李飞
Original assignee: Shougang Group Co Ltd
Current assignee: Shougang Group Co Ltd
Priority date: 2021-06-22
Filing date: 2021-06-22
Publication date: 2022-10-21
Anticipated expiration: 2041-06-22
Also published as: CN113528950A

Abstract

The embodiment of the invention discloses hot-dip galvanized high-strength steel with good welding performance and a preparation method thereof, wherein the method comprises the following steps: smelting and continuously casting the chemical components of the hot-dip galvanized high-strength steel with good welding performance to obtain a continuous casting slab; heating or/and rough rolling the continuous casting plate blank before rolling, then finish rolling, cooling after rolling and coiling to obtain a hot rolling finished product; pickling the hot rolled finished product, cold rolling, annealing, hot galvanizing, heat treatment and finishing treatment to obtain the hot galvanized high-strength steel with good welding performance; wherein the heat treatment temperature is 70-400 ℃, the heat treatment time is 10-60min, and the heat treatment is carried out in the atmosphere of 1-3% hydrogen by mass. The content of diffusible hydrogen in the hot-dip galvanized high-strength steel is less than or equal to 0.2ppm by adjusting and matching the components, so that the diffused hydrogen does not cause cracks to the material during welding, and the welding performance of the material is ensured.

Description

Preparation method of hot-dip galvanized high-strength steel with good welding performance

Technical Field

The embodiment of the invention relates to the technical field of steel preparation, in particular to hot-galvanized high-strength steel with good welding performance and a preparation method thereof.

Background

In recent years, with the increase in the requirements for collision safety and weight reduction in the automobile industry, the use of high-strength steel for vehicle bodies has increased year by year. As high-strength steel is used not only for structural members but also for other parts such as vehicle body panels, it is required to have higher ductility in addition to higher tensile strength.

Comparison document 1: the patent application with the application number of '201610542806.2' discloses 1000 MPa-grade low-carbon hot-galvanized dual-phase steel and a preparation method thereof, belonging to the technical field of high-strength automobile steel, and the steel comprises the following components in percentage by weight: c:0.05 to 0.10%, si:0.20 to 0.60%, mn: 1.40-1.90%, cr:0.20 to 0.70%, mo:0.20 to 0.50%, al:0.02 to 0.06 percent, ti:0.020 to 0.050%, nb:0.010 to 0.040%, B:0.0010 to 0.0030 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.006 percent of N, and the balance of Fe and inevitable impurities. The yield strength is 630-700 MPa, the tensile strength is 1010-1050 MPa, and the elongation is 11-14%. Although the strength of the steel plate of the high-strength steel reaches over 1000MPa through a component system and a manufacturing process, the high-strength steel also brings some negative effects. Because hydrogen is needed to be used as reducing atmosphere in the annealing process, part of the hydrogen can enter the steel structure, and the hydrogen is difficult to release from the steel plate due to the subsequent galvanizing procedure. Cracks can be generated due to the release of hydrogen in the subsequent welding process of automobile parts, and the service performance of the material is further influenced.

Therefore, how to solve the problem of welding performance deterioration caused by hydrogen release of the galvanized high-strength steel plate in the prior art becomes a technical problem to be solved urgently.

Disclosure of Invention

The embodiment of the invention aims to provide hot-dip galvanized high-strength steel with good welding performance and a preparation method thereof, and the prepared hot-dip galvanized high-strength steel has no crack in a molten core after welding and has good welding performance.

In order to achieve the above object, an embodiment of the present invention provides a hot-dip galvanized high-strength steel with good weldability, wherein the steel comprises the following chemical components by mass: c:0.10 to 0.30%, si:1 to 2.5%, mn:1.8 to 2.3%, P: less than or equal to 0.01 percent, S: less than or equal to 0.01 percent, al:0.01 to 0.5%, N:0.1 to 0.6 percent, and the balance of Fe and inevitable impurities.

Further, the chemical components of the steel are as follows in mass fraction: c:0.10 to 0.30%, si:1 to 2.5%, mn:1.8 to 2.3%, P: less than or equal to 0.01 percent, S: less than or equal to 0.01 percent, al:0.01 to 0.5%, N:0.1 to 0.6 percent of alloy elements and 0.005 to 0.5 percent of alloy elements, wherein the alloy elements comprise at least one of Ti, nb, V, zr, mo, cr, cu and Ni, and the balance is Fe and inevitable impurities.

Further, the metallographic structure of the steel matrix comprises the following components in volume fraction: 10 to 30 percent of ferrite, 40 to 80 percent of martensite, less than or equal to 10 percent of bainite and 4 to 20 percent of residual austenite.

Further, the grain size of the ferrite is 3 to 6 μm, the grain size of the martensite is 1 to 4 μm, the grain size of the bainite is 0.7 to 3.6 μm, and the grain size of the retained austenite is 0.6 to 1.8 μm.

The embodiment of the invention also provides a preparation method of the hot-dip galvanized high-strength steel with good welding performance, which comprises the following steps:

smelting and continuously casting the chemical components of the hot-dip galvanized high-strength steel with good welding performance to obtain a continuous casting slab;

heating or/and rough rolling the continuous casting plate blank before rolling, then finish rolling, cooling after rolling and coiling to obtain a hot rolling finished product;

pickling the hot-rolled finished product, cold rolling, annealing, hot galvanizing, heat treatment and finishing treatment to obtain the hot-galvanized high-strength steel with good welding performance; wherein the heat treatment temperature is 70-400 ℃, the heat treatment time is 10-60min, and the heat treatment is carried out in the atmosphere of 1-3% hydrogen by mass.

Further, the temperature of heating before rolling is 1100-1300 ℃, and the time of heating before rolling is more than or equal to 180min.

Further, the outlet temperature of the finish rolling is 800-950 ℃.

Furthermore, the coiling temperature is 450-700 ℃.

Further, the cold rolling reduction is 20-50%.

Further, the annealing comprises a heating section, a cooling section and an aging section in sequence, wherein the heating section is kept at 820-900 ℃ for 5-25 s; the cooling section is cooled to 400-550 ℃ from 820-900 ℃ at the rate of 4-10 ℃/s; the aging section is kept at the temperature of 400-550 ℃ for more than or equal to 8s; the annealing is carried out in an atmosphere of 2-10% hydrogen by mass.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the hot-dip galvanized high-strength steel with good welding performance provided by the embodiment of the invention comprises the following chemical components in percentage by mass: c:0.10 to 0.30%, si:1 to 2.5%, mn:1.8 to 2.3%, P: less than or equal to 0.01%, S: less than or equal to 0.01%, al:0.01 to 0.5%, N:0.1 to 0.6 percent, and the balance of Fe and inevitable impurities; according to the embodiment of the invention, the content of diffusible hydrogen in the hot-dip galvanized high-strength steel is less than or equal to 0.2ppm by adjusting the components. Under the condition that the content of the diffused hydrogen is less than or equal to 0.2ppm, the diffused hydrogen can not cause cracks to the material during welding, and the welding performance of the material is further ensured.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a metallographic structure diagram of a hot-dip galvanized high-strength steel with good weldability prepared in example 1 of the present invention;

FIG. 2 is a picture of a hot-dip galvanized high-strength steel with good welding performance and no crack after welding, which is prepared in example 1 of the invention;

FIG. 3 is a picture of cracks after welding of the hot-dip galvanized high-strength steel prepared in comparative example 1;

fig. 4 is a flowchart of a method for preparing hot-dip galvanized high-strength steel with good welding performance according to an embodiment of the invention.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the embodiments of the present invention will be more clearly apparent therefrom. It should be understood by those skilled in the art that the detailed description and examples are intended to illustrate, but not limit, the embodiments of the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention belong. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the examples of the present invention are commercially available or can be obtained by an existing method.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

according to a typical implementation manner of the embodiment of the invention, the hot-dip galvanized high-strength steel with good welding performance is provided, and the chemical components of the steel in percentage by mass are as follows: c:0.10 to 0.30%, si:1 to 2.5%, mn:1.8 to 2.3%, P: less than or equal to 0.01 percent, S: less than or equal to 0.01 percent, al:0.01 to 0.5%, N:0.1 to 0.6 percent, and the balance of Fe and inevitable impurities.

The hot-dip galvanized high-strength steel with good welding performance, which is formed by optimizing the constituent elements, is based on the following principle:

(1) The control principle in the chemical composition design of the embodiment of the invention is as follows:

the C element is the most important solid solution strengthening element and austenite stabilizing element in the dual-phase steel, and the content of the C element is adjusted to ensure that the steel material obtains enough martensite in the cooling process to ensure the strength and obtain a certain amount of retained austenite to improve the forming performance.

Si is also a strengthening element, which is helpful for enlarging a two-phase region, and is dissolved in ferrite to play a strengthening effect, and Si can effectively inhibit the decomposition of residual austenite and the precipitation of carbide. However, since excessive Si adversely affects the welding performance and surface quality, the Si content is controlled to 1 to 2.5% in the present invention.

Mn element is also an important element for solid solution strengthening and austenite stabilizing, and can prevent the transformation from austenite to pearlite in the cooling process, thereby improving the hardenability of the material and ensuring the problem of participating in austenite. While too high Mn content adversely affects the processability of the material, the Mn content of the present invention is controlled to 1.8-2.3%.

The P element is a harmful element of the material, and the segregation at the grain boundary can cause the reduction of the grain boundary strength so as to deteriorate the mechanical property of the material, so the content of the P element is controlled to be below 0.01 percent.

The S element also serves as a harmful element, and the excessive content of the S element in the material can cause the Mn element to combine with the Mn element to generate MnS, thereby influencing the hole expanding and corrosion resisting properties of the material. Therefore, the content of the S element is controlled below 0.01 percent.

The Al element can promote the generation of ferrite and effectively inhibit the decomposition of residual austenite and the precipitation of carbide, but the problem of non-metallic inclusion in the production process can be caused by the excessively high content of the Al element, so that the Al content needs to be cooperatively controlled in a proper range with the Si element with similar effect. The Al content of the invention needs to be controlled between 0.01 and 0.5 percent.

The N element can be combined with solid-solution aluminum to form AlN and prevent austenite grains from growing during heating of the material, so that the essentially fine-grained steel is obtained. Considering that the aging phenomenon is caused by the excessive content of N, the content of N is controlled to be 0.1-0.6 percent.

As an alternative embodiment, the steel further comprises 0.005% to 0.5% of an alloying element comprising at least one of Ti, nb, V, zr, mo, cr, cu and Ni;

alloy elements such as Ti, nb, V, zr, mo, cr, cu, ni and the like can improve austenite hardenability, so that enough martensite guaranteed strength is obtained, for example, ti is used as a microalloy element and can be combined with C to generate a TiC nano precipitated phase, the effects of grain refinement and precipitation strengthening are achieved, and the effects of improving the structure form and improving the yield strength are remarkable. But at the same time, the content of the alloy element is too much, which is not beneficial to the generation of residual austenite and can cause the cost to rise obviously, so the content of the alloy element is controlled to be 0.005-0.5%.

As an alternative embodiment, the metallographic structure of the steel matrix is, in terms of volume fraction: 10 to 30 percent of ferrite, 40 to 80 percent of martensite, less than or equal to 10 percent of bainite and 4 to 20 percent of residual austenite. The grain size of the ferrite is 3-6 mu m, the grain size of the martensite is 1-4 mu m, the grain size of the bainite is 0.7-3.6 mu m, and the grain size of the retained austenite is 0.6-1.8 mu m.

The embodiment of the invention further obtains further improvement of the performance through the precise control of the microstructure: martensite provides sufficient strength for the material, but too high martensite causes a significant reduction in the formability of the material, so the martensite content is set to 40 to 80%. Ferrite is a soft matrix of material, and geometric compatibility is ensured by obtaining a suitable amount of ferrite and causing additional deformation around it during plastic deformation. The retained austenite can enhance the formability of the material, but when the retained austenite is less than 4%, the elongation cannot be significantly increased due to the transformation induced plasticity effect during deformation, and if the content is too high, the alloy content must be greatly increased, which causes a cost increase and a waste of the formability.

According to another exemplary embodiment of the present invention, a method for preparing a hot-dip galvanized high-strength steel with good welding performance is provided, as shown in fig. 4, the method includes:

s1, smelting and continuously casting the chemical components of the hot-dip galvanized high-strength steel with good welding performance to obtain a continuous casting slab;

s2, heating or/and roughly rolling the continuous casting plate blank before rolling, then finely rolling, cooling after rolling and coiling to obtain a hot-rolled finished product;

the continuous casting plate blank can be heated and then subjected to rough rolling, or the continuous casting plate blank can be directly subjected to rough rolling;

the temperature of heating before rolling is 1100-1300 ℃, and the time of heating before rolling is more than or equal to 180min. The heating temperature of 1100 to 1300 ℃ is selected mainly to prevent coarsening of billet precipitates and to adversely affect the formation of the subsequent microstructure. If the heating temperature is too high or too low, the weaving is easily affected;

the outlet temperature of the finish rolling is 800-950 ℃. The selection of the finish rolling temperature can make the material structure more uniform and ensure the performance. If the outlet temperature of the finish rolling is too high or too low, the uniformity of the structure is easily influenced;

the coiling temperature is 450-700 ℃. The coiling temperature is selected to ensure tissue uniformity and to meet the final properties. If the coiling temperature is too high or too low, adverse effects on tissue uniformity are easily caused;

s3, carrying out acid washing, cold rolling, annealing, hot galvanizing, heat treatment and finishing treatment on the hot rolled finished product to obtain the hot galvanized high-strength steel with good welding performance; wherein the temperature of the heat treatment is 70-400 ℃, the time of the heat treatment is 10-60min, and the heat treatment is carried out in the atmosphere of 1-3% hydrogen by mass fraction.

The cold rolling reduction is controlled to be 20-50%. This limitation is to ensure that a uniform steel structure is obtained and that the surface structure is intact. The cold rolling reduction rate is less than 20% or more than 50% which easily causes adverse effect on the tissue uniformity;

the annealing process after the cold rolling mainly comprises a heating section, a cooling section and an aging section. Wherein the temperature of the heating section is 820-900 ℃, the heating time is 5-25 s, the aging section is 400-550 ℃, and the aging section time is more than or equal to 8s. The hydrogen content in the annealing furnace is 2-10%. The temperature of the heating section is 820-900 ℃, the heating time is 5-25 s, so that the steel structure is more uniform, and necessary martensite, residual austenite and bainite are generated. After the cooling section, under the condition that the aging section is 400-550 ℃ and the time of the aging section is more than or equal to 8s, bainite and residual austenite are generated, and meanwhile, hydrogen in part of steel is removed. From the viewpoint of manufacturing cost, the aging period is not preferably too long, but the tissue is not affected by the prolonged aging period. The hydrogen content in the annealing furnace is limited to 2 to 10%. Setting the hydrogen atmosphere to more than 2% of the reducing atmosphere mainly required for consideration, and controlling the hydrogen to less than 10% can prevent excessive hydrogen from entering the steel material, and ensure that the residual content of the hydrogen in the subsequent process can be controlled to a low level.

In the hot galvanizing procedure, the temperature is limited to 400-550 ℃ before entering a zinc pot, the retained austenite can be ensured by selecting the temperature below 550 ℃, and the early solidification of the zinc liquid caused by the over-low temperature of entering the zinc pot can be avoided by selecting the temperature above 400 ℃. If the temperature is higher than 550 ℃, the retained austenite is difficult to retain, and if the temperature is lower than 400 ℃, the zinc liquid is easy to solidify in advance.

The temperature of the heat treatment is 70-400 ℃, the time is 10-60min, and the hydrogen content in the heat treatment furnace is 1-3%. The hydrogen content can suppress the increase of hydrogen in the steel under the condition of ensuring the reducing atmosphere, and the hydrogen entering in the previous process in the steel is slowly released at the heat treatment temperature. If the hydrogen content is less than 1%, a sufficient reducing atmosphere cannot be provided, affecting the surface quality; if the hydrogen content is higher than 3%, internal hydrogen cannot be fully released due to the overhigh external hydrogen content;

the defined temperature and time of the heat treatment ensure the release time of hydrogen and reach the equilibrium of hydrogen entering and exuding in the time of at most about 1 h. If the temperature of the heat treatment is less than 70 ℃, the time is less than 10min, which is not beneficial to the diffusion of hydrogen; if the temperature of the heat treatment is higher than 400 ℃, the hydrogen diffused for 60min is easy to cause cracks to the material;

in conclusion, the hot-dip galvanized high-strength steel with good welding performance prepared by the embodiment of the invention has the diffusible hydrogen content of less than or equal to 0.2ppm in the hot-dip galvanized high-strength steel through the adjustment of components and processes. Under the condition that the content of the diffused hydrogen is less than or equal to 0.2ppm, the diffused hydrogen can not cause cracks to the material during welding, so that the welding performance of the material is ensured; the prepared hot-dip galvanized high-strength steel with good welding performance has the mechanical property parameter indexes as follows: the tensile strength is more than 980MPa, the yield strength is more than 700MPa, and the elongation rate of the gauge length at 80mm is more than or equal to 12 percent.

Hereinafter, a hot dip galvanized high strength steel having good weldability and a method for manufacturing the same according to the present invention will be described in detail with reference to examples, comparative examples, and experimental data.

S1, smelting molten steel through a converter, and obtaining a continuous casting slab by adopting a continuous casting mode; the actual chemical composition is shown in table 1;

TABLE 1 chemical composition (wt%) of hot-dip galvanized high-strength steel of each group

Composition (A)	C	Si	Mn	P	S	Al	N	Nb	Cr	Mo	Ti
												Example 1	0.17	1.66	2.06	0.005	0.002	0.43	0.15	-	-	-	-
Example 2	0.18	1.33	2.11	0.005	0.002	0.25	0.18	-	-	-	-
												Example 3	0.19	1.57	2.02	0.007	0.003	0.34	0.32	0.031	-	-	-
Example 4	0.21	1.61	2.14	0.006	0.003	0.27	0.15	-	0.21	-	-
												Example 5	0.19	1.67	2.04	0.005	0.002	0.44	0.54	-	-	0.11	-
Example 6	0.22	2.23	1.87	0.007	0.002	0.34	0.13	-	-	-	0.031
												Example 7	0.15	1.51	2.22	0.009	0.004	0.26	0.24	0.031	0.27	0.15	0.031
Comparative example 1	0.17	1.66	2.06	0.005	0.002	0.43	0.15	-	-	-	-
												Comparative example 2	0.17	1.66	2.06	0.005	0.002	0.43	0.15	-	-	-	-
Comparative example 3	0.08	0.2	2.3	0.005	0.005	0.6	-	-	0.7	0.3	0.04
												Comparative example 4	0.085	0.0	1.7	0.012	0.002	0.04	0.004	0.02	0.42	0.35	0.03

S2, obtaining a casting blank by a conventional process, and then carrying out hot rolling, wherein a method of directly hot rolling the casting blank can be adopted, the hot rolling heating temperature is limited to 1100-1300 ℃, the finish rolling temperature is limited to 800-950 ℃, and the coiling temperature is limited to 450-700 ℃. After the hot-rolled coil is subjected to a conventional pickling process, cold rolling is carried out, and the reduction rate of the cold rolling process is controlled to be 20-50%. The annealing process after cold rolling mainly comprises a heating section, a cooling section and an aging section. Wherein the temperature of the heating section is 820-900 ℃, the heating time is 5-25 s, the time of the aging section is 400-550 ℃, and the time of the aging section is more than or equal to 8s. The hydrogen content in the annealing furnace is 2-10%. The annealed steel plate enters a hot galvanizing procedure, and the temperature is limited to 400-550 ℃ before entering a zinc pot. And (3) carrying out subsequent heat treatment after galvanizing cooling, wherein the heat treatment temperature is 70-400 ℃, the time is 10 minutes-1 hour, and the hydrogen content in the heat treatment furnace is 1-3%. The details are shown in Table 2.

TABLE 2 Process parameters

And (5) sampling a finished product and testing the mechanical property of the sampled finished product. The steel plate samples were evaluated after removing the surface zinc layer. Wherein the surface hydrogen content was replaced by using argon gas in a quartz tube, and the hydrogen gas release amount was measured by a gas chromatograph. The method for evaluating the welding performance is to connect two steel plates by using a direct-current resistance spot welding machine, and the diameter of a nugget is enabled to reach about 4mm by controlling the current intensity. After the solder material was left for 24 hours, the nugget cross section was observed by SEM for cracks. The results are shown in Table 3.

TABLE 3 mechanics and weldability of hot-dip galvanized high-strength steel with good weldability

As can be seen from the data in Table 3:

in comparative example 1, the hydrogen content in the heat treatment stage was 0, which is less than the range of 1 to 3% in the example of the present invention, and the defect of poor surface quality was present;

in comparative example 2, the temperature of the heat treatment was 50 ℃ which is less than the range of 70 to 400 ℃ in the inventive example, but hydrogen release could not be achieved due to the lower temperature;

in comparative example 3, the chemical composition was different from that of example 1, and the post-galvanization heat treatment step was not performed, the tensile strength was low, and the nugget had cracks after welding;

in comparative example 4, the chemical composition was different from that of example 1, and the post-galvanization heat treatment step was not performed, the tensile strength was low, and the nugget had cracks after welding;

the hot-dip galvanized high-strength steel plates in the examples 1 to 6 have yield strength of over 700MPa, tensile strength of over 980MPa and elongation of over 12 percent. Meanwhile, the steel plate has low diffusible hydrogen content, and a nugget has no crack after welding, so that the steel plate has good mechanical property and welding property.

Detailed description of the drawings 1-3:

in the figure 1, the metallographic structure of the hot dip galvanized high strength steel with good weldability prepared by the embodiment 1 of the invention comprises 10-30% of ferrite, 40-80% of martensite, less than or equal to 10% of bainite and 4-20% of residual austenite.

In FIG. 2, the hot dip galvanized high strength steel in the embodiment 1 has no crack on the section of the nugget after welding;

in the figure 3, the hot galvanized high-strength steel in the comparative example 1 has cracks on the section of the nugget after being welded;

finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the embodiments of the present invention and their equivalents, the embodiments of the present invention are also intended to encompass such modifications and variations.

Claims

1. A preparation method of hot-dip galvanized high-strength steel with good welding performance is characterized by comprising the following steps:

smelting and continuously casting chemical components of hot-dip galvanized high-strength steel with good welding performance to obtain a continuously cast slab, wherein the chemical components comprise the following components in percentage by mass: c:0.10 to 0.30%, si:1 to 2.5%, mn:1.8 to 2.3%, P: less than or equal to 0.01%, S: less than or equal to 0.01%, al:0.01 to 0.5%, N:0.1 to 0.6 percent, and the balance of Fe and inevitable impurities;

heating or/and roughly rolling the continuous casting plate blank before rolling, finely rolling, cooling after rolling and coiling to obtain a hot rolling finished product;

pickling the hot-rolled finished product, cold rolling, annealing, hot galvanizing, heat treatment and finishing treatment to obtain the hot-galvanized high-strength steel with good welding performance; wherein the temperature of the heat treatment is 70-400 ℃, the time of the heat treatment is 10-60min, and the heat treatment is carried out in the atmosphere of 1-3% hydrogen by mass fraction;

the annealing comprises a heating section, a cooling section and an aging section in sequence, wherein the heating section is kept at 820-900 ℃ for 5-25 s; the cooling section is cooled to 400-550 ℃ from 820-900 ℃ at the speed of 4-10 ℃/s; the aging section is kept at the temperature of 400-550 ℃ for more than or equal to 8s; the annealing is carried out in the atmosphere of 2-10% hydrogen by mass;

the temperature of heating before rolling is 1100-1300 ℃, and the time of heating before rolling is more than or equal to 180min; the outlet temperature of the finish rolling is 800-950 ℃, the coiling temperature is 450-700 ℃, and the cold rolling reduction rate is 20-50%.

2. The method for preparing the hot-dip galvanized high-strength steel with good welding performance according to claim 1, characterized in that the steel comprises the following chemical components in percentage by mass: c:0.10 to 0.30%, si:1 to 2.5%, mn:1.8 to 2.3%, P: less than or equal to 0.01%, S: less than or equal to 0.01 percent, al:0.01 to 0.5%, N:0.1 to 0.6 percent of alloy elements and 0.005 to 0.5 percent of alloy elements, wherein the alloy elements comprise at least one of Ti, nb, V, zr, mo, cr, cu and Ni, and the balance is Fe and inevitable impurities.

3. The method for preparing the hot-dip galvanized high-strength steel with good welding performance according to claim 1, wherein the metallographic structure of a steel matrix is as follows in volume fraction: 10 to 30 percent of ferrite, 40 to 80 percent of martensite, less than or equal to 10 percent of bainite and 4 to 20 percent of residual austenite.

4. The method for preparing hot-dip galvanized high-strength steel with good weldability according to claim 3, characterized in that the grain size of ferrite is 3-6 μm, the grain size of martensite is 1-4 μm, the grain size of bainite is 0.7-3.6 μm, and the grain size of residual austenite is 0.6-1.8 μm.