CN114107860A

CN114107860A - Zinc-aluminum-magnesium-based alloy coating material for inhibiting liquid metal from being embrittled and improving wear resistance in hot forming process of high-strength steel and preparation method thereof

Info

Publication number: CN114107860A
Application number: CN202111213563.5A
Authority: CN
Inventors: 吴广新; 丁成发; 刘毅豪; 马征; 孙明飞; 张捷宇
Original assignee: SHANGHAI UNIVERSITY
Current assignee: SHANGHAI UNIVERSITY
Priority date: 2021-10-19
Filing date: 2021-10-19
Publication date: 2022-03-01
Anticipated expiration: 2041-10-19
Also published as: CN114107860B

Abstract

The invention discloses a zinc-aluminum-magnesium-based alloy coating material for inhibiting brittleness of liquid metal in a hot forming process of high-strength steel and a preparation method thereof, and provides a Zn-Al-Mg-Sn-Bi alloy coating material with excellent wear resistance. The alloy plating layer is added with Sn and Bi, and the alloy plating layer comprises, by mass, 0.2-5.0% of Al, 2.6-4.0% of Mg, 0-4.0% of Sn, 0-4.0% of Bi, and the balance of Zn and inevitable impurity content. In the hot forming process of the advanced high-strength steel, on one hand, the invention provides a restraining effect for embrittlement of a steel plate matrix caused by liquid zinc infiltration; on the other hand, the coating has excellent wear resistance and reduces the wear amount in the hot forming process. According to the invention, through a hot dip coating experiment, a heat treatment experiment, a coating section structure observation, a mechanical tensile property detection, a hardness detection and a friction experiment detection of a coating, an alloy coating material which can inhibit liquid metal from being brittle and has excellent wear resistance is provided for advanced high-strength steel.

Description

Zinc-aluminum-magnesium-based alloy coating material for inhibiting liquid metal from being embrittled and improving wear resistance in hot forming process of high-strength steel and preparation method thereof

Technical Field

The invention relates to a coating material and a preparation method thereof, in particular to a dip plating method for effectively increasing the fluidity of plating solution in the hot dip plating process, reducing the surface tension of the plating solution, improving the wettability and improving the surface quality and the mechanical property of a coating, and particularly relates to a coating material for inhibiting the brittleness caused by liquid metal in the hot stamping forming process of an advanced high-strength steel plate, a preparation method thereof and the improvement of the wear resistance of the coating in the hot stamping forming process.

Background

The problem of how to reduce energy consumption and environmental pollution in the trip field of automobiles and the like has become a serious challenge in various countries and automobile industries in the world.

The light weight of the automobile is one of effective ways for realizing energy conservation and emission reduction of the automobile, and along with the promotion of the light weight process of the automobile, the application of advanced high-strength steel to the automobile industry is more and more common.

The advanced high-strength steel not only can lighten the automobile and achieve the aim of energy conservation and emission reduction of the automobile, but also can improve the collision safety performance of the automobile, so that more and more high-strength steel plates are applied to manufacturing of some parts and structural members of the automobile by enterprises at present.

Now, parts in the automobile body fully utilize advanced high-strength steel to carry out hot forming stamping parts, so that the weight of the automobile body is reduced, and the safety performance of automobile body collision is improved.

In order to solve the problems of surface decarburization and oxidation peeling of a steel plate, corrosion resistance of hot forming parts and the like in the direct hot stamping forming process of an advanced high-strength steel bare plate, a high-strength steel coating technology is introduced.

The high-strength zinc-based steel plating layer can solve the problems of decarburization and oxidation during hot forming of a bare plate and can also provide excellent corrosion resistance and wear resistance. However, the zinc-based coating is melted in the hot forming process, and can penetrate into the steel sheet matrix, so that the steel sheet can be brittle after stress is applied, and in the hot forming process of the traditional high-strength zinc-based coating, cracks can be generated between a hot forming piece and a die due to friction, and the cracks can also propagate to the steel sheet matrix. Patent document CN 105648273a discloses that 0.3-0.5 wt% of W, 0.5-0.8 wt% of Ti and patent document CN110512118A disclose that 0.1-0.6 wt% of Cr, 0.2-1.0 wt% of Ti and 0.5-2.5 wt% of Cu are added to the base of the zinc-aluminum-magnesium coating to improve the surface quality and hardness of the coating, but the surface quality of the material and the brittleness of the liquid metal generated in the hot forming process of the high-strength steel cannot be both considered, and the performance and quality of the coating cannot meet the requirements of the automobile industry. At present, how to solve or inhibit the problem of metal embrittlement caused by reducing liquid zinc of a high-strength zinc-based coating and the problem of friction cracks generated between a hot-formed part and a die become important researches, and a coating applied to hot forming is urgently needed to be developed, so that the surface quality of the coating is improved, and the problems of liquid metal embrittlement and friction cracks are prevented.

Disclosure of Invention

In order to solve the problems of the prior art, the invention aims to overcome the defects in the prior art and provide a zinc-aluminum-magnesium-based alloy coating material for inhibiting the brittleness of liquid metal in the hot forming process of high-strength steel and a preparation method thereof, wherein the fluidity and the wettability of the coating are improved by adding low-content aluminum, magnesium, tin and bismuth elements into the traditional zinc-based coating so as to improve the surface quality of the coating; the liquid zinc embrittlement, the abrasion resistance and the corrosion resistance of the advanced high-strength steel zinc-based coating in hot forming are inhibited. The tin element is added, so that the Fe-Al alloy layer in the coating becomes thicker on the basis of the zinc-aluminum-magnesium coating, thereby delaying the molten liquid zinc from entering the steel plate matrix, and avoiding the brittle fracture of the steel plate matrix during hot forming; tin and magnesium elements are added to form fine Mg-Zn phase and Mg-Sn phase, so that the hardness and the wear resistance of the surface of the plating layer can be improved, and the loss caused by friction between a formed piece and a die in the hot forming process can be reduced; the magnesium element is added to form a Mg-Zn compound with the zinc element, so that the corrosion resistance of the plating layer is further improved, the bismuth element is added to effectively increase the fluidity of the plating solution in the hot dip plating process, reduce the surface tension of the plating solution, improve the wettability and improve the surface quality and the mechanical property of the plating layer.

In order to achieve the purpose, the invention adopts the following technical scheme:

a zinc-aluminum-magnesium-based alloy coating material for inhibiting liquid metal from being brittle in the hot forming process of high-strength steel is a Zn-Al-Mg alloy, a Zn-Al-Mg-Sn alloy or a Zn-Al-Mg-Sn-Bi alloy, and has the following components in percentage by weight: al: 0.2-5.0%; mg: 2.6-4%; sn:0 to 4.0%, Bi: 0-4.0%, and the balance of Zn and inevitable impurities.

Preferably, the zinc-aluminum-magnesium-based alloy coating material comprises the following components in percentage by weight: zn: 83.0-96.9%; al: 0.2-5.0%; mg: 2.6-4.0%; sn:0 to 4.0 percent; bi: 0 to 4.0% and the balance of inevitable impurities.

Preferably, the zinc-aluminum-magnesium-based alloy coating material comprises the following components in percentage by weight: zn: 83.0 to 93.7 percent; al: 0.2-3.5%; mg: 2.8-4.0%; sn:0 to 0.8 percent; bi: 0 to 4.0% and the balance of inevitable impurities.

Preferably, the zinc-aluminum-magnesium-based alloy coating material comprises the following components in percentage by weight: al: 0.2-3.5%; mg: 2.8-4%; sn:0 to 4.0 percent; bi: 0-4.0%, and the balance of Zn and inevitable impurities.

Preferably, in forming the Zn-Al-Mg-based alloy coating layer on the surface of the high-strength steel, an Fe-Al suppression layer having a thickness of not less than 0.5 μm is formed, the Fe-Al suppression layer including Fe₂Al₅And (4) phase(s). The invention forms a thicker Fe-Al inhibition layer in the tin-rich zinc-based coating formed on the surface of the steel. In the invention, in forming a tin-rich zinc-based plating layer on the surface of steel, Mg element, Zn element and Sn element are respectively formed into fine Mg₂Zn₁₁、MgZn₂Or Mg₂A Sn phase.

Preferably, the Zn-Al-Mg-based alloy coating is formed on the surface of the high-strength steel and comprises Mg₂Sn phase, Mg₂Zn₁₁Phase and MgZn₂At least one of the phases.

Preferably, the invention forms more smooth coating surface quality in forming the tin-rich zinc-based coating on the steel surface.

Preferably, the hardness Hv of the zinc-aluminum-magnesium-based alloy coating material is not less than 150. Further preferably, the hardness Hv of the zinc-aluminum-magnesium-based alloy coating material is not less than 170.

A preparation method of a zinc-aluminum-magnesium-based alloy coating material for inhibiting brittleness of liquid metal in a hot forming process of high-strength steel comprises the following steps:

a. the preparation process of the hot-dip plating solution comprises the following steps:

the raw materials are weighed and prepared according to the following element compositions and weight percentages thereof required by preparing the target zinc-aluminum-magnesium-based alloy coating material: al: 0.2-5.0%; mg: 2.6-4%; the balance of Zn and inevitable impurities, and Al blocks, Mg blocks and Zn blocks are used as raw materials;

a-1. preparation of covering agent:

the method can prevent the zinc plating solution from being oxidized in the preparation process of the plating solution, and adopts the covering agent which comprises the following components in percentage by mass: 50 wt.% of CaCl₂45 wt.% NaCl, 5.0 wt.% KCl;

a-2, under the protection action of a covering agent, smelting and preparing an alloy according to raw materials of a set formula in a resistance furnace;

a-3. preparation of Al-Mg intermediate alloy:

step 1: firstly weighing a part of Al block, and then adding a covering agent, wherein the covering agent comprises the following components: 50 wt.% CaCl after dehydration treatment₂A homogeneously mixed solid powder of 45 wt.% NaCl and 5 wt.% KCl;

step 2: heating to 600-700 ℃, preserving heat until the Al blocks are completely melted, gradually adding a part of Mg blocks prepared in advance, stirring, treating with argon, and cooling to room temperature to obtain an Al-Mg intermediate alloy;

a-4, preparing a tin-rich zinc-based plating material:

step 1: weighing Zn blocks, polishing and polishing, putting the Zn blocks into a crucible, and then adding a covering agent, wherein the covering agent comprises the following components: 50 wt.% CaCl after dehydration treatment₂A homogeneously mixed solid powder of 45 wt.% NaCl and 5 wt.% KCl;

step 2: putting the crucible into a resistance furnace, starting heating to raise the temperature to 600-700 ℃, keeping the temperature for at least 2h at 600-700 ℃ after the Zn blocks are completely melted, then starting adding the Al-Mg intermediate alloy prepared in the step a-3), keeping the temperature for at least 0.5h, and stirring to obtain a Zn-Al-Mg alloy melt; pouring the alloy into a mould for cooling and forming to prepare the tin-rich zinc-based plating alloy material;

b. and (3) hot dip coating process:

step 1: b, putting the tin-rich zinc-based plating alloy material prepared in the step a into a zinc pot, and melting to form a Zn-Al-Mg hot plating solution;

step 2: polishing the surface of the steel to be coated by using 400-2000 # abrasive paper to remove an oxide layer on the surface of the steel;

and step 3: preparing a mixed alkaline aqueous solution, wherein the NaOH mass percent concentration of the mixed alkaline aqueous solution is not less than 5 wt.%, and the NaCO of the mixed alkaline aqueous solution₃The mass percent concentration is not less than 5 wt.%, the mixed alkaline aqueous solution is put into a constant-temperature water bath kettle and heated to be not less than 80 ℃ and is kept warm, the oil stain on the surface of the steel is removed by the prepared alkaline solution, and the surface of the steel is subjected to alkaline cleaning treatment;

and 4, step 4: preparing an acidic aqueous solution, wherein the mass percent concentration of HCl in the acidic aqueous solution is not less than 5 wt.%, and the mass percent concentration of urotropine in the acidic aqueous solution is not less than 0.5 wt.%, cleaning the surface of the steel subjected to alkali washing treatment with deionized water and absolute ethyl alcohol in sequence, drying the steel by blowing, and placing the steel in the acidic solution to remove rust on the surface of the steel;

and 5: after the pickling process of the step 4 is completed, taking out the steel, cleaning the surface of the steel by deionized water and absolute ethyl alcohol in sequence, and drying;

step 6: blowing for completing the above step 5The dried steel plate is sent into a hot dipping experiment simulator to carry out reduction treatment on the surface of the steel plate, the reduction temperature is not lower than 630 ℃, and the reduction atmosphere is N₂And H₂Atmosphere of mixed gas containing H₂The volume percentage of the steel is not less than 10 vol.%, and the steel surface is continuously subjected to reduction treatment for 5-10 min;

and 7: after the reduction treatment in the step 6 is completed, soaking the steel into the molten Zn-Al-Mg hot plating solution prepared in the step 1 for hot dipping, wherein the hot dipping time is controlled to be 3-15 s;

and 8: and after the hot dipping is finished, cooling treatment is carried out, and water cooling is carried out immediately after the steel is extracted from the hot plating solution, wherein the water cooling temperature is 20-30 ℃, so that a zinc-aluminum-magnesium-based alloy coating is obtained on the surface of the steel.

the raw materials are weighed and prepared according to the following element compositions and weight percentages thereof required by preparing the target zinc-aluminum-magnesium-based alloy coating material: al: 0.2-5.0%; mg: 2.6-4%; sn is less than or equal to 4.0 percent, and the balance of Zn and inevitable impurities, wherein Al blocks, Mg blocks, Sn blocks and Zn blocks are used as raw materials;

1) preparation of a covering agent:

2) under the protection of a covering agent, smelting raw materials according to a set formula in a resistance furnace to prepare an alloy;

3) preparing an Al-Mg intermediate alloy:

4) preparing a Mg-Sn intermediate alloy:

step 1: taking the rest Mg blocks, and then adding a covering agent, wherein the covering agent comprises the following components: 50 wt.% CaCl after dehydration treatment₂A homogeneously mixed solid powder of 45 wt.% NaCl and 5 wt.% KCl;

step 2: heating to 600-700 ℃, preserving heat until the Mg blocks are completely melted, gradually adding the prepared Sn blocks, stirring, treating with argon, and cooling to room temperature to obtain an Mg-Sn intermediate alloy;

5) preparing a tin-rich zinc-based plating material:

step 2: putting the crucible into a resistance furnace, starting heating to raise the temperature to 600-700 ℃, keeping the temperature for at least 2h at 600-700 ℃ after the Zn blocks are completely melted, then starting adding the Al-Mg intermediate alloy prepared in the step 3), keeping the temperature for at least 0.5h, and stirring to obtain a Zn-Al-Mg alloy melt; then, mainly adding the Mg-Sn intermediate alloy prepared in the step 4) into the prepared Zn-Al-Mg alloy melt, preserving the heat for at least 1h, and stirring to obtain a Zn-Al-Mg-Sn alloy melt; pouring the alloy into a mould for cooling and forming to prepare the tin-rich zinc-based plating alloy material;

b. and (3) hot dip coating process:

step 1: b, putting the tin-rich zinc-based plating alloy material prepared in the step a into a zinc pot, and melting to form a Zn-Al-Mg-Sn hot plating solution;

and step 3: compounding mixMixing an alkaline aqueous solution, wherein the NaOH mass percent concentration of the mixed alkaline aqueous solution is not less than 5 wt.%, and the NaCO of the mixed alkaline aqueous solution₃The mass percent concentration is not less than 5 wt.%, the mixed alkaline aqueous solution is put into a constant-temperature water bath kettle and heated to be not less than 80 ℃ and is kept warm, the oil stain on the surface of the steel is removed by the prepared alkaline solution, and the surface of the steel is subjected to alkaline cleaning treatment;

step 6: sending the steel plate blow-dried in the step 5 into a hot dip plating experiment simulator, and reducing the surface of the steel plate at the reduction temperature of not less than 630 ℃ under the reducing atmosphere of N₂And H₂Atmosphere of mixed gas containing H₂The volume percentage of the steel is not less than 10 vol.%, and the steel surface is continuously subjected to reduction treatment for 5-10 min;

and 7: after the reduction treatment in the step 6 is completed, soaking the steel into the molten Zn-Al-Mg-Sn hot plating solution prepared in the step 1 for hot dipping, wherein the hot dipping time is controlled to be 3-15 s;

the raw materials are weighed and prepared according to the following element compositions and weight percentages thereof required by preparing the target zinc-aluminum-magnesium-based alloy coating material: al: 0.2-5.0%; mg: 2.6-4%; sn is less than or equal to 4.0 percent, Bi is less than or equal to 4.0 percent, and the balance is Zn and inevitable impurities, and Al blocks, Mg blocks, Sn blocks, Bi blocks and Zn blocks are used as raw materials;

1) preparation of a covering agent:

3) preparing an Al-Mg intermediate alloy:

4) preparing a Mg-Sn intermediate alloy:

5) preparing an Al-Bi intermediate alloy:

step 1: taking the rest Al blocks, and then adding a covering agent, wherein the covering agent comprises the following components: 50 wt.% CaCl after dehydration treatment₂A homogeneously mixed solid powder of 45 wt.% NaCl and 5 wt.% KCl;

step 2: heating to 600-700 ℃, preserving heat until the Al blocks are completely melted, gradually adding the prepared Bi blocks, stirring, treating with argon, and cooling to room temperature to obtain an Al-Bi intermediate alloy;

6) preparing a tin-rich zinc-based plating material:

step 2: putting the crucible into a resistance furnace, starting heating to raise the temperature to 600-700 ℃, keeping the temperature for at least 2h at 600-700 ℃ after the Zn blocks are completely melted, then starting adding the Al-Mg intermediate alloy prepared in the step 3), keeping the temperature for at least 0.5h, and stirring to obtain a Zn-Al-Mg alloy melt; then, mainly adding the Mg-Sn intermediate alloy prepared in the step 4) into the prepared Zn-Al-Mg alloy melt, preserving the heat for at least 1h, and stirring to obtain a Zn-Al-Mg-Sn alloy melt; then adding the Al-Bi intermediate alloy prepared in the step 5), preserving heat for at least 1h, stirring to obtain a Zn-Al-Mg-Sn-Bi alloy melt, pouring the Zn-Al-Mg-Sn-Bi alloy melt into a mold, and cooling and molding to prepare a tin-rich zinc-based plating alloy material;

b. and (3) hot dip coating process:

step 1: b, putting the tin-rich zinc-based plating alloy material prepared in the step a into a zinc pot, and melting to form a Zn-Al-Mg-Sn-Bi hot plating solution;

and 7: after the reduction treatment in the step 6 is completed, soaking the steel into the molten Zn-Al-Mg-Sn-Bi hot plating solution prepared in the step 1 for hot dipping, and controlling the hot dipping time to be 3-15 s;

Preferably, the raw materials are prepared according to the following element compositions and weight percentages thereof required for preparing the target zinc-aluminum-magnesium-based alloy coating material: al: 0.2-5.0%; mg: 2.6-4%; sn: 0.8-4.0%, Bi is less than or equal to 4.0%, and the balance of Zn and inevitable impurities.

The zinc-aluminum-magnesium-tin-bismuth alloy coating material inhibits the brittleness of liquid metal in the hot forming process of advanced high-strength steel and has excellent wear resistance.

Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:

1. the invention provides a liquid metal which has excellent surface quality, hardness and the like, inhibits the hot forming process of high-strength steel from causing brittleness, and has great research significance; the invention can inhibit and reduce the metal brittleness caused by liquid zinc of the high-strength steel zinc-based coating, prevent the friction crack generated between the hot forming piece and the die, is suitable for the coating applied to hot forming, improves the surface quality of the coating, and prevents the problems of the liquid metal brittleness and the friction crack.

2. The core function of the tin-rich zinc-based coating is mainly as follows: the method comprises the following steps of firstly, improving the fluidity of the plating solution in the hot dip plating process, reducing the surface tension of the plating solution, improving the wettability and improving the surface quality of a plating layer; secondly, the brittleness caused by liquid zinc in the hot forming process of the advanced high-strength steel zinc-based coating is inhibited; thirdly, the coating material is a coating material which improves excellent abrasion resistance during hot stamping forming; fourthly, a plating material with excellent corrosion resistance is provided for the advanced high-strength steel;

3. according to the invention, low-content Al and Mg elements are added into the traditional zinc-based plating solution to form a Fe-Al inhibition layer so as to inhibit the brittle failure phenomenon caused by the penetration of liquid zinc into a steel plate in the hot forming process;

4. the Sn element is added, so that a thicker Fe-Al inhibition layer is formed between the steel plate interface and the coating in the hot dip coating process to inhibit the brittle failure phenomenon caused by the penetration of liquid zinc into the steel plate in the hot forming process;

5. the Sn element added in the invention can generate fine Mg with Mg element₂Sn phase, and fine Mg₂The Sn phase can improve the hardness and the wear resistance of the surface of the plating layer;

6. the Mg element added in the invention can form Mg with good corrosion resistance with Zn element₂Zn₁₁And MgZn₂Thereby further improving the corrosion resistance of the plating layer.

7. The addition of Bi element can effectively increase the fluidity of the plating solution in the hot dip plating process, reduce the surface tension of the plating solution, improve the wettability and improve the surface quality and mechanical property of the plating layer.

Drawings

FIG. 1 is a microstructure and energy spectrum scan of a Zn-3.5 wt.% Al-2.8 wt.% Mg coating in accordance with an embodiment of the present invention.

FIG. 2 is a microstructure of Zn-3.5 wt.% Al-2.8 wt.% Mg-0.8 wt.% Sn plating in accordance with the second embodiment of the present invention.

FIG. 3 is a graph of hardness tests of a first Zn-3.5 wt.% Al-2.8 wt.% Mg coating and a second Zn-3.5 wt.% Al-2.8 wt.% Mg-0.8 wt.% Sn coating according to an embodiment of the present invention.

Detailed Description

The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:

the first embodiment is as follows:

in this embodiment, a Zn-Al-Mg based alloy coating material for inhibiting embrittlement of liquid metal during hot forming of high strength steel is a Zn-Al-Mg alloy having the following composition and weight percentage: 93.7 percent of Zn; al:3.5 percent; mg:2.8 percent; the balance of inevitable impurities.

In this embodiment, a method for preparing a zn-al-mg-based alloy coating material for inhibiting brittleness of liquid metal in a hot forming process of high-strength steel includes the following steps:

the raw materials are weighed and prepared according to the following element compositions and weight percentages thereof required by preparing the target zinc-aluminum-magnesium-based alloy coating material: the Al content is 3.5 wt.%, the Mg content is 2.8 wt.%, and the balance is Zn and inevitable impurities, and Al blocks, Mg blocks and Zn blocks are used as raw materials;

a-1. preparation of covering agent:

a-3. preparation of Al-Mg intermediate alloy:

step 1: firstly weighing a part of Al block, and then adding a covering agent, wherein the covering agent comprises the following components: 50 wt.% CaCl after dehydration treatment₂45 wt.% NaCl and 5 wt.% KClA homogeneously mixed solid powder;

a-4, preparing a tin-rich zinc-based plating material:

step 2: putting the crucible into a resistance furnace, starting heating to raise the temperature to 600-700 ℃, keeping the temperature for 2h at 600-700 ℃ after the Zn blocks are completely melted, then starting adding the Al-Mg intermediate alloy prepared in the step a-3), keeping the temperature for 0.5h, and stirring to obtain a Zn-Al-Mg alloy melt; pouring the alloy into a mould for cooling and forming to prepare the tin-rich zinc-based plating alloy material;

b. and (3) hot dip coating process:

and step 3: preparing a mixed alkaline aqueous solution, wherein the NaOH mass percent concentration of the mixed alkaline aqueous solution is 5 wt.%, and the NaCO of the mixed alkaline aqueous solution₃The mass percent concentration is 5 wt.%, and the mixed alkaline aqueous solution is put into a constant-temperature water bath kettle to be heated to 80 ℃ and insulated, the oil stain on the surface of the steel is removed by the prepared alkaline solution, and the surface of the steel is subjected to alkaline cleaning treatment;

and 4, step 4: preparing an acidic aqueous solution, wherein the mass percent concentration of HCl in the acidic aqueous solution is 5 wt.%, and the mass percent concentration of urotropine in the acidic aqueous solution is 0.5 wt.%, cleaning the surface of the steel subjected to alkali washing treatment with deionized water and absolute ethyl alcohol in sequence, drying the steel by blowing, and placing the steel into the acidic aqueous solution to remove rust on the surface of the steel;

step 6: sending the steel plate blow-dried in the step 5 into a hot dip plating experiment simulator, and reducing the surface of the steel plate at the reducing temperature of 630 ℃ under the reducing atmosphere of N₂And H₂Atmosphere of mixed gas containing H₂The volume percentage of (2) is 10 vol.%, and the surface of the steel is continuously subjected to reduction treatment for 5-10 min;

And (3) experimental detection and analysis:

the coated base material piece was taken out of the cooling water to obtain the desired Zn-3.5 wt.% Al-2.8 wt.% Mg alloy coating material. The embodiment solves the problems of brittle fracture of the steel plate caused by the penetration of liquid zinc into the steel plate matrix in the hot forming process of the advanced high-strength steel zinc-based coating and excellent corrosion resistance. Al and Mg elements are added into the plating solution, and then an Fe-Al inhibition layer is formed to inhibit the brittle fracture phenomenon caused by the penetration of liquid zinc into the steel plate in the hot forming process; and Mg is formed by adding Mg element and reacting with Zn element in the plating solution in the hot dipping process₂Zn₁₁And MgZn₂And the corrosion resistance of the plating layer is further improved. The microstructure and the energy spectrum scanning of Zn-3.5 wt.% Al-2.8 wt.% Mg series zinc-based coating are shown in figure 1.

The heat treatment method of the aluminum-rich zinc-based coating material comprises the following steps:

in order to obtain the liquid zinc infiltration condition of the coating of the hot-dip plated steel plate under the heat treatment process, the steel plate is placed into a vertical resistance furnace for heat treatment experiment, and the heat treatment temperature is 400-930 ℃. The specific experimental steps are as follows:

step 1: cutting a steel plate sample into 15mm multiplied by 15mm in a linear mode, and processing a round hole with the diameter of 3mm at a position 3mm away from the edge to be used for tying an experimental sample;

step 2: heating the vertical furnace to 930 ℃, measuring the position corresponding to the temperature in the hearth, and placing a graphite crucible filled with water below the vertical furnace;

and step 3: putting a sample tied with the high-temperature alloy wire into a position corresponding to the temperature in the furnace body from the top of the vertical resistor furnace, and reaching the corresponding temperature according to the corresponding time in the measured temperature curve;

and 4, step 4: and after the heat treatment time is up, opening a furnace door below the vertical furnace, cutting off the alloy wires above, and putting the sample into a crucible for water cooling to finish water quenching.

A method for detecting the infiltration condition of liquid zinc after heat treatment of an aluminum-rich zinc-based plating material in the embodiment comprises the following steps:

step 1: taking each group of samples after heat treatment, and cutting the samples into a size suitable for a sample holder of a scanning electron microscope by using a linear cutting instrument;

step 2: bonding each group of cut samples on a scanning electron microscope sample base by using a conductive adhesive, and observing the cross section of a coating of the heat-treated sample by using a scanning electron microscope (SEM + EDS) equipped with an X-ray energy spectrometer;

and step 3: determining the phase composition of the cutting section of the plating neutralization sample by adopting an X-ray diffractometer (XRD), and scanning at the speed of 4 DEG/min;

and 4, step 4: observing element distribution of a cutting section of a coating and a sample by adopting Electron Probe Microanalysis (EPMA);

and 5: analyzing the surface chemical components of the cut section of the coating neutralization sample layer by adopting a glow discharge emission atomic spectrometer (GDMS);

step 6: and (3) observing the finer texture structure of the cut section of the plating and sample by using a Transmission Electron Microscope (TEM).

A method for detecting the mechanical property of a steel plate after heat treatment of the aluminum-rich zinc-based plating material comprises the following steps:

in order to obtain the cracking behavior of the substrate of the hot-dip coated steel plate in the hot forming process, a Gleeble 3500 thermal simulation testing machine is adopted to carry out a uniaxial thermal tensile test on the steel plate, and the specific experimental steps are as follows:

step 1: heating the heat-treated steel plate to a target temperature of 930 ℃ in a Gleeble 3500 thermal simulation testing machine at a heating rate of 10 ℃/s, preserving the heat for 30s, and then preserving the heat for 0.5s^-1Strain rate of 40% strain;

step 2: after the strain is finished, quenching the steel plate at a cooling speed of over 60 ℃/s by using compressed air so as to obtain a martensite structure with ultrahigh strength;

and step 3: carrying out hot stretching on the steel plate along the rolling direction, breaking the steel plate after the hot stretching is finished, analyzing the breaking morphology of the steel plate, obtaining a crack sample of the steel plate, and identifying and analyzing the morphology and microstructure of the crack in the crack sample;

and 4, step 4: preparing a hot-dip plated steel plate hot tensile sample into a crack sample by adopting a metallographic sample preparation method, and analyzing the appearance and microstructure of the crack after grinding and polishing the sample;

and 5: observing the morphology and the structure of the cracks by using a scanning electron microscope (SEM + EDS) equipped with an X-ray energy spectrometer;

step 6: observing the element distribution of the coating and the substrate at the cracks by adopting Electron Probe Microanalysis (EPMA);

and 7: cutting and analyzing the microstructure of the interface between the coating and the substrate at the crack by using a double-beam Focused Ion Beam (FIB) and a field emission transmission electron microscope (FE-TEM);

and 8: and analyzing the elongation and tensile strength of the steel plate coated with the aluminum-rich zinc-based plating layer after hot dip plating by combining a stress-strain curve provided on a Gleeble 3500 thermal simulation testing machine.

Referring to fig. 3, the hardness Hv of the zn-al-mg-based alloy coating material of the present embodiment is not less than 150. The zinc-based coating rich in aluminum is plated on a hot stamping steel plate, so that the problems of decarburization and oxidation peeling of the surfaces of some steel plates in the hot stamping forming process can be solved, and the corrosion resistance of the steel plate can be improved. In the embodiment, aiming at the problem that the liquid zinc generated in the hot forming process permeates into the steel plate to cause the brittle fracture of the steel plate, the Al element is added to form the Fe-Al alloy layer, and the Fe-Al alloy layer can inhibit the contact of the liquid zinc which is molten under the influence of high temperature and the steel plate matrix in the hot forming process, so that the brittle fracture of the steel plate matrix can be avoided in the hot forming process.

Example two:

this embodiment is substantially the same as the first embodiment, and is characterized in that:

in this embodiment, a Zn-Al-Mg-based alloy coating material for inhibiting embrittlement of liquid metal during hot forming of high strength steel is a Zn-Al-Mg-Sn alloy having the following composition and weight percent: 92.9 wt.% Zn, Al:3.5 percent; mg:2.8 percent; sn:0.8 percent, and the balance of inevitable impurities.

the raw materials are weighed and prepared according to the following element compositions and weight percentages thereof required by preparing the target zinc-aluminum-magnesium-based alloy coating material: 92.9 wt.% Zn; 3.5 wt.% Al; 2.8 wt.% of Mg, 0.8 wt.% of Sn and the balance of inevitable impurities, wherein Al blocks, Mg blocks, Sn blocks and Zn blocks are used as raw materials;

1) preparation of a covering agent:

3) preparing an Al-Mg intermediate alloy:

step 1: first, a portion of the Al mass is weighed, thenThen adding a covering agent, which comprises the following components: 50 wt.% CaCl after dehydration treatment₂A homogeneously mixed solid powder of 45 wt.% NaCl and 5 wt.% KCl;

4) preparing a Mg-Sn intermediate alloy:

5) preparing a tin-rich zinc-based plating material:

step 2: putting the crucible into a resistance furnace, starting heating to raise the temperature to 600-700 ℃, keeping the temperature for 2h at 600-700 ℃ after the Zn blocks are completely melted, then starting adding the Al-Mg intermediate alloy prepared in the step 3), keeping the temperature for 0.5h, and stirring to obtain a Zn-Al-Mg alloy melt; then, mainly adding the Mg-Sn intermediate alloy prepared in the step 4) into the prepared Zn-Al-Mg alloy melt, preserving the heat for 1 hour, and stirring to obtain a Zn-Al-Mg-Sn alloy melt; pouring the alloy into a mould for cooling and forming to prepare the tin-rich zinc-based plating alloy material;

b. and (3) hot dip coating process:

and 4, step 4: preparing an acidic aqueous solution, wherein the mass percent concentration of HCl in the acidic aqueous solution is 5 wt.%, and the mass percent concentration of urotropine in the acidic aqueous solution is 0.5 wt.%, cleaning the surface of the steel subjected to alkali washing treatment with deionized water and absolute ethyl alcohol in sequence, drying the steel by blowing, and placing the steel in the acidic aqueous solution to remove rust on the surface of the steel;

step 6: sending the steel plate blow-dried in the step 5 into a hot dip plating experiment simulator to reduce the surface of the steel plate, wherein the reduction temperature is 630 ℃, and the reducing atmosphere is N₂And H₂Atmosphere of mixed gas containing H₂The volume percentage of (2) is 10 vol.%, and the surface of the steel is continuously subjected to reduction treatment for 5-10 min;

And (3) experimental detection and analysis:

taking out the coated base material piece from the cooling water to obtain the expectedZn-3.5 wt.% Al-2.8 wt.% Mg-0.8 wt.% Sn rich aluminum zinc based plating material. The embodiment solves the problems of brittle fracture of the steel plate caused by the penetration of liquid zinc into the steel plate matrix in the hot forming process of the advanced high-strength steel zinc-based coating and excellent corrosion resistance. Al and Mg elements are added into the plating solution, and then an Fe-Al inhibition layer is formed to inhibit the brittle fracture phenomenon caused by the penetration of liquid zinc into the steel plate in the hot forming process; by adding Sn element, fine Mg is formed by reaction with Zn element in plating solution in the process of hot dipping₂A Sn phase which can improve the surface hardness and the wear resistance of the plating layer; and Mg is formed by adding Mg element and reacting with Zn element in the plating solution in the hot dipping process₂Zn₁₁And MgZn₂And the corrosion resistance of the plating layer is further improved. The microstructure and spectrum scan of the Zn-3.5 wt.% Al-2.8 wt.% Mg-0.8 wt.% Sn tin-rich zinc-based plating are shown in fig. 2. Forming an Fe-Al inhibiting layer with a thickness of not less than 0.5 μm in the formation of the Zn-Al-Mg-based alloy coating on the surface of the high-strength steel, wherein the Fe-Al inhibiting layer comprises Fe₂Al₅And (4) phase(s).

The heat treatment method of the tin-rich zinc-based coating material comprises the following steps:

A method for detecting the infiltration condition of liquid zinc after heat treatment of a tin-rich zinc-based coating material in the embodiment comprises the following steps:

A method for detecting the mechanical property of a steel plate after heat treatment of the tin-rich zinc-based plating material comprises the following steps:

and 8: and analyzing the elongation and tensile strength of the steel plate coated with the tin-rich zinc-based plating layer after hot dip plating by combining a stress-strain curve provided on a Gleeble 3500 thermal simulation testing machine.

Referring to fig. 3, the hardness Hv of the zn-al-mg-based alloy coating material of the present embodiment is not less than 150. The tin-rich zinc-based plating layer is plated on a hot stamping steel plate, so that the problems of decarburization and oxidation peeling of the surfaces of some steel plates in the hot stamping forming process can be solved, and the corrosion resistance of the steel plate can be improved. In the embodiment, aiming at the problem that the liquid zinc generated in the hot forming process permeates into the steel plate to cause the brittle fracture of the base body, Al element is added to form a Fe-Al alloy layer, and the Fe-Al alloy layer can inhibit the contact of the liquid zinc which is molten under the influence of high temperature and the steel plate base body in the hot forming process, so that the brittle fracture of the steel plate base body can be avoided in the hot forming process; in addition, in the embodiment, Sn element is introduced, so that fine Mg can be generated by combining with Zn element in the plating solution in the hot dipping process₂The Sn phase can reduce the abrasion between the surface of the formed part and the die in the hot forming process, and can further control the extension of cracks generated by abrasion into the steel plate matrix.

Example three:

this embodiment is substantially the same as the previous embodiment, and is characterized in that:

in this example, a Zn-Al-Mg-based alloy coating material for inhibiting embrittlement of liquid metal during hot forming of high strength steel is a Zn-Al-Mg-Sn-Bi alloy having the following composition and weight percent: 85.7 wt.% Zn, Al:3.5 percent; mg:2.8 percent; sn: 4.0%, Bi:4.0 percent, and the balance of inevitable impurities.

the raw materials are weighed and prepared according to the following element compositions and weight percentages thereof required by preparing the target zinc-aluminum-magnesium-based alloy coating material: 85.7 wt.% Zn; 3.5 wt.% Al; 2.8 wt.% of Mg, 4.0 wt.% of Sn, 4.0 wt.% of Bi and the balance of inevitable impurities, wherein Al blocks, Mg blocks, Sn blocks, Bi blocks and Zn blocks are used as raw materials;

1) preparation of a covering agent:

3) preparing an Al-Mg intermediate alloy:

4) preparing a Mg-Sn intermediate alloy:

step 1: taking the rest Mg blocks, and adding covering agentThe components are as follows: 50 wt.% CaCl after dehydration treatment₂A homogeneously mixed solid powder of 45 wt.% NaCl and 5 wt.% KCl;

5) preparing an Al-Bi intermediate alloy:

6) preparing a tin-rich zinc-based plating material:

step 2: putting the crucible into a resistance furnace, starting heating to raise the temperature to 600-700 ℃, keeping the temperature for 2h at 600-700 ℃ after the Zn blocks are completely melted, then starting adding the Al-Mg intermediate alloy prepared in the step 3), keeping the temperature for 0.5h, and stirring to obtain a Zn-Al-Mg alloy melt; then, mainly adding the Mg-Sn intermediate alloy prepared in the step 4) into the prepared Zn-Al-Mg alloy melt, preserving the heat for 1 hour, and stirring to obtain a Zn-Al-Mg-Sn alloy melt; then adding the Al-Bi intermediate alloy prepared in the step 5), preserving heat for 1h, stirring to obtain a Zn-Al-Mg-Sn-Bi alloy melt, pouring the Zn-Al-Mg-Sn-Bi alloy melt into a mold, and cooling and molding to prepare a tin-rich zinc-based plating alloy material;

b. and (3) hot dip coating process:

and step 3: preparing a mixed alkaline aqueous solution, wherein the NaOH mass percent concentration of the mixed alkaline aqueous solution is 5 wt.%, and the NaCO of the mixed alkaline aqueous solution₃The mass percent concentration is 5 wt.%, the mixed alkaline aqueous solution is put into a constant-temperature water bath kettle and heated to 80 ℃ and is kept warm, the oil stain on the surface of the steel is removed by the prepared alkaline solution, and the surface of the steel is subjected to alkaline cleaning treatment;

This implementationThe hardness Hv of the zinc-aluminum-magnesium-based alloy coating material is not less than 150. The tin-rich zinc-based plating layer is plated on a hot stamping steel plate, so that the problems of decarburization and oxidation peeling of the surfaces of some steel plates in the hot stamping forming process can be solved, and the corrosion resistance of the steel plate can be improved. In the embodiment, aiming at the problem that the liquid zinc generated in the hot forming process permeates into the steel plate to cause the brittle fracture of the base body, Al element is added to form a Fe-Al alloy layer, and the Fe-Al alloy layer can inhibit the contact of the liquid zinc which is molten under the influence of high temperature and the steel plate base body in the hot forming process, so that the brittle fracture of the steel plate base body can be avoided in the hot forming process; in addition, in the embodiment, Sn element is introduced, so that fine Mg can be generated by combining with Zn element in the plating solution in the hot dipping process₂The Sn phase can reduce the abrasion between the surface of the formed part and the die in the hot forming process, and can further control the extension of cracks generated by abrasion into the steel plate matrix. The addition of Bi element in the embodiment can effectively increase the fluidity of the plating solution in the hot dip plating process, reduce the surface tension of the plating solution, improve the wettability and improve the surface quality and mechanical property of the plating layer.

In summary, the above embodiments suppress embrittlement of the liquid metal during hot forming and provide a Zn-Al-Mg-based alloy plating material having excellent wear resistance, and a method for producing the same. The invention mainly adds a new element Sn and Bi in the traditional zinc-aluminum-magnesium coating. In the hot forming process of the advanced high-strength steel, on one hand, the embodiment of the invention can provide a restraining effect for embrittlement of a steel plate matrix caused by liquid zinc penetration; on the other hand, the coating with excellent wear resistance can be provided, and the wear amount in the hot forming process is reduced. According to the embodiment of the invention, through a hot dip coating experiment, a heat treatment experiment, a coating section structure observation, a mechanical tensile property detection, a hardness detection and a friction experiment detection of the coating, the alloy coating material which can inhibit the liquid metal from being brittle and provide excellent wear resistance is provided for the advanced high-strength steel.

The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be replaced with equivalents as long as the object of the present invention is met, and the technical principle and the inventive concept of the present invention are not departed from the scope of the present invention.

Claims

1. a zinc-aluminum-magnesium-based alloy coating material that suppresses liquid metal brittleness in high-strength steel hot forming process, is characterized in that, it is Zn-Al-Mg alloy, Zn-Al-Mg-Sn alloy or Zn-Al- Mg-Sn-Bi alloy has the following composition and weight percentage: Al: 0.2-5.0%; Mg: 2.6-4%; Sn: 0-4.0%, Bi: 0-4.0%, and the rest are Zn and inevitable impurities .

2. The zinc-aluminum-magnesium-based alloy coating material for suppressing liquid metal embrittlement during hot forming of high-strength steel according to claim 1, characterized in that: its composition and weight percentage: Zn: 83.0-96.9%; Al: 0.2-5.0 %; Mg: 2.6-4%; Sn: 0-4.0%; Bi: 0-4.0%, and the rest are inevitable impurities.

3. The zinc-aluminum-magnesium-based alloy coating material for inhibiting liquid metal embrittlement during hot forming of high-strength steel according to claim 2, characterized in that: its composition and weight percentage: Zn: 83.0-93.7%; Al: 0.2-3.5 %; Mg: 2.8-4%; Sn: 0-0.8%; Bi: 0-4.0%, and the rest are inevitable impurities.

4. The zinc-aluminum-magnesium-based alloy coating material for inhibiting liquid metal embrittlement during hot forming of high-strength steel according to claim 1, characterized in that: its composition and weight percentage: Al: 0.2-3.5%; Mg: 2.8-4 %; Sn: 0-4.0%; Bi: 0-4.0%, and the rest are Zn and inevitable impurities.

5. The zinc-aluminum-magnesium-based alloy coating material for suppressing the brittleness caused by liquid metal in the hot forming process of high-strength steel according to claim 1, is characterized in that: in the zinc-aluminum-magnesium-based alloy coating formed on the surface of the high-strength steel, the thickness is not less than 0.5 μm Fe-Al suppression layer, the Fe-Al suppression layer includes Fe ₂ Al ₅ phase.

6. The zinc-aluminum-magnesium-based alloy coating material for suppressing liquid metal brittleness during hot forming of high-strength steel according to claim 1, wherein the zinc-aluminum-magnesium-based alloy coating formed on the surface of the high-strength steel comprises Mg ₂ Sn phase , at least one of the Mg ₂ Zn ₁₁ phase and the MgZn ₂ phase.

7 . The zinc-aluminum-magnesium-based alloy coating material for inhibiting liquid metal embrittlement during hot forming of high-strength steel according to claim 1 , wherein the hardness Hv is not less than 150. 8 .

8. A preparation method of a zinc-aluminum-magnesium-based alloy coating material that suppresses the brittleness caused by liquid metal in the hot forming process of high-strength steel, characterized in that it comprises the following steps:

a. Preparation process of hot-dip bath:

The raw materials are weighed and prepared according to the following elemental compositions and their weight percentages required for the preparation of the target zinc-aluminum-magnesium-based alloy coating material: Al: 0.2-5.0%; Mg: 2.6-4%; the rest are Zn and inevitable impurities, with Al Block, Mg block and Zn block as raw materials;

a-1. Preparation of covering agent:

To prevent oxidation of the galvanizing solution in the process of preparing the plating solution, the composition mass percentage ratio of the covering agent used is: 50wt.% CaCl ₂ , 45wt.% NaCl, 5.0wt.% KCl;

a-2. Under the protection of the covering agent, in the resistance furnace, smelt and prepare the alloy according to the raw materials of the set formula;

a-3. Preparation of Al-Mg master alloy:

Step 1: First weigh a part of the Al block, and then add a covering agent, the composition of which is: a uniformly mixed solid powder of 50 wt.% CaCl ₂ , 45 wt. % NaCl and 5 wt. % KCl after dehydration;

Step 2: Start heating up to 600-700 °C, keep the temperature until the Al blocks are completely melted, then start to gradually add a part of the Mg blocks prepared in advance, stir, and then after the treatment with argon, the furnace is cooled to room temperature to obtain the Al-Mg intermediate alloy;

a-4. Preparation of tin-rich zinc-based coating materials:

Step 1: The Zn block is weighed and polished, put into a crucible, and then a covering agent is added, the composition of which is: dehydrated 50wt.% CaCl ₂ , 45wt.% NaCl and 5wt.% KCl homogeneously mixed solid powder;

Step 2: Put the crucible into the resistance furnace, start heating, make the temperature rise to 600-700°C, wait for all the Zn blocks to melt, keep at 600-700°C for at least 2h, and then start adding in the step a-3. The Al-Mg master alloy prepared in ) is then kept for at least 0.5h and stirred to obtain a Zn-Al-Mg alloy melt; it is poured into a mold and cooled to form a tin-rich zinc-based coating alloy material. ;

b. Hot dip plating process:

Step 1: put the tin-rich zinc-based coating alloy material prepared in the step a into a zinc pot, and form a Zn-Al-Mg hot-dip bath after melting;

Step 2: Use 400-2000# sandpaper to polish the surface of the steel to be coated to remove the oxide layer on the surface of the steel;

Step 3: prepare a mixed alkaline aqueous solution, the NaOH mass percentage concentration of the mixed alkaline aqueous solution is not less than 5wt.%, and the _NaCO3 mass percentage concentration of the mixed alkaline aqueous solution is not less than 5wt.%, and the mixed The alkaline aqueous solution is placed in a constant temperature water bath and heated to not less than 80°C and kept warm. The prepared alkaline solution is used to remove the oil stains on the surface of the steel, and the surface of the steel is subjected to alkaline washing treatment;

Step 4: Prepare an acidic aqueous solution, the mass percentage concentration of HCl in the acidic aqueous solution is not less than 5wt.%, and the mass percentage concentration of urotropine in the acidic aqueous solution is not less than 0.5wt.%. The surface of the steel is cleaned with deionized water and anhydrous ethanol, then dried, and then put into an acid solution to remove the rust on the surface of the steel;

Step 5: After completing the pickling process in the above step 4, take out the steel, wash the surface of the steel with deionized water and anhydrous ethanol successively, and then blow dry;

Step 6: Send the dried steel sheet in the above step 5 into the hot dip coating experiment simulator, and carry out reduction treatment _on the surface of the steel, the reduction temperature is set to not lower _than 630 ° C, and the reduction atmosphere is a mixture of N In a gas atmosphere, the volume percentage of H ₂ in the mixed gas is not less than 10 vol.%, and the surface of the steel is continuously reduced for 5-10 minutes;

Step 7: After completing the reduction treatment in the above step 6, the steel is immersed in the molten Zn-Al-Mg hot dip solution prepared in the above step 1, and hot dip plating is performed, and the hot dip coating time is controlled to be 3-15s;

Step 8: After the hot dip plating is completed, a cooling treatment is performed, and the steel is taken out of the hot-dip bath and immediately water-cooled at a temperature of 20-30°C, thereby obtaining a zinc-aluminum-magnesium-based alloy coating on the surface of the steel.

9. A method for preparing a zinc-aluminum-magnesium-based alloy coating material that suppresses brittleness caused by liquid metal in the hot forming process of high-strength steel, characterized in that the method comprises the following steps:

a. Preparation process of hot-dip bath:

The raw materials are weighed and prepared according to the following element compositions and their weight percentages required for the preparation of the target zinc-aluminum-magnesium-based alloy coating material: Al: 0.2-5.0%; Mg: 2.6-4%; Sn≤4.0%, and the rest are Zn and unavoidable The impurity, with Al block, Mg block, Sn block and Zn block as raw material;

1) Preparation of covering agent:

2) Under the protection of the covering agent, in the resistance furnace, the alloy is prepared by smelting the raw materials according to the set formula;

3) Preparation of Al-Mg master alloy:

4) Preparation of Mg-Sn master alloy:

Step 1: take the remaining Mg block, and then add a covering agent, the composition of which is: a uniformly mixed solid powder of 50 wt.% CaCl ₂ , 45 wt. % NaCl and 5 wt. % KCl after dehydration;

Step 2: Start heating up to 600-700°C, keep the temperature until all the Mg blocks are melted, then start to gradually add the Sn blocks prepared in advance, and stir, and then after the treatment of argon, the furnace is cooled to room temperature to obtain the Mg-Sn intermediate alloy;

5) Preparation of tin-rich zinc-based coating material:

Step 2: Put the crucible into the resistance furnace, start heating, make the temperature rise to 600-700°C, wait for all the Zn blocks to melt, keep at 600-700°C for at least 2h, and then start adding in the step 3). The prepared Al-Mg master alloy is then kept for at least 0.5h and stirred to obtain a Zn-Al-Mg alloy melt; then the prepared Zn-Al-Mg alloy melt is mainly added in the step 4 The Mg-Sn master alloy prepared in the ;

b. Hot dip plating process:

Step 1: put the tin-rich zinc-based coating alloy material prepared in the step a into a zinc pot, and form a Zn-Al-Mg-Sn hot-dip bath after melting;

Step 5: After completing the pickling process in the above step 4, take out the steel, wash the surface of the steel with deionized water and anhydrous ethanol successively, and then dry it;

Step 7: After completing the reduction treatment in the above step 6, the steel is immersed in the molten Zn-Al-Mg-Sn hot-dip bath prepared in the above-mentioned step 1, and hot-dip plating is performed, and the hot-dip plating time is controlled to be 3- 15s;

10. A method for preparing a zinc-aluminum-magnesium-based alloy coating material for suppressing liquid metal brittleness during hot forming of high-strength steel, characterized in that the method comprises the following steps:

a. Preparation process of hot-dip bath:

The raw materials are weighed and prepared according to the following element compositions and their weight percentages required for the preparation of the target zinc-aluminum-magnesium-based alloy coating material: Al: 0.2-5.0%; Mg: 2.6-4%; Sn≤4.0%, Bi≤4.0%, and the rest For Zn and inevitable impurities, use Al block, Mg block, Sn block, Bi block and Zn block as raw materials;

1) Preparation of covering agent:

3) Preparation of Al-Mg master alloy:

4) Preparation of Mg-Sn master alloy:

5) Preparation of Al-Bi master alloy:

Step 1: take the remaining Al block, and then add a covering agent, the composition of which is: uniformly mixed solid powder of 50wt.% CaCl ₂ , 45wt.% NaCl and 5wt.% KCl after dehydration;

Step 2: Start heating up to 600-700 °C, keep the temperature until the Al blocks are completely melted, then start to gradually add the Bi blocks prepared in advance, stir, and then be treated with argon gas, and then the furnace is cooled to room temperature to obtain Al-Bi master alloys ;

6) Preparation of tin-rich zinc-based coating material:

Step 2: Put the crucible into the resistance furnace, start heating, make the temperature rise to 600-700°C, wait for all the Zn blocks to melt, keep at 600-700°C for at least 2h, and then start adding in the step 3). The prepared Al-Mg master alloy is then kept for at least 0.5h and stirred to obtain a Zn-Al-Mg alloy melt; then the prepared Zn-Al-Mg alloy melt is mainly added in the step 4 ), the Mg-Sn master alloy prepared in step 5) was kept for at least 1 h and stirred to obtain a Zn-Al-Mg-Sn alloy melt; then the Al-Bi master alloy prepared in the step 5) was added to carry out Keep the temperature for at least 1 hour and stir to obtain a Zn-Al-Mg-Sn-Bi alloy melt, which is poured into a mold to cool and form to prepare a tin-rich zinc-based coating alloy material;

b. Hot dip plating process:

Step 1: put the tin-rich zinc-based coating alloy material prepared in the step a into a zinc pot, and form a Zn-Al-Mg-Sn-Bi hot-dip bath after melting;

Step 6: Send the dried steel sheet from the above step 5 to the hot-dip plating experiment simulator to reduce the surface of the steel. _The reduction temperature is set to not lower _than 630°C, and the reduction atmosphere is a mixture of N In a gas atmosphere, the volume percentage of H ₂ in the mixed gas is not less than 10vol.%, and the surface of the steel is continuously reduced for 5-10min;

Step 7: After completing the reduction treatment in the above step 6, the steel is immersed in the molten Zn-Al-Mg-Sn-Bi hot dip solution prepared in the above step 1, and hot dip plating is performed, and the hot dip coating time is controlled to be 3-15s;

Step 8: After the hot dip plating is completed, a cooling treatment is performed, and the steel is removed from the hot-dip bath and immediately water-cooled at a temperature of 20-30°C, thereby obtaining a zinc-aluminum-magnesium-based alloy coating on the surface of the steel.