CN111618146A - A kind of hot stamping method of zinc-based coating coated steel and hot stamping forming component - Google Patents

Abstract

The invention provides a hot stamping method for coated steel with zinc-based coating, belonging to the technical field of metallurgical materials and hot stamping technology, comprising the following steps: preheating steel coated with zinc-based coating; heating the preheated steel to complete the steel Fully austenitized, hot stamped and quenched after transfer. The hot stamping method can effectively reduce steel plate cracks and reduce the crack depth, thereby improving the mechanical properties of the steel plate. The invention also discloses a hot stamping forming component of zinc-based coating coated steel.

Description

A kind of hot stamping method of zinc-based coating coated steel and hot stamping forming component

technical field

The invention belongs to the technical field of metallurgical materials and hot stamping technology, and in particular relates to a hot stamping method for zinc-based coating coated steel and a hot stamping forming component.

Background technique

The "lightweight" of automobiles can directly reduce emissions and reduce fuel consumption, which is the main direction and goal of the development of today's automobile manufacturing industry. The use of high-strength and ultra-high-strength steels has a positive and effective effect on the lightweight of automobile bodies. However, with the continuous improvement of the strength of the steel used in the body, its plasticity and formability are greatly reduced, and cracking and reclamation are easy to occur during the forming process. It will seriously affect the shape and dimensional accuracy of the parts. The hot stamping forming technology utilizes the characteristics of easy forming without springback at high temperature and quenching and cooling of the mold, and can obtain ultra-high strength parts greater than 1300MPa, which can well solve the problems of easy cracking and serious springback in cold forming.

There are mainly two existing hot stamping forming methods, namely direct hot stamping and indirect hot stamping. In the direct hot stamping method, the steel plate is directly heated to a temperature above the austenitization temperature, and kept for a certain period of time so that the structure of the steel plate is completely austenitized. Afterwards, the heated steel sheet is transferred to a forming die and formed therein into a finished component in a one-step forming process while quenching is achieved by means of cooling of the die (the cooling rate of the die is greater than the critical cooling rate of the steel sheet) to complete the martensitic transformation. In the indirect hot stamping method, the component is first formed to almost complete completion (usually 90% preform) in a multi-step forming process. It is then heated in a furnace until fully austenitized and held for a period of time. The heated element is then transferred to a forming mold for the final size of the element, with special care to take into account the thermal expansion of the preformed element. After the specific cooling of the mold is complete, the preformed element is cooled in the mold at a cooling rate greater than the critical cooling rate to achieve hardening. The direct hot stamping method is easier to implement, but only allows the production of parts that are relatively simple in shape. The indirect hot stamping process is more complex, but at the same time can produce parts with more complex shapes.

In addition, in order to avoid oxide scale and decarburization on the surface of hot stamped steel sheets, and at the same time to make hot stamped steel sheets highly resistant to corrosion, at present, the coatings used for hot stamping steel mainly include Al-Si coating, Gl coating, GA coating, X- TEC coating and Zn~Ni coating. Al-Si coating, Gl coating and GA coating have been commercialized, however, commercial application of X-TEC coating and ZnNi coating is rarely seen. The hot stamped steel plate with zinc-based coating can not only prevent surface oxidation and decarburization during the heating process, but also provide sacrificial anode protection without subsequent shot peening process, and improve the anti-corrosion performance after painting.

However, in the process of direct hot stamping, the problems of hot stamped steel plates with zinc-based coating are: the steel plate is embrittled, the surface cracks of the parts are generated and spread to the matrix, resulting in the reduction of strength and other problems, thus affecting the use of the steel plate. The use of indirect hot stamping reduces the number of matrix cracks during the subsequent post-forming hardening process, but again, cracks cannot be avoided, and multi-step preforming increases the cost of producing the part.

The application number is CN108138282A for the production of hot-pressed galvanized steel sheet and hot-pressed product, providing a galvanized steel sheet that can be used to suppress the occurrence of LME cracks in a hot-pressing process for a short heating time, and use This galvanized steel sheet is a special plated steel sheet for hot pressing obtained by hot pressing, and is characterized in that the interface between the galvanized layer and the base steel sheet has internal oxides on the base steel sheet side, and the heating for suppressing LME can be shortened. Time, no stamping method involved.

A hot stamping forming method for zinc-based plated steel sheet or steel strip with authorization number CN107127238B, by applying a pre-cooling device when the steel sheet leaves the annealing furnace, the steel sheet is cooled to 650-700°C at a cooling rate greater than 30°C/s , and then blanking according to the shape and size of the part, and then the steel plate is quickly transferred to the mold for hot stamping, where it is hardened at a speed higher than 30°C/s, and the hot stamping temperature is maintained at 400°C to between 650°C. Substrate cracks due to local stress and liquid metal embrittlement (LME) can be avoided to solve the problem that current zinc-based hot stamping steels cannot avoid substrate cracks. This patent performs hot stamping by pre-cooling to a lower temperature. The lower temperature forming increases the deformation resistance, increases the cost of die loss, and at the same time increases the pre-cooling device, which increases the production cost.

SUMMARY OF THE INVENTION

In order to solve the technical problem of cracks in hot-stamped steel sheets with zinc-based coating, the present invention provides a hot-stamping method for coated steel with zinc-based coating, which can effectively reduce steel plate cracks, reduce the crack depth, and further improve the strength of the steel plate.

The invention also discloses a hot stamping forming component of zinc-based coating coated steel.

The present invention is achieved through the following technical solutions:

A hot stamping method for zinc-based coating coated steel, comprising:

Preheat the steel coated with zinc-based coating. The preheating temperature is 500~800℃, and the temperature is kept for 60~300s. During the preheating process, the heating rate V1 between room temperature and 430℃ is less than 15℃/s, and heating after reaching 430℃ Rate V2＜10℃/s;

The preheated steel is heated to complete the complete austenitization of the steel, followed by hot stamping and quenching after transfer.

Wherein, the method for heating the preheated steel material is as follows: the preheated steel material is heated to a temperature above Ac3, and the temperature is kept for 60-200 s.

Further, the transfer time of the fully austenitized steel is less than 10S, the hot stamping temperature is 550-720°C, the hot stamping holding pressure is 200-1000 tons, and the holding time is 3-15 seconds.

A zinc-based coating-coated steel, the chemical composition of a zinc-based coating-coated steel substrate, by weight percentage, is: C: 0.15-0.40, Si: 0.02-0.5, Al: 0.02-1.5, Mn: 0.5-3.6, Cr : 0.01～0.7, Mo: 0.01～0.7, B: 0.001～0.005, S: ≤0.005, P: ≤0.01, N: ≤0.015, 0: ≤0.003;

Among them, 0.1%≤(Cr+Mo)≤1.0%; also add any one or more of Ti: 0.01-0.15, Nb: 0.01-0.15, V: 0.01-0.15, and must satisfy:

0.03%≤(Ti+Nb+V)≤0.45%; the rest are Fe and inevitable impurities.

Further, the thickness of the zinc-based coating layer on the substrate is 3-30 μm, and the zinc-based coating layer contains ≤3% by weight of aluminum.

A preparation method of zinc-based coating coated steel, comprising:

The cast billet is hot rolled, pickled and cold rolled to form chilled steel strip;

Chilled steel strips are annealed and galvanized, smoothed, stretched and straightened to adjust their shape, and then coiled into coils.

Wherein, the preparation process of the chilled steel strip is as follows:

The raw materials are smelted and cast to obtain the casting billet, the casting billet is heated to a temperature of 1100-1280 °C, the final rolling temperature of hot rolling is 750-950 °C, and the hot-rolling coiling temperature is 500-700 °C to obtain a hot-rolled coil. Wash, and then cold-roll to form a steel strip, and the cold-rolling reduction is 40-80%.

Further, the annealing galvanizing treatment method is as follows:

The chilled steel strip is heated to 720-850°C, continuously annealed after heat preservation, cooled to a hot-dip plating temperature at 5-50°C/s, and hot-dip galvanized in a zinc pot; the zinc pot temperature is 400°C- 520℃, hot dip plating time 2-20s, after hot dip plating, cool down to below 200℃ at 3-50℃/s.

A zinc-based coating-coated steel hot stamping forming component is prepared by using the above-mentioned zinc-based coating-coated steel by the above-mentioned hot stamping method.

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

The invention provides a hot stamping method for coated steel with zinc-based coating. The prepared steel coated with zinc-based coating is formed by the hot stamping method. The yield strength, elongation and other properties are not lower than those of traditional hot stamped steel sheets, and the depth of the hot stamped component crack propagation to the substrate is reduced to ≤5μm, which effectively solves the problems of steel plate embrittlement and cracks caused by the existing hot stamping process.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is the process flow chart of the hot stamping forming of the present invention.

2 is a scanning electron microscope (SEM) image of the coating structure after preheating in Example 1 of the present invention: the gray part at the bottom of the figure is the matrix, and the gray-white part above the matrix is the coating.

3 is a scanning electron microscope (SEM) image of the coating structure after preheating in Example 3 of the present invention: the gray part at the bottom of the figure is the substrate, and the gray-white part above the substrate is the coating.

Detailed ways

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

Throughout the specification, unless specifically stated otherwise, terms used herein are to be understood as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification takes precedence.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

The technical solutions provided by the embodiments of the present invention are to solve the above-mentioned technical problems, and the general idea is as follows:

In our research, we found that the problem of embrittlement and cracks in hot stamped steel sheets with zinc-based coating is mainly due to the liquefaction of the zinc-based coating at a high temperature of 900 °C, which results in the embrittlement of the steel sheet, that is, LME (Liquid Metal Embrittlement, Liquid Metal Embrittlement). ), so that the parts are prone to surface cracks during the high-temperature stamping forming process and expand to the matrix, resulting in problems such as strength reduction, thus affecting the use of steel plates.

The present application improves the hot stamping forming process of steel (steel plate, steel strip or steel coil). By adding a preheating process before the austenitizing process of the steel, the preheating temperature is 500-800°C, and the temperature is kept for 120-300s. During the preheating process, the heating rate V1 <15°C/s between room temperature and 430°C, After reaching 430°C, the heating rate V2<5°C/s.

After the preheating temperature exceeds the melting point of the zinc element, reduce the preheating heating rate, so that the Fe atoms on the surface of the steel plate can be fully diffused into the zinc layer to form a part of Zn-Fe alloy. The content of Fe element in the coating is more than 10%. Melting point, avoid the melting of the coating and reduce the volatilization of Zn element. It avoids the embrittlement of the steel plate caused by the liquefaction of the zinc-based coating at a high temperature of 900 ° C, resulting in cracks in the stamping process. In addition, in order to prevent the evaporation of Zn in the coating, the limitation of the narrow austenitizing window on the application of the steel sheet is avoided.

The hot stamping forming process combined with the applicant's adjustment of the steel composition and ratio, under the synergistic effect of the two, can further reduce the occurrence of cracks and reduce the crack depth.

The hot stamping forming process of the zinc-based coating-coated steel of the present application will be described in detail below with reference to the examples, comparative examples and experimental data.

Example 1

In this embodiment, a zinc-based coating-coated steel hot-stamped component has the weight percentage (wt, %) content of each component of the substrate: C: 0.22, Si: 0.43, AI: 0.039, Mn: 1.3, Cr: 0.2, Mo: 0.02, B: 0.003, Ti: 0.025, Nb: 0.045, V: 0.06, S: 0.0030, P: 0.009, N: 0.0050, 0: 0.001, and the rest were Fe and inevitable impurities.

The specific manufacturing method is as follows:

1) After smelting, casting, hot rolling, pickling and cold rolling to form chilled steel strip:

After smelting and casting, the casting billet is obtained; the casting billet is heated to a temperature of 1100-1280 °C, the final rolling temperature of hot rolling is 890 °C, and the hot rolling coiling temperature is 620 °C to obtain a hot rolled coil; after hot rolling, conventional pickling is performed to remove surface oxidation. skin; after pickling, cold-rolling to form a steel strip, and the cold-rolling reduction is 65%.

2) The pre-treatment process of galvanizing mainly includes degreasing with alkaline or acidic solution, water cleaning, electrolytic degreasing, pickling, water cleaning, etc. The strip surface remains clean.

3) Annealing and galvanizing treatment process:

The chilled steel strip is coated with hot-dip galvanizing and annealing, specifically, the chilled steel strip is heated to 720-850° C., continuously annealed after heat preservation, cooled to a hot-dip plating temperature at 15° C./s, and then carried out in a zinc pot. Hot-dip galvanizing; the temperature of the zinc pot is 450°C, the aluminum content of the zinc liquid is ≤3%, the hot-dip plating time is 4s, and the hot-dip plating is cooled to below 200°C at 10°C/s, and the galvanizing is 3-30μm.

4) After shearing, blanking, and preheating to 760°C for 60s, the heating rate V1 between room temperature and 430°C is 10°C/s, and the heating rate V2 between 430°C and 750°C is 7°C/s.

5) Transfer the preheated steel sheet to a heating furnace at 930°C for 140s, then transfer the steel sheet out of the heating furnace and cool it to 720°C, and then transfer it to the die for stamping and quenching. The quenching cooling rate is ≥30°C/s, and the holding pressure 700 tons, in-mold quenched for 8s, then taken out and cooled to room temperature.

Due to the high C content of the steel sheet of the present invention, the cold rolling reduction is likely to cause excessive burden on the rolling mill. At the same time, in order to ensure a considerable reduction ratio to control the grain size to meet the requirements of mechanical properties, the reduction ratio is preferably below 80%, and may be more preferably 40-75%.

Specifically, in the hot-stamped component, the Fe element of the substrate diffuses into the zinc-based coating after preheating, and the Fe element content in the component coating system after preheating is about 40%; the melting point of the coating is increased, which effectively inhibits the LME.

Preferably, the hot stamping forming temperature is 720°C, which can effectively improve the production efficiency.

In step 5), the austenitization can also heat the temperature above Ac3 by means of transverse magnetic flux induction heating, etc., and keep the temperature for 60-180 s. When using transverse magnetic flux induction heating, compared with traditional fuel heating, it not only has the advantages of fast heating, It has the advantages of high heating precision, less pollution, easy to realize automatic management, etc. It also has the advantages of low reactive power and effective energy saving.

Example 2

The present embodiment provides a zinc-based coating-coated steel hot stamping method and a hot stamping forming component thereof. The weight percentage (wt, %) contents of the substrate components are: C: 0.32, Si: 0.43, Al: 0.039, Mn: 1.6, Cr: 0.12, Mo: 0.12, B: 0.003, Ti: 0.025, Nb: 0.045, S: 0.0025, P: 0.006, N: 0.0045, 0: 0.001, the rest are Fe and inevitable inclusions; Include the following steps:

1) After smelting, casting, hot rolling, pickling and cold rolling to form chilled steel strip:

After smelting and casting, the casting billet is obtained; the casting billet is heated to a temperature of 1100-1280 °C, the final rolling temperature of hot rolling is 900 °C, and the hot rolling coiling temperature is 660 °C to obtain a hot rolled coil; after hot rolling, conventional pickling is performed to remove surface oxidation. Skin; after pickling, cold-rolling to form a steel strip, the cold-rolling reduction is 55%.

2) The pre-treatment process of galvanizing mainly includes degreasing with alkaline or acidic solution, water cleaning, electrolytic degreasing, pickling, water cleaning, etc. The strip surface is kept clean;

3) Annealing and galvanizing treatment process, the chilled steel strip is coated with hot-dip galvanizing annealing, specifically, the chilled steel strip is heated to 790°C, continuously annealed after heat preservation, and cooled to hot-dip galvanizing at 15°C/s Hot-dip galvanizing is carried out in a zinc pot after the temperature; the temperature of the zinc pot is 440°C, the aluminum content of the zinc liquid is ≤3%, the hot-dip plating time is 3s, and the hot-dip plating is cooled to below 200°C at 16°C/s, and the galvanized 3-30μm.

4) After shearing, blanking, and preheating to 550°C for 160s, the heating rate V1 between room temperature and 430°C is 13°C/s, and the heating rate V2 between 430°C and 550°C is 8°C/s.

5) Transfer the preheated steel sheet to a heating furnace at 900°C and keep it for 120s, cool the heating furnace where the steel sheet is transferred to 700°C, and then transfer it to the die for stamping and quenching, in-mold quenching for 9s, and quenching cooling rate ≥25°C/s , the holding pressure is 800 tons, the holding time is 9s, and then it is taken out and cooled to room temperature.

Specifically, due to the high C content of the steel sheet of the present invention, the cold rolling reduction is likely to lead to excessive burden on the rolling mill. At the same time, in order to ensure a considerable reduction rate to control the grain size to meet the mechanical performance requirements, the reduction rate is preferably less than 80%. More preferably, it is 35-70%.

Specifically, in the hot stamping component, the Fe element of the substrate diffuses into the zinc-based coating after preheating, and the Fe element content in the component coating system after the preheating is 20%; the melting point of the coating is increased, and the LME is effectively suppressed. .

Preferably, the hot stamping forming temperature is 700°C, which can effectively improve the production efficiency.

Example 3

The difference between this embodiment and Embodiment 1 is:

1. The substrates of zinc-based coating coated steel are different.

Specifically: a hot stamping method for zinc-based coating coated steel and a hot stamping forming component thereof provided in this embodiment, the weight percentage (wt, %) content of the substrate components are: C: 0.35, Si: 0.28, Al: 0.035 , Mn: 1.4, Cr: 0.16, Mo: 0.1, B: 0.003, Ti: 0.055, Nb: 0.051, S: ≤ 0.0028, P: ≤ 0.010, N: ≤ 0.0047, 0: ≤ 0.002, the rest are Fe and not Avoid impurities.

2. The preheating process is different.

Specifically: 4) After shearing, blanking, and preheating to 800°C for 180s, the heating rate V1 between room temperature and 430°C is 12°C/s, and the heating rate V2 between 430°C and 550°C is 4°C /s.

3. Different stamping processes

Specifically: transfer the preheated steel sheet to a heating furnace at 900°C for 160s, then transfer the steel sheet out of the heating furnace to cool to 680°C, and then transfer it to a die for stamping and quenching. Quenching cooling rate ≥25℃/s (supplementary), holding pressure of 700 tons, holding time of 8s, and then taken out and cooled to room temperature. Example 4

The differences between this embodiment and Embodiment 1 are: 1. The substrates of the steel coated with the zinc-based coating are different.

The present embodiment provides a hot stamping method for zinc-based coating coated steel and a hot stamping forming component thereof. The weight percentage (wt, %) content of each component of the substrate is: C: 0.22, Si: 0.50, Al: 0.55, Mn : 2.3, Cr: 0.2, Mo: 0.02, B: 0.003, Ti: 0.018, Nb: 0.045, V: 0.10, S: 0.0028, P: 0.009, N: 0.004, O: 0.0015, the rest are Fe and inevitable impurities .

2. Different pressure holding time (in-mold quenching): transfer the steel plate out of the heating furnace and cool it to 720℃, then transfer it to the mold for stamping and quenching, the cooling rate is ≥30℃/s, the holding pressure is 700 tons, and the holding time is 6s , and then take out the air and cool to room temperature naturally.

The following are comparative examples

Example 5

The difference between this embodiment and Embodiment 1 is that the preheating process is removed.

Step 5) is: the steel plate is transported to a heating furnace at 900°C for heating to complete complete austenitization, and then the heating furnace at the transfer place of the steel plate is cooled to 660-700°C, and then transferred to a die for stamping and quenching, and quenched in the die for 9s , the holding pressure is 800 tons, and then it is taken out and cooled to room temperature.

Example 6

The difference between this embodiment and Embodiment 1 is that the preheating process is different

The specific preheating process is: 4) After shearing, blanking, and preheating to 550°C for 200s, the heating rate is always maintained at 12°C/s.

The steel plate members prepared in Examples 1-6 were tested. The tensile strength Rm, yield strength Rp0.2, and total elongation of the steel were measured by INSTRON tensile testing machine, and the depth of microscopic crack propagation to the substrate, crack density and Fe content of the coating were measured by scanning electron microscope and EDS.

The test results are shown in the following table:

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Rm(MPa) 1526 1826 1966 1488 1516 1540 Rp0.2(MPa) 995 1215 1289 903 1105 1011 Total elongation (%) 6.5 4.5 4.3 8 6 5.5 Average crack depth (μm) 4 4 3 5 6.5 5.5 Iron content of preheated coating (%) 39 20 46 38 without preheating 8.5

It can be seen from the above table that:

The tensile strength, yield strength and total elongation of the steel plate components prepared in Examples 1-4 are comparable to those of the existing steel plates, the crack depth is less than 5 μm, and the Fe content of the pre-heated coating is greater than 10%, which is better than that of the existing zinc-based coating. The stamped steel plate member is slightly better than the steel plate member of Example 6, and significantly better than the steel plate member of Example 5.

The tensile strength, yield strength and total elongation of the steel plate member prepared in Example 6 are comparable to those of the existing steel plate, and the crack depth is slightly larger than that of the steel plate in Examples 1-4, but significantly better than that of the steel plate member prepared in Example 5.

The tensile strength, yield strength and total elongation of the steel plate components prepared in Examples 5-6 are comparable to those of the existing steel plates, and the crack depth is greater than 5 μm, and the maximum can reach 7-8 μm. The obtained steel plate has high brittleness and obvious cracks.

To sum up, the present invention improves the hot stamping process by adjusting the composition ratio of the steel plate, while ensuring that the tensile strength, yield strength, elongation and other properties of the steel plate are not lower than those of the traditional hot stamping steel plate, and at the same time, the hot stamping forming components are formed. The depth of crack propagation to the substrate is reduced to 4 μm, which effectively solves the problems of steel plate embrittlement and cracks caused by the existing hot stamping process.

This is of great significance to the development of zinc-based hot stamping steel. The process for obtaining excellent performance of the invention is simple, and has broad prospects for industrial practical application. It can be used to manufacture structural parts such as A/B pillars of automobile body-in-white, door anti-collision beams, front and rear bumpers, etc.

Finally, it should also be noted that the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device comprising a series of elements includes not only those elements, but also Also included are other elements not expressly listed or inherent to such a process, method, article or apparatus.

Although preferred embodiments of the present invention have been described, additional changes and modifications to these embodiments may occur to those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be construed to include the preferred embodiment and all changes and modifications that fall within the scope of the present invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Thus, provided that these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (9)

1. A hot stamping method for a zinc-based coating coated steel material is characterized by comprising the following steps:

preheating zinc-based coating steel, wherein the preheating temperature is 500-800 ℃, the heat preservation is carried out for 60-300 s, the heating rate V1 between room temperature and 430 ℃ is less than 15 ℃/s in the preheating process, and the heating rate V2 is less than 10 ℃/s after the temperature reaches 430 ℃;

heating the preheated steel to complete austenitizing of the steel, and performing hot stamping forming and quenching after transferring.

2. A method of hot stamping a zinc-based coated steel according to claim 1 wherein the method of heating the pre-heated steel comprises: and heating the preheated steel to a temperature above Ac3, and keeping the temperature for 60-200 s.

3. The hot stamping method for the steel coated with the zinc-based coating according to claim 1, wherein the transfer time of the steel subjected to complete austenitizing is less than 10S, the hot stamping forming temperature is 550-720 ℃, the hot stamping pressure maintaining pressure is 200-1000 tons, and the pressure maintaining time is 3-15 seconds.

4. The zinc-based coating coated steel is characterized in that the zinc-based coating coated steel substrate comprises the following chemical components in percentage by weight: 0.15 to 0.40, Si: 0.02 to 0.5, Al: 0.02 to 1.5, Mn: 0.5 to 3.6, Cr: 0.01 to 0.7, Mo: 0.01 to 0.7, B: 0.001 to 0.005, S: 0.005 or less, P: 0.015 or less, N: 0.01 or less, 0: less than or equal to 0.003;

wherein, the content of (Cr + Mo) is more than or equal to 0.1 percent and less than or equal to 1.0 percent; also added are Ti: 0.01 to 0.15, Nb: 0.01 to 0.15, V: 0.01-0.15, and simultaneously satisfies the following conditions: 0.03 percent to 0.45 percent (Ti + Nb + V); the balance of Fe and inevitable impurities.

5. A zinc-based coated steel product according to claim 4 wherein the zinc-based coating on the substrate has a thickness of 3 to 30 μm and comprises less than or equal to 3% by weight of aluminium.

6. A method of making a zinc-based coated steel product according to claim 4 or claim 5, including:

hot rolling, acid washing and cold rolling the casting blank to form a cold and hard steel strip;

and (3) annealing and galvanizing the cold and hard steel strip, finishing, straightening, adjusting the shape of the strip, and coiling the strip to form a steel coil.

7. A method of making a zinc-based coated steel product according to claim 6 wherein the process of making the cold-hardened steel strip is as follows:

the method comprises the following steps of smelting and casting raw materials to obtain a casting blank, heating the casting blank to a tapping temperature of 1100-1280 ℃, a hot rolling finishing temperature of 750-950 ℃, and a hot rolling coiling temperature of 500-700 ℃ to obtain a hot rolled coil, pickling after hot rolling, and then cold rolling to form a steel strip, wherein the cold rolling reduction is 40-80%.

8. A method of making a zinc-based coated steel product according to claim 6 wherein the annealing galvanization process is as follows:

heating the cold-hardened steel strip to 720-850 ℃, continuously annealing after heat preservation, cooling to the hot dipping temperature at the speed of 5-50 ℃/s, and carrying out hot galvanizing in a zinc pot; the temperature of the zinc pot is 400-520 ℃, the hot dipping time is 2-20s, and the zinc pot is cooled to below 200 ℃ at the speed of 3-50 ℃/s after hot dipping.

9. A zinc-based plated coated steel hot stamped member, which is produced by the hot stamping method according to any one of claims 1 to 3 using the zinc-based plated coated steel according to claim 4 or 5.

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