Hot stamping forming device and hot stamping method for high-strength steel parts

Abstract

The present invention relates to the technical field of high-strength steel parts production, and specifically to a hot stamping forming device and a hot forming method for high-strength steel parts. The hot stamping forming device includes a hot stamping die, and the hot stamping die includes an upper die and a lower die. The lower die is located in a water tank. When in use, the water tank is filled with hot water above 60°C, and part or all of the lower die is immersed in the hot water. The lower die is provided with at least two sheet metal supports, and the sheet metal support includes a fixed rod vertically fixed to the bottom surface of the water tank, and the upper end of the fixed rod is rotatably connected to a crossbeam through a rotating shaft. One end of the crossbeam of the sheet metal support cooperates with each other to support the sheet metal, and the other end of the crossbeam is rotatably connected to the upper end of the pull rod, and the lower end of the pull rod is connected to the fixed rod through a spring. In the initial state, the height of the crossbeam is higher than the hot water level. The present invention can shorten the holding time, and effectively solve the problem of LME cracking of parts, and directly mass produce in the existing parts production line.

Description

Technical Field

[0001] The present invention relates to the technical field of high-strength steel component production, and in particular to a hot stamping forming device and a hot forming method for high-strength steel components. Background Art

[0002] High-strength steel hot-formed parts are widely used in the field of lightweight automobiles due to their high strength and low springback after forming. At present, the hot-forming production process of parts is to first heat the sheet to austenitization and then transfer it to the mold for forming. Since the temperature of the sheet is high during forming, in order to ensure that the parts are cooled and quenched in the mold, it is necessary to improve the cooling efficiency of the mold and ensure that the temperature distribution on the mold surface is uniform. Therefore, it is necessary to set up a cooling water channel circuit in the upper and lower molds.

[0003] For example, CN216911789U discloses a high-strength hot stamping die for automobile exterior covering parts, in which a heat dissipation mechanism is arranged inside the lower die of the hot stamping die, and the heat dissipation mechanism includes a water inlet pipe, a water outlet pipe and a cooling water channel arranged in the side wall of the lower die, and the cooling water channel is connected to the water inlet pipe and the water outlet pipe. Although this technical solution solves the technical problems of slow mold profile forming and low working efficiency caused by the inconvenience of cooling the mold during use of traditional hot stamping molds, it increases the mold manufacturing cost and processing cycle. At the same time, in order to enable the parts to obtain high strength after the hot forming quenching process, the material still needs a certain holding time after the mold is closed, and the production cycle time of the parts cannot be further shortened.

[0004] In addition, low-melting-point coated hot stamping steels, such as GI, GA, ZnAlMg, etc., have a low melting point of Zn, which turns into liquid zinc during high-temperature heating. LME cracks are easily generated during high-temperature forming. Therefore, traditional hot forming methods are difficult to achieve mass production of low-melting-point and highly corrosion-resistant coated hot-formed parts. Summary of the invention

[0005] In view of the technical problems of high mold manufacturing cost, long processing cycle and inability to produce hot-formed parts with low melting point and high corrosion resistance coating under existing technical conditions in setting cooling water channel loops in existing hot stamping forming devices, the present invention provides a hot stamping forming device and hot forming method for high-strength steel parts. The present invention can realize the forming and cooling of high-temperature sheet materials in different media in turn, first using air medium to slowly cool the sheet materials to ensure a high forming temperature, and then using the vaporization film generated by the contact between hot water and high-temperature sheet materials on the surface of the steel plate to uniformly and slowly control the cooling rate. After the parts are formed, the cooling rate between the low-temperature parts and the hot water is faster, which can shorten the holding time and effectively solve the problem of LME cracking of parts, and directly mass-produce in the existing parts production line.

[0006] In a first aspect, the present invention provides a hot stamping forming device for a high-strength steel component, comprising a hot stamping die, the hot stamping die comprising an upper die and a lower die, the lower die being located in a water tank, the water tank being filled with hot water above 60° C. when in use, and part or all of the lower die being immersed in the hot water;

[0007] The lower mold is provided with at least two sheet material supports, which include a fixed rod vertically fixed on the bottom surface of the water tank. The upper end of the fixed rod is rotatably connected to a cross beam through a rotating shaft. One end of the cross beam of the sheet material support cooperates with each other to support the sheet material, and the other end of the cross beam is rotatably connected to the upper end of the pull rod. The lower end of the pull rod is connected to the fixed rod through a spring. In the initial state, the height of the cross beam is higher than the hot water level.

[0008] Furthermore, it also includes a controller;

[0009] A water level sensor and a thermometer are also provided in the water tank. A water inlet and a water outlet are provided on the side wall of the water tank. A water inlet valve is provided at the water inlet, and a water outlet valve is provided at the water outlet. The water level sensor and the thermometer are respectively connected to the controller signal, and the water inlet valve and the water outlet valve are respectively connected to the controller control.

[0010] In a second aspect, the present invention provides a method for hot forming a high-strength steel component, comprising at least the following steps:

[0011] During the mold closing process of the hot stamping forming device, as the upper mold moves downward, the high-strength steel sheet is first cooled in the air medium, and then driven by the upper mold, it gradually enters the hot water medium from the air medium until it is completely immersed in the hot water to form, and then the mold is pressure-maintained to achieve component quenching to obtain high-strength steel components;

[0012] The temperature of the hot water is above 60°C, and further, the temperature of the hot water is 60-100°C.

[0013] Furthermore, before hot stamping, the high-strength steel sheet is first heated to above AC3 to obtain an austenitic structure.

[0014] Furthermore, the forming start temperature of the high-strength steel sheet is not less than 680° C., and the forming start temperature refers to the sheet temperature when the upper die moves downward to contact the sheet.

[0015] Furthermore, the holding time of the hot stamping die is 1-10s.

[0016] Furthermore, the chemical element composition of the high-strength steel sheet is: C 0.05wt%-0.35wt%, Si 0.05wt%-0.6wt%, Mn 0.5wt%-2.2wt%, Cr≤0.5wt%, Mo≤0.5wt%, Ni≤0.5wt%, Ti≤0.04wt%, Nb≤0.2wt%, V≤0.2wt%, B 0.002wt%-0.006wt%, P≤0.020wt%, S≤0.003wt%, Al≤0.8wt%, N≤0.006wt%, and the balance is Fe and unavoidable impurities.

[0017] Furthermore, the high-strength steel sheet is an uncoated sheet or a coated sheet, and the coated sheet is selected from a zinc-based coated sheet or an aluminum-silicon coated sheet, wherein the zinc-based coated sheet can be a pure zinc-coated sheet (GI), a zinc-iron alloy-coated sheet (GA) or a zinc-aluminum-magnesium-coated sheet (Zn-5Al-3Mg), etc.

[0018] Furthermore, the high-strength steel sheet is a zinc-based coated sheet. After hot forming, the proportion of zinc-rich phase in the surface zinc-based coating of the high-strength steel parts is not higher than 40%. The proportion of zinc-rich phase can be controlled by specifying appropriate heating temperature and time according to the thickness of the high-strength steel sheet and the initial thickness of the coating.

[0019] The working principle of the hot forming method of the high-strength steel parts of the present invention is as follows:

[0020] When the high-strength steel sheet is transferred to the mold, it does not come into contact with hot water. Air is used as a cooling medium to cool the sheet. At this time, the cooling speed is slow, ensuring that the sheet begins to form at a higher temperature. As the upper mold continues to descend and close the mold, the sheet begins to deform after contacting the upper mold. At this time, the sheet is still in the air medium, and the sheet will not increase in strength due to excessive cooling speed, resulting in precision deviation of the parts. Then the sheet gradually enters the hot water from the air medium, and a uniform vaporization film is formed on the surface of the sheet in the hot water. The vaporization film can serve as an insulation layer to reduce the heat transfer rate between the sheet and the water, ensuring that the cooling speed of the sheet is slow and controllable. It can also improve the friction and stress state between the sheet and the mold during the forming process together with the hot water, and inhibit the expansion of the coating microcracks to the substrate during the forming process. After the parts are fully formed, the temperature of the parts is reduced, and at the same time the mold is fully closed, the surface vaporization film is destroyed, and the heat transfer rate between the low-temperature parts and the hot water is accelerated, which can achieve rapid quenching and shorten the mold holding time.

[0021] The beneficial effects of the present invention are:

[0022] (1) The method for hot forming high-strength steel parts provided by the present invention controls the high-temperature sheet to be formed in different media in succession, effectively controls the cooling rate and forming state at different forming stages, improves the dimensional accuracy of the parts, and can effectively avoid the risk of LME cracking of the coated sheet during direct hot forming. It is particularly suitable for the production of hot formed parts with low melting point and high corrosion resistance coatings.

[0023] (2) The method for hot forming high-strength steel parts provided by the present invention utilizes the uniform vaporization film generated on the surface of the high-temperature sheet during the cooling process in hot water to slowly control the cooling rate of the sheet. After the parts are fully formed, the surface vaporization film is destroyed, and the heat transfer rate between the low-temperature parts and the hot water is accelerated, thereby achieving rapid quenching, reducing the holding time, shortening the production cycle, and improving production efficiency.

[0024] (3) The hot stamping forming device provided by the present invention is matched with the hot forming method. The lower mold is placed in hot water. After the mold is closed, the upper and lower mold surfaces are both in hot water, which effectively ensures that the temperature distribution on the mold surface is uniform and constant. There is no need to design and process cooling water channels, which greatly reduces the mold processing cost and manufacturing cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 It is a schematic structural diagram of the hot stamping forming device of Example 1.

[0027] Figure 2 It is a schematic diagram of the structure of one of the sheet metal supports in the hot stamping forming device of Example 1.

[0028] Figure 3 This is a working principle diagram of one of the sheet metal supports in the hot stamping forming device of Example 1.

[0029] Figure 4 This is the cooling temperature drop curve of the high-strength steel sheet of Example 2 in hot water.

[0030] Figure 5 This is a microscopic image of the coating and microcracks on both sides of the high-strength steel component obtained in Example 2.

[0031] Figure 6 This is a two-phase distribution morphology of the coating of a high-strength steel component obtained in Example 2.

[0032] Figure 7 This is a microscopic image of the coating and microcracks on both sides of the high-strength steel component obtained in Example 3.

[0033] Figure 8 This is a two-phase distribution morphology of the coating of a high-strength steel component obtained in Example 3.

[0034] Fig. 9 This is a microscopic image of the coating and microcracks on both sides of the high-strength steel parts obtained in Example 1.

[0035] Fig.10 This is a two-phase distribution morphology of the coating on high-strength steel parts obtained in Example 1.

[0036] Fig.11 This is a microscopic image of the coating and microcracks on both sides of the high-strength steel parts obtained in Example 2.

[0037] Fig.12 This is a two-phase distribution morphology of the coating on high-strength steel parts obtained in Example 2.

[0038] In the figure, 1-upper die, 2-lower die, 3-water tank, 4-first sheet material support, 5-second sheet material support, 6-sheet material, 7-fixing rod, 8-crossbeam, 9-rotating shaft, 10-pull rod, 11-spring. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0040] Example 1

[0041] A hot stamping forming device for high-strength steel parts comprises a hot stamping die and a controller. The hot stamping die comprises an upper die 1 and a lower die 2. The lower die 2 is located in a water tank 3. A water level sensor and a thermometer are arranged in the water tank 3. A water inlet and a water outlet are arranged on the side wall of the water tank 3. A water inlet valve is arranged at the water inlet, and a water outlet valve is arranged at the water outlet. The water level sensor and the thermometer are respectively connected to the controller signal, and the water inlet valve and the water outlet valve are respectively connected to the controller control.

[0042] Sheet material supports (a first sheet material support 4 and a second sheet material support 5) are symmetrically arranged on both sides of the lower mold 2. Each sheet material support includes a fixing rod 7 vertically fixed to the bottom surface of the water tank 3. The upper end of the fixing rod 7 is rotatably connected to a cross beam 8 through a rotating shaft 9. One ends of the cross beams 8 of the two sheet material supports cooperate with each other to support the sheet material 6. The other end of the cross beam 8 is rotatably connected to the upper end of the pull rod 10. The lower end of the pull rod 10 is connected to the fixing rod 7 through a spring 11. In the initial state, the height of the cross beam 8 is higher than the hot water level.

[0043] When in use, the water tank 3 is filled with hot water above 60°C, the lower mold 2 is partially or completely immersed in the hot water, and the sheet 6 is placed on the crossbeam 8. At this time, the sheet 6 does not contact the hot water and the molding surface of the lower mold 2. The upper mold 1 moves downward to contact the sheet 6. The end of the crossbeam 8 that contacts the sheet 6 is forced to swing downward around the rotating shaft 9, driving the pull rod 10 connected to the other end to move upward, the spring 11 stretches, and the sheet 6 falls and contacts the lower mold 2; after the sheet 6 completely leaves the crossbeam, the spring 11 restores its initial length and automatically moves downward, and the pull rod 10 drives the crossbeam 8 to move upward and reset;

[0044] When the amount of hot water in the water tank 3 is small and the sheet material 6 cannot be completely immersed in the hot water medium, open the water inlet valve and add hot water into the water tank 3 through the water inlet until the hot water level rises to the point where the sheet material is completely immersed in the hot water; when the water temperature in the water tank 3 is lower than the required temperature, open the water outlet valve and discharge the low-temperature water outward through the water outlet, open the water inlet valve and add hot water into the water tank 3 through the water inlet until the water temperature in the water tank 3 reaches the required temperature.

[0045] In other embodiments, depending on the shape of the sheet, the number of sheet supports may be two or more, and the distribution of the sheet supports may be symmetrical or asymmetrical, so as to support the sheet and ensure that the sheet does not slip during the thermoforming process.

[0046] Example 2

[0047] Select thickness of 1.8mm and coating thickness of 150g / m 2 A (double-sided) hot-dip pure galvanized high-strength steel sheet is used to trial-produce a reinforcement plate component on the A-pillar of a certain vehicle model on a mass production line using the device of Example 1. The main components of the sheet are C 0.20wt%, Si 0.3wt%, Mn 1.6wt%, Cr 0.2wt%, Nb 0.02wt%, V 0.002wt%, B 0.002wt%, P 0.020wt%, and the remaining elements are Fe and unavoidable impurities.

[0048] The specific steps are as follows:

[0049] (1) The sheet is kept in a 900°C box-type heating furnace for 380 seconds to obtain an austenite structure, and the heated sheet is transferred to the hot stamping forming device of Example 1. The two ends of the sheet are placed on a first sheet support and a second sheet support, respectively. The water tank of the hot stamping forming device is filled with 95°C hot water, and the level of the hot water is flush with the upper end surface of the lower die;

[0050] (2) The upper die of the hot stamping forming device moves downward and then contacts the sheet. At this time, the sheet is in the air medium and the cooling speed is slow. The sheet temperature is kept above 680°C. The upper die continues to move downward, and the first sheet support and the second sheet support move downward in coordination. The sheet begins to deform in the air medium and cools slowly, avoiding the increase in strength due to excessive cooling and causing deviation in dimensional accuracy.

[0051] (3) The upper mold continues to move downward, the sheet metal is gradually immersed in the hot water, the mold is closed, and the sheet metal is completely formed into a component in the hot water. The mold closing time (i.e., the time spent in steps (2) and (3)) is 3 seconds in total.

[0052] (4) The mold is kept under pressure for 10 seconds. At this time, the vapor film on the surface of the sheet is destroyed, and the heat transfer rate between the low-temperature parts and the hot water is accelerated, so that the parts are quenched and the final parts are obtained.

[0053] The mechanical properties of the final parts were tested according to GB / T 228.1-2010 "Tensile tests on metallic materials - Part 1: Room temperature test methods". The results are as follows:

[0054] Tensile strength>1500MPa, elongation after break>5%; component dimensional accuracy testing is fully qualified.

[0055] The microscopic morphology of the coating and microcracks of the parts is as follows: Figure 5 As shown, Figure 5 The upper and lower pictures in the middle correspond to the microscopic morphology of the coating on the front and back sides of the component. No matrix microcracks > 8μm were found in any part of the component. Figure 6 As shown, Figure 6 The medium bright white area represents the zinc-rich phase, and the darker gray area represents the iron-rich phase. After analysis, the proportion of the zinc-rich phase is about 11%.

[0056] Example 3

[0057] The hot forming method of Example 3 is basically the same as that of Example 2, except that in step (1), a roller bottom heating furnace is used to heat the coated sheet, the sheet heating temperature is 890°C, the holding time is 320s, and the mold holding time in step (4) is shortened to 3s.

[0058] The mechanical properties of the final parts were tested according to GB / T 228.1-2010 "Tensile tests on metallic materials - Part 1: Room temperature test methods". The results are as follows:

[0059] Tensile strength>1500MPa, elongation after break>5%; component dimensional accuracy testing is fully qualified.

[0060] Observe the coating and micro cracks of parts, such as Figure 7 As shown in the figure, no matrix microcracks > 8μm were found in any part of the component. Figure 8 As shown, the proportion of bright white zinc-rich phase is about 20%.

[0061] Comparative Example 1

[0062] The hot forming methods of Comparative Example 1 and Example 2 are basically the same, the only difference is that the water tank of the hot stamping forming device does not contain hot water, and the sheet is continuously hot formed in the air medium.

[0063] The mechanical properties and dimensional accuracy of the final parts are qualified, and the proportion of zinc-rich phase is about 18% (such as Fig.10 However, the microcracks in the coating extended into the substrate with a depth of more than 30 μm (as shown in Fig. 9 As shown in the figure), the fatigue service requirements of components cannot be met.

[0064] Comparative Example 2

[0065] The thermoforming method of Comparative Example 2 is substantially the same as that of Example 2, except that in step (1), the level of the hot water in the water tank is flush with the upper end surface of the sheet material, and the sheet material is continuously thermoformed in the hot water medium.

[0066] The mechanical properties, coating and microcracks of the final parts are all qualified, and the proportion of zinc-rich phase is about 19% (such as Fig.12 However, the dimensional accuracy deviation of the parts is large and cannot meet the fatigue service requirements of the parts.

[0067] Example 4

[0068] Select thickness of 1.8mm and coating thickness of 150g / m 2 The aluminum-silicon coated high-strength steel sheet is used to trial-produce a reinforcement plate component on the A-pillar of a certain vehicle model on a mass production line using the device of Example 1. The main components of the sheet are C 0.2wt%, Si 0.2wt%, Mn1.2wt%, Cr 0.2wt%, Ti 0.04wt%, B 0.003wt%, S 0.001wt%, and N 0.001wt%, and the remaining elements are Fe and unavoidable impurities.

[0069] The specific steps are as follows:

[0070] (1) The sheet is kept in a 930°C box-type heating furnace for 300 seconds to obtain an austenite structure, and the heated sheet is transferred to the hot stamping forming device of Example 1. The two ends of the sheet are placed on a first sheet support and a second sheet support, respectively. The water tank of the hot stamping forming device is filled with 75°C hot water, and the level of the hot water is flush with the upper end surface of the lower die;

[0071] (2) The upper die of the hot stamping forming device moves downward and then contacts the sheet. At this time, the sheet is in the air medium and the cooling speed is slow. The sheet temperature is kept above 700°C. The upper die continues to move downward, and the first sheet support and the second sheet support move downward in coordination. The sheet begins to deform in the air medium and cools slowly, avoiding the increase in strength due to excessive cooling and causing deviation in dimensional accuracy.

[0072] (3) The upper mold continues to move downward, the sheet metal is gradually immersed in the hot water, the mold is closed, and the sheet metal is completely formed into a component in the hot water. The mold closing time (i.e., the time spent in steps (2) and (3)) is 5 seconds in total.

[0073] (4) The mold is kept under pressure for 8 seconds. At this time, the vapor film on the surface of the sheet is destroyed, and the heat transfer rate between the low-temperature parts and the hot water is accelerated, so that the parts are quenched and the final parts are obtained.

[0074] The mechanical properties of the final parts were tested according to GB / T 228.1-2010 "Tensile tests on metallic materials - Part 1: Room temperature test methods". The results are as follows:

[0075] The tensile strength is >1500MPa, and the elongation after fracture is >5%. The dimensional accuracy test of the parts is fully qualified, and no matrix microcracks >8μm are found in any part of the parts.

[0076] Example 5

[0077] A high-strength steel sheet with a thickness of 2.0 mm was selected, and the device of Example 1 was used to trial-produce a reinforcement plate component on the A-pillar of a certain vehicle model on a mass production line. The main components of the sheet were C 0.18wt%, Si 0.2wt%, Mn 1.5wt%, Cr 0.3wt%, B0.002wt%, S 0.001wt%, and the remaining elements were Fe and unavoidable impurities.

[0078] The specific steps are as follows:

[0079] (1) The sheet is kept in a 930°C box-type heating furnace for 360 seconds to obtain an austenite structure, and the heated sheet is transferred to the hot stamping forming device of Example 1. The two ends of the sheet are placed on a first sheet support and a second sheet support, respectively. The water tank of the hot stamping forming device is filled with 85°C hot water, and the level of the hot water is flush with the upper end surface of the lower die;

[0080] (2) The upper die of the hot stamping forming device moves downward and then contacts the sheet. At this time, the sheet is in the air medium and the cooling speed is slow. The sheet temperature is kept above 695°C. The upper die continues to move downward, and the first sheet support and the second sheet support move downward in coordination. The sheet begins to deform in the air medium and cools slowly, avoiding the increase in strength due to excessive cooling and causing deviation in dimensional accuracy.

[0081] (3) The upper mold continues to move downward, the sheet metal is gradually immersed in the hot water, the mold is closed, and the sheet metal is completely formed into a component in the hot water. The mold closing time (i.e., the time spent in steps (2) and (3)) is 8 seconds in total.

[0082] (4) The mold is kept under pressure for 3 seconds. At this time, the vapor film on the surface of the sheet is destroyed, and the heat transfer rate between the low-temperature parts and the hot water is accelerated, so that the parts are quenched and the final parts are obtained.

[0083] The mechanical properties of the final parts were tested according to GB / T 228.1-2010 "Tensile tests on metallic materials - Part 1: Room temperature test methods". The results are as follows:

[0084] The tensile strength is >1500MPa, and the elongation after fracture is >5%. The dimensional accuracy test of the parts is fully qualified, and no matrix microcracks >8μm are found in any part of the parts.

[0085] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A hot forming method for high-strength steel parts, characterized in that: At least the following steps are included: During the mold closing process of the hot stamping forming device, as the upper mold moves downward, the high-strength steel sheet is first cooled in the air medium, and then driven by the upper mold, it gradually enters the hot water medium from the air medium until it is completely immersed in the hot water to form, and then the mold is pressure-maintained to achieve component quenching to obtain high-strength steel components; The temperature of the hot water is above 60°C; The forming temperature of high-strength steel sheet is not less than 680℃. The forming temperature refers to the sheet temperature when the upper die moves down to contact with the sheet. The high-strength steel sheet is a zinc-based coated sheet; The hot stamping forming device includes a hot stamping die, which includes an upper die and a lower die. The lower die is located in a water tank. When in use, the water tank is filled with hot water above 60°C, and the lower die is completely immersed in the hot water. The lower die is provided with at least two sheet metal supports, and the sheet metal support includes a fixed rod vertically fixed to the bottom surface of the water tank. The upper end of the fixed rod is rotatably connected to a cross beam through a rotating shaft. One end of the cross beam of the sheet metal support cooperates with each other to support the sheet metal, and the other end of the cross beam is rotatably connected to the upper end of the pull rod. The lower end of the pull rod is connected to the fixed rod through a spring. In the initial state, the height of the cross beam is higher than the hot water level.

2. The hot forming method according to claim 1, characterized in that Also includes a controller; A water level sensor and a thermometer are also provided in the water tank. A water inlet and a water outlet are provided on the side wall of the water tank. A water inlet valve is provided at the water inlet, and a water outlet valve is provided at the water outlet. The water level sensor and the thermometer are respectively connected to the controller signal, and the water inlet valve and the water outlet valve are respectively connected to the controller control.

3. The hot forming method according to claim 1, characterized in that: Before hot stamping, the high-strength steel sheet is first heated to above AC3 to obtain an austenitic structure.

4. The hot forming method according to claim 1, characterized in that: The holding time of the mold is 1-10s.

5. The hot forming method according to claim 1, characterized in that: The chemical element composition of the high-strength steel sheet is: C 0.05wt%-0.35wt%, Si 0.05wt%-0.6wt%, Mn 0.5wt%-2.2wt%, Cr≤0.5wt%, Mo≤0.5wt%, Ni≤0.5wt%, Ti≤0.04wt%, Nb≤0.2wt%, V≤0.2wt%, B 0.002wt%-0.006wt%, P≤0.020wt%, S≤0.003wt%, Al≤0.8wt%, N≤0.006wt%, and the balance is Fe and unavoidable impurities.

6. The hot forming method according to claim 1, characterized in that: The proportion of zinc-rich phase in the surface zinc-based coating of the high-strength steel parts finally obtained after hot forming is no more than 40%.

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