Small-batch hot stamping mold based on direct surface air cooling, and cooling process

Abstract

A small-batch hot stamping mold based on direct surface air cooling, comprising a male mold (20) and a female mold (30), wherein a recess matching a punch of the male mold is provided on the female mold, a first cavity (21) recessed toward the interior of the male mold is provided on a surface of the male mold, a second cavity (31) recessed toward the interior of the female mold is further provided on a surface of the female mold, and the first cavity and the second cavity are configured to form an airflow cooling channel in communication with an external pipe; and water vapor introduced through the external pipe enters the mold, and circulates and exchanges heat in the airflow cooling channel formed by the first cavity and the second cavity and on the surface of the mold, so as to take away the heat from a stamped part and the surface of the mold. Further disclosed are a cooling method for a stamped part based on direct surface air cooling and a cooling method for a stamping mold based on direct surface air cooling. The stamping mold is provided with the cavities on the surface of the mold, the manufacturing cost and maintenance cost of the mold are low, and the production cost of a single piece is reduced.

Description

Small-batch hot stamping dies and cooling processes based on direct surface air cooling Technical Field

[0001] This invention relates to the field of hot stamping technology, and more specifically, to a small-batch hot stamping die and cooling process based on direct surface air cooling. Background Technology

[0002] High-strength steel structural components are an effective means of improving automotive collision safety. Hot stamping is one of the main processing methods for high-strength steel structural components, effectively solving the problems of poor formability and large springback of high-strength steel sheets under room temperature stamping, and is widely used in the automotive manufacturing field. There are two main types of steel sheets suitable for hot stamping. The most widely used is boron steel, which needs to be heated to 900-950℃ and held at that temperature for several minutes to austenitize the microstructure. Then it is quickly stamped and left in the mold for pressure quenching. The cooling rate is required to be no less than 27℃ / s to achieve the transformation of the austenitic structure into a martensitic structure and obtain high-strength stamped parts. The other type is medium-manganese steel. Due to the addition of an appropriate amount of manganese, the austenitizing temperature only needs to be 800-850℃, and the required cooling rate is also greatly reduced (no less than 0.5℃ / s is sufficient). For example, natural cooling in air can achieve complete martensitization and reach a high-strength state.

[0003] Because martensitic transformation requires a relatively high cooling rate, hot stamping of boron steel necessitates either mold cooling or direct water cooling; air cooling alone cannot achieve the required cooling rate. Medium manganese steel, on the other hand, undergoes martensitic transformation at a very low cooling rate during hot stamping. However, if it is removed from the mold and air-cooled in a free state after forming, significant deformation will occur, failing to meet dimensional accuracy requirements. Therefore, pressure cooling within the mold is also necessary, and the cooling rate cannot be too low considering production cycle time. The mass production molds and processes for hot stamping of medium manganese steel are basically the same as those for boron steel, and the molds for prototype parts are also similar. The mold structure and cooling methods differ between prototype manufacturing and mass production.

[0004] Prototype production typically involves small-scale trials (within a few hundred pieces), while mass production involves large-scale mass production (tens of thousands of pieces). The corresponding molds are called prototype molds (or soft molds) and mass production molds (or hard molds). Prototype molds are generally cast from cast iron and do not have internal water channels. They have a short manufacturing cycle and low cost. Due to the fewer stamping cycles and lower time-to-cycle, the mold is usually cooled manually or by automated spraying, with a water tank placed on the press table and the mold inside. Mass production molds have internal cooling water channels. Coolant circulates in these channels, carrying away the heat transferred from the sheet metal to the mold. Traditional cooling water channels include drilled straight-channel direct-flow cooling structures and drilled straight-channel mixed-flow cooling structures. The mold body consists of several inserts, each machined individually. Both straight-flow and mixed-flow structures suffer from drawbacks such as difficulty in machining and positioning straight water channels, high requirements for insert assembly positioning accuracy and sealing, and for parts with large undulations, straight water channels cannot guarantee uniform and sufficient cooling.

[0005] However, with the increasing demand from users for differentiated, personalized, and customized automobiles, small-batch, niche models are becoming more and more common. On the other hand, the sales volume of many new energy vehicles is difficult to predict. Often, the planned production volume is in the tens or even hundreds of thousands of units, but production is discontinued after only 20,000 or 30,000 units are sold. Here, small-batch models are defined as those with a life cycle production of less than 100,000 units and an annual production of less than 20,000 units, or even just a few thousand units. Obviously, traditional prototype molds cannot meet the requirements of production capacity and mold life, while traditional mass production molds result in overcapacity, high mold costs, and significant waste. Therefore, there is an urgent need for a hot stamping forming technology for high-strength steel structural components suitable for small-batch models. Summary of the Invention

[0006] Technical problem to be solved by the invention: The purpose of this invention is to overcome the above-mentioned technical defects and provide a small-batch hot stamping die and cooling process based on direct surface air cooling, so as to reduce the die manufacturing cost and unit production cost, and provide technical support for the production and manufacturing of small-batch vehicles.

[0007] Technical Solution: To achieve the above objectives, the present invention provides the following technical solution: a small-batch hot stamping die based on direct surface air cooling, comprising a punch and a die. The die has a recessed portion that matches the punch head. The surface of the punch has a first recessed cavity that is recessed inward, and the surface of the die also has a second recessed cavity that is recessed inward. The first and second cavities are used to form an airflow cooling channel connected to an external pipeline. Water vapor introduced by the external pipeline enters the die and circulates and exchanges heat in the airflow cooling channel formed by the first and second cavities to remove heat from the surface of the stamped part and the die.

[0008] As a further improvement of the present invention, the first cavity starts from one side of the punch and extends continuously along the width direction of the punch until it reaches the other side; the second cavity starts from one side of the die and extends continuously along the width direction of the die until it reaches the other side.

[0009] As a further improvement of the present invention, the first cavity and the second cavity are arranged alternately along the length direction of the punch and the die, respectively, thereby forming an airflow cooling channel on the surface of the punch and the die that is connected to the external pipeline.

[0010] As a further improvement of the present invention, the air inlet of the airflow cooling channel is connected to an air compressor through several compressed air pipelines, and the air outlet of the airflow cooling channel is used to discharge the heated gas.

[0011] As a further improvement of the present invention, the air outlet of the air compressor is connected to the water tank through a water pipe, and the pressure of the compressed air and the water flow rate are adjusted to form a mixture of compressed air and water mist in different proportions. The mixture undergoes heat exchange when it passes through the airflow cooling channel formed by the first cavity and the second cavity.

[0012] As a further improvement of the present invention, the first cavity on the surface of the punch, the second cavity on the surface of the die, and the upper and lower surfaces of the stamped part all form cavities. After the water mist mixture enters the cavity, it contacts the surface of the stamped part and the inner wall of the cavity on the surface of the die to exchange heat and remove the heat from the surface of the stamped part.

[0013] As a further improvement of the present invention, the punch and die are separated by a certain gap, and the water mist mixture is blown into the gap, where heat exchange occurs in the airflow cooling channel and on the mold surface to remove heat from the mold surface.

[0014] As a further improvement of the present invention, the cross-sectional shape of the first cavity and the second cavity is one of semi-circular, cylindrical, ridge-shaped, wavy, or triangular; the shape of the airflow cooling channel is straight, spiral, or cross-grid.

[0015] Another object of the present invention is to provide a cooling method for stamped parts based on direct surface air cooling, comprising the following steps:

[0016] S1. Adjust the air-to-water ratio: Adjust the air-to-water ratio to between 100 and 1000 to produce a lower concentration of water mist;

[0017] S2, Formation of water mist mixture: Compressed air generated by the air compressor draws water from the water tank in a siphon manner and mixes it to form a water mist mixture;

[0018] S3, Water mist mixture is blown into cooling: The water mist mixture is blown into the cavity formed by the first concave cavity and the upper surface of the stamping part, and the second concave cavity and the lower surface of the stamping part through the airflow cooling channel inlet end;

[0019] S4. Heat transfer and cooling: The water mist mixture transfers heat to the surface of the stamped part and the inner wall of the cavity, effectively removing heat from the surface of the stamped part.

[0020] S5. The heated airflow is discharged from the outlet of the airflow cooling channel.

[0021] Another object of the present invention is to provide a cooling method for stamping dies based on direct surface air cooling, comprising the following steps:

[0022] S1. Stop production and remove stamped parts: Stop the stamping operation, open the punch, and remove the cooled stamped parts;

[0023] S2. Adjust the mold gap and air-water ratio: Keep the gap between the punch and the die between 50-100mm so that the water mist mixture can fully enter and cover the mold surface; at the same time, adjust the air-water ratio to between 10-100 to produce a higher concentration of water mist.

[0024] S3. Forming and blowing in a water mist mixture: A high-concentration water mist mixture is formed by adjusting the compressed air and water flow rate, and then blown into the mold gap through the airflow cooling channel inlet end;

[0025] S4. Heat exchange and cooling: The water mist mixture exchanges heat with the first cavity, the second cavity and the mold surface, effectively removing heat from the mold and thus reducing the mold temperature.

[0026] S5. Exhaust heated airflow: After heat exchange, the heated airflow is discharged from the airflow cooling channel outlet, completing the mold cooling process. Beneficial effects:

[0027] 1. Compared with the traditional hot stamping die with cooling pipes inside, the stamping die provided by the present invention has a cavity on the die surface. Its manufacturing and maintenance costs are lower than those of mass production dies, and its lifespan and production capacity are higher than those of trial production dies.

[0028] 2. Based on the surface air cooling of the mold provided by the present invention, mass production can be achieved on the trial molding line due to the low production cycle, which reduces the production cost per piece and meets the production needs of small batch of vehicles. Attached Figure Description

[0029] Figure 1 is a schematic diagram of the structure of the hot stamping die punch and die provided by the present invention;

[0030] Figure 2 is a structural perspective view of the punch and die in Figure 1;

[0031] Figure 3 is a schematic diagram of the structure connecting the stamping die to the external pipeline and the water tank;

[0032] Figure 4 is a schematic diagram of the opening structure of the punch and die in Figure 3;

[0033] Figure 5 is a schematic diagram of the gas flow during pressure holding and cooling in the mold after the stamped part is formed;

[0034] Figure 6 is a schematic diagram of the wedge-shaped air inlet and wedge-shaped air outlet.

[0035] Figure 7 is a schematic diagram of the arrangement and cross-section of the cavities on the surfaces of the punch and die.

[0036] Explanation of the labels in the schematic diagram: 10, stamped part; 20, punch; 21, first cavity; 30, die; 31, second cavity; 40, air compressor; 41, compressed air pipeline; 50, water tank; 51, water pipe; 61, wedge-shaped air inlet; 62, wedge-shaped air outlet; 230, clearance between punch and die; 101, edge of stamped part; 102, starting point; 600, included angle. Detailed Implementation

[0037] To further understand the content of this invention, it will be described in detail with reference to the accompanying drawings and specific embodiments.

[0038] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0039] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0040] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0041] As shown in Figures 1-7, a small-batch hot stamping die based on direct surface air cooling includes a punch 20 and a die 30. The main bodies of the punch 20 and die 30 are integrally cast from alloy cast iron or assembled from hot work die steel inserts, resulting in low manufacturing and maintenance costs. In this embodiment, the upper die is the punch 20, and the lower die is the die 30. The punch is a roughly trapezoidal protrusion, and the die 30 has a recess that matches the punch. After stamping, the stamped part 10 remains in the die for pressure holding and quenching. The surface of the punch 20 has a first recess 21 that is recessed inward, and the surface of the die 30 also has a second recess 31 that is recessed inward. The first and second recesses 21 are machined by a CNC machine tool and serve as airflow cooling channels during cooling.

[0042] The first cavity 21 on the surface of the punch 20 starts from one side of the punch 20 and extends uninterruptedly through the punch punch along the width direction of the punch 20 until it reaches the other side. Multiple first cavities 21 are arranged sequentially and at intervals along the length direction of the punch 20, and may not be arranged at equal intervals, thereby constructing multiple parallel airflow cooling channels on the entire surface of the punch. Correspondingly, the second cavity 31 on the surface of the die 30 starts from one side of the die 30 and extends uninterruptedly through the recess of the die 30 along the width direction of the die 30 until it reaches the other side. Multiple second cavities 31 are also arranged sequentially and at intervals along the length direction of the die 30, and may not be arranged at equal intervals, thereby constructing multiple parallel airflow cooling channels on the entire surface of the die 30. One side of the airflow cooling channel formed by the first cavity 21 and the second cavity 31 is used for air intake, and the other side is used for exhaust of heated gas.

[0043] The arrangement and cross-sectional shape of the first cavity 21 and the second cavity 31 are shown in FIG7. The cross-section 210 of the first cavity 21 and the cross-section 310 of the second cavity 31 are both semi-circular, with a diameter preferably between 8-20 mm. The first cavity 21 and the second cavity 31 are arranged alternately, with a spacing preferably between 20-100 mm. As mentioned above, the adjacent cavities are not necessarily equidistant. In this embodiment, from the top view of the punch 20 and the die 30, the outlines of the first cavity 21 and the second cavity 31 are straight lines. However, they don't necessarily have to be straight lines; that is, the shape of the airflow cooling channels formed by the first cavity 21 and the second cavity 31 can be varied. They can be spiral-shaped cavities distributed in a spiral pattern on the mold surface. The spiral structure helps the cooling gas or water mist form a continuous rotating flow on the mold surface, thereby uniformly and effectively removing heat. Alternatively, they can be cross-grid cavities, where the cavities intersect to form a grid or checkerboard pattern. The purpose is to increase the total length and surface area of ​​the cavities, which can greatly improve cooling efficiency. At the same time, the cross structure helps to form turbulence, which can further enhance the cooling effect. They can also be inclined cavities, tilted towards a specific direction of the mold. Other shapes of cavities can also be used. In practical applications, the design is based on the specific shape of the mold and the desired cooling effect.

[0044] In addition, the cross-sections of the first cavity 21 and the second cavity 31 can be cylindrical, ridge-shaped, wave-shaped, triangular, or other shapes, in addition to being semi-circular. Considering both manufacturing convenience and cooling effect, a semi-circular shape with a diameter of 8-20mm is preferred.

[0045] When the punch and die are closed, a wedge-shaped air inlet 61 is provided on one side of the die. The wedge-shaped air inlet 61 is the air inlet end of the airflow cooling channel (i.e., the beginning of the air intake of the first cavity 21 and the second cavity 31). A wedge-shaped air outlet 62 for exhaust is provided on the other side of the die. The wedge-shaped air outlet 62 is the air outlet end of the airflow cooling channel (i.e., the end of the air exhaust of the first cavity 21 and the second cavity 31). The wedge-shaped air inlet 61 is connected to the air compressor 40 through several compressed air pipes 41. That is, the air inlet ends of the first cavity 21 and the second cavity 31 are connected to the compressed air pipes 41. The compressed air provided by the air compressor 40 flows through each cavity to remove the heat from the stamped parts and the die surface, thereby achieving the purpose of cooling. Both the wedge-shaped air inlet 61 and the wedge-shaped air outlet 62 adopt the same wedge shape, with an included angle 60° between 30 and 60°. The distance between the starting point 102 of the wedge-shaped air inlet 61 and the edge 101 of the stamped part in the mold is approximately 10 mm.

[0046] After stamping, the stamped part 10 remains in the mold for pressure holding and quenching. Each first cavity 21 on the surface of the punch 20 forms a cavity with the upper surface of the stamped part 10, and each second cavity 31 on the surface of the die 30 forms a cavity with the lower surface of the stamped part 10. The air compressor 40 is turned on to control the pressure of the gas in the compressed air pipeline 41. The compressed gas enters these cavities from the wedge-shaped air inlet 61 and comes into contact with the surface of the stamped part 10 and the inner wall of the cavity on the surface of the mold to conduct heat transfer. The heated gas flows out from the wedge-shaped air outlet 62, carrying away some of the heat from the stamped part 10 and the mold.

[0047] The connection between the compressed air pipeline 41 and the inlet end of the first cavity 21 and the second cavity 31 is defined as an air nozzle (not shown in the figure). An air nozzle can be set at the inlet of each first cavity 21 and second cavity 31, or one air nozzle can cover the inlet of multiple cavities. The specific design depends on the arrangement of the cavities. The shape of the air nozzle can be straight and round, or it can be a flat nozzle. There is no restriction here.

[0048] Furthermore, the air outlet of the air compressor 40 is connected to the water tank 50 via a water pipe 51. This is to mix the compressed air in the compressed air pipe 41 with the water in the water pipe 51 to generate a certain concentration of water mist, thereby accelerating the cooling effect. The water circuit can be opened and closed depending on the situation to cool different types of sheet metal. For example, when cooling bare sheet metal stampings, the water circuit is closed to prevent water mist from causing rust and exacerbating oxide scale formation. When cooling coated sheet metal stampings, the water circuit can be opened for cooling.

[0049] By controlling the pressure of compressed air and the flow rate of water inlet, a mixture of compressed air and water mist is formed. The mixture is blown into the mold through the wedge-shaped air inlet 61, passes through the airflow cooling channel formed by the first cavity 21 and the second cavity 31, exchanges heat with the mold surface, carries away the mold temperature, and is finally discharged through the wedge-shaped air outlet 62.

[0050] The principle for controlling the compressed air pressure and water flow rate is as follows: The compressed air generated by the air compressor 40 has a pressure between 3-7 Bar (atmospheric pressure). The water tank 50 is open, and the water in it is drawn into the nozzle by the force of the compressed air under natural atmospheric pressure, i.e., a siphon-type liquid supply method. Different proportions of water mist are used for cooling the stamped parts and the mold. When cooling the stamped parts, the compressed air pressure is increased to produce a lower water mist concentration, with an air-to-water ratio between 100 and 1000. When cooling the mold, the compressed air pressure is decreased to produce a higher water mist concentration, with an air-to-water ratio between 10 and 100. The air-to-water ratio refers to the volumetric flow rate ratio; the water flow rate is measured in liters per hour, and the air flow rate is measured in liters per minute.

[0051] Specifically, the cooling process of the stamped part 10 is as follows: First, the air-to-water ratio is adjusted to between 100 and 1000, so that the air flow rate is much greater than the water flow rate, thereby generating a low concentration of water mist. Then, the compressed air generated by the air compressor 40 draws water from the water tank in a siphon manner and mixes it to form a water mist mixture. Next, the water mist mixture is blown into the gap between the mold and the stamped part 10 through the wedge-shaped air inlet 61, that is, the cavity formed by the first cavity 21 and the upper surface of the stamped part 10, and the cavity formed by the second cavity 31 and the lower surface of the stamped part 10. Finally, the water mist mixture undergoes heat transfer with the surface of the stamped part 10 and the inner wall of the cavity, effectively removing the heat from the surface of the stamped part 10. The heated airflow is then discharged from the wedge-shaped air outlet 62. Referring to Figure 5, the gas flow during pressure holding and cooling of the stamped part 10 in the mold after forming is shown.

[0052] During the holding and cooling process of the stamped part 10, some of the heat is directly carried away by the airflow in the cavity. If the mold structure is relatively complex or the cooling rate requirement is high, the airflow cannot carry away all the heat. In this case, some of the heat of the stamped part will be conducted to the mold, causing the temperature of the mold to gradually rise from the room temperature at the beginning of production. When the mold temperature is higher than 200°C after quenching, continuing production will lead to defects such as insufficient cooling rate, incomplete martensite transformation, and unqualified mechanical properties. At this time, production should be suspended, the mold should be cooled down to about 50°C, and production should be resumed.

[0053] Referring to Figure 4, the method for cooling the mold is as follows: First, stop the stamping operation, open the punch, and remove the stamped part; then adjust the mold clearance and water-air ratio to keep the clearance 230 between the punch 20 and the die 30 between 50-100mm, so that the water mist mixture can fully enter and cover the mold surface. Adjust the air-water ratio to between 10-100 to form a mixture of compressed air and water mist, producing a high concentration of water mist; then, this high concentration of water mist is blown into the mold clearance 230 through the wedge-shaped air inlet 61; the water mist mixture exchanges heat with the first cavity 21, the second cavity 31, and the mold surface, carrying away the mold temperature; after heat exchange, the heated airflow is discharged from the wedge-shaped air outlet 62, completing the mold cooling process.

[0054] The heat released by the stamped part 10 during the cooling process is Q = M·C·ΔT, where M represents the mass of the stamped part, C represents the specific heat capacity of the stamped part material (the specific heat capacity of steel is approximately 460 J / (kg·℃)), and ΔT represents the temperature difference. Part of the heat Q released by the stamped part, Q1, is directly carried away by the compressed air (or mixed with a certain proportion of water mist), and the other part, Q2, is transferred to the mold, causing the mold to heat up. The total heat released by the stamped part is Q = Q1 + Q2.

[0055] Q1 = A·v·n·t·ρ·C1·ΔT1, where A is the cross-sectional area of ​​the groove on the mold surface, v is the air velocity in the groove, n is the number of grooves, t is the cooling time, ρ is the density of the gas or aerosol mixture in the groove on the mold surface, C1 is the specific heat capacity of the gas or aerosol mixture (approximately between 1004-1850 J / (kg·℃)), and ΔT1 is the temperature difference between the air flowing out of and into the mold. Q2 = M2·C2·ΔT2, where M2 can be the mass of the mold 30mm below the contact surface with the stamped part (including the punch and die), C2 is the specific heat capacity of the mold material, and ΔT2 is the temperature difference of the mold before and after each stamping operation.

[0056] If production is carried out on a hot stamping line in a continuous roller hearth furnace, the heating cycle of the sheet metal is very high. With each stamping, the die temperature rises by 5-10°C. After 15-30 consecutive stampings, the die temperature will rise from 50°C to the maximum allowable temperature of 200°C. At this point, production needs to be paused, the die opened, and cooled down to 50°C before production can continue. However, if small-batch hot stamping is carried out on a trial die line in a three-layer box furnace, the generation cycle is 120 seconds, while the pressure holding and cooling process only takes 26 seconds. Each stamping process has more than 90 seconds of sufficient time to cool the die, enabling continuous production.

[0057] Therefore, the small-batch hot stamping die based on direct surface air cooling provided by this invention can achieve mass production on a trial production line due to its low production cycle. Traditional hot stamping technology transfers the heat of the stamped part to the die, and then to water through internal pipes. The water flowing out of the die heats up and requires a water-cooling unit, which is an energy-consuming process. In other words, both the heating and cooling processes consume energy, and from the perspective of energy conservation, the energy consumption of the two processes is almost the same, resulting in a large energy consumption for the entire stamping process. The cooling technology provided by this invention carries the heat into the air. In winter, this heat forms warm air that remains in the workshop, providing heating. This saves energy consumption in both the cooling process and the workshop's heating costs. In hot summer weather, this warm air can be exhausted outdoors through ventilation ducts, saving most of the energy consumption in the cooling process.

Claims

1. A small-batch hot stamping die based on direct surface air cooling, comprising a punch (20) and a die (30), wherein the die (30) is provided with a recessed portion matching the punch, characterized in that: The surface of the punch (20) is provided with a first cavity (21) that is recessed inward, and the surface of the die (30) is also provided with a second cavity (31) that is recessed inward. The first cavity (21) and the second cavity (31) are used to form an airflow cooling channel connected to an external pipeline. Water vapor introduced by the external pipeline enters the mold and circulates and exchanges heat in the airflow cooling channel formed by the first cavity (21) and the second cavity (31) and in the mold surface, so as to remove the heat of the stamped part and the mold surface.

2. The small-batch hot stamping die based on direct surface air cooling according to claim 1, characterized in that: The first cavity (21) starts from one side of the punch (20) and extends continuously along the width direction of the punch (20) through the punch until it reaches the other side. The second cavity (31) starts from one side of the die (30) and extends continuously along the width direction of the die (30) through the die recess until it reaches the other side.

3. The small-batch hot stamping die based on direct surface air cooling according to claim 2, characterized in that: The first cavity (21) and the second cavity (31) are arranged alternately along the length of the punch (20) and the die (30), respectively, thereby forming an airflow cooling channel connected to the external pipeline on the surface of the punch (20) and the die (30).

4. The small-batch hot stamping die based on direct surface air cooling according to claim 3, characterized in that: The air inlet of the airflow cooling channel is connected to the air compressor (40) through several compressed air pipelines (41), and the air outlet of the airflow cooling channel is used to discharge the heated gas.

5. The small-batch hot stamping die based on direct surface air cooling according to claim 4, characterized in that: The air outlet of the air compressor (40) is connected to the water tank (50) through the water pipe (51). The pressure of the compressed air and the water flow rate are adjusted to form a mixture of compressed air and water mist in different proportions. The mixture undergoes heat exchange when it passes through the airflow cooling channel formed by the first cavity (21) and the second cavity (31).

6. The small-batch hot stamping die based on direct surface air cooling according to claim 5, characterized in that: The first cavity (21) on the surface of the punch (20) and the second cavity (31) on the surface of the die (30) form cavities with the upper and lower surfaces of the stamping part (10). After the water mist mixture enters the cavity, it contacts the surface of the stamping part and the inner wall of the cavity on the surface of the die to exchange heat and remove the heat from the surface of the stamping part.

7. The small-batch hot stamping die based on direct surface air cooling according to claim 5, characterized in that: The punch (20) is separated from the die (30) by a certain gap. The water mist mixture is blown into the gap and heat exchange occurs in the airflow cooling channel and on the mold surface to remove the heat from the mold surface.

8. The small-batch hot stamping die based on direct surface air cooling according to claim 1, characterized in that: The cross-sectional shape of the first cavity (21) and the second cavity (31) is one of semi-circular, cylindrical, ridge-shaped, wavy, or triangular; the shape of the airflow cooling channel is straight, spiral, or cross-grid.

9. A cooling method for stamped parts based on direct surface air cooling, comprising the following steps: S1. Adjust the air-to-water ratio: Adjust the air-to-water ratio to between 100 and 1000 to produce a lower concentration of water mist; S2, Forming a water mist mixture: The compressed air generated by the air compressor (40) draws in the water in the water tank (50) by siphon and mixes it to form a water mist mixture; S3, Water mist mixture is blown into cooling: The water mist mixture is blown into the cavity formed by the first concave cavity (21) and the upper surface of the stamping part, and the second concave cavity (31) and the lower surface of the stamping part through the airflow cooling channel inlet end; S4. Heat transfer and cooling: The water mist mixture transfers heat to the surface of the stamped part and the inner wall of the cavity, effectively removing heat from the surface of the stamped part. S5. The heated airflow is discharged from the outlet of the airflow cooling channel.

10. A cooling method for stamping dies based on direct surface air cooling, comprising the following steps: S1. Stop production and remove stamped parts: Stop the stamping operation, open the punch (20), and remove the cooled stamped parts (10); S2. Adjust the mold gap and air-water ratio: Keep the gap (230) between the punch (20) and the die (30) between 50-100mm so that the water mist mixture can fully enter and cover the mold surface; at the same time, adjust the air-water ratio to between 10-100 to generate a higher concentration of water mist. S3. Forming and blowing in a water mist mixture: A high-concentration water mist mixture is formed by adjusting the compressed air and water flow rate, and then blown into the mold gap through the airflow cooling channel inlet end; S4. Heat exchange and cooling: The water mist mixture exchanges heat with the first cavity (21), the second cavity (31) on the mold surface and the mold surface, effectively removing the heat from the mold and thus reducing the mold temperature. S5. Exhaust heated airflow: After heat exchange, the heated airflow is discharged from the airflow cooling channel outlet, completing the mold cooling process.

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