Immersion pressing method and apparatus for hot-formed steel

Abstract

This invention relates to the technical field of hot-pressed steel and discloses an immersion pressing method and apparatus for hot-formed steel. The method includes step 1, transporting a prepared hot-formed steel blank into a furnace for austenitizing heating, and step 2, immersing a lower forming punch in a liquid medium in a container assembly containing a liquid medium, and placing the heated blank into a blank holder using a loading robot. By employing an immersion pressing method, this invention optimizes the die structure, reduces water channel processing in conventional hot-press equipment, and lowers processing cycles and costs compared to the conventional direct hot-forming method. At the same time, it expands the range of material applications, eliminates oxide scale problems in unplated sheets and LIME problems in galvanized sheets, reduces investment costs, and facilitates automated control.

Description

Technical Field

[0001] The present invention relates to the technical field of hot press steel, and specifically to an immersion press method and apparatus for hot forming steel.

Background Art

[0002] In the field of automobile manufacturing, galvanized sheets are widely used because of their excellent corrosion resistance and strength, and their applications can be found in automobile body panels, chassis, and internal structural parts. Through the hot forming process, galvanized sheets can be processed into complex shapes to meet various needs of automobile design. This not only improves the appearance quality of automobiles but also enhances the rigidity and durability of automobiles.

[0003] The currently adopted commercial production process is an indirect hot press process. That is, first, the sheet metal is pre-cooled in a cold mold, formed by more than 95%, then austenitized, and complete deformation and quenching are carried out in another mold. The entire process is completed with two sets of molds.

[0004] However, those skilled in the art have discovered the following defects during production. First, the cost of mold manufacturing and auxiliary equipment required for producing hot press formed steel is high. Second, due to the uneven temperature control of the sheet metal during production, it is difficult to ensure complete pre-cooling. Third, there is no systematic production and manufacturing, the application range is narrow, and the efficiency is low.

[0005] Therefore, in the present invention, in order to solve the above problems, an immersion press method and apparatus for hot forming steel are proposed.

Summary of the Invention

[0006] The object of the present invention is to provide an immersion press method and apparatus for hot forming steel to solve the above problems.

[0007] The object of the present invention can be achieved by the following technical solutions.

[0008] A method for immersion pressing of hot-formed steel, comprising: step 1 transporting a prepared hot-formed steel blank into a furnace and austenitizing it; step 2 immersing a lower forming punch in a liquid medium of a container assembly, placing the blank obtained in step 1 into a blank holder by a loading robot, with the top of the blank holder below the liquid level; step 3 pressing down an upper die to align with a lower die and forming the blank by pressure holding; and step 4, after pressure holding is completed, ejecting the hot-pressed product from the liquid surface of the liquid medium by an eject module and removing the hot-pressed product.

[0009] In a further aspect of the present invention, a pickup robot transports the blank into the furnace, a loading robot places the heated blank into a blank holder, and an unloading robot removes the hot press-formed product.

[0010] In a further aspect of the present invention, oil is added to the surface of the liquid medium, and the oil includes industrial rust-preventive oil and lubricating oil, with the oil content set to 100 to 200 ml.

[0011] In a further aspect of the present invention, a plurality of heat bars are provided inside the container assembly, and the plurality of heat bars are arranged at equal intervals.

[0012] In a further aspect of the present invention, an error prevention system is provided in the unloading area, and the error prevention system includes a weight sensing system added to the unloading robot.

[0013] In a further aspect of the present invention, the thickness of the blank is 1 to 14 mm.

[0014] In a further aspect of the present invention, the liquid level of the liquid medium is controlled to 0 to 300 mm from the upper surface of the lower forming punch.

[0015] In a further aspect of the present invention, the liquid medium includes water or a mixture of water and a slow-cooling liquid, wherein the mixing ratio of the slow-cooling liquid to water is controlled to 1:5 to 1:10.

[0016] In a further embodiment of the present invention, in step 2, the heated blank is partially immersed in the liquid medium.

[0017] In a further aspect of the present invention, in step 2, the immersion time of the blank in the container is 3 to 5 seconds.

[0018] In a further aspect of the present invention, in step 3, the downward pressing speed of the upper mold is first increased and then decreased.

[0019] In a further aspect of the present invention, in step 3, the holding pressure during molding by holding the blank under pressure is 4000 to 20000 kN, and the pressure holding time is based on the following formula. T2 = t * 5 + 1 Here, T2 is the pressure holding time and t is the thickness of the blank.

[0020] In a further aspect of the present invention, a water level monitoring system is used to monitor the water level during the pressing process, and water is automatically replenished based on the monitoring results. The procedure is as follows.

[0021] Sensors acquire water level data from multiple locations within the container assembly. This data is then summed and averaged to obtain a real-time water level value HA of the liquid medium, thereby detecting and acquiring the real-time water level value of the liquid medium.

[0022] Water level influence data is acquired, which includes the volumetric influence and thermal influence of the blank.

[0023] Here, the volume effect of the blank is the height to which the water level rises after the blank enters the liquid medium, and the thermal effect of the blank is the height to which the water level drops due to the increased evaporation rate when the blank enters the liquid medium, causing the liquid to rise above the water surface in the form of vapor.

[0024] The process of obtaining the water level influence data is as follows.

[0025] Obtain the dimensions including the length value, width value, and height value of the blank, and calculate the volume value VX of the blank from the obtained length value, width value, and height value according to the volume formula.

[0026] Obtain the length value and width value of the container assembly, and calculate the bottom area SX of the container assembly according to the area formula.

[0027] Substitute into the formula HX = VX / SX to obtain the influence height HX of the water level of the liquid medium due to the volume of the blank.

[0028] Obtain the heat quantity of the blank after austenitizing heating according to the heat quantity formula Q = C * M * Δt, where Q is the absorbed heat quantity, M is the mass of the object, C is the specific heat capacity of the substance, and ΔT is the temperature change amount.

[0029] In the formula Q = M1 * L, Q is the total energy, M1 is the mass of the evaporated liquid medium, and L is the latent heat of vaporization of the liquid.

[0030] According to the above formulas Q = C * M * Δt and Q = M1 * L, the mass M1 of the evaporated liquid medium can be obtained, and by obtaining the density of the liquid medium through calculation processing, the volume VY of the evaporated liquid medium can be obtained.

[0031] Substitute into the formula HY = VY / SX to obtain the influence height HY of the water level of the liquid medium due to the heat quantity of the blank.

[0032] Obtain the water level prediction value HH according to the formula HH = HA + HX - HY.

[0033] Compare the water level prediction value HH with the water level threshold range [HM - HN], where the water level threshold range is 0 - 300 mm from the upper surface of the bottom forming punch.

[0034] When HH ∈ [HM - HN], generate a normal production signal.

[0035] When HH < HM, a water supply signal is generated.

[0036] When HH > HN, a drainage signal is generated.

[0037] Based on the above drainage signal, the solenoid valve is controlled to drive the water pump, extracting the liquid medium from the inside of the container assembly and maintaining the water level of the liquid medium within the water level threshold range [HM - HN].

[0038] Based on the above water supply signal, the solenoid valve is controlled to drive the water pump, replenishing the liquid medium inside the container assembly. At the same time, the influencing factors of the water supply time are analyzed, and the water supply speed is controlled based on the influencing factors, such that the water supply time is controlled within the time period from when the blank heating is completed to when it is transferred to the blank holder.

[0039] The minimum value of the height of the liquid medium that needs to be replenished is Hmin = HM - HH, and the maximum value of the height of the liquid medium that needs to be replenished is Hmax = HN - HH.

[0040] The influencing factors of the water supply time are obtained by processing the space transfer time ratio of the blank and the water body transfer time ratio of the blank.

[0041] The space transfer time ratio of the blank is the ratio of the time T1 required for the loading robot to transfer the heated blank to the upper side of the container assembly to the space transfer reference value T2.

[0042] The water body transfer time ratio of the blank is the ratio of the time T3 required for the loading robot to place the blank on the blank holder to the water body transfer reference value T4.

[0043] The influencing factor of the water supply time is K = T1 / T2 + T3 / T4, and K is taken as the influencing factor of the water supply time. JPEG2026522149000002.jpg12170Tx represents the reference time from when the loading robot finishes heating the blank until it is placed inside the liquid medium; this time is based on the operator's experience.

[0044] Based on the above formula, when the factors influencing the water replenishment time change, the minimum value of the adjusted water replenishment rate is Vx, and the maximum value of the water replenishment rate is Vy. By controlling the water replenishment rate, the water replenishment time is brought closer to the reference time Tx.

[0045] A further aspect of the present invention includes an immersion module, a molding module, a die set module, and an ejection module.

[0046] The immersion module includes a container assembly, and multiple sets of heat bars are provided inside the container assembly.

[0047] The molding module includes a lower molding punch located on the upper side of the container bottom plate, and blank holders are provided on both sides of the lower molding punch.

[0048] In a further aspect of the present invention, the immersion module includes a container assembly, the container assembly having a plurality of heat bars inside.

[0049] The container assembly includes four sets of container side plates, the four sets of container side plates arranged in a rectangular shape, two sets of container top lid plates are provided above the four sets of container side plates, and a container bottom plate is provided below the four sets of container side plates.

[0050] In a further aspect of the present invention, the immersion module further includes an insulating plate assembly, the insulating plate assembly includes insulating side plates provided on the outer surface of the container side plates, an insulating bottom plate provided below the insulating side plates, and the insulating bottom plate provided below the container bottom plate.

[0051] A junction box is fixedly connected to the outer surface of the aforementioned heat-insulating side plate.

[0052] The aforementioned junction box is connected to the temperature control electrical box via connecting wires.

[0053] In a further aspect of the present invention, the molding module includes two sets of lower forming punches provided on the upper side of the container bottom plate, with blank holders provided on both sides of the two sets of lower forming punches, and multiple sets of positioning pins provided on the outside of the ends of the two sets of lower forming punches.

[0054] In a further aspect of the present invention, the die set module includes a lower die set and a support block, wherein a liquid nozzle is provided on one side of the lower die set, and the liquid nozzle communicates with the inside of a container assembly.

[0055] In a further aspect of the present invention, the eject module includes a plurality of sets of eject pins provided on the upper surface of a lower forming punch, the eject pins being controlled to move up and down by a hydraulic cylinder eject assembly, the hydraulic cylinder eject assembly including a plurality of sets of hydraulic cylinders and spring hoses. [Effects of the Invention]

[0056] (1) By employing an immersion pressing method, the present invention optimizes the mold structure compared to the conventional direct hot forming method, reduces the water channel processing required in conventional hot pressing equipment, and lowers the processing cycle and cost. At the same time, it expands the range of applicable materials, eliminates the oxide scale problem of unplated sheets and the LIME problem of galvanized sheets, lowers investment costs, and facilitates automated control.

[0057] (2) By immersing the lower forming punch of the mold in a liquid medium within the container assembly, the present invention eliminates the need to add a cooling water channel to the lower forming punch of the mold, thereby reducing the water channel processing required in conventional hot press equipment, and lowering the processing cycle and costs.

[0058] (3) The present invention allows for the temperature of the lower forming punch to be indirectly adjusted by immersing the lower forming punch of the mold in the liquid medium of the container assembly, thereby reducing the possibility of blank warping after press forming and improving production yield.

[0059] (4) By partially immersing the blank in a liquid medium, the deformation of the blank is small, the degree of warping is low, and the molding resistance is high.

[0060] (5) In the process of pushing down the upper mold, the present invention not only ensures production cycle time but also prevents parts from cracking during molding by first increasing the speed and then decreasing it. [Brief explanation of the drawing]

[0061] The present invention will be described in more detail below with reference to the drawings. [Figure 1] This is a schematic perspective view of the overall structure according to the present invention. [Figure 2] This is a schematic bottom view of the overall structure according to the present invention. [Figure 3] This is a schematic top view of the overall structure according to the present invention. [Figure 4] This is a schematic diagram of the metal structure of a component, which is one specific example according to the present invention. [Figure 5] This is a schematic diagram of the strength of a component, which is one specific example according to the present invention. [Figure 6] This is a schematic diagram of the elongation rate of a component, which is a specific example according to the present invention. [Modes for carrying out the invention]

[0062] The technical concepts in embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments. It will be clear that the embodiments described are not all embodiments of the present invention, but only a selection. All other embodiments that a person skilled in the art could obtain without creative work based on the embodiments of the present invention are included within the scope of protection of the present invention.

[0063] Example 1 As shown in Figures 1 to 3, the present invention is an immersion pressing method for hot-formed steel, comprising austenitization (step 1), immersion pre-cooling (step 2), rapid forming (step 3), and prevention of picking errors (step 4).

[0064] By adopting the immersion pressing method, the die structure is optimized compared to the conventional direct hot forming method, reducing the amount of water channel processing required in conventional hot pressing equipment, thereby lowering the processing cycle and costs. At the same time, the range of applicable materials is expanded, the oxide scale problem of unplated sheets and the LIME problem of galvanized sheets are resolved, investment costs are lower, and automated control is easier.

[0065] Example 2 As shown in Figures 1 to 3, the immersion pressing method for hot-formed steel of the present invention, based on the above Example 1, further includes the following steps.

[0066] In Step 1, The blank material is hot-formed steel with a plate thickness of 1 to 14 mm. The prepared blanks are transported into the furnace by a pickup robot and heated to austenitize state.

[0067] Hot-formed steel materials include, but are not limited to, unplated sheets, aluminum-silicon plated sheets, and zinc-plated sheets.

[0068] Here, the heating time is based on the following formula for plate thickness. T1 = 100 * t + 150 The above formula for plate thickness is an empirical formula derived from production experience during the manufacturing process.

[0069] In step 2, After the blank has been austenitized, the loading robot transports the blank to the blank holder 22 according to the debugged program.

[0070] Compared to conventional immersion-type pre-cooling molding technology, immersing the lower forming punch 21 of the mold in the liquid medium within the container assembly eliminates the need to add cooling water channels to the lower forming punch 21 of the mold. This reduces the water channel processing required in conventional hot press equipment, resulting in the advantages of reduced processing cycles and costs.

[0071] Here, the container assembly 11 contains a liquid medium, the liquid level is controlled to be between 0 and 300 mm above the top surface of the molding punch, and at the same time, the top of the blank holder 22 is ensured to be below the liquid level.

[0072] Furthermore, by controlling the water level of the liquid medium to be below the top of the blank holder 22, the lower die is ensured to be submerged in the liquid medium during pressing. Pre-cooling is performed by adjusting the temperature of the lower die, and the blank is prevented from entering the liquid before molding. This makes it easier to quickly remove the molded product after molding, and also prevents water from overflowing during pressing, further improving safety during the processing.

[0073] Furthermore, the liquid medium includes, but is not limited to, water or a mixture of water and a slow-cooling liquid. The mixing ratio of the slow-cooling liquid to water is controlled to 1:5 to 1:10, and oil is added to the surface of the liquid medium.

[0074] Here, the oil includes, but is not limited to, industrial rust-preventive oil and lubricating oil. The oil content is controlled to 100-200 ml.

[0075] The purpose of adopting the above mixing ratio is to control the evaporation of water, shorten the heating time of the liquid medium, stabilize temperature changes, and ensure the formation of an air film.

[0076] The temperature of the liquid medium is controlled within the range of 80 to 100°C, and the heating method includes, but is not limited to, a heat bar 12 located inside the container assembly 11. The temperature control method includes, but is not limited to, feedback control using a temperature measuring bar.

[0077] Due to the Leidenfrost effect, if the blank's temperature is too high, the liquid near its surface forms a film of boiling, creating an air film that surrounds the blank. This reduces heat exchange between the blank and the liquid, lowering the heat transfer coefficient and ensuring that the blank's temperature is well above the martensitic transformation temperature before the upper mold is pressed down for forming.

[0078] Through the above process, after the blank has been austenitized, the lower forming punch 21 of the mold is immersed in a liquid medium, the temperature is controlled by the lower forming punch 21, and then the blank is pressed. This reduces dimensional deformation of the blank during the processing process and improves production efficiency and yield.

[0079] In step 3, The depressing speed should be increased first, then decreased, and the holding pressure during molding should be 4000 to 20000 kN. Here, the pressure holding time is based on the following formula for plate thickness. T2 = t * 5 + 1

[0080] When the mold is pressed down and brought into contact with the blank, the air film on the surface of the blank is broken, the heat exchange method between the blank and the liquid changes from film boiling to transition boiling, and the heat exchange gradually increases.

[0081] During the period from blank formation to pressure holding, heat exchange eventually leads to nucleation boiling, increasing heat exchange and thus the cooling rate, and the material structure of the molded product eventually becomes martensite.

[0082] In step 4, After the pressure holding is complete, the mold's eject module 4 ejects the hot-pressed product into the water, and then an unloading robot retrieves it according to a set program.

[0083] Furthermore, an error prevention system is installed in the unloading area to prevent mold damage and impact on cycle production caused by parts not being removed from the mold in a timely manner.

[0084] Error prevention systems include, but are not limited to, the following two types of methods.

[0085] A weight sensing system will be added to the unloading robot, and a function to prevent errors during production will be set up based on weight sensing.

[0086] A visual system is added above the unloading robot to detect and prevent errors using a visual counting method.

[0087] Example 3 Based on the above Example 2, in step 2 of the immersion pressing method for hot-formed steel, the present invention partially immerses the blank in a liquid medium. The thickness of the blank immersed in the liquid does not exceed 80% of the plate thickness. Because the blank is partially immersed in the liquid, the instantaneous cooling rate of the material is reduced compared to when it is fully immersed, and warping and deformation of the blank due to rapid cooling can be avoided. At the same time, because the amount of cooling is small, the temperature of the material during forming is higher, improving the forming performance of the material, and thus reducing the forming resistance during partial immersion.

[0088] Example 4 The liquid level is controlled to 0-300 mm above the top surface of the forming punch, and at the same time, the conical surface of the ejector pin is ensured to be exposed above the liquid level. The immersion time of the blank in the container is the time from when the robot places the blank until it pushes down the upper mold to form it, and this time is generally 3-5 seconds. The pushing speed is initially fast, then slowed down, and the holding pressure during forming is 4000-20000 kN, with the pressure holding time based on the following formula for plate thickness. T2 = t * 5 + 1

[0089] If the immersion time is too short, the surface coating cannot be transformed from liquid to solid, which can lead to cracking defects caused by the liquid during subsequent molding. If the immersion time is too long, the temperature of the material (blank) drops too low, causing a transformation from austenite to martensite in the material's structure, making subsequent molding extremely difficult or impossible. Setting the immersion time to 3-5 seconds not only prevents cracking defects caused by the liquid during subsequent molding, but also prevents the material's temperature from dropping too low.

[0090] When pressing down, the initial speed is 1000-1500 mm / s, and the speed after contact with the material is 100-150 mm / s. The high initial speed is to ensure a rapid descent of the press and maintain a good production cycle. The slower speed after contact with the material is to ensure good formability; if the forming speed is too high, the part will crack.

[0091] The following embodiments are further included, specifically as follows:

[0092] During the pressing process, the liquid medium level is controlled above the lower forming punch 21 and below the top of the blank holder 22. Therefore, if a loading robot is used to place the blank above the lower forming punch 21, a collision with the liquid medium occurs, causing liquid loss. Furthermore, if multiple pressings are repeated, liquid loss continues, causing the liquid medium level to change and affecting the production process.

[0093] Therefore, a water level monitoring system is necessary to monitor the water level during the pressing process and automatically replenish water based on the monitoring results.

[0094] The water level monitoring system includes a real-time monitoring module, an analysis and identification module, a water level control module, an automatic water replenishment module, and a cloud server.

[0095] The real-time monitoring module monitors the real-time water level of the liquid medium before the blank is introduced into the liquid medium, acquires water level impact data, and transmits this data to the cloud server.

[0096] The analysis and identification module calculates a predicted water level based on the water level change and media loss obtained through analysis processing of data received by the cloud server, performs judgment and recognition, and generates a control signal.

[0097] The water level control module dynamically controls the water level based on the generated control signals.

[0098] The automatic water supply module controls a solenoid valve to drive a water pump, supplying and discharging the liquid medium in the container assembly 11.

[0099] The specific monitoring procedure for the water level monitoring system is as follows:

[0100] The real-time water level of the liquid medium is obtained. Sensors acquire water level data from multiple locations within the container assembly 11, and these water level data are summed and averaged to obtain the real-time water level HA of the liquid medium.

[0101] Obtain water level influence data. This data includes the volumetric influence of the blank and the thermal influence of the blank.

[0102] Here, the volume effect of the blank is the height to which the water level rises after the blank enters the liquid medium, and the thermal effect of the blank is the height to which the water level drops due to the increased evaporation rate when the blank enters the liquid medium, causing the liquid to rise above the water surface in the form of vapor.

[0103] The process for acquiring water level impact data is as follows:

[0104] The dimensions of the blank, including its length, width, and height, are obtained, and the volume value VX of the blank is calculated from the obtained length, width, and height using the volume formula.

[0105] The length and width values ​​of the container assembly 11 are obtained, and the base area SX of the container assembly 11 is calculated using the area formula.

[0106] Substitute the values ​​into the equation HX = VX / SX to obtain the height HX, which is the effect of the liquid medium's water level on the volume of the blank.

[0107] Using the heat formula Q = C * M * Δt, the heat quantity of the blank after austenitization heating is obtained, where Q is the amount of heat absorbed, M is the mass of the object, C is the specific heat capacity of the substance, and ΔT is the change in temperature.

[0108] In the equation Q = M1 * L, Q is the total energy, M1 is the mass of the evaporated liquid medium, and L is the latent heat of vaporization of the liquid.

[0109] Latent heat of vaporization is a physical property of a substance. Its magnitude is not only related to the properties of the substance itself, but is also a function of temperature. Generally, the latent heat of vaporization value at a specific temperature is given in the material's property data table.

[0110] Using the equations Q=C*M*Δt and Q=M1*L above, the mass M1 of the evaporated liquid medium can be obtained, and by calculating the density of the liquid medium, the volume VY of the evaporated liquid medium can be obtained.

[0111] Substitute this into the equation HY = VY / SX to obtain the height HY, which is the effect of the water level of the liquid medium due to the heat of the blank.

[0112] The predicted water level value HH is obtained using the formula HH = HA + HX - HY.

[0113] The predicted water level value HH is compared with the water level threshold range [HM-HN]. Here, the water level threshold range is 0 to 300 mm from the top surface of the lower forming punch 21.

[0114] If HH∈[HM-HN], a normal production signal is generated.

[0115] When HH < HM, a water replenishment signal is generated.

[0116] When HH > HN, a drainage signal is generated.

[0117] Based on the above drainage signal, the solenoid valve is controlled to drive the water pump, extract the liquid medium from inside the container assembly 11, and maintain the water level of the liquid medium within the water level threshold range [HM - HN].

[0118] Based on the above water replenishment signal, the solenoid valve is controlled to drive the water pump, replenish the liquid medium inside the container assembly 11, and at the same time analyze the influencing factors of the water replenishment time, control the water replenishment speed based on the influencing factors, and control the water replenishment time within the time period from when the blank heating is completed to when it is transferred to the blank holder 22.

[0119] The minimum value of the height of the liquid medium that needs to be replenished is Hmin = HM - HH, and the maximum value of the height of the liquid medium that needs to be replenished is Hmax = HN - HH.

[0120] The influencing factors of the water replenishment time are obtained by processing the space transfer time ratio of the blank and the water body transfer time ratio of the blank.

[0121] The longer the transfer time in the blank's space, the greater the heat consumption of the blank, the change in the water level loss due to evaporation factors, and the impact on water level prediction. The shorter the transfer time in the blank's water body, the faster the loading robot places the blank, the greater the force on the blank's liquid, the longer the time until the water level stabilizes, and the impact on the start time of immersion.

[0122] The space transfer time ratio of the blank is the ratio of the time T1 required for the loading robot to transfer the heated blank to the upper side of the container assembly 11 to the space transfer reference value T2.

[0123] The blank water transfer time ratio is the ratio of the time T3 required for the loading robot to place the blank in the blank holder 22 to the water transfer reference value T4.

[0124] The factors influencing water replenishment time are K = T1 / T2 + T3 / T4, and K is considered the factor influencing water replenishment time.

[0125] JPEG2026522149000003.jpg13170Tx represents the reference time from when the loading robot finishes heating the blank until it is placed inside the liquid medium; this time is based on the operator's experience.

[0126] Based on the above formula, when the factors influencing the water replenishment time change, the minimum value of the adjusted water replenishment rate is Vx, and the maximum value of the water replenishment rate is Vy. By controlling the water replenishment rate, the water replenishment time is brought closer to the reference time Tx.

[0127] Example 5 As shown in Figures 1 to 6, based on the above-described Examples 1 and 2, the present invention is an immersion pressing method for hot-formed steel, and this embodiment is one example thereof.

[0128] We selected a galvanized sheet material with a base material of conventional 22MnB5, a plate thickness of 1.8 mm, and a galvanized layer thickness of 15 μm.

[0129] The prepared galvanized sheet blanks are picked up by a pickup robot, transported into the furnace, and heated at 900°C for 330 seconds, with nitrogen protection turned off during heating.

[0130] After the blank is heated, the loading robot transports the blank into the container according to the debugged program.

[0131] The container contains water and 100 ml of rust-preventive oil, the water level is controlled to 50 mm above the top surface of the molding punch, and it is immersed for 4 seconds to pre-cool.

[0132] At the same time, the press machine is operated at a high speed first, then slowed down to press down, with a holding pressure of 800 tons during molding and a pressure holding time of 10 seconds.

[0133] After the pressure holding is complete, the mold's ejection system ejects the hot-pressed galvanized sheet metal part from the water surface, and an unloading robot with an added visual error prevention system removes the hot-pressed part according to a set program.

[0134] The results of the produced parts are as follows:

[0135] The microstructure observation is shown in Figure 4. The substrate had a martensitic structure, the plating layer was 20-30 μm thick, and no fine cracks were found. Three points were measured on the component, and the strength results are shown in Figure 5, while the elongation is shown in Figure 6. In all cases, the requirements of tensile strength > 1300 MPa and elongation > 5% were met.

[0136] Example 6 As shown in Figures 1 to 3, the present invention is an immersion press apparatus for hot-formed steel, comprising an immersion module 1, a forming module 2, a die set module 3, and an ejection module 4.

[0137] The temperature of the lower forming punch 21 of the mold is adjusted by immersing it in the provided immersion module 1 and adjusting the temperature of the liquid medium.

[0138] Here, the immersion module 1 includes a container assembly 11, and multiple sets of heat bars 12 are provided inside the container assembly 11.

[0139] The container assembly 11 includes four sets of container side plates 111, which are arranged in a rectangular shape. Two sets of container top lid plates 112 are provided above the four sets of container side plates 111, and a container bottom plate 113 is provided below the four sets of container side plates 111.

[0140] As shown in Figure 1, the four container side plates 111 and the container bottom plate 113 form a box-shaped structure, and the container top lid plate 112 is symmetrically arranged and fixed to the container side plates 111, allowing a liquid medium to be placed inside and the lower forming punch 21 to be immersed in it.

[0141] The insulation plate assembly 14 includes an insulation side plate 141 provided on the outer surface of the container side plate 111, an insulation bottom plate 142 provided below the insulation side plate 141, and the insulation bottom plate 142 provided below the container bottom plate 113.

[0142] By providing the insulation plate assembly 14, the insulation side plate 141 is placed on the outside of the container side plate 111, and the insulation bottom plate 142 is placed on the underside of the container bottom plate 113, thereby insulating the container assembly 11 and reducing damage to workers and other workpieces due to overheating of the container assembly 11.

[0143] The junction box 13 is fixedly connected to the outer surface of the insulated side plate 141.

[0144] Multiple sets of junction boxes 13 are installed, and these multiple sets of junction boxes 13 are arranged in a linear array.

[0145] The junction box 13 is connected to the temperature control electrical box 16 via connecting wires.

[0146] Here, a temperature control system is provided inside the temperature control electrical box 16, and during the production process, the temperature of the liquid medium in the container assembly 11 is controlled by the temperature control system and maintained in the range of 80 to 100°C.

[0147] The molding module 2 includes two sets of lower forming punches 21 located on the upper side of the container bottom plate 113, with blank holders 22 provided on both sides of each of the two sets of lower forming punches 21, and multiple sets of positioning pins 23 provided on the outside of the ends of each of the two sets of lower forming punches 21.

[0148] Here, two sets of lower forming punches 21 are arranged symmetrically, installed blank holders 22 are spaced equally apart to support the blanks, and installed positioning pins 23 are used to limit the position of the blanks.

[0149] The die set module 3 includes a lower die set 31 and a support block 32, with a liquid nozzle 15 opening on one side of the lower die set 31, which communicates with the inside of the container assembly 11.

[0150] The liquid nozzle 15 is used to introduce the liquid medium into the container assembly 11, and when it is necessary to replace the liquid medium, the liquid medium is extracted through the liquid nozzle 15.

[0151] The eject module 4 includes multiple sets of eject pins 41 located on the upper surface of the lower forming punch 21, the eject pins 41 being controlled to move up and down by a hydraulic cylinder eject assembly 42. The hydraulic cylinder eject assembly 42 includes multiple sets of hydraulic cylinder assemblies 422 and a spring hose 421.

[0152] The installed eject module 4 is used to eject the formed blank after the blank has been pressed, by controlling a hydraulic cylinder assembly 422 to press a spring hose 421, which uses the elastic deformation of the spring hose 421 and the transmission of internal fluid pressure to apply force to the eject pin 41, ejecting the formed blank from the lower forming punch 21 onto the eject pin 41, and facilitating picking by a loading robot.

[0153] Although one embodiment of the present invention has been described in detail above, this is merely a preferred embodiment of the present invention and does not limit the scope of the present invention. Equivalent modifications and improvements made within the scope of the present invention are still considered to be within the scope of the claims of the present invention. [Explanation of Symbols]

[0154] 1 Immersion Module 11 Container Assembly 111 Container side plate 112 Container top cover plate 113 Container bottom plate 12 Heat Bars 13 Junction Box 14. Insulation board assembly 141 Insulated side panel 142 Insulated base plate 15 Liquid nozzles 16 Temperature-controlled electrical box 2 Molding Modules 21 Lower forming punch 22 Blank Holder 23 Positioning pins 3 Die Set Module 31 Lower Die Set 32 Support Blocks 4 Eject Modules 41 Ejector pins 42 Hydraulic Cylinder Ejector Assembly 421 Spring Hose 422 Hydraulic Cylinder Assembly

Claims

1. A immersion pressing method for hot-formed steel, Step 1 involves transporting the prepared hot-formed steel blank into the furnace and heating it to austenitize it. Step 2 involves immersing the lower forming punch (21) in the liquid medium of the container assembly, placing the blank obtained in step 1 into the blank holder (22), and positioning the top of the blank holder (22) below the liquid surface of the liquid medium. Step 3 involves pressing down the upper mold to align it with the lower mold and forming the blank by holding the pressure, Step 4 includes, after the pressure holding is completed, ejecting the hot press-formed product from the liquid surface of the liquid medium using the eject module (4) and removing the hot press-formed product. A method for immersion pressing hot-formed steel, characterized by the following features.

2. A pickup robot transports the blank into the furnace, a loading robot places the heated blank into the blank holder (22), and an unloading robot removes the hot-pressed product. The immersion pressing method for hot-formed steel according to feature 1.

3. Oil is added to the surface of the aforementioned liquid medium, and the oil includes industrial rust-preventive oil and lubricating oil, with the oil content set to 100 to 200 ml. The immersion pressing method for hot-formed steel according to feature 1.

4. Multiple sets of heat bars (12) are provided inside the container assembly (11), and the multiple sets of heat bars (12) are arranged at equal intervals. The immersion pressing method for hot-formed steel according to feature 1.

5. An error prevention system is provided in the unloading area, and this error prevention system includes a weight sensing system added to the unloading robot. The immersion pressing method for hot-formed steel according to feature 1.

6. The blank thickness is 1 to 14 mm. The immersion pressing method for hot-formed steel according to feature 1.

7. The liquid level of the liquid medium is controlled to be between 0 and 300 mm above the top surface of the lower forming punch. The immersion pressing method for hot-formed steel according to feature 1.

8. The liquid medium includes water or a mixture of water and a slow-cooling solution, with the ratio of the slow-cooling solution to water controlled to 1:5 to 1:

10. The immersion pressing method for hot-formed steel according to feature 1.

9. In step 2, the blank is partially immersed in the liquid medium. The immersion pressing method for hot-formed steel according to feature 1.

10. In step 2, the immersion time in the container for the blank is 3 to 5 seconds. The immersion pressing method for hot-formed steel according to feature 9.

11. In step 3, the downward pressing speed of the upper mold is increased first, then decreased. The immersion pressing method for hot-formed steel according to feature 1.

12. In step 3, the holding pressure during molding by holding the blank under pressure is 4000 to 20000 kN, and the pressure holding time is based on the following formula: T² = t * 5 + 1 Here, T2 is the pressure holding time and t is the thickness of the blank. The immersion pressing method for hot-formed steel according to feature 1.

13. The water level monitoring system monitors the water level during the pressing process and automatically replenishes water based on the monitoring results. The procedure is as follows: Sensors acquire water level data from multiple locations within the container assembly, and these water level data are summed and averaged to obtain the real-time water level value HA of the liquid medium, thereby detecting and acquiring the real-time water level value of the liquid medium. Water level influence data is acquired, and this data includes the volumetric influence of the blank and the thermal influence of the blank. Here, the volume effect of the blank refers to the height the water level rises after the blank enters the liquid medium, and the thermal effect of the blank refers to the height the water level drops due to the increased evaporation rate when the blank enters the liquid medium, causing the liquid to rise above the water surface in the form of vapor. The process for acquiring water level impact data is as follows: Obtain the dimensions of the blank, including its length, width, and height, and calculate the volume VX of the blank using the volume formula from the obtained length, width, and height values. The length and width values ​​of the container assembly are obtained, and the base area SX of the container assembly is calculated using the area formula. Substituting into the formula HX = VX / SX, we obtain the height HX, which is the effect of the water level of the liquid medium due to the volume of the blank. Using the heat formula Q = C * M * Δt, the heat quantity of the blank after austenitization heating is obtained, where Q is the amount of heat absorbed, M is the mass of the object, C is the specific heat capacity of the substance, and ΔT is the change in temperature. In the equation Q = M1 * L, Q is the total energy, M1 is the mass of the evaporated liquid medium, and L is the latent heat of vaporization of the liquid. Using the above equations Q = C * M * Δt and Q = M1 * L, the mass M1 of the evaporated liquid medium can be obtained, and by calculating the density of the liquid medium, the volume VY of the evaporated liquid medium can be obtained. Substituting into the formula HY = VY / SX, we obtain the height HY, which is the effect of the water level of the liquid medium due to the heat of the blank. The predicted water level value HH is obtained using the formula HH = HA + HX - HY. The predicted water level HH is compared with the water level threshold range [HM-HN], where the water level threshold range is 0 to 300 mm from the top surface of the lower forming punch. If HH ∈ [HM - HN], a normal production signal is generated. If HH < HM, a water supply signal is generated. If HH > HN, a drainage signal is generated. Based on the drainage signal above, the solenoid valve is controlled to drive the water pump, extracting the liquid medium from inside the container assembly and maintaining the liquid medium level within the water level threshold range [HM-HN]. Based on the above water supply signal, the solenoid valve is controlled to drive the water pump and supply the liquid medium to the container assembly. At the same time, the factors influencing the water supply time are analyzed, and the water supply rate is controlled based on these factors, so that the water supply time is controlled to fall within the time period from when the blank is heated to when it is transferred to the blank holder. The minimum height of the liquid medium requiring replenishment is Hmin = HM - HH, and the maximum height of the liquid medium requiring replenishment is Hmax = HN - HH. The factors influencing water replenishment time were obtained by processing the spatial transfer time ratio and the water transfer time ratio of the blank. The spatial transfer time ratio of the blank is the ratio of the time T1 required for the loading robot to transfer the heated blank to the top of the container assembly to the spatial transfer reference value T2. The blank water transfer time ratio is the ratio of the time T3 required for the loading robot to place the blank in the blank holder to the water transfer reference value T4. The factors influencing water replenishment time are K = T1 / T2 + T3 / T4, and K is the factor influencing water replenishment time. Tx is the reference time from when the loading robot finishes heating the blank until it is placed inside the liquid medium, and this time is based on the operator's experience. Based on the above formula, when the factors influencing the water replenishment time change, the minimum value of the adjusted water replenishment rate becomes Vx, and the maximum value of the water replenishment rate becomes Vy. By controlling the water replenishment rate, the water replenishment time can be brought closer to the reference time Tx. The immersion pressing method for hot-formed steel according to feature 1.

14. A immersion press apparatus for hot-formed steel, It includes an immersion module (1), a molding module (2), a die set module (3), and an eject module (4), The immersion module (1) includes a container assembly (11), and multiple sets of heat bars (12) are provided inside the container assembly (11). The molding module (2) includes a lower molding punch (21) provided on the upper side of the container bottom plate (113), and blank holders (22) are provided on both sides of the lower molding punch (21). An immersion-type press apparatus for hot-formed steel, characterized by the following features.

15. The container assembly (11) includes four sets of container side plates (111), the four sets of container side plates (111) arranged in a rectangular shape, two sets of container top lid plates (112) are provided above the four sets of container side plates (111), and a container bottom plate (113) is provided below the four sets of container side plates (111). The immersion press apparatus for hot-formed steel according to feature 14.

16. The immersion module (1) further includes an insulating plate assembly (14), the insulating plate assembly (14) includes an insulating side plate (141) provided on the outer surface of the container side plate (111), an insulating bottom plate (142) provided below the insulating side plate (141), and the insulating bottom plate (142) provided below the container bottom plate (113), A junction box (13) is fixedly connected to the outer surface of the aforementioned heat-insulating side plate (141). The junction box (13) is connected to the temperature control electrical box (16) via connecting wires. The immersion press apparatus for hot-formed steel according to feature 15.

17. The molding module (2) includes two sets of lower forming punches (21) provided on the upper side of the container bottom plate (113), with blank holders (22) provided on both sides of the two sets of lower forming punches (21), and multiple sets of positioning pins (23) provided on the outside of the ends of the two sets of lower forming punches (21). The immersion press apparatus for hot-formed steel according to feature 14.

18. The die set module (3) includes a lower die set (31) and a support block (32), with a liquid nozzle (15) provided on one side of the lower die set (31), and the liquid nozzle (15) is in communication with the inside of the container assembly (11). The immersion press apparatus for hot-formed steel according to feature 14.

19. The eject module (4) includes a plurality of eject pins (41) provided on the upper surface of the lower forming punch (21), the eject pins (41) being controlled to move up and down by a hydraulic cylinder eject assembly (42), the hydraulic cylinder eject assembly (42) including a plurality of hydraulic cylinder assemblies (422) and a spring hose (421). The immersion press apparatus for hot-formed steel according to feature 14.

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