Device and method for producing hot stamped parts

Abstract

An apparatus for producing hot-stamped parts, comprising a furnace unit and a hot-stamping unit, the furnace unit having a plurality of independent, airtight chambers containing a feed chamber (4), a heating chamber (6), and a discharge chamber (8) that are connected one after the other, the hot-stamping unit having a stamping machine (11), and the discharge chamber (8) being connected to the stamping machine (11). A method for producing hot-stamped parts and an aluminum-silicon-coated hot-stamped part. With this apparatus, the blank (1), in particular the aluminum-silicon-coated blank, is heat-treated in an airtight manner and hot-stamped with a stamping machine. The resulting high-strength aluminum-silicon-coated parts have a significantly lower hydrogen content than the high-strength aluminum-silicon-coated parts produced in conventional atmospheric furnaces. The risk of hydrogen embrittlement is lower.Therefore, the invention is particularly suitable for hot-formed aluminum-silicon coated parts with a strength of ≥1500 MPa.

Description

Cross-referenced citations

[0001] The priority claim of Chinese patent application No. 2022115604719 filed on December 7, 2022, and titled "Apparatus and Method for Manufacturing Hot Stamping Parts" and Chinese patent application No. 2022108965356 filed on July 28, 2022, and titled "Apparatus and Method for Manufacturing Hot Stamping Parts" is incorporated herein by reference. Field of the invention

[0002] The invention relates to the technical field of hot stamping, in particular to a device and a method for producing hot stamped parts. State of the art

[0003] In the hot stamping industry, aluminum-silicon coated sheet is currently the most widely used. This aluminum-silicon coated sheet can effectively solve the oxidation problem of the blank during the austenitizing heating process. Therefore, the currently widely used atmospheric furnace does not require oxygen potential control; only the water vapor content needs to be controlled by controlling the dew point. However, during the heating process of continuous mass production in a conventional atmospheric furnace, the aluminum-silicon coating easily reacts with the remaining water vapor in the hot air to generate hydrogen, resulting in hydrogen-induced delayed fracture. Hydrogen-induced delayed fracture, also known as hydrogen embrittlement, is a phenomenon in which hydrogen atoms dissolve in metal materials, leading to performance degradation or embrittlement.Hydrogen accelerates the propagation of cracks in metal, causing the properties of the metal fracture surface to change from ductility to brittleness. Currently, in actual production, the dew point in the austenitizing furnace should be controlled at -15°C ~ -20°C to prevent the formation of water vapor in the furnace, so as to avoid the generation of hydrogen due to the reduction reaction of water vapor with surface elements such as iron, aluminum, and silicon. However, the roller hearth furnace and box-type furnace, which are often used in mass production, do not have multiple airtight chambers. When the blank enters and exits the furnace, outside air containing a large amount of water vapor enters the furnace chamber, making the dew point in the furnace difficult to control. In addition, the blank may remain in the furnace for a long time due to equipment failure.All of these can cause a large amount of hydrogen atoms to be absorbed into the aluminum-silicon coating, raising the risk of hydrogen embrittlement. In addition, dry air is currently introduced into the austenitizing furnace to control the water vapor in the furnace, which can only alleviate the hydrogen absorption problem of the aluminum-silicon coating during the heating process. In the manufacturing process of aluminum-silicon coated sheets, the steel sheets are introduced into the molten aluminum liquid. A large amount of hydrogen is also absorbed in the aluminum liquid. Usually, dry, high-purity nitrogen is introduced into the aluminum liquid to remove hydrogen. However, some hydrogen still remains in the aluminum liquid, which cannot be removed by controlling the dew point in the austenitizing furnace.Vacuum heating is widely used in the heat treatment industry. Since conventional vacuum heating equipment is only suitable for small parts and the heating cycle is measured in hours, it cannot meet the large dimensions and high cycle times (tens of seconds) of automotive body parts. Therefore, heating in the hot forming of aluminum-silicon coated steel sheets has so far been carried out using non-airtight continuous roller hearth furnaces and box-type furnaces.

[0004] With the continuous increase in fuel consumption regulations, the demand for lightweight automobiles is becoming more and more urgent. More and more lightweight materials are being applied to various types of automotive parts. In recent years, press-hardened steel (PHS) has been favored by many automobile manufacturers due to its advantages such as ultra-high strength, good formability, and high dimensional accuracy. Currently, PHS steel with a tensile strength of 1500 MPa is widely used. PHS steel with a tensile strength above 1800 MPa is also mass-produced by some steel mills. The higher the strength, the greater the risk of hydrogen embrittlement. For steel with 1500 MPa, there is already a risk of hydrogen-induced delayed fracture.For steel with a strength of 1800 MPa or even 2000 MPa, the risk of hydrogen-induced delayed fracture is higher and more severe. The problem of hydrogen embrittlement severely limits the application of aluminum-silicon coating materials for ultra-high-strength steels above 1800 MPa. Moreover, the strain rate of coated steel sheets above 1500 MPa must be greater than 5%. The strain rate of coated steel sheets above 1800 MPa is only about 4%, and the bending angle is between 35 and 40 degrees. Insufficient toughness causes coated sheets above 1800 MPa to become brittle during collision, which seriously affects the application of coated sheets above 1800 MPa. Object of the invention

[0005] To overcome the deficiencies of the prior art, solve the problem of hydrogen embrittlement of coated sheets above 1800 MPa, and increase the toughness of coated steel sheets at 1800 MPa, the first object of the invention is to provide an apparatus for producing large quantities of hot stamped parts. The second object of the invention is to provide a method for producing large quantities of hot stamped parts. The third object of the invention is to provide the aluminum-silicon coated hot stamped part produced by this method.

[0006] These objects of the invention are achieved by the following technical solution: First, the invention provides an apparatus for producing large quantities of hot stamped parts, comprising: Oven unit and hot stamping unit, wherein the furnace unit comprises a plurality of independent airtight chambers including a feeding chamber, a heating chamber and a discharge chamber which are sequentially connected, wherein the hot stamping unit comprises a stamping machine, and wherein the discharge chamber is connected to the stamping machine.

[0007] In the above-mentioned apparatus, preferably, the inlet of the feed chamber is provided with an airtight feed furnace door and an airtight first insulation furnace door is provided between the outlet of the feed chamber and the inlet of the heating chamber.

[0008] In the above-mentioned device, preferably the outlet of the discharge chamber is provided with an airtight discharge furnace door, wherein an airtight second insulation furnace door is provided between the inlet of the discharge chamber and the outlet of the heating chamber.

[0009] In the above-mentioned device, the heating chamber is preferably a vacuum chamber or an atmospheric chamber.

[0010] In the above-mentioned apparatus, preferably, when the heating chamber is a vacuum chamber, the degree of vacuum in the heating chamber is 1-10000 Pa, preferably 100-1000 Pa, the temperature in the chamber is 880-1000 °C, preferably 930 °C, and the heating chamber is used for heating a plurality of groups of blanks simultaneously.

[0011] In the above-mentioned device, preferably, when the heating chamber is an atmospheric chamber, the atmosphere in the heating chamber consists of dry air or other dry gases, wherein the dry air or the other dry gas has a water vapor content of less than 1000 ppm (volume fraction), preferably 100 ppm (volume fraction), wherein the pressure in the chamber corresponds to the external atmospheric pressure and the temperature in the chamber is 880-1000 °C, preferably 930 °C, and wherein the heating chamber is used for simultaneously heating several groups of blanks.

[0012] In the above-mentioned device, the temperature of the dispensing chamber is preferably 400-800°C, preferably 600-700°C.

[0013] In the above-mentioned apparatus, a feed platform is preferably provided upstream of the feed chamber and a discharge platform is provided downstream of the discharge chamber. Secondly, the invention provides a method for producing large quantities of hot stamped parts, which uses the above-mentioned apparatus for producing large quantities of hot stamped parts and includes the following steps: the blank is inserted into the airtight feeding chamber and then the feeding chamber is evacuated to achieve a certain degree of vacuum; then the blank is placed in the airtight heating chamber to carry out the austenitizing heating to obtain a hot blank; The hot blank is introduced into the airtight discharge chamber; and the blank from the discharge chamber is transferred to the stamping machine for hot stamping.

[0014] In the above method, preferably, the blank is introduced into the feeding chamber through the feeding furnace door, the blank of the feeding chamber is introduced into the heating chamber through the first insulating furnace door, the blank of the heating chamber is introduced into the discharge chamber through the second insulating furnace door, and the blank of the discharge chamber is sent to the stamping machine through the discharge furnace door.

[0015] In the above-mentioned process, the blank is preferably an aluminum-silicon coated blank.

[0016] In the above method, preferably, when the heating chamber is a vacuum chamber, the blank is introduced into the feeding chamber through the feeding furnace door, and then the feeding chamber is evacuated to a vacuum degree of over 10000 Pa, preferably 100-1000 Pa; and after the vacuum degree in the feeding chamber becomes close to the vacuum degree of the heating chamber, the first insulation furnace door between the feeding chamber and the heating chamber is opened, and the blank is introduced into the heating chamber to perform austenitizing heating, after which the first insulation furnace door between the feeding chamber and the heating chamber is closed.

[0017] In the above-mentioned method, preferably, when the heating chamber is a vacuum chamber, the discharge chamber is evacuated to a vacuum level of over 10000 Pa, preferably 100-1000 Pa, before the blank is ready for discharge from the furnace after the heat treatment in the heating chamber; and after the degree of vacuum in the discharge chamber is close to the degree of vacuum in the heating chamber, the second insulation furnace door between the discharge chamber and the heating chamber is opened and the blank is introduced into the discharge chamber, after which the second insulation furnace door between the discharge chamber and the heating chamber is closed; and Before the discharge furnace door of the discharge chamber is opened, dry air or other dry gas is introduced into the discharge chamber until the outside air pressure is reached, after which the discharge furnace door is opened.

[0018] In the above-mentioned method, preferably, when the heating chamber is a dry atmosphere chamber, the feeding chamber is evacuated to a vacuum degree of over 10000 Pa, preferably 100-1000 Pa, after the blank enters the feeding chamber through the feeding furnace door, after which the dry air or other dry gas is introduced into the feeding chamber, wherein the water vapor content of the dry air or other dry gas is lower than 1000 ppm, preferably 100 ppm; and After the air pressure in the feeding chamber is close to the air pressure of the heating chamber, the first insulation furnace door between the feeding chamber and the heating chamber is opened and the tube ring is introduced into the heating chamber to carry out austenitizing heating, after which the first insulation furnace door between the feeding chamber and the heating chamber is closed.

[0019] In the above-mentioned method, preferably, when the heating chamber is a vacuum chamber, the discharge chamber is evacuated to a vacuum degree of over 10,000 Pa, preferably 100-1,000 Pa, before the blank is ready to be discharged from the furnace after the heat treatment in the heating chamber, and then the dry air or other dry gas is filled into the discharge chamber, the water vapor content of the dry air or other dry gas being lower than 1,000 ppm, preferably 100 ppm; after the vacuum degree in the discharge chamber is close to the vacuum degree in the heating chamber, the second insulation furnace door between the discharge chamber and the heating chamber is opened and the blank is placed into the discharge chamber, after which the second insulation furnace door between the discharge chamber and the heating chamber is closed;and before the discharge furnace door of the discharge chamber is opened, the dry air or other dry gas is filled into the discharge chamber until the outside air pressure is reached, after which the discharge furnace door is opened.;

[0020] In the above-mentioned method, the process of hot stamping in the stamping machine preferably includes laser welding of the delivered blank.

[0021] In the above-mentioned method, it is preferable to control the temperature of the blank during hot stamping in the stamping machine in the range of 500-700 °C and the heating rate lower than 7 °C / s.

[0022] Thirdly, the invention provides an aluminum-silicon coated hot stamping part manufactured by the above-mentioned method.

[0023] For the above-mentioned aluminum-silicon coated hot stamping part, the tensile strength of the hot stamping part is preferably ≥1500 MPa.

[0024] For the above-mentioned aluminum-silicon coated hot stamping part, the production cycle of the hot stamping part is preferably 20 - 40 seconds.

[0025] The advantages of the invention are as follows: The present invention uses a furnace with airtight chambers and evacuates these chambers to achieve a vacuum level of over 10,000 Pa. The water vapor content in the furnace is reduced to less than 1,000 ppm, and the corresponding dew point value of 1,000 ppm is approximately -15°C. Two heating methods can be used. In one method, the furnace is evacuated with independent chambers, and then dry air with a lower dew point is introduced to ensure that the air pressure inside and outside the furnace remains the same. In the other method, heating is carried out in the airtight chambers at a certain vacuum level, i.e., vacuum heating. In addition, vacuum heating promotes the diffusion of hydrogen in the raw material into the vacuum, thereby reducing the hydrogen content in the raw material. By using three independent airtight chambers, the disadvantages of general vacuum furnaces are cleverly avoided.That is, the atmosphere of the heating chamber, which simultaneously accommodates multiple groups of blanks, is always maintained at a certain vacuum level or a certain dry atmosphere. There is no need to frequently evacuate the heating chamber from atmospheric pressure to a certain vacuum level. This not only prevents damage to the evacuation equipment caused by high-temperature pumping, but also eliminates the long time required to evacuate large-volume chambers. Only the feed chamber and the discharge chamber are evacuated. The feed chamber and the discharge chamber accommodate only one group of blanks, thus having a small volume and a short evacuation time.If only a single independent chamber is used for feeding, discharging, and heating, firstly, evacuating high-temperature gas above 900°C will cause serious damage to the evacuation equipment. Secondly, since multiple groups of blanks need to be heated simultaneously in mass production, the evacuation time will be too long if the space of the feeding chamber and discharging chamber is too large. The discharging chamber has a certain furnace temperature, which is also one of the inventive points of the present invention. The reason is that after the austenitizing heating, the blank must be quickly transported to the stamping machine for stamping. If the transportation time exceeds 12 seconds, the martensite content in the product after hot stamping and quenching will be insufficient, and the mechanical properties of the product will be unqualified.When the blank comes out of the heating chamber and passes through the discharge chamber, there is a waiting time in the discharge chamber for the furnace door to open outside the discharge chamber. This results in the transportation time of the blank to the stamping machine being too long, thereby affecting the mechanical properties of the product. The inventor's research found that if the discharge chamber maintains a certain temperature, the blank can maintain a sufficient temperature while waiting in the discharge chamber, thereby qualifying the mechanical properties of the product after stamping. Although the discharge chamber also needs to be evacuated, the gas temperature is much lower than that of the heating chamber, so the evacuation system is not affected.

[0026] In order to make the above and other objects, features and advantages of the present invention more clearly understood, preferred embodiments will be described in detail below with reference to the accompanying drawings. Brief description of the drawings

[0027] In order to more clearly explain the embodiments of the present invention or the technical solutions in the related art, the drawings to be used in describing the embodiments or related art are briefly presented below. Of course, these are only some embodiments of the present invention. Those of ordinary skill in the art can create other drawings based on these drawings without requiring creative effort. Fig.1 is a schematic representation of the structure of the device for producing large quantities of hot stamped parts of the invention, Fig. 2 is a picture of the result of the spot welding test of the hot stamping part of Embodiment 1 of the invention, Fig. 3 is a picture of the result of the structural bonding test of the hot stamping part of Embodiment 1 of the invention, Fig. 4 is a picture of the result of the electrophoretic coating test of the hot stamping part of the invention. Description of the preferred embodiments

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort fall within the scope of the present invention.

[0029] The embodiment of the present invention provides an apparatus for producing large quantities of hot stamped parts. As shown in Fig. 1, the device comprises: Oven unit and hot stamping unit. The oven unit has several independent airtight chambers, including a feed chamber 4, a heating chamber 6, and a discharge chamber 8, which are connected in series. The hot stamping unit has an embossing machine 11. The discharge chamber 8 is connected to the embossing machine 11.

[0030] In a preferred embodiment, the entrance of the feed chamber 4 is provided with an airtight feed furnace door 3. Between the exit of the feed chamber 4 and the entrance of the heating chamber 6, an airtight first insulating furnace door 5 is provided.

[0031] In a preferred embodiment, the outlet of the discharge chamber 8 is provided with an airtight discharge oven door 9. Between the inlet of the discharge chamber 8 and the outlet of the heating chamber 6, an airtight second insulating oven door 7 is provided.

[0032] In a preferred embodiment, the heating chamber 6 is a vacuum chamber or an atmospheric chamber.

[0033] If the heating chamber 6 is a vacuum chamber in a preferred embodiment, the degree of vacuum in the heating chamber 6 is 1-10000 Pa, preferably 100-1000 Pa. The temperature in the chamber is 880-1000 °C, preferably 930 °C. The heating chamber 6 is used for simultaneous heating of several groups of blanks.

[0034] In a preferred embodiment, when the heating chamber 6 is an atmospheric chamber, the atmosphere in the heating chamber 6 consists of dry air or other dry gases. The dry air or other dry gas has a water vapor content of less than 1000 ppm (volume fraction), preferably 100 ppm (volume fraction). The pressure in the chamber corresponds to the external atmospheric pressure, and the temperature in the chamber is 880-1000 °C, preferably 930 °C. The heating chamber 6 is used for simultaneously heating multiple groups of blanks.

[0035] In a preferred embodiment, the temperature of the dispensing chamber 8 is 400-800°C, preferably 650°C.

[0036] In a preferred embodiment, a feed platform 2 is provided upstream of the feed chamber 4. A discharge platform 10 is provided downstream of the discharge chamber 8.

[0037] This embodiment also provides a method for producing large quantities of hot stamped parts. The method is carried out using the above-mentioned apparatus and includes the following steps: The blank 1 is introduced into the airtight feed chamber 4 and then the feed chamber 4 is evacuated to achieve a certain degree of vacuum.

[0038] The blank is then placed in the airtight heating chamber 6 to perform austenitizing heating to obtain a hot blank.

[0039] The hot blank is introduced into the airtight dispensing chamber 8.

[0040] The blank from the discharge chamber 8 is transferred to the embossing machine 11 for hot stamping.

[0041] In a preferred embodiment, the blank 1 is introduced into the feed chamber 4 through the feed furnace door 3. The blank from the feed chamber 4 is introduced into the heating chamber 6 through the first insulation furnace door 5. The blank from the heating chamber 6 is introduced into the discharge chamber 8 through the second insulation furnace door 7. The blank from the discharge chamber 8 is sent to the embossing machine 11 through the discharge furnace door 9.

[0042] In a preferred embodiment, the blank 1 is an aluminum-silicon coated blank.

[0043] If, in a preferred embodiment, the heating chamber 6 is a vacuum chamber, the blank 1 is introduced into the feed chamber 4 through the feed furnace door 3. Then, the feed chamber 4 is evacuated to a vacuum level of over 10,000 Pa, preferably 100-1,000 Pa.

[0044] After the vacuum level in the feed chamber 4 approaches the vacuum level in the heating chamber 6, the first insulation furnace door 5 between the feed chamber 4 and the heating chamber 6 is opened, and the blank is introduced into the heating chamber 6 to perform austenitizing heating. Then, the first insulation furnace door 5 between the feed chamber 4 and the heating chamber 6 is closed.

[0045] If, in a preferred embodiment, the heating chamber 6 is a vacuum chamber, the discharge chamber 8 is evacuated to a vacuum level of over 10,000 Pa, preferably 100-1,000 Pa, before the blank is ready for discharge from the furnace after the heat treatment in the heating chamber 6.

[0046] After the vacuum level in the discharge chamber 8 approaches the vacuum level in the heating chamber 6, the second insulation furnace door 7 between the discharge chamber 8 and the heating chamber 6 is opened, and the blank is introduced into the discharge chamber 8. Subsequently, the second insulation furnace door 7 between the discharge chamber 8 and the heating chamber 6 is closed.

[0047] Before the discharge furnace door 9 of the discharge chamber 8 is opened, dry air or another dry gas is introduced into the discharge chamber 8 until the outside air pressure is reached. Then, the discharge furnace door 9 is opened.

[0048] In a preferred embodiment, when the heating chamber 6 is a dry atmosphere chamber, the feed chamber 4 is evacuated to a vacuum level of over 10,000 Pa, preferably 100-1,000 Pa, after the blank 1 enters the feed chamber 4 through the feed furnace door 3. Then, the dry air or other dry gas is introduced into the feed chamber 4. The water vapor content of the dry air or other dry gas is less than 1,000 ppm, preferably 100 ppm.

[0049] After the air pressure in the feed chamber 4 is close to the air pressure in the heating chamber 6, the first insulation furnace door 5 between the feed chamber 4 and the heating chamber 6 is opened, and the tubular ring is introduced into the heating chamber 6 to perform austenitizing heating. Then, the first insulation furnace door 5 between the feed chamber 4 and the heating chamber 6 is closed.

[0050] If, in a preferred embodiment, the heating chamber 6 is a vacuum chamber, the discharge chamber 8 is evacuated to a vacuum level of over 10,000 Pa, preferably 100-1,000 Pa, before the blank is ready for discharge from the furnace after heat treatment in the heating chamber 6. Then, the dry air or other dry gas is introduced into the discharge chamber 8. The water vapor content of the dry air or other dry gas is less than 1,000 ppm, preferably 100 ppm.

[0051] After the vacuum level in the discharge chamber 8 approaches the vacuum level in the heating chamber 6, the second insulation furnace door 7 between the discharge chamber 8 and the heating chamber 6 is opened, and the blank is introduced into the discharge chamber 8. Subsequently, the second insulation furnace door 7 between the discharge chamber 8 and the heating chamber 6 is closed.

[0052] Before opening the discharge furnace door 9 of the discharge chamber 8, dry air or other dry gas is introduced into the discharge chamber 8 until the outside air pressure is reached. Then, the discharge furnace door 9 is opened.

[0053] In a preferred embodiment, the process of hot stamping in the stamping machine 11 includes laser welding of the delivered blank.

[0054] In a preferred embodiment, the temperature of the blank during hot stamping in the stamping machine 11 is controlled in the range of 500-700 °C and the heating rate is controlled to be lower than 7 °C / s.

[0055] This embodiment also provides an aluminum-silicon coated hot stamping part manufactured by the above-mentioned method.

[0056] In a preferred embodiment, the tensile strength of the hot stamped part is ≥1500 MPa. In a preferred embodiment, the production cycle of the hot stamped part is 20-40 seconds.

[0057] In the following, the invention is described in detail using specific embodiments: Embodiment 1:

[0058] First, the 1.8mm aluminum-silicon clad blank with a tensile strength of 1800 MPa is fed into a vacuum furnace with three airtight chambers for hot stamping. The three chambers are the feeding chamber 4, the heating chamber 6, and the discharge chamber 8. The vacuum degree of the vacuum furnace heating chamber is 10 Pa. The process is as follows: Before the blank enters the feeding chamber 4, air is injected into the feeding chamber 4 to reach the outside air pressure. Then, the feeding furnace door 3 is opened, the blank is inserted, and the feeding furnace door 3 is closed. The feeding chamber 4 is evacuated until a vacuum degree of 10-100 Pa is reached. Then, the airtight first insulation furnace door 5 between the feeding chamber 4 and the heating chamber 6 is opened, and the blank is introduced into the heating chamber 6 for heating. After austenitizing heating, the blank is placed into the discharge chamber 8.Before opening the airtight second insulation furnace door 7 between the heating chamber 6 and the discharge chamber 8, the discharge chamber 8 must first be evacuated to a vacuum degree of 10-100 Pa. Then, the second insulation furnace door 7 is opened, and the blank is placed into the discharge chamber 8. Then, the second insulation furnace door 7 is closed. Before opening the discharge furnace door 9, dry air or other dry gas with a dew point of -45°C is introduced until it reaches the outside air pressure. Then, the discharge furnace door 9 is opened. The furnace temperature is 930 degrees, and the heating time is 300 seconds. The blank is discharged from the furnace door and sent to the stamping machine 11 for stamping. Embodiment 2:

[0059] First, the 1.8mm aluminum-silicon clad blank with a tensile strength of 1800 MPa is fed into a vacuum furnace with three airtight chambers for hot stamping. The three chambers are the feeding chamber 4, the heating chamber 6, and the discharge chamber 8. The vacuum degree of the vacuum furnace heating chamber is 10 Pa. The process is as follows: Before the blank enters the feeding chamber 4, air is injected into the feeding chamber 4 to reach the outside air pressure. Then, the feeding furnace door 3 is opened, the blank is inserted, and the feeding furnace door 3 is closed. The feeding chamber 4 is evacuated until a vacuum degree of 10-100 Pa is reached. Then, the airtight first insulation furnace door 5 between the feeding chamber 4 and the heating chamber 6 is opened, and the blank is introduced into the heating chamber 6 for heating. After austenitizing heating, the blank is placed into the discharge chamber 8.Before opening the airtight second insulation furnace door 7 between the heating chamber 6 and the discharge chamber 8, the discharge chamber 8 must first be evacuated to a vacuum degree of 10-100 Pa. Then, the second insulation furnace door 7 is opened, and the blank is placed into the discharge chamber 8. Then, the second insulation furnace door 7 is closed. Before opening the discharge furnace door 9, dry air or other dry gas with a dew point of -45°C is introduced until the outside air pressure is reached. Then, the discharge furnace door 9 is opened. The furnace temperature is 930 degrees, and the heating time is 600 seconds. The blank is discharged from the furnace door and sent to the stamping machine 11 for stamping. Embodiment 3:

[0060] First, the 1.8 mm aluminum-silicon coated blank sheet with a tensile strength of 1800 MPa is fed into a vacuum furnace with three airtight chambers for hot stamping. The three chambers are the feeding chamber 4, the heating chamber 6, and the discharge chamber 8. The atmospheric dew point of the heating chamber 6 of the atmospheric furnace is -45°C, and the air pressure is atmospheric pressure. The process is as follows: Before the blank enters the feeding chamber 4, air is introduced into the feeding chamber 4 to achieve the outside air pressure. Then, the feeding furnace door 3 is opened, the blank is inserted, and the feeding furnace door 3 is closed. The feeding chamber 4 is evacuated until a vacuum level of 10-100 Pa is reached. Then, the dry air with a dew point of -45°C is filled into the feed chamber 4 until the air pressure, ie atmospheric pressure, is reached in the heating chamber 6.Then, the airtight first insulation furnace door 5 between the feeding chamber 4 and the heating chamber 6 is opened, and the blank is placed into the heating chamber 6 for heating. After austenitizing heating, the blank is placed into the discharge chamber 8. Before the airtight second insulation furnace door 7 between the heating chamber 6 and the discharge chamber 8 is opened, the discharge chamber 8 must first be evacuated to a vacuum degree of 10-100 Pa and filled with dry air with a dew point of -45°C to achieve air pressure, that is, atmospheric pressure, in the heating chamber 6. Then, the second insulation furnace door 7 is opened, and the blank is placed into the discharge chamber 8. After that, the second insulation furnace door 7 is closed. The furnace temperature is 930 degrees, and the heating time is 300 seconds. After that, the discharge furnace door 9 is opened.The blank is discharged from the furnace door and sent to the stamping machine 11 to perform the stamping forming. Comparison example 1:

[0061] First, the 1.8 mm thick, 1800 MPa aluminum-silicon-coated 22MnB5 sheet is placed in an atmospheric furnace with a dew point of -5 °C for hot stamping. The furnace temperature is 930 °C and the heating time is 300 seconds. After the austenitizing heating, the sheet is sent to the stamping machine for stamping. Comparison example 2:

[0062] First, the 1.8 mm thick, 1800 MPa aluminum-silicon coated 22MnB5 sheet is placed in an atmospheric furnace with a dew point of -5 °C for hot stamping. The furnace temperature is 930 °C and the heating time is 600 seconds. After the austenitizing heating, the sheet is sent to the stamping machine for stamping. Comparison example 3:

[0063] First, the 1.8 mm thick, 1800 MPa aluminum-silicon-coated 22MnB5 sheet is placed in an atmospheric furnace with a dew point of -15 °C for hot stamping. The furnace temperature is 930 °C and the heating time is 300 seconds. After the austenitizing heating, the sheet is sent to the stamping machine for stamping. Comparison example 4:

[0064] First, the 1.8 mm thick, 1800 MPa aluminum-silicon coated 22MnB5 sheet is placed in an atmospheric furnace with a dew point of -15 °C for hot stamping. The furnace temperature is 930 °C and the heating time is 600 seconds. After the austenitizing heating, the sheet is sent to the stamping machine for stamping. Table 1 Performance results of embodiments and comparative examples Oven Degree of vacuum dew point Heating time Tensile strength / MPa Yield strength / MPa Elongation % Three-point bend Hardness / HV Hydrogen content / ppm Embodiment 1 5pa / 300s 1874,01 1376,25 6,16 50,98° 619,5 0,03 Embodiment 2 5pa / 600s 1863,41 1372,69 7 52,51° 619,5 0,01 Comparison example 1 101523pa -5 °C 300s 1633,98 1340,33 1,66 34,29° 615,6 0,17 Comparison example 2 101523pa -5 °C 600s 1735,56 1388,7 2,64 36,55° 612.4 0,18 Comparison example 3 101523pa -15 °C 300s 1895,69 1388,35 4,5 41,35° 595,8 0,09 Comparison example 4 101523pa -15 °C 600s 1819,97 1371,35 4,12 43,07° 590,8 0,1

[0065] The parts manufactured in Embodiment 1, Embodiment 2, and Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 were sprayed with neutral salt spray for 10 minutes every 4 hours. The results are shown in Table 2. Table 2 Comparison results of four-point bending performance between embodiments and comparative examples Oven atmosphere Four-point bending Embodiment 1 5pa OK Embodiment 2 5pa OK Comparison example 1 -5 °C OK Comparison example 2 -5 °C crack Comparison example 3 -15 °C OK Comparison example 4 -15 °C crack

[0066] A spot welding test was conducted on the parts manufactured in Embodiment 1. The test results are shown in Table 3 and Fig. 2. It can be seen that the welding performance is OK. Table 3: Results of the spot welding test Condition Serial number Tensile strength Weld core Embodiment 1 1# 17,71 5,4 2# 23,14 7,4 3# 24,77 6,3 4# 25,41 6,7

[0067] A structural bonding test was conducted on the parts manufactured in embodiment 1. The results are shown in Fig. 3. It can be seen that the adhesive performance is OK.

[0068] An electrophoretic coating test was carried out on the parts produced in Example 1. The results are shown in Fig. 4. It can be seen that the coating properties are OK.

[0069] Furthermore, it can be seen from Table 1 and Table 2 that the parts produced by the inventive method have a lower diffusible hydrogen content, higher elongation than those produced by the normal atmospheric furnace method, better bending performance, and a lower risk of hydrogen embrittlement. There are no problems with welding, bonding, or coating performance. This is because, in the vacuum state of the inventive method, fewer H2O molecules react with the aluminum-silicon coating when the parts are heated, and less diffusible hydrogen is generated by the reaction. When heated in a normal atmospheric furnace, there are more H2O molecules in the furnace that react with the aluminum-silicon coating, thereby generating more hydrogen, which penetrates the heated austenitic blank.After cooling, the stress and defects in the martensite increase, increasing the risks of strain, bend angle, and hydrogen embrittlement. The present invention uses specific embodiments to illustrate the principles and implementation of the present invention. The description of the above embodiments is only intended to illustrate the method of the present invention and its core ideas. Changes in the specific implementation and scope of application will occur to those of ordinary skill in the art based on the ideas of the present invention. In summary, the content of this description should not be construed as limiting the present invention. List of reference symbols

[0070] Reference symbols: 1 blank, 2 feeding platform, 3 feeding furnace door, 4 feeding chamber, 5 first insulation furnace door, 6 heating chamber, 7 second insulation furnace door, 8 discharge chamber, 9 discharge furnace door, 10 discharge platform, 11 embossing machine QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] CN 2022115604719

[0001]

Claims

[1] Apparatus for producing large quantities of hot stamped parts, comprising: Oven unit and hot stamping unit, wherein the furnace unit comprises a plurality of independent airtight chambers including a feed chamber (4), a heating chamber (6) and a discharge chamber (8) which are connected in series, wherein the hot stamping unit comprises a stamping machine (11), and wherein the discharge chamber (8) is connected to the stamping machine (11). [2] Device according to claim 1, characterized by that the entrance of the feed chamber (4) is provided with an airtight feed furnace door (3) and an airtight first insulation furnace door (5) is provided between the exit of the feed chamber (4) and the entrance of the heating chamber (6). [3] Device according to claim 1, characterized bythat the outlet of the discharge chamber (8) is provided with an airtight discharge oven door (9), wherein an airtight second insulating oven door (7) is provided between the inlet of the discharge chamber (8) and the outlet of the heating chamber (6). [4] Device according to one of claims 1 to 3, characterized by that the heating chamber (6) is a vacuum chamber or an atmospheric chamber. [5] Device according to claim 4, characterized by that, when the heating chamber (6) is a vacuum chamber, the degree of vacuum in the heating chamber (6) is 1-10000 Pa, preferably 100-1000 Pa, the temperature in the chamber being 880-1000 °C, preferably 930 °C, and the heating chamber (6) is used for heating several groups of blanks simultaneously. [6] Device according to claim 4, characterized bythat, when the heating chamber (6) is an atmospheric chamber, the atmosphere in the heating chamber (6) consists of dry air or other dry gases, wherein the dry air or the other dry gas has a water vapor content of less than 1000 ppm (volume fraction), preferably 100 ppm (volume fraction), wherein the pressure in the chamber corresponds to the external atmospheric pressure and the temperature in the chamber is 880-1000 °C, preferably 930 °C, and wherein the heating chamber (6) is used for simultaneously heating several groups of blanks. [7] Device according to claim 1, characterized by that the temperature of the discharge chamber (8) is 400-800°C, preferably 600-700°C. [8] Device according to claim 1, characterized by that a feed platform (2) is provided upstream of the feed chamber (4) and a discharge platform (10) is provided downstream of the discharge chamber (8). [9] A method for producing large quantities of hot stamped parts, which uses the apparatus for producing large quantities of hot stamped parts according to any one of claims 1 to 8 and includes the following steps: the blank (1) is introduced into the airtight feed chamber (4) and then the feed chamber (4) is evacuated to achieve a certain degree of vacuum; then the blank is placed in the airtight heating chamber (6) to carry out the austenitizing heating to obtain a hot blank; the hot blank is introduced into the airtight dispensing chamber (8); and the blank from the discharge chamber (8) is transferred to the embossing machine (11) for hot stamping. [10] Method according to claim 9, characterized bythat the blank (1) is introduced through the feed furnace door (3) into the feed chamber (4), the blank of the feed chamber (4) is introduced through the first insulation furnace door (5) into the heating chamber (6), the blank of the heating chamber (6) is introduced through the second insulation furnace door (7) into the discharge chamber (8) and the blank of the discharge chamber (8) is sent through the discharge furnace door (9) to the embossing machine (11). [11] Method according to claim 9, characterized by that the blank (1) is an aluminum-silicon coated blank. [12] Method according to claim 10, characterized bythat, when the heating chamber (6) is a vacuum chamber, the blank (1) is introduced into the feeding chamber (4) through the feeding furnace door (3) and then the feeding chamber (4) is evacuated to a vacuum degree of over 10000 Pa, preferably 100-1000 Pa; and after the vacuum degree in the feeding chamber (4) becomes close to the vacuum degree of the heating chamber (6), the first insulation furnace door (5) between the feeding chamber (4) and the heating chamber (6) is opened and the blank is introduced into the heating chamber (6) to carry out the austenitizing heating, after which the first insulation furnace door (5) between the feeding chamber (4) and the heating chamber (6) is closed. [13] Method according to claim 10 or 12, characterized bythat, if the heating chamber (6) is a vacuum chamber, the discharge chamber (8) is evacuated to a vacuum degree of over 10,000 Pa, preferably 100-1,000 Pa, before the blank is ready for discharge from the furnace after the heat treatment in the heating chamber (6); and after the vacuum degree in the discharge chamber (8) approaches the vacuum degree in the heating chamber (6), the second insulation furnace door (7) between the discharge chamber (8) and the heating chamber (6) is opened and the blank is introduced into the discharge chamber (8), after which the second insulation furnace door (7) between the discharge chamber (8) and the heating chamber (6) is closed; and before the discharge furnace door (9) of the discharge chamber (8) is opened, dry air or another dry gas is introduced into the discharge chamber (8) until the outside air pressure is reached, after which the discharge furnace door (9) is opened. [14] Method according to claim 10, characterized bythat, when the heating chamber (6) is a dry atmosphere chamber, the feed chamber (4) is evacuated to a vacuum degree of over 10000 Pa, preferably 100-1000 Pa, after the blank (1) enters the feed chamber (4) through the feed furnace door (3); then the dry air or other dry gas is introduced into the feed chamber (4), the water vapor content of the dry air or other dry gas being less than 1000 ppm, preferably 100 ppm; and after the air pressure in the feed chamber (4) is close to the air pressure of the heating chamber (6), the first insulation furnace door (5) between the feed chamber (4) and the heating chamber (6) is opened and the tube ring is introduced into the heating chamber (6) to carry out the austenitizing heating, after which the first insulation furnace door (5) between the feed chamber (4) and the heating chamber (6) is closed. [15] Method according to claim 10 or 12, characterized bythat, if the heating chamber (6) is a vacuum chamber, the discharge chamber (8) is evacuated to a vacuum level of over 10,000 Pa, preferably 100-1,000 Pa, before the blank is ready for discharge from the furnace after the heat treatment in the heating chamber (6), and then the dry air or other dry gas is filled into the discharge chamber (8), wherein the water vapor content of the dry air or other dry gas is lower than 1,000 ppm, preferably 100 ppm; after the vacuum level in the discharge chamber (8) approaches the vacuum level in the heating chamber (6), the second insulating furnace door (7) between the discharge chamber (8) and the heating chamber (6) is opened and the blank is introduced into the discharge chamber (8), after which the second insulating furnace door (7) between the discharge chamber (8) and the heating chamber (6) is closed;and before the discharge oven door (9) of the discharge chamber (8) is opened, the dry air or other dry gas is filled into the discharge chamber (8) until the outside air pressure is reached, after which the discharge oven door (9) is opened.; [16] Method according to claim 9 or 10, characterized by that the hot stamping process in the stamping machine (11) includes laser welding of the delivered blank. [17] Method according to claim 9 or 10, characterized by that the temperature of the blank during hot stamping in the stamping machine (11) is controlled in the range of 500-700 °C and the heating rate is lower than 7 °C / s. [18] An aluminum-silicon coated hot stamped part produced by the method according to any one of claims 9 to 17. [19] Aluminum-silicon coated hot stamping part according to claim 18, characterized by that the tensile strength of the hot stamped part is ≥1500 MPa. [20] Aluminum-silicon coated hot stamping part according to claim 18, characterized by that the production cycle of the hot stamping part is 20 - 40 seconds.

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