Hot forming system and hot forming method for high-surface-quality zinc-based coating steel plate part

Abstract

The invention provides a hot forming system for a high-surface-quality zinc-based coated steel plate part, which comprises an induction heating furnace and a stamping forming device, and further comprises a mechanical arm clamping and transferring device, a hot bath and hot flushing device, a mechanical arm clamping and transferring device and a stamping forming device in sequence between the induction heating furnace and the stamping forming device. The invention further provides a hot forming method, and the hot forming method is suitable for a hot forming system of the high-surface-quality zinc-based coating steel plate part. According to the forming device and method for the high-surface-quality zinc-based coating steel plate part, the formed part has high strength and high surface quality, and the part has excellent corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the field of steel parts processing, and in particular relates to a hot forming system and a hot forming method for zinc-based coated steel plate parts with high surface quality. Background Art

[0002] With the development of the automobile industry, automobile lightweighting has become the focus of research and development in the automotive field, which also promotes the development of the field of high-strength steel. The strength of steel continues to increase, while the plasticity decreases, which leads to a decrease in the cold forming ability of high-strength steel. In order to solve this problem, the hot forming technology of high-strength steel has been gradually applied to the processing of automotive parts. This technology uses steel plates to be stamped after being heated to austenitizing temperature, and is simultaneously cooled and quenched in the mold. It can produce stamping parts with a strength of up to 1500MPa and above, which are widely used in front and rear bumpers, door anti-collision beams, and A-pillars, B-pillars, C-pillars, center channels and other body safety parts. Because it has the dual advantages of reducing weight and improving safety.

[0003] Hot-formed steel includes three types: bare plate (uncoated), aluminum-based coated and zinc-based coated. For bare plate (uncoated) and aluminum-based coated, they can be directly quenched after being taken out of the heating furnace; while for zinc-based coated hot-formed steel, if the zinc-based coated steel plate is taken out of the heating furnace and directly quenched, the steel plate surface faces the risk of liquid metal embrittlement (LME) due to the presence of liquid Zn on the steel plate surface. Therefore, the forming of zinc-based coated hot-formed steel is extremely difficult.

[0004] Chinese patent CN112522689B discloses an alloyed galvanized steel sheet surface treatment agent, preparation method, alloyed galvanized steel sheet, and hot-formed parts. The hot-formed parts are obtained through hot-forming stamping process, and the surface oxide film is dense. However, the process does not evaluate the risk of liquid metal brittleness.

[0005] In order to solve this problem, the patent of this invention provides a hot forming device and a hot forming method for high surface quality zinc-based coated steel plate parts, which can evenly control the cooling temperature of the steel plate and remove the surface oxide layer, effectively avoid the risk of LME of zinc-based coating, ensure the surface quality of the stamped product, and improve the yield rate. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a forming system and a hot forming method for zinc-based coated steel plate parts with high surface quality, aiming to uniformly control the forming temperature of zinc-based coated steel plate parts, effectively prevent the risk of LME (liquid metal embrittlement), and remove the micro-oxide layer on the coating surface to ensure the surface quality of the parts.

[0007] The object of the invention is achieved in this way:

[0008] A hot forming system for high surface quality zinc-based coated steel plate parts, comprising an induction heating furnace and a stamping forming device. The system further comprises a mechanical arm clamping and transferring device, a hot bath + hot washing device, and a mechanical arm clamping and transferring device in sequence between the induction heating furnace and the stamping forming device.

[0009] The induction heating furnace is used to heat the steel plate to a fully austenitized state.

[0010] The robot arm gripping transfer device is located behind the induction heating furnace and is used to transfer the austenitized steel plate to the subsequent hot bath + hot washing device tank.

[0011] The hot bath + hot flushing device includes a hot water circulation tank and a high-pressure hot water nozzle. The high-pressure hot water nozzle is fixed on the side walls of the hot water circulation tank. The high-pressure hot water nozzle is externally connected to a water pipe. Under the joint action of the two, the steel plate completes the process of cooling down and removing micro-oxides on the surface.

[0012] The function of the mechanical arm clamping transfer device is to transfer the cooled steel plate to the stamping forming device. After that, the steel plate completes the subsequent cooling and forming process in the stamping device.

[0013] Furthermore, the mechanical arm of the mechanical arm clamping transfer device is made of high-temperature resistant ceramic material with poor thermal conductivity to prevent local rapid cooling and contamination of the steel plate surface during the clamping process;

[0014] Furthermore, the hot bath water temperature of the hot water flushing is 80-100°C, and the flushing water temperature is 90-100°C; when the steel plate is directly placed in hot water, bubbles will be generated at the interface between the high-temperature steel plate and the hot water. The presence of bubbles affects the heat exchange efficiency, causing uneven cooling of the steel plate. At the same time, the bubbles on the lower surface of the steel plate are not easy to discharge, which will cause deformation of the steel plate. The present invention adopts a hot bath + hot water flushing cooling process. High-pressure hot water flushing can eliminate bubbles on the surface of the steel plate, improve heat exchange efficiency and temperature uniformity of the steel plate, and at the same time, through the adjustment of hot water flushing pressure and water volume and the change of steel plate flushing time, the terminal temperature is effectively controlled to improve the plate shape.

[0015] Furthermore, the high-pressure hot water nozzles are in groups of 2 to 16.

[0016] The second technical solution of the present invention provides a hot forming method using the above-mentioned high surface quality zinc-based coated steel plate component hot forming system,

[0017] Step 1: Place the steel plate in an induction heating furnace, set the heating temperature to 800-905℃, the heating time to 3-10min, and heat the steel plate to the austenitized state; strictly control the heating temperature and heating time to effectively prevent the occurrence of defects such as zinc liquid evaporation, coarse grains, and changes in the coating structure; if the temperature is too low, the steel plate will not be completely austenitized; if the temperature is too high and exceeds the evaporation point of zinc, it will cause the coating to evaporate; if the heating time is less than 3 minutes, the austenitization is not sufficient, and if the time exceeds 10 minutes, the coating will be heavily oxidized, the austenite grains will be coarse, and the Fe-Zn intermetallic compound with good corrosion resistance will completely disappear and transform into α-Fe(Zn) phase.

[0018] Step 2: Use a robotic arm to hold the transfer device and transfer the austenitized steel plate to the top of the hot bath + hot washing device tank; use the natural temperature drop of the steel plate in the air to control the temperature of the steel plate when entering the hot bath + hot washing device tank between 750-780°C; the purpose is to eliminate or minimize the liquid phase in the coating, improve the surface quality of the coating during hot water washing, and at the same time keep the steel plate temperature below 800°C, reduce the deformation of the steel plate during subsequent hot water washing, and improve temperature uniformity.

[0019] Step 3: After the steel plate drops to the target temperature, immerse the steel plate in the hot bath + hot flushing device tank, 10-80cm above the water surface; the hot bath water temperature is 80-100℃, the hot flushing water temperature is 90-100℃, and the hot flushing water pressure is 0.1-10.0MPa; the water temperature sprayed by the high-pressure nozzle is higher than the water temperature in the hot water bath, which can improve the uniformity of steel plate cooling, and at the same time make up for the loss of hot water bath temperature, and improve the cleaning effect of the oxide layer on the surface of the steel plate. The flushing nozzles are distributed on both sides of the steel plate, and can be flushed parallel or perpendicular to the plate surface to ensure the uniformity of the flushing water volume; according to the flushing end temperature requirements, adjust the flushing water volume and the movement speed of the steel plate.

[0020] Step 4: When the temperature of the zinc-based coated steel plate drops to 550-700°C, the zinc-based coated steel plate is transferred to the stamping device using a robotic arm clamping device; if the temperature is too low, the steel plate cannot maintain the austenitized state, and if the temperature is too high, it will cause liquid metal brittleness and severe oxidation on the surface of the steel plate, which is not conducive to improving the surface quality.

[0021] Step 5: The temperature of the zinc-based coated steel plate in the stamping section is 450-650℃, the holding time is 5-10S, the down pressure is 100-400kN, and the temperature out of the stamping section is 100-150℃; the temperature of the zinc-based coated steel plate in the stamping section is 450-650℃ to ensure the strength of the parts after quenching. The coated steel plate needs to be dried with hot air at 100-150℃ after leaving the stamping section for 3-7s; thorough drying of the steel plate is conducive to ensuring surface quality and avoiding corrosion.

[0022] Furthermore, the coating of the zinc-based coated steel sheet is a zinc-based coating or a GI coating or a GA coating.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention provides a forming device for high-surface-quality zinc-coated steel plate parts, the purpose of which is to prevent cracking caused by the brittleness of liquid metal on the surface of the zinc-coated steel plate through the uniform controlled cooling effect of high-temperature water flow; the flushing pressure in the flushing mode can remove the thin oxide layer on the surface of the steel plate, which is beneficial to ensure the surface quality of the parts.

[0025] 2. The present invention provides a forming device and method for high-surface-quality zinc-coated steel plate parts, so that the formed parts have both high strength and high surface quality, and the parts have excellent corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a forming device for a zinc-based coated steel plate component with high surface quality according to the present invention;

[0027] Figure 1 Middle: 1-induction heating furnace; 2-robotic arm clamping and transferring device; 3-heat bath device tank; 4-hot washing nozzle; 5-robotic arm clamping and transferring device; 6-stamping device. DETAILED DESCRIPTION

[0028] The present invention will be further described below by way of examples.

[0029] A hot forming system for high surface quality zinc-based coated steel plate parts, comprising an induction heating furnace and a stamping forming device. The system further comprises a mechanical arm clamping and transferring device 2, a hot bath + hot washing device, and a mechanical arm clamping and transferring device 5 between the induction heating furnace and the stamping forming device.

[0030] The induction heating furnace 1 is used to heat the steel plate to a fully austenitized state.

[0031] The robot arm gripping transfer device 2 is located behind the induction heating furnace and is used to transfer the austenitized steel plate to the subsequent hot bath + hot washing device tank.

[0032] The hot bath + hot flushing device comprises a hot water circulation tank 3 and a high-pressure hot water nozzle 4. The high-pressure hot water nozzle 4 is fixed on the side walls of the hot water circulation tank 3. The high-pressure hot water nozzle 4 is externally connected to a water pipe. Under the joint action of the two, the steel plate completes the process of cooling down and removing the surface micro-oxides.

[0033] The function of the mechanical arm clamping and transferring device 5 is to transfer the cooled steel plate to the stamping and forming device 6. Furthermore, the mechanical arm clamping and transferring device comprises a clamping section, and the mechanical arm of the clamping section is made of high temperature resistant ceramic material with poor thermal conductivity.

[0034] Furthermore, the high-pressure hot water nozzles are in groups of 2 to 16.

[0035] Furthermore, in the hot bath + hot washing device, the hot bath water temperature is 80-100°C, and the hot washing water temperature is 90-100°C;

[0036] A hot forming method is applicable to a hot forming system of a high surface quality zinc-based coated steel plate component of the present invention, the method comprising the following steps:

[0037] S1: placing the zinc-based coated steel plate in an induction heating furnace 1, setting the heating temperature to 800-905°C, the heating time to 3-10 minutes, and heating the steel plate to an austenitized state;

[0038] S2: Using the mechanical arm to hold the transfer device 2, the austenitized steel plate is transferred to the hot water circulation tank 3 of the hot bath + hot washing device; using the natural temperature drop of the steel plate in the air, the temperature of the zinc-based coated steel plate when entering the hot water circulation tank 3 is controlled between 750-780°C;

[0039] S3: After the zinc-based coated steel plate drops to the target temperature, the steel plate is immersed in the hot water circulation tank 3 of the hot bath + hot washing device, with a height of 10-80 cm from the water surface; the hot bath water temperature is 80-100°C, the hot washing water temperature is 90-100°C, and the hot washing water pressure is 0.1-10.0 MPa;

[0040] S4: When the temperature of the zinc-based coated steel sheet drops to 550-700°C, the zinc-based coated steel sheet is transferred to the stamping device by a mechanical arm clamping device;

[0041] S5: The temperature of the zinc-based coated steel sheet in the stamping section is 450-650°C, the holding time is 5-10S, the lower pressure is 100-400kN, and the temperature out of the stamping section is 100-150°C; the zinc-based coated steel sheet is dried with hot air at 100-150°C after exiting the stamping section, and the drying time is 3-7s.

[0042] Furthermore, the coating of the zinc-based coated steel sheet is a zinc-based coating or a GI coating or a GA coating.

[0043] The heating temperature and heating time of the zinc-based coated steel plate of the present invention are shown in Table 1, the various setting parameters of the hot water washing section are shown in Table 2, the various parameter settings of the stamping section are shown in Table 3, and the parameters of the drying process section are shown in Table 4.

[0044] Table 1 Heating temperature and heating time of zinc-based coated steel sheet

[0045] Coating Type Heating temperature / ℃ Heating time / s Example 1 GI 800 10 Example 2 Zn0.5Al 865 6 Example 3 Zn11Al 835 9 Example 4 GA 905 3 Example 5 Zn6Al 850 7.5 Example 6 GI 855 7 Example 7 Zn5Al2Mg 820 9.5 Example 8 GI 870 5.5 Example 9 Zn2Al 880 4.5 Example 10 GA 845 8

[0046] Table 2 Various setting parameters of hot water flushing section

[0047]

[0048] Table 3 Parameter settings of stamping section

[0049]

[0050]

[0051] Table 4 Drying process parameters

[0052] Drying temperature / ℃ Drying time / s Example 1 100 7 Example 2 113 6 Example 3 122 5.5 Example 4 128 5.5 Example 5 130 5 Example 6 137 4.5 Example 7 140 4 Example 8 143 4 Example 9 146 3.5 Example 10 150 3

[0053] The zinc-based coated steel sheets (Examples 2, 3, 5, and 9) using the hot forming system and hot forming method of the present invention have the coating structure from the surface to the steel matrix in the time and temperature range specified by the present invention: surface oxide layer, Fe-Zn intermetallic compound, α-Fe(Zn) phase, and austenite phase. The surface of the steel sheet is an extremely thin oxide film with a thickness of 0.1 to 2um. Under the oxide film is a Fe-Zn alloy phase (gamma phase), and the thickness varies according to the coating thickness and the hot forming process, ranging from 3um to 15um. Under the Fe-Zn alloy phase is a solid solution of a-Fe(Zn) with a thickness of 5um to 20um, containing Zn, and below is a martensitic steel matrix. Both the Fe-Zn alloy phase and the solid solution of a-Fe(Zn) have good corrosion resistance and good coating performance, so the parts have excellent corrosion resistance and coating performance.

[0054] In order to describe the present invention, the present invention is appropriately and fully illustrated by the examples in the above. The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made should be included in the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A hot forming system for high surface quality zinc-coated steel plate parts, comprising an induction heating furnace and a stamping forming device, characterized in that: The system further comprises, in sequence, between the induction heating furnace and the stamping forming device: a mechanical arm clamping and transferring device (2), a hot bath + hot washing device, and a mechanical arm clamping and transferring device (5). The induction heating furnace (1) is used to heat the steel plate to a completely austenitized state. The mechanical arm gripping transfer device (2) is located behind the induction heating furnace and is used to transfer the austenitized steel plate to the subsequent hot bath + hot washing device tank. The hot bath + hot flushing device comprises a hot water circulation tank (3) and a high-pressure hot water nozzle (4). The high-pressure hot water nozzle (4) is fixed on the side walls of both sides of the hot water circulation tank (3). The high-pressure hot water nozzle (4) is externally connected to a water pipe. Under the joint action of the two, the steel plate completes the process of cooling down and removing the micro-oxide on the surface. The function of the mechanical arm clamping and transferring device (5) is to transfer the cooled steel plate to the stamping and forming device (6).

2. The hot forming system for high surface quality zinc-coated steel plate parts according to claim 1, characterized in that: The mechanical arm of the mechanical arm clamping transfer device is made of high-temperature resistant ceramic material with poor thermal conductivity.

3. The hot forming system for high surface quality zinc-coated steel plate parts according to claim 1, characterized in that: The high pressure hot water nozzles are in groups of 2 to 16.

4. A hot forming method, characterized in that: A hot forming system for high surface quality zinc-coated steel plate parts according to any one of claims 1 to 3, wherein the method comprises the following steps: S1: placing the zinc-based coated steel sheet in an induction heating furnace (1), setting the heating temperature to 800-905° C. and the heating time to 3-10 min, and heating the steel sheet to an austenitized state; S2: using a mechanical arm to hold the transfer device (2) and transfer the austenitized steel plate to the top of the hot water circulation tank (3) of the hot bath + hot washing device; using the natural temperature drop of the steel plate in the air, the temperature of the zinc-based coated steel plate when entering the hot water circulation tank (3) is controlled between 750-780°C; S3: After the zinc-based coated steel sheet has dropped to the target temperature, the steel sheet is immersed in a hot water circulation tank (3) of a hot bath + hot washing device, at a height of 10-80 cm from the water surface; wherein the hot bath water temperature is 80-100°C, the hot washing water temperature is 90-100°C, and the hot washing water pressure is 0.1-10.0 MPa; S4: When the temperature of the zinc-based coated steel sheet drops to 550-700°C, the zinc-based coated steel sheet is transferred to the stamping device by a mechanical arm clamping device; S5: The temperature of the zinc-based coated steel sheet in the stamping section is 450-650°C, the holding time is 5-10S, the lower pressure is 100-400kN, and the temperature out of the stamping section is 100-150°C; the zinc-based coated steel sheet is dried with hot air at 100-150°C after exiting the stamping section, and the drying time is 3-7s.

5. A hot forming method according to claim 4, characterized in that: The coating of the zinc-based coated steel sheet is a zinc-based coating or a GI coating or a GA coating.

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