Floating punch hot forming die and hot stamping forming method for steel patch plate

Abstract

This patent discloses a floating punch hot forming die for a steel patch plate, including an upper die seat, a lower die seat, a concave die and a fixed punch. A floating punch is movably installed inside the fixed punch, and the upper surface of the floating punch is lower than the upper surface of the fixed punch. A nitrogen spring is provided between the bottom of the floating punch and the inner bottom end of the fixed punch or the lower die seat to push the floating punch upward in normal state, and the floating punch can move vertically up and down inside the fixed punch. The use of this die for hot stamping of steel patch plates can ensure that the sheet material is evenly pressed everywhere, complete the stamping, and the main plate and the patch plate are cooled and quenched synchronously, which improves production efficiency, makes the martensite completely transformed, and improves the hardness of the steel patch plate.

Description

Technical Field

[0001] This patent relates to a forming die and a forming method, specifically to a floating punch hot forming die and a hot stamping forming method for a steel patch plate, and belongs to the field of steel patch plate processing. Background Art

[0002] The hot forming of high-strength steel patch plates first spot welds the main plate and the hot stamped steel plate of the patch plate together, then heats the whole to about 930°C in a heating furnace and keeps it warm for a certain period of time, then completes the stamping in the hot forming mold, and finally performs pressure quenching through the cooling pipes of the male and female molds. Compared with traditional hot forming and ordinary stamping, the hot forming technology of patch plates is more complicated, and the mold design and stroke control are more difficult. Pressure quenching is a very important part of the hot forming of patch plates, which will directly affect the transformation process of austenite to martensite and the performance of the product.

[0003] During pressure quenching, the heat transfer coefficient between the sheet and the mold is mainly affected by the gap and contact pressure. Figure 4 , 5 The smaller the gap between the sheet and the mold, the greater the contact heat transfer coefficient, and the faster the sheet cools; the greater the contact pressure between the sheet and the mold, the greater the contact heat transfer coefficient, and the faster the sheet cools.

[0004] For conventional steel patch plate floating punch hot forming dies when working, see Figure 2 , 3 , because the thickness of the patch plate 4 has a tolerance of ±0.05mm, this tolerance brings the following results. If the patch plate 4 takes the negative tolerance lower limit, when the concave film 2 and the convex mold 11 are closed up and down, the upper and lower surfaces of the main material plate 3 are in contact with the concave film 2 and the convex mold 11 respectively, but the gap 12 between the lower surface of the patch plate 4 welded on the lower surface of the main material plate 3 and the bottom surface of the convex mold cavity is 0.05mm (see Figure 2 ).

[0005] If the patch plate 4 takes the upper limit of the positive tolerance, when the concave film 2 and the punch 11 are clamped together, the lower surface of the patch plate 4 contacts the bottom surface of the punch cavity, but the gap 13 between the main plate 3 and the upper surface of the punch is 0.05 mm (see Figure 3 ).

[0006] The above-mentioned gap exists between the sheet and the die, resulting in the pressure of the press cannot be evenly applied to the main sheet 3 and the patch sheet 4 through the upper and lower die seats and the concave and convex dies. Taking the negative tolerance of the patch sheet 4 as an example, the gap between the patch sheet 4 in the convex die cavity and the bottom surface of the die cavity is 0.05mm. The direct impact of this result is that the main sheet cools down several times faster than the patch sheet, resulting in low production efficiency. At the same time, the different cooling speeds cause incomplete transformation of martensite, thereby reducing the hardness of the parts. Summary of the invention

[0007] The purpose of this patent is to provide a floating punch hot forming mold for steel patch plates, which can simultaneously press and form the upper and lower surfaces of the sheet material by the mold when the mold is closed, so that the steel patch plates produced by multiple cavities can be cooled under the same conditions to achieve optimal production efficiency and protection of the mold, while ensuring the hardness and other mechanical properties of the steel patch plates.

[0008] The purpose of this patent can be achieved through the following technical solutions:

[0009] A floating punch thermoforming die for a steel patch plate comprises an upper die base, a lower die base, a die connected to the bottom of the upper die base, and a fixed punch connected to the top of the lower die base, wherein a floating punch is movably installed inside the upper end of the fixed punch, the upper surface of the floating punch is lower than the upper surface of the fixed punch, and a nitrogen spring is arranged between the bottom of the floating punch and the inner bottom end of the fixed punch or the lower die base to push the floating punch upward in normal state, and the floating punch can move vertically up and down inside the fixed punch.

[0010] Beneficial effects: During the sheet forming process, the die and the fixed punch are closed, the main sheet is squeezed in the middle, and at the same time the nitrogen spring can drive the floating punch to move upward, thereby pushing the patch plate. In this way, the upper and lower surfaces of the sheet fit the mold at the same time and are pressed and formed by the mold, eliminating the influence of the thickness tolerance of the patch plate and improving the production efficiency and the hardness of the produced parts.

[0011] As a technical optimization solution of this patent, cooling pipes are provided inside the fixed punch, die and floating punch. The cooling pipes can cool the patch plate and the main plate during sheet metal processing, accelerate the temperature drop, and achieve pressure-maintaining quenching of the sheet metal.

[0012] As a technical optimization solution of this patent, a linear guide rail for guiding the up and down movement of the fixed punch is arranged between the inner sides of the fixed punch and the side surfaces of the corresponding floating punch. The nitrogen spring can push the floating punch upward, and the linear guide rail can guide the floating punch during its movement, so that its movement direction is stable and it can maintain vertical up and down movement.

[0013] As a technical optimization solution of this patent, a cavity is provided between the bottom end of the fixed punch and the lower die base, and the nitrogen spring is installed inside the cavity. The cavity facilitates the installation of the nitrogen spring and facilitates maintenance and overhaul during use.

[0014] As a technical optimization solution of this patent, the floating punch has a stroke of less than 5mm when it moves up and down inside the fixed punch. The stroke of the floating punch is less than 5mm, which can maintain the accuracy in production, and the floating punch can push and extrude the sheet material at the top, eliminating the influence of the tolerance of the patch plate thickness of ±0.05mm and reducing the adverse effects caused by tolerance in processing.

[0015] This patent also discloses a hot stamping forming method for a steel patch plate, which can ensure that the plate is evenly pressurized everywhere, complete the stamping forming, and the main plate and the patch plate are cooled and quenched synchronously, thereby improving production efficiency, allowing the martensite to be completely transformed, and improving the hardness of the steel patch plate.

[0016] The hot stamping forming method of the steel patch plate is to spot weld the main material plate 3 and the patch plate 4 together, heat them as a whole to 880℃-930℃ in a heating furnace and keep them warm for a certain period of time, then hot press them in the above-mentioned floating punch hot forming mold, and then use the cooling medium flowing through the cooling pipe 7 to cool the hot-pressed main material plate 3 and patch plate 4 under the condition that the fixed punch 5 and the die 2 are closed, and then pressure quench them; during hot press forming, under the action of the nitrogen spring 9, the upper surface of the floating punch 10 contacts the bottom of the patch plate 4, and at the same time, the main material plate 3 located between the fixed punch 5 and the die 2 contacts the fixed punch 5 and the die 2.

[0017] In the hot stamping forming method of the steel patch plate, the cooling medium is water.

[0018] In the hot stamping forming method of the steel patch plate, when the mold is closed, the main plate 3 and the patch plate 4 are subjected to a pressure of not less than 10 MPa. The greater the contact pressure, the greater the contact heat transfer coefficient, the faster the plate cools, and the quenching quality is further guaranteed.

[0019] Beneficial effects of this patent:

[0020] The floating punch design is adopted. When the mold is at the bottom, the force of the nitrogen spring is used to control the fit between the mold and the sheet material, so that the parts produced by multiple cavities can be cooled at the same time under the same conditions, so that the martensite is completely converted, the hardness of the product is guaranteed, so as to achieve the best production efficiency and protection of the mold inserts, and reduce the defective rate. The patch plate is set on the upper part of the floating punch, and the floating punch + fixed punch replaces the previous single punch structure; the nitrogen spring provides the floating punch with floating ejection force, which can eliminate the influence of tolerance; the floating punch and the fixed punch are guided by a linear guide to keep the direction unchanged and the plate is evenly stressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to facilitate the understanding of those skilled in the art, this patent is further explained below in conjunction with the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the overall structure of this patent.

[0023] Figure 2 The schematic diagram of the structure for taking the negative tolerance lower limit of the existing forming die patch plate is shown.

[0024] Figure 3 A structural schematic diagram of taking the upper limit of the positive tolerance for an existing forming die patch plate.

[0025] Figure 4 It is a schematic diagram of the change of contact heat transfer coefficient with the gap between the sheet and the mold.

[0026] Figure 5 It is a schematic diagram of the change of contact heat transfer coefficient with the contact pressure between the sheet and the mold.

[0027] In the figure: 1. upper die base; 2. die; 3. main plate; 4. patch plate; 5. fixed punch; 6. lower die base; 7. cooling pipe; 8. linear guide; 9. nitrogen spring; 10. floating punch; 11. punch; 12. gap between patch plate and punch cavity; 13. gap between main plate and upper surface of punch. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solution of this patent in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of this patent, not all of them. Based on the embodiments in this patent, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

[0029] See also Figure 1 As shown, a floating punch hot forming die for a steel patch plate comprises an upper die base 1, a lower die base 6, a die 2 connected to the middle end of the bottom of the upper die base 1, and a fixed punch 5 connected to the middle end of the top of the lower die base 6. A floating punch 10 is movably installed in the middle of the fixed punch 5, and the upper surface of the floating punch 10 is lower than the upper surface of the fixed punch 5. The bottom of the floating punch 10 extends downward into the cavity between the bottom end of the fixed punch 5 and the lower die base 6. A plurality of nitrogen springs 9 are arranged between the lower surface of the lower die base 6 and the bottom of the floating punch 10, and the floating punch 10 can move vertically up and down inside the fixed punch 5. The nitrogen spring 9 is installed inside the cavity.

[0030] Cooling pipes 7 are provided inside the fixed punch 5 , the die 2 and the floating punch 10 .

[0031] Both sides of the interior of the fixed punch 5 are connected to the side surfaces of the floating punch 10 via linear guide rails 8 .

[0032] The travel of the floating punch 10 moving up and down inside the fixed punch 5 is less than 5 mm.

[0033] A hot stamping forming method for a steel patch plate, the process of which is as follows. The main material plate 3 and the patch plate 4 are spot welded together, heated to about 900°C in a heating furnace and kept warm for a certain period of time, and then hot-pressed in the above-mentioned floating punch hot forming mold. Then, when the mold is closed, the main material plate 3 and the patch plate 4 are cooled by cooling water flowing through the cooling pipe 7 for pressure quenching. During hot pressing, the temperature of the main material plate 3 and the patch plate 4 is 600-800°C. Under the action of the nitrogen spring (9), the upper surface of the floating punch (10) contacts the bottom of the patch plate (4). At the same time, the main material plate (3) located between the fixed punch (5) and the die (2) contacts the fixed punch (5) and the die (2). The main material plate (3) and the patch plate (4) are subjected to a pressure of about 20MPa.

[0034] When this patent is in use, the main material plate 3 is placed on the upper part of the fixed punch 5. When the mold is closed, the main material plate 3 between the punch 2 and the fixed die 5 is pressed and formed, and at the same time, the floating punch 10 presses the patch plate 4 under the action of the nitrogen spring 9 to eliminate the influence of the thickness tolerance of the patch plate 4; in this way, the main material plate 3 and the patch plate 4 are cooled synchronously by the cooling water in the cooling pipe 7, and the linear guide 8 guides the movement of the floating punch 10 to ensure that the direction of movement remains unchanged.

[0035] The preferred embodiments of this patent disclosed above are only used to help explain this patent. The preferred embodiments do not describe all the details in detail, nor do they limit the patent to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of this patent, so that technicians in the relevant technical field can understand and use this patent well. This patent is only limited by the claims and their full scope and equivalents.

Claims

1. A hot stamping method for a steel patch plate, characterized in that: The main material plate (3) and the patch plate (4) are spot welded together at the top and bottom, and the whole is heated to 880°C-930°C in a heating furnace and kept warm for a certain period of time, and then hot-pressed in a floating punch hot forming mold, and then the hot-pressed main material plate (3) and the patch plate (4) are cooled and pressure-maintained and quenched by a cooling medium flowing through a cooling pipe (7) when the fixed punch (5) and the die (2) are closed. During hot-pressing, the floating punch (10) is in contact with the bottom of the patch plate (4) under the action of a nitrogen spring (9), and at the same time, the main material plate (3) located between the fixed punch (5) and the die (2) is in contact with the fixed punch (5) and the die (2); The floating punch thermoforming die comprises an upper die base (1), a lower die base (6), a die (2) connected to the bottom of the upper die base (1), and a fixed punch (5) connected to the top of the lower die base (6); a floating punch (10) is movably installed inside the upper end of the fixed punch (5); the upper surface of the floating punch (10) is lower than the upper surface of the fixed punch (5); a nitrogen spring (9) is arranged between the bottom of the floating punch (10) and the lower die base (6) to push the floating punch upward in a normal state; the floating punch (10) can move vertically up and down inside the fixed punch (5); the fixed punch (5), the die (2) and the floating punch (10) are all provided with cooling pipes (7); a cavity is provided between the bottom end of the fixed punch (5) and the lower die base (6), and the nitrogen spring (9) is installed inside the cavity.

2. The hot stamping forming method of the steel patch plate according to claim 1, characterized in that: The cooling medium is water.

3. The hot stamping forming method of the steel patch plate according to claim 1, characterized in that: When the mold is closed, the main plate (3) and the patch plate (4) are subjected to a pressure of not less than 10 MPa.

4. The hot stamping forming method of the steel patch plate according to claim 1, characterized in that: Linear guide rails (8) for guiding the up and down movement of the floating punch (10) are arranged between the inner sides of the fixed punch (5) and the side surfaces of the opposite floating punch (10).

5. The hot stamping forming method of the steel patch plate according to claim 1, characterized in that: The travel of the floating punch (10) moving up and down inside the fixed punch (5) is less than 5 mm.

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