Local bulging device and method for large-size complex thin-wall high-strength steel pipe fitting

Abstract

The invention relates to a large-size complex thin-wall high-strength steel pipe local bulging device and method. The device comprises a water cooling plate, an upper die, a lower die, a punch and a heating assembly. The upper die and the lower die are symmetrically arranged up and down, and the opposite sides of the upper die and the lower die are respectively provided with a cavity corresponding to a to-be-bulged area of a pipe blank; the water cooling plates are respectively arranged on the outer sides of the upper mold and the lower mold; the punches are arranged between the left ends and the right ends of the upper die and the lower die respectively. And the heating assembly is arranged inside the upper mold and the lower mold or outside the end parts of the upper mold and the lower mold. According to the bulging method, in-situ heating and in-situ forming of the pipe blank can be achieved, heat loss caused by transferring of the hot-state pipe blank is omitted, and the pipe blank can meet the bulging shape requirement of a part under the condition of lower bulging pressure in the inflation bulging process. The problems that the local reducing difficulty of the large-size large-section-difference thin-wall high-strength steel original pipe blank is large, the cost of original pipe blank end cold / hot pipe expanding process equipment is high, and the flexibility is poor can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of local expansion forming of high-strength steel pipe fittings by hot gas pressure forming, and in particular to a local expansion forming device and method for large-size complex thin-wall high-strength steel pipe fittings. Background Art

[0002] In the context of vigorously promoting energy conservation and emission reduction in the automotive field, the combination of lightweight materials, lightweight structural design and advanced process means can significantly reduce the mass of automotive parts, thereby reducing the weight of the entire vehicle, improving fuel utilization and achieving energy conservation and emission reduction.

[0003] From the perspective of material application, lightweight materials mainly include aluminum alloy, titanium alloy and high-strength steel. High-strength steel has been widely used in the production of automotive A-pillars, B-pillars, bumpers, roof longitudinal beams, side rails and other structural parts, ensuring safety while making significant contributions to the lightweight of parts. From the perspective of structural lightweight, thin-walled hollow special-shaped overall structure is the optimal structure that takes into account both lightweight and safety. It is also a key structure to improve the reliability of transport equipment, with characteristics such as high strength, large size and small fillet. Tube hydraulic forming technology is an advanced forming technology for the integral forming of special-shaped thin-walled tubular structures. It has been successfully applied to the mass production of key parts of domestic brand cars and internationally renowned cars. However, when the strength of high-strength steel materials is higher than 1000MPa or higher, even when the tube is warm hydraulically formed, a very high bulging pressure is still required, which puts higher requirements on the equipment capacity, and the dimensional accuracy of the parts often cannot meet the design requirements.

[0004] Compared with liquid media, gas media have a higher operating temperature. The hot metal gas pressure forming process with gas as the forming medium can solve the problem of high-precision forming of lightweight and difficult-to-change pipes by increasing the forming temperature to improve the forming performance of the material. In addition, the increase in the material forming temperature greatly reduces the equipment tonnage requirements and reduces production costs. When using the hot metal gas pressure forming process to form complex and special-shaped cross-section pipes, a certain amount of pre-forming is usually required. The pre-forming process of the tube blank is usually carried out at room temperature through a pre-forming mold or in combination with a pipe bender to bend and pre-deform it to make it close to the cross-sectional shape and axis of the final part, so that the deformation of the part is more uniform and a reasonable wall thickness distribution is obtained.

[0005] However, when the deviation of the circumference of the part section is large (>10%), the small section circumference area of ​​the part is often reduced by punching and rolling. When the outer diameter of the original tube is large (>100mm), it is difficult to achieve local reduction of the tube using the above reduction process. In addition, the end forming process of the tube, such as local cold / hot expansion, can achieve the expansion of the diameter of the local area of ​​the end of the tube to meet the requirements of the circumference distribution of the part section. The cold / hot expansion process of the end of the tube often requires professional equipment to achieve, which has the disadvantages of high equipment cost and poor flexibility. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a local expansion device and method for large-sized complex thin-walled high-strength steel pipe fittings, which can effectively solve the problems of difficulty in local diameter reduction of large-sized, large-section, thin-walled high-strength steel original tube billets, high cost and poor flexibility of cold / hot expansion process equipment at the ends of the original tube billets, etc., so that the distribution of the circumference of the cross-section of the original tube billet is more reasonable, and the size of the local expansion position can be quickly and effectively adjusted.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The present invention proposes a local expansion device for large-size complex thin-walled high-strength steel pipe fittings, comprising a water-cooled plate, an upper mold, a lower mold, a punch and a heating assembly; the upper mold and the lower mold are symmetrically arranged up and down, and the opposite sides are respectively provided with cavities corresponding to the areas to be expanded of the tube blank; the water-cooled plates are respectively arranged on the outside of the upper mold and the lower mold; the punches are respectively arranged between the left and right ends of the upper mold and the lower mold; the heating assembly is arranged inside the upper mold and the lower mold or outside the ends.

[0009] Furthermore, a heat insulation plate is provided between the upper mold, the lower mold and the water cooling plate.

[0010] Furthermore, the heating component is a heating rod; the areas inside the upper mold and the lower mold corresponding to the cavity are evenly distributed with heating holes, and the heating rods are respectively arranged in the heating holes.

[0011] Furthermore, the heating component is a copper electrode; the copper electrodes are respectively arranged at the left and right ends of the upper mold and the lower mold, and the inner surfaces thereof are provided with arc grooves corresponding to the tube blank.

[0012] Furthermore, the heating component is an induction coil; the induction coil is correspondingly arranged on one side of the upper mold and the lower mold.

[0013] Furthermore, a vent hole connecting the tube blank with the outside is arranged inside the punch.

[0014] Furthermore, the cross section of the cavity is circular, trapezoidal, fan-shaped or irregular.

[0015] A local bulging method for large-size complex thin-wall high-strength steel pipe fittings, the method comprising the following steps:

[0016] S1. Analyze the cross-sectional profile and size of the part, determine the local bulging position and size of the tube, analyze the cross-sectional circumference of different positions along the axis of the part, and obtain the equivalent diameter at different cross-sectional positions according to d=C / π, where C represents the cross-sectional circumference and π is the pi; for the cross-sectional position where the equivalent diameter is larger than the original tube diameter, determine it as the part that needs local bulging;

[0017] S2. Design a bulging die according to the analysis result of step S1;

[0018] S3. Arrange a heat preservation module on the bulging die to reduce the heat loss during the subsequent pipe heating process;

[0019] S4, placing the original tube blank into the cavity of the mold, so that the local bulging part of the tube blank corresponds to the bulging cavity position of the mold, and closing the upper mold and the lower mold by controlling the main slide of the press;

[0020] S5, locally heating the local bulging position of the tube billet, and monitoring the temperature change of the local bulging section of the tube billet in real time;

[0021] S6, after the local bulging section of the tube billet is heated to a suitable temperature, the heating power supply is turned off and the heating is stopped;

[0022] S7, the left end punch and the right end punch seal the two ends of the tube blank under the axial thrust of the horizontal cylinder, and fill the tube blank with high-pressure gas through the vent hole inside the punch, and use the high-pressure gas to fit the local bulging area of ​​the tube blank with the cavity of the mold. The high-pressure gas is provided by a high-pressure gas source, and the pressure required inside the tube during forming is adjusted by controlling the high-pressure gas source;

[0023] S8. Turn off the gas source, exhaust the gas in the pipe, retract the left and right punches, open the mold, and take out the bulged parts.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. For large-size, large-section, thin-walled, high-strength steel pipes, the bulging position and bulging height of the pipe can be accurately and effectively controlled to achieve a reasonable distribution of the circumference of the pipe section.

[0026] 2. The local bulging method proposed in the present invention can realize in-situ heating and in-situ forming of the tube blank, eliminating the heat loss caused by the transfer of the hot tube blank, so that the tube blank can meet the bulging shape requirements of the part under lower bulging pressure conditions during the inflation bulging process.

[0027] 3. The partial bulging die proposed by the present invention allows the cross-sectional shape of the die cavity to be circular or irregular, so as to meet the bulging requirements of tube blanks of different shapes and sizes. The present invention can not only improve the versatility of the die, but also improve production efficiency, and the operation process is simple, making the application of the present invention more extensive and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of a first embodiment of a local bulging device for large-sized, complex, thin-walled, high-strength steel pipes proposed by the present invention;

[0029] Figure 2 This is a schematic diagram of the effect of the local expansion of a pipe fitting in an embodiment;

[0030] Figure 3 Schematic diagram of the internal structure of the water cooling plate in the present invention;

[0031] Figure 4 This is a schematic structural diagram of a second embodiment of a local bulging device for large-sized, complex, thin-walled, high-strength steel pipes proposed by the present invention;

[0032] Figure 5 for Figure 4 Schematic diagram of the structure of the copper electrode;

[0033] Figure 6 This is a schematic structural diagram of a third embodiment of a local bulging device for large-sized, complex, thin-walled, high-strength steel pipes proposed by the present invention.

[0034] Among them, the figure markings are: 1-upper water-cooling plate; 2-lower water-cooling plate; 3-upper insulation plate; 4-lower insulation plate; 5-upper mold; 6-lower mold; 7-left end punch; 8-right end punch; 9-vent; 10-mold cavity; 11-tube; 12-cooling water flow channel; 13-copper electrode; 14-induction coil; 15 transmission mechanism; 16-heating rod. DETAILED DESCRIPTION

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Embodiment 1

[0037] See attached Figure 1-2The local bulging device for large-size complex thin-walled high-strength steel pipe parts proposed in this embodiment includes an upper water-cooled plate 1, a lower water-cooled plate 2, an upper die 5, a lower die 6, a left-end punch 7, a right-end punch 8 and a heating assembly. The upper die 5 and the lower die 6 are symmetrically arranged up and down, and a cavity 10 corresponding to the area to be bulged of the tube blank 11 is arranged on the opposite side, and the cavity 10 is a circular cross section, a trapezoidal cross section, a fan-shaped cross section or other combined special-shaped cross sections.

[0038] The upper water cooling plate 1 is correspondingly arranged on the outer side of the upper mold 5, and the lower water cooling plate 2 is correspondingly arranged on the outer side of the lower mold 6. The upper water cooling plate 1 and the lower water cooling plate 2 are provided with cooling water channels 12. Figure 3 The left punch 7 is correspondingly arranged between the left ends of the upper die 5 and the lower die 6, and the right punch 8 is correspondingly arranged between the right ends of the upper die 5 and the lower die 6, and the left punch 7 and the right punch 8 are both provided with vent holes 9 connecting the inside of the tube blank 11 with the outside; the heating assembly is correspondingly arranged inside or outside the ends of the upper die 5 and the lower die 6.

[0039] Among them, an upper heat insulation plate 3 is arranged between the upper mold 5 and the upper water-cooling plate 1; and a lower heat insulation plate 4 is arranged between the lower mold 6 and the lower water-cooling plate 2.

[0040] In this embodiment, the heating component is a heating rod 16; a plurality of heating holes are evenly distributed in the areas inside the upper mold 5 and the lower mold 6 corresponding to the cavity 10, and the heating rods 16 are respectively inserted into the heating holes.

[0041] A local bulging method for large-size complex thin-walled high-strength steel pipe fittings is specifically implemented by the following steps:

[0042] S1. Analyze the cross-sectional profile and size of the target part, determine the local bulging position and size of the tube, analyze the cross-sectional perimeter of the part at different positions along the axial direction, and obtain the equivalent diameter at different cross-sectional positions according to d=C / π, where C represents the cross-sectional perimeter and π is the pi. For the cross-sectional position where the equivalent diameter is larger than the original tube diameter, it is determined as the local bulging position.

[0043] S2. According to the analysis result of S1, design the bulging mold, namely the upper mold 5 and the lower mold 6.

[0044] S3, design the heat preservation and water cooling module, namely the upper heat insulation board 3, the lower heat insulation board 4, the upper water cooling board 1 and the lower water cooling board 2. The water cooling board has internal openings and the flow channel is designed as follows Figure 3 As shown. The heat preservation and water cooling modules are reasonably assembled with the bulging mold, the water cooling plate is connected with the press slide and the press platform respectively, the heat insulation plate is arranged between the water cooling plate and the mold, and cooling water flows inside the water cooling plate.

[0045] S4, placing the original tube blank 11 at a specified position in the mold cavity 10, and closing the upper mold 5 and the lower mold 6 by controlling the upper slide of the press.

[0046] S5. Insert a heating rod 16 into the heating hole and energize it to heat the mold, thereby heating the tube blank 11 locally through heat conduction from the mold, and monitor the temperature change of the local bulging section of the tube blank 11 through a thermal imager / thermocouple.

[0047] S6. When the local bulging section of the tube blank 11 is heated to 800-950° C., the heating rod 16 is powered off.

[0048] S7, the left punch 7 and the right punch 8 seal the two ends of the tube blank 11 under the axial thrust of the horizontal cylinder, and fill the tube blank 11 with high-pressure gas through the vent hole 9 inside the punch, and use the high-pressure gas to fit the local bulging area of ​​the tube blank with the mold cavity. The high-pressure gas is provided by a high-pressure gas source, and the pressure required inside the pipe during forming can be adjusted by controlling the high-pressure gas source.

[0049] S8, turn off the gas source, exhaust the gas in the pipe, withdraw the left end punch 7 and the right end punch 8, open the mold, and take out the bulged parts.

[0050] Embodiment 2

[0051] See attached Figure 4 The local bulging device for large-sized complex thin-walled high-strength steel pipes proposed in this embodiment is different from that in the first embodiment in that: the heating assembly is a copper electrode 13; the copper electrodes 13 are respectively arranged at the left and right ends of the upper mold 5 and the lower mold 6, and the inner surfaces thereof are provided with arc grooves corresponding to the tube blank 11, such as Figure 5 shown.

[0052] A local bulging method for large-size complex thin-walled high-strength steel pipe fittings is specifically implemented by the following steps:

[0053] S1. Analyze the cross-sectional profile and size of the target part, determine the local bulging position and size of the tube, analyze the cross-sectional perimeter of the part at different positions along the axial direction, and obtain the equivalent diameter at different cross-sectional positions according to d=C / π, where C represents the cross-sectional perimeter and π is the pi. For the cross-sectional position where the equivalent diameter is larger than the original tube diameter, it is determined as the local bulging position.

[0054] S2. According to the analysis result of S1, design the bulging mold, namely the upper mold 5 and the lower mold 6.

[0055] S3, design the heat preservation and water cooling module, namely the upper heat insulation board 3, the lower heat insulation board 4, the upper water cooling board 1 and the lower water cooling board 2. The water cooling board has internal openings and the flow channel is designed as follows Figure 3As shown. The heat preservation and water cooling modules are reasonably assembled with the bulging mold, the water cooling plate is connected with the press slide and the press platform respectively, the heat insulation plate is arranged between the water cooling plate and the mold, and cooling water flows inside the water cooling plate.

[0056] S4, placing the original tube blank 11 at a specified position in the mold cavity 10, and closing the upper mold 5 and the lower mold 6 by controlling the upper slide of the press.

[0057] S5. Copper electrodes 13 are arranged at both ends of the upper mold 5 and the lower mold 6, respectively. The copper electrodes 13 are in close contact with the tube blank 11 through the circular grooves. By energizing the copper electrodes 13, the heat generated by the conductor under the action of resistance is used to accurately heat the local bulging area of ​​the tube blank 11.

[0058] S6. When the temperature of the local bulging zone of the tube blank 11 reaches 800-950°C, stop energizing the copper electrode 13.

[0059] S7, the left punch 7 and the right punch 8 seal the two ends of the tube blank 11 under the axial thrust of the horizontal cylinder, and fill the tube blank 11 with high-pressure gas through the vent hole 9 inside the punch, and use the high-pressure gas to fit the local bulging area of ​​the tube blank with the mold cavity. The high-pressure gas is provided by a high-pressure gas source, and the pressure required inside the pipe during forming can be adjusted by controlling the high-pressure gas source.

[0060] S8, turn off the gas source, exhaust the gas in the pipe, withdraw the left end punch 7 and the right end punch 8, open the mold, and take out the bulged parts.

[0061] Embodiment 3

[0062] See attached Figure 6 The local bulging device for large-sized complex thin-walled high-strength steel pipe parts proposed in this embodiment is different from that in the first embodiment in that the heating component is an induction coil 14; the induction coil 14 is correspondingly arranged on the right side of the upper mold 5 and the lower mold 6.

[0063] A local bulging method for large-size complex thin-walled high-strength steel pipe fittings is specifically implemented by the following steps:

[0064] S1. Analyze the cross-sectional profile and size of the target part, determine the local bulging position and size of the tube, analyze the cross-sectional perimeter of the part at different positions along the axial direction, and obtain the equivalent diameter at different cross-sectional positions according to d=C / π, where C represents the cross-sectional perimeter and π is the pi. For the cross-sectional position where the equivalent diameter is larger than the original tube diameter, it is determined as the local bulging position.

[0065] S2. According to the analysis result of S1, design the bulging mold, namely the upper mold 5 and the lower mold 6.

[0066] S3, design the heat preservation and water cooling module, namely the upper heat insulation board 3, the lower heat insulation board 4, the upper water cooling board 1 and the lower water cooling board 2. The water cooling board has internal openings and the flow channel is designed as follows Figure 3 As shown. The heat preservation and water cooling modules are reasonably assembled with the bulging mold, the water cooling plate is connected with the press slide and the press platform respectively, the heat insulation plate is arranged between the water cooling plate and the mold, and cooling water flows inside the water cooling plate.

[0067] S4, placing the area of ​​the original tube blank 11 that needs to be expanded outside the mold.

[0068] S5. An induction coil is arranged at the local bulging position of the tube blank 11. By energizing the induction coil 14, an eddy current is generated by utilizing the electromagnetic induction principle, thereby heating the local bulging area of ​​the tube blank 11.

[0069] S6. When the temperature of the local bulging zone of the tube blank 11 reaches 800-950°C, stop energizing the induction coil 14, and use the transmission mechanism 15 to move the tube blank 11 into the mold cavity 10 so that the local bulging portion of the tube blank 11 is aligned with the bulging cavity 10 of the mold.

[0070] S7, the left punch 7 and the right punch 8 seal the two ends of the tube blank 11 under the axial thrust of the horizontal cylinder, and fill the tube blank 11 with high-pressure gas through the vent hole 9 inside the punch, and use the high-pressure gas to fit the local bulging area of ​​the tube blank with the mold cavity. The high-pressure gas is provided by a high-pressure gas source, and the pressure required inside the pipe during forming can be adjusted by controlling the high-pressure gas source.

[0071] S8, turn off the gas source, exhaust the gas in the pipe, withdraw the left end punch 7 and the right end punch 8, open the mold, and take out the bulged parts.

[0072] The present invention utilizes resistance heating, electrode heating or induction heating to heat the area where the local cross-sectional circumference needs to be expanded, thereby reducing the flow stress of the material under high temperature conditions, and then introducing high-pressure gas into the closed tube cavity. Finally, under the constraint of the mold cavity, the cross-sectional circumference of the local heated area of ​​the tube blank is expanded.

[0073] Matters not described in detail in the present invention are all known technologies.

[0074] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A local bulging device for large-size, complex, thin-walled, high-strength steel pipe fittings, characterized in that: The device comprises a water-cooling plate, an upper die, a lower die, a punch and a heating assembly; the upper die and the lower die are symmetrically arranged up and down, and cavities corresponding to the areas to be expanded of the tube blank are arranged on opposite sides; the water-cooling plates are arranged on the outside of the upper die and the lower die respectively; the punches are arranged between the left and right ends of the upper die and the lower die respectively; the heating assembly is arranged inside or outside the ends of the upper die and the lower die.

2. According to claim 1, a local bulging device for large-size complex thin-walled high-strength steel pipe fittings is characterized by: A heat insulation plate is arranged between the upper mold, the lower mold and the water cooling plate.

3. The local bulging device for large-size complex thin-walled high-strength steel pipe according to claim 2 is characterized in that: The heating component is a heating rod; the areas inside the upper mold and the lower mold corresponding to the cavity are evenly distributed with heating holes, and the heating rods are respectively arranged in the heating holes.

4. The local bulging device for large-size complex thin-walled high-strength steel pipe according to claim 2 is characterized by: The heating components are copper electrodes; the copper electrodes are respectively arranged at the left and right ends of the upper mold and the lower mold, and arc grooves corresponding to the tube blanks are opened on the inner surfaces thereof.

5. The local bulging device for large-size complex thin-walled high-strength steel pipe according to claim 2, characterized in that: The heating component is an induction coil; the induction coil is correspondingly arranged on one side of the upper mold and the lower mold.

6. The local bulging device for large-size complex thin-walled high-strength steel pipe according to claim 2, characterized in that: The punch is provided with a vent hole inside for connecting the tube blank with the outside.

7. The local bulging device for large-size complex thin-walled high-strength steel pipe according to claim 2 is characterized by: The cross section of the cavity is circular, trapezoidal, fan-shaped or irregular.

8. A bulging method according to any one of claims 2 to 7, characterized in that: The method comprises the following steps: S1. Analyze the cross-sectional profile and size of the part, determine the local bulging position and size of the tube, analyze the cross-sectional circumference of different positions along the axis of the part, and obtain the equivalent diameter at different cross-sectional positions according to d=C / π, where C represents the cross-sectional circumference and π is the pi; for the cross-sectional position where the equivalent diameter is larger than the original tube diameter, determine it as the part that needs local bulging; S2. Design a bulging die according to the analysis result of step S1; S3. Arrange a heat preservation module on the bulging die to reduce the heat loss during the subsequent pipe heating process; S4, placing the original tube blank into the cavity of the mold, so that the local bulging part of the tube blank corresponds to the bulging cavity position of the mold, and closing the upper mold and the lower mold by controlling the main slide of the press; S5, locally heating the local bulging position of the tube billet, and monitoring the temperature change of the local bulging section of the tube billet in real time; S6, after the local bulging section of the tube billet is heated to a suitable temperature, the heating power supply is turned off and the heating is stopped; S7, the left end punch and the right end punch seal the two ends of the tube blank under the axial thrust of the horizontal cylinder, and fill the tube blank with high-pressure gas through the vent hole inside the punch, and use the high-pressure gas to fit the local bulging area of ​​the tube blank with the cavity of the mold. The high-pressure gas is provided by a high-pressure gas source, and the pressure required inside the tube during forming is adjusted by controlling the high-pressure gas source; S8. Turn off the gas source, exhaust the gas in the pipe, retract the left and right punches, open the mold, and take out the bulged parts.

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