A hot oil constant temperature forming device and method for magnesium alloy thin-walled pipe

Abstract

A magnesium alloy thin-walled pipe hot oil constant temperature forming device and method, the device includes constant temperature box, mould, left sealing assembly, right sealing assembly, left hydraulic pump mechanism, right hydraulic pump mechanism, electric heating element, stirring mechanism, thermocouple and displacement sensor. The method is: installing the pipe to be processed in the mould, using the left and right sealing assemblies to close the pipe orifice at both ends of the pipe; injecting hydraulic oil into the constant temperature box and covering the mould, heating and stirring the hydraulic oil until the temperature of the hydraulic oil and the temperature of the mould pipe forming cavity reach the design value; starting the left and right hydraulic pump mechanisms to inject the hydraulic oil in the constant temperature box into the pipe to generate bulging pressure in the pipe, forcing the pipe to gradually expand and deform, the hydraulic oil in the pipe forming cavity will be squeezed into the constant temperature box through the oil hole on the mould, and the deformation amount of the pipe is measured in real time through the displacement sensor during the expansion and deformation of the pipe until the deformation amount of the pipe reaches the design value, then the left and right hydraulic pump mechanisms are closed, and the pipe forming is completed.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy thin-walled tube forming technology, and in particular relates to a hot oil constant temperature forming device and method for magnesium alloy thin-walled tubes. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials, are increasingly widely used in the automotive, 3C, and aerospace industries to meet the energy-saving requirements of low density and high specific strength. Lightweight hollow shaped tubular components are indispensable structural parts in the lightweighting process. Currently, commonly used manufacturing methods mainly include centrifugal casting, extrusion, spinning, and hydraulic bulging. Among them, hydraulic bulging can simplify the process by allowing shaped tubular components to be formed in one step through mold design.

[0003] Currently, hollow structural components with complex variable cross-sections are typically welded together from multiple individual simple parts, which are then formed / stamped from sheet metal. The advantage of this method is its ability to produce large-sized and complex-shaped hollow components. However, this method also has significant drawbacks: it involves multiple operations, resulting in low productivity, and increases costs related to tooling, assembly, and material preparation.

[0004] In addition to the commonly used methods for preparing irregularly shaped tubular components mentioned above, there is also a hydroforming process. This process uses pressurized fluid as the forming medium to inflate tubular metal into the desired shape. It is a one-step forming method with high productivity and low processing cost. It can achieve lightweight, higher strength, better structural integrity, more stable power transmission system, and more flexible component geometry. It is considered to be the most promising technology for industrial application in producing high-quality tubular frame structure components.

[0005] However, due to the poor formability of magnesium alloys at low temperatures, excessive thinning can occur in localized areas during pipe deformation. To overcome this problem, the common practice is to use tools and heating devices to achieve a high-temperature hydraulic bulging process, primarily by heating the mold and axial feed plunger, utilizing surface heat conduction. While this method allows the hydraulic bulging process to take place at high temperatures, the temperature of the feed plunger and mold is higher than that of the pipe, causing excessive softening in the clamping area. This results in the plunger failing to provide an effective seal, leading to leakage of the forming medium, such as heat-resistant oil and inert gas. This leakage inevitably causes a drop in the internal pressure during bulging. When the internal pressure is less than the stress generated by the mold, wrinkling will occur in the softened area of ​​the pipe, thus affecting the forming quality of the irregularly shaped pipe. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a hot oil isothermal forming device and method for magnesium alloy thin-walled tubes. The mold and the tube are immersed in hot oil, and the hot oil uniformly heats the mold and the tube, preventing excessive softening of the tube and solving the problem of wrinkling. Since the tube is formed at a uniform temperature, the forming quality of the tube can be effectively improved and the generation of defects can be reduced. By controlling the feed rate during the tube forming process, the tube breakage caused by insufficient feed rate during large deformation can be effectively prevented.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a thermostatic forming device for magnesium alloy thin-walled tubes using hot oil, comprising a thermostatic chamber, a mold, a left sealing assembly, a right sealing assembly, a left hydraulic pump mechanism, and a right hydraulic pump mechanism; hydraulic oil is contained within the thermostatic chamber; the mold is located inside the thermostatic chamber and immersed in the hydraulic oil; the left sealing assembly is located at the left oil inlet of the mold; the right sealing assembly is located at the right oil inlet of the mold; both the left and right hydraulic pump mechanisms are located at... Outside the constant temperature chamber, the oil outlet of the left hydraulic pump mechanism is connected to the left pipe opening of the fitting inside the mold through the left sealing assembly and the left oil injection pipe; the oil outlet of the right hydraulic pump mechanism is connected to the right pipe opening of the fitting inside the mold through the right sealing assembly and the right oil injection pipe; the oil inlet of the left hydraulic pump mechanism is connected to the inner cavity of the constant temperature chamber through the left suction pipe, and the suction port of the left suction pipe is immersed in hydraulic oil; the oil inlet of the right hydraulic pump mechanism is connected to the inner cavity of the constant temperature chamber through the right suction pipe, and the suction port of the right suction pipe is immersed in hydraulic oil.

[0008] The left and right sealing assemblies have the same structure, each including an outer sleeve, a sealing plunger, a high-resilience sealing ring, and a traction mechanism. The outer sleeve is fitted over the outside of the sealing plunger, and the sealing plunger has axial sliding freedom relative to the outer sleeve. The sealing plunger is fixedly fitted over the outside of the left / right oil injection pipe. The high-resilience sealing ring is fitted behind the head of the sealing plunger, and a mating slot is provided at the opening of the outer sleeve behind the head of the sealing plunger, in which the high-resilience sealing ring is fixedly installed. The traction mechanism is set on the body of the outer sleeve, and the outer sleeve has axial sliding freedom relative to the left / right oil injection port of the mold. The axial sliding of the outer sleeve is driven by the traction mechanism, and the axial sliding of the sealing plunger is also driven by the traction mechanism.

[0009] An electric heating element is installed inside the constant temperature chamber to heat the hydraulic oil contained inside the chamber.

[0010] A stirring mechanism is installed inside the constant temperature chamber to agitate the hydraulic oil contained within.

[0011] Oil passage holes are provided at corresponding positions of the tube forming cavities in the upper and lower molds of the mold, and the inner cavity of the constant temperature box is connected to the tube forming cavity in the mold by the oil passage holes.

[0012] Thermocouples are installed inside the constant temperature chamber, and the temperature of the hydraulic oil contained in the constant temperature chamber and the temperature inside the forming cavity of the mold tube are measured by thermocouples.

[0013] Displacement sensors are installed at corresponding positions in the tube forming cavities of the upper and lower molds of the mold. The displacement sensors are located between the mold and the tube and measure the deformation of the tube.

[0014] The hydraulic oil contained in the constant temperature chamber is silicone oil.

[0015] A method for isothermal hot oil forming of magnesium alloy thin-walled tubes, employing the aforementioned isothermal hot oil forming apparatus for magnesium alloy thin-walled tubes, includes the following steps:

[0016] Step 1: Clamp the pipe fitting to be processed into the pipe fitting forming cavity between the upper and lower molds. Then, the traction mechanism controls the outer sleeves of the left and right sealing components to move toward the pipe fitting forming cavity until the pipe end is inserted into the mating slot. Then, control the sealing plungers of the left and right sealing components to move away from the pipe fitting forming cavity until the plunger head is pressed together with the high-resilience sealing ring. At this time, the pipe ends of the pipe fitting are sealed.

[0017] Step 2: Inject hydraulic oil into the constant temperature chamber until the hydraulic oil level covers the mold. After the hydraulic oil is injected, turn on the heating element to heat the hydraulic oil. At the same time, turn on the stirring mechanism to stir the hydraulic oil to ensure the temperature uniformity of the hydraulic oil. During the heating process, the temperature of the hydraulic oil and the temperature inside the forming cavity of the mold tube are measured in real time through thermocouples until the detected temperature values ​​reach the design value.

[0018] Step 3: Start the left and right hydraulic pump mechanisms to pressurize the hydraulic oil inside the constant temperature chamber and inject it into the pipe. As the hydraulic oil is continuously injected, expansion pressure will be generated inside the pipe, forcing the pipe to gradually expand and deform. As the pipe expands and deforms, the hydraulic oil in the forming cavity of the mold outside the pipe will be squeezed out into the constant temperature chamber through the oil passage. During the expansion and deformation process of the pipe, the deformation amount is measured in real time by the displacement sensor until the deformation amount reaches the design value. Then, the left and right hydraulic pump mechanisms are turned off, and the pipe forming is completed.

[0019] The beneficial effects of this invention are:

[0020] The magnesium alloy thin-walled tube hot oil isothermal forming apparatus and method of the present invention immerses the mold and the tube in hot oil, and uniformly heats the mold and the tube by the hot oil, avoiding excessive softening of the tube and solving the problem of wrinkling of the tube; since the tube is formed at a uniform temperature, the forming quality of the tube can be effectively improved and the generation of defects can be reduced; by controlling the feed amount during the tube forming process, the tube breakage caused by insufficient feed amount during large deformation can be effectively prevented.

[0021] Compared with traditional hydraulic forming processes, this invention further reduces production costs and shortens the production cycle; since the pipes are immersed in hot oil, they are prevented from contacting air, thus preventing oxidation during heating and deformation; and since the hydraulic oil used is silicone oil, it is non-toxic, harmless, smokeless, pollution-free, and reusable. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a magnesium alloy thin-walled tube hot oil constant temperature forming device according to the present invention;

[0023] Figure 2 This is a schematic diagram of the left / right sealing assembly of the present invention;

[0024] Figure 3 This is a schematic diagram of the pipe forming process;

[0025] In the diagram, 1—temperature control chamber, 2—mold, 3—left sealing assembly, 4—right sealing assembly, 5—left hydraulic pump mechanism, 6—right hydraulic pump mechanism, 7—hydraulic oil, 8—left oil injection pipe, 9—pipe fitting, 10—right oil injection pipe, 11—left oil suction pipe, 12—right oil suction pipe, 13—outer sleeve, 14—sealing plunger, 15—high-resilience sealing ring, 16—traction mechanism, 17—connection slot, 18—heating element, 19—stirring mechanism, 20—oil passage hole, 21—thermocouple, 22—displacement sensor. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] like Figures 1-3As shown, a thermostatic forming device for magnesium alloy thin-walled tubes using hot oil includes a thermostatic chamber 1, a mold 2, a left sealing assembly 3, a right sealing assembly 4, a left hydraulic pump mechanism 5, and a right hydraulic pump mechanism 6. Hydraulic oil 7 is contained within the thermostatic chamber 1. The mold 2 is located inside the thermostatic chamber 1 and is immersed in the hydraulic oil 7. The left sealing assembly 3 is located at the left oil inlet of the mold 2. The right sealing assembly 4 is located at the right oil inlet of the mold 2. Both the left and right hydraulic pump mechanisms 5 and 6 are located outside the thermostatic chamber 1. The oil outlet of the right hydraulic pump mechanism 6 is connected to the left port of the pipe 9 inside the mold 2 through the left sealing assembly 3 and the left oil injection pipe 8. The oil outlet of the right hydraulic pump mechanism 6 is connected to the right port of the pipe 9 inside the mold 2 through the right sealing assembly 4 and the right oil injection pipe 10. The oil inlet of the left hydraulic pump mechanism 5 is connected to the inner cavity of the constant temperature chamber 1 through the left suction pipe 11, and the suction port of the left suction pipe 11 is immersed in the hydraulic oil 7. The oil inlet of the right hydraulic pump mechanism 6 is connected to the inner cavity of the constant temperature chamber 1 through the right suction pipe 12, and the suction port of the right suction pipe 12 is immersed in the hydraulic oil 7.

[0028] The left sealing assembly 3 and the right sealing assembly 4 have the same structure, both including an outer sleeve 13, a sealing plunger 14, a high-resilience sealing ring 15, and a traction mechanism 16. The outer sleeve 13 is fitted outside the sealing plunger 14, and the sealing plunger 14 has axial sliding freedom relative to the outer sleeve 13. The sealing plunger 14 is fixedly fitted outside the left oil injection pipe 8 / right oil injection pipe 10. The high-resilience sealing ring 15 is fitted behind the plug head of the sealing plunger 14, and a docking slot 17 is provided at the pipe opening of the outer sleeve 13 behind the plug head of the sealing plunger 14. The high-resilience sealing ring 15 is fixedly installed in the docking slot 17. The traction mechanism 16 is set on the pipe body of the outer sleeve 13. The outer sleeve 13 has axial sliding freedom relative to the left oil injection port / right oil injection port of the mold 2. The axial sliding of the outer sleeve 13 is driven by the traction mechanism 16, and the axial sliding of the sealing plunger 14 is also driven by the traction mechanism 16.

[0029] Multiple sets of electric heating elements 18 are installed inside the constant temperature chamber 1 to heat the hydraulic oil 7 contained in the constant temperature chamber 1.

[0030] A stirring mechanism 19 is provided inside the constant temperature chamber 1 to stir the hydraulic oil 7 contained in the constant temperature chamber 1.

[0031] Oil passage holes 20 are provided at corresponding positions of the pipe forming cavities in the upper and lower molds of the mold 2, and the inner cavity of the constant temperature box 1 is connected to the pipe forming cavity in the mold 2 by the oil passage holes 20.

[0032] A thermocouple 21 is installed inside the constant temperature chamber 1. The temperature of the hydraulic oil 7 contained in the constant temperature chamber 1 and the temperature inside the forming cavity of the mold 2 pipe are measured by the thermocouple 21.

[0033] Displacement sensors 22 are installed at corresponding positions in the tube forming cavities of the upper and lower molds of the mold 2. The displacement sensors 22 are located between the mold 2 and the tube 9, and the deformation of the tube 9 is measured by the displacement sensors 22.

[0034] The hydraulic oil 7 contained in the constant temperature chamber 1 is silicone oil.

[0035] A method for isothermal hot oil forming of magnesium alloy thin-walled tubes, employing the aforementioned isothermal hot oil forming apparatus for magnesium alloy thin-walled tubes, includes the following steps:

[0036] Step 1: The pipe fitting 9 to be processed is clamped into the pipe forming cavity between the upper and lower molds of the mold 2. Then, the outer sleeve 13 of the left sealing assembly 3 and the right sealing assembly 4 is controlled by the traction mechanism 16 to move toward the pipe forming cavity until the pipe end of the pipe fitting 9 is inserted into the docking slot 17. Then, the sealing plunger 14 of the left sealing assembly 3 and the right sealing assembly 4 is controlled to move away from the pipe forming cavity until the plug of the sealing plunger 14 is pressed together with the high-resilience sealing ring 15. At this time, the pipe ends of the pipe fitting 9 are sealed.

[0037] Step 2: Inject hydraulic oil 7 into the constant temperature chamber 1 until the level of hydraulic oil 7 covers the mold 2. After the hydraulic oil 7 is injected, turn on the heating element 18 to heat the hydraulic oil 7. At the same time, turn on the stirring mechanism 19 to stir the hydraulic oil 7 to ensure the temperature uniformity of the hydraulic oil 7. During the heating process, the temperature of the hydraulic oil 7 and the temperature inside the forming cavity of the mold 2 are measured in real time through the thermocouple 21 until the detected temperature value reaches the design value.

[0038] Step 3: Start the left hydraulic pump mechanism 5 and the right hydraulic pump mechanism 6 to pressurize the hydraulic oil 7 inside the constant temperature chamber 1 and inject it into the tube 9. As the hydraulic oil 7 is continuously injected, expansion pressure will be generated inside the tube 9, forcing the tube 9 to gradually expand and deform. As the tube 9 expands and deforms, the hydraulic oil 7 in the forming cavity of the mold 2 outside the tube 9 will be squeezed out into the constant temperature chamber 1 through the oil passage 20. During the expansion and deformation process of the tube 9, the deformation amount is measured in real time by the displacement sensor 22 until the deformation amount reaches the design value. Then, the left hydraulic pump mechanism 5 and the right hydraulic pump mechanism 6 are turned off, and the forming of the tube 9 is completed.

[0039] In this embodiment, the design temperature range of hydraulic oil 7 is 120℃~250℃, the hydraulic oil 7 is injected into the pipe 9 by pulse injection, and the design value of the expansion pressure inside the pipe 9 is 20MPa~60MPa.

[0040] The solutions described in the embodiments are not intended to limit the scope of patent protection of this invention. All equivalent implementations or modifications that do not depart from the scope of this invention are included in the patent scope of this case.

Claims

1. A thermostatic hot oil forming apparatus for thin-walled magnesium alloy tubes, characterized in that: The utility model relates to a kind of hydraulic oil pipe forming device, including thermostat, mould, left sealing assembly, right sealing assembly, left hydraulic pump mechanism and right hydraulic pump mechanism;Hydraulic oil is contained in the thermostat;The mould is located inside thermostat and is immersed in hydraulic oil;The left sealing assembly is arranged at the left oil inlet of mould;The right sealing assembly is arranged at the right oil inlet of mould;Left hydraulic pump mechanism and right hydraulic pump mechanism are located outside thermostat, and the oil outlet of left hydraulic pump mechanism is communicated with the left pipe mouth of pipe fitting in mould by left sealing assembly and left oil injection pipe, and the oil outlet of right hydraulic pump mechanism is communicated with the right pipe mouth of pipe fitting in mould by right sealing assembly and right oil injection pipe;The oil inlet of left hydraulic pump mechanism is communicated with the inner chamber of thermostat by left oil suction pipe, and the oil suction pipe mouth of left oil suction pipe is immersed in hydraulic oil;The oil inlet of right hydraulic pump mechanism is communicated with the inner chamber of thermostat by right oil suction pipe, and the oil suction pipe mouth of right oil suction pipe is immersed in hydraulic oil;The left sealing assembly and right sealing assembly are same structure, and are all including outer sleeve, sealing plunger, high resilience seal ring and traction mechanism;The outer sleeve is sleeved outside sealing plunger, and sealing plunger has axial sliding freedom degree relative to outer sleeve;The sealing plunger is fixedly sleeved outside left oil injection pipe / right oil injection pipe;The high resilience seal ring is sleeved behind the plug head of sealing plunger, and the outer sleeve pipe mouth behind the plug head of sealing plunger is equipped with docking slot, and high resilience seal ring is fixedly equipped in docking slot;The traction mechanism is arranged on the outer sleeve pipe body, and the outer sleeve has axial sliding freedom degree relative to the left oil inlet / right oil inlet of mould, and the axial sliding of outer sleeve is driven by traction mechanism, and the axial sliding of sealing plunger is also driven by traction mechanism.

2. The hot oil thermostatic forming device for magnesium alloy thin-walled tube according to claim 1, characterized in that: An electric heating element is arranged inside the thermostat to heat the hydraulic oil contained in the thermostat.

3. The hot oil thermostatic forming device for magnesium alloy thin-walled tube according to claim 1, characterized in that: A stirring mechanism is arranged inside the thermostat to stir the hydraulic oil contained in the thermostat.

4. The hot oil thermostatic forming device for magnesium alloy thin-walled tube according to claim 1, characterized in that: Oil holes are formed at positions corresponding to pipe forming cavities of the upper die and lower die of the mould, and the inner chamber of the thermostat is communicated with the pipe forming cavities in the mould through the oil holes.

5. The hot oil thermostatic forming device for magnesium alloy thin-walled tube according to claim 1, characterized in that: A thermocouple is arranged inside the thermostat to measure the temperature of the hydraulic oil contained in the thermostat and the temperature in the pipe forming cavities of the mould.

6. The hot oil thermostatic forming device for magnesium alloy thin-walled tube according to claim 1, characterized in that: Displacement sensors are installed at positions corresponding to the pipe forming cavities of the upper die and lower die of the mould, and the displacement sensors are located between the mould and the pipe to measure the deformation of the pipe.

7. The hot oil thermostatic forming device for magnesium alloy thin-walled tube according to claim 1, characterized in that: The hydraulic oil contained in the thermostat is selected from silicon oil.

8. A hot oil thermostatic forming method of a magnesium alloy thin-walled tube using the hot oil thermostatic forming apparatus of the magnesium alloy thin-walled tube according to claim 1, characterized by The method comprises the following steps: Step one: clamp the pipe to be processed into the pipe forming cavity between the upper die and lower die of the mould, then move the outer sleeves of the left sealing assembly and right sealing assembly towards the pipe forming cavity by the traction mechanism until the pipe mouths of the pipe are inserted into the docking slots, then move the sealing plungers of the left sealing assembly and right sealing assembly away from the pipe forming cavity until the plug heads of the sealing plungers are pressed tightly together with the high resilience seal rings, and at this time, the pipe mouths at both ends of the pipe are sealed. Step two: inject hydraulic oil into the thermostat, until the liquid level of the hydraulic oil overflows the mold, after the hydraulic oil injection is completed, open the electric heating element, through the electric heating element to heat the hydraulic oil, at the same time, open the stirring mechanism, stir the hydraulic oil, ensure the uniformity of the temperature of the hydraulic oil, measure the temperature of the hydraulic oil and the temperature in the mold pipe forming cavity in real time through the thermocouple during the heating process, until the detected temperature value reaches the design value; Step three: start the left hydraulic pump mechanism and the right hydraulic pump mechanism, pressurize the hydraulic oil in the thermostat into the pipe, with the continuous injection of the hydraulic oil, the bulging pressure is generated in the pipe, forcing the pipe to gradually expand and deform, with the expansion and deformation of the pipe, the hydraulic oil in the mold pipe forming cavity outside the pipe will be extruded into the thermostat through the oil hole, the deformation of the pipe is measured in real time by the displacement sensor during the expansion and deformation process, until the deformation value reaches the design value, then the left hydraulic pump mechanism and the right hydraulic pump mechanism are closed, and the pipe forming is completed.

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