Stamping-bulging composite forming method for annular corrugated diaphragm of welded expansion joint

Abstract

The invention relates to a metal plate plastic forming method, in particular to a stamping-bulging composite forming method for an annular corrugated diaphragm of a welded expansion joint. The stress state of the formed diaphragm can be adjusted, the inner side pressure stress of the bent position of the corrugated diaphragm is converted into tensile stress, sufficient plastic deformation occurs in a formed area, and springback is reduced. By adjusting the stamping drawing force and the bulging internal pressure, the equivalent stress distribution of the diaphragm forming area can be more uniform, the stress difference of all the areas is reduced, then the warping of the forming area is reduced after the load is removed, and the forming precision is improved. The large radial stress can be generated in the diaphragm forming area only by applying small pressure to the middle area of the diaphragm blank, the large radial stress is used for adjusting the stress state of the diaphragm forming area, and therefore the high requirement of large bulging pressure on equipment and a die can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to a metal sheet plastic forming method, in particular to a method for stamping-expanding composite forming of a welded expansion joint annular corrugated diaphragm. BACKGROUND

[0002] An expansion joint is a thin-walled cylinder with a corrugated shape along the axial direction, which is an elastic component that can change shape and size under the action of a small external load, and the shape and size can be restored after unloading. Therefore, it has the functions of displacement compensation, shock absorption and noise reduction, stress release caused by structural thermal deformation, and sealing, and can be applied to the fields of aviation, ships, transportation, petrochemical industry, nuclear energy, etc. The expansion joint is mainly composed of a corrugated section and an end flange. The corrugated section has a large diameter, a small wall thickness, a small size of corrugated features, and low overall rigidity, so it has great forming difficulty.

[0003] The corrugated section of the expansion joint can be divided into two types: integral type and welded type. The welded expansion joint is first formed into an annular corrugated diaphragm by plastic deformation of a thin plate, and then is formed by alternating welding along the inner and outer edges. This method is relatively simple to implement, the wave spacing can be made very small, the wall thickness uniformity is high, and it can be flexibly applied to the manufacture of expansion joints with various special-shaped cross-sections.

[0004] The basic unit of the corrugated section of the welded expansion joint is the diaphragm, which is a typical complex variable cross-section high-temperature alloy thin-walled part. The forming methods mainly include stamping forming and liquid-filled expanding. The stamping forming is to apply pressure to the plate by a press to make it produce plastic deformation. The stamping forming of the expansion joint corrugated section has the problem of springback, which seriously affects the forming accuracy of the diaphragm. The liquid-filled expanding is to apply a certain pressure to the flowable liquid medium, so that the plate is formed into the required part shape under the action of the pressure. The liquid-filled expanding technology can effectively improve the defects such as fracture and wrinkling of the diaphragm. Due to the small radius of the corner on the corrugated diaphragm, a large expanding pressure is required, which puts high requirements on the equipment and die, and the forming area is prone to excessive thinning, making the maximum wall thickness thinning value exceed the required value. SUMMARY

[0005] The present application is to solve the problems of low forming accuracy, excessive expanding pressure, excessive thinning in the forming area, and springback in the manufacture of the welded expansion joint annular corrugated diaphragm by the existing method, and a stamping-expanding composite forming method for the welded expansion joint annular corrugated diaphragm is proposed, and the key is to develop a special die.

[0006] According to one aspect of the present application, a method for stamping-expanding composite forming of a welded expansion joint annular corrugated diaphragm is provided, which adopts a special die;

[0007] The die is composed of an upper die 1, a pressure ring 2, and a lower die 3.

[0008] The lower die 3 side wall is provided with a liquid filling hole 3-1, and the inside is a liquid filling cavity 3-2. The top corrugated part corresponds to the upper die forming process section profile 1-1, and its characteristics are consistent with the shape characteristics of the lower surface of the target expansion joint annular corrugated diaphragm 4. It is the lower die forming process section profile 3-3, and the inner side is provided with a sealing ring 3-4;

[0009] Among them, the upper die 1 and the lower die 3 are connected with the upper shaft and the lower shaft of the double-action press respectively, and the blank holder 2 is connected with the blank holder cylinder of the double-action press;

[0010] It includes the following steps:

[0011] Place the plate on the workbench on the upper surface of the lower die 3, close the upper die 1 and the lower die 2, complete the stamping process, fill liquid at the liquid filling hole 3-1, apply bulging pressure p to the plate, end the liquid bulging, the pressure in the liquid filling cavity 3-2 drops, the plate deformation ends, unloads, the blank holder 2 and the upper die 1 retreat, and the preliminary formed plate 5 is obtained. Cutting, removing the bulging area and the blank holder part of the preliminary formed plate 5, and obtaining the target expansion joint annular corrugated diaphragm 4.

[0012] The upper die 1 is disc-shaped, and the bottom contact area with the plate is processed into a corrugated shape with a specific size, which is consistent with the shape of the upper surface of the target expansion joint annular corrugated diaphragm 4, and is the upper die forming process section profile 1-1. The inside is provided with a plate forming cavity 1-2.

[0013] The blank holder 2 is circular ring-shaped, and the vertical section 2-1 is used for upper die positioning and calibration, the inner diameter is slightly larger than the outer diameter of the upper die 1, the bottom is a blank holding plane 2-2, and the outer ring diameter is the same as the outer edge diameter of the lower die 3.

[0014] The material of the plate is high-temperature alloy, aluminum alloy or stainless steel.

[0015] According to the size calculation of the target expansion joint annular corrugated diaphragm 4, the diameter D of the plate is determined, and the size of the matched die is determined accordingly;

[0016] Among them, the diameter D of the plate should be greater than the diameter D1 of the target expansion joint annular corrugated diaphragm 4, and enough blank holding width L should be reserved;

[0017] The outer diameter R1 of the upper die 1 is equal to the diameter D1 of the target expansion joint annular corrugated diaphragm 4, and the outer edge diameter R2 of the lower die 3 is equal to the sum of the diameter D1 of the target expansion joint annular corrugated diaphragm 4 and the blank holding width L.

[0018] The die closing includes the following process:

[0019] The blank holder cylinder of the double-action press moves the blank holder 2 downward to apply a certain blank holding force F to the plate QThe function is to fix the sheet, prevent the sheet from moving and wrinkling in the stamping process, and control the uniform inflow of the sheet into the inflation process;

[0020] The upper die 1 is driven downward by the beam of the double-action press, and gradually closes with the lower die 3 to apply a drawing force F on the sheet D , so that the sheet is plastically deformed until it completely matches the die; at this time, the sealing ring 3-4 seals the liquid-filled cavity 3-2.

[0021] The liquid is filled into the liquid-filled cavity 3-2, and the inflation pressure p is applied to the sheet; at this time, the upper die 1 and the blank holder ring 2 are fixed, and the sheet is in a stress state as shown in Figure 9 . Under the action of the inflation pressure p, the sheet is plastically deformed, thereby generating a certain radial tension Fr on the part of the sheet that is stamped and drawn to form the annular diaphragm, and further increasing the radial tensile stress σ r in the annular diaphragm forming area, as shown in Figure 10 . The stress state of the annular corrugated diaphragm bending arc outside the tensile stress and the inside compressive stress will change to tensile stress on the inside and outside, and the difference between the inside and outside stress will be smaller (as shown in Figure 11 ), thereby reducing the deformation rebound. By controlling the size relationship of the blank holder force F Q , the drawing force F D and the inflation pressure p, the sheet part in the blank holder area can flow into the annular corrugated diaphragm forming area, avoiding excessive thinning. The inflation pressure p can fully adjust the stress state of the sheet forming area, convert part of the compressive stress in the forming area to tensile stress, make the sheet fully deform, and reduce residual stress. The inflation pressure makes the stress distribution of the diaphragm more uniform in the radial direction, reduces the stress difference between the inside and outside of the bending arc, thereby reducing the deformation rebound and improving the forming precision of the diaphragm forming area. By controlling the size of the blank holder force F Q , the drawing force F D and the inflation pressure p, the wall thickness of the annular diaphragm forming area can be adjusted to avoid excessive thinning and improve the service life of the diaphragm.

[0022] The liquid is a 1-5wt% emulsion aqueous solution.

[0023] The inflation pressure can adjust the stress state of the sheet forming area, provide a tensile force from the non-forming area to the sheet forming area, convert part of the compressive stress in the annular corrugated diaphragm bending forming area to tensile stress, reduce the stress difference between the inside and outside of the bending arc, and further reduce the rebound; in addition, the sheet forming area is fully plastically deformed, the warping problem caused by uneven stress distribution is reduced, and the forming precision of the diaphragm forming area is improved. By changing the size of the stamping drawing force and the inflation internal pressure, the material in the blank holder area flows into the annular corrugated diaphragm forming area, which can reduce the problem of excessive thinning of the diaphragm and improve the service life of the diaphragm.

[0024] The beneficial effects of the present application are:

[0025] First, the device used in the present application has simple structure, is easy to realize and has low cost.

[0026] Second, the present application can adjust the stress state of the formed diaphragm, convert the compressive stress inside the bending part of the corrugated diaphragm into tensile stress, cause sufficient plastic deformation of the forming area, and reduce the springback.

[0027] Third, by adjusting the size of the stamping and drawing force and the bulging internal pressure, the present application can make the equivalent stress distribution of the diaphragm forming area more uniform, reduce the stress difference of each area, and thus reduce the warping of the forming area after the load is removed, and improve the forming precision.

[0028] Fourth, the present application only needs to apply a small pressure in the middle area of the diaphragm blank to generate a larger radial stress in the diaphragm forming area, which is used to adjust the stress state of the diaphragm forming area, so that the high requirement of the equipment and die for the larger bulging pressure can be avoided.

[0029] Fifth, the improvement of the diaphragm forming precision of the present application is beneficial to the subsequent welding step, which can make the diaphragm better fit the welding tooling, thereby improving the welding precision and the dimensional accuracy of the expansion joint part. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the process flow chart of Example 1;

[0031] Figure 2 is the process flow chart of Example 1;

[0032] Figure 3 is the process flow chart of Example 1;

[0033] Figure 4 is the process flow chart of Example 1;

[0034] Figure 5 is the process flow chart of Example 1;

[0035] Figure 6 is the process flow chart of Example 1;

[0036] Figure 7 is the process flow chart of Example 1;

[0037] Figure 8 is the process flow chart of Example 1;

[0038] Figure 9 is the process flow chart of Example 1;

[0039] Figure 10 is the process flow chart of Example 1; Figure 9 is the process flow chart of Example 1;

[0040] Figure 11 for Figure 9 Force diagram of region B;

[0041] Among them, 1 is the upper mold, 1-1 is the upper mold forming process section surface, 1-2 is the sheet forming cavity, 2 is the pressure ring, 2-1 is the vertical section, 2-2 is the pressure plane, 3 is the lower mold, 3-1 is the liquid filling hole, 3-2 is the liquid filling cavity, 3-3 is the lower mold forming process section surface, 3-4 is the sealing ring, 4 is the target expansion joint annular corrugated diaphragm, and 5 is the preliminary formed sheet. Detailed Implementation

[0042] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0043] Example 1

[0044] The following molds are used:

[0045] The mold consists of an upper mold 1, a pressure ring 2, and a lower mold 3;

[0046] The lower mold 3 has a liquid filling hole 3-1 on its side wall and a liquid filling cavity 3-2 inside. The corrugated part at the top corresponds to the upper mold forming process section surface 1-1. Its features are consistent with the shape features of the lower surface of the target expansion joint annular corrugated diaphragm 4. It is the lower mold forming process section surface 3-3, and a sealing ring 3-4 is provided on its inner side.

[0047] Among them, the upper mold 1 and the lower mold 3 are respectively connected to the upper shaft and the lower shaft of the double-action press, and the pressure ring 2 is connected to the pressure cylinder of the double-action press.

[0048] The upper mold 1 is disc-shaped, and the bottom area in contact with the plate is processed into a corrugated shape of a specific size. Its features are consistent with the shape of the upper surface of the target expansion joint annular corrugated diaphragm 4, which is the upper mold forming process section surface 1-1, and the plate forming cavity 1-2 is provided inside.

[0049] The pressure ring 2 is circular, with the vertical section 2-1 used for positioning and calibration of the upper mold. Its inner diameter is slightly larger than the outer diameter of the upper mold 1. The bottom is the pressure plane 2-2, and the outer diameter is the same as the outer edge diameter of the lower mold 3.

[0050] Target parts such as Figure 7 As shown, the part is made of GH4169 high-temperature alloy and has a thickness of 0.3mm.

[0051] The specific dimensions are as follows: diameter D1 = 304mm, the corrugated feature is composed of five arcs, with arc radii of r1 = 2.5mm, r2 = 2.14mm, r3 = 3.94mm, r4 = 3.24mm, and r5 = 5.2mm.

[0052] Step one, according to the size of the target part to determine the diameter of the plate D = 400 mm, the radius of the upper die R1 = 152 mm, the radius of the lower die R2 = 200 mm, the width of the blank holder L = 48 mm.

[0053] Step two, the circular GH4169 high-temperature alloy plate is placed on the upper surface of the lower die, and the distance between the upper and lower dies in the initial stage is 2 mm.

[0054] Step three, the blank holder cylinder of the press drives the blank holder to move downward, and the blank holder force F Q = 10t.

[0055] Step four, the upper beam of the press drives the upper die to move downward, and a drawing force of 20t is applied, so that the deformation of the plate blank forming area gradually fits the upper and lower dies, until the plate blank completely fits the die, and the sealing ring forms a seal;

[0056] Step five, the liquid is filled into the liquid-filled cavity, and an internal pressure of 3MPa is applied to the plate.

[0057] Step six, end of liquid expansion, the internal pressure of the liquid-filled cavity decreases, and the plate deformation ends.

[0058] Step seven, unload, the blank holder and the upper die retreat, and the initially formed plate is obtained.

[0059] Step eight, cutting, the plate material of the expansion area and the blank holder of the initially formed plate 5 is removed, and the target expansion joint annular corrugated diaphragm 4 is obtained.

[0060] The liquid used is an emulsion aqueous solution, wherein the mass ratio of emulsion to water is 1:20.

[0061] The press used is a commercial press with corresponding emulsion.

[0062] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can make several modifications or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1.A method for stamping-bulging compound forming of a welded expansion joint annular corrugated diaphragm, characterized in that, a special mold is used; the mold is composed of an upper mold (1), a blank holder (2) and a lower mold (3); the lower mold (3) is provided with a liquid filling hole (3-1) on the side wall, and the inside is a liquid filling cavity (3-2), and the top corrugated part corresponds to the upper mold forming process section profile (1-1), the feature of the lower surface of the target expansion joint annular corrugated diaphragm (4) is consistent with the lower mold forming process section profile (3-3), and the inner side is provided with a sealing ring (3-4); wherein the upper mold (1) and the lower mold (3) are connected with the upper shaft and the lower shaft of a double-action press respectively, and the blank holder (2) is connected with the blank holder cylinder of the double-action press; including the following steps: placing the plate material on the workbench on the upper surface of the lower mold (3), closing the upper mold (1) and the lower mold (3), after the stamping process is completed, filling liquid at the liquid filling hole (3-1), applying bulging pressure p to the plate material, ending the liquid bulging, the pressure in the liquid filling cavity (3-2) decreases, the plate material deforms, unloads, the blank holder (2) and the upper mold (1) retreat, and the initially formed plate material (5) is obtained, cutting, removing the bulging area and the blank holder part of the initially formed plate material (5), and obtaining the target expansion joint annular corrugated diaphragm (4). 2.According to the method of claim 1, characterized in that, the upper mold (1) is disc-shaped, the bottom part is processed into a corrugated shape with a specific size in the contact area with the plate material, and the feature is consistent with the upper surface shape of the target expansion joint annular corrugated diaphragm (4), which is the upper mold forming process section profile (1-1), and the inside is provided with a plate material forming cavity (1-2). 3.According to the method of claim 1, characterized in that, the blank holder (2) is circular ring-shaped, the vertical section (2-1) is used for upper mold positioning and calibration, the inner diameter is slightly larger than the outer diameter of the upper mold (1), the bottom part is a blank holding plane (2-2), and the outer ring diameter is the same as the outer edge diameter of the lower mold (3). 4.According to the method of claim 1, characterized in that, the material of the plate material is high-temperature alloy, aluminum alloy or stainless steel. 5.According to the method of claim 1, characterized in that, the diameter D of the plate material is determined according to the size calculation of the target expansion joint annular corrugated diaphragm (4), and the size of the matched mold is determined accordingly; wherein the diameter D of the plate material should be greater than the diameter D1 of the target expansion joint annular corrugated diaphragm (4), and sufficient blank holding width L is reserved; the outer diameter R1 of the upper mold (1) is equal to the diameter D1 of the target expansion joint annular corrugated diaphragm (4), and the outer edge diameter R2 of the lower mold (3) is equal to the sum of the diameter D1 of the target expansion joint annular corrugated diaphragm (4) and the blank holding width L. 6.According to the method of claim 1, characterized in that, the closing of the mold includes the following process: The double-action press blank holder cylinder moves the blank holder (2) downward to apply a certain blank holding force F to the sheet metal Q Its function is to fix the sheet metal, prevent the sheet metal from moving and wrinkling during the stamping process, and control the uniform flow of the sheet metal inward during the bulging process The upper die (1) is driven downward by the cross beam of the double-action press, and gradually closes with the lower die (3) to exert the drawing force F on the plate D and plastically deforms until completely conforming to the die; at this time, the sealing ring (3-4) seals the liquid-filled cavity (3-2). 7.According to the method of claim 6, characterized in that, Under the action of the bulging pressure p, the plate material plastically deforms, thereby generating a certain radial tension Fr on the part of the plate material that is punched and drawn to form the annular diaphragm, and further causing the annular diaphragm to additionally increase the radial tensile stress σ in the punched and drawn forming area r . 8.According to the method of claim 1, characterized in that, the liquid is a 1-5wt% emulsion aqueous solution.

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