A feedable superplastic gas inflation forming die and method

Abstract

The application belongs to the technical field of molds and provides a feedable superplastic gas bulging forming mold and method, the feedable superplastic gas bulging forming mold comprising: an upper mold and a lower mold, the lower mold having a cavity; the upper mold comprising an inner ring and an outer ring, the inner ring being a feedable preforming mold with a sealing ring, and the outer ring being a gas bulging forming mold with a sealing stem, the application does not need to additionally manufacture a rigid mold, realizes preforming by using gas under the premise that little sheet thinning occurs, saves the cost of mold manufacturing, avoids the defect of local excessive thinning of directly superplastic gas bulging formed parts, guarantees the forming precision and surface quality requirement of the parts, and improves the thickness uniformity of the parts.

Description

Technical Field

[0001] This invention relates to the field of mold-related technology, specifically a feedable superplastic air-expansion molding mold and method. Background Technology

[0002] Superplastic gas-formed parts are generally complex in shape or large in size, and the thickness of the formed parts is uneven. In particular, some box-shaped parts are prone to excessive thinning or even cracking. On the one hand, this affects the mechanical properties and load-bearing capacity of the parts, and on the other hand, it reduces the yield and increases the cost. They are widely used in aerospace, rail transportation and weaponry.

[0003] Currently, the main methods to solve the problem of excessive thinning of superplastic gas-formed parts are as follows:

[0004] 1. Regarding the original board material: compensate for the thickness loss in areas of excessive thinning by increasing the original board material thickness or designing uneven board thickness;

[0005] 2. Process aspects: The initial material thickness distribution in the final forming is improved by using pre-reverse air expansion deformation, or mechanical pre-forming is used to increase the volume of sheet material participating in the superplastic air expansion forming process.

[0006] Existing solutions have certain shortcomings: increasing the original sheet thickness increases the part's weight, contradicting lightweight design requirements; producing unequal-thickness blanks requires advanced technology, significantly increasing production costs; pre-expansion deformation reduces production efficiency; mechanical preforming may cause the sheet to crack upon contact with the preforming mold, and the shape of the mechanically preformed sheet is difficult to control, increasing mold manufacturing costs and the risk of sheet cracking and wrinkling. Therefore, to address these shortcomings, there is an urgent need for a feedable superplastic expansion forming mold and method to overcome the deficiencies in current practical applications. Summary of the Invention

[0007] The purpose of this invention is to provide a feedable superplastic gas-inflating mold and method, which aims to solve the problems in the above-mentioned technical background.

[0008] This invention is achieved by providing a feedable superplastic air-expansion molding die, which is mounted on a double-action press. The feedable superplastic air-expansion molding die comprises:

[0009] An upper mold and a lower mold, wherein the lower mold has a cavity;

[0010] The upper mold includes an inner ring and an outer ring. The inner ring is a feedable pre-forming mold with a sealing ring, and the outer ring is an air-expanding forming mold with a sealing ring.

[0011] As a further aspect of the present invention: the preform mold and the lower mold are respectively provided with an air inlet and an air outlet, the air inlet is provided with an air inlet pipe and the air outlet is provided with an air outlet pipe; the diameter of the air inlet and the air outlet is 2-4mm.

[0012] As a further aspect of the present invention: the air-expansion forming mold is provided with an air intake pipe auxiliary groove for connecting the air intake pipe and the air intake device.

[0013] As a further aspect of the present invention: a groove for placing a sealing ring is formed on the preform mold.

[0014] As a further aspect of the present invention: the sealing ring is located 10-20mm outside the outline of the part.

[0015] As a further aspect of the present invention, the lower mold is further provided with multiple sets of weight-reducing grooves.

[0016] A feedable superplastic gas forming method, applied to the feedable superplastic gas forming mold as described above, the method comprising the following steps:

[0017] Step 1: Install the upper and lower molds onto the double-action press. The pre-forming mold and the air-expansion forming mold of the upper mold are installed on the inner and outer slides of the press, respectively. The air inlet pipe is welded to the pre-forming mold.

[0018] Step 2: Pneumatic preforming. When the mold temperature reaches the superplastic forming temperature and the temperature is uniform, place the sheet material between the lower mold and the preforming mold. After keeping it warm for 5-10 minutes, open the air inlet valve. While the sealing ring prevents gas leakage, the sheet material is fed into the cavity of the lower mold under the action of gas.

[0019] Step 3: Superplastic air expansion forming. After the sheet metal flows and forms the basic shape of the part, the air expansion forming die moves down to press down the sheet metal around it, increasing the air pressure and using the sheet metal stretching to complete the superplastic air expansion forming.

[0020] As a further aspect of the present invention: in step two, graphite lubricant is sprayed on both sides of the sheet before unloading;

[0021] The gas pressure used for preforming is 0.1-1 MPa;

[0022] The upper and lower molds are installed on a heating platform, and the temperature of the heating platform is controlled by 8-16 temperature control units. The temperature is transferred to the upper and lower molds through heat conduction. After reaching the predetermined temperature, the temperature is maintained for 20-30 minutes to ensure uniform mold temperature.

[0023] As a further aspect of the present invention: in step three, when the air-forming mold descends, the sealing ring is used to fix the four sides of the sheet metal.

[0024] When the air pressure is increased, small and complex local shapes are formed. When there is basically no gas escaping from the exhaust pipe, the pressure is maintained for 3-5 minutes to complete the forming.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This feedable superplastic gas forming mold eliminates the need for additional rigid mold manufacturing. It achieves preforming using gas with almost no sheet metal thinning, saving mold manufacturing costs and avoiding the disadvantage of excessive local thinning in directly superplastic gas forming parts. It ensures the forming accuracy and surface quality requirements of the parts and improves the thickness uniformity of the parts.

[0027] Compared with reverse air expansion preforming technology, this method can save mold manufacturing costs, shorten product production time, form products with more complex shapes or deeper depths, and has a high product yield.

[0028] Compared with mechanical preforming, this method can save mold manufacturing costs and reduce the risk of cracking and wrinkling;

[0029] Because this method is carried out under low air pressure, the rubber sealing ring has a significant sealing effect on the gas. It can push the sheet into the cavity without significantly reducing the thickness, providing sufficient sheet volume for gas expansion molding, greatly improving the thickness uniformity of the molded product, improving the excessive thinning of parts, and improving the physical properties of the parts.

[0030] This method involves preforming the material under pressure feeding, followed by superplastic air expansion forming. The main shape of the part is formed by the flow of the sheet metal. Complex shapes that are difficult to form can be formed by thinning the sheet metal, which greatly improves the freedom of product design.

[0031] This invention offers unparalleled forming freedom compared to existing metal forming processes, allowing for greater diversity in product design in terms of shape complexity and size, and a wider range of applications. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the state of the sheet metal being placed in the mold according to an embodiment of the present invention.

[0033] Figure 2 for Figure 1 A magnified view of part A in the middle.

[0034] Figure 3 This is a schematic diagram showing the state at the end of the feeding preforming process according to an embodiment of the present invention.

[0035] Figure 4 for Figure 1 A magnified view of part B in the middle section.

[0036] Figure 5This is a schematic diagram showing the state at the end of the superplastic gas expansion molding process according to an embodiment of the present invention.

[0037] Figure 6 for Figure 1 A magnified view of part C in the middle.

[0038] Figure 7 This is a cloud map showing the thickness distribution of a simulated sheet metal for direct superplastic gas expansion forming, as shown in the embodiment of the present invention.

[0039] Figure 8 for Figure 7 A cross-sectional view of the sheet metal at point DD along the diagonal.

[0040] Figure 9 This is a cloud map showing the thickness distribution of a pre-formed sheet material under feed air pressure, as shown in the embodiment of the present invention.

[0041] Figure 10 for Figure 9 A cross-sectional view of the sheet metal along the diagonal at the EE section.

[0042] Figure 11 This is a cloud map showing the thickness distribution of a pre-formed sheet material under feed air pressure, as shown in the embodiment of the present invention.

[0043] Figure 12 for Figure 11 A cross-sectional view of the sheet metal along the diagonal at the FF section.

[0044] Figure 13 This is a comparison diagram of sheet metal profiles obtained by direct superplastic gas forming and the forming method of this invention.

[0045] In the attached diagram: 1-Pre-forming mold, 2-Air-expanding forming mold, 3-Sheet material, 4-Lower mold, 5-Weight reduction groove, 6-Exhaust pipe, 7-Sealing ring, 8-Sealing ring, 9-Inlet pipe, 10-Inlet pipe auxiliary groove. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0047] Please see Figures 1-6 This invention provides a feedable superplastic air-expansion molding die, which is mounted on a double-action press. The feedable superplastic air-expansion molding die includes:

[0048] Upper mold and lower mold 4, wherein the lower mold 4 has a cavity;

[0049] The upper mold includes an inner ring and an outer ring. The inner ring is a feedable pre-forming mold 1 with a sealing ring 7, and the outer ring is an air-expanding forming mold 2 with a sealing ring 8.

[0050] In the embodiments of the present invention, the sealing ring 7 is made of high-temperature resistant rubber. With the assistance of the high-temperature resistant rubber sealing ring 7, the sheet 3 is moved by gas to achieve air pressure preforming. During superplastic air expansion forming, the sealing ring 8 restricts the flow of the sheet 3, and the air expansion forms a complex and small shape. The double-movement structure of the upper mold (i.e., the preforming mold 1 and the air expansion forming mold 2) can not only form complex parts with high shape accuracy, but also effectively improve the uniformity of the part wall thickness, reduce the superplasticity requirements of the original sheet material for superplastic air expansion forming, and has a wide range of applications. Compared with the prior art, using this feedable superplastic air expansion forming mold, there is no need to manufacture an additional rigid mold. Preforming is achieved by gas without almost any sheet thinning, saving the cost of mold manufacturing, avoiding the disadvantage of local excessive thinning of parts in direct superplastic air expansion forming, ensuring the forming accuracy and surface quality requirements of the parts, and improving the thickness uniformity of the parts.

[0051] In one embodiment of the present invention, please refer to Figure 1 The preform mold 1 and the lower mold 4 are respectively provided with an air inlet and an air outlet. An air inlet pipe 9 is provided at the air inlet and an air outlet pipe 6 is provided at the air outlet. The diameter of the air inlet and the air outlet is 2-4mm. The air inlet is located at the center of the preform mold 1 and the air outlet is located at the last film-attached position of the sheet 3 of the lower mold 4.

[0052] The air-expansion forming mold 2 is provided with an air intake pipe auxiliary groove 10 for connecting the air intake pipe and the air intake device;

[0053] The preform mold 1 has a groove for placing the sealing ring 7, ensuring that the sealing ring 7 is 3-5mm higher than the lower surface of the preform mold 1 after being placed in the groove.

[0054] The sealing ring 8 is located 10-20mm outside the outline of the part;

[0055] The lower mold 4 is also provided with multiple sets of weight reduction grooves 5.

[0056] Please see Figures 1-13 A feedable superplastic gas forming method, applied to the feedable superplastic gas forming mold as described above, the method comprising the following steps:

[0057] Step 1: Install the upper mold and lower mold 4 onto the double-action press. The pre-forming mold 1 and the air-expansion forming mold 2 of the upper mold are respectively installed on the inner slide and outer slide of the press. The air inlet pipe 9 is welded to the pre-forming mold 1.

[0058] Step Two: Pneumatic Pre-forming. When the mold temperature reaches the superplastic forming temperature and is uniform, place sheet metal 3 between the lower mold 4 and the pre-forming mold 1. After holding at this temperature for 5-10 minutes, open the air inlet valve. While the sealing ring 7 prevents gas leakage, sheet metal 3 is fed into the cavity of the lower mold 4 under the action of gas. Figure 3 and Figure 4 As shown, the sheet metal 3 is pre-formed without significant thinning; the type and model of the sealing ring 7 are determined according to the superplastic forming temperature and the size of the part. The pre-forming mold 1 moves down until the sealing ring 7 contacts the upper surface of the sheet metal 3, and the sealing ring 7 is in a compressed state to ensure that the sheet metal 3 can flow and that gas will not overflow.

[0059] Step 3: Superplastic air expansion forming. After the sheet metal 3 flows to form the basic shape of the part, the air expansion forming mold 2 moves down to press down the sheet metal 3 around it, increasing the air pressure. The superplastic air expansion forming is completed by stretching the sheet metal 3.

[0060] In step two, graphite lubricant is sprayed on both sides of the sheet 3 before feeding to facilitate feeding during preforming and demolding after forming;

[0061] The gas pressure used for preforming is 0.1-1 MPa;

[0062] The upper mold and lower mold 4 are installed on the heating platform, and the temperature of the heating platform is controlled by 8-16 temperature control units. The temperature is transferred to the upper mold and lower mold 4 through heat conduction. After reaching the predetermined temperature, the temperature is maintained for 20-30 minutes to ensure uniform mold temperature.

[0063] In step three, as the air-forming mold 2 descends, the sealing rod 8 is used to fix the four sides of the sheet metal 3.

[0064] When the air pressure is increased, small and complex local shapes are formed. When there is basically no gas escaping from the exhaust pipe 6, the pressure is maintained for 3-5 minutes, and the forming is completed.

[0065] In this embodiment, the forming process of the direct superplastic gas forming method in this example is calculated using finite element simulation. The thickness distribution of sheet 3 is as follows: Figure 7 and Figure 8 As shown, DD is a cross-sectional view of sheet 3 along its diagonal. In this example, the initial thickness of sheet 3 is 2mm. It is formed by direct superplastic gas expansion molding. Severe thinning occurs at the bottom rounded corners, with a minimum thickness of 0.84mm, resulting in substandard product quality.

[0066] The forming process of this example using the method of the present invention was calculated using finite element simulation. The thickness distribution of sheet 3 after air pressure preforming is as follows: Figure 9 and Figure 10As shown, EE is a cross-sectional view of sheet 3 along the diagonal; after preforming, sheet 3 flows into the cavity to form the basic shape, and sheet 3 hardly thins.

[0067] After superplastic air expansion final forming, the thickness distribution of sheet 3 is as follows: Figure 11 and Figure 12 As shown, FF is a cross-sectional view of sheet 3 along the diagonal; compared with the direct air-expansion forming method, the final sheet 3 formed by the feedable superplastic air-expansion forming method of the present invention has less thinning and a more uniform thickness distribution.

[0068] like Figure 13 As shown, the sheet material line of direct superplastic gas expansion forming is solid line G, and the sheet material line is fixed in the initial position. However, using the method of the present invention, the final sheet material line is dashed line H, with obvious material feeding, which directly affects the final thickness distribution.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for feedable superplastic gas-inflated molding, characterized in that, An applicable superplastic air-expansion forming mold is applied to a feedable mold mounted on a double-action press. The mold includes an upper mold and a lower mold, the lower mold having a cavity. The upper mold comprises an inner ring and an outer ring; the inner ring is a feedable preform mold with a sealing ring, and the outer ring is an air-expansion forming mold with a sealing ring. The preform mold and the lower mold are respectively provided with an air inlet and an air outlet. An air inlet pipe is provided at the air inlet, and an air outlet pipe is provided at the air outlet. The diameter of both the air inlet and the air outlet is 2-4 mm. The method includes the following steps: Step 1: Install the upper and lower molds onto the double-action press. The pre-forming mold and the air-expansion forming mold of the upper mold are installed on the inner and outer slides of the press, respectively. The air inlet pipe is welded to the pre-forming mold. Step 2: Pneumatic preforming. When the mold temperature reaches the superplastic forming temperature and the temperature is uniform, place the sheet material between the lower mold and the preforming mold. After keeping it warm for 5-10 minutes, open the air inlet valve. While the sealing ring prevents gas leakage, the sheet material is fed into the cavity of the lower mold under the action of gas. Step 3: Superplastic air expansion forming. After the sheet metal flows and forms the basic shape of the part, the air expansion forming die moves down to press down the sheet metal around it, increasing the air pressure and using the sheet metal stretching to complete the superplastic air expansion forming.

2. The method for feedable superplastic gas expansion molding according to claim 1, characterized in that, In step two, graphite lubricant is sprayed on both sides of the sheet before unloading; The gas pressure used for preforming is 0.1-1 MPa; The upper and lower molds are installed on a heating platform, and the temperature of the heating platform is controlled by 8-16 temperature control units. The temperature is transferred to the upper and lower molds through heat conduction. After reaching the predetermined temperature, the temperature is maintained for 20-30 minutes to ensure uniform mold temperature.

3. The method for feedable superplastic gas expansion molding according to claim 1, characterized in that, In step three, as the air-forming mold descends, the sealing rings are used to fix the sheet metal around its perimeter. When the air pressure is increased, small and complex local shapes are formed. When there is basically no gas escaping from the exhaust pipe, the pressure is maintained for 3-5 minutes to complete the forming.

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