Molding process of complex structural part

Abstract

The invention provides a forming process of a complex structural part, which mainly comprises the following steps of: firstly, respectively designing a compaction sintering die and an extrusion forming die according to the shapes of a rough blank and the structural part, and carrying out multidirectional compaction on metal powder added into a die cavity of the compaction sintering die by utilizing the compaction sintering die to obtain the rough blank; the rough blank and the compaction sintering mold are put into sintering equipment together to be sintered, demolding is conducted after sintering, and a sintered blank is obtained; and the sintered blank is subjected to multi-directional extrusion forging through an extrusion forming die. According to the method, powder metallurgy and the multi-directional extrusion forging process are combined, the forming difficulty of the complex structural part is reduced, on one hand, the strength and the coherent structure of the joints of all the parts of the final structural part are guaranteed, and on the other hand, the overall forming precision and strength of the final structural part are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical structural parts forming, in particular to a forming process of complex structural parts. Background Art

[0002] With the continuous development of the modern machinery industry, the demand for complex structural parts (such as branches and asymmetric cross-section complex structural parts) in related fields such as general mechanical equipment, aerospace equipment, transportation vehicles, and heating pipes is increasing day by day. At the same time, specific functional properties such as strength and hardness are also required for the overall or local components. The above factors have greatly increased the difficulty of preparing these complex structural parts.

[0003] The preparation methods of components in the prior art mainly include mechanical milling, casting, forging, die-casting and powder sintering. However, there are some disadvantages when using these methods to prepare complex structural parts: the mechanical milling method has long processing time, high equipment requirements, low material utilization rate and extremely high preparation cost. Traditional casting is difficult to guarantee the performance requirements of such components due to defects such as looseness, pores, and inclusions. Traditional forging and other processes can only achieve the preparation of rough blanks, and a large number of processing steps and man-hours are still required later, and the production cost is still difficult to effectively reduce. Components with complex spatial shapes often require a combination of multiple mold modules to realize multiple demolding surfaces, and finally realize the demolding action of the mold after forming, making it difficult to mass-produce complex structural parts using die-casting and powder sintering technologies.

[0004] Therefore, it is necessary to design a forming process for complex structural parts to solve the technical problems existing in the prior art, such as high forming difficulty, high forming cost, inability to balance forming accuracy and mechanical properties, and waste of materials. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the present invention provides a forming process for complex structural parts. The present invention combines powder metallurgy with multi-directional extrusion forging technology, which reduces the difficulty of forming complex structural parts. On the one hand, it ensures the strength and coherent structure of the joints of various parts of the final structural parts, and on the other hand, it ensures the overall forming accuracy and strength of the final structural parts.

[0006] In order to achieve the above object, the specific scheme adopted by the present invention is: A molding process for complex structural parts mainly includes the following steps: Step 1, formulate the shape of the rough blank according to the structure of the structural part to be finally formed, the rough blank has the initial outline of the structural part, and design a compaction sintering mold and an extrusion forming mold according to the shapes of the rough blank and the structural part, respectively, the compaction sintering mold comprises a compaction die sleeve and a plurality of compaction punches, the die cavity of the compaction die sleeve is formed by at least two compaction modules through mold closing, the compaction die sleeve after mold closing has a plurality of compaction channels, the compaction punches cooperate with the corresponding compaction channels, and the directions of movement of the plurality of compaction punches along the compaction channels to the die cavity are not completely the same or completely different; the extrusion forming mold comprises an extrusion die sleeve and a plurality of extrusion punches, the die cavity of the extrusion die sleeve is formed by at least two extrusion modules through mold closing, the extrusion die sleeve after mold closing has a plurality of extrusion channels, the extrusion punches cooperate with the corresponding extrusion channels, and the directions of movement of the plurality of extrusion punches along the extrusion channels to the die cavity are not completely the same or completely different; Step 2: close the compaction die sleeve, add metal powder into the die cavity through multiple compaction channels, and then perform multi-directional compaction through multiple compaction punches to obtain a rough blank; Step 3: Place the rough blank together with the compacted sintering mold into a sintering device for sintering, and demould after sintering to obtain a sintered blank; Step 4: Place the sintered blank in the die cavity by closing the extrusion die sleeve, and then use the extrusion punch to perform multi-directional extrusion forging on the sintered blank to obtain a structural part.

[0007] Furthermore, the power for closing the compaction die sleeve or the extrusion die sleeve is provided by a press equipment or a die frame device; the power for the compaction punch or the extrusion punch is provided by a press equipment or a die frame device.

[0008] Furthermore, in step one, at least one compaction module has the same structure as at least one extrusion module, so that the compaction die sleeve and the extrusion die sleeve are at least partially identical.

[0009] Furthermore, in step 2, the metal powder is 7075 aluminum alloy powder.

[0010] Furthermore, in step three, the sintering temperature is 540-580 °C, the heating rate is 50 °C / min, the sintering pressure is 40 MPa, and the holding time is 4 h.

[0011] Furthermore, in step 4, a heating and heat preservation device is provided outside the extrusion die sleeve after the die is closed, the extrusion forging temperature is 410-470°C, and the loading speed is 8 mm / s.

[0012] Furthermore, in step 4, during extrusion forging, the temperature difference between the sintered billet and the extrusion die sleeve is less than 50°C.

[0013] Beneficial effects: (1) The present invention combines powder metallurgy and multi-directional extrusion forging processes to prepare complex structural parts, thereby reducing the difficulty of forming complex structural parts. On the one hand, the strength and coherent organization of the complex structural joints of various parts of the final complex structural parts are ensured, and on the other hand, the overall forming accuracy and strength of the final formed structural parts are ensured. At the same time, when performing powder compaction and extrusion forging, one punch is responsible for the main pressurization task, and other punches cooperate with the punch for extrusion, which can effectively prevent the mold from being damaged and failing due to unbalanced loading of the mold.

[0014] (2) The overall appearance of the rough blank and the structural part in the present invention is almost the same, and the main difference lies in the forming completeness of the local keyway, hole or boss and other fine structures. In this way, when designing the compaction sintering mold and the extrusion forming mold, the compaction die sleeve and the extrusion die sleeve are at least partially the same. After completing the powder compaction step, only the different modules need to be replaced and the compaction punch can be replaced with the extrusion punch. This can greatly reduce the production time of complex structural parts and reduce the processing costs required to prepare additional molds.

[0015] (3) The compaction die sleeve and the extrusion die sleeve in the present invention are both composed of a plurality of modules. When the modules at the vulnerable parts reach the end of their service life, they can be replaced individually without replacing the entire die sleeve, which can effectively reduce the cost of mold replacement in later production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the multi-directional compaction and multi-directional extrusion forging in the present invention.

[0017] Figure 2 This is a schematic diagram of the assembly principle of the die sleeve and the punch in the present invention.

[0018] Figure 3 The forming process of the structural part SP.1 provided in Example 1.

[0019] Figure 4 This is a schematic diagram of the compaction and sintering mold assembly in Example 1.

[0020] Figure 5 This is a schematic diagram of the extrusion die assembly in Example 1.

[0021] Figure 6 The forming process of the structural part SP.2 provided in Example 2.

[0022] Figure 7 This is a schematic diagram of the compaction and sintering mold assembly in Example 2.

[0023] Figure 8 This is a schematic diagram of the extrusion die assembly in Example 2.

[0024] The meanings of the symbols in the figure are explained as follows: Figure 1 In the figure, direction 1, direction 2, direction 3, direction 4, direction 5, and direction 6 refer to different extrusion directions; α, β, and γ refer to the angles between different local structures of complex parts; Figure 2 In the figure, F1 corresponds to the punch in direction 1, F2 corresponds to the punch in direction 2, F3 corresponds to the punch in direction 3, F4 corresponds to the punch in direction 4, F5 corresponds to the punch in direction 5, F6 corresponds to the punch in direction 6, and M1, M2, M3, M4, M5, M6, M7, and M8 refer to modules in different positions; Figure 3 In the figure, Metal power represents metal powder, P1 is the rough blank in Example 1, and SP.1 is the structural part in Example 1; stage ① represents the powder compaction stage; stage ② represents the extrusion forging stage; Figure 4 In the figure, A1, A2, A3, A4, and A5 represent the compaction punches used in Example 1, and B1, B2, B3, and B4 represent the compaction modules used in Example 1; Figure 5 In the figure, A1*, A2*, A3*, A4*, A5* represent the extrusion punches used in Example 1, and B1*, B2*, B3*, B4* represent the extrusion modules used in Example 1; Figure 6 In the figure, P2 is the rough blank in Example 2, and SP.2 is the structural part in Example 2; Figure 7 In the figure, C1, C2, C3, and C4 represent the compaction punches used in Example 2, and D1, D2, and D3 represent the compaction modules used in Example 2; Figure 8 In the figure, C1*, C2*, C3*, C4* represent the extrusion punches used in Example 2, and D1*, D2*, D3* represent the extrusion modules used in Example 2. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0027] A complex structural parts forming process that combines powder metallurgy and multi-directional extrusion forging technology. Figure 1 and Figure 2 , the process specifically includes the following steps: (1) The shape of the rough blank is determined according to the structure of the final structural part to be formed, and the rough blank has the initial outline of the structural part. According to the shapes of the rough blank and the structural part, the compaction sintering die and the extrusion forming die are designed respectively. The compaction sintering die and the extrusion forming die both include a die sleeve and a punch. The die cavity of the die sleeve is composed of multiple modules (such as Figure 2 The mold sleeve after mold closing has a plurality of channels, and the punches are matched with the corresponding channels. Figure 2 The directions of movement of F1-F6) along the channel toward the die cavity are not completely the same or completely different; when performing powder compaction and multi-directional extrusion forging, the module and the punch are installed on the corresponding module of the press equipment or the die frame device to perform multi-directional compaction or multi-directional extrusion forging; for the convenience of description below, the die sleeve in the compaction sintering die is called the compaction die sleeve, the die cavity of the compaction die sleeve is formed by at least two compaction modules through the die closing, the channel in the compaction die sleeve is called the compaction channel, and the punch matched with the compaction channel is called the compaction punch. The die sleeve in the extrusion forming die is called the extrusion die sleeve, the die cavity of the extrusion die sleeve is formed by at least two extrusion modules through the die closing, the channel in the extrusion die sleeve is called the extrusion channel, and the punch matched with the extrusion channel is called the extrusion punch; (2) Filling metal powder, compacting the sintering mold to achieve mold cavity closing, after mold closing, adding metal powder through compaction channels in different directions, and compacting the added metal powder through compaction punches in different compaction channels to obtain a rough blank. The multi-channel powder filling path and multi-directional compaction punch in this process can greatly save powder filling time and compaction time, effectively improve process preparation efficiency, and at the same time improve the size forming integrity of the rough blank.

[0028] (3) placing the rough blank together with the compacted sintering mold into a sintering device for sintering, and demolding after sintering to obtain a sintered blank; (4) The sintered blank is subjected to multi-directional forging and placed in an extrusion forming die. The extrusion forming die realizes the overall and local compaction of the blank through the combined extrusion action of the extrusion modules and the extrusion punch in different directions, and realizes the forming of local complex structures such as tooth shapes, splines, special-shaped bosses, holes, etc. with high-precision requirements to obtain structural parts.

[0029] In the present invention, at least one compaction module has the same structure as at least one extrusion module, so that the compaction die sleeve and the extrusion die sleeve are at least partially identical. When extrusion forging is performed after sintering, only the different modules need to be disassembled and replaced with extrusion punches for use, which can greatly reduce the production time of complex structural parts and reduce the processing costs required to prepare additional molds.

[0030] Example 1 Taking structural part SP.1 as an example, please refer to Figures 3 to 5 , the implementation steps are as follows: Step 1: According to the shape of the required formed structural part SP.1, the shape of the rough blank P1 with an initial contour is formulated, and the compaction sintering mold and the extrusion forming mold are designed according to the shapes of the rough blank and the structural part, respectively. The compaction punch A1-A5 or the extrusion punch A1*-A5* is installed on the corresponding module of the press equipment or the mold frame device, and the compaction module B1-B4 or the extrusion module B1*-B4* is installed on the corresponding module of the press equipment or the mold frame device; Step 2: Powder compaction is performed. After the compaction punch A2 runs to the specified stroke, it cooperates with the compaction modules B1-B4 to realize the mold cavity closing. Subsequently, 7075 aluminum alloy metal powder is filled in the compaction channels where the compaction punches A1, A3, A4 and A5 are located. The added metal powder is compacted by the compaction punches A1-A5 in different compaction channels to prepare the rough blank P1. During the entire powder compaction process, the extrusion punch A1 runs in the flower-shaped hole compaction channel above the compaction module B1, the compaction punch A2 runs in the circular extrusion channel below the compaction module B2, the compaction punches A3 and A4 run in the right circular and left circular combined extrusion channels of the compaction modules B1-B2, respectively, and the compaction punch A5 runs in the square combined compaction channel in front of the compaction modules B3-B4. In addition, the main functions of the compaction punches A1-A5 are compaction and auxiliary limiting, and the powder filling channels and compaction punches in multiple directions in the powder compaction process can greatly reduce the process time; Step 3: Place the compacted sintering mold with the rough blank P1 in step 2 into a sintering device for sintering at a sintering temperature of 540°C, a heating rate of 50°C / min, a sintering pressure of 40 MPa, and a holding time of 4 h. After sintering, demould and obtain a sintered blank. Step 4: Perform multi-directional extrusion forging on the sintered blank obtained in step 3 to prepare structural part SP.1. Replace the mold, put the sintered blank into the extrusion forming mold, extrusion punch A1* runs in the extrusion channel of extrusion module B1*, extrusion punch A2* runs in the extrusion channel of extrusion module B2*, extrusion punches A3* and A4* respectively run in the right circular and left circular combined extrusion channels of extrusion module B1*-B2*, and extrusion punch A5 respectively runs in the square combined extrusion channel in front of extrusion module B3*-B4*, thereby forming a complete extrusion action to achieve overall and local compaction of the sintered blank. Extrusion punch A1* is mainly responsible for forming spline ball grooves, extrusion punch A2* is mainly responsible for forming hexagonal grooves, extrusion punch A3* is mainly responsible for forming cylindrical bosses with holes, extrusion punch A4* is mainly responsible for forming keyways, and extrusion punch A5* is mainly responsible for forming square prisms. During the entire extrusion process, the functions of the extrusion punches A1*-A5* are local deformation, compaction and auxiliary limiting.

[0031] It should be noted that when replacing the mold in the above step 4, it is only necessary to replace the compaction punches A1-A5 with the extrusion punches A1*-A5*, replace the compaction module B1 with the extrusion module B1*, and replace the compaction module B2 with the extrusion module B2*. The compaction module B3 and the extrusion module B3*, and the compaction module B4 and the extrusion module B4* have the same structure and do not need to be replaced.

[0032] It should be noted that a heating and heat preservation device is provided on the outside of the extrusion die sleeve after the die is closed, the extrusion forging temperature is 420°C, and the loading speed is 8 mm / s.

[0033] Example 2 Taking structural part SP.2 as an example, please refer to Figures 6 to 8 , the implementation steps are as follows: Step 1. According to the shape of the required forming structural part SP.2, formulate the shape of the rough blank P2 with an initial contour, and design the compaction sintering mold and the extrusion forming mold according to the shapes of the rough blank and the structural part respectively. The number of molds required depends on the complexity of the structure of the required forming structural part. Usually, the more complex the part structure is, the more molds are required. The compaction punch C1-C4 or the extrusion punch C1*-C4* is installed on the corresponding module of the press equipment or the mold frame device, and the compaction module D1-D3 or the extrusion module D1*-D3* is installed on the corresponding module of the press equipment or the mold frame device; Step 2: Perform the powder compaction process. Specifically, fill 7075 aluminum alloy metal powder. The compaction modules D1-D3 cooperate with the corresponding compaction punch C4 to realize mold cavity closing. The compaction channel where the compaction punch C3 is located is used as the main powder adding path, and the compaction channels where the compaction punches C1 and C2 are located are used as auxiliary powder adding paths. After the compaction punch C4 runs to the specified stroke in its corresponding compaction channel, metal powder is added to the compaction channels at the compaction punches C1, C2 and C3. The filled metal powder is compacted by the compaction punches C1-C4 of different compaction channels at the same time to prepare the rough blank P2. During the entire powder compaction process, the main functions of the compaction punches C1-C4 are compaction and auxiliary limiting. Step 3: Place the compacted sintering mold with the rough blank P2 in step 2 into a sintering device for sintering at a sintering temperature of 560°C, a heating rate of 50°C / min, a sintering pressure of 40 MPa, and a holding time of 4 h. Demold after sintering to obtain a sintered blank; Step 4. Perform multi-directional extrusion forging on the sintered blank obtained in step 3 to prepare structural part SP.2. Specifically, replace the mold, place the sintered blank into the extrusion forming mold, and the extrusion punches C1*, C2*, and C4* run in the extrusion channel of the extrusion module D1*-D2*, and the extrusion punch C3* runs in the extrusion channel of the extrusion module D3*, thereby cooperating to form a complete extrusion action to achieve overall and local compaction of the sintered blank. The extrusion punch C3* is responsible for forming the key body structure, the extrusion punch C1* is responsible for forming the cylindrical boss structure, and the extrusion punch C2* is responsible for forming the boomerang-shaped structure. During the entire extrusion forming process, the functions of the extrusion punches C1*, C2*, and C3* are local deformation, compaction, and auxiliary limiting, and the extrusion punch C4* plays an auxiliary limiting and compaction role.

[0034] It should be noted that when replacing the mold in the above step 4, it is only necessary to replace the compaction punches C2-C3 with the extrusion punches C2*-C3*, and replace the compaction module D3 with the extrusion module D3*. The compaction punch C1 and the extrusion punch C1*, the compaction punch C4 and the extrusion punch C4*, the compaction module D1 and the multi-directional extrusion module D1*, and the compaction module D2 and the extrusion module D2* are all the same modules and do not need to be replaced.

[0035] It should be noted that a heating and heat preservation device is provided on the outside of the extrusion die sleeve after the die is closed, the extrusion forging temperature is 460°C, and the loading speed is 8 mm / s.

[0036] The above shows and describes the main features, methods of use, basic principles and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements according to actual conditions, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A molding process for complex structural parts, characterized in that: The main steps are as follows: Step 1, formulate the shape of the rough blank according to the structure of the structural part to be finally formed, the rough blank has the initial outline of the structural part, and design a compaction sintering mold and an extrusion forming mold according to the shapes of the rough blank and the structural part, respectively, the compaction sintering mold comprises a compaction die sleeve and a plurality of compaction punches, the die cavity of the compaction die sleeve is formed by at least two compaction modules through mold closing, the compaction die sleeve after mold closing has a plurality of compaction channels, the compaction punches cooperate with the corresponding compaction channels, and the directions of movement of the plurality of compaction punches along the compaction channels to the die cavity are not completely the same or completely different; the extrusion forming mold comprises an extrusion die sleeve and a plurality of extrusion punches, the die cavity of the extrusion die sleeve is formed by at least two extrusion modules through mold closing, the extrusion die sleeve after mold closing has a plurality of extrusion channels, the extrusion punches cooperate with the corresponding extrusion channels, and the directions of movement of the plurality of extrusion punches along the extrusion channels to the die cavity are not completely the same or completely different; Step 2: close the compaction die sleeve, add metal powder into the die cavity through multiple compaction channels, and then perform multi-directional compaction through multiple compaction punches to obtain a rough blank; Step 3: Place the rough blank together with the compacted sintering mold into a sintering device for sintering, and demould after sintering to obtain a sintered blank; Step 4: Place the sintered blank in the die cavity by closing the extrusion die sleeve, and then use the extrusion punch to perform multi-directional extrusion forging on the sintered blank to obtain a structural part.

2. A molding process for complex structural parts according to claim 1, characterized in that: The power for closing the compaction die sleeve or the extrusion die sleeve is provided by the press equipment or the die frame device; the power for the compaction punch or the extrusion punch is provided by the press equipment or the die frame device.

3. The molding process of a complex structural part according to claim 1, characterized in that: In step one, at least one compacting module has the same structure as at least one extrusion module, so that the compacting die sleeve and the extrusion die sleeve are at least partially identical.

4. The forming process of a complex structural part according to claim 1, characterized in that: In step 2, the metal powder is 7075 aluminum alloy powder.

5. A molding process for complex structural parts according to claim 4, characterized in that: In step three, the sintering temperature is 540~580 ℃, the heating rate is 50 ℃ / min, the sintering pressure is 40 MPa, and the holding time is 4 h.

6. The forming process of a complex structural part according to claim 4, characterized in that: In step 4, a heating and heat preservation device is provided outside the extrusion die sleeve after the die is closed, the extrusion forging temperature is 410-470°C, and the loading speed is 8 mm / s.

7. The molding process of a complex structural part according to claim 4, characterized in that: In step 4, during extrusion forging, the temperature difference between the sintered billet and the extrusion die sleeve is less than 50°C.

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