Die forging forming method for spherical shell type forgings

Abstract

The invention relates to a die forging forming method for spherical shell type forgings, which belongs to the technical field of forging and comprises the following steps: determining a small strain area of the spherical shell type forgings in the die forging forming process; a mold is manufactured, the mold comprises an upper mold body and a lower mold body, the upper mold body is provided with a cavity matched with the contour of the spherical shell type forge piece, the cavity wall of the cavity comprises a target area, and a groove is formed in the target area; placing the blank on a lower die; the upper die is driven to press downwards, the cavity wall of the cavity is used for extruding the blank so that the blank can be formed into a preformed forge piece, and a protrusion is formed in a small strain area of the preformed forge piece; the upper die is driven to ascend, and the preformed forge piece is driven to rotate on the lower die, so that the protrusions and the grooves are staggered; the upper die is driven to press downwards again, the old protrusion is flattened through the cavity wall of the cavity, and a new protrusion is formed in the small strain area of the preformed forge piece; repeating the two steps for multiple times to obtain a final forge piece with a bulge on the outer surface; and the protrusions on the outer surface of the final forging are removed through machining, and the spherical shell type forging is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of forging, and in particular relates to a die forging method for spherical shell forgings. Background Art

[0002] Spherical shell forgings have the characteristics of large curved surfaces and large diameter-to-wall thickness ratios. At present, they are generally formed by spinning or using multiple sets of dies in combination with forging. During the spinning process, with the help of expensive equipment, the deformation of each position of the forging can be better controlled to balance the deformation of each area; the deformation of the forging area can also be better controlled in the forging process with multiple sets of dies. However, multiple sets of dies and spinning equipment require a large investment. For large-scale production, the cost can be offset by profit, but for small-scale production, the cost will be greater than the profit.

[0003] Although the use of a single die can also forge spherical shell forgings with adapted contours at a relatively low cost, such dies currently cannot control the deformation of each region of the spherical shell forgings during the forging process, resulting in a large difference in the cumulative deformation of each region after the forging is formed, which can easily cause defects such as folding, cracking, and uneven stress distribution in the forgings. Summary of the invention

[0004] The present invention provides a spherical shell forging die forging forming method, which is used to solve the technical problem that a single die cannot control the deformation amount of each area of ​​the spherical shell forging, so that the cumulative deformation of each area after the forging is formed is very different, which easily causes defects such as folding, cracks, and uneven stress distribution in the forging.

[0005] The present invention is achieved through the following technical solutions: A spherical shell forging die forging method, comprising:

[0006] Step 1: determining a small strain region of the spherical shell forging during die forging;

[0007] Step 2: manufacturing a die for forging the spherical shell forging, wherein the die comprises an upper die and a lower die, wherein the upper die has a cavity adapted to the contour of the spherical shell forging, wherein a cavity wall of the cavity comprises a target area corresponding to the small strain area, and a groove is arranged in the target area;

[0008] Step 3: placing the blank on the lower die;

[0009] Step 4: driving the upper die to press downward, using the cavity wall of the die cavity to extrude the blank, so that the blank is formed into a preformed forging corresponding to the spherical shell forging, and a bulge is formed in the small strain area of ​​the preformed forging;

[0010] Step 5: driving the upper die to rise, and driving the preformed forging to rotate on the lower die, so that the protrusion and the groove are staggered;

[0011] Step 6: driving the upper die to press down again, using the cavity wall of the cavity to flatten the old protrusion, and forming a new protrusion in the small strain area of ​​the preformed forging;

[0012] Step 7: Repeat steps 5 and 6 for multiple times to obtain a final forging with a protrusion on the outer surface;

[0013] Step 8: removing the protrusions on the outer surface of the final forging by machining to obtain a spherical shell forging.

[0014] Further, in order to better implement the present invention, in step 1, the specific method for determining the small strain area of ​​the spherical shell forging includes:

[0015] Step 1.1: increasing the margin of the digital model of the spherical shell forging to obtain a simulated forging;

[0016] Step 1.2: According to the simulated forging, a corresponding conventional simulation mold is designed in the software, wherein the conventional simulation mold comprises a simulated upper mold and a simulated lower mold, wherein the simulated lower mold is the same as the lower mold, and the simulated upper mold has an upper cavity adapted to the simulated forging;

[0017] Step 1.3: In the simulation software, the simulated forging is die-forged using the conventional simulation die, and the small strain area of ​​the simulated forging during the die-forging process is calculated through finite element analysis.

[0018] Further, in order to better implement the present invention, in step 2, the specific method of determining the groove in the target area of ​​the cavity of the upper mold includes:

[0019] Step 2.1: According to the small strain area on the simulated forging obtained by simulation, the target area of ​​the simulated upper die is obtained, and n simulated grooves are added to the target area of ​​the simulated upper die in the software, and the n simulated grooves are evenly distributed around the central axis of the simulated upper die;

[0020] Step 2.2: by trial and error, applying a simulated upper die having simulated grooves with different parameters to the simulated forging to obtain a plurality of simulated final forgings, wherein the small strain regions of the plurality of simulated final forgings have n simulated protrusions with different parameters;

[0021] Step 2.3: In the simulation software, finite element analysis is used to calculate the deformation variables of small strain areas in the forming process of multiple simulated final forgings, and a simulated upper die corresponding to the simulated final forging with appropriate deformation variables of small strain areas is selected, and the groove on the target area of ​​the cavity of the upper die is determined according to the parameters of the simulated groove on the simulated upper die.

[0022] Furthermore, in order to better implement the present invention, the parameters of the simulated grooves include the number n, 6≤n≤10.

[0023] Furthermore, in order to better implement the present invention, the parameters of the simulated grooves also include a width s and a distance t between two adjacent grooves, wherein s=t.

[0024] Furthermore, in order to better implement the present invention, the parameters of the simulated groove also include a depth m, 10 mm ≤ m ≤ 20 mm.

[0025] Further, in order to better implement the present invention, in step 5, the specific method of driving the preformed forging to rotate on the lower die includes:

[0026] The preformed forging is held by hand and twisted, and the twisting angle ω=360°÷2n.

[0027] Furthermore, in order to better implement the present invention, in the step 1.1, when the spherical shell forging is increased in margin to obtain the simulated forging, the increased margin is 10 mm-15 mm.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The die forging method for spherical shell forgings provided by the present invention can obtain spherical shell forgings with uniform wall thickness and high wall surface accuracy by die forging with the help of a single die (including a lower die and an upper die with grooves on the cavity wall), which has lower cost and can effectively reduce the strain difference of each area of ​​the forging during the die forging process, so that the strain of each area of ​​the finally formed spherical shell forging is more consistent, so that the stress distribution in each area of ​​the finally formed spherical shell forging is more uniform, and the defects such as wrinkles of the spherical shell forgings during the die forging process are reduced, so that the stress distribution in each area of ​​the finally formed spherical shell forging is more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a flow chart of a die forging method of a spherical shell forging provided by an embodiment of the present invention;

[0032] Figure 2 It is a finite element analysis diagram of the small strain area of ​​spherical shell forgings analyzed by software;

[0033] Figure 3 is a cross-sectional view of a spherical shell forging having a protrusion on the outer wall in an embodiment of the present invention;

[0034] Figure 4 is a distribution position diagram of the protrusions on the spherical shell forging in an embodiment of the present invention;

[0035] Figure 5 is a schematic structural diagram of an upper mold in an embodiment of the present invention;

[0036] Figure 6 It is a schematic structural diagram of the lower mold in an embodiment of the present invention.

[0037] In the figure:

[0038] 100 - middle area, 200 - end area, 300 - middle groove, 400 - end groove, 500 - middle protrusion, 600 - end protrusion, 700 - boss. DETAILED DESCRIPTION

[0039] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0040] Embodiment 1:

[0041] This embodiment provides a die forging method for a spherical shell forging. Figure 1 As shown, the following steps are included:

[0042] Step 1: Determine the small strain area of ​​the spherical shell forging during the die forging process. The small strain area refers to the area on the spherical shell forging where the strain amount is small when the spherical shell forging is die forged using a conventional die (that is, the cavity of the upper die of the die is a smooth arc surface).

[0043] Since the die forging process of spherical shell forgings requires the metal material to be transformed from a flat surface to a curved surface by bending, stretching, etc., the strain in some areas of the spherical shell forgings will be smaller than that in other areas. The areas with small strain are prone to defects such as wrinkles, cracks, and uneven internal stress distribution. Conventional die forging cannot solve this problem.

[0044] Step 2: Make a die for forging spherical shell forgings, the die includes an upper die and a lower die, the upper die has a cavity adapted to the contour of the spherical shell forging, the cavity wall of the cavity includes a target area corresponding to the above-mentioned small strain area, and a groove is arranged in the target area, specifically as follows: Figure 5 Compared with the conventional mold, the upper cavity wall of the mold provided in this embodiment is provided with a groove, which is the most important technical point for implementing the method provided in this embodiment.

[0045] Step 3: Place the blank on the lower die. Figure 6 As shown, the lower die is provided with a convex column 700 adapted to the inner cavity of the spherical shell forging, and before the blank is placed on the lower die, a corresponding concave cavity needs to be provided on the blank. When the blank is placed on the lower die, the blank is inverted on the lower die so that the convex column 700 on the lower die is accommodated in the concave cavity on the blank. In this way, when the upper die presses the blank downward, the convex column 700 supports the blank from the inside.

[0046] Step 4: Drive the upper die to press downward, and use the cavity wall of the cavity to squeeze the blank, so that the blank is formed into a preformed forging corresponding to the spherical shell forging. Because the target area of ​​the cavity of the upper die is formed with a groove, during the pressing process, a bulge will be formed on the outer wall of the preformed forging corresponding to the groove. In this way, the above-mentioned bulge is formed in the small strain area of ​​the preformed forging, such as Figure 3 and Figure 4 shown.

[0047] Step 5: driving the upper die to rise so that the upper die leaves the preformed forging, and then driving the preformed forging to rotate on the lower die so that the protrusions and the grooves on the preformed forging are staggered.

[0048] Step 6: Drive the upper die to press down again, use the cavity wall to flatten the old protrusions on the preformed forging, and form new protrusions in the remaining positions of the small strain area of ​​the preformed forging. In this way, the strain amount of the small strain area of ​​the preformed forging is increased.

[0049] Step 7: Repeat the above steps 5 and 6 for many times to obtain a final forging with protrusions on the outer surface. In this way, the strain amount of the small strain area of ​​the preformed forging can be further increased, so that the strain amount of the small strain area of ​​the final forging (that is, the spherical shell forging with protrusions on the outer surface) is larger, so that the strain amounts of various areas of the final spherical shell forging are more consistent, and the probability of wrinkles and cracks in the spherical shell forging during the die forging process is reduced.

[0050] More importantly, by using the upper die with a groove in the die cavity and the method provided in this embodiment, only a single die can be used to forge the spherical shell forgings, which is more cost-effective. The spherical shell forgings with protrusions on the outer wall can also help eliminate wrinkles and cracks in the spherical shell forgings during the die forging process.

[0051] Step 8: Remove the protrusions on the surface of the final forging by machining to obtain qualified spherical shell forgings.

[0052] Through the above method, not only can spherical shell forgings with uniform wall thickness and more balanced strain in each area be obtained, but the cost is also lower, the implementation is simpler and more convenient, and it is conducive to promotion and application.

[0053] An optional implementation of this embodiment is as follows: In the above step 1, the specific method for determining the small strain area of ​​the spherical shell forging can be: die forging is performed by a conventional die, and the small strain area of ​​the spherical shell forging is determined by observing the positions of wrinkles and cracks on the outer surface of the spherical shell forging finally formed. This method has certain practicality, but it requires multiple trials and errors to summarize the complete small strain area, and the experimental cost is very high.

[0054] Therefore, in the best implementation mode of this embodiment, the specific method for determining the small strain area of ​​the spherical shell forging includes:

[0055] Step 1.1: The digital model of the spherical shell forging is increased by the allowance to obtain a simulated forging. The digital model of the spherical shell forging is a data model in a three-dimensional software, which can be obtained by drawing. The digital model is increased by the allowance to obtain a simulated forging. Specifically, in this step, the increased allowance is 10 mm-15 mm, such as 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, etc.

[0056] Step 1.2: Based on the simulated forging, a corresponding conventional simulation mold is designed in the software. The conventional simulation mold includes a simulated upper mold and a simulated lower mold. The simulated lower mold is the same as the lower mold of the mold provided in this embodiment, and the simulated upper mold only has an upper cavity adapted to the simulated forging, and no groove is set on the upper cavity wall of the simulated upper mold.

[0057] Step 1.3: In the simulation software, the simulated forging is die-forged using the conventional simulation die mentioned above. The small strain area of ​​the simulated forging during the die-forging process is calculated through the simulation and finite element analysis functions of the software. The small strain area is equivalent to the small strain area on the spherical shell forging. Figure 2 shown.

[0058] Through software simulation, the experimental cost in the process of determining the small strain area can be reduced, which is not only easier to operate but also more accurate.

[0059] An optional implementation of this embodiment is as follows: In the above step 2, the specific method of determining the groove in the target area of ​​the cavity of the upper mold includes:

[0060] Step 2.1: According to the small strain area on the simulated forging obtained by simulation, the target area of ​​the simulated upper die is obtained, and n simulated grooves are added to the target area of ​​the simulated upper die in the software. The n simulated grooves are evenly distributed around the central axis of the simulated upper die, so that the target area of ​​the simulated upper die has n simulated grooves.

[0061] Step 2.2: By trial and error, the simulated upper die action area with simulated grooves having different parameters is used to simulate the forging to obtain multiple simulated final forgings, and the small strain regions of the multiple simulated final forgings have n simulated protrusions with different parameters;

[0062] Step 2.3: In the simulation software, finite element analysis is used to calculate the deformation variables of small strain areas in the forming process of multiple simulated final forgings, and a simulated upper die corresponding to the simulated final forging with appropriate deformation variables of small strain areas is selected, and the groove on the target area of ​​the cavity of the upper die is determined according to the parameters of the simulated groove on the simulated upper die.

[0063] That is, multiple simulated upper molds are made through software, and the groove parameters on the upper cavity wall of different simulated upper molds are different. In this way, when different simulated upper molds act on simulated forgings, simulated protrusions with different parameters will appear in the small strain area of ​​the simulated forgings. At the same time, the strain amount in the small strain area of ​​the simulated forgings is also different. By statistically calculating the situation where the strain amount area of ​​the small strain area is consistent with that of the other areas, the groove with the corresponding parameters in this situation is screened out, and then the groove in this situation is used as the groove model on the cavity wall of the upper model, and when making the upper mold, it is made according to this parameter.

[0064] The use of software for simulation and analysis can greatly improve efficiency and accuracy, thereby obtaining the groove parameters on the wall of the upper model cavity more quickly, conveniently and accurately.

[0065] Optionally, in this embodiment, the parameters of the grooves include the number n, 6≤n≤10, and optionally, the number of the grooves is 6 or 7 or 8 or 9 or 10. The n grooves are evenly distributed around the central axis of the upper mold.

[0066] In addition, in this embodiment, the parameters of the groove also include the width s and the spacing t between two adjacent grooves. It should be noted that the width of the groove in this embodiment refers to the maximum width of the groove, and the spacing between two grooves refers to the maximum spacing.

[0067] Furthermore, in this embodiment, the parameters of the groove also include a depth m, 10 mm ≤ m ≤ 20 mm. For example, the depth of the groove is 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, or 20 mm.

[0068] Correspondingly, the height of the protrusions formed in the small strain region of the spherical shell forging is m, the width is s, the number is n, and the spacing between adjacent protrusions is t.

[0069] An optional implementation of this embodiment is as follows: In the above step 5, the specific method of driving the preformed forging to rotate on the lower die includes:

[0070] Hold the preformed forging by hand and twist it, the twisting angle ω=360°÷2n. In this way, when it is rotated once, the formed protrusion on the preformed forging is turned between the two grooves on the wall of the upper mold cavity. When the upper die is pressed down again, the old protrusion can be flattened, and a new protrusion is formed next to the old protrusion. This is repeated, so that the above-mentioned protrusion is intermittently formed at different positions in the small strain area. In this way, the strain amount in the small strain area can be better increased, so that the strain amount in the small strain area tends to be consistent with the strain amount in the rest of the forging area more quickly.

[0071] In fact, during the die forging process, there are two small strain areas on the spherical shell forgings, one of which is a middle area 100 close to the forging opening and an end area 200 away from the forging opening. Correspondingly, the target area on the upper die includes a middle target area and an end target area. The groove in the middle target area is a middle groove 300, and the groove in the end target area is an end groove 400. It is worth noting that the number of middle grooves 300 is n, and the number of end grooves 400 is also n. The protrusions formed on the spherical shell forgings include n middle protrusions 500 located in the middle area and n end protrusions 600 located in the end area.

[0072] Embodiment 2:

[0073] This embodiment is a specific implementation of the embodiment 1. The forging profile in this embodiment is about φ615*315, the forging weight is about 140Kg, and the die forging method includes:

[0074] The digital model of the spherical shell forging is increased by the allowance to obtain a simulated forging, and the increased allowance is 10mm;

[0075] The software determines that the small strain area of ​​the spherical shell forging includes the middle area 100 and the end area 200;

[0076] The most suitable groove parameters are determined by software: number n = 8, depth m = 12 mm. According to these parameters, the corresponding mold is made;

[0077] placing the blank on the lower die of the mold;

[0078] The upper die is driven downward to squeeze the blank with the cavity wall of the die cavity, so that the blank is formed into a preformed forging corresponding to the spherical shell forging, thereby forming 8 middle protrusions 500 with a height of 12 mm in the middle area 100 of the preformed forging and 8 end protrusions 600 with a height of 12 mm in the end area 200;

[0079] The upper die is driven to rise so that the upper die leaves the preform forging, and then the preform forging is rotated 22.5 degrees so that the middle protrusion 500 of the middle area 100 is staggered with the corresponding middle groove 300, and the end protrusion 600 of the end area 200 is staggered with the corresponding end groove 400;

[0080] The upper die is driven to press down again, and the previously formed bulge is flattened by the cavity wall of the upper die cavity, and a new bulge is pressed out at the remaining position of the small strain area of ​​the preformed forging;

[0081] The upper die is driven to rise and press down for multiple times, and the preformed forging is driven to rotate 22.5 degrees on the lower die each time it rises, so as to obtain a final forging with a convex surface;

[0082] The protrusions on the surface of the final forging are removed by machining to obtain qualified spherical shell forgings.

[0083] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A spherical shell forging die forging method, characterized in that: include: Step 1: determining a small strain region of the spherical shell forging during die forging; Step 2: manufacturing a die for forging the spherical shell forging, wherein the die comprises an upper die and a lower die, wherein the upper die has a cavity adapted to the contour of the spherical shell forging, wherein a cavity wall of the cavity comprises a target area corresponding to the small strain area, and a groove is arranged in the target area; Step 3: placing the blank on the lower die; Step 4: driving the upper die to press downward, using the cavity wall of the die cavity to extrude the blank, so that the blank is formed into a preformed forging corresponding to the spherical shell forging, and a bulge is formed in the small strain area of ​​the preformed forging; Step 5: driving the upper die to rise, and driving the preformed forging to rotate on the lower die, so that the protrusion and the groove are staggered; Step 6: driving the upper die to press down again, using the cavity wall of the cavity to flatten the old protrusion, and forming a new protrusion in the small strain area of ​​the preformed forging; Step 7: Repeat steps 5 and 6 for multiple times to obtain a final forging with a protrusion on the outer surface; Step 8: removing the protrusions on the outer surface of the final forging by machining to obtain a spherical shell forging.

2. The die forging method for spherical shell forgings according to claim 1, characterized in that: In the step 1, the specific method for determining the small strain area of ​​the spherical shell forging includes: Step 1.1: increasing the margin of the digital model of the spherical shell forging to obtain a simulated forging; Step 1.2: According to the simulated forging, a corresponding conventional simulation mold is designed in the software, wherein the conventional simulation mold comprises a simulated upper mold and a simulated lower mold, wherein the simulated lower mold is the same as the lower mold, and the simulated upper mold has an upper cavity adapted to the simulated forging; Step 1.3: In the simulation software, the simulated forging is die-forged using the conventional simulation die, and the small strain area of ​​the simulated forging during the die-forging process is calculated through finite element analysis.

3. The die forging method for spherical shell forgings according to claim 2, characterized in that: In step 2, the specific method of determining the groove in the target area of ​​the cavity of the upper mold includes: Step 2.1: According to the small strain area on the simulated forging obtained by simulation, the target area of ​​the simulated upper die is obtained, and n simulated grooves are added to the target area of ​​the simulated upper die in the software, and the n simulated grooves are evenly distributed around the central axis of the simulated upper die; Step 2.2: by trial and error, applying a simulated upper die having simulated grooves with different parameters to the simulated forging to obtain a plurality of simulated final forgings, wherein the small strain regions of the plurality of simulated final forgings have n simulated protrusions with different parameters; Step 2.3: In the simulation software, finite element analysis is used to calculate the deformation variables of small strain areas in the forming process of multiple simulated final forgings, and a simulated upper die corresponding to the simulated final forging with appropriate deformation variables of small strain areas is selected, and the groove on the target area of ​​the cavity of the upper die is determined according to the parameters of the simulated groove on the simulated upper die.

4. The die forging method for spherical shell forgings according to claim 3, characterized in that: The parameters of the simulated grooves include the number n, 6≤n≤10.

5. The die forging method for spherical shell forgings according to claim 4, characterized in that: The parameters of the simulated grooves also include a width s and a distance t between two adjacent grooves, wherein s=t.

6. The die forging method for spherical shell forgings according to claim 5, characterized in that: The parameters of the simulated groove also include a depth m, 10 mm ≤ m ≤ 20 mm.

7. The die forging method for spherical shell forgings according to any one of claims 3 to 6, characterized in that: In step 5, the specific method of driving the preform forging to rotate on the lower die includes: The preformed forging is held by hand and twisted, and the twisting angle ω=360°÷2n.

8. The die forging method for spherical shell forgings according to any one of claims 2 to 6, characterized in that: In the step 1.1, when the spherical shell forging is increased in margin to obtain the simulated forging, the increased margin is 10 mm to 15 mm.

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