CN110479843B - Forming die and multi-pass forming method of hemispherical component - Google Patents

Abstract

The invention discloses a forming die for a hemispherical component and a multi-pass forming method, belongs to the technical field of hemispherical body forming, and solves the problems of wrinkling, cracking and deep drawing forming of hemispherical components with a large aspect ratio in the prior art. It is difficult to control the process parameters and the uniformity of the wall thickness is poor. The forming die of the invention includes a concave die, a convex die, a blank holder and a positioning plate; the concave die and the convex die are used for forming hemispherical components; the blank holder is arranged between the concave die and the convex die, and the blank holder is matched with the concave die The blank is pressed to prevent the blank from wrinkling during the forming process; the blank holder is provided with a positioning plate, which is used to position the upper die and the lower die. The forming die and the forming method of the present invention are suitable for forming hemispherical components with a large aspect ratio.

Description

Forming die and multi-pass forming method for hemispherical component

technical field

The invention belongs to the technical field of hemispherical body forming, and particularly relates to a forming die for a hemispherical component and a multi-pass forming method.

Background technique

Hemispherical components are widely used in aerospace launch vehicle propulsion systems, satellite covers, pressure vessel heads and other products. According to the different working environments of the hemispherical body, its materials are mainly divided into titanium alloy, aluminum alloy, alloy steel and stainless steel. It is mostly used in extreme environments and has high requirements for pressure resistance, reliability, safety and service life, so its quality control is particularly important.

The hemisphere forming process is mainly spin forming and cold/hot deep drawing. The control of spinning process parameters is complicated, the manufacturing difficulty is large, the assembly and adjustment accuracy is low, and the production cost is high. After spinning, the residual stress of the workpiece is relatively large. After the stress is applied by the stacking machine, it is easy to cause deformation of the workpiece and affect the performance. In deep drawing, the diameter of the blank is reduced, and the sphere is gradually formed, which is more suitable for mass production. However, in actual production, wrinkling and cracking defects often occur, which seriously affect product quality and production efficiency. Especially for hard-to-deform materials such as titanium alloys and aluminum alloys with large aspect ratios, it is difficult to control the parameters of the deep drawing process, the uniformity of the wall thickness is poor, the surface quality of the product is poor, and the shape accuracy is difficult to guarantee. Therefore, the development of a high-quality and high-efficiency deep drawing method for hemispherical components is of great significance to meet the requirements for the use of large-scale and high-performance components in aerospace, eliminate wrinkles and breakage defects, and promote efficient production.

SUMMARY OF THE INVENTION

In view of the above analysis, the present invention aims to provide a forming die and a multi-pass forming method for a hemispherical component, so as to solve the problems of wrinkling and cracking in the deep drawing forming process of the large aspect ratio hemispherical component in the prior art, and the deep drawing forming process The parameters are difficult to control, the wall thickness uniformity is poor, the product surface quality is poor, and the shape accuracy is difficult to guarantee.

The object of the present invention is mainly achieved through the following technical solutions:

In one aspect, the present invention discloses a forming die for a hemispherical component, comprising a concave die, a convex die, a blank holder and a positioning plate;

Dies and punches are used to form hemispherical components;

The blank holder is arranged between the die and the punch, and the blank holder cooperates with the die to compress the blank to prevent the blank from wrinkling during the forming process;

The blank holder is provided with a positioning plate, which is used for positioning the upper die and the lower die.

Further, it also includes an adapter plate for increasing the ejection radius;

The bottom of the adapter plate is connected with the first ejector rod of the lower platform top cylinder of the forming machine, and the upper surface of the adapter plate is provided with a second ejector rod, which is used to push out the blank holder ring and apply the blank holder force.

Further, the punch includes a bottom plate and a cavity, the adapter plate is arranged in the cavity, and the bottom plate is provided with a bottom plate through hole through which the second ejector rod passes.

On the other hand, the present invention also discloses a multi-pass forming method for a hemispherical component, using the above-mentioned hemispherical component forming die, comprising the following steps:

S1. Determine the size of the blank;

S2. Fix the die and the punch on the upper platform and the lower platform of the forming machine respectively;

S3. Place the blank and perform the first pass of cold forming to obtain a preform;

S4. Performing strong pulse current to assist tissue regulation on the preform;

S5. Determine the number of cold forming passes, repeat steps S3 and S4 to complete the number of cold forming passes, and demold to take out the preform;

S6. Perform thermal correction on the preform to obtain a hemispherical component.

Further, step S1 specifically includes:

According to the size and shape of the hemispherical component, select the blank;

Numerical simulation of cold forming is performed to determine the net size of the blank, and the forming allowance is added to determine the final blank size.

Further, step S2 includes:

Place the punch on the lower platform of the forming machine, hang the blank holder on the bottom plate, the lower part of the positioning plate is in contact with the side of the punch, and the upper part of the positioning plate is in contact with the side of the punch. Fix the die and punch on the upper and lower platforms of the forming machine.

Further, step S3 includes:

The second mandrel goes up so that the upper plane of the blank holder exceeds the highest point of the punch;

Apply lubricating oil on the upper and lower surfaces of the blank, and place the blank between the blank holder and the die to ensure that the center of the blank and the center of the die coincide;

The die goes down to compress the blank, and then the die, the blank and the blank holder go down 50-200mm at the same time to complete the first pass forming;

The downward speed of the die is 1 to 2 mm/s.

Further, in step S4, when the billet is an aluminum alloy, the high-pulse current-assisted microstructure regulation temperature is 300-400°C; when the billet is commercial pure titanium, the high-pulse-current-assisted microstructure regulation temperature is 550-650°C.

Further, step S6 includes:

The surface of the preform is sprayed with anti-oxidation paint for thermal correction;

During hot calibration, the punch goes down until the mold is closed, keep the temperature for 20-60 minutes, and then take out the hemispherical component.

Further, in step S6, the downward speed of the punch is 0.5-1 mm/s;

When the billet is aluminum alloy, the thermal correction temperature of the hemisphere is 380～480℃;

When the billet is commercial pure titanium, the hemisphere thermal correction temperature is 550-650°C.

Compared with the prior art, the present invention can achieve at least one of the following technical effects:

1) The forming method of the present invention includes two processes of cold forming and hot forming, wherein the cold forming can be divided into 2 to 4 times according to the different forming heights, and the current-assisted regulation technology is used between the passes to optimize the organizational structure, so that it has the ability to continue to deform. It can realize the precise forming of hemispherical components with large height-diameter ratio, thus breaking through the bottleneck of the existing forming technology of hemispherical components and effectively improving the product quality and qualification rate.

The hemispherical member with a large aspect ratio is a hemispherical member with a diameter of 500-700 mm and a ratio of height to radius above 1.2. The invention solves the wrinkling and cracking defects of the hemispherical shell with a large aspect ratio during deep drawing, and can significantly improve the uniformity of the wall thickness.

2) The microstructure is optimized by using the current-assisted regulation technology between passes, the pulse current is used to achieve rapid heating and short-term heat preservation, the deformed structure is regulated, and the pulse current is used to bridge the micro-cracks, so that it has the ability to continue deformation and eliminate the After forming, the internal micro-cracks of the plate will equiax the deformed structure, improve its re-deformation ability, and prevent local rupture during forming. In addition, the present invention utilizes the rapid heating technology of pulsed strong current, which can significantly shorten the intermediate heat treatment time and improve the production efficiency.

3) The present invention adopts a set of molds to realize the cold forming and hot forming processes, which greatly saves the processing cost.

4) After multi-pass cold deformation process and short-time strong pulse current auxiliary treatment, the microstructure and grain size after forming are refined, and the product performance is improved.

Other features and advantages of the present invention will be set forth in the description which follows, and in part may become apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims.

Description of drawings

The drawings are for the purpose of illustrating specific embodiments only and are not to be considered limiting of the invention, and like reference numerals refer to like parts throughout.

Figure 1 is a diagram of a cold forming die for a hemispherical component;

Figure 2 is a cross-sectional view of a cold forming die for a hemispherical component;

Fig. 3 is the structure diagram of strong pulse current auxiliary tissue regulation system;

Figure 4 is a diagram of a hot-correction mold for a hemispherical component.

Reference number:

1-concave die; 2-blank; 3-positioning plate; 4-blank holder; 5-punch; 6-second ejector; 7-transfer plate; 8-pulse power supply; 9-temperature feedback adjustment system; 10-clamping mechanism; 101-electrode; 102-pressing plate; 103-U-shaped copper body; 104-wire bundle; 11-electrode support; 12-preform.

Detailed ways

The following describes a hemispherical component forming mold and multi-pass forming method in further detail with reference to specific embodiments. These embodiments are only used for comparison and explanation purposes, and the present invention is not limited to these embodiments.

Example 1

This embodiment provides a forming die for a hemispherical component, as shown in Figures 1-2, including a concave die 1, a punch 5, a blank holder 4 and a positioning plate 3; the concave die 1 and the punch 5 are used for A hemispherical component is formed; the blank holder 4 is arranged between the die 1 and the punch 5, and the blank holder 4 cooperates with the die 1 to press the blank 2 to prevent the blank 2 from becoming unstable and wrinkling during the forming process; Two adjacent sides of the blank holder 4 are respectively provided with a positioning plate 3, and the positioning plate 3 is used for positioning the upper die and the lower die. The positioning plate 3 is screwed on the side surface of the blank holder 4 and the positioning plates 3 are vertically distributed.

It also includes an adapter plate 7 for increasing the ejection radius; the lower platform of the forming machine includes a lower ejection cylinder and a first ejector rod, but the ejection radius formed by the first ejector rod is small, and the ejection radius is fixed, in order to meet the needs of large If the diameter of the hemisphere needs to be formed, the adapter plate 7 is used to increase the ejection radius. The bottom of the adapter plate 7 is connected with the first ejector rod of the lower platform top cylinder of the forming machine. The upper surface of the adapter plate 7 is provided with a second ejector rod 6. The second ejector rod 6 is used to push out the blank holder ring 4. The ejection radius formed by the second ejector pins 6 evenly arranged around the center of the adapter plate 7 is relatively large, and can be changed according to the size of the shaped hemispherical component.

The punch 5 includes a bottom plate and a cavity, the adapter plate 7 is arranged in the cavity, and the unilateral gap between the adapter plate 7 and the side wall of the punch 5 is 1-3 mm, so that the adapter plate 7 can move smoothly in the cavity; In the bottom plate through hole through which the second top rod 6 passes, four second top rods 6 are symmetrically distributed on the upper surface of the adapter plate 7. When the adapter plate 7 is located at the bottom of the cavity, the second top rod 6 is placed on the bottom plate of the punch 5. In the through hole and not exceeding the upper surface of the bottom plate, the distance between the second ejector rod 6 and the upper surface of the bottom plate is 3 to 5 mm, so that the second ejector pin 6 will not hinder the placement of the blank holder 4 on the punch 5, and the through hole of the bottom plate is connected to the first The unilateral gap of the two ejector rods 6 is 2-4 mm, so that the second ejector rod 6 can run smoothly in the through hole of the bottom plate when it is lifted and lowered.

A multi-pass forming method for a hemispherical component, comprising two processes of cold forming and hot forming, two formings share a set of molds, wherein the cold forming can be divided into 2 to 4 passes according to the different forming heights, and the The current-assisted regulation technology optimizes the organizational structure and enables it to continue to deform. Using the above-mentioned hemispherical component multi-pass forming mold, including the following steps:

S1. Determine the size of blank 2;

S2. respectively fix the die 1 and the punch 5 on the upper platform and the lower platform of the forming machine;

S3. Place the blank 2, and perform the first pass of cold forming to obtain the preform 12;

S4. Performing strong pulse current to assist tissue regulation on the preform 12;

S5. Select the optimal number of cold forming passes, and repeat steps S3 and S4 until the mold is closed, demould and take out the preform 12;

S6. Perform thermal correction on the preform 12 to obtain a hemispherical component.

Step S1 specifically includes:

According to the size and shape of the hemispherical component, the plate is selected; mesh is divided, material properties and boundary conditions are set, and numerical simulation of cold forming is performed to determine the net size of the blank 2, increase the forming allowance for the sheet in the radial direction, and determine the final blank 2 size.

Step S2 is specifically:

Place the punch 5 on the lower platform of the forming machine, and hang the blank holder 4 on the bottom plate. Side contact, the upper part of the positioning plate 3 is in contact with the side of the die 1, and after the positioning of the die 1 and the punch 5 is completed, the die 1 and the punch 5 are respectively fixed on the upper platform and the lower platform of the forming machine.

Step S3 specifically includes:

The second mandrel 6 goes up so that the upper plane of the blank holder 4 exceeds the highest point of the punch 5; the upper and lower surfaces of the blank 2 are smeared with lubricating oil, and the blank 2 is placed between the blank holder 4 and the die 1 to ensure that the center of the blank 2 The center of the die is coincident; the die 1 goes down to press the blank 2, and then the die 1, the blank 2 and the blank holder 4 descend at the same time for a certain distance, such as 50-200mm, to complete the first pass forming; in order to ensure the uniform deformation of the blank 2, To control the effect of work hardening, the downward speed of the die 1 is set to 1-2 mm/s.

Step S4 specifically includes:

Remove the lubricating oil from the preform 12, spray the anti-oxidation paint, and perform a strong pulse current-assisted structure control on the blank 2 through the current-assisted control system; eliminate the micro-cracks inside the sheet after forming, equiax the deformed structure, and improve its ability to deform again. , to prevent local rupture during forming.

As shown in FIG. 3 , the current-assisted regulation system includes an electrode holder 11 , a pulse power source 8 , a wire harness 104 , a clamping mechanism 10 and a temperature feedback regulation system 9 ;

The clamping mechanism 10 is symmetrically distributed on both sides of the preform 12. The clamping mechanism 10 includes an electrode 101, a U-shaped copper body 103 and a pressing plate 102. The electrode 101 and the U-shaped copper body 103 are connected by a wire harness 104, and the bolts are screwed into the threaded holes. The hole is in contact with the pressing plate 102. Under the action of the bolt pre-tightening force, the pressing plate 102 and the U-shaped copper body 103 clamp and fix the preform 12 in step S3, and turn on the external water-cooling circulating pump, the pulse power supply 8 switches and the temperature feedback adjustment system. 9. Input the initial current value and target temperature, start heating, after reaching the target temperature, keep the temperature for 20-30min, turn off the pulse power switch 8; take out the preform 12 when it drops to room temperature.

When the billet 2 is an aluminum alloy, the temperature of the high-pulse current-assisted structure regulation is 300-400°C; when the billet 2 is commercial pure titanium, the high-pulse-current-assisted structure control temperature is 550-650°C.

Step S5 specifically includes:

Carry out a process test to determine the descending distance of each pass, and the blank holder force is determined according to the thickness of the blank 2, material strength, and blank diameter. Generally, as the forming progresses, the wrinkling tendency becomes more obvious, and the blank holder force should also gradually increase. Under the condition that no wrinkling or wrinkling tendency is guaranteed, the lower limit of the blank holder force should be taken, so that the blank 2 can not only move to the center of the mold under the action of the punch during the forming process, but also prevent the blank 2 from playing wrinkle for wall thickness uniformity control.

Preferably, the cold forming numerical simulation process described in step S1 can be used to determine the distribution range of the safe area and the dangerous area, divide the cold forming into 2-4 passes, and determine the approximate descending distance, so as to narrow the test range and reduce the number of tests . During the cold forming simulation, the thickness is reduced by less than 30% on the basis of the original thickness to be the safe area, and the thickness reduced by more than 30% is the dangerous area.

Step S6 specifically includes:

The surface of the preform 12 is sprayed with anti-oxidation paint to perform hot shaping; hot shaping and cold forming share a set of molds, as shown in Figure 4, the hot forming mold consists of punch 5, blank holder 4, concave die 1, positioning It consists of plate 3; during hot calibration, punch 5 is the upper die, and concave die 1 is the lower die.

Hot calibration and cold forming share a set of molds, but the initial state is different, as shown in Figure 4. During cold forming, an ejector rod is required, and the ejector cylinder and ejector rod are arranged on the lower platform. At this time, the punch 5 is the lower mold, and the concave mold 1 is the upper mold. During hot calibration, the punch 5 is the upper die, and the concave die 1 is the lower die, which is easy to demould.

The downward speed of punch 5 is 0.5～1mm/s; when billet 2 is aluminum alloy, the temperature of hemisphere thermal correction is 380～480℃; when billet 2 is commercial pure titanium, the thermal correction temperature of hemisphere is 550～650℃ °C.

Since the material expands at high temperature, but the expansion coefficients of different materials are different, in order to make the size of the final component and the mold consistent, the forming mold is appropriately scaled and processed according to the size of the hemispherical component when designing the mold.

Example 2

Taking the 5083 aluminum alloy hemispherical component as an example, its external dimensions are shown in Figure 1, the component thickness is 4mm, the height-diameter ratio is 1.2:1, and the total height is 260mm.

The specific forming process is carried out as follows:

Step (1) Determine the size of the blank 2: select the 4mm thick 5083 aluminum alloy raw material sheet required for forming, and supplement the allowance and process flange edge according to the characteristics of the component, as shown in Figure 2. Using FormingSuite software to carry out numerical simulation, the number of meshes is 6900, the material strain hardening index is 0.25, the Young's modulus is 70GPa, the Poisson's ratio is 0.33, the blank holder force is 5t, the drawing force is 200t, and the numerical value of the sheet metal drawing process is carried out. Simulation, unfolding to determine the size of the blanking material is 4 × Φ850mm. When blanking, two lugs are added at the relative positions of the blank 2, so that the blank 2 can be clamped when the strong pulse current assists the tissue regulation.

Step (2) Design the forming mold and carry out installation and positioning: design and manufacture the mold required for cold forming and hot forming, and then appropriately enlarge the cavity of the forming mold according to the size of the aluminum alloy hemispherical component, and the amplification factor is 5‰; The forming die is installed and positioned by the positioning plate 3 on the side of the blank holder.

Step (3) The first pass of cold forming of the plate: the second ejector pin 6 goes up, so that the upper plane of the blank holder 4 exceeds the highest point of the punch 5 . Apply lubricating oil on the upper and lower surfaces of the blank 2, place the blank 2, and ensure that the center of the blank 2 coincides with the center of the mold. The concave die 1 goes down to press the blank 2, and then the concave die 1, the blank 2 and the blank holder 4 go down 170mm at the same time to complete the first pass forming, and the preform 12 is obtained. The blank holder force was 5t, and the speed of the upper die was 2mm/s.

Step (4) Auxiliary structure control of preformed part by strong pulse current: remove lubricating oil from preform 12, spray anti-oxidation paint, carry out strong pulse current auxiliary structure control, eliminate microcracks inside the plate after forming, and equiax the deformed structure , to improve its re-deformation ability and prevent local rupture during forming. The current auxiliary regulation system is mainly composed of an electrode support 11 , a pulse power supply 8 , a clamping mechanism 10 and a temperature feedback regulation system 9 . The clamping mechanism 10 clamps and fixes the preform 12 obtained in step (3), turns on the external water-cooled circulating pump, the pulse power supply 8 switch and the temperature feedback adjustment system 9, inputs the initial current value of 4000A and the target temperature of 350°C, and starts. Heating, after reaching the target temperature, keep the temperature for 20 minutes, and turn off the pulse power switch 8; when it reaches room temperature, take out the component.

Step (5) The second pass of cold forming of the plate: the second ejector pin 6 goes up, so that the upper plane of the blank holder 4 exceeds the highest point of the punch. In step (4), lubricating oil is applied to the upper and lower surfaces of the preform 12, and the preform 12 is placed to ensure that the center of the preform 12 coincides with the center of the mold. The concave die 1 goes down to press the preform 12, and then the concave die 1, the preform 12 and the blank holder 4 go down 90mm at the same time to complete the second pass forming. The blank holder force was 8t, and the speed of the upper die was 2mm/s.

Step (6) hot shape correction: the surface of the preform 12 obtained in step (5) is sprayed with anti-oxidation paint to perform hot shape correction. The hot forming and the cold forming share a set of molds, and the hot forming mold is mainly composed of a punch 5 , a blank holder 2 , a concave die 1 , and a positioning plate 3 . During hot calibration, the punch 5 descends until the mold is closed, the descending speed is 0.5 mm/s, and after 20 minutes of heat preservation, the hot pressing of the preform 12 is completed, and the hemispherical component is taken out.

The dimensional accuracy of the aluminum alloy hemispherical component prepared by this example is less than ±0.4mm, the profile accuracy is within ±0.2mm, the surface roughness is Ra3.2, the wall thickness uniformity is good, the maximum thinning rate is 5%, and there is no Tendency to wrinkle and break.

Example 3

Taking the TA2 pure titanium hemispherical component as an example, its external dimensions are shown in Figure 1, the thickness of the component is 6mm, the height-diameter ratio is 1.3:1, and the total height is 310mm.

The specific forming process is carried out as follows:

Step (1) Determine the size of the blank 2: select the 6mm thick TA2 pure titanium raw material sheet required for forming, and supplement the allowance and process flange edge according to the characteristics of the component (as shown in Figure 2). Using FormingSuite software to carry out numerical simulation, the number of meshes is 7800, the material strain hardening index is 0.13, the Young's modulus is 103GPa, the Poisson's ratio is 0.35, the blank holder force is 20t, and the drawing force is 400t, and the numerical value of the sheet metal drawing process is carried out. Simulate, expand and determine the blanking size to be 6×Φ940mm. When blanking, two lugs are added at the relative positions of the blank 2, so that the blank 2 can be clamped when the strong pulse current assists the tissue regulation.

Step (2) Design the forming mold and carry out the installation and positioning: Design and manufacture the mold required for cold forming and hot forming, because the thermal expansion coefficient of the mold is larger than that of the titanium alloy, so it needs to be reduced and processed, and the cavity of the forming mold is based on the titanium alloy hemisphere. The size of the shaped member is appropriately reduced, and the reduction factor is selected as 6‰; the forming die is installed and positioned through the positioning plate 3 on the side of the blank holder.

Step (3) The first pass of cold forming of the plate: the second ejector pin 6 goes up, so that the upper plane of the blank holder 4 exceeds the highest point of the punch 5 . Apply lubricating oil on the upper and lower surfaces of the blank 2, place the blank 2, and ensure that the center of the blank 2 coincides with the center of the mold. The concave die 1 goes down to press the blank 2, and then the concave die 1, the blank 2 and the blank holder 4 go down 200mm at the same time, and the first pass of forming is completed, and the preform 12 is obtained. The blank holder force was 10t, and the speed of the upper die was 2mm/s.

Step (4) Auxiliary structure control of preformed part by strong pulse current: remove lubricating oil from preform 12, spray anti-oxidation paint, carry out strong pulse current auxiliary structure control, eliminate microcracks inside the plate after forming, and equiax the deformed structure , to improve its re-deformation ability and prevent local rupture during forming. The current auxiliary regulation system is mainly composed of an electrode support 11 , a pulse power supply 8 , a clamping mechanism 10 and a temperature feedback regulation system 9 . The clamping mechanism 10 clamps and fixes the preform 12 obtained in step (3), turns on the external water-cooled circulating pump, the pulse power supply 8 switch and the temperature feedback adjustment system 9, inputs the initial current value of 4000A and the target temperature of 630°C, and starts. Heating, after reaching the target temperature, keep the temperature for 30 minutes, and turn off the pulse power switch 8; when it reaches room temperature, take out the component.

Step (5) The second pass of cold forming of the plate: the second ejector pin 6 goes up, so that the upper plane of the blank holder 4 exceeds the highest point of the punch 5 . Apply lubricating oil on the upper and lower surfaces of the preform 12 in step (4), place the blank 2, and ensure that the center of the blank 2 coincides with the center of the mold. The upper die 1 goes down to press the blank 2, and then the upper die 1, the blank 2 and the blank holder 4 go down 110mm at the same time to complete the second pass forming. The blank holder force was 15t, and the speed of the upper die was 2mm/s.

Step (6) Thermal shape correction: the surface of the preform is sprayed with anti-oxidation paint to perform thermal shape correction. The hot forming and the cold forming share a set of molds, and the hot forming mold is mainly composed of a punch 5 , a blank holder 4 , a concave die 1 , and a positioning plate 3 . During the hot calibration, the punch 5 descends until the mold is closed, the descending speed is 0.5mm/s, and after 30min of heat preservation, the hot pressing of the plate is completed, and the hemispherical component is taken out.

The dimensional accuracy of the pure titanium hemispherical component prepared by this example is less than ±0.3mm, the profile accuracy is within ±0.2mm, the surface roughness is Ra3.2, the wall thickness uniformity is good, the maximum thinning rate is 7%, and there is no Tendency to wrinkle and break.

Table 1 Accuracy of hemispherical components

The dimensional accuracy of the hemispherical components prepared by the multi-pass forming method of the present application is less than ±0.5mm, the profile accuracy is within ±0.3mm, the wall thickness uniformity is good, the maximum thinning rate is within 20%, and there is no tendency to wrinkle and rupture. The dimensional accuracy of the hemispherical components prepared by the prior art is ±0.8-1mm, the profile accuracy is ±0.6-0.7mm, the surface roughness is about Ra3.2, the uniformity of the wall thickness is poor, it is easy to crack, and the maximum thinning rate is 50 to 70%, there is a tendency to wrinkle and rupture. Compared with the prior art, the preparation method of the present application has greatly improved the wall thickness uniformity, product surface quality, shape accuracy and other properties.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention.

Claims (9)

1. a multi-pass forming method of a hemispherical component is characterized in that, the hemispherical component forming die adopted comprises a concave die, a punch, a blank holder and a positioning plate; The die and punch are used for forming hemispherical components; The blank holder is arranged between the die and the punch, and the blank holder cooperates with the die to compress the blank to prevent the blank from wrinkling during the forming process; The blank holder is provided with a positioning plate, and the positioning plate is used for positioning the upper die and the lower die; The multi-pass forming method includes the following steps: S1. Determine the size of the blank; S2. Fix the die and the punch on the upper platform and the lower platform of the forming machine respectively; S3. Place the blank and perform the first pass of cold forming to obtain a preform; S4. Performing strong pulse current to assist tissue regulation on the preform; S5. Determine the number of cold forming passes, repeat steps S3 and S4 to complete the number of cold forming passes, and demold to take out the preform; S6. Hot-correcting the pre-formed parts. Hot-correcting and cold-forming share a set of molds, but the initial states are different. During hot-correcting, the punch is the upper mold, and the concave mold is the lower mold to obtain a hemispherical component. 2. The multi-pass forming method of the hemispherical component according to claim 1, wherein the forming die of the hemispherical component further comprises an adapter plate for increasing the ejection radius; The bottom of the adapter plate is connected with the first ejector rod of the lower platform top cylinder of the forming machine, and the upper surface of the adapter plate is provided with a second ejector rod. The second ejector rod is used to push out the blank holder and apply the blank holder force. . 3 . The multi-pass forming method for a hemispherical component according to claim 2 , wherein the punch comprises a bottom plate and a cavity, the adapter plate is disposed in the cavity, and the bottom plate is disposed on the bottom plate. 4 . There is a bottom plate through hole for the second ejector rod to pass through. 4. The multi-pass forming method for a hemispherical component according to claim 1, wherein the step S1 comprises: selecting a blank according to the size and shape of the hemispherical member; Numerical simulation of cold forming is performed to determine the net size of the blank, and the forming allowance is added to determine the final blank size. 5. The multi-pass forming method for a hemispherical component according to claim 3, wherein the step S2 comprises: The punch is placed on the lower platform of the forming machine, the blank holder is hung on the bottom plate, the lower part of the positioning plate is in contact with the side of the punch, and the upper part of the positioning plate is in contact with the side of the concave die to complete the concave and convex After the positioning of the die, the concave die and the punch are respectively fixed on the upper platform and the lower platform of the forming machine. 6. The multi-pass forming method for a hemispherical component according to claim 3, wherein the step S3 comprises: The second ejector rod goes up, so that the upper plane of the blank holder exceeds the highest point of the punch; Apply lubricating oil on the upper and lower surfaces of the blank, and place the blank between the blank holder and the die to ensure that the center of the blank and the center of the die coincide; The concave die goes down to compress the blank, and then the concave die, the blank and the blank holder go down 50-200mm at the same time to complete the first pass forming; The downward speed of the die is 1-2 mm/s. 7 . The multi-pass forming method for a hemispherical component according to claim 6 , wherein, in the step S4 , when the blank is an aluminum alloy, the high-pulse current-assisted microstructure regulation temperature is 300-400° C.; the blank is When commercial pure titanium is used, the temperature is 550 to 650 ℃ for tissue regulation by strong pulse current. 8. The multi-pass forming method for a hemispherical component according to claim 7, wherein the step S6 comprises: The surface of the preform is sprayed with anti-oxidation paint for thermal correction; During hot calibration, the punch goes down until the mold is closed, keep the temperature for 20-60 minutes, and then take out the hemispherical component. 9. The multi-pass forming method for a hemispherical component according to any one of claims 1-8, wherein in the step S6, the downward speed of the punch is 0.5-1 mm/s; When the blank is an aluminum alloy, the thermal correction temperature of the hemispherical component is 380-480°C; When the blank is commercial pure titanium, the thermal correction temperature of the hemispherical component is 550-650°C.

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