CN110479843B - Forming die and multi-pass forming method of hemispherical component - Google Patents
Forming die and multi-pass forming method of hemispherical component Download PDFInfo
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- CN110479843B CN110479843B CN201910902706.XA CN201910902706A CN110479843B CN 110479843 B CN110479843 B CN 110479843B CN 201910902706 A CN201910902706 A CN 201910902706A CN 110479843 B CN110479843 B CN 110479843B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/20—Deep-drawing
- B21D22/22—Deep-drawing with devices for holding the edge of the blanks
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
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Abstract
The invention discloses a forming die and a multi-pass forming method for a hemispherical component, belongs to the technical field of hemispherical body forming, and solves the problems of wrinkling and cracking in deep drawing forming, difficulty in controlling parameters of a deep drawing forming process and poor wall thickness uniformity of the hemispherical component with a large height-diameter ratio in the prior art. The forming die comprises a female die, a male die, a blank holder and a positioning plate; the female die and the male die are used for forming the hemispherical component; the blank holder is arranged between the female die and the male die, and the blank holder and the female die are matched to compress the blank, so that the blank is prevented from being folded in the forming process; the blank holder is provided with the locating plate, and the locating plate is used for fixing a position last mould and lower mould. The forming die and the forming method are suitable for forming the hemispherical component with the large height-diameter ratio.
Description
Technical Field
The invention belongs to the technical field of hemispherical body forming, and particularly relates to a forming die and a multi-pass forming method for a hemispherical component.
Background
The hemispherical member is widely applied to products such as a space-borne rocket propulsion system, a satellite cover body, a pressure vessel end enclosure and the like, the hemispherical member is mainly made of titanium alloy, aluminum alloy, alloy steel and stainless steel according to different working environments of the hemispherical body, and the hemispherical member is mostly applied to extreme environments and has higher requirements on pressure resistance, reliability, safety, service life and the like, so that the quality control of the hemispherical member is particularly important.
The forming process of the hemispheroid mainly comprises spinning forming and cold/hot drawing forming. The spinning forming process has the advantages of complex parameter control, high manufacturing difficulty, low assembly and adjustment precision and high production cost. The residual stress of the workpiece after spinning is large, and the workpiece is easy to deform after the stress is applied by the laminating machine, so that the use performance is influenced. In the deep drawing forming process, the diameter of the blank is reduced, and the ball is gradually formed, so that the ball forming machine is more suitable for batch production. However, in actual production, wrinkling and cracking defects often occur, and the product quality and the production efficiency are seriously influenced. Particularly for materials which are difficult to deform, such as titanium alloy, aluminum alloy and the like with large height-diameter ratio, the drawing forming process parameters are difficult to control, the wall thickness uniformity is poor, the surface quality of products is poor, and the shape precision is difficult to guarantee. Therefore, the development of the high-quality high-efficiency deep drawing forming method of the hemispherical component has important significance for meeting the use requirements of aerospace large-size high-performance components, eliminating the wrinkle and fracture defects and promoting high-efficiency production.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a forming die for a hemispherical member and a multi-pass forming method, so as to solve the problems in the prior art that the hemispherical member with a large aspect ratio is wrinkled and cracked during drawing, the drawing process parameters are difficult to control, the uniformity of the wall thickness is poor, the surface quality of the product is poor, the shape precision is difficult to ensure, and the like.
The purpose of the invention is mainly realized by the following technical scheme:
on one hand, the invention discloses a forming die of a hemispherical component, which comprises a female die, a male die, a blank holder and a positioning plate;
the female die and the male die are used for forming the hemispherical component;
the blank holder is arranged between the female die and the male die, and the blank holder and the female die are matched to compress the blank, so that the blank is prevented from being folded in the forming process;
the blank holder is provided with the locating plate, and the locating plate is used for fixing a position last mould and lower mould.
Further, the device also comprises an adapter plate for increasing the ejection radius;
the bottom of the adapter plate is connected with a first ejector rod of a top cylinder of a lower platform of the forming machine, a second ejector rod is arranged on the upper surface of the adapter plate and used for ejecting the blank holder and applying blank holding force.
Further, the male die comprises a bottom plate and a cavity, the adapter plate is arranged in the cavity, and a bottom plate through hole for the second ejector rod to penetrate through is formed in the bottom plate.
On the other hand, the invention also discloses a multi-pass forming method of the hemispherical component, which adopts the hemispherical component forming die and comprises the following steps:
s1, determining the size of a blank;
s2, respectively fixing the female die and the male die on an upper platform and a lower platform of the forming machine;
s3, placing the blank, and performing cold forming for the first time to obtain a preformed piece;
s4, performing strong pulse current auxiliary tissue regulation and control on the preformed piece;
s5, determining the number of times of cold forming channels, repeating the steps S3 and S4 to finish the number of times of the cold forming channels, demolding and taking out the preformed piece;
and S6, carrying out thermal correction on the preformed piece to obtain the hemispherical component.
Further, step S1 specifically includes:
selecting a blank according to the size and shape of the hemispherical member;
and (5) performing cold forming numerical simulation, determining the net size of the blank, and increasing the forming allowance to determine the size of the final blank.
Further, step S2 includes:
the male die is placed on the lower platform of the forming machine, the blank holder is hung on the bottom plate, the lower portion of the positioning plate is in contact with the side face of the male die, the upper portion of the positioning plate is in contact with the side face of the female die, and after the female die and the male die are positioned, the female die and the male die are fixed on the upper platform and the lower platform of the forming machine respectively.
Further, step S3 includes:
the second ejector rod moves upwards to enable the plane of the blank holder to exceed the highest point of the male die;
coating lubricating oil on the upper surface and the lower surface of the blank, placing the blank between the blank holder and the female die, and ensuring that the center of the blank is coincided with the center of the die;
descending the female die, compacting the blank, and then descending the female die, the blank and the blank holder by 50-200mm at the same time to finish the first forming;
the descending speed of the female die is 1-2 mm/s.
Further, in the step S4, when the blank is an aluminum alloy, the temperature of the strong pulse current auxiliary tissue is 300-400 ℃; when the blank is commercial pure titanium, the temperature of the tissue is regulated and controlled to be 550-650 ℃ by the aid of strong pulse current.
Further, step S6 includes:
spraying an anti-oxidation coating on the surface of the preformed piece, and performing thermal sizing;
and during thermal sizing, the male die descends until the die is closed, the temperature is kept for 20-60min, and the hemispherical component is taken out.
Further, in the step S6, the descending speed of the male die is 0.5-1 mm/S;
when the blank is aluminum alloy, the hot shaping temperature of the hemisphere is 380-480 ℃;
when the blank is commercial pure titanium, the hot shaping temperature of the hemisphere is 550-650 ℃.
Compared with the prior art, the invention can at least realize one of the following technical effects:
1) the forming method comprises two working procedures of cold forming and hot sizing, wherein the cold forming can be divided into 2-4 times according to different forming heights, the organization structure is optimized by adopting a current auxiliary regulation and control technology between the times, the structure has continuous deformation capacity, and the precision forming of the hemispherical component with the large height-diameter ratio is realized, so that the bottleneck of the forming technology of the existing hemispherical component is broken through, and the product quality and the qualification rate are effectively improved.
The hemispherical member with a large height-diameter ratio is a hemispherical member with a diameter of 500-700 mm and a height-to-radius ratio of 1.2 or more. The invention solves the problems of wrinkling and cracking during the drawing forming of the hemispherical shell with large height-diameter ratio and can obviously improve the uniformity of wall thickness.
2) The microstructure is optimized by adopting a current auxiliary regulation and control technology among passes, rapid heating and short-time heat preservation are realized by using pulse current, the deformation structure is regulated and controlled, the micro-cracks are subjected to bridging action of the pulse current, so that the micro-cracks have continuous deformation capacity, the micro-cracks in the formed plate are eliminated, the deformation structure is equiaxial, the secondary deformation capacity of the micro-cracks is improved, and local breakage during forming is prevented. The invention can obviously shorten the intermediate heat treatment time and improve the production efficiency by utilizing the rapid heating technology of the pulse strong current.
3) The invention adopts a set of die to realize cold forming and hot forming procedures, thereby greatly saving the processing cost.
4) After the cold deformation process of multiple times and the short-time strong pulse current auxiliary treatment, the grain size of the microstructure is refined after the forming, and the product performance is improved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a drawing of a hemispherical component cold forming die;
FIG. 2 is a cross-sectional view of a hemispherical component cold-forming die;
FIG. 3 is a diagram of a strong pulse current assisted tissue regulation system;
fig. 4 is a diagram of a hemispherical component thermal sizing die.
Reference numerals:
1-a female die; 2-blank material; 3, positioning a plate; 4-blank holder; 5-a male die; 6-a second ejector rod; 7-an adapter plate; 8-a pulse power supply; 9-temperature feedback regulation system; 10-a clamping mechanism; 101-an electrode; 102-a platen; 103-U type copper body; 104-a wire harness; 11-an electrode holder; 12-preform.
Detailed Description
A hemispherical member forming mold and a multi-pass forming method will be described in further detail with reference to specific examples, which are provided for comparison and explanation purposes only and to which the present invention is not limited.
Example 1
The embodiment provides a forming die of a hemispherical component, which comprises a female die 1, a male die 5, a blank holder 4 and a positioning plate 3, as shown in fig. 1-2; the female die 1 and the male die 5 are used for forming a hemispherical component; the blank holder 4 is arranged between the female die 1 and the male die 5, and the blank holder 4 is matched with the female die 1 to tightly press the blank 2 and is used for preventing instability and wrinkling in the forming process of the blank 2; two adjacent side faces 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 face of the blank holder 4 and the positioning plate 3 is vertically distributed.
The device also comprises an adapter plate 7 for increasing the ejection radius; the forming machine lower platform comprises a lower ejection cylinder and a first ejector rod, the ejection radius formed by the first ejector rod is smaller, the ejection radius is fixed, and in order to meet the forming requirement of a large-diameter hemisphere, the ejection radius is increased by adopting an adapter plate 7. The bottom of the adapter plate 7 is connected with a first ejector rod of a top cylinder of a lower platform of the forming machine, a second ejector rod 6 is arranged on the upper surface of the adapter plate 7, the second ejector rod 6 is used for ejecting the blank holder 4, the second ejector rod 6 has a larger ejection radius formed by the second ejector rods 6 evenly distributed around the center of the adapter plate 7, and the ejection radius can be changed according to the size of a formed hemispherical component.
The male die 5 comprises 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 male die 5 is 1-3 mm, so that the adapter plate 7 can smoothly lift in the cavity; be provided with the bottom plate through-hole that is used for second ejector pin 6 to pass on the bottom plate, four second ejector pins 6 of adapter plate 7 upper surface symmetric distribution, when adapter plate 7 is located the cavity bottom, in 5 bottom plate through-holes of terrace die were arranged in to second ejector pin 6 and not more than the bottom plate upper surface, second ejector pin 6 and bottom plate upper surface distance 3 ~ 5mm, make second ejector pin 6 can not hinder the placing of blank holder 4 on terrace die 5, 2 ~ 4mm in the unilateral clearance of bottom plate through-hole and second ejector pin 6, it is smooth to move in the bottom plate through-hole when making second ejector pin 6 go up and down.
A multi-pass forming method for a hemispherical component comprises two working procedures of cold forming and hot shaping, wherein the two forming procedures share a set of die, the cold forming can be divided into 2-4 passes according to different forming heights, and the tissue structure is optimized by adopting a current auxiliary regulation and control technology between the passes so that the hemispherical component has continuous deformation capability. The multi-pass forming die for the hemispherical component comprises the following steps:
s1, determining the size of a blank 2;
s2, respectively fixing the female die 1 and the male die 5 on an upper platform and a lower platform of the forming machine;
s3, placing the blank 2, and performing cold forming for the first time to obtain a preformed piece 12;
s4, performing strong pulse current auxiliary tissue regulation on the preformed piece 12;
s5, selecting the optimal cold forming channel times, repeating the steps S3 and S4 until the mold is closed, demolding and taking out the preformed piece 12;
s6, performing thermal correction on the preformed piece 12 to obtain the hemispherical component.
Step S1 specifically includes:
selecting a plate according to the size and the shape of the hemispherical component; and dividing grids, setting material properties and boundary conditions, performing cold forming numerical simulation, determining the net size of the blank 2, adding forming allowance to the plate in the radial direction, and determining the size of the final blank 2.
Step S2 specifically includes:
the method comprises the following steps of placing a male die 5 on a lower platform of a forming machine, hanging a blank holder 4 on a bottom plate, enabling a gap between a central hole of the blank holder 4 and a single edge of a raised vertical edge part of the male die 5 to be 2mm, enabling the lower part of a positioning plate 3 to be in contact with the side surface of the male die 5, enabling the upper part of the positioning plate 3 to be in contact with the side surface of a female die 1, and fixing the female die 1 and the male die 5 on the upper platform and the lower platform of the forming machine.
Step S3 specifically includes:
the second ejector rod 6 moves upwards to enable the upper plane of the blank holder 4 to exceed the highest point of the male die 5; lubricating oil is smeared on the upper surface and the lower surface of the blank 2, and the blank 2 is placed between the blank holder 4 and the female die 1 to ensure that the center of the blank 2 is coincided with the center of the die; the female die 1 descends to compress the blank 2, and then the female die 1, the blank 2 and the blank holder 4 descend simultaneously for a certain distance, such as 50-200mm, so as to complete the first forming; in order to ensure uniform deformation of the blank 2 and control the work hardening effect, the descending speed of the female die 1 is set to be 1-2 mm/s.
Step S4 specifically includes:
removing lubricating oil from the preformed piece 12, spraying an anti-oxidation coating, and performing strong pulse current-assisted tissue regulation on the blank 2 through a current-assisted regulation system; micro-cracks in the formed plate are eliminated, the deformed structure is equiaxial, the secondary deformation capacity of the plate is improved, and local breakage is prevented during forming.
As shown in fig. 3, the current auxiliary regulating system comprises an electrode bracket 11, a pulse power supply 8, a wire bundle 104, a clamping mechanism 10 and a temperature feedback regulating system 9;
the clamping mechanisms 10 are symmetrically distributed on two sides of the preformed piece 12, each clamping mechanism 10 comprises an electrode 101, a U-shaped copper body 103 and a pressing plate 102, the electrodes 101 are connected with the U-shaped copper bodies 103 through a wire bundle 104, bolts are screwed into the threaded through holes and are in contact with the pressing plates 102, the preformed piece 12 in the step S3 is clamped and fixed by the pressing plates 102 and the U-shaped copper bodies 103 under the action of the pretightening force of the bolts, an external water-cooling circulating pump, a pulse power supply 8 switch and a temperature feedback adjusting system 9 are started, an initial current value and a target temperature are input, heating is started, after the target temperature is reached, heat preservation is carried out for; the preform 12 is removed when it has cooled to room temperature.
When the blank 2 is aluminum alloy, the temperature of the strong pulse current auxiliary tissue is 300-400 ℃; when the blank 2 is commercial pure titanium, the temperature of the tissue is regulated and controlled to be 550-650 ℃ by the aid of strong pulse current.
Step S5 specifically includes:
and (3) performing a process test to determine the descending distance of each pass, wherein the blank pressing force is determined according to the thickness of the blank 2, the material strength and the blank diameter, generally, the wrinkling tendency is more obvious along with the forming, and the blank pressing force is also gradually increased. Under the condition of ensuring no wrinkling or small wrinkling tendency, the lower limit value of the blank holder force is required to be taken, so that the blank 2 can move towards the center of the die under the action of the male die in the forming process, and the blank 2 can be prevented from wrinkling, thereby realizing the control of the uniformity of the wall thickness.
Preferably, the distribution range of the safe area and the dangerous area can be determined through the cold forming numerical simulation process described in the step S1, the cold forming is divided into 2 to 4 passes, and the approximate descending distance is determined, so as to reduce the test range and the test times. During cold forming simulation, the thickness is reduced by less than 30% on the basis of the original thickness to form a safety area, and the thickness is reduced by more than 30% to form a dangerous area.
Step S6 specifically includes:
spraying an anti-oxidation coating on the surface of the preformed piece 12, and performing thermal sizing; the hot sizing and cold forming share a set of die, as shown in fig. 4, the hot forming die is composed of a male die 5, a blank holder 4, a female die 1 and a positioning plate 3; and during hot shape correction, the male die 5 is an upper die, the female die 1 is a lower die, the male die 5 descends until die assembly is carried out, and the hemispherical component is taken out after heat preservation for 20-60 min.
Hot sizing and cold forming share a set of dies, but the initial state is different, as shown in fig. 4. And a mandril is needed to be used during cold forming, the jacking cylinder and the mandril are arranged on the lower platform, the male die 5 is a lower die at the moment, and the female die 1 is an upper die. The male die 5 is an upper die and the female die 1 is a lower die during hot shape correction, so that the die is easy to demould.
The descending speed of the male die 5 is 0.5-1 mm/s; when the blank 2 is aluminum alloy, the hot shaping temperature of the hemisphere is 380-480 ℃; when the blank 2 is commercial pure titanium, the thermal shaping temperature of the hemisphere is 550-650 ℃.
Because the materials expand at high temperature, but the expansion coefficients of different materials are different, in order to make the final component consistent with the size of the mould, the mould is designed to be properly scaled according to the size of the hemispherical component.
Example 2
Taking a 5083 aluminum alloy hemispherical member as an example, the external dimension of the member is shown in figure 1, the thickness of the member is 4mm, and the height-diameter ratio is 1.2: 1, total height of 260 mm.
The specific forming process is carried out according to the following steps:
step (1) determining the size of a blank 2: a5083 aluminum alloy raw material plate with the thickness of 4mm required by forming is selected, and allowance and a process flange edge are supplemented according to the characteristics of the component, as shown in figure 2. Numerical simulation is carried out by adopting FormingSuite software, the number of divided grids is 6900, the material strain hardening index is 0.25, the Young modulus is 70GPa, the Poisson ratio is 0.33, the blank pressing force is 5t, the drawing force is 200t, numerical simulation is carried out on the sheet drawing process, and the blanking size is determined to be 4 x phi 850mm after expansion. Two lugs are respectively added at the opposite positions of the blank 2 during blanking, so that the blank 2 can be clamped when strong pulse current assists in tissue regulation.
Designing a forming die and installing and positioning: designing and manufacturing a mold required by cold forming and hot sizing, and then carrying out appropriate amplification processing on a cavity of the forming mold according to the size of the aluminum alloy hemispherical component, wherein the amplification factor is 5 per mill; and installing and positioning the forming die through the blank holder side positioning plate 3.
Step (3), performing cold forming on the plate for the first pass: the second ejector rod 6 moves upwards to enable the upper plane of the blank holder 4 to exceed the highest point of the male die 5. And (3) coating lubricating oil on the upper and lower surfaces of the blank 2, placing the blank 2 and ensuring that the center of the blank 2 is coincided with the center of the die. And (3) allowing the female die 1 to descend to compact the blank 2, and allowing the female die 1, the blank 2 and the blank holder 4 to descend simultaneously by 170mm to finish the first-pass forming to obtain a preformed piece 12. The edge pressing force is 5t, and the descending speed of the upper die is 2 mm/s.
And (4) performing strong pulse current assisted tissue regulation on the preformed piece: the lubricating oil is removed from the preformed piece 12, the anti-oxidation coating is sprayed, strong pulse current is used for assisting tissue regulation, microcracks in the formed plate are eliminated, the deformed tissue is equiaxial, the secondary deformation capability of the deformed tissue is improved, and local cracking is prevented during forming. The current auxiliary regulation and control system mainly comprises an electrode bracket 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 preformed piece 12 obtained in the step (3), an external water-cooling circulating pump, a pulse power supply 8 switch and a temperature feedback adjusting system 9 are started, an initial current value 4000A and a target temperature 350 ℃ are input, heating is started, after the target temperature is reached, heat preservation is carried out for 20min, and the pulse power supply 8 switch is turned off; when the temperature is reduced to room temperature, the component is taken out.
And (5) performing cold forming on the plate for a second pass: the second ejector rod 6 moves upwards to enable the upper plane of the blank holder 4 to exceed the highest point of the male die. And (4) coating lubricating oil on the upper surface and the lower surface of the preformed piece 12 in the step (4), and placing the preformed piece 12 to ensure that the center of the preformed piece 12 is coincident with the center of the mould. The female die 1 descends to compact the preformed piece 12, and then the female die 1, the preformed piece 12 and the binder 4 descend simultaneously for 90mm to finish the second-pass forming. The edge pressing force is 8t, and the descending speed of the upper die is 2 mm/s.
Step (6), hot sizing: and (5) spraying an anti-oxidation coating on the surface of the preformed piece 12 obtained in the step (5) for thermal sizing. The hot forming and the cold forming share one set of die, and the hot forming die mainly comprises a male die 5, a blank holder 2, a female die 1 and a positioning plate 3. And during thermal sizing, the male die 5 descends until the die is closed, the descending speed is 0.5mm/s, after heat preservation is carried out for 20min, namely, the hot press forming of the preformed piece 12 is finished, and the hemispherical component is taken out.
The aluminum alloy hemispherical component prepared by the embodiment has the size precision of less than +/-0.4 mm, the profile precision within +/-0.2 mm, the surface roughness Ra3.2, the wall thickness uniformity is good, the maximum thinning rate is 5%, and no wrinkling and cracking tendency is caused.
Example 3
Taking a TA2 pure titanium semispherical member as an example, the external dimension of the semispherical member is shown in figure 1, the thickness of the member is 6mm, and the height-diameter ratio is 1.3: 1, the total height is 310 mm.
The specific forming process is carried out according to the following steps:
step (1) determining the size of a blank 2: selecting a TA2 pure titanium raw material plate with the thickness of 6mm required by forming, and supplementing allowance and a process flange edge according to the characteristics of the component (as shown in figure 2). Carrying out numerical simulation by adopting FormingSuite software, wherein the number of divided grids is 7800, the strain hardening index of the material is 0.13, the Young modulus is 103GPa, the Poisson ratio is 0.35, the blank pressing force is 20t, and the drawing force is 400t, carrying out numerical simulation on the sheet drawing process, and unfolding to determine the blanking size to be 6 multiplied by phi 940 mm. Two lugs are respectively added at the opposite positions of the blank 2 during blanking, so that the blank 2 can be clamped when strong pulse current assists in tissue regulation.
Designing a forming die and installing and positioning: designing and manufacturing a mold required by cold forming and hot sizing, wherein the thermal expansion coefficient of the mold is larger than that of the titanium alloy, so that the mold needs to be reduced, the cavity of the forming mold is properly reduced according to the size of the titanium alloy hemispherical component, and the reduction coefficient is selected to be 6 per mill; and installing and positioning the forming die through the blank holder side positioning plate 3.
Step (3), performing cold forming on the plate for the first pass: the second ejector rod 6 moves upwards to enable the upper plane of the blank holder 4 to exceed the highest point of the male die 5. And (3) coating lubricating oil on the upper and lower surfaces of the blank 2, placing the blank 2 and ensuring that the center of the blank 2 is coincided with the center of the die. And (3) the female die 1 descends to compact the blank 2, and then the female die 1, the blank 2 and the blank holder 4 descend by 200mm at the same time to finish the first-pass forming to obtain a preformed piece 12. The edge pressing force is 10t, and the descending speed of the upper die is 2 mm/s.
And (4) performing strong pulse current assisted tissue regulation on the preformed piece: the lubricating oil is removed from the preformed piece 12, the anti-oxidation coating is sprayed, strong pulse current is used for assisting tissue regulation, microcracks in the formed plate are eliminated, the deformed tissue is equiaxial, the secondary deformation capability of the deformed tissue is improved, and local cracking is prevented during forming. The current auxiliary regulation and control system mainly comprises an electrode bracket 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 preformed piece 12 obtained in the step (3), an external water-cooling circulating pump, a pulse power supply 8 switch and a temperature feedback adjusting system 9 are started, an initial current value 4000A and a target temperature 630 ℃ are input, heating is started, heat preservation is carried out for 30min after the target temperature is reached, and the pulse power supply 8 switch is closed; when the temperature is reduced to room temperature, the component is taken out.
And (5) performing cold forming on the plate for a second pass: the second ejector rod 6 moves upwards to enable the upper plane of the blank holder 4 to exceed the highest point of the male die 5. And (4) coating lubricating oil on the upper surface and the lower surface of the preformed piece 12 in the step (4), placing the blank 2, and ensuring that the center of the blank 2 is coincided with the center of the die. And (3) the upper die 1 descends to compact the blank 2, and then the upper die 1, the blank 2 and the blank holder 4 descend simultaneously by 110mm to finish the second-pass forming. The edge pressing force is 15t, and the descending speed of the upper die is 2 mm/s.
Step (6), hot sizing: and spraying an anti-oxidation coating on the surface of the preformed piece, and performing thermal sizing. The hot forming and the cold forming share one set of die, and the hot forming die mainly comprises a male die 5, a blank holder 4, a female die 1 and a positioning plate 3. And during hot sizing, the male die 5 descends until the die is closed, the descending speed is 0.5mm/s, the temperature is kept for 30min, namely the plate is subjected to hot press forming, and the hemispherical component is taken out.
The pure titanium hemispherical component prepared by the embodiment has the size precision of less than +/-0.3 mm, the profile precision within +/-0.2 mm, the surface roughness Ra3.2, good wall thickness uniformity, the maximum thinning rate of 7 percent and no wrinkling and cracking tendency.
TABLE 1 hemispherical Member accuracy
The hemispherical component prepared by the multi-pass forming method has the size precision of less than +/-0.5 mm, the profile precision within +/-0.3 mm, good wall thickness uniformity, the maximum thinning rate within 20 percent and no wrinkling and cracking tendency. The size precision of a hemispherical component prepared by the prior art is +/-0.8-1 mm, the profile precision is +/-0.6-0.7 mm, the surface roughness is about Ra3.2, the wall thickness uniformity is poor, the hemispherical component is easy to crack, the maximum thinning rate is 50-70%, and the hemispherical component has a wrinkling and cracking tendency. Compared with the prior art, the preparation method has the advantages that the wall thickness uniformity, the product surface quality, the shape precision and other properties are greatly improved.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (9)
1. A multi-pass forming method of a hemispherical component is characterized in that an adopted hemispherical component forming die comprises a female die, a male die, a blank holder and a positioning plate;
the female die and the male die are used for forming the hemispherical component;
the blank holder is arranged between the female die and the male die, and the blank holder and the female die are matched to compress the blank, so that the blank is prevented from being folded in 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 comprises the following steps:
s1, determining the size of a blank;
s2, respectively fixing the female die and the male die on an upper platform and a lower platform of the forming machine;
s3, placing the blank, and performing cold forming for the first time to obtain a preformed piece;
s4, performing strong pulse current auxiliary tissue regulation and control on the preformed piece;
s5, determining the number of times of cold forming channels, repeating the steps S3 and S4 to finish the number of times of the cold forming channels, and demolding to take out a preformed piece;
and S6, performing thermal correction on the preformed piece, wherein the thermal correction and the cold forming share one set of die, but the initial state is different, and the male die is an upper die and the female die is a lower die during the thermal correction to obtain the hemispherical component.
2. The multi-pass forming method of a hemispherical member according to claim 1, wherein the forming mold of the hemispherical member further comprises an adapter plate for increasing an ejection radius;
the bottom of the adapter plate is connected with a first ejector rod of a lower platform jacking cylinder of the forming machine, a second ejector rod is arranged on the upper surface of the adapter plate and used for ejecting the blank holder and applying blank holding force.
3. The method for multipass forming of a hemispherical member as claimed in claim 2, wherein the male die comprises a base plate and a cavity, the adapter plate is disposed in the cavity, and the base plate is provided with a base plate through hole for the second ejector pin to pass through.
4. The multi-pass forming method of a hemispherical member as claimed in claim 1, wherein the step S1 comprises:
selecting a blank based on the hemispherical member size and shape;
and (5) performing cold forming numerical simulation, determining the net size of the blank, and increasing the forming allowance to determine the size of the final blank.
5. The multi-pass forming method of a hemispherical member as claimed in claim 3, wherein the step S2 comprises:
and placing the male die on a lower platform of the forming machine, hanging the blank holder on the bottom plate, contacting the lower part of the positioning plate with the side surface of the male die, contacting the upper part of the positioning plate with the side surface of the female die, and fixing the female die and the male die on an upper platform and a lower platform of the forming machine respectively after the positioning of the female die and the male die is completed.
6. The multi-pass forming method of a hemispherical member as claimed in claim 3, wherein the step S3 comprises:
the second ejector rod moves upwards to enable the plane of the blank holder to exceed the highest point of the male die;
coating lubricating oil on the upper surface and the lower surface of the blank, placing the blank between the blank holder and the female die, and ensuring that the center of the blank is coincided with the center of the die;
the female die descends to compact the blank, and then the female die, the blank and the blank holder descend simultaneously by 50-200mm to finish the first forming;
and the descending speed of the female die is 1-2 mm/s.
7. The method for forming a hemispherical member in multiple passes according to claim 6, wherein in step S4, when the blank is an aluminum alloy, the temperature of the structure is controlled to be 300-400 ℃ by the aid of the strong pulse current; when the blank is commercial pure titanium, the temperature of the tissue is regulated and controlled to be 550-650 ℃ by the aid of strong pulse current.
8. The multi-pass forming method of a hemispherical member as claimed in claim 7, wherein the step S6 comprises:
spraying an anti-oxidation coating on the surface of the preformed piece, and performing thermal sizing;
and during thermal sizing, the male die descends until the die is closed, the temperature is kept for 20-60min, and the hemispherical component is taken out.
9. A method for forming a hemispherical member as claimed in any one of claims 1 to 8, wherein in step S6, the downward speed of the male die is 0.5 to 1 mm/S;
when the blank is aluminum alloy, the thermal correction temperature of the hemispherical component is 380-480 ℃;
when the blank is commercial pure titanium, the thermal sizing temperature of the hemispherical component is 550-650 ℃.
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