阅读说明：本技术 极小圆角半径深腔薄壁金属构件的成形方法 (Forming method of deep-cavity thin-wall metal component with extremely-small fillet radius ) 是由 袁杭 何祝斌 苑世剑 于 2021-09-10 设计创作，主要内容包括：本发明属于深腔薄壁金属构件的成形制造领域,提供了一种极小圆角半径深腔薄壁金属构件的成形方法。本发明的极小圆角半径深腔薄壁金属构件的成形方法,利用刚性模具拉深成形出整体腔体,利用刚性模具小圆角推挤成形出极小圆角,使拉深成形过程与极小圆角成形过程相互独立,避免了两者同时成形过程中出现起皱、开裂等问题,能够解决极小圆角成形难甚至无法成形的问题。本发明的极小圆角半径深腔薄壁金属构件的成形方法,整体腔体拉深成形加局部小圆角推挤成形的方法针对性强,可操作性强,放宽了对拉深成形各处圆角尺寸的要求,可大幅减少拉深成形的道次,并可有效提升具有极小圆角半径深腔薄壁金属构件的成形性和成形效率。(The invention belongs to the field of forming and manufacturing of deep-cavity thin-wall metal components, and provides a forming method of a deep-cavity thin-wall metal component with an extremely small fillet radius. According to the forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius, the rigid die is used for drawing to form the integral cavity, and the small fillet of the rigid die is used for pushing and extruding to form the extremely-small fillet, so that the drawing forming process and the extremely-small fillet forming process are independent from each other, the problems of wrinkling, cracking and the like in the forming processes of the drawing forming process and the extremely-small fillet forming process are avoided, and the problem that the extremely-small fillet forming is difficult or even cannot be formed can be solved. According to the forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius, the method of integral cavity deep-drawing forming and local small fillet push-extrusion forming is strong in pertinence and operability, the requirement on the fillet size of each part of deep-drawing forming is relaxed, the pass of deep-drawing forming can be greatly reduced, and the formability and the forming efficiency of the deep-cavity thin-wall metal component with the extremely-small fillet radius can be effectively improved.)

1. A forming method of a deep-cavity thin-wall metal component with a very small fillet radius is characterized by comprising the following steps:

step one, geometric analysis and process path determination of the component with the minimum fillet radius: respectively making a forming process route of an integral cavity and a local transition fillet according to the cavity depth of the component, the geometric shape of the cross-sectional shape and the size analysis; wherein, the section shape mainly comprises the number of side walls, the section thickness and the radius of a transition fillet; the whole cavity is integrally drawn and formed by a rigid die, and the local round angle is formed by locally pushing and extruding the rigid die;

step two, process parameter formulation and parameter optimization: and (3) determining the size and technological parameters of the deep-drawing formed part by combining the first step and theoretical analysis: r, n, m and the technological parameters of small fillet extrusion forming: d, r; the number of straight wall sides of the side wall is n, the radius of a drawing forming bottom and a side wall fillet is R, the depth of a cavity is h, the drawing forming pass is m, the pushing amount of a pushed small fillet is d, and the radius of the pushed small fillet is R; establishing a multivariate function f (R, m, n, R, d) as 0, and assigning values to R, n and m to obtain a corresponding relation between the extrusion amount d of the extruded small fillet and the radius R of the extruded minimum fillet so as to determine process parameters; analyzing the whole body cavity deep drawing forming and the local small fillet extruding forming through numerical simulation, optimizing the matching relation of process parameters, and ensuring that the multi-pass deep drawing forming and the small fillet extruding forming are both carried out smoothly;

step three, designing and processing a die tool: designing and processing a die tool for integral cavity drawing forming and local small fillet pushing forming according to the dimension R, h of the drawing forming part determined in the step two and the optimized technological parameters m, R, d, and determining the overall scheme and equipment parameter requirements of the die tool;

step four, drawing and forming a rigid die of the integral cavity: utilizing the integral cavity deep drawing forming die designed and processed in the third step, and carrying out integral deep drawing forming on the original thin-wall metal plate blank according to the technological parameters formulated in the second step to obtain the cavity depth, the special-shaped section shape and the size which are determined in the second step and are consistent with the final deep-cavity thin-wall metal component, wherein the obtained side wall fillet radius and the obtained bottom fillet radius are about 2.0-4.0 times of the fillet radius required by the final metal component;

step five, pushing and extruding the rigid die with local round corners to form: utilizing the local extrusion forming die designed and processed in the third step, further extruding and forming the semi-finished product integral cavity obtained in the fourth step according to the technological parameters formulated in the second step, and further reducing the fillet radius of the side wall and the fillet radius of the bottom to fillet sizes meeting the requirements on the premise of ensuring that most areas on the integral cavity are not deformed, wherein the fillet sizes are 1-3 times of the wall thickness;

step six, local trimming: and C, performing flange edge cutting or side wall punching on the semi-finished product of which the integral cavity and the local fillet obtained in the step five meet the requirements of the final metal component to obtain the final deep-cavity thin-wall metal component with extremely small fillet radius.

Technical Field

The invention belongs to the field of forming and manufacturing of deep-cavity thin-wall metal components, and particularly relates to a forming method of a deep-cavity thin-wall metal component with an extremely small fillet radius.

Background

Thin-wall metal components are very important components in the fields of aviation, aerospace, automobiles, high-speed rails and the like, generally bear complex force and thermal load, and put high requirements on the dimensional accuracy and dimensional stability of the thin-wall metal components. Meanwhile, in order to achieve reasonable and reliable assembly with other adjacent components, the thin-wall metal component is generally designed to have a structural form with a deep cavity, a special-shaped section and local small round corners. With the increasingly high requirements of high-end equipment such as aerospace, automobiles and the like on indexes such as light weight, high reliability, long service life and the like, the structural shape of a thin-wall metal component is increasingly complex, the requirement on dimensional accuracy is increasingly high, and new challenges are provided for the traditional forming and manufacturing technology. For example, in a new energy automobile, a square box-shaped aluminum alloy shell of a lithium battery is a very important and large-consumption component, the cross section of the square or rectangular aluminum alloy shell is mainly square or rectangular, the depth of the square or rectangular aluminum alloy shell reaches 100-300 mm, the transition fillet radius of the square or rectangular aluminum alloy shell reaches 3-10 mm, and the square or rectangular aluminum alloy shell is a typical deep-cavity thin-wall metal component with a very small fillet radius. For example, in high-end electronic products, a square box-shaped aluminum alloy, magnesium alloy or stainless steel shell is also used to mount and fix internal electronic components, chips and the like, and the types of the components and the chips are various and have different requirements. The deep-cavity thin-wall metal component with the extremely-small fillet radius is designed mainly for reducing the clearance between adjacent components as much as possible, enhancing the overall rigidity of an assembly structure and improving the effective cavity volume inside each independent component when a plurality of same components are closely arranged and combined for use. At present, the metal shell becomes the most important product in the industries of new energy automobiles and high-grade electronic products, and the forming manufacturing and the mass production of the products represent the highest level of the advanced manufacturing industry.

At present, the deep-cavity thin-wall metal component with the extremely small fillet radius is mainly manufactured by adopting a multi-pass rigid die drawing technology. The technology utilizes a plurality of sets of rigid punches and drawing female dies (progressive dies) to carry out multi-pass drawing forming on a plane metal plate blank, a semi-finished product prepared by a former drawing pass of a latter drawing pass is used as a blank, each pass only enables the blank to generate certain deformation, and necessary heat treatment such as annealing and the like is generally carried out on the blank between adjacent drawing passes. For aluminum alloy plates with poor forming performance at room temperature, the final deep-cavity thin-wall metal component can be obtained only by drawing and forming 6-8 times. If any one of the problems of the structural design of the die, the matching of the deformation of each drawing pass and the intermediate annealing heat treatment exists, the forming failure of the component can be directly caused. For example, when a profiled cross-section member is formed, due to asymmetric geometric shapes of a rigid die and a blank and uneven and unreasonable stress on the blank, deformation of each area on the original blank is uneven and unreasonable, and common forming defects or quality problems include: (1) the wall thickness is not uniformly distributed, which mainly means that the fillet area of the side wall close to the bottom is locally thinned or even cracked due to the elongation deformation; (2) local wrinkling, mainly wrinkling in the transition area of the side wall near the flange area due to uneven material flow and mutual pushing; (3) poor dimensional stability and poor sticking degree, mainly means that the side wall and the bottom surface are easy to deform after being stuck with a mould due to insufficient material deformation and serious resilience; (4) the size of the local round angle which can be achieved is limited, mainly means that when the size of the round angle between the side walls and the transition area of the side walls and the bottom surface is too small, the phenomenon of wrinkling is easy to occur, and qualified parts cannot be formed. In practice, when the minimum fillet radius, namely the fillet radius of the side wall and the fillet radius of the bottom, of the component is less than 5.0 times of the original slab wall thickness, the forming defect or quality problem is more serious, and the deep-cavity thin-wall metal component with the minimum fillet radius which meets the requirements cannot be obtained by adopting the conventional rigid die for multi-pass deep drawing. In addition, the rigid die multi-pass deep drawing technology has complex working procedures and low production efficiency, and the technology has high requirements on the die processing precision and the performance stability of the original metal plate blank, has high requirements on the adopted equipment, and must use a high-grade servo punch with high displacement/force load control precision, good stability and high speed, so the equipment and the die are extremely expensive. Therefore, the technology for forming the deep-cavity thin-wall component by adopting multi-pass rigid die drawing is not mature, so that the wide application of the component in new energy automobiles and high-grade electronic products is greatly limited. The invention patent (patent number: CN201610689208.8) provides an expansion composite forming method aiming at the small corner characteristic of a thin-wall part, the method forms a small round corner through two procedures of hydro-mechanical drawing and expansion composite forming, the method is mainly used for forming the small round corner at the bottom of a deep cavity component, the simultaneous forming of the bottom round corner and the side wall round corner on the deep cavity thin-wall box-shaped component cannot be realized, the size of the formed minimum round corner is still limited, when the size of the small round corner is extremely small and reaches 2.0 times of material thickness, the problems of side wall instability, round corner and straight line section transition region protrusion and the like are easy to occur, and the method is not applicable any more.

In order to solve the problems that when the existing forming technology is used for manufacturing a deep-cavity thin-wall metal component with a tiny fillet radius, the deformation of each area on the original blank is unreasonable due to the fact that a rigid die and the blank are irregular in geometric shape and the blank is uneven and unreasonable in stress, so that the wall thickness distribution is uneven, local wrinkling, poor die attaching degree, overlarge fillet size, insufficient precision and the like occur, the existing bulging composite forming technology has high requirements on pressure regulation and control of a liquid chamber, a high-pressure source, high-pressure sealing and the like, a high-grade servo press machine is required to be adopted, small fillets at the bottom and around cannot be formed at the same time and the like, and a new forming and manufacturing method of the deep-cavity thin-wall metal component with the tiny fillet radius is urgently needed to be developed.

Disclosure of Invention

The invention aims to provide a novel forming manufacturing method, which solves the problems that when the existing forming technology is used for manufacturing a deep-cavity thin-wall metal component with a tiny fillet radius, all areas on an original blank are not uniformly deformed due to irregular geometric shapes of a rigid die and the blank and non-uniform stress conditions of the blank, so that the wall thickness distribution is not uniform, local wrinkles, poor die attachment degree, and the dimensional precision of a local fillet is not sufficient, and the problems that the existing bulging composite forming technology has high requirements on pressure regulation and control of a liquid chamber, a high-pressure source, high-pressure sealing and the like, needs a high-grade servo press, cannot simultaneously form small fillets at the bottom and the periphery, and causes extremely low forming efficiency or incapability of forming the deep-cavity thin-wall metal component with the tiny fillet radius.

The technical scheme of the invention is as follows:

the forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius comprises the following specific steps:

step one, geometric analysis and process path determination of the component with the minimum fillet radius: respectively making a forming process route of an integral cavity and a local transition fillet according to the cavity depth of the component, the geometric shape of the cross-sectional shape and the size analysis; wherein, the section shape mainly comprises the number of side walls, the section thickness and the radius of a transition fillet; the whole cavity is integrally drawn and formed by a rigid die, and the local round angle is formed by locally pushing and extruding the rigid die;

step two, process parameter formulation and parameter optimization: and (3) determining the size and technological parameters of the deep-drawing formed part by combining the first step and theoretical analysis: r, n, m and the technological parameters of small fillet extrusion forming: d, r; the number of straight wall sides of the side wall is n, the radius of a drawing forming bottom and a side wall fillet is R, the depth of a cavity is h, the drawing forming pass is m, the pushing amount of a pushed small fillet is d, and the radius of the pushed small fillet is R; establishing a multivariate function f (R, m, n, R, d) as 0, and assigning values to R, n and m to obtain a corresponding relation between the extrusion amount d of the extruded small fillet and the radius R of the extruded minimum fillet so as to determine process parameters; analyzing the whole body cavity deep drawing forming and the local small fillet extruding forming through numerical simulation, optimizing the matching relation of process parameters, and ensuring that the multi-pass deep drawing forming and the small fillet extruding forming are both carried out smoothly;

step three, designing and processing a die tool: designing and processing a die tool for integral cavity drawing forming and local small fillet pushing forming according to the dimension R, h of the drawing forming part determined in the step two and the optimized technological parameters m, R, d, and determining the overall scheme and equipment parameter requirements of the die tool;

step four, drawing and forming a rigid die of the integral cavity: utilizing the integral cavity deep drawing forming die designed and processed in the third step, and carrying out integral deep drawing forming on the original thin-wall metal plate blank according to the technological parameters formulated in the second step to obtain the cavity depth, the special-shaped section shape and the size which are determined in the second step and are consistent with the final deep-cavity thin-wall metal component, wherein the obtained side wall fillet radius and the obtained bottom fillet radius are about 2.0-4.0 times of the fillet radius required by the final metal component;

step five, pushing and extruding the rigid die with local round corners to form: and (3) further extruding and forming the semi-finished product integral cavity obtained in the fourth step by using the local extrusion forming die designed and processed in the third step according to the technological parameters formulated in the second step, and further reducing the fillet radius of the side wall and the fillet radius of the bottom to fillet sizes meeting the requirements on the premise of ensuring that most areas on the integral cavity are not deformed, wherein the fillet sizes are 1-3 times of the wall thickness.

Step six, local trimming of a flange edge area: and C, performing flange edge cutting or side wall punching on the semi-finished product of which the integral cavity and the local fillet obtained in the step five meet the requirements of the final metal component to obtain the final deep-cavity thin-wall metal component with extremely small fillet radius.

The invention has the beneficial effects that:

(1) according to the forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius, the rigid die is used for drawing to form the integral cavity, and the small fillet of the rigid die is used for pushing and extruding to form the extremely-small fillet, so that the drawing forming process and the extremely-small fillet forming process are independent from each other, the problems of wrinkling, cracking and the like in the forming processes of the drawing forming process and the extremely-small fillet forming process are avoided, and the problem that the extremely-small fillet forming is difficult or even cannot be formed can be solved.

(2) According to the forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius, disclosed by the invention, in the first step of deep drawing forming process, the small fillet radii of the bottom and the side wall can be set to be 2-5 times of the target fillet radius, so that the phenomenon of uneven and unreasonable material flow is reduced to a certain extent, the problems of excessive thinning of the deep-drawn side wall close to the bottom fillet region and serious wrinkling of the top flange fillet region can be effectively reduced, and the problem of uneven and unreasonable wall thickness distribution is solved.

(3) According to the forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius, the second small-fillet pushing and forming process ensures that the straight-wall section is not deformed under the constraint condition in a manner of constraining and pushing the side wall, the pushing and forming of the large fillet and the small fillet in the fillet area are realized, and the problems of poor attaching degree, insufficient size precision of the local fillet and the like in the fillet area can be effectively solved.

(4) The invention relates to a forming method of a deep-cavity thin-wall metal component with a minimum fillet radius, which adopts deep drawing forming and local fillet pushing forming processes, and uses only a common press and a pushing mechanism with a lateral loading unit. The dependence on the die machining precision, the material stability and high-grade servo equipment can be effectively reduced.

(5) According to the forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius, the method of integral cavity deep-drawing forming and local small fillet push-extrusion forming is strong in pertinence and operability, the requirement on the fillet size of each part of deep-drawing forming is relaxed, the pass of deep-drawing forming can be greatly reduced, and the formability and the forming efficiency of the deep-cavity thin-wall metal component with the extremely-small fillet radius can be effectively improved.

(6) The forming method of the deep-cavity thin-wall metal component with the extremely-small fillet radius can be applied to the deep drawing-pushing forming of the deep-cavity thin-wall metal component with the extremely-small fillet radius with different section shapes (such as square sections, trapezoid sections and the like), the extremely-small fillet radius can be formed only by small pushing amount, the compatibility between the front and the rear working procedures is strong, the mass production of the deep-cavity thin-wall component with the extremely-small fillet radius can be realized, and the cost can be greatly reduced.

Drawings

FIG. 1 is a schematic view of a deep-cavity thin-walled metal component having a very small fillet radius according to the present invention;

FIG. 2 is a dimensional schematic of a deep-cavity thin-walled component having a generally very small fillet radius;

FIG. 3 is a flow chart of a forming method according to the present invention;

FIG. 4 is a schematic diagram of the rigid die multi-pass drawing of the present invention, (a) being an initial-pass drawn part, (b) being an intermediate-pass drawn part, and (c) being a final-pass drawn part;

FIG. 5 is a schematic diagram of the pushing and forming of a small corner of the rigid mold according to the present invention, (a) is a schematic diagram of the pushing and forming of a bottom corner, and (b) is a schematic diagram of the pushing and forming of a circumferential corner;

FIG. 6 is a schematic diagram showing the change in cross-sectional shape and size before and after the small round corner is formed by extrusion;

FIG. 7 is a dimension diagram of the square box-shaped deep-cavity thin-wall component.

In the figure: the method comprises the following steps of 1, 2, 3, 4, 5, 6, 7, 8, 9, R, m, R, L, T, H, M, R, D, L, T, C.

Detailed Description

The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.

Example 1: the forming method of the ultra-small fillet radius deep cavity thin-wall metal component is described by combining the figures 1, 2, 3, 4, 5 and 6, and the method is carried out according to the following steps:

step one, geometric analysis and process route determination of the thin-wall component: as shown in figure 6, for the part given in the embodiment, the part cavity depth is 100mm, the wall thickness is 2.5mm, the fillet radius of the small transition fillet is 5mm, and the part is a typical deep-cavity thin-wall metal member with a tiny fillet radius. The diameter-thickness ratio of the small round corner of the component is 2, the component is difficult to form only by drawing forming, the forming process of the whole cavity is determined to be rigid die multi-pass drawing forming, and the forming process of the local small round corner is determined to be rigid die pushing forming.

Step two, process parameter formulation and process parameter optimization: taking a square box-shaped part as an example, assuming that the circumferential perimeter is unchanged, the quantitative relationship between the single-side extrusion amount of the side wall and the bottom surface and the small fillet size change is obtained through theoretical analysis and is as follows:when the radius of the fillet is changed from 10mm to 5mm, the single-side extrusion amount is 1.075 mm; when the radius of the fillet is changed from 15mm to 5mm, the single-side extrusion amount is 2.150 mm; when the radius of the fillet is changed from 20mm to 5mm, the single-side extrusion amount is 3.225 mm. Considering that the smaller the extrusion amount, the higher the extrusion success rate, the larger the fillet radius, the simpler the drawing forming, the initial drawing forming fillet size is 15mm, the drawing forming passes are 3 times, and the cavity depth after each pass of drawing is 50mm, 80mm and 100 mm. Through numerical simulation, the deep drawing forming and the local small fillet extrusion forming of the part are analyzed, the initial parameters are optimized, and the zero of each forming stage is determinedPiece size and major process parameters.

Step three, designing and processing a die tool: and designing and processing a die tool for integral cavity drawing forming and local small fillet pushing forming according to the size and the technological parameters of the drawing forming part determined in the step two. The size of the drawing die is determined according to the size of the determined drawing forming part, and other parts are designed according to the design standard of the drawing die. The sizes of the inner supporting plate and the outer supporting plate of the side face and the bottom face of the small fillet pushing die are reasonably selected according to the size of a part, the contour shapes of the inner supporting plate and the outer supporting plate, the side wall and the bottom face of the part are required to be consistent, the inner supporting plate and the outer supporting plate are movable, the pushing process can be retreated, the rigid extrusion plate is adopted on the outer portion, and the pushing function is realized by fixing the inner supporting plate and the outer supporting plate on a feeding mechanism.

Step four, deep drawing of a rigid die of the whole cavity: and step three, performing multi-pass integral deep drawing forming on the original thin-wall metal plate blank by using the integral deep drawing forming die to obtain the cavity depth, the special-shaped section shape and the size which are basically consistent with those of the final deep-cavity thin-wall metal component, wherein the radius of the fillet between the side walls and the radius of the fillet between the side wall and the bottom surface are 15mm, and are 3.0 times of the radius of the fillet required on the final component.

Step five, pushing the rigid die with local round corners: and (3) further extruding and forming the whole cavity of the semi-finished product obtained in the fourth step by using the local extrusion forming die in the third step, and further reducing the radius of the fillet of the side wall and the radius of the fillet of the bottom to 5mm which is 2.0 times of the wall thickness of the original plate blank on the premise of ensuring that most regions of the whole cavity are not deformed.

Step six, local trimming of areas such as flange edges and the like: and C, performing flange edge cutting or side wall punching on the semi-finished product of which the integral cavity and the local fillet obtained in the step five meet the requirements of the final component, and obtaining the final deep-cavity thin-wall metal component with extremely small fillet radius.

The beneficial effect of this embodiment is: by adopting the process of multi-pass deep drawing forming and local small corner pushing and extruding forming, the problem that the small corner of the deep-cavity thin-wall member is extremely low in forming efficiency or cannot be formed can be solved. The problem of uneven and unreasonable material flow can be solved by enlarging the size of the drawing-formed transition fillet, and the problems of wrinkling, cracking, uneven wall thickness distribution and the like which are easy to occur when the traditional multi-pass drawing-formed part with the minimum fillet radius is used are solved to a certain extent. A theoretical model is established through geometric analysis, the quantitative relation between the extrusion process parameter and the size of a deep-drawing formed part is determined, the most reasonable process parameter is determined through optimization of finite element simulation, guidance is provided for die design and processing, coordination of the relation between the front process and the rear process is facilitated, the forming difficulty of each process is reduced, and the forming performance of the deep-cavity thin-wall component with the extremely-small fillet is improved.

Example 2: referring to fig. 5, in steps one to five, geometric analysis can be performed on different materials or different parts with different cross-sectional shapes in a targeted manner, and the element that the perimeter of the cross section is not changed before and after extrusion is grasped, that is, only the shape is changed but compression is not generated during extrusion, the straight wall section is not changed, deformation is mainly concentrated in a fillet area, and the main deformation form is bending forming of a large fillet and a small fillet. According to the section shape of a specific component, establishing a relation between the coordinated pushing amount of a theoretical model and the size of a deep drawing forming fillet, if the small deep drawing forming fillet is difficult to realize, the size of the deep drawing forming fillet can be enlarged to reduce the difficulty of deep drawing forming, and the pushing amount is increased to meet the size requirement; if the extrusion forming is difficult to realize, the size of the drawing forming fillet can be reduced to reduce the extrusion amount, thereby reducing the extrusion forming difficulty. The other steps are the same as in example 1.

The beneficial effect of this embodiment is: the coordination relationship between the size of the drawing forming fillet and the pushing forming extrusion amount can be flexibly established for parts of different materials, structural shapes and extremely small fillet radius sizes, and finally the requirement on the size precision of the component can be met. The embodiment shows that the relation between the front and rear working procedures of the forming process of the method has a certain adjusting space, and the problem that the whole forming difficulty is increased even high-grade special equipment is adopted because a certain working procedure is difficult to form can be solved.

Example 3: referring to fig. 4, in the first to fifth steps, the order of pushing the rounded corners of the side and bottom surfaces should be considered when pushing the small rounded corners, and the process parameters and the design and tooling of the mold are determined according to the determined pushing order. And the extrusion is carried out in all directions preferentially, so that the deformation of the intersection area of the fillet and the fillet is more coordinated. The small round corner part can be pushed separately, the two horizontal directions are respectively pushed and added with the bottom surface, and the coordinated deformation of the junction area can be controlled through different pushing amounts, so that the small round corner part can be pushed smoothly, and the part meeting the requirement of dimensional accuracy can be obtained. The other steps are the same as in example 1.

The beneficial effect of this embodiment is: the pushing sequence is reasonably selected according to different forming difficulties, so that the flexibility of the process path and the adjustable space for formulating the process parameters are increased. On the other hand, simultaneous pushing requires simultaneous feeding in multiple directions, and coordination among devices needs to be controlled; the separated pushing is relatively simple, has low requirement on equipment and is easy to develop. Namely, the extrusion forming of small round corners can be carried out under different equipment level and die manufacturing level conditions, and the embodiment shows that the method provided by the invention has good applicability.

Example 4: referring to fig. 4, in the first to fifth steps, for a small fillet which cannot be formed by drawing but can be formed when the pushing amount is extremely small, an internal supporting mode in rigid die pushing forming can be selected in a targeted manner, if the required internal supporting pressure is not too high, the small fillet can be formed, hydraulic support can be considered preferentially, and at the moment, the pressure is not high, the requirements on sealing, high-pressure systems and the like are not high, and the implementation is simple. If the pushing amount is large, the internal support is required to provide high pressure, the rigid support can be selected, for example, a nitrogen spring is arranged inside the rigid support, or the backward movement of the internal support plate in the pushing process is synchronously realized through mechanical structures such as a wedge and the like, so that the problems of high-pressure sealing, high-pressure system leakage, low efficiency and the like can be solved. The other steps are the same as in example 1.

The beneficial effect of this embodiment is: the internal supporting modes of the side wall and the bottom surface can be flexibly selected according to different internal pressure supporting requirements when parts of different materials, structural shapes and extremely small fillet sizes are formed. The relationship among feasibility, cost and efficiency is comprehensively considered, and the benefit maximization is realized.