CN114345971A

CN114345971A - Microchannel tube forming die and method

Info

Publication number: CN114345971A
Application number: CN202210066636.0A
Authority: CN
Inventors: 赵国群; 王跃林
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2022-01-20
Filing date: 2022-01-20
Publication date: 2022-04-15
Anticipated expiration: 2042-01-20
Also published as: CN114345971B

Abstract

The invention provides a microchannel tube forming die and a method, which relate to the field of die forming and comprise a die main body, wherein the die main body is provided with a feeding channel, a welding chamber and a forming channel which are sequentially communicated, a multi-stage sequentially communicated shunting channel is formed in the feeding channel, a die core neck is arranged in the welding chamber, one end of the die core neck is connected with a die core consisting of a series of sub die cores distributed in an array manner, the die core extends into the forming channel, an inner wall channel for communicating a sub die core gap with the shunting channel is formed in the die core neck, and an outer wall channel for communicating the shunting channel with the forming channel is formed between the die core neck and the welding chamber; aiming at the problem that the quality requirement is difficult to achieve when the existing microchannel pipe is extruded and formed through a die, a multistage shunting channel is adopted to promote blank flowing, so that the die stress is reduced, and meanwhile, flow guide channels are correspondingly arranged on the outer wall and the inner wall of the microchannel pipe respectively, so that the flowing uniformity of a deformation material is promoted, the distortion of a section bar is reduced, and the structural size of the formed microchannel pipe is ensured to meet the precision requirement.

Description

Microchannel tube forming die and method

Technical Field

The invention relates to the field of mold forming, in particular to a microchannel tube forming mold and a microchannel tube forming method.

Background

The problems of poor heat dissipation, short service life, poor stability and the like of a heat dissipation element in a traditional refrigeration system exist, and a product meeting the energy efficiency standard is difficult to manufacture. In recent years, microchannel tubes have been increasingly used as heat dissipation elements to replace conventional heat dissipation elements in aerospace, lightweight automobiles, 3C electronics, and household appliances. The microchannel tube is made of aluminum, copper, magnesium and the likeA colored metallic material and alloys thereof. Compared with the traditional radiating element, the microchannel tube has small volume and high radiating efficiency, can meet higher energy efficiency standard, and can use water, oil, cooling liquid and the like as heat exchange media. Meanwhile, the microchannel tube has excellent pressure resistance and can also contain CO₂The refrigerant is refrigerated, which is beneficial to environmental protection.

The prior micro-channel pipe mainly adopts a single-row channel structure, such as a micro-channel flat pipe for heat dissipation of an automobile air conditioner; micro-channel flat tubes for heat dissipation of commercial and household appliances (such as air conditioners); micro-channel flat tubes for heat dissipation of a communication base station; micro-channel flat tubes for cooling batteries of electric vehicles; the micro-channel flat tube for the air energy water heater; micro-channel flat tubes for generator heat dissipation; micro-channel flat tubes and the like for heat dissipation of electronic products such as computers, servers and the like. The heat dissipation efficiency and volume of the single-row channel structure still cannot meet the requirements of refrigeration and heat dissipation, so that multiple rows of microchannel tubes gradually appear to improve the heat dissipation efficiency and reduce the volume, for example, a frequency conversion module microchannel heat dissipation aluminum substrate and the like in the household air-conditioning refrigeration system shown in fig. 1. The microchannel tube is generally produced by adopting a hot extrusion mode, but a forming die of a single-row microchannel tube is not suitable for extrusion forming of a plurality of rows of microchannel tubes, the interiors of the plurality of rows of microchannel tubes have complicated inner wall structures, and the flow of materials in the die is difficult to control when the traditional die is adopted for extrusion, so that the corresponding inner structures of the plurality of rows of microchannel tubes are difficult to effectively form; in addition, the multi-row microchannel tubes are formed in an extrusion mode, and have a plurality of problems, namely, the blank is more difficult to flow, and the service life of the die is reduced due to higher die stress; secondly, the blank flows unevenly, so that the section bar is seriously twisted, the forming quality is poor, and the yield is low; thirdly, the mold core of the mold is insufficient in strength, and deflection easily occurs in the forming process, so that the extruded microchannel tube has a wall deflection phenomenon, and the dimensional accuracy of the microchannel structure is difficult to reach the standard.

Disclosure of Invention

The invention aims to provide a microchannel tube forming die and a microchannel tube forming method aiming at the defects in the prior art, wherein a multi-stage flow dividing channel is adopted to promote material flow, so that the die stress is reduced, and meanwhile, flow guide channels are respectively and correspondingly arranged on the outer wall and the inner wall of a microchannel tube, so that the material flow uniformity is improved, the section bar distortion is reduced, the structural size of the formed microchannel tube meets the requirement, and the forming quality is ensured.

The invention aims to provide a microchannel tube forming die, which adopts the following scheme:

including the mould main part, be equipped with the pan feeding passageway that communicates in proper order in the mould main part, the seam room and the passageway that takes shape, form the multistage reposition of redundant personnel passageway that communicates in proper order in the pan feeding passageway, be equipped with the mold core neck in the seam room, wherein, the mold core is connected to mold core neck one end, the mold core comprises the submodule core that a plurality of arrays distribute, the submodule core is used for the intraductal shaping that corresponds the passageway of microchannel, the mold core probes into the passageway that takes shape, form the inner wall passageway of intercommunication submodule core clearance and reposition of redundant personnel passageway in the mold core neck, form the outer wall passageway of intercommunication reposition of redundant personnel passageway and shaping passageway between mold core neck and the seam room.

Furthermore, at least two stages of flow dividing bridges are sequentially arranged in the feeding channel along the axial direction of the feeding channel, and the distances of the flow dividing bridges of different stages relative to the inlet end face of the feeding channel are different.

Furthermore, the shunting bridge separates the pan feeding passageway that corresponds the position and forms many shunting channels, and the top surface that the shunting bridge faced pan feeding passageway entry terminal surface is the arcwall face.

Furthermore, the surface of the neck of the mold core, which faces one side of the welding chamber, is an arc-shaped flow guide surface, one end of the mold core is in butt joint with the flow guide surface in the welding chamber, and the other end of the mold core extends into the forming channel and is arranged at intervals with the forming channel.

Further, the inner wall passageway runs through the mold core neck, and the water conservancy diversion face corresponds adjacent child mold core clearance position and is equipped with the drainage groove, and drainage groove intercommunication inner wall passageway and outer wall passageway.

Further, the sub-mold cores are arranged in a rectangular array, an inner forming channel is formed between every two adjacent sub-mold cores, so that the material forms the inner wall of the workpiece, and an outer forming channel is formed between the mold cores and the forming channel, so that the blank forms the outer wall of the workpiece.

Furthermore, a flow blocking block is arranged at the bottom of the welding chamber to adjust the feeding speeds of different positions and balance the metal flow.

Furthermore, one end, far away from the mold core neck, of the side wall of the sub-mold core is provided with a first idle cutter so as to reduce the friction resistance between the material and the side wall of the local sub-mold core, and one end, far away from the welding chamber, of the forming channel is provided with a second idle cutter so as to reduce the friction resistance between the workpiece and the forming channel.

Further, the mould main body comprises at least two mould single bodies, and the feeding channel and the forming channel are positioned on different mould single bodies.

A second object of the present invention is to provide a microchannel tube forming method using the microchannel tube forming die as described above, comprising the steps of:

feeding the blank into a feeding channel and forming a plurality of strands of materials under the action of a shunting channel;

part of the material enters the gap of the sub-die core through the inner wall channel to form the inner wall of the workpiece; part of the material passes through the outer wall channel and is distributed around the mold core to form the outer wall of the workpiece;

the inner wall of the workpiece and the outer wall of the workpiece are in contact welding in the welding chamber, and the welded microchannel tube workpiece is output through the forming channel.

Compared with the prior art, the invention has the advantages and positive effects that:

(1) the problem that the quality requirement is difficult to reach when the microchannel tube passes through mould extrusion forming at present is solved, adopt multistage reposition of redundant personnel passageway to promote the material flow, and then reduce mould stress, correspond respectively to the outer wall and the inner wall of microchannel tube simultaneously and set up the water conservancy diversion passageway, promote the homogeneity that the material flows, reduce the section bar distortion to guarantee that the structure size of shaping back microchannel tube satisfies the requirement, guarantee the shaping quality.

(2) Adopt multistage reposition of redundant personnel bridge to form the multistage reposition of redundant personnel bridge structure that communicates in proper order, multistage reposition of redundant personnel bridge dislocation is not co-altitude and arranges, compare in traditional height-equal reposition of redundant personnel bridge, multistage reposition of redundant personnel bridge structure can adjust the reposition of redundant personnel bridge height alone, utilize the specific resistance of reposition of redundant personnel passageway to the material flow of altitude mixture control, thereby carry out corresponding control to the material flow in the specific reposition of redundant personnel passageway, the material volume in the different reposition of redundant personnel passageways of rational distribution, and simultaneously, the reposition of redundant personnel bridge that is located the lower position also can let out and reduce mould stress, play the guard action to the mould.

(3) The top surface design of reposition of redundant personnel bridge is the arcwall face, and the arcwall face can form the slope structure at reposition of redundant personnel bridge top, compares in traditional top surface for planar reposition of redundant personnel bridge, and the arcwall face can shift the material to the inclined plane on acting on planar pressure to let out and subtract mould stress, reduce material flow resistance simultaneously, improve the feed speed of forming process material.

(4) The mold core neck that sets up combines with the seam room to form the outer wall passageway, forms the inner wall passageway in the mold core neck, and the material that the reposition of redundant personnel will be shunted is imported respectively to inner wall passageway and outer wall passageway, realizes that the inner wall of microchannel pipe takes shape and the outer wall takes shape, shortens the flow path of shaping in-process material to reduce the material flow unbalance and the section bar distortion problem that leads to, and then improve the shaping quality.

(5) One side of the neck of the mold core, which corresponds to the welding chamber, is provided with an arc-shaped surface, so that the strength of the neck of the mold core is improved, the deflection of the mold core is reduced, the feeding speed of the outer wall position of a workpiece is conveniently adjusted, the metal flow is balanced, and the stability of material flow in the forming process is improved; and the friction resistance between the workpiece and the forming channel is further reduced by combining the second blank cutter, and the adjustment of the internal resistance and the external resistance of the die core is realized by adjusting the position and the length of the first blank cutter, so that the flow speed of the internal material and the external material of the die core is balanced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic view of a microchannel heat dissipation aluminum substrate according to the background of the invention;

FIG. 2 is a schematic view of a microchannel tube forming die in accordance with example 1 or 2 of the present invention;

FIG. 3 is a schematic cross-sectional view of a microchannel tube forming die in accordance with example 1 or 2 of the present invention;

FIG. 4 is a schematic cross-sectional view of an upper mold in embodiment 1 or 2 of the present invention;

FIG. 5 is a schematic view of a flow dividing channel in embodiment 1 or 2 of the present invention;

FIG. 6 is a schematic view of a neck portion of a mold core in embodiment 1 or 2 of the present invention;

FIG. 7 is a schematic diagram showing the arrangement of the neutron cores in embodiment 1 or 2 of the present invention;

FIG. 8 is an enlarged view of the sub-core shown at B in FIG. 7;

FIG. 9 is a side view of the daughter core shown in FIG. 8;

FIG. 10 is a schematic structural view of a lower mold in embodiment 1 or 2 of the present invention;

FIG. 11 is a schematic sectional view of a lower mold in embodiment 1 or 2 of the present invention;

fig. 12 is a schematic structural view of a workpiece formed in embodiment 1 or 2 of the present invention.

In the figure, 1-upper die, 2-multistage shunt bridge, 3-shunt channel, 4-die core neck, 5-die core, 6-lower die, 7-welding chamber, 8-choke block, 9-forming channel, 10-second hollow knife, 2-1-first-stage sinking bridge, 2-2-second-stage sinking bridge, 2-3-third-stage sinking bridge and 2-4-fourth-stage sinking bridge.

Detailed Description

Example 1

In an exemplary embodiment of the present invention, a microchannel tube forming die is shown in fig. 2-12.

The microchannel tube forming die shown in fig. 2 is used for extrusion forming of microchannel tubes, in particular to an extrusion forming die for multi-row microchannel flat tubes in a refrigeration system, and solves the problems of high die stress and unbalanced blank flowing in the extrusion forming process of the multi-row microchannel flat tubes through the structural arrangement of the diversion channel 3, the welding chamber 7 and the forming channel 9 through which materials flow, so that the effects of improving the quality of workpieces and prolonging the service life of the die are achieved. The microchannel tube forming die mainly comprises a die body, wherein the die body can be an integrated die or a split die as shown in fig. 2 and 3, and can adopt a form of matching an upper die 1 and a lower die 6; because the internal characteristic structure of the die body is complex, the form of matching the upper die monomer, the middle die monomer and the lower die monomer can be adopted. It should be noted that, when the split-type mold is adopted for the mold body, the matching of the three mold monomers is not limited, and other numbers can be selected.

In the present embodiment, as shown in fig. 2 and 3, the mold body is divided into two mold units, i.e., an upper mold 1 and a lower mold 6, wherein the upper mold 1 has a diameter of 238mm × 70mm and the lower mold 6 has a diameter of 238mm × 80 mm. Corresponding structures are respectively arranged on the upper die 1 and the lower die 6, a complete die structure is formed after the upper die and the lower die are matched, a die main body formed by combining the upper die and the lower die can be installed on extrusion forming equipment, and a blank is extruded and formed under the driving of the extrusion forming equipment to obtain the microchannel tube workpiece.

As shown in fig. 3, a feeding channel, a multi-stage flow-dividing bridge 2, a mold core neck 4 and a mold core 5 are arranged on the upper mold 1, and the multi-stage flow-dividing bridge 2 is arranged in the feeding channel, so that a multi-stage flow-dividing channel 3 is formed in the feeding channel; the mold core neck 4 is positioned at the tail end of the feeding channel, and the mold core 5 is arranged on the mold core neck 4; the lower die 6 is provided with a welding chamber 7, a flow blocking block 8 and a forming channel 9. Taking the main structure of the die shown in fig. 2 as an example, the upper die 1 and the lower die 6 adopt a columnar structure, and feature structures are processed in the inner part or the end surface of the columnar structure to form a feeding channel, a welding chamber 7 and a forming channel 9 required by extrusion forming.

One end of the mold core neck 4 is connected with a mold core 5 consisting of a series of sub mold cores distributed in an array mode, the mold core 5 extends into the forming channel 9, an inner wall channel communicated with the sub mold core gap and the shunting channel 3 is formed inside the mold core neck 4, and an outer wall channel communicated with the shunting channel 3 and the forming channel 9 is formed between the mold core neck 4 and the welding chamber 7.

In the extrusion process, taking the metal blank extrusion forming of the double-row micro-channel flat tube as an example, under the action of high temperature and high pressure, the blank is extruded into the shunting channel 3 to form a plurality of metal streams, the plurality of metal streams are welded in the welding chamber 7 again, and are extruded from a gap between the sub die core and the forming channel 9 to form the double-row micro-channel flat tube. The length and the width of the cross section of the forming channel 9 correspond to the width and the thickness of the double-row micro-channel flat tubes, and the gaps between the sub-die cores and between the die core 5 and the forming channel 9 correspond to the wall thickness of the double-row micro-channel flat tubes.

As shown in fig. 3, the upper die 1 and the lower die 6 are coaxially assembled, the die core 5 is inserted into the forming channel 9 in the lower die 6, and the outer side surface of the die core 5 is parallel to the side wall of the forming channel 9.

In the upper die 1 shown in fig. 4, at least two stages of flow-dividing bridges are sequentially arranged in the feeding channel along the axial direction of the feeding channel, and the distances between the different stages of flow-dividing bridges and the inlet end face of the feeding channel are different, so that the distances between the top end faces of the different stages of flow-dividing bridges and the inlet end face of the feeding channel are different. In this embodiment, a four-stage shunt bridge is provided, and in other embodiments, a two-stage shunt bridge, a five-stage shunt bridge, or the like may be used, but the number of stages of the shunt bridge is not less than two.

The multistage flow distribution bridge 2 in this embodiment adopts a four-stage sinking bridge structure, the axial direction of the end face in fig. 3 is taken as the vertical direction, the plane of the feeding end is taken as the upper side, the first-stage sinking bridge 2-1 is arranged in a highest and inclined manner, the upper surface of the first-stage sinking bridge is arc-shaped, the heights of the second-stage sinking bridge 2-2, the third-stage sinking bridge 2-3 and the fourth-stage sinking bridge 2-4 are sequentially reduced, and the distances from the second-stage sinking bridge 2-2, the third-stage sinking bridge 2-3 and the fourth-stage sinking bridge 2-4 to the plane of the feeding end of the upper die 1 are respectively 30mm, 40mm and 45mm, as shown in fig. 4. The upper die 1 is divided into 12 flow-dividing channels 3 by four-stage flow-dividing bridges, and the flow-dividing channels 3 are symmetrically distributed to balance the metal flow, as shown in fig. 5.

The multi-stage flow dividing bridge 2 divides a feeding channel of the upper die 1 into different flow dividing channels 3, so that the flowing materials are guided, and the height of the flow dividing bridge corresponding to the region, in which the inner wall of the microchannel tube is difficult to flow, is reduced so as to reduce the flow resistance of the deformed materials and increase the metal flow; the height of the flow-dividing bridge corresponding to the easy flowing area of the outer wall of the microchannel tube is increased so as to improve the flowing resistance of the deformation material and properly reduce the flow of the deformation material.

In this embodiment, one end of the shunting bridge facing the feeding port is obliquely arranged relative to the plane of the feeding port of the upper die 1, and the inclination angle ranges from 20 ° to 60 °, preferably from 40 ° to 50 °.

As shown in fig. 2, fig. 3 and fig. 4, the top surface of reposition of redundant personnel bridge orientation pan feeding passageway entry terminal surface is the arcwall face, and the arcwall face can form the slope structure at reposition of redundant personnel bridge top, compares in traditional top surface for planar reposition of redundant personnel bridge, and the arcwall face can shift the material to on the inclined plane with the planar pressure transfer of action on to let out and reduce mould stress, can reduce the resistance that the material flows simultaneously, improve the feed rate of shaping in-process material, in order to satisfy the demand of forming process.

As shown in fig. 6, the surface of the mold core neck 4 facing the welding chamber 7 is an arc-shaped flow guide surface, one end of the mold core 5 is butted against the flow guide surface in the welding chamber 7, and the other end of the mold core extends into the forming channel 9 and is arranged at a distance from the forming channel 9.

In the embodiment, the arc-shaped flow guide surface of the mold core neck 4 is of an arch structure, the inner wall channel penetrates through the mold core 5, the flow guide surface is provided with a drainage groove corresponding to the gap position of the adjacent sub-mold cores, and the drainage groove is communicated with the inner wall channel and the outer wall channel; the sub-mould cores are arranged in a rectangular array, an inner forming channel is formed between every two adjacent sub-mould cores so that the material forms the inner wall of the workpiece, and an outer forming channel is formed between the mould core 5 and the forming channel 9 so that the material forms the outer wall of the workpiece; the width of drainage groove is the interval between the adjacent child mold core, and in this embodiment, the width of drainage groove is 0.94 mm.

The arch size of the mold core neck 4 is based on the width A of the forming channel, the range of the arch radius R is 0.8A-5A, and the preferable range is 1A-2A; the range of the arch width W is 0.8A-4A, and the preferable range is 2A-3A.

The sub-mould cores of the mould core 5 are of a structure in a multi-row array arrangement, a first idle cutter is arranged at one end, away from the mould core neck 4, of the side wall of each sub-mould core so as to reduce the friction resistance between materials and the side wall of a local sub-mould core, and a second idle cutter 10 is arranged at one end, away from the welding chamber 7, of the forming channel 9 so as to reduce the friction resistance between a workpiece and the forming channel.

For the first blank cutter, a plurality of blank cutters are arranged on the sub-die core, and the inner side of the sub-die core is provided with the blank cutters, as shown in fig. 7 in the embodiment. The cross-sectional dimension of a single sub-mold core is 3.8mm multiplied by 2.94mm, the length is 6mm, the length of the idle cutter is adjusted according to the actual metal flowing condition and does not exceed 2/3 of the length of the sub-mold core, as shown in fig. 8 and 9. The width of the blank cutter is 0.38mm, the length of the blank cutter is 3mm, the distance between the upper row of the sub-mold cores and the lower row of the sub-mold cores is 1.5mm, the distance between two adjacent rows of the sub-mold cores is 0.94mm, the distance between the outer side of the mold core 5 and the long side of the forming channel 9 is 2mm, and the distance between the outer side of the mold core 5 and the short side of the forming channel 9 is 12.5 mm.

As shown in fig. 10 and 11, the forming channel 9 has working strips of different lengths, with longer ends and shorter middle, and the second idle knife 10 is arranged at the end of the forming channel remote from the welding chamber.

The welding chamber 7 is of an approximate rectangular structure, the size of the welding chamber corresponds to that of a discharge port of the upper die 1, the welding chamber receives materials output by the upper die 1, two same flow blocking blocks 8 are symmetrically distributed at two ends of a forming channel at the bottom of the welding chamber 7, and the flow blocking blocks 8 are used for adjusting feeding speed and balancing metal flow.

In this embodiment, as shown in FIG. 10, the welding chamber 7 has a depth of 15mm, the choker block 8 has a height of 3mm, a width of 2mm, and a distance of 1mm from the forming channel 9.

Because the die needs to work in a high-temperature and high-pressure environment for a long time, in order to ensure the strength, hardness, wear resistance and stability of the die, the die main body in the embodiment is made of H13 hot work die steel and is subjected to nitriding treatment; the extrusion blank is nonferrous metals such as aluminum, copper, magnesium and the like and alloys thereof, the extrusion blank used in the embodiment is a homogeneous AA3003 aluminum alloy rod, and the specification of the aluminum alloy rod is phi 127 multiplied by 410 mm.

The preheating temperature of the blank is 550 ℃, the speed of the extrusion rod is 2mm/s, the extrusion ratio is 13.3, the temperature of the die is 520 ℃, the temperature of the extrusion cylinder is 490 ℃, and the blank residual pressure is 30 mm.

The blank is extruded by a micro-channel forming die to form a double-row micro-channel flat tube workpiece, and the extruded workpiece is cooled by an air cooling mode. The extruded double row microchannel flat tube is shown in fig. 12.

Example 2

In another exemplary embodiment of the present invention, as shown in fig. 2-12, a microchannel tube forming method is provided, utilizing a microchannel tube forming die as in example 1.

The microchannel tube forming method comprises the following steps:

feeding the blank into a feeding channel and forming a plurality of strands of materials under the action of a diversion channel 3;

part of the material enters the gap of the sub-die core through the inner wall channel to form the inner wall of the workpiece; part of the blank is distributed around the die core 5 through the outer wall channel to form the outer wall of the workpiece;

the inner wall and the outer wall of the workpiece are in contact welding in the welding chamber 7, and the welded microchannel tube workpiece is output through the forming channel 9.

The mold core neck 4 that sets up combines with the seam room 7 and forms the outer wall passageway, and mold core neck 4 is inside to form the inner wall passageway, and reposition of redundant personnel passageway 3 will be imported respectively to inner wall passageway and outer wall passageway through the material of reposition of redundant personnel, realizes that the inner wall of microchannel pipe takes shape and the outer wall takes shape, shortens the flow path of shaping in-process material to reduce the unbalance that the blank flows and the section bar distortion problem that leads to, and then improve the shaping quality.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides a microchannel tube forming die, a serial communication port, which comprises a die body, be equipped with the pan feeding passageway that communicates in proper order in the mould main part, the seam room and the passageway that takes shape, form the multistage reposition of redundant personnel passageway that communicates in proper order in the pan feeding passageway, be equipped with the mold core neck in the seam room, the mold core that the sub-mold core that distributes by a plurality of arrays is connected to mold core neck one end, the sub-mold core is used for the intraductal shaping that corresponds the passageway of microchannel, the mold core probes into the passageway that takes shape, form the inner wall passageway of intercommunication sub-mold core clearance and reposition of redundant personnel passageway in the mold core neck, form the outer wall passageway of intercommunication reposition of redundant personnel passageway and shaping passageway between mold core neck and the seam room.

2. The microchannel tube forming die of claim 1, wherein at least two stages of flow bridges are sequentially disposed in the feed channel in the axial direction of the feed channel, and the flow bridges of different stages have different distances from the inlet end face of the feed channel.

3. The microchannel tube forming die of claim 2, wherein the splitter bridge separates the inlet channel at corresponding locations to form a plurality of splitter channels, and wherein a top surface of the splitter bridge facing an inlet end surface of the inlet channel is arcuate.

4. The microchannel tube forming die of claim 1, wherein the surface of the core neck on the side facing the weld chamber has an arcuate flow guide surface, one end of the core abutting the flow guide surface in the weld chamber and the other end extending into and spaced from the forming channel.

5. The microchannel tube forming die of claim 4, wherein the inner wall channel extends through the die core neck, and the flow directing surface has flow directing grooves corresponding to the gap between adjacent die cores, the flow directing grooves communicating the inner wall channel with the outer wall channel.

6. The microchannel tube forming die of claim 1, wherein the sub-dies are arranged in a rectangular array, with inner forming channels formed between adjacent sub-dies to form material into an inner wall of the workpiece and outer forming channels formed between the dies and the forming channels to form material into an outer wall of the workpiece.

7. The microchannel tube forming die of claim 1, wherein a choke block is provided at the bottom of the seaming chamber to adjust feed rates at different locations.

8. The microchannel tube forming die of claim 1, wherein the end of the sub-core sidewall distal from the core neck is provided with a first clearance to reduce frictional resistance of material against the partial sub-core sidewall, and the end of the forming channel distal from the weld chamber is provided with a second clearance to reduce frictional resistance of the workpiece against the forming channel.

9. The microchannel tube forming die of claim 1, wherein the die body comprises at least two die segments, the feed channel and the forming channel being located on different die segments.

10. A microchannel tube forming process using the microchannel tube forming die of any one of claims 1-9, comprising the steps of:

part of the material enters the gap of the sub-die core through the inner wall channel to form the inner wall of the workpiece; part of the material is distributed around the die core through the outer wall channel to form the outer wall of the workpiece;