CN109396208B

CN109396208B - Synchronous extrusion forming method for steel H-shaped connecting pieces with different wall thicknesses

Info

Publication number: CN109396208B
Application number: CN201811538536.3A
Authority: CN
Inventors: 徐健; 张治民; 王强; 薛勇; 赵熹; 闫林
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2018-12-03
Filing date: 2018-12-03
Publication date: 2020-01-03
Anticipated expiration: 2038-12-03
Also published as: CN109396208A

Abstract

The invention discloses a synchronous extrusion forming method of steel H-shaped connecting pieces with different wall thicknesses, which relates to a synchronous extrusion forming die of the steel H-shaped connecting pieces with different wall thicknesses, wherein the die comprises an upper die assembly, a lower die assembly and a guiding and ejecting device assembly; the method is subjected to three deformation processes of preheating a die and a blank before forming, then extruding by a concave-convex die and finally leading out after forming. The invention adopts the warm extrusion synchronous forming to realize the precise plastic forming of the H-shaped connecting piece with different wall thicknesses, aims to effectively overcome the problems brought by the traditional processing and manufacturing method, improves the formability of the alloy, improves the comprehensive mechanical property of a formed piece, greatly improves the material utilization rate and the production efficiency, saves energy and reduces emission.

Description

Synchronous extrusion forming method for steel H-shaped connecting pieces with different wall thicknesses

Technical Field

The invention belongs to the technical field of plastic processing and forming of metal materials, and particularly relates to a synchronous extrusion forming method of steel H-shaped connecting pieces with different wall thicknesses.

Background

With the rapid development of aerospace technology, high and new technology weaponry and ocean development in China, H-shaped connecting pieces with different wall thicknesses (the upper and lower inner parts of a workpiece are hollow, a partition wall is arranged in the middle, and the wall thicknesses of the upper wall and the lower wall are different) are more and more widely applied to various fields of military and civilian. For example, the joint of the missile warhead, the aircraft, the automobile and other parts of the weapon equipment and the joints of various pipes with different diameters can be seen everywhere in daily life. The "H" shaped parts may have varying degrees of steps and re-entrant corners within the part and may be thin walled, as is conventionally done by welding, casting or most commonly machining the part between two "U" shaped pieces. Welding seams of the welding parts are cracked, shrunk and fall off to different degrees, and the welding performance of a plurality of materials is poor; the casting also has the defects of incompact casting structure, shrinkage cavity, air bubble, uneven grain size and the like; the simple machining has low production efficiency, serious raw material waste, time consumption and labor consumption. These methods have disadvantages and difficulties in meeting the service requirements of the part.

The forming difficulty of the parts is that the upper wall and the lower wall are formed at different thicknesses, the instability of the cup wall in the axial direction is prevented, and the uniformity of the finally formed wall thickness and the fact that the lower wall is thin are easy to take out and keep intact without fracture are ensured.

Disclosure of Invention

Aiming at the current situation of the prior processing technology, the invention provides a synchronous extrusion forming method of an H-shaped connecting piece made of steel with different wall thicknesses, which adopts warm extrusion synchronous forming to realize the precise plastic forming of the H-shaped connecting piece with different wall thicknesses, and aims to effectively overcome the problems brought by the traditional processing and manufacturing method, improve the formability of alloy, improve the comprehensive mechanical property of a formed piece, greatly improve the material utilization rate and the production efficiency, save energy and reduce emission.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a synchronous extrusion forming method of an H-shaped connecting piece made of steel with different wall thicknesses relates to a synchronous extrusion forming die of the H-shaped connecting piece made of steel with different wall thicknesses, and the die comprises an upper die component connected with the upper part of a press machine, a lower die component connected with the lower part of the press machine and a guiding and ejecting device component; the upper die assembly comprises an upper die plate connected with an upper workbench of the press machine, an insert and an upper die base connected with the upper die plate, a male die and an upper die sleeve plate connected with the insert, and a screw ring and a withdrawing ring connected with the upper die base; the lower die assembly comprises a bottom core and a female die which are connected with a lower workbench of the press machine; an inner flange is formed inside the female die, and the bottom core and the male die form a transition fillet and an inclination; the guiding and ejecting device assembly comprises an ejector rod, a bottom plate and a pull rod, and the method specifically comprises the following steps:

(1) preparation before forming: preheating a blank, uniformly spraying a water-based graphite lubricant, uniformly coating the water-based graphite lubricant on the surfaces of a male die, a withdrawing ring, a female die and a bottom core, preheating, putting the blank on the bottom core after preheating is finished, moving an upper die plate downwards, lowering a pull rod, lowering an ejector rod and the bottom core, returning the bottom core to the bottom blank of the female die to a pre-extrusion position, and preparing for extrusion forming;

(2) forming process: the press drives the downward motion of upper die assembly, and the terrace die contacts the blank and continues the extrusion downwards, along with the extrusion downwards of terrace die, moves back in the ring also can enter into the die, and the blank experiences the deformation in three stages under the effect of terrace die:

firstly, in the H-shaped forming stage, when the blank is just extruded, the blank is limited by an inner flange of a female die, the radial resistance of the blank is greater than the axial direction, the blank flows into a bottom core and a female die cavity, the lower the bottom core is inclined, the smaller the space is, the greater the resistance is, the radial resistance of the blank is smaller than the axial direction, the upsetting action of the blank is intensified, the blank is filled in the inner flange part of the female die and moves upwards along the inclined wall of the male die, and the H-shaped pre-form is formed;

secondly, in the growth stage of the H-shaped upper wall and the H-shaped lower wall, the male die is driven by the press machine to continue to extrude downwards, the working band of the male die has an upward inclination, and the space between the male die and the female die is larger than the space between the bottom core and the female die, so that the resistance of the upper part is smaller than that of the lower part, and the material of the lower part also moves from top to bottom, so that the growth speed of the height of the upper wall is larger than that of the lower wall, and the female die is filled with the upper wall in the radial direction at the moment;

thirdly, in the H-shaped full forming stage, the press machine continues to downwards extrude the blank with the male die, at this time, the H shape is basically finished, the upper wall does not reach the final height, and the bottom angle difficult forming area of the lower wall does not finish the final forming, at this time, the withdrawing ring is already contacted with the upper wall, the withdrawing ring and the screw ring are matched with each other at a certain height, when the male die continues to descend, the upper wall pushes the withdrawing ring to upwards move, when the withdrawing ring is contacted with the upper die sleeve plate, the withdrawing ring stops ascending, at this time, the male die, the withdrawing ring and the female die form a closed die cavity, the only flowing direction of the blank is the bottom angle difficult forming area of the lower wall, and the extrusion final forming is finished along with the completion of the filling of the bottom angle of downward;

(3) after the extrusion forming is finished: stopping the downward movement of the upper workbench of the press machine, enabling the upper workbench of the press machine to move upwards in the reverse direction, driving the male die to ascend and separate from the upper wall of the workpiece, and automatically dropping the withdrawing ring for a certain distance along with the ascending of the male die to separate from the male die; and in the process of lifting the upper die plate, the pull rod is driven to lift, the pull rod drives the bottom plate to lift at the same time, the bottom plate is contacted with the ejector rod after lifting for a certain distance and drives the bottom core to lift and separate from the female die together with the workpiece, the workpiece can be automatically ejected out of the female die after separating from the die, and finally the workpiece is taken down, so that the extrusion part is formed.

Preferably, the inclination of the bottom core is 10 °.

Preferably, the inclination of the punches is 12 °.

After the scheme is adopted, the invention has the beneficial effects that:

1. the male die, the female die and the bottom core jointly form a forming inner cavity of the H-shaped connecting piece, the stress condition of the H-shaped piece in the extrusion deformation process is changed by controlling process parameters (the gradient of each part of the forming inner cavity and a transition zone fillet), the smooth realization of the upper wall and the lower wall growth and the final forming stage in the forming stage is ensured, the metal stress state, the equivalent strain, the plastic deformation, the tissue uniformity and the like are better controlled, the forming is ensured to be carried out smoothly, and the final size and performance requirements of the H-shaped connecting piece are met;

2. the stripper ring cooperates with the guide and ejector assembly. The part withdrawing ring has a positioning and guiding function, can play a role of positioning a male die and ensure good forming of a lower wall difficult-to-form area in a final forming stage in the downward movement process of the press, and can be matched with a reverse pull rod structure to realize smooth demoulding of workpieces from top to bottom in the part withdrawing stage; the reverse pull rod type linkage ejection structure can be matched with any press machine for use, has no requirement on an ejection cylinder of the press machine, greatly increases the applicability of an extrusion die, and reduces the production cost;

3. the warm extrusion forming technology is adopted, so that the extrusion force is greatly reduced compared with cold extrusion, and the comprehensive mechanical property of the material is ensured to be optimal while the near-net forming is ensured.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings.

Drawings

FIG. 1 is a sectional view showing the overall structure of a die without a blank material being inserted in the embodiment of the present invention;

FIG. 2 is a cross-sectional view of a guide and ejector assembly in an embodiment provided by the present invention;

FIG. 3 is a cross-sectional view of the working state of the die when a billet is placed before extrusion in the embodiment provided by the invention;

FIG. 4 is a sectional view of the working state of the die when the blank is to be extruded according to the embodiment of the invention;

FIG. 5 is a cross-sectional view of the blank in the "H" blank forming deformation stage in the working state of the die in the embodiment provided by the invention;

FIG. 6 is a sectional view of the working state of the die at the stage of the growth of the upper and lower walls of the blank in the embodiment of the invention;

FIG. 7 is a sectional view of the die operating state of the blank in the extrusion final forming stage according to the embodiment of the present invention;

FIG. 8 is a schematic view of the male mold structure in an embodiment provided by the present invention;

FIG. 9 is a cross-sectional view of a female mold structure in an embodiment provided by the present invention;

FIG. 10 is a schematic view of a bottom core structure in an embodiment provided by the present invention;

FIG. 11 is a cross-sectional view of an exemplary stripper ring structure provided in accordance with the present invention;

FIG. 12 is a schematic illustration of a billet prior to extrusion in an embodiment provided by the present invention;

FIG. 13 is a schematic view of an extruded "H" shaped connector according to an embodiment of the present invention.

Description of reference numerals:

1, a lower template; 2-hexagonal socket cap screw in the lower die; 3, a lower die cylindrical pin; 4, a lower die base plate; 5, a top rod; 6, a guide pillar; 7-hexagonal socket head cap screw in the lower die; 8-bottom core; 9-lower die supporting plate; 10, pressing a sleeve; 11-a shrink sleeve; 12-a female die; 13-male die; 14-backing ring; 15-a helicoid; 16, a guide sleeve; 17-upper die base; 18, upper template; 19-an upper die cylindrical pin; 20-an insert; 21-upper die sleeve plate; 22-an upper die hexagon socket head cap screw; 23-a spring washer; 24-hexagonal nut; 25-a base plate; 26-a pull rod; 27-a sleeve; 28-a nut; 29-connecting rod; 30-hexagonal nut; 31-inner flange; 32-transition fillets.

Detailed Description

The invention discloses a synchronous extrusion forming method of an H-shaped connecting piece made of steel and with different wall thicknesses, and relates to a synchronous extrusion forming die of the H-shaped connecting piece made of steel and with different wall thicknesses, and with reference to figures 1-13, the die comprises an upper die assembly connected with the upper part of a press machine, a lower die assembly connected with the lower part of the press machine and a guiding and ejecting device assembly.

As shown in fig. 1, the upper mold assembly includes: an upper die plate 18 connected to an upper table of the press, an insert 20 and an upper die base 17 connected to the upper die plate 18, a punch 13 and an upper die sleeve plate 21 connected to the insert 20, and a coil 15 and a stripper ring 14 connected to the upper die base 17. The insert 20 is arranged in the upper die base 17, the screw ring 15 is sleeved below the upper die base 17, the male die 13 penetrates through the upper die base 17 and the screw ring 15, the upper die sleeve plate 21 is arranged between the upper die base 17 and the male die 13, and the withdrawing ring 14 is arranged between the screw ring 15 and the male die 13. More specifically, the punch 13, the upper die sleeve plate 21 and the insert 20 are assembled together by clearance fit, and the stripper ring 14 is inserted into the threaded ring 15 and passes through the punch 13 to be connected with the upper die base 17 by fastening threads. The upper die base 17 and the upper die plate 18 are circumferentially positioned by an upper die cylindrical pin 19 and then assembled together by an upper die hexagon socket head cap screw 22 with a spring washer 23. The upper die plate 18 is mounted on the upper table of the press by means of fastening bolts (not shown in the figures).

As shown in fig. 1, the lower mold assembly includes: the lower die plate comprises a lower die plate 1, a lower die base plate 4, a lower die supporting plate 9, a bottom core 8, a pressing sleeve 10, a tightening sleeve 11 and a female die 12, wherein the lower die plate is connected with a lower workbench of a press machine. Lower bolster 1, lower mould backing plate 4 and lower mould backup pad 9 are placed from supreme down, after lower bolster 1, lower mould backing plate 4 and lower mould backup pad 9 pass through 3 circumference location of lower mould cylindric lock, lower bolster 1 and lower mould backing plate 4 assemble together through lower mould hexagon socket head cap screw 2, and lower mould backing plate 4 and lower mould backup pad 9 assemble together through lower mould hexagon socket head cap screw 7. The female die 12 is sleeved above the bottom core 8, and as shown in fig. 8, 9 and 10, an inner flange 31 is formed inside the female die 12, and the bottom core 8 and the male die 13 form a transition fillet 32 and inclinations α and β. The lower template 1 and the lower die backing plate 4 are provided with sliding grooves communicated with the core grooves for the insertion of the ejector rods 5, as shown in a combined figure 10, the upper ends of the ejector rods 5 are in clearance fit with the bottom cores 8, and the lower ends of the ejector rods 5 are supported by the bottom plate 25. The middle of the lower die supporting plate 9 is provided with a core groove, the bottom core 8 is placed in the core groove to be in clearance fit with the core groove, the female die 12 is matched with a corresponding clamping groove through the upper end of the lower die supporting plate 9, the tightening sleeve 11 is matched with the female die 12 through the corresponding clamping groove, the pressing sleeve 10 is matched with the outside of the tightening sleeve through the corresponding clamping groove, and the pressing sleeve 10 and the lower die supporting plate 9 are tightly connected together through fastening threads. The lower template 1 is assembled on the lower worktable of the press machine by fastening bolts. The lower die assembly also comprises a knockout plate and a top block; the ejector block and the ejector rod 5 are connected together in a threaded fastening mode, and corresponding grooves are formed in the female die 12 and the lower template 1 to position the ejector block; the knockout plate is a T-shaped key, and a corresponding matched T-shaped groove is arranged on the female die 12.

As shown in fig. 1 and 2, the guiding and ejecting device assembly includes a guide post 6, a guide sleeve 16, a top rod 5, a bottom plate 25, a pull rod 26, a sleeve 27 and a connecting rod 29. The guide post 6 is arranged on the upper template 18, the guide sleeve 16 is arranged on the lower template 1, the guide post 6 is matched and connected with the guide sleeve 16, and the guide post 6 and the guide sleeve 16 play a role in guiding between the upper template 18 and the lower template 1. The ejector rod 5 is installed when the lower die assembly is installed, the lower end of the ejector rod is supported by a bottom plate 25, the bottom plate 25 is fixed at the lower end of a pull rod 26 through a hexagon nut 24, the pull rod 26 penetrates through a through hole in the lower die plate 1 and is connected with a connecting rod 29 through a sleeve 27, the distance between the upper part and the lower part of the pull rod 26 can be adjusted through an adjusting nut 28, and the connecting rod 29 is fixed on the upper die plate 18 through a hexagon nut 30. When the upper die plate 18 moves downwards, the pull rod 26 takes the ejector rods 5 to descend together to finish extrusion, when the extrusion is finished, the upper die plate 18 ascends, and the pull rod 26 supports the ejector rods 5 to jack the extrusion piece, so that the extrusion piece can be conveniently taken out.

A synchronous extrusion forming method for H-shaped connecting pieces made of steel with different wall thicknesses is briefly described by taking 45 steel as an example, and comprises the following steps:

(1) preparation before forming: putting 45 steel bar materials into a tubular electric frequency induction heating furnace, heating to 200 ℃ at low temperature, uniformly spraying a water-based graphite lubricant, and heating to 950 ℃; mounting the mold in the assembled relationship illustrated in FIG. 1 on a press; and uniformly placing heated preheating mould bars inside and outside the cavity of the female mould and around the male mould to preheat the mould.

Referring to fig. 3, water-based graphite lubricant is uniformly coated on the surfaces of the male die 13, the bottom of the withdrawing ring 14, the cavity on the inner wall of the female die 12 and the bottom core 8 which are to be in contact with the steel piece, and after the preheating of the die is finished, the blank is placed on the bottom core 8. After completion, the upper platen 18 is moved downwards and the tie rods 26 are lowered, the lift pins 5 and the bottom core 8 are automatically lowered, and the bottom core 8 is returned to the bottom blank of the die 12 to the pre-extrusion position, as shown in fig. 4, ready for extrusion.

(2) Forming process: referring to fig. 5, 6 and 7, the press drives the upper die plate 18, the insert 20, the upper die sleeve plate 21, the upper die base 17, the male die 13 and the stripper ring 14 of the upper die assembly to move downward, the male die 13 contacts with the blank and continues to extrude downward, and the stripper ring 14 also enters the female die 12 along with the downward extrusion of the male die 13, so that a certain positioning effect on the male die 13 can be achieved. Since the punch 13 is provided with an inclination α, the matrix 12 with an inner flange 31 and the bottom core 8 with a transition radius 32 and an inclination β, as shown in fig. 8, 9 and 10, the blank undergoes three stages of deformation under the action of the punch 13:

firstly, in the stage of forming an H-shaped blank, referring to fig. 5 and 9, when the blank is just extruded, the blank is limited by an inner flange 31 of a female die, the radial resistance of the blank is greater than the axial direction, the blank flows into a bottom core 8 and a cavity of the female die 12 firstly, and the radial resistance of the blank is smaller than the axial direction as the bottom core 8 has a gradient of 10 degrees and the resistance is smaller as the space is smaller as the bottom core is lower, so that the blank upsetting action is intensified, the blank is filled in the inner flange 31 of the female die and moves upwards along the inclined wall of the male die 13, and an H-shaped preform is formed;

secondly, in the stage of increasing the upper wall and the lower wall of the H shape, as shown in fig. 6 and 8, as the press drives the male die 13 to continue to extrude downwards, the male die 13 has an upward inclination of 12 degrees, and the space between the male die 13 and the female die 12 is larger than the space between the bottom core 8 and the female die 12, so that the resistance of the upper part is smaller than that of the lower part, and the material of the lower part also moves from top to bottom, so that the height of the upper wall is higher than that of the lower wall, and at the moment, the space is filled in the female die 12 in the radial direction, and the height of the upper wall and the lower wall is not increased in the radial direction in the stage, but the height of the upper wall and the lower wall is increased, and the upper wall and the lower wall contact the bottom of the stripper;

and thirdly, in the H-full forming stage, as shown in fig. 7, the press continues to press the blank downwards with the male die 13, at this time, the H shape is substantially completed, the upper wall has not reached the final height and the bottom corner hard-forming region of the lower wall has not completed final forming, at this time, the stripper ring 14 has contacted the upper wall, the stripper ring 14 and the coil 15 have a certain height fit, when the male die 13 continues to descend, the upper wall pushes the stripper ring 14 to move upwards, when the stripper ring 14 contacts the upper die sleeve plate 21, the stripper ring 14 stops rising, at this time, the male die 13, the stripper ring 14 and the female die 12 form a closed cavity, the only flow direction of the blank is the bottom corner hard-forming region of the lower wall, and the bottom corner filling is completed with the downward impact force, and the extrusion final forming is completed.

(3) After the extrusion forming is finished: stopping the downward movement of the press machine workbench, and driving the male die 13 to ascend and separate from the upper wall of the workpiece by the upward movement of the press machine workbench in the reverse direction, wherein even if the upper part of the male die 13 is not automatically separated, the upper part of the withdrawing ring 14 is automatically dropped for a certain distance by gravity along with the ascending of the male die 13, and the workpiece is separated from the male die 13 by a downward impact force; the pull rod 26 is driven to ascend in the ascending process of the upper die plate 18, the pull rod 26 simultaneously drives the bottom plate 25 to ascend, the bottom plate 25 contacts the ejector rod 5 after ascending for a certain distance and drives the bottom core 8 to ascend together with a workpiece to separate from the female die 12, the time of the whole extrusion process is short, the workpiece can automatically pop up the female die 12 after separating from the die, the workpiece can be smoothly and easily taken down, and the extrusion part is formed.

Compared with the prior art, the invention has the following technical effects:

1. the male die 13, the female die 12 and the bottom core 8 jointly form a forming inner cavity of the H-shaped connecting piece, the stress condition of the H-shaped piece in the extrusion deformation process is changed by controlling process parameters (the gradient and the transition fillet of each part of the forming inner cavity), the smooth realization of the upper wall and the lower wall growth and the final forming stage in the forming stage is ensured, the metal stress state, the equivalent strain, the plastic deformation, the tissue uniformity and the like are better controlled, the forming is ensured to be carried out smoothly, and the final size and performance requirements of the H-shaped connecting piece are met;

2. the stripper ring cooperates with the guide and ejector assembly. The part withdrawing ring 14 with the positioning and guiding functions can play a role of positioning the male die 13 and ensure good forming of a lower wall difficult-to-form area in the final forming stage in the downward movement process of the press, and the part withdrawing ring 14 is matched with a reverse pull rod structure to realize smooth demoulding of workpieces from top to bottom in the part withdrawing stage; the reverse pull rod type linkage ejection structure can be matched with any press machine for use, has no requirement on an ejection cylinder of the press machine, greatly increases the applicability of an extrusion die, and reduces the production cost;

It should be noted that, as regards the first forming difficulty, the present case overcomes it by using a female die 12 with an internal flange 31 and a male die 13 and a bottom core 8 with a specific inclination α, β and a transition radius 32. The forming surfaces of the female die 12, the male die 13 and the bottom core 8 can optimize an optimal forming curve according to corresponding part drawings, and the optimal forming curve is matched with the inner flange 31 of the female die 12, so that the axial instability of the cup wall can be prevented, and the upper wall and the lower wall can be formed well. For the second forming difficulty, the mechanism adopts a male die 13 with a withdrawing ring 14, and combines a guide and ejection device component to realize the reverse pull rod type linkage ejection for overcoming. The part withdrawing ring 14 on the male die 13 and the male die 13 enter the female die 12 together to play a good positioning role, and the part withdrawing ring 14 and the structures of the male die 12 and the female die 13 form three-way pressure stress on the cup wall in the final forming stage, so that the uniformity of the wall thickness can be ensured, and a certain complementary role can be played for the complete forming of the lower wall. The part returning ring is matched with the guide and ejection device assembly to play a role in conveniently taking materials, and the die is ingenious in design structure, good in reliability and high in forming precision.

The above are merely specific examples of the present invention, and do not limit the scope of the present invention. All equivalent changes made according to the design idea of the present application fall within the protection scope of the present application.

Claims

1. A synchronous extrusion forming method of an H-shaped connecting piece made of steel with different wall thicknesses relates to a synchronous extrusion forming die of the H-shaped connecting piece made of steel with different wall thicknesses, and the die comprises an upper die component connected with the upper part of a press machine, a lower die component connected with the lower part of the press machine and a guiding and ejecting device component; the upper die assembly comprises an upper die plate connected with an upper workbench of the press machine, an insert and an upper die base connected with the upper die plate, a male die and an upper die sleeve plate connected with the insert, and a screw ring and a withdrawing ring connected with the upper die base; the lower die assembly comprises a bottom core and a female die which are connected with a lower workbench of the press machine; an inner flange is formed inside the female die, and the bottom core and the male die form a transition fillet and an inclination; the guiding and ejecting device assembly comprises an ejector rod, a bottom plate and a pull rod, and the method specifically comprises the following steps:

2. The synchronous extrusion forming method of the steel H-shaped connecting piece with different wall thicknesses as in claim 1, characterized in that: the inclination of the bottom core is 10 degrees.

3. The synchronous extrusion forming method of the steel H-shaped connecting piece with different wall thicknesses as in claim 1, characterized in that: the inclination of the male die is 12 degrees.