CN115090774A - A kind of equal-wall thickness shrinking die and shrinking process - Google Patents

Abstract

The invention discloses a pipe reducing mould with equal wall thickness and a pipe reducing process, wherein the pipe reducing mould is of a binary structure and comprises a binary unit and a binary unit, the maximum distance between the binary unit and the binary unit forms a sliding binary distance, the binary structure can realize that a pipe blank smoothly enters a mould to reduce the pipe and returns a core rod to draw the core to trim the wall thickness of the pipe blank, the binary distance is closed to enable the head of a core rod of the mould to move forwards to a mould entering expansion port, and the condition that the pipe blank enters the mould to have enough clearance is ensured; when the die is withdrawn, the distance is gradually increased, the position of the mandrel head of the die is moved to the straight section of the die core, and the original wall thickness of the tube blank is kept after the tube blank is contracted. Therefore, the problem of large-proportion equal-wall-thickness cold-extrusion compression pipes of workpieces such as low-carbon steel seamless steel pipes and the like in the industry at present is effectively solved, the utilization rate of product materials can reach more than 95%, and the proportion of the contracted pipes can reach more than 2.5. The mould adopts binary structural design, and reducible power unit is constituteed, is favorable to promoting the efficiency, the quality and the reduce cost of batch production.

Description

A kind of equal-wall thickness shrinking die and shrinking process

technical field

The invention relates to the technical field of metal workpiece processing, in particular to a shrinking die and a shrinking process for shrinking a metal pipe.

Background technique

Metal tubular hollow products are applied in many fields. Such products are generally pre-formed to obtain the initial tube blank, such as the tube blank used for the inner high-pressure integrated axle housing, and then the tube blank is subjected to a shrinking process through a tube shrinking machine combined with a tube shrinking die and other equipment. Finally, the finished tube blank is obtained. However, for products such as low-carbon steel seamless steel pipes with a small self-tensile coefficient, it is a common practice in the industry to reduce the diameter by cold extrusion, but the current shrinkage ratio in the industry is only about 1.5, but the shrinkage ratio of about 1.5 cannot be Meet the requirements of use in many fields. Moreover, the current process also cannot achieve large-scale reduction (usually the reduction ratio is about 2.5) without increasing or reducing the wall thickness of the pipe, that is, it is difficult to achieve a large-scale reduction of the same wall thickness. .

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to aim at the shortcomings of the prior art, and to provide a mold with a simple structure and a more reasonable design, which can realize the equal-wall-thickness shrink-tube forming of low-stretch system materials such as carbon steel pipes and other workpieces. Shrinking die and shrinking process.

In order to solve the above-mentioned technical problem, the present invention adopts the following technical scheme: a kind of equal-wall-thickness tube shrinking die, which is installed on the tube shrinking equipment with a slidable structure, it is characterized in that: the tube shrinking die includes a binary unit and a binary unit, The binary unit is arranged on the outside of the unary unit, and the two are respectively installed in a sliding fit on the tube shrinking device to form a binary structure with a synchronous sliding process and an independent sliding process, wherein the sliding distance of the binary unit is greater than the sliding distance of the unary unit. Distance, the extra sliding distance of the binary unit forms the binary distance, and the binary distance is also the maximum distance between the binary unit and the binary unit in the independent sliding process;

The unitary unit includes a shrink-tube mold core, and the shrink-tube mold core is installed at the front end of a sliding support body to form a structure that can move synchronously with the sliding support body; the sliding support body has a molding cavity, and the molding cavity is located in the sliding support body. A mold mandrel is inserted in the middle, and the tail end of the mold mandrel is mounted on the binary unit to form a structure that can move synchronously with the binary unit; the binary unit is connected with a drive mechanism, and the binary unit is driven by the drive mechanism. Slide, and drive the binary unit to move to complete the shrinking tube forming;

The inner cavity of the shrinkable tube core includes a flared section and a straight tube section, the flared section is located at the front end and faces the tube blank, the straight tube section is located at the rear end and is butted with the tail of the flared section; the minimum inner diameter of the flared section is larger than the tube blank. The outer diameter of the blank, the inner diameter of the straight section is equivalent to the outer diameter of the tube blank; the head of the mold mandrel is located in the straight section of the shrinking mold core when the mold is open, and the outer surface of the head of the mold mandrel The minimum distance between the inner wall of the straight section of the shrink tube core and the wall thickness of the tube blank is the same; when the shrink tube die is closed, the binary unit and the unary unit are attached to each other, and the head of the die mandrel enters into the shrink tube core. In the flared section, the distance between the head of the die mandrel and the inner wall of the flared section is greater than the wall thickness of the tube blank.

Further, the flared section of the shrinking tube core is a tapered structure that gradually shrinks inwards, and the head of the die mandrel is a thickening head with a diameter larger than the diameter of the main part of the die mandrel, and the thickening head can be The front section is set in a round bar shape, and the rear section is in the shape of a tapered tapered shape, and the tapered shape part is connected to the main part of the die core; the thickening head is located in the straight section of the shrinking die core when the mold is opened, and thickens The minimum distance between the outer surface of the head and the inner wall of the straight section of the shrinking die core is the same as the wall thickness of the tube blank; when the shrinking die is closed, the binary unit and the unary unit fit each other, and the thickening head enters the shrinking die. In the flared section of the core, the distance between the thickening head and the inner wall of the flared section is greater than the wall thickness of the tube blank.

Further, the sliding support body is installed on a first support seat, and the first support seat is installed on the guide rail of the tube shrinking device through a sliding block.

Further, the binary unit includes a second support seat, the second support seat is mounted on the guide rail through another slider, and is located outside the first support seat.

Further, the binary unit further includes a cooling mechanism, and the cooling mechanism extends into the molding cavity of the sliding support body and aligns the mold core rod and the tube blank inserted into the molding cavity.

Further, the cooling mechanism includes a water inlet pipe and a cooling pipeline, the water inlet pipe is arranged on the second support seat, the cooling pipeline is connected with the water inlet pipe and extends to the molding cavity through the second support seat; in the cooling pipe At the outlet of the road, a water nozzle is installed through the water channel cover. The water nozzle is aimed at the mold mandrel and the tube blank inserted into the molding cavity. The cooling water or cooling liquid is sprayed onto the tube blank and the inside of the mold through the water nozzle.

Further, the second support seat is connected with the side cylinder rod of the side cylinder as the driving mechanism through a side cylinder flange, and the decimal distance is the maximum distance between the second support seat and the first support seat when they slide relative to each other. .

Preferably, a set of tube shrinking dies is provided on each of the left and right sides of the tube blank, and the tube shrinking dies on both sides are symmetrically arranged. This arrangement is mainly for workpieces that need to be simultaneously tube-reduced on both sides.

A tube shrinking process based on the aforementioned equal-wall-thickness tube shrinking mold, characterized in that: carrying out the following steps,

Step 1. Put the tube blank into the fixture of the tube shrinking equipment;

Step 2. Under the control of the numerical control system, the tube shrinking equipment clamps the middle shape of the tube blank, and the left and right cylinders push the tube shrinking die under the control of the system to start shrinking the tube blank;

Step 3. The side cylinder rod pushes the tube shrinking die to move towards the tube blank, so that the die mandrel and the tube shrinking core also move towards the tube blank; when the tube shrinking core contacts the tube blank, due to the resistance of the tube blank into the mold, a The binary unit slides backward under the action of resistance, and the sliding distance reaches the binary unit and then fits with the binary unit; at this time, the thickening head of the die mandrel protrudes into the flared section of the shrinking die core, due to the gap here It is larger than the gap in the straight section, so that the tube blank can smoothly pass through the shrinking core and enter the molding cavity when it is introduced into the shrinking mold;

Step 4. During the process of the tube blank entering the molding cavity, the wall thickness of the tube blank is affected by the extrusion of the shrinking tube core and the die core rod, so that the thickness of the tube blank increases and becomes a wavy irregular shape;

Step 5. After the set length of the tube blank completely enters the shrinking die, the binary unit starts to retreat under the drive of the side cylinder rod; at this time, the unitary unit will remain stationary due to the frictional force with the tube blank. Under the retracting action of the binary unit, it is pulled apart to the decimal distance, and at the same time, the thickening head of the die mandrel is pulled back to the straight section of the shrinking die core. This process is a binary action;

Step 6. The binary unit continues to retreat, and the unitary unit is driven to make the shrinking die begin to pull back as a whole. Since the gap between the thickening head of the die mandrel and the inner wall of the straight section of the shrinking core is the same as the original wall thickness of the tube blank, the die core The pullback of the rod makes the increased wall thickness of the tube blank re-trimming and thinning to the original thickness;

Step 7. After the overall retraction of the tube shrinking mold is completed, the tube blank is restored to the original wall thickness and the whole is smooth and flat, the cooling system is turned off, and the tube shrinking is completed. Of course, the whole tube shrinking process can be divided into several (such as three) processes, each process completes a certain tube shrinking process, and the final tube shrinking of the tube blank is realized after all the processes are completed.

Further, when the tube blank enters and exits the inside of the tube shrinking die, the tube shrinking die and the tube blank are lubricated and cooled through the water nozzle, so as to ensure the smooth progress of the tube shrinking process and protect the die.

The invention designs the tube shrinking die into a binary structure, which is composed of a unitary unit and a binary unit, and the maximum distance between the two forms a sliding binary distance. The die is pushed forward in a large proportion to shrink the tube, and the core is pulled back to ensure equal wall thickness. . The binary structure can realize the smooth entry of the tube blank into the mold shrinking tube and the retraction of the mandrel. Pull the core to trim the wall thickness of the tube blank. The opening and closing of the binary distance is mainly reflected in the position change of the working position of the core pulling head. The head moves forward to the flaring part of the mold to ensure that the tube blank has enough clearance; when the mold is retracted, the distance is widened, and the position of the head of the mold mandrel follows and moves to the straight section of the mold core to ensure that the tube blank shrinks. After maintaining the original wall thickness.

This effectively solves the industry's current problems with cold-extruded compressed tubes with a large proportion of equal-wall thickness for low-carbon steel seamless steel pipes and other workpieces. The material utilization rate of the product can reach more than 95%, and the shrinkage ratio can reach more than 2.5. The mold itself has a cooling and lubricating circulation mechanism, and the overall modular design is easy to replace and maintain, which can change the low-efficiency and dirty manufacturing environment of the industry. The mold adopts the binary structure design, which can reduce the composition of the power mechanism, which is conducive to the realization of miniaturization and simplification, and can achieve the effect of completing four actions in two directions with one power. The efficiency, quality and cost of mass production are qualitatively improved. It is suitable for automated production and can realize pollution-free, standardized and automated modern production.

Description of drawings

Fig. 1 is the change schematic diagram of the process of shrinking tube from mold closing to mold opening in the molding process of the present invention;

Fig. 2 is the structural representation of the tube shrinking die of the present invention;

Fig. 3 is a partial enlarged view of Fig. 2;

4 is a schematic diagram of the changing state of the shrinking tube die and the tube blank during the molding process of the present invention;

Fig. 5 is the installation schematic diagram of the shrinking die in the shrinking machine;

FIG. 6 is a schematic diagram of the variation of the tube blank forming process of the present invention.

In the figure, A is a unitary unit, B is a binary unit, 1 is the water inlet pipe, 2 is the cooling pipeline, 3 is the water channel cover, 4 is the water nozzle, 5 is the die mandrel, and 6 is the shrinking die core , 61 is the flared section, 62 is the straight cylinder section, 7 is the sliding support body, 71 is the molding cavity, 8 is the first support seat, 9 is the second support seat, 10 is the side cylinder rod, 11 is the slider, 12 is the Guide rail, 13 is the side cylinder flange, 14 is the tube blank.

Detailed ways

In this embodiment, referring to FIGS. 1 to 6 , the tube shrinking die with equal wall thickness is installed on a tube shrinking device (such as a tube shrinking machine) in a slidable structure, and the tube shrinking die includes a binary unit A and a binary unit. Unit B, the binary unit B is arranged on the outside of the unary unit A, and the two are respectively installed on the shrinking tube device to form a binary structure with a synchronous sliding process and an independent sliding process, wherein the sliding distance of the binary unit B is greater than The sliding distance of the unary unit A, the extra sliding distance of the binary unit B forms the unitary distance L4, and the unitary distance L4 is also the maximum distance between the unitary unit A and the binary unit B in the independent sliding process;

The unary unit A includes a shrink-tube mold core 6, and the shrink-tube mold core 6 is installed at the front end of a sliding support body 7 to form a structure that can move synchronously with the sliding support body 7; the sliding support body 7 has a Molding cavity 71, a mold mandrel 5 is inserted in the molding cavity 71, and the tail end of the mold mandrel 5 is mounted on the binary unit B to form a structure that can move synchronously with the binary unit B; the binary unit B is connected with A driving mechanism is connected, and the binary unit B is driven by the driving mechanism to slide, and the binary unit A is driven to move by the binary unit B to complete the shrinkage forming;

The inner cavity of the shrinkable tube core 6 includes a flared section 61 and a straight cylinder section 62, the flared section 61 is located at the front end and faces the tube blank 14, and the straight cylinder section 62 is located at the rear end and is butted with the tail of the flared section 61; The minimum inner diameter of the mouth section 61 is larger than the outer diameter of the tube blank 14, and the inner diameter of the straight tube section 62 is equivalent to the outer diameter of the tube blank 14 (reduced tube part); the head of the die mandrel 5 is in the shrinkage position when the mold is opened. In the straight section 62 of the tube core 6, and the minimum distance between the outer surface of the head of the die mandrel 5 and the inner wall of the straight section 62 of the tube shrink core 6 is the same/equivalent to the wall thickness H of the tube blank 14; During molding, the binary unit B and the unary unit A are attached to each other, the head of the mold mandrel 5 enters the flared section 61 of the shrinkable mold core 6, and the head of the mold mandrel 5 is connected to the inner wall of the flared section 61. The distance between them is greater than the wall thickness H of the tube blank 14 .

The flared section 61 of the tube shrinking die core 6 is a tapered structure that gradually shrinks inward, and the head of the die mandrel 5 is a thickening head with a diameter larger than the diameter of the main part of the die mandrel 5. The thickening head The front section can be set to be in the shape of a round bar, and the rear section is in the shape of a tapered tapered shape, and the tapered shape part is connected to the main part of the die core rod 5; the thickening head is located in the straight section 62 of the shrink tube core 6 when the mold is opened. , and the minimum distance between the outer surface of the thickening head and the inner wall of the straight section 62 of the shrinking die core 6 is the same as the wall thickness H of the tube blank 14; when the shrinking die is clamped, the binary unit B and the unary unit A are attached to each other. , the thickening head enters into the flared section 61 of the tube shrinking die core 6 , and the distance between the thickening head and the inner wall of the flared section 61 is greater than the wall thickness H of the tube blank 14 .

The sliding support body 7 is installed on the first support base 8 , and the first support base 8 is installed on the guide rail 12 of the tube shrinking device through a sliding block 11 .

The binary unit B includes a second support base 9 . The second support base 9 is mounted on the guide rail 12 through another slider 11 and is located outside the first support base 8 .

The binary unit B also includes a cooling mechanism. The cooling mechanism extends into the molding cavity 71 of the sliding support body 7 and aligns with the mold core rod 5 and the tube blank 14 inserted into the molding cavity 71 .

The cooling mechanism includes a water inlet pipe 1 and a cooling pipeline 2. The water inlet pipe 1 is arranged on the second support seat 9, and the cooling pipeline 2 is connected with the water inlet pipe 1 and extends through the second support seat 9 to the molding cavity. 71; A water nozzle 4 is installed at the outlet of the cooling pipeline 2 through the waterway cover plate 3, and the water nozzle 4 is aligned with the mold mandrel 5 and the tube blank 14 inserted into the molding cavity 71, and the cooling water is injected through the water nozzle 4. Or the cooling liquid is sprayed onto the tube blank 14 and inside the mold.

The second support seat 9 is connected with the side cylinder rod 10 of the side cylinder as the driving mechanism through the side cylinder flange 13, and the metric distance L4 is generated when the second support seat 9 and the first support seat 8 slide relative to each other. maximum spacing.

A set of tube shrinking dies are provided on the left and right sides of the tube blank 14, and the tube shrinking dies on both sides are symmetrically arranged. This arrangement is mainly for workpieces that need to be shrinked and formed on both sides at the same time.

Based on the aforementioned shrinking process of the equal-wall-thickness shrinking die, proceed as follows:

Step 1. Put the tube blank 14 into the jig (lower shaping die) of the tube shrinking equipment;

Step 2. Under the control of the numerical control system, the tube shrinking device clamps the middle shape of the tube blank 14, and the left and right cylinders push the tube shrinking die under the control of the system to start shrinking the tube blank 14;

Step 3. The side cylinder rod 10 pushes the tube shrinking die to move towards the tube blank 14, so that the die mandrel 5 and the tube shrinkage core 6 also move towards the tube blank 14; 14 Due to the resistance of the mold entry, the unary unit A slides backwards under the action of resistance, and the sliding distance reaches the unitary distance L4 and then fits with the binary unit B; at this time, the thickening head of the die mandrel 5 extends to the shrinking tube In the flared section 61 of the mold core 6, since the gap here is larger than the gap in the straight section 62, the tube blank 14 can smoothly pass through the tube shrinking mold core 6 and enter the molding cavity 71 when it is introduced into the tube shrinking mold;

Step 4. During the process of the tube blank 14 entering the molding cavity 71, the wall thickness H of the tube blank 14 is affected by the extrusion of the shrink tube die core 6 and the die core rod 5, so that the thickness of the tube blank 14 increases to H1, and becomes It is a wavy irregular shape;

Step 5. After the length set by the tube blank 14 completely enters the shrinking die, the binary unit B starts to perform a retraction action under the drive of the side cylinder rod 10; It will remain still, and will be pulled apart to the binary distance L4 under the retraction action of the binary unit B, and at the same time, the thickening head of the die mandrel 5 will be pulled back to the straight section 62 of the shrinking die core 6. This process is binary. action;

Step 6. The binary unit B continues to retreat, and drives the unitary unit A to make the shrinking die begin to pull back as a whole. Because the gap between the thickening head of the die mandrel 5 and the inner wall of the straight section 62 of the shrinking die core 6 and the original tube blank 14 The wall thickness H is the same, and the pulling back of the die mandrel 5 makes the increased wall thickness H1 of the tube blank 14 re-trimmed and thinned to the original thickness H;

Step 7. After the overall retraction of the tube shrinking mold is completed, the tube blank 14 is restored to the original wall thickness H and the whole is smooth and flat, the cooling system is turned off, and the tube shrinking is completed.

When the tube blank 14 enters and exits the inside of the tube shrinking die, the water spray nozzle 4 lubricates and cools the tube shrinking die and the tube blank 14, so as to ensure the smooth tube shrinking process and protect the die.

Of course, the whole tube shrinking process can be divided into several (such as three) processes, each process completes a certain tube shrinking process, and the final tube shrinking of the tube blank is realized after all the processes are completed.

The following three steps are taken as an example to further illustrate:

1) The length L of the tube blank 14 is increased to L1 by the shrinking die of the first station, and the first process of shrinking the tube is completed;

2) After the first process of shrinking the tube is completed, the automatic feeding mechanism of the tube shrinking equipment starts to work under the control of the system, and the tube blank 14 after the first process of shrinking is sent to the jig of the second station, and then repeats the aforementioned In the tube shrinking process, the length L1 of the tube blank 14 is increased to L2, and the second process of shrinking the tube is completed;

3) After the second process of tube shrinking is completed, the automatic feeding mechanism of the tube shrinking equipment starts to work under the control of the system, and the tube blank 14 after the tube shrinking in the second process is completed is sent to the jig of the third station, and then repeat the above In the tube shrinking process, the length L2 of the tube blank 14 is increased to L3, the third process of tube shrinkage is completed, the tube blank 14 is sent out through the automatic feeding mechanism, and the tube shrinkage is completed.

The present invention has been described in detail above. The above descriptions are only preferred embodiments of the present invention, and should not limit the scope of implementation of the present invention. inventions are covered.

Claims (10)

1. The utility model provides a wall thickness reducing pipe mould to slidable structure installs on reducing pipe equipment, its characterized in that: the pipe reducing mold comprises a binary system unit and a binary system unit, wherein the binary system unit is arranged at the outer side of the binary system unit and is respectively installed on pipe reducing equipment in a sliding mode to form a binary system structure with a synchronous sliding process and an independent sliding process, the sliding distance of the binary system unit is larger than that of the binary system unit, the excessive sliding distance of the binary system unit forms a binary system distance, and the binary system distance is also the maximum distance between the binary system unit and the binary system unit in the independent sliding process;

the first system unit comprises a pipe reducing mold core, and the pipe reducing mold core is arranged at the front end of a sliding support body to form a structure capable of moving synchronously with the sliding support body; the sliding support body is provided with a molding cavity, a mold core rod is inserted in the molding cavity, and the tail end of the mold core rod is installed on the binary system unit so as to form a structure capable of synchronously moving along with the binary system unit; the binary unit is connected with a driving mechanism, the binary unit is driven to slide through the driving mechanism, and the binary unit drives the first unit to move so as to complete pipe shrinking forming;

the inner cavity of the pipe contracting mold core comprises an expanding section and a straight cylinder section, the expanding section is positioned at the front end and faces the pipe blank, and the straight cylinder section is positioned at the rear end and is butted with the tail part of the expanding section; the minimum inner diameter of the flaring section is larger than the outer diameter of the tube blank, and the inner diameter of the straight cylinder section is equivalent to the outer diameter of the tube blank; when the mold core rod is in a mold opening state, the head of the mold core rod is positioned in the straight cylinder section of the pipe reducing mold core, and the minimum distance between the outer surface of the head of the mold core rod and the inner wall of the straight cylinder section of the pipe reducing mold core is the same as the wall thickness of the pipe blank; when the pipe reducing mold is closed, the binary system unit and the binary system unit are attached to each other, the head of the mold core rod enters the flaring section of the pipe reducing mold core, and the distance between the head of the mold core rod and the inner wall of the flaring section is larger than the wall thickness of the pipe blank.

2. The constant wall thickness reducing pipe mold according to claim 1, wherein: the flaring section of the pipe reducing mold core is of a conical structure which gradually shrinks inwards, the head of the mold core rod is an increasing head with the diameter larger than the diameter of the main body part of the mold core rod, the increasing head is positioned in the straight cylinder section of the pipe reducing mold core in the mold opening state, and the minimum distance between the outer surface of the increasing head and the inner wall of the straight cylinder section of the pipe reducing mold core is the same as the wall thickness of the pipe blank; when the pipe reducing mold is closed, the binary unit and the binary unit are attached to each other, the thickening head enters the flaring section of the pipe reducing mold core, and the distance between the thickening head and the inner wall of the flaring section is larger than the wall thickness of the pipe blank.

3. The equal wall thickness reduction mold of claim 2, wherein: the sliding support body is arranged on a first support seat, and the first support seat is arranged on a guide rail of the pipe reducing device through a sliding block.

4. The equal wall thickness reduction mold of claim 3, wherein: the binary system unit comprises a second supporting seat, and the second supporting seat is arranged on the guide rail through another sliding block and is positioned on the outer side of the first supporting seat.

5. The equal wall thickness reduction mold of claim 4, wherein: the binary system unit also comprises a cooling mechanism, and the cooling mechanism extends into the forming cavity of the sliding support body and is aligned with the die core rod and the pipe blank inserted into the forming cavity.

6. The equal wall thickness reduction mold of claim 5, wherein: the cooling mechanism comprises a water inlet pipe and a cooling pipeline, the water inlet pipe is arranged on the second supporting seat, and the cooling pipeline is connected with the water inlet pipe and penetrates through the second supporting seat to extend to the forming cavity; and a water spray nozzle is arranged at the outlet of the cooling pipeline through a water channel cover plate and is aligned with the mold core rod and the pipe blank inserted into the forming cavity.

7. The equal wall thickness reduction mold of claim 6, wherein: the second supporting seat is connected with a side cylinder rod of a side cylinder serving as a driving mechanism through a side cylinder flange, and the carry-over distance is the maximum distance generated when the second supporting seat and the first supporting seat slide relatively.

8. The equal wall thickness reduction mold of claim 7, wherein: the left side and the right side of the tube blank are respectively provided with a set of pipe contracting dies, and the pipe contracting dies on the two sides are symmetrically arranged.

9. A pipe shrinking process based on the equal-wall-thickness pipe shrinking mold of claim 8, wherein: the method comprises the following steps of (1),

step 1, placing the tube blank into a jig of a pipe reducing device;

step 2, the pipe reducing equipment clamps the middle shape of the pipe blank under the control of a numerical control system, and the left and right side cylinders drive a pipe reducing die to start pipe reducing under the control of the system;

step 3, the side cylinder rod pushes the pipe contracting mold to move towards the pipe blank, so that the mold core rod and the pipe contracting mold core also move towards the pipe blank; when the pipe contracting mold core contacts the pipe blank, the first system unit slides backwards under the action of resistance due to the action of the resistance of the pipe blank entering the mold, and the sliding distance reaches the first system distance and then is attached to the second system unit; at the moment, the thickening head of the mold core rod extends into the flaring section of the pipe reducing mold core, and the gap at the position is larger than the gap in the straight cylinder section, so that the pipe blank can smoothly pass through the pipe reducing mold core and enter the forming cavity when being guided into the pipe reducing mold;

step 4, in the process that the tube blank enters the forming cavity, the thickness of the tube blank is influenced by the extrusion of the pipe shrinking die core and the die core rod, so that the thickness of the tube blank is increased and is changed into a wavy irregular shape;

step 5, after the set length of the pipe blank completely enters the pipe reducing die, the binary system unit starts to do a return action under the driving of the side cylinder rod; at the moment, the first system unit can be kept still due to the action of friction force with the pipe blank, the first system unit is pulled to a first system distance under the action of the retraction of the second system unit, and meanwhile, the thickening head of the mold core rod is pulled back to the straight cylinder section of the pipe reducing mold core, and the process is the second system action;

step 6, the binary system unit continuously returns to drive the binary system unit to enable the pipe reducing die to start to integrally pull back, and due to the fact that the gap between the thickening head of the die core rod and the inner wall of the straight cylinder section of the pipe reducing die core rod is the same as the original wall thickness of the pipe blank, the pulling back of the die core rod enables the increased wall thickness of the pipe blank to be trimmed again and thinned to the original thickness;

and 7, after the integral retracting action of the pipe reducing die is finished, the pipe blank returns to the original wall thickness and is integrally smooth and flat, the cooling system is closed, and pipe reducing is finished.

10. A pipe shrinking process according to claim 9, wherein: and lubricating and cooling the pipe contracting die and the pipe blank through a water nozzle when the pipe blank enters and exits from the interior of the pipe contracting die.

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