EP3812056A1

EP3812056A1 - Medium/small-diameter thick-walled metal tube and preparation method therefor

Info

Publication number: EP3812056A1
Application number: EP19838335.8A
Authority: EP
Inventors: Qingle HAO; Jingtao HAN
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-07-17
Filing date: 2019-07-09
Publication date: 2021-04-28
Also published as: CN110722016A; JP2021530363A; JP7106004B2; WO2020015556A1; EP3812056A4

Abstract

The invention discloses a small-aperture thick-wall metal tube and a preparation method thereof. The cross-sectional diameter of the metal tube ranges from 30mm to 160mm, the dimensional accuracy is ±0.2mm, and the ratio of the outer diameter of the metal tube to the wall thickness of the metal tube is greater than 2 to less than or equal to 20. The inner wall and outer wall of the metal tube are free of peeling, dents, or cracks. The metal tube is made of steel, copper, aluminum, magnesium, titanium, or alloy. The invention has the characteristics of forging and rolling, can realize single pass and large deformation amount processing of the metal tube blank, and has the advantages of short process flow, high product dimensional accuracy (±0.2mm), good quality of the inner wall and outer wall surface, and low cost.

Description

Technical Field

The invention involves the technical field of metal tube material processing. Furthermore, the invention involves a medium-small-aperture thick-wall metal tube and a preparation method thereof.

Background Art

At present, the method for forming the medium-small-aperture thick-wall (D/S is in the range of 2-20) metal tube mainly comprises extrusion, rolling, and the like. The extrusion forming production efficiency is low so that the product cost is high, the market competitiveness is not achieved, and the method is generally used for producing very few metal tubes which cannot be or are difficult to produce by other processes. Hot rolling forming mainly includes periodic tube rolling, three-roller skew rolling forming and tension-reducing forming.
The rotary forge mill feeds the tubing into a rolling groove composed of a mandrel and a periodic reciprocating moving roll-pass at a certain frequency. The inner wall of the tube is supported by the mandrel, and the tube blank is rolled by a gradually shrinking variable-cross-section roll-pass so that the functions of reducing the diameter and reducing the wall are realized. The common rotary forge mill is mainly the two-roller pilger mill. However, due to the reciprocating movement of the rack and the rollers during the rolling process, many moving parts are needed and the inertia is large, the stability of the rolling process is poor, the structure of the rolling mill is complicated, and the maintenance and adjustment are difficult; the tubing rolled by the two-roller rolling mill has low dimensional accuracy and poor surface quality.
The three rollers of the three-roller skew rolling mill are uniformly distributed around the rolling center line at 120 degrees, and the axes of the rollers and the rolling center line are inclined and crossed to form a certain angle (i.e. a rolling angle and a feeding angle), so that the tube blank spirally advances under the action of the rollers, and the outer surface of the rolled tubing can form a "spiral line", influencing the surface quality, and the rolling jamming being caused by a "triangular" defect which easily appears at the tail part.
A three-roller tension reducing mill generally comprises more than 10 racks to form a series of roll-passes. Tension is provided through the speed difference of the rotating speeds of rollers of adjacent racks, so that hollow reducing of the tube blank is completed. But due to a large number of racks, the equipment investment is large, the production line is long, the occupied area is large, and the equipment adjustment and control are complicated.

Summary of the Invention

In order to solve the problems in the prior art, the invention provides a medium-small-aperture thick-wall metal tube and a preparation method thereof. The invention has the characteristics of forging and rolling, can realize single pass and large deformation amount processing of the metal tube blank, and has the advantages of short process flow, high product dimensional accuracy (±0.2mm), good quality of the inner wall and outer wall surface and low cost.
One object of the present invention is to provide a medium-small-aperture thick-wall metal tube. The cross-sectional diameter of the metal tube ranges from 30mm to 160mm, dimensional accuracy is ±0.2mm, and a ratio of an outer diameter of the metal tube to a wall thickness of the metal tube is greater than 2 to less than or equal to 20.
Preferably:

the cross-sectional diameter of the metal tube ranges from 30mm to 100mm;
the ratio of the outer diameter of the metal tube to the wall thickness of the metal tube is greater than 2 to less than or equal to 12; more preferably greater than 2 to less than or equal to 10; and most preferably greater than 2 to less than or equal to 5.

The inner wall and outer wall of the metal tube are free of peeling, dents, or cracks.
The metal tube is preferably made of steel, copper, aluminum, magnesium, titanium, or alloy. Another object of the present invention is to provide a preparation method for a medium-small-aperture thick-wall metal tube.
The preparation method comprises:

(1) selecting a tube blank and cutting to length;
(2) mounting the tube blank on a feeding rack, wherein a tail end of the tube blank is tightened by a clamping device, a front end of the tube blank is supported by a supporting roller, and it is ensured that a core mold device passes through an inner hole of the tube blank;
(3) feeding the tube blank in by 5-30mm by a feeding mechanism before starting each pass at a feeding speed of 1-3m/min, and feeding the tube blank into a composite forging and rolling forming device for forming;
(4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 15∼ 90° around a central axis of the tube blank;
(5) repeating process steps (3) and (4) until the front end of the tube blank enters a receiving rack, wherein a receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until a whole tube blank is formed; and
(6) cooling and shearing to length.

Wherein, preferably:
in step (1), the outer diameter of the tube blank is 40-180mm and the cut length is 0.5-10m.
In step (3), when cold forming is carried out, the tube blank is fed and then directly fed into a composite forging and rolling forming device; when hot forming is carried out, the blank is heated to a target temperature through an induction heating device and then fed into the composite forging and rolling forming device.
In step (3) during the hot forming, the induction heating device is a medium-frequency induction heating coil and the target temperature range is 800-1200°C.
The composite forging and rolling forming device is composed of three swinging mold blocks, the mold blocks are arranged at equal intervals around the central axis of the tube blank at 120 °, the mold blocks synchronously swing through a crank connecting rod mechanism driven by a motor, the mold blocks rotate around a connecting shaft thereof and simultaneously do reciprocating linear movement with the connecting shaft, straight gears connected through flat keys are mounted at two ends of the connecting shaft, and the moving displacement and rotating angle of the mold are controlled by the straight gears.
The invention can specifically adopt the following technical scheme.
The process comprises the following steps: (1) selecting an appropriate tube blank and cutting to length; (2) mounting the tube blank on a feeding rack, wherein a tail end of the tube blank is tightened by a clamping device, a front end of the tube blank is supported by a supporting roller, and it is ensured that a core mold device passes through an inner hole of the tube blank; (3) feeding the tube blank in by 5-30mm by a feeding mechanism before starting each pass at a feeding speed of 1-3m/min, wherein, when cold forming is carried out, the tube blank is fed and then directly fed into a composite forging and rolling forming device; when hot forming is carried out, the blank is heated to a target temperature through an induction heating device and then fed into the composite forging and rolling forming device; (4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 15-90° around the central axis of the tube blank, feeding in the tube blank by 5-30mm again, and then feeding the tube blank into the composite forging and rolling forming device again for forming; (5) repeating process steps (3) and (4) until the front end of the tube blank enters a receiving rack, wherein a receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until a whole tube blank is formed; and (6) cooling and shearing to length.
The process mainly comprises the following steps:

(1) selecting an appropriate tube blank and cutting to length;
(2) mounting the tube blank on a feeding rack, wherein a tail end of the tube blank is tightened by a clamping device, a front end of the tube blank is supported by a supporting roller, and it is ensured that a core mold device passes through an inner hole of the tube blank;
(3) feeding the tube blank in by 5-30mm by a feeding mechanism before starting each pass at a feeding speed of 1-3m/min, wherein, when cold forming is carried out, the tube blank is fed and then directly fed into a composite forging and rolling forming device; when hot forming is carried out, the blank is heated to a target temperature through an induction heating device and then fed into the composite forging and rolling forming device;
(4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 15-90° around the central axis of the tube blank, feeding in the tube blank by 5-30mm again, and then feeding the tube blank into the composite forging and rolling forming device again for forming;
(5) repeating process steps (3) and (4) until the front end of the tube blank enters a receiving rack, wherein a receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until a whole tube blank is formed; and
(6) cooling and shearing to length.

The blank selected in the invention comprises a high-frequency longitudinal welded tube and a seamless tube, the material requirement comprises a steel tube and nonferrous metal tubes such as aluminum, copper, magnesium and titanium and the like, the outer diameter of the tube blank is 40-180mm, and the cut length is 0.5-10m.
According to the forming mold disclosed by the invention, the forming mold is composed of three swinging mold blocks, the mold blocks are arranged at equal intervals around the central axis of the tube blank at 120 °, the mold blocks synchronously swing through a crank connecting rod mechanism driven by a motor, the mold blocks rotate around a connecting shaft thereof, and meanwhile, the connecting shaft is doing a reciprocating linear movement, and the moving displacement and the rotating angle of the mold blocks strictly correspond to each other. According to the invention, the feeding speed of the blank is 1-3m/min, and the feeding amount of each time is 5-30mm;
According to the invention, the process can be used for cold forming and hot forming, the induction heating device in step (3) is a medium-frequency induction heating coil, and the forming temperature range is 800-1200°C;
The invention is suitable for forming medium-small-aperture metal tubes made of various metal materials, the outer diameter of the product is in the range of 30-160mm, and the ratio (D/S) of the outer diameter of the product to the wall thickness of the product is greater than 2 to less than or equal to 20.
The dimensional accuracy of the metal tube product obtained in the invention is ±0.2mm;
the beneficial effects of the above-mentioned technical scheme provided by the invention are as follows:

(1) the single pass and large deformation amount variable cross-section processing of the metal tube blank can be realized;
(2) the process flow is short and the equipment investment is small;
(3) the product has high dimensional accuracy (±0.2mm), and the surface quality of the inner wall and the outer wall is good;
(4) the process has the characteristics of forging and rolling, deformation particles are in a three-dimensional pressure stress state, and the process can be used for cold forming and hot forming of medium-small-aperture metal tubes made of various metal materials.

Brief Description of the Drawings

Fig. 1 is a schematic view of a composite forging and rolling metal tube forming machine of the present invention;
Fig. 2 is a schematic view of a transmission of the present invention;
Fig. 3 is a schematic view of a composite forging and rolling forming device of the present invention;
Fig. 4 is a side sectional view of Fig. 3;
Fig. 5 is a schematic view of an induction heating coil of the present invention;
Fig. 6 is a schematic view of a core mold device of the present invention;
Fig. 7 is a schematic view of a feeding device of the present invention;
Fig. 8 is a schematic view of a receiving device of the present invention;
Fig. 9 is a schematic view of a small-aperture thick-wall metal tube product of the present invention;
Fig. 10 is a schematic cross-sectional view of Fig. 9.

Description of Reference Numerals:

1 receiving rack; 2 driving rack; 3 forming rack; 4 induction heating coil; 5 induction heating equipment control cabinet; 6 blank; 7 core mold; 8 feeding rack; 9 eccentric gear connecting rod; 10 forming rack base; 11 main driving shaft; 12 intermeshed driving bevel gear A; 13 intermeshed driving bevel gear B; 14 intermeshed driving bevel gear C; 15 intermeshed driving bevel gear D; 16 intermediate driving shaft; 17 eccentric gear shaft; 18 eccentric gear; 19 connecting shaft; 20 bearing block connecting rod; 21 sector mold block; 22 mold shaft; 23 stroke straight gear; 24 spline; 25 mold rail box; 26 feeding supporting roller; 27 hydraulic chuck; 28 servo motor; 29 decelerating pinion; 30 decelerating gearwheel; 31 chuck seat; 32 walking trolley; 33 walking trolley guide wheel; 34 positioning guide rail; 35 core mold positioning seat; 36 feeding platform; 37 supporting leg; 38 walking trolley motor; and 39 receiving supporting roller.

Detailed Description of the Invention

The invention is further illustrated in combination with the following embodiments.
Taking steel tube 6 as a blank, the tube blank is mounted on a feeding rack 7, and the tail end of the tube blank is tightened by a hydraulic chuck 27. Meanwhile ensuring that core mold device 7 passes through the inner hole of the tube blank, the blank is fed in 25mm at a feeding speed of 1.5 m/min. The tube blank enters an induction heating coil 4 and is heated to 1000 °C and then enters a forming rack 3. Each time the tube blank is formed in the composite forging and rolling forming device, the tube blank is rotated by 60 ° around the central axis of the tube blank, and the tube blank is fed in 25mm again for forming until the front end of the tube blank enters a receiving rack 1. The receiving mechanism clamps the front end of the tube blank, while the material feeding rack releases the tail end of the tube blank. The tube blank continues to advance under the driving of the receiving mechanism until the whole tube blank is formed, and the tube blank is cooled and then cut to length.

Embodiment 1
1. (1) Selecting a Q235 high-frequency longitudinal welded tube as a blank, wherein the original outer diameter of the blank is 86mm, the wall thickness is 4.5mm, and the cut length is 3m;
2. (2) mounting the tube blank on a feeding rack, wherein the front end of the tube blank is supported by a supporting roller, and the tail end of the tube blank is tightened by a clamping device so that the core mold device is ensured to pass through the inner hole of the tube blank and the diameter of a linear section of the mandrel is 54 mm;
3. (3) feeding the tube blank in by 25mm by a feeding mechanism before starting each pass at a feeding speed of 1.5 m/min, heating the blank to 1000°C by an induction heating coil, and feeding the blank into a composite forging and rolling forming device;
4. (4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 60 ° around the central axis of the tube blank, feeding in the tube blank by 25mm again, heating the tube blank by an induction coil, and feeding the tube blank into the composite forging and rolling forming device again for forming;
5. (5) repeating the process steps (3) and (4) until the front end of the tube blank enters the receiving rack, wherein the receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until the whole tube blank is formed;
6. (6) cooling and shearing to length; and
  the tube blank obtained by adopting the forming process having the advantages that the outer diameter is 65mm, the wall thickness is 5.5mm, the product dimensional accuracy is ± 0.2 mm, and the inner wall and the outer wall have no defects such as warped skin, pits and the like.
Embodiment 2
1. (1) Selecting 08Al seamless steel tube as a blank, wherein the original outer diameter of the blank is 60mm, the wall thickness is 3.8mm, and the cut length is 5m;
2. (2) mounting the tube blank on a feeding rack, wherein the front end of the tube blank is supported by a supporting roller, and the tail end of the tube blank is tightened by a clamping device so that the core mold device is ensured to pass through the inner hole of the tube blank and the diameter of a linear section of the mandrel is 25mm;
3. (3) feeding the tube blank in by 20mm by a feeding mechanism before starting each pass at a feeding speed of 2m/min, heating the blank to 900 °C by an induction heating coil, and feeding the blank into a composite forging and rolling forming device;
4. (4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 75° around the central axis of the tube blank, feeding in the tube blank by 20mm again, heating the tube blank by an induction coil, and feeding the tube blank into the composite forging and rolling forming device again for forming;
5. (5) repeating the process steps (3) and (4) until the front end of the tube blank enters the receiving rack, wherein the receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until the whole tube blank is formed;
6. (6) cooling and shearing to length; and
  the tube blank obtained by adopting the forming process having the advantages that the outer diameter is 35mm, the wall thickness is 5mm, the product dimensional accuracy is ± 0.18mm, and the inner wall and the outer wall have no defects such as warped skin, pits and the like.
Embodiment 3
1. (1) Selecting a purple copper tube as a blank, wherein the original outer diameter of the blank is 60mm, the wall thickness is 4mm, and the cut length is 6m;
2. (2) mounting the tube blank on a feeding rack, wherein the front end of the tube blank is supported by a supporting roller, and the tail end of the tube blank is tightened by a clamping device so that the core mold device is ensured to pass through the inner hole of the tube blank and the diameter of a linear section of the mandrel is 18mm;
3. (3) feeding the tube blank in by 10mm by a feeding mechanism before starting each pass at a feeding speed of 3m/min, and feeding the tube blank into a composite forging and rolling forming device;
4. (4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 45° around the central axis of the tube blank, feeding in the tube blank by 10mm again, and then feeding the tube blank into the composite forging and rolling forming device again for forming;
5. (5) repeating the process steps (3) and (4) until the front end of the tube blank enters the receiving rack, wherein the receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until the whole tube blank is formed;
6. (6) shearing to length; and
  the aluminum tube product obtained by adopting the cold forming process having the advantages that the outer diameter is 30mm, the wall thickness is 6.5mm, the inner wall and the outer wall are bright and clean, the aluminum tube product has no defects such as warped skin, pits and the like, and the dimensional accuracy of the product is ±0.2mm.
Embodiment 4
1. (1) Selecting a pure aluminum tube as a blank, wherein the original outer diameter of the blank is 140mm, the wall thickness is 10mm, and the cut length is 8m;
2. (2) mounting the tube blank on a feeding rack, wherein the front end of the tube blank is supported by a supporting roller, and the tail end of the tube blank is tightened by a clamping device so that the core mold device is ensured to pass through the inner hole of the tube blank and the diameter of a linear section of the mandrel is 85mm;
3. (3) feeding the tube blank in by 8mm by a feeding mechanism before starting each pass at a feeding speed of 3m/min, and feeding the tube blank into a composite forging and rolling forming device;
4. (4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 25° around the central axis of the tube blank, feeding in the tube blank by 8mm again, and then feeding the tube blank into the composite forging and rolling forming device again for forming;
5. (5) repeating the process steps (3) and (4) until the front end of the tube blank enters the receiving rack, wherein the receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until the whole tube blank is formed;
6. (6) shearing to length; and
  the aluminum tube product obtained by adopting the cold forming process having the advantages that the outer diameter is 110mm, the wall thickness is 12.5mm, the inner wall and the outer wall are bright and clean, the aluminum tube product has no defects such as warped skin, pits and the like, and the dimensional accuracy of the product is ±0.2mm.

The above are the preferred embodiments of the present invention. It should be pointed out that for ordinary technologies in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the scope of the present invention.

Claims

A small-aperture thick-wall metal tube, characterized in that
a cross-sectional diameter of the metal tube ranges from 30mm to 160mm, dimensional accuracy is ±0.2mm, and a ratio of an outer diameter of the metal tube to a wall thickness of the metal tube is greater than 2 to less than or equal to 20.
The small-aperture thick-wall metal tube according to claim 1, characterized in that the cross-sectional diameter of the metal tube ranges from 30mm to 100mm;
the ratio of the outer diameter of the metal tube to the wall thickness of the metal tube is greater than 2 to less than or equal to 12.
The small-aperture thick-wall metal tube according to claim 2, characterized in that the ratio of the outer diameter of the metal tube to the wall thickness of the metal tube is greater than 2 to less than or equal to 10.
The small-aperture thick-wall metal tube according to claim 1, characterized in that an inner wall and outer wall of the metal tube are free of peeling, dents, or cracks.
The small-aperture thick-wall metal tube according to any one of claims 1 to 4, characterized in that
the metal tube is made of steel, copper, aluminum, magnesium, titanium or alloy.
A preparation method for medium-small-aperture thick-wall metal tube according to any one of claims 1 to 5, characterized in that the method comprises:
(1) selecting a tube blank and cutting to length;

(2) mounting the tube blank on a feeding rack, wherein a tail end of the tube blank is tightened by a clamping device, a front end of the tube blank is supported by a supporting roller, and it is ensured that a core mold device passes through an inner hole of the tube blank;

(3) feeding the tube blank in by 5-30mm by a feeding mechanism before starting each pass at a feeding speed of 1-3m/min, and feeding the tube blank into a composite forging and rolling forming device for forming;

(4) after each forming of the tube blank in the composite forging and rolling forming device is completed, rotating the tube blank by 15-90° around a central axis of the tube blank;

(5) repeating process steps (3) and (4) until the front end of the tube blank enters a receiving rack, wherein a receiving mechanism clamps the front end of the tube blank while the feeding rack releases the tail end of the tube blank, and the tube blank continues to advance under the driving of the receiving mechanism until a whole tube blank is formed; and

(6) cooling and shearing to length.
The preparation method for the small-aperture thick-wall metal tube according to claim 6, characterized in that
in step (1), the outer diameter of the tube blank is 40-180mm and a cut length is 0.5-10m.
The preparation method for the small-aperture thick-wall metal tube according to claim 6, characterized in that
in step (3), when cold forming is carried out, the tube blank is fed and then directly fed into the composite forging and rolling forming device; when hot forming is carried out, the blank is heated to a target temperature through an induction heating device and then fed into the composite forging and rolling forming device.
The preparation method for the small-aperture thick-wall metal tube according to claim 8, characterized in that
in step (3) during the hot forming, the induction heating device is a medium-frequency induction heating coil and the target temperature range is 800-1200°C.
The preparation method for the small-aperture thick-wall metal tube according to claim 6, characterized in that
the composite forging and rolling forming device is composed of three swinging mold blocks, the mold blocks are arranged at equal intervals around the central axis of the tube blank at 120°, the mold blocks synchronously swing through a crank connecting rod mechanism driven by a motor, the mold blocks rotate around a connecting shaft thereof and simultaneously do reciprocating linear movement with the connecting shaft, straight gears connected through flat keys are mounted at two ends of the connecting shaft, and moving displacement and rotating angle of the mold are controlled by the straight gears.