Machining method and machining equipment for machining internal threads of seamless tube

Abstract

The invention provides a method for machining an internal thread on a seamless tube. The method comprises the following steps: A, putting a spinning die core into a spinning head; b, a seamless metal pipe penetrates through a gap between the spinning mold core and the spinning head; c, the seamless metal pipe is pulled in the axial direction, before pulling, the seamless metal pipe is heated, and when the seamless metal pipe enters the gap, a spinning head rotates to conduct spinning; d, the seamless metal pipe is completely pulled to pass through the spinning head, and internal threads are formed; e, solution annealing is conducted, and the metal pipe with the internal threads is obtained; by limiting the material of the spinning mold core and the shape of the spiral groove in the spinning mold core and matching with the surface smoothness and the heating spinning mode, the inner thread with the tooth height of 0.15-2.5 mm can be rolled on the inner wall of the high-hardness and high-yield-strength thin-wall seamless metal pipe with the hardness of 175-300 HV and the wall thickness of 0.4-3 mm, and high production efficiency is kept; the machining equipment for machining the internal threads of the seamless tube can well adapt to the machining method, and batch machining is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of seamless pipe processing internal spiral patterns, and in particular relates to a processing method and processing equipment for seamless pipe processing internal spiral patterns. Background Art

[0002] Internal spiral metal tubes are common heat transfer tubes. In pursuit of higher heat transfer efficiency, the wall thickness of existing internal spiral metal tubes is getting thinner and thinner. At the same time, their materials are mostly limited to copper and copper alloys. Limited by the characteristics of the material itself, the pressure resistance of this type of internal spiral metal tube will be greatly weakened as the wall thickness decreases, making it difficult to apply to efficient heat transfer of high-pressure fluids.

[0003] To solve this problem, it is necessary to change the material and use high hardness and high yield strength materials such as stainless steel and titanium alloy to make internal spiral metal tubes. However, this will greatly increase the difficulty of rolling spiral patterns on the inner wall. In particular, it is difficult to roll internal spiral patterns on seamless stainless steel tubes with small diameters (less than 12 mm), seamless titanium alloy tubes and various high-strength seamless alloy tubes. If the flat plate is rolled and then welded, it is easy to form a weak pressure-resistant area at the weld, which has limited effect on improving the pressure resistance performance.

[0004] At the same time, due to the high hardness and yield strength of the material, the higher the tooth height of the spiral pattern, the more difficult it is to roll, and the inner wall of the tube after manufacture is more likely to have hidden cracks and cracks. As a result, the tooth height of existing high-hardness, high-yield strength internal spiral metal tubes is mostly below 0.10mm, which is difficult to break through. Summary of the invention

[0005] The purpose of the present invention is to overcome one or more disadvantages in the prior art and to provide a method and equipment for processing inner spiral patterns on seamless pipes.

[0006] To achieve the above object, the method in the technical solution adopted by the present invention is a method for processing inner spiral patterns on seamless pipes, comprising the following steps: A. Place a spinning mold core with a spiral groove on its outer wall into the spinning head along the axial direction. The spinning mold core is a cylindrical tungsten steel core. The spiral grooves have multiple paths and are evenly distributed around the axis of the spinning mold core. The surface finish Ra of the inner wall of the spiral groove and the outer wall of the spinning mold core is 0.01 to 0.02 μm. B. passing a seamless metal tube having a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm through the gap between the spinning die core and the spinning head; C. pulling the seamless metal tube in the axial direction, and before pulling, heating the portion of the seamless metal tube that is about to enter the gap to a temperature of 500 to 1300° C. to reduce hardness and enhance fluidity; When the heated seamless metal tube enters the gap, the spinning head is rotated around the axial direction, and the ball in the spinning head is moved in the radial direction, so as to reduce the width of the gap to be smaller than the wall thickness of the seamless metal tube, thereby squeezing the seamless metal tube onto the spinning die core, deforming the seamless metal tube, reducing its diameter and forming teeth with a tooth height of 0.15 to 2.5 mm on its inner wall; D. pulling the entire seamless metal tube through the spinning head so that the teeth extend along the direction of the spiral groove to form an inner spiral pattern; E. Performing solution annealing treatment on the seamless metal tube pulled through the spinning head in step D to obtain the internal spiral metal tube.

[0007] Preferably, the groove bottom cross-section of the spiral groove is a first arc segment, the center of the first arc segment is located above the groove bottom, the radius of the first arc segment is 65% to 75% of the tooth height, the groove top cross-section of the spiral groove is a second arc segment, the center of the second arc segment is located below the groove top, the radius of the second arc segment is 175% to 185% of the radius of the first arc segment, and the second arc segment has a smooth transition with the first arc segment at the junction.

[0008] Further preferably, the method for making the spinning mold core comprises the following steps: S1. Blank making, manufacturing a core blank with a center hole by powder metallurgy sintering, and processing the inner diameter of the center hole and the outer diameter of the core blank to a set size; S2. Grooving, a groove extending spirally in the axial direction of the core blank is formed on the outer wall of the core blank by a first grinding wheel, the first grinding wheel is a double-beveled grinding wheel, the cross section of the groove is composed of a bottom arc segment and a straight segment connecting the outer wall of the core blank and the bottom arc segment, and the straight segments are symmetrically distributed on both sides of the bottom arc segment; S3. shaping, grinding the connection between the outer wall of the core blank and the straight section by a second grinding wheel having a larger angle than the first grinding wheel, forming a new straight section between the outer wall of the core blank and the straight section, wherein the second grinding wheel is a double-bevel grinding wheel; S4. Shaping, extruding the abrasive distributed in the viscoelastic matrix medium into the groove and toward the outer wall of the core blank through an extrusion honing machine, polishing the outer wall of the core blank and the bottom arc segment through the reciprocating motion of the abrasive along the axial direction of the core blank, and at the same time, rounding and polishing the connection between the outer wall of the core blank and the straight segment and the connection between the adjacent straight segments to form the first arc segment and the second arc segment with smooth transition, thereby obtaining the spinning core with the spiral groove.

[0009] Further preferably, during the grinding in step S3, the connection between the straight section on both sides of the bottom arc section and the outer wall of the mold core is ground synchronously, and step S3 is repeated at least twice, and the grinding wheel angle used in the latter time is greater than the grinding wheel angle used in the previous time.

[0010] Further preferably, before performing step S4, the angle between adjacent straight sections is a first angle, the angle between adjacent outer walls of the mold core and the straight section is a second angle, and the angle difference between the first angle and the second angle does not exceed ±1°.

[0011] In order to achieve the above-mentioned purpose, the product in the technical solution adopted by the present invention is a processing device for processing inner spiral patterns of seamless pipes, comprising: A machine body, wherein a spinning mechanism is provided on the machine body, and the spinning mechanism comprises a base and a spinning head rotatably arranged in the base; A mold core feeding mechanism, which is arranged at the rear of the spinning mechanism and is used to feed the spinning mold core into the spinning head from the back to the front; A material pulling mechanism, which is arranged in front of the spinning mechanism and is used to pull the end of the seamless metal pipe passing through the spinning head forward; The spinning head comprises two coaxially arranged spinning rings and a plurality of balls sandwiched between the two spinning rings. The two spinning rings can be arranged to move closer to or farther from each other. The surfaces of the spinning rings facing each other are provided with an annular groove which is in communication with the inner hole of the spinning ring. The annular groove is used to accommodate the balls. The outer groove wall of the annular groove is a conical surface. When the two spinning rings move closer to each other, the conical surface is used to resist the balls and force them to move inward to achieve spinning. The processing equipment also includes a high-frequency heating coil, which is arranged between the spinning mechanism and the core feeding mechanism and close to the entrance of the spinning mechanism. The high-frequency heating coil is used to heat the seamless metal tube entering the spinning mechanism.

[0012] Preferably, the spinning head also includes a spinning ring sleeve that can move forward and backward, and the spinning mechanism also includes a lever for driving the spinning ring sleeve to move forward and backward. The spinning ring sleeve is coaxially sleeved on the spinning ring and at least covers one of the spinning rings. The middle part of the spinning ring sleeve in the length direction is recessed, and a step that resists the spinning ring is formed on the inner wall of the spinning ring sleeve, and an annular groove is formed on the outer wall of the spinning ring sleeve. The lever extends horizontally in the front-to-back direction, and the inner end of the lever is inserted in the annular groove, and the outer end of the lever passes through the base.

[0013] Preferably, the spinning head also includes a first spring for driving the two spinning rings away from each other, the first spring is clamped between the two spinning rings and located on the outside of the annular groove, and the surfaces of the spinning rings facing each other are also provided with a receiving hole for accommodating the end of the first spring.

[0014] Preferably, the pulling mechanism includes a pulling rack, a pulling plate mounted on the pulling rack movably forward and backward, and a tube clamping unit connected to the pulling plate, the tube clamping unit includes a pair of openable and closable strip-shaped jaws, the front end portion of the strip-shaped jaws has a clamping surface extending vertically along the front and rear directions, and the clamping surface is provided with serrations. When the strip-shaped jaws are closed, the end of the seamless metal tube can be clamped by the clamping surface, and the seamless metal tube can be completely pulled through the spinning head in conjunction with the forward movement of the pulling plate.

[0015] Further preferably, the tube clamping unit also includes a tube clamping seat, an inclined groove, a matching hole, a push rod and a second spring, the tube clamping seat is connected to the upper surface of the pulling plate, the inclined groove is opened on the upper surface of the tube clamping seat and is symmetrically distributed on the left and right sides of the axis of the spinning ring, forming an eight-shaped shape that gradually opens forward and outward, the strip clamping claw can be slidably embedded in the inclined groove, the matching hole is opened on the front surface of the tube clamping seat and extends backward, the matching hole and the inclined groove penetrate, the push rod can be movably arranged in the matching hole forward and backward, when the push rod moves forward, it can push the strip clamping claw forward to slide forward and inward along the inclined groove to achieve closing, the two ends of the second spring are respectively connected to the strip clamping claw and the tube clamping seat, the second spring has a tendency to drive the strip clamping claw to open.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The processing method of internal spiral patterns on seamless tubes provided by the present invention can roll internal spiral patterns with a tooth height of 0.15 to 2.5 mm on the inner wall of a thin-walled seamless metal tube with high hardness and high yield strength and a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm, by limiting the material of the spinning die core and the shape of the spiral groove thereon, in combination with the surface finish and the heating spinning method, while maintaining a relatively high production efficiency.

[0017] The processing equipment for processing internal spiral patterns on seamless tubes provided by the present invention can adapt well to the above-mentioned processing method through a spinning head with a specific structure and in combination with a high-frequency heating coil, thereby cooperating with a spinning mold core to achieve batch processing of thin-walled internal spiral pattern metal tubes with high hardness, high yield strength, high tooth height and high pressure resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a left schematic diagram of the internal spiral pattern metal pipe processing equipment in the present invention.

[0019] Figure 2 yes Figure 1 A three-dimensional schematic diagram of the invention, wherein the high-frequency heating coil is not shown.

[0020] Figure 3 yes Figure 1 A local enlarged schematic diagram of point A in the middle.

[0021] Figure 4 yes Figure 2 A local enlarged schematic diagram of point B in the middle.

[0022] Figure 5 yes Figure 2 Schematic diagram of the spinning mechanism.

[0023] Figure 6 yes Figure 5 Schematic top view of .

[0024] Figure 7 yes Figure 6 Schematic cross-sectional view in the CC direction.

[0025] Figure 8 yes Figure 7 Schematic cross-sectional view along the DD direction.

[0026] Fig. 9 yes Figure 7 The cross-sectional view in the EE direction shows the front cover omitted.

[0027] Fig.10 yes Figure 5 A three-dimensional schematic diagram with some structures hidden.

[0028] Fig.11 yes Figure 1 A partial enlarged schematic diagram of the middle pulling mechanism.

[0029] Fig.12 yes Fig.11 A three-dimensional schematic diagram of .

[0030] Fig.13 yes Fig.12 Schematic diagram after the clamp holder cover is hidden.

[0031] Fig.14 It is a cross-sectional schematic diagram of the mold core blank after slotting in the present invention.

[0032] Fig.15 It is a schematic cross-sectional view of the mold core blank after one-time shaping in the present invention.

[0033] Fig.16 It is a schematic cross-sectional view of the mold core blank after secondary shaping in the present invention.

[0034] Fig.17 It is a cross-sectional schematic diagram of the mold core blank after being shaped in the present invention.

[0035] Fig.18 It is a schematic diagram of the grinding part when the mold core blank is shaped in the present invention.

[0036] Fig.19 yes Figure 3 A partial enlarged schematic diagram of point F in the middle.

[0037] Among them: 10. Machine body; 20. Spinning mechanism; 211. Main body; 212. Front cover; 213. Rear cover; 22. Spinning head; 221. First spinning ring; 222. Second spinning ring; 223. Ball; 224. Spinning ring sleeve; 2241. Step; 2242. Annular groove; 2243. Blind hole; 2244. Synchronous guide column; 225. First spring; 226. Annular groove; 227. Accommodating hole; 23. Support sleeve; 231. Outer sleeve; 232. Pulley; 241. Driving motor; 251. Push rod; 252. Transmission rod; 253. Transmission plate; 2531. Pin; 254. Driving cylinder; 2541. Crossbeam; 255. Matching bearing; 30. Core feeding mechanism; 31. Core rod ; 32. Support rod frame; 33. Push rod cylinder; 40. Pulling mechanism; 41. Pulling frame; 42. Pulling plate; 43. Tube clamping unit; 431. Strip clamping claw; 432. Tube clamping seat; 433. Inclined groove; 434. Matching hole; 435. Push rod; 436. Second spring; 437. Tube clamping cylinder; 441. Rack; 442. Gear; 443. Pulling motor; 50. High-frequency heating coil; 60. Spinning core; 61. Spiral groove; 611. First arc segment; 612. Second arc segment; 62. Center hole; 63. Core blank; 64. First grinding wheel; 65. Groove; 651. Bottom arc segment; 652. First straight segment; 653. Second straight segment; 654. Third straight segment; 66. Second grinding wheel; 67. Third grinding wheel. DETAILED DESCRIPTION

[0038] like Figures 1 to 19 As shown, the processing equipment for processing inner spiral patterns of seamless pipes provided by the present invention comprises a machine body 10, a spinning mechanism 20, a core feeding mechanism 30, a material pulling mechanism 40 and a high-frequency heating coil 50, wherein: The spinning mechanism 20 is arranged on the machine body 10, and the spinning mechanism 20 includes a base, a spinning head 22, a supporting sleeve 23, a first driving mechanism, and a second driving mechanism; The base includes a body 211, a front cover 212 disposed at the front end of the body 211, and a rear cover 213 disposed at the rear end of the body 211; The spinning head 22 is rotatably arranged in the front cover 212, and the spinning head 22 includes a first spinning ring 221 and a second spinning ring 222 spaced apart and coaxially arranged in the front-to-back direction, a plurality of balls 223 sandwiched between the first spinning ring 221 and the second spinning ring 222, a spinning ring sleeve 224 that can move forward and backward, and a first spring 225; the first spinning ring 221 and the second spinning ring 222 have the same inner and outer diameters, the first spinning ring 221 is located behind the second spinning ring 222, the first spinning ring 221 and the second spinning ring 222 can be arranged to move closer to or farther from each other, and the surfaces of the first spinning ring 221 and the second spinning ring 222 facing each other are provided with a groove corresponding to their inner holes The annular groove 226 is through, and the annular groove 226 is used to accommodate the ball 223. The outer groove wall of the annular groove 226 is a conical surface. When the two spinning rings are close to each other, the conical surface is used to resist the ball 223 and force it to move inward to achieve spinning. A plurality of balls 223 are evenly distributed along the axis of the first spinning ring 221 and the second spinning ring 222; the spinning ring sleeve 224 is coaxially sleeved on the first spinning ring 221 and the second spinning ring 222, and covers the two spinning rings. The middle part of the spinning ring sleeve 224 in the length direction (front and back direction) is concave inward, and a surface for resisting the first spinning ring 221 away from the second spinning ring 222 is formed on the inner wall of the spinning ring sleeve 224. A step 2241 is formed on the surface (the rear surface of the first spinning ring 221), and an annular groove 2242 is formed on the outer wall of the spinning ring sleeve 224. A blind hole 2243 is opened on the step 2241. A synchronous guide post 2244 is inserted in the blind hole 2243. The front end of the synchronous guide post 2244 extends forward and passes through the first spinning ring 221 and the second spinning ring 222 in sequence, so that the first spinning ring 221, the second spinning ring 222 and the spinning ring sleeve 224 rotate synchronously. There are multiple blind holes 2243, and the multiple blind holes 2243 are evenly distributed around the axis of the spinning ring sleeve 224; the first spring 225 is used to drive the first spinning ring 221 and the second spinning ring 222 away from each other The first spring 225 is sandwiched between the first spinning ring 221 and the second spinning ring 222 and is located on the outside of the annular groove 226. There are multiple first springs 225 and they are evenly distributed around the axis of the first spinning ring 221 and the second spinning ring 222. In the circumferential direction, the first spring 225 and the synchronous guide column 2244 are staggered. In order to prevent the first spring 225 from detaching, further, the surfaces of the first spinning ring 221 and the second spinning ring 222 facing each other are further provided with a receiving hole 227 for receiving the end of the first spring 225. The receiving hole 227 penetrates the first spinning ring 221 and the second spinning ring 222 in the thickness direction to form a fluid channel for cooling. The support sleeve 23 is inserted into the base, the front end of the support sleeve 23 is aligned with the inner hole of the first spinning ring 221, the rear end of the support sleeve 23 is connected to the rear end surface of the rear cover 213, and the support sleeve 23 is used to insert a seamless metal tube without an inner spiral pattern. A rotatable outer sleeve 231 is coaxially sleeved on the support sleeve 23, and the outer sleeve 231 extends in the front and rear directions. The rear end of the outer sleeve 231 is sleeved with a pulley 232 for driving the outer sleeve 231 to rotate. The rear end of the spinning ring sleeve 224 can be slidably sleeved on the front end of the outer sleeve 231 through the cooperation of a key and a keyway and keep synchronous rotation with the outer sleeve 231. The first driving mechanism is used to drive the pulley 232 to rotate. The first driving mechanism includes a driving motor 241 and a synchronous belt (not shown in the figure) tightened between the pulley of the output shaft of the driving motor 241 and the pulley 232. When the first motor 241 rotates, the outer sleeve 231 and the spinning ring sleeve 224 can be driven to rotate synchronously through the pulley 232, and the first spinning ring 221 and the second spinning ring 222 can be driven to rotate through the blind hole 2243 and the synchronous guide column 2244. The second driving mechanism is used to drive the first spinning ring 221 to move forward, so that the first spinning ring 221 and the second spinning ring 222 are close to each other, thereby resisting the ball 223 and forcing it to move inward, radially extruding the seamless metal tube that passes through the front end of the support sleeve 213 and enters the spinning head 22, and then cooperating with the rotation of the first spinning ring 221 and the second spinning ring 222, the ball 223 can follow the rotation of the first spinning ring 221 and the second spinning ring 222 during the extrusion process to achieve spinning. The second driving mechanism includes a lever 251, a transmission rod 252, a transmission plate 253, and a driving cylinder 254. The axis of the lever 251 is perpendicular to the axis of the spinning ring sleeve 224. The lever 251 is used to drive the spinning ring 224 to move forward and backward, so that the first spinning ring 221 moves forward. Specifically, the lever 251 extends horizontally in the left-right direction, and the inner end of the lever 251 (the end close to the spinning ring 224) is inserted into the annular groove 2242. The outer end of the lever 251 passes through the waist-shaped hole extending in the front-to-back direction of the side wall of the front cover 212 and extends outward. The transmission rod 252 extends horizontally in the front-to-back direction, and the front end of the transmission rod 252 is connected to the outer end of the lever 251. The rear end of the transmission rod 252 is embedded in the slide groove opened on the side wall of the body 211 and can be moved forward and backward. The transmission plate 253 extends in the up-down direction. The lower end portion is located at the outer side of the transmission rod 252 and is rotatably connected to the side wall of the body 211. The lower end portion of the transmission plate 253 is rotatably connected to the rear end portion of the transmission rod 252 through a pin 2531. The pin 2531 extends horizontally in the left-right direction. The pin 2531 is rotatably and slidably inserted into a waist-shaped hole extending vertically in the up-down direction and opened at the lower end portion of the transmission plate 253. The pin 2531 is located above the rotation axis of the transmission plate 253. The driving cylinder 254 is fixed to the top of the body 211. The cylinder rod of the driving cylinder 254 can be extended forward. The end of the cylinder rod is connected to a crossbeam 2541 extending horizontally in the left-right direction. The two ends of the crossbeam 2541 are connected to the transmission rod 252. The upper end of the movable plate 253 is rotatably connected. When the cylinder rod extends forward, it can drive the front end of the transmission plate 253 to rotate forward, thereby pushing the transmission rod 252 forward, driving the shift rod 251 to move forward, and driving the spin-pressing ring sleeve 224 to move forward. In order to reduce friction, the second driving mechanism further includes a matching bearing 255. The matching bearing 255 is sleeved on the inner end of the shift rod 251 and embedded in the annular groove 2242. The outer diameter of the matching bearing 255 is smaller than the groove width of the annular groove 2242. When the cylinder rod of the driving cylinder 254 retracts backward, the matching bearing 255 can abut against the rear groove wall of the annular groove 2242 to drive the spin-pressing ring sleeve 224 to move backward.

[0039] The core feeding mechanism 30 is arranged at the rear of the spinning mechanism 20. The core feeding mechanism 30 is used to feed the spinning core 60 from the back to the front into the spinning head 22. Specifically, the core feeding mechanism 30 includes a core rod 31, a support rod frame 32, and a core rod cylinder 33. The core rod 31 is a hollow round rod extending in the front-to-back direction. The front end of the core rod 31 is used to install the spinning core 60. The length of the core rod 31 is greater than the length of a single seamless metal tube. The core rod 31 can be supported on the support rod frame 32 to move forward and backward. The core rod cylinder 33 is arranged at the rear end of the support rod frame 32. The cylinder rod of the core rod cylinder 33 is connected to the rear end of the core rod 31. When the core rod cylinder 33 is actuated, it can drive the core rod 31 to move forward and backward, thereby feeding the spinning core 60 into the spinning head 22 or moving it out of the spinning head 22.

[0040] The material pulling mechanism 40 is arranged in front of the spinning mechanism 20, and is used to pull the end of the seamless metal tube passing through the spinning head 22 forward. Specifically, the material pulling mechanism 40 includes a material pulling frame 41, a material pulling plate 42 mounted on the material pulling frame 41 and movable forward and backward, a tube clamping unit 43 connected to the material pulling plate 42, and a third driving unit for moving the material pulling plate 42 forward and backward. The tube clamping unit 43 includes a pair of openable and closable strip-shaped clamping claws 431, a tube clamping seat 432, an inclined groove 433, a matching hole 434, a push rod 435, a second spring 436, and a tube clamping cylinder 437. The front end of 431 has a clamping surface extending vertically in the front-to-back direction, and a serration 4311 is arranged on the clamping surface. When the strip-shaped clamping jaws 431 are closed, the end of the seamless metal tube can be clamped by the clamping surface, and the seamless metal tube can be pulled through the spinning head 22 in coordination with the forward movement of the drawing plate 42. The tube clamping seat 432 is connected to the upper surface of the drawing plate 42, and the inclined grooves 433 are opened on the upper surface of the tube clamping seat 432 and symmetrically distributed on the left and right sides of the axis of the first spinning ring 221 and the second spinning ring 222, forming an eight-shaped shape that gradually opens forward and outward, and the strip-shaped clamping jaws 431 can be slidably embedded in the inclined grooves 433 The mating hole 434 is provided on the front surface of the clamping tube seat 432 and extends backward. The mating hole 434 penetrates the inclined groove 433. The push rod 435 is arranged in the mating hole 434 so as to be movable forward and backward. When the push rod 435 moves forward, the strip clamping claw 431 can be pushed forward to slide backward and inward along the inclined groove 433 to achieve closing. The two ends of the second spring 436 are respectively connected to the strip clamping claw 431 and the clamping tube seat 432 through the connecting column. The second spring 436 has the tendency to drive the strip clamping claw to open (move forward and outward). The clamping tube cylinder 437 is arranged on the pulling plate 42. The cylinder 437 is used to drive the push rod 435 to move forward and backward. The third driving unit includes a rack 441 provided on the pulling rack 41 and extending in the front-to-back direction, a gear 442 meshing with the rack 441, and a pulling motor 443 used to drive the gear 442 to rotate. The pulling motor 443 is installed on the pulling plate 42 and is located on one side of the rack 441. The gear 442 is mounted on the output shaft of the pulling motor 443 and rotates synchronously with the output shaft. When the pulling motor 443 is in action, it can drive the pulling plate 42 to move forward and backward relative to the pulling rack 41 through the meshing transmission of the gear 442 and the rack 441.

[0041] The high-frequency heating coil 50 is arranged between the spinning mechanism 20 and the core feeding mechanism 30, and is close to the entrance of the spinning mechanism 20. The high-frequency heating coil 50 is used to heat the seamless metal tube entering the spinning mechanism 20. Specifically, when the tube is inserted, the seamless metal tube is first sleeved on the top core rod 31, and then moved forward, passed through the high-frequency heating coil 50, and then fed into the spinning head 22 of the spinning mechanism 20.

[0042] The method for processing an inner spiral metal pipe using the above processing equipment comprises the following steps: A. Start the ejector cylinder 33 to place (send) the spinning core 60 with a spiral groove 61 on the outer wall into the spinning head 22 along the axial direction; B. Push the seamless metal tube with a hardness of 175HV to 300HV and a wall thickness of 0.4 to 3mm, which is sleeved on the top core rod 31, forward, pass through the high-frequency heating coil 50, enter the spinning mechanism 20, and pass through the gap between the spinning core 60 and the spinning head 22, so that the front end of the seamless metal tube is exposed and extends to the gap between the strip clamping jaws 431; C. Start the tube clamping cylinder 437 to clamp the front end of the seamless metal tube through the bar-shaped clamping claw 431, and then start the material pulling motor 443 to drive the material pulling plate 42 to move forward, and pull the seamless metal tube forward in the axial direction; Before pulling (before starting the material pulling motor 443), the high frequency heating coil 50 is turned on to heat the portion of the seamless metal tube that is about to enter the gap between the spinning die core 60 and the spinning head 22, so that its temperature reaches 500 to 1300°C, so as to reduce the hardness and enhance the fluidity; When the heated seamless metal tube enters the gap between the spinning die core 60 and the spinning head 22, the driving motor 241 is started to rotate the spinning head 22 around the axial direction, and the ball 223 in the spinning head 22 moves inward in the radial direction, so as to reduce the width of the gap between the spinning die core 60 and the spinning head 22 to be smaller than the wall thickness of the seamless metal tube, thereby squeezing the seamless metal tube onto the spinning die core 60, deforming the seamless metal tube, reducing its diameter and forming teeth with a tooth height of 0.15 to 2.5 mm on its inner wall; D. The pulling motor 443 is operated to pull all the seamless metal tubes through the spinning head 22, so that the teeth extend along the direction of the spiral groove 61 to form an inner spiral pattern; E. The seamless metal tube pulled through the spinning head 22 in step D is subjected to solution annealing treatment to obtain an internal spiral metal tube.

[0043] In order to improve the rolling effect of the internal spiral metal tube, in this embodiment, the spinning core 60 is a cylindrical tungsten steel core, the inclination angle of the spiral groove 61 is plus or minus 45°, the spiral groove 61 has multiple channels and is evenly distributed around the axis of the spinning core 60, the surface finish Ra of the inner wall of the spiral groove 61 and the outer wall of the spinning core 60 is 0.01 to 0.02 μm, the groove bottom section of the spiral groove 61 is a first arc segment 611, the center of the first arc segment 611 is located above the groove bottom of the spiral groove 61, and the radius of the first arc segment 611 is 65% to 75% of the above-mentioned tooth height, the groove top section of the spiral groove 61 is a second arc segment 612, the center of the second arc segment 612 is located below the groove top of the spiral groove 61, the radius of the second arc segment 612 is 175% to 185% of the radius of the first arc segment 611, and the junction of the second arc segment 612 and the first arc segment 611 is smoothly transitioned.

[0044] Furthermore, the method for manufacturing the spinning mold core 60 comprises the following steps: S1. Blank making, manufacturing a core blank 63 with a center hole 62 by powder metallurgy sintering, and processing the inner diameter of the center hole 62 and the outer diameter of the core blank 63 to a set size; S2. Grooving, a groove 65 extending spirally in the axial direction of the core blank 63 is formed on the outer wall of the core blank 63 by a first grinding wheel 64, the first grinding wheel 64 is a double-beveled grinding wheel, and the cross section of the groove 65 is composed of a bottom arc segment 651 and a first straight segment 652 connecting the outer wall of the core blank 63 and the bottom arc segment 651, and the first straight segment 652 is symmetrically distributed on both sides of the bottom arc segment 651; S3. Reshaping, grinding the outer wall of the core blank 63 and the connection of the first straight section 652 by the second grinding wheel 66 having an angle greater than that of the first grinding wheel 64, forming a second straight section 653 between the outer wall of the core blank 63 and the straight section 652, and the second grinding wheel 66 is a double bevel grinding wheel; Then, the connection between the outer wall of the mold core blank 63 and the second straight section 653 is ground by the third grinding wheel 67 having a larger angle than the second grinding wheel 66, so as to form a third straight section 654 between the outer wall of the mold core blank 63 and the second straight section 653. The third grinding wheel 67 is a double-beveled grinding wheel. S4. Shaping: The abrasive distributed in the viscoelastic matrix medium is squeezed into the groove 65 and squeezed toward the outer wall of the core blank 63 by an extrusion honing machine. The outer wall of the core blank 63 and the bottom arc segment 651 are polished (the removal amount is small, not shown in the figure) by the reciprocating motion of the abrasive along the axial direction of the core blank 63. At the same time, the connection between the outer wall of the core blank 63 and the third straight segment 654 and the connection between adjacent straight segments are rounded and polished to form a first arc segment 611 and a second arc segment 612 with a smooth transition, thereby obtaining a spinning core 60 with a spiral groove 61.

[0045] Preferably, during grinding in step S3, the connection between the first straight section 652 and the second straight section 653 on both sides of the bottom arc section 651 and the outer wall 63 of the mold core is ground synchronously. Before performing step S4, the angle between the first straight section 652 and the second straight section 653 is the first angle α, the angle between the second straight section 653 and the third straight section 654 is the second angle β, and the angle between the third straight section 654 and the outer wall of the mold core blank 63 (corresponding to the connecting line of the two ends of the third straight sections) is the third angle γ. The sizes of the first angle α, the second angle β, and the third angle γ are preferably controlled within a range of 150° to 170° to reduce the load of the extrusion honing machine during honing and improve the processing efficiency. At the same time, the angle difference between the first angle α, the second angle β, and the third angle γ does not exceed ±1° to ensure the smoothing effect between the first arc section 611 and the second arc section 612 after processing to adapt to spinning.

[0046] The processing method of internal spiral patterns on seamless tubes provided by the present invention can roll high-tooth-height internal spiral patterns with a tooth height of 0.15 to 2.5 mm on the inner wall of a thin-walled seamless metal tube with high hardness and high yield strength and a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm, by limiting the material of the spinning die core and the shape of the spiral groove thereon, in combination with the surface finish and the heating spinning method, while maintaining a relatively high production efficiency.

[0047] The processing equipment for processing internal spiral patterns on seamless tubes provided by the present invention can adapt well to the above-mentioned processing method through a spinning head with a specific structure and in combination with a high-frequency heating coil, thereby cooperating with a spinning mold core to achieve batch processing of thin-walled internal spiral pattern metal tubes with high hardness, high yield strength, high tooth height and high pressure resistance.

[0048] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for processing inner spiral patterns on seamless pipes, characterized in that: The following steps are involved: A. Place a spinning mold core with a spiral groove on its outer wall into the spinning head along the axial direction. The spinning mold core is a cylindrical tungsten steel core. The spiral grooves have multiple paths and are evenly distributed around the axis of the spinning mold core. The surface finish Ra of the inner wall of the spiral groove and the outer wall of the spinning mold core is 0.01 to 0.02 μm. B. passing a seamless metal tube having a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm through the gap between the spinning die core and the spinning head; C. pulling the seamless metal tube in the axial direction, and before pulling, heating the portion of the seamless metal tube that is about to enter the gap to a temperature of 500 to 1300° C. to reduce hardness and enhance fluidity; When the heated seamless metal tube enters the gap, the spinning head is rotated around the axial direction, and the ball in the spinning head is moved in the radial direction, so as to reduce the width of the gap to be smaller than the wall thickness of the seamless metal tube, thereby squeezing the seamless metal tube onto the spinning die core, deforming the seamless metal tube, reducing its diameter and forming teeth with a tooth height of 0.15 to 2.5 mm on its inner wall; D. pulling the seamless metal tube through the spinning head so that the teeth extend along the direction of the spiral groove to form an inner spiral pattern, and the speed of pulling the seamless metal tube is 0.4 to 0.6 m / min; E. Performing solution annealing treatment on the seamless metal tube pulled through the spinning head in step D to obtain the internal spiral metal tube.

2. The processing method according to claim 1, characterized in that: The groove bottom cross-section of the spiral groove is a first arc segment, the center of the first arc segment is located above the groove bottom, the radius of the first arc segment is 65% to 75% of the tooth height, the groove top cross-section of the spiral groove is a second arc segment, the center of the second arc segment is located below the groove top, the radius of the second arc segment is 175% to 185% of the radius of the first arc segment, and the second arc segment and the first arc segment have a smooth transition at the junction.

3. The processing method according to claim 2, characterized in that: The method for making the spinning mold core comprises the following steps: S1. Blank making, manufacturing a core blank with a center hole by powder metallurgy sintering, and processing the inner diameter of the center hole and the outer diameter of the core blank to a set size; S2. Grooving, a groove extending spirally in the axial direction of the core blank is formed on the outer wall of the core blank by a first grinding wheel, the first grinding wheel is a double-beveled grinding wheel, the cross section of the groove is composed of a bottom arc segment and a straight segment connecting the outer wall of the core blank and the bottom arc segment, and the straight segments are symmetrically distributed on both sides of the bottom arc segment; S3. shaping, grinding the connection between the outer wall of the core blank and the straight section by a second grinding wheel having a larger angle than the first grinding wheel, forming a new straight section between the outer wall of the core blank and the straight section, wherein the second grinding wheel is a double-bevel grinding wheel; S4. Shaping, extruding the abrasive distributed in the viscoelastic matrix medium into the groove and toward the outer wall of the core blank through an extrusion honing machine, polishing the outer wall of the core blank and the bottom arc segment through the reciprocating motion of the abrasive along the axial direction of the core blank, and at the same time, rounding and polishing the connection between the outer wall of the core blank and the straight segment and the connection between the adjacent straight segments to form the first arc segment and the second arc segment with smooth transition, thereby obtaining the spinning core with the spiral groove.

4. The processing method according to claim 3, characterized in that: During the grinding in step S3, the connection between the straight section on both sides of the bottom arc section and the outer wall of the mold core is ground synchronously, and step S3 is repeated at least twice, and the grinding wheel angle used in the latter time is greater than the grinding wheel angle used in the previous time.

5. The processing method according to claim 3, characterized in that: Before performing step S4, the angle between adjacent straight sections is a first angle, the angle between adjacent outer walls of the mold core and the straight section is a second angle, and the angle difference between the first angle and the second angle does not exceed ±1°.

6. A processing device for processing inner spiral patterns on seamless pipes, comprising: A machine body, wherein a spinning mechanism is provided on the machine body, and the spinning mechanism comprises a base and a spinning head rotatably arranged in the base; A mold core feeding mechanism, which is arranged at the rear of the spinning mechanism and is used to feed the spinning mold core into the spinning head from the back to the front; A material pulling mechanism, which is arranged in front of the spinning mechanism and is used to pull the end of the seamless metal pipe passing through the spinning head forward; Features: The spinning head comprises two coaxially arranged spinning rings and a plurality of balls sandwiched between the two spinning rings. The two spinning rings can be arranged to move closer to or farther from each other. The surfaces of the spinning rings facing each other are provided with an annular groove which is in communication with the inner hole of the spinning ring. The annular groove is used to accommodate the balls. The outer groove wall of the annular groove is a conical surface. When the two spinning rings move closer to each other, the conical surface is used to resist the balls and force them to move inward to achieve spinning. The processing equipment also includes a high-frequency heating coil, which is arranged between the spinning mechanism and the core feeding mechanism and close to the entrance of the spinning mechanism. The high-frequency heating coil is used to heat the seamless metal tube entering the spinning mechanism.

7. The processing equipment according to claim 6, characterized in that: The spinning head also includes a spinning ring sleeve that can move forward and backward, and the spinning mechanism also includes a lever for driving the spinning ring sleeve to move forward and backward. The spinning ring sleeve is coaxially sleeved on the spinning ring and at least covers one of the spinning rings. The middle part of the spinning ring sleeve in the length direction is recessed, and a step that abuts against the spinning ring is formed on the inner wall of the spinning ring sleeve, and an annular groove is formed on the outer wall of the spinning ring sleeve. The lever extends horizontally in the front-to-back direction, and the inner end of the lever is inserted in the annular groove, and the outer end of the lever passes through the base.

8. The processing equipment according to claim 6, characterized in that: The spinning head also includes a first spring for driving the two spinning rings away from each other. The first spring is clamped between the two spinning rings and located outside the annular groove. The surfaces of the spinning rings facing each other are also provided with a receiving hole for accommodating the end of the first spring.

9. The processing equipment according to claim 6, characterized in that: The pulling mechanism includes a pulling frame, a pulling plate mounted on the pulling frame and movably mounted forward and backward, and a tube clamping unit connected to the pulling plate, the tube clamping unit includes a pair of openable and closable strip-shaped jaws, the front end portion of the strip-shaped jaws has a clamping surface extending vertically along the forward and backward directions, and the clamping surface is provided with serrations. When the strip-shaped jaws are closed, the end of the seamless metal tube can be clamped by the clamping surface, and the seamless metal tube can be completely pulled through the spinning head in conjunction with the forward movement of the pulling plate.

10. The processing equipment according to claim 9, characterized in that: The tube clamping unit also includes a tube clamping seat, an inclined groove, a matching hole, a push rod and a second spring. The tube clamping seat is connected to the upper surface of the pulling plate. The inclined groove is opened on the upper surface of the tube clamping seat and is symmetrically distributed on the left and right sides of the axis of the spinning ring, forming an eight-shaped shape that gradually opens forward and outward. The strip clamping claw can be slidably embedded in the inclined groove, and the matching hole is opened on the front surface of the tube clamping seat and extends backward. The matching hole and the inclined groove penetrate the push rod, and the push rod can be moved forward and backward in the matching hole. When the push rod moves forward, it can push the strip clamping claw forward to slide forward and inward along the inclined groove to achieve closing. The two ends of the second spring are respectively connected to the strip clamping claw and the tube clamping seat, and the second spring has a tendency to drive the strip clamping claw to open.

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