A processing method and processing equipment for machining internal spiral threads on seamless pipes

Abstract

The processing method for machining internal spiral threads on seamless pipes provided by the present invention includes the following steps: A. Place the spinning mandrel into the spinning head; B. Pass the seamless metal pipe through the gap between the spinning mandrel and the spinning head; C. Pull the seamless metal pipe in the axial direction. Before pulling, heat the seamless metal pipe. When it enters the gap, rotate the spinning head for spinning; D. Pull the entire seamless metal pipe through the spinning head to form internal spiral threads; E. Perform solution annealing to obtain an internal spiral thread metal pipe; By defining the material of the spinning mandrel and the shape of the spiral groove thereon, and cooperating with the surface finish and the method of heating and spinning, internal spiral threads with a tooth height of 0.15 to 2.5 mm can be rolled on the inner wall of high-hardness and high-yield-strength thin-walled seamless metal pipes with a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm, and a relatively high production efficiency can be maintained; The processing equipment for machining internal spiral threads on seamless pipes provided by the present invention can well adapt to the above processing method and realize batch processing.

Description

Technical Field

[0001] The present invention belongs to the technical field of processing internal spiral threads of seamless pipes, and particularly relates to a processing method and processing equipment for processing internal spiral threads of seamless pipes. Background Art

[0002] Internal spiral-threaded metal pipes are common heat transfer pipes. In the pursuit of higher heat transfer efficiency, the wall thickness of existing internal spiral-threaded metal pipes is getting thinner and thinner. At the same time, their materials are mostly limited to copper and copper alloys. Due to the limitations of the characteristics of the materials themselves, the pressure resistance performance of such internal spiral-threaded metal pipes will be greatly weakened as the wall thickness decreases, and it is difficult to be applied to the efficient heat transfer of high-pressure fluids.

[0003] To solve this problem, it is necessary to replace the material and use materials with high hardness and high yield strength such as stainless steel and titanium alloy to make internal spiral-threaded metal pipes. However, in this way, the difficulty of rolling spiral threads on their inner walls will be greatly increased. In particular, it is difficult to achieve rolling internal spiral threads for seamless stainless steel pipes, seamless titanium alloy pipes with a small diameter (less than 12 mm), and various high-strength seamless alloy pipes. If the method of using flat rolling teeth and then butt welding is adopted, it is easy to form a pressure-resistant weak area at the weld, and the effect of improving the pressure resistance performance is limited.

[0004] At the same time, due to the high hardness and high yield strength of the material, the higher the tooth height of the spiral thread, the greater the rolling difficulty, and the inner wall of the pipe after being made is more likely to appear hidden cracks, cracks and other phenomena. As a result, the tooth height of existing internal spiral-threaded metal pipes with high hardness and high yield strength is mostly below 0.10 mm, and it is difficult to break through. Summary of the Invention

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

[0006] To achieve the above purpose, the method in the technical solution adopted by the present invention is a processing method for processing internal spiral threads of seamless pipes, including the following steps:

[0007] A. Place a spinning die core with spiral grooves on its outer wall axially into the spinning head. The spinning die core is a cylindrical tungsten steel core. There are multiple spiral grooves evenly distributed around the axis of the spinning die core. The surface roughness Ra of the inner wall of the spiral groove and the outer wall of the spinning die core is 0.01 to 0.02 μm;

[0008] B. Pass a seamless metal pipe with 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;

[0009] C. Pull the seamless metal tube in the axial direction. Before pulling, heat the part of the seamless metal tube that is about to enter the gap so that its temperature reaches 500 to 1300 °C to reduce hardness and enhance fluidity.

[0010] When the heated seamless metal tube enters the gap, make the spinning head rotate around the axial direction and make the balls in the spinning head move in the radial direction to narrow the width of the gap to less 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.

[0011] D. Pull the entire seamless metal tube through the spinning head so that the teeth extend along the direction of the spiral groove to form internal spiral threads.

[0012] E. Perform solution annealing on the seamless metal tube pulled through the spinning head in step D to obtain the internal spiral thread metal tube.

[0013] Preferably, the bottom cross-section of the spiral groove is a first arc segment, the center of the first arc segment is located above the bottom of the groove, the radius of the first arc segment is 65% to 75% of the tooth height, the top cross-section of the spiral groove is a second arc segment, the center of the second arc segment is located below the top of the groove, the radius of the second arc segment is 175% to 185% of the radius of the first arc segment, and the connection between the second arc segment and the first arc segment is smoothly transitioned.

[0014] Further preferably, the manufacturing method of the spinning die core includes the following steps:

[0015] S1. Blank making, manufacture a die core blank with a central hole by powder metallurgy sintering, and process the inner diameter of the central hole and the outer diameter of the die core blank to the set dimensions.

[0016] S2. Grooving, open a groove that spirally extends along the axial direction of the die core blank on the outer wall of the die core blank by a first grinding wheel. The first grinding wheel is a double bevel grinding wheel. The cross-section of the groove is composed of a bottom arc segment and straight segments connecting the outer wall of the die core blank and the bottom arc segment. The straight segments are symmetrically distributed on both sides of the bottom arc segment.

[0017] S3. Shaping, grind the connection between the outer wall of the die core blank and the straight segment by a second grinding wheel with an angle greater than the first grinding wheel to form a new straight segment between the outer wall of the die core blank and the straight segment. The second grinding wheel is a double bevel grinding wheel.

[0018] 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.

[0019] 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.

[0020] 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°.

[0021] 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:

[0022] 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;

[0023] 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;

[0024] 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;

[0025] 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.

[0026] 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.

[0027] Preferably, the spinning head further includes a spinning ring sleeve that can move back and forth. The spinning mechanism further includes a lever for driving the spinning ring sleeve to move back and forth. The spinning ring sleeve is coaxially sleeved on the spinning ring and covers at least one of the spinning rings. The middle of the spinning ring sleeve in the length direction is recessed, forming a step on the inner wall of the spinning ring sleeve that abuts against the spinning ring, and forming an annular groove on the outer wall of the spinning ring sleeve. The lever extends horizontally in the front-back direction, and the inner end of the lever is inserted into the annular groove, and the outer end of the lever penetrates through the base.

[0028] Preferably, the spinning head further 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 is located outside the annular groove. A receiving hole for receiving the end of the first spring is further provided on the opposing surfaces of the spinning rings.

[0029] Preferably, the material pulling mechanism includes a material pulling frame, a material pulling plate movably mounted on the material pulling frame in the front-back direction, and a pipe clamping unit connected to the material pulling plate. The pipe clamping unit includes a pair of openable and closable strip-shaped clamping jaws. The front end of the strip-shaped clamping jaws has a clamping surface extending vertically in the front-back direction. Teeth are provided on the clamping surface. When the strip-shaped clamping jaws are closed, the end of the seamless metal pipe can be clamped through the clamping surface, and the seamless metal pipe can be completely pulled through the spinning head in cooperation with the forward movement of the material pulling plate.

[0030] Further preferably, the pipe clamping unit further includes a pipe clamping seat, an inclined groove, a matching hole, a push rod and a second spring. The pipe clamping seat is connected to the upper surface of the material pulling plate. The inclined groove is opened on the upper surface of the pipe clamping seat and is symmetrically distributed on the left and right sides of the axis of the spinning ring, forming an eight-shaped gradually opening forward and outward. The strip-shaped clamping jaws are slidably embedded in the inclined groove. The matching hole is opened on the front surface of the pipe clamping seat and extends backward. The matching hole penetrates through the inclined groove. The push rod is movably inserted through the matching hole in the front-back direction. When the push rod moves forward, it can push the strip-shaped clamping jaws forward, causing them 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-shaped clamping jaws and the pipe clamping seat, and the second spring has a tendency to drive the strip-shaped clamping jaws to open.

[0031] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0032] The processing method for internal spiral threads of seamless pipes provided by the present invention can roll internal spiral threads with a tooth height of 0.15 to 2.5 mm on the inner wall of thin-walled seamless metal pipes with a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm, while maintaining a high production efficiency, by defining the material of the spinning die core and the shape of the spiral grooves thereon, and cooperating with the surface finish and hot spinning method.

[0033] The processing equipment for internal spiral threads of seamless pipes provided by the present invention can well adapt to the above processing method through a spinning head with a specific structure and in cooperation with a high-frequency heating coil, so as to realize the batch processing of thin-walled internal spiral thread metal pipes with high hardness, high yield strength, high tooth height and high pressure resistance performance in cooperation with the spinning die core. Description of the Drawings

[0034] Figure 1 It is a left view schematic diagram of the processing equipment for internal spiral thread metal pipes in the present invention.

[0035] Figure 2 It is Figure 1 a three-dimensional schematic diagram of, with the high-frequency heating coil not shown.

[0036] Figure 3 It is Figure 1 a partial enlarged schematic diagram at A in.

[0037] Figure 4 It is Figure 2 a partial enlarged schematic diagram at B in.

[0038] Figure 5 It is Figure 2 a three-dimensional schematic diagram of the spinning mechanism in.

[0039] Figure 6 It is Figure 5 a top view schematic diagram of.

[0040] Figure 7 It is Figure 6 a sectional view schematic diagram in the C-C direction in.

[0041] Figure 8 It is Figure 7 a sectional view schematic diagram in the D-D direction in.

[0042] Figure 9 It is Figure 7 a sectional view schematic diagram in the E-E direction in, with the front cover removed.

[0043] Figure 10 It is Figure 5 a three-dimensional schematic diagram of with some structures removed.

[0044] Figure 11 It is Figure 1Partial enlarged schematic diagram of the middle material pulling mechanism.

[0045] Figure 12 is Figure 11 a three-dimensional schematic diagram of...

[0046] Figure 13 is Figure 12 a schematic diagram after hiding the cover plate of the pipe clamping seat.

[0047] Figure 14 is a cross-sectional schematic diagram of the die core blank after grooving in the present invention.

[0048] Figure 15 is a cross-sectional schematic diagram of the die core blank after the first shaping in the present invention.

[0049] Figure 16 is a cross-sectional schematic diagram of the die core blank after the second shaping in the present invention.

[0050] Figure 17 is a cross-sectional schematic diagram of the die core blank after sizing in the present invention.

[0051] Figure 18 is a schematic diagram of the grinding part during the sizing of the die core blank in the present invention.

[0052] Figure 19 is Figure 3 a partial enlarged schematic diagram at position F in...

[0053] Wherein: 10. Machine body; 20. Spinning mechanism; 211. 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 post; 225. First spring; 226. Annular groove; 227. Accommodating hole; 23. Support sleeve; 231. Outer sleeve; 232. Pulley; 241. Driving motor; 251. Lever; 252. Transmission rod; 253. Transmission plate; 2531. Pin shaft; 254. Driving cylinder; 2541. Cross beam; 255. Matching bearing; 30. Die core feeding mechanism; 31. Core ejector rod; 32. Bracing frame; 33. Ejector rod cylinder; 40. Material pulling mechanism; 41. Material pulling frame; 42. Material pulling plate; 43. Pipe clamping unit; 431. Strip-shaped jaw; 432. Pipe clamping seat; 433. Inclined groove; 434. Matching hole; 435. Ejector rod; 436. Second spring; 437. Pipe clamping cylinder; 441. Rack; 442. Gear; 443. Material pulling motor; 50. High-frequency heating coil; 60. Spinning die core; 61. Spiral groove; 611. First arc segment; 612. Second arc segment; 62. Central hole; 63. Die 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 implementation mode

[0054] As Figures 1 to 19 shown, the processing equipment for inner spiral threads of seamless pipes provided by the present invention includes a machine body 10, a spinning mechanism 20, a die core feeding mechanism 30, a material pulling mechanism 40 and a high-frequency heating coil 50, wherein:

[0055] The spinning mechanism 20 is arranged on the machine body 10, and the spinning mechanism 20 includes a base, a spinning head 22, a support sleeve 23, a first driving mechanism and a second driving mechanism;

[0056] The base includes a body 211, a front cover 212 covering the front end of the body 211 and a rear cover 213 covering the rear end of the body 211;

[0057] 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.

[0058] The support sleeve 23 is inserted through 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 face of the rear cover 213. A seamless metal tube without rolled internal spiral threads is arranged to pass through the support sleeve 23. A rotatable outer sleeve 231 is coaxially sleeved on the support sleeve 23. The outer sleeve 231 extends in the front-rear direction. A pulley 232 for driving the outer sleeve 231 to rotate is sleeved on the rear end of the outer sleeve 231. The rear end of the spinning ring sleeve 224 is slidably sleeved on the front end of the outer sleeve 231 through the cooperation of a key and a keyway and rotates synchronously with the outer sleeve 231;

[0059] 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) tensioned between the pulley on the output shaft of the driving motor 241 and the pulley 232. When the first motor 241 rotates, it can drive the outer sleeve 231 and the spinning ring sleeve 224 to rotate synchronously through the pulley 232, and drive the first spinning ring 221 and the second spinning ring 222 to rotate through the action of the blind hole 2243 and the synchronous guide post 2244;

[0060] 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 approach each other, thereby pressing against the ball 223 and forcing it to move inward, and radially extruding the seamless metal tube that passes through the front end of the support sleeve 213 and enters the spinning head 22. Then, in cooperation with the rotation of the first spinning ring 221 and the second spinning ring 222, the ball 223 can rotate following 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 line of the lever 251 is perpendicular to and intersects with the axis line of the spinning ring sleeve 224. The lever 251 is used to drive the spinning ring sleeve 224 to move back and forth, so as to make the first spinning ring 221 move forward. Specifically, the lever 251 extends horizontally in the left-right direction. The inner end (the end close to the spinning ring sleeve 224) of the lever 251 is inserted into the annular groove 2242. The outer end of the lever 251 penetrates through the waist-shaped hole extending in the front-back direction on the side wall of the front cover 212 and extends outward. The transmission rod 252 extends horizontally in the front-back direction. 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 movably embedded in the chute opened on the side wall of the main body 211. The transmission plate 253 extends in the up-down direction. The lower end of the transmission plate 253 is located outside the transmission rod 252 and is rotatably connected to the side wall of the main body 211. The lower end of the transmission plate 253 is rotatably connected to the rear end of the transmission rod 252 through a pin shaft 2531. The pin shaft 2531 extends horizontally in the left-right direction. The pin shaft 2531 is rotatably and slidably inserted into the waist-shaped hole extending vertically in the up-down direction opened at the lower end of the transmission plate 253. The pin shaft 2531 is located above the rotation axis line of the transmission plate 253. The driving cylinder 254 is fixed on the top of the main body 211. The cylinder rod of the driving cylinder 254 is arranged to be able to extend forward. The end of the cylinder rod is connected with a cross beam 2541 extending horizontally in the left-right direction. The two ends of the cross beam 2541 are rotatably connected to the upper end of the transmission plate 253. 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 lever 251 to move forward, and driving the spinning ring sleeve 224 to move forward. To reduce friction, further, the second driving mechanism also includes a mating bearing 255. The mating bearing 255 is sleeved on the inner end of the lever 251 and is embedded in the annular groove 2242. The outer diameter of the mating bearing 255 is smaller than the groove width of the annular groove 2242. When the cylinder rod of the driving cylinder 254 retracts backward, it can abut against the rear groove wall of the annular groove 2242 through the mating bearing 255 to drive the spinning ring sleeve 224 to move backward.

[0061] The die core feeding mechanism 30 is arranged behind the spinning mechanism 20. The die core feeding mechanism 30 is used to feed the spinning die core 60 from the rear to the front into the spinning head 22. Specifically, the die core feeding mechanism 30 includes a core pushing rod 31, a support rod frame 32, and a push rod cylinder 33. The core pushing rod 31 is a hollow round rod extending in the front-rear direction. The front end of the core pushing rod 31 is used to install the spinning die core 60. The length of the core pushing rod 31 is greater than the length of a single seamless metal tube. The core pushing rod 31 is supported by the support rod frame 32 so as to be movable back and forth. The push rod cylinder 33 is arranged at the rear end of the support rod frame 32. The cylinder rod of the push rod cylinder 33 is connected to the rear end of the core pushing rod 31. When the push rod cylinder 33 operates, it can drive the core pushing rod 31 to move back and forth, so as to feed the spinning die core 60 into the spinning head 22 or move it out of the spinning head 22.

[0062] The material pulling mechanism 40 is arranged in front of the spinning mechanism 20. The material pulling mechanism 40 is used to pull forward the end of the seamless metal tube passing through the spinning head 22. Specifically, the material pulling mechanism 40 includes a material pulling frame 41, a material pulling plate 42 movably mounted on the material pulling frame 41 in the front and rear directions, a pipe clamping unit 43 connected to the material pulling plate 42, and a third driving unit for moving the material pulling plate 42 in the front and rear directions. The pipe clamping unit 43 includes a pair of openable and closable strip-shaped clamping jaws 431, a pipe clamping seat 432, an inclined groove 433, a mating hole 434, a push rod 435, a second spring 436, and a pipe clamping cylinder 437. The front end of the strip-shaped clamping jaw 431 has a clamping surface vertically extending in the front and rear directions. Serrations 4311 are provided on the clamping surface. When the strip-shaped clamping jaws 431 are closed, the end of the seamless metal tube can be clamped through the clamping surface, and in cooperation with the forward movement of the material pulling plate 42, the seamless metal tube can be completely pulled through the spinning head 22. The pipe clamping seat 432 is connected to the upper surface of the material pulling plate 42. The inclined groove 433 is opened on the upper surface of the pipe 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 gradually opening forward and outward. The strip-shaped clamping jaws 431 are slidably embedded in the inclined groove 433. The mating hole 434 is opened on the front surface of the pipe clamping seat 432 and extends backward. The mating hole 434 penetrates the inclined groove 433. The push rod 435 is movably inserted through the mating hole 434. When the push rod 435 moves forward, it can push the strip-shaped clamping jaws 431 forward, causing them 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-shaped clamping jaws 431 and the pipe clamping seat 432 through connecting columns. The second spring 436 has a tendency to drive the strip-shaped clamping jaws to open (move forward and outward). The pipe clamping cylinder 437 is arranged on the material pulling plate 42. The pipe clamping cylinder 437 is used to drive the push rod 435 to move back and forth. The third driving unit includes a rack 441 arranged on the material pulling frame 41 and extending in the front and rear directions, a gear 442 meshing with the rack 441, and a material pulling motor 443 for driving the gear 442 to rotate. The material pulling motor 443 is installed on the material pulling plate 42 and is located on one side of the rack 441. The gear 442 is sleeved on the output shaft of the material pulling motor 443 and rotates synchronously with it. When the material pulling motor 443 operates, it can drive the material pulling plate 42 to move back and forth relative to the material pulling frame 41 through the meshing transmission between the gear 442 and the rack 441.

[0063] The high-frequency heating coil 50 is arranged between the spinning mechanism 20 and the die core feeding mechanism 30 and is close to the inlet 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, during pipe threading, first, the seamless metal tube is sleeved on the top core rod 31, and then it is moved forward, passed through the high-frequency heating coil 50, and then fed into the spinning head 22 of the spinning mechanism 20.

[0064] The processing method for processing the internal spiral thread metal tube using the above processing equipment includes the following steps:

[0065] A. Start the ejector rod cylinder 33 and place (feed) the spinning die core 60 with a spiral groove 61 on its outer wall into the spinning head 22 along the axial direction;

[0066] B. Push forward the seamless metal tube with a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm sleeved on the core rod 31, so that it passes through the high-frequency heating coil 50 and enters the spinning mechanism 20, and passes through the gap between the spinning die 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-shaped jaws 431;

[0067] C. Start the pipe clamping cylinder 437, clamp the front end of the seamless metal tube with the strip-shaped jaws 431, and then start the pulling motor 443 to drive the pulling plate 42 to move forward and pull the seamless metal tube forward along the axial direction;

[0068] Before pulling (before starting the pulling motor 443), turn on the high-frequency heating coil 50 to heat the part 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 to reduce the hardness and enhance the fluidity;

[0069] When the heated seamless metal tube enters the gap between the spinning die core 60 and the spinning head 22, start the drive motor 241 to make the spinning head 22 rotate around the axial direction, and make the balls 223 in the spinning head 22 move inward in the radial direction to narrow the width of the gap between the spinning die core 60 and the spinning head 22 to less than the wall thickness of the seamless metal tube, so as to squeeze 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;

[0070] D. Through the action of the pulling motor 443, pull the seamless metal tube completely through the spinning head 22, so that the above-mentioned teeth extend along the direction of the spiral groove 61 to form internal spiral threads;

[0071] E. Perform solution annealing treatment on the seamless metal tube pulled through the spinning head 22 in step D to obtain an internal spiral thread metal tube.

[0072] To improve the rolling effect of the internally helically threaded metal tube, in this embodiment, the spinning die core 60 is a cylindrical tungsten carbide core, the inclination angle of the spiral groove 61 is ±45°, there are multiple spiral grooves 61 which are evenly distributed around the axis of the spinning die core 60, the surface roughness Ra of the inner wall of the spiral groove 61 and the outer wall of the spinning die core 60 is 0.01 to 0.02 μm, the bottom cross-section of the spiral groove 61 is a first arc segment 611, the center of the first arc segment 611 is located above the bottom of the spiral groove 61, the radius of the first arc segment 611 is 65% to 75% of the above-mentioned tooth height, the top cross-section of the spiral groove 61 is a second arc segment 612, the center of the second arc segment 612 is located below the 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 connection between the second arc segment 612 and the first arc segment 611 is smoothly transitioned.

[0073] Further, the manufacturing method of the above-mentioned spinning die core 60 includes the following steps:

[0074] S1. Blank making, a die core blank 63 with a central hole 62 is made by powder metallurgy sintering, and the inner diameter of the central hole 62 and the outer diameter of the die core blank 63 are processed to the set dimensions;

[0075] S2. Grooving, a groove 65 that spirally extends along the axial direction of the die core blank 63 is opened on the outer wall of the die core blank 63 by a first grinding wheel 64. The first grinding wheel 64 is a double bevel grinding wheel. 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 die core blank 63 and the bottom arc segment 651. The first straight segment 652 is symmetrically distributed on both sides of the bottom arc segment 651;

[0076] S3. Shaping, the connection between the outer wall of the die core blank 63 and the first straight segment 652 is ground by a second grinding wheel 66 with an angle greater than that of the first grinding wheel 64, and a second straight segment 653 is formed between the outer wall of the die core blank 63 and the straight segment 652. The second grinding wheel 66 is a double bevel grinding wheel;

[0077] Then, the connection between the outer wall of the die core blank 63 and the second straight segment 653 is ground by a third grinding wheel 67 with an angle greater than that of the second grinding wheel 66, and a third straight segment 654 is formed between the outer wall of the die core blank 63 and the second straight segment 653. The third grinding wheel 67 is a double bevel grinding wheel;

[0078] S4. Shaping: The abrasive distributed in the viscoelastic matrix medium is extruded into the groove 65 and towards the outer wall of the mandrel blank 63 by an abrasive flow machining machine. Through the reciprocating movement of the abrasive along the axial direction of the mandrel blank 63, the outer wall and the bottom arc section 651 (with less removal amount, not shown in the figure) of the mandrel blank 63 are polished. Meanwhile, the connection between the outer wall of the mandrel blank 63 and the third straight section 654 and the connections between adjacent straight sections are rounded and polished to form a smoothly transitioning first arc section 611 and second arc section 612, and a spinning mandrel 60 with a spiral groove 61 is obtained.

[0079] Preferably, during the grinding in step S3, the connections 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 of the mandrel 63 are ground synchronously. Before 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 mandrel blank 63 (corresponding to the connection line of the ends of two third straight sections) is the third angle γ. The magnitudes of the first angle α, the second angle β, and the third angle γ are preferably controlled within 150° to 170° to reduce the load during the honing of the abrasive flow machining machine and improve the processing efficiency. Meanwhile, the angular difference between the first angle α, the second angle β, and the third angle γ does not exceed ±1° to ensure the smoothness between the first arc section 611 and the second arc section 612 after processing and adapt to spinning.

[0080] The processing method for the internal spiral thread of seamless pipes provided by the present invention, through the limitation of the spinning mandrel material and the shape of the spiral groove thereon, in combination with the surface finish and the hot spinning method, can roll high-tooth-height internal spiral threads with a tooth height of 0.15 to 2.5 mm on the inner wall of thin-walled seamless metal pipes with a hardness of 175 HV to 300 HV and a wall thickness of 0.4 to 3 mm, and maintain a high production efficiency.

[0081] The processing equipment for the internal spiral thread of seamless pipes provided by the present invention, through a spinning head with a specific structure and in combination with a high-frequency heating coil, can well adapt to the above processing method, and thus cooperate with the spinning mandrel to achieve the batch processing of thin-walled internal spiral thread metal pipes with high hardness, high yield strength, high tooth height, and high pressure resistance.

[0082] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within 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.

Images