Medium-frequency heating device for thick-wall steel pipe

Abstract

The invention provides a thick-wall steel pipe medium-frequency bent pipe heating device which comprises a medium-frequency heating ring, and the medium-frequency heating ring comprises an outer heating ring and an inner heating ring. And the outer heating ring and the inner heating ring are hollow and are provided with water injection nozzles communicated with the cavities.

Description

Technical Field

[0001] The invention belongs to the field of medium frequency pipe bending, and in particular relates to a medium frequency pipe bending heating device. Background Art

[0002] Medium frequency pipe bending is to put a medium frequency induction coil on the part of the steel pipe to be bent after cutting the straight pipe, clamp the pipe head with a mechanical rotating arm, and pass a medium frequency current into the induction coil to heat the steel pipe. When the temperature of the steel pipe rises to the plastic state, the rear end of the steel pipe is pushed forward with mechanical thrust to bend it. The bent steel pipe part is quickly cooled with a coolant. In this way, the pipe is continuously bent while heating, pushing, bending, and cooling. Hot-bent pipe bending is mainly used in many industries such as building arc steel structures, tunnel supports, roof curved beams, subway projects, aluminum doors and windows, ceilings, cylindrical inner skeletons, balcony handrails, shower room doors, production line tracks, fitness equipment, etc.

[0003] Patent CN106734426A discloses an integrated coreless pipe bending equipment, "insert the tube blank 2 from the end of the cooling water pipe 4, and fix the end of the tube blank 2 on the clamp 8, turn on the medium frequency heating device, push the end of the tube blank 2 through the propulsion device, so that it moves in the medium frequency heating device, and the induction heating ring 5 in the medium frequency heating device heats it, and the pipe bending operation is realized by cooperating with the rotation of the clamp 8. The outer cooling ring 6 welded to the induction heating ring 5 cooperates with the inner cooling ring 7 at the end of the cooling water pipe 4 to realize the cooling of the tube blank 2, thereby ensuring the quality of the bent pipe." However, for seamless steel pipes with thicker pipe walls, ordinary medium frequency heating devices cannot heat the part to be bent to the required temperature, affecting the quality of the bent pipe; and when bending the pipe, the inner arc and the outer arc have different lengths and different moving speeds, and cannot be cooled at the same time, and the cooling speed will also affect the mechanical properties of the bent pipe. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a medium-frequency bending heating device for thick-walled steel pipes.

[0005] The object of the present invention is achieved in the following manner: A medium frequency bending heating device for thick-walled steel pipes comprises a medium frequency heating coil, wherein the medium frequency heating coil comprises an outer heating coil and an inner heating coil; the outer heating coil and the inner heating coil are hollow and water is passed through, and a water spray port communicating with the cavity is arranged.

[0006] In the medium-frequency bending heating device for thick-walled steel pipes, the spacing between the water spray holes on one side of the heating ring is 1.5-3 times the spacing between the water outlet holes on the other side.

[0007] The thick-walled steel pipe medium-frequency bending heating device has a double-layer structure of the inner heating ring and the outer heating ring, including a water inlet heating ring and a water outlet heating ring; a hole connecting the cavities of the two layers of heating rings is arranged between the water inlet heating ring and the water outlet heating ring, a water spray port is arranged on the water outlet heating ring, and two water inlet pipes are connected at the notch of the water inlet heating ring; a stabilizing structure is arranged on the water inlet pipe; The thick-walled steel pipe medium-frequency bending heating device, the stabilizing structure includes bolts, insulating wood, and nuts. The bolts are welded on two water inlet pipes, the insulating wood is provided with fixing holes, the bolts pass through the fixing holes, and are tightened and fixed with nuts.

[0008] In the medium frequency bending heating device for thick-walled steel pipes, the water inlet pipe of the inner heating ring extends from the notch into the circle and then extends outward along the axial direction, and a supporting structure is arranged on the stable structure of the inner heating ring.

[0009] The thick-walled steel pipe medium-frequency bending heating device, the support structure includes a support frame, a pulley, a support rod and a stable structure are fixedly connected, and the support rod and the support pulley are hinged.

[0010] In the medium frequency bending heating device for thick-walled steel pipes, at least one auxiliary water inlet pipe is arranged on the circular ring portion of the water inlet heating ring of the outer heating ring.

[0011] Compared with the prior art, the present invention heats the tubes with thicker walls by means of two inner and outer heating rings, so that the tubes with thicker walls can reach the required bending temperature and bend the rear wall tubes; the water spray nozzles for cooling are unevenly distributed in the inner and outer arcs to ensure that the cooling speeds of the inner and outer arcs are consistent, thereby ensuring that the mechanical properties of the bent tubes meet the standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the present invention. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] like Figure 1As shown, a medium-frequency heating device for thick-walled steel pipes includes a medium-frequency heating coil, which is a hollow circular ring with a notch, including an outer heating coil 1 and an inner heating coil 2; the medium-frequency heating coil is hollow and water is passed through it, and a water spray port 11 connected to the cavity is provided. The medium-frequency heating coil heats the steel pipe by passing a medium-frequency current, so the target temperature cannot be reached when heating a thicker steel pipe. Two inner and outer heating coils are provided to heat from two directions, so that a thicker steel pipe can be heated. After heating, the steel pipe is stretched and bent, and needs to be cooled after stretching and bending. Water is passed through the hollow heating coil, and water is sprayed out from the water spray port 11 to cool the steel pipe. The temperature is high during medium-frequency heating, and passing water through the heating coil can cool the heating coil to prevent the heating coil from burning.

[0015] In the medium frequency heating device for thick-walled steel pipes, the water holes 11 are unevenly distributed on the water outlet heating ring, and the spacing between the water holes on the inner arc side is 1.5-3 times that of the water holes on the outer arc side. The medium frequency pipe bending should be stretched and bent after medium frequency heating, and then cooled and quenched. During stretching and bending, the outer arc speed is larger and cools faster, while the inner arc speed is smaller and cools slower, which will cause inconsistent cooling speeds of the inner and outer arcs, affecting the quenching of the steel pipe and further affecting the mechanical properties of the steel pipe. Therefore, the spacing between the water outlets on the inner arc side of the heating ring is smaller than the spacing between the water outlets on the outer arc side, so that the cooling speeds on both sides can be kept consistent to ensure the mechanical properties of the steel pipe.

[0016] In the medium-frequency heating device for thick-walled steel pipe, the inner heating coil 2 and the outer heating coil 1 are both double-layer structures, including a water inlet heating coil 12 and a water outlet heating coil 13; a hole connecting the cavities of the two layers of heating coils is arranged between the water inlet heating coil 12 and the water outlet heating coil 13, a water spraying port 11 is arranged on the water outlet heating coil 13, and the water inlet heating coil 12 is connected to two water inlet pipes 121; a stabilizing structure 122 is arranged on the water inlet pipe 121. When the heating coil sprays water, the water pressure of the water spraying port close to the water inlet pipe is relatively large, and the water pressure of the water spraying port far from the water inlet pipe is relatively small, so a double-layer heating coil is arranged, and the cooling water first enters the water inlet heating coil, and then enters the water outlet heating coil through the holes evenly arranged between the water inlet heating coil and the water outlet heating coil, and the water pressure difference at various places in the water outlet heating coil is relatively small, and the water pressure difference is relatively small when sprayed out from the water spraying port.

[0017] The described medium-frequency heating device for thick-walled steel pipes, the described stabilizing structure 122 includes bolts 1211, insulating wood 1212, and nuts 1213. The bolts 1211 are welded to two water inlet pipes, and the insulating wood is provided with fixing holes, through which the bolts pass, and are tightened and fixed with nuts. Since the heating coil itself is a circular ring with a notch, the notch is unstable, and the expansion or contraction of the notch will cause the circular ring to deform, affecting the heating of the medium-frequency heating coil. The water inlet pipe is connected to the notch, and a stabilizing device is provided on the water inlet pipe, so that the distance between the two water inlet pipes can be kept constant, thereby keeping the distance between the notches constant, thereby ensuring the stability of the circular ring shape. The insulating wood is used to prevent the medium-frequency heating coil from being short-circuited.

[0018] In the medium frequency heating device for thick-walled steel pipes, the water inlet pipe of the inner heating ring 2 extends from the notch into the circle, and then extends outward along the axial direction, and a support structure 123 is provided on the stable structure 122 of the inner heating ring 2. The inner heating ring is inside the steel pipe when working, so the water inlet pipe needs to extend outward to pass water and electricity. However, when the pipe is long, it is unstable and will shake up and down, changing the position of the inner heating ring in the pipe and making the heating effect poor. Setting a support structure can support the water inlet pipe to prevent the water inlet pipe from shaking up and down, ensuring that the position of the inner heating ring does not change, and ensuring a stable heating effect.

[0019] The described medium-frequency heating device for thick-walled steel pipes, the support structure 123 includes a support rod 1231 and a pulley 1232. The support rod 1231 is fixedly connected to the stabilizing structure 122, and the support rod 1231 is hinged to the support pulley 1232. The support structure arranged inside the pipeline needs to be in contact with the pipeline. When the pipeline is pushed forward, there is friction between the pipeline and the support structure. The support using support rods and support rollers can reduce friction and facilitate the forward pushing of the pipeline. Multiple groups of support rods and support rollers can be arranged inside the pipeline to ensure that the position of the heating coil is stable inside the pipeline. The support rod outside the pipeline can be fixed or the support roller can be locked to ensure that the inner heating coil will not be driven forward when the pipeline is pushed forward.

[0020] In the thick-walled steel pipe medium frequency heating device, at least one auxiliary water inlet pipe 14 is provided on the annular portion of the water inlet heating coil 12 of the outer heating coil 1. The auxiliary water inlet pipe is provided on the outer heating coil, so that the water pressure at each part of the water inlet heating coil is relatively balanced, and then the water pressure of the water outlet heating coil is relatively balanced when spraying water, and at the same time, the water inlet amount can be increased to ensure the cooling effect. Specific embodiment: For X65 seamless steel pipes with an outer diameter of 508mm and a wall thickness of 40mm, the product qualification standard is a yield strength of 450-600MPa and a Vickers hardness of less than or equal to 230HV10.

[0022] If an ordinary heating device is used, the inner diameter of the hot ring is 538mm, the width is 35mm, the water nozzle diameter is 1.5mm, the inner arc spacing is 10mm, the water spray angle is 35 degrees, the outer arc spacing is 10mm, and the water spray angle is 35 degrees. The product obtained by using this heating device has an arc starting yield strength of 457 MPa and a hardness of 265 HV10; an arc falling yield strength of 456 MPa and a hardness of 305 HV10; an inner arc yield strength of 452MPa and a hardness of 243 HV10; an outer arc yield strength of 443 MPa and a hardness of 245 HV10; a straight pipe section yield strength of 457 MPa and a hardness of 229 HV10; the yield strength is qualified, but the hardness is too large. The excessive hardness of the steel pipe will increase its brittleness, thereby reducing the toughness and impact resistance of the steel pipe. When subjected to external forces, it is easy to break or break, thereby affecting the service life of the steel pipe. Secondly, excessive hardness will also deteriorate the processing performance of the steel pipe and increase the difficulty of processing.

[0023] The invention is used to perform medium frequency pipe bending, wherein the inner diameter of the outer heating ring is 538 mm, the width is 35 mm, the outer diameter of the inner heating ring is 448 mm, the diameter of the water spray port is 1.5 mm, the inner arc spacing is 10 mm, the water spray angle is 35 degrees, the outer arc spacing is 20 mm, the water spray angle is 30 degrees, and the pipe is cooled to about 120° C. in one minute. After the pipe is bent, the arc starting yield strength of the product is 512 MPa, and the hardness is 265 HV10; the arc falling yield strength is 456 MPa, and the hardness is 305 HV10; the inner arc yield strength is 452 MPa, and the hardness is 243 HV10; the outer arc yield strength is 443 MPa, and the hardness is 245HV10; the straight pipe section yield strength is 457 MPa, and the hardness is 229 HV10; the yield strength and hardness meet the standards.

[0024] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several changes and improvements can be made without departing from the overall concept of the present invention, which should also be regarded as the scope of protection of the present invention.

Claims

1. A medium frequency bending heating device for thick-walled steel pipes, comprising a medium frequency heating coil, characterized in that: The medium frequency heating coil comprises an outer heating coil (1) and an inner heating coil (2); the outer heating coil (1) and the inner heating coil (2) are hollow and water-permeable, and are provided with water spray ports (11) communicating with the cavities.

2. A medium frequency bending heating device for thick-walled steel pipes as claimed in claim 1, characterized in that: The spacing between the water spray holes (11) on one side of the heating coil is 1.5-3 times the spacing between the water outlet holes on the other side.

3. A medium frequency bending heating device for thick-walled steel pipes as claimed in claim 1, characterized in that: The inner heating ring (2) and the outer heating ring (1) are both double-layer structures, including a water inlet heating ring (12) and a water outlet heating ring (13); a hole connecting the cavities of the two layers of heating rings is provided between the water inlet heating ring (12) and the water outlet heating ring (13); a water spray port (11) is provided on the water outlet heating ring (13); two water inlet pipes (121) are connected at the notch of the water inlet heating ring (12); and a stabilizing structure (122) is provided on the water inlet pipe (121).

4. A medium frequency bending heating device for thick-walled steel pipes as claimed in claim 3, characterized in that: The stabilizing structure (122) comprises bolts (1211), insulating wood (1212), and nuts (1213); the bolts (1211) are welded to the two water inlet pipes; the insulating wood is provided with fixing holes; the bolts pass through the fixing holes and are tightened and fixed by nuts.

5. A medium frequency bending heating device for thick-walled steel pipes as claimed in claim 3, characterized in that: The water inlet pipe of the inner heating ring (2) extends from the notch into the circle and then extends outward along the axial direction. A support structure (123) is provided on the stable structure (122) of the inner heating ring (2).

6. A medium frequency bending heating device for thick-walled steel pipes as claimed in claim 5, characterized in that: The support structure (123) comprises a support rod (1231) and a support pulley (1232); the support rod (1231) is fixedly connected to the stabilizing structure (122); and the support rod (1231) and the support pulley (1232) are hinged.

7. A medium frequency bending heating device for thick-walled steel pipes as claimed in claim 3, characterized in that: At least one auxiliary water inlet pipe (14) is provided on the annular portion of the water inlet heating coil (12) of the outer heating coil (1).

Images