Seamless metal composite pipe direct hot-charging rolling composite equipment and method

Abstract

This invention provides a direct hot-rolling composite equipment and method for seamless metal composite tubes, including a heating furnace, a first feeder, a skew rolling piercing mill, a piercing device, an intermediate feeder, an online heating device, and a three-roll skew rolling mill unit. Solid bar billets are heated in the heating furnace and then conveyed to the skew rolling piercing mill via the first feeder. The piercing device inserts a mandrel into the inner tube and delivers the mandrel, fitted with the inner tube, to the piercing position of the skew rolling piercing mill, where a mandrel is installed. The skew rolling piercing mill performs piercing rolling to obtain the outer tube, which then passes through the mandrel and wraps around the inner tube to obtain the composite tube billet. The intermediate feeder delivers the billet to the three-roll skew rolling mill unit for three-roll skew rolling composite processing. This invention utilizes skew rolling piercing equipment to produce seamless metal composite tube billets simultaneously with piercing, realizing the preparation of seamless metal composite tubes from solid bar billets on a single production line. The preparation process is simple and convenient, shortens the process flow, improves production efficiency, and reduces costs.

Description

Technical Field

[0001] This invention relates to the field of seamless metal composite tube manufacturing technology, specifically to a direct hot-rolling composite equipment and method for seamless metal composite tubes. Background Technology

[0002] Seamless metal composite pipes possess the properties of both metals, combining the advantages of each component and saving precious metal materials. Due to their superior comprehensive performance, seamless metal composite pipes are widely used in aerospace, rail transportation, petrochemical, defense, and marine engineering, promoting the development of major national science and technology projects such as lightweight and green equipment.

[0003] Seamless metal composite tubes, with fewer interfaces and better stability, have become a future development trend due to their superior performance and high cost-effectiveness. Due to their stable process and high production efficiency, rolling composite method has become one of the most promising technologies for manufacturing seamless metal composite tubes. Among them, the three-roll skew rolling composite process can achieve continuous forming of seamless metal composite tubes, producing high-performance tubes. However, this process requires finished tubes for assembly, resulting in high costs. Furthermore, it is limited by the diameter and wall thickness of the finished tubes, making it impossible to achieve full-size assembly. In addition, the larger the gap between the inner and outer tubes during assembly, the more detrimental it is to interfacial bonding and ensuring the uniformity of the circumferential wall thickness of the composite tube. Therefore, assembly often uses interference or transition fitting methods, which significantly increases the difficulty of assembling large aspect ratio tubes. To ensure high interfacial bonding strength, the surfaces to be bonded must be cleaned and polished before assembly. Cleaning the inner surface of the outer tube is particularly difficult, time-consuming, and labor-intensive, greatly reducing production efficiency. In addition, before the three-roll skew rolling composite, the composite tube blank needs to be heated as a whole. When rolling a long tube, the length of the heating furnace is also required to be higher, which greatly increases the energy consumption.

[0004] To address the problems existing in the three-roll skew rolling seamless metal composite tubes mentioned above, developing a low-cost and high-efficiency manufacturing method is of great significance for the industrial mass production of seamless metal composite tubes. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a direct hot-rolling composite equipment and method for seamless metal composite tubes. This method utilizes a skew rolling piercing device to prepare a composite tube blank for the production of seamless metal composite tubes while piercing. The preparation of seamless metal composite tubes from solid bar blanks is realized on a single production line. The preparation process is simple and convenient, significantly shortening the process flow and improving production efficiency.

[0006] This invention provides a direct hot-loading composite rolling equipment for seamless metal composite tubes, comprising a heating furnace, a first feeder, a skew rolling mill, a piercing device, an intermediate feeder, an online heating device, a three-roll skew rolling mill, and a second feeder arranged sequentially. The heating furnace heats the solid bar billet. The first feeder transports the heated solid bar billet to the skew rolling mill. The piercing device inserts a mandrel into the inner tube and then sends the mandrel with the inner tube to the piercing position of the skew rolling mill to install the mandrel. The skew rolling mill pierces and rolls the heated solid bar billet to obtain the outer tube, which then passes through the mandrel and wraps around the inner tube for direct hot loading to obtain the composite tube blank. The intermediate feeder transports the composite tube blank to the inlet of the three-roll skew rolling mill. The three-roll skew rolling mill uses the online heating device to heat the composite tube blank, inserts a mandrel, and performs three-roll skew rolling composite rolling. The second feeder delivers the seamless metal composite tube to the next process.

[0007] The piercing device includes a mandrel, a push rod, a tube stopper, an inner tube receiving trough, a guide rail, and a piercing trolley arranged sequentially along the piercing axis. The piercing trolley is placed on the guide rail. The mandrel and push rod have air supply pipes inside, and the mandrel has air outlets evenly arranged around its circumference. The tube stopper includes a base and a fully automatic three-jaw chuck. The fully automatic three-jaw chuck is fixed on the base and can adjust the diameter of the tube stopper's hole. The inner tube receiving trough is used to hold the surface-treated inner tube.

[0008] Insert the push rod into the inner tube so that the inner tube is fitted onto the push rod. During this process, adjust the diameter of the tube stopper to be smaller than the outer diameter of the inner tube to prevent the inner tube from sliding forward when the push rod is inserted.

[0009] After the push rod is inserted into the inner tube, the diameter of the hole of the tube stopper is adjusted to be larger than the outer diameter of the inner tube. Then the inner tube with the push rod is sent to the piercing position of the skew rolling mill and the mandrel is installed.

[0010] The inner end of the top head has a recessed hole in the middle, and multiple top head protrusions are evenly arranged on the side wall of the recessed hole. The outer surface of the top head protrusions is on the same horizontal plane as the outer surface of the top head. The outer surface of the inner end of the top head has top head magnetic suction posts evenly arranged in the same number and corresponding positions as the top head protrusions. The outer end of the top rod has a protrusion that can extend into the recessed hole in the middle. Multiple top rod protrusions are evenly arranged on the outer surface of the protrusion. The top head protrusion can extend into the groove between two adjacent top rod protrusions. There is a top rod magnetic suction post that cooperates with the top head magnetic suction post between two adjacent top rod protrusions. After the top head protrusion is inserted into the groove between two top rod protrusions, the top head is rotated to make the top head magnetic suction post contact the top rod magnetic suction post to complete the top head installation.

[0011] After the mandrel is installed, the heated solid bar billet is pierced and rolled to obtain the outer tube. The outer tube passes through the mandrel and wraps around the inner tube, directly hot-fitting it to obtain the composite tube blank. Then, the mandrel is rotated to misalign the mandrel magnetic column with the mandrel rod magnetic column. The mandrel is then rotated upward to separate the mandrel from the mandrel rod, and the mandrel rod is pulled out from the composite tube blank. During this process, the diameter of the tube stopper is adjusted to be between the diameter of the mandrel rod and the outer diameter of the inner tube to prevent the inner tube from sliding backward during piercing. After the composite tube blank is obtained by piercing and rolling, the mandrel rod can be pulled out from the inside of the composite tube blank, and the inner tube is prevented from being pulled out with the mandrel rod.

[0012] Preferably, the online temperature compensation device includes an electromagnetic induction coil and an infrared thermometer, both of which are arranged on the rolling axis of the three-roll skew mill.

[0013] Preferably, the fully automatic three-jaw chuck includes a drive unit, a chuck body, and three jaws arranged circumferentially at 120° intervals. The drive unit drives the three jaws to move synchronously to achieve stepless adjustment of the diameter of the tube stopper's orifice.

[0014] Depending on the outer diameter of the inner tube, the fully automatic three-jaw chuck can adjust the diameter of the tube stopper hole to prepare blanks of different sizes of tubes, and to limit the movement of the push rod when it enters the inner tube, when the solid bar blank is pierced and fitted into the inner tube, and when the push rod is pulled out of the composite tube blank.

[0015] Preferably, there are three of each of the top head boss and the top rod boss, the top head boss is elongated and the top rod boss is L-shaped.

[0016] Preferably, during piercing rolling, both the inner and outer tubes are in a high-temperature state after being assembled. Inert protective gas is introduced into the gas supply pipe of the mandrel and sprayed out from the gas outlet of the mandrel to cool the mandrel and the composite tube blank. The inert protective gas is used to prevent oxidation of the inner surface of the outer tube and the outer surface of the inner tube in the high-temperature state obtained by piercing rolling.

[0017] Preferably, the diameter of the mandrel is equal to or greater than the outer diameter of the inner tube, so that the outer tube obtained by piercing and rolling can cover the inner tube.

[0018] On the other hand, the present invention also provides a method for direct hot-charging and composite forming of seamless metal composite tubes, which includes the following steps:

[0019] S1. Solid bar billet heating: The solid bar billet is placed in a heating furnace and heated to the temperature required for piercing and held at that temperature for subsequent piercing rolling to prepare the outer tube;

[0020] S2. Inserting the push rod into the inner tube: Prepare the inner tube and perform surface treatment. Feed it into the inner tube receiving slot of the piercing device through the feeding rack. Use the drive unit to drive the jaws of the fully automatic three-jaw chuck to move forward synchronously, so that the diameter of the tube stopper's hole is smaller than the outer diameter of the inner tube to restrict the inner tube from sliding forward. The piercing carriage connected to the push rod moves forward and inserts the push rod into the inner tube. After insertion, drive the jaws to move backward synchronously so that the diameter of the tube stopper's hole opens up to allow the inner tube to pass through. Then the piercing carriage continues to move forward and sends the push rod with the inner tube to the piercing position. The jaws move forward synchronously so that the diameter of the tube stopper's hole is between the diameter of the push rod and the outer diameter of the inner tube. Then insert the push head boss into the groove between the two push rod bosses and rotate the push head so that the push head magnetic column contacts the push rod magnetic column to complete the push head installation.

[0021] S3. Piercing, rolling and mounting: The heated solid bar billet is transported to the guide trough of the skew piercing mill by the first feeder for piercing and rolling. Then, the solid bar billet passes through the mandrel under the action of the rolls and is wrapped on the inner tube to directly heat-load the composite tube blank. After piercing and rolling, the mandrel is rotated to make the mandrel magnetic column and the mandrel rod magnetic column misaligned. The mandrel is then rotated upward to separate the mandrel and the mandrel rod. The diameter of the tube stopper hole is kept between the diameter of the mandrel rod and the outer diameter of the inner tube. The piercing carriage moves backward and the mandrel rod is pulled out from the composite tube blank using the tube stopper to obtain the composite tube blank. The composite interface achieves metallurgical bonding at high temperature.

[0022] S4. Three-roll skew rolling reinforced composite: According to the target composite tube diameter, select a mandrel of appropriate diameter and adjust the position of the skew rolls and guide plates. The composite tube blank is transported to the feed port of the three-roll skew rolling mill through the intermediate feeder. After the composite tube blank is heated by the online heating device, the mandrel is inserted and three-roll skew rolling composite is performed to obtain a high-strength metallurgically bonded seamless metal composite tube of the target size. The seamless metal composite tube is sent to the next process through the second feeder.

[0023] Preferably, in step S4, while perforating, inert protective gas is introduced into the top rod and ejected from the vent holes arranged circumferentially on the top.

[0024] Preferably, in steps S1 and S2, solid bar blanks and inner tubes of appropriate sizes are selected according to the size requirements of the finished tube.

[0025] Preferably, outer tubes of different sizes can be obtained by changing the reduction rate and mandrel diameter of the skew rolling mill.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) This invention utilizes a skew rolling piercing equipment to directly heat-assemble the inner layer tube while preparing the outer layer tube through piercing rolling, thus preparing a composite tube blank for producing seamless metal composite tubes. The interface bonding strength is high, and the preparation of solid bar blanks into seamless metal composite tubes is realized on a single production line. The overall preparation process is simple and convenient, significantly shortening the process flow and improving production efficiency.

[0028] (2) The diameter of the hole of the tube stopper in this invention can be infinitely adjusted to realize the preparation of blanks of different sizes of tubes. At the same time, it satisfies the limiting function of the push rod entering the inner tube, the solid bar blank being pierced and fitted into the inner tube, and the push rod being pulled out from the composite tube blank, thus realizing one machine for multiple uses.

[0029] (3) By changing the reduction rate and mandrel diameter of the skew rolling piercing mill, this invention can flexibly produce outer tubes with different diameters, wall thicknesses, and inner diameters. Combined with inner tubes of different sizes, it can be used to produce a series of seamless metal composite tubes of different specifications, realizing multiple specifications of product sizes. This solves the problem that when both inner and outer tubes are finished tubes, existing production equipment is limited by the size of the inner and outer tubes and cannot be assembled and produced into seamless metal composite tubes of specific sizes.

[0030] (4) In this invention, only the inner tube is made from finished tubes, while the outer tube is made online by skew rolling and piercing. Compared with the use of finished tubes for all blanks, the production cost is greatly reduced. In addition, this invention does not require cleaning or polishing of the inner surface of the outer tube during the production process, which also reduces the production cost and improves the production efficiency to a certain extent.

[0031] (5) This invention utilizes an outer tube produced by piercing rolling, which is then combined with an inner tube in a three-roll skew rolling process without leaving the production line. The billet still maintains a relatively high temperature. Unlike traditional heating furnaces that require heating the composite tube billet from room temperature to a rollable temperature, this invention only requires induction heating to replenish the temperature of the composite tube billet, significantly reducing energy consumption. Furthermore, induction heating is not limited by the length of the billet, has a fast heating speed, can improve production efficiency and reduce production costs, and the reduced energy consumption is beneficial to environmental protection.

[0032] (6) The equipment of the present invention improves the internal structure of the mandrel and the mandrel rod and sets up a gas flow channel. When preparing composite tube blanks by piercing and rolling, inert protective gas such as N2 is sprayed from the mandrel to cool the mandrel and the head of the inner tube, preventing the mandrel from failing due to excessive temperature and the inner tube head from deforming due to excessive temperature. More importantly, inert protective gas such as N2 can ensure that the inner surface of the outer tube and the outer surface of the inner tube under the high temperature state obtained by piercing and rolling are not oxidized, thereby producing a seamless metal composite tube with high metallurgical bonding strength at the interface.

[0033] (7) The connection between the top head and the top rod of the present invention adopts a combination of mechanical locking and magnetic attraction. When in use, the top rod drives the top head to rotate in the locking direction, which is not easy to fall off. At the same time, this connection method can also realize online quick installation and disassembly. The disassembled top head can be reused repeatedly, avoiding the head temperature from becoming too high and failing prematurely due to continuous work. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0035] Figure 2 This is a schematic diagram of the perforation device in this invention;

[0036] Figure 3 This is a schematic diagram of the fully automatic chuck in this invention;

[0037] Figure 4 This is a schematic diagram of the top rod penetrating the inner tube in this invention;

[0038] Figure 5 This is a schematic diagram of the perforated sleeve in this invention;

[0039] Figure 6 This is a schematic diagram of the ejector rod being pulled out of the composite tube blank in this invention;

[0040] Figure 7 This is a schematic diagram of the process for direct hot-rolling composite bonding of seamless metal composite tubes according to the present invention.

[0041] Figure 8 This is a schematic diagram of the top structure of the present invention;

[0042] Figure 9 This is a schematic diagram of the top rod structure of the present invention.

[0043] The following are some of the reference numerals in the attached diagram: 1. Heating furnace; 2. First feeder; 3. Inclined rolling mill; 4. Piercing device; 5. Intermediate feeder; 6. Online heating device; 7. Three-roll skew rolling mill; 8. Second feeder; 9. Inner tube; 10. Outer tube; 401. Mandrel; 4011. Mandrel boss; 4012. Mandrel magnetic column; 4013. Concave hole; 402. Mandrel rod; 4021. Mandrel boss; 4022. Groove; 4023. Mandrel magnetic column; 4024. Protruding column; 403. Tube stopper; 404. Inner tube receiving groove; 405. Guide rail; 406. Piercing carriage; 4031. Base; 4032. Fully automatic three-jaw chuck; 40321. Chuck body; 40322. Jaw. Detailed Implementation

[0044] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0045] like Figure 1-6As shown, the present invention provides a seamless metal composite pipe manufacturing equipment including a heating furnace 1, a first feeder 2, a skew rolling piercing mill 3, a piercing device 4, an intermediate feeder 5, an online heating device 6, a three-roll skew rolling mill 7, and a second feeder 8. Heating furnace 1 is used to heat the outer tube billet. First feeder 2 is used to transport the heated outer tube billet to the skew rolling piercing mill. Piercing device 4 is used to insert the mandrel into the inner tube 9 and send the mandrel with the inner tube 9 to the piercing position of the skew rolling piercing mill to install the mandrel. Skew rolling piercing mill 3 is used to pierce and roll the heated solid bar billet to obtain the outer tube 10. At the same time, the outer tube 10 passes through the mandrel and covers the inner tube 9 to directly heat-fit the composite tube billet. Intermediate feeder 5 is used to transport the composite tube billet to the feed port of the three-roll skew rolling mill. The three-roll skew rolling mill 7 is used to heat the composite tube billet with the online heating device 6, insert the mandrel and perform three-roll skew rolling composite. Second feeder 8 is used to send the seamless metal composite tube to the next process. This production line directly prepares composite tube blanks during piercing and rolling, realizing the preparation of seamless metal composite tubes from solid bar blanks on a single production line. The overall preparation process is simple and convenient, significantly shortening the process flow and improving production efficiency.

[0046] The piercing device 4 includes a mandrel 401, a mandrel 402, a tube stopper 403, an inner tube receiving groove 404, a guide rail 405, and a piercing carriage 406 arranged sequentially along the piercing axis. The piercing carriage 406 is placed on the guide rail 405 and can move on the guide rail 405. The inner tube receiving groove 404 is used to hold the surface-treated inner tube 9. The mandrel 401 and mandrel 402 have internal gas supply pipes, and gas outlets are evenly arranged around the mandrel 401. During piercing rolling, the high-temperature outer tube 10 is directly fitted onto the inner tube 9. After the inner tube 9 and outer tube 10 are fitted, they are both in a high-temperature state. At this time, inert protective gas is introduced into the gas supply pipe of mandrel 402 and sprayed out from the gas outlet of mandrel 401 to cool mandrel 401 and composite tube blank, preventing mandrel 401 from overheating and failing and the head of inner tube 9 from overheating and deforming. More importantly, the inert protective gas is used to prevent oxidation of the inner surface of the outer tube and the outer surface of the inner tube under the high temperature state obtained by piercing rolling. That is, inert protective gas such as N2 can fill the gap of the composite tube blank, thereby preventing oxidation of the surfaces to be bonded and avoiding the large amount of oxide scale that would reduce the bonding strength of the composite tube interface during the subsequent three-roll skew rolling composite process.

[0047] The tube stopper 403 includes a base 4031 and a fully automatic three-jaw chuck 4032. The fully automatic three-jaw chuck 4032 is fixed to the base 4031 by bolts and can adjust the diameter of the tube stopper 403's bore. A boss is provided on the exterior of the base 4031. The online temperature compensation device 6 includes an electromagnetic induction coil and an infrared thermometer, both of which are arranged on the rolling axis of the three-roll skew mill 7. The fully automatic three-jaw chuck 4032 includes a drive unit, a chuck body 40321, and three jaws 40322 arranged circumferentially at 120°. The diameter between the three jaws, i.e., the diameter of the tube stopper 403's bore, can be adjusted by moving the three jaws. The drive unit can drive the synchronous movement of the three jaws 40322 and the stepless adjustment of the diameter of the tube stopper through hydraulic and pneumatic means, thereby adjusting the diameter of the tube stopper before, during and after piercing. It can also enable the push rod 402 to be inserted into the inner tube 9 before piercing and the push rod 402 to be pulled out of the composite tube blank after piercing for tubes of different sizes.

[0048] like Figure 8 As shown, a recessed hole 4013 is provided in the middle of the inner end of the top head 401. Multiple top head protrusions 4011 are evenly arranged on the sidewall of the recessed hole 4013; in this embodiment, there are three. The outer surface of the top head protrusions 4011 is on the same horizontal plane as the outer surface of the inner end of the top head 401. A number of top head magnetic posts 4012, matching the number of top head protrusions 4011, are evenly arranged on the outer surface of the inner end of the top head 401. The top head magnetic posts 4012 are positioned corresponding to the top head protrusions 4011.

[0049] like Figure 9 As shown, a protrusion 4024 that can extend into a recessed hole 4013 is provided in the middle of the outer end of the push rod 402. Multiple push rod protrusions 4021 are evenly provided on the outer surface of the protrusion 4024. The push head protrusion 4011 can extend into the groove 4022 between two adjacent push rod protrusions 4021. A push rod magnetic column 4023 that cooperates with the push head magnetic column 4012 is provided between two adjacent push rod protrusions 4021. The top boss 4011 is elongated, and the top rod boss 4021 is L-shaped. Therefore, the groove 4022 between the two top rod bosses 4021 is also L-shaped, which includes a horizontal first groove and a vertical second groove. During installation, the top boss 4011 is first inserted into the vertical second groove. After rotating the top head 401 downward, the top boss 4011 enters the horizontal first groove. At this time, the top magnetic column 4012 contacts and attracts the top rod magnetic column 4023 on the top rod. During disassembly, the top head 401 is rotated upward to make the top magnetic column 4012 on the top head misalign with the top rod magnetic column 4023 on the top rod. Continue to rotate to make the top boss 4011 enter the vertical second groove, and then pull out the top head 401 to complete the disassembly of the top head 401.

[0050] When installing the top head 401, keep the top rod 402 stationary, insert the top head boss 4011 into the groove 4022 between two adjacent top rod bosses 4021, and then rotate the top head 401 downwards so that the top head magnetic post 4012 installed on the top head 401 contacts and attracts the top rod magnetic post 4023 on the top rod, thus completing the installation of the top head.

[0051] When disassembling the top head 401, keep the top rod 402 stationary, rotate the top head 401 upwards to misalign the top head magnetic column 4012 on the top head with the top rod magnetic column 4023 on the top rod, continue to rotate upwards to lower the top head 401 into the vertical second groove and pull it out, thus completing the disassembly of the top head 401.

[0052] Insert the push rod 402 into the inner tube 9 so that the inner tube 9 is fitted onto the push rod 402. During this process, based on the outer diameter of the inner tube, adjust the orifice diameter of the tube stopper 403 to be smaller than the outer diameter of the inner tube to prevent the inner tube 9 from sliding forward when the push rod 402 is inserted. After the push rod 402 is fitted into the inner tube 9, adjust the orifice diameter of the tube stopper 403 to be larger than the outer diameter of the inner tube, and then send the inner tube 9 with the push rod fitted to the piercing position of the skew rolling mill to install the mandrel 401. During installation, rotate the mandrel 401 downwards, and the mandrel boss 4011 enters the groove 4022 of the push rod 402. Rotate the mandrel 401 so that the mandrel magnetic column 4012 contacts and attracts the push rod magnetic column 4023 on the push rod, completing the installation of the mandrel 401 and the push rod 402. After the mandrel 401 is installed, the heated solid bar billet is pierced and rolled to obtain the outer tube. The outer tube passes through the mandrel and wraps around the inner tube, directly hot-fitting the composite tube blank (this process is also called piercing and rolling). Then, the mandrel is rotated to misalign the mandrel magnetic column with the mandrel rod magnetic column, and the mandrel is rotated upward to separate the mandrel from the mandrel rod. The mandrel rod 402 is then pulled out of the composite tube blank. During this process, the diameter of the tube stopper 403 is adjusted to be between the diameter of the mandrel rod and the outer diameter of the inner tube to prevent the inner tube from sliding backward during piercing and to allow the mandrel rod to be pulled out from inside the composite tube blank after hot-fitting the composite tube blank, while preventing the inner tube from being pulled out with the mandrel rod. In addition, the diameter of the mandrel 401 should be equal to or slightly larger than the outer diameter of the inner tube 9 to facilitate the smooth and direct fitting of the pierced and rolled outer tube 10 onto the inner tube 9.

[0053] The top head 401 and the top rod 402 are connected and locked by mechanical connectors and magnetic attraction devices. During use, the top rod 402 drives the top head 401 to rotate in the locking direction, making it less likely to fall off. At the same time, this connection method can also achieve quick online installation and disassembly. The disassembled top head can be reused, avoiding premature failure due to excessive head temperature caused by continuous operation.

[0054] In other embodiments, the fully automatic three-jaw chuck 4032 can adjust the diameter of the tube stopper hole according to the different outer diameters of the inner tube, so as to realize the preparation of blanks of different sizes of tubes, and realize the limiting of the push rod entering the inner tube, the solid bar blank being pierced and fitted into the inner tube, and the push rod being pulled out from the composite tube blank.

[0055] On the other hand, the present invention also provides a method for preparing a seamless metal composite tube, such as... Figure 7 As shown, it includes the following steps:

[0056] S1. Solid bar billet heating: The solid bar billet is placed in heating furnace 1 and heated to the temperature required for piercing and held at that temperature for a period of time for subsequent piercing rolling to prepare the outer tube.

[0057] S2. Inserting the push rod into the inner tube: Prepare the inner tube and perform surface treatment. Feed it into the inner tube receiving slot of the piercing device via a feeding rack. The drive unit drives the jaws of the fully automatic three-jaw chuck 4032 to move forward synchronously, making the diameter of the tube stopper's aperture smaller than the outer diameter of the inner tube to restrict its forward sliding. The piercing carriage connected to the push rod 402 moves forward, inserting the push rod 402 into the inner tube. After insertion, the drive jaws retract synchronously, opening the aperture diameter of the tube stopper to... Once the inner tube can pass through, the perforating carriage continues to move forward, delivering the push rod 402, which contains the inner tube, to the perforation position. Simultaneously, the jaws move forward, ensuring the diameter of the tube stopper's hole is between the push rod diameter and the inner tube's outer diameter. Then, the mandrel 403 is installed. Specifically, the mandrel boss 4011 is inserted into the groove 4022 between the two push rod bosses 4021, and then the mandrel 401 is rotated so that the mandrel magnetic column 4012 contacts the push rod magnetic column 4023, completing the mandrel installation. In steps S1 and S2, solid bar blanks of appropriate sizes and the inner tube are selected according to the size requirements of the finished tube.

[0058] S3. Piercing, Rolling and Assembly: The heated solid bar billet is transported to the guide trough of the skew piercing mill by the first feeder for piercing and rolling. Then, the solid bar billet passes through the mandrel under the action of the rolls and is wrapped on the inner tube to directly heat-assemble the composite tube blank. After piercing and rolling, the mandrel is rotated to misalign the mandrel magnetic column with the mandrel rod magnetic column. The mandrel is then rotated upward to separate the mandrel from the mandrel rod. Then, the diameter of the tube stopper is kept between the diameter of the mandrel rod and the outer diameter of the inner tube. The piercing carriage is moved backward, and the mandrel rod is pulled out from the composite tube blank using the tube stopper to obtain the composite tube blank. The composite interface achieves metallurgical bonding at high temperature.

[0059] S4. Three-roll skew rolling for enhanced composite: Based on the target composite tube's aperture, select a mandrel of appropriate diameter and adjust the positions of the skew rolls and guide plates. The composite tube blank is transported to the feed inlet of the three-roll skew rolling mill via an intermediate feeder. After heating the composite tube blank using an online heating device 6, the mandrel is inserted, and three-roll skew rolling is performed to obtain a high-strength, metallurgically bonded seamless metal composite tube of the target size. The seamless metal composite tube is then sent to the next process via a second feeder. During step S4, inert protective gas is introduced into the mandrel while it is being pierced, and the gas is ejected from the circumferentially arranged outlet holes on the mandrel. Specific Implementation

[0061] This embodiment produces a seamless metal composite tube, and its production method includes the following steps:

[0062] S1. Heating of solid bar billet: According to the size requirements of the finished tube, select a suitable size of 45 steel solid bar billet, place it in heating furnace 1 and heat it to 1200℃ and keep it at that temperature for a period of time as needed. In this embodiment, the temperature is kept for 2 hours, and then it is used for subsequent piercing rolling to prepare the outer tube 10.

[0063] S2. Inserting the top rod into the inner tube: Prepare an inner tube blank of appropriate size and perform surface treatment. Then, feed it into the inner tube receiving groove 404 of the piercing device 4 through the feeding rack. In actual applications, the inner tube 9 is generally a finished inner tube. In this embodiment, the inner tube is made of 304 stainless steel. The jaws 40322 of the fully automatic three-jaw chuck 4032 are driven forward synchronously by hydraulic or pneumatic means, so that the diameter of the tube stopper 403 is smaller than the outer diameter of the inner tube to restrict the inner tube from sliding forward. Then, the piercing carriage 406 connected to the push rod 402 moves forward to insert the push rod 402 into the inner tube. After insertion, the jaws 40322 are driven to move backward synchronously to open the diameter of the tube stopper 403 so that the inner tube 9 can pass through. Then, the piercing carriage 406 continues to move forward, sending the push rod 402 with the inner tube 9 on it to the piercing position. The jaws 40322 move forward synchronously, so that the diameter of the tube stopper 403 is between the diameter of the push rod and the outer diameter of the inner tube. Then, the mandrel 401 is installed. This ensures that the inner tube 9 does not slide backward during piercing, thus affecting the preparation of the composite tube blank. The process of the push rod inserting into the inner tube is as follows: Figure 4 As shown.

[0064] S3. Direct Assembly via Piercing Rolling: The heated solid bar billet is transported to the guide trough of the skew piercing mill 3 via the first feeder 2 for piercing rolling. Simultaneously, inert protective gas such as N2 is introduced into the mandrel 402 and ejected from the vents arranged circumferentially around the mandrel 401. During rolling, both the inner tube 9 and the outer tube 10 are at high temperatures. Inert protective gas is introduced into the gas supply pipe of the mandrel and ejected from the vents of the mandrel to cool the mandrel and the composite tube billet. The inert protective gas ensures that the inner surface of the outer tube 10 and the outer surface of the inner tube 9, at the high temperature obtained through piercing rolling, are not oxidized. The solid bar billet passes through the mandrel 401 under the action of the rolls and is directly heat-packed onto the inner tube 9 to obtain the composite tube billet. After piercing rolling, the diameter of the die of the tube stopper 403 is kept between the diameter of the push rod 402 and the outer diameter of the inner tube 9. Then, the piercing carriage 406 retracts, and the push rod 402 is pulled out of the composite tube blank using the tube stopper 403, obtaining a composite tube blank for producing seamless metal composite tubes. The composite interface achieves metallurgical bonding at high temperature. The process of pulling the push rod out of the composite tube blank is as follows: Figure 6 As shown.

[0065] S4. Three-roll skew rolling reinforced composite: Based on the set target composite tube diameter, a mandrel of appropriate diameter is selected, and the positions of the skew rolls and guide plates are adjusted. The composite tube blank is transported to the feed inlet of the three-roll skew rolling mill 7 via the intermediate feeder 5. The temperature of the composite tube blank is monitored by the online heating device 6, and the blank is heated in real time according to the target rolling temperature. Afterward, the mandrel is inserted, and three-roll skew rolling is performed to obtain a high-strength metallurgically bonded seamless metal composite tube of the target size. The resulting seamless metal composite tube is sent to the next process via the second feeder 8 for subsequent sizing and straightening. Finally, a 45 / 304 composite tube is obtained, with good interfacial bonding, uniform wall thickness, and high-strength metallurgical bonding.

[0066] In other embodiments, by changing the reduction rate and mandrel diameter of the skew rolling piercing mill, outer tubes of different sizes, i.e., different diameters, wall thicknesses, and inner diameters, can be flexibly produced. This allows for the production of inner tubes of different sizes, enabling the production of a series of seamless metal composite tubes of different specifications and achieving multi-specification production of product sizes.

[0067] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A seamless metal composite pipe direct hot-charging rolling composite equipment, characterized in that: It includes, in sequence, a heating furnace, a first feeder, a skew rolling mill, a piercing device, an intermediate feeder, an online heating device, a three-roll skew rolling mill unit, and a second feeder. The heating furnace is used to heat the solid bar billet. The first feeder is used to transport the heated solid bar billet to the skew rolling mill. The piercing device is used to insert the mandrel into the inner tube and then send the mandrel with the inner tube to the piercing position of the skew rolling mill to install the mandrel. The skew rolling mill is used to pierce and roll the heated solid bar billet to obtain the outer tube and then pass the outer tube through the mandrel to cover the inner tube for direct hot charging to obtain the composite tube billet. The intermediate feeder is used to transport the composite tube billet to the feed port of the three-roll skew rolling mill unit. The three-roll skew rolling mill unit is used to heat the composite tube billet with the online heating device, insert the mandrel, and perform three-roll skew rolling composite. The second feeder is used to send the seamless metal composite tube to the next process. The piercing device includes a mandrel, a push rod, a tube stopper, an inner tube receiving trough, a guide rail, and a piercing trolley arranged sequentially along the piercing axis. The piercing trolley is placed on the guide rail. The mandrel and push rod have air supply pipes inside, and the mandrel has air outlets evenly arranged around its circumference. The tube stopper includes a base and a fully automatic three-jaw chuck. The fully automatic three-jaw chuck is fixed on the base and can adjust the diameter of the tube stopper's hole. The inner tube receiving trough is used to hold the surface-treated inner tube. Insert the push rod into the inner tube so that the inner tube is fitted onto the push rod. During this process, adjust the diameter of the tube stopper to be smaller than the outer diameter of the inner tube to prevent the inner tube from sliding forward when the push rod is inserted. After the push rod is inserted into the inner tube, the diameter of the tube stopper is adjusted to be larger than the outer diameter of the inner tube. Then, the inner tube with the push rod is sent to the piercing position of the skew rolling mill and the mandrel is installed. The inner end of the top head has a recessed hole in the middle, and multiple top head protrusions are evenly arranged on the side wall of the recessed hole. The outer surface of the inner end of the top head has top head magnetic suction posts that are the same number and position as the top head protrusions. The outer end of the top rod has a protrusion that can extend into the recessed hole in the middle. Multiple top rod protrusions are evenly arranged on the outer surface of the protrusion. The top head protrusion can extend into the groove between two adjacent top rod protrusions. There is a top rod magnetic suction post that cooperates with the top head magnetic suction post between two adjacent top rod protrusions. After the top head protrusion is inserted into the groove between two top rod protrusions, the top head is rotated so that the top head magnetic suction post contacts the top rod magnetic suction post to complete the top head installation. After the mandrel is installed, the heated solid bar billet is pierced and rolled to obtain the outer tube. The outer tube passes through the mandrel and wraps around the inner tube, directly hot-fitting it to obtain the composite tube blank. Then, the mandrel is rotated to misalign the mandrel magnetic column with the mandrel rod magnetic column. The mandrel is then rotated upward to separate the mandrel from the mandrel rod, and the mandrel rod is pulled out from the composite tube blank. During this process, the diameter of the tube stopper is adjusted to be between the diameter of the mandrel rod and the outer diameter of the inner tube to prevent the inner tube from sliding backward during piercing. After the composite tube blank is obtained by piercing and rolling, the mandrel rod can be pulled out from the inside of the composite tube blank, and the inner tube is prevented from being pulled out with the mandrel rod.

2. The seamless metal composite tube direct hot-charging rolling composite equipment according to claim 1, characterized in that: The online temperature compensation device includes an electromagnetic induction coil and an infrared thermometer, both of which are arranged on the rolling axis of the three-roll skew mill.

3. The seamless metal composite pipe direct hot-charging rolling composite equipment according to claim 1, characterized in that: The fully automatic three-jaw chuck includes a drive unit, a chuck body, and three jaws arranged circumferentially at 120° intervals. The drive unit drives the three jaws to move synchronously to achieve stepless adjustment of the diameter of the tube stopper's orifice. Depending on the outer diameter of the inner tube, the fully automatic three-jaw chuck can adjust the diameter of the tube stopper hole to prepare blanks of different sizes of tubes, and to limit the movement of the push rod when it enters the inner tube, when the solid bar blank is pierced and fitted into the inner tube, and when the push rod is pulled out of the composite tube blank.

4. The seamless metal composite tube direct hot-charging rolling composite equipment according to claim 3, characterized in that: There are three of each of the top head boss and the top rod boss. The top head boss is long and narrow, and the top rod boss is L-shaped.

5. The seamless metal composite tube direct hot-charging rolling composite equipment according to claim 1, characterized in that: During piercing rolling, both the inner and outer tubes are in a high-temperature state after being assembled. Inert protective gas is introduced into the gas supply pipe of the mandrel and sprayed out from the gas outlet of the mandrel to cool the mandrel and the composite tube blank. The inert protective gas is used to prevent oxidation of the inner surface of the outer tube and the outer surface of the inner tube under the high temperature state obtained by piercing rolling.

6. The seamless metal composite tube direct hot-charging rolling composite equipment according to claim 1, characterized in that: The diameter of the mandrel is equal to or greater than the outer diameter of the inner tube, so that the outer tube obtained by piercing and rolling can cover the inner tube.

7. A method for direct hot-charging and rolling composite of seamless metal composite tubes based on the direct hot-charging and rolling composite equipment of seamless metal composite tubes according to claim 1, characterized in that: It includes the following steps: S1. Solid bar billet heating: The solid bar billet is placed in a heating furnace and heated to the temperature required for piercing and held at that temperature for subsequent piercing rolling to prepare the outer tube; S2. Inserting the push rod into the inner tube: Prepare the inner tube and perform surface treatment. Feed it into the inner tube receiving slot of the piercing device through the feeding rack. Use the drive unit to drive the jaws of the fully automatic three-jaw chuck to move forward synchronously, so that the diameter of the tube stopper's hole is smaller than the outer diameter of the inner tube to restrict the inner tube from sliding forward. The piercing carriage connected to the push rod moves forward and inserts the push rod into the inner tube. After insertion, drive the jaws to move backward synchronously so that the diameter of the tube stopper's hole opens up to allow the inner tube to pass through. Then the piercing carriage continues to move forward and sends the push rod with the inner tube to the piercing position. The jaws move forward synchronously so that the diameter of the tube stopper's hole is between the diameter of the push rod and the outer diameter of the inner tube. Then insert the push head boss into the groove between the two push rod bosses and rotate the push head so that the push head magnetic column contacts the push rod magnetic column to complete the push head installation. S3. Piercing, rolling and mounting: The heated solid bar billet is transported to the guide trough of the skew piercing mill by the first feeder for piercing and rolling. Then, the solid bar billet passes through the mandrel under the action of the rolls and is wrapped on the inner tube to directly heat-load the composite tube blank. After piercing and rolling, the mandrel is rotated to make the mandrel magnetic column and the mandrel rod magnetic column misaligned. The mandrel is then rotated upward to separate the mandrel and the mandrel rod. The diameter of the tube stopper hole is kept between the diameter of the mandrel rod and the outer diameter of the inner tube. The piercing carriage moves backward and the mandrel rod is pulled out from the composite tube blank using the tube stopper to obtain the composite tube blank. The composite interface achieves metallurgical bonding at high temperature. S4. Three-roll skew rolling reinforced composite: According to the target composite tube diameter, select a mandrel of appropriate diameter and adjust the position of the skew rolls and guide plates. The composite tube blank is transported to the feed port of the three-roll skew rolling mill through the intermediate feeder. After the composite tube blank is heated by the online heating device, the mandrel is inserted and three-roll skew rolling composite is performed to obtain a high-strength metallurgically bonded seamless metal composite tube of the target size. The seamless metal composite tube is sent to the next process through the second feeder.

8. The method for direct hot-charging and composite forming of seamless metal composite tubes according to claim 7, characterized in that: In step S3, while perforating, inert protective gas is introduced into the top rod and ejected from the vent holes arranged around the top.

9. The method for direct hot-charging and composite forming of seamless metal composite tubes according to claim 7, characterized in that: In steps S1 and S2, solid bar blanks and inner tubes of appropriate sizes are selected according to the size requirements of the finished tube.

10. The method for direct hot-charging and composite rolling of seamless metal composite tubes according to claim 7, characterized in that: By changing the reduction rate and mandrel diameter of the skew rolling mill, outer tubes of different sizes can be obtained.

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