Electromagnetic induction brazing process and apparatus for manufacturing a seam-welded pipe from a layered composite metal strip

Abstract

The present application relates to the technical field of induction heating, in particular to an electromagnetic induction brazing process and device for manufacturing a spiral-welded pipe by using a layered composite metal strip, the electromagnetic induction brazing process and device for manufacturing a spiral-welded pipe by using a layered composite metal strip is a welding method using ultra-high frequency or high frequency, medium frequency induction current as a heat source, high frequency heating is suitable for welding thin-walled pipe fittings, the medium frequency induction brazing equipment can replace the backward preheating means such as oxyacetylene heating, coal oven heating, box-type electric furnace heating and resistance heating, and can be used as a preheating equipment before brazing, the cooperation of the two can greatly improve the product quality, effectively save more than 60% of electric energy, and improve the labor conditions.

Description

Technical Field

[0001] This invention relates to the field of induction heating technology, specifically to the electromagnetic induction brazing process and apparatus for manufacturing coiled welded pipes from layered composite metal strips. Background Technology

[0002] Induction brazing equipment mainly consists of an AC power supply and an induction coil, along with auxiliary clamps for holding and positioning. AC power supplies can be categorized by frequency: mains frequency, intermediate frequency, and high frequency. Mains frequency is rarely used for brazing; intermediate and high frequencies are more common. Induction brazing generators typically operate at frequencies between 100 and 500 kHz. There are two ways to place the induction coil: one is to place it outside the container, where the induction coil heats the workpiece (in this case, the container material is conductive); the other is to place the induction coil inside the container, where the workpiece is directly heated by the induction coil. In this case, a glass container is often used to facilitate observation of the brazing process.

[0003] An induction coil is a component that transmits induced current. Designed specifically for parts, especially those with complex shapes, its design is generally based on experience and experimentation. When dealing with parts with varying cross-sectional sizes, the heating method can be adjusted by combining different basic design forms. To ensure rapid, uniform, and efficient heating, the induction coil is typically made of 4–12 mm round or flat pure copper tubing, cooled by water flow inside during operation. A gap should be maintained between the induction coil and the workpiece to prevent short circuits, but to improve heating efficiency, the gap between the coil turns and the workpiece should be minimized. Auxiliary tools are often needed to clamp and position the workpiece during induction brazing. The gap between induction brazed parts is typically 0.038–0.051 mm. Furthermore, the skin effect in induction brazing is related to the resistivity and permeability of the part material. Higher resistivity and lower permeability result in a weaker skin effect, and vice versa. Therefore, the power supply frequency and power should be adjusted according to the specific characteristics of the brazed parts to achieve the best brazing results.

[0004] Electromagnetic induction brazing technology and equipment for manufacturing coiled welded pipes from layered composite metal strips is a welding method that uses ultra-high frequency, high frequency, or medium frequency induced current as a heat source. High frequency heating is suitable for welding thin-walled pipes, while medium frequency induction brazing equipment can replace outdated preheating methods such as oxyacetylene heating, coal-fired oven heating, box-type electric furnace heating, and resistance heating. The combined use of these two methods can significantly improve product quality, effectively save over 60% of electrical energy, and improve working conditions. Summary of the Invention

[0005] To address the above situation and overcome the shortcomings of existing technologies, this solution provides an electromagnetic induction brazing device for manufacturing coiled pipes from layered composite metal strips. This device is achieved through the following specific technical means: it includes a multi-layer coiled pipe forming unit, an induction brazing heater, a waste gas collector and purifier, and a pipe cooler. The induction brazing heater consists of a medium-frequency induction heater and an ultra-high frequency or high-frequency induction heater. The medium-frequency induction heater contains a medium-frequency induction preheating coil, and the ultra-high frequency or high-frequency induction heater contains an ultra-high frequency or high-frequency induction brazing coil. The multi-layer coiled pipe forming unit is used to wind the layered composite metal strip into a composite metal material pipe. After the composite metal material pipe is formed, it passes sequentially through the medium-frequency induction preheating coil and the ultra-high frequency or high-frequency induction brazing coil for induction heating brazing. Simultaneously, the induction brazing heater is filled with a protective gas during induction heating. The waste gas collector and purifier is connected to the induction brazing heater to collect and purify the waste gas generated during the brazing process. The pipe cooler is connected to the induction brazing heater to cool the brazed composite metal material pipe.

[0006] Preferred technical solution 1: The rear end of the tube cooling machine is also equipped with a brazing quality monitor, a surface passivation and drying machine and a coiling machine in sequence. After cooling, the composite metal tube is first tested for brazing quality by the brazing quality monitor, and then passed through the surface passivation and drying machine for surface passivation and drying before being coiled by the coiling machine.

[0007] Preferred technical solution 2: A cutter for cutting the composite metal material tube is provided between the winding machine and the surface passivation and drying machine.

[0008] The medium-frequency induction preheating coil and the ultra-high frequency or high-frequency induction brazing coil are made of hollow copper tubes. During induction heating, a liquid cooling medium is passed through the hollow copper tubes of the medium-frequency induction preheating coil and the ultra-high frequency or high-frequency induction brazing coil.

[0009] Preferred technical solution 3: The protective gas can be an inert protective gas such as nitrogen, argon, or helium; or a protective gas medium with reducing properties such as a nitrogen-hydrogen mixture.

[0010] Preferred technical solution four: The multi-layer welded pipe forming unit is connected in sequence to the front side of the trimming machine and the strip uncoiling machine. After the metal strip passes through the strip uncoiling machine, it forms a layered composite metal strip, and the trimming machine grinds or rolls the edges of the layered composite metal strip.

[0011] This solution also discloses an electromagnetic induction brazing process for manufacturing coiled welded pipes from layered composite metal strips, including the following steps:

[0012] Step 1: After passing through the strip uncoiler, the metal strip is formed into a layered composite metal strip. The layered composite metal strip consists of a base metal and a cladding metal covering the base metal. The base metal is a high-strength, high-melting-point metal, and the cladding metal is a metal with a melting point lower than that of the base metal.

[0013] Step 2: Before the layered composite metal strip is wound into shape, the edges of the layered composite metal strip are flattened into triangles by grinding or rolling to ensure that the thickness of the joint part and other parts is consistent after winding. The layered composite metal strip is then wound into shape by the multi-layer coiled pipe forming unit.

[0014] Step 3: The composite metal material tube passes through the medium frequency induction preheating coil and the ultra-high frequency or high frequency induction brazing coil in sequence. The high frequency generator on the medium frequency induction preheating coil and the ultra-high frequency or high frequency induction brazing coil is started for induction heating. During induction heating, the low melting point cladding metal to be brazed should be in a non-active protective gas medium, and at the same time, a liquid cooling medium is passed through the hollow copper tube.

[0015] Step 4: During induction heating, the composite metal tube contains a high-temperature and wear-resistant core rod, which creates internal pressure between the tube wall layers to ensure that the cladding metal, i.e. the brazing layer metal, can densely fill the space between the two base metal layers, thus achieving full welding.

[0016] Step 5: After brazing, the composite metal material tube leaves the induction brazing heater and enters the tube cooler for rapid cooling to ensure that the brazed metal layer does not have defects such as flow, scabs, or cavities, which would cause uneven or incomplete circumferential metal thickness of the tube wall.

[0017] Step six: Use a brazing quality monitoring system to monitor and inspect the welding temperature, speed, quality, and dimensional tolerances of the brazed composite metal pipe. Set different welding temperatures and speeds according to different base metals. The welding process parameters can be automatically adjusted online in a closed loop based on the test results.

[0018] Step six: The inspected composite metal tube is cut and wound up.

[0019] The above structure gives this solution the following advantages:

[0020] 1. This invention offers advantages such as adaptability to various pipe diameters, stable quality, high production efficiency, and smooth surface finish. It enables high-speed automatic detection and adjustment. It produces brazed double (multi)-layer coiled pipes that are free of weld lines, nodules, and incomplete welds, with an aesthetically pleasing appearance, meeting the strength and precision requirements of relevant national standards or special user requirements. This coiled pipe possesses both the surface of the cladding metal and the performance of the base layer technology, significantly enhancing the pipe's strength. While ensuring the corrosion resistance of both inner and outer layers, it significantly reduces cladding consumption. It can be widely used in refrigerator systems, automotive piping, air conditioning refrigeration, and other industries, as well as in brazed layered coiled pipes made from multi-layered strips composed of special copper and specific steel materials.

[0021] 2. This is a welding method that uses ultra-high frequency, high frequency, or medium frequency induced current as a heat source. High frequency heating is suitable for welding thin-walled pipes. Medium frequency induction brazing equipment can replace outdated preheating methods such as oxyacetylene heating, coal oven heating, box furnace heating, and resistance heating. The combined use of these two methods can greatly improve product quality, effectively save more than 60% of electrical energy, and improve working conditions.

[0022] 3. The present invention also includes a brazing fume collection and purification function to ensure environmental friendliness. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0024] Figure 1 A schematic diagram of the overall structure of the electromagnetic induction brazing device for manufacturing coiled welded pipes from layered composite metal strips in this scheme.

[0025] Figure 2 This is a schematic diagram of the structure of the medium-frequency induction preheating coil in this scheme;

[0026] Figure 3 This is a schematic diagram of the structure of the ultra-high frequency or high frequency induction brazing coil in this scheme;

[0027] Figure 4 This is a schematic diagram of the layered composite metal strip structure of this scheme;

[0028] Figure 5 This is a schematic diagram of the single-layer composite metal tube structure in this scheme;

[0029] Figure 6 This is a schematic diagram of the structure of the multi-layer composite metal tube in this scheme.

[0030] Among them, 1. Multi-layer coiled pipe forming unit, 2. Waste gas collection and purification unit, 3. Pipe body cooler, 4. Medium frequency induction heater, 5. Medium frequency induction preheating coil, 6. Ultra-high frequency or high frequency induction heater, 7. Ultra-high frequency or high frequency induction brazing coil, 8. Brazing quality monitor, 9. Surface passivation and drying machine, 10. Cutting machine, 11. Coiling machine, 12. Trimming machine, 13. Strip uncoiling machine, 14. Layered composite metal strip, 1401. Base metal, 1402. Coating metal. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Please see Figures 1-3The electromagnetic induction brazing device for manufacturing coiled pipes from layered composite metal strips is achieved through the following specific technical means: It includes a multi-layer coiled pipe forming unit 1, an induction brazing heater, a waste gas collector and purifier 2, and a pipe cooler 3. The induction brazing heater consists of a medium-frequency induction heater 4 and an ultra-high frequency or high-frequency induction heater 6. The medium-frequency induction heater 4 is equipped with a medium-frequency induction preheating coil 5, and the ultra-high frequency or high-frequency induction heater 6 is equipped with an ultra-high frequency or high-frequency induction brazing coil 7. The multi-layer coiled pipe forming unit 1 is used to wind the layered composite metal strip 14 into a composite metal material pipe. After the composite metal material pipe is formed, it passes sequentially through the medium-frequency induction preheating coil 5 and the ultra-high frequency or high-frequency induction brazing coil 7 for induction heating brazing. Simultaneously, the induction brazing heater is filled with a protective gas during induction heating. The protective gas can be an inert protective gas such as nitrogen, argon, or helium, or a reducing protective gas medium such as a nitrogen-hydrogen mixture. In this assembly, the exhaust gas collector and purifier 2 is connected to the induction brazing heater to collect and purify the exhaust gas generated during the brazing process. The tube cooler 3 is connected to the induction brazing heater to cool the brazed composite metal tube. The tube cooler 3 is also equipped with a brazing quality monitor 8, a surface passivation and drying machine 9, and a coiler 11 in sequence at its rear end. After cooling, the composite metal tube is first inspected for brazing quality by the brazing quality monitor 8, and then passivated and dried by the surface passivation and drying machine 9 before being coiled by the coiler 11. A cutter 10 for cutting the composite metal tube is provided between the coiler 11 and the surface passivation and drying machine 9. The multi-layer coiled pipe forming unit 1 is connected to the front side of the trimming machine 12 and the strip uncoiling machine 13 in sequence. After passing through the strip uncoiling machine 13, the metal strip forms a layered composite metal strip 14, which is then flattened into a triangle by the trimming machine 12 through edge grinding or rolling.

[0033] The medium-frequency induction preheating coil 5 and the ultra-high frequency or high-frequency induction brazing coil 7 are both connected to a high-frequency generator.

[0034] Please see Figures 2-3An electromagnetic induction brazing device for manufacturing coiled pipes from layered composite metal strips is described. The intermediate-frequency induction preheating coil 5 and the ultra-high-frequency or high-frequency induction brazing coil 7 are made of hollow copper tubes. During induction heating, a liquid cooling medium, such as cooling water, flows through the hollow copper tubes of these coils to ensure controllable heater body temperature. The hollow copper tubes of these coils are made of hollow pure copper tubes, gold-copper tubes, or layered composite copper tubes, with a wall thickness less than the current penetration depth, typically 1-3 mm. The specifications, coil size, and number of turns of the hollow copper tubes of the intermediate-frequency induction preheating coil 5 and the ultra-high-frequency or high-frequency induction brazing coil 7 are determined based on the specific product requirements, such as the dimensions, material properties, mechanical properties, surface requirements, and brazing efficiency of the single (or multi) layered composite metal material tube to be brazed, as well as the required power frequency, power, and other energy and medium parameters.

[0035] Please see Figure 1 An electromagnetic induction brazing apparatus for manufacturing coiled pipes from layered composite metal strips is described. In the induction brazing heater, a non-metallic support is provided between the hollow copper tubes of the medium-frequency induction preheating coil 5 and the ultra-high-frequency or high-frequency induction brazing coil 7 and the composite metal material tube body to maintain a gap and prevent short circuits. To improve heating efficiency, the gap between the turns of the medium-frequency induction preheating coil 5 and the ultra-high-frequency or high-frequency induction brazing coil 7 and the composite metal material tube body is minimized.

[0036] This solution also discloses an electromagnetic induction brazing process for manufacturing coiled welded pipes from layered composite metal strips, including the following steps:

[0037] Step one: After the metal strip passes through the strip uncoiler 13, it forms a layered composite metal strip 14. The layered composite metal strip 14 consists of a base metal 1401 and a cladding metal 1402 covering the base metal 1401, as shown below. Figure 4 As shown, the base metal 1401 is a high-strength, high-melting-point metal, such as steel or stainless steel; the cladding metal 1402 is a metal with a melting point lower than that of the base metal 1401, such as copper, aluminum, zinc, or tin; the cladding metal 1402 can be single-sided or double-sided, and is combined with the base metal 1401 to form a whole through layered composite processes such as rolling composite, casting-rolling composite, and reverse solidification.

[0038] Step two: Before winding the layered composite metal strip 14, the edges of the layered composite metal strip 14 need to be flattened into triangles by grinding or rolling to ensure that the thickness of the joint part and other parts is consistent after winding. The layered composite metal strip 14 can be wound into a single layer by a multi-layer coiling and welding pipe forming unit 1, or it can be double-layered or multi-layered composite and then wound into a composite metal material tube by a multi-layer coiling and welding pipe forming unit 1. Figures 5-6 ;

[0039] Step 3: The composite metal material tube passes through the medium frequency induction preheating coil 5 and the ultra-high frequency or high frequency induction brazing coil 7 in sequence. The high frequency generator on the medium frequency induction preheating coil 5 and the ultra-high frequency or high frequency induction brazing coil 7 is started for induction heating. During induction heating, the low melting point cladding metal 1402 to be brazed should be in a non-active protective gas medium, and at the same time, a liquid cooling medium is passed through the hollow copper tube.

[0040] Induction heating can be performed in stages or all at once. In staged heating, preheating is first achieved through medium-frequency induction, followed by rapid heating through high-frequency or ultra-high-frequency induction, which rapidly raises the temperature of the cladding metal 1402, i.e., the brazing layer metal, to the required temperature. In all-time heating, either medium-frequency induction heating or high-frequency or ultra-high-frequency induction heating can be used.

[0041] Based on the characteristics of the layered composite metal strip 14, such as the number of layers, thickness, type of brazing layer metal, and other brazing characteristics and mechanical performance requirements, the frequency and power of the induction heating power supply and the traveling speed of the composite metal tube can be adjusted to heat the brazing layer metal to near its melting point, making it a semi-molten porridge state. Under the mutual pressure between the layers of the composite metal tube wall, the low melting point cladding metal 1402 on each surface fuses to form a braze.

[0042] Step 4: During induction heating, there is a high-temperature and wear-resistant core rod inside the composite metal tube, which creates internal pressure between the tube wall layers to ensure that the cladding metal 1402, i.e. the brazing layer metal, can be densely filled between the two base metal layers 1401, thus achieving full welding between them.

[0043] Step 5: After brazing, the composite metal material tube leaves the induction brazing heater and enters the tube cooler 3 for rapid cooling to ensure that the brazed metal layer does not have defects such as flow, scabs, or cavities, which would cause uneven or incomplete circumferential metal thickness of the tube wall.

[0044] Step 6: Use an 8-line brazing quality monitor to monitor and detect the welding temperature, speed, quality, and dimensional tolerances of the brazed composite metal tube. Set different welding temperatures and speeds according to different base metals 1401. The welding process parameters can be automatically adjusted online in a closed loop based on the test results.

[0045] Step six: The inspected composite metal tube is cut and wound up.

[0046] For example, if the outer diameter of the composite metal material tube is Φ2.6-Φ19.05mm and the wall thickness is 0.3-1.4mm, a copper-clad steel strip with a total thickness of 0.15-0.7mm is selected, in which the thickness of the copper layer on both sides accounts for 6%-20% of the total thickness (the thickness of the copper layer on both sides of the steel strip can be different). This is a cold-rolled layered metal composite strip of copper / steel / copper, and the materials of the copper layer and the steel layer can be selected by the user.

[0047] After the copper-clad steel strip is slit and edge-treated, it is formed into double (multi) layer coiled pipes by the multi-layer coiled pipe forming unit 1 to ensure the pipe diameter tolerance and roundness tolerance. Then it enters the medium frequency induction preheating coil 5 and the ultra-high frequency or high frequency induction brazing coil 7 group, which are composed of medium frequency induction heater 4 and ultra-high frequency or high frequency induction heater 6, and continuous copper layer brazing is carried out in the protective gas.

[0048] The brazing process parameters are as follows: Medium-frequency induction preheating current frequency is 0.5-10KHz, and the induction preheating temperature is controlled at 700℃-950℃; high-frequency induction brazing current frequency is 100-300KHz; ultra-high-frequency induction brazing current frequency is below 800KHz; the induction brazing temperature is controlled at 1080℃-1400℃; and the composite metal pipe travel speed is 20m / min-80m / min. The current frequency and power can be adjusted according to production parameters such as pipe diameter, wall thickness, and brazing speed.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An electromagnetic induction brazing apparatus for manufacturing coiled welded pipes from layered composite metal strips, characterized in that, The system includes a multi-layer coiled pipe forming unit (1), an induction brazing heater, a waste gas collector and purifier (2), and a pipe cooler (3). The induction brazing heater consists of a medium-frequency induction heater (4) and an ultra-high frequency or high-frequency induction heater (6). The medium-frequency induction heater (4) is equipped with a medium-frequency induction preheating coil (5), and the ultra-high frequency or high-frequency induction heater (6) is equipped with an ultra-high frequency or high-frequency induction brazing coil (7). The multi-layer coiled pipe forming unit (1) is used to coil layered composite metal strip (14) into a composite metal material pipe. After the composite metal material pipe is coiled, it passes through the medium-frequency induction preheating coil (5) and the ultra-high frequency or high-frequency induction brazing coil (7) in sequence for induction heating brazing. At the same time, the induction brazing heater is filled with protective gas during induction heating. The waste gas collector and purifier (2) is connected to the induction brazing heater to collect and purify the waste gas generated during the brazing process. The pipe cooler (3) is connected to the induction brazing heater to cool the brazed composite metal material pipe.

2. The electromagnetic induction brazing apparatus for manufacturing coiled welded pipes from layered composite metal strips according to claim 1, characterized in that, The tube cooling machine (3) is also equipped with a brazing quality monitor (8), a surface passivation and drying machine (9) and a winding machine (11) in sequence at the rear end. After cooling, the composite metal tube is first tested for brazing quality by the brazing quality monitor (8), and then passed through the surface passivation and drying machine (9) for surface passivation and drying before being wound by the winding machine (11).

3. The electromagnetic induction brazing apparatus for manufacturing coiled pipes from layered composite metal strips according to claim 2, characterized in that, A cutter (10) for cutting composite metal tubes is provided between the winding machine (11) and the surface passivation and drying machine (9).

4. The electromagnetic induction brazing apparatus for manufacturing coiled welded pipes from layered composite metal strips according to claim 1, characterized in that, The medium-frequency induction preheating coil (5) and the ultra-high frequency or high-frequency induction brazing coil (7) are made of hollow tubes. During induction heating, the hollow tubes of the medium-frequency induction preheating coil (5) and the ultra-high frequency or high-frequency induction brazing coil (7) are filled with liquid cooling medium.

5. The electromagnetic induction brazing apparatus for manufacturing coiled welded pipes from layered composite metal strips according to claim 1, characterized in that, The protective gas is an inert protective gas or a protective gas with reducing properties.

6. The electromagnetic induction brazing apparatus for manufacturing coiled welded pipes from layered composite metal strips according to claim 1, characterized in that, The multi-layer welded pipe forming unit (1) is connected in sequence to the front side of the trimming machine (12) and the strip uncoiling machine (13). After the metal strip passes through the strip uncoiling machine (13), it forms a layered composite metal strip (14), and the trimming machine (12) grinds or rolls the edge of the layered composite metal strip (14).

7. An electromagnetic induction brazing process, characterized in that, The electromagnetic induction brazing apparatus for manufacturing coiled welded pipes using the layered composite metal strip as described in claim 6 includes the following steps: Step 1, after the metal strip passes through the strip uncoiler (13), a layered composite metal strip (14) is formed. The layered composite metal strip (14) is composed of a base metal (1401) and a cladding metal (1402) covering the base metal (1401). The base metal (1401) is a high-strength, high-melting-point metal, and the cladding metal (1402) is a metal with a melting point lower than that of the base metal (1401). Step 2: Before the layered composite metal strip (14) is wound into shape, the edge of the layered composite metal strip (14) is flattened into a triangle by grinding or rolling to ensure that the thickness of the joint part and other parts is consistent after winding. The layered composite metal strip (14) is wound into a composite metal material tube by a multi-layer roll welding tube forming unit (1). Step 3: The composite metal material tube passes through the medium frequency induction preheating coil (5) and the ultra-high frequency or high frequency induction brazing coil (7) in sequence. The high frequency generator on the medium frequency induction preheating coil (5) and the ultra-high frequency or high frequency induction brazing coil (7) is started for induction heating. During induction heating, the low melting point cladding metal (1402) to be brazed should be in a non-active protective gas medium, and a liquid cooling medium is passed through the hollow tube at the same time. The brazing layer metal is heated to near its melting point and becomes a semi-molten porridge state. Under the mutual pressure between the layers of the composite metal material tube wall, the low melting point cladding metal (1402) on each surface fuses to form a brazing layer. Step 4: During induction heating, the composite metal tube contains a high-temperature and wear-resistant core rod, which creates internal pressure between the tube wall layers to ensure that the cladding metal (1402), i.e. the brazing layer metal, can densely fill the space between the two base metal layers, thus achieving full welding between them. Step 5: After brazing, the composite metal material tube leaves the induction brazing heater and enters the tube cooler (3) for rapid cooling to ensure that the brazed metal layer does not produce defects that would cause uneven or incomplete circumferential metal thickness of the tube wall. Step 6: Use the brazing quality monitor (8) to monitor and detect the welding temperature, speed, quality, and dimensional tolerance of the brazed composite metal tube; set different welding temperatures and speeds according to different base metals (1401); Step 7: The inspected composite metal tube is cut and wound up.

8. The electromagnetic induction brazing process according to claim 7, characterized in that, The cladding metal (1402) can be configured with either a single side or a double side, and can be combined with the base metal (1401) to form a single unit through layered composite processes such as rolling composite, casting-rolling composite, and reverse solidification.

9. The electromagnetic induction brazing process according to claim 7, characterized in that, The layered composite metal strip (14) is wound into a composite metal tube by a single layer through a multi-layer roll-weld pipe forming unit (1), or by a double layer or a multi-layer composite and then wound into a composite metal tube by a multi-layer roll-weld pipe forming unit (1).

10. The electromagnetic induction brazing process according to claim 7, characterized in that, The induction heating can be performed using either segmented heating or one-time heating. In segmented heating, preheating is first performed by medium-frequency induction, followed by rapid heating by high-frequency or ultra-high-frequency induction, so that the cladding metal (1402), i.e. the brazing layer metal, can be heated rapidly to the required temperature of the brazing layer metal. In one-time heating, either medium-frequency induction heating, high-frequency induction heating, or ultra-high-frequency induction heating can be performed.

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