Method for manufacturing copper-steel composite plate by annealing combined with cold rolling using electromagnetic induction heating

Abstract

The application discloses a method for preparing a copper-steel composite plate by using electromagnetic induction heating rolling process, which comprises the following steps: S1, cold rolling of a copper-steel copper three-layer plate; S2, induction heating of the cold-rolled copper-steel composite plate; the thermal effect generated by eddy current heating can rapidly increase the temperature of the steel plate, so that the temperature of the steel plate reaches 750 DEG C-1000 DEG C, and the temperature of the copper plate reaches 550 DEG C-680 DEG C; S3, tempering; the plate blank after heating is subjected to tempering treatment by using induction heating; and S4, flattening and straightening. The method for producing the copper-steel composite plate greatly reduces the work hardening of the copper-steel composite plate and improves the subsequent processing performance. The obtained copper-steel composite plate has good mechanical properties and high bonding strength.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal laminated composite plate preparation, and particularly relates to a method for preparing a high-performance copper-steel composite plate by using electromagnetic induction technology in combination with a cold rolling process. BACKGROUND

[0002] Laminated metal composite plates can realize the compounding of the advantageous properties of different metal materials, such as wear resistance, corrosion resistance, heat resistance, thermal conductivity, magnetic conductivity, electromagnetic shielding, and different materials are combined to form new multifunctional composite materials. The cold rolling compounding process can partially replace the "plating" process to produce clad plates, which is not only environmentally friendly and pollution-free in production mode, but also can improve the density and thickness of the cladding metal and improve the cladding quality.

[0003] Ordinary metals are used to replace rare and precious metals, thereby saving rare and precious metals while meeting or improving surface properties, comprehensive mechanical properties, and welding forming properties, which can greatly reduce material costs. For example, a new functional material with steel / stainless steel as a substrate and single-sided or double-sided copper compounding. The composite plate has both the electrical conductivity of copper and the strength and elasticity of steel, and can replace brass, phosphor copper, beryllium copper, etc. for conductive punches, connectors, and effectively avoids the aging crack defects of brass.

[0004] The cold rolling compounding process is complex and has great technical difficulty. However, compared with explosion compounding, hot rolling compounding, hot rolling and cold rolling compounding, and mechanical compounding, cold rolling compounding has obvious advantages in production efficiency, variety and specification adaptability, surface quality, environmental protection and energy saving, and technical economy, and has the following advantages: one-time compounding and forming, continuous production, high production efficiency; can adapt to the compounding of various metals; high process yield, good compounding economy; energy saving and environmental protection in production process; good product shape and good surface quality.

[0005] In order to make the copper-steel composite plate have good bending resistance and high bonding performance, reduce the work hardening of the copper-steel composite plate, and improve the processing performance of the composite plate, it is necessary to study a better method for preparing a copper-steel composite plate by combining a cold rolling process. SUMMARY

[0006] The application provides a method for preparing a copper-steel composite plate by electromagnetic induction heating in a protective atmosphere, which mainly utilizes the principle that the thermal effect generated by eddy current heating can rapidly increase the temperature of ferromagnetic materials in a short time, and obtains a method for preparing a copper-steel composite plate by electromagnetic induction heating and annealing in combination with a cold rolling process.

[0007] The electromagnetic induction heating device used in the method of the present application is a KPS-160 / 2.5 thyristor medium-frequency induction heating furnace, which adopts a ring copper coil customized and developed for plate-shaped samples. During the induction heating process, due to the skin effect, the coil is more than 15 mm away from the surface of the clad plate. The induction heating to the entire rolling process realizes the mixed gas of H2+N2 in a volume ratio of 1:3, which can cool the copper while preventing the oxidation of the surface of the plate during the heating process.

[0008] The method of the present application comprises the following steps:

[0009] The present application first provides an induction heating cold rolling system, which comprises a conveying system and an induction heating system controlled by a computer control system. The induction heating system is composed of an induction heater and an induction heating power supply. The induction heater is an electromagnetic induction heating device, which comprises a copper ring induction heating coil in the inside, and the copper steel clad plate to be heated can pass through the middle of the coil.

[0010] The parameters of the induction heating coil in the electromagnetic induction heating device 3 are adjusted by the computer control system;

[0011] The electromagnetic induction heating device is provided with an infrared thermal imager to measure the temperature of the interface on the side of the copper-steel-copper bonding layer;

[0012] It also includes an air inlet channel 7 through which the cooling gas can be delivered into the sealed electromagnetic induction heating device 3, and the air outlet is directed at the upper and lower surfaces of the incoming copper steel clad plate 5, and an exhaust duct 8 is used to exhaust the cooling gas;

[0013] The electromagnetic induction heating device adopts sealing measures. For single plate production process, a heating cover is used for sealing, specifically by sealing silica gel strips in the inner cover and sealing packing in the heating cover. For continuous production process, gas sealing is adopted: the inside of the induction heating device 3 is under micro-positive pressure, and oxygen cannot enter the heating furnace.

[0014] Preferably, the electromagnetic induction heating device is a medium-frequency induction heating furnace, such as a KPS-160 / 2.5 thyristor medium-frequency induction heating furnace.

[0015] In addition, the infrared thermal imager 6 is designed on the front and rear three sides of the electromagnetic induction heating device 3; the computer control system is a PLC system; and the conveying system comprises a guide rail 2.

[0016] Specifically, the protective gas is H2+N2 gas mixed in a volume ratio of 1:3.

[0017] The present application particularly provides a method for preparing a copper steel clad plate by using the induction heating cold rolling system in combination with a cold rolling process, which comprises the following steps:

[0018] S1, cold rolling of copper-steel-copper three-layer plate: selecting one steel strip and two copper strips with the same width, covering copper on the outer side of steel, selecting preset rolling speed and rolling reduction, pushing into the rolling mill for rough rolling to obtain copper-steel composite plate;

[0019] S2, induction heating of copper-steel composite plate: conveying the copper-steel composite plate to the electromagnetic induction heating device through the conveying system of the induction heating cold rolling system for heating treatment, and blowing the copper surface with mixed gas for cooling;

[0020] S3, tempering: vacuumizing and tempering at a temperature of 120-350 DEG C for one hour, and then slowly cooling to 10-30 DEG C;

[0021] S4, flattening and straightening: after the copper-steel composite plate is cooled after tempering, the copper-steel composite plate is subjected to cold straightening and flattening treatment.

[0022] Specifically, the middle layer raw material used in step S1 is IF gap-free steel, and the thickness and width of the steel plate are 6.0*510 mm; the upper layer raw material and the lower layer raw material are both H65 brass, and the thickness and width of the copper plate are 0.28*540 mm.

[0023] Preferably, in step S2, the induction heating current ranges from 50A to 1500A, the heating time is 10s-60s, the steel plate is heated to 750-1000 DEG C and then air-cooled, and the copper plate is heated to 550-680 DEG C and then air-cooled.

[0024] In the specific embodiment, the rolling force in step S1 is 1055t, and the rolling is performed to 2.2*510 mm, and then to 0.4 mm through 4 passes, and then to the target thickness of 0.13±0.005 mm through 5-6 reversible passes.

[0025] In another embodiment, the entire strip is wound on the uncoiling drum of the cold rolling mill in step S1, and wood blocks are used for support due to the difference between the roll diameter and the inner diameter of the strip, and the strip is flattened and passed through the medium tension without pressure, and then wound on the steel sleeve of the coiling machine.

[0026] Preferably, the copper-steel composite plate is flattened to 0.13 mm in step S4.

[0027] The advantage of the present application is that the heat effect generated by the annular coil eddy current heating can rapidly increase the temperature of the ferromagnetic material in a short time, and a temperature field required for copper-steel coordinated deformation composite is constructed, which greatly reduces the work hardening phenomenon of the composite plate and is beneficial to improve the forming performance of the composite plate, so as to prepare a copper-steel composite plate with coordinated deformation and high bonding strength.

[0028] Because the annealing temperature required by copper and steel is different, and the heat conduction of copper is fast. If the existing heating method is adopted, in order to refine the grain of steel for annealing, it will cause the copper to enter the molten state, resulting in material default, and also causing damage to the heat treatment furnace box. This situation is particularly serious for thin plate materials, at which time the present application is more advantageous.

[0029] In addition, because there is a big difference in material properties such as resistivity and specific heat capacity between copper and steel, if copper and steel are heated at the same time by electromagnetic induction, a temperature difference will be generated. By taking advantage of the fact that the resistance of copper is much smaller than that of steel, under the same current, the parameters can be adjusted so that the heat in the steel is hundreds of times that in the copper. That is, the steel layer with a high melting point is heated to a high temperature alone, and the copper layer with a low melting point is at a lower temperature, so that both materials are annealed at appropriate temperatures.

[0030] In the present application, the whole composite plate is heated (both copper and steel are heated, but the temperatures reached are different, that is, both copper and steel are annealed at appropriate temperatures), the grain size is obviously refined, and the dynamic recrystallization of the grain is promoted. A large number of crystal nuclei are generated at the grain boundary to form recrystallized grains, which further refines the grains. The refined grains improve the mechanical properties of the material matrix, and part of the shear fracture occurs in the matrix, so the bonding strength is also improved.

[0031] In addition, the tempering step in the present method is carried out in the same induction heating furnace used for annealing, realizing online tempering and reducing the process complexity. In summary, the present method can prepare copper-steel composite plates with coordinated deformation and high bonding strength. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Schematic diagram of electromagnetic induction heating;

[0033] Figure 2 Flow direction diagram of cooling air flow in electromagnetic induction heating device (single plate production process);

[0034] Figure 3 Flow direction diagram of air flow in electromagnetic induction heating device (continuous production process);

[0035] Wherein, the reference signs are as follows: 1 is a roller, 2 is a guide rail, 3 is an induction heating device control system, 4 is an induction heating coil, 5 is a copper-steel composite plate to be heated, 6 is an infrared temperature measuring device, 7 is an air inlet channel, 8 is an air outlet channel, 9 is a sealing plug sealing silica gel strip, 10 is a heating device sealing cover. DETAILED DESCRIPTION

[0036] The present application will be described below through specific embodiments, in order to better understand the present application, but it does not constitute a limitation on the present application.

[0037] Embodiment one: electromagnetic induction heating device

[0038] In a general induction heating cold rolling process, it includes a conveying system and an induction heating system controlled by a PLC control system. The induction heating system is composed of an induction heater and an induction heating power supply. The key component is the induction heater, which usually adopts a method of generating heat in the material through an alternating magnetic field.

[0039] Figure 1 The schematic diagram of the electromagnetic induction heating device is shown. The heater adopts electromagnetic induction heating device 3, specifically KPS-160 / 2.5 thyristor intermediate frequency induction heating furnace. Inside the furnace includes copper induction heating coil 4, in the middle of which the copper-steel composite plate 5 to be heated can pass through. The size and shape of the induction heating coil 4 should ensure that the magnetic field mainly acts on the steel layer, and the influence on the copper layer is minimized. Specifically, a ring-shaped copper coil is used as the induction heating coil 4 for plate-shaped samples. The principle is that the coil is made of copper, and due to the shielding effect of copper on the magnetic field, the influence of the magnetic field on the copper layer is small.

[0040] The electromagnetic induction heating device 3 is provided with an infrared thermal imager 6, which is designed on the front and rear sides of the electromagnetic induction heating device 3, and measures the temperature of the interface on the side of the copper-steel-copper bonding layer (see Figure 2 ). The infrared thermal imager 6 can be used to record the temperature distribution of the slab at different times. At the same time, the parameters of the heating coil 4 in the electromagnetic induction heating device 3 are adjusted by a computer such as a PLC system to realize accurate control of the heat in the steel layer, so as to achieve the purpose of heating only the steel and not the copper. The principle is that the heating depth is inversely proportional to the 0.5 power of the frequency, so that by using intermediate frequency induction heating, the frequency can be reduced to some extent and the heating depth can be increased, that is, the steel in the middle layer is concentratedly heated.

[0041] H2+N2 gas mixed at a volume ratio of 1:3 is introduced into the gas inlet channel 7 and sprayed to the upper and lower surfaces of the plate to cool the surface layer of copper. The sealing system is a silica gel strip for the inner cover, and a packing ring for the heating cover. Specifically, after the composite plate 5 is sent into the heating furnace 3 by the guide rail 2, the heating cover 10 is put down, and the edge is sealed with a packing ring. In addition, the gas inlet channel 7 and the exhaust channel 8 are sealed with a silica gel strip 9 at the contact with the inner cover (applicable to the single plate production process). The gas inlet channel 7 delivers the gas into the sealed electromagnetic induction heating device, which not only protects the atmosphere, but also cools the copper surface by blowing cold mixed gas. The mixed gas flows out through the side exhaust channel 8.

[0042] When in operation, the copper-steel clad plate after cold rolling by the roller 1 is transmitted into the induction heating device 3 through the guide rail 2. After the induction heating coil 4 is electrified, an alternating magnetic field is generated inside the coil, which makes the magnetic moment in the steel layer change, thereby generating heat to heat the copper-steel clad plate 5 in it.

[0043] For continuous production process, gas sealing is adopted: micro-positive pressure inside the induction heating device 3, oxygen cannot enter the heating furnace. As shown in the figure, the airflow direction in the electromagnetic induction heating device is shown, and there are no 8 exhaust channels and 10 heating device sealing covers. Figure 3

[0044] Example Two: Method for preparing single-plate copper-steel clad plate

[0045] The method for preparing copper-steel clad plate by adopting the annealing combined with cold rolling process described in Example One (single-plate production) includes the following steps:

[0046] 1) Cold rolling of copper-steel copper three-layer plate: select a steel strip and two copper strips with the same width as raw materials - select IF interstitial-free steel (thickness and width are 6.0*510 mm) as the middle layer raw material, select H65 brass (thickness and width are 0.28*540 mm) as the upper layer raw material and the lower layer raw material, select a rolling force of 1055 t, and roll to 2.2*510 mm. After 4 passes of rolling, roll to 0.4 mm, and adopt 5-6 passes of reversible rolling to the target thickness of 0.13±0.005 mm to obtain the copper-steel clad plate.

[0047] 2) Induction heating of copper-steel clad plate: the copper-steel clad plate is transported to the heating link provided with the electromagnetic induction device described in Example One by a conveying system. The induction heating current ranges from 50 A to 1500 A, and the heating time is 10 s-60 s; after the steel plate is heated to 750-1000 °C and then air-cooled, the copper plate is heated to 550-680 °C and then air-cooled. The copper surface is blown with a mixed gas of H2 and N2 gas from the pipeline 7 to cool down.

[0048] 3) Tempering: vacuumizing and N2 protection, tempering temperature is 120-350 °C. After one hour of heat preservation, slowly cool to room temperature.

[0049] 4) Leveling and straightening: after the copper-steel clad plate after tempering is cooled, the copper-steel clad plate is subjected to cold straightening treatment, and leveled to 0.13 mm.

[0050] In the specific example, the following parameters are adopted:

[0051] ​1) The middle layer raw material is selected as IF interstitial-free steel (1000x6.0x510mm in length, thickness and width), the upper layer raw material and the lower layer raw material are both selected as H65 brass (1000x0.28x540mm in length, thickness and width), the rolling force is selected as 1055t, and rolling is performed to 1000x2.2x510mm. After 4 passes of rolling, 0.4mm is obtained, and 5-6 passes of reversible rolling is adopted to reach the target thickness of 0.13mm.

[0052] 2) The inductive heating current is selected as 1250A, and the heating time is 38s, so that the temperature of the steel plate is higher than the temperature of the copper plate by a temperature difference △T=230℃.

[0053] 3) The composite plate is tempered at 250℃, and the temperature is kept for one hour and then slowly cooled to room temperature. The warped copper-steel composite plate is subjected to cold straightening treatment by using a roller type plate straightening machine.

[0054] 4) The copper-steel composite plate obtained in the embodiment is deformed in coordination, and the obtained plate has relatively uniform structures in each layer. According to the YS / T 550-2006 standard, the test of the shear strength of the composite interface is performed, and the results are shown in Table 1. The average shear strength of the copper-steel composite interface is measured as 109MPa. In the prior art, the cover type annealing furnace is used for annealing: after 7 hours of heating to 680℃, the temperature is kept for 1 hour, the furnace is cooled, the heating cover is opened at 500℃, and the water cooling is performed below 300℃, and the furnace is discharged at 20℃. The cover type annealing furnace method uses a single temperature of 680℃ for the entire composite plate, which is far from the required annealing temperature of the steel layer. The average shear strength is less than 100MPa, and the results are shown in Table 2.

[0055] Table 1 Average shear strength of the copper-steel composite plate interface obtained in the embodiment two

[0056]

[0057] Table 2 Average shear strength of the copper-steel composite plate interface obtained by the cover type annealing furnace

[0058]

[0059] Example three: method for continuously producing copper-steel composite plate

[0060] For the continuous production process, the composite strip after rolling and compounding directly enters the annealing furnace for heat treatment, and after the steps of annealing, tempering and cooling in the inductive heating device, the finished product coil is directly exported. Unlike the single plate in the embodiment two which needs to be sealed by a sealing cover, the embodiment adopts gas sealing: the inductive heating furnace 3 has a slight positive pressure inside, and oxygen cannot enter the furnace. As shown in Figure 3 Compared with the embodiment two, there is no 8 exhaust passage and 10 sealing cover of the heating device.

[0061] Finally, it should be noted that the above-described embodiments are merely used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be replaced equivalently; and these modifications or replacements do not cause the essential nature of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing copper-steel composite plate by using an induction heating system combined with a cold rolling process, wherein the induction heating system is matched with a conveying system and controlled by a computer control system; the induction heating system is composed of an induction heater and an induction heating power supply; the induction heater is an electromagnetic induction heating device, which comprises a copper annular induction heating coil in the interior, and the copper-steel composite plate to be heated can pass through the middle of the induction heating coil; the parameters of the induction heating coil in the electromagnetic induction heating device are adjusted by the computer control system; the electromagnetic induction heating device is provided with an infrared thermal imager for measuring the temperature of the interface on the side of the copper-steel-copper bonding layer; and the electromagnetic induction heating device further comprises an air inlet channel through which cooling gas can pass into the sealed electromagnetic induction heating device, and the air outlet channel is used for discharging the cooling gas. The electromagnetic induction heating device is sealed by a heating cover for single plate production process, and the air inlet channel and the air outlet channel are sealed by sealing silica gel strips at the contact positions with the inner cover; or the electromagnetic induction heating device is sealed by gas for continuous production process, so that the inside of the electromagnetic induction heating device is under a slight positive pressure, and oxygen cannot enter the heating furnace. characterized in that The method comprises the following steps: S1. Cold rolling of copper-steel-copper three-layer plate: selecting one steel strip and two copper strips with the same width, covering the copper on the outer side of the steel, selecting a preset rolling speed and rolling reduction, and then pushing into the rolling mill for rough rolling to obtain a copper-steel composite plate; S2. Induction heating of copper-steel composite plate: conveying the copper-steel composite plate to the electromagnetic induction heating device by the conveying system for heating treatment, and blowing the copper surface with mixed gas for cooling; S3. Tempering: vacuumizing and passing protective gas, tempering temperature is 120-350℃, holding for one hour, and then slowly cooling to 10-30℃; S4. Leveling and straightening: after the copper-steel composite plate is cooled after tempering, the copper-steel composite plate is subjected to cold straightening and leveling treatment.

2. The method of claim 1, wherein, The electromagnetic induction heating device is a medium frequency induction heating furnace.

3. The method of claim 2, wherein, The medium frequency induction heating furnace is a KPS-160 / 2.5 thyristor medium frequency induction heating furnace.

4. The method according to claim 2 or 3, characterized in that: The sealing method of the electromagnetic induction heating device by the heating cover is as follows: after the composite plate is sent into the heating furnace by the guide rail, the heating cover is put down, and the sealing silica gel strips of the inner cover are sealed in the edge sealing packing of the heating cover.

5. The method of claim 1, wherein, The infrared thermal imager is designed on the front and rear three sides of the electromagnetic induction heating device; and the computer control system is a PLC system.

6. The method of claim 1, wherein, The cooling gas is 1:3 volume ratio mixed H2+N2 gas.

7. The method of claim 1, wherein: In step S1, the middle layer raw material is IF interstitial-free steel, and the thickness and width of the steel plate are 6.0*510 mm; the upper layer raw material and the lower layer raw material are both H65 brass, and the thickness and width of the copper plate are 0.28*540 mm.

8. The method of claim 1, wherein: In step S2, the induction heating current ranges from 50A to 1500A, the heating time is 10s-60s, the steel plate is heated to 750-1000℃, and then air cooled, and the copper plate is heated to 550-680℃, and then air cooled.

9. The method of claim 1, wherein: The rolling force in step S1 is 1055t, and the rolling is to 2.2*510mm, and through 4 passes, to 0.4mm, and through 5-6 passes of reversible rolling, to the target thickness of 0.13±0.005mm.

10. The method of claim 1, wherein: In step S1, the whole strip coil is loaded on the opening reel of the cold rolling mill, and since the reel diameter is different from the inner diameter of the strip coil, wood blocks are used for support, and the strip is leveled with no pressure and medium tension, and is rewound to the steel sleeve of the coiler.

11. The method of claim 1, wherein: In step S4, the copper-steel composite plate is leveled to 0.13mm.

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