Heterogeneous-heterogeneous double-structure preparation method of high-strength copper / steel composite plate

Abstract

The invention discloses a preparation method of a heterogeneous-heterogeneous double structure of a high-strength copper / steel composite board, which comprises the following steps: realizing metallurgical bonding between copper and steel heterogeneous metals through the synergistic effect of a laser energy field and a rolling force, and promoting formation of a martensite structure near a composite interface; then, the surface of the steel side is subjected to online heat treatment through a flat-topped laser beam, and the purposes that the outer surface layer structure of the steel side is completely converted into martensite, the martensite structure at a bonding interface is converted into tempered sorbite, the residual stress of the copper side is reduced, and a heterogeneous structure with the grain size in gradient distribution is formed on the copper side are synchronously achieved; the tensile strength, the interface bonding strength and the toughness of the copper-steel composite plate are synergistically improved.

Description

Technical Field

[0001] The invention relates to the technical field of composite plate processing, and in particular to a method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate. Background Art

[0002] Heterogeneous metal composite materials effectively bring into play the performance advantages of each component metal, while significantly reducing material costs, and have broad application prospects. Among them, copper-steel composite plates are a metallurgical combination of copper and steel, which have both the high electrical conductivity and thermal conductivity and corrosion resistance of copper, and the high strength and cost-effectiveness of steel. They are widely used in power equipment, shipbuilding, chemical pipelines, and new energy storage systems.

[0003] At present, the preparation process of copper-steel composite plate mainly includes explosive composite method, diffusion welding method, rolling method, etc. For example, the invention patent with application number CN202410346392.0 proposes a preparation method of copper-steel composite plate with tensile strength exceeding 230MPa. The method arranges explosives and uses shock waves to instantly combine the two plates after detonation. The production process of this method is simple, but it is not suitable for thin-gauge metal plates, and the strength of the prepared composite plate is still not high. The invention patent with application number CN202411229580.1 proposes a copper-steel composite plate and its preparation method. The method prepares a copper-steel composite plate by combining copper-steel billets, vacuum diffusion welding, heating, rolling and heat treatment processes, but the tensile strength of the copper-steel composite plate prepared by this method is only about 359MPa. It can be found that the copper-steel composite plates prepared by the existing process generally have the problem of low strength and cannot meet the needs of high-strength copper-steel composite plates in specific industrial environments. How to improve the strength of copper-steel composite plates while maintaining their excellent toughness and achieving short processes is an urgent problem to be solved.

[0004] Therefore, the present invention proposes a heterogeneous-heterogeneous dual-structure preparation method for a high-strength copper-steel composite plate, which utilizes a one-step forming rolling composite + laser surface annealing treatment process under laser-assisted heating to greatly improve the tensile strength of the copper-steel composite plate. Moreover, the preparation method is suitable for a variety of thickness specifications and improves production efficiency at the same time. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned background technology, the present invention provides a heterogeneous-heterogeneous dual-structure preparation method of a high-strength copper-steel composite plate, which utilizes the synergistic effect of laser-induced thermal effect and rolling force to quickly and efficiently realize the metallurgical lamination of copper plates (i.e., forming a heterogeneous structure), and then utilizes laser surface annealing technology to simultaneously realize microstructure isomerization and residual stress elimination, thereby synergistically improving the tensile strength, interface bonding strength and toughness of the composite plate.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper-steel composite plate, comprising the following steps: S1. Centering: After uncoiling, the copper strip and steel strip enter the CPC system (automatic centering system for plates and strips) through pinch rollers for centering. The system detects the edge position of the composite slab in real time through a laser rangefinder or a photoelectric sensor, calculates the deviation between the current center line and the preset target center line, and the controller drives the servo motor to adjust the guide device through a PID+fuzzy hybrid algorithm (a combination of PID control and fuzzy logic control).

[0007] S2. Grinding treatment of the surface to be composited: The surface to be composited of the copper plate and the steel plate is roughened. After the grinding treatment is completed, the dust adsorption system is used to remove the particles remaining on the surface to be composited.

[0008] S3. Rolling composite processing: Based on the synergistic effect of laser-assisted heating and rolling mill pressure, metallurgical lamination of copper and steel is implemented to form a heterogeneous structure.

[0009] Specifically, the line spot used for rolling composite processing has a flat-top feature in its spot energy distribution and has the characteristic of adjustable spot length. The two plates are opened at the unpressed part to form an opening, and the flat-top line spot is irradiated at the copper-steel interface to be composited. At the same time, the maximum laser-induced heating temperature on the steel side is controlled at 980-1130°C, that is, the surface layer on the steel side close to the bonding interface is austenitized; while the maximum laser-induced heating temperature on the copper side is controlled at 900-1150°C, that is, the surface to be bonded on the copper side is slightly melted, or even not melted, to reduce the tendency of defects such as pores on the bonding interface. In order to improve the deformation coordination between dissimilar metals in the micro-region of the composite interface, the speed ratio of the working rolls on the steel side and the copper side of the four-roll asynchronous rolling mill is controlled at 1.1-1.5, and the speed of the unwinding machine unwinding the copper-steel strip is synchronously and collaboratively adjusted according to the requirements of the rolling composite process.

[0010] S4. Online laser surface heat treatment: The copper-steel composite plate after rolling and compounding enters the laser heat treatment chamber under the protection of inert atmosphere, and a heterogeneous structure of tempered troostite at the bonding interface and martensite on the outer surface is constructed on the steel side, and a heterogeneous structure with a grain size that decreases gradually from the bonding interface to the contact surface of the roller is constructed on the copper side.

[0011] Specifically, the steel side surface of the copper-steel composite plate after rolling and compounding is laser irradiated with a flat-top wide spot, and multiple effects such as copper side annealing, steel side high-temperature tempering and surface quenching are achieved simultaneously. On the one hand, the heat conduction effect induced by the irradiation of the flat-top wide spot on the steel side causes annealing on the copper side, with the highest heating temperature being 450-580°C, and the laser-induced annealing heating temperature presents a gradient distribution characteristic. At the same time, the above-mentioned annealing phenomenon is used to reduce the residual stress on the copper side, annihilate dislocations, and improve the plastic deformation capacity, and the grain size of copper near the bonding interface is relatively larger. On the other hand, laser irradiation of the outer surface of the steel with a flat-top wide spot will induce martensitic phase transformation within a depth range of 0.3-0.8 mm from the surface layer, and at the same time, the martensitic structure formed at the bonding interface during the rolling and compounding process is subjected to high-temperature tempering treatment to transform it into a tempered troostite structure.

[0012] Furthermore, in step S1, the deviation threshold between the center line of the plate and the preset target center line is 0.1 mm.

[0013] Furthermore, in step S2, a grinding roller is used for surface roughening treatment, the rotation speed of the grinding roller is adjustable within 500-3000 r / min, and the grinding roller can be made of a wire brush, a nylon brush, a diamond coating brush, etc.; the air volume Q of the dust adsorption system is ≥10000m 3 / h, wind pressure P≥10000Pa, motor power P=75kW.

[0014] Furthermore, in step S2, the angle of the opening of the copper steel where it is not pressed is 25 to 60 degrees.

[0015] Furthermore, in step S3, the maximum output power of the laser is 40 kW, the length of the light spot is 200 to 600 mm, the width is 2 mm, and the uniformity of the light spot energy distribution is ≥95%.

[0016] Furthermore, in step S3, the maximum rolling pressure of the four-roll asynchronous rolling mill is 8000 kN, and the rolling reduction ratio is ≥50%.

[0017] Furthermore, in step S4, the maximum output power of the laser is 60 kW, the length of the homogenized light spot is 200-600 mm, the width is 5 mm, and the uniformity of the light spot energy distribution is ≥95%.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) By introducing a heterogeneous and heterogeneous dual structure, the tensile strength is significantly improved without changing the material composition. On the one hand, the difference in plastic deformation capacity of the micro-regions of the copper and steel bonding interface during the rolling composite process is reduced by laser-assisted heating, and at the same time, a laminated interface without defects such as pores is formed by relying on a large rolling force, which effectively ensures the tensile strength; on the other hand, by introducing a heterogeneous structure on the steel side (i.e., tempered troostite at the bonding interface and martensite near the outer surface, and a gradient grain structure is formed on the copper side), combined with the coupling effect of the heterogeneous structure, the strength of the composite plate is significantly improved based on the mutation-induced strengthening effect.

[0019] (2) The present invention proposes an online laser heat treatment method for copper-steel composite plates, which not only reduces the process flow and improves production efficiency, but also implements targeted heat treatment on each layer of metal through the gradient heating effect induced by laser heat treatment, that is, the surface layer on the steel side is laser quenched to improve the surface wear resistance and play the role of hard phase in the heterogeneous structure; the bonding interface layer on the steel side is subjected to high-temperature tempering to soften the structure to reduce the difference in deformation capacity between dissimilar metals near the bonding interface; annealing is performed on the copper side to reduce residual stress, construct a gradient grain structure, improve the deformation capacity of the structure, and ensure the toughness of the composite plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 This is a diagram of the preparation process of the heterogeneous and heterogeneous dual structure of the high-strength copper-steel composite plate of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1 A method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper-steel composite plate comprises the following steps: S1. Centering treatment: 2mm thick T2 copper and 2mm thick Q235 steel strips are used as composite materials, and their widths are both 200mm. After uncoiling, the copper strip and steel strip enter the CPC system through pinch rollers for centering processing. The deviation threshold between the center line of the plate and the preset target center line is 0.1mm.

[0024] S2. Grinding treatment of the surface to be composited: The surfaces of the copper plate and the steel plate to be bonded are roughened by grinding rollers. The speed of the grinding motors matched with the grinding rollers is adjusted to 3000r / min for the copper belt and 500r / min for the steel belt. After the grinding process is completed, the dust adsorption system is used to remove the particles remaining on the surfaces to be bonded. The air volume Q of the dust removal equipment in the dust adsorption system is ≥10000m 3 / h, wind pressure P≥10000Pa, motor power P=75kW.

[0025] S3, rolling composite processing: Based on the synergistic effect of laser-assisted heating and rolling mill pressure, metallurgical lamination of copper and steel is implemented to form a heterogeneous structure. The laser parameters are set, and the integral mirror spot shaping and homogenization mechanism is used to obtain a flat-top spot with a length of 200mm and a width of 2mm. The laser output power is 25kW, and the spot energy distribution uniformity is ≥95%. The two plates are opened at a 25° angle at the unpressed part, and the flat-top line spot is irradiated at the copper-steel composite interface. At the same time, the maximum laser-induced heating temperature on the steel side is controlled at 1000±20℃, that is, the surface layer close to the bonding interface on the steel side is austenitized; while the maximum laser-induced heating temperature on the copper side is controlled at 925±25℃, that is, the surface to be bonded on the copper side is micro-melted to reduce the tendency of defects such as pores on the bonding interface. The rotation speed of the upper and lower rollers of the asynchronous rolling mill is adjusted, and the rolling speed of the copper strip is adjusted to 0.2m / min, and the rolling speed of the steel strip is adjusted to 0.3m / min.

[0026] S4, Online laser surface heat treatment: The copper-steel composite plate after rolling and cladding enters the laser heat treatment chamber under the protection of inert atmosphere, and a heterogeneous structure of tempered troostite at the bonding interface and martensite on the outer surface is constructed on the steel side. The heat conduction effect induced by the flat-top wide spot irradiation on the steel side ensures that the maximum annealing temperature on the copper side is 480±30℃, and a heterogeneous structure with a grain size decreasing gradually from the bonding interface to the contact surface of the roller is constructed on the copper side. The steel surface of the copper-steel composite plate after rolling and cladding is laser irradiated with a flat-top wide spot, and multiple effects such as copper side annealing, steel side high-temperature tempering and surface quenching are simultaneously achieved, that is, a heterogeneous structure with an average grain size decreasing gradually from 22μm at the bonding interface to 4μm near the contact surface of the roller is formed on the copper side, and a 0.3mm thick martensite layer is obtained near the bonding interface on the steel side. Among them, the spot length is consistent with the width of the composite plate, the laser power is 30kW, the length of the homogenized spot is 200mm, the width is 5mm, and the uniformity of the spot energy distribution is ≥95%.

[0027] The tensile strength test method is: according to GB / T228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method", a tensile test is performed on the copper-steel composite plate prepared in this embodiment on a universal material testing machine to measure its tensile strength.

[0028] After testing, the T2 / Q235 composite plate with a tensile strength of 834MPa was finally obtained.

[0029] Example 2 A method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper-steel composite plate comprises the following steps: S1. Centering treatment: 0.8mm thick T2 copper and 1.5mm thick Q355 steel strips are used as composite materials, both of which have a width of 400mm. After uncoiling, the copper strip and steel strip enter the CPC system through pinch rollers for centering processing. The deviation threshold between the center line of the plate and the preset target center line is 0.1mm.

[0030] S2. Grinding treatment of the surface to be composited: The surfaces of the copper plate and the steel plate to be bonded are roughened by grinding rollers. The speed of the grinding motors matched with the grinding rollers is adjusted to 1800r / min for the copper belt and 800r / min for the steel belt. After the grinding process is completed, the dust adsorption system is used to remove the particles remaining on the surfaces to be bonded. The air volume Q of the dust removal equipment in the dust adsorption system is ≥10000m 3 / h, wind pressure P≥10000Pa, motor power P=75kW.

[0031] S3, rolling composite processing: Based on the synergistic effect of laser-assisted heating and rolling mill pressure, metallurgical lamination of copper and steel is implemented to form a heterogeneous structure. The laser parameters are set, and the integral mirror spot shaping and homogenization mechanism is used to obtain a flat-top spot with a length of 400mm and a width of 2mm. The laser output power is 30kW, and the spot energy distribution uniformity is ≥95%. The two plates are opened at a 40° angle at the unpressed part, and the flat-top line spot is irradiated at the copper-steel composite interface. At the same time, the maximum laser-induced heating temperature on the steel side is controlled at 1050±30℃, that is, the surface layer close to the bonding interface on the steel side is austenitized; while the maximum laser-induced heating temperature on the copper side is controlled at 1080±30℃, that is, the surface to be bonded on the copper side is micro-melted to reduce the tendency of defects such as pores on the bonding interface. The rotation speed of the upper and lower rollers of the asynchronous rolling mill is adjusted, and the rolling speed of the copper strip is adjusted to 2.5m / min, and the rolling speed of the steel strip is adjusted to 3m / min.

[0032] S4, Online laser surface heat treatment: The copper-steel composite plate after rolling and cladding enters the laser heat treatment chamber under the protection of inert atmosphere, and a heterogeneous structure of tempered troostite at the bonding interface and martensite on the outer surface is constructed on the steel side. The heat conduction effect induced by the flat-top wide spot irradiation on the steel side ensures that the maximum annealing temperature on the copper side is 500±30℃, and a heterogeneous structure with a grain size decreasing gradually from the bonding interface to the contact surface of the roller is constructed on the copper side. The steel surface of the copper-steel composite plate after rolling and cladding is laser irradiated with a flat-top wide spot, and multiple effects such as copper side annealing, steel side high-temperature tempering and surface quenching are simultaneously achieved, that is, a heterogeneous structure with an average grain size decreasing gradually from 25μm at the bonding interface to 5μm near the contact surface of the roller is formed on the copper side, and a 0.5mm thick martensite layer is obtained near the bonding interface on the steel side. Among them, the spot length is consistent with the width of the composite plate, the laser power is 40kW, the length of the homogenized spot is 400mm, the width is 5mm, and the uniformity of the spot energy distribution is ≥95%.

[0033] The tensile strength test method is: according to GB / T228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method", a tensile test is performed on the copper-steel composite plate prepared in this embodiment on a universal material testing machine to measure its tensile strength.

[0034] After testing, the T2 / Q355 composite plate with a tensile strength of 974MPa was finally obtained.

[0035] Example 3 A method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper-steel composite plate comprises the following steps: S1. Centering treatment: 0.5mm thick T2 copper and 1mm thick Q690 steel were used as the composite materials, both of which were 600mm wide. After uncoiling, the copper strip and steel strip were respectively fed into the CPC system through pinch rollers for centering processing. The deviation threshold between the center line of the plate and the preset target center line was 0.1mm.

[0036] S2. Grinding treatment of the surface to be composited: The surfaces of the copper plate and the steel plate to be bonded are roughened by grinding rollers. The speed of the grinding motors matched with the grinding rollers is adjusted to 1500r / min for the copper belt and 1000r / min for the steel belt. After the grinding process is completed, the dust adsorption system is used to remove the particles remaining on the surfaces to be bonded. The air volume Q of the dust removal equipment in the dust adsorption system is ≥10000m 3 / h, wind pressure P≥10000Pa, motor power P=75kW.

[0037] S3, rolling composite processing: Based on the synergistic effect of laser-assisted heating and rolling mill pressure, metallurgical lamination of copper and steel is implemented to form a heterogeneous structure. The laser parameters are set, and the integral mirror spot shaping and homogenization mechanism is used to obtain a flat-top spot with a length of 600mm and a width of 2mm. The laser output power is 40kW, and the spot energy distribution uniformity is ≥95%. The two plates are opened at a 60° angle at the unpressed part, and the flat-top line spot is irradiated at the copper-steel composite interface. At the same time, the maximum laser-induced heating temperature on the steel side is controlled at 1090±40℃, that is, the surface layer close to the bonding interface on the steel side is austenitized; while the maximum laser-induced heating temperature on the copper side is controlled at 1100±50℃, that is, the surface to be bonded on the copper side is micro-melted to reduce the tendency of defects such as pores on the bonding interface. The rotation speed of the upper and lower rollers of the asynchronous rolling mill is adjusted, and the rolling speed of the copper strip is adjusted to 2m / min, and the rolling speed of the steel strip is adjusted to 2.2m / min.

[0038] S4, Online laser surface heat treatment: The copper-steel composite plate after rolling and cladding enters the laser heat treatment chamber under the protection of inert atmosphere, and a heterogeneous structure of tempered troostite at the bonding interface and martensite on the outer surface is constructed on the steel side. The heat conduction effect induced by the flat-top wide spot irradiation on the steel side ensures that the maximum annealing temperature on the copper side is 540±40℃, and a heterogeneous structure with a grain size decreasing gradually from the bonding interface to the contact surface of the roller is constructed on the copper side. The steel surface of the copper-steel composite plate after rolling and cladding is laser irradiated with a flat-top wide spot, and multiple effects such as copper side annealing, steel side high-temperature tempering and surface quenching are simultaneously achieved, that is, a heterogeneous structure with an average grain size decreasing from 32μm at the bonding interface to 6μm near the contact surface of the roller is formed on the copper side, and a 0.8mm thick martensite layer is obtained near the bonding interface on the steel side. Among them, the spot length is consistent with the width of the composite plate, the laser power is 60kW, the length of the homogenized spot is 600mm, the width is 5mm, and the uniformity of the spot energy distribution is ≥95%.

[0039] The tensile strength test method is: according to GB / T228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method", a tensile test is performed on the copper-steel composite plate prepared in this embodiment on a universal material testing machine to measure its tensile strength.

[0040] After testing, the T2 / Q690 composite plate with a tensile strength of 1187MPa was finally obtained.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate, characterized in that: The following steps are involved: S1. Centering treatment: After uncoiling, the copper strip and steel strip enter the CPC system through the pinch rollers for centering treatment; S2. Grinding treatment of the surface to be bonded: The surface to be bonded of the copper plate and the steel plate is subjected to surface roughening treatment. After the grinding treatment is completed, the particles remaining on the surface to be bonded are removed by using a dust adsorption system; S3, rolling composite processing: the unpressed part of the two plates is opened to form an opening, and the laser processing head outputs a flat-top line spot, which is irradiated on the interface between copper and steel to be composited. Then, the rolling mill is started, and the laser processing head emits light to heat the interface between the steel plate and the copper plate to be composited. Based on the synergistic effect of laser-assisted heating and rolling mill pressure, metallurgical lamination of copper and steel is implemented to form a heterogeneous structure; during laser irradiation, the maximum laser-induced heating temperature on the steel side is controlled at 980-1130°C, and the surface layer on the steel side close to the bonding interface is austenitized; while the maximum laser-induced heating temperature on the copper side is controlled at 900-1150°C, and the surface to be composited on the copper side is slightly melted or not melted; the rolling mill is a four-roll asynchronous rolling mill, and the speed ratio of the working rolls on the steel side and the copper side of the four-roll asynchronous rolling mill is controlled at 1.1-1.5, and the unwinding speeds of the copper strip and the steel strip are synchronously and collaboratively adjusted according to the requirements of the rolling composite process; S4. Online laser surface heat treatment: The copper-steel composite plate after rolling and compounding enters the laser heat treatment chamber under the protection of inert atmosphere, and a heterogeneous structure of tempered troostite at the bonding interface and martensite on the outer surface is constructed on the steel side, and a heterogeneous structure with a grain size gradually decreasing from the bonding interface to the surface layer near the copper side is constructed on the copper side.

2. The method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate according to claim 1, characterized in that: In the step S1, the deviation threshold between the center line of the plate and the preset target center line is 0.1 mm.

3. The method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate according to claim 1, characterized in that: In step S2, a grinding roller is used for surface roughening treatment. The speed of the grinding roller is adjustable within 500 to 3000 r / min. The grinding roller is made of a wire brush, a nylon brush or a diamond coating brush. The air volume Q of the dust adsorption system is ≥ 10000m 3 / h, wind pressure P≥10000Pa, motor power P=75kW.

4. The method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate according to claim 1, characterized in that: In step S3, the angle of the opening of the copper-steel plate at the unpressed portion is 25 to 60 degrees.

5. The method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate according to claim 1, characterized in that: In step S3, the maximum output power of the laser is 40 kW, the length of the light spot is 200-600 mm, the width is 2 mm, and the uniformity of the light spot energy distribution is ≥95%.

6. The method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate according to claim 1, characterized in that: In step S3, the maximum rolling pressure of the four-high asynchronous rolling mill is 8000 kN, and the rolling reduction ratio is ≥50%.

7. The method for preparing a heterogeneous heterogeneous dual structure high-strength copper / steel composite plate according to claim 1, characterized in that: In the step S4, the maximum annealing heating temperature of the copper side is 450-580° C., and the annealing temperature is distributed in a gradient; the martensitic phase transformation is induced in the steel side within a depth range of 0.3-0.8 mm from the surface layer.

8. The method for preparing a heterogeneous-heterogeneous dual structure of a high-strength copper / steel composite plate according to claim 7, characterized in that: In step S4, the maximum output power of the laser is 60 kW, the length of the homogenized light spot is 200-600 mm, the width is 5 mm, and the uniformity of the light spot energy distribution is ≥95%.

Images