Nitriding treatment of bimetallic surface smoothing and differential temperature rolling composite process and auxiliary equipment

Abstract

This invention relates to the field of rolling process technology and equipment, and in particular to a composite process and auxiliary device for nitriding-treated bimetallic surfaces with corrugated and uneven temperature rolling. The composite process includes pre-roll mechanical grinding of the surfaces to be bonded, nitriding treatment of the metal surfaces, pulsed current heating of the sheet metal, rapid billet assembly, pre-composite rolling with corrugated rolls, and flat roll rolling. The auxiliary device includes a lifting frame with a pulsed power supply heating device and a conveyor roller table, which can achieve rapid heating, billet assembly, and feeding for metal sheets of different specifications. This invention can effectively reduce the difference in plastic deformation between dissimilar metals, promote interfacial bonding, and achieve the goal of synergistic optimization of the shape and properties of bimetallic laminates.

Description

Technical Field

[0001] This invention relates to the field of rolling technology, and in particular to a composite process and auxiliary device for nitriding-treated bimetallic surfaces with wave smoothing and different temperatures during rolling. Background Technology

[0002] Double-layer metal laminate is a new type of metal material made from two different metal sheets through rolling and other methods. This material not only possesses high strength, rigidity, and corrosion resistance, but is also lightweight and inexpensive, making it widely used in aerospace, automotive, shipbuilding, and construction industries.

[0003] Double-layer metal laminate rolling process involves a series of steps, including surface cleaning, wiping, pre-pressing, forming, uniform heating, and rolling, from two different metal sheets. During rolling, parameters such as the size and number of rolls, rolling pressure, and rolling speed are adjusted to control the thickness and shape of the sheet, achieving the desired product performance and quality. This process plays a significant role in reducing material costs and expanding the applications of materials.

[0004] Interface strength is a crucial performance parameter in bilayer metal composite rolling processes. Among the factors influencing interface strength, metal surface quality is a significant one. The presence of cracks, oxidation, or other defects on the metal surface severely impacts interface strength. This is especially true for metals with easily oxidized surfaces; rolling composite processes under heating conditions can easily lead to a decrease in interfacial bonding due to interface oxidation. Furthermore, for rolling composites of two metals with significantly different plasticities, conventional rolling composite processes can easily result in severe warping or even interfacial cracking due to asynchronous plastic elongation during deformation. Therefore, there is an urgent need to develop a novel rolling composite process and supporting equipment specifically for metals with easily oxidized surfaces or those exhibiting significant differences in plasticity.

[0005] Problems with traditional double-layer metal rolling composite processes:

[0006] 1. Limited selection of metal materials: Traditional rolling composite processes are only suitable for metals with good ductility and stable properties, while the bonding strength of metals with easily oxidized surfaces is not ideal;

[0007] 2. The billet assembly process is complex. In order to reduce interface oxidation before traditional bimetallic hot rolling composite, billet assembly welding and vacuuming are required, which is complex, costly and inefficient.

[0008] 3. Severe warping of the sheet metal: Due to the difference in plastic deformation capacity between dissimilar metals, the sheet metal after traditional rolling composite rolling will warp, which limits the industrial application of laminated plates.

[0009] 4. Low interfacial bonding strength: In the traditional rolling composite method for preparing bimetallic laminates, the interfacial normal stress is relatively small, and oxidation easily occurs at the interface during heating, resulting in low interfacial bonding strength. This is especially true for some difficult-to-deform metal combinations, where initial interfacial bonding cannot be achieved. Furthermore, due to the different coefficients of thermal expansion of the metal materials, significant stress and strain are generated at the interface between the metal materials, leading to poor interfacial reliability.

[0010] Therefore, it is essential to develop a novel double-layer metal rolling composite process that is suitable for various metal combinations and can achieve high-strength interfacial bonding and good post-rolling sheet shape. Summary of the Invention

[0011] In view of the above-mentioned existing technical problems, the purpose of this invention is to solve the technical problem that the surfaces to be bonded are easily oxidized during the production of bimetallic laminates, resulting in low bonding strength, poor material ductility, and poor mechanical properties. The invention provides a nitriding treatment process for flattening and uneven temperature rolling composite of bimetallic surfaces and an auxiliary device.

[0012] The technical solution adopted by this invention to solve its technical problem is as follows:

[0013] A composite process for nitriding-treated bimetallic surfaces with smoothed, unevenly heated rolling, characterized by the following steps:

[0014] 1) Surface grinding: Before rolling, use an angle grinder equipped with a wire brush to mechanically grind the surfaces of the metal sheets to be bonded until the surface is "frosted";

[0015] 2) Nitriding treatment: The surfaces of the metals to be bonded are subjected to salt bath nitriding treatment in a nitriding equipment until a dense nitride layer is formed on the surface;

[0016] 3) Pulse current heating: The board material is heated to the target temperature using a pulse current device.

[0017] 4) Rapid assembly: The two metal sheets to be joined are stacked face to face for rapid assembly;

[0018] 5) Corrugated roll pre-composite: The assembled slab is rough rolled and pre-composite using a corrugated roll mill with a drum-shaped corrugated roll upper roll and a flat roll lower roll;

[0019] 6) Flat roll rolling: The corrugated laminate is then precision rolled to obtain a bimetallic laminate with a flat surface and a corrugated interface.

[0020] 7) Annealing: The flattened bimetallic laminate is annealed and then cooled;

[0021] 8) Finishing: Straighten, cut the head, cut the tail, trim the edges, and finally bundle and pack.

[0022] As a further improvement to the technical solution of the present invention, in step 1), surface polishing, the metal surface is polished with a wire brush to remove oil and impurities from the metal surface, so that the surface is "frosted".

[0023] As a further improvement to the technical solution of the present invention, in step 2), the metal plate after surface grinding is placed in a nitriding equipment and a certain pressure and temperature are maintained so that nitrogen gas can penetrate into the metal plate to be bonded, so that a dense nitride layer is formed on the surface to prevent oxidation of the metal to be bonded surface.

[0024] As a further improvement to the technical solution of the present invention, in step 3) pulse current heating, the plate is placed on a lifting platform equipped with a pulse current heating device for power-on heating treatment.

[0025] As a further improvement to the technical solution of the present invention, in step 4) rapid assembly, the lifting platform is controlled to rapidly stack and assemble the polished surfaces of the substrate and the composite plate.

[0026] As a further improvement to the technical solution of the present invention, in step 4) rapid billet assembly, the lifting platform is equipped with a slide rail for width adjustment to accommodate different specifications of plates.

[0027] As a further improvement to the technical solution of the present invention, in step 5) corrugated roll pre-composite rolling, the corrugated roll is a drum-shaped corrugated roll with a certain number of periodic patterns engraved on its surface.

[0028] As a further improvement to the technical solution of the present invention, in step 5) corrugated roll pre-composite, the metal bonding surface undergoes plastic deformation, the dense nitride layer is broken, and the two-layer metal bonding surfaces come into contact and bond.

[0029] As a further improvement to the technical solution of the present invention, in step 6) during the flat roll rolling process, the metal bonding surface undergoes plastic deformation, the dense nitride layer is further broken, the exposed metal bonding surface increases, and the double-layer metal bonding surface further contacts and bonds.

[0030] The auxiliary device for nitriding bimetallic surface smoothing and isothermal rolling is characterized by:

[0031] 1) The lifting frame uses chain drive to lift the plates to suit low-speed, heavy-load conditions;

[0032] 2) The lifting frame uses slide rails and lead screws to achieve width adjustment to accommodate different specifications of sheet metal;

[0033] 3) The plate is heated and kept warm by connecting the pulse current to the lifting platform through a pulse current device;

[0034] 4) The assembled metal sheets are sent to the rolling mill for compounding via conveyor rollers.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. After grinding the metal sheet to be bonded before rolling, perform salt bath nitriding treatment until a dense nitride layer is formed on the surface. On the one hand, it can protect the metal to be bonded surface from oxidation. On the other hand, the nitrided layer on the metal surface is a brittle layer, which is very easy to break during the rolling deformation process, exposing the fresh metal underneath, providing more bonding area for the metal to bond and improving the bonding performance of the laminate.

[0037] 2. Since the nitrided layer formed at the interface has a high melting point and high density, most metal combinations can be rolled at large temperature differences without the need for vacuuming, which effectively reduces the warping of the rolled laminate and expands the range of materials to be selected for differential rolling.

[0038] 3. Since there is no need for billet welding and vacuuming, the billet making process is greatly simplified, improving work efficiency and reducing costs;

[0039] 4. Using pulsed current-assisted heating equipment to heat the sheet material can not only quickly heat the sheet material to the target temperature, but also the pulsed current can improve the plasticity and uniformity of the metal material, which is conducive to promoting the bonding of the sheet material interface and improving the stability of the mechanical properties of the rolled laminate.

[0040] 5. The wave rolling process can create strong shear forces and localized strong stresses at the interface, which can accelerate the breakage of the dense nitride layer on the metal surface, promote the contact and bonding between the fresh metal to be bonded in the bottom layer, reduce the pre-bonding reduction rate of the sheet, and reduce the equipment load. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a diagram of the nitriding-treated bimetallic laminate blank according to the present invention. In the diagram: 1-substrate, 2-cladding plate, 3-nitriding equipment, 4-dense nitride layer, 5-blank;

[0043] Figure 2 This is a schematic diagram of the pre-composite structure of the corrugated roll rolling according to the present invention. In the figure: 6-drum-shaped corrugated roll, 7-ordinary flat roll, 8-bimetallic corrugated laminate, 9-bimetallic laminate, 10-corrugated rolling schematic diagram, 11-flat roll rolling schematic diagram.

[0044] Figure 3 for Figure 2 A partial enlarged view of the schematic diagram of corrugated rolling in section 10. In the diagram: 12-dense nitride layer, 13-double-layer metal bonding region, 14-rough rolling pre-composite stage;

[0045] Figure 4 for Figure 2 A partially enlarged view of the schematic diagram of the 11-flat roll rolling process, in which: 15-finishing and finishing stage;

[0046] Figure 5 This is a schematic diagram of the composite process of nitriding treatment of bimetallic surface corrugated and uneven temperature rolling according to the present invention. In the figure: 16-pulse current device, 17-lifting frame, 18-drum corrugated roll mill, 19-flat roll mill, 20-flat roll, 21-drum corrugated roll, 22-flat roll, 23-substrate, 24-clad plate, 25-transfer roller table.

[0047] Figure 6 This is a schematic diagram of auxiliary equipment for a composite process. In the diagram: 26 - lifting platform. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0049] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0050] The nitriding treatment of bimetallic surfaces and the composite process of uneven temperature rolling include the following steps:

[0051] 1) Surface grinding: Before rolling, use an angle grinder equipped with a wire brush to mechanically grind the surfaces of the metal sheets to be bonded until the surface is "frosted";

[0052] 2) Nitriding treatment: such as Figure 1 As shown, the surface of the metal to be bonded is subjected to salt bath nitriding treatment in nitriding equipment 3 until a surface nitriding process is completed. Figure 1 The dense nitride layer 4 shown;

[0053] 3) Pulse current heating: using methods such as... Figure 5 The pulsed current device 16 shown applies electricity to heat the plate to the target temperature.

[0054] 4) Rapid billet assembly: using methods such as... Figure 5 The lifting frame 17 shown stacks two types of metal sheets for rapid assembly;

[0055] 5) Corrugated roll pre-compounding: such as Figure 5 The assembled slab is rough-rolled and pre-composite 14 using a drum-shaped corrugated roll mill 18 with an upper roll equipped with a drum-shaped corrugated roll 21 and a lower roll with a flat roll 22;

[0056] 6) Flat roll rolling: This is followed by processes such as... Figure 5 The flat roll mill 19 shown performs precision rolling and bonding 15 on the corrugated laminate to obtain a bimetallic laminate with a smooth surface and a corrugated bonding interface.

[0057] 7) Annealing: The flattened bimetallic laminate is annealed and then cooled;

[0058] 8) Finishing: Then straighten, cut the head, cut the tail, and trim the edges, and finally bundle and pack.

[0059] In this invention, during step 1) surface polishing, the metal surface is polished with a wire brush to remove oil and impurities, resulting in a "frosted" surface. Specifically, depending on the material, a combination of surface cleaning methods such as mechanical cleaning, chemical cleaning, and electrochemical cleaning can be used to achieve the best cleaning effect.

[0060] Furthermore, in step 2), the nitriding process involves placing the polished metal sheet in a nitriding device 3, maintaining certain pressure and temperature conditions to allow nitrogen to penetrate the metal sheet to be bonded, forming a dense nitride layer 4 on the surface to prevent oxidation of the metal to be bonded surface.

[0061] Furthermore, in step 3) pulse current heating, the plates are placed on the lifting frame 17 equipped with a pulse current heating device and heated to the target temperature.

[0062] Furthermore, in step 4) rapid assembly, the lifting frame is controlled to rapidly stack and assemble the surfaces of the substrate 23 and the composite plate 24 to be joined.

[0063] Furthermore, in step 4) rapid billet assembly, the lifting frame 17 is equipped with a slide rail for width adjustment to accommodate different specifications of plates.

[0064] Furthermore, in step 5) corrugated roll pre-composite, the corrugated roll is a drum-shaped corrugated roll 21 with a certain number of periodic patterns engraved on its surface.

[0065] Furthermore, in step 5) the pre-composite process of corrugated roll rolling, the metal bonding surface undergoes plastic deformation, the dense nitride layer breaks up, and the two-layer metal bonding surfaces partially come into contact and bond.

[0066] Furthermore, during step 6) of the flat roll rolling process, the metal bonding surface undergoes plastic deformation, the dense nitride layer is further broken up, the exposed metal bonding surface increases, and the double-layer metal bonding surface further contacts and bonds.

[0067] The technical solution of the present invention will be described in detail below through specific embodiments.

[0068] Example 1

[0069] Adopting attachment Figure 1 , 2 The method shown is used to prepare titanium / aluminum laminates:

[0070] 1) Surface polishing: Select a TC4 titanium alloy plate with dimensions of 200 mm (length) × 50 mm (width) × 2 mm (height) as the base plate 1 and a 1060 aluminum alloy plate with dimensions of 200 mm (length) × 50 mm (width) × 2 mm (height) as the cladding plate 2. Use an angle grinder equipped with a wire brush to mechanically polish the surfaces of the metal plates to be joined until the surface is "frosted".

[0071] 2) Nitriding treatment: The TC4 titanium alloy metal surface to be bonded is subjected to salt bath nitriding treatment in nitriding equipment 3 until a dense nitride layer 4 is formed on the surface. The treatment time is 3 hours and the temperature is 750℃.

[0072] 3) Pulse current heating: The nitrided TC4 titanium alloy plate is placed on the lifting frame 17 equipped with a pulse current heating device and heated to 800°C. The mechanically polished 1060 aluminum alloy plate is placed on the lifting frame 17 without heating.

[0073] 4) Rapid assembly: The lifting frame 17 is controlled to quickly snap and stack the surfaces of the substrate 23 and the composite plate 24 to be joined together.

[0074] 5) Corrugated roll pre-composite: The roughing pre-composite is carried out using a corrugated roll mill 18 with a drum-shaped corrugated roll 21 on the upper roll and a flat roll 22 on the lower roll. The average diameter of the upper and lower rolls is D=150mm, the drum height H and the roll body length L are 2mm and 150mm respectively, the rolling reduction rate is 30%, and the titanium / aluminum corrugated laminate 8 is obtained.

[0075] 6) Flat roll rolling: The titanium / steel corrugated laminate 8 is placed into a flat roll mill 19 with ordinary flat rolls 20 on both the upper and lower rolls for flat rolling, resulting in a titanium / aluminum laminate 9 with a flat surface and corrugated joint surface.

[0076] 7) Annealing: The flattened titanium / aluminum laminate 9 is annealed at a temperature of 300℃~600℃ for a time of 60min~120min.

[0077] 8) Finishing: Then straighten, cut the head, cut the tail, and trim the edges, and finally bundle and pack.

[0078] Comparative Example 1

[0079] 1) Blank preparation: Select a TC4 titanium alloy plate with a length of 200 mm (length) × 50 mm (width) × 2 mm (height) as the base plate and a 1060 aluminum alloy plate with a length of 200 mm (length) × 50 mm (width) × 2 mm (height) as the cladding plate. Use an angle grinder equipped with a wire brush to mechanically grind the surfaces of the metal plates to be joined until the surface is "frosted". Then, align the ground surfaces of the base plate and the cladding plate to assemble the blank.

[0080] 2) Heating: The assembled titanium / aluminum laminate blank is heated to 660℃ in a heating furnace;

[0081] 3) Flat roll rolling: The heated titanium / aluminum laminate slab is placed into a flat roll mill equipped with ordinary flat rolls on both the top and bottom for rolling and compounding. The rolling reduction rate is 30%, and the first titanium / aluminum laminate is obtained.

[0082] 4) Heating: The first-pass titanium / aluminum laminate is heated in a heating furnace for 10 minutes to compensate for the heat lost during rolling, thereby ensuring the metal's plastic deformation ability;

[0083] 5) Flat roll rolling: The heated first-pass titanium / aluminum laminate is placed into a flat roll mill with ordinary flat rolls on both the top and bottom for a second-pass rolling composite. The rolling reduction rate is 30%, and a flat-rolled titanium / aluminum laminate is obtained.

[0084] 6) Annealing: The rolled titanium / aluminum laminate is annealed at a temperature of 400℃~600℃ for 60min~120min.

[0085] 7) Finishing: Then straighten, cut the head, cut the tail, and trim the edges, and finally bundle and pack.

[0086] In a further embodiment of the present invention, the properties of the titanium / aluminum laminate 9 with a smooth surface and a corrugated interface obtained in step 6) of the method and the laminate obtained by two rolling processes in the comparative example were observed respectively, and the properties are shown in the table below.

[0087] Table 1 Comparison of Plate Performance

[0088] project Example Comparative Example Shear strength (MPa) 113 73 Interface integration rate 94% 63%

[0089] As can be seen from the table above, the bonding strength of titanium / aluminum laminates prepared by the nitriding treatment of bimetallic surface wave flat differential temperature rolling composite process is significantly higher than that of traditional flat roll two-pass rolling. The interface bonding rate of the sheet after nitriding treatment is significantly improved, and the plasticity of the sheet after pulse current treatment is improved, effectively reducing edge cracking of the laminate.

[0090] The shear strength was determined by testing the shear strength of the laminate specimens on a DNS200 electronic universal testing machine at a tensile speed of 1 mm / min. The dimensions of the shear test specimens were determined in accordance with GB / T6396-1995 Test Methods for Mechanical and Technological Properties of Laminates. The test results are shown in the table above.

[0091] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A process for nitriding a bimetallic surface wave flat equal temperature rolling composite, characterized by Includes the following steps: 1) Surface grinding: Before rolling, use an angle grinder equipped with a wire brush to mechanically grind the surfaces of the metal sheets to be bonded until the surface is "frosted"; 2) Nitriding treatment: The surface of the metal to be bonded is subjected to salt bath nitriding treatment in the nitriding equipment (3) until a dense nitride layer is formed on the surface (4). 3) Pulse current heating: The plate is heated to the target temperature using a pulse current device (16); 4) Rapid assembly: The two metal sheets to be joined are stacked face to face for rapid assembly; 5) Corrugated roll pre-composite: The assembled slab is rough rolled and pre-composite using a two-roll mill (18) with a drum-shaped corrugated roll (21) on the upper roll and a flat roll (22) on the lower roll (14). 6) Flat roll rolling: The corrugated laminate is then precision rolled (15) to obtain a bimetallic laminate with a flat surface and a corrugated interface. 7) Annealing: The flattened bimetallic laminate is annealed and then cooled; 8) Finishing: Straightening, head cutting, tail cutting, and edge trimming are performed, followed by bundling and packaging. In step 3), pulse current heating, the plates are placed on the lifting frame (17) equipped with a pulse current heating device and heated to the target temperature. In step 4) rapid assembly, the lifting frame (17) is controlled to quickly snap the surfaces of the substrate (23) and the composite plate (24) together and stack them for assembly.

2. A process for nitro-processing bimetallic surface wave flatness equalization rolling composite according to claim 1, characterized in that: In step 1), surface polishing, the metal surface is polished with a wire brush to remove oil and impurities, giving the surface a "frosted" appearance.

3. The process as claimed in claim 1, wherein the nitriding treatment of bimetallic surface wave flatness equalization rolling composite process is characterized by: In step 2), the metal plate after surface grinding is placed in the nitriding equipment (3) and a certain pressure and temperature are maintained so that nitrogen gas can penetrate into the metal plate to be bonded, so that a dense nitride layer (4) is formed on the surface to prevent oxidation of the metal to be bonded surface.

4. The process as claimed in claim 1, wherein the nitriding treatment of bimetallic surface wave flatness equalization rolling composite process is characterized by: In step 4) rapid billet assembly, the lifting frame (17) is equipped with a slide rail for width adjustment to accommodate different specifications of plates.

5. The process as claimed in claim 1, wherein the nitriding treatment of bimetallic surface wave flatness equalization rolling composite process is characterized by: In step 5), the corrugated roll pre-composite is a drum-shaped corrugated roll (21) with a certain number of periodic patterns engraved on its surface.

6. The composite process for nitriding-treated bimetallic surfaces with wave smoothing and differential temperature rolling according to claim 1, characterized in that: In step 5), during the pre-composite process of corrugated roll rolling, the metal bonding surface undergoes plastic deformation, the dense nitride layer breaks up, and the two metal bonding surfaces come into contact and bond.

7. The composite process for nitriding-treated bimetallic surfaces with wave smoothing and differential temperature rolling according to claim 1, characterized in that: In step 6), during the flat roll rolling process, the metal bonding surface undergoes plastic deformation, the dense nitride layer is further broken up, the exposed metal bonding surface increases, and the double-layer metal bonding surface further contacts and bonds.

Images