Cold spray surface modified stainless steel / copper precision thin strip rolling composite process

Abstract

The present invention provides a cold-spray surface-modified stainless steel / copper precision thin strip rolling composite process. By cold-spraying stainless steel micron-sized particles onto the copper precision thin strip, the process promotes the strengthening of the copper precision thin strip, resulting in nano-sized near-interface grains. This facilitates atomic diffusion during post-rolling annealing and improves the metallurgical bonding strength of the interface. Simultaneously, the cold-spraying of stainless steel micron-sized particles onto the copper precision thin strip achieves micron-level roughening of the surface, increasing surface roughness and hardness, and raising the probability of mechanical interlocking after rolling composite processing. In summary, this composite process effectively improves the bonding strength of the prepared stainless steel / copper composite strip. Furthermore, the low-pressure cold-sprayed stainless steel micron-sized particles do not bond with the copper precision thin strip, allowing for the reuse of the stainless steel micron-sized particles. The process is simple and feasible, providing a technical path for the high-quality industrialization and development of precision thin strip rolling composite processes.

Description

Technical Field

[0001] This invention belongs to the field of rolling technology, and particularly relates to a composite rolling process for stainless steel / copper precision thin strips with cold spray surface modification. Background Technology

[0002] Copper and copper alloys possess excellent electrical and thermal conductivity, making them important conductive media; however, they are expensive and have low strength. Stainless steel precision strips offer high strength and corrosion resistance, making them suitable for structural devices, but their electrical conductivity is relatively poor. Given the immense application potential of precision strips in micro / nano manufacturing, combining stainless steel and copper precision strips not only leverages the electrical and thermal conductivity of copper but also utilizes the high strength and corrosion resistance of stainless steel. This innovative combination of structure and function meets the functional requirements of electrical conductivity, thermal conductivity, and corrosion resistance in micro-manufacturing and micro-forming fields, and will undoubtedly further promote the application of precision strips in micro / nano manufacturing.

[0003] Currently, in the process of preparing stainless steel / copper composite strip using rolling, the excellent toughness of copper and its oxides makes it difficult for the hardened layer to break during rolling, severely affecting the diffusion at the stainless steel and copper interface. Furthermore, the large specific surface area of ​​the precision thin strip makes it difficult for fresh metal to be extruded during rolling, further inhibiting interface diffusion. In addition, the thinner and wider the strip, the more pronounced the strip shape problem becomes; the internal stress generated by local warping can easily exceed the interfacial bonding strength, causing composite interface separation. Conventional wire brush polishing alone cannot achieve higher bonding strength for the stainless steel / copper composite strip. Therefore, a precision thin strip rolling composite process that can solve the above technical problems is urgently needed. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, a cold-spray surface-modified stainless steel / copper precision thin strip rolling composite process is provided. This process can solve the problems of low bonding strength in existing stainless steel / copper composite strip preparation processes due to difficulties in pre-bonding and limited interfacial metallurgical bonding.

[0005] The cold-spray surface modification process for stainless steel / copper precision strip rolling composite, provided to achieve the purpose of this invention, includes the following steps in sequence:

[0006] S1: The stainless steel precision strip is annealed and softened at high temperature to remove surface impurities, dust and oil stains. Then, the surface of the stainless steel precision strip and the copper precision strip is polished with a wire brush to form a surface hardening layer.

[0007] S2: The surface of the copper precision thin strip obtained in step S1 is coated with stainless steel particles using a cold spraying process, wherein the supersonic cold spraying pressure is 1-1.5 MPa and compressed air is used as the medium.

[0008] S3: The surfaces of the stainless steel precision thin strip obtained in step S1 and the copper precision thin strip obtained in step S2 are interlocked and one end is fixed to form a blank.

[0009] S4: The billet obtained in step S3 is fed into the inlet side of the rolling mill, and after being rolled by a small-diameter multi-roll rolling mill, the stainless steel / copper composite strip semi-finished product is output from the outlet side of the rolling mill.

[0010] S5: The stainless steel / copper composite strip semi-finished product obtained in step S4 is placed in an annealing furnace with a protective atmosphere for annealing treatment, thereby obtaining the stainless steel / copper composite strip finished product.

[0011] As a further improvement to the above scheme, in step S1, the thickness of the stainless steel precision strip is 0.1-0.2 mm, the thickness of the copper precision strip is 0.2-0.4 mm, and the thickness ratio of the stainless steel precision strip to the copper precision strip is 1:2.

[0012] As a further improvement to the above scheme, in step S1, the annealing temperature of the stainless steel precision strip is 450°C and the annealing time is 1 hour.

[0013] As a further improvement to the above scheme, the stainless steel particles in step S2 are spherical particles with a particle size of 20 to 40 μm.

[0014] As a further improvement to the above solution, the spraying process in step S2 is to position the nozzle of the spray gun perpendicular to the surface of the copper precision thin strip and keep the distance between the spray gun and the surface of the copper precision thin strip within 10 to 15 mm, with the nozzle moving speed being 90 to 120 mm / s and the overlap width of the area swept by the spray gun being 5 mm.

[0015] As a further improvement to the above scheme, in step S4, the stainless steel / copper composite strip semi-finished product output from the mill exit side of the small-diameter multi-roll mill adopts pre-tension traction, and the billet input from the mill inlet side adopts low-tension traction.

[0016] As a further improvement to the above scheme, the cold rolling reduction rate of the small-diameter multi-roll mill in step S4 is greater than 45%.

[0017] As a further improvement to the above scheme, the annealing temperature in step S5 is 600-1000℃, and the holding time is 1 hour.

[0018] The beneficial effects of this invention are:

[0019] Compared with existing technologies, the cold-spray surface-modified stainless steel / copper precision thin strip rolling composite process provided by this invention promotes the strengthening of the copper precision thin strip by cold-spraying stainless steel micron particles onto the copper precision thin strip, resulting in nano-sized near-interface grains of the copper precision thin strip. This facilitates atomic diffusion during post-rolling annealing and improves the metallurgical bonding strength of the interface. At the same time, cold-spraying stainless steel micron particles onto the copper precision thin strip achieves micron-level roughening of the copper precision thin strip surface, improving surface roughness and hardness, and increasing the probability of mechanical interlocking after rolling composite.

[0020] In summary, this composite process effectively improves the bonding strength of the prepared stainless steel / copper composite strip. In addition, the stainless steel micron particles cold-sprayed onto the copper precision thin strip do not bond with the copper precision thin strip, enabling the reuse of the stainless steel micron particles. The process is simple and feasible, providing a technical path for the high-quality development of the precision thin strip rolling composite industry. Attached Figure Description

[0021] Figure 1 This is a comparison image of three-dimensional morphology;

[0022] in Figure 1 (a) is a three-dimensional morphology of the surface of the copper precision strip after polishing in the existing preparation process; Figure 1 Image (b) is a three-dimensional morphology of the surface of the copper precision thin strip after cold spraying surface modification in this invention.

[0023] Figure 2 Comparison of grain features at the cross-section;

[0024] in Figure 2 (a) shows the grain characteristics of the cross-section of the copper precision strip after polishing in the existing manufacturing process; Figure 2 Image (b) shows the grain characteristics of the cross-section of the copper precision thin strip after cold spraying surface modification in this invention.

[0025] Figure 3 This is a photograph of the semi-finished stainless steel / copper composite strip obtained in step S4 of this invention.

[0026] Figure 4 This is a physical image of the finished stainless steel / copper composite strip obtained in step S5 of this invention.

[0027] Figure 5 This is a scanning electron microscope (SEM) schematic diagram of the diffusion layer at the cross-section of the stainless steel / copper composite strip obtained in step S5 of this invention.

[0028] Figure 6 Comparison of diffusion layer line scan results at the cross-section of the finished stainless steel / copper composite strip;

[0029] in Figure 6(a) shows the diffusion layer line scan results at the cross-section of the finished stainless steel / copper composite strip obtained by the existing preparation process; Figure 6 (b) shows the diffusion layer line scan results at the cross-section of the stainless steel / copper composite strip product obtained by the present invention.

[0030] Figure 7 This is a comparison chart of the peeling performance of stainless steel / copper composite strips prepared by existing processes and those prepared by the present invention.

[0031] Figure 8 This is a schematic diagram showing the average peel force of the stainless steel / copper composite strip products prepared under different working conditions in Example 2.

[0032] Figure 9 This is a schematic diagram showing the average peel force of the stainless steel / copper composite strips prepared at different annealing temperatures in Example 3.

[0033] Figure 10 This is a schematic diagram showing the average peel force of the stainless steel / copper composite strips prepared under different heat preservation times in Example 4. Detailed Implementation

[0034] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings:

[0035] Example 1

[0036] This invention provides a cold-spray surface-modified stainless steel / copper precision strip rolling composite process, which includes the following steps:

[0037] S1: The stainless steel precision strip is annealed and softened at high temperature to remove surface impurities, dust, and oil stains. Then, the surfaces of the stainless steel and copper precision strips are polished with a wire brush to form a surface hardened layer. The thickness of the stainless steel precision strip is 0.1-0.2 mm, the thickness of the copper precision strip is 0.2-0.4 mm, and the thickness ratio of the stainless steel precision strip to the copper precision strip is 1:2. The annealing temperature is 450℃, and the annealing time is 1 hour.

[0038] S2: Stainless steel particles are sprayed onto the surface of the copper precision strip obtained in step S1 using a cold spraying process. The supersonic cold spraying pressure is 1-1.5 MPa, and compressed air is used as the medium. The spraying method involves positioning the nozzle of the spray gun perpendicular to the surface of the copper precision strip and maintaining a distance of 10-15 mm between the spray gun and the surface of the copper precision strip. The nozzle moving speed is 90-120 mm / s, and the overlap width of the area swept by the spray gun is 5 mm. The stainless steel particles used are spherical particles with a particle size of 20-40 μm.

[0039] like Figure 1 This is a comparison image of three-dimensional morphology, in which Figure 1 (a) is a three-dimensional morphology of the surface of the copper precision strip after polishing in the existing preparation process; Figure 1 Image (b) is a three-dimensional morphology of the surface of the copper precision thin strip after cold spraying surface modification in this invention.

[0040] Figure 2 This is a comparison image of grain characteristics at the cross-section, where Figure 2 (a) shows the grain characteristics of the cross-section of the copper precision strip after polishing in the existing manufacturing process; Figure 2 Image (b) shows the grain characteristics of the cross-section of the copper precision thin strip after cold spraying surface modification in this invention; Figure 1 , Figure 2 It can be seen that after cold spraying surface modification, the surface grains of copper precision thin strip are significantly refined, and the refined particle layer is significantly thicker than that of grinding alone.

[0041] S3: The surfaces of the stainless steel precision thin strip obtained in step S1 and the copper precision thin strip obtained in step S2 are interlocked and one end is fixed to form a blank.

[0042] S4: The billet obtained in step S3 is fed into the inlet side of the rolling mill, rolled by a small-diameter multi-roll mill, and the stainless steel / copper composite strip semi-finished product is output from the outlet side of the rolling mill. Figure 3 As shown; the stainless steel / copper composite strip semi-finished product output from the mill exit side of the small-diameter multi-roll mill adopts front tension traction, while the billet input from the mill inlet side adopts low tension traction; the cold rolling reduction rate of the small-diameter multi-roll mill is greater than 45%.

[0043] S5: The semi-finished stainless steel / copper composite strip obtained in step S4 is placed in an annealing furnace with a protective atmosphere for annealing treatment, thereby obtaining the finished stainless steel / copper composite strip. Figure 4 As shown; the annealing temperature for the annealing treatment is 800℃, and the holding time is 1 hour.

[0044] Then, the diffusion layer at the cross-section of the stainless steel / copper composite strip obtained in step S5 was subjected to electron microscopy and line scanning. See details below. Figures 5-6 The results showed that the stainless steel / copper composite strip obtained in step S5 had good interfacial mechanical interlocking, and the diffusion layer thickness was significantly thicker than that of the stainless steel / copper composite strip obtained by the existing preparation process.

[0045] Finally, the peel strength of the stainless steel / copper composite strip obtained in step S5 was tested, and the results are detailed in [link to results]. Figure 7 ,Depend on Figure 7 It can be seen that the peel strength of the stainless steel / copper composite strip product prepared by the present invention is better than that of the stainless steel / copper composite strip product prepared by the existing preparation process.

[0046] Example 2

[0047] This invention provides a cold-spray surface-modified stainless steel / copper precision strip rolling composite process, which includes the following steps:

[0048] S1: The stainless steel precision strip is annealed and softened at high temperature to remove surface impurities, dust, and oil stains. Then, the surfaces of the stainless steel and copper precision strips are polished with a wire brush to form a surface hardened layer. The thickness of the stainless steel precision strip is 0.1-0.2 mm, the thickness of the copper precision strip is 0.2-0.4 mm, and the thickness ratio of the stainless steel precision strip to the copper precision strip is 1:2. The annealing temperature is 450℃, and the annealing time is 1 hour.

[0049] S2: Stainless steel particles are sprayed onto the surface of the copper precision strip obtained in step S1 using a cold spraying process. The supersonic cold spraying pressure is 1-1.5 MPa, and compressed air is used as the medium. The spraying method involves positioning the nozzle of the spray gun perpendicular to the surface of the copper precision strip and maintaining a distance of 10-15 mm between the spray gun and the surface of the copper precision strip. The nozzle moving speed is 90-120 mm / s, and the overlap width of the area swept by the spray gun is 5 mm. The stainless steel particles used are spherical particles with a particle size of 20-40 μm.

[0050] S3: The surfaces of the stainless steel precision thin strip obtained in step S1 and the copper precision thin strip obtained in step S2 are interlocked and one end is fixed to form a blank.

[0051] S4: The billet obtained in step S3 is fed into the mill inlet side and rolled by a small-diameter multi-roll mill. The stainless steel / copper composite strip semi-finished product is then output from the mill outlet side. The stainless steel / copper composite strip semi-finished product output from the mill outlet side of the small-diameter multi-roll mill is pulled by front tension, while the billet input from the mill inlet side is pulled by low tension. The cold rolling reduction rate of the small-diameter multi-roll mill is greater than 45%.

[0052] S5: The stainless steel / copper composite strip semi-finished product obtained in step S4 is placed in an annealing furnace with a protective atmosphere for annealing treatment to obtain the stainless steel / copper composite strip finished product; wherein the annealing temperature is 800℃ and the holding time is 1 hour.

[0053] In addition, the different processing methods of stainless steel precision thin strip and copper precision thin strip were used as distinguishing points to divide them into four groups with different working conditions: R1, R2, R3, and R4. The average peel force of the stainless steel / copper composite strip products prepared under different working conditions was tested, and the specific results are as follows: Figure 8 As shown.

[0054] Table 1 Classification of Different Working Conditions

[0055]

[0056] Depend on Figure 8 It can be seen that the average peel force of R4, which adopts the treatment method of stainless steel precision thin strip (annealing at 450℃ for 1 hour + grinding treatment) and copper precision thin strip (grinding treatment + surface spraying of stainless steel particles), is higher than the average peel force of R1, which adopts the treatment method of stainless steel precision thin strip (grinding treatment) and copper precision thin strip (grinding treatment) in the existing process.

[0057] Example 3

[0058] This invention provides a cold-spray surface-modified stainless steel / copper precision strip rolling composite process, which includes the following steps:

[0059] S1: The stainless steel precision strip is annealed and softened at high temperature to remove surface impurities, dust, and oil stains. Then, the surfaces of the stainless steel and copper precision strips are polished with a wire brush to form a surface hardened layer. The thickness of the stainless steel precision strip is 0.1-0.2 mm, the thickness of the copper precision strip is 0.2-0.4 mm, and the thickness ratio of the stainless steel precision strip to the copper precision strip is 1:2. The annealing temperature is 450℃, and the annealing time is 1 hour.

[0060] S2: Stainless steel particles are sprayed onto the surface of the copper precision strip obtained in step S1 using a cold spraying process. The supersonic cold spraying pressure is 1-1.5 MPa, and compressed air is used as the medium. The spraying method involves positioning the nozzle of the spray gun perpendicular to the surface of the copper precision strip and maintaining a distance of 10-15 mm between the spray gun and the surface of the copper precision strip. The nozzle moving speed is 90-120 mm / s, and the overlap width of the area swept by the spray gun is 5 mm. The stainless steel particles used are spherical particles with a particle size of 20-40 μm.

[0061] S3: The surfaces of the stainless steel precision thin strip obtained in step S1 and the copper precision thin strip obtained in step S2 are interlocked and one end is fixed to form a blank.

[0062] S4: The billet obtained in step S3 is fed into the mill inlet side and rolled by a small-diameter multi-roll mill. The stainless steel / copper composite strip semi-finished product is then output from the mill outlet side. The stainless steel / copper composite strip semi-finished product output from the mill outlet side of the small-diameter multi-roll mill is pulled by front tension, while the billet input from the mill inlet side is pulled by low tension. The cold rolling reduction rate of the small-diameter multi-roll mill is greater than 45%.

[0063] S5: The stainless steel / copper composite strip semi-finished product obtained in step S4 is placed in an annealing furnace with a protective atmosphere for annealing treatment, thereby obtaining the stainless steel / copper composite strip finished product.

[0064] In step S5, the annealing temperatures were selected as 450℃, 600℃, 800℃, and 1000℃, with a holding time of 1 hour. The average peel strength of the stainless steel / copper composite strips prepared at different annealing temperatures was tested, and the specific results are as follows: Figure 9 As shown.

[0065] Depend on Figure 9 It can be seen that when the annealing temperature is 600℃, 800℃ and 1000℃, the average peel force of the stainless steel / copper composite strip is better than the average peel force under working condition R1 in Example 1.

[0066] Example 4

[0067] This invention provides a cold-spray surface-modified stainless steel / copper precision strip rolling composite process, which includes the following steps:

[0068] S1: The stainless steel precision strip is annealed and softened at high temperature to remove surface impurities, dust, and oil stains. Then, the surfaces of the stainless steel and copper precision strips are polished with a wire brush to form a surface hardened layer. The thickness of the stainless steel precision strip is 0.1-0.2 mm, the thickness of the copper precision strip is 0.2-0.4 mm, and the thickness ratio of the stainless steel precision strip to the copper precision strip is 1:2. The annealing temperature is 450℃, and the annealing time is 1 hour.

[0069] S2: Stainless steel particles are sprayed onto the surface of the copper precision strip obtained in step S1 using a cold spraying process. The supersonic cold spraying pressure is 1-1.5 MPa, and compressed air is used as the medium. The spraying method involves positioning the nozzle of the spray gun perpendicular to the surface of the copper precision strip and maintaining a distance of 10-15 mm between the spray gun and the surface of the copper precision strip. The nozzle moving speed is 90-120 mm / s, and the overlap width of the area swept by the spray gun is 5 mm. The stainless steel particles used are spherical particles with a particle size of 20-40 μm.

[0070] S3: The surfaces of the stainless steel precision thin strip obtained in step S1 and the copper precision thin strip obtained in step S2 are interlocked and one end is fixed to form a blank.

[0071] S4: The billet obtained in step S3 is fed into the mill inlet side and rolled by a small-diameter multi-roll mill. The stainless steel / copper composite strip semi-finished product is then output from the mill outlet side. The stainless steel / copper composite strip semi-finished product output from the mill outlet side of the small-diameter multi-roll mill is pulled by front tension, while the billet input from the mill inlet side is pulled by low tension. The cold rolling reduction rate of the small-diameter multi-roll mill is greater than 45%.

[0072] S5: The stainless steel / copper composite strip semi-finished product obtained in step S4 is placed in an annealing furnace with a protective atmosphere for annealing treatment, thereby obtaining the stainless steel / copper composite strip finished product.

[0073] In step S5, the annealing temperature was selected as 800℃, and the holding time was selected as 0.5h, 1h, and 2h, respectively. The average peel force of the stainless steel / copper composite strips prepared under different holding times was tested, and the specific results are as follows: Figure 10 As shown.

[0074] Depend on Figure 10 It can be seen that when the heat preservation time is 1 hour, the average peel force of the stainless steel / copper composite strip is better than that of other heat preservation times.

[0075] The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments can be combined with each other to form new embodiments. The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the technical solutions of the present invention.

Claims

1. A cold spray surface modified stainless steel / copper precision thin strip rolling composite process characterized by: The steps are as follows: S1: The stainless steel precision strip is annealed and softened at high temperature to remove surface impurities, dust and oil stains. Then, the surface of the stainless steel precision strip and the copper precision strip is polished with a wire brush to form a surface hardening layer. S2: The surface of the copper precision thin strip obtained in step S1 is coated with stainless steel particles using a cold spraying process, wherein the supersonic cold spraying pressure is 1-1.5 MPa and compressed air is used as the medium. S3: The surfaces of the stainless steel precision thin strip obtained in step S1 and the copper precision thin strip obtained in step S2 are interlocked and one end is fixed to form a blank. S4: The billet obtained in step S3 is fed into the inlet side of the rolling mill, and after being rolled by a small-diameter multi-roll rolling mill, the stainless steel / copper composite strip semi-finished product is output from the outlet side of the rolling mill. S5: The stainless steel / copper composite strip semi-finished product obtained in step S4 is placed in an annealing furnace with a protective atmosphere for annealing treatment, thereby obtaining the stainless steel / copper composite strip finished product.

2. The cold spray surface modified stainless steel / copper precision thin strip roll-bonding process of claim 1, wherein: In step S1, the thickness of the stainless steel precision strip is 0.1-0.2 mm, the thickness of the copper precision strip is 0.2-0.4 mm, and the thickness ratio of the stainless steel precision strip to the copper precision strip is 1:

2.

3. The stainless steel / copper precision thin strip rolling composite process for cold spray surface modification according to claim 1, characterized in that: In step S1, the annealing temperature of the stainless steel precision strip is 450°C and the annealing time is 1 hour.

4. The stainless steel / copper precision thin strip rolling composite process for cold spray surface modification according to claim 1, characterized in that: The stainless steel particles in step S2 are spherical particles with a particle size of 20-40 μm.

5. The stainless steel / copper precision thin strip rolling composite process for cold spray surface modification according to claim 1, characterized in that: The spraying process in step S2 involves positioning the nozzle of the spray gun perpendicular to the surface of the copper precision thin strip and maintaining a distance of 10-15 mm between the spray gun and the surface of the copper precision thin strip. The nozzle moving speed is 90-120 mm / s, and the overlap width of the area swept by the spray gun is 5 mm.

6. The stainless steel / copper precision thin strip rolling composite process for cold spray surface modification according to claim 1, characterized in that: In step S4, the stainless steel / copper composite strip semi-finished product output from the mill exit side of the small-diameter multi-roll mill is pulled by front tension, while the billet input from the mill inlet side is pulled by low tension.

7. The stainless steel / copper precision thin strip rolling composite process for cold spray surface modification according to claim 1, characterized in that: In step S4, the cold rolling reduction rate of the small-diameter multi-roll mill is greater than 45%.

8. The stainless steel / copper precision thin strip rolling composite process for cold spray surface modification according to claim 1, characterized in that: In step S5, the annealing temperature is 600-1000℃, and the holding time is 1 hour.

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