A method for preparing ultrathin and ultrawide silver foil

Abstract

This invention discloses a method for preparing ultrathin and ultrawide silver foil. Utilizing the excellent ductility of oxygen-free copper and its processing properties similar to pure silver, pure silver foil is coated and rolled using oxygen-free copper sheets, avoiding direct contact between the silver foil and the rolls. Simultaneously, through the coordinated control of heat treatment and rolling deformation, silver foil with a width greater than 300 mm and a thickness of 4–5 μm is obtained. The silver foil prepared by this invention can have a minimum thickness of 1 μm and a width greater than 300 mm, possessing the advantages of ultrathin thickness and large width. Furthermore, the preparation equipment is a conventional sheet and strip rolling mill, eliminating the need for expensive foil rolling mills. This method offers advantages such as lower requirements for operator skill and mill control precision, simple process, convenient operation, high production efficiency, and low process cost, making it particularly suitable for the production of ultrawide and ultra-wide silver foil.

Description

Technical Field

[0001] This invention relates to the field of precious metal foil preparation technology, specifically to a method for preparing ultrathin and ultrawide silver foil. Background Technology

[0002] Pure silver has the best electrical and thermal conductivity of all metals and excellent machinability. Silver is commonly used to manufacture highly sensitive physical components; electrical contacts in various automated devices, rockets, submarines, computers, nuclear devices, and communication systems are made of silver or silver alloys. Due to the high price of silver, it is generally processed into silver foil to reduce usage costs. Early silver foil processing was done manually, which could only produce small-sized pure silver foil sheets with inconsistent thickness, high production costs, and required highly skilled personnel. Furthermore, it could not be produced into strips, limiting the application range of silver foil. Currently, technologies for manufacturing silver foil using mechanical equipment have emerged. For example, Chinese patent CN104722595A discloses a method for manufacturing wide-width ultra-thin pure silver foil. However, this technology uses a process of drawing silver sheets followed by rolling and annealing. Due to the casting structure, the thickness of the rolled silver foil can only reach 0.01 mm, making it impossible to produce silver foil thinner than 0.01 mm. It can only produce pure silver foil strips with a width of less than 160 mm and a thickness of more than 50 μm.

[0003] Existing technologies produce ultrathin silver foil with relatively small widths, and it is difficult to achieve ultrathin silver foil with a thickness of less than 0.01 mm, which limits the industrial production and application of silver foil strips. Summary of the Invention

[0004] To address the technical challenge of preparing ultra-wide and ultra-thin silver foil using existing technologies and to meet the needs of the domestic aerospace and surface decoration fields, this invention provides a method for preparing ultra-thin and ultra-wide silver foil, the technical solution of which includes the following steps:

[0005] (1) Pure silver plates with a purity of 99.99% are melted and cast into silver plates using vacuum induction melting. The width of the cast silver plates is 120mm to 150mm and the thickness is 15mm to 20mm.

[0006] (2) The surface of the plate is milled by a milling machine to remove casting defects such as cold shuts, inclusions and porosity;

[0007] (3) The silver plate after milling is rolled in the width direction using a ф360mmх400mm two-roll mill. The deformation of the rolling pass is 10% to 20%, and the total deformation is 60% to 70%. The width of the rolled silver plate is 320 to 350mm and the thickness is 6 to 10mm.

[0008] (4) After cleaning the expanded silver plate, anneal it in a vacuum annealing furnace at a temperature of 600–700℃ for 15–60 minutes, with a vacuum degree of 10⁻¹–10⁻¹. -3 Pa;

[0009] (5) The annealed silver plate is rolled along the length direction to a thickness of 0.5 to 0.6 mm using a ф360х400 two-roll mill, with a deformation amount of 10% to 15% per pass and a total deformation amount of 70% to 90%.

[0010] (6) Anneal the silver plate obtained in step (5) in a vacuum annealing furnace at a temperature of 600–700℃ for 15–60 minutes, with a vacuum degree of 10⁻¹–10⁻¹. -3 Pa;

[0011] (7) After annealing, the silver plate is cut off the cracked edges using a slitting machine so that the width of the plate is not less than 320mm;

[0012] (8) The silver plate obtained in step 7 is rolled into pure silver strip with a thickness of 0.05 to 0.10 mm by a D400mm precision four-roll mill through multiple passes. The deformation per pass is 10% to 15%, and the total deformation is 70% to 90%.

[0013] (9) Anneal the silver strip obtained in step (8) in a vacuum annealing furnace at a temperature of 400℃~600℃ for 15min~60min and a vacuum degree of 10⁻¹~10⁻¹. -3 Pa;

[0014] (10) The annealed pure silver strip is cut into silver sheets with a width of 320mm and a length of 400mm to 600mm using a precision shearing machine and then cleaned with alcohol using ultrasonic waves.

[0015] 11. Select oxygen-free copper sheets with a thickness of 0.25-0.3mm, a width of 350-360mm, and a length of 1500-2000mm. After vacuum annealing at 600℃-700℃ for 30 minutes, apply a separating lubricant to one side of the oxygen-free copper sheet and then fold it in half.

[0016] ⑿ Wrap the silver sheet obtained in step ⑽ in the middle of the oxygen-free copper sheet obtained in step ⑾ to form a sandwich-structured copper-clad silver sheet;

[0017] 13. Using a D400mm precision four-roll mill, copper-clad silver sheets are rolled in multiple passes to a total thickness of 0.2-0.3mm, a silver foil thickness of 0.01-0.02mm, a pass deformation of 5%-10%, and a total deformation of 50%-70%.

[0018] 14. The semi-finished silver foil obtained in step 13 is subjected to low-temperature annealing in a vacuum annealing furnace. The annealing temperature is 200℃~400℃, the holding time is 30min~60min, and the vacuum degree is 10⁻¹~10⁻¹. -3 Pa, and prepare the coated lap-rolled billet again according to the method described in step 12;

[0019] 12 The coated and rolled billet obtained in step 14 is rolled in multiple passes using a D450mm precision six-roll mill to obtain a copper-clad silver foil with a total thickness of 0.05mm. After peeling off the copper layer, a pure silver foil with a thickness of 4-5µm is obtained.

[0020] The beneficial effects of this invention are:

[0021] This invention utilizes the excellent ductility and processing properties similar to pure silver of oxygen-free copper in the silver foil preparation process. It employs oxygen-free copper sheets to coat pure silver sheets during the coating and rolling process, avoiding the shear deformation of the silver sheet's surface metal layer caused by direct contact between the pure silver sheet and the rolls. This alters the stress state of the intermediate silver sheet, subjecting it to uniform triaxial compressive stress, resulting in more uniform deformation and significantly reducing the tearing damage caused by roll friction. This yields ultra-thin and ultra-wide silver foil. Simultaneously, the use of oxygen-free copper sheet coating and rolling greatly reduces the stringent requirements on operator skill and equipment precision in silver foil preparation. It avoids the use of expensive and highly difficult-to-control foil rolling mills, allowing the production of ultra-thin silver foil using ordinary precision strip rolling mills. The silver foil prepared by this invention can reach a minimum thickness of 1µm and a width of over 300mm, possessing advantages such as ultra-thin thickness, large width, good thickness uniformity, and high tensile strength. Meanwhile, the preparation equipment is a conventional sheet and strip rolling mill, which does not require an expensive foil rolling mill. It has the advantages of low requirements for operator skill level and rolling mill control precision, simple process, convenient operation, high production efficiency and low process cost, and is particularly suitable for the production of ultra-wide and ultra-thin silver foil. Detailed Implementation

[0022] The present invention will be further described below through specific embodiments:

[0023] Example 1

[0024] This embodiment, as a basic embodiment of the present invention, discloses a method for manufacturing wide silver foil, specifically including the following steps:

[0025] (1) A pure silver plate with a purity of 99.99% was vacuum induction melted and cast into a silver plate with a casting width of 120 mm. ±2.0 mm, thickness is 20 ±1.0 mm;

[0026] (2) The surface of the plate is milled by a milling machine to remove casting defects such as cold shuts, inclusions and porosity;

[0027] (3) The silver plate after milling is subjected to wide-stretch rolling along the width direction using a ф360mmх400mm two-roll mill. The deformation per pass in the wide-stretch rolling is 10%–20%, and the total deformation is 60%–70%. The width of the silver plate after rolling is 320mm. ±2.0 mm, thickness 10.0 ±0.1 mm;

[0028] (4) After cleaning the expanded silver plate, it is annealed in a vacuum annealing furnace at a temperature of 700℃, a holding time of 15min, and a vacuum degree of 10. -3 Pa;

[0029] (5) The annealed silver plate is rolled along its length to a thickness of 0.6 mm using a ф360 mm х400 mm two-roll mill. ±0.05 For a silver plate of mm, the deformation per pass is 10% to 15%, and the total deformation is 70% to 90%.

[0030] (6) Anneal the silver plate obtained in step (5) in a vacuum annealing furnace at a temperature of 600℃ for 30 minutes and a vacuum degree of 10. -3 Pa;

[0031] (7) After annealing, the silver plate is trimmed of the cracked edges using a slitting machine, so that the width of the plate is 320 mm. ±1.0 mm;

[0032] (8) The silver plate obtained in step (7) is rolled in multiple passes using a D400mm precision four-roll mill to a thickness of 0.10 mm. ±0.01 For pure silver strip of mm, the deformation per pass is 10% to 15%, and the total deformation is 70% to 90%.

[0033] (9) Anneal the silver strip obtained in step (8) in a vacuum annealing furnace at a temperature of 500℃ for 45 minutes and a vacuum degree of 10. -3 Pa;

[0034] (10) The annealed pure silver strip is cut into strips with a width of 320 mm using a precision shearing machine. ±1.0 mm, length is 600 ± 1.0 The silver sheet was cleaned with alcohol using ultrasonic cleaning.

[0035] (11) Select a thickness of 0.25. ±0.01 mm, width is 340 ±1.0 After being vacuum annealed at 600℃~700℃ for 30 minutes, an oxygen-free copper sheet with a length of 2000mm is coated with a release lubricant on one side and then folded in half.

[0036] (12) Wrap the silver sheet obtained in step 10 around the oxygen-free copper sheet obtained in step 11 to form a sandwich-structured copper-clad silver sheet;

[0037] (13) The copper-clad silver sheet was rolled to a total thickness of 0.3 mm using a D400mm precision four-roll mill through multiple passes. ±0.01 mm, silver foil thickness is 0.02 mm. ±0.002 mm, the deformation per pass is 5% to 10%, and the total deformation is 50% to 70%;

[0038] (14) The semi-finished silver foil obtained in step 13 is subjected to low-temperature annealing in a vacuum annealing furnace. The annealing temperature is 400℃, the holding time is 30min, and the vacuum degree is 10. -3 Pa, and prepare the coated lap-rolled billet again according to the method described in step 12;

[0039] (15) The coated and rolled billet obtained in step 14 is rolled in multiple passes using a D450mm precision six-roll mill to obtain a copper-clad silver foil with a total thickness of 0.05mm. After peeling off the copper layer, a pure silver foil with a thickness of 4-5um is obtained.

[0040] Example 2

[0041] This embodiment, as a basic embodiment of the present invention, discloses a method for manufacturing wide silver foil, specifically including the following steps:

[0042] (1) A pure silver plate with a purity of 99.99% is vacuum induction melted and cast into a silver plate with a casting width of 150 mm. ±2.0 mm, thickness is 15 mm ±1.0 mm;

[0043] (2) The surface of the plate is milled by a milling machine to remove casting defects such as cold shuts, inclusions and porosity;

[0044] (3) The milled silver plate is then subjected to wide-stretch rolling along the width direction using a ф360mmх400mm two-roll mill. The deformation per pass in the wide-stretch rolling is 10%–20%, and the total deformation is 60%–70%. The width of the rolled silver plate is 330mm. ± 2.0 mm, thickness is 6.0 mm. ±0.1 mm;

[0045] (4) After cleaning the expanded silver plate, it is annealed in a vacuum annealing furnace at a temperature of 600℃ for 30 minutes and a vacuum degree of 10. -3 Pa;

[0046] (5) The annealed silver plate is rolled along its length to a thickness of 0.5 mm using a ф360mm х400mm two-roll mill. ±0.05For a silver plate of mm, the deformation per pass is 10% to 15%, and the total deformation is 70% to 90%.

[0047] (6) Anneal the silver plate obtained in step (5) in a vacuum annealing furnace at a temperature of 600℃ for 30 minutes and a vacuum degree of 10. -3 Pa;

[0048] (7) After annealing, the silver sheet is trimmed at the cracked edges using a slitting machine to make the sheet width 330 mm. ±1.0 mm;

[0049] (8) The silver plate obtained in step (7) is rolled in multiple passes using a D400mm precision four-roll mill to a thickness of 0.05 mm. ± 0.005 For pure silver strip of mm, the deformation per pass is 10% to 15%, and the total deformation is 70% to 90%.

[0050] (9) Anneal the pure silver strip obtained in step (8) in a vacuum annealing furnace at a temperature of 400℃ for 60 minutes and a vacuum degree of 10. -3 Pa;

[0051] (10) The annealed pure silver strip is cut into strips with a width of 330 mm using a precision shearing machine. ±1.0 mm, length is 400 ±1.0 The silver sheet was cleaned with alcohol using ultrasonic cleaning.

[0052] ⑪ Select a thickness of 0.3 mm. ±0.01 mm, width is 350 ±1.0 After being vacuum annealed at 600℃~700℃ for 30 minutes, an oxygen-free copper sheet with a length of 1500mm is coated with a release lubricant on one side and then folded in half.

[0053] ⑿ Wrap the silver sheet obtained in step ⑽ in the middle of the oxygen-free copper sheet obtained in step ⑾ to form a sandwich-structured copper-clad silver sheet;

[0054] 13. Copper-clad silver sheets are rolled to a total thickness of 0.2 mm using a D400mm precision four-roll mill through multiple passes. ±0.01 mm, silver foil thickness is 0.02 mm. ±0.002 mm, the deformation per pass is 5% to 10%, and the total deformation is 50% to 70%;

[0055] 14. The semi-finished silver foil obtained in step 13 is subjected to low-temperature annealing in a vacuum annealing furnace. The annealing temperature is 300℃, the holding time is 30min, and the vacuum degree is 10. -3 Pa, and prepare the coated lap-rolled billet again according to the method described in step 12;

[0056] 12 The secondary coated and rolled billet obtained in step 14 is rolled in multiple passes using a D450mm precision six-roll mill to obtain copper-clad silver foil with a total thickness of 0.08mm. After peeling off the copper layer, pure silver foil with a thickness of 8-9um is obtained.

[0057] Example 3

[0058] This embodiment, as a basic embodiment of the present invention, discloses a method for manufacturing wide silver foil, specifically including the following steps:

[0059] (1) A pure silver plate with a purity of 99.99% is vacuum induction melted and cast into a silver plate with a width of 130 mm. ±2.0 mm, thickness is 18 ±1.0 mm;

[0060] (2) The surface of the silver plate is milled using a milling machine to remove casting defects such as cold shuts, inclusions and pores.

[0061] (3) The milled silver plate is then subjected to wide-stretch rolling along the width direction using a ф360mmх400mm two-roll mill. The deformation per pass in the wide-stretch rolling is 10%–20%, and the total deformation is 60%–70%. The width of the rolled silver plate is 330mm. ±2.0 mm, thickness is 6.0 mm. ±0.1 mm;

[0062] (4) After cleaning the expanded silver plate, anneal it in a vacuum annealing furnace at a temperature of 700℃ for 30 minutes and a vacuum degree of 10. -3 Pa;

[0063] (5) The annealed silver plate is rolled along its length to a thickness of 0.5 mm using a ф360mm х400mm two-roll mill. ±0.05 For a silver plate of mm, the deformation per pass is 10% to 15%, and the total deformation is 70% to 90%.

[0064] (6) Anneal the silver plate obtained in step (5) in a vacuum annealing furnace at a temperature of 600℃ for 60 minutes and a vacuum degree of 10. -3 Pa;

[0065] (7) After annealing, the silver sheet is trimmed at the cracked edges using a slitting machine to make the sheet width 320 mm. ±1.0 mm;

[0066] (8) The silver plate obtained in step (7) is rolled in multiple passes using a D400mm precision four-roll mill to a thickness of 0.03 mm. ± 0.003 For pure silver strip of mm, the deformation per pass is 10% to 15%, and the total deformation is 70% to 90%.

[0067] (9) Anneal the pure silver strip obtained in step (8) in a vacuum annealing furnace at a temperature of 400℃ for 60 minutes and a vacuum degree of 10. -3 Pa;

[0068] (10) The annealed pure silver strip is cut into strips with a width of 320 mm using a precision shearing machine. ±1.0 mm, length is 400 ±1.0 The silver sheet was cleaned with alcohol using ultrasonic cleaning.

[0069] ⑪ Select a thickness of 0.3 mm. ±0.01 mm, width is 340 ±1.0 After being vacuum annealed at 600℃~700℃ for 30 minutes, an oxygen-free copper sheet with a length of 1500mm is coated with a release lubricant on one side and then folded in half.

[0070] ⑿ Wrap the silver sheet obtained in step ⑽ in the middle of the oxygen-free copper sheet obtained in step ⑾ to form a sandwich-structured copper-clad silver sheet;

[0071] 13. Copper-clad silver sheets are rolled to a total thickness of 0.2 mm using a D400mm precision four-roll mill through multiple passes. ±0.01 mm, silver foil thickness is 0.01 mm. ±0.002 mm, the deformation per pass is 5% to 10%, and the total deformation is 50% to 70%;

[0072] 14. The semi-finished silver foil obtained in step 13 is subjected to low-temperature annealing in a vacuum annealing furnace. The annealing temperature is 200℃, the holding time is 60min, and the vacuum degree is 10. -3 Pa, and prepare the coated lap-rolled billet again according to the method described in step 12;

[0073] 12 The secondary coated and rolled billet obtained in step 14 is rolled in multiple passes using a D450mm precision six-roll mill to obtain copper-clad silver foil with a total thickness of 0.03mm. After peeling off the copper layer, pure silver foil with a thickness of 1-2µm is obtained.

Claims

1. A method for preparing ultrathin and ultrawide silver foil, characterized in that... Includes the following steps: Step 1: Vacuum induction melting of a pure silver plate with a purity of 99.99% and casting it into a silver plate; the silver plate has a width of 120mm~150mm and a thickness of 15mm~20mm; Step 2: The surface of the silver plate is milled using a milling machine to remove surface cold shuts, inclusions and pores; Step 3: The milled silver plate is rolled in the width direction using a two-roll mill. The deformation amount of each rolling pass is 10%~20%, and the total deformation amount is 60%~70%. The width of the rolled silver plate is 320mm~350mm and the thickness is 6mm~10mm. Step 4: After cleaning the expanded silver plate, anneal it in a vacuum annealing furnace. Step 5: Roll the annealed silver plate along its length using a two-roll mill. The deformation per rolling pass is 10% to 15%, and the total deformation is 70% to 90%. The thickness of the rolled silver plate is 0.5 mm to 0.6 mm. Step 6: Anneal the silver plate obtained in Step 5 using a vacuum annealing furnace; Step 7: Use a slitting machine to cut off the cracked edges of the annealed silver plate so that the width of the plate is not less than 320mm. Step 8: The silver plate is rolled in multiple passes using a four-roll mill. The deformation per pass is 5% to 10%, and the total deformation is 70% to 90%. After rolling, a silver strip with a thickness of 0.05 mm to 0.1 mm is obtained. Step 9: Anneal the silver strip obtained in Step 8 using a vacuum annealing furnace; Step 10: Cut the annealed silver strip into silver sheets with a width of 320mm~330mm and a length of 400mm~600mm using a precision shearing machine, and clean them with alcohol using ultrasonic cleaning. Step 11: Select oxygen-free copper sheets with a thickness of 0.25mm~0.3mm, a width of 340mm~360mm, and a length of 1500mm~2000mm, vacuum anneal them, then apply a separating lubricant and fold them in half; Step 12: Wrap the silver sheet obtained in step 10 in the middle of the oxygen-free copper sheet obtained in step 11 to form a sandwich structure copper-clad silver sheet; Step 13: The copper-clad silver sheet is rolled in multiple passes using a four-roll mill. The deformation per pass is 5% to 10%, and the total deformation is 50% to 70%. After rolling, a silver foil semi-finished product with a thickness of 0.01 mm to 0.02 mm is obtained. Step 14: The silver foil semi-finished product obtained in step 13 is subjected to low-temperature annealing in a vacuum annealing furnace, and the coated and rolled billet is prepared again according to step 12. Step 15: The coated and rolled billet obtained in step 14 is rolled in multiple passes using a precision six-roll mill. The deformation per pass is 3% to 5%, and the total deformation is 50% to 70%. The total thickness of the copper-clad silver foil rolled in multiple passes is 0.05 mm. After peeling off the copper layer, a pure silver foil with a thickness of 4 to 5 μm is obtained.

2. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: The vacuum annealing temperature in steps 4 and 6 is 400℃~600℃, the holding time is 30~60min, and the vacuum degree is 10. -1 Pa ~10 -3 Pa.

3. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: The isolation lubricant mentioned in step 11 is a polyethylene solution.

4. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: In step 11, the vacuum annealing temperature of the oxygen-free copper sheet is 600℃~800℃, the holding time is 30~60min, and the vacuum degree is 10. -1 Pa ~10 -3 Pa.

5. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: In step 12, the copper-clad silver sheet has a sandwich structure, with a pure silver sheet in the middle and oxygen-free copper sheets on the top and bottom.

6. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: In steps 9 and 14, the vacuum annealing temperature is 200℃~400℃, the holding time is 30~60min, and the vacuum degree is 10. -1 Pa ~10 -3 Pa.

7. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: In step 14, the coated and rolled blank is a semi-finished silver foil with a thickness of 0.01mm to 0.02mm coated with annealed oxygen-free copper sheet, and the inner surface of the oxygen-free copper sheet is coated with a separating lubricant.

8. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: In steps 3 and 5, the two-roll mill is a ф360mmх400mm two-roll mill.

9. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: In steps 8 and 13, the four-roll mill is a D400mm precision four-roll mill.

10. The method for preparing ultrathin and ultrawide silver foil according to claim 1, characterized in that: In step 15, the six-roll mill is a D450mm precision six-roll mill.