C2680 brass reflow tin-plated belt and production method thereof

Abstract

The invention discloses a C2680 brass reflow tin-plated belt and a production method thereof. The production method comprises the following steps of: preparing raw materials; smelting, semi-continuous casting, saw cutting, stepping furnace heating, hot rolling, double-face milling, rough rolling, thick edge shearing, bell-type furnace annealing, thick strip cleaning, pre-finish rolling, intermediate rolling annealing, finished product rolling, stress relief annealing, finished product cleaning, low-tension mode stretch bending straightening, low-elongation mode stretch bending straightening, finished product cleaning, intermediate striping, hot rolling, double-face milling, rough rolling, thick edge shearing, bell-type furnace annealing, thick strip cleaning, pre-finish rolling, intermediate rolling annealing, finished product rolling, stress relief annealing, finished product cleaning and middle striping. Performing reflow tin plating; slitting a finished product; the thickness of the alloy layer of the C2680 brass reflow tin-plated belt produced by the production method is 1 / 4-1 / 2 of the thickness of the tin-plated layer, the surface quality of the C2680 brass reflow tin-plated belt is high, and the adhesiveness of the tin layer is good.

Description

Technical Field

[0001] The invention belongs to the technical field of brass strips, and in particular relates to a C2680 brass reflow tinning strip and a production method thereof. Background Art

[0002] With the rapid development of China's 5G communications, new energy vehicles, precision electronic components, intelligent equipment and other industries, the demand for high-precision tin-plated copper strip products is increasing day by day. However, only a very small number of companies in Germany, Japan and other countries can produce this high-end tin-plated copper strip product, and a large amount of imports are needed.

[0003] Copper strips and copper alloy strips are mainly produced by chemical tinning and physical tinning. Tinned strip products are mainly used in the manufacture of connector products, which utilize the functional advantages of surface tinning, which can reduce contact resistance and protect copper materials from corrosion.

[0004] Reflow tinning is an electroplating process that is different from conventional electroplating and improves weldability. First, a layer of tin is plated on the surface of the copper material using chemical and electroplating deposition. Through heat treatment, which is the so-called reflow process, the plated tin layer is melted, and an intermetallic phase of tin and copper is generated in the contact layer. Then it is rapidly cooled. Due to the surface tension of the molten tin, the free tin surface will appear mirror-like. The elimination of the residual stress of the electroplating layer can inhibit the growth of tin whiskers, and the reducing atmosphere in the furnace prevents the oxidation of the surface tin at high temperatures.

[0005] Compared with conventional electroplating, reflow tinning has the following advantages: (1) Reflow tinning helps to increase the adhesion between the tin layer and the raw material; (2) After reflow tinning, the copper strip exhibits good corrosion resistance, which is better than the conventional electroplated tin products; (3) After reflow tinning, the copper strip can provide a surface thickness that is uniform and smooth, and the bright surface presentation is particularly suitable for microelectronics such as micro connectors; (4) After reflow tinning, the copper strip can eliminate some of the internal stress of the strip, effectively reduce the generation of tin whiskers, reduce the plug-in and pull-out force of plug-ins, and provide better ductility and formability for the subsequent stamping processing of the tinned copper strip. (5) Reflow tinning is lead-free tin electroplating, which is environmentally friendly electroplating and meets the ROHS standard requirements.

[0006] Today, as the requirements for tin-plated materials become more and more stringent and the market competition becomes more and more fierce, the market requirements for tin-plated materials are also more refined and special. The copper strip needs to maintain good surface quality and low residual stress before tin-plating. There should be no scratches, pits, etc. on the surface. The thickness of the tin-plated alloy layer on the copper surface is also very important. If it is too thin, it will peel off, and if it is too thick, the anti-aging performance will deteriorate. Therefore, in order to improve the material to achieve good metallurgical bonding, thereby ensuring the adhesion of the tin layer, it is very important to effectively control the thickness of the tin-plated layer alloy. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a C2680 brass reflow tin-plated strip and a production method thereof. The alloy layer thickness of the C2680 brass reflow tin-plated strip produced by the production method is 1 / 4-1 / 2 of the thickness of the tin-plated layer, the surface quality is high, and the adhesion of the tin layer is good.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A production method for C2680 brass reflow tin-plated strip, comprising the following steps: smelting → semi-continuous casting → sawing → walking furnace heating → hot rolling → double-sided milling → rough rolling → thick shear edge → bell-type furnace annealing → thick strip cleaning → pre-finishing rolling → intermediate rolling annealing → finished product rolling → stress relief annealing → finished product cleaning → low tension mode bending and straightening → low elongation mode bending and straightening → finished product cleaning → intermediate stripping → reflow tinning → finished product stripping.

[0010] The reflow tinning process specifically includes the following steps: cathode degreasing→water washing→anode degreasing→water washing→water washing→water washing→acid washing→water washing→water washing→copper plating→water washing→tin plating→water washing→water washing→hot water→heat drying→reflow→water cooling→drying→winding.

[0011] Furthermore, the production method comprises the following steps:

[0012] 1) Melting;

[0013] 2) Semi-continuous casting;

[0014] 3) Sawing and stepping furnace heating: Cut off the defects at the head and tail, and then send them into the stepping furnace for heating at a temperature of 800-1000℃;

[0015] 4) Hot rolling: The annealed red ingot is rolled to a thickness of 15-16 mm in 9 passes through a two-roll reversible rolling mill, and then water-cooled in a cooling section and coiled in a coiling section;

[0016] 5) Double-sided milling: Mill the upper and lower surfaces and both sides of the copper strip in step 4) to remove surface defects and oxide layers, with a single-sided milling amount of 0.8-1.0 mm and a single-sided milling amount of 2-4 mm;

[0017] 6) Rough rolling: The copper strip in step 5) is rolled using a 4-roll rolling mill, and then rolled into a copper strip of 2-2.5 mm through multiple passes;

[0018] 7) Thick shearing edge: the copper strip in step 6) is sheared to a width of 28 to 38 mm, and the width after shearing is controlled at 610 to 630 mm;

[0019] 8) bell-type furnace annealing: anneal the copper strip in step 7) in a bell-type furnace at a temperature of 380-500° C.;

[0020] 9) Thick strip cleaning: The surface of the copper strip in step 8) is subjected to degreasing, pickling, grinding, and passivation treatment, and the cleaning speed is controlled at 18-25m / min;

[0021] 10) Pre-finishing rolling: The copper strip in step 9) is subjected to full oil multi-pass rolling on a 20-roller finishing mill, and the thickness after rolling is 0.3-0.5 mm, and the roughness Ra of the working rolls used is 0.12-0.18 μm;

[0022] 11) Intermediate rolling annealing: the copper strip in step 10) is subjected to intermediate rolling annealing in an air cushion furnace, the annealing temperature is 580-650° C., and the annealing speed is 60-70 m / min;

[0023] 12) Finished product rolling: The copper strip in step 11) is rolled in multiple passes with full oil on a 6-roller finishing mill, and the thickness after rolling is 0.1-0.3 mm, and the roughness Ra of the working rolls used is 0.06-0.12 μm;

[0024] 13) Stress relief annealing: The copper strip in step 12) is subjected to stress relief annealing in an air cushion furnace at a temperature of 400-600° C. and an annealing speed of 60-80 m / min;

[0025] 14) Finished product cleaning: The copper strip in step 13) is cleaned on a thin strip degreasing machine, firstly alkali-washed and then pickled, without grinding and polishing with a grinding brush;

[0026] 15) Low-tension mode bending and straightening: The copper strip in step 14) is straightened by bending and straightening, and a low-tension roller mode is adopted, and the tension is set at 30-80MPa; that is, the plate shape is corrected and stress relief is performed by tension straightening;

[0027] 16) Low elongation mode bending and straightening: The copper strip in step 15) is bent and straightened again, and the low elongation mode is adopted, and the elongation is set at 0.3-3.0%; that is, stress relief treatment and plate shape correction are performed by roller straightening;

[0028] 17) Finished product cleaning: Wash the copper strip in step 16) with water;

[0029] 18) Middle strip;

[0030] 19) Reflow tinning;

[0031] 20) Finished product stripping.

[0032] In the semi-continuous casting step, the initial casting speed is 25-35 mm / min, the cooling water temperature is 20-30° C.; the normal casting speed is 150-170 mm / min, and the water flow rate is 60-100 L / min.

[0033] In the intermediate slitting step, the slitting speed is controlled at 50-80 m / min.

[0034] In the reflow tinning step, the cathode degreasing and anode degreasing currents are 120-320A, and the unwinding tension is 8-12N / mm 2 , electroplating tension 15~25N / mm 2 , Tension in reflow oven 8~12N / mm 2 , Winding tension 15~25N / mm 2 .

[0035] In the copper plating step, the copper plating solution includes the following components: copper ion concentration 25g / L-80g / L, sulfuric acid concentration 65-140g / L, NaCl 20-40μg / L, iron ion concentration ≤400μg / mL; copper plating speed 10-30m / min; copper plating current 450-750A.

[0036] In the tin plating step, the tin plating solution includes the following components: tin ion concentration 30g / L-70g / L, sulfuric acid concentration 60-150g / L; tin plating speed 15-25m / min; tin plating current 600-900A.

[0037] In the reflow step, the temperature of the reflow furnace is 480-720° C., the atmosphere of the reflow furnace is a reducing atmosphere, the reducing atmosphere is a mixture of hydrogen and nitrogen, and the volume percentage of hydrogen is 1-2.5%. The plated tin layer is melted in the reflow furnace, and an intermetallic phase of tin and copper, i.e., an alloy layer, is generated in the contact layer, which is then rapidly cooled by cooling water.

[0038] In the water cooling step, the temperature of the cooling water is controlled at 30-50°C.

[0039] In the finished product slitting step, the slitting speed is controlled at 50-80 m / min.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The production method of C2680 brass reflow tin-plated strip provided by the present invention adopts multiple cleaning, that is, step 14) and step 17) are added. Step 14) can prevent the formation of defects such as white spots in the acid solution in the subsequent stretching and bending straightening process due to incomplete cleaning of the air cushion furnace after stress relief annealing. The role of not using a grinding brush in step 14) is to make the copper strip structure more compact and prevent the grinding brush from being pressed too low to cause surface scratches; adding step 17) after the stretching and straightening step, that is, using a degreasing machine for deionized water washing, can effectively remove dust and other debris generated on the surface of the copper strip during the two stretching and straightening, so as to provide a high-quality strip surface before tinning;

[0042] (2) The present invention performs stress relief annealing in step 13) after the finished product is rolled to eliminate the metastable state of the structure and performance of the strip caused by cold deformation.

[0043] (3) After the finished product cleaning step of step 14), the present invention sequentially adopts the low tension mode and low elongation mode to straighten the copper strip, thereby effectively reducing the internal stress of the copper strip and correcting the plate shape of the strip.

[0044] (4) In the reflow tinning process, by adding some trace elements, such as Na and Cl, to the copper plating tank, the fluidity of the solution in the copper plating tank can be increased, effectively avoiding the surface of the strip from being burned. By keeping the concentration of copper ions and tin ions in the copper plating tank and the tin plating tank at a certain value, the thickness of the tin layer and the alloy layer of the tin-plated strip can be effectively controlled by controlling the current size of each plating tank, the temperature of the reflow furnace and the speed of the strip running, thus avoiding the uneven thickness of the tin-plated strip due to the different concentrations of copper ions, tin ions and sulfuric acid in the copper plating tank and the tin plating tank, and the large difference in the thickness of the tin-plated layer before and after. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a morphology image of the coating of the C2680 brass reflow tin-plated strip prepared in Example 1;

[0046] Figure 2 This is a morphology image of the coating of the C2680 brass reflow tin-plated strip prepared in Comparative Example 1;

[0047] Figure 3 This is a morphology image of the coating of the C2680 brass reflow tin-plated strip prepared in Comparative Example 2. DETAILED DESCRIPTION

[0048] The invention provides a production method of a C2680 brass reflow tin-plated strip, which comprises the following steps: smelting→semi-continuous casting→sawing→walking furnace heating→hot rolling→double-sided milling→rough rolling→thick shear edge→hood furnace annealing→thick strip cleaning→pre-finishing rolling→intermediate rolling annealing→finished product rolling→stress relief annealing→finished product cleaning→low tension mode bending and straightening→low elongation mode bending and straightening→finished product cleaning→intermediate stripping→reflow tinning→finished product stripping.

[0049] The reflow tinning process specifically includes the following steps: cathode degreasing→water washing→anode degreasing→water washing→water washing→water washing→acid washing→water washing→water washing→copper plating→water washing→tin plating→water washing→water washing→hot water→heat drying→reflow→water cooling→drying→winding.

[0050] Furthermore, the production method specifically comprises the following steps:

[0051] 1) Melting;

[0052] 2) Semi-continuous casting;

[0053] 3) Sawing and stepping furnace heating: Cut off the defects at the head and tail, and then send them into the stepping furnace for heating at a temperature of 800-1000℃;

[0054] 4) Hot rolling: The annealed red ingot is rolled to a thickness of 15-16 mm in 9 passes through a two-roll reversible rolling mill, and then water-cooled in a cooling section and coiled in a coiling section;

[0055] 5) Double-sided milling: Mill the upper and lower surfaces and both sides of the copper strip in step 4) to remove surface defects and oxide layers, with a single-sided milling amount of 0.8-1.0 mm and a single-sided milling amount of 2-4 mm;

[0056] 6) Rough rolling: The copper strip in step 5) is rolled using a 4-roll rolling mill, and then rolled into a copper strip of 2-2.5 mm through multiple passes;

[0057] 7) Thick shearing edge: the copper strip in step 6) is sheared to a width of 28 to 38 mm, and the width after shearing is controlled at 610 to 630 mm;

[0058] 8) bell-type furnace annealing: anneal the copper strip in step 7) in a bell-type furnace at a temperature of 380-500° C.;

[0059] 9) Thick strip cleaning: The surface of the copper strip in step 8) is subjected to degreasing, pickling, grinding, and passivation treatment, and the cleaning speed is controlled at 18-25m / min;

[0060] 10) Pre-finishing rolling: The copper strip in step 9) is subjected to full oil multi-pass rolling on a 20-roller finishing mill, and the thickness after rolling is 0.3-0.5 mm, and the roughness Ra of the working rolls used is 0.12-0.18 μm;

[0061] 11) Intermediate rolling annealing: the copper strip in step 10) is subjected to intermediate rolling annealing in an air cushion furnace, the annealing temperature is 580-650° C., and the annealing speed is 60-70 m / min;

[0062] 12) Finished product rolling: The copper strip in step 11) is rolled in multiple passes with full oil on a 6-roller finishing mill, and the thickness after rolling is 0.1-0.3 mm, and the roughness Ra of the working rolls used is 0.06-0.12 μm;

[0063] 13) Stress relief annealing: The copper strip in step 12) is subjected to stress relief annealing in an air cushion furnace at a temperature of 400-600° C. and an annealing speed of 60-80 m / min;

[0064] 14) Finished product cleaning: The copper strip in step 13) is cleaned on a thin strip degreasing machine, firstly alkali-washed and then pickled, without grinding and polishing with a grinding brush;

[0065] 15) Low tension mode bending and straightening: The copper strip in step 14) is bent and straightened in a low tension roller mode with a tension set at 30-80 MPa;

[0066] 16) Low elongation mode bending and straightening: The copper strip in step 15) is bent and straightened again in a low elongation mode with the elongation set at 0.3-3.0%;

[0067] 17) Finished product cleaning: Wash the copper strip in step 16) with water;

[0068] 18) Middle strip;

[0069] 19) Reflow tinning;

[0070] 20) Finished product stripping.

[0071] In the semi-continuous casting step, the initial casting speed is 25-35 mm / min, the cooling water temperature is 20-30° C.; the normal casting speed is 150-170 mm / min, and the water flow rate is 60-100 L / min.

[0072] In the intermediate slitting step, the slitting speed is controlled at 50-80 m / min.

[0073] In the reflow tinning step, the cathode degreasing and anode degreasing currents are 120-320A, and the unwinding tension is 8-12N / mm 2 , electroplating tension 15~25N / mm 2, Tension in reflow oven 8~12N / mm 2 , Winding tension 15~25N / mm 2 .

[0074] In the copper plating step, the copper plating solution includes the following components: copper ion concentration 25g / L-80g / L, sulfuric acid concentration 65-140g / L, NaCl 20-40μg / L, iron ion concentration ≤400μg / mL; copper plating speed 10-30m / min; copper plating current 450-750A.

[0075] In the tin plating step, the tin plating solution includes the following components: tin ion concentration 30g / L-70g / L, sulfuric acid concentration 60-150g / L; tin plating speed 15-25m / min; tin plating current 600-900A.

[0076] In the reflow step, the temperature of the reflow furnace is 480-720° C., and the atmosphere of the reflow furnace is a reducing atmosphere.

[0077] In the water cooling step, the temperature of the cooling water is controlled at 30-50°C.

[0078] In the finished product slitting step, the slitting speed is controlled at 50-80 m / min.

[0079] The present invention is described in detail below with reference to the embodiments.

[0080] Example 1

[0081] A method for producing a C2680 brass reflow tinned strip with a finished product thickness of 0.3 mm, a tinned thickness of 1.0 μm, and a state of H, comprising the following steps:

[0082] 1) Smelting: Add cathode copper and other metals into the smelting furnace in order and proportion → adjust the composition to meet the requirements → heat up to the converter temperature of 1080℃ for smelting;

[0083] 2) Semi-continuous casting: Tilt the furnace of the holding furnace to allow the copper liquid to flow into the crystallizer, and then pull out the copper ingot through the ingot drawing machine. The initial drawing speed is 30 mm / min, the cooling water temperature is 20°C, the subsequent drawing speed is 160 mm / min, and the water flow rate is 80 L / min;

[0084] 3) Sawing and heating in a walking furnace: remove the defects at the head and tail, and then send them into a walking furnace for heating at 870°C;

[0085] 4) Hot rolling: The annealed red ingot is rolled to a thickness of 16 mm in 9 passes through a two-roll reversible rolling mill, and then water-cooled in a cooling section and coiled in a coiling section;

[0086] 5) Double-sided milling: Mill the upper and lower sides and both sides of the copper strip in step 4) to remove surface defects and oxide layers. The single-sided milling amount is 0.8 mm and the single-sided milling amount is 2 mm.

[0087] 6) Rough rolling: The copper strip in step 5) is rolled using a 4-roll rolling mill and rolled into a 2.5 mm copper strip through multiple passes;

[0088] 7) Thick shearing edge: The copper strip in step 6) is sheared to a width of 28 mm, and the width after shearing is controlled at 610 mm;

[0089] 8) bell-type furnace annealing: the copper strip in step 7) is annealed in a bell-type furnace at an annealing temperature of 420° C.

[0090] 9) Thick strip cleaning: The surface of the copper strip in step 8) is subjected to degreasing, pickling, grinding, and passivation treatment, and the cleaning speed is controlled at 18m / min;

[0091] 10) Pre-finishing rolling: The copper strip in step 9) is subjected to full oil multi-pass rolling on a 20-roller finishing mill, and the thickness after rolling is 0.5 mm, and the roughness Ra of the working rolls used is 0.12 μm;

[0092] 11) Intermediate rolling annealing: the copper strip in step 10) is subjected to intermediate rolling annealing in an air cushion furnace at an annealing temperature of 580° C. and an annealing speed of 60 m / min;

[0093] 12) Finished product rolling: The copper strip in step 11) is rolled in multiple passes with full oil on a 6-roller finishing mill, and the thickness after rolling is 0.3 mm, and the roughness Ra of the working rolls used is 0.06 μm;

[0094] 13) Stress relief annealing: The copper strip in step 12) is subjected to stress relief annealing in an air cushion furnace at a temperature of 500° C. and an annealing speed of 60 m / min;

[0095] 14) Finished product cleaning: The copper strip in step 13) is cleaned on a thin strip degreasing machine, firstly alkali-washed and then pickled, without grinding and polishing with a grinding brush;

[0096] 15) Low tension mode bending and straightening: The copper strip in step 14) is bent and straightened in a low tension roller mode with the tension set at 38 MPa;

[0097] 16) Low elongation mode stretching and straightening: The copper strip in step 15) is stretched and straightened again in a low elongation mode with the elongation set at 1.2%;

[0098] 17) Finished product cleaning: Wash the copper strip in step 16) with water;

[0099] 18) Intermediate stripping: The copper strip in step 17) is stripped in the middle, and the stripping speed is controlled at 55m / min;

[0100] 19) Reflow tinning: The specific process is as follows: cathode degreasing → water washing → anode degreasing → water washing → water washing → water washing → water washing → pickling → water washing → water washing → copper plating → water washing → tin plating → water washing → water washing → hot water → hot drying → reflow → 25℃ water cooling → drying → winding;

[0101] The concentration of each ion in the copper plating tank is controlled as follows: copper ion concentration 50g / L, sulfuric acid concentration 100g / L, NaCl 25μg / L, and iron ion concentration 100μg / mL;

[0102] a. Control of ion concentration in tinning bath: Sn 2+ Concentration 45g / L, SO4 2- Concentration 100g / L;

[0103] The specific operating parameters of tinning are as follows: operating speed 20m / min, degreasing current 200A, copper plating current 600A, tinning current 750, unwinding tension 10N / mm 2 , electroplating tension 20N / mm 2 , Tension in reflow oven 10N / mm 2 , Winding tension 20N / mm 2 , the temperature of the reflow furnace is 600°C, the atmosphere of the reflow furnace is a reducing atmosphere, and the composition is a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 1-2.5%.

[0104] 20) Finished product slitting: The copper strip in step 19) is slit into finished products according to customer requirements, and the slitting speed is controlled at 55m / min.

[0105] The stress comparison of the samples taken from the tail of the strip before and after stress relief annealing in this embodiment is shown in Table 1. The detection equipment is an X-ray residual stress analyzer, and the equipment model is μ-X360s, wherein R1 represents the first point tested in the RD direction, i.e., the rolling direction, and T1 represents the first point tested in the vertical rolling direction.

[0106] Table 1

[0107]

[0108]

[0109] In this embodiment, the stress of the sample taken from the tail of the strip after bending and straightening in step 16) is shown in Table 2.

[0110] Table 2

[0111]

[0112] Different positions of the C2680 brass reflow tinning strip produced in this embodiment were randomly selected to test the distribution of the tinning layer thickness. The results are shown in Table 3.

[0113] Table 3

[0114]

[0115] The surface coating morphology of the C2680 brass reflow tinning strip produced in this embodiment is as follows Figure 1 As shown in the figure, it can be seen that the thickness of the alloy layer is 1 / 4-1 / 2 of the thickness of the tin-plated layer. At this time, good metallurgical bonding is achieved, the adhesion of the tin layer is guaranteed, and the surface quality is good, and the surface is mirror-like.

[0116] Example 2

[0117] A method for producing a C2680 brass reflow tinned strip with a finished product thickness of 0.1 mm, a tinned thickness of 1.0 μm, and a state of H, comprising the following steps:

[0118] 1) Smelting: Add cathode copper and other metals into the smelting furnace in order and proportion → adjust the composition to meet the requirements → heat up to the converter temperature of 1100°C for smelting;

[0119] 2) Semi-continuous casting: Tilt the furnace of the holding furnace to allow the copper liquid to flow into the crystallizer, and then pull out the copper ingot through the ingot drawing machine. The initial drawing speed is 30 mm / min, the cooling water temperature is 30°C, the subsequent drawing speed is 160 mm / min, and the water flow rate is 80 L / min;

[0120] 3) Sawing and stepping furnace heating: remove the defects at the head and tail, and then send them into the stepping furnace for heating at 945℃;

[0121] 4) Hot rolling: The annealed red ingot is rolled to a thickness of 15 mm in 9 passes through a two-roll reversible rolling mill, and then water-cooled in a cooling section and coiled in a coiling section;

[0122] 5) Double-sided milling: Mill the upper and lower sides and both sides of the copper strip in step 4) to remove surface defects and oxide layers. The single-sided milling amount is 1.0 mm and the single-sided milling amount is 4 mm.

[0123] 6) Rough rolling: The copper strip in step 5) is rolled by a 4-roll rolling mill and rolled into a 2 mm copper strip through multiple passes;

[0124] 7) Thick shearing edge: The copper strip in step 6) is sheared to a width of 38 mm, and the width after shearing is controlled at 630 mm;

[0125] 8) bell-type furnace annealing: anneal the copper strip in step 7) in a bell-type furnace at an annealing temperature of 480° C.

[0126] 9) Thick strip cleaning: The surface of the copper strip in step 8) is subjected to degreasing, pickling, grinding, and passivation treatment, and the cleaning speed is controlled at 25m / min;

[0127] 10) Pre-finishing rolling: The copper strip in step 9) is subjected to full oil multi-pass rolling on a 20-roller finishing mill, and the thickness after rolling is 0.3 mm, and the roughness Ra of the working rolls used is 0.18 μm;

[0128] 11) Intermediate rolling annealing: The copper strip in step 10) is subjected to intermediate rolling annealing in an air cushion furnace at a temperature of 642° C. and an annealing speed of 70 m / min;

[0129] 12) Finished product rolling: The copper strip in step 11) is rolled in multiple passes with full oil on a 6-roller finishing mill, and the thickness after rolling is 0.1 mm, and the roughness Ra of the working rolls used is 0.12 μm;

[0130] 13) Stress relief annealing: The copper strip in step 12) is subjected to stress relief annealing in an air cushion furnace at a temperature of 550° C. and an annealing speed of 80 m / min;

[0131] 14) Finished product cleaning: The copper strip in step 13) is cleaned on a thin strip degreasing machine, firstly alkali-washed and then pickled, without grinding and polishing with a grinding brush;

[0132] 15) Low tension mode bending and straightening: The copper strip in step 14) is bent and straightened in a low tension roller mode with the tension set at 75 MPa;

[0133] 16) Low elongation mode bending and straightening: The copper strip in step 15) is bent and straightened again in a low elongation mode with the elongation set at 2.6%;

[0134] 17) Finished product cleaning: Wash the copper strip in step 16) with water;

[0135] 18) Intermediate stripping: The copper strip in step 17) is stripped in the middle, and the stripping speed is controlled at 80m / min;

[0136] 19) Reflow tinning: The specific process is as follows: cathode degreasing → water washing → anode degreasing → water washing → water washing → water washing → water washing → pickling → water washing → water washing → copper plating → water washing → tin plating → water washing → water washing → hot water → hot drying → reflow → 35℃ water cooling → drying → winding;

[0137] The concentration of each ion in the copper plating tank is controlled as follows: copper ion concentration 46g / L, sulfuric acid concentration 85g / L, NaCl 30μg / L, and iron ion concentration 50μg / mL;

[0138] b. Control of ion concentration in tinning bath: Sn 2+ Concentration 40g / L, SO4 2- Concentration 85g / L;

[0139] The specific operating parameters of tinning are as follows: operating speed 25m / min, degreasing current 180A, copper plating current 600A, tinning current 800A, unwinding tension 12N / mm 2 , electroplating tension 15N / mm 2 , Tension in reflow oven 8N / mm 2 , Winding tension 15N / mm 2 , the temperature of the reflow oven is 615°C, the atmosphere of the reflow oven is a reducing atmosphere, and the composition is a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 1-2.5%.

[0140] 20) Finished product slitting: The copper strip in step 19) is slit into finished products according to customer requirements, and the slitting speed is controlled at 80m / min.

[0141] Different positions of the C2680 brass reflow tinning strip produced in this embodiment were randomly selected to test the distribution of the tinning layer thickness. The results are shown in Table 4.

[0142] Table 4

[0143]

[0144] As can be seen from the above, the upper and lower surfaces of the C2680 brass reflow tin-plated strip produced in this embodiment are uniformly plated. The alloy layer thickness of the C2680 brass reflow tin-plated strip produced in this embodiment is 1 / 4-1 / 2 of the thickness of the tin-plated layer, achieving good metallurgical bonding, ensuring the adhesion of the tin layer, and having good surface quality and a mirror-like surface.

[0145] Comparative Example 1

[0146] The same as Example 1, except that the reflow furnace temperature is 650°C, the surface coating morphology of the C2680 brass reflow tinned strip produced in this example is as follows: Figure 2 As shown in the figure, it can be seen that the thickness of the alloy layer is too thick, and excessive thickness of the alloy layer will lead to poor anti-aging performance of the tin-plated strip, and the required number of uses and service life cannot be achieved.

[0147] Comparative Example 2

[0148] The same as Example 1, except that the reflow furnace temperature is 550°C. The surface coating morphology of the C2680 brass reflow tinned strip produced in this example is as follows: Figure 3 As shown in the figure, it can be seen that the growth of the alloy layer is not obvious, and the thickness of the alloy layer is too thin, resulting in the peeling of the tin plating layer in subsequent processing.

[0149] Comparative Example 3

[0150] The rest is the same as in Example 1, except that the low elongation mode stretch bending straightening in step 16) is not performed.

[0151] The residual stress values ​​after one straightening (i.e. after step 15) are shown in Table 5.

[0152] Table 5

[0153]

[0154] From the comparison between Table 2 and Table 3, it can be seen that the residual stress of the strip is significantly reduced after secondary straightening.

[0155] The distribution of the thickness of the tinned layer was tested at different positions of the C2680 brass reflow tinned strip produced in this comparative example at random. The results are shown in Table 6.

[0156] Table 6

[0157]

[0158] As can be seen from Table 6, the coating thickness of the C2680 brass reflow tin-plated strip produced in the comparative example is significantly different from the target thickness, and the uniformity is poor.

[0159] The detailed description of a C2680 brass reflow tin-plated strip and its production method with reference to the above-mentioned embodiment is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for producing C2680 brass reflow tinning strip, characterized in that: The production method comprises the following steps: smelting → semi-continuous casting → sawing → walking furnace heating → hot rolling → double-sided milling → rough rolling → thick shear edge → bell furnace annealing → thick strip cleaning → pre-finishing rolling → intermediate rolling annealing → finished product rolling → stress relief annealing → finished product cleaning → low tension mode bending and straightening → low elongation mode bending and straightening → finished product cleaning → intermediate stripping → reflow tinning → finished product stripping.

2. The production method according to claim 1, characterized in that The reflow tinning process specifically comprises the following steps: Cathode degreasing → water washing → anode degreasing → water washing → water washing → water washing → water washing → pickling → water washing → water washing → copper plating → water washing → tin plating → water washing → water washing → hot water → hot drying → reflux → water cooling → drying → winding.

3. The production method according to claim 1 or 2, characterized in that: The production method comprises the following steps: 1) Melting; 2) Semi-continuous casting; 3) Sawing and stepping furnace heating: Cut off the defects at the head and tail, and then send them into the stepping furnace for heating at a temperature of 800-1000℃; 4) Hot rolling: The annealed red ingot is rolled to a thickness of 15-16 mm in 9 passes through a two-roll reversible rolling mill, and then water-cooled in a cooling section and coiled in a coiling section; 5) Double-sided milling: Mill the upper and lower surfaces and both sides of the copper strip in step 4) to remove surface defects and oxide layers, with a single-sided milling amount of 0.8-1.0 mm and a single-sided milling amount of 2-4 mm; 6) Rough rolling: The copper strip in step 5) is rolled using a 4-roll rolling mill, and then rolled into a copper strip of 2-2.5 mm through multiple passes; 7) Thick shearing edge: the copper strip in step 6) is sheared to a width of 28 to 38 mm, and the width after shearing is controlled at 610 to 630 mm; 8) bell-type furnace annealing: anneal the copper strip in step 7) in a bell-type furnace at a temperature of 380-500° C.; 9) Thick strip cleaning: The surface of the copper strip in step 8) is subjected to degreasing, pickling, grinding, and passivation treatment, and the cleaning speed is controlled at 18-25m / min; 10) Pre-finishing rolling: The copper strip in step 9) is subjected to full oil multi-pass rolling on a 20-roller finishing mill, and the thickness after rolling is 0.3-0.5 mm, and the roughness Ra of the working rolls used is 0.12-0.18 μm; 11) Intermediate rolling annealing: the copper strip in step 10) is subjected to intermediate rolling annealing in an air cushion furnace, the annealing temperature is 580-650° C., and the annealing speed is 60-70 m / min; 12) Finished product rolling: The copper strip in step 11) is rolled in multiple passes with full oil on a 6-roller finishing mill, and the thickness after rolling is 0.1-0.3 mm, and the roughness Ra of the working rolls used is 0.06-0.12 μm; 13) Stress relief annealing: The copper strip in step 12) is subjected to stress relief annealing in an air cushion furnace at a temperature of 400-600° C. and an annealing speed of 60-80 m / min; 14) Finished product cleaning: The copper strip in step 13) is cleaned on a thin strip degreasing machine, firstly alkali-washed and then pickled, without grinding and polishing with a grinding brush; 15) Low tension mode bending and straightening: The copper strip in step 14) is bent and straightened in a low tension roller mode with a tension set at 30-80 MPa; 16) Low elongation mode bending and straightening: The copper strip in step 15) is bent and straightened again in a low elongation mode with the elongation set at 0.3-3.0%; 17) Finished product cleaning: Wash the copper strip in step 16) with water; 18) Middle strip; 19) Reflow tinning; 20) Finished product stripping.

4. The production method according to claim 1 or 2, characterized in that: In the semi-continuous casting step, the initial casting speed is 25-35 mm / min, the cooling water temperature is 20-30° C.; the normal casting speed is 150-170 mm / min, and the water flow rate is 60-100 L / min.

5. The production method according to claim 1 or 2, characterized in that: In the intermediate slitting step, the slitting speed is controlled at 50-80 m / min.

6. The production method according to claim 2, characterized in that: In the copper plating step, the copper plating solution includes the following components: copper ion concentration 25g / L-80g / L, sulfuric acid concentration 65-140g / L, NaCl 20-40μg / L, iron ion concentration ≤400μg / mL; copper plating speed 10-30m / min; copper plating current 450-750A.

7. The production method according to claim 2, characterized in that: In the tin plating step, the tin plating solution includes the following components: tin ion concentration 30g / L-70g / L, sulfuric acid concentration 60-150g / L; tin plating speed 15-25m / min; tin plating current 600-900A.

8. The production method according to claim 2, characterized in that: In the reflow step, the temperature of the reflow furnace is 480-720° C., and the atmosphere of the reflow furnace is a reducing atmosphere.

9. The production method according to claim 1 or 2, characterized in that: In the finished product slitting step, the slitting speed is controlled at 50-80 m / min.

10. C2680 brass reflow tinning strip produced by the production method according to any one of claims 1 to 9.

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