Key to Produce Electrolytic Capacitor Negative Foil by Electrolytic Aluminum Liquid

[China Aluminum Network] Negative foil is the key material for producing electrolytic capacitors. China's Aluminum Electrolytic Capacitors have developed rapidly. According to statistics, it has become the world's largest producer of electrolytic capacitors. It consumes about 8kt of aluminum foil and increases it at a rate of 20%. 2000 Before the year, negative foils mainly depended on imports. Our company developed AL-MN-CU and AL-CU-FE negative foils according to market needs. After nearly 4 years of hard work, we mastered the key technologies for anode foil production, and the quality of our products was greatly improved. The finished product rate has been increased from the original 35% to the present 80%, and the users have responded well. After etching, the surface of the aluminum foil is smooth and uniform, and the specific volume is stable. This article focuses on the use of AL-CU-FE alloy production of electrolytic capacitor negative foil technology.

1 Quality requirements for negative foils 1.1 Performance requirements The basic performance requirements for negative foils of AL-CU-FE alloys are as follows:

1 specific volume not less than 450 F/cm?

2 The thickness does not decrease after etching 3 The strength is good, the number of bendings is more than 80 times, and the strength after corrosion is RM≥2. 2N/cm?

4 The hydration stability is good, and the specific volume is less than 8%

5 residue chlorine ion is not more than 0. 08mg/m?, residual CU is not more than 12mg/m?

6 Adhesive strength of tape is not less than 0. 95N/cm

1.2 chemical composition of the AL-CU-FE alloy elements of the mass fraction of W (CU) = 0.2% ~ 0. 23%; W (FE) = 0.16% ~ 0. 19%; W (SI ) Not more than 0.08%; Others are not more than 0.005%.

1.2 surface and size requirements 1 thickness 0. 04 ~ 0. 05mm, deviation ± 0. 002mm

2The surface is uniform, no scratches, scratches, or roll marks. The surface is smooth and smooth after etching. There are no holes, wrinkles, flanging and other defects. 3 The surface is ash-free after corrosion. 4 Plate shape is not more than 40I.

2 Cathode foil production The production process of anode foil is electrolytic aluminum bath → smelting, batching → refining → online degassing → slagging → cast rolling → cold rolling → annealing → cold rolling → annealing → finish rolling 2.1 Ingredients Purity 99 85% electrolytic aluminum liquid 70%, purity 99.7% aluminum ingot or primary waste 30%, AL-CU, AL-FE master alloy.

2.2 Decontamination of Ingredients Electrolytic aluminum liquid has high melt temperature, complex impurity content, gas impurities, etc. The temperature of the special electrolytic aluminum liquid is generally above 950°C, and the aluminum liquid is mixed with impurities such as FE, CU, SI and each Electrolyte, metal and non-metal oxides, and H2 content of up to 2.5ml/100g/AL, and contains CO, CH4 and other gases, therefore, the electrolytic aluminum solution must be refined, generally outside the furnace cooling, degassing, addition Slag, in-furnace refining, and on-line degassing and slag removal.

When the electrolytic aluminum liquid is added to the smelting furnace, degassing, slagging, and cooling are performed in the opening packet, and the filter is introduced into the smelting furnace, so that the solid material is first added in the furnace to melt, and is melted and stirred until the metal temperature is 720 to 730°C. After batching, after the ingredients are qualified, the metal temperature reaches 735-740°C and the furnace is guided, and the slag is raked for 20 minutes before the furnace is introduced.

2.3 In the furnace refining furnace, edge guide edge refining, refining agent 99. 995% of high purity argon + 5% CCL4, refining 15 ~ 18min, refining to be uniform and thorough, eight net surface scum, and Guarantee melt temperature is 720 ~ 730 °C.

2.4 Out-of-furnace refining and filtration The on-line refining technology is adopted outside the furnace. The bath temperature is maintained at (730±5)°C. The refining agent is 99.9998% high-purity argon and the gas pressure is not less than 0.4 MPa. The rotation speed is not less than 120r/min, and the negative pressure of the refining tank is maintained to prevent oxidizing and inducing slagging. By online refining, the hydrogen content is generally less than or equal to 0. 12ml/100gAL

In-line continuous double-layer filtration technology was used outside the furnace to maintain the filtration pressure, with a 30-mesh filter plate on the front layer and a 40-mesh filter plate on the second layer.

2.5 Refine Grains Online