Production Process Of Aluminum Sheet Strip

The production process of aluminum sheet strip includes the following steps:

• Scalping: to remove surface defects such as segregation, slag inclusion, scars, and surface cracks, and improve the surface quality of the sheet. The scalping machine mills both sides and edges of the slab, with a milling speed of 0.2m/s. The maximum thickness to be milled is 6mm, and the weight of the aluminum scraps produced is 383kg per slab, with an aluminum yield of 32.8kg.

• Heating: the scalped slab is then heated in a pusher-type furnace at a temperature of 350℃ to 550℃ for 5-8 hours. The furnace is equipped with 5 zones, each with a high-flow air circulation fan installed on the top. The fan operates at a speed of 10-20m/s, consuming 20m3/min of compressed air. There are also 20 natural gas burners installed on the upper part of the furnace, consuming approximately 1200Nm3/h of natural gas.

• Hot Rough Rolling: the heated slab is fed into a reversible hot rolling mill, where it undergoes 5 to 13 passes to be reduced to a thickness of 20 to 160mm.

• Hot Precision Rolling: the rough rolled plate is further processed in a hot precision rolling mill, with a maximum rolling speed of 480m/s. It undergoes 10 to 18 passes to produce plates or coils with a thickness of 2.5 to 16mm.

Cold Rolling Process

The cold rolling process is used for aluminum coils with the following specifications:

• Thickness: 2.5 to 15mm

• Width: 880 to 2000mm

• Diameter: φ610 to φ2000mm

• Weight: 12.5t

The process consists of the following steps:

• Cold Rolling: the aluminum hot rolled coils with a thickness of 2-15mm are cold rolled in a non-reversible cold rolling mill for 3-6 passes, reducing the thickness to 0.25 to 0.7mm. The rolling process is controlled by computer systems for flatness (AFC), thickness (AGC), and tension (ATC), with a rolling speed of 5 to 20m/s, and up to 25 to 40m/s during continuous rolling. The reduction rate is generally between 90% to 95%.

• Intermediate Annealing: to eliminate work hardening after cold rolling, some intermediate products require annealing. The annealing temperature ranges from 315℃ to 500℃, with a holding time of 1 to 3 hours. The annealing furnace is electrically heated and equipped with 3 high-flow fans on the top, operating at a speed of 10 to 20m/s. The total power of the heaters is 1080Kw, and the compressed air consumption is 20Nm3/h.

• Final Annealing: after cold rolling, the products undergo final annealing at a temperature of 260℃ to 490℃, with a holding time of 1 to 5 hours. The cooling rate of the aluminum foil should be less than 15℃/h, and the discharge temperature should not exceed 60℃ for the foil. For other thicknesses of coils, the discharge temperature should not exceed 100℃.

Finishing Process

The finishing process is carried out to achieve the desired specifications of the aluminum products. It includes the following steps:

• Specifications of the Finished Products:

  • Thickness: 0.27 to 0.7mm

  • Width: 880 to 1900mm

  • Diameter: φ610 to φ1800mm

  • Weight: 12.5t

• Equipment Configuration:

  • 2000mm Cross Cutting Line (2 to 12mm) – 2 sets

  • 2000mm Tension Leveling Line (0.1 to 2.5mm) – 2 sets

  • 2000mm Cross Cutting Line (0.1 to 2.5mm) – 2 sets

  • 2000mm Thick Plate Straightening Line – 2 sets

  • 2000mm Coil Automatic Packaging Line – 2 sets

  • MK8463×6000 CNC Roll Grinding Machine – 2 units

• Process and Parameters:

  • Cross Cutting Production Line: precise cross-cutting of aluminum and aluminum alloy coils with a thickness of 2 to 12mm, with a maximum length of 11m.

  • Tension Leveling Production Line: the aluminum coil is subjected to tension by the tension rolls, with a tension force of 2.0 to 20 kN. It passes through multiple sets of small-diameter bending rolls arranged alternately, allowing for stretching and bending to improve the flatness of the strip. The line operates at a speed of up to 200m/min.

  • Thick Plate Straightening Production Line: the rolls are positioned at an angle to the direction of movement of the product. There are two or three large active pressure rolls driven by motors rotating in the same direction, and several small passive pressure rolls on the other side, rotating through friction caused by a rotating rod or pipe. These small rolls can be adjusted forward or backward simultaneously or separately to achieve the required compression of the product. The product undergoes continuous linear or rotational motion, resulting in compression, bending, and flattening deformations, ultimately achieving the purpose of straightening. The straightening force of the production line is 30MN.

Further Processing Techniques

1. Drawing Process: The process involves degreasing, sanding, and water washing. In the aluminum sheet drawing process, a special film technique is used after anodizing treatment. Generally, a stainless steel wire brush or nylon sanding belt with a diameter of 0.1mm is used to create a film layer on the surface of the aluminum sheet, giving it a fine and silky appearance. The metal drawing process is increasingly used in the production of aluminum sheet products, providing both aesthetics and corrosion resistance.

2. Etching Process: The process involves grinding with jujube wood carbon to remove grease and scratches, creating a matte surface. Then, a pattern is printed using a screen printing plate, with ink models such as 80-39, 80-59, and 80-49. After printing, the sheet is dried in an oven, sealed at the back with instant adhesive, and the edges are sealed with tape. The sheet then undergoes the etching process. The etching solution for aluminum sheet consists of 50% ferric chloride and 50% copper sulfate, mixed with an appropriate amount of water, at a temperature between 15°C to 20°C. During etching, the sheet should be placed flat, and any reddish residue overflowing from the pattern should be removed with a brush. Bubbles will emerge on the aluminum surface, carrying away the residue. The etching process takes approximately 15 to 20 minutes to complete.

3. Electrophoretic Coating Process: The process includes the following steps: degreasing, hot water washing, water washing, neutralization, water washing, anodizing, water washing, electrolytic coloring, hot water washing, water washing, electrophoresis, water washing, and drying. In addition to the anodized film, a water-soluble acrylic paint film is uniformly applied to the surface of the profile through electrophoresis. This forms a composite film of anodized film and acrylic paint film. The aluminum sheet enters an electrophoretic tank with a solid content of 7% to 9%, a temperature of 20°C to 25°C, pH of 8.0 to 8.8, resistivity (20°C) of 1500 to 2500Ωcm, voltage (DC) of 80 to 25OV, and current density of 15 to 50 A/m2. The sheet undergoes electrophoresis for 1 to 3 minutes to achieve a coating thickness of 7 to 12μm.