Aluminum alloy processing technology

Aluminum is the most widely used and widely applied metallic material among non-ferrous metals, and its applications are still expanding. Aluminum produces an endless variety of aluminum products. According to statistics, there are more than 700,000 kinds, from the building decoration industry to the transportation industry, aerospace and other industries have different needs. Today, I will introduce the machining process of aluminum products and how to avoid machining deformation.

The advantages and characteristics of aluminum are as follows:

• 1, low density. The density of aluminum is about 2.7g/cm3. its density is only 1/3 of that of iron or copper.
• 2, high plasticity. Aluminum has good ductility, can be made into various supplies by extrusion, stretching and other pressure processing means.
• 3, corrosion resistance. Aluminum is a kind of negatively charged metal, under natural conditions or anodic oxidation the surface will produce a protective oxide film, which has better corrosion resistance than steel.
• 4, easy to strengthen. Pure aluminum is not strong, but anodizing can improve its strength.
• 5, easy surface treatment. Surface treatment can further improve or change the surface properties of aluminum. Aluminum anodic oxidation process is quite mature, stable operation, has been widely used in aluminum products processing.
• 6, good conductivity, easy to recycle.

Aluminum Processing

Stamping of aluminum products

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1、Cold Punch

Use material aluminum pellets. Using an extruder and die for one-time molding, it is suitable for columnar products such as oval, square, and rectangular products or product shapes that are difficult to achieve with the stretching process. (For example, products in Fig. 1, Fig. 2 and Fig. 3)
The tonnage of the platform used is related to the cross-sectional area of the product. The gap between the upper die punch and the lower die tungsten is the wall thickness of the product, and the vertical gap between the upper die punch and the lower die tungsten is the top thickness of the product.
Advantages: short cycle time for mold opening, lower development cost than stretching molds.
Disadvantages: long production process, large fluctuations in product size, high labor costs.

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2. Stretching

Use material aluminum skin. Applicable to non-cylindrical body (aluminum bending products), using continuous mold machine and mold for multiple deformation to meet the shape requirements.

Advantages: Stable dimensional control of complex and variable shaped products during the production process, and smooth surface of the products.
Disadvantages: High mold cost, long development cycle, high requirements for machine selection and precision.

3. Mechanical processing

Also known as CNC machining, automatic lathe machining, CNC lathe machining, and so on.
(1) Processing mold parts with general-purpose machine tools such as turning, milling, planing, drilling, grinding, etc., and then carrying out the necessary clamp repairs to assemble various molds.
(2) high precision requirements of the mold parts, only with ordinary machine tool processing is difficult to ensure high machining accuracy, so you need to use precision machine tool processing.
(3) In order to make the machining of mold parts, especially convex molds with complex shapes, concave mold holes and cavities, more automatic and reduce the workload of assemblers, it is necessary to use CNC machine tools (such as three-coordinate CNC milling machines, machining centers, CNC grinding machines and other equipment) to process mold parts.

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4、Laser cutting

By means of a laser cutter or Laser tube cutting machine A focused, high power density laser beam irradiates the workpiece, causing the material to rapidly heat up to the evaporation temperature and evaporate to form a hole. At the same time, the molten material is blown away by a high-speed air stream coaxial to the beam. With the movement of the laser beam, these holes continuously form a narrow width (e.g., 0.1 mm or so) seam, thus completing the cutting of the material.

5、Precision casting

Precision casting, which is a special casting. Generally speaking, parts obtained by this method do not need to be reworked. Examples include investment casting and pressure casting. Compared with the traditional casting process, precision casting is a casting method. It can obtain relatively accurate topography and high casting precision. The more common methods are: first design and make (very small or non-remaining) molds according to the product requirements, casting wax and obtaining the original wax molds; repeating the coating and sand process, hardening the shells and drying; then dissolving the internal wax molds and obtaining the cavities; baking the shells to obtain sufficient strength; pouring the required metal materials; and de-shelling and sanding the shells in order to obtain a high-precision finished product. Heat and cold treatments are carried out according to the needs of the product or.

6、Powder metallurgy

Powder metallurgy is a technology for manufacturing metal powders, using metal powders (and sometimes small amounts of non-metallic powders) as raw materials, which are mixed, molded, and sintered to create a material or product. It includes two parts of manufacturing metal powder (also including alloy powder, collectively referred to as "metal powder"). (2) Manufacture of materials (known as "powder metallurgy materials") or products (known as "powder metallurgy products"), metal powder (sometimes adding a small amount of non-metallic powder) as raw materials, mixing, molding and sintering.

7、Injection molding of aluminum alloy parts

Solid powder is mixed well with organic binder, granulated under heating and plasticizing state (~150℃) and injected into the mold cavity by injection molding machine for curing and molding, then the binder in the molded billet is removed by chemical or thermal decomposition, and finally the final product is obtained by sintering and densification. Compared with the traditional process, its products are widely used in electronic information engineering, biomedical equipment, office equipment, automotive, machinery, hardware, sports equipment, watch industry, weapons, aerospace and other industries.

8、Aluminum alloy casting

Aluminum Casting It is a manufacturing method in which aluminum alloys are melted, cast in a casting process, and then cooled and solidified to obtain the desired product or part.

Aluminum sand casting: This is a casting method for producing aluminum alloy castings in a sand mold. This casting method uses a sand mold as a mold, injects molten aluminum alloy into the sand mold, and obtains the desired casting after cooling. Since sand casting materials are relatively cheap, the cost is relatively low and suitable for mass production. In addition, during the casting process, temperature, time and cooling rate need to be controlled to ensure the quality and performance of the castings.

Aluminum alloy investment casting: It is a precision casting method, also known as "lost wax casting". In investment casting, a fusible material (e.g. wax or plastic) is first used to make an accurate appearance. The model is made according to the shape and size of the desired casting. Then, several layers of refractory material are applied to the surface of the exterior to form a shell. This shell serves to protect the internal appearance and to maintain the shape of the casting during the casting process. The internal appearance is then melted and drained to obtain a casting without parting surfaces. This type of casting can be used for filling sand and pouring molten aluminum alloys. The casting is cooled and hardened after pouring. The castings are baked at high temperatures and are ready for subsequent processing or use. The advantage of investment casting is that very precise and complex castings can be produced.

aluminumpressure casting : It is a method of using high pressure to press liquid metal into a precision metal mold cavity at high speed, and then cooling and solidifying to form a casting. Liquid metal is injected into the mold cavity under high pressure for pressure casting. This high pressure allows the liquid metal to fill the cavity quickly and cool and solidify in a short period of time. Because the liquid metal flow under high pressure, can produce complex shape and structure of the casting. Because the die casting can quickly cool and solidify the liquid metal, so it can reduce the defects and stresses inside the casting.

aluminumLow-pressure casting : Indeed refers to the lower pressure (usually 0.02) ~ in the range of 0.06MPa), the liquid metal is filled and casting, and crystallization under pressure to form castings. The method is also known as "low-pressure casting" or "low-pressure filling casting". The liquid metal is injected into a sealed crucible during the low-pressure casting process and then transferred to the mold through a piping system. This process takes place under tightly controlled air pressure and temperature conditions of the metal liquid. Once the metal liquid fills the mold cavity, the excess metal liquid flows back into the crucible. The mold is then cooled under a certain pressure, allowing the metallic liquid to crystallize under pressure to obtain the desired casting.

Aluminum alloy centrifugal casting: It is a casting method in which the liquid metal is poured into the rotational casting under centrifugal force, filling the casting and solidifying the mold. In the centrifugal casting process, the liquid metal is first poured into the rotational casting. The casting is usually made of refractory material and has the desired shape and size. As the liquid metal enters the rotational casting, centrifugal force pulls the liquid metal to the inner wall of the casting, thus filling the entire casting. The liquid metal is rapidly cooled and solidified by the centrifugal force. Due to the centrifugal force, the liquid metal forms a thicker metal layer on the inner wall of the casting and a thinner metal layer in the center of the casting. This structure gives the casting better strength and stiffness.

aluminumGravitational casting : This is a molding method that uses liquid metal to fill the metal casting under gravity and cool and solidify in the type. Liquid metal is injected into the metal casting during the metal casting process and cooled and solidified during the casting process. The casting is usually made of heat-resistant metal and has the desired shape and size. When liquid metal is injected into the casting, the liquid metal fills all parts of the casting due to gravity. The liquid metal gradually solidifies during cooling to form the casting. Due to the high thermal conductivity and heat capacity of the metal casting, the casting cools quickly, which helps to obtain a dense casting organization and good mechanical properties.

Aluminum Vacuum Die Casting: It is an advanced die-casting process, by removing the gas in the die-casting mold cavity during the die-casting process, so as to eliminate or significantly reduce the porosity and dissolved gases in the die-castings, and improve the mechanical properties and surface quality of the die-castings. The gas in the mold cavity in the vacuum die casting process first extracted, so that the cavity to form a negative pressure. Then the liquid metal is injected into the cavity, and fill the cavity under negative pressure. Due to the existence of negative pressure, the gas in the liquid metal is more easily discharged, thus reducing the formation of porosity and dissolved gas.

Aluminum Alloy Extrusion Casting: It is a method of solidifying and flowing liquid or semi-solid metal under high pressure to obtain parts or blanks directly. It has the advantages of high utilization rate of liquid metal, simplified process, stable quality, etc. It is an energy-saving metal molding technology with potential application prospects. Liquid or semi-solid metal is injected into the mold cavity during the squeeze casting process and solidifies and flows under high pressure. This process is usually carried out at high temperatures and high pressures to promote rapid solidification and flow of the metal.

Aluminum alloy disappearance mold casting (also known as solid casting): This is a new casting method. The basic principle is that paraffin or foam models of similar size and shape to the casting are bonded into model clusters, which are then coated with a refractory coating and dried. Next, the models are vibrationally shaped by encasing them in dry quartz sand. Pouring under negative pressure vaporizes the model and liquid metal takes its place, solidifying and cooling to form the casting.

Continuous Casting Aluminum Alloys: This is an advanced casting method. It is based on the principle that molten metal is continuously poured into a special type of metal called a crystallizer. The casting is gradually formed as the liquid metal cools and solidifies. The continuous casting process allows solidified castings to be obtained continuously from one end of the crystallizer. These castings can range from any length to a specific length.

Surface treatment of aluminum products

1. Sand blasting (shot blasting)

The process of cleaning and roughening the metal surface by using the impact of high-speed sand flow. This method of aluminum surface treatment can make the surface of the workpiece have a certain degree of cleanliness and different roughness, improve the mechanical properties of the surface of the workpiece, so as to improve the fatigue resistance of the workpiece, increase the adhesion with the coating, prolong the durability of the coating, but also conducive to the coating of the smooth and decorative. We often see this process in various Apple products.

2、Polishing
The use of mechanical, chemical or electrochemical action, reduce the surface roughness of the workpiece to obtain a bright, smooth surface treatment method. Polishing process is mainly divided into: mechanical polishing, chemical polishing, electrolytic polishing. Aluminum parts using mechanical polishing Electrolytic polishing can be close to the stainless steel mirror effect, giving a sense of high-grade simplicity, fashionable future.

3、Drawing

Metal drawing is the manufacturing process of repeatedly scraping out lines of aluminum sheet with sandpaper. Wire drawing can be divided into straight wire drawing, messy wire drawing, spinning wire drawing and thread drawing. Metal brushing process , each subtle silk marks can be clearly shown, so that the metal matte in the fine hair luster, products both fashion sense and sense of technology.

4、High light cutting

The diamond cutter is reinforced with a fine engraver to cut parts on a high speed rotating (typically 20,000 rpm) fine engraving machine spindle, creating localized highlights on the surface of the product. The brightness of the cutting highlights is affected by the speed of the milling drill. The faster the drill speed, the brighter the cutting highlights. Conversely, the darker it is, the more likely it is to produce knife lines. In recent years, some high-end TV metal frames have adopted the high-gloss milling process, coupled with the anodizing and brushing process, which gives the TV an overall sense of fashion and technology.

5、Anodic oxidation

Anodizing refers to the process of forming oxide film on aluminum products (anode) under the corresponding electrolyte and specific process conditions. Anodic oxidation can not only solve the defects of aluminum surface hardness and abrasion resistance, but also prolong the service life of aluminum and improve the aesthetics, it has become an indispensable part of aluminum surface treatment, and it is the most widely used and successful process at present.

6、Double color anode

Two-color anodizing refers to oxidizing anode on the product and giving different colors in specific areas. Due to the complexity and high cost of the process, the two-color anodizing process is less used in the TV industry; however, the high-end unique appearance of the product is better reflected by the two-color contrast. There are many reasons for the deformation of aluminum parts processing, including material, part shape, production conditions, etc.. There are mainly the following aspects: deformation caused by internal stress in the blank, deformation caused by cutting force and cutting heat, and deformation caused by clamping force.