Aluminum alloy is widely used in the production of aluminum profile heat dissipation equipment due to its lightweight and beautiful appearance, good thermal conductivity of industrial aluminum profiles, and easy processing into complex shapes. There are three main types of aluminum alloy heat dissipation equipment: flat wide, comb shaped, or fishbone shaped; The outer heat sink of a circular or elliptical shape is radiating; Branch shaped. As shown in Figure 1. Their common feature is that the distance between heat sinks is short, and a groove is formed between adjacent heat sinks, with a large aspect ratio; The wall thickness difference is large, and generally the heat dissipation fins are thin, while the bottom plate thickness at the root is large. Therefore, it brings great difficulty to the mold design, manufacturing, and production of heat dissipation profiles.

Aluminum profile manufacturers have a portion of radiator profiles that are relatively small in size and symmetrical in shape, making it easier to produce. Most of the radiator profiles are flat and wide in shape, with larger overall dimensions and some being asymmetrical. The depth to width ratio of the grooves between the heat sinks is large, making it difficult to produce. To successfully produce radiator profiles, it is necessary to cooperate with ingots, molds, and extrusion processes. The alloy used for extruding radiator profiles must have good extrudability and thermal conductivity, generally including alloys such as 1A30, 1035, and 6063. At present, 6063 alloy is widely used because it not only has good compressibility and thermal conductivity, but also has good mechanical properties.

The production of aluminum alloy radiator profiles should start from the quality of the ingot, the material and design of the mold, reducing extrusion pressure, and the extrusion process of aluminum profiles.

1. Quality requirements for ingots

The alloy composition of the ingot should strictly control the impurity content to ensure the purity of the alloy. For 6063 alloy, the content of Fe, Mg, and Si should be controlled. The content of Fe should be less than 0.2%, and the content of Mg and Si should generally be controlled within the lower limit of national standards, with Mg content ranging from 0.45% to 0.55% and Si content ranging from 0.25% to 0.35%. The ingot needs to undergo sufficient homogenization treatment to ensure a uniform and consistent structure and properties of the ingot.

The surface of the ingot should be smooth, and there should be no segregation or sticking of sand or mud. The end face of the ingot should be flat and cannot be cut into a stepped shape or with a large cutting angle (the cutting angle should be within 3mm). Due to the large step shape or cutting slope, when using a flat die to extrude the heat dissipation profile, if there is no design of a flow guide, the ingot directly touches the mold. Due to the uneven end face of the ingot, some places first contact the mold, resulting in stress concentration, which can easily break the tooth shape of the mold or cause different discharge sequences, leading to mold blockage or poor extrusion molding.

2. Requirements for molds

Because the molds for radiator profiles are made of many slender teeth that need to withstand significant extrusion pressure, each tooth must have high strength and toughness. If there is a significant difference in performance between them, it is easy to cause the teeth with poor strength or toughness to fracture. Therefore, the quality of mold steel must be reliable, using H13 steel produced by reliable manufacturers or selecting high-quality imported steel. The heat treatment of the mold is very important. Vacuum heating quenching and high-pressure pure nitrogen quenching can ensure uniform performance of all parts of the mold after quenching. After quenching, three tempering steps should be taken to ensure that the hardness of the mold is maintained at HRC48-52 and has sufficient toughness. This is an important condition to prevent mold tooth breakage.

The key to successful extrusion of radiator profiles is to have a reasonable mold design and precise aluminum profile manufacturing. Generally, try to avoid direct extrusion of the ingot onto the mold working strip. For the flat and wide comb shaped radiator profile, the aluminum profile is designed with a small center and large side guide mold to allow the metal to flow towards both sides, reduce the extrusion pressure on the working strip of the mold, and ensure uniform pressure distribution. Due to the large wall thickness difference in the cross-section of the radiator profile, it is necessary to maintain their differences when designing the mold work strip. That is, the work strip should be specially increased in areas with large wall thickness, which can be as large as 20mm to 30mm. The position of the tooth tip should break through the convention and reduce the work strip to a small size. In short, it is necessary to ensure the uniformity of metal flow in various places. For flat and wide radiators, to ensure a certain degree of stiffness in the mold, the thickness of the mold should be appropriately increased. The increase in thickness is about 30-60%. The production of the mold should also be very precise, and the empty cutter should maintain symmetry in the top, bottom, left, right, and middle. The machining error between teeth should be less than 0.05mm, and large machining errors are prone to tooth deviation, which means that the thickness of the heat sink is uneven, and even tooth breakage may occur.

For sections with mature design, using embedded alloy steel molds is also a good method, because alloy steel molds have good rigidity and wear resistance, are not prone to deformation, and are conducive to the formation of radiator profiles.

3. Reduce squeezing force

To prevent mold tooth breakage, the extrusion force should be minimized as much as possible, which is related to factors such as the length of the ingot, the resistance to alloy deformation, the state of the ingot, and the degree of deformation. Therefore, the casting rod for extruded heat dissipation aluminum profiles should not be too long, approximately 0.6-0.85 times the normal casting rod length. Especially during mold testing and extrusion of a casting rod, to ensure the smooth production of qualified products, shorter casting rods, i.e. casting rods with a normal length of 0.4-0.6 times, are used for mold testing.

For complex shaped heat dissipation shouting profiles, in addition to shortening the length of the casting rod, it is also possible to consider using pure aluminum short castings for a trial extrusion. After successful trial extrusion, normal ingots can be used for extrusion production.

Homogenization annealing of ingots can not only achieve uniform microstructure and properties, but also improve extrusion performance and reduce extrusion pressure, so it is required that ingots must be homogenized and annealed. As for the impact of deformation degree, due to the large cross-sectional area of radiator profiles and the extrusion coefficient generally within 40, its impact is relatively small.

4. Extrusion process