What are the guarantees for the forming quality in the production process of aluminum profiles?

December 24, 2024

Aluminum profiles are mainly made of aluminum as the main raw material, and processed through processes such as hot melt and extrusion to form long strip materials with specific cross-sectional shapes and sizes under the action of molds. These profiles have a variety of cross-sectional shapes, ranging from simple squares and circles to complex irregular structures with multiple cavities, slots, ribs, etc., to meet the needs of different industries and construction fields. Below, the editor will summarize:

Quality control of raw materials

Aluminum ingot purity and alloy composition:

The purity of aluminum ingots is crucial for the quality of aluminum profiles. High purity aluminum ingots can ensure basic material properties such as good ductility and plasticity. During the production process, the purity of aluminum ingots should be strictly controlled, and the impurity content should generally be kept at a low level. For example, for 6063 aluminum alloy, the main alloying elements are magnesium and silicon, and the impurity content (such as iron, copper, etc.) should comply with relevant standards. The iron content is usually required to not exceed 0.35%, because excessive impurities can affect the crystallization process of the alloy, leading to defects such as cracks and looseness in the profile.

Accurately controlling the proportion of alloy composition is the key to ensuring the quality of profiles. Different alloy compositions endow aluminum profiles with different properties. Taking 6061 aluminum alloy as an example, the ratio of magnesium to silicon will affect the strength and corrosion resistance of the profile. In the smelting process, precise batching and advanced smelting equipment are required to control the error of alloy composition within a small range. Generally, the content error of each main alloy component does not exceed ± 0.1%, in order to ensure that aluminum profiles have stable physical and chemical properties.

Pre treatment quality of raw materials:

The pretreatment of aluminum ingots before melting includes steps such as cleaning and drying. Cleaning is to remove impurities such as oil stains and oxide scales on the surface of aluminum ingots. If the surface impurities are not completely removed, inclusions will form during the melting process, affecting the quality of the aluminum liquid. For example, using alkaline washing to remove oil stains, then rinsing with clean water, and then drying to ensure that the surface of the aluminum ingot is clean and free of moisture, providing high-quality raw materials for smelting.

Melting and Casting Process

Melting temperature and time control:

The melting temperature directly affects the quality of aluminum liquid. Different aluminum alloys have their suitable melting temperature ranges. For example, the melting temperature of 6063 aluminum alloy is generally between 720-750 ℃. Excessive temperature can lead to excessive suction of aluminum liquid, resulting in porosity defects; If the temperature is too low, it will prevent the alloy elements from fully melting, affecting the uniformity of the composition. At the same time, the melting time also needs to be reasonably controlled. Prolonged melting time will increase the opportunity for aluminum liquid to come into contact with air, leading to increased oxidation and suction phenomena. Generally, the melting time is controlled at around 3-5 hours based on factors such as furnace capacity and power.

During the smelting process, appropriate fluxes and refining agents should be used to remove gases and inclusions from the aluminum liquid. For example, refining agents such as hexachloroethane are used for refining treatment, and hydrogen and other gases in the aluminum liquid are discharged through chemical reactions to reduce porosity. At the same time, the flux can adsorb oxide inclusions in the aluminum liquid, making the aluminum liquid purer and improving the quality of the profile.

Casting process optimization:

The selection of casting methods (such as semi continuous casting, continuous casting, etc.) will affect the quality of aluminum profile blanks. The cooling rate of semi continuous casting is relatively slow, which is beneficial for obtaining uniformly structured billets; Continuous casting has high production efficiency, but requires better control of cooling rate. During the casting process, it is important to control the casting speed and cooling rate. Excessive casting speed can cause stress concentration inside the ingot, leading to cracks; If the cooling rate is too fast, it will cause significant differences in the microstructure between the surface and interior of the ingot, which will affect the subsequent processing performance. For example, for ingots with a diameter of 100-200mm, the casting speed is generally controlled between 50-100mm/min, and the cooling speed is adjusted according to the alloy composition and ingot size to ensure uniform cooling of the ingot.

Extrusion molding process

Mold quality and design:

The quality of extrusion molds directly determines the forming quality of aluminum profiles. The material of the mold should have high hardness, high strength, and good wear resistance. For example, using high-quality mold steel such as H13 steel to make molds. The machining accuracy of the mold is also very important. The dimensional tolerance of the mold cavity is generally controlled within ± 0.05mm, and the surface roughness reaches Ra0.8 μ m or less, in order to ensure the dimensional accuracy and surface quality of the profile.

The design of the mold should comply with the shape and size requirements of the aluminum profile. Reasonable design of diversion holes, working belts, and mold cores can ensure uniform flow of aluminum materials within the mold. For example, for complex shaped profiles, it is necessary to optimize the size, shape, and distribution of the diversion holes to guide the aluminum material to evenly fill the mold cavity, avoiding defects such as profile distortion and deformation caused by uneven flow velocity.

Adjustment of extrusion process parameters:

The extrusion temperature and speed are key process parameters. The extrusion temperature of different aluminum alloy profiles varies, and the extrusion temperature of 6063 aluminum alloy profiles is generally between 450-500 ℃. Appropriate temperature can reduce the deformation resistance of aluminum material, making the extrusion process smoother. The extrusion speed should be adjusted according to the shape, size, and mold conditions of the profile, and is generally controlled between 1-10m/min. Excessive speed can cause the surface temperature of the profile to be too high, resulting in surface roughness, oxidation, and other issues; If the speed is too slow, it will affect production efficiency. At the same time, it is necessary to control the extrusion force well to avoid damage to the mold or residual stress inside the profile due to excessive pressure.

Surface treatment quality assurance

Pre treatment process effect:

Before surface treatment, aluminum profiles need to be pre treated, including steps such as degreasing, alkali etching, and polishing. Degreasing is to remove oil stains from the surface of profiles, usually using alkaline degreasing agents. The degreased profile surface should be free of visible oil stains. Alkali corrosion can remove the natural oxide film on the surface of profiles, making the surface more uniform. The alkaline etching time and alkaline solution concentration should be adjusted according to the material and surface condition of the profile. For example, the alkaline etching time is generally between 1-3 minutes, and the alkaline solution concentration is between 30-50g/L. Light treatment is used to remove the hanging dust on the surface of the profile after alkali corrosion, making the surface of the profile bright.

Surface treatment methods and quality control:

Common surface treatment methods include anodizing, electrophoretic coating, and powder coating. Anodizing can improve the corrosion resistance and wear resistance of aluminum profiles. During the anodizing process, it is important to control parameters such as oxidation voltage, current density, and oxidation time. For example, for general building aluminum profiles, the oxidation voltage is between 12-18V, the current density is between 1-2A/dm ², and the oxidation time is between 20-30 minutes. This can result in a uniformly thick and high-quality oxide film. Electrophoretic coating can provide rich colors and good decorative properties on the surface of profiles. Attention should be paid to the quality of electrophoretic paint and coating process parameters, such as electrophoretic voltage, time, and paint temperature. Powder spraying requires ensuring the quality of the powder coating and the uniformity of spraying, avoiding problems such as coating peeling and uneven thickness.

Author:

Mr. zhichengaluminumindustry

E-mail:

zcd.aluminum@gmail.com

Phone/WhatsApp:

+852 64053048