What are the key quality control points for analyzing aluminum profile processing?

December 23, 2024

Aluminum profiles are aluminum materials with different cross-sectional shapes obtained by hot-melt and extrusion of aluminum rods. Due to its many advantages such as light weight, high strength, good corrosion resistance, and strong decorative properties, it is widely used in many fields such as construction, industry, and transportation. Next, let me introduce the key points of quality control in aluminum profile processing:

Raw material quality control

Purity and composition of aluminum ingots:

The basis of aluminum profile processing is aluminum ingot, and its purity directly affects the performance of the profile. For aluminum profiles with different purposes, the purity of aluminum ingots should be strictly controlled. For example, high-purity aluminum profiles used in the electronics industry (such as the 1000 series) require an aluminum content of over 99%. In the procurement process, suppliers must be required to provide quality certificates that specify the purity level of aluminum ingots.

The alloy composition is also crucial. Taking 6063 alloy aluminum profiles as an example, the content of magnesium (Mg) and silicon (Si) needs to be precisely controlled. The ratio of magnesium to silicon will affect the strength and processability of the profile. The appropriate proportion can ensure good flowability of the profile during the extrusion process while ensuring the strength of the finished product. Before melting, advanced spectral analyzers should be used to detect the alloy composition of aluminum ingots to ensure that the composition meets the standards.

Raw material inspection:

Inspect the appearance of each batch of aluminum ingots to see if there are any obvious impurities, pores, or other defects. If there are many impurities on the surface of the aluminum ingot, new impurities may be introduced during the melting process, affecting the quality of the aluminum liquid.

To conduct sampling chemical analysis, in addition to detecting the main alloying elements, attention should also be paid to the content of trace elements. Some trace elements may have adverse effects on the performance of profiles, such as excessive iron (Fe) content, which can reduce the corrosion resistance of profiles.

Quality control of smelting process

Melting equipment parameters:

Temperature control is the key to melting. Different aluminum profile alloys have their suitable melting temperature ranges. For example, the melting temperature of 6063 alloy is generally between 720-750 ℃. If the temperature is too high, it will cause alloy element burnout, affecting the alloy composition and properties of the profile; If the temperature is too low, the aluminum ingot cannot be completely melted, which affects subsequent processing. Use high-precision temperature sensors and intelligent temperature control systems to ensure precise control of melting temperature.

The melting time also needs to be reasonably controlled. Excessive melting time can increase energy consumption and the risk of metal oxidation. At the same time, it is necessary to ensure that the stirring device inside the melting equipment is working properly, so that the alloy elements are evenly distributed in the aluminum liquid. The stirring speed is generally adjusted according to the capacity of the melting furnace and the weight of the aluminum liquid to ensure the consistency of the aluminum liquid composition.

Removing impurities and refining:

Effective impurity removal operations should be carried out during the smelting process. Use slag remover to remove the floating slag on the surface of aluminum liquid, which is mainly impurities such as alumina. The amount of slag remover should be adjusted reasonably according to the amount and impurities of the aluminum liquid, generally added at 0.3% -0.5% of the weight of the aluminum liquid.

Using refining agents for refining, removing gases and small impurities from aluminum liquid. During the refining process, inert gas (such as argon) is introduced into the aluminum liquid to fully utilize the refining agent. After refining, the aluminum liquid should be tested for gas content to ensure that the hydrogen content in the aluminum liquid is below a certain standard. Generally, the hydrogen content is required to be below 0.15ml/100g to prevent defects such as porosity during the solidification process of the profile.

Quality control of extrusion molding

Mold quality and maintenance:

The design of the mold must comply with the cross-sectional shape and size requirements of the profile. For profiles with complex cross-sections, the design of the working zone of the mold is particularly important. The length of the work belt should be accurately calculated based on the wall thickness and metal flow characteristics of each part of the profile. For example, when designing profile molds with thin-walled and thick walled parts, it is necessary to adjust the length of the working belt appropriately to ensure that the metal flows evenly to each part during the extrusion process, avoiding uneven wall thickness.

The material quality of the mold directly affects its service life and profile quality. High quality mold steel (such as H13 steel) should have high hardness, good toughness, and thermal fatigue performance. During the use of the mold, regular maintenance should be carried out, including cleaning, nitriding treatment, etc. Nitriding treatment can improve the surface hardness of the mold. Generally, the depth of the nitride layer is required to be between 0.02-0.05mm. After nitriding treatment, the mold can effectively reduce the surface strain and wear of the profile.

Extrusion process parameters:

The extrusion temperature and speed are key process parameters. For most 6063 alloy aluminum profiles, the extrusion temperature is controlled between 480-520 ℃. Within this temperature range, the deformation resistance of aluminum is relatively low, which is conducive to the extrusion of profiles. Meanwhile, the extrusion speed should be adjusted according to the complexity and size of the cross-section of the profile. For example, for small materials with simple cross-sections, the extrusion speed can reach 10-20m/min; For large materials with complex cross-sections, the extrusion speed may need to be reduced to 2-5m/min to prevent defects such as cracks and distortions on the surface of the profile.

The control of squeezing force is also important. Excessive extrusion force can cause damage to the mold and dimensional deviation of the profile, while insufficient extrusion force cannot smoothly extrude the profile. Real time monitoring of extrusion pressure through pressure sensors and adjustment based on the actual extrusion situation of the profile.

Surface treatment quality control

Quality control of anodizing:

The quality of electrolyte for anodizing is one of the key factors. For the sulfuric acid anodizing process, the concentration of sulfuric acid electrolyte is generally controlled between 16% and 20%. Excessive or insufficient electrolyte concentration can affect the growth rate and quality of the oxide film. At the same time, regular testing and maintenance of the electrolyte should be carried out to replenish the sulfuric acid and additives consumed by electrolysis.

The thickness and quality of the oxide film are key control objects. The thickness of the oxide film is generally adjusted by controlling the electrolysis time, current density, etc. For example, the thickness of the oxide film on building aluminum profiles is required to be between 10-15 μ m. Regularly check the thickness of the oxide film using a non-contact film thickness measuring instrument to ensure that the thickness meets the requirements. The quality of oxide film also includes its hardness, wear resistance, and corrosion resistance. Evaluate the quality of the oxide film through hardness testing (such as pencil hardness testing) and corrosion resistance testing (such as salt spray testing).

Quality control of powder coating:

The surface pretreatment quality before powder spraying directly affects the adhesion of the coating. Pre treatment includes steps such as degreasing and chroming. Defatting should be thorough to ensure that the surface of the profile is free of oil stains. After chroming treatment, a uniform conversion film should be formed on the surface of the profile, and the chroming effect can be judged by detecting the weight of the conversion film (generally required to be between 20-50mg/m ²).

The quality and spraying process control of powder coatings are key. The particle size of powder coating should be uniform, generally requiring a particle size between 20-80 μ m. During the spraying process, it is important to control the voltage, current, and spraying distance of the spray gun. The voltage of the spray gun is generally between 60-90kV, and the spraying distance is between 15-30cm to ensure that the powder coating is evenly adsorbed on the surface of the profile. The thickness of the cured coating is generally between 60-120 μ m, which is measured by a coating thickness gauge.

Deep processing quality control (if any)

Cutting quality control:

Cutting accuracy is key. Whether it is sawing or laser cutting, it is necessary to ensure that the cutting size of the profile meets the design requirements. For sawing, the accuracy of the sawing machine needs to be calibrated regularly, and the selection of the saw blade should be based on the cross-sectional shape and thickness of the profile. For example, when cutting thick walled profiles, it is necessary to choose a saw blade with a larger tooth pitch to ensure cutting efficiency and accuracy. The error range is generally required to be within ± 0.5mm.

The surface quality of the cut profile is also important. Check if the cutting surface is flat and free of burrs. For laser cutting, attention should also be paid to the size of the heat affected zone. The heat affected zone should be minimized as much as possible to prevent deformation and other issues of the profile during subsequent use.

Quality control of drilling and tapping:

When drilling, the appropriate drill bit should be selected according to the size of the required bolts or rivets. The speed and feed rate of the drill bit should be reasonably controlled, usually adjusted according to the material and thickness of the profile. For example, when drilling aluminum alloy profiles, the drill bit speed can be controlled between 1000-2000r/min and the feed rate between 0.1-0.2mm/r. After drilling, the dimensional accuracy and surface quality of the hole should be checked, and the diameter error of the hole should be controlled within ± 0.1mm.

The quality of tapping directly affects the connection strength of threads. When tapping, it is necessary to choose a suitable tap, and the accuracy of the tap should meet the requirements. During the tapping process, it is important to control the rotation direction and feed rate of the tap to ensure that the thread profile is complete and the dimensions are accurate. The accuracy level of threads generally needs to reach 6H or above.

Finished product quality inspection and packaging and transportation quality control

Finished product quality inspection:

Visual inspection is the most basic step. Check the surface of the profile for cracks, scratches, bubbles, uneven color defects. For coated profiles, the adhesion of the coating should also be checked, and a grid cut test can be used to detect it. The area of coating detachment after grid cutting should not exceed 5%.

Dimensional accuracy testing uses tools such as calipers and micrometers. The cross-sectional dimensions, length, and other parameters of the profile should be tested, and the error range should meet the design requirements. For example, the cross-sectional dimension error of profiles is generally required to be within ± 0.3mm, and the length error is within ± 1mm.

Performance testing includes mechanical performance and corrosion resistance testing. Mechanical performance testing mainly includes tensile strength, yield strength, etc., which are tested through tensile testing according to relevant standards (such as GB/T 5237-2017). Corrosion resistance testing can use neutral salt spray test to observe the corrosion of the profile within a specified time (such as 48 hours or 72 hours).

Packaging and transportation control:

The selection of packaging materials should be appropriate. For coated profiles, packaging materials with cushioning and protection functions, such as plastic foam, air cushion film, etc., shall be used. During the packaging process, it is necessary to ensure that the profiles are firmly fixed to avoid collisions and friction during transportation.

Attention should be paid to environmental conditions during transportation. Avoid the profile from being damp, exposed to sunlight, or corroded by chemical substances. For long-distance transportation or transportation in harsh environments, corresponding protective measures should be taken, such as using sealed containers.

Author:

Mr. zhichengaluminumindustry

E-mail:

zcd.aluminum@gmail.com

Phone/WhatsApp:

+852 64053048