Process control
The biggest feature of 6082 aluminum alloy is that it contains the refractory metal Mn. The proper amount of Mn can easily cause dendritic segregation and reduce the plasticity in the solid-liquid zone, which leads to insufficient crack resistance. Therefore, there are three main points to pay attention to in the casting process: First, during melting, the temperature should be controlled between 740~760°C and stirred evenly to ensure the metal is fully melted, the temperature is accurate, and the composition is uniform. Second, in casting, consider that the Mn in the metal increases the alloy's viscosity, reducing its fluidity and affecting its casting performance. The casting speed should be appropriately reduced, controlled within 80~100 mm/min. Third, increase the cooling intensity and speed up cooling, as this helps eliminate dendritic segregation in the aluminum profiles. Control the primary cooling intensity and increase the secondary cooling intensity to reduce stress concentration during casting and avoid ingot cracking defects. The cooling water pressure should be maintained between 0.1~0.3 MPa.
Reasons why aluminum profiles can't be dyed and how to deal with it:
1. The anodized film thickness is insufficient. To fix this, check if the anodizing process is standard, and see if factors like temperature, voltage, and conductivity are stable. If there's any abnormality, adjust accordingly. If everything is fine, you can slightly extend the oxidation time to ensure the film reaches the required thickness.
2. The dye solution's pH is too high. In this case, you can use ice acetic acid to bring the pH to the normal range.
3. The workpiece has been left in the water tank for too long after oxidation. It's recommended to dye the piece promptly. If this has already happened, you can put the workpiece back into the anodizing tank or the nitric acid neutralization tank for some activation before dyeing again, and it should turn out well.
4. The dye chosen is not appropriate. You need to pick the right dye.
5. The dye has decomposed or gone moldy. In this case, the dye should be replaced.
6. The oxidation temperature is too low, resulting in a dense film. You can slightly raise the oxidation temperature.
7. Poor conductivity. This could be due to bad contact between the anodic copper rod or cathodic lead plate, causing batch-wide conductivity issues. Make sure to clean the anodic copper rod and cathodic lead plate to ensure good conductivity.
Since radiator profiles have molds with many thin, long teeth that need to withstand high extrusion pressure, each tooth must have high strength and toughness. If there's a big difference in performance between teeth, the ones with lower strength or toughness can easily break. So, the quality of the mold steel has to be reliable-it's best to use H13 steel from trustworthy manufacturers or high-quality imported steel. Heat treatment of the mold is really important too. Vacuum heating and quenching should be used, ideally with high-pressure pure nitrogen quenching, to make sure all parts of the mold have even performance after quenching. After quenching, the mold should be tempered three times, so that while the hardness stays at HRC48–52, it has enough toughness. This is key to preventing the mold teeth from breaking.
