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Causes and treatment methods of aluminum profiles that are not dyed

Posted by: Alloy 2021-07-15 Comments Off on Causes and treatment methods of aluminum profiles that are not dyed

Process control

Since the most important feature of 6082 aluminum alloy is that it contains refractory metal Mn. The presence of an appropriate amount of Mn can easily cause intragranular segregation and decrease of plasticity in the solid-liquid zone, resulting in insufficient crack resistance. Therefore, three main points should be paid attention to in the melting and casting process: Pay attention to control the temperature between 740~760℃ and stir evenly to ensure that the metal is completely melted, the temperature is accurate, and the composition is uniform. Second, the casting should consider that the metal Mn increases the viscosity of the alloy and reduces its fluidity, which affects the casting performance of the alloy. The casting speed should be appropriately reduced and controlled within the range of 80~100mm/min. Third, increase the cooling intensity and speed up the cooling rate, and the aluminum profile can help eliminate the phenomenon of intragranular segregation. Control the intensity of primary cooling and increase the intensity of secondary cooling to reduce stress concentration during casting and avoid ingot cracks. The cooling water pressure should be controlled within the range of 0.1~0.3MPa.

The cause and treatment of the aluminum profile not being dyed:

  • The anodic oxide film thickness is insufficient. The solution is to check whether the anodic oxidation process is standardized, and to see whether the temperature, voltage, conductivity and other factors are stable. If there is an abnormality, please adjust the specifications accordingly. If there is no abnormality, the oxidation time can be appropriately extended to ensure that the film thickness meets the standard.
  • The pH value of the dyeing solution is too high. At this time, glacial acetic acid can be used to adjust the pH value to the standard value.
  • After oxidation, the workpiece has been placed in the sink for too long. Promote timely dyeing. If this situation has occurred, you can place the workpiece in an anodizing tank or a nitric acid neutralization tank and then perform dyeing after proper activation treatment. The effect will be very good.
  • Improper selection of dyes. Need to select suitable dyes.
  • The dye has been decomposed or mildewed, and the dye needs to be replaced at this time.
  • ​​The oxidation temperature is too low, resulting in a dense film. The oxidation temperature can be appropriately increased.
  • Poor conductivity. Possibly the anode copper rod or the cathode lead plate has poor contact. Pay attention to cleaning the anode copper rod and cathode lead plate to ensure good conduction.

Because the mold of the radiator profile is made of many slender teeth, they have to withstand a large extrusion force, and each tooth must have high strength and toughness. If there is a big difference in performance between them, it is easy The teeth with poor strength or toughness are broken. Therefore, the quality of mold steel must be reliable, and it is best to use H13 steel produced by a reliable manufacturer or use high-quality imported steel. The heat treatment of the mold is very important. It should be quenched by vacuum heating. It is best to use high-pressure pure nitrogen quenching to ensure that the performance of each part of the mold is uniform after quenching. After quenching, three times of tempering are required to ensure that the hardness of the mold is under the premise of HRC48-52, and it has sufficient toughness. This is an important condition to prevent mold tooth breakage.

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