The main reason for the pores in the composition of the casting is that the casting-china.com' target='_blank'>aluminum alloy contains excessive H. The hydrogen content accounts for% to% of the total gas content. The rest is N, O CO, etc., and H is derived from the atmosphere and various metal raw materials and fluxes. And the moisture in the coating is thermally differentiated, and the HO = H + + O-reaction occurs under high-temperature conditions, which is a reversible reaction. The differentiated oxygen easily generates AlO with a higher melting point with the metal liquid. The reaction equation is: Al + + O-= AlO. This promotes the high-temperature differentiation of water vapor and the hydrogen ions are continuously dispersed into the alloy liquid.
Hydrogen exists in the aluminum solution in two ways: the first is to differentiate into atomic state and dissolve in the aluminum solution, called dissolved type, accounting for about%; the second type of hydrogen is adsorbed to the appearance of inclusions in the form of molecular bubbles Or in the gap, it is called adsorption type. Since the solubility of hydrogen in the aluminum alloy liquid increases with temperature, the alloy liquid will absorb a lot of H during the melting process. In the process of crystal coagulation, due to the temperature drop, the surface of the alloy liquid first condenses and the viscosity of the alloy increases. Although the solubility of hydrogen needs to be separated from the molten metal, it is now difficult to stay in the alloy liquid. This constitutes a stomata defect. The longer the melting and holding time, the higher the hydrogen content.
The solubility of tritium hydrogen in the alloy liquid is not only proportional to the temperature, but also proportional to the pressure and the humidity of the air, that is, the partial pressure of hydrogen.
Aluminum alloy elements and their content also have a certain effect on solubility. When the content of silicon and copper is added, the solubility of hydrogen decreases, and when the content of magnesium is added, the solubility of hydrogen is added. The critical content of hydrogen in the alloy liquid is different with different aluminum alloy components. Aluminum alloy has the largest hydrogen absorption when it is a hypoeutectic aluminum-silicon alloy.
As an Aluminum Alloy Die Cast Part Factory, share with you the reasons for the occurrence of mucosa in the production of die casting molds.
The mucosa is a very common phenomenon in die casting production. The following are summarized
1. Die Casting Mould temperature adjustment is too high, exceeds the required range.
2. Insufficient demolding angle, too small mucosa.
3. The die-casting mold is not polished properly.
4. the release agent is not sprayed in place.
5. the problem of aluminum alloy raw materials.
6. The irrational design of the runner will also cause the mucosal phenomenon of the die-casting mold.
Solution:
1. First check the mold temperature and combine it with the previous production plan to see if the temperature is too high.
2. Check the proportion and usage of the release agent to see if it meets the production requirements.
3. Improve the mold's pouring system and cooling system.
4. Improve the parameters of the pressing process and modify their parameters appropriately.
