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How to Remove Hydrogen from Aluminum Alloy Castings?

How to Remove Hydrogen from Aluminum Alloy Castings?

Pulished on Feb. 28, 2020

As an Aluminum Alloys Die Casting Parts Manufacturer, share with you.

In the production process, in order to avoid the defects of aluminum alloy pores, effective measures must be taken to reduce the moisture of the raw materials as much as possible, strengthen the quality management of the smelting, and improve the exhaust energy of the mold. The details are as follows:

Precision Aluminum Die Casting Parts

Precision Aluminum Die Casting Parts

The main reason for the pores in the casting is that the aluminum alloy contains excessive H. The hydrogen content accounts for% ~% 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 flux And the moisture in the coating is differentiated by heat, 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 molten metal. 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 conditions and dissolve in the aluminum solution, which is 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 crystallization and condensation, due to the temperature drop, the surface layer of the alloy liquid mainly condenses and the viscosity of the alloy increases. Although the decrease in the solubility of hydrogen needs to be separated from the metal liquid, 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 the 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. With different aluminum alloy components, the critical content of hydrogen in the alloy liquid is also different. ZL aluminum alloy has the largest hydrogen absorption when it is a hypoeutectic aluminum silicon alloy.


The solution of uneven depressions on Precision Aluminum Die Casting Parts:


1. Negotiate with the customer to coordinate the structure of the casting, even the wall thickness of the casting, so that the heat dissipation is more uniform, and the heat knot is eliminated.

2. Control the quality of aluminum alloy raw materials and choose aluminum alloy materials with small shrinkage.

3. When designing the mold, design the pouring system reasonably, and increase the size of the gate appropriately.

4. Adjust the injection force of the die casting machine. It should not be too high or too low.

5. Reasonable application of mold temperature, adjustment of thermal equilibrium conditions, temperature control device and cooling.

Our company provides OEM Precision Cast Metal Parts, welcome to consult.


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