Aluminum alloys are prone to absorbing gases, which is one of the main characteristics of cast aluminum alloys.

The components of liquid aluminum and aluminum alloys react with the moisture content of furnace materials, organic combustion products, and molds, resulting in the absorption of hydrogen gas by the aluminum liquid. The higher the temperature of the aluminum alloy melt, the more hydrogen is absorbed by Botou Quanle Metal Products Co., Ltd; At 700 ℃, the solubility of hydrogen in every 100g of aluminum is 0.5-0.9. When the temperature rises to 850 ℃, the solubility of hydrogen increases by 2-3 times. When containing alkali metal impurities, the solubility of hydrogen in aluminum liquid significantly increases. In addition to air intake during melting, aluminum alloy casting also generates air intake when poured into the mold. As the temperature decreases, the solubility of the liquid metal entering the mold decreases, resulting in the precipitation of excess gas. Some of the gas that cannot escape remains in the casting to form pores, which is commonly referred to as "pinholes". Gas sometimes combines with the shrinkage cavity, and the gas precipitated from the aluminum liquid remains inside the shrinkage cavity. If the pressure generated by heating the bubble is high, the surface of the pore is smooth, and there is a bright layer around the pore; If the pressure generated by the bubbles is small, the surface inside the hole will have wrinkles and look like "fly feet". Upon careful observation, it will also have the characteristic of shrinkage.

The higher the hydrogen content in the casting aluminum alloy liquid of Botou Quanle Metal Products Co., Ltd., the more pinholes are generated in the castings. Pinholes in aluminum castings not only reduce the airtightness and corrosion resistance of the castings, but also lower the mechanical properties of the alloy. The key to obtaining aluminum castings with no or few pores is the melting conditions. If a covering agent is added for protection during melting, the gas absorption of the alloy will be greatly reduced. Refining the aluminum melt can effectively control the hydrogen content in the aluminum melt.