Luoyang Judian Metal Hot Processing Equipment Co., LTD is mainly engaged in the manufacture of complete sets of equipment in the metal thermal processing industry and the integration of the entire production line.
Liquid aluminum has several key physical properties
Liquid aluminum
Its density is lower than that of solid aluminum and decreases as temperature rises. Like solid aluminum, the density of liquid aluminum increases slightly as purity decreases. The variation of density with temperature for aluminum of different purities is shown.
The thermal conductivity of liquid aluminum is also lower than that of solid aluminum, and within a certain temperature range it increases as temperature rises.
The melting point of aluminum is 2750 K. The maximum evaporation rate is 0.7 × 10³ g/(cm²·s); beyond this rate, volatilization will occur.
The thermal conductivity of pure liquid aluminum is lower than that of solid pure aluminum at the melting point, and it increases with temperature. The variation of thermal conductivity of industrial pure liquid aluminum with temperature is shown in Table 1-8.
Table 1-8 Thermal conductivity of industrial pure liquid aluminum as a function of temperature
Many common gaseous elements and their compounds can dissolve in molten aluminum and aluminum alloys, among which hydrogen accounts for more than 85%.
Aluminum does not react with hydrogen; however, liquid aluminum readily absorbs hydrogen. Its solubility is high and increases with temperature.
At the melting point, the hydrogen solubility in 100 g of solid aluminum is 0.036 cm³. At the same temperature, the ratio of hydrogen solubility in liquid aluminum to solid aluminum is 19:1.
The gas dissolved in liquid aluminum is released during solidification, which has a significant effect on the number and distribution of pores in ingots or castings.
Therefore, in the melting process, strict control must be applied to prevent interaction between gases (especially water vapor) and molten aluminum to avoid gas absorption; and effective refining measures must be taken to remove gases from the melt.
FAQ: Liquid Aluminum Physical Properties
1. What are the main physical properties of liquid aluminum?
Liquid aluminum mainly exhibits properties such as density, thermal conductivity, viscosity, and gas solubility. These properties vary significantly with temperature and purity, directly affecting casting quality and process control.
2. How does the density of liquid aluminum change with temperature?
The density of liquid aluminum decreases as temperature increases. Additionally, lower purity slightly increases density, similar to solid aluminum behavior.
3. Is liquid aluminum more or less thermally conductive than solid aluminum?
Liquid aluminum has lower thermal conductivity than solid aluminum at the same temperature. However, its thermal conductivity increases gradually as temperature rises within a certain range.
4. How does viscosity change in molten aluminum?
The viscosity of liquid aluminum decreases as temperature increases. This means the metal becomes more fluid at higher temperatures, improving flowability during casting.
5. Why is hydrogen important in molten aluminum?
Hydrogen is the primary gas dissolved in molten aluminum, accounting for over 85% of total dissolved gases. It significantly affects casting quality because it can form pores during solidification.
6. Does aluminum chemically react with hydrogen?
No, aluminum does not chemically react with hydrogen. However, liquid aluminum can easily absorb hydrogen, especially at higher temperatures where solubility increases.
