ALUMINIUM DEGASSING MACHINES
Degassing Operations for Die Casting Foundries
Aluminium Degassing Machines
Normtech - DGS500
The degassing machine is designed to wash molten aluminum ore and adjust the hydrogen gas ratio.
- In our portfolio there are single and double gas controlled models.
- Manual flow rate and automatic flow rate adjustment options are valid. With automatic flow rate control, variable gas flow rates can be adjusted with PLC control during the process.
- Any desired connection type for the graphite rotor shaft is possible.
- The degassing machine can be made mobile, fixed or rotary-headed.
- Siemens PLC Control and unlimited recipe creation
- 7inch touch screen
- Height control with encoder (adjustable from recipe)
- Variable rotor speed during the process (adjustable from recipe)
- Gas pressure control and flux presence control
- Low gas and flux warning system
- Desired type of rotor shaft connection head
- In automatic model, PID control of gas flow rate during the process with sensitive flow meter and proportional valve
- Adjustment feature for flux amount (adjustable from recipe)
- 0-100ml/min gas flow capacity
- Compatible with N2 and Ar gases (please contact us for other gases)
- Compatible with sending 2 different gases
Degassing Process for Casting Products
In aluminum casting factories, one of the most important quality criteria of cast aluminum is porosity and the amount of shrinkage of the metal. In order to control these criterias, the amount of hydrogen in the molten aluminum must be minimized. Aluminum degassing process mentioned here is performed to reduce the amount of hydrogen in molten aluminum.
After the degassing process is completed, hydrogen measurement must be performed to understand whether the process was successful. As NORMTECH, we manufacture automated machines for aluminum degassing and hydrogen measurement systems.
Contact us to get more information about foundry machines.
Graph: Degassing efficiency with degassing of hyrogen gas
Table: - Correction Factors with Alloy Composition
Degassing Process Parameters
Effect of Aluminum Alloys on Degassing Process
Another factor that has an effect on hydrogen solubility is the elements in the alloy. The effect of alloying elements is characterized by changes in the alloy correction factor, and some common casting alloys are shown in Table 1. Alloys with larger alloy correction factors are more difficult to degas, so that, for example, aluminum 535 takes four times as long to degas as pure aluminum. Fortunately, these factors can be controlled, and the gas content and process required to eliminate excessive porosity during aluminum casting can be achieved without much difficulty in most cases.
Practical Degassing Procedures
Degassing is usually performed in one of three areas of a metal casting facility:
- In a transfer ladle, which is used to transport metal between the melting and holding furnaces.
- In ladle furnaces, usually just prior to pouring molten aluminum.
- In a sequential system, when the metal is conveyed through a chute to the holding furnaces.
Die Casting Degassing Process Steps
When the rotary head aluminum degassing unit is completely lowered into the liquid metal, the degassing process begins. The best shaft position is slightly above or below the centerline of the ladle or crucible to help prevent vortex formation in the liquid metal by its circular rotation. An offset distance of 5-6 cm from the centerline is usually sufficient.
In addition, the use of equipment called a “baffle plate” during the degassing process is also very useful. This baffle plate reduces the vortex formation of the aluminum ore.
The shaft end should be able to operate at different speeds in suitable different positions. While the shaft rotates slowly as it enters the melt, it should be able to rotate at different speeds in the melt at different times. The inert gas flow should also be open at all times, and the gas flow rate and shaft speed should operate at the values they are automatically set in the recipe. Otherwise, there is a risk of molten aluminum entering the machine’s gas lines. The gas flow should be increased until gas bubbles appear floating on the surface of the liquid metal. As the gas flow increases, the size of the bubbles should also increase.
In addition, in some cases, a type of gas known as a nitrogen/hydrogen mixture can be introduced into the system. In this case, the hydrogen gas in the melt can be reduced to even lower values.
The desired result is good dispersion of small bubbles while maintaining a relatively calm surface. Once an optimal combination of flow rate and shaft rotation speed has been found, its parameters should be entered into the recipe for future use. In addition, unless temperatures are very high or the amount of gas required is low, the total degassing time, which is normally somewhere between four and eight minutes, can be sufficient.
Referanslarımız
