company news about How Do They Degas Aluminum?

The affinity of molten aluminum for picking up hydrogen is an insidious threat to production—it takes it up from wet raw materials, moist air, or contaminated lubricants and releases it in the form of bubbles when it solidifies. The bubbles create porosity, blisters, and reduced mechanical properties. It is not a question of option for manufacturers ranging from the automotive to aerospace industry. But how do manufacturers degas aluminum? The solution is found in a blend of effective techniques and accurate equipment, aluminum degassing machines being the foundation of contemporary purification.

Before exploring the "how," let's grasp the stakes. Molten aluminum is 50 times more prone to embrittlement than solid aluminum. When metals cool, hydrogen solubility drops dramatically, and dissolved gas produces defects: pinholes in foil, cracks in engine blocks, or structural weaknesses in aircraft. Trace amounts (greater than 0.15 cm³/100g) can reduce tensile strength by 30% and contribute 15–20% to annual scrap. Degassing isn't just a process step but a required quality control procedure.

1. Traditional Chemical Degassing: Convenient but Incomplete

   For small-scale foundries, chemical methods are typically the method of choice. They use reactive fluxes to bond hydrogen into compounds that may be removed, and the process works in the following manner:

   Operators submerge chlorine-releasing tablets (hexachloroethane, for instance) or flux granules into molten aluminum in a preheated perforated bell. High-temperature decomposed fluxes evolve gases such as aluminum chloride. The formed bubbles have extremely low hydrogen partial pressure, and the dissolved hydrogen is drawn into them by diffusion. They carry hydrogen and non-metallic inclusions upwards on their ascent, from which they are skimmed off as slag.

   Though cheap and simple to apply, chemical degassing has drawbacks: toxic chlorine vapors (which demand severe ventilation), flux residues can pollute high-purity alloys, and its highest efficiency is 40%—not high enough for critical applications. Nowadays, it is mainly reserved for small lots or as preliminary treatment for mechanical refining.

2. Inert Gas Degassing: The Industrial Standard (and the Role of Aluminum Degassing Machines)

   In industrial manufacturing, inert gas degassing is the norm—and equipment for aluminum degassing ensures its success. It makes use of partial pressure difference phenomenon: inert gas bubbles (nitrogen or argon) are "sponges," absorbing hydrogen from molten metal (where it is found) into the bubbles (where it is not).

   How Aluminum Degassing Machines Drive Results

   
   

   The key to this process is creating extremely small, evenly sized bubbles—and this is exactly what aluminum degassing machines excel at. Here is a step-by-step breakdown of how it's done:

   • Gas Injection: High-purity inert gas (99.996% nitrogen or argon, dried to prevent moisture contamination) is blown by the machine into the molten aluminum.
   • Microbubble creation: A rotary rotor—typically made of graphite, silicon carbide, or silicon nitride—shears the gas into very fine bubbles (≤5mm diameter) at 300–600 RPM. This provides 10–20 times larger gas-metal surface area than hand bubbling.
   • Diffusion & Removal: Hydrogen is diffused into the rising bubbles. At the same time, surface tension makes non-metallic inclusions adhere to the surfaces of bubbles. When bubbles reach the surface, they release hydrogen into the atmosphere, and inclusions get drained off as slag.

   More sophisticated aluminum degassing technologies now include flux injection, allowing for simultaneous degassing and deslagging. For instance, Pyrotek's SNIF™ process employs a proprietary rotating nozzle to inject gas in a non-turbulent manner, reducing half of dross formation and attaining a hydrogen removal efficiency of 60–80%.

3. Vacuum Degassing: For High-End Applications

   When very low hydrogen content (≤0.05 cm³/100g) is required—like in aerospace alloys or capacitor foil—vacuum degassing is used by producers. It is achieved by subjecting molten aluminum to a sealed, low-pressure container: reduced pressure reduces solubility for hydrogen, pushing the gas out as bubbles that float up and vent.

   Even though extremely effective, vacuum degassing is capital and energy expensive. In order to save time and cost, it is usually preceded by pre-treatment on an aluminum degassing machine that removes the bulk of the hydrogen before the vacuum step.

4. Critical Factors for Successful Degassing

   Success with any process depends on the control of key factors—most of which relate to aluminum degassing machines:

   • Temperature: Degassing is optimal between 710°C and 750°C. Too high a temperature increases hydrogen absorption; too low a temperature makes the melt too viscous to permit bubbles to rise.
   • Bubble Size: The smaller the bubble, the greater the surface area for hydrogen absorption. Rotator design (e.g., spiral grooves) and machine rotation speed of the aluminum degassing machine directly influence the bubble size—smaller speeds produce bigger bubbles, decreasing efficiency.
   • Equipment Maintenance: Rough or worn rotors disrupt bubble formation. Motor wheel manufacturer Hayes-Lemmerz found that their silicon carbide rotors on their aluminum degassers kept going for 800 cycles (compared to 300 for graphite), minimizing downtime and providing consistency.
5. Real-World Degassing: How Manufacturers Put It into Practice

   The best approach is a function of scale of production and quality requirements:

   
   

   • Small Foundries: In-house aluminium degassing systems, along with clean, environmentally friendly fluxes, treat batches of up to 50kg, for maximum efficiency and cost savings.
   • Automotive Lines: In-line aluminium degassing systems (e.g., Pyrotek's SNIF Sheer Neo) are used in continuous casting operations, treating over 1,000 kg of molten metal per hour. Such systems interface with launders, purifying aluminium as it is introduced into casting machines without stopping production.
   • Aerospace: Vacuum degassing is then treated in a box-type aluminum degassing machine, with as low as 0.09 cm³/100g of hydrogen for structural parts.

Aluminum degassing began as a rough chemical process and is now advanced engineering—and equipment for aluminum degassing is the pinnacle of it. By converting inert gas to an extremely precise purification tool, such equipment enables uniform, efficient hydrogen removal less expensively and with fewer defectives. Used with fluxes for limited-production runs or integrated into continuous aerospace manufacture, they yield molten aluminum of higher quality.

For manufacturers, the message is clear: find the degassing process that works best for you, but do not underestimate the aluminum degassing machine. It is not just machinery—it is the difference between making scrap and making a working product.