Simple Solutions That Work! Issue 6

As aluminum casters look to improve quality, degassing processes are often on the short list for areas to find improvement. Degassing is a common process used to battle hydrogen absorption in aluminum prior to casting. Hydrogen is appreciably soluble in molten aluminum. In fact, its solubility is directly related to temperature and pressure. Hydrogen exists all around us from moisture within the air which interacts with the melt surface, contributing both a buoyant dross from the oxygen and hydrogen dissolved into the melt. Disturbances in the melt layer exacerbate this interaction. Alloyed products like magnesium also present an increase in this occurrence by forming oxide reaction products that offer reduced resistance of hydrogen in the melt layer. The Result? The hydrogen comes out of solution upon solidification resulting in porosity or void formation within the casted part, resulting in lower quality and higher scrap rate. Given the above, it behooves the aluminum die caster to look for the best and most efficient way to degas their metal. Let’s review some of the degassing options available and some improvements that are possible using advanced materials. DEGASSING SYSTEMS Many degassing systems have evolved, but they are generally divided into two categories: static and dynamic. The static designs include so-called porous plugs or spargers that are installed in the vessel bottom, and some lance- type systems suspended in the melt through the metal surface. The most prevalent static systems can treat a greater percentage of the melt because of their location at the bottom, and require no moving parts, suggesting less maintenance. The static systems are more prevalent in larger vessels, where installation cost may be higher, but long life may be expected with little or no maintenance. Smaller vessels, often crucibles in foundries, may be unable to accommodate bottom modification, and are usually better served by dynamic degassers. The dynamic systems generally have rotors suspended in the melt. PHILIP GEERS Molten Metal Market Manager BLASCH PRECISION CERAMICS ARTICLE TAKEAWAYS: 1. Increase aluminum part quality with degassing 2. Static versus Dynamic degassing systems 3. Maximum efficiency – large number of small bubbles SYSTEMS INTEGRATION 倀爀漀搀甀挀椀渀最 儀甀愀氀椀琀礀  䌀攀爀愀洀椀挀 䌀漀洀瀀漀渀攀渀琀猀  昀漀爀 琀栀攀 䄀氀甀洀椀渀甀洀  䤀渀搀甀猀琀爀礀 昀漀爀 伀瘀攀爀  吀栀爀攀攀 䐀攀挀愀搀攀猀 䐀椀攀 䌀愀猀琀椀渀最 椀猀 漀渀攀 漀昀 琀栀攀 洀漀猀琀 挀栀愀氀氀攀渀最椀渀最 瀀爀漀挀攀猀猀攀猀 昀漀爀 挀攀爀愀洀椀挀猀 眀栀攀爀攀 洀愀琀攀爀椀愀氀猀 猀攀攀  栀椀最栀 琀栀攀爀洀愀氀 猀栀漀挀欀 愀渀搀 氀漀渀最  攀砀瀀漀猀甀爀攀 琀漀 洀漀氀琀攀渀 愀氀甀洀椀渀甀洀⸀   䈀氀愀猀挀栀 栀攀氀瀀猀 礀漀甀 洀攀攀琀 琀栀愀琀  28 IMPROVED CERAMIC MATERIAL FOR ALUMINIUMDEGASSING