Gas control in liquid aluminium
One of the most important factors affecting the quality of aluminium castings in the foundry is the presence of gas, mainly hydrogen, inside the liquid metal. This phenomenon leads to diffuse microporosity that can affect the quality of the die casting, compromising its mechanical and structural characteristics. GAS ALUCONTROL is a technology based on the STRAUBEPFEIFFER method that allows the user to verify the amount present in an aluminum alloy specimen taken from a liquid metal furnace.
The specimen after solidification, which takes place under vacuum, visually highlights the presence of gas in the alloy and therefore allows any degassing operations before proceeding with the casting.
How it works
A liquid sample of the aluminium alloy to be analysed is poured into the preheated steel crucible which is placed under the glass bell jar using pliers. By means of an electric pump, vacuum conditions are created inside the bell until the metal sample is completely solidified. During the vacuum solidification process, the gas, included in the metal, is released by forming numerous bubbles (in relation to the amount of gas present in the metal) on the surface. The observation of this phenomenon allows the operator to visually estimate the amount of gas present in the metal; the following analysis of the upper part of the sample, after solidification and cooling, allows an evaluation of the gas content according to the principle that a sample, slightly gassed, has a concave surface, and a highly gassed sample, has a convex surface.
For more precise information, the metal sample must be sectioned vertically.
The size and quantity of the internal pores, compared to reference specimens, will indicate the amount of gas present in the sampled aluminum. The sample is solidified in a vacuum because, in these conditions, the pores that are formed take on significantly larger dimensions and therefore allow easier evaluation.