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Purification Techniques of Precision Casting Parts

Release time:

2023-11-13

In industrial production, purification methods such as clarification, flux and steam are mainly used, and some purification methods such as fixed-term curing and filtration are also used.

1. Flux purification Flux purification refers to the application of the flux in the aluminum liquid to the aluminum liquid to form a viscous liquid, so that the metal oxides in the aluminum liquid are absorbed and dissolved by this liquid to form a new liquid that rises to the surface, and forms sludge removal after refrigeration. The cleaning flux is composed of salts with low melting point, low relative density, low surface support, high vitality and strong adsorption to air oxidation slag. During the application process, a small piece of flux is first loaded into the cage, and then pierced into the bottom of the mixing furnace to stir back and forth. Alloy steel precision castings can be cast until the flux melts and the cage is removed, and the surface sludge can be removed for 5 to 10 minutes. Depending on requirements, the flux may also be removed from the surface to provide a capping effect.

2 steam purification gas purification is one of the main primary aluminum purification methods. Commonly used steam is chlorine, nitrogen or a mixture of chlorine and nitrogen.

(1) chlorine purification. Previously, active steam chlorine was used as a scavenger (chlorination process). In the chlorination process, when chlorine gas is introduced into the aluminum liquid, many unusually thin AlCl3 and bubbles are formed, which are fully mixed in the aluminum liquid. Hydrogen dissolved in the molten aluminum and some alloy aluminum investment casting equipment impurities are adsorbed on the AlCl3 bubbles and discharged as the AlCl3 bubbles rise to the surface of the molten aluminum. When entering chlorine, it can also chlorinate some elements that are more negatively charged than aluminum, such as calcium, sodium and magnesium. These elements produce corresponding chlorides due to entering chlorine and are separated. Therefore, the chlorination process is a very effective method for the purification of primary aluminum. The amount of chlorine used is 500-700 grams per ton of aluminum. However, due to the harmfulness and preciousness of O2, in order to avoid gas damage and reduce the production cost of waste aluminum, in the contemporary aluminum industry, the chlorination method has gradually been replaced by the rare gas nitrogen purification method.

(2) nitrogen purification method. Also known as the smoke-free continuous purification process, alumina balls (418mm) are used as the filter material. N2 immediately enters the aluminum liquid. The aluminum liquid is continuously fed into a purification furnace, passed through a filter layer of alumina balls, and subjected to a nitrogen purge. Therefore, the non-metallic materials, impurities and dissolved hydrogen in the aluminum liquid are removed, and then continuously discharged, resulting in uniform distribution of thin nitrogen bubbles in the dissolved solution.

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