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Causes of air leakage and characteristics of vacuum suction casting


The weight of cast aluminium piece and dimension range are very wide, the weight is only a few grams of light, can achieve 400 tons of heavy, wall thickness is only 0.5 millimeter, thick can exceed 1 meter, length can arrive 10 meters by a few millimeter, can satisfy the use requirement of different industry branch.Generally, the surface roughness of aluminum castings can be determined by comparing samples, and the surface micro-cracks can be examined by coloring method and magnetic powder method.The internal mass of cast aluminum can be examined and determined by means of audio, ultrasound, eddy current, X-ray and gamma rays.

The quality of cast aluminum has great influence on the performance of mechanical products.For example, all kinds of pump impeller, the size of the shell as well as hydraulic lumen, lines of accuracy and surface roughness, directly affects the working efficiency of the pump and the hydraulic system, energy consumption and the development of the corrosion, etc., the internal combustion engine cylinder block, cylinder head, cylinder liner, piston ring, the strength of the exhaust pipe such as cast aluminum and quench heat shock resistance, and directly affects the working life of the engine.

In addition to containing free silicon, there are various compounds and other inclusions between metals.Moreover, due to the loose structure of the cast aluminum, there may be uneven segregation of chemical components and other phenomena. At the same time, dense oxide film will be formed on the unprocessed surface during the cooling process after casting.Short time of alkali corrosion, the cast aluminum may not be removed, and because the dissolution rate of the cast aluminum during alkali corrosion is relatively fast, the caustic corrosion of the cast aluminum will often lead to the change of tolerance size, and even lead to the scrap of the product.

In view of the above situation, we can change the alkali corrosion program to solve, namely, the alkali corrosion treatment after casting.Operating according to this process can not only prevent the caustic corrosion and scrap of the parts, but also benefit the surface quality after oxidation.The alkali etching method mentioned above can avoid the over corrosion of the workpiece. After alkali etching, 1-1 hydrochloric acid can be used for 2-3s fast light emission to replace the more toxic hydrofluoric acid, which is not only conducive to environmental protection, improving labor conditions, but also can reduce the production cost.

Causes of air leakage in aluminum casting:

1.It is forbidden to spray aluminum on molds.

2.To prevent local overheating mold caused by uneven shrinkage crack air leakage, so mold to ensure that the cooling water smooth, maintain the heat balance.

3.Ensure that the height of the alloy liquid cleaning, degassing slag, and regulate the temperature of a suitable alloy liquid, if not the appearance of the thin wall parts, using 620 ° ~ 630 ° is preferred.

4.In the process of production, ensure that the parting surface of the mold is highly clean and free of air exhaust, and do not leave any moisture in the cavity after spraying, until blowing.

5.According to the wall thickness of the product, the proportion is between 15~~25mm25~ 35mm to ensure the thickness of the cake.

Features of vacuum absorption casting of cast aluminum:

1.Good casting quality, no pinholes, no air holes and no sand holes.

2.Compact residual phase structure and fine grain.

3.The mechanical properties of the tensile strength, elongation, hardness and sand casting, are significantly improved.

4.Castable castings with large wall thickness difference and high thin-wall quality requirements.

5. High productivity, easy to realize mechanization.