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Porosity Of Die-Casting Parts

Porosity Of Die-Casting Parts

The pore defects of zinc alloy die castings are the general term for pore defects of different sizes and shapes generated on the surface and inside of zinc alloy die castings, mainly including pores, gas shrinkage cavities, pinholes, surface pinholes, subcutaneous pores, choking fire, etc. Shrinkage defects, shrinkage holes, shrinkage porosity, leakage, etc. Its definition and characteristics are as follows:

Pores are holes-like defects formed by gas in the casting. The surface is generally smooth, mainly pear-shaped, round and oval. Generally, it is not exposed on the surface of the casting. Large holes often exist in isolation, while small holes appear in groups.

Shrinkage porosity is a void casting defect formed by the combination of dispersive porosity, shrinkage porosity and shrinkage porosity.

Pinholes are generally precipitating pores with the size of the needles distributed on the cross-section of the casting. Such pores often appear in aluminum alloy castings, which are very harmful to the performance of the castings.

Surface pinholes are scattered pores distributed in clusters on the surface of the casting. Its characteristics and reasons are the same as the subcutaneous pores, which are usually exposed on the surface of the casting and can be removed after machining 1-2 mm.

Subcutaneous pores are dispersed pores located under the surface of the casting. It is the reactive pores produced by the chemical reaction between the molten metal and the sand mold. The switches are needle-shaped, tadpole-shaped, spherical, pear-shaped, and so on. Different in size and depth. It is usually found after machining or heat treatment.

Fire choking means that a large amount of gas generated during the pouring process cannot be smoothly discharged, and boiling occurs in the molten metal, resulting in a large number of pores in the casting, and even defects such as incomplete casting.

With one hand to inventory and the other to promote consumption, companies continue to add and subtract in production and operation. However, although there has been an upward trend in non-ferrous metal prices since last year, the market generally believes that this is nothing.

Taking zinc as an example, it is understood that the national zinc consumption in 2015 was 6.28 million tons, with an annual growth rate of 2.6%. Among them, zinc plating is still the largest downstream zinc consumption sector, accounting for 57%. Therefore, although the consumption of zinc oxide and zinc alloy die-casting has shrunk, battery consumption has basically stagnated. The closer to the consumer end of the industrial chain, the smaller the price elasticity and the greater the stickiness; conversely, the further upstream, the greater the price elasticity and the smaller the stickiness. “So in a deflationary environment, the further downstream companies are generally less impacted, because the price of raw materials falls faster than the decline of finished products, profit margins may increase, and upstream companies suffer more severely.