Calcined Coal For Casting Molds

Calcined coke is commonly used in the metal casting industry for making molds. Metal casting is the melting of metals, the pouring into the cavity of a mould and the cooling to form the finished part. To ensure the quality of casting, many processes must be used. This is followed by the preparation and characterization process of the moldingsand.

The green sand is a mixture of bentonite, mineral coal dust and water. The sand must be rammed onto a mould to produce the desired form (a top-half or cope is booked with a bottom-half or drag to form a complete cavity). It is important that the sand be hard and durable enough to keep the desired shape during pouring, yet soft enough to give the resulting casting good mechanical characteristics. The sand composition should also have low moisture content to avoid breakage during the metal pouring and to prevent excessive heat generation in the sand.

This material performs extremely well when it is bentonite bound with coal dust. It can also be used for aluminum, bronze and iron castings. The sand produced with this material has excellent mold plasticity and compactibility, preventing breakage during the forming of the castings and especially during their extraction from the cast. This material has low moisture to prevent problems of wetting or water absorption.

It is common to combine a greensand with calcium carbonate or phenolics in order to increase its performance. These additives prevent sintering, and also improve bonding between sand particles and metallic melt. Although adding these materials is time consuming and costly, the resultant sand performs well when used in metal casts.

Another important additive is a recarburizer, which helps to distribute graphite particles throughout the sand. It increases the amount of eutectic granules formed when sand comes into contact with metal molten, improving the flow characteristics of the material and reducing the white mouth defect. Recarburizers can also be combined with phosphates to improve the corrosion resistance.

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