Alloy cast iron is used in cases that require extreme resistance to abrasion, heat, or corrosion. In addition, these cast irons are used when unconventional physical features such as low expansion of heat, or non-magnetic properties. Casting parts of cast iron must be produced by professionals; because adding 3 to 30 percent of the alloying element to molten cast iron requires using melting equipment, casting techniques and quality control. The identification and determination of the specific properties required in alloy cast irons is often very difficult. Thus, they are always determined by their chemical composition. Alloy cast irons are classified according to their unconventional usage and their specific characteristics.