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Mould Materials


To ensure optimal performance, moulds must keep their original specifications at mean operating temperatures as long as possible, and must, above all, have adequate heat transfer capacity. Thermal stresses which arise mainly on the hot faces in the area of the meniscus result in more or less rapid and permanent deformation of the mould, thus cutting short its life. The seriousness of this phenomenon is related to the temperature level inside the mould, and to temperature differences between the hot faces and the cold faces, and between the area of the meniscus and the area immediately below it.

The appropriate solution for each of the various operating conditions depends on choosing one of the following materials:
CuDHP


Phosphorus Deoxidized Copper


DHP copper was developed as a standard material for mould tubes under normal service conditions at temperatures in the meniscus area of up to about 300°C. The properties of this material are widely known. DHP copper is still today the most widely used material to manufacture moulds for the continuous casting of billets, where the thermal flow is usually moderate and the thickness of the moulds not excessive. The material displays excellent heat and creep resistance at high temperatures and its workability is good.

CuAg


Silver Bearing Copper


Adding about 0.10% silver to the copper increases the re-crystallization temperature by approx. 100°C. Thanks to its special properties, this alloy is used to manufacture moulds for the casting of blooms and slabs, where the temperature at the meniscus reaches and exceeds 300°C. Such high temperatures are due to the considerable thickness of the walls and to the high thermal flow inside the mould. 

CuAg alloy is used in applications in which higher thermal stresses and wall temperatures

occur. CuAg alloy has a higher thermal conductivity, which means that the temperatures in the mould can be kept on lower levels. In addition, it has higher temperature resistance to softening than CuDHP.

The fact that this material maintains its initial hardness, HB>80, for long periods of exposure at 300°C, also makes it possible to re-process plates that have been subjected to repeated wear before reaching the minimum prescribed thickness. CuAg alloy is also widely used for moulds producing billets in special conditions, such as weekly sequential casting, high casting speeds, cooling conditions which are not optimal, high temperature of the cooling water, and others.
CuCrZr


Copper Chromium Zirconium


CuCrZr alloy which has excellent mechanical properties, both at room and higher temperatures. High heat conductivity, a very high softening temperature, high creep resistance and high resistance to alternating thermal stresses are exceptional properties that set this alloy apart from the copper alloys previously presented. The good combination of properties achieved in this material is made possible by the use of alloying elements and a special thermomechanical treatment.

CuNiSiZn


Copper Nickel Silicon Zinc


Developed for electromagnetic stirrers, this alloy offers reduced electrical conductivity to minimize current loss in use. Ni2Si precipitation hardening provides strength and heat resistance superior to CuCrZr alloy, and the addition of Zn enhances platability significantly.