Those who are not familiar with aluminium casting tend to think that it must be very easy because of its low melting point. Those familiar with aluminium know that is has some unusual and tricky properties.
- One is its high thermal mass;
- Another is its ability to reduce refractories, especially those containing silica;
- A third one is its rapid oxidation;
- Also, it has a very high surface tension;
- Due to the last two properties, it makes a lot of dross which traps a lot of metal, gets hard, reacts to form noxious gases;
- In spite of its low melting point, it readily dissolves iron and other metals.
Keramicalia has done a lot of development in this interesting area.
Kerasic is a fine, pourable “refractoramic” material. With Kerasic we can make extremely thin walled crucibles, which give faster heat transfer, and are inexpensive. Kerasic is also used to make automatic ladles, which do not require daily coating maintenance. It is also used for very intricate element cages, for highly efficient electrical heating. Kerasic is also used for Globar protection tubes and riser tubes.
Element Boards and Element Panels are used to heat crucibles in holding furnaces and low pressure die casting furnaces. We also make a wide range of element bricks.
We do a lot of development work for Silca South Africa. They bring us problems to solve and we develop products specially for them.
We have made large holding furnaces for aluminium casters in Hollocast 1 cellular insulation. This is a robust castable, self-flowing, and also insulating. It is important to keep the 600 ̊C isotherm inside the wall, so that molten aluminium cannot run into the outer backup insulation through cracks. Hollocast 1 is great for ladles.
We make several types of silica free refractories to prevent corundum formation. Corundum formation is a thermit reaction where molten aluminium reduces silica in a highly exothermic reaction. This reaction can progress right through a lining, as it is self-accelarating. You are left with a furnace with a screaming hot shell yet the aluminium freezes in it. The impregnated lining is a cermet: A composite of alumina ceramic in a metal matrix. It is hard and extremely tough. You cannot break it out. You have to cut the shell off to remove it. Corundum formation can be prevented by smearing Alpatch over the metal-air interface surface.
Aluminium non-wetting paint is wonderful stuff. Paint it over the rough surface of refractories and it prevents aluminium from sticking. Just peel off the oxide skin, and avoid the damage done by cleaning launders etc. It can extend the life of refractories about 5 fold. Using various material and casting tricks we can get extremely smooth aluminium contact surfaces which last very long.
Fibre Plasters are excellent insulators. They have hundreds of applications. Weight saving is often very useful.
We do hotspot repair with Kerapump.
Thermal cups are useful for protecting cables, hoses etc., around furnaces. They remain flexible but protected from molten metal splash.
For many more materials and precast products, Contact Us