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
Keratuff has an exceptionally high strength to density ratio, which makes it suitable for thin walled shapes such as launders or runners.
Keratuff has a very fine microstructure of closed pores which, gives it excellent thermal insulation properties. Used as a launder, the heat losses of the molten metal are considerably reduced and skull does not form easily.
Ketatuff is non-wetting to aluminum, so that the metal flows cleanly, smoothly and rapidly.
The above factors eliminate metal freezing in a well-controlled operation, so that no cleaning is ever required.
Keratuff is very easily patched by hand, using keratuff. The bond is assisted by fibres which, protrude from broken surfaces. (Fibres do not protrude from the surface of cast or plastered surfaces.) Patching dries easily and rapidly. Preheat or drying is not deemed necessary.
Keratuff can easily be cut or machined. It is asbestos free and non-toxic.
From the above it will be clear that Keratuff is fundamentally superior to dense castables, has all the ideal characteristics for aluminium launders, and should be treated very differently. Keratuff should be treated as a permanent lining, not a short-lived consumable material.
Full technical specifications are available on the Keratuff data sheet.
1. Induction Coil Coating: A hard, strong, 93% alumina putty for protecting coils. Use it between coils and as a thin cover to prevent molten metal contact.
2. Kerasic: A hard strong, abrasion resistant material for inside the coils. Make it into a sleeve or skid rails.
3. Hollocast 1: An inexpensive, pleasure to install, quick setting insulation material. Use it as a support outside of the coils to keep them straight and in line. Easy to break out without destroying the coils.
4. Glyptal: A red insulating paint to prevent electrical shorting between coils.
5.Electrical Paint: A higher temperature resistant alternative to Glyptal. Use on slings. Dip the sling into the paint, switch it on for a few seconds and remove it. Switch on for another 10 seconds to dry and harden it.
6. Kerinduct 2: A dry spiking lining of spinel forming composition. Expands on sintering to make a tight lining. Use as a working lining in coreless induction furnaces for melting stainless steel and high temperature alloys.
7. Chloresist: A solid, almost impervious castable lining for channel induction furnaces. Use for zinc especially.
8. Mica sheet: Use for a slip plane between Kerinduct 2 and the Induction Coil Coating.
9. Asbestos Board: A durable, heat resistant board for the end plates of induction coils and the tops of coreless induction furnaces. stock boards 1m x 1m x 20mm.
10. Capping: A very fast setting material to give a decent hard capping against which a "gwala " can be levered. It requires no heat to set.
11. Kerapatch: An excellent hot patching material.
12. Slag Coagulant: To thicken the slag and enable its removal.
13. Keratherm: An insulation cover which spreads nicely. Carbon free.
14. Keraplas Ramming: An excellent ramming material with green chromic oxide.