Perlite insulation is used in high temperature applications in the steel and foundry industries such as ladle topping, hot topping and risering, in topping compounds, in exothermic and insulating shapes, as a cushioning agent, in moulding sand and in the manufacture of refractory blocks and bricks. High temperature performance of expanded perlite has been well documented.
Expanded or unexpanded granular ore forms of perlite are added to molten metal pouring ladles. Most often the ore form is used which reacts slag in the ladle to allow easy removal of the slag layer. In cases where it is desirable to maintain a metal temperature in a ladle, the expanded perlite layer forms an efficient insulating blanket.
When introduced during ladle filling, a gentle rolling motion is produced which cleanses the metal by coagulating impurities. In addition, ladle-lining life is increased by virtue of a vitreous residual coating left on the refractory by the perlite. An added advantage of perlite is in this application is that no objectionable smoke or noxious fumes are produced.
Hot Topping and Risering
Perlite is often mixed with exothermic powders and used in hot tops and risers to prevent shrinkage cavities in ingots and castings. Perlite is the most used light weight filler used for these applications because of its availability, competitive price, and superior properties. Normal additions of perlite to insulating and exothermic compounds are in the range of 3 to 20% by weight.
Perlite is used in the manufacture of refractories where the average temperature does not exceed 1100°c. Its excellent insulating properties ensure substantial usage of perlite in refractory castables, bricks and blocks. In higher duty applications, perlite refractories are used as reserve insulating layers for higher duty refractories.
Foundry Core and Moulding Sand
Perlite is added to foundry core and moulding sand mixtures as a cushioning agent to compensate for the expansion of crystalline silica as it goes through the phase of changes of temperature in excess of 540°c. Casting defects such as buckles, veining, fissuring and penetration are minimised and cleaning room costs are reduced. In addition, perlite improves permeability of core sands thus reducing defects attributable to poor venting.
Our foundry grade perlite is distributed throughout New Zealand, North and South East Asia, Australia, and Southern Africa. We are adept at producing the required product, in the best packaging and supplying at the requested destination quickly and efficiently.
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