PERLITE FOR THE FOUNDRY INDUSTRY

Perlite in the ore form is used in high temperature application in the steel, ferrous and non-ferrous industries, as a slag coagulation agent, in ladle topping compounds, as an ingredient in exothermic and insulating sleeves and as a cushioning agent in moulding and core sand

Perlite ore is used in the granular form in size –8 + 40 # as a slag coagulant in continuous induction furnaces and in ladles. The ore will expand when it comes into contact with the melt, forming a light weight, viscous cellular mass. This mass attracts all individual slag particles in the metal and prevent retention or re-entry of the impurities into the metal bath, virtually eliminating the problem of slag inclusion. The alkaline compounds present in the perlite ore also helps in reducing sulphur and phosphorous compounds in the melt. CONSUMPTION NORM : The quality of perlite ore will depend on the viscosity and coagulative nature of the melt. However, 1 to 2 kgs per ton of melt in ladle / furnace is recommended. Larger quantity can be used to get additional benefit of sulphur and phosphorous reduction. ADVANTAGES: •Produces cleaner metal. •Coagulates slag and traps all impurities. •Simplifies ladle skimming and removal of slag without raking. •Reaction with melt produces no smoke or fume of health hazards. •Additional benefit of sulphur and phosphorous reduction.

Perlite ore in size –8 + 40 # can be added to molten metal pouring ladles to act as an insulating cover. The ore on expansion will prevent heatless maintaining the pouring temperature of the melt longer, especially in continous casting requiring longer hold time. CONSUMPTION NORM : 10 to 15 kgs per ton of metal, depending on the size of the ladle. ADVANTAGES: •Facilities holding of melt for longer time permitting deoxidation and decarburisation Process. •Energy saving as heat loss during transfer of melt from furnace to ladle can be eliminated. •Eliminates shrinkage defects in cast materials.

Perlite ore can be used to protect the refractory lining of ladles thereby avoiding frequent relining. Addition of perlite forms a glassy coating on the ladle wall, which increases the life of the lining. CONSUMPTION NORM : 10 to 15 kgs per ton of melt. ADVANTAGES: •Prolongs refractory ladle lining life.

Perlite can be used as an insulating compound to avoid chilling effects in casting and prevent heatloss from the metal surface during solidification. 10 to 15 kgs per ton of metal, depending on the size of the ladle CONSUMPTION NORM : 2 TO 3 % by weight of the casting, powder to be sprinkled on the top of the mould after pouring. ADVANTAGES: •Retards quick solidification of the castings. •Reduced chilling effects, permits easy machinability of the castings.

Perlite is added to foundry and moulding sand mixture as a cushioning agent to compensate for the expansion of silica as it goes through phase transformation or temperature in excess of 600 deg. C. Perlite being volume stable upto its fusion point will absorb the growth of the silica grain CONSUMPTION NORM : 0.5% of the weight of sand in case of ferrous metals and 0.1% of the weight of sand in case of non-ferrous metals. ADVANTAGES: •Casting defects such as buckles, veining, fissuring and penetration are thus minimized and cleaning room costs reduced. •Perlite also provides better permeability to core sands reducing defects attributable to poor venting.

Perlite is used as an insulating ingredient of the fibrous matrix, which forms exothermic sleeves which is used as riser and sideboard panels for hot tops.