The cupola – reduction costs
Briquettes and briquetted steel scrap
The reduction of batch costs for a cupola furnace is achieved by using various types of briquettes as well as briquetted steel scrap.
Ferro-alloys, silicon carbide, graphite, and fine steel scrap can be briquetted. Fine fractions of raw materials and their sludges, which could not be fed directly into the metallic zone of the cupola, are utilised in this way.
Briquetted raw materials with a strictly defined content of the main component and high resistance to crumbling (which is important for loading the cupola and contact with the metal input) easily and completely penetrate the slag zone, supplying precisely melted metal with the dosed element.
The best solutions
The briquetted raw materials are cemented together, which further contributes free calcium reducing the amount of calcium scale used. The prices of basic components, e.g. silicon or manganese in briquettes, are roughly half the prices of the same first-grade piece raw materials. This makes it possible to reduce batch costs.
As for silicon dosing, silicon can be extracted from briquettes of both FeSi and SiC. It is said that FeSi “likes” iron scrap and SiC “likes” steel scrap.
Two types (shapes) of briquettes are used worldwide: cubes (cuboids) and hexagons. In Poland, briquettes in the shape of cubes (cuboids) are used. They always have 1 kg of the basic raw material (silicon, manganese, chromium, phosphorus, etc.) in them. When putting one briquette (cube) into the cupola furnace, you add 1 kg of the basic raw material, which greatly facilitates dosing of the cupola and communication between the technologist and his staff.
Briquettes from steel scrap
And there is yet another way to reduce the batch cost of charges for the cupola furnace, namely briquettes made from fine steel scrap at an attractive price, compared to the price of scrap steel. They are magnetic so there is no problem with loading them mechanically into the cupola.