Melting

A blast furnace is the oldest method of melting iron, known as a cupola where a bed of coke is ignited. The coke we import from Poland, it is about 150 mm cube in size and we use around 10% weight of metal to melt with.

• Above, where the air comes into the furnace, are layers of coke and metal.
• Air is forced into the furnace through vents (Tuyeres) and oxygen in the air super heats the coke to above 1500^oC.
• Heat travels up the furnace and melts the layer of metal above the coke.
• Metal melts and flows down through the coke into the well at the bottom.
• When one layer of metal is melted the next layer of coke drops down and melts the metal layer above.
• New metal is charged at the top
• Molten iron is created at 3 tonnes/hour

When there is sufficient metal in the well below the tuyeres it is removed through the tapping hole, flows down a trough and into the ladle. The tapping hole is then bodded with a piece of clay on the end of a rod, which in turn is removed when more metal is collected.

To stop the shell from melting when the heat is on, ceramic bricks, forming a circle, are used to line the inside of the furnace building up to form an internal chimney. This in turn is sealed by ganister, a clay and aggregate mixture used to fill the cracks between the bricks and is applied daily to repair the wear and tear

Metal, when it is molten, stills weighs the same, so the head pressures can squeeze the liquid through the tiniest of gaps. This can then weaken the outer shell allowing the extremely hot metal to cut through the thin outer shell, like the proverbial hot knife through butter. We take all precautions to ensure the furnace is sealed and have an effective method developed in case of emergencies.

Recycled Iron

Scrap metal consisting of old brake drums, engine blocks and other quality produced parts are supplied in sizes suitable for handling. Metals such as aluminium are removed from the scrap as it may cause gas holes in the finished castings. Copper left in will strengthen the metal.

Charging the Cupola

The materials for charging include steel to dilute carbon and silicon levels, coke for melting, pig iron for increasing the silicon level, manganese for reducing sulphur in the iron and limestone for balancing the acidity of liquid contents as the iron melts through the coke while also increasing the fluidity of the slag.

The Slag Hole

Slag floats on the top of the metal, as the metal level rises the slag pours out through a hole 700 mm above the base of the furnace. The picture shows just the air blast coming out of the slag hole before the slag reaches that level.