What is a Bloom in steel industry?

A bloom is a semi-finished product produced by a continuous casting process (bloom caster) to be used in the production of heavy structural long products and rails. Blooms can have a square or rectangular cross-section with sides ranging from 200 to 600 mm.

The block casting process starts with a casting pan full of liquid steel suspended above a tundish. The tundish provides a buffer during the change of the casting pan, allowing the casting process to continue continuously. The tundish also provide the last opportunity for any inclusions and impurities to float out of the steel into the slag before it enters the solidification mould.

The molten steel in the tundish flows to nozzles suspended above the continuous casting moulds. Bloom casters usually feed multiple moulds and cast several strands of steel at once.

As the steel flows from the tundish into the moulds, the moulds rock up and down to push the liquid steel deeper into the mould. The copper-clad moulds are cooled with water to prevent them from melting due to the heat of the molten steel.

Moulding powder is steadily applied to the top of the moulds, which melts and lubricates the interface between the molten steel and the copper-coated moulds. As they move through the oscillating moulds, enough heat is dissipated to form a thin solidified shell on the surface of the strands, keeping them intact as they leave the moulds.

When the strands come out of the moulds and enter the spray chambers, most of the steel in the strands is still molten. The spray chamber provides controlled cooling by water sprays to further solidify the steel in the strands as they move down through the casting process. The point in the process where the strand is fully solidified is called the metallurgical length of the caster.

In the end, the solidified strands are bent from vertical to horizontal and then cut into individual blooms by a gas burner. The blooms are small enough to be handled by an overhead crane, rail wagons or mobile carriers to transport them to a beam plant, rail plant or seamless pipe.