Billet is the most important commodity in the middle of steel production. The importance of billet is the aftermarket products (which are actually marketed and used in general) are specifically related and depend to the quality of the billet.
strength, elasticity and flexibility of the rebar, as well as the quality and polish of the slabs, etc. depend on the quality of these intermediate products.
Various methods of production of billets have been considered from the beginning, which have either been changed or lost in nature with the advances of industry and technology, and have been replaced by other methods.
In the following two up-to-date and applied methods with the highest quality of production and its popularity in the world are discussed and the types of products manufactured by these two methods are presented below.
Electric Arc Furnace (EAF) and Induction Melting Furnace (IMF):
In this methods, the scrap iron is poured with special baskets in the arc furnace and then sponge iron is added to the furnace with flux such as coke, lime, bentonite, and so on. After adding these materials, the sample is oxygenated, homogenized, and analyzed to convert the material into the furnace into molten steel.
The molten steel is taken to the casting unit after the impurities are separated by the melt carriers. In the casting, the molten material is thrown into a container called the Tundish, and then poured into the mold by means of a nozzle of molten copper, the walls of which are cooled by water. Water cools the molten material inside it. Then cut the cooled billets to the desired length.
Blast Furnace (BF):
More than 90% of the world’s ore is used in blast furnaces. In this method, the iron ore is pre-annealed and clumped together with coke and lime into the blast furnace and crude iron or pig iron is obtained.
The crude iron is converted into molten steel in the converter then the raw steel impurities such as carbon are separated by oxygen to obtain the crude steel. The molten steel is then taken to the casting unit after the impurities are separated by the melt carriers.
The molten material is poured into the casting unit into the billet molds and placed on a roller and cooled by splashing water and then cutting the steel billet to the desired length.
The difference between ingot, billet, bloom and slab:
To understand the differences between these four semi-manufactured products, also known as intermediate steel rolling products, it is best to first understand their definitions.
The ingot has a trapezoidal surface with a maximum length of 2 m in each branch. The appearance of the bars makes them easy to transport.
The billet is longer than the ingot and has a circular or square surface with a width of less than 15 cm or a cross-sectional area of less than 230 cm and having a length of 6 and 12 meters.
Bloom is actually the same as billet but more than 15cm wide, the cross section is larger than 230 cm, so Bloom and Billet are usually grouped together. Most of Bloom’s uses are for rails, shields, studs, cans, beams, and more.
Unlike Bilt and Bloom, the surface of the slab is rectangular and is usually 230 mm thick, 1.25 m wide and 12 m long. Slabs are the raw materials for making steel sheets.
According to the above definitions, it can be concluded that the difference between these two products is in the cross section and its dimensions.