Hot Mill Steel
Hot Mill Steel –
Manufacturing for modern world
Quite late in the civilization advancement scenario did human race recognize that the true wealth was buried
deep under their feet. The sedimentation of billions & billions of years had resulted into a boon for us. Had
the climatic changes not taken place before the human race came into existence, we would not have had minerals
underneath. One of such advancements was the discovery of iron ore.
Iron ore is the sediment form of iron & is found in rocks & minerals from which it is economically
extracted with ease. The major drawback with the iron extracted in such a manner was that due to its chemical
properties, changes into another chemical, generally know as rust, thus destroying the original, reusable format of
the material. For this purpose only, a new alloy was manufactured using the iron ore as the major ingredient. This
came to be known as STEEL.
Steel is an alloy consisting of mainly iron, coal, carbon, magnesium & Aluminum. Other constituents are
Silicon, Sulphur & Phosphorus present in nominal quantities. This steel is alloyed out in huge blast furnaces
in mills known as HOT STEEL MILLS. Each hot steel mill has a huge blast furnace implanted for extraction &
purification process of the ore.
Iron ore, the primary raw material used in the process in iron ore along with coal & limestone. These
constituents are blasted in a blast furnace at regular batches. This lets the outlet of excess oxygen from the
ingredients & the iron gets converted into its liquid form. This liquid iron upon cooling is termed as PIG
IRON. This was the historical process known as BESSEMER’S PROCESS of Steel manufacture. Lower down the time stages,
this process got replaced with oxygen blast process in a furnace called BASIC OXYGEN FURNACE.
The pig iron can directly be transmitted into vessels where it is further alloyed with Silicon, Sulphur &
Phosphorus. These elements are added to generate new properties in steel contrary to the properties of the parent
element iron ore.
The temperature of the furnace & the liquid steel goes up to over 2400°C thus the mills are termed to be hot
steel mills. This steel mixture is then amalgamated with Aluminum to extract any of the left over impurities. The
contamination floats on the surface of liquid steel & can be easily removed.
Steel differs from iron in many of the properties it neither rusts, nor is influenced by any magnetic
characteristics. It is more malleable & ductile than iron itself. It can easily be drawn in wires, sheets or
balls. It has more tensile strength than iron has. The steel thus manufactured of hot mills is used at almost every
possible location in rails, construction of building, electrolysis process, steel wires, pipes, channels etc. The
list is ever lasting. A normal steel mill manufactures around 50,000 to 100,000 tonnes of steel a year. The amount
goes high with sophisticated & state-of-the art mills, ascending in size & structure. ArcellorMittal, the
largest steel manufacturing organization in the world, produces around 200 million tonnes of steel a year, a mere
10% of the total world consumption. It is likely to shoot to 12% in 3-5 years.
Source: Hot rolling of steel, Volume 10 of Manufacturing engineering and materials
processing by William L Roberts, CRC Press, 1983, ISBN # 0824713451, 9780824713454