BLOOMING  & BILLET MILL:

         

          This mill is also known as the Mother Mill and is responsible for catering to the needs of the other mills. The ingots produced are first sent to this mill. Top pouring in the steel melting shop produces these ingots. The ingots are first fed into a soaking pit. The ingots have to be heated and in these pits at a temperature of around 1300⁰C. These are mainly reheating furnaces. These pits can handle 14 ingots at a time and they are side fired. The heating and the soaking time is 3/2 of track time. Soaking helps in uniform heat distribution. TRACK TIME: it is the time interval between heat tapped in steel melting shop to last ingot charged. There are four soaking pits whose specifications are as following:

          After soaking is over the ingots are taken out of the furnace and then fed into the rolling mills by the means of an EOT Crane, this crane is also known as Vertical Ingot Charger. Its capacity is 35 T. The ingots are placed on the ingot chariot running on a special track along the outer row of pits for the length of the building and up to the mill-receiving tables. The bloom is prepared by rolling the heated ingots a given numbers of times in two high rolling mills reducing cross section to the required size. The Fish Tails produced during the rolling process are cut by shear and again cut to required size before being sent to dispatch. The ingots are also produced by bottom pouring method are also rolled to produce blooms, which are then sent to the Wheel & Axle Plant for the production of the axles. A brief explanation of the rolling mills employed is mentioned below.

42” BLOOMING MILL:

          The blooming mill is 42”, two high reversing type arranged for twin motor drive 3000HP DC motors at a mill speed of 0/40/80 rpm. The roll diameter varies in size from 950 to 1100 mm and hence it is called 42” rolling mill. Generally the mill rolls the ingots down to 12”×10” blooms in approximately 13 passes.

          All blooms from the 42” mill are sheared by a 1200-ton shear. The front and the back ends of the blooms which develop fish tails during rolling are cropped and discarded. The shear can cut a max cross section of 256 sq. inch.

32” INTERMEDIATE MILL:

          This is a two high reversing mill driven by one 4500 HP DC motor. The roll diameter varies from 800 mm to 925 mm. The rolls are spring balanced. The roll is driven by the main motor through pinions and universal spindles with the speed range of 0/80/120 rpm. All the blooms are cut or cropped to length at the secondary hot bloom shear with the nominal blade load of 700 tons and is of the same construction as that of the primary shear.

The size of the blooms produced are 230mm×160mm×4.4m.

          The blooms having some defects like surface cracks etc. are unsatisfactory for further rolling operation. They are removed by the process known as “SCARBING”.

BILLET MILL:

          It is continuous type of mill. It provides 8 stands I & IV stands are vertical stands where as the rest are horizontal stands. Twisting jaws have been provided to twist the material through 90⁰ C after the no. 5 & 7 stands. First four stands are known as the roughing stands and last four are known as the finishing stands. First two stands are driven by 800 HP motor whereas the next two stands are driven by 1000 HP motors. The finishing stands are run by reduction gears and pinion arrangement. A single 2500 KW generator supplies power to the 4 individual motor of the roughing stands. Just before the first stand there is up & down cut shear that is used in emergency cases.

         Billets mill rolls billets and slabs are also produced with further reduced cross section the slabs are used in the skelp mill for the production of skelp coil. Some of the billets produced are directly sold to the market, and some are sent to the merchant mill for the merchant for the production of bars and rounds.

Billet Mill dispatch: the billet mill dispatch has two bays and each bay is provided with two cranes for handling the materials. This section stacks and sends the material to the Merchant Mill, skelp mill and also dispatches the billets to the outside buyers. The size of the billets produced is 125mm×125mm×4.4m.