PROJECT REPORT ON ROLLING MILL PRODUCTION
Established in the year 1990, “Kajal Steel Industries, Ahmedabad” is one of the leading firm involved in the Manufacturing, Supplying and Exporting Steel Rolling Mill Plant Machines and Spares. Their range of products is featured with robust construction, durability, abrasion & corrosion resistance and high tensile strength.
This organization is a pool of experts, state-of-the-art technologies, innovative engineers that enable us in providing international quality products. They are also involved in the import of scrap and steel machinery from overseas markets. Each product provided by us is designed and manufactured by keeping in mind the demands and requirements of the clients. With the help of advanced technical expertise, This firm is capable of offering customized products so as to meet the specifications of our clients. Moreover, Their firm is also involved in offering customized packaging solutions according to the individual specifications of our clients. Furthermore, as It is well-connected with all major roads, harbors and airports due to which we have been able to timely d0eliver our consignments at the client’s sites.
1. BLUE NILE ROLLING MILL LTD., Nairobi– 14″ Mill 3 Stand & 10″ Mill 8 Stand complete
turnkey project with DC drive in continuous mill
2. JUMBO NORTH KENYA LTD., Eldoret, Kenya, Additional Machineries, spares, furnace
3. ROLL MILL KENYA LTD., Nairobi, 14″ Mill 3 Stand, additional machineries & spares
4. EMCO STEEL & BILLETS LTD., Nairobi, additional machineries for Mill
5. MORRIES & COMPANY (2004) LTD., Nairobi, additional machineries for Mill
And many more
1. RAM LAKHAN STEEL PVT. LTD., Jalna, Maharashtra, 8″ Mill Complete Project, commissioning of Complete plant, additional machineries ; additional machineries ; spare
2. VINAYAK TMT BARS PVT LTD. Ahmedabad, Complete plant additional machineries, spares,
mill stand parts, commissioning of complete project(Automatic mill 150 MT per day production Capacity) additional machineries ; Spares for mill
3. OMSAIRAM STEEL ALLOYS PVT. LTD. , Jalna, Complete plant additional machineries,
spares, mill stand parts.
4. MARUTI STEELS PVT. LTD. Jalna, 8″ Mill Complete Project.4. ASHTLAXMI RE-ROLLS JALNA PVT. LTD – 8″ Mill Complete Project, additional machineries ; Spares.
MANUFACTURING PROCESS OF TMT BARS
Let us have a through review about the entire manufacturing process in a brief manner. Just like the
schematic shown above there are different stages in the manufacturing of the TMT bars. It shows stage by stage development from the raw material and gradually how the finished product is emerged.
These stages adopted here are a universal sequence to manufacture the TMT bars and is followed in general practice. This is the best way to attain the finished products using the equipment efficiently. Now let us briefly explain every stage in the process. Note that every stage brings the raw material closer to the final product and any miscalculation in any stage or occurrence of breakdown will result in loss of raw materials, wastage of power and delay in production. Hence every process is equally important. Now let us have a brief insight stage wise.
After quality testing, the ingots are ready to be fed in the furnace. It is necessary for the ingots to have a high temperature for the rolling process through the rollers. This is where the furnace comes to play. The ingots are fed into the furnace wherein they are constantly heated for 4 hours. The material, on exit is suitable to undergo Rolling. The furnace generates heat energy by the combustion of coal gas, which is produced in a coal gas plant located near by.
The furnace has three processes:-
The feeding of the raw material into the furnace is done with the help of conveyer rollers. The ingots are placed on the conveyer rollers manually; tongs are used in the positioning onto the conveyor system, which transports the raw material to the feeding bed. Once the ingots are stacked one after the other on the feeding bed, they are pushed into the pre-heating chamber of the furnace with a mechanism which consists of a worm gear pushing the ingots into the furnace. This mechanism is also controlled manually by a person due to discontinuity in feeding.
Entire Feeding Process
Mechanism used for pushing ingots
In the below figure, the entrance of the furnace can be seen and the feeding bed and the pusher are ready to operate. This type of operation decreases lead time and is comfortable while starting the plant again.
The pusher mechanism pushing ingots into furnace
The Heating Chamber or furnace is the chamber where the ingots are made molten, which makes it feasible to pass it through the rollers. The furnace is a fuel consuming chamber which works on coal gas. The furnace has a total of 8 burners. There is a preheating zone, which leads to the intermediate zone ultimately leading to the final zone.
The gas plant is where the coal gas is produced. There is a pipeline system which leads the gas to the burners. The peak temperature in the furnace goes up to 1200?C. The gas is streamlined to vary the temperature.
Lot of precaution is taken as there is immense heat in proximity to the furnace.
The furnace interior is made of refractory bricks to withstand the high temperatures. There are also certain doors at the side for inspection during maintenance. There is another controller near the exit of the furnace to guide the red hot ingots outside of the furnace and position them onto the rollers; leading them to the rolling mill.
The above picture shows the structure of the furnace. Several pipelines can be seen at the entrance of the furnace, for exhaust. The pipes present near the burners
Consist of the gas fuel pipeline. The doors or gates present at the side are used for inspection or to replace the refractory bricks during maintenance.
The 8 burners balance the heat such that there is uniform temperature. In usual practice the last 4 burners are usually varied.
Final furnace burners
The above figure shows the four burners placed inline. And the pipes are the carriers of coal gas. Usually during maintenance the pipes are cleaned and the soot is removed.
After heating, the ingot is ready for the roughing mill. Authorized personnel are stationed at various nodal points to navigate the heated raw material from the Furnace to the Roughing mill. The exit door is opened by the person who removes the ingot.
The furnace exit is shown in the above figure. The gate opens when an ingot is ready to be rolled and the rollers in the path provided, carry the heated ingot onto the roughing mill. This describes the process involved in the furnace.
Just after the ingot comes out of the furnace it is slowly led to the roughing mill. The roughing mill is the first mill among the three mills present there. The mills are operated with a high capacity motor. There is a gear reduction of ratio 1:6 to provide the necessary torque required for rolling. The roughing mill is where there is very slight elongation and gradually decreases in diameter and this is the main function of the roughing mill. There are three sets of rollers present in the roughing mill.
This figure shows the entire set of the roughing mill. There are three sets of rollers and each set has three rollers placed one over each other. Now the hot ingot is moved into the first roller. A single roller is something like described below
The single motor shaft is transmitted to three shafts through the distributer. The sequence of the alignment of the motor, couplings, bearings are as shown in the figure below.
Here is the order of the layout of the roughing mill. “C” stands for coupling and “B” stands for bearing. While entering the first set of the roughing mill it roles at about seven times at the same roller in different slots.
The different slots are shown in diag.2 which are the gray parts and the molten ingot passes through these slots and then manually put back into the next slot and after 7 times in the first set of rollers it moves through the guide way which leads it to the second set of rollers and again leading it through the third roller and then the roughing mill is over.
The roughing mill is where most of the elongation is done and the area cross section gradually decreases and the length increases. But the ingot is still in the molten state and it continuously moves on to the next rollers through the guide ways.
The motor used for the roughing mill has a capacity of 800HP. Enough power has to be produced to as the shaft power has to be divided among three shafts.
Roughing mill main motor
Here in the above picture it can be seen that on the motor shaft there is the coupling and the the bearing is present. This kind of setup gives proper stability and utilization of the shaft power.
In the following picture fig.12 the flywheel can be seen and then the bearing and followed by the coupling. After the coupling there is the gear box which later on goes to the 3 shaft divider.
The gear box used has a gear ratio of 1:6.Which shows that there is enough torque required in reducing the speed of the motor to about 6 times.
flywheel ; gearbox of roughing mill
After the roughing mill it passes to the next mill that is the intermediate roller and to actuate its movement out of the roughing mill there are some accelerators placed at certain intervals. These are called pinch rolls. There are springs on these pinch rolls which puts the pressure on the moving rod. The motor used in the pinch rolls have a power of 50HP.
When the rollers in a mill get worn out then the same rollers are machined at the machining section of the plant. Heavy lathe machines are used. When the dimensions of the rollers slightly vary they are compensated by the universal joint which is at the shaft attached to the rollers.
The slight angle between the shafts is visible in the above figure.
After the roughing mill it moves through the guide ways which are mostly made of cast iron and these guides also provide an open top jus in case the rod expands and comes out of the guide. The guide ways are sometimes placed with a cone which decreases miss alignment.
These guide ways helps the tip of the red hot rod to enter into the next roller that is the intermediate mill. This is the automated part of the mill which does not need the manual method of feeding like in the roughing mill.
Hence there are front and back cutters which remove the front and back tip of the hot rod as to allow proper entering into the next mill.
Fig.14 Shearer or cutter
Here the cutter blade is visible it moves in a to and fro motion and as the red hot rod is still soft it easily shears it. These shearers are sensory activated and are automated. The sheared waste pieces are put aside as scrap. They usually fall beside the cutter it self and are removed during maintenance. In the picture fig.15 the cut pieces are shown laying aside. These pieces actually fly off when they are cut. Shearing is easy as the rod is red hot and still not fully hardened. This helps in easy shearing of these pieces. The front and back tips of the rod are cut to enable it to freely pass through the next roller.
Pieces of rod cut from cutters
After every roller there is increase in the length of the rod which results in bending or misalignment while entering into the roller. For that reason there are some special cones placed while entering into the roller shown in the figure below.
47625064467These cones help the rod to enter in and align properly and go into the allocated grove in the roller. Without this it may result in the slipping or entering into the wrong grove. These are usually made of cast iron and are long lasting. They are made in such a way so it would be easy while changing or removing the setup.
After passing through the roughing mill, the rod is led into the Intermediate mill. It should be observed that, there is a considerable decrease of the size of the rod after passing through the Roughing mill. The main function of the Intermediate mill is to prepare the specimen for the finishing mill. The figure below shows the Intermediate mill. Each roller is placed adjacent to the other. The guide way can also be seen in the picture.
Fig. 17 Intermediate mill
This is the sequence of the intermediate mill. There is a speed increaser placed as shown. This facilitates for the smooth movement of the rod as the motor is incapable of giving the entire push to the rod. The speed increaser is placed wherever more thrust is required.
After the intermediate mill, two pinch rolls are placed. A Shearer is placed before the finishing mill.The picture shows the speed increaser. A pneumatic piston can be seen, which pushes the rod and presses it between the two rollers. A speed increaser is placed where more power is required. As all power cannot be given by the motor, auxiliary power is given by these speed increasers.
FIG.18 Speed Increaser
The picture shows a screw which is used to lower or heighten the roller position which is compensated by the universal joint. The rollers are machined at the plant itself which enables them to machine the same rollers even after they are worn out.
The finishing mill is the main roller where the required dimension is obtained. The rollers are made with precision and in such a way that the exact dimension can be obtained. Quality is of great importance, since the manufactured products are graded and approved by the ISI. This gives the company an edge over its competitors. The finishing mill also facilitates for the brand imprint to be put onto the rod. The picture shows the finishing mill.
FIG.20 Finishing Mill
The last three rollers of the finishing mill are placed inline. Separate motors are used for each roller. The motors can also been seen coupled to the rollers with shafts and universal joints.
Just before entering the finishing mill, two pinch rolls are placed to improve the speed and then, the red hot feed subsequently enters the roller through a
Shearer. The shearer is placed in such a way that the force of the rod itself removes its tip. The schematic below describes the entrance of the finishing mill.
The final dimensions of the TMT steel bar are achieved by finishing rollers. The rods, after passing through the finishing rollers; are still soft due to high temperature. There is a special guide way present after the finishing rollers which leads the rods to the TMT quenching box. The conic shaped guide way helps in the alignment of the rods while movement to prevent torsion.
FIG. 21 conic guide ways
Before the finishing mill there is a Shearer which cuts the edge suitably, to enter the finishing mill. The sequence of the finishing mill is shown below.
TMT QUENCHING BOX:
One of the most important parts of the plant is the TMT box where the hardening takes place. Water is sprayed on the red hot rod to reduce the temperature abruptly which results in the hardening of the outer surface of the rod. The amount of hardening depends on the pressure of the water from the nozzle.
FIG.23 TMT quenching box
This fig. shows the quenching process. Various pipes can be seen which carry water and several gauges are present for the measurement of water pressure. The pipes in blue show the passage, through which hot rod passes.
The rods are made to fall on the cooling bed after the TMT treatment, but the speed of the rods is too high due to the motor power and various pinch rolls. Hence to reduce the speed before the rod on exit, a breaker is used. It reduces the speed of the incoming rod.
The breaker provides safety to the labor and prevents accidents.
FIG 24 BREAKERS (SPEED REDUCER)
The finished products are then organized for Dispatch.