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A NEW PROCESS FOR CONTINUOUS DISCHARGE OF SLABS FROM WALKING BEAM FURNACE OF PLATE MILL
FIELD OF THE INVENTION
The present invention relates to a new process for continuous discharge of slabs from walking beam furnace of plate mill. More particularly the present invention is related to a method of step charging of slabs in the furnace for eliminating the down time of the mill after rolling two slabs, thereby increasing in rolling rate of the mill, and increasing the mill utilization and productivity.
BACKGROUND ART
The invention is applicable to Walking Beam Furnaces of plate mill. In plate mills, the furnaces are provided with four skids. Generally slabs are charged in side the furnace in two rows. The left side row and the right side row. Two skids are used to form a row. The slabs are pushed in side the furnace by the pushers on the charging side and are operated from the charging pulpit. The slabs are extracted from the furnace by the extractors and are operated from the discharge pulpit. The activities involved in charging and discharging of slabs in the furnace are -
1. Spot the slab before the left side pusher.
2. Open the door.
3. Push the slab inside the Furnace.
4. Take back pusher to the original position.
5. Close the door.
6. Bring the slabs to right side pusher.
7. Centre the right slab.
8. Open the door.
9. Push the right slab.

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10. Take back the pusher to the original position.
11. Close the door. (These activities 1 to 11 take 1 min. 45 sec. and
carried out from charging pulpit.)
12. Forward the beam by 2/3 steps. (One step takes 50 seconds)
13. Wait for the beam position ready for extracting.
14. Take the extractor to "in position".
15. Lift the left side arm.
16. Take out the extractor with the slab.
17. Lower down the arms to keep the slab on the roller table.
(Activity 14 to 17 takes 45 seconds and carried out from discharge pulpit.)
After discharge of 2 slabs from the furnace the activities are repeated. PROBLEMS EXPERIENCED
After discharging the right side slabs activity 1 to 17 is continued. This takes (1 Min. 45 Secs. + 2 Min. 30 Secs. (3 steps) + 45 secs.) 5 minutes to complete the cycle. But the rolling of the right side slab takes max. 3 minutes. Hence, the Mill remains idle for 2 minutes. In other wards after every 6 minutes the Mill goes down by 2 minutes. So, rolling of 14 to 16 slabs take place in one hour. In case of any breakdown there is no scope for making up the production in the subsequent hours. Scale formation on the slabs is more, if the slab remains inside the furnace for a longer period and there is wastage of heat energy also.
SUMMARY OF THE INVENTION
Therefore, it is the primary object of the present invention to modify or rectify the error-prone and long, tedious old process for the discharge of slabs from from walking beam furnace of plate mill. The present invention provides a new process for continuous discharge of slabs. More particularly the present invention

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is related to step charging of slabs in the furnace in order to ensure stable, reliable data and continuous discharge of slabs.
In accordance with the present invention, the new process has been devised to eliminate the down time of the mill after rolling two slabs.
As per another aspect of the present invention in order to eliminate the down time of the mill, the rolling rate of the mill is increased thereby increase in mill utilization and increase in mill productivity.
By providing the faster rolling rate there is a considerable reduction in heat consumption and power consumption is achieved and thereby reduction in the off grade diversion of the slabs.
In accordance with an advantageous feature, the scale formation in the slabs is drastically reduced and thereby increase in tested acceptance of the slabs.
In accordance with another advantageous feature, the profit margin is increased.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which;

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FIG. 1 is a schematic illustration of the portion of a conventional existing hot rolling train before the implementation of the process;
FIG. 2 is a schematic illustration of the portion of a hot rolling train after the implementation of the disclosed process.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In plate mills, the slabs are charged in side the furnace in two rows namely left side and right side rows. Two skids are used to form a row. The furnaces are provided with four skids. The slabs are pushed in side the furnace by the pushers on the charging side and are operated from the charging pulpit the left side row and the right side row. The slabs are extracted from the furnace by the extractors and are operated from the discharge pulpit.
In the prior art (Ref fig1) two slabs are charged on both the beams of the Furnace. Slab of the left beam is extracted first. Rolling of the first slab takes about three minutes. After that right slab is extracted and rolled which also takes three minutes time. After extracting the slab of the right side beam, two slabs are charged, one on left beam and other on the right beam. This process was taking 3 minutes & 30 seconds. Then the beams are moved forward by 2 steps in 1 minute and 40 seconds. Hence, a total time of 5 minutes & 10 seconds was needed to extract the left side slab. Thereby the Mill was going idle for 2 minutes and 10 seconds. In other words about 2 minutes time is lost after rolling out two slabs. Hence, Maximum 15 slabs were rolled in 1 hr. This was the main constraint in increasing the rolling rate.
The drawbacks associated in the prolonged lengthy process of charging and discharging is overcome by a novel process known as STEP CHARGING of slabs in the Furnace.

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In the step charging process the centered slab is kept in front of the left side pusher.The furnace door is opened and the slab is pushed inside the furnace. The pusher then taken back from the furnace and the doors are closed.The beam is then forwarded by one or two steps and then the next slab is brought in front of the right side pusher The slab is centered with respect to the pusher and the furnace and then waited for the pushing signal On getting the signal the slab is pushed inside the furnace and then pusher is taken back from the furnace and the door is closed
The beam is again forwarded by one or two steps depending upon the width of the slab and then again waited for the discharge signal in the discharge pulpit. On getting the ready signal the extractor is taken to "in position" and the left side arms are lifted. The extractor is then taken out from the furnace with the left side slab. The arms of the extractor are lowered and the slab is kept on the roller table. The beam is forwarded then for one or two steps This created a gap on the left beam on the charging side, and the centered slab on the left side is pushed in. Then the same aforesaid process is repeated for extracting the right side slab on the discharge pulpit. The beam is then forwarded by one or two steps. This created a gap on the right side beam on charging side and the centered slab is pushed in. Hence, the process became continuous and slabs are charged and discharged simultaneously from the furnace.
Fig 2 is a schematic illustration of the portion of a hot rolling train after the implementation of the aforesaid disclosed process. After charging the slab on the left side beam of the furnace the beam is moved one step forward. Then the slab on the right side beam is charged and the beams are moved forward by one step. In the process the left side slab reaches the discharge side first and takes 3 minutes to be rolled out. During this period the beam is allowed to move one step forward which takes about 50 seconds and charging of 1 slab takes about 1 minute & 45 seconds. In other words within 2 minutes and 40 seconds the

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furnace is ready to discharge one more slab. Hence, no time is lost in charging and extracting a slab before the Mill goes idle.
While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles

8 We Claim:-
1. A process for continuous discharge of slabs from walking beam
furnace of plate mill comprising the steps of:
placing the slab in front of the left side pusher in a centered position;
opening the furnace door;
pushing the slab inside the furnace;
taking the pusher back from the furnace and thereby closing the door
of the furnace;
forwarding the beam by one or two steps and then the next slab is
brought in front of the right side pusher;
placing the next slab in front of the right side pusher in a centered
position and waiting for the pushing signal;
pushing the slab inside the furnace on getting the signal and then
taking the pusher back from the furnace and thereby closing the door.
2. A process for continuous discharge of slabs from walking beam
furnace of plate mill as claimed in claim 1, further comprising the steps
of:
pushing the extractor inside the furnace on getting the ready signal;
left side arms of the extractor are lifted;
left side slab from the furnace is extracted and arms are lowered for
keeping the slab on the roller table;
the process is repeated for extracting the right side slab and the beam
is forwarded.
3. A process for continuous discharge of slabs from walking beam
furnace of plate mill as claimed in claim 1, further comprising the steps
of:
repeating the process of charging the left side slab to the furnace after extracting the right side slab from the furnace.