CLIAMS:We Claim:
1. A system for removal of furnace discharge hearth scale from the combined walking beam furnace comprising
- Means provided at the bottom of the scale window(W) of the furnace to direct the scale into the flushing trough (T)
- means to open the door of scale extracting window
- means to drag the scale towards outward from the window towards the slanted plate(I) welded below the window(W), by a scrapper welded to a 5 meters rod
- a flushing trough(T) provided with a plurality of jet nozzles(J1, J2, J3, J4) for spraying pressurized water jet to ensure the flow of the scale through the flushing trough(J) directing the quenched scale into the scale pit.

2. A System for removal of furnace discharge hearth scale as claimed in claim 1, wherein the means provided at the bottom of the scale window (W) of the furnace to direct the scale into the flushing trough is a slanted plate(I) attached to the flushing trough.

3. A System for removal of furnace discharge hearth scale as claimed in claim 1, wherein the means for opening the window door are door opening tools.

4. A System for removal of furnace discharge hearth scale as claimed in claim 1, wherein water pressure jets are welded at four different stages, along the length of the trough.

5. A System for removal of furnace discharge hearth scale as claimed in claim 1, wherein the mechanism to drag the scale is a scrapper welded to a cylindrical rod(R) of at least 5 meters in length of diameter of about 20 mm and supporting the rod on the support plate welded on the trough(T).

6. A system for removal of furnace discharge hearth scale as claimed in claim 1, wherein trough is fixed at a inclination of ratio of at least 1:1.92, along the width of the furnace, parallel to the scale extracting doors.

7. A process of removal of furnace discharge hearth scale from the combined walking beam furnace comprising the following steps-
- dragging the scale manually into the scale flushing trough(T) with scrapper,.
- flushing the scale through trough with the help of water jet, wherein
- the flushing water pressurized at regular intervals along the length of the flush pipe by means of nozzles(J1, J2, J3, J4), the pressurized water facilitates the hot scale to get cooled immediately and also getting flushed towards the exit of the pipe, directing the scale into the scale pit tunnel.

8. A process of removal of furnace discharge hearth scale as claimed in claim 7, wherein the scale is dragged out into the flushing trough, without stopping the furnace activities while furnace is operating at its full capacity keeping the process of rolling active.

9. A process of removal of furnace discharge hearth scale as claimed in claim 7, wherein the scale removed per amount of time is less as such the scale do not stay and get quenched and flushed to the scale tunnel immediately.
,TagSPECI:Field of the Invention:

The invention relates to a system for removal of hearth scale from reheating furnaces in rolling mills, in particular for scale removal from combined walking beam type reheating furnaces to avoid sticking of scale to the discharge hearth furnace. The scale is removed during the continuous rolling process without stopping the rolling process.

Background of the invention

In Wire Rod Mill (Hot rolling mills) in steel industry, combined reheat walking beam furnace are utilized to reheat the billets/blooms/slabs to attain the uniform rolling temperature prior to hot rolling in a continuous mode for hot rolling mills. The billets are fed into the furnace from the charging side at atmospheric temperature. The billets shift towards charging side batch by batch, by the movement of the walking beam cycle. The furnace is divided into four temperature zones. The billets gain the temperature as it is exposed to the zone temperatures. During this process, the hot steel surface of the billets react with oxidizing atmosphere inside the furnace, which results in the formation of a layer of Iron oxide or which commonly known as scale in steel industry.

As the billets move from the hearth surface to the skid post area, the scale falls into the furnace during the operation of the furnace cycle. The scale formation at the soaking zone is very high as compared to the pre-soaking zone. The billets are pushed on to the discharge hearth before it is discharged, out of the furnace for the rolling from the furnace hearth surface. The scale which is carried by the hot soaked billets gets accumulated on the hearth surface. The scale has to be removed continuously during the process of rolling, as the batches of the billets continuously carry the scale on the top of the hearth. The scale which gets deposited on the hearth has to be removed by scrapping process when it is in loose state. If it is not removed in loose state the scale becomes hard and gets stuck to the hearth’s refractory blocks. After which it cannot be removed manually by scrapping process. The scale which gets stuck on hearth surface obstructs the movement of the billets to get discharged, resulting in the displacement of the hearth blocks, which obstructs the billets movement during the walking beam cycle. These damage to the discharge hearth blocks lead to stoppage of rolling. The repair of the hearth blocks has to be carried out after stopping the furnace at the cost of production. Frequent stoppage of the furnace, which happens due to the, scale stuck up to the hearth which becomes integral part of hearth blocks if not removed for a longer period. The stoppage adversely affects the discharge hearth blocks life and also results in heavy production loss and unscheduled capital or major repairs.

Prior Art:

Prior to this invention the only way to remove the scale from the hearth was to drag the hot scale into a wheel barrow manually by using a scrapper and directing the scale into the wheel barrow. After that the wheel barrow full of scale is carried out to the nearest scale fume tunnel. The scale from the discharge hearth could be removed only during the rolling stoppage or shut down day or pass change day, as during the dumping of the scale into the scale tunnel the expose of the rolling billets and the hot scale temperature while carrying through wheel barrow to the human being is highly unsafe due to high temperatures. The scale on the hearth can also be removed by stopping the rolling process and emptying the hearth. To scrap the scale on the hearth towards inwards, so that the scale will fall into the gap below the skid posts the accumulated scale has to be removed. This could be removed only during the complete shut down of the furnace and only after the temperature of the furnace is low enough for the safe entrance of persons, who are engaged to lift the scale manually an dump into an scale pit near by. The generated amount of the resulted scale is very high in quantity and the removal amount of scale is very less due to the process of manual removal by using the wheel barrow or by the method of scrapping into the empty gap near the skid post base.

Japanese Patent No. JPS6050848 teaches to discharge the scale on the hearth without stopping a heating furnace of an intermediate charging and walking type and without carrying out the material from the furnace inside by providing a scale hopper, a scale discharging hole and a scale hopper in the specific positions of said furnace. A scale discharging hole 15 is provided on the stationary hearth 4 nearer the furnace top side than the port 5 and a scale hopper 15a is provided thereunder. A scale hopper 16 is provided below the opening in the divided parts of the hearths 8, 9. The ordinary cycle of the hearth 9 is interrupted in the stage of a scale discharging operation, and the hearth 9 is raised from the set stand-by point W of the start point up to the position D' slightly higher than the hearth 4 and after the hearth is retreated to C', the hearth is moved to the position B' slightly lower than the hearth 4 and to the point W', then the ordinary cycle is resumed. It is possible to discharge continuously the scale

The factor affecting the amount of scale generation depends on the soaking and rate of rolling. It is very clear that the problem of scale deposition is common in combined walking beam furnaces and the removal of heavy generated scale form the discharge hearth is difficult and unsafe by the above process.

On one hand the removal of the scale is necessary for the uninterrupted process of rolling, and on the other hand the process of manual removal of the scale by using the wheel barrow, and dumping the scale to the nearest scale fume tunnel is highly unsafe and accident prone and leads to fire accidents also fire burns, to the human beings.

Object of the Invention:
The object of the present invention is to avoid the scale sticking to the discharge hearth blocks which occurs due to the long stay of the scale on the hearth. Previous to this invention, the frequency of scale removal is less due to the unsafe process of scale dragging into the wheel barrow and carrying manually to dump into the nearest scale fume pit. The incidents of fire burns and fire incidents during the process of dumping the scale into the scale pit are also removed by the inventive method. The damage to the discharge hearth blocks is lessened, which gets lifted up during the process of billets pushing by the discharging machine, due to the uneven surface formed on the base by the deposition and sticking of scale on the hearth block.

The another object of the present invention is to provide a safe and speedy system of scale removal from the hearth of combined walking beam type reheating furnace of Wire Rod Mill, which requires less effort and is a safe method of removal of the huge amount of scale generated. The present process is carried out safely during the process of rolling of billets. This also avoids any fire accidents and incidents which occur during the dumping of scale into the nearest scale fume pit at the time of dumping during the mill stoppage day, which happens due to the absence of water and presence of oil in the scale pit.

The another object of the invention is to totally avoid the exposure to the high temperatures (1100 degrees Centigrade), to the persons who drag and carry the scale into the wheel barrow to the nearest scale fume pit. The scale is dragged from a long distance, to avoid the expose of high furnace temperature to the person’s body.
Another object of the invention is to match the frequency of the scale removal from the hearth of walking beam furnace with that of the quantity which is generated during the continuous process of rolling of billets. The scale, fallen into the pipe trough is flushed to the scale pit nearest to the furnace, in this case the scale is flushed and directed towards the scale pit near the billet discharging machine, which operates to push the billets from the furnace to the Mill.

Detailed description
The present method of scale removal from the discharge hearth is cost effective and safe method adopted to remove the scale manually by using a long scrapper and is simple to carry out, in particular, from the combined walking beam type reheating furnaces of rolling mills.

The basic aspect of the invention is to flush the hot scale which is generated during the rolling process and stays on the discharge hearth. The scale is shifted towards the scale extracting windows, during the process of the placement of billets on the hearth by the walking beam furnace moving skids.

The flushing process is carried out by the water jets created by the reducers welded at the end of the flushing pipeline. The hot scale is forced and directed towards the scale tunnel by means of water jets provided at different intervals, along the scale extracting doors, on the top of semi opened pipe trough. The frequent, unscheduled stoppage of the furnace, for the repair of the damaged hearth block is total avoided by this method.

The scale door opened manually by the door opening tool. The scrapper welded to the 5 meters rod of diameter 20 mm is used to drag the scale by supporting the rod on the plate welded on the pipe. The scrapper is pushed inside the scale door by sliding. The weight of the scrapper assembly is selected on the base of a weight to be lifted by a person manually and to rest it on the support plate.

According to an embodiment a system for removal of furnace discharge hearth scale from the combined walking beam furnace comprising
- means provided at the bottom of the scale window of the furnace to direct the scale into the flushing trough
- means to open the door of scale extracting window
- means to drag the scale outside the window towards the slanted plate, by a scrapper welded to a 5 meters rod
- a flushing trough provided with a plurality of jet nozzles for spraying pressurized water jet to ensure the flow of the scale through the flushing trough directing the quenched scale into the scale pit.

The scrapper welded to the 5 meters rod of suitable diameter is used to drag the scale by supporting the rod on the support plate welded on the flushing trough.

The system of flushing of the scale means the dragging of the scale into the inclined pipe of an inclination of 1:1.92. The scale is directed to fall into the scale flushing trough, through the slanted plate which guides the entire scale, when dragged by the scrapper, into the opening of the trough. Water pressure jets are welded at three different stages, along the length of the trough.

According to another embodiment a method of removal of furnace discharge hearth scale from the combined walking beam furnace, the method comprises-
- dragging the scale manually into the scale flushing trough with scrapper.
- flushing the scale through trough with the help of water jet.

The process of directing the scale to the scale fume tunnel at one end, by means of the pressurized water system, diverted from the supply of mill water system. The scale is dragged out into the flushing trough, without stopping the furnace activities while furnace is operating at its full capacity and the process of rolling is not stopped. The scale removed per amount of time is less as such the scale does not stay and get flushed to the scale tunnel immediately.

The material of the flat portion of the plate is selected to be cooled after it gets hot while entering into the furnace, which is welded at the end of scale scrapper, is then moved behind the scale and the scale is dragged outside the scale extracting door. The shape and size of the flat portion is selected based on the clearances at the entry of the scale extracting doors.

The red hot scale is pulled towards outside, the scale then falls on the slanted plate welded to the bottom of the scale window, which directs the hot scale to fall into the flushing trough .The plate also has sideways diverters, so that the hot scale do not spill outside and ensure the entire mass to fall directly into the scale flushing unit.

The hot scale after falling into the flushing unit comes into the contact of high pressure water flow. The quenched scale follows the path of the water flow, towards the slope downwards. The scale along with the water, flow along the pipe bend and finally falls out into the scale tunnel below the open end of the pipe.

The process is repeated until the entire scale was flushed out of the window. The window is closed manually by means of the window open/close tool. The process of the scale removal form the hearth is carried out once in 8 hrs. The process is carried without stopping the production. During the production the billets are pushed from the hearth to outside, and during the process of pushing of the billets the scale is also dragged towards one end, i.e. towards scale extracting windows.

The process of scale removal manually is carried out for different windows as such entire scale generated on the hearth is flushed out. The flushing water pressurized at regular intervals along the length of the flush pipe by means of nozzles. The pressurized water facilitates the hot scale to get cooled immediately and also getting flushed towards the exit of the pipe , which directs the scale into the scale pit tunnel.

As the scale is removed from a distance of 5 meters the effects of high temperatures on workers is eliminated. Thus it is a very safe method of the scale removal. The scale is also quenched before going to scale pit hence there is no chance of the fire incidents can occur.

By this inventive scale removal method, the production loss due to the stoppage of the furnace, for the repair of the damage occurred on the furnace hearth surface by long time scale accumulation and low frequency of the scale removal system is reduced. It is also to a safe and cost effective method of removal of the scale from the discharge hearth of the combined walking beam furnace of Wire Rod Mill.

The present technique is further described hereinafter with reference to the accompanying drawings, wherein

Fig 1: is showing a scrapper welded to a rod .
Fig 2: is showing the door opening tool.
Fig 3: is showing flushing pipe with scale window and inclination arrangement

Fig: 1 shows the scrapper used in dragging the scale from the hearth to the slanted plate (I) welded to the bottom of the scale window (W) to direct the scale into the trough (T). The scrapper is welded to the 5 meters rod(R) of suitable diameter which is used to drag the scale by supporting the rod on the support plate(S) welded on the flushing trough. The slanted plate (I) welded below the window(W), directs the hot scale to fall into the flushing trough .The plate also has sideways diverters(D), so that the hot scale do not spill outside and ensure the entire mass to fall directly into the scale flushing unit.

Fig: 2 shows the door opening tool used to open the door of the scale window (W). It is a rod with a bend of triangular shape at one end to hold manually and other end is having a bend of 90 degree to facilitate the hooking of the door handle to drag the door out.

Fig 3 shows the flushing pipe arrangement though which the scale is flushed out to the scale pit. Water pressure jets (J1, J2, J3, J4) are welded at four different stages, along the length of the trough (T).
The flushing process is carried out by the water jets (J1, J2, J3, J4) created by the reducers welded at the end of the flushing pipeline. The hot scale is forced and directed towards the scale tunnel by means of water jets(J1, J2, J3, J4) provided at different intervals, along the scale extracting doors, on the top of semi opened pipe trough(TS). The hot scale after falling into the flushing unit comes into the contact of high pressure water flow. The quenched scale follows the path of the water flow, towards the slope downwards. The scale along with the water, flow along the pipe bend and finally falls out into the scale tunnel below the open end of the pipe.

While the present invention has been described in detail with reference to a preferred embodiment, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the invention as set forth in the appended claims.