Pushing machine moveable on rail for operating into the slag hole of steel smelting electric furnaces

A pushing machine is described, which is capable of running to opposite directions, upon remote control, along a length of rail provided in front of the mouth or slag hole of an electric furnace (10) for the smelting of iron products. It shows, at the end of an arm (5, 5a) telescopically extensible and preferably pivoting to be able to swing also in the vertical plane, a head or front shield (6) mounted on a frame (1) which can be anchored to the ground and is slidable on rails by means of wheels (2, 2' . . . ), at least two of which are driving wheels. Said shield (6), having a size slightly smaller than the slag hole, has the function of keeping the scrap at the inside of the furnace during the charging operation and keeping the threshold free of the slag without any operator's intervention.

FIELD OF THE INVENTION 
The present invention relates to a pushing machine movable on rail, adapted 
to operate into the slag hole of electric furnaces for smelting of steel 
or iron products in general, to be remotely controlled. 
BACKGROUND OF THE INVENTION 
It is known that the electric furnaces for smelting of iron based scraps 
being directly discharged from the top have a front opening, also called 
"slag hole" whose threshold or lower step forms the so-called "dam" 
suitable to keep the molten bath within the furnace and to be overflown by 
the slag only, which then is drained at an underlying level through a trap 
provided on the floor immediately at the outside of the slag hole. The 
latter also provides the passage for the oxygen lance through which oxygen 
gas is blown at very high speed directly into the melting zone for 
refining the melt. 
Also some important inconveniences are known, in connection said slag hole 
and with the presence of mainly deriving from the top charge of the scrap, 
which causes the obstruction, at least partial, of the so-called "slag 
runner" which connects the outer mouth of the hole with the molten bath 
and must remain unobstructed, in particular to allow the oxygen lance 
without obstacles. 
On the other hand it is also known that usually it is necessary to await 
that a cast is over to carry out, before the subsequent one begins, the 
so-called operation of "slag hole cleaning", in other words removing the 
slag, now cooled, that has deposited on the threshold of said hole, as 
well as remaking the "dam". Of course this involves longer standstill 
times between one cast and another, with consequent reduction of the 
production capacity, since it is impossible to carry out these operations 
by hand with the electrodes being fed, near high temperatures and with the 
operators under the danger of being hit by sparks or jets of molten metal. 
Not only, but the removal of eventually cooled, solid slag, forming an 
integral block with the underlying step of refractory material (usually 
dolomite), resulted in a substantial demolition of the step itself or 
"dam" and its remaking, with an additional extension of the plant 
standstill time. 
It has been thought of over coming these inconveniences by using a power 
shovel that can hold the batch of charged scrap at the inside of the 
furnace while keeping the slag runner free, but the required presence of 
an operator on board renders extremely dangerous and nearly impossible 
this solution unless the operator of the mechanical shovel undergoes 
unlikely performances such as the temporary leaving of the vehicle as the 
material drops. Similarly unfeasible results to be the cleaning of the 
slag hole with active electrodes, when considering the high electric power 
involved (up to 65 MW). 
Therefore the object of the present invention is that of providing an 
apparatus capable of carrying out the above-mentioned operations, under a 
remote control and without the presence of an operator on place. 
With the pushing machine according to the present invention, during the 
scrap charge into the furnace a first series of advantages is obtained, 
among which the most apparent one is that of preventing the scrap from 
escaping the slag hole, thus increasing the yield, i.e. the ratio between 
produced steel and charged scrap. Another important advantage in this 
stage is that the slag runner, as above defined, is kept free and the 
scrap drops entirely within the furnace, not on the threshold thereof, 
where it would be lost, thus reducing even more the yield, and wherefrom 
it should have to be removed with difficulty once solidifyed, with a 
partial demolition of the threshold itself which then should have to be 
restored. Furthermore the completely free slag runner means immediate 
exploitation of the oxygen in the zone where melting occurs, without 
danger of damaging the lance and anyhow without possible presence of scrap 
between lance and melt bath which would interfere with the oxygen blow, 
thus reducing its speed and shielding the temperature gradient. 
Another series of advantages afforded by the pushing machine according to 
the present invention is due to the fact that it can be used for cleaning 
the slag hole and remaking of the dam at about half casting, when for 
example the electrodes have delivered a prefixed quantity of specific 
power (such as for example 200 KWh/ton) and are still active. Thus the 
power delivery is not interrupted and the standstill time between two 
subsequent casts is strongly reduced, while the slag overflow level is 
ensured, as the height of the head shield, being controlled to have the 
fixed values, keeps automatically constant such a level, thus slag is 
removed when it is hot, thereby extremely crumbly, without problems of 
re-building the dam with additional dolomite, all this occurring without 
any personal intervention, what would clearly involve some risks. 
SUMMARY OF THE INVENTION 
Briefly stated, the present invention comprises a pushing machine 
travelling on a rail for operating in the slag hole of steel smelting 
electric furnaces. The pushing machine comprises a support frame having a 
front zone and a rear zone mounted on a plurality of sliding wheels, at 
least two of which are driving wheels. A motor is mounted on the support 
frame for driving the at least two driving wheels. An extensible arm is 
mounted on said support frame and includes a front shield having a 
cross-section slightly smaller than the opening of said slag hole of the 
furnace. Anchoring means are provided for anchoring said support frame to 
a fixed location and means for remote control operation of forward and 
backward movement of the machine, and for separately remotely controlling 
extension and retraction of the extensible arm and the operation of the 
anchoring means are provided.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
With reference to the drawings, the pushing machine according to the 
invention essentially comprises a metal frame 1, mounted on four wheels 
(which could also be of greater number), at least two of which are driving 
wheels. In the drawings the rear wheels 2, 2' are assumed to be driving, 
whereas the front ones 2a, 2'a are driven. A geared electric motor 3, 
having for example a power of about 4 HP, directly actuates, through 
suitable drive mechanisms, a driving axle 3' at the ends of which there 
are mounted the wheels 2, 2', thus being able to develope a speed of about 
20 m/min. The electric feeding of the geared motor 3 is accomplished 
through an electric cable wound on a reel 13, which is sidely mounted on 
the frame and is designed to automatically release the cable by unwinding 
the same at approaching the machine to the furnace 10 and vice versa 
re-winding it automatically when the machine is caused to move backwards. 
On the frame 1 there is centrally mounted an extensible arm formed of two 
coaxial tubes 5, 5a, here shown as having a square cross-section, which 
however could have any different cross-section shape, at the end of the 
inner one, designated 5a, there is integrally provided a metal head or 
shaped shield 6 that forms the actual tool of the apparatus. The tube 5a 
of smaller cross-section slides within the outer tube 5 as it is fixed, 
preferably at its end zone near to the head 6, as better shown in FIG. 3, 
to a central piston rod of a piston-cylinder 15 having the cylinder 
fixedly mounted to the outer tube 5 of the extensible arm. It preferably 
shows stiffening ribs 12 spaced along the length and is supported on the 
frame 1 through a cradle formed of two vertical brackets or lugs 11, 11' 
between which a pin 17 is mounted. About pin 17 two holed flanges 21 can 
rotate, which are fixed to the outer tube 5 and consequently the 
extensible arm. In a rear side zone of tube 5, its outer surface is also 
fixed to the piston rod, preferably having a fork shape 19, of another 
cylinder 16 which is vertically mounted on the frame 1. Both cylinders are 
operated by a pressurized fluid means such as air or preferably oil, in 
the latter case there being provided a hydraulic system formed of a tank 7 
and a pomp-motor unit 4 also fixedly mounted on the frame 1 of the machine 
and fed by an electric cable, other than that for feeding the geared motor 
3. Both cables are independently wound on the reel 13 and through remote 
controls (not shown), preferably doubled in a control deck and in an 
emergency push-button panel hanging on the sliding floor of the machine, 
the forward and backward movements or the stop of the machine itself are 
controlled, as well as of forward, backward, upward and downward movements 
of the extensible arm. 
Still with reference to FIGS. 2 and 3 there are preferably provided, near 
the rear wheels 2, 2', anchoring means to the ground, mounted in the 
central zone of the frame 1 at a distance therebetween equal to about the 
distance between the wheels and formed of two vertical posts 8 
longitudinally movable with reciprocating movements as being actuated by a 
driving cylinder 18. The stroke of posts 8 is such as to reach downwards a 
position lower than that of contact rail-wheels, thereby the posts can 
firmly fit into seats formed in the rails themselves or the surrounding 
floor so that the pushing machine is anchored during its operating 
manoeuvres, in particular during the forward movement of the extensible 
arm with shield 6, thus avoiding that by reaction the frame 1 can move 
backward and the push onto the scrap to be kept within the furnace may 
fail. The cylinders 18 will be preferably fed through the same hydraulic 
system comprising the pump 4 and tank 7 upon controls that are also of the 
remote-type, different from those provided for operating the extensible 
arm. This anchoring means can of course show any other different 
embodiment known in the art. 
Finally the pushing machine according to the invention will be preferably 
provided with front horizontal studs 9, 9' mounted on bumper plates 23, 
23' fixedly mounted onto the frame and positioned before the front wheels 
2a, 2'a to shield them from impacts. The two front studs 9, 9' are 
designed to fit into corresponding holes (not shown) formed in metal 
seats, such as rail sections, embedded in the structure 20 or retaining 
wall placed before the threshold of the slag hole, against such a wall the 
pushing machine being blocked at the end of its forward stroke. Thus it is 
avoided that the machine may undergo a tilting moment during the operation 
of cleaning and remaking of the dam or in general when the arm 5, 5a is 
swinging in the vertical plane. 
From the foregoing it is clear the operation of the pushing machine 
according to the present invention, which will be moved forward, with 
shield 6 completely retracted, until reaching its stroke end where the 
anti-tilting studs 9 are fitted into the seats of structure 20, whereafter 
the anchoring posts 8, 8' are lowered and the machine is ready for its 
action through extension of the inner arm 5a to carry the head shield 6 
near the melting bath, thus ensuring that the slag runner 10a is kept 
clear of scrap during the subsequent charge. Possible manoeuvres of 
movement can be carried out also in vertical direction, when it is 
required to push to the inside of furnace 10 pieces of scrap which may 
assume undesired positions. As the charge is over and melting is at 
beginning, the machine can move backward to allow the introduction of the 
oxygen lance through the runner 10a, for the direct action of refining 
onto the molten product. The lance, whose direction is controlled from 
outside, is not subject to the risks of damages since the runner is free 
and the oxygen, flowing at a speed that can be even supersonic, is blown 
in till the inside of the molten bath. 
Subsequently, at about half casting, when the electrodes have delivered a 
prefixed quantity of energy, e.g. 200 KWh/ton, as measured at the control 
deck the oxygen lance is withdrawn and the pushing machine is caused to 
move forward again to perform the cleaning and the dam re-building 
operations, thus ensuring the overflow level of the slag being constant. 
This operation, carried out with subsequent forward and backward movements 
of the movable arm, with possible displacement also in the vertical plane 
to augment the mechanical action on the slag itself, occurs easily upon 
remote control of an operator who is however able to observe the working 
area. It will be noticed that when working in these conditions, the slag 
is at high temperature, thereby is crumbly and easily removable from the 
underlying layer of dolomite or other refractory material which does not 
require demolitions and subsequent re-building. Mention has been already 
made before about the advantages in terms of time, of operating in this 
stage without prolonging the waiting time between two subsequent casts.