US1968443A

US1968443A - Means for heating metal for rolling

Info

Publication number: US1968443A
Application number: US620676A
Authority: US
Inventors: Emerson L Clark; Earl W Clark
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-07-02
Filing date: 1932-07-02
Publication date: 1934-07-31
Anticipated expiration: 1951-07-31

Description

y 3 93 E. L. CLARK EAL 1,968,443

I MEANS FOR HEATING METAL FOR R OLLING Filed July 2. 1932 2 Sheets-Sheet 1 v INVENTORS 6M1 W. M.

July 31, 1934. E. CLARK ET AL 1,968,443

MEANS FOR HEATING METAL FOR ROLLING Filed July 2. 193?. 2 Sheets-Sheet 2 so on the steel during the heating process.

Patented July 31, 1934 Emerson L. Clark andoll'lfiarl W. Clark, Hartford,

Application July 2, 1932, Serial No. 620,676

3Claims.

This invention relates to the process of and also the means for preparing and heating, preparatory to further rolling or forming, metallic substances such, for example, as slabs from the I blooming mill.

One of the primary objects of our invention is to so prepare and-heat the slabs that they are supplied to the mill for rerolling with all surfaces substantially free from scale. A number of important advantages are secured by supplying the mill with scale-free steel. For example, the finished product, as it leaves the mill, will have a uniformly good surface and will be free from scale pits and scale scratches. These surface defects, due to the present strict specifications of the purchaser, cause heavy rejections and losses in present rolling mill practice. In present practice high pressure water sprays are directed onto the steel to remove the scale which has formed These sprays cause a drop in the temperature of the steel amounting to several hundred degrees and when rolling the lighter gages the finishing temperature is much lower than is necessasry to secure the character of finish desired. Further, it is necessary, due to the loss in temperature caused by the hydraulic sprays, to heat the slabs in the furnace to a higher temperature than is necessary for rolling and this high temperature causes additional scale to form on the slabs and frequently also causes the scale to combine with the steel in such a manner that the scale cannot be removed by the sprays.

When rolling slabs heated by our process and type of furnace the present hydraulic sprays are not necessary because the slabs will be free from scale when they are supplied to the mill. Further, the cooling action of the sprays being absent it will not be necessary to heat the slabs to so high an initial temperature. A direct saving in.

fuel is thus effected due to the lower quantity of heat energy imparted to the slabs and the smaller quantity of heat radiation losses from the furnace due to lower temperature of operation. Again, with our process, the hydraulic sprays not being required, the steel loses less heat during the rolling operation and can be rolled and finished at a higher temperature than is nowpossible. A saving is thus effected in the power required for rolling and the rolling machinery will'be subject to less wear and breakage due to the lower roll neck pressures resulting from the higher temperature of the steel. I

In present rolling 'practicathe scale formed 66 on the slabs during the heating is not completely removed by the hydraulic sprays and becomes imbedded in the steel and accumulates in the guides, troughs and on the table aprons. The abrasive action of this scale causes rapid wear of the roll surfaces and also scratches the steel. When rolling slabs heated by" our process and type of furnace this scale'is absent and hence the rolls will wear much longer and the steel will not be subject to scale scratches.

Another object of our invention is to provide a furnace that heats the individual slabs uniformly throughout and also heats all the slabs supplied to the mill to a certain predetermined temperature.

With the foregoing and other objects in view, 70 which will. appear in the following description, our invention resides in the novel combination and arrangement of parts and in the details of construction and methods of operation herein described, illustrated and claimed.

In the drawings:

Fig. 1 is a sectional plan view taken just above the hearth of the furnace showing the relative arrangement of the charging mechanism, the electric heating device, the soaking furnace, the slab feeding device and the slab discharging device and the first working roll stand of the rolling Fig. 2 is a sectional elevation thru the furnace taken along line 2-2 of Fig. 1.

Fig. 3 is a cross sectional elevation taken along line 33 of Fig. 1, which is a section thru the electric heating chamber of the furnace.

Fig. '4 is a section thru the soaking chamber of the furnace taken along line 4-4 of Fig. 2.

Fi 5 is a fragmentary section taken along line 5'5 of Fig. 1 showing the gas barrier and door at the discharge opening of the soaking chamber.

Fig. 6 is a fragmentary section taken along line 6-6 of Fig. 1 showing a section of the slab feeding pusher. 4

Fig. '1 is a wiring diagram of one unit of the electric heating device for passing heating current lengthwise thru the slab.

Fig. 8 is a wiring diagram of one unit of-the electric heating device for passing heating current thru the thickness of the slab at the ends for preheating the ends of the slab.

4 Referring now to the drawings more in detail wherein like numerals refer to like or corresponding parts thruout the several views, number 1 of Fig. i represents the slabs to be heated for rolling. 2 the skids on which the slabs are fed to the charging pusher 3 operated by the pinch rolls 4 of usual construction, 5 the door at the charging opening, 6 the gas barrier which is shown in secin diagram Fig. 8 and are thus arranged to pass tion in Fig. 5 and which consists of a mass of closely packed wires suspended in a vertical position and which closely hug the slab while it is being pushed thru the opening and retard the escape of gas while the door is open. 7 is the water cooled skid on which the slab is pushed into the furnace. 8 is a door which protects the slab feeding device from the furnace heat, this door is opened when it is desired to push the slabs thru the furnace, 9 are the pushers of the slab feeding device, 10 are fingers which are pivoted to pushers 9 on hollow shafts 11 which can be rocked by motion transmitted thru squared shaft 12 links 13 and air cylinder 14. The squared shaft 12 telescopes within the hollow shaft 11 and engages it thru a squared socket therein as shown in Fig. 6. Hollow shaft 12 is attached to and moves with the pusher 9, while squared shaft 12 is stationary and has a rocking motion, only. This rocking motion is used to swing the fingers 10 from the position shown in full lines Fig. 6 wherein it will clear the slabs to the position shown dotted wherein it will engage the slabs for pushing them thru the furnace. Three fingers 10 are spaced along each of the two pushers 9 starting at the forward end as shown in Figs. 1

and 2. This spacing corresponds to the group spacing of the electric heating units. These heating units will be described later. The pushers are driven thru racks on 9 by means of pinions 15.

The pushers 9 are supported by fixed rollers 16 Fig. 2 and movable carriage 17 which runs on rails 18.

19 Fig. l is a group of contacting clamps adapted to distribute contact points across substantially the entire -width of a slab thru a plurality of independently operated clamping jaws, the several members of the group being electrically connected in parallel. Each clamp consists of a top and bottom lever pivoted between the clamping end and the operating cylinder end. Each of these pairs of clamps may be opened or closed by means of hydraulic cylinder 21 arranged substantially as shown in Fig. 3. The top and bottom levers are insulated from each other at their pivot points and from the operating cylinder.

Electric current is supplied tothe' clamping levers 19 and thru flexible conductors 22. The group of contact clamps 19 Fig. 1 and Fig. 3 is used for preheating the ends of the slabs by passing a current between the top and bottom clamp levers of each pair of clamps directly thru the thickness of the slab at the end. The electrical connections are shown in Fig. 7.

The group at contact clamps 20 Fig. -1 are of the same construction as the group.19 already described, but are electrically connected as shown an electrical current from the group of clamps on one side of the furnace to the corresponding group of clamps on the opposite side of the furnace thru the length of the slab between the two sets of clamps, thus heating up the entire body of the slab, giving the ends a slight superheat depending upon the amount of heat supplied in the preceding group 19.

The two groups of contact clamps '19 and 20 are spaced apart a distance exceeding the width of the widest slab to be heated by an amount sufficient to provide space betweenthe adjacent slabs within the clamps to permit the entrance between the slabs of the pusher fingers 10 as shown in Fig. 1. A similar space exists between the edge of the slab in clamping group 20 and the next adjacent slabin the soaking chamber.

A similar space also is provided between the slab in clamps 19 and the slab as introduced into the furnace by the charging pusher 3. Door 23 separates the soaking chamber from the electric heating chamber and is lowered into the space between the slabs substantially as shown in Figs. 1 and2.

When the slab in clamps 20 has been heated to the desired temperature, and the last slab at the discharge endof the soakingchamber has beenejected from the furnace thru the gas barrier 6 and door 5, Fig. l by discharge pusher 24 operated by pinch rolls 25 of usual construction, the

clamps

19 and 20 are all opened thus releasing both slabs held therein, door 8 is raised and pusher rams 9 are brought forward so that the fingers 10 can be dropped behind the rear edges of the first three slabs in the electric heating chamber, door 23 is then raised, and the above three slabs are simultaneously pushed forward a distance equal to the center to center spacing of the

clamping groups

19 and 20. This operation transfers the slab in clamps 20 to the soaking chamber and all the slabs in the soaking chamber are pushed forward a distance equal to the width @0 of one slab. The above operation is visible thru window 26. The pusher is withdrawn and

doors

23 and 8 are lowered. Clamp gr0ups19:and 20 are now clamped on to the slabs which have just been positioned in the clamps by the preceding 11 operation, and a cold slab is introduced into the heating chamber by pusher 3 thus completing the cycle of operation.

The soaking chamber is a bottom fired muflle furnace having a refractory bottom provided with 1-10 slab skids 27. The heating flues 28 have a burner 29 at one end and discharge into the stack flue 30 at the opposite end. The gas flow in adjacent time is in opposite directions.

The furnace comprising the soaking chamber, u

the electric heating chamber and the chamber for the feeder pusher rams are all enclosed in a gas tight shell outside of the refractory linings, and inert gas is supplied to the interiors of the various chambers thru tubes 31 Figs. 2 and 3 to maintain. 129 a slight positive pressure inside the chambers. When heating slabs for certain products carbon difl'usion burners may be mounted on tubes 31 for maintaining a partially inert atmosphere within the furnace. Pyrometers 32 Fig. 2 sighting thru the roof of' the chambers are provided for determining the temperature of the slabs. We further provide a very useful means of withdrawing all of the slabs from the soaking chamber so that it can be entirely emptied with ease which is desirable when changing to a different width of slab and also when the furnace is to be shut down for a period of time. This is accomplished by means of a slab puller consisting of two rams 33 which have hooks on the furnace 13 end and are pivoted in cross head 39 at the other end. These rams are rotatable thru degrees by means of gears 37 and intermeshing crank driven pinion 38. The rams are driven by pinch rolls 34, thru stufling boxes inthe furnace wall. Doors 36 are provided for protecting the ram ends from the furnace heat while not in In the operation of the furnace slab pulling device, the rams are driven into the furnace by means of the pinch rolls, immediately over but 14,5 clearing the slabs and. with the hooked ends in the horizontalposition until the hooks have passed beyond the furthest slab. The rams are then rosoaking chamber thru the edge contact with the means withdrawn a sumcient amount to center a slab with the discharge opening. We supply the furnace with scale free slabs as mentioned above, these may be prepared by either pickling or sandblasting.

Direct current is necessary in the heating on account of the large section of the resistors and conductors involved, which would cause great dimculty with alternating current on account of skin effect.

The progress of a slab thru the furnace is as follows: First it is pushed lengthwise thru the door 5 of the heating chamber Fig. l on to skids 7 by charging pusher 3. The piece is then pushed laterally from skids '7 into clamp group 19 by pusher rams 9. After the ends are sufliciently heated the piece is pushed from clamp group 19 to clamp group 20 on skids 27 by pusher rams 9. After the whole of the slab is sufliciently heated in clamp group 20 it is pushed on into the soaking I chamber by the same pusher on the same skids. The piece is'now pushed in successive steps thru the soaking chamber until it comes opposite the ejector pusher when it is pushed out of the furnace'into the rolling mill by pusher 24. In continuous operation a new piece is introduced into each clamping group by the same motion of the pusher which ejects the one previously clamped. The pusher Qengages the piece on skids 'l and the pieces in

clamp groups

19 and 20 independently and simultaneously and pushes the pieces in the following pieces. The soaking chamber of our furnace is provided to permit the slabs to acquire a substantially uniform temperature thruout because some nonuniformity in temperature will develop in electric heating because of nonuniformity in the resistance of the steel and the influence of the massive end clamps further introduce a certain amount of nonuniformity. The amount of heat necessary to be supplied to .the soaking chamber is small in comparison to that required in present heating furnaces, being substantially the amount lost by radiation.

From the foregoing description it is evident thatour furnace is compact, efflcient, easily operated, and that our process and furnace produces results not now obtainable and has many other advantages over present practice.

While one embodiment of our invention has been shown and described in comparative detail for the purpose of adequate disclosure, the broader idea of our invention is not limited iii-any of the details disclosed herein, but instead includes such embodiments thereof as are within the scope oi the subjoined claims.

What we claim is:

1. A furnace for heating short lengths of metal for hot rolling comprising a chamber containing clamps for making electrical contact with the metal at the ends transversely across the width of the piece with contact pressure parallel to thethickness thereof, said clamp being adapted to receive the metal pieces by a horizontal movement of the piece at right angles to its length, a soaking chamber horizontally displaced from the heating chamber so as to receive the metal pieces by a continuation of the same horizontal motion.

2. A furnace for heating short lengths of metal forhot rolling comprising a chamber containing clamps for making electrical contact with the metal at the ends transversely across the width of the piece with contact pressure parallel to the thickness thereof and subdivided into a plurality of independently acting pressure units said clamps being adapted to receive the metal pieces by a horizontal movement of the piece at right angles to its length, a soaking chamber horizontally displaced from the heating chamber so as to receive the metal pieces by a continuation of the same horizontal motion and a door between the soaking chamber and the heating chamber to protect the clamps from the heat of the soaking chamber.

3. A furnace for heating short lengths of metal for hot rolling comprising achamber containin clamps for making electrical contact with the ends of the metal pieces, a soaking chamber on one side of the heating chamber and a pusher on the other side thereof adapted to push the pieces horizontally in the direction of their width both into the clamps and thence into the soaking chamber, a puller on one side of the soaking chamber opposite the heating chamber adapted to engage the pieces in the soaking chamber and pull them therethru horizontally in the direction of their width for the purpose of emptying the soaking chamber of the metal pieces.

' EMERSON L. CLARK.

EARL W. CLARK.