US2261352A - Method of making thin metal sheets - Google Patents

Description

Nov. 4, 1941.

A. D. EVANS METHOD OF MAKING THIN METAL SHEETS Filed Sept 21, 1959 INVENIOR. ARCH/BALD D. EVA N5 M rmfla' ATTORNEYS.

Patented Nov. 4, 1941 UNITED STATES PATENT OFFICE METHOD OF MAKING THIN METAL SHEETS Archibald D. Evans, Niles, Ohio Application September 21,1939, Serial No. 295,879

4 Claims.

This invention relates to the art of making thin metal sheets. It is particularly concerned with a new and improved method of pack rolling ferrous metal sheet or tin plate bars into thin sheets and removing oxides therefrom, and with a new and improved system or arrangement of apparatus for carrying out this method.

Heretofore ferrous metal sheet and tin plate products have been pack rolled by two methods, viz: the single-mill method and the double-mill method. The large ingots were rolled lengthwise into long pieces of metal ranging in thickness from about to about 1" and in width from about 8" to about 12". Then these long pieces of metal were cut crosswise into bars varying in length from about 24" to about 60". The width of sheet desired determined the length of the bars and the length of sheet desired determined the width and thickness of the bars.

According to the single-mill method bars of the desired size were heated to rolling temperature and were withdrawn from the heating furnace two at a time. These bars were crossrolled singly in the mill, 1. e., they were fed alternately one at a time between the rolls'and the rolling was in the direction of the width of the bar and crosswise as compared with the direction of rolling of the long pieces of metal from which the bars were out. These bars were rolled singly until the mill could no longer exert proper reducing forces on the single piece, whereupon without reheating the sheets resulting from such rolling were matched, 1. e., one was placed on top of the other. Then the rolling was continued until the mill could no longer exert proper reducing forces on the pack of two sheets. Then the two sheets were doubled to form a pack of 4 sheets or a third or fourth sheet was added thus forming a pack of 3 or 4 sheets of the same length and the resulting pack was reheated and rerolled. Where the mill could reduce the thickness of this 3-high or 4-high pack to the desired gage the pack was finish-rolled, sheared, opened and either pickled or pickled and annealed. When thinner gage sheets were desired, the reheated 3-high or i-high pack was rolled until the mill could no longer exert proper reducing forces thereon, then the pack was doubled and sheared, reheated and finish-rolled, after which it was side sheared and end sheared, opened and pickled or pickled and annealed, depending upon the surface desired. In some cases, where even thinner gages were desired, two doubled packs of 8 sheets were matched, reheated and finishrolled. This practice was called tagger rolling.

This single-mill method possessed certainfundamental advantages and disadvantages. The outstanding advantage was that all the rolling was done on a single pair of rolls with but small loss of time between successive beatings and rollings and as a result the rolls remained heated to an approximately constant temperature and possessed an approximately constant contour. Thus during the entire rolling. cycle the contour of the rolls corresponded to the contour of the metal previously rolled so that there was no tendency, during rerolling, for the pack to twist and pinch or to be deformed because the crosssection of the product corresponded in shape with the cross-section of the mill.

Another advantage of the single mill was that it was necessary to change only one set of rolls when it was desired to roll sheets of a width which was outside the capability of the rolls then in the mill. In the case of the double mill it was necessary to change two sets of rolls.

An extremely important disadvantage in the single-mill method was that the bars were so narrow that they could not be mechanically fed and caught. It was, therefore, necessary to feed and catch the bars manually with the high labor costs incident thereto.

According to the double-mill method the conventional bars were fed and caught manually on one mill during the preliminary or breakdown operation and the breakdowns were reheated and finished on a second mill equipped with mechanical feeders and catchers. The double-mill method reduced labor costs during the secondary or finish rolling and to that extent was cheaper than the single-mill method. However, the double-mill method inherently complicated the difficulties of controlling the temperature and contour of two difierent pairs of rolls. In prac-' tice it is pactically impossible to maintain identical roll contour in two mills. When the contour varies the breakdowns having the characteristic contour of the first mill tend to twist and pinch and be deformed in the second mill where the roll contour is different and the resulting product is not so true to gage and does not have as good a surface as is the case when the single-mill method'is used.

Thus the single-mill method gives a better product than the double-mill method, but at a higher labor cost, and the double-mill method has been substituted largely for the single-mill method to reduce labor costs, but at the expense of equality of product and yield of saleable material.

The present invention possesses the advantages of both single and double-mill methods and avoids the disadvantages of each method.

The present invention may be briefly described as follows: I employ sheet or tin plate bars which have about twice the lineal foot weight of the conventional bars heretofore used. For example, the prior conventional bar measuring 36" x 12" x was used to produce a sheet 36" wide, 5 feet long and thick. A bar which I may use in place of such a conventional bar to produce a similar sheet is 36" x 24" x These bars are withdrawn one at a time from the heating furnace instead of two at a time as in the previous methods and are rolled, doubled, reheated and re-rolled. Where the gage of the metal in such rerolled Z-high packs is that desired, the pack is end and side sheared then the outside scale is removed mechanically as by blasting or abrading. Then the pack is opened and pickled or pickled and annealed, or annealed in a reducing atmosphere without pickling. When thinner gages are desired the rerolled 2-high pack is redoubled, end sheared and reheated. The reheated 4-high pack is then finished as described, or, it is redoubled to form an B-high pack, is reheated, rerolled and finished as above described. If still thinner gages are desired the 8-high pack may be matched with a second 8-high pack, reheated and rerolled.

In order that bars, 2-high packs and 4-high packs, may be heated simultaneously and rolled in turn I employ a double furnace. Bars are charged into one side of the furnace and the 2- high and 4-high packs are charged into the other side of the furnace. Then the bars and packs are rolled alternately, i. e., the bar, a 2- high pack and a 4-high pa'ck, another bar, another 2-high pack and another l-high pack, as will be the case after the rolling has progressed far enough so that 2-high and 4-high packs have attained rolling temperatures and have passed through the furnace. It will be understood that the foregoing operation will be altered by omitting the l-high packs if the 2-high packs can be rolled to the desired gage and that 8-high packs or two 8-high packs may be added to the foregoing operation where the gage obtainable from the 4-high packs is thicker than is desired.

The present invention includes, as above noted, the step of removing scale from the outer surfaces of a pack by mechanical means such as blasting or abrading. Sand blasters and abraders are well known in the art. Typical abraders which may be used for this purpose are shown in U. S. 1,953,566. This abrading operation removes the scale from the outer surfaces of the pack to an extent which makes it unnecessary to resort to pickling. Abrading is an advantage, for if after the pack is opened the sheets are pickled, the amount of oxide to be removed is substantially uniform on all surfaces and hence the pickling time is substantially the same for both inside and outside surfaces of all the sheets and unnecessary loss of metal and acid is avoided. It will be understood that in a 4-high pack there are eight sheet surfaces, of which two are rather heavily scaled, while the six remaining surfaces carry only a light oxide. These six surfaces may be cleaned either by pickling or deoxidizing. Pickling is usually resorted to when the steel is to be normalized but otherwise these surfaces may be deoxidized in an annealing pot.

In the drawing accompanying and forming part of this specification:

Figure 1 is a diagrammatic, partly sectional, plan view of one form of apparatus suitable for use in practicing the present invention; and,

Figure 2 is a side elevational View, partly in section of the apparatus of Fig. 1.

In the drawing, I designates a double chamber, continuous heating furnace from the discharge ends of which roller-conveyors 2 extend to a feeder 3 which can be moved to the various positions indicated on Fig. 2. In the lowermost position of the feeder, bars and packs discharged from furnace I may be fed between the rolls of a 2-high mill 4. When bars are being returned over the top of the mill the feeder 3 is preferably elevated to the middle position shown on Fig. 2 to insure that the bars will be delivered onto the feeder and will not be permitted to pass down between the top roll and the feeder. When the bars have been elongated into sheets, or when packs are being rolled, the feeder 3 may be elevated to the uppermost position to catch such articles when they are being returned to the feeding side of the mill.

On the discharge side of mill 4 a catcher 5 is located. This catcher consists of lower and upper substantially parallel conveyors 6 and I and a tiltable conveyor 8 pivoted at its end remote from conveyors I5 and I and movable to its lower position as shown in dotted lines on Fig. 2 to receive bars, sheets and packs from the mill 4, and then movable to the upper full line position shown in Fig. 2 to return these articles onto the conveyor I for their return over the top roll of mill 4 to the feeding side.

A dispatching conveyor 9 leads from the discharge side of catcher 5 to a doubling machine III. .A run-back conveyor I I leads from the doubling machine II) to a clipping shear I2 and a circle conveyor I3 leads from the shear to one side of furnace I. Bar charging conveyors I4 are located at the entrance side of the furnace I, but it will be understood that when bars are being charged only into one side of the furnace and packs are being charged into the other side, one of these charging conveyors I4 will not be in service.

A finish-rolled-article conveyor leads from the discharge end of catcher 5 to a mechanical cleaning machine I6 such as a sand blaster or wheel abrader.

The present invention, altho described in some detail hereinabove, will perhaps be better understood by describing the operation in some detail as carried out on bars, 2-high and l-high packs in the apparatus of Fig. 1 and 2.

Bars which have twice the lineal foot weight of prior conventional bars for sheets of the desired size, are charged on conveyors I4 into both sides of the furnace I, wherein they are moved progressively thru the furnace and heated to rolling temperature. When heated, a bar is removed from one side of the furnace along one branch of conveyor 2 to feeder 3 and is passed broad side on between the rolls of mill 4, is caught by conveyor 6 and is passed onto conveyor 8 located in the dotted line position of Fig. 2. Then this conveyor is pivoted to the full line position, the direction of the conveyor travel is reversed and the piece is delivered onto conveyor 1 which returns it over the top roll of mill 4 onto the feeder 3 which in the meantime has been elevated to the middle position of Figure 2. These rolling operations are continued until the metal has been reduced to such a thickness that the mill can no longer exert proper reducing forces thereon and when the piece has been elongated sufiiciently the feeder 3 is elevated to its uppermost position to receive the piece on its return over the rolls. Then the sheet resulting from this rolling of the bar is transported on conveyor 9 to the doubling machine I9 where it is doubled into a Z-high pack. This pack is carried by conveyor II to conveyor I 3 which charges the pack into one side of the furnace. Bars are alternately withdrawn from opposite sides of the furnace and rolled and doubled in the foregoing manner until all of the bars have been withdrawn from the one side of the furnace into which the 2-high packs are being charged. Meanwhile, bars have been charged into the other side of the furnace to keep it substantially filled.

After the last bar has been removed from the pack side of the furnace, the rolling of bars and packs proceeds alternately as previously described for the bars alone, that is, a bar from one side of the furnace is rolled as above described and then a Z-high pack is rolled, then another bar, then another pack. When a Z-high pack is withdrawn from the furnace for re-rolling, it is repeatedly rolled by mill 4 until its thickness has been reduced to the point where the rolls do not exert effective reducing forces thereon. Then the 2-high pack is conveyed to the doubling machine ID and redoubled, thereby making a 4-high pack with a fold at each end. This pack is end sheared on the trailing end by a shearing machine l2 and is then charged into the side of the furnace containing 2-high packs. The alternate rolling of bars and 2-high packs is continued until a 4-high pack is ready to be discharged from the furnace. At that time the bar side of the furnace will contain only bars and the pack side of the furnace will contain Z-high and 4.-high packs alternately arranged. After the first 4-high pack is withdrawn from the furnace the rolling sequence is a bar, a 2-high pack and a l-high pack, and this sequence is repeated thereafter.

The 4-high packs are finish-rolled by mill 4 to the desired gage and are then discharged onto conveyor I 5 where the outer surfaces are cleaned off mechanically as by a sand blaster or wheel abrader. Then the pack is opened. If the sheets are to be normalized they are pickled after normalizing. If, however, they are not to be normalized but box annealed then the oxide film need not be removed from the surfaces which were within the pack by pickling, but these films will be removed when the sheets are annealed in the annealing pot in a reducing atmosphere Which deoxidizes the inside surfaces.

It will be understood from the foregoing rather specific description that the portion relating to 4-high packs may not apply where the gages desired are obtainable in a 2-high pack and also that where the gages obtainable in a 4- high pack are not as thin as are desired, an 8- high pack may be made by doubling of the 4- high pack after it is rolled.

The present invention retains the advantages of th single-mill method and avoids the hand labor incident to that method. The present invention employing, as it does, bars which have at least twice the lineal foot weight of conventional bars, permits use of the single-mill method and avoids the disadvantages incident to matching two or more breakdown sheets and the troubles incident thereto. Furthermore, the metal is all rolled in one set of rolls and the elapsed time between each heating and rolling is so small that the roll temperature does not vary widely and the contour is maintained more or less uniform. As a, result, the articles produced are uniform in gage and surface and scrap loss due to mismatching and other causes is avoided with the result that greater tonnage of salable product is obtained. Moreover, the labor cost is greatly decreased as compared both with the prior singlemill and double-mill methods, for all feeding and catching is done mechanically. The wider bars and the fact that the feeder can be brought into such close proximity to the upper roll of the mill that the bars can be satisfactorily caught by the feeder on their return over the mill, combine to produce the new result of carrying out not only the preliminary o-r break-down operations but also the secondary and finishing operations on a single mill and to mechanically feed and catch not only the bars but the other products resulting therefrom.

Thus the present invention products a better quality product than the two-mill method and. does it cheaper than either the prior one-mill or two-mill method. The mechanical removal of scale before pickling is a factor of considerable commercial importance, Whether or not the oxide films are removed from the inside sheets. When they are removed later either by pickling or de-oxidizing, the cost of such removal is reduced and the present method is important from an economical standpoint.

Having thus described the present invention so that those skilled in the art may be able to understand and practice the, same, I state that the scop of my invention is defined in what is claimed.

What is claimed is:

l. The method of rolling sheet or tin plate bars which includes the steps of heating such bars having a foot weight sufficient to produce a sheet of twice the desired length, rolling such bars one at a time, doubling the resulting sheet to form a 2-high pack and reheating the said pack, rolling the reheated Z-high pack, doubling the resulting product into a 4-high pack, shearing the 4-high pack, reheating and rolling the 4-high pack, all said rolling steps being performed by one mill.

2. The method of rolling sheet and tin plate b-ars including the steps of simultaneously heating bars having a foot weight sufficient to produce sheets of twice the length desired, 2-high packs resulting from prior rolling of such bars and 4-high packs resulting from prior rolling of such Z-high packs, and successively rolling such bars, Z-high packs and ll-high packs, in one mill.

3. The method of rolling sheet and tin plate bars which includes the steps of simultaneously heating bars having a foot weight suflicient to produce sheets of twice th desired length, and successively rolling such a heated bar into a sheet, doubling the sheet into a Z-high pack and reheating the said pack, rolling said reheated pack, doubling it to form a 4-high pack, reheating said 4-high pack and finish-rolling it, and successively rolling, in turn, in one mill such a bar, 2-high pack and 4-high pack.

4. The method of rolling sheet and tin plate bars which comprises the steps of heating such bars having a foot weigth sufficient to produce sheets of twice the desired length, rolling the bars, doubling the resulting sheet and reheating, rerolling and finishing the metal, all said rolling operations being carried out in one mill.

ARCHIBALD D. EVANS.

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