US1860613A - Method of rolling metal sheets - Google Patents

Description

May 31, 1932. F. E. FLYNN METHOD 0F ROLLING METAL SHEETS Filed Aug. 22, 1929 .N .LL

l Patented May 31, 1932 UNITED STATES PATENT OFFICE FRANKl E. -IEIYNN, -OF WARREN, OHIO, ASSIGNOR TO REPUBLIC STEEL CORPORATION,

OF PITTSBURGH, PENNSYLVANIA, A CORPORATION F NEW JERSEY METHOD OF ROLLING METAL SHEETS Application led August 22, 1929. Serial No. 387,635.

My invention relates to a method of producing steel sheets and, particularly, to the production of full finished strip sheet.

Under the present practice, the strips are hot rolled and coiled, and then pickled preparatory to cold rolling. The pickling is effected by soaking the coiled strips in a dilute acid solution to remove the outside scale formed during the hot rolling. The, cold 1o stripvis then passed through a plurality of tandem cold mill stands and coiled. Because of the fact that the strip is passed through a number of different sets of rolls, it is necessary to shape each set of rolls in order to produce a flat strip. Even though therolls are carefully shaped, it is necessary to pass the strip through an ironing-out roll to remove any irregularities in the surface of the strip.

The heat treatment to which the strip is subjected in the processes now employed consists of box annealing the strip in coils. After box annealing the strip is temper rolled and coiled, and finally, passed through 5 a roller leveller and sheared into lengths.

There are a number of objectionable features in the present process. The first of these has `already been mentioned, namely, that it is diicult to produce a flat sheet by passing the cold strip through a succession of of different cold mill stands and an ironingout pass is necessary.. This additional pass necessitates an extra handling of the material.

, Another objection to the present method is that the strip, is box annealed in coils. Becauseof the shape of the coils, it is impossible to stack them in the boxes efficiently and only a comparatively small amount of strip may be placed in one box. In a representative operation it'was found impossible to place more than 12,000 pounds of steel in a box which. with its bottom, weighed 33,250

pounds. It follows that the heat eiiiciency of an operation which requires the continued heating of such a box to anneal the relatively small amount of steel therein. is very low.

I substitute for the successive cold mill stands of the present process, a singlecold mill stand through which I pass the strip .under tension, after pickling, a plurality of .times suiicient to bring about the desired re- A duction in the gauge of the strip. In my process, the strip is then passed through leveling rolls and sheared into lengths. It is an important feature of this process that all steps subsequent vto the initial cold rolling are preformed upon the material in the form of sheets instead of long strips in coils. This features is responsible for a number ofadvantages characteristic of the process such as economic handling, eiicient treating, and the like. .The next step consists in annealing the sheets in a normalizing furnace. The normalizing treatment consists in heating and cooling the sheets in the presence of air. This step improves the grain structure of the sheets, makes possible further cold rolling, and is accompanied by the formation of a coat of oxide or scale on the surface of the sheet. This coat may be removed by the usual pickling process, after which the sheets are again annealed, this time in a boxannealing furnace. Because the steel to be box-annealed is in the formYY of sheared sheets, it maybe treated more efiiciently. As an example, it is possible to stack 36,000 pounds of steel sheets into a 33,000-pound box as compared to 12,000 pounds of strip steel in coils.

Upon removal from the box-annealing furnace the sheets are again lightly pickled 'or scru bed in a suitable machine and, finally, temper rolled in a single cold mill stand.

The sequence of the operations involved in ,the method of my invention is indicated in the accompanying drawings, in which Figure 1 is a schematic plan view of the apparatus necessary to provide the abovedescribed treatment for the strip and sheets; an

Figure 2 is a schematic elevation of the apparatus shown inFigure 1.

Referring .particularly to Figure 1, hot steel strip is supplied from the hot millin coils and pickled in the pickling tank 10. After the pickling process, the steel strip is passed back and forth between the reels 11 and 12 under tension, through the cold mill 100 stand 13. On the last pass through the cold mill stand 13, the strip is coiled by means of a coiler 14.

The coiled strip is next passed through a roller leveler 15 to a shear 16 where it is cut into the desired lengths.

The normalizing fiirnace is indicated at 17 and the sheared sheets are passed therethrough by means of a conveyor, after which they are again subjected to the pickling treatment in the tank 18 to remove the scale which is formed in normalizing. The normalized and pickled sheets are then given a treatment in theboX-annealing furnace 19. This step is effected in a reducing atmosphere such as that provided by supplying coke-oven, natural, or charcoal gas to the annealing furnace in the known manner. Since no oxide coat is formed on the sheets during this step, a light pickling or scrubbing is sufficient to prepare the sheets for the final cold roll, and even this treatment may be omitted. This pickling or scrubbing treatment is applied in the tank 20.

From the tank 20, the sheets are passed to the cold mill stand 21, in which the sheets are temper rolled and finished.

The apparatus involved in the process above described is shown in elevation in Figure 2 and corresponding reference numerals indicate similar portions of the equipment.

The process of my invention is characterized by several marked advantages over the method now in use. The first of these is a lower unit cost which results from a higher yield or a lower percentage of scrapped sheets. This lower percentage of scrapped sheets results partially from the scrubbing operation which makes it possible to reclaim a considerable percentage of steel that might otherwise be scrapped because of grease spots.

Another factor contributing to the lower cost per unit is the more efficient handling which is made possible by the elimination of the ironing-out pass. The cost of the box annealing is reduced because of the fact that the boxes can be more eiiiciently stacked with sheets than with coiled strip as indicated by examples given above.

Another advantage of the proposed method is that the product possesses mechanical characteristics superior to those of any product of the present method. These characteristics result from the heat treatment to which the sheets are subjected in the normalizing and box-annealing furnaces. There is no objection to this sequence of operations as there might be to box annealing subsequent to the first-cold rolling operation. In the latter case, the hard shiny surface of the cold rolled steel sheets causes them to adhere to each other with the result that cross breaks are formed in the sheets when they are separated upon opening the box. This difficulty is avoided in the proposed method becausethe normalizing treatment, followed by pickling, removes the shiny surface so that the sheets show no tendency to adhere and may readily be separated after box annealin Another advantage accrues om the fact that the final cold rolling is applied to the steel as sheets instead of as coiled strip. After annealing, the steel is in a condition known as dead soft and when cold rolled in coils, cross breaks in the strip are formed which cannot be rolled out. These defects necessitate scrapping a portion of the output. The tendency to form cross breaks is materially lessened by finally cold rolling the product as sheets instead of as coiled strip.

Although I have described a specific sequence of steps for performing the method of my invention, it is to be understood that these steps are merely a preferred example o practicing my invention. It is not my intention to be limited to the exact steps and sequence of operations described and the only limitations to be imposed upon the scope of my invention are those necessitated by the terms of the 'appended claims.

I claim:

1. In a method of producing steel sheets, the steps which consist in pickling coiled steel strip, passing said strip cold through a single set of rolls a plurality of times, shearing said strip into lengths, normalizing said lengths, pickling the lengths and annealing them in a non-oxidizing atmosphere, lightly pickling and scrubbing said lengths and passing them cold through a second set of rolls.

2. In a method of rolling steel sheets, the steps which consist in pickling steel strip in coils, reeling said strip cold, under tension, through a single set of rolls a plurality of times, shearing said strip into lengths, heattreating said lengths, removing the scale formed thereon during said treatment, annealing said lengths in a non-oxidizin atmosphere, cleaning and again cold-ro ling them.

3. In a method of rolling steel sheets, the steps which consist in pickling steel strip, cold-rolling it under tension through one set of rolls a plurality of times, shearing the strip into sheets, passing the sheets through a normalizing furnace, repickling the sheets, annealing them in a box furnace, cleaning and again cold-rolling the sheets.

4. In a process for making steel sheets, the steps comprising cold-rolling pickled steel strip under tension a plurality of times in a. single set of rolls, shearing said strip into sheets, normalizing said sheets, pickling and annealing them in a box furnace and again cold-rolling said sheets.

5.' In a process for the cold-working of steel, the steps including cold-rolling, normalizing, pickling, annealing and again coldrolling. K

6. In a method of making sheets, the steps consisting in normalizing the sheets, pickling the sheets and box-annealing them.

7. In a method of making sheet metal, the steps consisting in cold-rolling a metal strip under tension through a single set of rolls a plurality of times, shearing the strip, normalizing the sheets produced, pickling and annealing the sheets in the absence of oxygen, cleaning the sheets and finally cold-rolling them again.

8. In a metal-Working process, the method which consists in cold-rolling metal strips into sheets by passing said strips repeatedly through a single set of'rolls, under tension, normalizing the sheets, annealing them in the absence of oxygen and again cold-rolling them.

9. In a method of producing sheets, the steps consisting in cold-rolling strip metal, shearing the strip into sheets, heat-treating said sheets, annealing them in a slightly7 reducing atmosphere and again cold-rolling them.

10. In a metal-working process, the steps consisting inY cold-Working a mass of metal heat-treating it, annealing it in a reducing atmosphere and again cold-working it.

11. In a heat-treating process for sheet steel, the steps including' heating the sheets in an oxidizing atmosphere, pickling the sheets and annealing them in a non-oxidizing atmosphere.

In testimony whereof I have hereunto set m hand.

y FRANK E. FLYNN.

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