US1971005A - Method of rolling - Google Patents

Description

Aug. 21, 1934. HASWELL 1,971,005

METHOD OF ROLLING Filed Jan. 12, 1952 INVENTOR Aer/10E 5. 1%JWELL BY H IS ATTORN EYS Mew Patented Aug. 21, 1934 METHOD OF ROLLING Arthur B. Haswell, Birmingham, Ala. Application January 12, 19s2, Serial No- 586,211

2 Claims.

This invention relates to an improved method and apparatus for rolling an intermediate sheet product known in the art as a breakdown. These breakdowns are usually formed by subjecting so 5 called sheet bars or strip to repeated rolling operationsin order to reduce the thickness of the work in successive steps, thus effecting a breaking down in the thickness of the stock and preparing it for subsequent rolling into 0 sheets. The improved method to be presently described and means for carrying it out are concerned chiefly with production of this intermediate product known as a breakdown. The,

invention will be apparent from the following specification when read in connection with the accompanying single figure, which conventionally illustrates a suitable mill for carrying out the improved method.

In the drawing, W represents the sheet bar 0 stock, which is to be reduced in thickness by subjecting it to only one single rolling operation. By way of illustration, a suitable apparatus will include a pair of rolls RR', thm being of a considerably greater diameter than the rolls heretofore used in conventional practice.

As will be pointed out more fully hereinafter, I consider it advantageous to drench one side only of the roll with water, this water being expelled from pipes P, P against the exit side 0 only of the rolls. For preventing the cooling water reaching the entrance side of the rolls, I provide swabs or wipers S and S mounted on suitable brackets or holders H and H.

The old style sheet mill consists of two rolls, the bottom roll is always driven and in certain cases the top roll is also driven, but as a rule when rolling light sheet bar, the top roll is run as an idle roll. The old rolls are 32" or less in diameter, the length of roll depending upon the width ofsheet that is to be made; the old roll necks are 25" or less in diameter. 'I'hese' old mills as a rule run from 28 to 30 R. P. M., or a. speed of about 210 feet per minute, to about 250 feet per minute on the periphery of the rolls.

Customary practice when rolling breakdowns is to heat the steel, called sheet bars, pairs or strip, ranging in thickness from say 1%" up, to a temperature of somewhere between 1300 and 1400 F. These pieces of steel are then passed between two rolls of a mill for what is called the first reduction, which seldom exceeds 33%% reduction, or 50% elongation. To get the total reduction or elongation required for a breakdown, this steel. is given several passes on the same mill by returning the steel idly over the top roll and then passing it between the top and bottom rolls, the top roll being lowered by means of a screwdown for each pass. Two pieces of steel are often matched through several passes after first taking a few single passes and finished to breakdowns by rolling them double or matched. These rolls as a rule are run wet; in other words a liberal amount of water is allowed to play over substantially the entire sur-- face of the rolls at all times in order to prevent 55 distortion of the rolls by heating.

7 The improved method of rolling disclosed herein contemplates making breakdowns from single or matched sheet bars or strip in a single pass on a mill especially designed for this novel method. It is essential that the mill for accomplishing my improved method of rolling shall have rolls of a diameter greatly in excess of those used at present date in conventional practice. For example, I prefer to use rolls at least one third greater in diameter as compared with the conventional rolls 30" in diameter heretofore used. These large rolls are necessary in order. to prevent excessive deflection, so as to maintain uniform gauge of the breakdown and to provide liberal rolling surface on the rolls. This will-also reduce roll cost for the reason that such liberal surface permits a proper cooling of rolls. My large rolls also provide a forging or pressing action on the steel'in the bite of the 35 rolls rather than a tearing action which takes placewhen the small rolls of conventional prior practice are used. Thus, by my method, the forging or pressing action will give a better grain structure in the steel than is obtained by conventional prior practice. The greatly enlarged rolls which I consider essential will also have correspondingly enlarged roll necks.

It is realized that the use of large diameter rolls will be required due to the increased pressure between rolls when making the total reduction in one pass as compared to the pressure required when using small diameter rolls, and making the total reduction in severalpasses, however, the many advantages more than off-set any additional cost of heavier equipment. The above mentioned rolls will be placed in special enlarged housings properly designed to give ample strength for the work imposed. Each housing will be provided with the usual screwdowns con sisting of one or more screws, operated either mechanically or by hand which screws will be of suificient strength to hold the toproll in position. The rolls may be provided with the ordinary type of mill bearings or with special bearper minute or less on the periphery of the rolls is recommended. This slow speed, is intended to give an improved grain structure in the steel; and it will also contribute to improved bearing conditions on the mill due to the very slow turn-' ing of the roll necks in the bearings.

Ordinarily it is preferable that the mill will be run wet and a liberal amount of water will be applied only to that side of the rolls on which the sheet makes its exit from the mill, special means being provided and precautions being taken to prevent any quantity of water from being in contact with the entering side ofthe rolls. This feature of applying the water only to the exit sideof the rolls and excluding it from the entering side is regarded of prime importance because such novel practice conserves the heat on the entering side of the work being rolled and thus contributes to the novel result of effecting the breakdown in a single pass.

The water falling on the exit side of the work therefore cools that side only. This cooling at the exit is no detriment for the reduction in thickness has already been accomplished. It is possible, however, and sometimes preferable to run the mill as a hot mill, that is, without play-- ing water on any part of the rolls.

It is proposed to heat steel for this mill in any number of furnaces or in any type of furnace that will provide steel of a uniform temperature. The steel may be heated and rolled at a temperature equal to present day practice, which is about 1375 F., but I preferably heat the stock to approximately 1475 F.

By the improved method of this invention, this steel starting in the form of strip, bars or pairs of any reasonable thickness, will be reduced to the required thickness of a breakdown by taking only one pass in the above mentioned mill, the preferred thickness of a breakdown being approximately .05". I may roll each sheet singly or in multiples so far as thickness is concerned. Preferred practice will be to match the steel and roll double; that is, to lay one piece of steel on top of another before passing through the mill. The starting material, which it is clear from the above may be in either the form of strip, bars or pairs comprising matched bars or the like of required thickness, will be referred to herein for brevity as the work This work comprising either single or matched sheet bars or matched strip will be reduced to the required breakdown thickness in one single rolling operation or pass through the mill.

By this method all of the work of breaking down is accomplished in one single pass on the steel while it is at a relatively high temperature and easy to work, as compared to the old practice of breaking down in several passes, wherein each pass is made at a lower or cooler temperature than the preceding one, and harder and harder to work.

The rolls of the breakdown mill may be of steel, iron or any suitable alloy. Although described as a breakdown mill, 9. mill of the samesuitable rolls for giving a prop surface to finished sheets.

According to practice prior to the invention, three-high mills, comprising a large top roll, a large bottom roll and a small middle roll, are used to some extent for making breakdowns. Heretofore, to keep the rolls in proper shape and to prevent excessive spalling of the rolls it was necessary to keep the rolls drenched with water on both sides of the mill. The steel, therefore, when rolled on conventional threehigh mills is reduced in temperature materially by this large amount of water before it can be passed through the required number of passes between the bottom and middle rolls and between the middle and top rolls. This rolling in several passes and at low temperatures causes excessive roll cost on such a mill. It is eliminated, however, by the use of my improved novel method of rolling disclosed and claimed herein.

Although a mill having two rolls of large diameter has been mentioned the same method of rolling can be accomplished by using three-high mills, comprising a very large bottom roll, a very large top roll and a relatively small middle roll; the top roll. to be used for stiffness only; the mill to be worked as a single pass mill, taking the pass preferably between the bottom and middle rolls. The same applies to four-high type or cluster type mills,-but in each case the peripheral speed of the rolls, in contact with the steel being rolled, is to be reduced very materially below present day conventional practice.

So far, in this description of improved. method of rolling reference has been .made to steel or iron sheet mill practice. The same principle can also be carried outin tin mill practice.

In speaking of a breakdown, it is understood that this is not a finished product. The breakdowns after leaving the mill will ordinarily be reheated and rolled to finished products on other mills. Some of the sheets, however, as mentioned above can be finished in packs by the improved method of rolling herein described.

The mill used in carrying out my improved method of rolling may have any type of feeding table, mechanically or hand operated and may be equipped with a power operated discharge table or delivery table.

The following advantages accrue from the practice of my improved method of rolling:

Fzrst.Enormous increase in tonnage as compared to present day conventional practice, either on two-high or three-high mills, due to the fact that the breakdown 'work is accomphshed in only one pass and the mill may be practically continuously fed. This continuous feeding of a mill is in striking contrast to the conventional present day' practice of -irolling, which not only requires several passes, each successive pass taking longer than the first, but also involves a time loss in passing the steel from the catcher (exit) side to the roller (entrance) side over the top roll in the case of the two-high mill, and in manipulating the front and back feed tables in the case of the threehigh mill.

v Second.-Reduction in labor cost per ton of steel rolled. Present day conventional practice on a two-high mill producing breakdowns is to employ a rougher and screw boy on the front side of the mill and a "catcher on the back side of the mill. These three men must be skilled in the art of rolling as the screwdown on the mill must be properly set for each pass and must be very accurately set for the finishing pass, and if not, the breakdown will be offgauge. The crew required to operate a threehigh mill when producing breakdowns with mechanical feed tables front and back consists of three men. The three-high mill also requires the same accuracy of screwdown adjustment as the two-high mill. Using my improved method of rolling the crew consists of two men, one man on the furnace side of the mill who will, by the use of mechanical mechanism, feed the steel to the mill as it comes from the furnaces; one man back of the mill to take the steel away as it is discharged from the mill or delivery table. This latter man can be a low price man compared to the present day mill catcher. In addition to this reduction in operating crew, this reduced crew will produce several times the tonnage per mill as compared to the present day two-high or three-high mills.

Third.A reduction in roll cost per ton of steel rolled will be obtained as compared to present day conventional practice. This is due to the fact that the large diameter rolls will afford more surface for cooling and can on that account be better cooled, which will result in maintaining a better condition on the surface of the rolls than is possible under prior practice.

Fourth.The power consumption per ton of steel rolled will be less than in prior practice due to the fact that all of the work is being done while the steel is at a higher temperature than the average temperature at which it was rolled heretofore. This holds true even though the initial heat on the steel is not in excess of conventional practice.

Fifth-My method will give a better grain structure in the steel than is obtained'by present day conventional practice, due to the fact that the steel is being worked while hot instead of relatively cold. The steel by my improved method of rolling is worked very slowly and in addition to this, I accomplish a forging or pressing of the steel with the large diameter rolls, as distinguished from the somewhat tearing action of small diameter rolls.

Sixth-A more uniform gauge or thickness of breakdowns can be obtained by my method than can be obtained from present day conventional practice, due to the fact that the latter necessitates setting the screwdown accurately for each pass; the accuracy of finished gauge, therefore, depending upon the human element. My improved method of rolling doesnot require the setting of the screwdown for several passes, because it contemplates only one pass. The screwdowns will be set once for the proper gauge of the material as it leaves the rolls and this setting will not be changed except as may be necessary to adjust for wear on the bearings or for dimensional variations of the rolls or housings which may occur due to change in temperature.

The foregoing description is to be interpreted in an illustrative rather than a limiting sense since various modifications may be made by those skilled in the art without departing from the invention as defined in the appended claims, it being understood that the claims are to be construed as broadly as is consistent with the teachings of the prior art.

What I claim is:

1. In the rolling of breakdowns, the method which consists in reducing the work to the required breakdown thickness by subjecting the work to one pass between rolls of relatively great diameter as compared to the conventional thirty inch rolls heretofore used, applying cooling water to the exit side of said rolls and excluding said water from the entrance side of the rolls so as to conserve the temperature of the entering part of the work.

2. In the rolling of breakdowns, the method which consists in subjecting the work to only one single rolling operation while the entering side of the work is maintained at the optimum rolling temperature, and applying a cooling medium to the exit side of the rolls;

ARTHUR B. HASWELL.

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