US2030891A - Rolling mill roll, method of making same, and product of such roll - Google Patents

Description

Feb. 18, 1936. w. H. PAYNE 2,030,891

ROLLING MILL ROLL, METHOD OF MAKING SAME, AND PRODUCT OF SUCH ROLL Filed Nov. IS, 1931 I NVENTOR Patented Feb. 18, l 1936 UNlT STATES PATENT OFFICE ROLLING NULL ROLL, METHOD OF MAKING SAME, AND PRODUCT OF SUCH ROLL Application November 5, 1931, Serial No. 573,307

3 Claims.

My invention relates to the rolling of sheet metal and the product produced thereby in which a surface is developed on the sheets which will permit of forming an even film of enamel coating thereon, which coating will persist during firing; The invention is particularly valuable in vitreous enameling.

Enamelers have in the past sought to key their enamel to surfaces of metal sheets by developing a roughness in the sheets prior to enameling, and to that end have acid treated the surface of chilled rolls usedin cold rolling the sheets, and also have acid treated the sheets themselves. The surfaces so developed have not been satisfactory from the 5 point of view of application of the liquid enamel film, however, and do not serve the purpose of my invention herein.

The-surface which I produce by my invention might be described as one which has a surface energyfor enamel films (such as water and silicate particles), that is highly developed without such roughness as would impart to the enamel film itself when applied, other than a perfectly smooth; surface. By surface energy is meant the power to retain and hold at a large number of pointsor small areas a film which would otherwise slip and flow, thus preventing the forming of uneven patches in the enamel, providing a perfectly regular and smooth coating easily applied, and permitting of the use of thicker coatings than would otherwise be possible.

I find that the surface required by my invention. is one consisting of tiny areas visible to the eye and alternately raised and depressed and which, incidentally, are a pattern of the intermixed hard and soft particles to be found in the portion next within the chilled portion of ordinary chilled rolls used in cold rolling of sheet metal.

0 While the roughened surface which I provide maybe, in a way, helpful in bonding the enamel coating to the sheet, the principal object of my invention is not directed to this purpose, the indentations forming the roughened surface being 5 of too large area to serve directly as a tooth for the coating; they rather subdivide the surface area to be coated into a multiplicity of very small areas. These small subdivided areas are bounded by irregular, more or less sharply raised ridges resulting from impressions imparted to the sheet surface according to my invention by a cold rolling operation between rolls whose characteristics will now be described.

Reference is now made to the drawing, wherein:

Figure 1 is a partial sectional view of a roll Gil showing in purely diagrammatic form the various constituent layers thereof as hereinafter described.

Fig. 2 is a drawing made from a photograph upon a considerably enlarged scale of the surface of a sheet treated by my process. This surface is the counterpart of the surface of the rolls employed to treat the sheets.

Generally stated, the rolls which I employ in producing sheets of novel roughened surface can be most readily prepared from rolls having an effective outer layer of alternating hard and soft constituents, for best results these constituents being of maximum hardness and maximum soft? ness, respectively, and maximum size, which may be possibly obtained in a cast metal structure. Such hard constituents are e. g., combinations of carbon and iron, such as cementite, while ferrite, combinations of ferrite and cementite (pearlite and its variants) and graphite may constitute the soft constituents of said effective surface layer of the rolls, the hard and soft areas being of such size as to be well perceptible to the unaided eye.

The rolls which I employ in producing my novel roughened surface on sheets which are to be subsequently coated, have initially a surface condition quite different from that of rolls usually employed in sheet rolling, including cold rolling, whose surface is made of as uniform hardness as practicable, e. g., chilled cast iron, which is uniformly dense, hard, and capable of receiving a very high polish. In contradistinction to this, the rolls which I employ have a surface of nonuniform hardness, hard and soft constituents such as cementite and pearlite and perhaps graphite alternating, as for instance, filler and binder alternate in a molded compound.

From a roll of the above described characteris-' tics I produce a roll suitable for giving sheets a treatment resulting in that roughened surface sought for by the present invention by merely removing the softer constituents of the roll surface to the extent that the harder constituents will appear in relief. There are many ways of producing a roll whose surface may be made suitable for my process, and its production by those skilled in the art will afford no difiiculty without specific instructions, after the principle is once elucidated. However, in the following the best and most economical manner known to me shall bedescribed.

The usual cast iron chilled roll employed in rolling mills is formed of two kinds of iron, a central core of gray iron I, and an outer surface of chilled iron 2. The outer chilled surface does not terminate abruptly, but forms with the gray iron an intermediate zone 3, in which .both gray iron and chilled iron are found together with small particles of graphitic carbon. The chilled iron is intermixed in the gray iron mass through this zone inthe form of small particles and sometimes in thin tree-like bodies known technically as dendrites, principally consisting of cementite in this case, whichi as is well known, is extremely hard. The intermediate zone containing the dendrites, or cementite particles, graphitic carbon and gray iron will, in this specification, be referred to as the dendrite zone, whether or not the characteristic dendrites are present.

In the cold rolling of sheet iron and steel, the rolls are from'time to time polished and trued up by revolving them against each other inthe presence of water, but as soon as the outer chilled surface is worn away and the dendrite zone begins to come into evidence, the rolls have in the past been scrapped as worthless, or used for roughing rolls in the hot mill.

In practice I may use these discarded rolls, 5

which when applied to steel or iron sheets will give them a roughness matching that of, the rolls,

which is the type of roughness required.

According to my process, I may thus employ chilled rolls which have been worn and polished downso as to be valueless for hot rolling orordinary cold rolling, or, of course, may employ chilled rolls from which the chill has been ground off, for likewise uncovering the dendrite zone.

One method of treating suchv rolls to" build up.

the surface required is to grind them against each other in the presence of water, as in polishing, which grinding action is continued for around eight hours. celerated by mixing with the water flown on the idling rolls some grinding compound which is of such hardness that it will attack the softer constituents of the roll surface, but not the harder.

ones. A material suitable as such a' grinding compound is, for instance, fine open-hearth flue dust. The rolls are then ready for use and are -employed, as in ordinary cold rolling, to impart oped is sharply marked. The rolls. so produced are used in the same way as surface finishing cold rolls in ordinary practice. The acid treatment of itself can be carried on in the same way that cold rolls have been treated in the past.

Another mode of providing a suitable roll for my purpose is to heat-treat chilled rolls, thereby modifying the carbon content in the original chilled surface and subsequently developing a roughened surface as hereinbefore described.

The grinding action may be ac- I have not attempted any other modes titrat- Q ing chilled rolls to develop a toothed surface roughness or marking,'but believe that other methods might be developed, once the efiectiveness of cold rolling-sheets with chilled rolls bared to the dendrite zone is known. Being, as I believe, the first to develop this idea, however, I

consider the general method to be my invention irrespective of how the roughness'is developed, 1

or the nature of the, structure in the dendrite zone that gives rise to the roughness. Special methods ofheat treating and chilling could no doubtbe'worked out which would produce a zone that would have a suitable roughness, without any treatment other than to remove the outer chill, or without having, to remove any portion of the chill.

I have indicated in Fig. 2 a portion of 9. treated sheet 5, having surface markings 6 shown on a considerably enlarged scale.

The product of rolling with cold rolls having a toothed rough or marked surface in the dendrite zone, or what corresponds to it, is quitedifferent in surface from any sheethitherto produced and with which I am familiar. The impressions in the sheet are fine in character and the bounding walls of the markings are sharp, that is to say, they project at an abrupt angle from the top of a projection to the bottom of a depression, and will persist after pickling, a step usually resorted to in the final metal sheets for enameling. The sheets have found great popularity with enamelers and are highly prized for vitreous enameling work.

- The invention has application, however, whenever the rough surface typical of a dendrite zone impression is desirable.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: 1. A process of preparing rolls for the formation' of roughenedsheets characterized by a dendritic pattern which comprises removing the chilled portion from a chilled cast-iron roll to leave a surface characteristic of a zone intermediate the chilled portion and the gray iron portion, and treating said surface by removing, in part at least, the softer portions thereof so that the harder portions thereof stand up in relief in accordance with the structure of said zone.

2. A roll for rolling. sheet metal to be used as enameling stock, the entire working surface of said roll which is used in the rolling operation be-. ing a roughened surface of a pattern characteristic of the dendritic structure of that intermediate zone in a chilled casting which lies between the chilled outer layer and the gray iron inner body of the casting, the harder portions of the surface in said dendritic zone standing in relief above the softer portions thereof.

3. A sheet of ferrous metal particularly adapted for use as enameling stock, said sheet having a surface which, irrespective of its metallurgical structure, is characterized by deep, sharp edged pits which are a counterpart of a relief pattern of the dendritic structure of that intermediate zonein a chilled casting which lies between the chilled outer layer and the gray iron inner body of the casting.

WILLIAM H. PAYNE.

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