US2120318A - Method and apparatus for making sheet metal - Google Patents

Description

June 14, 1938.

R. 4. WEAN METHOD AND APPARATUS FOR MAKING SHEET METAL 2 Sheets-Sheet 1 Filed Nov. 17, 1956 m QZEwaEm INVENTOR} RaymonJJWean June 14, 1938. R J. w A

METHOD AND APPARATUS FOR MAKING SHEET METAL Filed Nov. 17, 1956 2 Sheets-Sheet 2 y MzM Patented June 14, 1938 UNITED STATES PATIEINT OFFICE METHOD AND APPARATUS FOR. MAKING SHEET MET L Application November 17, 1936, Serial No. 111.210

1 Claim.

This invention relates to the manufacture of sheet metal and, in particular, to the preparation of material of intermediate gauge in strip form for reduction by cold rolling to final gauge.

It has been the general practice in the manufacture of sheet metal heretofore to pickle hot rolled strip of intermediate gauge, cold roll it to final gauge, and then subject it to a heat treatment. It has been found, however, that stretcher strains, cross breaks and the like appear frequently in the strip while being cold rolled. Such defects, of course, result in the rejection of a portion of the product as below standard quality.

I have invented a method and apparatus for preparing strip of intermediate gauge for cold rolling to final gauge whereby the occurrence of stretcher strains, cross breaks and the like is avoided, and a much higher percentage of prime material is obtained from a coil of a give weight.

In accordance with my invention, I subject hot rolled strip of intermediate gauge to an op eration which I designate by the term tempering. This greatly increases the plasticity of the material and facilitates the cold reduction thereof. After tempering, the strip is subjected to an abrasive blast for the removal of scale therefrom. This blasting operation roughens the surface of the strip considerably. After scrubbing, drying and coiling, the material is ready for. cold rolling. I subject the material to a plurality of cold rollings either in a continuous mill or a reversing mill, and adjust the rolls of the mill so that a reduction of at least 20% in the thickness of the strip is made on the first few passes between reducing rolls, at least.-

I find that my invention makes it possible to produce a sheet metal having a bright, highly polished surface from a material which at the start has a rough surface and a dull appearance. This is entirely contrary to the belief which is general in the rolling art that it would not be possible to produce a smooth, highly polished final product from a starting product characterized by surface roughness and a dull finish.

My invention is described in greater detail hereinafter, with reference to the drawings illustrating diagrammatically a preferred arrangement of the apparatus for practicing my method and a novel feature of the apparatus itself. In the drawings,

Fig. 1 is a diagrammatic elevation illustrating the steps of my method;

Figs. 2A and 2B, when disposed side by side with the former on the right, constitute a diagrammatic plan view of the apparatus for carrying out a certain portion of the method;

Figs. 3A and 33 together constitute a diagrammatic side elevation of the apparatus shown in Figs. 2A and 2B; and

Fig. 4 illustrates diagrammatically a novel feature of the apparatus shown in Figs. 2A and 3A.

Referring in detail to the drawings, the material for the treatment of which my invention is particularly adapted may be made by passing a heated slab I through the several stands of a continuous mill 2 to produce a coil of hot rolled strip 3 of intermediate gauge. The hot rolled strip is then subjected to a series of treatments preliminary to cold rolling. It is these treatments, together with certain novel steps in the cold rolling itself, which constitute the present invention. In Fig. 1, the apparatus for treating the strip preliminary to cold rolling is represented diagrammatically by a rectangle 4. This apparatus is more fully shown in the other figures of the drawings, and will be described with reference thereto. After the preliminary treatment, the material in coils is advanced to a mill 5 where it is cold rolled to final gauge. I prefer a continuous mill for this operation, but a reversing mill may be employed. In any event, I find it desirable to employ a mill comprising a stand or stands having two work rolls and two or more backing rolls.

Referring now more particularly to Figs. 2A, 23, 3A and 3B, hot rolled strip of intermediate gauge, in coils-is delivered from the mill 2 on a conveyor 6 to a processing uncoiler I. The details of construction of this apparatus are wellknown, and it may be purchased in the open market so that it is unnecessary to describe the structure fully. The coil of strip is supported in the uncoiler and the material is progressively worked as it is unwound from the coil. The processing uncoiler I has the eifect of greatly increasing the plasticity of the strip, thus facilitating further reduction in the thickness thereof by. cold rolling.

As the end. of a coil is unwound, it is fed by pinch rolls 8 to an abrasive cleaning apparatus 9 comprising units I0 and I I. A stitcher l2 between the uncoiler and pinch rolls permits the leading end of one coil'to be attached to the trailing end of the previous coil whereby the material is passed through the remaining processing apparatus in an endless strand. The units l0 and II are also well known and purchasable from suppliers of mill equipment, so that a detailed description is superfluous. It is sufflcient to state that I prefer abrasive discharge apparatus incorporating a centrifugal abrasive throwing wheel, such as that wheel through a control valve. It is to be un-" derstood, furthermore, that the units l0 and H are effective to clean both surfaces of the strip.

I prefer to utilize a relatively coarse abrasive in the unit Hi. This removes the scale or oxide from the strip. In the unit H a finer abrasive is used. This produces a surface on the strip characterized by greater softness than that resulting from the first abrasive treatment, whereby final reduction in the thickness of the strip by cold rolling is further facilitated.

The material is drawn through the abrasive units I and II by pinch rolls l3. A shear I4 is provided for cutting out the stitched joint between adjacent strip lengths to permit recoiling thereof in separate coils. Before. being recoiled, the strip passes through a scrubber l5, which is effective to wash any remaining abrasive from the surface thereof, and through a continuous drier l6. Thence the material passes to a coiler l1 where itis rewound in coils.

The apparatus just mentioned is also well known and needs no detailed description. Each unit has its own operating motor, and is controlled in accordance with the usual practice. My invention contemplates, however, a novel form of control for the abrasive supplied to the units I0 and II. As stated, the abrasive is delivered to the centrifugal impellers through valved ducts or passages. I provide means for closing the valves in the abrasive supply 'ducts on stoppage of the strip passing through the units, for any reason. This prevents excessive abrasion of a portion of the strip in case it should be necessary to stop the movement of the latter at any time, for example, when stitching together the ends of adjacent strips, or shearing them apart. To accomplish this result, I employ a cylinder l8 (see Fig. 4) having a piston l9 therein adapted to be operated by fluid under pressure contained in a suitable source 20 and controlled by a valve 2|. The valve 2| is operated electromagnetically, an operating winding being shown at 22. A switch 23 is effective to close an energizing circuit for the winding 22 to operate the valve 2|. When so operated, fluid under pressure is admitted to the right-hand end of the cylinder 3, whereas, the other end is vented to the atmosphere. The resulting movement of the piston is effective through suitable mechanical connections, not shown, to operate the valve controlling the supply of abrasive to the centrifugal impellers disposed in the units l0 and II. The switch 23 may be operated in any convenient manner, in accordance with the movement of a strip through the units 10 and I I, so long as the arrangement is such that the switch 23 will remain open while the strip continues to move but will be closed in the event of stoppage thereof. The switch 23 may conveniently be a centrifugal switch mounted on the pinch rolls I3, although other types of switches operating in accordance with movement of the strip may be employed as well.

After the strip has been coiled in the coiler [1, it is delivered to the cold mill and there cold rolled to final gauge. As a typical example of a mill which may be employed for this purpose, I show a continuous mill composed of four 4-high stands, that is, each having two working rolls and two backing rolls. After passing through the processing line, indicated diagrammatically at 4 in Fig. 1 and in detail in the other figures, the strip is characterized by a roughened surface, the result of the abrasive treatment, a dull finish and a high degree of plasticity, the latter resulting from the treatment in the processing uncoiler. I find it desirable to take relatively heavy reductions on the strip at least in the first two or three passes through the cold mill. These reductions in ,thickness should be around 20%. This procedure makes it possible to produce a final product having a smooth surface and a bright, highly polished finish from a starting'material characterized by a rough surface and dull finish.

The rolls of the mill 5 should be ground and polished to a very high lustre, i. e., that which can best be described as giving them a dark bluish appearance. The theory I have evolved to explain the possibility of producing a smooth, bright, highly finished product from a dull roughened material, although I do not wish to be bound thereby, is that the metal on the entering side of the rolls of the stands of the mill 5 is dammed back by the bite of the rolls to such an extent that the roughness of the starting material is largely rolled out in the first few passes in the cold mill. The highly polished surface of the rolls permits the metal to flow relative thereto with comparatively little surface friction.

The roughness of the starting material is removed to a large extent as the material passes through the first stand of the cold mill. A large portion of the remaining roughness is removed on passage through the second stand, and by the time the material has passed through the third and fourth stands, it is entirely free from roughness and is characterized by the bright, smooth surface heretofore mentioned. I also prefer to apply back tension to the material entering the first stand of the cold mill, as this aids in removing the surface roughness from the starting material. Any convenient means may be employed for introducing this tension.

The advantages of my invention will be apelimination of stretcher strains and cross breaks is of great importance in producing high quality material with a minimum of scrap. This appears to result from the increased plasticity introduced into the strip by the processing uncoiler. The cost and speed of operation inaccordance with my invention compare very favorably with the previous practice, and as manual handling. of the material is reduced to a minimum, high production rates can be obtained.

Although I have illustrated and described but a preferred practice of the invention and apparatus therefor, it will be understood that many changes in the procedure or construction of the several devices involved may be made within the terms of the following claim.

I claim:

In a method of making sheet metal of a predetermined gauge, the steps including plasticizing hot-rolled strip of a thickness several times said gauge by placing a coil thereof in a processing uncoiler and drawing strip from the coil and through the uncoiler; uniformly cleaning and roughening the surface of the strip by moving it past a centrifugal abrasive-throwing mechanism, and reducing the thickness of the strip to said' gauge by subjecting the roughened strip to repeated reducing passes between highly polished rolls while cold.

' RAYMOND J. WEAN.

' parent from what has already been said. The

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