US2922223A

US2922223A - Method for the production of a nonfrilled metal strip from metal powder

Info

Publication number: US2922223A
Application number: US627662A
Authority: US
Inventors: Boughton Arthur Reginald; Worn David Kenneth
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1955-12-15
Filing date: 1956-12-11
Publication date: 1960-01-26
Anticipated expiration: 1977-01-26

Description

Jan. 26, 1960 .BOUGHTON ETAL 2,922,223

METHOD FOR THE PRODUCTION OF A NON-FRILLED ME STRIP FROM METAL POWDER 2 Sheets-Sheet 1 Filed Dec. 11. 1956 Jan. 26, 1960 Filed D60. 11, 1956 A. R. BOUGHTON ETAL 2,922,223 METHOD FOR THE PRODUCTION OF A NON-FRILLED METAL STRIP FROM METAL POWDER 2 Sheets-Sheet 2 FIG. 3

ARTHUR REGINALD BOUGHTON DAVID KENNETH WORN INVENTOR.

BY MK ATTORNEY NIETHOD FOR THE PRODUCTION OF A NON- FRILLED METAL STRIP FROM METAL POWDER Arthur Reginald Boughton, Northfield, Birmingham, and

David Kenneth Worn, Hall Green, Birmingham, England, assignors to The International Nickel Company, Inc., New York, N.Y., a corporation of Delaware Application December 11, 1956, Serial No. 627,662-

Claims priority, application Great Britain December 15, 1955 3 Claims. (Cl. 29-4205) The present invention is directed to a method for producing metal strip by the direct compression or compacting of metal powder and more particularly to a method for the direct rolling of metal powder to fiat strip having a width in excess of about one inch and being free of frilling along the edges.

It is known to form metal strip from metal powder by a series of steps. In the first step, the powder is fed between a pair of horizontal cylindrical rolls, with their axes arranged in a plane which may for example be horizontal, which compact the powder into a continuous strip having sufficient mechanical strength to withstand a limited amount of further handling. The compacted strip is next sintered by passage through a furnace at a high temperature and the sintered strip, which is still porous, is then subjected to a series of cold rolling operations, with intermediate annealing stages, to reduce it to a dense, non-porous strip.

In the first step, the powder has hitherto been fed from a hopper directly into the roll gap, or alternatively onto one roll, which as it revolves carries the powder into the roll gap as a layer uniform in thickness throughout its'width. These methods give satisfactory results in making narrow strip with a width of up to about one inch. As the width of the strip produced is increased, for example, to about six inches, it is found that the edges of the strip tend to form into frills to an increasing extent in the course of subsequent cold rolling. This effect is aggravated if, in order to avoid contamination of the porous material by lubricant, the cold rolling is carried out using unlubricated rolls. Further attempts to cold roll such frilled strip only lead to very severe distortion and even splitting of the strip, and no convenient way of restoring it to the desired flat state is known.

It is an object of the present invention to provide a method for rolling metal powder to fiat metal strip having a width in excess of about one inch and being free of frilling along the edges.

Another object of the invention is to provide a method for directly compacting metal powder into metal strip exceeding about one inch in width such that the resulting compacted strip can be brought to a substantially non-porous state by cold rolling and annealing while remaining fiat and being free of frilling along the edges.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing in which:

Figure 1 depicts an elevation of a rolling mill adapted to roll metal powder into metal strip and having powder feeding meanscontemplated in accordance with the invention; a

Fig. 2 depicts a plan view of the apparatus shown in elevation in Fig. 1; and

. Fig. 3 ,depictsa schematic representation for carrying outthe" process .of the present invention for rolling metal powder into metal strip which is free from frilling along the edges.

According to this invention, frilling of the edges of 2,922,223 Patented Jan. 26, 1950 the strip is eliminated or reduced by feeding the powder to the compacting rolls so that the amount delivered to the'rolls to form the center of the strip is greater than that at the sides.

Preferably, the powder to be compacted, e.g., rolled, in accordance with the invention is fed to the compacting rolls through a gap which is relatively wider in the region of the center of the rolls than'in the region of the roll edges such that powder feeding through the gap is formed into a layer which has a cross-section which is relatively thicker at the center than at the edges and the powder layer having the said cross-section is then fed into the rolls. We have found that when the conventional uniform feed of powder is used the powder tends to be forced from'the center to the sides of the rolls during the initial compacting, giving rise to a band of metal of higher density along each edge of the strip. As soon as the porosity of the strip has been reduced by cold rolling to such an extent that the effect of the cold work is to elongate the metal strip as well as to eliminate porosity, the diiference in density across the width of the strip leads to differential elongation of the center and edge zones which shows itself as frilling of the edges. The extra initial supply of powder in the center of the strip compensates for this tendency for the powder to be forced outwards during compacting and avoids the formation of zones of high density along the edges of the strip.

The rolls commonly used in. cold strip mills in the breaking-down stages are slightly cambered. When such rolls are used it is preferred to supply such an excess of powder to the center of the strip that the spreading effect of the compacting rolls is slightly overcompensated and there is a zone of higher density along the center of the strip in the early stages of cold rolling. When the cold rolling takes place the cambered rolls spread the metal outwards from the central zone of higher density and a flat product is obtained at the end of the series of cold rolling operations. In the case of compacting rolls arranged in the same horizontal or near horizontal plane, the invention may-be carried out by controlling the thickness of the layer of powder on the feed roll by means of a spreader plate so shaped that the gap between the edge of the plate and the roll surface is greater at the center than at the sides. A layer of powder is thus formed having a thickness which decreases progressively from the center to each side. The spreader edge may, for example, be concave in the form of an arc of a circle. The powder may be fed to the roll from a hopper extending above the gap, and the spreader plate may be mounted in the hopper and inclined to extendacross the gap nearly into contact with one roll as shown in Fig. 1 of the drawing. The inclination of the plate may be adjustable to give easy means of varying the thickness of the layer as a whole.

We have found that the relative amounts of powder fed to the center and sides of the rolls to form a strip of a given thickness will vary with the bulk density and flowing power of the powder used.

We have further found that the surface of the compacting rolls tends to become polished with use. The degree of polish may vary from side to side of the rolls. The amount of powder carried into the gap between a given pair of rolls at a given point of their width and compacted there decreases as the degree of polish of the rolls at that point increases so that it may be necessary from time to time to adjust the relative amounts of powder fed to the rolls at difierent points across their width. All these variations can be compensated for by the use of a set of difierently shaped spread er plates but it is preferred to use a spreader plate in which the contour of the controlling edge is adjustable.

One form of apparatus contemplated'in accordance with the invention is depicted in Figs. 1 and 2 wherein Fig. 1 depicts the section 11 of Fig. 2. In the drawing, 1 and 2 are the compacting rolls, 3 is a hopper for holding powder to be rolled and 4 is a form of adjustable spreader plate The spreader plate 4 consists of a number of narrow strips 6 of metal or other abrasionresistant material arranged side by side in a support 5 to form a pla'te'in which the lower ends of the strips define the controlling edge. The broken line 9 represents the element on the feed roll 1 which with the controlling edge of the spreader plate 4 forms a gap which controls the cross-sectional form of the powder layer entering the compacting rolls. It will be seen that the gap is wider in the region of the center of the roll than in the region of the roll edges. Each of strips 6 is longitudinally adjustable in the support. The strips may be slotted, the slots receiving screws 8 which enter the support and can be tightened to hold the strips in position. Alternatively, the support may be slotted as shown at 10. Finer and more convenient adjustment can be obtained, however, by making each strip engage the end of a set-screw mounted to turn in the support and in so doing to move the strip longitudinally.

Instead of feeding the powder onto only one of the rolls, it may be fed direct from the hopper into the roll gap, the flow being controlled by a wedge supported above the roll gap. Again, powder may be fed onto both the compacting rolls in two separate flows, each controlled by a spreader plate. This variation is useful if it is desired to form a composite strip from two different metal powders. r

Fig. 3 depicts schematically the method for rolling metal powder into metal strip having a width of at least about one inch and which is free from frilling along the edges. As shown in Fig. 3, metal powder 12 is held in hopper 3 and is fed to compacting rolls 1 and 2 between the gap defined by spreader plate 4 and the surface of roll 1. As more fully shown in Figs. 1 and 2, the gap between spreader plate 4 and the surface of roll 1 is greater in the region of the center of the roll than in the region of the roll edges. Powder 12 is compacted by rolls 1 and 2 into compacted strip 14, which is then sintered in sintering furnace 15. The sintered strip is then cold rolled in rolls 16 and 16'7after which it is annealed in annealing furnace 17 and again cold rolled in rolls 18 and 18'. Further successive stages of cold rolling with intermediate annealing may be employed. The dense, rolled strip, which is free from frilling along the edges, may be coiled on coiling drum 19.

As an example, in rolling a strip 5% inches wide from pure carbonyl nickel powder using a pair ofcompacting rolls each twelve inches wide and eight inches in diameter starting with a uniform powder layer about oneeighth of an inch thick delivered to the compacting rolls and said rolls having a roll gap such as to give a compacted strip 30/ 1000 of an inch thick, it was found that after sintering and two stages of cold rolling, with an intermediate annealing treatment, to give a total reduction of /1000 of an inch, the strip issuing from the rolls was badly frilledat the edges. Attempts to restore the strip to flatness by annealing and further cold rolling only increased the buckling. When the powder was delivered to therolls at the same rate but using a spreader plate so shaped that the thickness of the powder layer increased in a series of steps from zero at the sides to one-quarter inch at the center, it was found that using the same rolling speed a compacted strip, also about 30/1000 of an inch thick, was obtained which after sintering could be progressively cold rolled down in four stages to a fully consolidated, non-porous strip with a. uniform thickness of 5/1000 of an inch without any frilling or other distortion occurring.

It will be appreciated that in accordance with the invention metal strip can be produced in any desired length since it is only necessary to continue feeding powder to the mill in order to produce the desired amount of strip. Furthermore, it is to be pointed out that there is no necessity for employingany sort of carrier strip for the purpose of conducting the powder through the compacting rolls. The compacted powder emerging from the rolls has sufficient strength that it can be handled in subsequentjdesired annealing and/ or rolling operations designed to reduce the strip to a substantially compact, non-porous form.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim: 7

1. The method for producing substantially flat, dense metal strip by the direct rolling of metal powder which comprises feeding to compacting rolls a layer of uncompacted metal powder greater than about 1 inch in width, the cross section of said layer being relatively thicker toward the center thereof and decreasing in thickness towards each edge,.rolling said powder layer to compact said powder layer to metal strip, sintering the resulting compacted metal strip, cold rolling and annealing the compacted and sintered metal strip to produce substantially fiat, dense metal strip greater than about 1 inch in width andbeing substantially free from frilling along the edges. a

2. The method for producing substantially fiat, dense metal strip by the direct rolling of metal powder which comprises forming metal powder into an uncompacted layer at least about 1 inch wide and having a cross sectional thickness relatively greater towards the center thereof and decreasing in thickness towards each edge, feeding said powder layer through compacting rolls to compact said powder layer into metal strip, sintering the resulting compacted metal strip, cold rolling and annealing the compacted and sintered metal strip to produce substantially dense, flat metal strip wider than about 1 inch and substantially free from frilling along the edges.

3. The method for producing substantially flat, dense metal strip by the direct rolling of metal powder which comprises forming metal powder into'an uncompacted layer at least about 1 inch wide and having a cross sectional thickness relatively greater towards the center thereof and decreasing in thickness towards each edge by passing metal powder through a gap defined by a surface of a compacting roll and a spreader which is fixed further from the said roll in the region of the roll center than at the roll edges, feeding said powder layer through compacting rolls to compact said powder layer into metal strip, sintering the resulting compacted metal strip, and subjecting the compacted and sintered metal strip to a series of cold rolling operations with intermediate annealing stages to produce substantially dense, flat metal strip wider than about 1 inch and substantially free from frilling along the edges.

- References Cited in the file of this patent 7 Germany June 20, 1936