US3122423A - Method and apparatus for hot rolling high quality metal sheet - Google Patents

Description

Feb. 25, 1964 B. H. HESSLER 3,122,423

METHOD AND APPARATUS FOR HOT ROLLING HIGH QUALITY METAL SHEET Filed April 4, 1960 2 Sheets-Sheet 1 F|G.l B 36 FIG.2 |2

:w 30 36 g) Ti? 32 IE/ INVENTOR 22 Burton H. Hessler 26-- 3O E! 4 1 h m r/ I ATTORNEYS Feb. 25, 1964 B. H. HESSLER 3,122,423

METHOD AND APPARATUS FOR HOT ROLLING HIGH QUALITY METAL SHEET 2 Sheets-Sheet 2 Filed April 4, 1960 1 INVENTOR Barton H.Hessler ATTORNEY$ United States Patent 3,122,423 ldETHGD AND APPARATUS FOR HOT ROLLING IHGH QUALITY METAL Sl-EET Barton Hamiltnn Hessler, Reading, Pa., assignor to The Beryiiium Corporation, Reading, Pa, a corporation of Deiaware Filed Apr. 4, 1969, Ser. No. 19,870 1 Claim. (6i. 29187.5)

This invention relates generally to a new and improved method of hot rolling metal into sheets and is directed particularly to such a method designed particularly for hot rolling high quality beryllium metal into sheet form. While the present invention is primarily directed to the fabricating of beryllium sheet, it is also applicable to such other metals as titanium (Ti), zirconium (Zi) and hafnium (Hf).

In connection with the formation of beryllium metal sheet, the second, as practiced prior to the present invention, embodies the cladding of the hot pressed billet prior to rolling in a husky mild steel jacket. This jacket consists of a central portion in the shape of what is termed a picture frame made of four frame-like members with mitered corners and adapted to receive the billet therein. This frame member with the billet therein is then placed between a pair of metal plates and the three parts of the structure encasing the billet are then welded together. This assembly is then heated to the desired temperature and while in heated condition it is subjected to rolling pressure.

The purpose of the jacket in which the billet is encased is, first, to provide necessary edge restraint during rolling to thus prevent cracking of the sheet and, secondly, to protect the metal of the billet from oxidation.

The cladding method as heretofore practiced has the disadvantage that it often causes cracking of the beryllium sheet during cooling after rolling due to the thermal expansion (or contraction) differential between the beryllium and the steel cladding. In addition this prior method tends to produce a rough surface on the finished beryllium sheet.

A particular object of the present invention is to provide a new and novel method and means for carrying out the same whereby the cracking of the metal s ieet due to thermal difierential, as above stated, between the same and the encasing body, is eliminated.

Another object of the invention is to provide by the present method a means of producing a high quality su face finish on the eryllium sheet.

More particularly the present invention has for an important object a new and novel procedure whereby the bonding of the beryllium metal billet and the encasing structure or cladding is prevented and thereby thermal stresses and associated cracking of the metal during cooling after rolling are eliminated.

It is still another object of the invention to provide a method and apparatus for carrying out the same wherein the formation of a bubble or bubbles within the assembly is prevented, such as may occur in connection with the carrying out of the procedure heretofore used due to the expansion of entrapped air when the assembly is heated for rolling so that, as a result of the absence of entrapped air within the cladding structure of the present invention, the cracking of the sheet during the cooling after rolling is prevented and an improved surface finish results.

The foregoing and other important objects are attained according to the present invention by the provision of a frame structure consisting of a sheet of boiler plate of suitable weight having an aperture cut therein, together with other plates of metal between which the frame structure is placed. The beryllium billet is enclosed within a carbon steel jacket and introduced into the frame which jacket is preferably formed of two channel members, and acts as a spacer between the billet and the frame and plate members. The channel members forming the jacket are left, and used, with the oxidized surface, commonly known as mill scale, thereon and this mill scale acts as a parting compound for preventing the bonding between the billet and the encasing metal.

Means is also provided for evacuating the chamber in which the jacket and billet are enclosed so that the formation of an air bubble by expansion of entrapped air on the heating of the assembly is avoided.

After placing the jacketed billet in the frame and placing the covering plates thereover, the parts are welded together after which the evacuation of the chamber is effected and the chamber is sealed.

The invention will be best understood from a consideration of the following detail description taken in connection with the accompanying drawings forming part of the specification, with the understanding, however, that the invention is not confined to a strict conformity with the showing of the drawing but may be changed or modified so long as such changes or modifications mark no material departure from the salient features of the invention as expressed in the appended claim.

In the drawings:

FIG. 1 is a view in perspective showing the complete assembly ready for the heating and rolling operation, the central portion of the illustrated structure being broken away;

FIG. 2 is a transverse sectional view taken substantially on the line 22 of FIG. 1;

FIG. 3 is a longitudinal section taken substantially on the line 33 of FIG. 1;

FIG. 4 is a perspective view of the parts of the assembly in separated or exploded relationship and as seen from a side of the assembly;

FIG. 5 is a perspective view of the parts of thee assembly in separated or exploded relationship as seen from an end of the assembly;

FIG. 6 is a view of the assembled frame and side or cover plates prior to welding the same together;

FIG. 7 is a perspective view on an enlarged scale of the channel members of which the billet encasing jacket is made up and showing the mill scale thereon.

IG. 8 illustrates in perspective an assembly wherein is shown another groove or channel form for receiving sealing weld material;

FIG. 9 is a partial sectional detail taken substantially on the line 9 of FIG. 8.

Referring now more particularly to the drawings, the numeral 10 in FIGS. 1 to 3 generally designates the complete assembly or composite unit in the final form thereof ready for the hot rolling operation.

The complete assembly includes an outer casing or jacket generally designated 12, an inner shell generally designated 14 and, of course, the beryllium metal billet which is designated B.

The casing 12 is completely sealed in a manner as here inafter described, and comprises the central frame body 16 and the cover plates 18 between which the frame body 16 is positioned as shown in FIGS. 2 and 3.

The frame body 16 is formed from a solid sheet of hot rolled mild steel boiler plate, preferably SAE steel 1010 or 1020. The plate from which the frame body is formed is provided with a central opening 20 which is formed by cutting through the plate so that the finished frame is a complete or solid one-piece body as contrasted with the heretofore employed frame body made up of four side and end members having mitered corner connections and welded together.

The frame body 16 and also the cover plates 18 are here illustrated as being of rectangular form although it is to be understood that they may be of square Outline if desired, or if this form is found to be more satisfactory for accomplishing the desired results.

Each of the longitudinal edges and each of the transverse end edges of the frame body is grooved or channeled as indicated, respectively, at 22 and 24. These grooves or channels are approximately J-shaped with the long leg of the J lying parallel to the adjacent edge face, as best seen in FIGS. 2, 3 and 6.

The cover plates 13 are of the same over-all dimensions as the frame body 16. These cover plates are preferably formed of the same type of steel as the frame body 16 and have smooth inner faces 26 for forming a good contact with the opposing faces 28 of the intermediately positioned frame body 16 when the parts are assembled.

Each of the bodies 18 has the side and end corners adjacent to the inner face cut out to form respectively a J channel or groove 30 and 31, of the same size as the grooves or channels 22 and 24 with which they are respectively matched when the parts are assembled.

At one end the frame body 16 has the longitudinally directed bore or passage 32 formed therethrough which opens into the central opening 20 of the frame and by means of which passage the area in which free volume surrounding the hereinafter described billet and its encasing jacket, is evacuated. Thus when the frame body 16 and the plates 18 are assembled in the manner shown in FIGS. 2, 3 and 6, the joining J grooves together form encircling substantially U-shaped channels 34 for the reception of weld material by which the elements of the casing are hermetically sealed together.

When the parts or elements of the casing are thus assembled there is formed a closed chamber 35 in which the shell encased billet is housed.

The shell 14 which encloses the billet B is formed of two corresponding channel members, which are shown in FIG. 7 and designated 36 and 37. These channel members are proportioned so that one may be joined to the other so as to form a closed chamber and they are also so proportioned that when they are joined together they will fit with close tolerance within the chamber 35 of the casmg.

As illustrated in FIG. 7 the channel member 36 comprises the elongate web portion 38 and the longitudinal right angularly related legs 39. The channel member 37 also comprises the longitudinal web portion 40 and the transversely extending perpendicularly related end flanges 41. These members fit one into the other as, for example, the length of the web portion 38 of the member 36 approximates the distance between the inner faces of the transverse end flanges 41 of the member 37 and the length of the side flanges 39 also approximates this distance so that these side flanges will also fit between the end flanges 41 of the member 37 to thus form a closed shell or jacket.

The members 36 and 37 forming the shell or jacket for the billet are fabricated from carbon steel and an important feature of the present invention resides in the fact that these members of the shell or jacket are used with the mill scale remaining thereon. This mill scale which is commonly recognized in the industry as, what may be termed, an interditfusion of oxides of iron, namely FeO, Fe O and Fe O covers all of the surfaces of the members 36 and 37 as illustrated particularly in FIG. 7 where such scale is indicated by the reference character S. The mill scale acts effectively as a parting material or compound which prevents cracking and checking of the surface of the billet as the assembly cools and which cracking and checking would otherwise occur by reason of the differential expansion and contraction characteristics of the assembly. In other words, this mill scale in acting as a parting compound, prevents bonding between the billet and the encasing shell or jacket and accordingly eliminates thermal stresses which otherwise would result in the said cracking and checking of the sheet.

In the fabrication of the shell or jacket members and the billet which they enclose, close control is kept of the cumulative tolerances one with respect to the other and with respect to the opening of the frame, it being preferred that such cumulative tolerances be kept to a maximum of .017 inch.

In assembling the parts the billet B is placed within the shell or jacket formed by assembling the parts 36 and 37 thereof in the manner described. Obviously the over-all height, length and Width of the shell or jacket must be approximately the same as the dimensions of the frame opening 20 so that when the cover plates 18 are placed in position against the two faces of the frame member there will be formed a tight interface, as clearly illustrated in FIGS. 2 and 3.

The parts 16 and 18 are then welded together by depositing the welding substance 43 in the channels 34.

After the assembly has been established as illustrated, a suitable connection is made with the evacuating passage or opening 32 as by means of a nipple 44 and by means of evacuating apparatus the interior of the chamber 35 and the area surrounding the billet is preferably evacuated to a pressure of less than 50 microns of mercury, whereupon the passage is sealed by compressing the nipple body, as indicated at 45 or in any other suitable manner.

Following the sealing of the billet encasing structure the assembly is heated to a temperature of between 1400" and 1525 F. and rolled while so heated.

By this new and novel structure and method of rolling beryllium metal the hereinbefore described desirable objects are attained. The attainment of such objects is, of course, primarily a result of the hot rolling of the assembly while the billet is encased in a hot rolled mild steel spacer shell or jacket which, together with the mill scale which is retained thereon, functions as the parting material.

It is, of course, known that in other arrangements designed to circumvent disastrous effects produced by thermal expansion differential, other types of parting compounds have been employed to prevent the beryllium billet and steel cladding from becoming bonded. Such compounds have included relatively inert powders such as graphite, beryllium oxide and aluminum oxide but no previous use has been made of a spacer jacket or other ferrous metal spacer carrying mill scale which functions as a parting compound, as stated, in association with the metal spacer.

While the U-shaped channels hereinbefore referred to and illustrated particularly in FIGS. 2, 3 and 6, are preferred for receiving welding material whereby to hermetically seal the frame and cover plates together, use may be made of channels of V cross section such as are shown in FIGS. 8 and 9. Here such channels are generally designated 53 and as is readily apparent, they are formed or produced by beveling the longitudinal and transverse edges of the centrally located frame member, generally designated 54, and by beveling one encircling edge of each of the cover plates which are generally designated 55 so that when the cover plates are 5 placed in position against the opposite faces of the frame 54, the V channel will be obtained, as will be obvious.

With this construction one-half 56 of a V channel will be formed around the frame 54 adjacent to each side face thereof and a cooperating half 57 of the V channel will be formed around the one edge of the cover plate 55. Except for this different form of channel or groove for the reception of the welding material to seal the plates together, the assembly is both interiorly and exteriorly the same as illustrated and described in the preceding figures.

I claim:

A structure for cladding a billet of beryllium metal for hot rolling the metal into a flat sheet, said cladding structure comprising a one piece thick metal frame sandwiched between two solid metal cover plates, a shell formed to provide a liner to fit Within said frame and shaped to fully and closely envelop a billet of the metal and consisting of two pieces of hot rolled mild steel,

relatively smooth finished surface to the sheet, means for hermetically sealing the frame and cover plates together, and means whereby evacuation of the frame and shell may be effected.

References Cited in the file of this patent UNITED STATES PATENTS 490,236 Wood Jan. 17, 1893 734,795 Allis July 28, 1903 1,895,299 Tytus Jan. 24, 1933 2,064,684 Ostendorf Dec. 15, 1936 2,159,043 Orr May 23, 1939 2,593,460 Johnson Apr. 22, 1952 2,645,842 Orr July 21, 1953 2,653,494 Creutz Sept. 29, 1953 2,820,751 Saller Jan. 21, 1958 2,872,363 Macherey Feb. 3, 1959 OTHER REFERENCES Mechanical Engineering, vol. 80, No. 8, August 1958, pub. by A.S.M.E., 20th and Northampton Streets, Easton, Pad pp. 67-71.

Nuclear Fuel Elements, ed. by Henry H. Hausner and James F. Schumar, Reinhold Pub. Corp, New York, @1959, pp. 48-58, 65 and 66.

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