US 2663558 A
Description (OCR text may contain errors)
Dec. 22, 1953 'QRNITZ ETAL 2,663,558
FURNACE CONVEYER ELEMENT Filed Jan. 21, 1949 INVENTORJ M TIN N.ORNITZ 8 AY H.ENGLISH \%-J4'7U-IWAEI Patented Dec. 22, 1953 UNITED STATES PATENT OFFICE FURNACE CONVEYER ELEMENT of Delaware Application] anuary 21, 1949, Serial No. 71,886
i This invention relates to furnace rqconveyor -ele- .ments and the manufacture thereof. It has to do with furnace :conveyor elements on which work is supported .and advanced through heating furnaces to be heated .therein and to the making-ofsuchelements. Apurpose of the invention is to provide furnace conveyor elements which :are superior in that they have no deleterious eifectu-ponthe work carried thereby in the presence of the furnace atmosphere at temperatures above 1200 as, for example, in the annealing of sheets at about 1600" F., yet are of relatively simple construction and economical to manufacture.
Our invention is applicable to furnace conveyor elements and the manufacture thereof generally but for purposes of explanation and illustration the invention will be described as embodied in a furnace conveyor roll .and as practiced in the manufacture of such a roll. We shall describe the structure and manufacture of a roll for conveying sheets through an annealing furnace.
Those skilled in the art are aware of the difficulties encountered in the use of metallic conveyor elements in heating furnaces. For example, conveyor rolls used in sheet annealing furnaces tend to collect accretions of material from the sheets which dent the sheets passing thereover. The problem is particularly acute in the treatment of high silicon steels and other steels requiring high annealing temperatures. Thephenomenon of accretion formation is complex and is influenced by the composition of the sheets carried by the rolls, the pressure of the sheet on the roll and the composition and temperature of the furnace atmosphere as wellas the character of the roll surface. The problem and one solution of it are explained in Patent No. 1,951,766. That patent teaches the use of refractory inserts such as inserts of silicon carbide in furnace conveyor elements, the refractory inserts engaging the Work passing through the furnace. While no oxide coating forms on silicon carbide inserts and such rolls are satisfactory for certain steels, it has been found that accretions do form on the surface of silicon carbide inserts when used in the annealing of high siliconsteels. Furthermore, the provision and application of the refractory inserts entail substantial labor and expense. The present invention is an improve-- ment rendering refractory inserts unnecessary.
We provide a'furnace conveyor element having an oxidized surface which has the advantages of refractory inserts as in Patent No. 1,951,766 but can be fabricated. at materially reduced cost,
provides a generally superior construction and has wider application. We provide a furnace conveyor element having a work-engaging .portion comprising aluminum oxide. Our furnace conveyor element may comprise a metal body with a Work-engaging portion thereon containing aluminum oxide in powdery form. If .desired, only a portion of the body is covered with aluminum oxide to provide a Work-engaging portion.
Desirably our faceconveyor element-comprises a metal body having aluminum alloyed .to the surface thereof, the surface of the aluminum being oxidized to form a Work-engaging surface. The conveyor element may be in the form of .a conveyor roll comprising a metal body having at at least a portion of the peripheral surface thereof a Work-engaging area comprising aluminum oxide. The thickness of the coating should be greater than .005".
We further provide a methodof makinga furnace conveyor element comprising providing a metal conveyor element body, bonding aluminum to at least a portion of the surface of the body and heat treating the aluminum coated body to form aluminum oxide at the surface thereof to provide a work-engaging portion. Thealuminum may be applied to the conveyor element body in any suitable Way. We find it-convenient to spray the aluminum onto the conveyor ele- ,ment body using any metalizing spray gun as well known in the art. The aluminum should be sprayed onto the body to a depth greater than .005 and should cover that portion of thesurface of the body which is to be the work-engaging portion of the element.
, Desirably the conveyor element'body with the aluminum applied to the surface portion thereof is first heat treated to bond the aluminumitothe surface portion of the body and thereafter the conveyor element body withthealuminumbonded to the surface portion thereof is separately heat treated to oxidize the surface of the aluminum to provide a work-engaging portion. The aluminum which has been applied to the body is preferably covered, as, for example, with aluminum paint, to protect'it against oxidation during bonding. The bonding is accomplished at a temperature of the order of i200-l F. and the oxidizing of the aluminum is accomplished at a temperature of the order of 1600-1760 F.
Other details, objects and advantages of the invention Will become apparent as thefoll'ovving description of a present preferred embodiment thereof and a present preferred method of practicing the same proceeds.
9 and are journalled in the bearings H.
l400 coated conveyor element body so that its tem- In the accompanying drawings we have illus trated a present preferred method of practicing the invention and have shown a present preferred form of furnace conveyor element prepared in accordance therewith, in which Figure 1 is a perspective view of a furnace conveyor roll shown as having its work-engaging surface sprayed with aluminum;
Figure 2 is a diagrammatic fragmentary cross-.
sectional view to enlarged scale through the body of the roll;
Figure 3 is a diagrammatic and fragmentary plan view of a lower portion of a sheet steel annealing furnace having rolls therein of the kind illustrated in Figures 1 and 2, said plan view being taken generally along line IIIIII of Figure 4; and
Figure 4 is a diagrammatic and fragmentary view in elevation of the furnace portion shown in Figure 3 taken generally along line IV-IV thereof.
Referring now more particularly to the drawings, a hollow furnace conveyor roll is designated generally by reference numeral 2. The roll comprises a body of work-engaging portion 3, necks 4 and conical portions 5 joining the necks to the roll body. The roll may be a steel or alloy roll of known composition. A plurality of such rolls 2 may be mounted for rotation within the refractory walls 9 forming the chamber of an annealing furnace Hi. The necks 4 of the rolls 2 extend through registering openings in the walls There is provided means for spraying aluminum onto the roll body 3, such means being shown diagrammatically in Figure l as a metalizing gun 6 by which the aluminum is melted and applied. Preferably the roll is rotated and the gun trav ersed along the roll until the roll body 3 is covered to the thickness desired. 7
The roll body -is covered with aluminum to a depth greater than .005" and to perhaps a depth of .01" to .02. The aluminum forms a solid coating on the roll. As initially applied it is simply adherent to the roll. Prior to bonding the aluminum to the roll the aluminum may be protected to prevent oxidation during bonding, as, for example, by painting it with a protective coating of aluminum paint. The bonding is effected at a temperature of the order of 1200- F. Preferably we heat the aluminum perature rises slowly to about 1200 F. and we then hold the temperature at about 1200 F. for
about two hours, whereafter we raise the temperature to about 1400 F. and hold it there for about one hour. This effects the bonding of the aluminum to the body. We thereafter raise the has a dusty or powdery appearance and is of a whitish-grayish cast.
When the aluminum is coated with aluminum paint to protect it during bonding it is not necessary to remove the aluminum paint during the full temperature of the conveyor element body with V 4 oxidizing stepas at the higher oxidizing temperatures the paint largely oxidizes and, in any event, has no substantial protective effect.
At the end of the oxidizing step the roll is cooled in the furnace and any residual oxidized paint is flaked or rubbed off. The roll is then ready for service.
Referring to Figure 2 of the drawings, the roll body is shown at 3 and the coating is designated 1. The alloy layer through which the coating is bonded to the roll body is designated 8. The figure is, of course, largely diagrammatic.
It is old in the art to aluminum-coat metal for resistancegto oxidation but, so far as we are aware, the provision of an aluminum oxide coating on a furnace conveyor element to counteract the tendency of the conveyor element to col lect accretions of metal from work passing through the furnace is new. In our structure the aluminum oxide coating has only the accretion inhibiting function and does not function to protect against oxidation. Indeed, the surface of the aluminum oxide coated element may be somewhat porous, possibly to a depth penetrating the alloy layer, and does not afford adequate protection of the base metal against oxidation at high temperatures.
When conveyor elements other than rolls are made the process employed is generally the same, the coating being applied to the surface portion or portions of the conveyor element normally coming in contact with the Work during operation of the furnace.
While we have shown and described a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.
1. In combination, a furnace conveyor element having a work-supporting ferrous or alloy body, said body having a melting point above about 1400" F., an aluminum oxide surface covering the work-engaging portion of said body, said surface being in weld relation to the work-engaging exterior portion of said body.
2. In combination, a furnace conveyor element having a ferrous or alloy body, a thin aluminum coating covering said body in bonded relation thereto and having a work-engaging surface con sisting essentially of aluminum oxide, said body having a melting point above about 1400 F.
3. In combination, a furnace conveyor element having a ferrous or alloy body and a thin aluminum coating in weld relation thereto over the in terface between the body and said coating, said body having a melting point above about 1400" F., said coating covering the work-engaging exterior area of said body and having a depth greater than about .005 inch, said coating further having its work-engaging surface comprising aluminum oxide.
4. In combination, a furnace for heat treating metal work at 1400" F. or above, at least one conveyor element in said furnace to engage Work passing through said furnace, said conveyor ele ment having a work-supporting ferrous or alloy body, said metal body having a work-engaging portion, said work-engaging portion having an aluminum oxide surface, whereby the formation of accretions is inhibited when work engages said aluminum oxide surface.
5. In combination, a furnace for heat treating metal work at 1400 F. or above, at least one conveyor element in said furnace to engage Work passing through said furnace, said conveyor element having a work-supporting ferrous or alloy body, a thin aluminum coating in weld relation to said body along the interface between said body and said coating, said coating having a workengaging surface of aluminum oxide, whereby the formation of accretions is inhibited when work engages said aluminum oxide surface.
MARTIN N. ORNITZ. RAY H. ENGLISH.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,409,017 Ortiz Mar. 7, 1922 Number 6 Name Date Brown May 20, 1930 Jalens July 14, 1936 Fallon Nov. 1, 1938 Rowe Mar. 21, 1939 Laing Mar. 21, 1939 Whitfield et al Aug. 1, 1939 Simmons June 3, 1947 Stookey Sept. 30, 1947