US1819291A - Method of annealing sheet copper - Google Patents

Description

Aug. 18, 1931. G. A. HEMPSTEAD 1,819,291

METHOD OF ANNEALING SHEET COPPER Filed Jan. 30, 1930 WITNESSES INVENTO R W d 3 W Q WQ w 1o yention is especially applicable to the heats sheet copper as ust copper in muflle,

2 to heat sheet copper directly by i have considered it to be impossible to so heat ity of the material by reason of the alloying Patented Aug. 18, 1931 UNITED STATES PATENT OFFICE".

To run narrower. BRASS a or onto GEORGE A. HEMIPSTEAD, OF LISBON, OHIO, ASSIGNOB COPPER 00., OF LISBON, OHIO, A CORPORATION MEilTHOD OF ANNEALIIVG SHEE'IP'COPPEB Application filed January 30, 1930. Serial No. 424,567.

The invention relates to the heating of I The invention is predicated upon my dissheet metal, andwhile in its broader aspects covery, made after extensive study and exit is unlimited to the heating of any particuerimentation, that sheet copper may be lar sheet metal, it has been found to be espereadily heated at low fuel, labor and furnace ciall applicable to the heating of sheet cop installation and up-keep costs, by impinging per, by which is meant throughout the speciupon the top and bottom of the sheet jet flames of raw fuel gas confined in a furnace chamber constructed to supply air for supporting combustion of the gas. I have further discovered that when sheet copper is annealed in the manner thus generally explained, and as will presently be described in greater detail, the sheet is of superior quality, that there is a minimum loss of metal due to oxidation, and that the surface of the sheet is not injured. Specifically, sheet copper thus heated becomes coated with a film of black oxide after being removed from the furnace, which coating is much thinner than the oxide scale coatings formed on such sheet when heated according to the prevailing practice. This thin film of oxide may be readily removed without material loss of copper by passing the sheet through a bath of sodium or potassium cyanide, or other suitable chemical. In the practice of the invention sheet copfication, and in the claims, any copper base sheet material containing not less than about 50% by weight of copper. Because'the in-. mg, either for working or for annealing, o defined, it is herein described with reference to such applicability. The prevailing practice is to heat sheet or semi-muffle furnaces, by the latter of which is meant a furnace in which heating flames are prevented from directly impinging upon the sheet. Because such attempts as have heretofore been made flames have resulted in producing on the sheet what is generally designated as an orange skin surace, which is a roughness that cannot be re-' moved by pickling, those sldlled in the art this material. Also, because copper readily alloys with various elements, previous atper, and sheets of other metals or. alloys tempts toheat sheet copper'by 'directflames WlllCh may be similarly treated, are heated,

either'for working or for annealing, by causing them to move continuously through an open-ended low-tunnel furnace in which the sheet is heated by direct contact with imping ing neutral jet flames of natural or artificial fuel gas which envelop the sheet and protect it against oxidation. The fuel gas is preferably supplied directly to the tunnel of the furnace without being previously mixed with air or any other oxygen supply, the oxygen for supporting the combustion of the gas being supplied by air which enters the open ends of the tunnel. Preferably, the impinging flames of fuel gas are placed at each end of the tunnel, both above and below the sheet passing throu h it, and the products of combustion are withdrawn from the central portion of the tunnelso that the heating sheetimpinging and sheet-enveloping flames flow from both ends of the tunnel towards its center.

The invention may have resulted in the impairment of the qualof the copper with elements found in or mmgled with the products of combustion. Furthermore, in the prior heating of sheet copper in muflle or semi-mufile furnaces, the procedure is slow, and the fuel, labor and furnace up-keep costs .are .high. In' such furnaces the heating of the sheet copper is effected by radiation from the bottoms, sides and crowns of the heating chambers which must be first heated to a high temperature, and which, on account of such high heating, readily spall, crumble and wear away. uch furnaces are also'objectionable because efiicient and proper operating conditions are diflicult to obtain and maintain due to the human element entering into their operation, as well as to openings in the furnace doors, and to unskillful firing and poor balance of flames on account of the failure of mechanical fuel mixtures to function umformly.

be further explained with reference to the accompanying drawings which somewhat diagrammatically illustrate a simple form of apparatus with which it may be practiced. In the drawings, Fig. 1 is a longitudinal central sectional View of an annealing furnace, and Fig. 2 a transverse sectional view-taken on the line II-II, Fig. 1.

In Fig. 1 there is shown a tunnel furnace comprising two like units, the number of which may be varied depending upon the clifferent requirements of service. Each furnace comprises a 10v; tunnel 1 open at each end and provided centrally with a flue 2 for of excess products of continuous conveyor 3 adapted to be moved at various suitable speeds, as by a variable speed electric motor 11. The sheets are moved from left to right through the furnace as viewed in Fig. 1, and emerge from the furnace on an exposed extension of the conveyor. Raw fuel gas, either natural or artificial, is supplied to each end of each tunnel y burner pipes 4, connected to a supply pipe 5, and arranged above and below conveyor 3.

he arrangement of pipes 4, and the disposition of the burner openings in them is such flames impinge directly upon and entirely envelop the sheets passing through furnace. The entire supply of oxygen or supporting the combustion of the fuel gas is that of the air entering the open ends of the tunnel.

I have found that by properly controlling the supply of gas to products of y properly regulating the rate of travel of continuous conveyor 3, sheet copper may be rapidly heated and annealed by their direct contact with combusted fuel gas impinging flames which also protect the sheet against excessive oxidation. The copper, being a rapid conductor of heat, absorbs for useful The heating or annealing being effected by direct contact with the combusted impinging jet gas flames, the furnace maybe of much eating types of furnace which are wasteful of fuel and expensiveto construct and maintain. Different furnaces may be constructed to heat or anneal diflerent sized sheets, thus making it unnecessary to operate large furnaces forvsmall sheets. These and other ad vantages of my invention have been well established by extensive commercial prac tice.

1 By way of example, and not of limitation, I have found that a standard sheet of copper. 30 inches wide, 96 inches long and .0215 of y. of the tunnel.

for supporting combustion being an inch in thickness, may be fully annealed by passing it at the rate of 42 feet per minute through a double unit furnace of the form shown in the drawings,

copper sheet may be raised to its annealing temperature of about 1100 F. with a furnace temperature as low as 400 F. However, prolonged use of the furnace results in its temperature being increased materially above this amount. I have raised the temperature of copper sheet to about 1500 F. without the formation of sufficient oxide on the sheet to cause it to scale. Over an extended period of time full annealing of this material has been effected in this furnace by an average consumption of 557 cubic feet of natural gas per 1000 pounds of metal.

According to the provisions of the patent statutes, I have explained the principle and mode of construction and operation of my invention and have described the preferred manner of practicing it, and have illustrated apparatus whereby it may be practiced. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described and illustrated.

I claim as my invention:

1. The method of heating sheet copper, which consists of passing such sheet continu-- ously throug an open ended tunnel furnace, and heating the sheet therein by'enveloping it in impinging jet flames of fuel gas to which 2. The method of heating sheet, copper,

which consists of passing such sheetcontinuously through an open ended tunnel furnace, and heating the sheet therein by enveloping it in impinging jet flames offuel gas applied at each end of the tunnel, the oxygen for supporting combustion of thefuel gas eing supplied by air entering the open ends combustion fromthe central portion of the tunnel.

end of the tunnel, the oxygen of the fuel gas supplied solel open ends of the tunnel, and removing the products of combustion from the central portion of the tunnel.

In testimony whereof, I.

GEORGE A.

sign my name.

HEMPSTEAD.

and removing the products of r y by air entering the l

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