US1902039A - Metal heating method and apparatus - Google Patents

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, March 21, 1933. J. J. MOLAUGHLIN METAL HEATING METHOD AND APPARATUS Filed May 9, 1932 2 Sheets-Sheet l INVENTOR Jbkn J/l/ Zing/2162i ATTGRNEY METAL HEATING METHOD AND APPARATUS Filed May 9, 1932 I 2 Sheets-Sheet 2 ATTORNEY Patented Mar. 21, 1933 JOHN.J'OSEPH..MCLAU'.GHLIN, OF NORTH TQTNAWANDAjNEW YORK mar-AL HEATING- .METHOD AND APPARATUS.

1 Applicationiled May 9, 1932. Serial No. 610,058.

My present invention concerns metal heating apparatus of the-type shown in Patents Nos, 1,243,44234.and1,302,843. These pat.- ents relate to progressively heating a contin- 5 -uous length of metal while feeding it automatically into, through and outof a furnace in such manner as to maintain an endless supply of hot metal for use inautoma-tic machines adapted to forge spikes, screws, bolts, nuts', or

0 the like.

Preferably, the blanks are as long as obs tai-nable and, where the bundle coils are used, successive coils may be electrically welded end to end to maintain a continuous unbroken length of material progressing through the furnace and to the forging machine. Effective heating to forgingtemperature requires that the metal passing through the furnacebe'kept freely exposed on al-lsides to high heat for a considerable time. To :do this with metal passing straight through the furnace would require either a very slow feed or a very long furnace, whereas it is desirable to use the relatively small compact furnace and to give the metal a desired highrate of feed into and out of the furnace combined with a relatively slow rate. of progress through the furnace. Consequently, it has been a common practice to bend the metal in more or .less open loops idisposed transversely to the adirection of feed through the furnace, adjacent loops being maintained in orderly relation by sliding them along a metal support.

In said patents, particularly Nos. 1,243,442

I and 1,302,843, this involves bending the material so .as to give it .a predetermined initial shape and .setin the curvature of an open coil or helix of desired diameter and length, suitable for the stiffness of the material and the size of the furnace.

By suitably predetermining the length, form and arrangement of the interior support and the number of turns of the helix for travel ofeach turn through the furnace may be as long as necessary. Hence, it is possible to maintain the required rate of output of heated material while using a relatively small, compact furnace.

hanging thereon, the length of time required Because ofthe efi'ec't of the heat upon the coiled material softening it, it is necessary to carefully control the rates of movement of the metal at the supply end and the exit end,

so that it will be-unwoundfrom the exit end i of the helix by the time it has become softened to the proper degree and before it becomes too soft to maintain proper separation of the turns of the helix.

It has also been proposed to b end themetal .in other shapes for'sliding it through the furnace, but in all cases, so far as I am aware, it has been found necessary to water-cool the support along which the metal slides, and the cold support cools the part of .the metal .in

vcontact therewith, with theresult that itis vdelivered to the forging machine having some portions of its length substantiallycooler and therefore harder than others. For this reason, it has been the practice to make the furvnace temperatures very high in order to properly heat the parts that are subject to cooling by contact with the water-cooledhanger; and

as maybe inferred from the specifications of some of said patents, such high temperatures make it difiicult to prevent theuncooled parts of the coil from becoming .too soft to maintain proper separation of the turns of. .thehe- .lix. or from becoming softened to the welding point.

During many years of practical experience in large quantity production'of bolts and the like, according to the above high temperature method of operation, the soft metal, high temperatures and water-cooled hanger were:

supposed to be necessary, and more 'thancompensated for by the ease with which highly heated, relatively soft iron can be shaped in the forging machine; but more recently I began to appreciate more fully the objectionable features; that the high temperature involves great waste of heat, particularly by heat losses through the walls of the furnace; makes it more diflicult to maintain the desired non-oxidizing temperature in the furnace; o and makes it more diificult to avoid scale formation on the hotter parts of the metal, resulting in an undesirable percentage of inferior product in the forging machine.

So I have "made certain observations and experiments, and as a result I have discovered that the forging machines, even though they may require more power, can be made to operate successfully on metal which is of 5 a much lower temperature, and correspondingly harder; that the resulting forged articles are superior; that the correspondingly lower temperature required for thefurnace eliminates danger of scale formation and makes it a relatively simplematter to maintain a non-oxidizing atmosphere. Secondly and incidentally, I have discovered that this lower range of useful metal temperatures is low enough so that the water cooling of the hanger may be entirely dispensed with; that thus the hanger is permitted to assume the temperature of the hot gases in the furnace. Third, that contrary to expectation, the hot hanger does not have the effect of producing arrangement 'of mechanical parts. somewhat for preferably, somewhere between that and as. concerns the forging machines; and that hot, over-heated, over-soft spots on the parts of the coil in contact therewith. That is to say, by the new method, the heat-imparting temperature-drop from the hot hanger metal to the fully heated coil metal in contact therewith, is enormously less than was the heat- "abstracting drop from heated coil to the water-cooled hanger and the coil metal in contact therewith. Moreover, the hot hanger that is imparting heat to the part of the coil in contact therewith, is at the same temperature as the hot gases that are in contact with the remainder of the coil. Fourth: Experiment shows that temperatures near 1530 F 1200 F. for the.iron,'are entirely practical temperatures substantially, above 1530 F. are practical as concerns metals available for hangersthat'are'not water-cooled. An ample margin of safetyisattainable by making the hanger of certain varieties of stainless steel of low carbon content containing large percentages of chromium, say 17% "with nickel, from 8% to 10% to 19%, or preferably 25% to 26%. Such metals will notgbecome soft or sticky, and in fact will afford exceptionally low frictional resistance to the sliding of the coiled metal along the same.

Having thus explainedmy new method,

the details for practicing] it may be more fully understood from the following description inconnection with the drawings, in which Fig. l is a vertical central section through a furnace showing the novel construction of the apparatus, in combination with the fea- ..tures which are old.

F ig 2 is. a horizontal section throughthe furnace walls disclosing a-plan' view of the mandrel, hanger and coilsof material which are being heated. 7

These figures show a furnace, and general like those of Figs. 3 and 1}, respectively, of Patent'No. 1,302,813, except that the parts whereby the coil material is set in the proper curvature and fed into the furnace. are omitted. Such mechanism may be the same or different from that of said patent, the essential novelty of the apparatus residing in the combination with the furnace of the novel hanger and the novel method of operating the furnace in connection therewith.

. The furnacein which the materialis heat- .ed is shown as including a reverberatory chamberl adapted to be maintained at desired temperatures by a non-oxidizing atmosphere of flaming gases and products of combustion. The functions of the fire brick regenerator shown at 4 need not be described s nce these parts are only such as are commonly employed in regenerative reverberatory furnaces. The sidewalls 5, 6 and the end wall 7 are sloped inward to the bottom of the furnace so as to bring them closer to the helical coil which is to be heated thereby but without danger of contact'therewith. The heating chamber within the furnace is of suitable dimensions to provide for a helix 53, 54:. Th mandrel 19 does not require cooling. Q

' Extending forward from the uppermost portion of the annular mandrel 19 is a hanger 25 in suitable relation for receiving the successive helical turns of the material and for holding them freely suspended and exposed to the beaten all sides. The hanger com- 'prises a U-shaped memberwhich extends to about the middle of, the heating space and thedlstance from its freeendto the exit opening is such that a loop of the helix when drawn off of the end will have space enough to hang in an open loop without danger of drawing a kink.

In the present case,'the successive turns of the helix are caused to slide along the hanger by having the hangerslope downward for about two-thirds of its length, downward sliding being facilitated by gravity, the resiliency of the helix and also by slight vibration imparted by operation of associated machinery.

Because of the new method employed, the hanger 25 is preferably of solid rod or bar material; or, if a pipe is used, it is not watercooled; also, the sides of the'U are preferjably parallel, ;there being no necessity for shifting points of contact with the coil, be-

cause by the new method the hanger is approximately as hot as the highest heat to be imparted to the coil. Furthermore, the material not being heated to sticky or welding temperature by the new method, there is no danger of forming a loop by welding contact of adjacent loops, as Patent 1,302,843 says might happen in operating by the old method. Consequently, as shown in Fig. 1, the inclination of hanger 25 is such that when successive loops are pushed free of mandrel 19, they slide down almost to the center of the furnace,'where a short length of the mandrel is substantially horizontal. So most of the loops being heated can be concentrated at this relatively central point in the furnace cavity. The free end of the hanger 25 curves upward quite abruptly, the greater stiffness of the material due to the lower heat, making it desirable to have a sharp upturn of the hanger at this point in order that the coils may be drawn off one at a time, and only when the pull of the forging machine feed makes this necessary.

The exit opening through which the material is withdrawn is approximately in line with one side of the helix of heated material and on the level of the top of said helix. The side which it is on is selected with reference to the direction of winding of the helix so that the successive turns will be drawn straight off endwise with minimum recurving tendency. This means that if the helix is wound in the direction of a left-hand screw, the exit opening will be at the upper lefthand side of the furnace.

The circular interior of the mandrel is formed so as to support the lining of firebrick 19a adapted to protect the exterior sup porting parts from the interior heat and at the same time to furnish reverberatory heating surface for the interior of the furnace.

By suitable mechanism, as, for instance, that described in the prior patent, a sufiicient number of turns of the helix are deposited on the hanger and the free end brought out through the exit opening.

The number of turns and the speed of operation will be governed with respect to the heat of the furnace and the size of the material so that the material will be properly heated by the time it reaches the end of the hanger.

At the rear of the furnace is a door 110 through which the helical material may be manipulated either initially or during operation. At the side of the doorway is a laterpeated. It will be evident, however, that in ly different apparatus for bending and transversely feeding along a support in a furnace, a continuous supply of hot, rod-like material for use in hot forging'machines or the like.

I claim 1. In apparatus for heating continuous lengths of rod-like metal for forging and the like, a reverberatory furnace and an un-- cooled support therein, arranged for sliding the rod-like material along the same in small area contact therewith, the uncooled support being of metal having a softening point higher than the intended temperature of a heating medium in the furnace and approximating the higher forging temperatures for the rod-like metal.

2. In the art of heating continuous lengths of rod-like metal which has been formed in loops adapted for suspension from and sliding along a metal support in a furnace, a method of uniformly heating the metal to hot-forging temperature, which includes employing as the material for the support, a

metal which softens at a substantially highmissible and adequate by reason of the above described heating of the support.

Signed at North Tonawanda, in the county of Niagara and State of New York, this 5th day of May A. D. 1932.

J ()HN JOSEPH MoLAUGI-ILIN.

ally and downwardly extending slot 112 in which the rod material may be inserted laterally. The portion of the slot unfilled by the rod is covered by the pivoted, gravity latch 113.

The operation of this specific apparatus,

for practice of my new method as above described, is obvious, and need not be here re-

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