US2110781A - Method and apparatus for cutting and treating metals - Google Patents

Description

March 8, 1938. R L, WAGNER 2,110,71

METHOD AND APPARATUS FOR CUTTING AND TREATING METALS Filed Nov. 29, 1933 in I lNVENTOR ROBEPTL. WA G/VER BY I N. 2 l r ATTORNEY Patented Mar. 8, 1938 mrrnon AND APPARATUS FOR CUTTING AND TREATING METALS Robert L. Wagner, Astoria, N. Y., assignor, by ,mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York Application November 29, 1933, Serial No. 700,171

7 1s Claims. This invention relates to the art of cutting 1 metals, and more particularly to a method of to cool rapidly in aim-conditions which are ap-- preventing or removing certain objectionable metallurgical changes which are, produced in high carbon and alloy steels when they are severed by means of high temperature heating and oxidizing agents, e. g., the oxy-acetylene cutting flame, and allowed to cool undisturbed to atmospheric temperature. 1

when certain grades of steels are cut by the oxy-fuel gas process, the severed sections are ordinarily allowed to cool undisturbed to atmospneric temperature. supplemented by the heat conduction away from the cut edges into the adjoining body portions of the sections, is sufficiently rapid to constitute an effective quench for the cut edges of high carbon and alloy steels in which a very marked and undesirable hardening usually takesplace which is due to the enhanced hardening properties of these steels. The hardened zone thus produced seldom extends beyond a fraction of an inch from the cut surface or edge but is sufllciently deep to reduce eifectively the ductility and produce other changes which limit the usefulness of sections of such steels when cut by the oxy-fuel gas process. This increase in hardness is accompanied by a decided embrittlement of the metal at the cut edges and makes these out surfaces very difllcult to machine. This hardened zone also serves as a starting point for cracks which may propagate readily into-the u aifected metal when mechanical or thermal stressesare present. These characteristics are particularly true of those. grades of steel (such as carbon steels containing above about 0.35% carbon, the structural silicon steels and some steel alloys containing nickel, chromium, manganese or vanadium) whose compositions are such as to impart to them the property of air hardening when they are heated beyond their recrystallization temperature and allowed proached and/or duplicated in the severing of such metals by the ordinarypractices of hightemperature flame cutting;

Accordingly, the principal objects of this invention are to provide an improved method ofor by reestablishing therein the desirableprop-f erties of the metal, during or immediately after the cutting operation, so that the cut section may be used directly for structural purposes without-- The rate of cooling in air,

machining off hardened edges and without subsequent heat treatment or the customary furnace heat treatment of the entire piece of steel. The above and other objects, as well as the novel features of this invention, will become more 7 apparent from the following description considered in connection with the accompanying drawing; in which:

Figs. 1 and 2 are side and end views, respectively, of an apparatus embodying this invention and adapted for use in, practicing the improved method;

Figs. 3. and 4 are side and end views, respectively, of a modified form of an oxy-fuel gas apparatus embodying this invention and adapted for use in practicing a variation of the improved method; and

Fig. 5 is a side elevation similar to Fig. 1 showing an apparatus employing cutting and heating electrodes.

Ordinarily when the oxy-acetylene cutting flame (consisting of one or more high temperature gaseous heating jets and a gaseous oxidizing jet) progressively severs metal, such as a plate the metal at the point of cutting attains a very high..' temperature which drops very rapidly at 1 the moment the cutting flame leaves each successive point. This rapid temperature drop is due to the chilling or quenching effect of the adjacent air and the adjoining mass of metal, and

results in decided and objectionable changes in or more relatively small high-temperature oxv:.,

fuel gas flames. I 1

In the preferred procedure of this invention the heattreatingoperation, is integrated with the cutting operation. One or more oxy-acetylene or similar high -temperature heating fl .arearranged so as to progressively 'follow he'"------- kerf as it is formed by-the cutting flame and to impinge on thesurfaces and edges exposed and a thermally affected by the cutting operation. The cutting flame and the heat treating flame or flames preferabiymove in unison relative to the work: and the distance between-the cutting flame and-the heat treatingflame or flames as well as the intensitytof-thelatter murmw iderably depending largely upon variable factors of the cutting operation such as the nature of the cutting medium, the composition and thickness of the work, the speed of cutting, etc.

The heat treating flame or flames are preferably located near and desirably immediately behind the cutting flame and, in this position, the intensity of the post-heating means and its spread along the kerf need only be suflicient to retard rapid cooling of the cut surfaces and thereby prevent the otherwise sudden drop of theirtemperature to a point where the quenching action of the air and adjoining metal would be effective to objectionably harden the cut surfaces and edges of the metal. These surfaces and edges then may cool gradually, so as to anneal the metal; that is to say, the metal, having been heated above the critical temperature, has additional localized heat applied thereto whereby it is permitted to cool at such a slow rate as will result in a desirable softening or non-hardening effect on the steel. 0n the other hand, satisfactory results may be obtained when the heat treating flame or flames are applied to the'cut surfaces at a substantial distance behind the cutting flame, even beyond a point where the temperature of the cut surfaces has dropped to or below the recrystallization temperature. For example, the additional heat'supplied to the cut surfaces by the supplemental flame or flames may be sufllcient to normalize the metal of such surfaces, 1. e., to reestablish the desired metallurgical structure thereof by reheating them above a critical point, holding at that temperature for a period, and then allowing cooling in air at room temperature.

In some instances, it is desirable to apply localized heat to the flame cut surface both immediately behind the cutting flame and at a substantial distance behind as just described; and with either or both of these arrangements it is sometimes also desirable to apply additional 10- calized heat ahead of or alongside the cutting flame. In any event, the localized heat so applied may be of the same or graduated intensity in a. direction away from the cutting point, and may be either manually-or mechanically propelled with the cutting flame over the work to be cut and the exposed and thermally affected surface or edge to be treated.

While the kerf is being produced or after the out has been completed, the two opposed surfaces thus exposed may be simultaneously locally and progressively heat treated, as described. Such concurrent treatment or reconditioning of the metallurgical structure of both exposed surfaces saves both time and gas, especially if done during the cutting operation. In the latter case, the two surfaces are quite close together and, since the heat applied thereto is more effectively utilized, less heat is required to recondition them than would be necessary later, after they are separated or have partially or completely cooled.

Usually it is desirable to progressively and locally heat treat the entire flame-cut edge or surface. However, certain situations arise in which it is desirable to apply the localized heat to soften only a portion of a hardened surface, to render such portion more readily workable for a specific purpose; after which the worked portion may be restored to its original condition, as by re-hardening it.

The principles of this invention are especially adapted for use in the practice of severing metal with an oxy-fuel gas cutting flame, such as the progresses and in such a manner that sufficient heat will be added to the metal to offset the cf.-

fects of conduction of heat from the cutting flame or arc into the body of the metal and the cooling air quench which occurs in the cut surfaces immediately after they are out.

It will be evident that the localized heat treatment may be utilized for annealing, tempering, normalizing or drawing, as required by the composition of the metal to establish therein the desired properties. For example, by locally applying the auxiliary source of heat in the immediate vicinity of the cutting point while cutting, the metal will absorb a considerable amount of heat by conduction and will then cool slowly to anneal the cut surface. Also, the metal of the cut surfaces may be similarly either tempered or normalized by locally applying the auxiliary source of heat to the cut edges at a considerable distance behind the cutting flame or along the cut edges after they have cooled appreciably from the flame-cutting operation. In general, the localized heat treatment may be so adjusted and applied as to change or restore the metal surface treated to any desired or predetermined condition; and it therefore will be understood that the procedure herein disclosed is subject to various changes without departing from the principles of the invention.

The accompanying drawing illustrates an apparatus for practicing the procedure just described. A preferred form of the apparatus, as shown in Figs. 1 and 2, may comprise a cutting blowpipe A of a common or usual design and heating units B and C rigidly connected therewith and so arranged in relation to the cutting blowpipe A that high temperature heating jets may be directed onto the work both ahead of and behind the cutting flame in alignment with the cut to be made. The high temperature heating jets from the units B and C are desirably aligned with the lowerend or nozzle ID of the cutting blowpipe A and are spaced at a relatively short distance therefrom, the distance being exactly determinable by the effect to be produced by these jets. However, the high temperature heating jets do not necessarily need to be in alignment with the cutting jet, but may be arranged so as to direct heat on the general area both preceding and following the cutting flame and the cut in the workpiece W.

The blowpipe A is provided with a mixing chamber and with both preheating gas and cutting oxygen passages of a construction common to cutting blowpipes, and also with the usual type of control valves ll, l2 and I3, valves II and I! being operable in governing the flow of preheating oxygen and acetylene respectively from intake connections and conduits I 4 and 15 to a suitable mixer. The valve l3 controls the supply of cutting oxygen and may'have a handle l8 suitable for quickly turning on or shutting off the cutting oxygen jet.

A bracket l1 and frame l8 may be secured to the body of the blowpipe A in order to support a liver heatvbehind the cutting blowpipe A only.

I acetylene gases may be delivered through passages, which are conveniently arranged in the head and controlled by valves 24, 24 and 25, 25'

respectively, to mixing devices 26 and 21 of the type common to weldingblowpipes.

From the mixing devices 26 and 27 the mixed oxygen and acetylene gases are then delivered through stems 2B and 29 to manifolds within blocks 30 and 3| respectively, the blocks 30 and 3| being preferably secured to the blowpipe A at a substantial distance above the nozzle ill and being disposed on each side of the 'blowpipe so as to be above the line of cut of the work. ,Orie

or more heating nozzles 32, 33 may be fixed to the manifold blocks 30 and 3| and extend downward to within a short distance of the work and desirably toa plane slightly above the end of the nozzle Ill.

In order to produce a sufllcient amount of heat.

over a relatively large area of the work not only ahead of and behind the cutting jet but also. at

least partially alongside thereof, the manifold blocks '30 and 3! are-made arcuate in shape and three nozzles 32, 33 are connected with each of the blocks. The middle nozzle attached to each block is preferably aligned with the cutting nozzle l so that heat will be applied directly in line with the out ahead of thecutting jet and also along the edges E of the finished cut.

It will be appreciated that with the apparatus described the entire area immediately surrounding the newly formed out may be raised to an intermediate temperature, or to a degree of heat substantially below that produced by the'cutting jet, which prevents sudden air quench. of the metal from the high temperatures produced by the cutting flame and the oxidizing jet to room or atmospheric temperature. As a result the edges E of the metal do not harden, or in the event that hardening does begin to take place, the post heating jets from the nozzles 33 prevent its continuation and restore the condition of the metal substantially to the original state.

In order to further retard the rate of cooling of the metal following the cut, a refractory material R may be employed underneath the metal on either side of and closely adjacent the line of the cut. Fire brick or other suitable nonfusing material when placed under the metal will assist in retaining the heat of the cutting flame as well as the heat from the blowpipe units I B andLC.- The use of refractory material is 50 especially advantageous when the metal is relathe edges of the cut.

tively thick and subject to rapid conduction of the heat into the body thereof away from the cut edges, the refractory material serving in such instances to reflect and retain the heat in the metal so that slow cooling will take place along Another form of apparatus embodying this invention is shown in part in Figs; 3 and 4. This apparatus may comprise a cutting blowpipe A and only a post-heating unit C which are rigidly connected together to move in unison., This unit may consist of a header 39 to receive and distribute the gaseous heating mixtureito ,a vgroup of nozzles 40, 4|, 42 and 43' secured to the header and forming part of the unit ,0 arranged'to de- These nozzles may be desirably positioned so that two or more outer nozzles 40 and 43 direct jets alongside of 'the newly made out, while two inner nozzles 4| and 42 direct jets at acute angles to der surface or for the 'full depth of the plate. The converging jets from the nozzles 4| and 42 form an intense, penetrating flame which is ca- 1 pable of heating the sidewalls E of the cut completely to the bottom thereof for most commercial sizes of plate. The heat produced by the nozzles of the unit 0' may be adequate to heat the area of the metal inthe region of the cut to such a degree as to prevent sudden air quench without the aid of preheating nozzlesarranged ahead of the cutting blowpipe A. Whether or not a preheating unit need be employed is determinable by such factors as the thickness of the metal, the speed of cutting, the desired type post-heat them, or a combination of the gaseousand electrical heating' media may be used-one for preheating and the other for post-heating.

The several types of apparatus here disclosed are designed both to out the metal and to prevent or counteract objectionable changes in the metallurgical structure of the surfaces exposed and thermally affected by the cutting operation. The flame or heat applied behind and in line with the high-temperature cutting device extends into the kerf produced by the latter and retards the cooling of both surfaces of the cut. Such post-heating is desirably of considerably less intensity than the heat at the cutting point and may he graduated, as by applying a series of flames of-decreasing intensity along the kerf after said portions have cooled to below the critical, temperature, thereby raising the temperature of the cooled portions to counteract harmful metallurgical changes in the metal resulting from the cutting operation. a

2. The method of flame-cutting ferrous metals such as air-hardening andquench-hardening steels and counteracting the thermal effects of the cutting operation on the flame-cut face and the edges adjoining the cut, comprising flamecutting the metal by locally heating successive portions of the metal to be out and simultaneously applying an oxygen jet to such locally heated portions; and progressively applying local high-temperature heat to heat and thereby temper the flame-cut portions and the edges of the metal adjoining the successive cut portions after such edges and portions have partially cooled to a point sumciently below the recrystallization temperature to effect a tempering action.

3. A method of cutting ferrous metals so as to substantially counteract changes in the metallurgical structure of the cut and thermally-affected edges of the metal which comprises applying a high temperature heating and oxidizing jet to make the cut, applying sources -'of high temperature heat to the surface of the metal both ahead of and behind the cut, and moving the heating and oxidizing jet and the sources of h'gh temperature heat simultaneously relative to the surface of the metal.

4. The method of flame cutting metal and counteracting the thermal effects of the cutting operation on the edges adjoining the cut, comprising locally heating successive portions of the metal to be cut; directing an oxygen cutting jet against the successive locally heated portions; applying a first source of local high temperature heat progressively to the edges adjoining the successive cut portions after the edges have cooled to below the recrystallization temperature and subsequently applying a second source of local high temperature heat progressively to the edges adjoining the successive cut portions to efiect a tempering action after the edges have partially cooled from the application of said first source of heat.

5. The method of flame cutting metal and counteracting the thermal effects of the cutting operation on the opposed edges adjoining the out, comprising locally heating successive portions of the metal to be cut; directingan oxidizing cutting jet against the successive locally heated portions for cutting the metal; allowing the edges adjoining the cut to partially cool; directing a plurality of converging heating jets within the kerf formed by the cutting jet; and exposing the successive portions of the opposed and partially cooled edges of the kerf to the action of the converging jets.

6. An apparatus for flame-cutting ferrous metals such as air-hardening and quench-hardening steels and for counteracting the hardness imparted to the edges during cooling from the flame-cutting operation, comprising means for projecting a flame-cutting jet against and progressively along a surface of the metal; and tempering means for directing localized high-temperature heat progressively along said surface to portions of the metal thermally afiected by said flame-cutting jet, said tempering; means progressing in unison with said jet-projecting means and being located an appreciable distance behind said jet-projecting means so that the metal thermally affected by said flame-cutting jet cools to below the recrystallization temperature before being exposed to the action of the localized high-temperature heat from said tempering means.

7. An apparatus for flame-cutting ferrous metals such as air-hardening and quench-hardening steels and for counteracting the hardness imparted to the edges during cooling, comprising means for projecting a flame-cutting jet downwardly upon and progressively along the top surface of the metal; and post-heating means for directing localized high-temperature heat downwardly upon and progressively along the top surface portions adjoining the successive portions cut by said flame-cutting jet, said post-heating means progressing in unison with said jet-projecting means and being located an appreciable distance behind said jet-projecting means so that the metal thermally affected by said flame-cutting jet cools tobelow the recrystallization temperature before being exposed to the action of the localized high-temperature heat from said post-heating means.

8. Apparatus asclaimed in claim '7 wherein said post-heating means comprises a heating unit having a plurality of nozzles for projecting localized high-temperature heat in a zone spaced a a substantial distance behind said jet-projecting means.

- 9. Apparatus as claimed in claim 7 wherein said post-heating means comprises nozzle means for directing localized high-temperature heat against said top surface at a point an appreciable distance behind said jet-projecting means and in oifset relation at one side of the line 0!.

cut.

10. An apparatus for cutting metal comprising high temperature oxidizing means to eifect a cut, and metallurgical structure-restoringmeans comprising means for applying high tem-- perature heat at a relatively short distance ahead of and behind said oxidizing means, said metallurgical structure-restoring means being separate from the preheating meansassociated with said high-temperature oxidizing means.

11. An apparatus for cutting metal so as to prevent the hardening of metal along the edges of the out, which comprises a cutting blowpipe;

and at least two oxy-fuel gas blowpipes arranged therebehind for introducing converging jets of high temperature gases against the newly cut edges of the metal.

12. An apparatus for cutting ferrous metal and for counteracting hardening of the metal along the edges of the out, which comprises a cutting blowpipe movable with respect to the metal; and

a plurality of means attached to said cutting 0 blowpipe in spaced relation thereto for applying high temperature heat along the newly-cut and partially cooled edges of the metal at successive substantially spaced intervals from the cutting blowpipe.

13. An apparatus for cutting metals and retaining good metallurgical structure therein, said apparatus comprising a cutting electrode movable along the surface of the metal, and at least one heating electrode attached a substantial distance ahead of and at least one heating electrode attached a substantial distance behind said cutting electrode to apply high temperature heat to the surface of the metal in the region of the cut, whereby objectionable change. in metallurgical structure isprevented.

ROBERT 1. WAGNER.

Images