US2451422A - Thermochemical removal of metal with a flux-forming powder in the oxygen cutting stream - Google Patents

Description

2,451 ,422 guxmonume R. L. WAGNER THERMOCHEMICAL REMOVAL OF METAL WITH POWDER IN THE OXYGEN CUTTING AM Filed March 24, 1945 3 Sheets-Sheet l INVENTOR ROBERT L. WAGN ER BY ATTORNEY Oct. 12, 1948. R. L. WAGNER 2,451,422

THERIOCHEMICAL REMOVAL OF METAL WITH A FLUX-FORMING POWDER IKTHE OXYGEN CUTTING STREAM Filed March 24, 1945 3 Sheets-Sheet 2 Ill! visua /4 I .......,,..w.......|.i nun INVENTOR ROBER? L. WAGNER BY ATTOFZN EY R. L. WAGNER Oct. 12, 1948.

THERMOCHEMICAL REMOVAL OF METAL WITH A FLUX-FORMING POWDER IN THE OXYGEN CUTTING- STREAM I5 Sheets-Sheet 3 Filed larch 24 1945 INVENTOR ROBERT L. WAGNER BY ATTORNEY Patented Oct. 12, 1948 THERMOCHEMICAL REMOVAL OF METAL WITH A FLUX-FORMING POWDER IN THE OXYGEN CUTTING STREAM Robert L. Wagner, Niagara Falls, N. Y., assignnr to The Linde Air Products Company, a corporation of Ohio Application March 24, 1945, Serial No. 584,715

19 Claims. (Cl. 148-9) This invention relates to a method of and apparatus for thermochemically removing metal by a stream or jet of oxygen from heated bodies of metals and alloys which are immune to or resist progressive oxidation by the conventional thermochemical metal-removing action of only a preheating flame and a stream or jet of oxygen. Examples of such oxidation resistant metal bodies are ferrous metals such as stainless steel and cast iron, nonferrous metals such as copper, aluminum, and nickel, and various alloys. Essentially, the present invention depends upon the conjoint action of a preheating medium, an oxygen jet, and a stream of finely divided adjuvant material on an oxidation resistant metal to effect the thermochemical removal of metal.

Previous attempts to thermochemlcally flame machine a surface layer of metal from a body of steel containing over 10% chromium to eliminate surface defects such as seams, snakes, and scabs, or to flame machine special contours in such an alloy steel body, have met with little or no success. However, stainless steel plates have been thermochemically cut by placing a mild steel plate over the stainless steel plate, and flame cutting through the mild steel plate so that the molten slag from the mild steel kerf flows into the kerf in the stainless steel. This procedure is slow, large amounts of mild steel are wasted, and cuts of poor quality are produced. Another cutting procedure has involved moving an ordinary cutting torch in short strokes back and forth alon the line of cut with a sawing motion in such a way as to advance the torch heating and cutting jets intermittentlya short forward increment followed by a relatively shorter reverse or backward movement. This method also is slow, inaccurate, uneconomical, and results in the formation of Wide kerfs and rough cut surfaces. Even when the chromium content is between 5% and there is considerable resistance to flame cutting by conventional procedures.

A surface layer of metal likewise could not be removed from cast iron by any prior known thermochemical method, and the cast iron could be thermochemically out only with difficulty. In cutting, the cutting torch was moved from side to side in a wide are as it was advanced along the kerf, so that a wide rough kerf was produced, large amounts of metal were removed, and excessive amounts of cutting oxygen were used.

Non-ferrous metals have been difficult or impossible to cut or machine thermochemically, although cutting solely by melting has sometimes been done. For instance, a bar of substantially pure nickel cannot be progressively oxidized and cut by the usual oxy-acetylene cutting method, nor can bars of copper or aluminum. Also, corrosion and oxidation resistant alloys such as nickel-base alloys containing molybdenum, nick el-base alloys containing molybdenum and chromium, cobalt-chromium tungsten alloys, and various silicon bronzes cannot be successfully cut or machined by conventional thermochemical technique.

Amon the objects of this invention are to provide a novel method of steadily thermochemically removing metal from metal and alloy bodies which are immune to or resist progressive oxidation by the sole action of a stream of oxygen upon a heated portion thereof as in ordinary flame cutting; to provide such a method which can be carried out with greater speed, accuracy, economy, and neatness than prior procedures; to provide such a method which is simple yet operable under widely varying conditions on metal bodies of diiierent compositions; to provide such a method by which a metal removing reaction can be carried steadily and continuously across a resistant or immune metal body without special manipulation of a torch, in a manner similar to the thermochemical removal of metal from ordinary carbon steels; to provide a procedure which is especially effective for removin surface metal from resistant or immune metal bodies, as for deseaming, gouging, or otherwise flame machining them; and to provide another procedure which is especially effective for cutting deep narrow kerfs in resistant or immune metal bodies, as for severing them.

Still other objects are the provision of novel apparatus which is suitable for thermochemically removing metal from oxidation resistant metal bodies by the novel method; which includes as one modification a blowpipe capable of discharging a low velocity oxygen jet associated with adjuvant material, especially suitable for removing surface metal; which includes as another modification a blowpipe capable of discharging a high velocity oxygen jet associated with adjuvant material, especially suitable for cutting a deep kerf; which can be used in conjunction with existing apparatus for thermochemically removing metal; and which is simple in construction, easy to manipulate, and safe in operation.

In accordance with the method of this invention, metal is thermochemically removed from a resistant or immune metal body by applying an oxygen jet against a heated zone of action on the body while concurrently and continuously flowing 3 a stream of finely-divided adluvant material into the zone of action so as to oxidize part of the constituents of the body and produce reaction products sufiiciently fluid to be expelled by the oxygen jet, sometimes augmented by the force of gravity. Successive portions of the metal body on a path extending alon its surface can be thermochemically removed by effecting a steady and continuous relative movement or travel between the body and the jet of oxygen and stream of adjuvant material across the surface. Heating of the successive zones of action preferably is accomplished by oxy-acetylene flames applied along said path concurrently with said stream of oxygen and such stream of finely-divided adjuvant mat rial. In flame machining operations. wherein only metal near the surface is removed. a sufficiently fluid reaction product is one which can be blown ahead of the reaction zone by the oxygen jet to expose a fresh metal surface to the jet, and to preheat the surface portion to be removed next. In cutting operations, such as severing, sufllciently fluid reaction products are those which can be blown through and out of the kerf, thus exposing fresh metal surfaces against which the oxygen jet impinges.

Flame machining to remove urface metal is carried out by advancing along the surface in the direction of gas flow a low velocity oxygen jet directed obliquely at a small angle against successive heated zones on the surface of the metal body, while introducing the finely-divided material into the successive zones. Here also heating is preferably accomplished by concurrently applying one or more oxy-acetylene flames to the surface. In this procedure the oxygen let velocity generally is maintained less than 980 ft./sec. (the acoustic velocity in oxygen) as it leaves the blowpipe nozzle.

In flame severin or other cutting operations a high velocity oxygen Jet preferably'flowing at or above the acoustic velocity is directed at a large angle, such as 90, against the hot metal body while continuously introducing the finely divided material into the reaction zone where the oxygen impinges. In severing, the oxygen jet passes completely through the body of metal and forms a deep kerf which is advanced along a selected path by steadily advancing the oxygen jet so as to impinge against successive heated zones of the body. If a kerf extending only partly through the body is wanted, the jet is advanced at a rate rapid enough to prevent complete penetration.

'I'he adjuvant material apparently acts to flux the tenacious refractory metal oxides formed by the oxygen to produce a fluid product which is sufllciently fluid to be removable by the Joint action of the flame, oxygen jet, and powder stream. Finely-divided adjuvant materials have been used most successfully which burn readily in oxygen to liberate intense heat and form compounds which flux the refractory oxides to form a fluxible Slag mixture, as exemplified by various combustible metal powders. Some instances are known, however, in which combustible adluvant material apparently acts principally by its intense heating effect, with but little, if any, fluxing action. Therefore, the term adjuvant material? as used herein embraces finely-divided materials which assist or promote the metal-removing reaction in any way. including both materials which themselves flux the oxide products and those which burn exothermically.

In further accordance with this invention, the finely-divided adjuvant material is carried 3 9 the reaction zone in close association with the metal-removing oxygen itself, which is supplied in large volume sufllcient to leave for oxidizing at least part of the resistant metal an abundant excess of oxygen over that consumed for burning adluvant material. The minimum ratio of oxygen to combustible adluvant material for successful metal removal 'will vary somewhat for difierent materials and diflerent compositions of the metal bodies from which metal is to be removed. This ratio can be determined empirically and thereafter provision should be made for maintaining the ratio of oxygen to adluvant material well above the minimum so that a large excess of oxygen is available for oxidizing the resistant metal body.

The finely-divided adiuvant material may be brought into association with the oxygen in any suitable manner either in a blowpipe nozzle or just outside of the nozzle after the oxygen emerges therefrom. Each procedure has special advantages for certain metal-removing operations to be described hereinafter. Introducing the adjuvant material with the preheating combustible gas mixture is undesirable because of the possibility of flashbacks into the blowpipe, which would cause the adjuvant material to burn or melt within the blowpipe and clog the passages.

The adjuvant material itself may be chosen from a number of materials which have been used successfully for thermochemically cutting, deseaming, or desurfacing oxidation resistant metal bodies. Furthermore, these adiuvant materials can vary widely in fineness while producing satisfactory results. Powders as coarse as mesh (.0117 in. openings) and powders finer than 150 mesh (.0041 in. openings)- have been used successfully. For thermochemically cutting or desurfacing oxidation resistant steels such as heat resistant steel containing about 25% chromium, cutlery steel containing 12% to 14% chromium, and particularly austenitic stainless steels, such as those containing approximately 18% chromium and 8% nickel or manganese, finely-divided adjuvant materials such as powdered ferromanganese, iron, mild steel, an alloy of iron and tin, manganese metal, mixtures of manganese or ferromanganese with steel, and mixtures of manganese or ferromanganese with cast iron, have been used successfully. These adjuvant materials may also be used for thermochemically cutting or machining cast iron.

For thermochemically removing metal from non-ferrous metal bodies, powdered low carbon ferromanganese and iron have given particularly good results in cutting nickel, copper, aluminum, a cobalt-chromium-tungsten alloy, an alloy con taining over copper with the remainder principally silicon, and brass containing about 50% copper and 50% zinc. For most effective results it is necessary to preheat copper, aluminum, and nickel bodies prior to cutting. Some progress can be made, however, on cold nickel and aluminum bodies.

Ferromanganese and iron powders are also useful for cutting substantially non-ferrous alloys having only slight amounts of iron, such as a nickel-base alloy containing approximately 20% molybdenum, 20% iron, and 60% nickel; one containing approximately 30% molybdenum, 5% iron, and 65% nickel; and one containing approximately 17% molybdenum, 8% iron, 60% nickel, and 15% chromium.

Although the novel method of the invention can be performed successfully with many different about 20% of the mixture by weight.

finely divided adjuvant materials, outstanding results with respect to high speed, low cost, and good characteristics of the resultant metal surface have been provided on most metals by powdered iron, manganese, and intimate mixtures or alloys of these two materials with one another. Ferromanganese is generally used as the source of the manganese. Since ferromanganese powder is quite unstable in oxygen and burns rapidly with the liberation of intense heat it is particularly valuable for increasing the combustibility of a powder comprising relatively inexpensive impure forms of iron such as steel or cast iron. Reducing the cost of the adjuvant powder without impairing the efficiency of the process unduly is of great importance in flame cutting and machining because the cost of powder consumed is about equivalent to the sum of the costs charged to labor and gases. Any of the commercially available grades of ferromanganese, which usually contain about 82% manganese, can be used successfully, but the best over-all results with respect to cost and speed have been obtained with medium carbon ferromanganese wherein the carbon content is between 0.75% and 1.50%.

Extensive experiments have shown that the optimum results with an adjuvant powder mixture containing iron and ierromanganese are obtained when the iron is in the form of a steel powder which constitutes a major part of the mixture, preferably about 80%, and the ferromanganese constitutes a minor part, preferably The iron in such a mixture can be furnished in a relatively impure state, as in the form of a powder containing about 90% to 95% free iron, about 0.15% or less carbon, balance mostly iron oxides. It is not considered disadvantageous to have iron oxides present in the mixture in amount between 5% and by weight because the oxides tend to be reduced by ferromanganese in an exothermic chemical reaction, thus aiding in the transfer of heat to the resistant metal body from which metal is to be removed.

Using the above-described 80% Fe-% FeMn adjuvant powder the following results were obtained in cutting stainless steel billets of the 18% Cr-8% Ni type when concurrently but separately discharging the oxygen, adjuvant powder, and

When using steel powders containing dissolved carbon considerably in execess of 0.15% improved results are often obtained by increasing the ferromanganese in the mixture to an amount between 20% and Both gray and white cast iron powders also can be used successfully when between 30% and of the mixture by weight is ferromanganese, but the rate of metal removal using cast iron powders is slower than with steel powder. One cast iron powder which was used successfully in mixture with ferromanganese contained 3.39% carbon, 1.8% silicon, and 1.12% manganese.

I have found it desirable, but not essential that the above-described 80-20 mixture of powdered iron and ferromanganese be in such a physical condition that about 10% is between 60 mesh (.0097 in. openings) and mesh (.0069 in. openings) 30% is finer than 300 mesh (.0018 in. openings), and the remainder is in the range from 80 to 300 mesh.

With the above described 80-20 mixture of steel and ferromanganese powders used according to this invention on 18-8 stainless steel, evidence indicates that if the oxygen-to-powder ratio decreases below 20 cu. ft. of oxygen to 1 pound of powder so much of the oxygen is consumed for burning the powder that there is insufficient oxygen left over for oxidizing the stainless steel efficiently if at all, and metal removal is prevented or proceeds at an unsatisfactorily slow speed. In cutting, when the ratio is less than 20 to 1 there is an undesirably large lag in the keri. An oxygen-to-powder ratio greater than 40 to 1 could not be used effectively when the powder was quite coarse, i. e. contained less than 40% through- 325 mesh (.0017 in. openings), because insufficient heat was produced and the slag was not fluid enough, thus preventing efiicient metal removal, or reducing operating speed, or permissible advance of the cutting nozzle and impairing the quality of the product. The upper ratio limit varies with the powder fineness, the type of metal being cut, and the quantity of metallic iron in the powder, and under some conditions is greater than 40 to 1.

It has also been found that in thermochemically removing metal from resistant metal bodies the cost, the speed of progress, and the character of the metal surface are afiected to a surprisingly large extent by the physical fineness of the adjuvant powder, When impure iron powder unmixed with other ingredients is suificiently line the thermochemical removal of metal can proceed at a rate considerably faster than with coarse particles of the same composition, almost as rapidly as with an iron-ferromanganese mixture, and at considerably lower cost. Excellent results have been obtained with iron in the form of unbonded impure steel adjuvant powder comprising by weight 80% to metallic iron, less than 0.20% carbon, balance incidental impurities such as FeO, SiOz and minor quantities of other impurities. Such an adjuvant powder desirably is prepared by reduction from a virgin oxide such as iron ore, or from an artificial iron oxide, such as mill scale, as by hydrogen, carbon monoxide, or natural gas. One specific example of such an adjuvant powder had the following composition:

Per cent Fe (metallic) 92.14

FeO 3.60 SiOz 3.12

Balance other impurities.

A careful screening of the impure iron powder to eliminate coarse particles is essential, and it is particularly important that all of the screened powder pass through a mesh screen (.0058 in. openings) and at least 70% by weight pass through a 200 mesh screen (.0029 in. openings). It is also advantageous but not essential that at least 50% of the powder by weight pass through a 300 mesh screen (.0018 in. openings).

Using impure iron adjuvant powder of the above-described chemical and physical analysis, the following results were obtained in cutting stainless steel billets of the 18% Cir-8% Ni type when concurrently .but separately discharging the oxygen, adjuvant powder, and preheating gases from a blowpipe nozzle:

Thickness Cutting 0, Powder 58 Inch" fL/hr- -Mr. In ./min.

With the above-described impure iron adjuvant powder used according to this invention on 18-8 stainless steel, evidence indicates'that if the oxygen-to-powder ratio decreases below 15 cu. ft. of oxygen to 1 pound of powder, so much of the oxygen is consumed in burning the powder that there is insufllcient oxygen left over for oxidation of the metal body, and metal removal is prevented or proceeds at an unsatlsfactorily slow speed. In cutting, less than a. 15 to 1 ratio also results in incomplete penetration. 0n theother hand, if

the ratio of oxygen to powder increases beyond about 100 to 1, insufllcient heat is produced and the slag is not liquid enough to be blown away by the oxygen jet.

The important influence of adjuvant powder particle size is strikingly illustrated by comparing with one another the oxy-powder factors determined by flame planing along a metal surface at similar speeds grooves of similar dimensions with powders of the same chemical composition but difl'erent degrees of fineness. Upon completing each of the several similar grooves the total oxygen and powder consumptions were determined and the resulting figures expressed as the cubic feet of oxygen consumed per pound of powder at standard conditions of temperature and pressure, called the oxy-powder factor. Since an important influence on the economy of operation is the cost of adjuvant powder, the need for a relatively small powder consumption reflected in a high oxy-powder factor is evident, and the higher the factor the lower is the cost of operation.

In a series of tests on austenitic Cr-Ni stainless steel involving flame planing grooves of various depths, the following results were obtained using an impure iron adjuvani; powder having the screen analysis shown:

In the above table the factor 17 in example #1 using coarse powder should be compared to the factor 37 in example #2 using flne powder; and the factor 37 in example #1 should be were determined on similar shallow grooves and the larger factors for each example were determined on similar deep grooves. This indicates that the same performance requires more than twice as much coarse powder as fine powder, and the use of v the fine powder consequently greatly reduces the cost of operation.

In tests on flame planing at similar speeds 0.075 inch deep similar grooves on 8" x 7" billets of 12% Ni-17.5% Cr stainless steel using an adjuvant powder analyzing 88.45% metallic Fe, 6.64% Feo, 2.95% 5102, 0.57% Mn, 0.089% 8, 0.098% 0, balance incidental impurities, the fol= lowing results were obtained:

The critical effect of powder fineness on performance is emphasized by examples #3 and #4 above showing that an increase of only 14% in the quantity of powder pasing through a 200 mesh screen resulted in almost a increase in the oxy-powder factor and almost a 40% decrease in the quantity of powder required for equivalent performance.

Inthe foregoing tests speed of progress along the billet surface was maintained constant to provide a comparison of powder consumptions. However, a finer powder also permits greater flame planing speeds than are obtainable with a coarser powder and the same or even a smaller oxy-powder ratio. For example, on cold stainless steel the maximum speed with a relatively coarse steel powder was 8 ft./min., but with the preferred fine powder described above a speed of 12 ft./min. was maintained with a smaller powder consumption.

.Although the foregoing discussion of the effect o'fadjuvant powder particle size relates specifically to flame planing, this is only by way of example because the same principles apply to flame cutting and other procedures for thermochemically removing metal.

pp t s o C yi out the foregoing method, and constructed in accordance with this invention, is illustrated in the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional view of a blowpipe nozzle in position for flame planing a body of resistant metal by the novel method;

Fig. 2 is an exploded elevational view of the parts of the nozzle of Fig. 1;

Fig. 3 is a cross-sectional view taken along line 3-3 of Fig. 1;

Figs. 4 and 5 are end views of two of the nozzle parts shown in the exploded view of Fig. 2 as seen from the lines 4-4 and 5-5, respectively;

Fig. 6 is a side elevational view of an alternative form of nozzle in position for cutting a kerf through a body of resistant metal by the novel method;

Fig. '7 is an enlarged perspective view of the nozzle of Fig. 6 rotated about 90 from its position in Fig. 6;

Fig. 8 is a perspective view of a resistant metal billet having a groove or furrow flame planed therein by the novel method.

Fig. 9 is a cross-sectional view taken along the compared to the factor 90 in example #2, be''" "'line 99 in Fig.8.

cause the smaller factors for each example Fig. 10 is an elevational view, on a reduced scale,

of the cut surface of a resistant metal body flamecut by the novel method; and

Fig. 11 is a reproduction of a photomicrograph showing a portion of a section of a flame-out austenitic stainless steel body taken along the line Il-H in Fig. 10 and magnified 100 diameters.

When thermochemically removing metal in accordance with this invention, portions of a body B of a metal or alloy which resists or is substantially immune to the thermochemical removal of metal solely by a jet of oxygen, are removed by a Jet of oxygen associated with flowing finelydivided adjuvant material, usually acting in concert with a heating medium such as an oxyacetylene flame which preheats successive portions of the metal body. Referring to Fig. 1, the oxygen jet is discharged from a suitable source, such as an outlet In of a blow-pipe nozzle N, and is preferably discharged internally of and distinct from a ring of heating flame formed by the burning of combustible gas mixture jets leaving annularly arranged outlets II in the nozzle so that the oxygen flows in unconfined space alongside and lengthwise of the flame within the ring of heating flame. Adiuvant powder also leaves outlet III in suspension in the oxygen stream. When a continuous relative movement between the metal body B and the nozzle N is effected to advance the nozzle N relatively to the body in the direction in which the nozzle is pointing and parallel to the surface S, successive portions in the path of movement are partially oxidized and partially melted to a depth depending upon several factors such as the angle of impingement oi the oxygen jet, the velocity of the oxygen jet, and the speed of relative movement. The resulting slag comprising a mixture of molten-metal and molten oxides is continuously blown out of the reaction zone by the oxygen jet to expose additional portions of the body B to the action of the oxygen and powder.

Nozzle N, for assembly purposes, comprises a front section F and a rear section R secured in a blowpipe head i8; and the oxygen outlet 10 is the terminal portion of a central passage or bore extending longitudinally through the nozzle. A portion of this central passage comprises a passage l2 which extends centrally through rear section B and conveys oxygen to a constricted axial bore IS in a nozzle or ejector tube M which extends axially into the central nozzle bore and is spaced at least in part inwardly from the inside bore surface to form an annular space communicating with the part of the central bore in front of ejector l4 but behind outlet ill. Ejector l4 threadedly engages rear section R and thus can be readily replaced in case of wear or if a larger or smaller ejector is needed. For sealing purposes, ejector ll is provided at its rear end with a beveled seat l5 which cooperates with a correspondingly beveled seat on section R. Elector H extends into a suction chamber IS in front section F comprising a part or the nozzle bore and has a central outlet within the central nozzle bore spaced but a short distance from outlet "I. An outlet passage or conduit H for adjuvant powder extends laterally in non-communicative 10 to and intersecting the axis of the central bore. Upon discharge of oxygen from bore i3 which converges forwardly toward the axis of the central nozzle bore adjuvant powder is aspirated from the duct i1 laterally inwardly between and past two adjacent combustible gas streams flowing in a pair of the passages 28 and into the oxygen passage or chamber IS in back of the point of oxygen injection and is drawn forward into the confined oxygen stream to produce continuously a powder-carrying oxygen stream before the oxygen leaves the nozzle and flows in unconfined space. As the powder carrying oxygen stream passages through the forward portion of chamber l8 and outlet Hi it expands so that the oxygen jet discharged from outlet ill ordinarily has a low velocity especially suitable for removingsurface metal as in desurfacing or deseaming operations, which usually require a lower velocity than is customarily employed for cutting deep kerfs in a metal body, as in severing. Howev r, it will be understood that by suitable changes in the various passages and chambers, a quite high relation with preheat gas passages 28 from the en'- velocity may be imparted to the oxygen jet, and that the nozzle N can be used successfully for cutting kerfs.

Passage I2 receives oxygen from a supply conduit or passage [9 in the head i8. A combustible oxy-acetylene or other mixture of gases, formed in the blowpipe in a suitable manner as by conventional mixing means, is supplied from a conduit or passage 20 in the head ill to an annular chamber 2| surrounding the rear end of the nozzle N and communicating with a plurality of iongi-tudinal passages 22 surrounding oxygen passage in spaced relation thereto. Oxygen supply passage i9 and annular chamber iii are in non-communicative relation with one another, being sealed from each other and from the atmosphere by beveled seats 23 cooperating with corresponding beveled seats in the head 53, the nozzle being drawn tightly into the head by a nut 24. For additional sealing purposes, a gasket 25 is placed outside a threaded projection 26, into which ejector I i is threaded and which itself is threaded into front section F to connect the front and rear sections of the nozzle. Gasket 25 prevents leakage from chamber is to an annular gas distributing channel 21 to which passages 22 lead and from which lead heating gas passages 28, each of the latter connecting with one of the preheat outlets H which are spaced outwardly from and surround oxygen outlet 50 adjacent thereto but separate therefrom. In addition, a gasket 29 prevents leakage of combusti lole mixture from channel 21 to the atmosphere. Thus the oxygen and combustible gas mixture conduits or passages are in non-communicative relation with one another so that the combustible gas jets are discharged in such a way that any mixture of combustible gas with metal-removing oxygen and with adjuvant powder occurs only after discharge thereof from the nozzle, and not within the nozzle.

The powdered adjuvant material which is aspirated into and becomes suspended in the oxygen stream in chamber I6 is supplied to powder outlet passage I1 and thence to the space between ejector l4 and the inside surface of the nozzle bore behind the outlet of the ejector through a flexible tube duct 3!, one end of which is brazed or otherwise suitably secured to nozzle N at a position spaced forwardly from head l8. The opposite and open inlet end of tube 3! dips into a shallow pile 32 of powdered adjuvant material amaze contained in a'separate container such as a small pan 33, which is supplied with powder from a hopper 34 controlled by a valve 05. Pan 30 is preferably kept filled all the time, so that a constant depth of material is maintained. The sides of pan 33 are low enough to prevent the pile 32 from becoming too deep, and any material falling over the sides is caught in an overflow pan 36.

To regulate the supply of adjuvant material to nozzle N, air or other suitable gas can be sucked into tube 38 through a tube 3?, controlled by a valve 38 to reduce the suction on the powder.

The pickup end of the suction tube 01 preferably should not be buried too deeply in the pile of powdered material, as feeding from a, shallow depth apparently permits the inclusion of some air in the suction line and thus prevents clogging. The valve 38 is opened to permit air or gas to be sucked into tube 8! only when the suction effect of the oxygen discharging from core i is so great that an excess of adjuvant material is drawn into the owgen stream. Normally, in flame machining operations where the oxygen Jet has a velocity less than that in severing or other cutting operations, such a condition will not occur. It is evident that the powder can be supplied in other ways, as by a gas at superatmospheric pressure.

In an application of this invention carried out with a nozzle such as illustrated in Figs. 1-5, a deseaming blowpipe nozzle N was positioned at an angle of approximately 10 with respect to the surface S of a billet B, as shown in Fig. 1. Oxyacetylene preheating flames were then turned on and a small area on the surface heated. As soon as this area reached a temperature high enough to initiate the metal removing reaction, the flow of deseaming oxygen through the passage i0 obliquely against and along the surface S was started, the adjuvant material was aspirated through tube 3!, and a layer of surface metal was removed. Upon advancing the nozzle parallel to the surface in the direction of gas flow indicated by an arrow, the metal removing reaction was extended along the selected path leaving a shallow groove G in the surface of the metal body. The proper temperature for starting the flow of powder-laden oxygen is determined empirically by the operator, either from his experience, or by repeatedly applying bursts of powderladen oxygen to the metal body until the metalremoving reaction begins. The size of oxygen outlet III was about 0.125 inch; the bore I3 of ejector H was about 0.0635 inch; and the oxygen pressure, at the entrance to approximately 15 feet of in. hose leading to the blowpipe, was between 20 and 30 lb. per sq. inch gage. The powdered adjuvant material was ferromanganese containing approximately 0.10% carbon, 83% manganese, with the remainder principally iron, and the particle size was approximately 60 to 80 mesh. The composition of the billet or workpiece B was 18.86% chromium, 8.6% nickel, 0.11% carbon, less than 1% each of silicon, manganese, and columbium, and the remainder principally iron. The nozzle was advanced at a rate of about 12 inches per minute and a smooth surface groove G about A inch in maximum depth and inch in width was produced. During the entire operation, the slag at all times was fluid and flowed away readily.

In contrast, when attempts were made to deseam thermochemically the identical body without introduction of powdered adjuvant material, no progress could be made. After the initial surface section had been heated by the. oxy-acetylene preheating flames, the flow of deseaming oxygen was started, but only an extremely small amount of metal was removed before the entire heated area quickly cooled down to blackness. When the same surface was reheated and a jet of oxy laden with adiuvant material was applied, the deseaming operation began promptly and -pro-= ceeded smoothly.

A billet of 18% (Er-8% Ni type stainless steel was similarly deseamed successfully using 17.8 cu. ft. of oxygen per pound of iron powder dis-' charged from a blowpipe nozzle like that of Fig. 1.

The cutting of resistant metal bodies by the novel method also was carried out with a nozzle similar to that illustrated in Figs. 1-5 wherein omen outlet 00 was No. 31 drill size (0.0635 inch). Low carbon ferromanganese ground to pass through an 80-mesh screen was drawn into the cutting oxygen stream through tube 08, and utilized in cutting various non-ferrous and substantially non-ferrous metal bodies by positioning the nozzle N at a large angle with respect to the body, as approximately normally, so that the jet of oxygen passed completely through the body and formed a kerf as the nozzle was moved continuously parallel to the surface. For instance, in' cutting the molybdenum-iron-nickel and molybdenum-iron nickel chromium alloys mentioned previously, the kerf was developed and maintained for the full thickness of the body, and the severing operation progressed at a satisfactory rate and continued for the full width of the body. Thicknesses up to 2 inches were cut, and

. the surface of the cut face was smooth. Iron powderwhich passed a -mesh screen was also utilized successfully in cutting these nickel-base alloys.

The apparatus of Fig. 1 was also utilized successfully with both ferromanganese and iron powder to cut inch thick electrolytic nickel; and ierromanganese powder was used in cutting V2 inch thick high copper-silicon alloy plate, a 50% copper and 50% zinc brass body, and a cobaltchromium-tungsten alloy.

It was found that copper plate inch thick and nickel plate inch thick could not be eflectively cut thermochemlcally when cold, but that when the plates were preheated to about 900 (3., satisfactory cutting was produced with both low carbon ferromanganese powder and iron powder. The keri was slightly wider than would be expected in flame cutting plain carbon steel, but the metal removal action was definitely themechemical in nature and not primarily due to melting. Similarly, an aluminum bar 1 inches thick, when preheated to approximately 400 C., was readily cut with ferromanganese and with iron powders, both carried by oxygen streams. The kerf produced was again relatively wide but the operation was definitely thermochemical in nature rather than solely due to melting.

Stainless steel bars containing 19.68% Cr and 10.71% Ni and having a 2% inch square crosssection were cut with a blowpipe similar to Fig. 1 passing 200 cu. ft./hr. of cutting oxygen and about 10 lbs./hr. of ferromanganese powder which was finer than 80 mesh. Similar bars of an 18% Cr- 8% Ni type steel were cut at a rate of 16.8 ft./hr. using 3.7 pounds of pure iron powder finer than 100 mesh for each 100 cu. ft. of cutting oxygen.

In the above described cutting operations, the oxygen pressure for cutting metal bodies ranging in thickness from inch to 1 inches was between 30 and 45 lb. per sq. in. gage; and for bodies ranging in thickness from 1 inches to 3 inches, between 45 and 65 lb. per sq. inch gage. In cutting with the same nozzle a stainless steel billet 5 inches in thickness containing approximately 18% chromium and 8% nickel, the oxygen pressure was about 85 lb. per sq. inch gage.

Cutting, machining, and other metal removing procedures by the method of this invention may be carried out, of course, by other apparatus, as by that illustrated in Figs. 6 and 7 in which nozzle N is a standard flame cutting nozzle having a central passage 40 for cutting oxygen surrounded by a series of passages 4| spaced from the central passage for continuously discharging a group of flowing and burning combustible gas jets through outlets spaced apart around the oxygen outlet. Thus the burning combustible gas jets are spaced apart along a circle around the oxygen jet and flow lengthwise thereof to provide preheating flames on an annular zone surrounding and alongside the oxygen jet. The inlet end of the nozzle N is similar in construction to the inlet end of the nozzle N and is secured in a blowpipe head i8 in a similar manner. Also, the oxygen and preheat gas passages in nozzle N correspond to passages l2 and 22 respectively of the rear section R of nozzle N, but extend throughout the length of the nozzle N. Instead of aspirating the powdered adjuvant material into the stream of cutting oxygen internally of the nozzle, the powdered material is discharged separately but concurrently through the space between a pair of the discharging combustible gas jets and becomes associated with the cutting oxygen jet while the latter is flowing in free space just after it emerges from the nozzle and prior to impingement against the body B. For this purpose, an adaptor or orifice block 42 is suitably secured, as by welding or brazing, to nozzle N adjacent the end thereof and a powder outlet 43 in the block is arranged close to the mouth of cutting oxygen passage 40 with its axis at an angle thereto and intersecting the extended axis of passage 4|] outside the nozzle. Powder outlet 43 lies in a plane extending lengthwise of nozzle N between two adjacent preheating gas passages 4i and their outlets, to deliver a stream of powder from outlet 43 inwardly of and beyond the encircling group of combustible gas streams along an axis intersecting the externally extended axis of passage 40 to a position between the central oxygen jet and the annular zone on which the preheat flames are arranged. Thus the powder is discharged laterally toward and into the oxygen jet discharging from passage 40 while the oxygen is flowing in free space after issuing from the nozzle, thereby providing a powder-carrying oxygen stream within and flowing alongside and lengthwise of the ring of preheat flames. A tube 44 is suitably attached to block 42, and supplies powdered adjuvant material, as in the apparatus of Figs. 1-5.

A relatively high velocity jet of cutting oxygen is discharged from passage 40 and produces a suction effect across the powder outlet 43, thereby aspirating the powdered material into the oxygen jet. The powder is instantly heated to its ignition temperature by the preheating flames and ignites, after which the burning powder is blown by the oxygen jet against the metal body B directly into the kerf K where it cooperates with the oxygen jet and the preheating flames to remove metal thermochemically and cause the cutting action to proceed as continuous relative movement between the body and the blowpipe is effected. Of course, the powdered adjuvant ma- 14 terial may be supplied to the oxygen jet in any other suitable manner, as by compressed air.

The nozzle N of Figs. 6 and 1, and the method performed therewith, are especially advantageous for cutting kerfs in metal bodies because the oxygen jet from passage 40 forms a narrow kerf because of its relatively'small cross-sectional area and has great penetrating power because of its relatively high velocity. Nozzle N, on the other hand, while especially suitable for deseaming or flame machining, is less efl'ective for cutting be cause the oxygen stream from the ejector tube l4 expands within the nozzle to aspirate powder and the powder-carrying oxygen stream emerges from the enlarged orifice III at considerably reduced velocity and with a relatively large crosssectional area.

Other advantages of the nozzle N over the nozzle N are its simplicity, and the fact that a standard flame cutting nozzle can be modified without difliculty to produce the described construction.

An advantage of nozzle N over nozzle N is that the suction effect on the adjuvant powder is normally considerably greater and can be controlled more readily and effectively in the former. However, a cutting nozzle N which discharges a relatively high velocity jet of oxygen, such as one having a velocity near the acoustic velocity (980 ft./sec. in oxygen) normally will produce sufflcient suction effect to draw all of the powder needed into the reaction zone. Furthermore, the nozzle N is more desirable than the nozzle N for flame planing wherein surface metal is removed to form a shallow groove, because the lower velocity of the oxygen jet from orifice it! prevents too deep penetration.

Using the nozzle N shown in Figs. 6 and 7 a body of 18-8 stainless steel was successfully out and bodies of stainless steel and cast iron were successfully flame planed using about 263 cu. ft./hr. of oxygen and 7.1 lb./hr. of low carbon ferromanganese powder having a particle size smaller than 60 mesh. Also, two bars of white cast iron analyzing 3.15% O-0.65% Si, and 2.40% 043.80% Si, respectively, were easily cut continuously under similar conditions. Additionally, a body of an iron alloy containing approximately 15% Si, which could not be out under conventional thermo-chemical cutting conditions, was satisfactorily severed in a similar manner.

Fromthe fact that the melting point of chromium is about 1880 C. and the melting points of various chromium and chrome-nickel bearing steels range from 1175" C. to about 1525 C., while that of chromic oxide, CrzOs, is about 1900 (3., and that the melting point of nickel is about 1452 C., while nickel oxide, N10, melts at about 2090 0., it appears that chromium and nickel are recalcitrant constituents which hinder the nor mal thermochemical cutting of stainless steels because chromic oxide and nickel oxide both melt at considerably higher temperatures than the base metal and apparently form a tenacious refractory oxide film which prevents further oxidation under conventional thermochemical metalremoving conditions. This difliculty is overcome by my method because the intense heat of combustion of the adjuvant powder and the direct impingement or the burning particles on the metal body heat the recalcitrant constituents suiflciently to cause ignition and burning in the oxygen, and because the resulting adjuvant powder oxides apparently act as fluxes to form mixtures or solutions with chromic oxide and nickel asemca oxide which remain liquid or relatively fluid down to temperatures approaching or below the melting point of the base metal. Thus, when powdered iron, manganese, ferromanganese, or mixturesthereof are used as adjuvant materials it appears that the molten or fluid particles or ferrous or manganese oxide formed by combustion of the metal powder are carried by the gases against the body from which metal is to be removed, and form with the chromic' and nickel oxides such a mixture or solution which remains fluid and can be blown away by the oxygen jet to uncover a fresh surface with which the oxygen can react to continue the thermochemical reaction. It also appears that the high temperature heat liberated by exothermic oxidation of the adjuvant powder particles superheats the progressively formed oxide products of the reaction, thus assisting in rendering them sumciently fluid to be removed as rapidly as they are formed. The same theory is believed applicable to the thermochemical removal from other resistant bodies with the same or other powdered adjuvant materials.

An oxidation resistant metal product resulting from thermochemically removing metal by the method of the invention, such as steel containing over chromium, is characterized by a flame treated surface which is quite regular, contains numerous small open shallow pores like small pin pricks distributed over the entire surface area and, due to the presence of many minute pimple-like protuberances, has a slightly rough feel like fine emery paper both on areas of the surface to which a thin oxide scale adheres and on any unsealed metallic areas.

In a flame planed body, such as'the stainless steel body B shown in Figs. 8 and 9, the shallow .arcuate groove or furrow G has a surface which is usually wholly covered with a thin layer 50 of black oxide scale (exaggerated in Fig. 9) although shiny metallic areas are sometimes present also. It is possible to remove the scale layer .50 and expose a metallic surface by passing an intense flame along the groove after the metal has cooled.

In addition to having the above-described characteristics, the flame-cut surface 52 shown on a three inch thick stainless steel body B in Fig. 10 is substantially plane and has an area or band 54 near the top of the body which is sub-' stantially free from scale and is shiny and metallic in appearance, due to the spontaneous break-away of scale from the metal. There is often a narrow oxide coated band or area 55 at the top of the cut surface above the shiny area. Below the shiny area 54 the metal is usually encrusted with a thin black oxide layer 56. In

thin bodies of metal, or in thicker bodies when extremely large flows of cutting oxygen have been used, substantially the whole cut surface is shiny and metallic like the area 54. Other kinds of resistant metals sometimes are covered with oxide scale over the entire cut surface area. Fig. 11 shows magnified 100 diameters the structure ,of a flame cut body of austenitic stainless steel understood that various changes in the apparatus andmethod can be made within the scope of the it invention, and that the principles of this invention are applicable to the removal of metal from metal bodies other than those described and to the use of adluvant materials other than those mentioned. In addition other changes may be made without departing from the spirit and scope of the invention as defined in the appended claims.

This application is a continuation-in-part of my abandoned application Serial No. 456,667 filed August 29, 1942.

Iclalm: I

1. Thermochemical metal-removing apparatus comprising, in combinaiton, a nozzle having an oxygen passage therein provided with an outlet for discharging a stream of oxygen into the atmosphere and against successive preheated portions of a metal body; said nozzle also having a plurality of combustible gas mixture passageways therein extending lengthwise of and spaced apart around said oxygen passage, said mixture passageways having outlets adjacent but spaced apart around such oxygen outlet, for discharging combustible mixture jets to produce preheating flames in the atmosphere outside said nozzle and separate from but alongside and around such discharging oxygen stream to preheat such successive portions of said metal body; a powder container separate from said nozzle, for holding a supply of adjuvant powder; and a powder supply conduit leading from said container to said nozzle but non-communicating with said mixture passageways, said conduit having a powder inlet communicating with said container and a part connected to said nozzle and provided with a powder outlet having its axis intersecting the axis of said oxygen passage and disposed in a plane extending lengthwise of said nozzle between two adjacent combustible mixture passageways, sald powder outlet being constructed and arranged to discharge adjuvant powder laterally into an oxygen stream passed through said oxygen passage and produce a powder-carrying oxygen stream flowing within and lengthwise of the flames produced by the combustible mixture jets discharging from the outlets of said mixture passageways.

2. Thermochemical metal-removing apparatus as claimed in claim 1 and wherein the axis of said powder outlet intersects the extended axis of said oxygen passage outside said nozzle and in front of said oxygen outlet, the aforesaid construction and arrangement being such that said powder outlet will deliver powder through the space between a pair of such discharging combustible mixture jets and toward and laterally into said oxygen stream after the latter discharges from said oxygen outlet.

3. Thermochemical metal-removing apparatus as claimed in claim 1 and wherein the axis of said powder outlet intersects the axis of said oxygen passage within said nozzle, the aforesaid construction and arrangement being such that said powder outlet will deliver powder inwardly between a pair of such mixture passageways and toward and laterally into said oxygen passage and into an oxygen stream flowing through the latter.

4. Thermochemical metal-removing apparatus as 'claimed in claim Land in combination with control means operable to'vary the quantity of adjuvant powder flowing from said container through said powder outlet into an oxygen stream passed through said oxygen passage.

5. Thermochemical metal-removing apparatus 17 comprising, in combination, a nozzle having an oxygen passage therein provided with a first outles; for discharging a powder-carrying metal-removing oxygen stream into unconfined space outside said nozzle and against successive preheated portions of a metal body to remove metal therefrom; said nozzle also having combustible gas passage means therein provided with other outlet means adjacent but separate from said first outlet, for discharging one or more combustible gas jets into such unconfined space to produce a preheating flame outside said nozzle but alongside such discharging powder-carrying oxygen stream for preheating such successive portions of said metal body; a powder container separate from said nozzle for holding a supply of adjuvant powder; and a powder supply conduit leading from said container to said nozzle, said conduit having a powder inlet communicating with said container and a part connected to said nozzle and provided with a powder outlet opening into said oxygen passage but in non-communicating relation with said combustible gas passage means, said powder outlet being constructed and arranged to discharge adjuvant powder from said conduit into said oxygen passage and into an oxygen stream flowing therethrough so that said powder will become suspended in said oxygen stream and provide a powder-carrying oxygen stream within said oxygen passage and discharging through said first outlet toward and against the portions of said body preheated by said flame, to remove metal from said body.

6. Thermochemical metal-removing apparatus apart around and separate from said central out- 7 let, said other outlets being constructed and arranged to discharge jets of combustible gas mixture into such unconfined space alongside but distinct from said powder-carrying oxygen stream to provide high temperature flames for preheating such successive portions of said metal body; first conduit means connected to said mixture passages for supplying thereto gas for said jets of combustible gas mixture; second conduit means connected to said bore for supplying oxygen thereto; other conduit means non-communicative with said mixture passages but connected to and intersecting said central bore for delivering adjuvant powder thereto to provide said powder-carrying metal-removing oxygen stream flowing within said bore and discharging therefrom through said central outlet and within said flames to progressively remove metal along a path on a surface of a metal body; and means, including an adjuvant powder container communicating with said other conduit means, for supplying adjuvant powder to said other conduit means for delivery to said bore.

7. Metal-removing blowpipe apparatus comprising, in combination, a blowpipe nozzle having a central longitudinal bore therein and provided with a central outlet in the front end of said nozzle for discharging a powder-carrying metal-removing oxygen stream into unconfined space outside said nozzle, said nozzle also having combustible gas mixture passage means spaced apart from and extending lengthwise of said bore and non-communicating therewith but provided with outlet means in said front end of said nozzle spaced apart from said central outlet and constructed and arranged to discharge one or more combustible gas mixture Jets to produce a heating flame in such unconfined space adjacent and around said powder-carrying oxygen stream; an oxygen ejector extending axially-into and spaced at least in part inwardly from the inside surface of said bore and having an axial oxygen passage provided with an oxygen outlet within said bore behind said central outlet in the front end of said nozzle; and a powder supply conduit secured to said nozzle and having a powder outlet communicating with such space between said ejector and said inside surface of said bore but behind said oxygen outlet of said ejector, said space communicating with said bore behind said central outlet whereby powder delivered through said conduit will flow through said powder outlet and said space and become suspended in the stream or oxygen entering said bore through said ejector, to produce said powder-carrying oxygen stream within said bore and discharging through said central outlet of the nozzle.

8. Metal-removing blowpipe apparatus com prising, in combination, a blowpipe nozzle hav= ing a central longitudinal bore therein and provided with a central outlet in the front end of said nozzle; said nozzle also having combustible gas mixture passage means extending longitudinally of but spaced outwardly from said bore and provided with gas mixture outlet means in said front end of said nozzle around and spaced outwardly and separate from said central outlet; first conduit means connected to said mixture passage means for providing such gas mixture therein; second conduit means connected to said central bore for supplying oxygen thereto; adjuvant powder conduit means including a duct secured to said nozzle and having a powder outlet whose axis converges forwardly toward and intersects the axis of said bore, said outlet being in non-communicative relation with said mixture passage means and constructed and arranged to discharge powder inwardly of and beyond the gas mixture passed through said mixture passage means but into an oxygen stream passed through said central bore to thereby produce a powder-carrying oxygen stream flowing within a preheating flame formed by burning the combustible gas mixture discharged from said gas mixture outlet means.

9. Thermochemical metal-removing apparatus comprising, in combination, a nozzle having an oxygen passage therein provided with, an outlet for discharging a stream of oxygen into the atmosphere and against successive preheated portions of a metal body; said nozzle also having a plurality of combustible gas mixture passageways therein extending lengthwise of and spaced apart around said oxygen passage, said mixture passageways having outlets, adjacent but spaced apart around such oxygen outlet, for dischargin combustible mixture jets to produce a preheating flame in the atmosphere outside said nozzle and separate from but alongside and around such discharging oxygen stream to preheat such successive portions of said metal body; a powder container separate from said nozzle, for holding a supply of adjuvant powder; powder supply conduit means communicating with said container and leading from said container to said nozzle but non-communicating with said mixture passageways, said conduit means including an orifice block secured to said nozzle and provided with a powder discharge outlet having its axis intersecting the extended axis of said oxygen passage outside said nozzle in front of said oxygen outlet, the aforesaid construction and arrangement being such that said powder outlet will deliver powder inwardly of and into the space within said discharging combustible mixture jets and laterally into said oxygen stream after the latter discharges from said oxygen out-- let. 10. A process of substantially uniformly, steadily and progressively thermochemically removing metal on a path extending along a surface of a metal or alloy body which is substantially immune to such thermochemical metal removal by the conventional procedure of steadily and concurrently advancing only a heating flame and an oxygen stream along said path while concurrently impinging only said flame and said oxygen stream against successive areas of said surface, said processcomprising progressively, steadily and concurrently advancing along said path and impinging against successive areas thereof both a heating flame and a powder-carrying oxygen stream distinct from but flowing alongside said flame; the powder in said powdercarrying stream consisting of flnely-diyided adjuvant material substantially all finer than 50 mesh and characterized by its ability to flux refractory metallic oxide and provide a removable fluid mixture of oxides along said path while said powder-carrying oxygen stream and said flame are so impinging against'said successive areas; and, during such advancing of said flame and said powder-carrying oxygen .stream, continuously producing said powder-carrying stream by introducing such finely-divided material into aflowing'oxygen stream in a. proportion of one pound of such material for from 15 cubic feet to'100 cubic feet of oxygen.

11. A process of substantially uniformly, steadily and progressively thermochemically removing metal on a path extending along a surface of a metal or'alloy body which is substantially immune to such thermochemical metal removal by the conventional procedure of steadily and concurrently advancing only a heating flame path and impinging against successive areas i thereof both a heating flame and a powder-carrying oxygen stream distinct from but flowing. alongside'said flame, at least 80% of the powder carried by said powder-carrying stream consistingof combustible ferrous metal and substantiallyall of such powder having a smaller size "than the smallest size of powder that will be retained on a 100 mesh screen and being characterized by its ing the combustible powder carried by saidv pow- I vder-carrying oxygen stream.

12. A process of substantially uniformly, steadily and progressively thermochemically removing metal on a path extending along a surface of a metal or alloy body which is substantially immune to such thermochemical metal removal by the conventional procedure of steadily and congen stream distinct from-but flowing within and lengthwise of said flame; continuously producing said heating flame by continuously flowing and burning a group of combustible gas streams lengthwise of and spacedgapart along a circle around sa d powder-carrying oxygen stream; the

' powder carried by said powder-carrying stream consisting of finely-divided adiuvant material substantially all finer than 50 mesh and characterized by its ability to flux refractory oxide produced along said path by the impingement one pound of powder'per 15 cubic feet to 100 abilityto assist'in produclnga removable. fluid. product along said path while said 'powder-carrying oxygen stream and said flame are soimpinging against said successive areas, and the'oxygen,

of said powder-carrying stream flowing in sum-.

cient volume to leave for the oxidizing of constit-' uents of said metal body an abundant excess ofoxygen over that consumed in oxidizing and burn'-.

bustible ferrous metal ness that thereof will -mesh screen and at least '70 against'said body of oxygen in said powder-carrying oxygen stream; and during such advancing, continuously producing said powder-carrying stream by, continuously injecting such powder inwardly past such encircling group of combustible gas streams and into a stream of oxygen continuously flowing lengthwise of and within such encircling group of combustible gas streams, such powder being so injected in a proportion of cubic feet of such flowlngstream of oxygen.

13. A process of substantially uniformly, steadily and progressively thermochemically removing metal on a path extending along a surface of a ferrous metal body containing more than 5% of chromium which resists-such removal by the concurrent impingement thereon of only an oxygen jet and a heating flame traveling steadily along said path, due at least partially to the for.-

mation on said path of tenacious refractory chromium oxide,vsaid process comprising: progressively, steadily and concurrently advancing along said path and progressively impinging against successive areas thereof a heating flame r su tin from burning a stream of combustible.

fluid, a jet of oxygen alongside but distinct from said flame, and a stream of burning combustible ferrous metal powder, while concurrently impinging said flame and said jet of oxygen against said body and while continuously blowing such burning combustible ferrous metal powder by said jet of oxygen onto the successive areas on said body against which said flame and said jet impinge, thereby oxidizing constituents of said body including chromium, producing a fluid product whichis removable, and progressivelyblow-v ing said fluid product from said path; said comthereof will pass through a- 200 mesh screen; the oxygen of said :jet'flowing in suflicient volume to leave for the oxidizing of constituents of said body an abundant excess of oxygenover that consumed in burning said combustible ferrous metal powder.

' 14. A process for substantially uniformly and I steadily thermochemically cutting'a kerf on a path extending along a surface of a metalor alpowder being of such fine pass through a 100 loy body which is substantially immune to such thermochemical cutting by the procedure of concurrently advancing uniformly and steadily only a heating flame and an oxygen jet along said path while impinging only said flame and said oxygen jet against said body, said process comprising continuously delivering separately but concurrently to a locality in free space adjacent to but spaced from a surface of said body a high velocity jet of oxygen flowing at a large angle to such path, a heating flame, and a stream of combustible metal powder substantially all finer than 100 mesh and at least 80% thereof consisting of combustible ferrous metal, injecting said metal powder into said jet of oxygen in such free space; burning such injected metal powder both to produce heat and to form metal oxide at successive reaction zones along said path; oxidizing constituents of said body and producing a removable fluid product at such reaction zones by applying said heating flame, said jet of oxygen alongside of and distinct from said heating flame, and said burning metal powder concurrently against said body, said burning metal powder being blown against said body with said jet of oxygen; and formin a hen? by concurrently advancing said jet of oxygen, said stream of powder, and said heating flame steadily along such path relatively to said body while progressively removing said fluid product from said body and while flowing the oxygen of said jet in sumcient volume to leave for the oxidizing of constituents of said body an abundant excess of oxygen over that consumed in burning such injected metal powder.

15. A process of substantially uniformly, steadfly and progressively removing metal on a path extending along a surface of a metal or alloy body which is substantially immune to such thermochemical metal removal by the procedure of steadily and concurrently advancing only a heating flame and an oxygen stream along said path while impinging only said flame and said stream against successive areas of said surface; said process comprising progressively, steadily and concurrently advancing along said path and impinging against successive areas thereof both a heating flame and a powder-carrying oxygen stream distinct from but flowing within and lengthwise of said flame; substantially all of the powder carried by said stream being finer than 50 mesh and'consisting of finely-divided adjuvant material characterized by its ability to flux refractory oxide produced along said path by such impingement of the oxygen of said powdercarrying oxygen stream; and during such advancing, continuously producing said powder-carrying oxygen stream by continuously injecting such powder into a flowing oxygen stream while the latter is continuously flowin in free space within said flame, such owder being so injected in a proportion of one pound of powder per 15 cubic feet to 100 cubic feet of such flowing oxygen stream.

16. A process of substantially uniformly and steadily thermochemically cutting a kerf on a path extending along a surface of a ferrous metal body containing more than of chromium which resists such cutting by the concurrent impingement thereon of only an oxygen jet and a heating flame traveling steadily along said path, due at least partly to the formation of tenacious refractory chromium oxide, said process comprising: continuously delivering separately but concurrently to a locality in free space adjacent to but spaced from a surface of said body a high velocity jet of oxygen flowing at a large angle to such path, a heating flame alongside but distinct from said jet of oxygen, and a stream of combustible ferrous metal powder all finer than mesh and at least 70% thereof finer than 200 mesh; injecting said powder into said jet of oxygen in such free space; burning such, injected powder to produce heat and from "iron oxide at successive reaction zones along said path; oxidizing constituents of said body and producing a removable fluid product at each reaction zone by applying said heating flame, said jet of oxygen distinct from but alongside said heating flame, and said burning metal powder concurrently against said body, said burning powder being blown against said body with said jet of oxygen; and forming a kerf by concurrently advancing said jet of oxygen, said stream oi;

powder, and said heating flame steadily along such path relatively to said body while progressively removing said fluid product from said body and while flowing the oxygen of said jet in suiflcient volume to leave for the oxidizing of constituents of said body an abundant excess of oxygen over that consumed in burnin said powder.

1']. A process of substantially uniformly, steadily and progressively thermochemically removing metal on a path extending along a surface of a metal or alloy body which is substantially im- ,mune to such thermochemical metal removal by the conventional procedure of steadily and concurrently advancing only a heating flame and an oxygen stream along said path while concurrently impinging only said flame and said oxygen stream against successive areas of said surface, such immunity being due at least partly to the formation on such surface of a tenacious refractory product which has a substantially higher melting temperature than the metal of said body, said process comprising steadily, progressively and concurrently advancing along said path and impinging against successive areas thereof both a heating flame and a powder-carrying metalremoving oxygen stream distinct from but flowing in unconfined space alongside said flame; producing said powder-carrying oxygen stream, before flowing the same is unconfined space alongside said flame, by introducing finely-divided adjuvant material into a confined oxygen stream in a proportion oi one pound of such material per 15 cubic feet to 100 cubic feet of oxygen in said confined oxygen stream, substantially all of such finely-divided material being finer than 50 mesh and being characterized by its ability to form with such refractory product a fluxible slag mixture having a melting temperature close to that of the metal of said body so that such slag mixture becomes fluid and removable from such successive surface areas by the joint action of said flame and said powder-carrying oxygen stream as the latter and said flame are so advanced along said path to thermochemically remove metal from said body.

18. A process as claimed in claim 17 and wherein said flame is produced by burning a combustible mixture of fuel and oxidizing gas in unconfined space around said powder-carrying oxygen stream; said combustible mixture consists of a plurality of combustible gas streams flowing lengthwise of and spaced apart around but out of contact with said confined oxygen stream; and said finely-divided adjuvant material is discharge inwardly between and past two adjacent 23 combustible gas streams into said confined oxygen stream to produce said powder-carrying oxygen stream before the latter flows into unconfined space and within said flame.

19. A-process of substantially-uniformly, steadily and progressively thermochemically removing surface metal by flame machining on a path extending along a surface of a metal or alloy body which is substantially immune to such thermochemical metal removal by the conventional procedure of steadily and concurrently advancing only a heating flame and an oxygen stream along said path while concurrently impinging only said flame and said oxygen stream against successive areas of said surface, such immunity being due.

at least partly to the formation on such surface of a tenacious refractory product which has a substantially higher melting temperature than the metal of said body, said process comprising steadily, progressively and concurrentl advancing along said path and impinging against successive areas thereof both a heating flame. and a low velocity powder-carrying metal-removing oxygen stream distinct from but flowing in unconfined space alongside said flame, said powdercarrying metal-removing oxygen stream being directed obliquely at a small angle against said surface in the direction of said advance; producing said powder-carrying oxygen stream, before flowing the same in unconfined space alongside said flame, by introducing finely-divided adjuvant material into a confined oxygen stream in a proportion of one pound of such material per cubic feet to 100 cubic feet of oxygen in said conflned oxygen stream, substantially all of such finely-divided material consisting of combustible ferrous metal powder finer than 100 mesh and characterized both by its ability to burn exothermically and supplement the heat applied to successive areas along said path and by its ability to assist in producing a fluid product which is removable from such successive surface areas by the joint action of said flame and said powdercarrying oxygen stream as the latter and said flame are so advanced along said path to thermochemically remove metal from said body.

ROBERT L. WAGNER.

REFERENCES CITIEU The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 650,124 Coleman May 22, 1900 968,350 Harrison Aug. 23, 1910 999,099 Debus July 25, 1911 1,013,379 Dunn Jan. 2, 1912 1,178,551 Stolle Apr. 11, 1916 1,305,726 Leonard et a1 June 3, 1919 1,311,815 Harris July 29, 1919 1,359,504 Harris Nov. 23, 1920 1,412,656 Jenkins Apr. 11, 1922 1,441,094 Jenkins Jan. 2, 1923 1,494,003 Ma1sher May 13, 1924 1,519,582 Harris Dec. 16, 1924 1,606,013 Wulfi Nov. 9, 1926 1,775,159 Donaldson Sept. 9, 1930 1,808,967 Plumbly June 9, 1931 1,922,038 Hardy -1 Aug. 15, 1933 2,033,915 Aubert Mar. 17, 1936 2,041,480 Oexmann May 19, 1936 2,181,095 Ness Nov. 21, 1939 2,221,788 Doyle Nov. 19, 1940 Re. 21,991 Walker Dec. 30, 1941 2,286,191 Aitchison et al. June 16, 1942 2,286,192 Aitchison et al. June 16, 1942 2,326,838 Crafts Aug. 17, 1943 2,327,337 Burch Aug. 24, 1943 2,327,482 Aitchison Aug. 24, 1943 2,327,496 Burch Aug. 26, 1943 2,359,401 Wulfi Oct. 3, 1944 2,366,787 Hoifman Jan. 9, 1945 2,415,815 Deming Feb. 18, 1947 FOREIGN PATENTS Number Country Date 641/26 Australia Feb. 19, 1926 253,073 Great Britain Oct. 21, 1926 549,781 Germany 'May 2, 1932 OTHER REFERENCES land. Ohio.

2.5 26 Certificate of Correction Patent No. 2,451,422. October 12, 1948.

ROBERT L. WAGNER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 26, forpasing read passing; column 10, line 14, for passages read passes; column 15, line 6, for or second occurrence, read of; line 22, after the word removal insert of metal,- line 66, for 18.33% read 18.83%; column 16, line 14, claim 1, for combinaiton read combination; column 20, line 46, claim 13, for partially read partly; column 22, line 9, claim 16, forfrom read form line 49, claim 17, for same is read some in; line 75, claim 18, for the syllable charge read charged;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oifice.

Signed and sealed this 25th day of January, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'ssioner of Patents.

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