US2349902A - Deseaming and desurfacing apparatus - Google Patents

Description

W 1944- J. H. BUCKNAM 2,349,902

DESEAMING AND DESURFACING APPARATUS Original Filed Jan. 14. 1939 2 Sheets-Sheet l INVENTOR JAHAS #5005401 ATTORNEY May 30, 1944., J. H. BUCKNAM DESEAMING AND DESURFACING APPARATUS Original Filed Jan. 14, 1939 2 s s t 2 INVENTOR m m 6 H. m M

//v// J 7////// w////// 7//// ATTORNEY Patented May 30, 1944 DESEAMIN G AND DESURFACIN G APPARATUS James H. Bucknam, Cranford, N. J., asslgnor to Union Carbide and Carbon Corporation, a corporation of New York Original application January 14, 1939, Serial No.

250,965. Divided and this application February 21, 1940, Serial No. 320,092

7 Claims.

rolling operations.

This application is a division of my'copending application, Serial No. 250,965, filed January 14,

1939, which issued as Patent No. 2,215,577 on September 24, 1940.

Heretofore it has been the practice in deseaming to remove surface defects, such as seams, cracks, scabs, overlaps, and the like, from iron and steel bodies, such as billets, ingots, blooms,

and the like, by means of a deseaming blowpipe having a single nozzle adapted to discharge'a jet of oxygen along and obliquely against a ferrous metal surface for thermochemical reaction with surface metal initially raised to the kindling temperature by a concentric series of heating Jets discharged from the same nozzle, and maintained at such temperature by the heat of the reaction alone or assisted by said heating Jets.-

Also, heretofore it has been the practice to desurface a surface area of a ferrous metal body by directing several oxygen streams from a plurality of nozzles disposed in a row or bank, along and obliquely against such area for combustion by thermochemical reaction with the surface metal. Where a single oxygen stream is used for deseaming, a shallow groove is formed in the surface of the work; whereas when several oxygen streams are applied to the work for desurfacing, parallel channels or grooves with ridges therebetween generally are formed.

In either case, on the work surface along the margins of the treated area, slag and waste material including molten metal tends to flow out of the undercut space and accumulate in a thin layer or film which, when solidified, is termed a fin. The slag is not all iron oxide but contains considerable metallic iron which has been displaced in the molten state due to the heat of the reaction. It is the metal content of the slag which causes the same to freeze on the edge of the groove and form tenacious fins. Such slag or fin formations are highly objectionable because they form surface defects when rolled into the work by subsequent rolling operation. Likewise, fins may tend to form on the ridges between adpacent grooves. The ridges are also very ob- Jectionable as they may contain surface defects and it is most desirable that such ridges be reduced to a minimum to prevent blemishes in the finished products.

The nozzles in a multiple nozzle desurfacing head must be spaced apart to make room for fastening the nozzles in the nozzle block. The outside of the nozzles usually are circular and the deseaming oxygen Jet passage is encircled by a series of preheating jets. The desurfacing oxygen jets are, therefore, spaced apart an appreciable distance, and in the past, the nozzles used had a round outlet orifice preceded by a circular straight sided passage and there was only a small amount of intermingling of the edge portions of adjacent oxygen streams. The oxygen jet from each nozzle made a longitudinal concave groove and between such grooves were ridges of uncut or partially cut metal which sometimes contained defective metal. The grooves at their greatest depth were deeper than usually necessary, but in spite of this some defective metal would still be left on the surface while some good metal would be removed unnecessarily, With such standard nozzles having circular orifices, it was impossible to obtain a cut of uniform depth across the surface which would remove approximately all of the defective surface metal with a minimum removal of good metal.

The main objects of this invention, therefore, are to provide an apparatus for preventing or inhibiting: undesirable formation or slag accumulation, when, as in desurfacing or deseaming, a fluid is projected along and obliquely against a body for combustion onfthermochemical reaction with ferrous surface metal; means for inhibiting fin formation when several streams of fluid are directed along and obliquely against the surface of a body for thermochemical reaction with surface metal; a blowpipe having a nozzle provided with means for automatically inhibiting fin formation on the work as a result of the operation of the blowpipe; means for preventing any undesirable formation attending the grooving of a surface area of a ferrous metal body with an oxidizing medium by thermochemical reaction; an improved desurfacing or deseaming blowpipe nozzle having means associated therewith for controlling fin formation; an improved desurfacing or deseaming. apparatus; and blowpipe apparatus that is simple and economical in its parts and very eflicient and effective in operaion.

Another object is generally to improve desurfacing and deseaming by overcoming the disadvantages and difllculties of the prior art in the inatger of the undesirable fin formation referred o a ove.

The novel apparatus of the present invention for desurfacing preferably comprises means for impinging large jets of fluid along and against a work surface for thermochemical reaction with surface material to form parallel shallow channels therein, and means for simultaneously impinging small jets of fluid along and against the work surface near the outer margins of said channels for thermochemical reaction with fln forming material discharged from said channels as a result of said first-named thermochemical reaction, or means for impinging small Jets on ridges between the channels to control the size of ridge formation between said channels.

In another aspect, the novel apparatus comprises means for applying a iet of oxygen along and against a work surface for thermochemical reaction with surface material to form a groove or scarf therein, and simultaneously diverting a portion of said Jet of oxygen along and against the work surface at an edge of the groove or channel in such a manner as to inhibit undesirable formation, such as fln formation-thereon.

The use of the apparatus of the invention for scarflng or deseaming a ferrous metal body results in an article of manufacture comprising a ferrous metal body having a shallow groove therein that is free of tin or slag formation overlying the surface at the lateral edge or border of the groove.

Referring to the drawings:

Fig. 1 is a fragmentary perspective view of a known deseaming blowpipe in operation, the work being shown in cross-section to illustrate undesirable slag or fln formation along the opposite edges of the groove;

Fig. 2 is a view similar to Fig. .1 of a gang of'deseaming or desurfacing blowpipes in. operation, to illustrate the undesirable ridge formation between grooves as well as the undesirable fin formation thereon and along a border of the outer groove;

Fig. 3 is a view in front elevation of the nozzle end of a blowpipe embodying features of this invention;

Fig. 4 is a fragmentary view in section taken on line 4-4 of Fig. 3;

Fig. 5 is a fragmentary view in section taken on line 55 of Fig. 3, and showing the relation of the blowpipe to the work undergoing surface removal;

' Fig. 6 is a view similar to Fig. 3 of a modification;

Fig. '7 is a view in front elevation of another modification;

F18. 8 is a view insection taken on line 8@ of Fig. 'I;

. Fig. 9 is a view in section taken on line 9-9 of Fig. 8:

Fig. 10 is a view similar to Fig. 9 of a modification wherein the auxiliary fluid jets are directed in parallel relation instead of inwardly;

Fig. 11 is a view similar to Fig. 10 of a further modification wherein the auxiliary fluid is conducted through an external pipe instead of an internal passage in the nozzle;

Fig. 12 is a sectional view of another modification wherein a single auxiliary fluid jet is used;

Fig. 13 is a view in front end elevation of the nozzle shown in- Fig.12;

Fig. 14 is a view in section of another desurfacing or deseaming nozzle embodying features of'this invention: and

Fig. 15 is a fragmentary perspective view of a gang of desurfacing nozzles, similar to the nozzle of-Fig. 14, for preventing the formation of.

fins along the ridges between the channels and along the outer edges of the desurfaced area.

Iron and steel when heated to its ignition temperature will burn in an atmosphere of oxygen. This thermochemical reaction is used in the removal of defects from ferrous metal bodies and involves the formation of iron oxide which has a lower melting point that that of iron or steel. Consequently, it melts and forms a fluid slag which is blown away from the region of the operation, exposing fresh surfaces of iron or steel to the action of the oxygen desurfacing or deseaming fluid. A source of heat is required to heat the metal to the proper ignition temperature for starting the operation. The heat of combustion is suiiicient in itself to carry on the reaction when once started, even on cold work. Preheating Jets or flames are used also during the operation as a practical matter to increase the efllciency of metal removal, because more metal is removed in a molten state, with the net result that more metal is removed per unit of gas consumed when preheating flames are used. The oxy-acetylene flame generally is used for providing such a source of heat. Deseaming blow-pipes thus generally provide an oxygen jet to do the actual surface removal and one or more oxy-acetylene flames to heat the metal to the proper temperature for the thermochemical reaction of the surface ferrous metal with the oxygen of said jet.

The United States Patent No. 1,957,351 to Samuel R. Olrlham, dated May 1, 1934, entitled Method of removing metal from metal articles" is a good example of the prior art. This patent discloses another type of deseaming nozhle wherein the heating gas outlets are grouped to project the heating flame against the work surface underneath the oxygen stream.

In hand or machine deseaming with a single blowpipe, if the nozzle is held so that its axis is in a plane coinciding with the direction of movement, a relatively shallow groove is formed, and half oxidized molten slag is blown from the groove, resulting in parallel fins which adhere to either side of the groove. If the blowpipe is inclined laterally the formation of a fin may be minimized or controlled at the near side of the groove, but a larger fin results on the far side of the groove toward which the slag is driven. In hand scarflng, operators also attempt to remove or prevent fin formation by manipulating the deseaming nozzle over the surface of the work so as to impede their growth, but this is tiring on the operator, slow and unsatisfactory from an economical standpoint, because it wears away the nozzle and wastes oxygen. An untidy sur= face, crossed by sharp metallic fins, also impedes inspection and sometimes necessitates additional desurfacing.

In machine desurfacing involving the use of a row or bank of deseaming blowpipes, an attempt has been made to inhibit fin and ridge formations, by inclining the outer nozzles inwardly as that as much as possible of the slag and molten metal tending to overflow the deseamed area is urged inwardly and the oxygen jets sweep at an angle across the ridges. An example of such attempt is shown by the United States Patent 2,- 125,179 to Edmund A. Doyle, dated July 26, 1938, and entitled "Method of and apparatus for removing metal from the surfaces of metallic bodies." However, this slows down the process, faster desurfacing being obtained when the nozzles are parallel to their direction of travel. Also,

fins are formed along the two outside edges of the relatively wide cut and may be formed along the ridges between the channels.

In general, this invention solves the foregoing problem by applying auxiliary oxygen against the work surface simultaneously with the application of the oxygen Jet, so that the fin forming material tending to flow out of the scarf and over the work surface is inhibited by thermochemical combustion. For carrying out this process there is used a blowpipe nozzle having a central oxygen emitting passage and a concentric series of heating gas emitting passages, together with means associated with the blowpipe nozzle for projecting auxiliary oxygen Jets or streams against the edges of the scarf to prevent fln formation. The auxiliary oxygen jet passages are preferably provided in the wall ,of the nozzle, and are so located therein as to divert a small portion of the main oxygen jet onto, and thereby reduce, the fins that are left by a nozzle or the fins and ridges that are left by a bank of nozzles of conventional construction, each having a single oxygen orifice. When these novel deseaming nozzles are used in a bank or head, the inside, adjacent auxiliary oxygen passages are so located that there is an overlap of the diverted oxygen jets and are so proportioned as to inhibit the form'ation of fins along the ridges or are so proportioned as to reduce the ridges while the outside auxiliary passages are.

so located and proportioned as most efficiently toremove the fins.

The auxiliary oxygen passages may be in the form of drilled holes or slots or pipes, that may be in parallel or inclined relationship with the main oxygen passage, and such auxiliary oxygen passages may direct a portion of the oxygen either outwardly or outwardly and downwardly or inwardly or inwardly and'upwardly depending on the relative positions of the passages and the position of the nozzles in relation to the work and the particular effects desired.

When a. number of deseaming nozzles are used in a bank, the ridges formed between the grooves cause the cross-section of the scarfed plate to have a wavy or fluted appearance. The deseaming head is usually tilted so that the nozzles will be both inclined to the workand angularly disposed to the direction of travel. The auxiliary oxygen passages in such deseaming nozzles are so located that there is an overlap of auxiliary oxygen jets and are so proportioned as to either reduce the ridges between the grooves or eliminate any fins along the ridges. By reducing the ridges, the appearance of the work is not only enhanced, but any surface imperiec- 'tions which might be hidden by such ridges and any fins along the ridges are removed.

Referring to Fig. 1 of the drawings, B is a conventional deseaming blowpipe having a. nozzle N provided with a central oxygen discharging passage Oi surrounded by heating gas discharging passages H. The arrangement is such that when the blowpipe B is moved relative to the surface T of a ierrous metal body W, a shallow groove G is formed in the work. As a result of this deseaming operation, fins F, F are formed from a molten mixture of slag and metal which flows over the edges E, E of the deseamlng groove G and solidifies on top '1 of the relatively cold work W. These fins usually form along each longitudinal side or edge E of each scarf G. The carbon content of the metal de- Steels having a low carbon content produce highly tenacious fins. Another factor increasing fin formation is the temperature of the work,

because molten metal adherence is more severe when the work is hot than when cold. The

- main purpose of this invention is to inhibit formotion of the fins F, F in a known deseaming process of the character shown by Fig. 1..

When a bank of customary desurfacing nozzles are used, as shown by Fig. 2, there results a plurality of parallel channels or grooves G" extending across the treated area. Between the grooves G are undesirable ridges R having a certain amount of undesirable fin formation FR thereon. The outer border of the outer groove also has left thereon a fin F, as pointed out above in connection with Fig. 1. An equally important purpose of this invention is to inhibit the ridge formation R and/or the fin formation FR, as well as the fin formation F alone.

Referring to Figs. 3, 4 and 5 of the drawings, there is shown one embodiment of the invention. In this embodiment the blowpipe B comprises a nozzle NI having a'bore Oi adapted to discharge a deseaming jet of oxygen for thermochemical reaction with surface material of the work W, such as a ferrous metal body, when said jet is impinged obliquely against and along the work surface T, and resulting in the formation of a shallow groove G in the work. The nozzle Ni is provided with a pair of slots S, S, each in the shape of an imaginary short triangular prism in the wall of the bore Oi, each slot B being positioned so that the lateral faces of the prism are disposed, respectively, at the bore 0i, at the outer end P of the nozzle Ni, and at the bottom oxygen which impinge against, the work surface along the opposite edges E, E of the groove G to inhibit undesirable formation, such as ridge or fin formation or both depending upon the size of slots S, S and the velocity of the auxiliary streams of oxygen.

The nozzle Ni of the deseaming blowpipe B is provided with a concentric series of heating gas emitting passages H surrounding and concentric with the central oxygen emitting passage Oi. The blowpipe B is otherwise of conventional design and construction well known to those skilled in the art.

The purpose of the auxiliary oxygen streams or Jets is to oxidize either the metal in the fin forming material or the metal in the ridges while at an ignition temperature. My deseaming nozzle Ni thus makes scarfs without the fins, especially in low carbon steel. If desired, only one auxiliary stream or sheet of oxygen may be diverted from the main oxygen passage to inhibit the formation of a fin along one border area of the groove.

In operation, where a single blowpipe B having the nozzle Ni for deseaming or desurfacing is used, the nozzle is first held in an upright position to direct the heating jets issuing from the passages H against the surface T of the work W to heat the same to its kindling temperature termines how difficult such fins are to remove. 15 with oxygen. When the heated area of the work 90 degrees.

surface is substantially at its kindling temperature, the omen issuing from the passage Oi reacts thermochemically with the ferrous surface metal and at the same time the blowpipe is tilted so as to impinge the main oxygen jet obliquely against the surface to be deseamed, as shown by Fig. 5. The nozzle NI is then advanced alon the surface T to form the groove G, blowing the slag and molten metal M forwardly over the uncut surface of the base lnetaL- At the same time the auxiliary oxygen of the sheets or streams issuing from the slots S, S thermochemically reacts with the molten metal in the slag tending to flow laterally out of the groove and over the base metal along the opposite edges of the groove, to thereby inhibit fin formation.

Where a plurality of the hiowpipes or nozzles NI are used in a bank to deseam or desurface a ferrous metal body, the auxiliary sheets or streams of oxygen overlap and impinge against the work surface in the areas of ridge formation between the grooves. In such case the oxygeh burns the molten metal in the fin forming slag between the grooves or reduces the ridge formation depending upon the velocity of the ongen, while the outer laterally projected oxygen streams act to inhibit fin formation along the borders of the desurfaced area, leaving the base metal substantially clean and the desurfaced area substantially clean or clean and level. Referring to Fig. 6, there is shown another deseaming nozzle N2 wherein the slots S2, S! are similar to those described above in connection with Figs. 3-5 but are disposed at an angle of 180 degrees relative to one another instead of The operation of the nozzle N2 shown in Fig. 6 is substantially similar to but not quite as effective for the purpose intended as that shown by Figs. 3-5. The blowpipe nozzle N2 has a central oxygen emitting passage 02 and a concentric series of heating gas emitting passages H for scarfing a plane surface, while the slots S2,

S2 in the wall of the oxygen emitting passage project auxiliary sheets of oxygen against the edges of the scarf to prevent any undesirable formatiomsuch as ridgesor fins or both ridgesand fins, thereon.

Referring to the modification shown in Figs. '7, 8 and 9 of the drawings, the deseaming or scarflng nozzle N3 is provided with a pair of auxiliary oxygen passages S3, S3, which extend downwardly and laterally from the main oxygen bore 03 at l8, l5 and then forwardly and inwardly toward the outer end face of the nozzle member. The passages S3, S3, are disposed and arranged to direct auxiliary, coplanar oxygen jets inwardly along and against the edges of the uncut are: of the work to control slag formation thereon. The angle of impingement of the auxiliary jets is substantially less than that of the main jet passage from the bore 03. In this aaaaeos 84, Bl which extend downwardly and laterally from the oxygen bore 04 and then forwardly to the outer end face of the nozzle member N4. The passages S6, S4, are disposed and arranged to direct the coplanar auxiliary oxygen jets in parallel relation over the opposite edges of the work surface adjacent the groove made by the main oxygen Jet. It will be seen that the outer portionsfof the auxiliary oxygen passages 84 have axes which are preferably parallel to a vertical longitudinal plane containing the longitudinal axis of the main passage 04, and also at a small angle with respect to another plane containing such longitudinal axis of the main passage 04 and which is perpendicular to the first-mentioned longitudinal plane. Thus, as the nozzle is advanced, parallel auxiliary oxygen jets are impinged along and obliquely against the work surface at the borders of the groove formed by the impingement of the main deseaming oxygen -jet along and obliquely against such surface. The angle of impingement and the velocity of these auxiliary lets is substantially less than that of the main jet and these auxiliary jets also successfully inhibit fin formation.

In the modification of Figs. 12 and 13, the deseaming nozzle N5 has an auxiliary oxygen passage Oh that is connected at its inlet end It to the main oxygen passage 05, and has its outlet portion parallel with said main oxygen passage 05. This auxiliary passage S5 directs an oxygen let down along the edge of the scarf and tends to keep the molten slag from flowing over base metal at the edge of the scarf, and oxidizes the molten metal in the slag that does reach the edge. An operator can deseam faster with this nozzle than with a conventional deseaming nozzle since the fin inhibition i substantially automatic. The deseaming nozzle N5 shown in Figs. 12 and 13 is otherwise substantially similar to a conventional deseaming nozzle, being provided with oxy-acetylene heating gas pwages H sur rounding the central oxygen passage 05; the

auxiliary owgen passage S5 occupying the position of one of the oxy-acetylene passages. The blowpipe nozzle N5 is preferably held so that it is inclined to the direction of travel, the auxiliary oxygen passage S5 being positioned so that -its the latter, without harming the base metal while is oxygen jet impinges along the edge of the deseamlng groove at the far side thereof, to thus thermochemically react with the material that tends to flow out of the groove. In this way fln formation along the far side of the groove is substantially entirely eliminated. The angle and direction of impingement of the auxiliary oxygen jet may be controlled readily by the operator by manipulating the blowpipe.

In .the nozzles N3, N4 and N5, the outlet portions of the small'auxiliary oxygen passages are so related to the main oxygen passage that the longitudinal axes of the outlet portions or the auxiliary passages, when extended will each pass through a point in a longitudinal plane containing the axis of the main passage, and such point will be a short distance in front of the end face of the respective nozzle and will be located laterally of the main passage axis a distance slight- 1y greater than the radius of the main passage. Such relationship is necessary in order to have the auxiliary om'gen jets impingealong the edges of the scarf or channel being produced by the main oxygen jet at the place where the main oxygen jet impinges obliquely against the work surface.

Referring to Fig. 11, there is shown a blowpipe nozzle N6 for deseaming, the nozzle being provided with a branch pipe or conduit C connected at its inlet end to the main oxygen passage 06, the branch conduit C being curved inwardly to direct an auxiliary jet of oxygen inwardly and downwardly against the edge of the area undergoing desurfacing treatment by the main oxygen jet. This nozzle is also provided with heating gas passages H surrounding the main oxygen passage 08 in concentric relation. If desired, the nozzle shown in Fig. 11 may be provided with two branch conduits for diverting auxiliary jets of oxygen from the main oxygen passage 06. The operation of the device is substantially similar to that described above in connection with the blowpipe shown in Figs. 12 and 13.

Referring to Fig. 14, the desurfacing or deseaming nozzle N1 is provided with a main oxygen bore 01 and with a pair of outwardly inclined auxiliary oxygen bores 51 for diverting 4,

some of the oxidizing fluid from the main bore obliquely against and along the surface of the work to inhibit ridge and fin formation. When used in a deseaming head the outwardly inclined auxiliary oxygen jets may be so proportioned as to coact in controlling ridge formation between the scarflng grooves made by the thermochemical reaction of the main oxygen jets with ferrous surface material of the work. The outer nozzles are provided with auxiliary oxygen passages for directing auxiliary jets of oxygen along and against the surface of the work adjacent the area undergoing deseaming treatment to inhibit fin formation.

Referring to Fig. 15, a plurality of nozzles N1 are shown mounted in a bank so that the fininhibiting oxygen jets issuing from the auxiliary oxygen bores B1 are directed along the ridges between the channels formed by the main oxygen Jets and are directed along the outer edges of the outer channels. The fin-inhibiting jets prevent the formation of fins on the ridges and along the outer edges of the desurfaced area.

While there is great similarity between the deseaming nozzles having auxiliary oxygen jets for in control and the desurfacing nozzles having auxiliary oxygen jets for ridge control, there is a decided difference between these nozzles as to where and how they are used and as to the percentage of the total oxygen stream which is diverted into the auxiliary jets. The deseaming and desurfacing nozzles which are designed for fin control preferably pass only a small quantity of oxygen at a low, non-deseaming velocity through the auxiliary jets. so as not to affect the base metal of the work. Thus, such nozzles prevent the formation of fins by a combination bf a. blowing oil of the molten slag or metallic oxide and further oxidation of a small amount of molten metal in the slag without affecting the base metal. The desurfacing nozzles for ridge. control divert a larger percentage of the total desurfacing oxygen (in their auxiliary jet to oxidize the surface metal in the usual ridges.

While the nozzles shown in Figs. 3-6 and 14 are intended primarily for ridge elimination, and the nozzles shown in Figs. 7-13 are intended primarily for fin removal, it will be understood by those skilled in the art that the primary use of these nozzles may be changed by changing the nozzle proportions to vary the amount of and velocity of the oxygen in the auxiliary sheets or jets. The nozzles shown in Figs. 3-6, inclusive, give much better results when used for ridge control than the old nozzles having round orifices: the ridges being greatly reduced and the grooves being more nearly flat by virtue of their operation. The nozzle shown in Figs. 3-5 is especially useful for scariing around the corners of a billet in which case such nozzle is placed at the end of a bank of nozzles, adapted to scarf a lateral surface, to project an oxygen stream at least partially around the billet corner or edge.

The invention is applicable to the deseaming or desurfacing treatment of ferrous metal bodies of low carbon alloy and high carbon steels, both cold and while hot and by machine or hand operation. By eliminating fin and ridge formations the resulting product is substantially free of surface defects, and in the practice of the invention no more oxygen is used than in the past where ridges and fins were formed, and substantially less than where it was attempted unsuccessfully to reduce-ridge and fin formation.

Iclaim:

1. A blowpipe nozzle comprising an elongated body member having an outer end face, a relatively large longitudinal bore opening at its outer end in the outer end face or said member for discharging a main jet of oxidizing fluid obliquely against and along a work surface for'thermochemical reaction with surface material to form an undercut space, and a pair of relatively small bores each of which opens at its inner end to said large bore, extends downwardly and laterally therefrom and then forwardly and inwardly toward said-outer end face of said memher, said small bores opening at their outer ends to said face for discharging auxiliary jets of such oxidizing fluid obliquely against and along the work surface at the margins of said undercut space, the angle of impingement and the velocity of said auxiliary jets being substantiall less than that of said main jet.

2. A blowpipe nozzle comprising an elongated body member having an outer end face, a relatively large longitudinal bore opening at its outer end in the outer end face of said member for discharging a main jet of oxidizing fluid obliquely against and along a work surface for thermochemical reaction with surface material to form an undercut space, and a pair of relatively small bores each of which opens at its inner end to said large bore, extends downwardly and laterally therefrom and then forwardly and in parallel relation to a vertical longitudinal plane containing the longitudinal axis of said large bore, said small bore opening at their outer ends to said face for discharging auxiliary jets of such oxidizing fluid obliquel against and along the work surface at the margins of said undercut space, the angle of impingement and the velocity of said auxiliar jets being substantially less than that of said main jet.

3. In a blowpipe for desurfacing or scarfing a ferrous metal body, nozzle means having an end face and a relatively large main oxygen passage opening at its outer end in said end face for discharging a main stream of oxygen obliquely against and along a surface of said body for thermochemical reaction with heated surface metal to form a scarf; at least one but not more than two relatively small auxiliary passage means for discharging an auxiliary jet of oxygen 6 Q aacasos obliquely against said surface and along a margin of said scarf to inhibit in formation along said margin, the discharge portion of said auxiliary passage ending substantially in the plane of said end face and having its axis at such angular relation to and spacing from the axis of said main oxygen passage that said auxiliary axis passes through a point in a longitudinal plane containing the axis of said main passage. said point being located a short distance in front of said end face and laterally of said main axis at a distance therefrom slightly greaterthan the radius of said main bore: and a connection between said auxiliary passage and said main passage arranged to supply oxygen from said large passage to said auxiliary passage at such rate that the velocity of flow of said auxiliary Jet is less than that of in the plane of said end face and having their axes inclined inwardly andalso at an angle to a said main stream whereby said auxiliary jet does not materially affect the surface metal of said body while inhibiting such fin formation.

a ferrous metal body, nozzle means having: an end face and a relatively large main oxygen-passage opening at its outer end in said end face for discharging a main stream of oxygen oblique- 1y against and along a surfaceof said body for thermochemical reaction with heated surface metal to form a scarf: at least one relatively small auxiliary passage means for discharging an auxil iary jet of oxygen obliquely against said surface and along .a marginal said scarf to inhibit fin formation along said margin, the discharge portion of said auxiliary passage ending substantially in the plane of said and face and having its axis substantially parallel to a vertical longitudinal plane containingthe lon itudinal axis of said main oxygen passage and also at a small angle with respect to another plane containing said longitudinal axis and disposed -perpendicular to the said vertical longitudinal plane: and means for' supplying oxygen to said auxiliary passage at a rate such that the velocity of said auxiliary jet is less than the. velocity of said main stream.

5. In a blowpipe for desurfacing or scarfing a ferrous metal body. nozzle means having an 'end face and a relatively large main oxygen pas sage opening at its discharge end in said end face plane containing the longitudinal axis of said main oxygen passage which plane is equi-distant from the outlets of said auxiliar passages; and means for supplying oxygen to said auxiliary passages at a rate such that the velocity of said auxiliary lets is 1cm than the velocity of said main stream,

6. A blowpipe nozzle comprising an elongated body member having an end face, a relatively large main bore opening at its outer end in said end face for discharging a main jet of oxidizing gas obliquely against and along a work surface for thermochemical reaction with surface material to form an undercut space or channel, and two relatively small passages opening at-their outer ends in said end face for discharging auxiliary jets of such oxidizing fluid obliquely against and along the work surface at the lateral margins of said undercut space. the outlet portions of said small passages being so related to said main bore that the axes of the small passages pass through points in a longitudinal plane containing the axis of said main bore, said points being located a short distance in front of said end face and laterally to each side of said main axis at a distance therefrom slightly greater than the radius of said main bore; and connections between said small pusages and said main bore constructed and arranged to supply oxidizing gas from said main bore to said small passages at a rate such that the velocity of flow of said auxiliary jets is less than the velocity of flow of said main Jet.

7. A blowpipe nozzle comprising an elongated body member. having an outer end face, a relatively large longitudinal bore opening at its outer end in said end face for discharging a main jet of oxidizing gas obliquely against and along a work surface for thermochemical reaction with surface material to form an undercut space or channel, and at least one relatively small passage having a connection at its inner end to said large vbore, said small passage extending laterally therefrom and then forwardly and in substantially parallel relation to a longitudinal plane containing the longitudinal axis .of said large bore: said auxiliary passage opening at the outer end in said end face for discharging an auxiliary jet of oxidizing gas obliquely against and along the work surface at the margin of said undercut

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