US2157095A - Method and apparatus for desurfacing ferrous metal bodies - Google Patents

Description

y 9, 1939. J. H. BUCKNAM 2,157,095

METHOD AND APPARATUS FOR DESURFACING FERROUS METAL BODIES 7 Filed Oct. 24, 1936 INVENTOR ORNEYS Patented May 9, 1 93 9 STATES METHOD AND APPARATUS Fon'DEsUrtFAcunoramtous METAL ooms e James Harold Bucknam, Cranford, N.,J.I. assignor 3 I to. The Linde Products company 'New 'ffyork, N-j a corporation of ohm v I I .-Application:.0ctober 24, 193 Serial No.1 I

Claims. (menses), I

. This invention relates to a method and apparatus for desurfacingferrous metal bodies, and more particularly, to 'a method and apparatus for conserving the shape and heat of the relatively 1 teristics and efiectsare had.

A specificobject ofthe invention is toprovide' a procedure for'assistingthe surface tension-of the reaction puddle to act in a manner tending to a reaction puddlei'ntact'in a central position with large reaction puddle which is formed thermochemically when desurfacing with a gang of nozzles applying oxidizing-gas on a' hot surface of a ferrous metal body.

The invention has for its object generally the provision of an improved procedure and steps in a method of the character-set forth, together with suitable apparatus for carrying the'same' into efiect, whereby improved operating'char'ac effect the desired conservation and to retain the respect to 'the gang of nozzles on the body b eihg desurfaced; 1 a v Another object is to provide means for apply- Y ing an"external"comp'onent'of force in a manner the puddle as a unitary mass "and to prevent its sloughing off at the sides;

Another'object is to provide an optimum range for the' angular orientations taught in the U. S. Patent to E. A. Doyle, No. 2,125,179, issued July 26, 1938, for the oxygen impinging nozzles about axes perpendicular to the surface being removed.

Still another object of the invention is to provide an arrangement of nozzles for multiple nozzle I desurfacing adapted to give components of force which tend to urge the reaction puddle to a central position and maintain it there ahead of the reaction zone. v

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangements of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of .the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawing, in

which:

Fig. 1 is-a sideelevation showing an arrangement for multiple nozzle de'surfaoing, of a billet when the top surface is being removed in accordment used in"con nection with the illu'st tlon'in Fi 1 and depicts 'the mutual inclination of the oxidizing gas streams employed in the'ipractice of the'invention; and- 7 j Fig. 3 shows'a-modified arrangement of the nozzles where the number is different from that shown in Fig. 2.

In the art of desurfacingferr'ous metal bodies with oxidizing gas, it is now common practice to remove the surface of ingots,-billets,and'the like, to a desired relatively shallow depth in comparatively wide cuts, by impinging a plurality orrelatively voluminous side-foy-jside' streams of oxidizing gas upon aregionof surfaee'extending'transversely to the direction in'which' a"-cutis tofbe taken; and-at acute angles tef 'a plane which is tangent-to the surface at the points of impinge;

' merit; the'applicationof gas being'in the-general. direction of the metal removal. 'Ifhdpxidizihg' gasemployed may be either commercially pure" oxygen era-mixture of" oxygen"and a neutral gas; the 'noz'zle exityelocity with which thegas is supplied 'is preferablyoi a relatively lowvalue. A' suitable' velocity 'ofjt'his character 'has as "its upper limit the acoustic. velocity andmayhave, a

value taken within thegeneral range of fr'om'200 to11000 ft. per. second, as' set-'forthjin the U. S

Patent"to; Oldham,No.1951351. g

The surface removed by; the thermo-chemical reaction of the oxidizing gas" impinged upon the surface of the ferrous metal body mustbe initially raised to the temperature at which the oxygen will react, i. e., to the oxygen ignition temperature, in order that the thermo-chemical reaction may take place. The elevating of the surface to such ignition temperature 'may be accomplished by the application of a suitablepreheating gas flame to the surface at a period of time and in a position somewhat ahead of the time and region at which the oxidizing gas is applied.' A mixture of oxygen and acetylene is suitable as the heating gas mixture to be supplied in the practice of the present invention. Where the ingot or billet is to be desurfaced while hot, as a step in a steel mill manufacturing process, it may be unnecessary to practice the preheating of the surface to the ignition temperature since the uncooled billet is frequently at or above such ignition temperature.

nozzle desurfacing, the nozzles are usually so.

closely spaced that the several reaction puddles coalesce, and a single puddle results that moves over the surface as the desurfacing nozzles and the metal body are removed relatively. While the puddle thus formed is a relatively viscous mass and has a'relatively high surface tension,

it has been found in practice that the puddle has as a rule has a substantial portion in contact over a considerable area of the metal body ahead of the gas applying nozzles, and hence imparts conductively a relatively large amount of heat to the surface to be removed. The puddle thus assists in attaining the desired preheating efiect on the surface metal in advance of the out.

In the practice of the presentinvention a step is taken for supplementing the effect of the S111? face tension in the reaction puddle in a transverse direction so as to minimize the tendency of sloughing off at the sides and thereby accomplish a conservation of the heat of the puddle. This conservation also makes for greater uniformity "in depth of the cut which is made.

In order to carry out this step, an arrangement of nozzles is employed which imparts the desired assistance to the surface tension as a supplemental external force, such force being derived from the velocity of the' gas applied. To this end, a plurality of nozzles are oriented to- -ward each other through small angles about axes substantially perpendicular to the plane tangent to the surface being removed so as to apply transverse velocitycomponents to the surface of the puddle. ,Whe re more than two nozzles are employed, this is seen to involve the inclining of each pair of nozzles on opposite sides of a center line mutually toward each other. In this manner, the normal cohesive forces of surface tension in the reaction puddle are supplemented externally so that the puddle is retained as a unitary mass moving ahead of the reaction zone. 4

Referring now to the drawing, and particularl to Fig. 1, B denotes a fragmentary portion of. a billet whose top surface is being thermo-chemically removed by a gang of nozzles l0 arranged in accordance with'the invention. These nozzles may be of any suitable type, for example, of the conventional type having cylindrical bores, as now commonly used in the art. Here, the nozzles [0 have connections II for supplying both oxidizing gas and heating gas to the nozzle passages after traversing a head [2 which may be watercooled, if desired (water-cooling connections being omitted from the drawings in the interests of cleamess of illustration). The oxidizing gas is shown as a stream i 3 impigning upon the top surface of the billet B, and making an acute angle in a vertical plane of about 25 degrees with its trace in the tangent plane, the stream l3 being surrounded by a plurality of small heating gas jets l4. The region of the surface impinged by the several streams of oxidizing gas is the region 01 zone where the thermo-chemical reaction takes place and burns off, as it were, the surface metal to be removed to a desired depth, for example, to an average depth of inch. A puddle of slag, as indicated at P, forms ahead of the impigned gas in the reaction zone and has a billowslike crwt R which moves ahead of the portion more immediately adjacent the reaction zone.

In Fig. 2, an arrangementof nozzles is shown whereby external components of force are applied to the surface of the puddle P to assist in its retention centrally on the billet being desurfaced. Here, an even number ofoxidizing gas supplying nozzles are depicted and denoted respectively l0, l0", 1, and 10 The two inside nozzles l and |0 are seen to be mutually inclined toward the center line 2-3: of the billet at small angles. which may have values, forexample, of from 5 to 15 degrees.- The outside ,nozzleslll' and iii are also mutually inclined, but at increasingly greater angles than the inner nozzles, since in this way the supplemental components of force may be made to have comparatively large values at the edge of the puddle. In practice, the nozzles Hi and HI may be inclined at angles of from 10' to 20 degrees. Any suitable mechanical spac- I ing means, for example,'a toothed bar as shown at 15, may be employed for retaining the nozzles properly .spaced -and in the desired mutually inclined positions.

To make a desurfacing cut with the arrangement shown in .Figs. 1 and 2, preheating gas flames are first applied tothe place ,where the cut is to start. When this place is at the oxy en ignition temperature, the oxidizing gas :streams are turned on.. After this, the billet and the heads carryingthe oxidizing gas applying noz-. zles are moved relatively at, a suitable speed, for example, at ft. per minute. .The oxidizing gas thereby impinged upon the surface is applied not only at an acute angle to the tangent plane of the billet's surface at-the place ,of impingement but isinclined somewhat "laterallylthrough. angles having axes substantially perpendicular to the tangent plane so as to give lateral components of force thatare applied to the surface-of the-re-.

action puddle and supplement the normal c0- hesive forces operating in the surface of the. pud-' dle producing resultants which tend to have equilibrium only along the center line of .thebillet.

reaction .zone with little liability to substantiallosses through sloughing off at thesides.

.In Fig. ,3, an, arrangement of-vnozzles employ-- ing an add number iashown.- Five nozzles are.

depicted and are denoted respectively l0, Jflfilfl,

In and I0. Here, it is seen that the-central nozzle Ill is not oriented throughany anglelabout a vertical axis but has its projection parallel to the center line :c '-a:' of the billet. The two inside nozzles In and III are mutually inclined toward the center line through small angles as were the nozzles I 0* and "1 in Fig. 2, while the two outside nozzles- H) and Ill are oriented through somewhat greater angles. Thus, it is seen that external components of force, increasing with the approach to the outer edges of the reaction puddle, are provided, whichoperate to retain the reaction puddle centrally as an imperforate unitary fused mass moving ahead of the reaction zone when a desurfacing cut is being taken.

Since certain changes in carrying out the above process and in the constructions set forth, which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be inbeing applied through nozzles arranged to supply gas in relatively large volumes at acute angle to a plane tangent to the surface being removed in the region of impingement and in the general di rection of, advance of the desurfacing reaction, inclining said streams mutually toward each other by orientations through angles of from five to twenty degrees about axes substantially perpendicular to said tangent plane, saidorientation having a direction and magnitude such as to derive an-external component of force supplementing the normal cohesive forces which operate in the surface of the reaction puddle that forms in the region impinged by said oxidizing gas streams to an extent which causes the reaction puddle to move centrally ahead of the reaction zone with little liability to sloughing 05 at the sides, and imparting relative motion to said plurality of oxidizing gas streams and said metal bdy1 2. The process of thermo-chemically desurfacing a ferrousmetal body which comprises applying heating gas flames to the surface to be removed to raise the temperature of the same to the oxygen ignition temperature, impinging a plurality of oxidizing gas streams upon a region extending across a surface of said body when at the oxygen ignition temperature, said streams being applied through nozzles arranged to supply gas in relatively large volumes at acute angles to a plane tangent to the surface being removed in the region of impingement and in the general direction of the desurfacing reaction, inclining the streams of oxidizing gas on each side of a center line mutually toward each other by orientations through angles about axes substantially perpendicular to said tangent plane, said orientations adjacent said center line being relatively small and. of a value from five to fifteen degrees and having a direction such as to derive an external 'component of force supplementing the normal cohesive forces which operate in the surfaces of the reaction puddle that forms in the region impinged by said oxidizing gas streams, said orientations for the streams outside of those immediately adjacent said center line being from ten to twenty'degrees and progressively increased whereby the transverse components of force tend to move the reaction puddle to the center of the reaction zone, there being a region of equilibrium along the center line, and imparting relative motion of said plurality of oxidizing gas streams and said metal body.

3. Apparatus for thermo-chemically desurfacing a ferrous metal body comprising, in combination, means for supporting a body in a position to be operated upon, a group of heads movably supported above said supporting means, each of haid heads having a nozzle for impinging a relatively voluminous stream of oxidizing gas upon a surface to be removed of a metal body when on said supporting means, said streams being impinged at acute angles to a plane tangentto the surface being removed in the region of impingement and in the general direction in which a desurfacing reaction takes place, means for holding said heads in positions such that the streams of oxidizing gas are mutually inclined toward each other on opposite sides of a center line, said inclinations being through angles of from five to twenty degrees about axes substantially perpendicular to said tangent plane,- said angles being selected to have directions and magnitudes which derive external components of force from the velocity of said gas streams and supplement the normal cohesive forces operating in the surface of the reaction puddle that forms in the region impinged by said oxidizing gas streams, and means for moving said group of heads relatively to said supporting means.

4. Apparatus for thermo-chemically desurfacing a .ferrous metal body comprising, in'combination means for supporting a body in a position to be operated upon, a group consisting of an even numberq-of heads operatively disposed with respect to said supporting means, each of said heads having a nozzle for impinging a relatively voluminous streamof oxidizing gas upon a surface to be removed of a metalbody when on said supporting means, said streams being impinged at acute angles to a plane tangent to the surface being removed in the region of impingement and in the general direction in which a desurfacing reaction takes place, means for holding a pair of heads on opposite sides of a center line mutually inclined toward each other through angles about axes substantially perpendicular to said tangent plane, said angles having a magnitude of from 5 to degrees and directions such as to give external components of force derived from the velocity of said gas streams which supplement the normal cohesive forces operating in the surface of the reaction puddle that forms in the region impinged by said oxidizing gas streams, a pair of nozzles which are outside of said first-named pair and on opposite sides of said center line being mutually inclined toward each other through angles of slightly greater magnitude than said first-named angles, and means for moving said group of heads relatively to said supporting means.

5. Apparatus for thermo-chemically desurfacing a. ferrous metal body comprising, in combination, means for supporting a body in a position to be operated upon, a group consisting of an odd number of heads operatively disposed with respect to said supporting means, each of said heads having a nozzle for impinging a relatively voluminous stream of oxidizing gas upon a surface to be removed of a metal body when on said supporting means, said streams impinging at acute angles to a plane tangent to the surface being removed in the region of impingement and in the direction in which a desurfacing reaction takes place, means for holding the central head in said group in a position such that the projection of the streamof oxidizing gas impinged on the surface to be removed is parallel to the center line of said group, the pair of heads adjacent said central head being inclined toward each other through angles whose axes are substantially perpendicular to said tangent plane, said angles having a magnitude of from 5 to 15 degrees and a direction such as to give a component of force derived from the velocity of said gas streams operating inwardly toward said center line, the pair of heads next adjacent said first-named pair of heads being inwardly inclined through angles about axes substantially perpendicular to said tangent plane and havingmagnitudes of from 10 to degrees and directions such as to give external components of force directed toward said center line, and means for moving said group of heads relatively to said supporting means.

JAMES HAROLD BUCKNAM.

CERTIFICATE OF CORRECTION.

P en n 2,151 095 m y 9,, 195.9.

JAMES-HAROLD BUCKNAMQ" It 5 5 her certified that error a ear in the printedepecifieation of theiabove numbered patent. requiring correction as follows: Page 2, "first cplimzh; line fih fif jfimpignirig" read impinging; line 65-66, foi "impighed" read. impinged} eame page, secend column -fline 1 5', for the word "add read, odd; page first c m line 2, claim l, for 16" read angles; line 59', f0; "ha-id read said; and that the said Letters Patent should be read with this; corfec tion therein thet the same may confoi'm to the reco rd of the case inthe Patent Office. v

Signed and sealed this 15th day of June A. D. 19 9.

Henry Van Arsdale (869.1) Acting Commissioner of Patents.

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