US2347758A - Method of removing metal from metal bodies - Google Patents

Description

" IMay 2, 1944. w. s. WALKER ETAL METHOD OF REMOVING METAL FROM METAL BODIES Driginal Filed Nov. 26, 1937 |NvENToRs WESLEY S. WALKE I BY WILGOT J. JACOBSON ATTORNEY Patented May 2, 1944 METHOD OF BEMOVING METAL FROM METAL BODIES Wesley S. Walker, Larchmont, N. Y.,

and wum J. Jacobsson, Plainfield, N. J., assignors to The Linde Air Products Company, a corporation of Ohio Application November 26, 1937, Serial No. 176,400,

now Patent No. 2,266,834,

1941, which is a No. 536,254, May

dated December 23,

division of application Serial 9, 1931. Divided and this aD- plication May 28, 1940, Serial N0. 337,632

3 Claims.

This invention relates to a method of thermochemically removing surface metal from ferrous metal bodies and more particularly to a method of scarring or removing surface metal in relatively wide shallow paths or channels. Such method is particularly useful for removing seams or other defects from steel slabs, blooms, or billets. It is important that all defective metal portions in the surface of such masses of metal be removed before they are initially rolled and before each succeeding rolling process. When metal containing surface fissures or other surface defects is rolled, the defects are not eliminated and they are sometimes rolled into the body of the metal inthe form of concealed unbonded'seains or cracks. Also, when the surface of metal having steep projections thereon or grooves therein with steep sides is rolled out, the sides of these irregular surfaces fold over and include oxides within the folds and cause concealed cracks in the body of the metal in the same way. In order to eliminate the defects and the formation of seams within the body of the metal, it is necessary to remove the defective metal portions so that only sound bonded metal remains and so that the slopes of the depressions and elevations that may be left on the surface of the billet will be so gradual that these slopes will not be folded over and rolled into the body of the metal when it is rolled.

This application is a division of our copending application Serial No. v176,40() filed November 26,

, 1937, entitled Blowpipe nozzle, now United States Patent No. 2,266,834 issued December 23, 194i, which is a division of our application Serial No. 536,254, filed May 9, 1931.

We have discovered that much time and labor can be saved by removing the defective surface portions of the steel or iron thermo-chemically with the use of an oxidizing stream of gas, and that the desired contour of the groove cutby the oxidizing gas can be obtained with a blowplpe nozzle constructed to permit the passage of a suitable volume of gas at a relatively low'oriilce velocity, such as,` for example, about 585 feet per second, and that the contour of the cut can be controlled by the shape of the orifice and the velocity of the oxidizing stream issuing therefrom. Velocities of the gas stream commonly used for oxygen cutting or severing of metals are equal to or higher than the velocity that is produced by gas flowing through a passage of uniform cross-sectional area. Therefore, the rela- 'tively low predetermined orifice velocity desired for removing surface metal is one which is below thatcommonly used for cutting kerfs.

The principal object of this invention is there. fore to provide a method of thermo-chemically removing surface metal from ferrous metal bodies to form wide shallow channels having gradual sid'e slopes and substantially uniform de th.

, 'lihe above and other objects of our invention will be best understood by referring to the following description and accompanying drawing, in which:

Fig. 1 is a longitudinal cross-sectional view of an exemplary form of our blowpipe nozzle having its discharge end face perpendicular to the axis of the nozzle and having an oblong or transversely elongated discharge oriflce in said face;

Fig. 2 is a longitudinal cross-sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a view of the discharge orifice end of i the nozzleshown in Figs. 1 and 2;

Fig. 4 is a view of a transverse section taken lon the line 4-4 of Fig. 1; and, i

Fig. 5 is a semi-diagrammatic side view of the nozzle showing its relation to the work surface during operation.

Referring to Figs. 1 and 2, the blowpipe nozzle III has an inlet end suitably formed to be attached to the head (not shown) of a suitable blowpipe. The external threads I2 on the coupling nut I3 cooperate with internal -threads in the blowpipe head to maintain the inlet portion Il of a central oxygen passage I5 and the inlet portions |601' the ring of combustible gas mixture passages I1 in the nozzle in communication with corresponding oxygen and combustible gas supply passages in the blowpipe head. The combined area of the combustible mixture passages I1 is made suicient to maintain a flame of sufficient size and intensity to heat the metal quickly to the ignition temperature to start the scariing cut, the heat of the flame thereafter assisting in producing a clean cut or channel by adding heat to the oxygen and the burning metal.

'I'he oxygen passage I5 in the nozzle I0 is enlarged adjacent to the inlet Il by a gradually tapered or ared portion I! which extends divergently toward the discharge orifice 20. In order that the gas stream passing through the portion I9 may have its flow velocity reduced, it is apparent that the gradually ared portion I9 should be proportioned to have a sufficient degree of expansion to cause the velocity of the gas stream to be reduced. The tapered portion terminates in a plane a substantial distance from the disu being slightly smaller.

charge annee il, and the bore from the termination of the taper il for a short distance toward the discharge orifice 2li continues as a cylindrical A enlarged portion Il. As seen in Fig. 3 the orifice 20 is oblong or widened and has relatively flat upper and lower walls and rounded side walls and the walls extend inwardly to a portion II' connecting the orifice 2l with the enlarged portion i8.

Exclusive of the coupling nut i3. this nozzle comprises three parts which are welded or sliver soldered together. The stem 2 is provided with a head 22 conical seats I of the body I8 of the type having 23 to fit complementary seats (not shown) in a blowpipe headadapted to resoldered to the end of the orifice piece 2l and to the outer wall of the stem 2i. A large number of equally spaced combustible mixture passages I1 are formed in the wall of the orifice piece 28 about the relatively wide oblong or slot-shaped oxygen passage 28. Preferably about I2 combustible gas mixture passages I1 are formed in the orifice piece 2l in order to envelope the sheetlike stream of oxygen which may issue from the orifice piece Il with a flame of uniform crosssectlonal intensity. I'he mixture passages il on the broader sides of the orifice piece 26 converge toward the oxygen discharge orifice 20.

, The combustible gas mixture, passages I1 and the oxygen passage 2li in: the orifice piece 28 are straight and have the same area of crosssection as their substantial distance backward therefrom.

I'he wide slot-like oxygen outlet orifice 20 of the oxygen passage communicates through the `enlarged cylindrical portion Il with the large conical divergent passage It, smoothly connecti118 the portion Il with the inlet portion Il. It will be` seen, therefore, that the relatively large oxygen e of the nozzle is unconstricted and of either constant or gradually increasing cross-sectional area from the inlet portion up to the outlet orifice 2li and that the maximum respective discharge orifices for a :animas worlr "W and to initiate a desurfacing cut,l the heating dames produced by the heating mixture orices i1 are applied to a transverse zone of surface metal where the cut is to begin until the zone reaches an ignition temperature, then the oxidizing gas stream is turned on and the nozzle advanced relatively to the work at a uniform speed in a direction parallel te the surface and in the general direction of flow of -the ribbon-like stream.

The speed of cutting and the contour of groove obtained with our nozzle depends upon the kind of metal being removed, the shape, volume and velocity of the discharged oxygen stream, and the rate of delivery and distribution of the combustible gas mixture. As a specific example in the process oi removing seams from steel billets having about .4% of carbon and 1.05% chromium with the usual amounts of impurities it has been found that a nozzle having a circular oxygen orifice .438" in diameter, when employing an oxygen discharge velocity of 585 it per sec., will successfully remove at a speed cross-sectional area occurs in the cylindrical portion l I, the cross-sectional area of theorifice 2l The slot-like orifice 20 cylindrical porticm Il by having side walls that diverge from the width of the portion Il to the width of the Vorifice It and upper and lower walls that converge from the height dimension of the por- ;ion Il to the height dimension of the orifice is connected with the the portion Il' When the nozzle described herein is used for making surface cuts, such as channels or scarfs. the main axis of the oxygen Vpassage Il in the nozzle is `held at an acute angle to the surface of the work and in ja plane which will include the direction of movement and which is normal to the surface of the work. As the scarf is made the nozzle is advanced parallel to the surface in thefdirection of the inclination of the nozzle and toward the surface portions to be removed. One of the broad sides of the orifice Il; is positioned Decent to and Parallel to the surface of the of 6 ft. per min. a seam in. in depth and leave a groove 11/2 in. in width at the top which ls suitable to be rolled out without causing its sides to be folded over. In the above example the axis of the nozzle was held at an angle of about 38 with the surface of the work.

The figures given herein are in reference to a nozzle having a circular oxygen orifice disclosed in our aforementioned United States Patent No. 2,266,834 and are given as a specific example only. and it is to be understood that these g ures may be varied within wide limits depending upon vvarying conditions and results desired. For example, the discharge velocity of the oxygen may be increased when it is desirable to increase the speed of cutting and the depth of the cut, and th velocity may be decreased to decrease the speed of cutting and the depth of the cut.

'I'he curvature of the scarf may be controlled by the shape of the oxygen discharge orifice for any given projected length of orifice opening upon the work. It has been found that a nozzle hav.- lng a circular orifice of a given diameter cuts a scarf with a smaller radius of curvature at the bottom than a nozzle having an oblong orifice with a major axis equal to the diameter of the circular orifice. The selection of a nozzle having a particular shape of orifice depends upon the class of work to be done. For example, in cutting out isolated seams, the circular orifice is suitable. In making broad surface cuts. as when the surface of the metal is skinned 01T, the nozzle described herein adapted to discharge an oblong or sheet-like column of oxygen is preferable, because ay greater area of surface metal can be removed per cubic foot of oxygen consumed.

ermore, the surface of the metal is left in a smoother condition because wider scarfs, each having a greater radius of curvature, can be 1. Method of scariing or gouging a shallow layer of surface metal from a ferrous metal body, such as a steel billet,l which comprises heating at or at the marginal edges of the scarf is least a portion of the surface of said billet to be aouged to an ignition temperature; providing a relatively voluminous stream of oxidizing gas; reducing the velocitar oi charging said stream through an orifice elongated transversely ot the @direction of :flow to provide a substantially slieet-lilie stream having a predetermined velocity; directing said stream at an acute angie against the preheated surface portion; maintaining said sheetliire stream positioned with its longer transverse dimension substantially paralisi to said suri'ace; and relatively moving said stream. and said surface in a direction par allei to tbe suriface and in tbe general direction oi fiori ci said stream.

2. Method oi' scaring or gouging a shallow laver of surface metal from a errous metal body, suoli. as a steel billet, .at least a portion oi the billet surface to be removed being at an ignition temperature, which method comprises termina a relatively voluminous oiiidiaing gas stream to flow as a transversely Wide thin slieetdilte stream havinf; a predetermined velocity; directing said stream at, an acute angle against said surface heated to ignition temperature While maintainina the wide transverse dimension of said stream substantially parallel to said surface; and relatively moving:4 said stream along said surface in flow of said stream; disa direction parallel to said surface and in the general direction of flow of said stream.

3. Method of scarfing or gouging a shallow layer of surface metal from a ferrous metal body, such as a stee, billet, ieast a portion of the billet surface to be removed being at an ignition temperature, which meti comprises forming a relativeiy voluminous oxidizing gas stream to iiow as a transversely wide thin sneet-like stream. having a predetermined velocity; directing said stream at an acute angle against said surface heated to ignition temperature while maintaining the wide transverse dimension of said stream substantially parallel to said surface; simultaneously applying a Wide substantially sheet-like stream of combustible gas against said surface while maintaining such combustible gas stream adjacent a. Wide side of said sheet-like oxidizing gas stream, said stream of combustible gas providing a flame oi' substantially uniform intensity throughout; and relatively moving said streams in unison along said surface in a direction parallel to said surface and in the general direction of flow of the oxidizing gas stream.

WESLEY S. WALKER. WILGOT J. JACOBSSON.

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