US2493802A - Process of thermochemically conditioning metal bodies - Google Patents

Description

Jan. 10, 1950 J, BUCKNAM ETAL 2,493,802

A PROCESS OF THERMOCHEMICALLY CONDITIONING METAL BODIES Filed May 10, 1949 JAMES Q QJEmAM fi/gi IVAN RTHOMPSON ATTORN EY Patented Jan. 10, 1950 PROCESS OF THERMOCHEMICALLY CONDI- TIONING METAL BODIES James H. Bucknam, Cranford, and Ivan P. Thompson, Elizabeth, N. 3., assignors to The Linde Air Products Company, a corporation of Ohio Application May 10, 1949, Serial No. 92,274

3 Claims. (Cl. 148-95) This application is a continuation-in-part of application Serial No. 478,202, filed March 6, 1943 for Blowpipe nozzle, which was patented on August 19, 1947, No. 2,425,709; and of abandoned application Serial No. 517,472, filed January 7, 1944 for Process of thermochemically conditioning metal bodies.

The invention relates to the art of thermochemically conditioning metal bodies and, more particularly, to the removal of surface defects in ferrous metal bodies with an oxidizing stream and in conjunction with externally mixed excessoxygen oxy-acetylene preheating flames.

Above a red heat, iron combines with pure oxygen so rapidly that it actually burns. Thus, if a spot on a piece of iron or steel is heated to the kindling temperature, and a jet of oxygen is directed against such heated spot, the iron will begin to burn vigorously with the generation of heat. Although the result of this combination of iron and oxygen is the formation of iron oxide, a product that is solid at ordinary temperatures, the iron oxide melts at a temperature somewhat below the melting point of iron or steel. During oxy-acetylene cutting, the heat generated by the burning iron is sufficient to melt the iron oxide so that it runs off as a molten slag, not only exposing more iron to the action of the oxygen jet but also carrying away with it some iron that has become molten at the temperature of the operation, but which has not actually become oxidized.

Radiation at the surface, pieces of dirt or scale on the metal, and the fact that heat is conducted into the metal body when cold, make it necessary for additional heat to be supplied or the cut will stop or be lost. It is customary, therefore, to provide a blowpipe nozzle having small orifices for oxy-acetylene heating flames surrounding an opening that supplies the cutting oxygenv jet or stream. In making a out, such preheat flames are used to heat a spot to a red heat, and the cut is started by opening a valve controlling the oxygen jet and directing the stream of oxygen at the heated spot. The preheating flames remain burning while cutting is in progress to make up for the heat that is lost during the operation. It is thus seen that the thermochemical cutting of ferrous metal is a thermochemical reaction.

The thermochemical removal of surface de-' fects in steel bodies during manufacture is accomplished by a process variously known as deseaming, scarflng, or conditioning. Generally, however, the term deseaming, that is, the removal of surface seams or cracks, is used when the operation is performed with a hand blowpipe,

parent on the surface of the metal body.

fire, the affected machine parts must be taken.

In mechanized steel conditioning, a shallow layer of the entire surface of the billet, bloom, or slab, is removed by a conditioning machine located in the rolling mill line. Such machine re-v moves a thin layer containing surface defects from one, two, or four sides of the body simultaneously and the operation is performed while the metal is still hot and Without interrupting the rolling operation. volving the removal of deeper defects generally is performed by hand deseaming after the steel has cooled down.

Prior to the present invention, oxy-acetylene scarfing machines for removing surface defects from semi-finished steel bodies consisted of mechanized batteries of oxy-acetylene blowpipes comprising mixers for premixing oxygen and acetylene for producing the preheating flames. mixers are not only expensive to manufacture and maintain, but they produce an oxy-acetylene gas mixture that is highly combustible, rendering the machines subject to backfire. A backfire is an explosion of the gases within the apparatus which maybe caused by overheating of the apparatus, improper gas pressure, loose connections or unclean internal surfaces. In the event of a backapart for thorough cleaning, since a backfire fouls the interior of many of the parts with carbon. As a result, the gas hoses, valves, mixers,

nozzles and other parts must be disassembled, re-

flashback requires replacement of the mixer, if burned out, as well as cleaning of the parts, so

that the machine must be temporarily taken out of operation. In any case, the tendency of pre-- mixed oxy-acetylene desurfacing equipment to backfire presents a serious maintenance problem especially in the scarflng of hot steel. The principal object of this invention, therefore, is to solve such problem.

' tively short, being of the order of to inch long, and since the face of each nozzle is about H; inch at its center from the surface undergoing conditioning, such face being at an angle with such surface, the ends of such inner cones do not impingeagainst such surface but are always Secondary conditioning in- Such Another object of the invention, therefore, is to i provide an oxy-acetylene preheating flame that is moreeflicient and efiectlve for'starting and) carrying on a thermochemical metal" removal operation.

Prior desurfacing machines. of the.:premixed"' oxy-acetylene preheating flame type iemploym 1 a series of nozzles produce a conditioned surface that generally has low parallel ridges-betweenthe cuts. It is desirable to have such ridges as'l'ow or flat as possible, the ideal conditionedL-surfa'ce being one that is flat or entirely ridge-free. Therefore, another object of the invention is :to provide a novel'desurfacing process which produces-a conditioned surface which is flatter and of better quality than thos produced by prior rocesses.

Des'u-rfacing equipment in the past has also been very expensive to manufacture and maintain, owing to the large number of complicated parts, including mixers and valves, that are in volved. 'A further object of this invention is to provide an improved processto simplify the required equipment for desur-facing, entirely eliminating. the mixers and as many control valves andxother parts as possible.

Other important objects of the invention are to increase the metal removal efficiency of theoxygen, to reduce the preheating period for initial starting, to obtain faster cuts especially with cold steel, and to improve the stability 'of the operation.

According to the present invention, an entirely novel post-mixed excess-oxygen oxy-acetylene. flame comprising a stream of oxygen is first applied against a preselected spot on the surface of the metal body: The excess oxygen in suchflam'e causes the metal in the spot to become luminous at the very instant the temperature of such metal is raised to the ignition point. The body is then movedwith respect to the flame (or the flame ismoved with'respect to the body), and the velocity of the oxygen stream is increased to a desurfacing value at the approximate instant the movement of the body is started, in order to prevent any nicking or gouging of the work by such oxygen stream at the starting spot. The amount of acetylene supplied to the oxygen stream is not changed. As a result, the post-mixed preheating flame assists the OXygen stream in progressively removing or skinning metal from the surface of' the body, molten slag containing oxides being caused to flow ahead of the zone of thermochemical reaction between the oxygen and the heated metal.

The post-mixed oxy-acetylene preheating flame for starting and carrying on the operation according to the invention is quite hard andintensely hot, the temperature even approaching that of a premixed flame, the inner cones of the.

post-mixed flame, however, being extended andv applied directly against the surface of the .body

which is being conditioned. For preheating the work to start the operation, the post-mixedflames of the presentinvention have inner cones or pri-a mary combustion zones which extendaboutll/ inch from the face of the nozzle, a decided im provement over the premixed typeofpreheating;

' ing .gaslstream It which is flat.

desurfacing a cold steel body, however, the

body is backed into position so that the flames are-applied directly against the edge or edges of thebody. In either case, since the post-mixed flames contain an excess of oxygen, the temperature .of ignition becomes visible much more quicklylthan in. the case of premixed flames, and not only enables the operator to start the desurfacing movement of the body at the proper time, but also reduces the starting time compared with thatofvthe' premixed flames.

Referring to the drawings:

Fig. 1 is a fragmentary perspective view of a steel body in'starting position under a battery of post-mixed nozzles in a head which is supplied with oxygen and acetylene according to the invention; I

Fig. 2 is a similar view showing the body undergoing the thermochemical desurfacing operation;

Fig. 3 is an enlarged fragmentary cross-sectional view of the head and a post-mixed nozzle carrying out the-present invention; and

Fig. 4 is a view in front end elevation of the nozzle shown in Fig. 3. I

In the illustrated example, a desurfacing head H- isprovided with a plurality of blowpipe nozzles N. E'achnozzle N comprises atubular body member having a central cutting oxygen passage [2 extending longitudinallytherethrough. Such passage l2 includes a cylindrical inlet portion of constant diameter, a flared irusto-conical portion, ashort cylindrical portion of constant diameter, and an outlet portion which gradually changes from circular to flat cross section, the discharge end of the passage being oblong as shown at 13, with its longer'axis disposed parallel to the work surface. The passage i2 thus is adapted to discharge a characteristic desurfacing oxidizbody member I I is also provided with a plurality of acetylene passages l5 arranged in spaced parallel relation to the longitudinal axis of the oxygen passage E2, :the passages l5 terminating above and below theoxygen orifice 13 in inclined plane surfaces l6, it at the end of the member I I. r The oxygen orifice it lies in a plane disposed at right angles to the longitudinal axis of the member H, and at the bottom of a peripheral recess l1.

The gas inlet end of the tubular body member II also is provided witha pair of radially and longitudinally spaced frusto-conical annular seats I8 and [9, which are adapted to mate with corresponding seats at and 2! in the head H. The member-l i is alsoprovided with an annular flange 23 which is engaged by a hollow screw 24 threaded in a socket 25 in a body 25 of the head H, for locating the nozzle N in proper position in the head; The nozzle is coupled to the body 26 so that the acetylene is delivered to the acetylene passages HS and oxygen is delivered to the central oxygen passage it through an oxygen channel 21 and an acetylene channel 28 in such body.

The outer end of the body member H is provided with thesbevelled surfaces it which cooperate with inner walls of an end cap 29 to provide upper-and lower transverse acetylene distributing passages 39, tu having slot 'like outlets The tubular V 3|, 3| above and below the oblong oxygen orifice l3. The cap 29 comprises a cylindrical skirt 32 which fits the end portion 33 of the nozzle body II, the edge of the skirt being bronze-welded or silver-soldered at 34 to the body to secure such parts together. The cap includes a bottom panel 35 which is relatively thick to inhibit deformation or damage in use. The bottom panel of the cap has a slot 36corresponding in position to the oxygen orifice l3, the upper and lower walls .of the slot being parallel to and outwardly offset with respect to the top and bottom edges of the peripheral recess or groove ll. The groove ll causes eddy currents and thus provides a fringe of low velocity oxygen around the otherwise solid oxygen stream, for admixture with the acetylene discharged by the slots 3|, to form a post-mixed oxy-acetylene preheating flame F, when the oxygen stream [4 is discharged at a desurfacing velocity; and prevents such flame from being blown out. With this arrangement, acetylene discharged by the acetylene slots 3| is directed inwardly from above'and below against the single flat stream of oxygen l4 discharged by the central passage I2 as the latter leaves the discharge end of the nozzle.

While nozzles N of the type shown in the drawings and described above, are preferred, similar nozzles of the type disclosed and claimed in our Patents 2,425,709 and 2,425,710 may also be employed.

The body 25 of the head is provided with a row of the sockets 25 into each one of which a nozzle N is secured by the hollow screw 24. The head H is also provided with a removable shoe 37 having a row of openings 38, there being an opening through which each nozzle N projects. Each nozzle is provided with a packing ring 39 which is held in place against the inner wall of the shoe by a coiled compression spring 4!! disposed around the nozzle and between the hollow screw 24 and an annular bearing member 4| that engages the packing ring 39. Thus, when a chamber 42 is filled with cooling water, leakage between the nozzles N and the openings 38 is prevented, The shoe 37 is also provided with an outer layer of heat and wear resistant metal such as Stellite alloy, having spaced runners 43 adapted to ride on the surface S of the work W.

The body 26 of the head H is supplied with oxygen through pipes 44, and with acetylene through pipes 45, having gas distributing headers 46 and 47, respectively. The acetylene header 41 is connected to a suitable acetylene supply source A by means including a conduit 48 containing a pressure regulator 49 and a normally closed valve 50. The oxygen header 46 is connected to suitable sources of oxygen OP and OD by means including a conduit 5| having two- inlet pipes 52 and 53. The inlet pipe 52 contains a pressure regulator 54 and a normally closed valve 55. The inlet pipe 53 contains a pressure regulator 56, a normally closed valve 57, and a reverse flow check valve 58. The valves 50, 51 and 55 are each adapted to be opened by an armature 60 when a coil Si is energized by an electric current. The regulators 49 and 5B are set to maintain the pressure of the acetylene and oxygen passing therethrough at a predetermined low value, between 3 and 4 pounds per square inch for example, so

that when the valves 50 and 51 are open all of the.

acetylene fiames. The regulator 54 is set to main-- tain the pressure of the oxygen passing therethrough at a predetermined high value, between 30 and '75 pounds per square inch for example, so that when the valve 55 is open all of the nozzles N are supplied with oxygen in suflicient quantity to discharge desurfacing oxygen streams.

The control circuit including the coils Si is such that the preheating acetylene and oxygen valves 55 and 57 are opened at the same time. At the end of the starting preheating period the desurfacing oxygen valve 55 is opened. All of the valves are kept open until the desurfacing operation is completed, whereupon all of the valves are closed. The movement of the work W is automatically started at the approximate instant the desurfacing oxygen valve 55 is opened.

A ferrous metal body W is thermochemically conditioned according to the present process as follows: the body, supported by a roll R, is moved into a starting position with respect to the de surfacing head H and preheating oxygen and acetylene are supplied to all of the nozzles N. These gases mix externally to produce a postmixed flame which is applied against a local surface portion of the body. Since the flame contains an excess amount of oxygen for complete combustion, the portion of the surface being preheated becomes visible at the instant it reaches the kindling temperature because of the reaction of such excess oxygen with the heated metal. This enables the operator to start movement of the body W exactly at the proper time, reducing the starting time and making the operation more uniform when applied to successive bodies. Shortly after movement of the body W is started, the velocity of the oxygen stream is increased to a desurfacing value for thermochemical reaction with the heated metal without changing the quantity of acetylene discharge from the nozzles. By maintaining the quantity of acetylene supplied to the nozzles unchanged, much control equipment is eliminated.

Acetylene is supplied to the nozzles at the rate of about 109 cubic feet per hour. During the starting preheat period oxygen is supplied to the nozzles at a slightly higher rate, resulting in a fairly efiicient post-nixed oxy-acetylene flame, which contains an excess amount of oxygen for complete combustion of the acetylene. During the desurfacing operation oxygen is supplied to each of the nozzles at the rate of between 1790 and 4000 cubic feet per hour, the exact rate depending upon the composition of the metal and the depth of the conditioning desired. After the body has moved sufficiently to be desurfaced throughout its entire length the oxygen and acetylene are shut off.

Calculated acetylene flows Acetylene Total Acety- Velocity Velocity Pressure at lene Flow thlough each through each Nozzle Seat, Through Noz- Rectangular Drilling,

p. s. i. zle in c. f. h. Passage, f. p. s. f. p. s.

49 52. 4 139 110 71 65. 2 173 137 85 75. 0 199 157 l. l 85; 5 227 1. 7 108.0 287 227 '2. l 128. 5 342 271 2. 6 138. 2 368 291 2.9 151. 2 403 318 3. 4 165. 9 441 349 NOTE.The above velocities are calculated from the formula nozzleis 0.074 sq. in. and with no regard-to the acoustical velocity eegaaaaoa 7 .5; Each fofithezsix acetylene zdrillirrgs' 1-15. is 020635 1. -inch :insdiameteri and :has: 'am:area: of 0.003 167 =:-.-squarei inch.

;' area-of 0.0075 square inch.

' Normal operatingrange isrfrom 90 to 100cubic feet/hour (about 240-267 feet/second" through passage 3!).

Calculated oxygen flows Vacuum on Pressure OX 5 i -.V.'eloc1ty at ygen Flow, Acetylene .At Seat, m f Passage Endf of lllozzle p. s. 1. v y Water p.

39.9 2,955 6.0 .1, 580 i 46. 2 3, 355 13. 3 1,810 51.5 3, 650 31.0 1,950 53 3, 738 4 9. 5 2,.010 59 3, 890 0.1 m. Hg 2, 090 04.5 4, 200 6.8 2,260 "170.5 4,550 x 6.9 2,440

NoTE.The;above velocities are calculated iromv-the'iformula wheirthe normal area. of oxygenpassage'li-i'atv burningxend' of limitation which is about 982 i'or'oxygen. Normal 0 erating range .during preheat period is 250 to 300 cubicieet/hourabout 135461 vfeet/second through, passage 13).

Normal operating range .during scarfing period is 2000 to 3000 cubic feet/hour (not to exceed3500 cubic feet/hour), i. c., about 1080-1610 feet/second through passage 13.

'In considering the novel process of thermochemically conditioning the surface of a hot ferrous metal body, according to the invention; it will be understood that the process comprises discharging acetylene from a series of outlets, in this case upper and lower slots 31, arranged in uni formly spaced relation to an'edge of the bodywW and at the same time discharging streams ofz oxygen from orifices; in this case theoblong orifices l3, adjacent, i.e., between such acetylene outlets, to form a series of externally miXed'oxy-acetylene flames. Such flamesare applied againstithe body W in spaced parallel relation to=such edge only until the temperature of the metal alongsuch edge is raised to the ignition pointJ-The surface S3155 and such orifices are then moved with'respect to each other; in the illustrated examplerthe body W is moved in the direction'of its length'ancl with respect to the stationary .nozzles N, as indicated by the arrow in Fig. 2. The velocity of all of the oxygen streams is then increased to a predetermined value for thermochemical reaction with such heated metal, preferably without -changing the quantity of acetylene discharged from the outlets, so that each acetylene stream still is pro-Q:

'vided with sufficient oxygen at the. point of exit of the acetylene from the orifices to "form :an externally mixed oxy-acetylene flame F adjacent, in this case above and below, said-oxygen stream to provide the preheatv flames needed for .lo'iflames. I This: not-xonl enables: .itheroperatorcto .start' the desurfacing movement or. the bodyrexactly at the proper instant, ";but.-.=reduces 'thel'starting period 1 compared to that: 'of '.premixed..flames. Furthermore increasing" the cpressure btf the foxy- .1 5 gen suppli'ed to the-nozzles 'Iat the inStahtZthe desurfacing movement of 'the' body is A startedgsso that such bodystar ts -moving at the sameiinsta'nt the 'desurfacing 'streams are applied,' inhibits gouging of the work surface in the startingzone.

1:2 The' desurfacing or cutting 'action of. the=postmixed 'de'surfacing names is more efli'cientthan that of premixed flamesyboth 'in startingand'in carrying" on the operation; I because the inneror primarycombustion 201195201 the post-mixed flamesare quitelong andare applied close to the surface of the body. Since the greatest-heater an "oxy-acetylene flame is 1 adjacent "the surface of the primary combustion-zone'or inner cone, -it can be readily appreciated-that theworkis x2130- more efiectively heated according *to'the present invention with post-mixed flames than withpremixed flames. "Furthermorefthe shape of the post-mixed flames is'somewh'atbushyand luminous during the" starting period when the "oxygen 035 and acetylene are delivered tothe nozzles insubstantially equal volumes. "When" the (oxygen streams are increased to a desurfacing Velocity, however, at; the endof the startingprehea-t period, the1 post-mixed preheating 11 flames. change 'in 40 "shape; becoming more non-luminous and well defined. In order to make the "equipment as simple as possible-the quantity of acetylene supplied to the nozzles remains unchanged during the deseaming operation, but itwill beuhderstdod that the quantity 'of acetylene supplied'to' "the '"nozzles'may be changed in somecaseswithout departing from the invention, should suchch'a n'ge become necessary or desirable.

A beneficial feature "of the .presentinvention is "the avoidance of flashbacks. This reduces the cost of maintenance :and repair to a considerable extent. The equipment necessary. .to. carry out the present processlis .verytsimple andinexpen- .sive compared to that .necessary foraproducing premixed flames. The present;-.processremoves metal fastenand the numberrof-poundsofmetal removed per cubic .ioot of oxygen. is increased, so that the .presen-tprocess is more efiicient than any prior desurfacing processs-rAnotherfeature ot the present .-invention is :high stability, xi.e.-,v freedom from-loss of. cut;:-in the =-desurfacing-,.operation. '1. Another advantage'of. the: presentiinvention iszathe improvement: in over,-'all:efficiencyof the desur- :facing operation'tcompar'edztoi those of the :prior :art. The surface resulting tfrom:the;-zoperation :lS'IOfxhigh :quality, in which the ridges are :almost flat.

.1 Asused :in the-f?followingclaims the term -"1 acety1ene is 'inten'dedto cover any suitable combustible gas butnot a mixture of suchgases with aeombustion supporting gas. -Also, *as used iiithe claimsjtheterm externally mixed='means-=mixed outside of the'blowpipe nozzle; -and-"-post-mixed 7 *meansmixed after-leaving thedolowpipe'nozzle.

per second, simultaneously feeding thinner substantially flat upper and lower streams of commercially pure acetylene at acute angles directly into said stream of oxygen at a calculated velocity of about 240-267 feet per second, igniting the resulting mixtures of oxygen and acetylene, thereby producing a substantially flat stream of scarfing oxygen which is sandwiched between adjoining stable longitudinally extended upper and lower substantially fiat post-mixed oxy-acetylene scarfing preheating flames having primary combustion zones which are about 1 and /4 inches long, applying the primary combustion zones of such flames and the scarfing oxygen stream at an acute "angle directly against the surface of said body, and moving said body along a longitudinal path in a direction opposed to the flow of such stream, so that the body is thermochemically scarfed by such oxygen stream while the reaction is supported by said flames which also screen the scarfing zone from the atmosphere.

2. Process of thermochemically scarfing a ferrous metal body which is at a hot-rolling temerature, which process comprises discharging a substantially flat stream of commercially pure oxygen at a calculated velocity of about 135-161 feet per second, feeding thinner substantially flat upper and lower streams of commercially pure acetylene at acute angles into said stream of oxygen at a calculated velocity of 240-267 feet per second, igniting the resulting substantially flat stream of mixed oxygen and acetylene, thereby producing outside of the nozzle a relatively long oxidizing post-mixed substantially flat starting preheating flame having a primary combustion zone extending about 1 and inches from said nozzle, applying the primary combustion zone of such preheating flame directly against the surface of said body with the transverse axis of the flame parallel and the longitudinal axis of the flame at an acute angle to such surface, holding said body substantially stationary until the hot ferrous metal is further 10 heated by such flame sufllciently to be ignited by the excess oxygen of such flame, and thereupon simultaneously starting to advance said body along a path parallel to the surface of the ;body, and increasing the flow of oxygen to increase the velocity of the discharged oxygen stream to a calculated velocity of about 1000-1610 feet per second while maintaining the flow of acetylene at a calculated velocity of about 240-267 .ifeet per second, thereby producing a scarfing stream of oxygen which is substantially fiat and is sandwiched between adjoining stable extended upper and lower post-mixed oxy-acetylene scarfing preheating flames which have hard primary combustion zones which are in direct contact with the surface of the body, and thermochemically scarfing the ferrous metal body therewith by movement of the body along such path.

3. Process of scarfing a hot ferrous metal body, as defined by claim 2, in which a plurality of such streams are similarly operated in side-byside relation so that the preheating flames and streams of scarfing oxygen merge laterally to preheat and scarf a relatively wide area of the body in a single pass.

JAMESH. BUCKNAM. IVAN P. THOMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 703,940 Menne July 1, 1902 968,350 Harrison Aug. 23, 1910 1,311,815 Harris July 29, 1919 1,519,582 Harris Dec. 16, 1924 1,957,351 Oldham May 1, 1934 2,210,402 Gaines Aug. 6, 1940 2,215,577 Bucknam Sept. 24, 1940 2,267,405 Jones Dec. 13, 1941 2,290,295 Scheller July 21, 1942 FOREIGN PATENTS Number Country Date 11,380 Great Britain July 22, 1915 of 1914 617,256 France Nov. 19, 1926 817,708 France May 31, 1937

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