US2754234A

US2754234A - Thermochemical metal removal

Info

Publication number: US2754234A
Application number: US343034A
Authority: US
Inventors: Edward M Holub; Carl E Hartmann
Original assignee: Union Carbide and Carbon Corp
Current assignee: Union Carbide Corp
Priority date: 1953-03-18
Filing date: 1953-03-18
Publication date: 1956-07-10
Anticipated expiration: 1973-07-10

Description

y 1956 E. M. HOLUB ET AL THERMOCHEMICAL METAL REMOVAL 2 Sheets-Shea t 1 Filed March 18, 1953 Powder Dispenser- W Y/gm? S m n THR nN mDF.

JC Y B July 10, 1956 E. M. HOLUB ETAL 2,754,234

THERMOCHEMICAL METAL REMOVAL Filed March 18, 1953 2 Sheets-Sheet 2 0% EDWARD M.HOLUB 29 CARL E.HARTMANN RMJXM ATTORNEY 2,754,234 Patented July 10, 1956 ice 2,754,234 mRMocmMrcAr. nmTAL REMovAr.

Application March 18, 1953, Serial No. 343,034 7 Claims. (Cl. 148-95) This invention relates to thermochemical metal remova1, and more particularly to method and apparatus for machine scarfing of hot stainless steel of approximately rolling temperatures and at approximately rolling speeds.

The conditioning of stainless steels has always been a costly and time-consuming process, and is one of the major bottlenecks in the production of stainless steel today. The use of the powder scarfing process has materially aided the reduction of cost and time in stainless steel conditioning, but such powder scarfing has been done on cold workpieces, and at speeds much too slow to keep pace with rolling speeds.

it is, therefore, the main object of the present invention to provide method and apparatus for machine scarfing of hot stainless steel of approximately rolling temperatures and at approximately rolling speeds.

Prior attempts to hot scarf stainless steel were not successful for a number of reasons, one of which is because the hot slag from the scarfing zone projected ahead onto the hot workpiece would adhere tenaciously and virtually Weld itself to the hot workpiece to the extent of rendering the process inoperative. By contrast, with a cold workpiece, the hot slag impinging on the cold surface does not adhere but instead is chilled to a brittle or friable state and is comparatively easily removed.

it is, therefore, another object of the present invention to facilitate the removal of hot slag produced in the hot scarfing of stainless steels.

Another problem in the prior attempts to hot scarf stainless steel was the ditficulty of distributing the powder to the multiple nozzles of a standard desurfacing machine. When gas-borne powder is conducted horizontally, the powder tends to separate out by gravity, and when passing around a bend the powder tends to separate out by centrifugal force or inertia.

The importance of powder control is reflected in the expensive metal lost by removing too much metal by too deep a cut. Contrary to the expected result, too little powder below a critical degree at any point across the body removes excessive metal along a groove, and too little powder uniformly distributed across the surface results in too deep a cut for economic operation, and produces an undesirably rough, irregular surface. On the other hand, too much powder takes up the oxygen, leaving too little oxygen to burn the steel.

it is, therefore, another object of the present invention to provide improved powder distribution for the hot scarfing of stainless steels.

According to the present invention a refractory metal body, such as a workpiece of stainless steel, is desurfaced by applying preheat to a local surface portion of such body at substantially rolling relatively flat stream of oxidizing gas at an acute angle against such heated portion, discharging a separate relatemperatures, discharging a tively flat stream of gas containing uniformly transversely distributed powdered solid fuel at an acute angle toward such oxidizing gas stream, so that such streams form angles with one another and with such surface portion of the body, and relatively moving the body and such streams at substantially rolling speed so that successive surface portions thereof are progressively removed thermochemically by the combined scarfing action of the powdered solid fuel and the oxidizing gas stream. Preferably the powder is supplied to the process by passing a stream of gas containing powdered solid fuel through a distributor wherein it is divided into a plurality of separate equal paths, and discharging the gas-borne powder from said paths through a row of outlets forming a relatively flat stream of gas-borne powder.

Fig. l is a diagrammatic view of the apparatus for hot scarfing stainless steel with the use of ferrous metal powder according to, and for carrying out the method of the present invention;

Fig. 2 is a side elevation of the scarfing head shown in Fig. 1;

Fig. 3 is a detail section of the powder distributor;

Fig. 4 is a cross section taken along the line 44 of Fig. 3;

Fig. 5 is a detail section of the air injector;

Fig. 6 is a front elevation of a desurfacing head similar to Fig. l but showing a modification;

Fig. 7 similarly shows a further modification; and

Fig. 8 shows the provision for scarfing the under side of a workpiece, and for scarfing four sides simultaneousl As shown in the drawings, the illustrated scarfing apparatus S is mounted on a suitable support above the path of the work W, such as a hot slab of stainless steel to be scarfed at substantially rolling temperatures and speeds. The apparatus S includes a relatively flat powder nozzle 10 mounted on a modified scarfing head 12 having a plurality of fiat slotted nozzles 14 for discharging a relatively fiat stream 29 of commercially pure oxygen against the work W, as Well as upper and lower rows of

ports

16 and 18 for discharging preheating gas flames adjacent such scarfing oxygen stream. The preheating gas flames 22 and 24 extend above and below the oxygen stream 20, forming dihedral angles with the work surface 25.

Oxygen is supplied to the head 12 and slotted nozzles 14- from a suitable source of oxygen under pressure. At the same time, a suitable combustible gas is supplied to the preheating

flame ports

16 and 18. The powder nozzle it) is mounted directly on the blowpipe nozzle head 12, and comprises a metal base 34 and a metal cover 35 suitably bolted together. The base 34 and the cover 36 have convergent inner walls as shown in Fig. 2 and are provided with a channel or mating channels which have divergent sides but parallel axes as shown in l, forming closely and uniformly spaced slots 39 for discharging a suitable relatively flat powder-laden carrier gas stream 45 which can be any suitable gas, such as air, nitrogen or oxygen for example. The discharge face of the powder nozzle lll is positioned on the blowpipe nozzle head 12 so that the slots discharge the separate powder laden carrier gas streams from flat orifices 41 located above the front upper edge of the nozzle 12. These streams combine to form the transversely continuous powder laden gas stream 40 which forms a dihedral angle with the oxygen stream 29, and with the work surface 25.

Each of the slots 3? is in connection with an individual branch tube 42 of a battery of such tubes leading from a distributor 44, which in turn is connected to a powder laden gas supply line 45. The line :5 is provided with a booster 46, another booster 47, an air operated pinch valve 48, and is finally connected to a powder dispenser 56 of standard or conventional construction.

The distributor 44 is shown in detail in Figs. 3 and 4 and comprises a cylindrical shell 52 provided with a hollow insert 43,- having is its top a central inlets? essnect'ed to the supply line 45. The base of the shell 52 has inserted thereon a rubber plug 51, and a group of outlets 54 is annularly uniformly spaced therearonnd and respectively connected to the branch tubes 42. The insert 43 is locked in position to provide a distributing chamber therebelow, in which the plug 51 forms a cushionfor the incoming powder stream being distributed to the branch tubes 32. v

The

boosters

46 and 43 are shown in detail in Fig; 5; and eachcomprises an entrance iacket 55 surrounding the powder laden line 45 and having a compressed air inlet 56 connected to a suitable source of air under pressure. Within the jacket 55, the air-powder line 45 is drilled on a long angle in the direction of movement, forming uniformly distributed bores 57 which direct the additional air in the direction to increase the velocity, and in the case of the booster 46, to aid the distribution of the powder. 7

As shown in Fig. 1, there is provided a water supply nozzle 5?; for discharging a flat stream of water 59, above and across the top surface of the work W to continuously deflect and remove slag resulting from the desurfacing operation. This nozzle is located 6 to' 12' inches ahead of the nozzle head 12. This cross-fire water jet contributes greatly to the success of the operation.

A modification of the invention is shown in Fig. 6 which is identical in construction with the preferred embodiment hereinbefore described, except that in lieu of the flat slotted powder outlets 39 thereof, the modification employs round powder outlets 69; This construction is less expensive, does not clog up as readily' and surprisingly functions just as well for the hot scarfing of stainless steel.

Another modification of the invention is shown in-Fig. 7 in which the powder nozzle 10 identical with the preferred embodiment is mounted on a desurfacing head which, in lieu of the slotted nozzles 14-, is provided with a transversely continuous slotted nozzle 62 having an oxygen slot 63 and upper and lower rows of

preheat flame ports

64 and 65. The sheets of oxygen and powder laden gas have the same dihedral angle relation as in Fig. 2 and function in the same manner.

Fig. 8 shows the head of Figs. 1 and 2 arranged to scarf thefour sides of rectangular Work simultaneously. Inasmuch as the present invention is operative on the sides and bottom of the work, which has never been done heretofore on hot stainless steel, it is readily adapted for this simultaneous operation.

In operation, the mixture of air andpowder from the dispenser 50 is passed through a suitable hose to the pinch valve 48, and thence through the booster 47 located immediately adjacent the dispenser, the purpose of the booster 47 being to increase the velocity of the airpowder mixture and make it airborne.

booster 46 again increases the velocity of the air-borne powder stream and also sets up a turbulence which re distributes any powder settled out by centrifugal force in bends in the powder line, and causes the powder to'be uniformly distributed in the tube leading to thedistributor 44. From the distributor the air-bornelpowder mixture is equally divided among the multiple outlets 5'4, and passes on through the battery of equal tubes 42 ontoithe scarfing zone through the powder nozzle 10.

With the apparatus as above described, satisfactory ho't scarfing was accomplished onthe top, sides and bottom of stainless steel slabs and billets. It was further found" that the slotted oxygen nozzle, the ounclorificse powder outlet, which is much simpler and cheaper than This increase in velocity prevents the powder settling out by gravity in the horizontal run on the way from the dispenser 50. The

the slotted type; produced equally as satisfactory a scarfed surface as the slotted type of powder orifice.

The advantages of hot machine scarfing of stainless steels with this equipment are as follows: A relatively smooth flat surface results which can readily be examined for deep seams or breaks and which will roll out into a satisfactory strip, sheet or plate mill product. Stainless steel was scarfed at speeds up to 120 feet per min ute with no indication of loss of stability. With the preheat gases burning, starts can be made almost instantaneously with the turning on of the powder stream. The process is more efficient than cold scarfing from the standpoint of powder consumed. For cold scarfing powder consumption is on thesorder of 20 pounds per ton of steel; for hot scarfing according to the present invention on the order of two pounds per ton. Also, as to metal loss, it is easier to make a shallow cut-compared to cold scarfing; the metal loss is enormoiisly reduced.

rm'pertaat contributing factors to the successful 'operation of the process are: the powder distribution equipment which allows a single powder streamlto be divided equally and directed over a multiplicity of scarfing nozzles or to a continuous oxygen slot. Also, a cross-fire water jet of high pressure water directed across the steel being scarfed transverse to the direction of scarfing to remove the slag from the surface of the steel before it has time to solidify: Without the cross-fire water jet it is difiicult, if not impossible, to maintain a stable reaction. i

The following are the operating conditions" found to produce the most satisfactory surface on a 9 /2 width unit:

Depth of cut- Oxygen pressure Table speed inch.

45 pounds per square inch.

feet perminute-can be varied to vary depth of cut.

4 to 5 ounces per minute per scarfing nozzle, total 40 ounces per minute. Round orifice outlets inclined A p I I fowardthe work at an angle of 60.

Nozzle height ,4 inch.

Cross-fire water Jets setto impinge approximately 8 in. in front of scarfing nozzle center line. Water pressure 80 to pounds per square inch, delivering approximately 30 to gallons per minute.

Powder We claim: p

1. Process of desurfacing a; refractory; metal body, which comprisesapplying preheat to a local surface portion of such body at substantially rolling temperature, discharging a relatively flat streani' oflo'xidizing gas at an acute angle against such heated portion,- separately passf ing a gas borne mixture of gas a'nd adj uva nt powder through a supply line'to a distributor wherein it divid'ed into a plurality of separate paths, introducing additional gas under pressure to said supply line ahead of saiddistributor to increase the" velocity of the gas borne powder stream prior to division'thereof, discharging the gas borne powder frorri said paths through; a row ofseparate outlets'forming a separate relatively flat stream of gas containing-uniformly transversely distributedpowdered solidfuel'at an acute angle toward such oxidizing gas stream, so that such streams form a'cuteangles with one another and with such surface portion of the body, and-relatively moving the bod'y' and such streams at substantially rollingspeed so that successive surfaceportions thereof are progressively removed thermochemieally by the combined scarfing action of the powdered solid fuel and ,the' oxidizing gas stream.

2. Processof desurfacing a refractory metal body, h h' mpr e app1v -ptch a a local r q portion of such body at substantially rolling temperature, discharging a relatively fiat stream of oxidizing gas at an acute angle against such heated portion, passing a separate stream of gas containing powdered solid fuel through a distributor wherein it is divided into a plurality of separate equal paths, discharging the gas-borne powder from said separate equal paths through a row of separate aligned outlets forming a relatively fiat stream of gasborne powder separate from and at an acute angle toward such oxidizing gas stream, so that such flat streams form dihedral angles with one another and with such surface portion of the body, and relatively moving the body and such streams at substantially rolling speed so that successive surface portions thereof are progressively removed thermochemically by the combined scarfing action of the powdered solid fuel and the oxidizing gas stream.

3. Process of desurfacing a refractory metal body, which comprises applying preheat to a local surface portion of such body at substantially rolling temperature, discharging a relatively flat stream of oxidizing gas at an acute angle against such heated portion, passing a mixture of gas and adjuvant powder from a dispenser through a supply line to a booster to increase the velocity of the gas-powder mixture and make it gas borne, passing the gas-borne mixture through a distributor wherein it is divided into a plurality of separate equal paths, and discharging the gas-borne powder from said separate equal paths through a row of spaced outlets forming a relatively flat stream of gas-borne powder separate from and at an acute angle toward such oxidizing gas stream, so that the central planes of such fiat streams form acute angles with one another and with such surface portion of the body, and relatively moving the body and such streams at substantially rolling speeds so that successive portions thereof are progressively removed thermochemically by the combined scarfing action of the powdered solid fuel and oxidizing gas stream.

4. Apparatus for desurfacing a refractory metal body, which comprises means for applying preheat to a local surface portion of such body at substantially rolling temperature, means for discharging a relatively flat stream of oxidizing gas at an acute angle against such heated portion, means for separately passing a gas borne mixture of gas and adjuvant powder through a supply line to a distributor wherein it is divided into a plurality of separate paths, means for introducing additional gas under pressure to said supply line ahead of said distributor to increase the velocity of the gas borne powder stream prior to division thereof, means for discharging the gas borne powder from said paths through a row of separate outlets forming a separate relatively flat stream of gas containing uniformly transversely distributed powdered solid fuel at an acute angle toward such oxidizing gas stream, so that such streams form dihedral angles with one another and with such surface portion of the body, and means for relatively moving the body and such streams at substantially rolling speed so that successive surface portions thereof are progressively removed thermochemically by the combined action of the powdered solid fuel and the oxidizing gas stream.

5. Apparatus for desurfacing a refractory metal body, which comprises means for applying preheat to a local surface portion of such body at substantially rolling temperature, means for discharging a relatively flat stream of oxidizing gas at an acute angle against such heated portion, means for passing a separate stream of gas containing powdered solid fuel through a distributor wherein it is divided into a plurality of separate equal paths, means for discharging the gas-borne powder from said separate equal paths through a row of separate aligned outlets forming a relatively flat stream of gas-home powder separate from and at an acute angle toward such oxidizing gas stream, so that such flat streams form adjacent angles with one another and with such surface portion of the body, and means for relatively moving the body and such streams at substantially rolling speed so that successive surface portions thereof are progressively removed thermochemically by the combined scarfing action of the powdered solid fuel and the oxidizing gas stream.

6. Apparatus for desurfacing a refractory metal body, which comprises means for applying preheat to a local surface portion of such body at substantially rolling temperature, means for discharging a relatively flat stream of oxidizing gas at an acute angle against such heated portion, means for passing a mixture of gas and adjuvant powder from a dispenser through a booster to increase the velocity of the gas-powder mixture and make it gas borne, means for passing the gas-borne mixture through a distributor wherein it is divided into a plurality of separate equal paths, and means for discharging the gasborne powder from said separate equal paths through a row of spaced outlets forming a relatively flat stream of gas-borne powder at an acute angle toward such oxidizing gas stream, so that the central planes of such flat streams form dihedral angles with one another and with such surface portion of the body, and means for relatively moving the body and such streams at substantially rolling speeds so that successive portions thereof are progressively removed thermochemically by the combined scarfing action of the powdered solid fuel and oxidizing gas stream.

7. Process of desurfacing a refractory metal body, which comprises applying preheat to a local surface portion of such body at substantially rolling temperature, discharging a relatively flat stream of oxidizing gas at an acute angle against such heated portion, separately passing a gas borne mixture of gas and adjuvant powder through a supply line to a distributor wherein it is divided into a plurality of separate paths, introducing additional gas under pressure to said supply line ahead of said distributor to increase the velocity of the gas home powder stream prior to division thereof, discharging the gas borne powder from said paths through a row of separate outlets forming a separate relatively flat stream of gas containing uniformly transversely distributed powdered solid fuel at an acute angle toward such oxidizing gas stream, so that such streams form acute angles with one another and with such surface portion of the body, relatively moving the body and such streams at substantially rolling speed so that successive surface portions thereof are progressively removed thermochemically by the combined scarfing action of the powdered solid fuel and the oxidizing gas stream, and a stream of slag is formed and projected ahead of the reaction zone, and discharging a stream of water transverse to the workpiece and ahead of the reaction zone to continuously deflect and remove such slag.

References Cited in the file of this patent

Claims

1. PROCESS OF DESURFACING A REFARACTORY METAL BODY, WHICH COMPRISES APPLYING PREHEAT TO A LOCAL SURFACE PORTION OF SUCH BODY AT SUBSTANTIALLY ROLLING TEMPERATURE, DISCHARGING A RELATIVELY FLAT STREAM OF OXIDIZING GAS AT AN ACUTE ANGLE AGAINST SUCH HEATED PORTION, SEPARATELY PASSING A GAS BORNE MIXTURE OF GAS AND ADJUVANT POWDER THROUGH A SUPPLY LINE TO A DISTRIBUTOR WHEREIN IT IS DIVIDED INTO A PLURALITY OF SEPARATE PATHS, INTRODUCING ADDITIONAL GAS UNDER PRESSURE TO SAID SUPPLY LINE AHEAD OF SAID DISTRIBUTOR TO INCREASE THE VELOCITY OF THE GAS BORNE POWDER STREAM PRIOR TO DIVISION THEREOF, DISCHARGING THE GAS BORNE POWDER FROM SAID PATHS THROUGH A ROW OF SEPARATE OUTLETS FORMING A SEPARATE RELATIVELY FLAT STREAM OF GAS CONTAINING UNIFORMLY TRANSVERSELY DISTRIBUTED POWDERED SOLID FUEL AT AN ACUTE ANGLE TOWARD SUCH OXIDIZING GAS STREAM, SO THAT SUCH STREAMS FORM ACUTE ANGLES WITH ONE ANOTHER AND WITH SUCH SURFACE PORTION OF THE BODY, AND RELATIVELY MOVING THE BODY AND SUCH STREAMS AT SUBSTANTIALLY ROLLING SPEED SO THAT SUCCESSIVE SURFACE PORTIONS THEREOF ARE PROGRESSIVELY REMOVED THERMOCHEMICALLY BY THE COMBINED SCARFING ACTION OF THE POWDERED SOLID FUEL AND THE OXIDIZING GAS STREAM.

4. APPARATUS FOR DESURFACING A REFRACTORY METAL BODY, WHICH COMPRISES MEANS FOR APPLYING PREHEAT TO A LOCAL SURFACE PORTION OF SUCH BODY AT SUBSTANTIALLY ROLLING TEMPERATURE, MEANS FOR DISCHARGING A RELATIVELY FLAT STREAM OF OXIDIZING GAS AT AN ACUTE ANGLE AGAINST SUCH HEATED PORTION, MEANS FOR SEPARTELY PASSING A GAS TURE OF GAS AND ADJUVANT POWDER THROUGH A SUPPLY LINE TO A DISTRIBUTOR WHEREIN IT IS DIVIDED INTO A PLURALITY OF SEPARATE PATHS, MEANS FOR INTRODUCING ADDITIONAL GAS UNDER PRESSURE TO SAID SUPPLY LINE AHEAD OF SAID DISTRIBUTOR TO INCREASE THE VELOCITY OF THE GAS BORNE POWDER STREAM PRIOR TO DIVISION THEREOF, MEANS FOR DISCHARGING THE GAS BORNE POWDER FROMS AID PATHS THROUGH A ROW OF SEPARATE OUTLETS FORMING A SEPARATE RELATIVELY FLAT STREAM OF GAS CONTAINING UNIFORMLY TRANSVERSELY DISTRIBUTED POWDERED SOLID FUEL AT AN ANGLE TOWARD SUCH OXIDIZING GAS STREAM, SO THAT SUCH STREAMS FORM DIHEDRAL-ANGLES WITH ONE ANOTHER AND WITH SUCH SURFACE PORTION OF THE BODY, AND MEANS FOR RELATIVELY MOVING THE BODY AND SUCH STREAMS AT SUBSTANTIALLY ROLLING SPEED SO THAT SUCCESSIVE SURFACE PORTIONS THEREOF ARE PROGRESSIVELY REMOVED THERMOCHEMICALLY BY THE COMBINED ACTION OF THE POWDERED SOLID FUEL AND THE OXIDIZING GAS STREAM.