US3752460A - Oxygen trap scarfing apparatus - Google Patents
Oxygen trap scarfing apparatus Download PDFInfo
- Publication number
- US3752460A US3752460A US00227147A US3752460DA US3752460A US 3752460 A US3752460 A US 3752460A US 00227147 A US00227147 A US 00227147A US 3752460D A US3752460D A US 3752460DA US 3752460 A US3752460 A US 3752460A
- Authority
- US
- United States
- Prior art keywords
- oxygen
- scarfing
- preheat
- ports
- gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K7/00—Cutting, scarfing, or desurfacing by applying flames
- B23K7/06—Machines, apparatus, or equipment specially designed for scarfing or desurfacing
Definitions
- ABSTRACT The time required for scarfing the surface of a metal body is decreased by shortening the preheating time. This is accomplished by directing a row of trap" oxygen streams from ports located above the upper preheat fuel gas ports so that the oxygen streams form a plane which intersects the surface of the metal body in such way as to form a wedge shaped pocket to confine the burning preheating gases. This results in faster puddle formation and causes the puddle to be formed at a location just ahead of the projected converging point of the fuel and oxygen gas streams, rather than in back of the converging point where it would be formed by prior art methods.
- This invention relates to the thermochemical conditioning of ferrous metal bodies, commonly referred to as scarfing; and more particularly to apparatus capable of decreasing the time required for a complete scarfing cycle with post-mixed, fuel-oxygen preheat gas scarfing units by decreasing the time required for preheating the metal workpiece to be scarfed.
- the present invention is applicable to scarfing of hot as well as cold metal workpieces.
- a scarfing reaction is caused to take place by first raising the temperature of the metal surface to be scarfed to the ignition temperature of the metal in an oxygen atmosphere. This temperature, which may be lower than the melting point of the metal in air, is referred to as the reaction temperature. When the reaction temperature is reached, a puddle of molten metal is formed. The metal is removed that is, the thermochemical scarfing reaction is caused to take place by impinging a stream of oxygenon the puddle. In other words, in order to initiate a scarfing reaction a puddle must be formed before the scarfing oxygen stream can be turned on for the thermochemical scarfing reaction to begin.
- a complete scarfing cycle consists of four steps. First, the workpiece is positioned in register with the scarfing machine. Second, the scarfing units are closed,
- preheating of the workpiece is caused to take place by means of fuel-oxygen preheat flames so that a puddle of molten metal is formed on the stationary workpiece; and fourth, the scarfing reaction is carried out by initiating the flow of scarfing oxygen and setting the workpiece in motion. For example, when scarfing a 30 foot slab at 2,000F,-positioning takes about 3 seconds, closing about 5 seconds, preheating about seconds, and
- the time required for a complete scarfing cycle results in a scarfing rate or speed that is in some cases slower than the rate at which steel is rolled in a conventional mill. It is therefore desirable to decrease the time required to complete a scarfing cycle in order that the scarfing operation keep up with the production of the mill. Reduction in scarfing time may obviously be accomplished by reducing'the time required for any of the above mentioned four steps which take place during a complete scarfing cycle. Since positioning and closing require a total of only about 8 seconds, the amount of improvement possible in these two steps is relatively small. Consequently, the logical steps to shorten in order to improve the speed of a scarfing cycle are the preheating and/or scarfing steps.
- preheating time fails to improve. For example, if
- FIG. 1 is a side elevation of a scarfing unit according to the present invention which is provided with a row of trap oxygen orifice ports located in the upper preheat block above the row of preheat fuel gas ports.
- the upper and lower preheat fuel gas streams l1 and 12 in FIG. 1, as well as the scarfing oxygen stream 9 emanating from the central slot 8 are all directed so that their straight line projections converge at point A on the surface of the workpiece W.
- the puddle 20 forms not at the point A, but rather in back of it by several inches at point B. Consequently, it has been necessary, in accordance with prior art practice, as shown for example in U.S. Pat. No.
- the oxygen curtain or plane above the preheat fuel gas streams formed by the trap oxygen streams causes a wedge shaped pocket to be formed between itself and the surface of the metal being scarfed.
- oxygen curtain is formed by a parallel row of oxygen ports 23 located above the row of upper preheat block fuel gas ports 15.
- High velocity fuel gas from both upper and lower preheat blocks 1 and 2 is directed into the pocket, becoming trapped in the pocket and consequently forced to mix intimately with the oxygen 9 emanating from the continuous slot 8.
- the oxygen curtain provides a two-fold effect; first, it acts as a physical barrier to contain or trap the fuel and oxygen preheat gases causing them to burn in place; and second it permits an increase in the total amount of oxygen, thereby causing a hotter flame to be produced.
- the combination of these two effects improved heat transfer to the workpiece and concentrates the heat at a particular spot.
- the scarfing unit is comprised of an upper preheat block 1, a lower preheat block 2, a head 3 and a shoe 4 which rides on skids 6.
- the lower surface 6 of upper preheat block 1 and the upper surface 7 of lower preheat. block 2 form a continuous slot passage 8 for the oxygen stream 9.
- the rear end 10 of oxygen passage 8 communicates with an oxygen supply manifold 25, to which the supply of oxygen is controlled by valve 26.
- passage 8 is used to provide oxygen for combustion of the upper and lower preheat fuel gas streams 11 and 12. After the puddle 13 has been formed, the oxygen flow in stream 9 is increased to provide sufficient oxygen for the scarfing reaction.
- Upper preheat block 1 is provided with a plurality of preheat fuel gas passages 14 which terminate at the front face of the preheat block 1 in a row of fuel gas ports 15.
- Gas passages 14 communicate with a fuel gas header 24 located in head 3 from which they receive their supply of fuel gas.
- Natural gas is the preferred fuel gas; however, other fuel gases may also be employed such as, for example, methane,propane or coke oven gas.
- Lower preheat block 2 contains a plurality of fuel gas passages 17 which communicate with and receive a supply of fuel gas from header 18 located in head 3. Passages 17 terminate at the front face of the lower preheat block 2 in a row of lower preheat fuel gas ports 19.
- Both the upper preheat fuel gas ports 15 and the lower preheat fuel gas ports 19 are directed so that the straight line projections of the gas streams 11 and 12 emanating therefrom will converge with the straight line projection of the sheet-like stream of oxygen 9 at the converging point A on the surface of the metal workpiece W. Due to the aerodynamic effect of the hot gas streams as previously explained, the puddle 20 is formed upon the surface of the workpiece W at point B by prior art methods, i.e., without the use of the trap oxygen stream 21.
- the upper preheat block 1 is provided with a plurality of oxygen passages 22 which terminate at the front face of said preheat block in a row of trap" oxygen ports 23.
- Oxygen is supplied to passages 22 from an oxygen header 16 located in head 3.
- the trap oxygen streams 21 emanating from ports 23 are also directed to converge with the fuel gas stream projections 11 and 12 and oxygen stream projection 9 at point A.
- the plane formed by the plurality of trap oxygen streams 21 forms a wedge shaped pocket between itself and the surface of the workpiece W to confine the preheating gas streams 11 and 12 and the oxygen stream 9 thereby improving heat transfer to workpiece W and concentration of the heat within the wedge shaped pocket formed thereby.
- the trap oxygen flow may be kept on, shut off completely, or lowered just to bleed slightly in order to prevent ports 23 from becoming plugged by the splatter of molten metal and slag. This can be effectuated by adjustment of valve 26 or other conventional flow control means. Keeping the trap oxygen on at full flow rates during the scarfing step has not been found to produce any beneficial results.
- FIG. 3 is a graph comparing preheating time using a post-mixed fuel-oxygen scarfing unit of the prior art with a unit in accordance with the present invention containing a row of trap oxygen ports above the upper preheat fuel gas ports to provide the oxygen curtain of the present invention.
- the flow rates of preheat fuel gas (natural gas) were approximately 3,500 C.F.H. in both cases.
- the total amount of oxygen was likewlse thesame in both cases, i.e., about 7,500 C.F.H.
- the distribution of the oxygen was different.
- the significance of the faster preheat time obtained in accordance with this invention is that it improves the prehating time at 2,000F, for example, by about 7 seconds, thereby cutting the scarfing cycle described previously from 38 seconds to about 30 seconds. This is an improvement of over 20 percent in the scarfing cycle and is sufficient to enable the scarfing machine to keep up with a higher production rate than was formerly possible. It should be noted that the present Invention also provides a saving in preheating time by elimination of the need for backing up the workpiece or scarfing unit prior to initiation of the scarfing oxygen reaction, in addition to the shortening of the preheating time as shown in FIG. 3.
- a continuous slot, post-mixed fuel-oxygen scarfing apparatus wherein said slot is formed between an upper preheat block and a lower preheat block which are in spaced relation to one another, wherein means are provided for controllably discharging a sheet-like stream of oxidizing gas through said slot for reacting with a metal surface to be scarfed as well as for burning preheat fuel gas, and wherein said scarfing apparatus is provided with a row of ports communicating with supply passages for discharging a plurality of parallel streams of preheat fuel gas from at least the upper preheat block to converge with said stream of oxidizing gas, the improvement comprising: a row of oxygen ports located in said upper preheat block above said row of fuel gas ports communicating with oxygen supply passages, means for controlling the flow of oxygen through said oxygen supply passages independently of the flow of said sheet-like stream of oxidizing gas, said row of oxygen ports being capable of discharging a plurality of parallel streams of oxygen gas which form a sheet-like oxygen gas curtain, said oxygen ports
Abstract
Description
Claims (2)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US83623369A | 1969-06-25 | 1969-06-25 | |
US22714772A | 1972-02-17 | 1972-02-17 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3752460A true US3752460A (en) | 1973-08-14 |
Family
ID=26921211
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US00227147A Expired - Lifetime US3752460A (en) | 1969-06-25 | 1972-02-17 | Oxygen trap scarfing apparatus |
Country Status (1)
Country | Link |
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US (1) | US3752460A (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3850704A (en) * | 1972-02-15 | 1974-11-26 | Hilti Ag | Scarfing |
US3966504A (en) * | 1973-05-21 | 1976-06-29 | Centro-Maskin I Goteborg Ab | Method and apparatus for thermochemical gas scarfing |
US4103877A (en) * | 1975-11-08 | 1978-08-01 | Messer Griesheim Gmbh. | Device for the flame treatment of a work-piece |
US4115154A (en) * | 1977-09-26 | 1978-09-19 | Union Carbide Corporation | Method and apparatus for producing a post-mixed, stabilized scarfing pre-heating flame |
US4243436A (en) * | 1979-11-05 | 1981-01-06 | Union Carbide Corporation | Instantaneous scarfing by means of a pilot puddle |
US4287005A (en) * | 1979-11-05 | 1981-09-01 | Union Carbide Corporation | Instantaneous scarfing by means of a pilot puddle |
WO2011069539A1 (en) * | 2009-12-09 | 2011-06-16 | Gesellschaft Für Autogenmaschinen Und -Geräte Mbh | Scarfing block assembly |
GB2483219A (en) * | 2010-08-10 | 2012-03-07 | Harsco Metals Group Ltd | Surface Treatment |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2622048A (en) * | 1950-04-18 | 1952-12-16 | Union Carbide & Carbon Corp | External powder scarfing process and apparatus |
-
1972
- 1972-02-17 US US00227147A patent/US3752460A/en not_active Expired - Lifetime
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2622048A (en) * | 1950-04-18 | 1952-12-16 | Union Carbide & Carbon Corp | External powder scarfing process and apparatus |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3850704A (en) * | 1972-02-15 | 1974-11-26 | Hilti Ag | Scarfing |
US3966504A (en) * | 1973-05-21 | 1976-06-29 | Centro-Maskin I Goteborg Ab | Method and apparatus for thermochemical gas scarfing |
US4103877A (en) * | 1975-11-08 | 1978-08-01 | Messer Griesheim Gmbh. | Device for the flame treatment of a work-piece |
US4115154A (en) * | 1977-09-26 | 1978-09-19 | Union Carbide Corporation | Method and apparatus for producing a post-mixed, stabilized scarfing pre-heating flame |
US4161413A (en) * | 1977-09-26 | 1979-07-17 | Union Carbide Corporation | Method and apparatus for producing a post-mixed, stabilized scarfing pre-heating flame |
US4243436A (en) * | 1979-11-05 | 1981-01-06 | Union Carbide Corporation | Instantaneous scarfing by means of a pilot puddle |
US4287005A (en) * | 1979-11-05 | 1981-09-01 | Union Carbide Corporation | Instantaneous scarfing by means of a pilot puddle |
WO2011069539A1 (en) * | 2009-12-09 | 2011-06-16 | Gesellschaft Für Autogenmaschinen Und -Geräte Mbh | Scarfing block assembly |
GB2483219A (en) * | 2010-08-10 | 2012-03-07 | Harsco Metals Group Ltd | Surface Treatment |
GB2483219B (en) * | 2010-08-10 | 2018-01-10 | Harsco Metals Group Ltd | Surface Treatment |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: L-TEC COMPANY, NEW YORK Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:UNION CARBIDE CORPORATION;REEL/FRAME:004436/0460 Effective date: 19850712 Owner name: L-TEC COMPANY, 666 THIRD AVENUE, NEW YORK, NY 100 Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:UNION CARBIDE CORPORATION;REEL/FRAME:004436/0460 Effective date: 19850712 |
|
AS | Assignment |
Owner name: SECURITY PACIFIC BUSINESS CREDIT INC., A DE CORP. Free format text: SECURITY INTEREST;ASSIGNOR:L-TEC COMPANY A NY LIMITED PARTNERSHIP;REEL/FRAME:004445/0860 Effective date: 19850716 |
|
AS | Assignment |
Owner name: L-TEC COMPANY, SOUTH CAROLINA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:UNION CARBIDE CORPORATION, A CORP OF NY.;REEL/FRAME:004610/0384 Effective date: 19860828 Owner name: L-TEC COMPANY, EBENEEZER ROAD, POST OFFICE BOX F-6 Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:UNION CARBIDE CORPORATION, A CORP OF NY.;REEL/FRAME:004610/0384 Effective date: 19860828 |