US3645718A - Method for making steel - Google Patents
Method for making steel Download PDFInfo
- Publication number
- US3645718A US3645718A US64936A US3645718DA US3645718A US 3645718 A US3645718 A US 3645718A US 64936 A US64936 A US 64936A US 3645718D A US3645718D A US 3645718DA US 3645718 A US3645718 A US 3645718A
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- US
- United States
- Prior art keywords
- oxygen
- line
- temperature
- signal
- bath
- 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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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
Definitions
- ABSTRACT This invention relates to a method and apparatus for making steel in a converter top-blown with oxygen.
- the invention relates to operating a converter top-blown with oxygen by monitoring the temperature on the area of the bath surface contacted by the oxygen jet, which is the reaction zone, determining the reaction-zone temperature decrease indicating the end of desiliconization of the bath, and thereupon increasing the amount of oxygen and preferably also decreasing the height of the oxygen lance above the bath surface during the carbon-removal portion of oxygen blowing. The increased oxygen flow rate and decreased lance height is maintained for the remainder of the steelmaking operation.
- One known practice for making steel in a top-blown oxygen converter is to use a fixed lance height and fixed oxygen flow rates substantially throughout each heat. This practice is inefficient and does not take into the account that the oxygen first reacts principally with the silicon present in the molten metal, and then later principally with the carbon. During the later part of a heat, when the removal of carbon is the principal reaction, greater oxygen flow rates can be tolerated than during and immediately after the desiliconization period.
- this practice becomes undependable when the initial silicon content of the iron is high, e.g., over 1.5 percent, because when the iron contains that much silicon, the slag volumes are necessarily larger and the bath becomes hotter, with the result that the decarburization rate is appreciable even while desiliconization proceeds, all of this also promoting slopping.
- this practice does not provide a distinct indication of the end of the desiliconization period.
- high-silicon baths tend to slop more readily, so that it is even more important with them than with the low-silicon baths to obtain a sufficiently rapid indication of the changes that are taking place in the bath reactions in order to obtain adequate and effective control.
- the primary object of the present invention to provide for the effective determination of the end of desiliconization during the operation of top-blown, oxygen converter. This result is achieved by monitoring the chemical reaction whereby silicon is removed from the bath by monitoring the temperature at the reaction zone of the bath. An abrupt temperature decrease at the reaction zone signals the end of desiliconization.
- FIGURE is a schematic diagram of one embodiment of equipment useful for the of a preferred embodiment of the invention.
- the invention involves following the bath chemical reactions by monitoring the temperature in the reaction zone, which is in the vicinity at which the oxygen impinges upon the molten iron to be refined, and using before the silicon end point a suitable low-oxygen flow rate and high-lance height, and after the silicon end point, a suitable higher oxygen flow rate and lower lance height.
- apparatus for following the bath chemical reactions by monitoring the temperature in the reaction zone, and control means responsive to the above-mentioned temperature-following means for suitably increasing the oxygen flow rate when the temperature in the reaction zone decreases as a result of the end of desiliconization.
- the means for following the reaction temperature comprises a radiation pyrometer sighting down the lance.
- automatic means are provided responsive to signals emitted by the radiation-pyrometer means for gradually increasing the oxygen flow rate from an initial relatively low value used during the desiliconization period to a second relatively higher value used after the silicon end point.
- the invention is in no way concerned with measuring the temperature of the molten metal bath, either at the reaction zone thereof or otherwise. In addition, it is the temperature change at the reaction zone rather than the bath temperature which is the prime control function of the invention.
- the apparatus of the present invention comprises a conventional open-top converter 2 having an exterior steel shell 4 and an interior lining 6 of refractory material, the converter being arranged to rotate about trunnions (not shown) to permit charging and subsequently discharge of molten steel upon the completion of the refining operation.
- a lance 8 by means of which oxygen from a source 10 is blown upon surface 12 of a bath 14 of molten iron contained in converter 2.
- Hood 16 provides means by which fume-laden gases produced during the refining operation are removed for cleaning and disposal.
- a device 18, such as a radiation pyrometer that is used to sense the temperature in the region 20, which is the reaction zone, of the bath 14.
- the output of the radiationsensitive device 18 is a suitable electrical signal conveyed by line 21 to a strip-chart recorder 22. Flow of oxygen from the source 10 to the lance 8 is controlled by means of a valve 24.
- the recorder 22 may be of the known strip-chart type containing a null-balance potentiometer and servomotor by means of which voltages incoming on line 21 are translated into a pen position indicative of the value of such voltage.
- the recorder 22 is mechanically connected as at 25 with an upper limit switch 26 and a lower limit switch 28, and the recorder 22 also contains or drives a potentiometer 30, for a purpose which will hereinafter be more fully explained.
- One side of each of the limit switches 26 and 28 is connected to a suitable source of current 32 by means of lines 34 and 36.
- the other side of the upper limit switch 26 is connected by line 38 to a bistable multivibrator 40.
- lower limit switch 28 is connected by line 42 to an AND-gate 44, to which the output of multivibrator 40 is connected by means of the line 46.
- the output of AND-gate 44 is connected by line 48 to a second bistable multivibrator 50, the output of which is connected by a line 52 to relay-driving means 54, which is connected by line 56 to coil 58 of a relay having normally open contacts 58C! and thence to ground at 60.
- the output of the recorder-driven potentiometer 30 is passed by line 62 to a differentiation circuit 64 and thence by line 66 to a potentiometer 68.
- the output of potentiometer 68 is transmitted by line 70 to a dead-band function generator 72, the output of which is passed by a line 74 to a potentiometer 76.
- the output of potentiometer 76 is passed by line 78 to a summing amplifier 80, to which there is fed through a line 82 from a source 84 a constant potential opposite in polarity to that on the line 78.
- the output of the summing amplifier appears on the line 86.
- the apparatus of the invention further comprises potentiometers 88, 90, and 92, upon which are set respectively, the initial oxygen flow rate, the rate of change of flow rate during the transition period (transition between predominately silicon blow to predominately carbon blow), and the desired final oxygen flow rate.
- means for raising and lowering the lance with respect to the bath comprising a motor 91, takeup reel 93 and cable 95 passing over sheaves 97.
- Potentiometer 88 is connected to a source of current 94 through the line 96, and its output is connected by a line 98 with an integrating device 100, the output of which is fed by a line 102 to a flow control 104 and by a line 106 to a comparator device 108.
- the other signal fed to the comparator device 108 is the desired final flow set on the potentiometer 92, which is powered from a source 110 through the line 112, the output of potentiometer 92 being conveyed to the comparator device 108 by line 114.
- the comparator device 108 operates, whenever the signal on the line 106 is as great as that on line 114, to energize coil 118 via line 116.
- Coil 118 is the coil ofa relay having'normally closed contacts 118C1. It is located in line 86.
- the flow controller 104 receives indications of actual oxygen flow from flow transmitter 120, via line 122, and emits, via line 124, a suitable command signal to the flow-control valve 24.
- the apparatus described above may be operated in the following manner. After a suitable hot-metal charge 14 is placed in the converter vessel 2, appropriate values are set on the potentiometers 88, 90 and 92 and the circuit is actuated. At the outset, considering that contacts 58C1 are open, as shown in the FIGURE, the signal on line 102 corresponds to the initial flow rate set on potentiometer 88, which may be calibrated in standard cubic feet per minute. MINUTE. When the reaction temperature sensed by device 18 rises above the setting of lower limit switch 28, that switch, which is normally closed, will open.
- the AND-gate 44 is enabled, such that if it should detect a signal on the line 42, it will pass a signal across the line 48 and thus, operating through the multivibrator 50 and the relay driver 54, energize relay 58 to connect with the integrating device 100 the signal on line 86 and thus initiate a change in the oxygen flow rate.
- the temperature detected by the device 18 falls rapidly at the end of the silicon blow. As it drops below the setting of upper limit switch 26, that switch will open again, but of course multivibrator 40 will not change state. As the detected temperature drops below the setting of lower limit switch 28, switch 28 will again close to produce a signal across line 42 and the AND-gate 44 will thus operate to change the state of multivibrator 50, with the results described above.
- the reference voltage 84 is connected by line 86 with the potentiometer 90, which may be calibrated in standard cubic feet per minute per minute.
- the output of integrating device 100 will now increase at a preselected rate, which is determined by the setting of potentiometer 90, thereby changing the command signal to the flow controller 104 and at the same time the setting of flow control valve 24 and consequently the rate at which oxygen is delivered to the converter 2 through the lance 8.
- the operator also operates motor 91, which then acts through takeup reel 93 and cable 95 to lower the lance 8 a suitable and substantial selected distance toward the bath.
- the lance-bath distance may be reduced from 150 inches before the silicon end point to 90 inches after the silicon end point, but these numbers are strictly illustrative, the optimal practice depending upon such factors as the oxygen flow rates used, the size and shape of the furnace vessel, and the weight and composition of the charge.
- Comparator 108 is a bistable device that will energize and latch the relay 118 when the input of line 106 is equal to or greater than the input through the line 114.
- the switching point is determined by the setting of the potentiometer 92, which is calibrated in terms of standard cubic feet per minute.
- the comparator 108 opens the input to the potentiometer 90, so that the signal on line 102 does not change further.
- the potentiometer 76 is set at a value other than zero. Let us assume, for example that the setting on potentiometer 76 is such that it can pass on the line 78 a signal capable of cancelling that on the line 82. This would mean that, when contact 58C] is closed, there might result, with an appropriate signal on the line 74, no input to the integrator 100 through the potentiometer 90, and no change in the output of the integrating device 100, I
- the differentiation circuit 64 senses the rate of change, with respect to time, of the temperature detected by the device 18, a value corresponding to this detected rate of change appearing on line 66.
- the signal on line 66 is modified by potentiometer 68, and said modified signal appears on line 70.
- the operation of the dead-band function generator 72 is such that it produces a signal on line 74 when the magnitude of the signal on line 70 exceeds the deadband set on the function generator. If the signal on line 70 is within the dead-band, then the signal on line 74 will be constant as will be the signal from the summing amplifier 80 on the line 86. In the operation of the circuit, when the relay 58 is closed, a signal on line 74 other than constant will affect the oxygen flow rate.
Abstract
Description
Claims (3)
- 2. A method as defined in claim 1, characterized in that the means by which said jet is directed onto said iron is moved closer to said iron when said rate of flow of oxygen-containing gas is increased.
- 3. A method as defined in claim 1, characterized in that said monitoring of the temperature in said reaction zone is dove by sighting a pyrometer onto said reaction zone and obtaining therefrom signals indicative of said temperature.
- 4. A method as defined in claim 3, characterized in that said pyrometer is sighted axially of said jet.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US67366667A | 1967-10-09 | 1967-10-09 | |
US6493670A | 1970-07-31 | 1970-07-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3645718A true US3645718A (en) | 1972-02-29 |
Family
ID=26745050
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US64936A Expired - Lifetime US3645718A (en) | 1967-10-09 | 1970-07-31 | Method for making steel |
Country Status (1)
Country | Link |
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US (1) | US3645718A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3837841A (en) * | 1971-03-25 | 1974-09-24 | Vacmetal Gmbh | Process for controlled removal of carbon under vacuum from highly alloyed steels |
US4149877A (en) * | 1974-06-27 | 1979-04-17 | Centre De Recherches Metallurgiques, Centrum Voor Research In De Metallurgie | Controlling pig iron refining |
CN102564151A (en) * | 2012-01-04 | 2012-07-11 | 中国恩菲工程技术有限公司 | Smelting converter control equipment |
WO2015046027A1 (en) * | 2013-09-30 | 2015-04-02 | Jp Steel Plantech Co. | Lance system, metallurgical furnace using the same, and lance positioning method |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2801161A (en) * | 1956-04-30 | 1957-07-30 | Bethlehem Steel Corp | Process for operating a bessemer converter |
US2807537A (en) * | 1954-11-01 | 1957-09-24 | Bethlehem Steel Corp | Method of controlling the partial blowing of bessemer steel |
GB879680A (en) * | 1959-05-04 | 1961-10-11 | United Steel Companies Ltd | Improvements relating to oxygen blowing in steel-making and to apparatus for use therein |
GB933414A (en) * | 1961-06-02 | 1963-08-08 | Richard Thomas & Baldwins Ltd | Improvements relating to the production of steel |
US3161499A (en) * | 1960-10-12 | 1964-12-15 | Percy James Ward | Metallurgical process control |
US3528800A (en) * | 1966-02-14 | 1970-09-15 | Leeds & Northrup Co | Optimized blowing control for basic oxygen furnaces |
-
1970
- 1970-07-31 US US64936A patent/US3645718A/en not_active Expired - Lifetime
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2807537A (en) * | 1954-11-01 | 1957-09-24 | Bethlehem Steel Corp | Method of controlling the partial blowing of bessemer steel |
US2801161A (en) * | 1956-04-30 | 1957-07-30 | Bethlehem Steel Corp | Process for operating a bessemer converter |
GB879680A (en) * | 1959-05-04 | 1961-10-11 | United Steel Companies Ltd | Improvements relating to oxygen blowing in steel-making and to apparatus for use therein |
US3161499A (en) * | 1960-10-12 | 1964-12-15 | Percy James Ward | Metallurgical process control |
GB933414A (en) * | 1961-06-02 | 1963-08-08 | Richard Thomas & Baldwins Ltd | Improvements relating to the production of steel |
US3528800A (en) * | 1966-02-14 | 1970-09-15 | Leeds & Northrup Co | Optimized blowing control for basic oxygen furnaces |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3837841A (en) * | 1971-03-25 | 1974-09-24 | Vacmetal Gmbh | Process for controlled removal of carbon under vacuum from highly alloyed steels |
US4149877A (en) * | 1974-06-27 | 1979-04-17 | Centre De Recherches Metallurgiques, Centrum Voor Research In De Metallurgie | Controlling pig iron refining |
CN102564151A (en) * | 2012-01-04 | 2012-07-11 | 中国恩菲工程技术有限公司 | Smelting converter control equipment |
WO2015046027A1 (en) * | 2013-09-30 | 2015-04-02 | Jp Steel Plantech Co. | Lance system, metallurgical furnace using the same, and lance positioning method |
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Owner name: COLT INDUSTRIES OPERATING CORP. Free format text: MERGER AND CHANGE OF NAME;ASSIGNOR:CRUCIBLE CENTER COMPANY (INTO) CRUCIBLE INC. (CHANGED TO);REEL/FRAME:004120/0308 Effective date: 19821214 |
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