Start-up system for continuous casting mold

Claim 2

In a continuous casting system of the type in which a control signal is developed which is predominately proportional to the height of molten metal in a continuous casting mold which signal is used in normal operation to control the speed of withdrawal of the continuous casting from the mold by a drive system, the improvement in a start-up system comprising: means for detecting the onset of casting; second means coupled to said detecting means for governing the speed of the drive system in a definite manner for a definite start-up period after the detected onset so as to control the drive system independenTly of the detected height for that period and for automatically restoring the control signal to its normal operating condition at the end of that predetermined period; means coupled to said detecting means for energizing the drive system and in response to the detection of the onset of casting; said second means governing the drive system speed by altering the control signal; and said casting onset detecting means is coupled to the level control signal for operation of the energizing means and said second means when the control signal passes a threshold value; said detecting means including: a switching device coupled to the control signal for control thereby, and a relay coil connected to said switching device for energization and de-energization in response thereto; said drive energizing means is a first relay switch controlled by said relay coil; and said second means including: at least, one additional relay switch controlled by said relay coil, a second switching device coupled alternately change the control signal and to not effect the control signal, and a timing circuit coupled to both said second switching device and said at least one additional relay switch, for controlling said second switching device in response to the relay coil so as to change the control signal for the predetermined period and to thereafter not effect that signal; whereby the continuous casting system may automatically reach normal operating conditions from the onset of casting without the necessity of human observation and control and without molten metal spill-over or break-out caused by transient startup conditions.

Claim 3

The improvement in a start-up system for a continuous casting system as defined in claim 1 wherein: said detecting means switching device is a solid-state bi-directional switch (224) which has its control electrode connected to receive the signal and is so biased so as to be conducting for signals indicating that the height of molten metal in the mold is below a certain level and to be non-conducting for signals indicating that the height is above that level; said first switch (206) is a normally closed switch; said additional relay switch (232) is a normally closed switch connected in series with a source of potential (B''+) and said timing circuit (248, 246) so as to connect said potential source and said timing circuit when closed; said timing circuit includes a resistance (246) and a capacitance (248) in circuit connection together and connected to said second switching device; said second switching device (250) is a transistor having its emitter-collector circuit connected between a plane of potential and the control signal source, and its base connected to said timing circuit; and said second means further includes a third relay switch (233) that is normally open, is controlled by said relay coil, and is connected across said capacitance (248); so that for low levels of molten metal in the mold said solid-state bi-directional switch is maintained conductive so as to maintain said first switch open, said additional switch open and said third switch closed to insure that said capacitance is effectively uncharged, and for reversing the conditions of said switches when the molten metal height exceeds said certain height thereby causing the energization of the drive system, the rendering of the second transistor conductive to alter the control signal for a period depending upon the charging time of said resistance and capacitance timing circuit and for thereafter rendering said second transistor non-conductive.

Claim 4

A mold level control system for controlling the level of molten metal in the mold core of a continuous casting mold of the type that has a core which includes a highly conductive layer and which mold receives molten metal from a source and from which a continuous billet of at least partly hardened metal is extracted by a variable speed drive system, a mold Level detector, which detector is positioned adjacent to the mold core; and said mold level detector comprises a first coil and a second coil; means coupled to said mold level detector and to the billet drive system for controlling the speed of the billet drive system in response to said detector so as to vary the speed thereof to maintain, during normal operation, the level of the molten metal within a desired predetermined range; said controlling means including: a signal source coupled to said one coil for exciting it with an ac input signal, means coupled to said second coil for deriving an output signal therefrom which is related to the input signal and to the level of molten steel in the mold; a source of a second signal related to the input signal but phase shifted therefrom, and means coupled to said output signal deriving means and said second signal source for deriving a dc mold level control signal whose amplitude varies in proportion with changes in the level of molten steel in the mold core from a predetermined level therein; means coupled to said billet drive speed control means for, during start-up, operating the billet drive system at a programed rate of speed for a definite time period after the onset of casting and for restoring the system to normal operation after that time period; said start-up means including: a casting onset detector coupled to receive the control signal; switching means coupled to the casting onset detector and the billet drive system for energizing and de-energizing that drive system when the control signal is above or below a predetermined threshold amplitude; a timed speed-up signal source coupled to said casting onset detector and said control signal deriving means for coupling a speed-up signal thereto for altering the control signal to cause the billet drive system to operate at the programed rate of speed, said speed-up signal source including timing means for discontinuing the speed-up signal at the end of a predetermined time period from the detection of casting onset.

Claim 5

A mold level control system for controlling the level of molten metal in the mold core of a continuous casting mold of the type that has a core which includes a highly conductive layer and which mold receives molten metal from a source and from which a continuous billet of at least partly hardened metal is extracted by a variable speed drive system, a mold Level detector, which detector is positioned adjacent to the mold core; and said mold level detector comprises a first coil and a second coil; means coupled to said mold level detector and to the billet drive system for controlling the speed of the billet drive system in response to said detector so as to vary the speed thereof to maintain, during normal operation, the level of the molten metal within a desired predetermined range; said controlling means including: a signal source coupled to said one coil for exciting it with an ac input signal, means coupled to said second coil for deriving an output signal therefrom which is related to the input signal and to the level of molten steel in the mold; a source of a second signal related to the input signal but phase shifted therefrom, and means coupled to said output signal deriving means and said second signal source for deriving a dc mold level control signal whose amplitude varies in proportion with changes in the level of molten steel in the mold core from a predetermined level therein; means coupled to said billet drive speed control means for, during start-up, operating the billet drive system at a programed rate of speed for a definite time period after the onset of casting and for restoring the system to normal operation after that time period; said start-up means including: a casting onset detector coupled to receive the control signal; switching means coupled to the casting onset detector and the billet drive system for energizing and de-energizing that drive system when the control signal is above or below a predetermined threshold amplitude; a timed speed-up signal source coupled to said casting onset detector and said control signal deriving means for coupling a speed-up signal thereto for altering the control signal to cause the billet drive system to operate at the programed rate of speed, said speed-up signal source including timing means for discontinuing the speed-up signal at the end of a predetermined time period from the detection of casting onset.

Claim 6

The mold level control system for controlling the level of molten metal in a mold core, as defined in claim 3, wherein: said casting onset detector includes: a switching device coupled to the control signal for control thereby, and a relay coil connected to said switching device for energization and de-energization in response thereto; said drive energizing means is a first relay switch controlled by said relay coil; and said second means includes: at least, one additional relay switch controlled by said relay coil, a second switching device coupled alternately change the control signal and to not effect the control signal, and a timing circuit coupled to both said second switching device and said at least one additional relay switch, for controlling said second switching device in response to the relay coil so as to change the control signal for the predetermined period and to thereafter not effect that signal.

Claim 7

The mold level control system for controlling the level of molten metal in a mold core, as defined in claim 4, wherein: said detecting means switching device is a Triac bi-directional switch (224) which has its control electrod connected to receive the signal and is so biased so as to be conducting for signals indicating that the height of molten metal in the mold is below a certain level and to be non-conducting for signals indicating that the height is above that level; said first switch (206) is a normally closed switch; said additional relay switch (232) is a normally closed switch connected in series with a source of potential (B''+) and said timing circuit (248, 246) so as to connect said potential source and said timing circuit when closed; said timing circuit includes a resistance (246) and a capacitance (248) in circuit connection together and connected to said second switching device; said second switching device (250) is a transistor having its emitter-collector circuit connected between a plane of potential and the control signal source, and its base connected to said timing circuit; and said second means further includes a third relay switch (233) that is normally open, is controlled by said relay coil, and is connected across said capacitance (248); so that for low levels of molten metal in the mold said triac is maintained conductive so as to maintain said first switch open, said additional switch open and said third switch closed to insure that said capacitance is effectively uncharged, and for reversing the conditions of said switches when the molten metal height exceeds said certain height thereby causing the energization of the drive system, the rendering of the second transistor conductive to alter the control signal for a period depending upon the charging time of said resistance and capacitance timing circuit and for thereafter rendering said second transistor non-conductive.

Claim 8

A continuous steel casting system comprising: a source (12) of molten steel, a mold unit (20) having a generally vertical core into which said source pours molten steel at an approximately constant and continuous rate, and about which a coolant is circulated and from which a continuous steel billet is produced; an inductance level detector (30) positioned in said mold unit adjacent to but outside of said core to detect the level of molten steel in the core; a billet drive system (16) that is responsive to a drive control signal to vary the rate of removal of the billet from the mold core; a source (41) of excitation signals coupled to said inductance detector, means (40 and 21) coupled to said inductance level detector for extracting therefrom a signal indicative of the level of molten steel therein and for determining there-from a variable drive control signal therefrom, and for coupling that control signal to said billet drive system; start-up means (200) responsive to the control signal indicating a low level below predetermined level of molten steel in said mold unit for de-energizing said drive system and, in response to a control signal indicative of the rise of molten steel above that predetermined level for re-energizing said drive system and for altering said control signal, for a short predetermined time period, so as to operate said drive system at a high rate of speed of billet withdrawal for that short predetermined time period, and for then automatically ceasing that signal alteration.

Claim 9

A continuous steel casting system comprising: a source (12) of molten steel, a mold unit (20) having a generally vertical core into which said source pours molten steel at an approximately constant and continuous rate, and about which a coolant is circulated and from which a continuous steel billet is produced; an inductance level detector (30) positioned in said mold unit adjacent to but outside of said core to detect the level of molten steel in the core; a billet drive system (16) that is responsive to a drive control signal to vary the rate of removal of the billet from the mold core; a source (41) of excitation signals coupled to said inductance detector, means (40 and 21) coupled to said inductance level detector for extracting therefrom a signal indicative of the level of molten steel therein and for determining there-from a variable drive control signal therefrom, and for coupling that control signal to said billet drive system; start-up means (200) responsive to the control signal indicating a low level below predetermined level of molten steel in said mold unit for de-energizing said drive system and, in response to a control signal indicative of the rise of molten steel above that predetermined level for re-energizing said drive system and for altering said control signal, for a short predetermined time period, so as to operate said drive system at a high rate of speed of billet withdrawal for that short predetermined time period, and for then automatically ceasing that signal alteration.

Claim 10

In a continuous casting system of the type in which a control signal is developed which is predominately proportional to the height of molten metal in a continuous casting mold which signal is used in normal operation to control the speed of withdrawal of the continuous casting from the mold by a drive system, the improvement in a start-up system comprising: first means for detecting the onset of casting coupled to receive and respond to the height proportional control signal; second means coupled to said first means for governing the speed of the drive system in a definite manner for a definite start-up period after the detected onset so as to control the drive system independently of the detected height for that period and for automatically restoring the control signal to its normal operating condition at the end of that definite start-up period; whereby the continuous casting system may automatically reach normal operating conditions from the onset of casting without the necessity of human observation and control and without molten metal spill-over or break-out caused by transient start-up conditions.

Claim 11

In a continuous casting system of the type in which a control signal is developed which is predominately proportional to the height of molten metal in a continuous casting mold which signal is used in normal operation to control the speed of withdrawal of the continuous casting from the mold by a drive system, the improvement in a start-up system comprising: first means for detecting the onset of casting coupled to receive and respond to the height proportional control signal; second means coupled to said first means for governing the speed of the drive system in a definite manner for a definite start-up period after the detected onset so as to control the drive system independently of the detected height for that period and for automatically restoring the control signal to its normal operating condition at the end of that definite start-up period; whereby the continuous casting system may automatically reach normal operating conditions from the onset of casting without the necessity of human observation and control and without molten metal spill-over or break-out caused by transient start-up conditions.

Claim 12

The improvement in a start-up system for a continuous casting system as defined in claim 7, wherein said start-up system further includes: means coupled to said first means for energizing the drive system and in response to the detection of the onset of casting; and wherein said second means governs the drive system speed by altering the control signal impressed thereto.

Claim 13

The improvement in a start-up system for a continuous casting system as defined in claim 8, wherein: said first means is coupled to the level control signal for operation of the energizing means and said second means when the control signal passes a threshold value.