CN115138812A - Method and device for improving quality of casting blank - Google Patents
Method and device for improving quality of casting blank Download PDFInfo
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- CN115138812A CN115138812A CN202210782845.5A CN202210782845A CN115138812A CN 115138812 A CN115138812 A CN 115138812A CN 202210782845 A CN202210782845 A CN 202210782845A CN 115138812 A CN115138812 A CN 115138812A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D2/00—Arrangement of indicating or measuring devices, e.g. for temperature or viscosity of the fused mass
- B22D2/006—Arrangement of indicating or measuring devices, e.g. for temperature or viscosity of the fused mass for the temperature of the molten metal
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D46/00—Controlling, supervising, not restricted to casting covered by a single main group, e.g. for safety reasons
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
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Abstract
The invention discloses a method and a device for improving the quality of a casting blank, wherein the method comprises the following steps: s1, setting a distance threshold value, and periodically measuring the temperature T of molten steel at the molten steel surface when the distance between the molten steel surface and a ladle opening is smaller than or equal to the distance threshold value A And according to T A Controlling and setting a ladle opening molten steel temperature rising device to heat molten steel near a ladle opening; s2, simultaneously and periodically measuring the temperature T of the molten steel at the steel outlet B According to T B Controlling a molten steel temperature slow-falling device to cool molten steel at the lower part of a steel ladle; s3, impacting the steel tapping hole through the electromagnetic impact device, simultaneously obtaining the opening degree U of the sliding water gap, and adjusting the instantaneous impact current and impact frequency output by the electromagnetic impact device according to the UAnd (4) rate. According to the method and the device for improving the quality of the casting blank, disclosed by the invention, the axial temperature gradient of molten steel in the steel ladle is formed, so that the floating of impurities in the molten steel is promoted, the superheat degree of the molten steel at the steel tapping hole of the steel ladle is reduced, a high-melting-point compound is eliminated from being attached to the steel tapping hole of the steel ladle, and the comprehensive quality of the casting blank is finally improved.
Description
Technical Field
The invention relates to the field of metal smelting. More particularly, the present invention relates to a method and apparatus for improving the quality of a cast slab.
Background
The steel materials are dominant in structural materials and are important components in national economic construction. With the increase of resources, energy and environmental awareness, people put higher demands on steel materials and production technologies thereof, namely, the production of high-homogenization and high-cleanness steel products is required. The casting blank is a primary product of steel, and various defects such as central shrinkage cavity of the casting blank, central segregation of the casting blank, overproof inclusions in the casting blank and the like exist in the casting blank due to the solidification characteristic of the casting blank in the production process. The current research shows that the temperature gradient of a billet shell can be reduced by reducing the superheat degree of molten steel in a ladle in the pouring process, the level of the central shrinkage cavity defect of a casting billet is reduced, the central equiaxed crystal proportion of the casting billet is increased, the central segregation of the casting billet is basically eliminated, and the method is a feasible scheme for improving the quality of the casting billet. However, the overall reduction of the temperature of molten steel in a ladle also brings other problems, such as that inclusions at the upper opening of the ladle are difficult to float upwards and remove due to low temperature of the molten steel, low-superheat-degree pouring easily causes high-melting-point compounds to adhere to the steel tapping opening of the ladle to grow and enter a casting blank along with steel flow, and the molten steel in the ladle does not form a temperature gradient meeting metallurgical quality conditions, so that the comprehensive quality of the casting blank cannot be improved.
Disclosure of Invention
The invention aims to provide a method and a device for improving the quality of a casting blank, which promote floating of impurities in molten steel, reduce the grade of the central shrinkage cavity defect of the casting blank, increase the central equiaxial crystal proportion of the casting blank, improve the central segregation of the casting blank and eliminate high-melting-point compounds in the casting blank, thereby improving the comprehensive quality of the casting blank.
To achieve these objects and other advantages in accordance with the present invention, there is provided a method for improving quality of a cast slab, comprising the steps of:
s1, setting a distance threshold, pouring molten steel into a steel ladle until the distance between the molten steel surface in the steel ladle and a steel ladle opening is smaller than or equal to the distance threshold, and periodically measuring the temperature T of the molten steel at the molten steel surface A And according to T A Controlling the temperature rise of molten steel at the ladle opening of the ladle the device heats the molten steel near the ladle opening;
s2, periodically measuring the temperature T of molten steel at the steel ladle steel outlet at the same time B According to T B Controlling a molten steel temperature slow-falling device arranged on a steel ladle to cool molten steel at the lower part of the steel ladle;
and S3, impacting the steel ladle steel-tapping hole through the electromagnetic impact device to prevent the steel-tapping hole from being attached with high-melting-point compounds, simultaneously obtaining the opening degree U of the steel ladle sliding water gap, and adjusting the instantaneous impact current and impact frequency output by the electromagnetic impact device according to the U.
Preferably, in the method for improving the quality of the cast slab, the T is the basis of the T in S1 A When the ladle mouth molten steel temperature rising device arranged on the ladle heats the molten steel near the ladle mouth, the method comprises the following steps:
s1.1, setting a first temperature T 1 A second temperature T 2 And a power threshold, wherein T 1 ＜T 2 ；
S1.2, when T A ≤T 1 When the ladle opening molten steel temperature rising device starts to heat the molten steel near the ladle opening, the output power of the ladle opening molten steel temperature rising device is larger than the power threshold value, and the calculation method is as follows:
wherein P is the output power of the ladle opening molten steel temperature rising device; a is a power compensation factor; q is a dielectric constant; t is the superheat degree of molten steel at a ladle opening;
is a temperature sensitive factor;
when T is 1 ＜T A ≤T 2 When the temperature of the molten steel at the ladle opening rises, the molten steel near the ladle opening is kept warm by the ladle opening molten steel temperature rising device, and the output power of the ladle opening molten steel temperature rising device is smaller than the power threshold value;
when T is A ＞T 2 And when the temperature rises, the ladle opening molten steel temperature rising device stops working.
Preferably, in the method for improving the quality of the cast slab, T is in S1.1 1 At 30 ℃ T 2 The temperature was 40 ℃.
Preferably, in the method for improving the quality of the casting blank, the power threshold in S1.1 is 510KW.
Preferably, in the method for improving the quality of the cast slab, the T is the basis of the T in S2 B When the molten steel temperature slow-falling device is controlled to cool the molten steel at the lower part of the ladle, the method comprises the following steps:
s2.1, setting a third temperature T 3 ；
S2.2, when T B ≥T 3 When the temperature of the molten steel slowly-falling device starts to work, the calculation method of the flow of the circulating cooling water comprises the following steps:
q is the flow of circulating cooling water of the molten steel temperature slow-falling device; mu ranges from 12.1 to 14.9; rho is a circulating water convection coefficient; t is the superheat degree of molten steel at a steel outlet; delta is a temperature correction value; theta is a temperature offset coefficient;
when T is B ＜T 3 And when the temperature of the molten steel is lowered, the molten steel temperature slow-lowering device stops working.
Preferably, in the method for improving the quality of the cast slab, T is in S2.1 3 The temperature was 12 ℃.
Preferably, in the method for improving the quality of the casting blank, when the instantaneous impact current and the impact frequency output by the electromagnetic impact device are adjusted according to L in S3, the method includes the following steps:
s3.1, calculating the target opening degree U 0 ：
S3.2 when 5% U 0 ＜U＜10％U 0 The instantaneous impact current and the impact frequency output by the electromagnetic impact device are respectively 3A-100A and 2Hz-70Hz;
when U is not less than 10% 0 When the electromagnetic impact device is used, the instantaneous impact current and the impact frequency output by the electromagnetic impact device are respectively more than 100A and more than 70Hz;
when U is less than or equal to 5% 0 And when the electromagnetic impact device stops working.
Preferably, in the method for improving the quality of the cast slab, U in S3.1 0 The calculation method of (2) is as follows:
U 0 ＝ωe (V-V0)/γ (3)
wherein, U 0 The target opening degree of the ladle sliding nozzle; omega is a constant; v0 is a pulling rate deviation; the value range of gamma is 0.467-0.529.
The invention also provides a device for improving the quality of a casting blank, which adopts any one of the methods for improving the quality of the casting blank and is characterized by comprising a controller, and a ladle opening automatic temperature measuring device, a ladle opening molten steel temperature rising device, a ladle bottom automatic temperature measuring device, a molten steel temperature slow-falling device, a circulating water supply device and an electromagnetic impact device which are respectively electrically connected with the controller, wherein the controller is electrically connected with a sliding water gap opening and closing device of a ladle; the molten steel temperature slow-falling device is arranged at the steel tapping hole of the steel ladle to cool molten steel at the lower part of the steel ladle, a water inlet and a water outlet of the circulating water supply device are respectively communicated with a water outlet end and a water inlet end of the molten steel temperature slow-falling device, and the electromagnetic impact device is arranged at the steel tapping hole of the steel ladle to impact the steel tapping hole.
Based on the conditions of high molten steel temperature at the ladle opening and low ladle bottom temperature of the ladle, the invention realizes that the inclusions in the molten steel fully float upwards through transition from high to low of the molten steel temperature in the ladle, and can reduce the molten steel temperature at the steel tapping hole of the ladle, thereby reducing the temperature of molten steel for casting blank forming, reducing the rating of the shrinkage cavity defect at the center of a casting blank, increasing the isometric crystal proportion at the center of the casting blank, improving the center segregation of the casting blank and reducing the number of the inclusions in the steel.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a flow chart of a method for improving the quality of a cast slab according to an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a device for improving the quality of a casting blank according to the invention;
FIG. 3 is a comparison graph of the cast blank center equiaxial crystal ratio according to the present invention;
FIG. 4 is a comparison of the center segregation of a cast slab according to the present invention;
FIG. 5 is a comparison graph of the number of inclusions in different sizes at 1/4 position of the inner arc side of the casting blank according to the present invention.
Detailed Description
The present invention is further described in detail below with reference to examples so that those skilled in the art can practice the invention with reference to the description.
It should be noted that in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
The embodiment of the invention provides a method for improving the quality of a casting blank, which comprises the following steps:
s1, setting a distance threshold, pouring molten steel into a steel ladle until the distance between the molten steel surface in the steel ladle and a steel ladle opening is smaller than or equal to the distance threshold, and periodically measuring the temperature T of the molten steel at the molten steel surface A And according to T A Controlling the temperature rise of molten steel at the ladle opening of the ladle the apparatus 1 heats molten steel near a ladle opening;
s2, periodically measuring the temperature T of molten steel at the steel ladle steel outlet at the same time B According to T B Controlling a molten steel temperature slow-falling device 2 arranged on a steel ladle to cool molten steel at the lower part of the steel ladle;
and S3, impacting the steel ladle steel-tapping hole through the electromagnetic impact device 3 to prevent the steel-tapping hole from being attached with high-melting-point compounds, simultaneously obtaining the opening degree U of the steel ladle sliding water gap, and adjusting the instantaneous impact current and impact frequency output by the electromagnetic impact device 3 according to the U.
Wherein, in S1, according to T A When the ladle opening molten steel temperature rising device 1 arranged on the ladle heats the molten steel near the ladle opening, the method comprises the following steps:
s1.1, setting a first temperature T 1 A second temperature T 2 And a power threshold, wherein T 1 ＜T 2 ；
S1.2, when T A ≤T 1 When the ladle opening molten steel temperature rising device 1 starts to heat the molten steel near the ladle opening, the output power of the ladle opening molten steel temperature rising device 1 is larger than the power threshold value, and the calculation method is as follows:
wherein P is the output power of the ladle opening molten steel temperature rising device 1; a is a power compensation factor; q is a dielectric constant; t is the superheat degree of molten steel at a ladle opening;
is a temperature sensitive factor;
when T is 1 ＜T A ≤T 2 When the temperature of the molten steel at the ladle opening is higher than the power threshold value, the ladle opening molten steel temperature rising device 1 starts to preserve the temperature of the molten steel near the ladle opening, and the output power of the ladle opening molten steel temperature rising device 1 is lower than the power threshold value;
when T is A ＞T 2 And when the temperature rises, the ladle opening molten steel temperature rising device 1 stops working.
Wherein, T in S1.1 1 At 30 ℃ T 2 The temperature was 40 ℃.
Wherein the power threshold in S1.1 is 510KW.
Wherein, in S2, according to T B When the molten steel temperature slow-falling device 2 is controlled to cool the molten steel at the lower part of the ladle, the method comprises the following steps:
s2.1, setting a third temperature T 3 ；
S2.2, when T B ≥T 3 When the molten steel temperature slow-falling device 2 starts to work, the calculation method of the circulating cooling water flow is as follows:
wherein Q is the flow rate of the circulating cooling water of the molten steel temperature slow-falling device 2; mu ranges from 12.1 to 14.9; rho is a circulating water convection coefficient; t is the superheat degree of molten steel at a steel outlet; delta is a temperature correction value; theta is a temperature offset coefficient;
when T is B ＜T 3 And when the temperature of the molten steel is lowered, the molten steel temperature slow-lowering device 2 stops working.
Wherein, T in S2.1 3 Is 12 ℃.
Wherein, when the instantaneous impact current and the impact frequency output by the electromagnetic impact device 3 are adjusted according to U in S3, the method comprises the following steps:
s3.1, calculating the target opening degree U 0 ：
S3.2 when 5% U 0 ＜U＜10％U 0 The instantaneous impact current and the impact frequency output by the electromagnetic impact device 3 are respectively 3A-100A and 2Hz-70Hz;
when U is not less than 10% 0 When the utility model is used, the water is discharged,the instantaneous impact current and the impact frequency output by the electromagnetic impact device 3 are respectively more than 100A and more than 70Hz;
when U is less than or equal to 5% 0 At this time, the electromagnetic impact device 3 stops operating.
Wherein, U in S3.1 0 The calculation method of (2) is as follows:
U 0 ＝ωe (V-V0)/γ (3)
wherein, U 0 The target opening degree of the ladle sliding nozzle; omega is a constant; v0 is the pulling rate deviation; the value range of gamma is 0.467-0.529.
In the embodiment, based on the conditions that the temperature of molten steel at the ladle opening is high and the temperature of the ladle bottom is low, the molten steel near the ladle opening is heated, so that the transition from high to low of the temperature of the molten steel is realized in a ladle, impurities in the molten steel can be fully floated, the temperature of the molten steel at the steel tapping opening of the ladle can be reduced by cooling the molten steel at the lower part of the ladle, the temperature of molten steel for casting blank forming can be reduced, the rating of shrinkage cavity defects in the center of a casting blank can be reduced, the isometric crystal ratio of the center of the casting blank can be increased, the center segregation of the casting blank can be improved, and the number of the impurities in the steel can be reduced. In addition, the present embodiment also eliminates the high melting point compound adhered to the steel ladle tap hole by the electromagnetic impact device 3, and prevents the compound grown to a larger size from entering the cast slab with the steel flow to become foreign inclusion defects of the cast slab.
The invention also provides a device for improving the quality of a casting blank, which comprises a controller 8, and a ladle opening automatic temperature measuring device 4, a ladle opening molten steel temperature rising device 1, a ladle bottom automatic temperature measuring device 5, a molten steel temperature slow-falling device 2, a circulating water supply device 6 and an electromagnetic impact device 3 which are respectively electrically connected with the controller, wherein the controller is electrically connected with a sliding water gap opening and closing device of a ladle 17, the ladle opening automatic temperature measuring device is arranged at the upper end of the ladle 17 to measure the temperature of the molten steel at the molten steel surface, the ladle opening molten steel temperature rising device is arranged on the ladle 17 to heat the molten steel near the ladle opening of the ladle 17, and the ladle bottom automatic temperature measuring device is arranged at the lower end of the ladle 17 to measure the temperature of the molten steel at the steel outlet of the ladle 17; the molten steel temperature slow-falling device is arranged at the steel-tapping hole of the steel ladle 17 to cool the molten steel at the lower part of the steel ladle 17, a water inlet and a water outlet of the circulating water supply device are respectively communicated with a water outlet end and a water inlet end of the molten steel temperature slow-falling device, and the electromagnetic impact device is arranged at the steel-tapping hole of the steel ladle 17 to impact the steel-tapping hole.
In the embodiment, a ladle opening automatic measuring device 4 is arranged at a ladle opening position of a ladle 17, the ladle opening automatic measuring device 4 is connected with a controller 8 through a ladle opening automatic measuring device signal wire 13 to complete the tasks of providing power electricity and transmitting temperature signals, a ladle opening molten steel temperature rising device 1 is arranged at the upper part of the ladle 17 and is connected with a power supply system 7 through a ladle opening molten steel temperature rising device connecting cable 10, a molten steel temperature slow-lowering device 2 is arranged at the middle lower part of the ladle 17 and is connected with a water treatment system 6 through a circulating water pipe 9 to form a circulating cooling water path, an electromagnetic impact device 3 is arranged at a steel tapping opening of the ladle 17 and is connected with the power supply system 7 through an electromagnetic impact device connecting cable 11, a ladle bottom automatic temperature measuring device 5 is arranged at a position close to the steel tapping opening of the ladle 17, the ladle bottom automatic temperature measuring device 5 is connected with the controller 8 through a ladle bottom automatic temperature measuring device signal wire 12 to complete the tasks of providing power electricity and transmitting temperature signals, the power system 7 is connected with the controller 8 through an electromagnetic impact device signal wire 14 and a ladle opening and closing parameter signal wire 16, and a water treatment system signal transmission parameter is transmitted by a water treatment system signal wire 16; the sliding gate opening and closing device 18 is installed below the electromagnetic impact device 3, a sliding gate opening and closing device signal line 19 connects the controller 8 with the sliding gate opening and closing device 18, and transmits data information of the opening degree of the sliding gate opening and closing device to the controller 8.
When the device for improving the quality of the casting blank is used, the method comprises the following steps:
step one, pouring liquid molten steel into a steel ladle 17;
step two, when the distance between the liquid level height of the molten steel and the upper edge of the ladle opening is less than or equal to 500mm, the controller 8 sends an opening signal through a signal wire 13 of the automatic ladle opening temperature measuring device, the automatic ladle opening temperature measuring device 4 is opened to measure the temperature of the molten steel at the ladle opening, the device is installed at the ladle opening of a ladle 17, the depth of the automatic ladle opening temperature measuring device 4 inserted into the molten steel is more than or equal to 1cm, the measuring frequency is more than or equal to 1 time/minute, and the measured temperature information of the molten steel at the ladle opening is transmitted to the controller 8 through the signal wire 13 of the automatic ladle opening temperature measuring device;
thirdly, the controller 8 researches and judges according to the temperature data information transmitted by the automatic temperature measuring device 4:
1. when the measured molten steel temperature is less than or equal to 30 ℃, the controller 8 sends a starting signal to the power supply system 7 through the ladle opening molten steel temperature rising device signal wire 15, the power supply system 7 provides a starting power supply to the ladle opening molten steel temperature rising device 1 to heat molten steel in a ladle opening area of a ladle 17, the output power of the power supply system is more than 510KW, and the controller 8 calculates the basic formula as follows:
wherein P is the power supply system to provide power for the ladle opening molten steel temperature rising device, A is the power compensation factor, Q is the dielectric constant, T is the superheat degree of the molten steel at the 17-opening of the ladle,
is a temperature sensitive factor;
2. when the measured temperature range of the molten steel is 31-40 ℃, the controller 8 sends a heat preservation signal to the power supply system 7 through the ladle opening molten steel temperature rising device signal wire 15, an on-starting power supply is provided for the ladle opening molten steel temperature rising device 1 through the power supply system 7, heat preservation treatment is carried out on the molten steel in the ladle opening region of the ladle 17, and the output power of the ladle opening molten steel temperature rising device is 30KW-510KW;
3. when the measured molten steel temperature is higher than 40 ℃, the controller 8 sends a closing signal to the power supply system 7 through the ladle opening molten steel temperature rising device signal wire 15, closes the ladle opening molten steel temperature rising device 1, and stops heating the molten steel in the ladle opening area of the ladle 17.
Step four, the controller 8 sends an opening signal to the circulating water supply device 6 and opens the circulating water supply device 6, and circulating cooling water is provided for the molten steel temperature slow-decreasing device 2 through a circulating water pipe 9 to cool the molten steel temperature at the middle lower part of the steel ladle 17;
fifthly, the ladle bottom automatic temperature measuring device 5 measures the temperature of the molten steel near the steel outlet of the ladle 17, the depth of the ladle bottom automatic temperature measuring device 5 inserted into the molten steel is more than or equal to 5mm, the measuring frequency is more than or equal to 1 time/minute, and the measured temperature information of the molten steel near the steel outlet of the ladle 17 is transmitted to the controller 8 through a signal wire 12 of the ladle bottom automatic temperature measuring device;
step six, the controller 8 carries out matching calculation according to the temperature of the molten steel near the steel tapping hole of the steel ladle 17 measured by the automatic temperature measuring device 5 at the bottom of the steel ladle, transmits a parameter adjusting signal through a circulating water supply device signal wire 16, and automatically adjusts the quantity of the circulating water delivered to the temperature slow-decreasing device 2 of the steel ladle 17 by the circulating water supply device 6:
1. when the temperature of the molten steel near the steel outlet of the steel ladle 17 measured by the automatic ladle bottom temperature measuring device 5 is more than or equal to 12 ℃, and the quantity of the circulating water delivered to the temperature slow-lowering device 2 of the steel ladle 17 by the circulating water supply device 6 exceeds 10 tons/day, the temperature change of the molten steel at the middle lower part of the steel ladle 17 is controlled by the circulating water. The controller 8 matching calculation process is as follows:
q is the flow of circulating cooling water provided by a circulating water supply device to a molten steel temperature slow-falling device, the value range of mu is 12.1-14.9, rho is the convection coefficient of circulating water, T is the superheat degree of molten steel at a steel outlet, delta is a temperature correction value, and theta is a temperature convection coefficient;
2. when the temperature of the molten steel near the steel tapping hole of the steel ladle 17 measured by the automatic temperature measuring device 5 at the bottom of the steel ladle is less than 12 ℃, the controller 8 sends a closing signal to the circulating water supply device 6 through the circulating water supply device signal wire 16, and the circulating water supply device 6 stops conveying circulating cooling water to the temperature slow-decreasing device 2 of the steel ladle 17.
Step seven, the controller 8 sends an opening signal to the power supply system 7 through the electromagnetic impact device signal wire 14, the electromagnetic impact device 3 is opened, the electromagnetic impact device is used for preventing a high-melting-point compound from being attached to the steel tapping hole of the steel ladle 17, the output current of the electromagnetic impact device 3 is variable power instantaneous impact current, and the opening degree information data of the sliding nozzle is transmitted to the controller 8 through the sliding nozzle opening and closing device signal wire:
1. when the opening degree of the sliding water gap exceeds the range of 5% -10% of the target opening degree value, the controller 8 sends a starting signal and a parameter setting signal to a power supply system through a signal line of the electromagnetic impact device, starts the electromagnetic impact device 3, outputs the instantaneous impact current in the range of 3A-100A, and has the impact frequency of 2Hz-70Hz;
2. when the opening degree of the sliding water gap exceeds a target opening degree value by 10%, the controller 8 sends an opening signal and a parameter setting signal to the power supply system 7 through the electromagnetic impact device signal line 14, the electromagnetic impact device 3 is opened, the range of output instantaneous impact current is more than 100A, and the impact frequency is more than 70Hz;
3. when the opening degree of the sliding water gap does not exceed 5% of the target opening degree value, the controller judges that no high-melting-point compound is attached to the steel tapping hole of the steel ladle 17, and the controller 8 sends a closing signal to a power supply system through a signal line of the electromagnetic impact device to close the electromagnetic impact device;
calculating the target opening degree of the opening and closing device of the sliding gate:
U＝ωe (V-V0)/γ
wherein, U is the target opening degree of the sliding water gap opening and closing device, omega is a constant, V0 is the pulling speed deviation, and the value range of gamma is 0.467-0.529.
According to the above method, the present invention provides the following examples:
example 1
Step one
The casting steel is the gear steel with the mark number of 20CrMnTi, and molten steel is cast into a steel ladle 17;
step two
When the liquid level of the molten steel is about 400mm away from the upper edge of the steel ladle 17, the controller 8 sends a starting signal to the automatic ladle opening temperature measuring device 4, the automatic temperature measuring device measures the temperature of the molten steel at the frequency of 10 times/min, the automatic temperature measuring device measures the temperature of the molten steel at 1527 ℃, and temperature information is fed back to the controller 8;
step three
The controller 8 calculates the superheat degree of the molten steel at the 17 opening of the steel ladle to be delta ℃ =1527 ℃ temperature measurement temperature-1510 ℃ liquidus temperature =17 ℃, sends a starting signal to the power supply system through the controller 8, starts the molten steel temperature rise device 1 at the opening of the steel ladle, heats the molten steel near the 17 opening of the steel ladle, and the output power of the dual-power-supply control system is 670-890KW;
step four
The controller 8 sends a starting signal to the circulating water system, starts the circulating water system and supplies water to the molten steel temperature slow-decreasing device 2;
step five
The controller 8 sends an opening signal to the bottom-wrapping automatic temperature measuring device 5, the temperature measuring function is started, the temperature measuring frequency is 20 times/minute, the temperature of the molten steel measured by the bottom-wrapping automatic temperature measuring device 5 is 1529 ℃, the temperature is transmitted to the controller 8 for calculation, and the superheat degree of the molten steel at the bottom of the ladle 17 is calculated to be delta DEG C =1529 ℃ temperature measurement temperature-1510 ℃ liquidus temperature =19 ℃;
step six
After the output water amount is adjusted to 10-13 tons/hour through calculation of the controller 8, after 50 seconds, the temperature of the molten steel measured by the ladle bottom automatic temperature measuring device 5 is 1520 ℃, the superheat degree of the molten steel at a steel outlet is 10 ℃, the controller 8 sends a closing signal to the circulating water supply device 6, and the circulating cooling water is stopped being supplied to the molten steel temperature slow-falling device 2;
step seven
The target opening degree of the sliding gate opening and closing device is 90mm, the actual opening degree is 97mm, actual opening degree information is transmitted to the controller 8, the controller 8 calculates that the actual opening degree of the sliding gate opening and closing device exceeds the target opening degree by 7.8%, the controller 8 sends an opening signal and a parameter setting signal to a power supply system, and the electromagnetic impact device 3 is opened and the parameters are set: the output instantaneous impact current is 50A, and the impact frequency is 24Hz.
Example 2
Step one
The cast steel is alloy structural steel with the mark number of 40Cr, and molten steel is cast into a steel ladle 17;
step two
When the liquid level of the molten steel is about 450mm away from the upper edge of the steel ladle 17, the controller 8 sends a starting signal to the automatic ladle opening temperature measuring device 4, the automatic temperature measuring device measures the temperature of the molten steel, the measuring frequency is 10 times/minute, the automatic temperature measuring device measures the temperature of the molten steel to be 1517 ℃, and temperature information is fed back to the controller 8;
step three
The controller 8 calculates the superheat degree of the molten steel at the opening of the steel ladle 17 to be delta =1517 ℃ and the temperature measurement temperature is-1497 ℃ and the liquidus temperature =20 ℃, sends an opening signal to the power supply system through the controller 8, opens the molten steel temperature rise device 1 at the opening of the steel ladle, heats the molten steel near the opening of the steel ladle 17, and the output power of the dual power supply control system is 610-780KW;
step four
The controller 8 sends a starting signal to the circulating water system, starts the circulating water system and supplies water to the molten steel temperature slow-lowering device 2;
step five
The controller 8 sends an opening signal to the automatic bottom-covering temperature measuring device 5, the temperature measuring function is started, the temperature measuring frequency is 20 times/minute, the temperature of the molten steel measured by the automatic bottom-covering temperature measuring device 5 is 1520 ℃, the temperature is transmitted to the controller 8 for calculation, and the superheat degree of the molten steel at the bottom of the ladle 17 is calculated to be delta ℃ =1520 ℃ temperature measurement temperature-1497 ℃ liquidus temperature =23 ℃;
step six
After the output water amount is adjusted to 12-14 tons/hour through calculation of the controller 8, after 60 seconds, the temperature of the molten steel measured by the automatic ladle bottom temperature measuring device 5 is 1508 ℃, the superheat degree of the molten steel at a steel outlet is 11 ℃, and the controller 8 sends a closing signal to the circulating water supply device 6 to stop supplying circulating cooling water to the molten steel temperature slow-drop device 2;
step seven
The target opening degree of the sliding gate opening and closing device is 95mm, the actual opening degree is 96mm, actual opening degree information is transmitted to the controller 8, the controller 8 calculates that the actual opening degree of the sliding gate opening and closing device does not exceed the target opening degree by 5%, the controller 8 sends a closing signal to a power supply system, and the electromagnetic impact device 3 keeps a closing state.
Example 3
Step one
The cast steel is bearing steel with the mark GCr15, and molten steel is cast into a steel ladle 17;
step two
When the liquid level of the molten steel is about 450mm away from the upper edge of the steel ladle 17, the controller 8 sends a starting signal to the automatic ladle opening temperature measuring device 4, the automatic temperature measuring device measures the temperature of the molten steel, the measuring frequency is 10 times/minute, the automatic temperature measuring device measures the temperature of the molten steel to be 1495 ℃, and temperature information is fed back to the controller 8;
step three
The controller 8 calculates the superheat degree of the molten steel at the opening of the steel ladle 17 as delta ℃ =1495 ℃ temperature measurement temperature-1453 ℃ liquidus temperature =42 ℃, and sends a closing signal to a power supply system through the controller 8, and the molten steel temperature rising device 1 at the opening of the steel ladle keeps a closing state;
step four
The controller 8 sends a starting signal to the circulating water system, starts the circulating water system and supplies water to the molten steel temperature slow-lowering device 2;
step (ii) of five of them
The controller 8 sends an opening signal to the automatic bottom temperature measuring device 5, the temperature measuring function is started, the temperature measuring frequency is 20 times/minute, the temperature of the molten steel measured by the automatic bottom temperature measuring device 5 is 1500 ℃, and the temperature is transmitted to the controller 8 for calculation, and the superheat degree of the molten steel at the bottom of the ladle 17 is calculated to be delta ℃ =1500 ℃ temperature measurement temperature-1453 ℃ liquidus temperature =47 ℃;
step six
After the calculation by the controller 8, the output water amount is adjusted to 20 tons/hour, after 120 seconds, the temperature of the molten steel measured by the ladle bottom automatic temperature measuring device 5 is 1468 ℃, the superheat degree of the molten steel at a steel outlet is 15 ℃, and the output water amount is adjusted to 10-13 tons/hour by the controller 8;
step seven
The target opening degree of the sliding gate opening and closing device is 95mm, the actual opening degree is 96mm, actual opening degree information is transmitted to the controller 8, the controller 8 calculates that the actual opening degree of the sliding gate opening and closing device does not exceed the target opening degree by 5%, the controller 8 sends a closing signal to a power supply system, and the electromagnetic impact device 3 keeps a closing state.
Comparative test
Comparative examples 1 to 3 were set in the present invention, and molten steel of the same temperature and composition was poured in the same ladle 17 and under the same conditions as in examples 1 to 3, respectively, in comparative examples 1 to 3, but the method for improving the quality of a cast slab according to the present invention was used in the examples, and the conventional pouring method was used in comparative examples 1 to 3.
Detection assay
After the molten steel of the embodiments 1-3 and the comparative examples 1-3 is respectively poured, molded and cast, and a casting blank is completely solidified, sawing a casting blank sample for detection and analysis; table 1 is a comparison table of casting blank center shrinkage cavity ratings of casting blank samples obtained in examples 1 to 3 and comparative examples 1 to 3, and FIGS. 3 to 5 are a comparison chart of casting blank center equiaxial crystal occupation ratios, a comparison chart of casting blank center segregation, and a comparison chart of the number of inclusions in different scales at 1/4 positions on the inner arc side of a casting blank of the casting blank samples obtained in examples 1 to 3 and comparative examples 1 to 3 in this order.
TABLE 1 comparative table of rating of central shrinkage cavity of casting blank
| Example 1 | Comparative example 1 | Example 2 | Comparative example 2 | Example 3 | Comparative example 3 | |
| |
1.0 | Level | 0 | 1.5 grade | Grade 0.5 | Grade 2.5 |
Correlation data base in connection with FIGS. 3-5In example 1, the center shrinkage cavity defect rating of the cast slab using the method of the present invention was reduced from 1.0 to 0, the percentage of equiaxed crystals in the center of the cast slab was increased from 17% to 33%, the center segregation index of the cast slab was reduced from 1.21 to 1.02, and the number of inclusions with a size of 3 to 5 μm at 1/4 position on the inner arc side of the cast slab was reduced from 31 inclusions/mm 2 Reduced to 11 pieces/mm 2 5-10 μm of inclusions in a number of 14/mm 2 Reduced to 6 pieces/mm 2 The number of inclusions larger than 10 μm is 7/mm 2 Reduced to 1/mm 2 。
In example 2, the rating of the central shrinkage cavity defect of the cast slab using the method of the present invention was reduced from 1.5 to 0, the percentage of equiaxed crystals in the center of the cast slab was increased from 19% to 36%, the central segregation index of the cast slab was reduced from 1.22 to 1.02, and the number of inclusions with a size of 3 to 5 μm on the 1/4 position on the inner arc side of the cast slab was reduced from 43 inclusions/mm 2 Reduced to 13 pieces/mm 2 The number of 5-10 μm inclusions is 19/mm 2 Reduced to 8 pieces/mm 2 The number of inclusions larger than 10 μm is 9/mm 2 Reduced to 1 piece/mm 2 。
In example 3, the rating of the central shrinkage cavity defect of the cast slab by using the method of the invention is reduced from 2.5 to 0.5, the percentage of the central equiaxial crystals of the cast slab is increased from 23% to 39%, the central segregation index of the cast slab is reduced from 1.26 to 1.04, and the number of inclusions with the size of 3-5 mu m on the 1/4 position on the inner arc side of the cast slab is reduced from 27 inclusions/mm 2 Reduced to 8 pieces/mm 2 The number of 5-10 μm inclusions is 11/mm 2 Reduced to 3 pieces/mm 2 The number of inclusions larger than 10 μm is 10/mm 2 Reduced to 1 piece/mm 2 。
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details given herein and to the embodiments shown and described without departing from the generic concept as defined by the claims and their equivalents.
Claims (9)
1. A method of improving the quality of a cast slab, comprising the steps of:
s1, settingDetermining a distance threshold, and periodically measuring the temperature T of the molten steel at the molten steel surface when the molten steel is poured into the steel ladle until the distance between the molten steel surface in the steel ladle and the ladle opening is less than or equal to the distance threshold A And according to T A Controlling a ladle opening molten steel temperature rising device arranged on a ladle to heat molten steel near a ladle opening;
s2, simultaneously and periodically measuring the temperature T of the molten steel at the steel outlet of the steel ladle B According to T B Controlling a molten steel temperature slow-falling device arranged on a steel ladle to cool molten steel at the lower part of the steel ladle;
and S3, impacting the steel ladle steel-tapping hole through the electromagnetic impact device to prevent the steel-tapping hole from being attached with high-melting-point compounds, simultaneously obtaining the opening degree U of the steel ladle sliding water gap, and adjusting the instantaneous impact current and impact frequency output by the electromagnetic impact device according to the U.
2. The method of claim 1, wherein S1 is based on T A When the ladle mouth molten steel temperature rising device arranged on the ladle heats the molten steel near the ladle mouth, the method comprises the following steps:
s1.1, setting a first temperature T 1 A second temperature T 2 And a power threshold, wherein T 1 ＜T 2 ；
S1.2, when T A ≤T 1 When the ladle opening molten steel temperature rising device starts to heat the molten steel near the ladle opening, the output power of the ladle opening molten steel temperature rising device is larger than the power threshold value, and the calculation method is as follows:
wherein P is the output power of the ladle opening molten steel temperature rising device; a is a power compensation factor; q is a dielectric constant; t is the superheat degree of molten steel at a ladle opening;
is a temperature sensitive factor;
when T is 1 ＜T A ≤T 2 When the temperature of the molten steel at the ladle opening rises, the molten steel near the ladle opening is kept warm by the ladle opening molten steel temperature rising device, and the output power of the ladle opening molten steel temperature rising device is smaller than the power threshold value;
when T is A ＞T 2 And when the temperature rises, the ladle opening molten steel temperature rising device stops working.
3. A method of improving slab quality as claimed in claim 2 wherein T is S1.1 1 At 30 ℃ T 2 The temperature was 40 ℃.
4. A method according to claim 2, wherein the power threshold at S1.1 is 510KW.
5. The method of claim 1, wherein S2 is based on T B When the molten steel temperature slow-falling device is controlled to cool the molten steel at the lower part of the ladle, the method comprises the following steps:
s2.1, setting a third temperature T 3 ；
S2.2, when T B ≥T 3 When the molten steel temperature slow-falling device starts to work, the calculation method of the circulating cooling water flow is as follows:
q is the flow of circulating cooling water of the molten steel temperature slow-falling device; mu ranges from 12.1 to 14.9; rho is a circulating water convection coefficient; t is the superheat degree of molten steel at a steel tapping hole; delta is a temperature correction value; theta is a temperature offset coefficient;
when T is B ＜T 3 And when the temperature of the molten steel slowly falls, the molten steel temperature slowly falling device stops working.
6. A method of improving slab quality according to claim 5,t in S2.1 3 The temperature was 12 ℃.
7. The method for improving the quality of the casting blank according to claim 1, wherein the step of adjusting the instantaneous impact current and the impact frequency output by the electromagnetic impact device according to U in S3 comprises the following steps:
s3.1, calculating the target opening degree U 0 ：
S3.2 when 5% U 0 ＜U＜10％U 0 The instantaneous impact current and the impact frequency output by the electromagnetic impact device are respectively 3A-100A and 2Hz-70Hz;
when U is not less than 10% 0 When the electromagnetic impact device is used, the instantaneous impact current and the impact frequency output by the electromagnetic impact device are respectively more than 100A and more than 70Hz;
when U is less than or equal to 5% 0 And when the electromagnetic impact device stops working.
8. A method of improving strand quality as claimed in claim 1, wherein U in S3.1 0 The calculation method of (2) is as follows:
U 0 ＝ωe (V-V0)/γ (3)
wherein, U 0 The target opening degree of the ladle sliding nozzle; omega is a constant; v0 is the pulling rate deviation; the value range of gamma is 0.467-0.529.
9. A device for improving the quality of a casting blank by adopting the method for improving the quality of the casting blank according to any one of claims 1 to 8, which is characterized by comprising a controller (8), and a ladle opening automatic temperature measuring device (4), a ladle opening molten steel temperature rising device (1), a ladle bottom automatic temperature measuring device (5), a molten steel temperature slow-falling device (2), a circulating water supply device (6) and an electromagnetic impact device (3) which are respectively electrically connected with the controller (8), wherein the controller (8) is electrically connected with a sliding water gap opening and closing device of a ladle, the ladle opening automatic temperature measuring device (4) is arranged at the upper end of the ladle to measure the temperature of molten steel at the molten steel surface, the ladle opening molten steel temperature rising device (1) is arranged on the ladle to heat the molten steel near the ladle opening, and the ladle bottom automatic temperature measuring device (5) is arranged at the lower end of the ladle to measure the temperature of the molten steel at a steel tapping hole of the ladle; the molten steel temperature slow-falling device (2) is arranged at a steel ladle steel-tapping hole to cool molten steel at the lower part of a steel ladle, a water inlet and a water outlet of the circulating water supply device (6) are respectively communicated with a water outlet end and a water inlet end of the molten steel temperature slow-falling device (2), and the electromagnetic impact device (3) is arranged at the steel ladle steel-tapping hole to impact the steel-tapping hole.
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