CN113927005A - Method for reducing slab off-angle cracks - Google Patents
Method for reducing slab off-angle cracks Download PDFInfo
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- CN113927005A CN113927005A CN202010606582.3A CN202010606582A CN113927005A CN 113927005 A CN113927005 A CN 113927005A CN 202010606582 A CN202010606582 A CN 202010606582A CN 113927005 A CN113927005 A CN 113927005A
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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
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/168—Controlling or regulating processes or operations for adjusting the mould size or mould taper
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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
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
- B22D11/053—Means for oscillating the moulds
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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
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
- B22D11/057—Manufacturing or calibrating the moulds
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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
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/166—Controlling or regulating processes or operations for mould oscillation
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Abstract
The invention relates to a method for reducing slab deviation angle cracks, which comprises the following steps: step 1, analyzing the formation and distribution rule of a liquid/solid slag film and an air gap in a crystallizer: step 2, adjusting and testing the broadside taper, and determining the appropriate broadside taper; step 3, designing a gasket; step 4, reducing the influence of the angle seam on the width taper; and 5, measuring and optimizing the taper of the narrow side of the crystallizer: step 6, arc alignment control of the crystallizer: and 7, monitoring and adjusting the vibration of the crystallizer. The method analyzes the online use process of the crystallizer, combines actual use and empirical record, researches the optimization scheme of the taper of the wide side of the crystallizer when a single factor changes, realizes the optimization of the taper of the crystallizer and the adjustment of the supporting roller set under the complex production condition, ensures the rhythm of high-efficiency continuous casting production, and reduces the slab deviation angle cracks.
Description
Technical Field
The invention relates to a method for reducing slab deviation angle cracks, and belongs to the technical field of steelmaking continuous casting.
Background
In the inner cavity of the crystallizer, because the continuous vibration of the crystallizer and the stress advance of the casting blank under the traction of the driving roller set of the continuous casting machine, not only heat flow conduction exists between the plate blank and four copper plates of the crystallizer, but also mutual acting force exists between the plate blank and the four copper plates of the crystallizer, and simultaneously, because of the influence of a plurality of factors such as stress, heat and the like, the copper plates also deform, so the heat flow/stress state in the crystallizer is complicated, liquid molten steel is cooled in the crystallizer to crystallize into a primary blank shell, and because the primary blank shell is very thin, the primary blank shell is influenced by the taper of the crystallizer, circulating cooling water, a vibration mechanism of the crystallizer and the like, and a plurality of defects of the continuous casting blank all occur in the crystallizer.
When the taper of the crystallizer is too large, the casting blank corner is depressed due to the fact that the crystallizer copper plate extrudes the casting blank, the friction resistance of the casting blank is increased when the crystallizer runs downwards, the abrasion of a coating of the crystallizer is aggravated, copper leakage of the copper plate even is serious, and the generation of star-shaped cracks of the casting blank is caused. In the corner area formed by the wide-surface copper plate and the narrow-surface copper plate, the air gap is large to form a hot spot, which can cause the blank shell of the casting blank to be thinned and is easy to crack.
When the taper of the crystallizer is too small, the air gap between the casting blank and the copper plate wall is enlarged, so that the heat flux density is reduced, the blank shell is thinned, and steel leakage is easy to occur; in addition, the taper of the crystallizer is too small, so that corners can rotate, and subcutaneous cracks and longitudinal depressions can occur.
In actual production, the broadside copper plate is generally defaulted to be parallel up and down, and only the narrow-side taper is detected and maintained, so that the attention to the broadside copper plate taper is ignored. The broadside taper of the on-line crystallizer is measured, so that the broadside taper is usually smaller or negative, impurities which are obviously unfavorable for pouring float upwards in an abnormal state, and the thermal stress and the mechanical stress born by a solidified blank shell are influenced; due to the fact that the taper of the wide side of the crystallizer is unreasonable, quality defects such as deviation angles and the like can even cause serious production safety accidents such as steel leakage.
Disclosure of Invention
The invention provides a method for reducing the slab deviation angle cracks aiming at the problems in the prior art, and the technical scheme aims to improve the functional precision of continuous casting crystallizers, ensure uniform stress of a shell in the crystallizers and a 0# section area, and effectively avoid serious production safety accidents such as steel leakage and the like caused by quality defects such as deviation angles and the like.
In order to achieve the above object, the present invention provides a method for reducing slab off-angle cracks, comprising the steps of:
step 1, analyzing the formation and distribution rule of a liquid/solid slag film and an air gap in a crystallizer:
step 2, adjusting and testing the broadside taper, and determining the appropriate broadside taper;
step 3, designing a gasket;
and 5, measuring and optimizing the taper of the narrow side of the crystallizer:
step 6, arc alignment control of the crystallizer:
and 7, monitoring and adjusting the vibration of the crystallizer.
Further, step 1, analyzing the formation and distribution rule of the liquid/solid slag film and the air gap in the crystallizer: the distribution of the covering slag and the air gap in the crystallizer is divided into 3 states:
the method comprises the following steps: model I (T)s>Tfsol)；
When the surface temperature of the casting blank is higher than the solidification temperature of the covering slag, liquid slag and solid slag coexist in the slag channel,
secondly, the step of: model II (T)s＝Tfsol)
Along with the downward movement of the casting blank, when the surface temperature of the blank shell is reduced to the solidification temperature of the casting powder, the liquid slag film just disappears, only a solid slag film exists in the gap between the crystallizer and the casting blank,
③: model III (T)s＜Tfsol)
The surface temperature of the blank shell is gradually reduced along with the continuous transmission of the heat of the casting blank, when the surface temperature of the casting blank is lower than the solidification temperature of the covering slag, the clearance between the blank shell and the crystallizer is in a solid slag-air gap coexisting state, and the air gap thickness is obtained by the simultaneous solution of the following equation:
Tb＝Ts-q×Rs
Ra rad＝0.5δ(εf+εm)(Tm 2+Tb 2)(Tm+Tb)
wherein T isbTemperature, K, representing the solid slag/air gap interface; ra，Ra con，Ra radRespectively representing the total thermal resistance, the thermal conductivity thermal resistance and the radiation thermal resistance of the air gap, m2·℃/W；daRepresents the air gap thickness, m; kaDenotes the air gap thermal conductivity, W/(m deg.C).
And (4) conclusion: the thickness of the air gap has great influence on the total thermal resistance, and how to reduce the air gap through the adjustment of the width taper of the crystallizer provides a finding direction;
further, step 2, adjusting and testing the broadside taper, and determining the appropriate broadside taper, which is specifically as follows:
the method comprises the following steps: the taper is generally defined for a single sided crystallizer as:
b is the taper of the single-side crystallizer, WtThe width W of the upper opening of the crystallizerbThe width of the lower opening of the crystallizer;
secondly, the step of: setting the single-side broadside taper of the crystallizer as 0mm/0.5mm/1.0mm/1.5mm respectively, and performing adjustment tracking test;
③: the slab quality tracking and the crystallizer abrasion condition are comprehensively analyzed, the single-side taper of the inner arc and the outer arc of the wide edge of the crystallizer is more than 0.5mm, and the sum of the taper of the inner arc and the taper of the outer arc is between 1.5 and 2.0mm, which is most suitable.
Further, step 3, designing the gasket specifically as follows: establishing the relationship between the gasket and the broadside taper of the crystallizer, wherein the relationship conversion formula is as follows:
gasket0.5mmThe broadside taper is 1/0.28.
Further, step 4, reducing the influence of the corner seam on the width taper, specifically as follows:
the method comprises the following steps: the crystallizer cleaning mode is optimized by combining the TRIZ theory, a high-pressure water gun, a steel plate inserting tool and a scraper knife are adopted to clean the angle joint of the crystallizer in the production gap, the influence of the large angle joint on the width taper of the crystallizer is eliminated, and the precision of the width taper is ensured;
secondly, the step of: correcting the influence of the abrasion of the crystallizer copper plate on the broadside taper: after the crystallizer is used for a certain time, the copper plate at the lower part is abraded to different degrees, and when the steel passing amount of the crystallizer is respectively more than 6 ten thousand tons and more than 10 ten thousand tons, the broadside taper is tracked, measured and readjusted.
Further, step 5, measuring and optimizing the taper of the narrow side of the crystallizer, specifically as follows:
the method comprises the following steps: according to the vibration characteristic of the hydraulic plate spring, determining that the taper of the crystallizer is measured when the crystallizer is in vibration stop position to a low position;
secondly, the step of: measuring the taper of the narrow side of the crystallizer by using a taper instrument, and calibrating in time when the deviation is large to ensure that the taper deviation is within 0.5 mm;
③: considering that the taper of the crystallizer can deviate in the production process, and the deviation of the taper of the narrow side of the crystallizer and a standard value is in a positive deviation of 0 mm-0.5 mm.
Further, step 6, arc alignment control of the crystallizer:
the method comprises the following steps: cleaning and confirming the cleanliness of a foot roller of the crystallizer before arc alignment, and ensuring the accuracy of measurement;
secondly, the step of: completely releasing the stress of the copper plate and the foot roller and then carrying out arc alignment operation;
③: adjusting the positions of the eccentric wheels on the left side and the right side of the crystallizer: taking the outer arc as a reference, and simultaneously measuring the radian of the inner arc, so that the radian of the inner arc and the radian of the outer arc on the same side are prevented from deviating to the same direction at the same time;
fourthly, the method comprises the following steps: arc deviation of 4 measurement points is within +/-0.3 mm;
further, step 7, monitoring and adjusting the vibration of the crystallizer:
the method comprises the following steps: selecting typical vibration frequency and amplitude to carry out vibration detection and calibration;
ensuring that the vibration polarization of the crystallizer meets the standard through optimized adjustment: the invention relates to an improvement of the invention, wherein the polarization in the X direction is less than or equal to 0.15mm, the polarization in the Y direction is less than or equal to 0.2mm, the amplitude deviation is less than or equal to 3%, and the vibration frequency deviation is less than or equal to 2 times/min.
Compared with the prior art, the method has the advantages that the technical scheme is that the crystallizer is analyzed in the online use process, the actual use and experience record are combined, the optimization scheme of the broadside taper of the crystallizer is researched when a single factor is changed, and slab deviation angle cracks are obviously reduced. Meanwhile, the high-efficiency continuous casting production rhythm is ensured, and the floating of the nonmetallic inclusion is more favorable. According to the shrinkage characteristic of steel, the blank shell can be better contacted with the crystallizer copper plate, the heat transfer between the blank shell and the copper plate is improved, the lubrication is improved, the effect of reducing the longitudinal crack of the surface of a casting blank is achieved, meanwhile, the stress between the blank shell and the crystallizer copper plate is more uniform, and the abrasion of the crystallizer copper plate is reduced.
Drawings
FIG. 1 is a schematic view of an air gap distribution;
FIG. 2 is a single side crystallizer taper;
FIG. 3 is a shim dimension;
FIG. 4 is a plan view of the entire mold and taper measuring points;
FIG. 5 is a schematic view of crystallizer arc-alignment detection.
The specific implementation mode is as follows:
for the purpose of enhancing an understanding of the present invention, the present embodiment will be described in detail below with reference to the accompanying drawings.
Example 1: referring to fig. 1-5, a method of reducing off-angle cracking of a slab, the method comprising the steps of: step 1, analyzing the formation and distribution rule of a liquid/solid slag film and an air gap in a crystallizer:
in the production process, the covering slag is added on the liquid level at the top of the crystallizer, the covering slag in contact with molten steel is rapidly melted in a high-temperature state, and the melted covering slag flows into a gap between the crystallizer and a casting blank from a meniscus along with the vibration of the crystallizer. At the upper part of the crystallizer, the temperature of the copper plate is far lower than that of molten-state covering slag, and the covering slag is rapidly solidified at one side close to the copper plate and forms a glassy slag film under the strong cooling action of the crystallizer copper plate; along the horizontal direction, the slag film gradually evolves into a crystalline state along with the reduction of the cooling speed, and a solid-state slag film close to one side of the crystallizer is formed; due to the shrinkage of the mold flux in the solidification process, a large interface thermal resistance is formed between the crystallizer and the solid slag, and the thermal resistance changes along with the change of the thickness of the solid slag film. On the side close to the casting blank, the temperature of the casting blank is higher than the solidification temperature of the casting powder, so the casting powder is still in a liquid state, and a state of coexistence of a solid-liquid slag film is formed along the horizontal direction. With the progress of drawing, the heat of the casting blank is continuously transmitted to the crystallizer and taken away by cooling water, the surface temperature of the blank shell is continuously reduced, when the temperature of the casting blank is reduced to the solidification temperature of the covering slag, the liquid covering slag is completely solidified, and at the moment, a gap between the crystallizer and the casting blank is only filled with the solid covering slag. With a further reduction in temperature, the gap increases continuously under the combined action of the strand shrinkage and the mold powder shrinkage, whereupon no liquid mold powder flows in, the slag film detaches from the mold wall, and air gaps arise as a result. FIG. 1 is a schematic view and a distribution state of the mold flux and the air gap distribution in the mold.
The method comprises the following steps: model I (T)s>Tfsol)
When the surface temperature of the casting blank is higher than the solidification temperature of the covering slag, liquid slag and solid slag coexist in the slag channel, and according to the heat transfer characteristics of the liquid slag and the solid slag, the thermal resistance between the casting blank and the crystallizer is shown as a model I in figure 1.
Secondly, the step of: model II (T)s＝Tfsol)
When the surface temperature of the shell of the casting blank is reduced to the solidification temperature of the casting powder along with the downward movement of the casting blank, the liquid slag film just disappears, only a solid slag film exists in the gap between the crystallizer and the casting blank, and the thermal resistance is considered as shown in a model II in figure 1.
③: model III (T)s＜Tfsol)
The surface temperature of the shell is gradually reduced along with the continuous heat transfer of the casting blank, and when the surface temperature of the casting blank is lower than the solidification temperature of the casting powder, the clearance between the shell and the crystallizer is in a solid slag-air gap coexisting state, and the thermal resistance is shown by a model III in figure 1. Since the liquid slag film disappears and cannot be replenished continuously, and the solidification shrinkage of the mold flux is ignored in the present model, it is considered that the thickness of the solid slag film is maintained constant.
The air gap thickness is solved simultaneously by the following equation:
Tb＝Ts-q×Rs
Ra rad＝0.5δ(εf+εm)(Tm 2+Tb 2)(Tm+Tb)
wherein T isbTemperature, K, representing the solid slag/air gap interface; ra，Ra con，Ra radRespectively representing the total thermal resistance, the thermal conductivity thermal resistance and the radiation thermal resistance of the air gap, m2·℃/W；daRepresents the air gap thickness, m; kaDenotes the air gap thermal conductivity, W/(m deg.C).
And (4) conclusion: the thickness of the air gap has great influence on the total thermal resistance, and how to reduce the air gap through the adjustment of the width taper of the crystallizer provides a finding direction;
step 2, adjusting and testing the broadside taper, and determining the appropriate broadside taper;
the method comprises the following steps: the taper is generally defined for a single sided crystallizer as:
as shown in particular in fig. 2;
secondly, the step of: setting the single-side broadside taper of the crystallizer as 0mm/0.5mm/1.0mm/1.5mm respectively, and performing adjustment tracking test;
③: comprehensively analyzing the slab quality tracking and the crystallizer abrasion condition, wherein the single-side taper of the inner arc and the outer arc of the wide edge of the crystallizer is more than 0.5mm, and the sum of the taper of the inner arc and the taper of the outer arc is between 1.5 and 2.0 mm;
step 3, designing a gasket;
the method comprises the following steps: designing the size of the gasket according to the sizes of the crystallizer and the vibration frame, wherein the specific size is shown in figure 3;
secondly, the step of: establishing the relationship between the gasket and the broadside taper of the crystallizer, wherein the relationship conversion formula is as follows:
gasket0.5mm1/0.28 of broadside taper;
the method comprises the following steps: the crystallizer cleaning mode is optimized by combining the TRIZ theory, the angle joint of the crystallizer is cleaned by adopting a method of cleaning a high-pressure water gun, a steel plate inserting tool and a scraper knife in a production gap, and the influence of the large angle joint on the width surface taper of the crystallizer is eliminated, so that the precision of the width edge taper is ensured;
secondly, the step of: correcting the influence of the abrasion of the crystallizer copper plate on the broadside taper: after the crystallizer is used for a certain time, the copper plate at the lower part is abraded to different degrees, and when the steel passing amount of the crystallizer is respectively more than 6 ten thousand tons and more than 10 ten thousand tons, the broadside taper is tracked, measured and readjusted;
and 5, measuring and optimizing the taper of the narrow side of the crystallizer:
the method comprises the following steps: according to the vibration characteristic of the hydraulic plate spring, determining that the taper of the crystallizer is measured when the crystallizer is in vibration stop position to a low position;
secondly, the step of: measuring the taper of the narrow side of the crystallizer by using a taper instrument, and calibrating in time when the deviation is large to ensure that the taper deviation is within 0.5 mm;
③: considering that the taper of the crystallizer can deviate in the production process, and ensuring that the deviation of the taper of the narrow side of the crystallizer and a standard value is in a positive deviation of 0 mm-0.5 mm;
step 6, arc alignment control of the crystallizer:
the method comprises the following steps: cleaning and confirming the cleanliness of a foot roller of the crystallizer before arc alignment, and ensuring the accuracy of measurement;
secondly, the step of: completely releasing the stress of the copper plate and the foot roller and then carrying out arc alignment operation;
③: adjusting the positions of the eccentric wheels on the left side and the right side of the crystallizer: taking the outer arc as a reference, and simultaneously measuring the radian of the inner arc, so that the radian of the inner arc and the radian of the outer arc on the same side are prevented from deviating to the same direction at the same time;
fourthly, the method comprises the following steps: arc deviation of 4 measurement points is within +/-0.3 mm;
step 7, monitoring and adjusting the vibration of the crystallizer:
the method comprises the following steps: selecting typical vibration frequency and amplitude to carry out vibration detection and calibration;
ensuring that the vibration polarization of the crystallizer meets the standard through optimized adjustment: the polarization in the X direction is less than or equal to 0.15mm, the polarization in the Y direction is less than or equal to 0.2mm, the amplitude deviation is less than or equal to 3 percent, and the vibration frequency deviation is less than or equal to 2 times/min.
The concrete application is as follows:
firstly, measuring and adjusting the broadside taper:
1. feeding a new crystallizer on line: hoisting the crystallizer to the upper seat of the vibration frame of the crystallizer by using a travelling crane;
2. measuring the broadside taper of the crystallizer: measuring the width edge taper of the crystallizer by using a taper instrument, wherein the number of the inner arcs and the number of the outer arcs are respectively 3, the measuring points are shown in figure 4, and corresponding taper values are recorded;
3. the taper measurement requirement is as follows: 1.2.3 is a measuring point of the outer arc broad surface of the crystallizer, and 4.5.6 is a measuring point of the inner arc broad surface of the crystallizer. Wherein 1/4, 2/5 and 3/6 correspond to the inner arc and the outer arc, the copper plate of the inner cavity of the crystallizer is determined to be clean before measurement, and the taper of the position of the measurement point is measured by using a taper instrument;
4. adjusting the broadside taper: taking the measuring point 1/4 as an example, when the measured values are respectively 0.2/1.4mm, a gasket is added between the crystallizer on the left side of the inner arc of the crystallizer and the vibrating frame0.5mm2, dividing the blocks; width re-measurementThe side taper ensures that the taper of the single side of the inner arc and the outer arc of the wide side of the crystallizer is more than 0.5mm, and the sum of the taper of the inner arc and the taper of the outer arc is between 1.5 and 2.0 mm;
5. reduce the influence of angle seam to broadside tapering: cleaning the angle joint of the crystallizer by adopting a method of cleaning a high-pressure water gun, a steel plate inserting tool and a shovel cutter in a production gap, and eliminating the influence of large angle joint on the wide-surface taper of the crystallizer so as to ensure the precision of the wide-edge taper;
6. correcting the influence of the abrasion of the crystallizer copper plate on the broadside taper: after the crystallizer is used for a certain time, the copper plate at the lower part is abraded to different degrees, and when the steel passing amount of the crystallizer is respectively more than 6 ten thousand tons and more than 10 ten thousand tons, the broadside taper is tracked, measured and readjusted;
7. and (3) measuring and optimizing the taper of the narrow side of the crystallizer:
8. when the crystallizer operation mode is automatic, the vibration mechanism is influenced by the tension of the spring at the moment, the vibration stroke is in a free stop state (between a high position and a low position), different heights of vibration stops at east and west sides may exist, the taper measurement of the crystallizer has deviation, and the vibration mechanism is shown as the following figure 5;
9. the vibration mode of the crystallizer is changed into a manual mode, so that the vibration mechanisms on two sides of the crystallizer are located at low positions;
10. measuring the taper of the narrow side of the crystallizer by using a taper instrument, and calibrating in time when the deviation is large;
11. the deviation of the taper of the narrow side of the crystallizer and the standard value is within the positive deviation of 0 mm-0.5 mm;
12. arc alignment control of the crystallizer:
13. cleaning the arc measuring point by using a high-pressure water gun after final pouring, cleaning impurities on a foot roller of the crystallizer, and ensuring the accuracy of measurement;
the specific operation is as follows:
confirming the field environment before preparing to use a high-pressure cleaning machine water gun;
checking whether the connection of a power line and a water pipe of a water gun of the high-pressure cleaning machine is firm 30min before final pouring, pushing the water gun to the middle position of the two streams from the side of the working room station for placing, and connecting for use after the water gun is firmly fastened;
after the two flows are finally poured, before the high-pressure cleaning machine is used, a water inlet pipe (a quick connector) of a water gun of the high-pressure cleaning machine is connected with an on-site water pipe, a valve of the water inlet pipe is opened, a power supply is plugged into a socket, and whether a power supply signal of the high-pressure cleaning machine is normally displayed is checked;
during cleaning operation, the water pipe is pulled to the site in a tidy manner, the handle of the water gun trigger is tightly held by two hands, the water gun trigger is opened, the gun head faces to the crystallizer copper plate or the open place, people and electrical equipment are strictly forbidden, a 'start' button of the high-pressure cleaning machine is started, and cleaning is started;
when the floating objects are cleaned, people cannot be too close to the floating objects, the cleaning and blowing foreign objects are prevented from falling into sensitive positions such as eyes of people, the gun cannot be too far away when stubborn dirt is cleaned, and the cleaning is carried out by the mask;
when the water gun of the high-pressure cleaning machine is not used, a stop button is pressed in time, when the cleaning machine operates, the closing time of a water gun injection wrench cannot exceed 30 seconds, otherwise, the internal temperature of the cleaning machine is high, the automatic power-jump self-protection is realized, or a motor of the cleaning machine is burnt out;
when the high-pressure cleaning machine is not used, the water inlet pipe valve is timely closed, the machine is started to dewater, residual water in the pump, the pipe and the gun head is drained, then the power supply is pulled out, the power line and the water inlet pipe are pulled out and wound, and meanwhile, the water gun pipe is wound. Tidy in collection and timely push back to the original placement position;
the high-pressure cleaning machine is special cleaning equipment for crystallizer copper plates and angle joints, other equipment cannot be washed, and daily maintenance and maintenance are carried out by the day class.
14. Carrying out arc alignment operation 30min after final casting to completely release the stress of the copper plate and the foot roller;
15. the radian of the crystallizer is detected by using an arc plate, 4 measuring points are arranged, and the measuring points are all positioned at positions 100mm away from the narrow edge on the wide surface, and the specific operation is as shown in the following figure 5;
16. adjusting the positions of the eccentric wheels on the left side and the right side of the crystallizer: taking the outer arc as a reference, and simultaneously measuring the radian of the inner arc, so that the radian of the inner arc and the radian of the outer arc on the same side are prevented from deviating to the same direction at the same time;
17. arc deviation of 4 measurement points is within +/-0.3 mm;
18. monitoring and adjusting the vibration of the crystallizer:
19. detecting the vibration of the crystallizer by utilizing daily repair or overhaul time, placing the detector at the middle position of the outer arc of the crystallizer, and selecting typical vibration frequency and amplitude;
20. periodically monitoring the vibration, and detecting and adjusting the vibration of the crystallizer when the vibration device is abnormal or replaced;
firstly, the crystallizer is lifted away, and the vibration of the crystallizer is stopped. Changing the vibration mode of the crystallizer into the operation mode to be manual;
fixing a dial indicator to the center position of the single-side vibration mechanism to measure the stroke of the vibration mechanism, and simultaneously recording a measured value R and an electric display value S;
correcting the error between the displayed value and the actual value; the correction rate is calculated as D/S100%;
after the crystallizer is returned to the original position, the vibration is started and the vibration is measured on site;
and seventhly, ensuring that the vibration polarization of the crystallizer meets the reference through optimized adjustment: the polarization in the X direction is less than or equal to 0.15mm, the polarization in the Y direction is less than or equal to 0.2mm, the amplitude deviation is less than or equal to 3 percent, and the vibration frequency deviation is less than or equal to 2 times/min.
It should be noted that the above-mentioned embodiments are not intended to limit the scope of the present invention, and all equivalent modifications and substitutions based on the above-mentioned technical solutions are included in the scope of the present invention as defined in the claims.
Claims (8)
1. A method of reducing off-angle cracking of a slab, the method comprising the steps of:
step 1, analyzing the formation and distribution rule of a liquid/solid slag film and an air gap in a crystallizer:
step 2, adjusting and testing the broadside taper, and determining the appropriate broadside taper;
step 3, designing a gasket;
step 4, reducing the influence of the angle seam on the width taper;
and 5, measuring and optimizing the taper of the narrow side of the crystallizer:
step 6, arc alignment control of the crystallizer:
and 7, monitoring and adjusting the vibration of the crystallizer.
2. The method for reducing the slab off-angle cracks according to claim 1, wherein in the step 1, the formation and distribution rules of the liquid/solid slag film and the air gaps in the crystallizer are analyzed: the distribution of the covering slag and the air gap in the crystallizer is divided into 3 states:
the method comprises the following steps: model I (T)s>Tfsol)；
When the surface temperature of the casting blank is higher than the solidification temperature of the covering slag, liquid slag and solid slag coexist in the slag channel,
secondly, the step of: model II (T)s＝Tfsol)
When the surface temperature of the blank shell is reduced to the solidification temperature of the casting powder along with the downward movement of the casting blank, the liquid slag film just disappears, only a solid slag film exists in the gap between the crystallizer and the casting blank,
③: model III (T)s＜Tfsol)
The surface temperature of the blank shell is gradually reduced along with the continuous transmission of the heat of the casting blank, when the surface temperature of the casting blank is lower than the solidification temperature of the covering slag, the clearance between the blank shell and the crystallizer is in a solid slag-air gap coexisting state, and the air gap thickness is obtained by the simultaneous solution of the following equation:
Tb＝Ts-q×Rs
Ra rad＝0.5δ(εf+εm)(Tm 2+Tb 2)(Tm+Tb)
wherein T isbTemperature, K, representing the solid slag/air gap interface; ra，Ra con，Ra radRespectively representing the total thermal resistance, the thermal conductivity thermal resistance and the radiation thermal resistance of the air gap, m2·℃/W；daRepresents the air gap thickness, m; kaDenotes the air gap thermal conductivity, W/(m deg.C).
3. The method for reducing slab off-angle cracks according to claim 2, wherein in the step 2, the broadside taper adjustment test determines the appropriate broadside taper, and specifically comprises the following steps:
the method comprises the following steps: the taper is generally defined for a single sided crystallizer as:
b is the taper of the single-side crystallizer, WtThe width W of the upper opening of the crystallizerbThe width of the lower opening of the crystallizer;
secondly, the step of: setting the single-side broadside taper of the crystallizer as 0mm/0.5mm/1.0mm/1.5mm respectively, and performing adjustment tracking test;
③: the slab quality tracking and the crystallizer abrasion condition are comprehensively analyzed, the single-side taper of the inner arc and the outer arc of the wide edge of the crystallizer is more than 0.5mm, and the sum of the taper of the inner arc and the taper of the outer arc is between 1.5 and 2.0mm, which is most suitable.
4. The method for reducing slab off-angle cracks according to claim 3, wherein the step 3, gasket design, is as follows: establishing the relationship between the gasket and the broadside taper of the crystallizer, wherein the relationship conversion formula is as follows:
gasket0.5mmThe broadside taper is 1/0.28.
5. The method for reducing slab deviation angle cracks according to claim 3 or 4, wherein in the step 4, the influence of the angle seam on the broadside taper is reduced, and the method comprises the following specific steps:
the method comprises the following steps: the crystallizer cleaning mode is optimized by combining the TRIZ theory, a high-pressure water gun, a steel plate inserting tool and a scraper knife are adopted to clean the angle joint of the crystallizer in the production gap, the influence of the large angle joint on the width taper of the crystallizer is eliminated, and the precision of the width taper is ensured;
secondly, the step of: correcting the influence of the abrasion of the crystallizer copper plate on the broadside taper: after the crystallizer is used for a certain time, the copper plate at the lower part is abraded to different degrees, and when the steel passing amount of the crystallizer is respectively more than 6 ten thousand tons and more than 10 ten thousand tons, the broadside taper is tracked, measured and readjusted.
6. The method for reducing the slab off-angle cracks according to claim 5, wherein in the step 5, the measurement optimization of the taper of the narrow side of the crystallizer is carried out, and the method comprises the following specific steps:
the method comprises the following steps: according to the vibration characteristic of the hydraulic plate spring, determining that the taper of the crystallizer is measured when the crystallizer is in vibration stop position to a low position;
secondly, the step of: measuring the taper of the narrow side of the crystallizer by using a taper instrument, and calibrating in time when the deviation is large to ensure that the taper deviation is within 0.5 mm;
③: considering that the taper of the crystallizer can deviate in the production process, and the deviation of the taper of the narrow side of the crystallizer and a standard value is in a positive deviation of 0 mm-0.5 mm.
7. The method for reducing the slab off-angle cracks of claim 6, wherein step 6, the crystallizer controls the arc:
the method comprises the following steps: cleaning and confirming the cleanliness of a foot roller of the crystallizer before arc alignment, and ensuring the accuracy of measurement;
secondly, the step of: completely releasing the stress of the copper plate and the foot roller and then carrying out arc alignment operation;
③: adjusting the positions of the eccentric wheels on the left side and the right side of the crystallizer: taking the outer arc as a reference, and simultaneously measuring the radian of the inner arc, so as to avoid the radian of the inner arc and the outer arc on the same side from deviating to the same direction at the same time;
fourthly, the method comprises the following steps: the arc deviation of 4 measurement points is within +/-0.3 mm.
8. The method for reducing slab off-angle cracking of claim 6, wherein step 7 crystallizer vibration is monitored and adjusted:
the method comprises the following steps: selecting typical vibration frequency and amplitude to carry out vibration detection and calibration;
ensuring that the vibration polarization of the crystallizer meets the standard through optimized adjustment: the polarization in the X direction is less than or equal to 0.15mm, the polarization in the Y direction is less than or equal to 0.2mm, the amplitude deviation is less than or equal to 3 percent, and the vibration frequency deviation is less than or equal to 2 times/min.
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