CN114632919A - Method for treating surface scratches of continuous casting slab - Google Patents
Method for treating surface scratches of continuous casting slab Download PDFInfo
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- CN114632919A CN114632919A CN202210142410.4A CN202210142410A CN114632919A CN 114632919 A CN114632919 A CN 114632919A CN 202210142410 A CN202210142410 A CN 202210142410A CN 114632919 A CN114632919 A CN 114632919A
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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
- B22D11/20—Controlling or regulating processes or operations for removing cast stock
- B22D11/207—Controlling or regulating processes or operations for removing cast stock responsive to thickness of solidified shell
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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
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1226—Accessories for subsequent treating or working cast stock in situ for straightening strands
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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
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
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Abstract
The invention provides a method for processing continuous casting slab surface scratches, which comprises the following steps: step A: the position is piled up to judgement scale not shutting down, judge scale not shutting down and pile up the position and include: preliminarily judging whether the part with smaller strength stacked on the slab shell or the part with larger strength stacked on the slab shell is positioned at the position and the depth of the scratch on the surface of the slab; and B: and judging the iron scale accumulation position according to the current history record of each sector-shaped segment pulling-straightening roller of the continuous casting machine. The invention can take the accumulated iron scale out of the continuous casting machine, eliminate the surface scratch of the plate blank and keep the continuity of production.
Description
The application is as follows: application No.: 2020114050800, filing date: 12/3/2020, name: a method for treating scratches on the surface of a continuous casting slab is applied by divisional application.
Technical Field
The invention relates to the field of metallurgy, in particular to the field of continuous casting, and especially relates to a method for treating scratches on the surface of a continuous casting slab.
Background
When the slab caster is produced, high-temperature molten steel passes through the crystallizer to form a continuous casting billet, the outer part of which is a thin solid billet shell and the inner part of which is liquid. Due to the fact that the solid shell is thin, the situation that the surface of the solid shell is light and is scratched seriously, and even dents or cracks easily occurs in production.
Once the surface of the slab has scratches and depressions, in order to ensure the quality and the production safety of the slab, the prior art needs to stop the production of a continuous casting machine, search a continuous casting roller with poor rotation in a shutdown state and replace corresponding equipment. The treatment method has good safety, but the production organization of steel making and continuous casting is disturbed, the temperature of the molten steel is kept, the molten steel is returned, the service life of the tundish does not reach the standard, the production efficiency is low, and the time cost and the economic cost are improved.
In summary, the following problems exist in the prior art: when the slab caster is produced, once scratches and depressions appear on the surface of a slab, the continuous casting roller with the oxide scale accumulation position or poor rotation can be found only by stopping maintenance, molten steel is treated to be warm and returned to a furnace, and the service life of a tundish does not reach the standard.
Disclosure of Invention
The invention provides a method for treating scratches on the surface of a continuous casting slab, which aims to solve the problems that once scratches and depressions appear on the surface of the slab, a continuous casting roller with poor rotation due to the accumulation of iron scales can be found only by stopping for maintenance, and the service life of a tundish cannot reach the standard due to the temperature waiting and the furnace returning of molten steel caused by stopping for treatment.
Therefore, the invention provides a method for processing scratches on the surface of a continuous casting slab, which comprises the following steps of:
step A: the position is piled up to judgement scale not shutting down, judge scale not shutting down and pile up the position and include: preliminarily judging whether the part with smaller strength stacked on the slab shell or the part with larger strength stacked on the slab shell is positioned at the position and the depth of the scratch on the surface of the slab;
step E: according to the iron scale accumulation position, the machine is not stopped, the pulling speed is reduced, the cooling strength is increased, the stopping operation of a withdrawal and straightening machine is carried out, and the accumulated iron scale is embedded into a casting blank shell and then is taken out of a continuous casting machine.
Further, the step of judging the position of the accumulated iron scale without stopping the machine further comprises the following steps: and judging the iron scale accumulation position according to the current history record of each sector-shaped segment pulling-straightening roller of the continuous casting machine.
Further, the step of judging the position of the accumulated iron scale without stopping the machine further comprises the following steps: and judging the position of the iron scale accumulation according to the historical records of the vibration and the working noise of the frame of each fan-shaped section of the continuous casting machine.
Furthermore, a vibration detection device and a noise detection device are correspondingly added in each fan-shaped section of the continuous casting machine, numerical values are connected into a computer, historical records of the vibration and the working noise of the frame of each fan-shaped section of the continuous casting machine are checked, the blank drawing resistance is increased after the iron scales are stacked, and the vibration and the working noise of the fan-shaped section at the position where the iron scales are stacked obviously increase and are obviously larger than those of the fan-shaped sections at the adjacent positions. The vibration and the working noise of the fan-shaped section at the accumulation part of the iron scale obviously rise as follows: the vibration and working noise rise amplitude of the fan-shaped section at the oxide scale accumulation part are respectively more than 25% and more than 30%.
Further, in the step a, the iron scale deposition position where the iron scale is deposited on the portion of the slab shell with higher strength is specifically as follows: the depth of the scratch on the surface of the slab is less than 6mm, and the depth increase rate of the scratch is smaller along with the time extension after the scratch appears, namely the depth of the scratch is less than 8 mm/h, only the width is obviously increased, namely the width of the scratch is increased by more than 10 mm/h, and the position of the oxide scale accumulation is determined to be positioned at the horizontal section in the fan-shaped section of the continuous casting machine.
Further, in the step a, the part of the blank shell of the slab with smaller strength deposited by the iron scale is specifically: the depth of the scratches on the surface of the plate blank is more than or equal to 6mm, the depth increasing rate of the scratches is larger along with the time extension after the scratches appear, namely, the depth of the scratches is more than or equal to 8 mm/h, and the width of the scratches is also obviously increased, namely, the width of the scratches is increased by more than 10 mm/h, and the positions of the continuous casting rolls which rotate badly are positioned at the bending section, the arc section and the wide-face foot roll of the crystallizer in the fan-shaped section of the continuous casting machine.
Further, the air conditioner is provided with a fan,
the step B specifically comprises the following steps: after the scratch appears, the sector section of the pulling and straightening roller with gradually and obviously increased average current intensity is the iron scale accumulation position; the gradual and obvious increase of the average current intensity of the pulling and straightening roller is as follows: the rise amplitude of the average current intensity of the pulling and straightening roller reaches more than 20 percent,
if the current of each section does not rise obviously, the oxide scale is accumulated on the bending section without the pulling and straightening roller and the wide-face foot roller of the crystallizer.
Further, the reduction of the pulling rate specifically comprises: when the superheat degree of a tundish of a continuous casting machine is 20-30 ℃, the pulling speed can be reduced to 80% of the pulling speed in the conventional production according to the speed of 0.1m/min, and when the superheat degree of the tundish of the continuous casting machine is above 30 ℃, the pulling speed can be reduced to 60% -70% of the pulling speed in the conventional production according to the speed of 0.1 m/min; when the superheat degree of the tundish of the continuous casting machine is less than 20 ℃, the drawing speed is not reduced.
Further, the air conditioner is provided with a fan,
the increase of the cooling strength is specifically as follows: after the pulling speed is reduced, the secondary cooling water control mode of a wide-surface foot roller, an arc section or a bending section or a horizontal section of the crystallizer of the continuous casting machine is changed into manual control, and the water quantity is increased by 20-40%.
Further, the air conditioner is provided with a fan,
after judging the specific position of the continuous casting roll with poor rotation caused by the surface scratch of the continuous casting slab,
the development of the stopping operation of the withdrawal and straightening machine is specifically as follows: after the cooling strength is increased by 5min, the thickness of a blank shell of a casting blank is increased, the stopping operation of a withdrawal and straightening machine is carried out, the control mode of a stopper rod of a continuous casting machine is changed into manual operation, an operator closes the stopper rod, the withdrawal and straightening machine is stopped after the liquid level of a crystallizer is lowered, then the withdrawal and straightening machine is started again, the stopping operation process keeps the secondary cooling water at the continuous casting roll with the bad rotation of the continuous casting machine in manual control, the pulling and fixing accident caused by the bulging of the casting blank when the cooling is low is avoided, the control mode of the secondary cooling water at the continuous casting roll with the bad rotation of the continuous casting machine is changed into automatic control after the withdrawal and straightening machine is started for 30 seconds to 1min, the production is started at the pulling speed of 0.4-0.5 m/min, and the pulling speed is increased for 0.05m/min every 30 seconds until the pulling speed reaches the normal production pulling speed.
Further, the air conditioner is provided with a fan,
when the surface scratch of the continuous casting slab is judged to occur at the beginning of the horizontal segment, the method for processing the surface scratch of the continuous casting slab further comprises the following steps: after the withdrawal and straightening machine is stopped, if the accumulated iron scale is not taken out, and scratches on the surface of the plate blank still exist, the segment lifting operation can be carried out in the process of pulling speed increase after the stopping operation, so that the accumulated iron scale is taken out;
the segment lifting operation specifically comprises: after the withdrawal and straightening machine is stopped, if the accumulated iron scale is not taken out, the horizontal section of the accumulated iron scale can be manually lifted by 5-15 cm in the process of pulling speed lifting, after the accumulated iron scale reaches the next horizontal section, the next horizontal section is lifted and the previous horizontal section is pressed down, and the accumulated iron scale is taken out of the continuous casting machine in sequence.
Further, the air conditioner is provided with a fan,
and after the service life of the tundish reaches the standard, stopping the production of the continuous casting machine and replacing a new horizontal section, or a new bending section, a new arc section or a new wide-face foot roll of the crystallizer by using prepared spare parts.
The applicant found in production: when the continuous casting machine is used for production, the continuous casting roller clamps a casting blank and rotates along with the casting blank all the time, once the continuous casting roller rotates badly, iron oxide scales on the surface of the casting blank can be accumulated at the position of the continuous casting roller, and then the accumulated iron oxide scales press the casting blank to generate scratches. The position of the scale deposit can be found from the position of the poorly rotating continuous casting roll, that is, the position where the scratch occurs can be judged or vice versa.
Through the operation, the invention can independently or comprehensively judge the oxide scale accumulation position and the position of the continuous casting roller with poor rotation under the condition that the production line does not stop, the whole continuous casting process is not needed, the continuous casting device stops all the continuous casting device from the tundish to the crystallizer, after the oxide scale accumulation position and the position of the continuous casting roller with poor rotation are judged, the continuous casting device can adopt the processing measures of preparing the continuous casting roller with poor rotation and the like and not stopping to finish the blank drawing, and after the service life of the tundish reaches the standard, the continuous casting device stops the production and replaces new spare parts, thereby maintaining the production continuity, creating more preparation time for subsequent processing, improving the production efficiency, reducing the temperature of molten steel and returning the molten steel, and leading the service life of the tundish to be reasonably applied.
Furthermore, the invention can accurately judge the iron scale accumulation position, and when iron scales are accumulated in the horizontal section, 100 percent of the accumulated iron scales can be taken out of the continuous casting machine on line when the temperature of molten steel is enough; when the iron scale is accumulated on the wide-surface foot roller, the bending section and the arc section of the crystallizer, the probability of bringing the accumulated iron scale out of the continuous casting machine on line is over 90 percent when the temperature of molten steel is enough.
Detailed Description
The present invention will now be described in order to more clearly understand the technical features, objects, and effects of the present invention.
1. The method for searching the iron oxide scale accumulation position comprises the following steps: determining the position of the iron scale accumulation and the position of a continuous casting roller with poor rotation according to the position, the depth and the size of the scratch on the surface of the slab and the working vibration and the abnormal sound of the fan-shaped section of the continuous casting machine;
(1) the depth of the scratch on the surface of the plate blank is less than 6mm, the depth increasing rate of the scratch is smaller along with the time extension after the scratch appears, namely the depth of the scratch is less than 8 mm/h, only the width is obviously increased, namely the width of the scratch is increased by more than 10 mm/h, and at the moment, the position of the oxide scale accumulation is determined to be positioned at a horizontal section in a fan-shaped section of a continuous casting machine;
the depth of the scratches on the surface of the plate blank is more than or equal to 6mm, the depth increasing rate of the scratches is larger along with the time extension after the scratches appear, namely, the depth of the scratches is more than or equal to 8 mm/h, and the width of the scratches is also obviously increased, namely, the width of the scratches is increased by more than 10 mm/h, and the positions of the continuous casting rolls which rotate badly at the moment are positioned at the bending section, the arc-shaped section and the wide-face foot roll of the crystallizer in the fan-shaped section of the continuous casting machine.
(2) Checking the current history records of the straightening rollers of each fan-shaped section of the continuous casting machine, wherein the withdrawal resistance is increased after oxide scales are accumulated, and the average current intensity of the straightening rollers of the corresponding fan-shaped sections gradually rises after scratches appear; if the current of each section does not rise obviously, the oxide scale is accumulated on the bending section without the pulling and straightening roller and the wide-face foot roller of the crystallizer.
(3) Adding a corresponding vibration detection device and a corresponding noise detection device in each fan-shaped section of the continuous casting machine, connecting numerical values into a computer, checking historical records of rack vibration and working noise of each fan-shaped section of the continuous casting machine, increasing the blank drawing resistance after the iron scales are accumulated, and obviously increasing the vibration and the working noise of the fan-shaped section at the iron scale accumulation part and being obviously larger than the fan-shaped section at the adjacent position; if the vibration and working noise of each fan-shaped section are not obviously increased and are not obviously larger than those of the fan-shaped sections at the adjacent positions, the iron oxide scale is accumulated in the arc-shaped section in the closed space and the wide-surface foot roller of the crystallizer.
(4) If the fan-shaped section of the continuous casting machine is provided with the observation hole, a highlight flashlight is used for checking whether iron oxide sheets are accumulated between the continuous casting rollers of the fan-shaped section of the continuous casting machine.
(5) The above operations can be used alone or in combination to determine the specific position of the iron scale accumulation at the place where the strength of the shell is smaller or larger.
2. Method for treating wide-face foot roller and bent section of crystallizer by accumulating iron scale
(1) The wide-surface foot roller and the bent section of the crystallizer of the continuous casting machine are positioned in a closed space, the blank shell of a casting blank is thinnest and low in strength, scratches on the surface of the blank are easy to expand after oxide scales are accumulated, the risk of fracturing the blank shell of the casting blank is high, and relevant treatment measures, such as preparation of new bent sections and crystallizer spare parts, are required to be taken immediately and replaced when the continuous casting machine stops production.
(2) Reasonably reducing the pulling speed: the reduction of the drawing speed can increase the thickness of the blank shell and improve the strength, and is beneficial to taking out the accumulated iron scale from the continuous casting machine; when the superheat degree of a tundish of a continuous casting machine is 20-30 ℃, the pulling speed can be reduced to 80% of the pulling speed in the conventional production according to the speed of 0.1m/min, and when the superheat degree of the tundish of the continuous casting machine is above 30 ℃, the pulling speed can be reduced to 60% -70% of the pulling speed in the conventional production according to the speed of 0.1 m/min; when the superheat degree of the tundish of the continuous casting machine is less than 20 ℃, the drawing speed is not reduced.
(3) And (3) increasing the cooling strength: after the drawing speed is reduced, the secondary cooling water control mode of the wide-surface foot roller and the bending section of the crystallizer of the continuous casting machine is changed into manual control, the water quantity is increased by 20-40%, the cooling strength is increased, the thickness of a blank shell is increased, and the strength is improved.
(4) And (3) carrying out the shutdown operation of the withdrawal and straightening machine: after the cooling strength is increased by 5min, the casting blank shell thickness is increased, the shutdown operation can be carried out, the control mode of the stopper rod of the continuous casting machine is changed into manual operation, an operator closes the stopper rod, the withdrawal and straightening machine is stopped immediately after the liquid level of the crystallizer descends, and then the withdrawal and straightening machine is quickly started (the time from stopping the withdrawal and straightening machine to restarting the withdrawal and straightening machine is controlled within 2 seconds). The 'stopping operation' process keeps the secondary cooling water of the bending section of the continuous casting machine and the wide-face foot roll of the crystallizer to be manually controlled, and the pulling-out accident caused by the bulging of the casting blank when the cooling is low is avoided. And (3) after the withdrawal and straightening machine is started for 1min, converting the secondary cooling water control mode of the bending section of the continuous casting machine and the wide-surface foot roller of the crystallizer into automatic control, starting production at a pulling speed of 0.4-0.5 m/min, and increasing the pulling speed by 0.05m/min every 30 seconds until the pulling speed reaches the normal production pulling speed. And the stopping operation after the thickness of the casting blank shell is increased can be used for embedding the accumulated iron scale into the casting blank shell and then taking the casting blank shell out of the continuous casting machine.
(5) The shutdown operation of the withdrawal and straightening machine can form a 'heavy skin' (a reconnection mark when the surface of the plate blank is stopped in the crystallizer) on the surface of the plate blank, after the plate blank with the 'heavy skin' is discharged from the continuous casting machine after the operation, scratches on the surface of the plate blank disappear, and after the service life of the tundish reaches the standard, the production of the continuous casting machine is stopped and a new bending section and the crystallizer are replaced; if the surface scratch of the slab with the 'heavy slab' still does not disappear after the slab exits from the continuous casting machine, repeating the operations from (1) to (4) once, and if the scratch still exists, stopping the production of the continuous casting machine and replacing a new bending section and a new crystallizer.
3. Method for processing iron scale accumulated on arc-shaped section
(1) The casting blank shell of the arc-shaped section of the continuous casting machine has a certain thickness, the strength is improved compared with that of a bent section, the scratch on the surface of a plate blank is slowly expanded after oxide scales are accumulated, the risk of fracturing the casting blank shell basically does not exist, the risk of judging waste after the scraping of the casting blank is too deep exists, and relevant treatment measures are taken immediately. And a new arc segment spare part is prepared and replaced when the continuous casting machine stops production.
(2) Reasonably reducing the pulling speed: the reduction of the drawing speed can increase the thickness of the blank shell and improve the strength, and is beneficial to taking out the accumulated iron scale from the continuous casting machine; when the superheat degree of a tundish of a continuous casting machine is 20-30 ℃, the pulling speed can be reduced to 80% of the pulling speed in the conventional production according to the speed of 0.1m/min, and when the superheat degree of the tundish of the continuous casting machine is above 30 ℃, the pulling speed can be reduced to 60% -70% of the pulling speed in the conventional production according to the speed of 0.1 m/min; when the superheat degree of the tundish of the continuous casting machine is less than 20 ℃, the pulling speed is not reduced.
(3) And (3) increasing the cooling strength: after the pulling speed is reduced, the secondary cooling water control mode of the wide-face foot roller, the bent section and the arc section of the crystallizer, which are upward at the oxide scale accumulation position of the continuous casting machine, is changed into manual control, the water quantity is increased by 20% -40%, the water quantity is increased smaller when the water quantity is closer to the crystallizer, the water quantity is increased larger when the water quantity is closer to the oxide scale accumulation position, the cooling strength can be increased, the thickness of a blank shell is increased, the strength is improved, and the pulling-out accident caused by too low temperature of a casting blank can be avoided.
(4) And (3) carrying out the shutdown operation of the withdrawal and straightening machine: after the cooling strength is increased by 5min, the thickness of the blank shell of the casting blank is increased, the shutdown operation can be started, the control mode of the stopper of the continuous casting machine is changed into manual operation, an operator closes the stopper, the withdrawal and straightening machine is stopped immediately after the liquid level of the crystallizer is reduced, and then the withdrawal and straightening machine is started quickly. The 'stopping operation' process keeps the secondary cooling water of the wide-surface foot roll, the bending section and the arc section of the crystallizer of the continuous casting machine to be manually controlled, and the pulling-out accident caused by the bulging of the casting blank when the cooling is low is avoided. And (3) after the withdrawal and straightening machine is started for 30 seconds, converting the corresponding secondary cooling water control mode of the continuous casting machine into automatic control, starting production at a pulling speed of 0.4-0.5 m/min, and increasing the pulling speed by 0.05m/min every 30 seconds until the pulling speed reaches the normal production pulling speed. And the stopping operation after the thickness of the casting blank shell is increased can be used for embedding the accumulated iron scale into the casting blank shell and then taking the casting blank shell out of the continuous casting machine.
(5) The stopping operation of the withdrawal and straightening machine can form 'heavy skin' on the surface of the slab, after the slab with the 'heavy skin' is discharged from the continuous casting machine after the operation, the scratches on the surface of the slab disappear, and after the service life of the tundish reaches the standard, the production of the continuous casting machine is stopped and a new arc-shaped section is replaced; if the surface scratches of the slab with the 'heavy skin' still do not disappear after the slab exits from the continuous casting machine, repeating the operations (1) to (4) once, if the scratches still exist and exceed the standard, judging to be waste, stopping the production of the continuous casting machine and replacing a new arc-shaped section.
4. Method for processing iron scale accumulated on horizontal section
(1) The casting blank shell of the horizontal section of the continuous casting machine is thick, the horizontal section close to the outlet of the casting machine even the casting blank is solidified, the strength is high, the scratch on the surface of the plate blank is slowly expanded after the oxide scales are accumulated, the risk of cracking the casting blank shell is avoided, the risk of judging waste after the scraping of the casting blank is too deep is also generated, and relevant treatment measures are taken immediately. And a new spare part for the horizontal section is prepared and replaced when the continuous casting machine stops production.
(2) Reasonably reducing the pulling speed: the reduction of the drawing speed can increase the thickness of the blank shell and improve the strength, and is beneficial to taking out the accumulated iron scale from the continuous casting machine; when the superheat degree of a tundish of a continuous casting machine is 20-30 ℃, the pulling speed can be reduced to 80% of the pulling speed in the conventional production according to the speed of 0.1m/min, and when the superheat degree of the tundish of the continuous casting machine is above 30 ℃, the pulling speed can be reduced to 60% -70% of the pulling speed in the conventional production according to the speed of 0.1 m/min; when the superheat degree of the tundish of the continuous casting machine is less than 20 ℃, the pulling speed is not reduced.
(3) And (3) increasing the cooling strength: after the pulling speed is reduced, the secondary cooling water control mode of a wide-face foot roller, a bending section, an arc section and a horizontal section of the crystallizer, which are upward at the oxide scale accumulation position of the continuous casting machine, is changed into manual control, the water quantity is increased by 20-40%, the water quantity is increased smaller when the water quantity is closer to the crystallizer, the water quantity is increased when the water quantity is closer to the oxide scale accumulation position, the cooling strength can be increased, the thickness of a blank shell is increased, the strength is improved, and the pulling-out accident caused by too low temperature of a casting blank can be avoided.
(4) Carrying out the stopping operation of the withdrawal and straightening machine: after the cooling strength is increased by 5min, the thickness of the blank shell of the casting blank is increased, the shutdown operation can be started, the control mode of the stopper of the continuous casting machine is changed into manual operation, an operator closes the stopper, the withdrawal and straightening machine is stopped immediately after the liquid level of the crystallizer is reduced, and then the withdrawal and straightening machine is started quickly. The 'stopping operation' process keeps the secondary cooling water of the wide-surface foot roll, the bending section, the arc section and the horizontal section of the crystallizer of the continuous casting machine to be manually controlled, and the pulling-out accident caused by the bulging of the casting blank when the cooling is low is avoided. And (3) after the withdrawal and straightening machine is started for 30 seconds, converting the corresponding secondary cooling water control mode of the continuous casting machine into automatic control, starting production at a pulling speed of 0.4-0.5 m/min, and increasing the pulling speed by 0.05m/min every 30 seconds until the pulling speed reaches the normal production pulling speed. And the stopping operation after the thickness of the casting blank shell is increased can be used for embedding the accumulated iron scale into the casting blank shell and then taking the casting blank shell out of the continuous casting machine.
(5) After the withdrawal and straightening unit is stopped, if the accumulated iron scale is taken out and scratches on the surface of the plate blank disappear, stopping the production of the continuous casting machine and replacing a new horizontal section after the service life of the tundish reaches the standard; if the accumulated iron scale is not taken out and the scratch on the surface of the plate blank still exists, the 'segment lifting operation' can be carried out in the process of pulling speed lifting after the parking operation, so that the accumulated iron scale is taken out.
(6) Carrying out segment lifting operation: after the withdrawal and straightening machine is stopped, the solidification tail end of the casting blank moves towards the crystallizer, and the thickness of the casting blank shell is enough. If the accumulated iron scale is not taken out, the horizontal section of the iron scale accumulation part can be manually lifted by 5-15 cm in the process of pulling speed lifting, the iron scale is lifted up a little when being accumulated thick, and the iron scale is lifted up a little when being accumulated little. After the accumulated iron scale reaches the next horizontal section, the next horizontal section is lifted and the previous horizontal section is pressed down, and the accumulated iron scale can be taken out of the continuous casting machine in sequence. And (4) taking out the accumulated iron oxide scales, enabling scratches on the surface of the plate blank to disappear, stopping the production of the continuous casting machine and replacing a new horizontal section after the service life of the tundish reaches the standard.
Example (c):
the continuous casting machine is a straight crystallizer continuous bending and continuous straightening arc-shaped continuous casting machine, the continuous casting machine is composed of a crystallizer, 1 bending section (0 section), 8 arc-shaped sections (1-8 sections) and 5 horizontal sections (9-13 sections), the production section is 220mm x 1500mm, and scratches are found on the surface of a plate blank when the 8 th furnace steel of a tundish is produced.
1. Confirmation of iron scale deposition position (scratch occurrence position)
(1) The depth of the scratch is 4mm, the width of the scratch is 20mm, the depth increasing rate of the scratch is 5 mm/h along with the time extension after the scratch appears, and the width is 12 mm/h, which indicates that the iron scale is accumulated on the part with larger strength of the slab shell, and the possibility of a horizontal section in the fan-shaped section of the continuous casting machine is higher.
(2) And (3) looking up the current history record of the withdrawal and straightening rolls at the horizontal section of the continuous casting machine, and finding that the average current intensity of the withdrawal and straightening rolls at 10 sections gradually rises by 25 percent after the occurrence of scratches.
(3) By checking the history of the vibration and the working noise of the frame of each sector section of the continuous casting machine, the vibration and the working noise of 10 sections are obviously increased by 30 percent and 40 percent respectively and are obviously larger than the adjacent sector section.
(4) The observation holes on the fan-shaped section of the continuous casting machine are inspected by using a highlight flashlight, and the 10-section 2 nd roller does not rotate and has iron oxide scales to be accumulated.
2. Processing method
(1) The maintenance personnel are notified of the readiness of new horizontal segment replacement parts for replacement when the caster is stopped from production.
(2) Reasonably reducing the pulling speed: the reduction of the drawing speed can increase the thickness of the blank shell and improve the strength, and is beneficial to taking out the accumulated iron scale from the continuous casting machine; at the moment, when the superheat degree of the tundish is 25 ℃, the pulling speed in the conventional production is 1.5m/min, and the pulling speed is reduced to 1.2m/min at the first gear of 0.1 m/min.
(3) And (3) increasing the cooling strength: after the drawing speed is reduced, the secondary cooling water control mode of the wide-surface foot roll, the bending section, the arc section and the horizontal section of the crystallizer with the upward 10 sections of the continuous casting machine is changed into manual control, the water amount is respectively increased by 20%, 25%, 30% and 40%, the cooling strength is increased, the thickness of a blank shell is increased, the strength is improved, and the drawing failure caused by the over-low temperature of a casting blank can be avoided.
(4) And (3) carrying out the shutdown operation of the withdrawal and straightening machine: and (3) starting parking operation after the cooling strength is increased by 5min, switching the control mode of the stopper of the continuous casting machine into manual operation, closing the stopper by an operator, stopping the withdrawal and straightening unit immediately after the liquid level of the crystallizer is reduced, and then quickly starting the withdrawal and straightening unit. The 'stopping operation' process keeps the secondary cooling water of the wide-face foot roll, the bending section, the arc section and the horizontal section of the crystallizer of the continuous casting machine to be manually controlled, and avoids the pulling accident caused by the bulging of the casting blank when the cooling is low. And after the withdrawal and straightening unit is started for 30 seconds, the corresponding secondary cooling water control mode of the continuous casting machine is converted into automatic control, the production is started at the drawing speed of 0.4m/min, and the drawing speed is increased by 0.05m/min every 30 seconds until the drawing speed reaches 1.5 m/min.
(5) After the withdrawal and straightening machine is stopped, the observation holes in the fan-shaped section of the continuous casting machine are inspected by using a strong light flashlight, so that the accumulated iron oxide scales are brought out, scratches on the surface of a plate blank produced subsequently disappear, and the scratches are successfully treated.
(6) And stopping the production of the continuous casting machine and replacing a new horizontal section after the service life of the tundish reaches the standard. Before the continuous casting machine stops production, the tundish and the crystallizer are still in a production state, so the method can bring accumulated iron scales out of the continuous casting machine, eliminate surface scratches of a plate blank, maintain the production continuity, create more preparation time for subsequent treatment, improve the production efficiency, reduce the waiting temperature of molten steel, return the molten steel and reasonably apply the service life of the tundish.
The above description is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention. In order that the components of the present invention may be combined without conflict, it is intended that all equivalent changes and modifications made by those skilled in the art without departing from the spirit and principles of the present invention shall fall within the protection scope of the present invention.
Claims (6)
1. The method for processing the surface scratches of the continuous casting slab is characterized by comprising the following steps of:
step A: the position is piled up to judgement scale not shutting down, judge scale not shutting down and pile up the position and include: preliminarily judging whether the part with smaller strength stacked on the slab shell or the part with larger strength stacked on the slab shell is positioned at the position and the depth of the scratch on the surface of the slab;
step E: according to the iron scale accumulation position, the machine is not stopped, the pulling speed is reduced, the cooling strength is increased, the stopping operation of a withdrawal and straightening machine is carried out, and the accumulated iron scale is embedded into a casting blank shell and then is taken out of a continuous casting machine.
The step B of judging the position of the accumulated iron scale without stopping the machine further comprises the following steps: judging the position of the iron scale accumulation according to the current history record of each sector-shaped segment pulling-straightening roller of the continuous casting machine;
the reduction of the pulling speed is specifically as follows: when the superheat degree of a tundish of a continuous casting machine is 20-30 ℃, the pulling speed can be reduced to 80% of the pulling speed in the conventional production according to the speed of 0.1m/min, and when the superheat degree of the tundish of the continuous casting machine is above 30 ℃, the pulling speed can be reduced to 60% -70% of the pulling speed in the conventional production according to the speed of 0.1 m/min; when the superheat degree of the tundish of the continuous casting machine is less than 20 ℃, the drawing speed is not reduced.
2. The method for processing scratches on the surface of a continuously cast slab as set forth in claim 1, wherein said judging the locations of the scales deposited without stopping further comprises the step of C: and judging the position of the iron scale accumulation according to the historical records of the vibration and the working noise of the frame of each fan-shaped section of the continuous casting machine.
3. The method for treating surface scratches of a continuous cast slab according to claim 1, wherein,
the step B specifically comprises the following steps: after the scratch appears, the sector section of the pulling and straightening roller with gradually and obviously increased average current intensity is the iron scale accumulation position;
if the current of each section does not rise obviously, the oxide scale is accumulated on the bending section without the pulling and straightening roller and the wide-face foot roller of the crystallizer.
4. The method for treating surface scratches of a continuous cast slab according to claim 1, wherein,
the increased cooling strength is specifically: after the pulling speed is reduced, the secondary cooling water control mode of a wide-surface foot roller, an arc section or a bending section or a horizontal section of the crystallizer of the continuous casting machine is changed into manual control, and the water quantity is increased by 20-40%.
5. The method for treating surface scratches of a continuous cast slab according to claim 1, wherein,
after judging the specific position of the continuous casting roll with poor rotation caused by the surface scratch of the continuous casting slab,
the development of the stopping operation of the withdrawal and straightening machine is specifically as follows: after the cooling strength is increased by 5min, the thickness of a blank shell of a casting blank is increased, the stopping operation of a withdrawal and straightening machine is carried out, the control mode of a stopper rod of a continuous casting machine is changed into manual operation, an operator closes the stopper rod, the withdrawal and straightening machine is stopped after the liquid level of a crystallizer is lowered, then the withdrawal and straightening machine is started again, the stopping operation process keeps the secondary cooling water at the continuous casting roll with the bad rotation of the continuous casting machine in manual control, the pulling and fixing accident caused by the bulging of the casting blank when the cooling is low is avoided, the control mode of the secondary cooling water at the continuous casting roll with the bad rotation of the continuous casting machine is changed into automatic control after the withdrawal and straightening machine is started for 30 seconds to 1min, the production is started at the pulling speed of 0.4-0.5 m/min, and the pulling speed is increased for 0.05m/min every 30 seconds until the pulling speed reaches the normal production pulling speed.
6. The method for treating surface scratches of a continuous cast slab according to claim 1, wherein,
when the continuous casting slab surface scratch is judged to occur in the initial horizontal segment, the continuous casting slab surface scratch processing method further comprises the following steps: after the withdrawal and straightening machine is stopped, if the accumulated iron scale is not taken out, and scratches on the surface of the plate blank still exist, the segment lifting operation can be carried out in the process of pulling speed increase after the stopping operation, so that the accumulated iron scale is taken out;
the segment lifting operation specifically comprises: after the withdrawal and straightening unit stops operating, if the accumulated iron scale is not taken out, the horizontal section of the accumulated part of the iron scale can be manually lifted by 5-15 cm in the process of pulling speed lifting, after the accumulated iron scale reaches the next horizontal section, the next horizontal section is lifted and the previous horizontal section is pressed down, and the accumulated iron scale is taken out of the continuous casting machine in sequence.
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| CN112692248B (en) | 2022-03-11 |
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