CN115608944A - Method for uniformly regulating and controlling solidification structure of casting blank - Google Patents
Method for uniformly regulating and controlling solidification structure of casting blank Download PDFInfo
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- CN115608944A CN115608944A CN202211184400.3A CN202211184400A CN115608944A CN 115608944 A CN115608944 A CN 115608944A CN 202211184400 A CN202211184400 A CN 202211184400A CN 115608944 A CN115608944 A CN 115608944A
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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
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
Abstract
The invention discloses a method for uniformly regulating and controlling a casting blank solidification structure, which belongs to the technical field of ferrous metallurgy, and is characterized in that preset parameters are set, and continuous casting equipment is operated; working condition information of continuous casting equipment in the running process is read in real time, and running parameters of a crystallizer and a secondary cooling section are adjusted in time through a PLC control system, so that each section of a casting blank is cooled to a target temperature; the regulation and control method is simple, the h area and the j area of the secondary cooling section still keep certain spraying strength, the structure air suction system timely removes excessive hot steam, compared with the independent regulation and control of cooling strength, the regulation and control difficulty is favorably reduced, the 'black mark' on the surface of the casting blank can be effectively prevented, the cooling processes of the upper surface and the lower surface of the casting blank in the secondary cooling section are favorably kept consistent, the central high-temperature area of the casting blank is positioned in the center of the section, the temperature return processes of the upper surface and the lower surface of the casting blank are favorably kept uniform and consistent during air cooling forging, the generation of internal cracks is reduced, the phenomenon of head splitting of the casting blank in the rolling process is prevented, and the yield of the casting blank is favorably increased.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for uniformly regulating and controlling a casting blank solidification structure.
Background
The steel is iron-carbon alloy, the solidification of the molten steel is completed in a certain temperature range, and the solidification is completed in a resin crystal growth mode because the solute generates overcooling in distribution, namely the solidification is within a certain range and is not positioned in a plane. The macrostructure of a cast slab generally consists of three regions, namely a superficial fine crystalline region, a columnar crystalline region, and a central coarse equiaxed crystalline region. The fine grain area on the surface layer is formed by a layer of fine equiaxial crystal grain area formed on the surface of the cold mould wall by generating large supercooling degree and non-uniform nucleation effect during pouring; the columnar crystal area is formed by that the temperature of the mold wall rises, the crystallization releases latent heat, the super-cooling degree of the liquid at the front edge of the fine crystal area is reduced, the nucleation is difficult, and the directional heat dissipation of the mold wall is added, so that the existing crystal grows along the direction opposite to the heat dissipation direction; the central coarse equiaxed crystal area is formed by continuous release of crystallization latent heat, continuous reduction of heat dissipation speed, stopping growth of columnar crystals, and forming a plurality of equiaxed crystals with larger sizes in a non-uniform nucleation mode under the action of impurities when the core liquid is completely cooled to be below the actual crystallization temperature.
The quality and performance of the casting blank are closely related to the solidification structure of the casting blank, and mainly depend on the proportion of columnar crystal areas and equiaxed crystal areas and the size of crystal grains. Casting defects of the casting blank are of various types, and are commonly shrinkage cavity, porosity, segregation, slag inclusion, white point, crack and the like, which damage the performance of the casting blank.
The solidification structure of the casting blank is accelerated and cooled in the second cooling section, in order to ensure that the casting blank is cooled uniformly, the foot roll section of the second cooling section adopts a full water cooling mode, the rest sections are air-water cooling modes, the cooling strength of the lower side of the casting blank is low, because the area of the casting blank per se can limit the steam dissipation, the overlarge spraying strength can be limited by the thermal resistance in the casting blank, the utilization efficiency of cooling water is reduced, even the surface of the casting blank is subjected to 'black mark', and the casting blank is cooled unevenly. Because the solidification and cooling effect of the casting blank is influenced by factors such as cooling strength, pulling speed and the like, the regulation and control difficulty is higher.
In the cooling process, the central temperature of the casting blank is still high, uneven cooling can cause the first cooling effect on all parts of the surface of the casting blank, the overlarge cooling strength or uneven cooling among all sections can cause the surface temperature of the casting blank to periodically rise, so that the shell of the casting blank expands, when the tensile stress applied to the solidification front exceeds the high-temperature allowance and critical strain of the casting blank, internal cracks along a columnar crystal boundary can occur between the surface and the center of the casting blank, and when the internal cracks are serious, the head splitting phenomenon can occur in the rolling process of the casting blank, the yield of steel rolling is reduced, and even steel rolling equipment is damaged.
In order to ensure that the casting blank can be uniformly cooled in the secondary cooling section and facilitate simultaneous temperature return everywhere, a method for uniformly regulating and controlling the solidification structure of the casting blank is provided.
Disclosure of Invention
The invention aims to provide a method for uniformly regulating and controlling a casting blank solidification structure, which aims to solve the problems in the background technology.
The purpose of the invention can be realized by the following technical scheme:
a method for uniformly regulating and controlling a casting blank solidification structure comprises the following steps:
the method comprises the following steps: setting preset parameters and operating continuous casting equipment;
step two: and (3) reading working condition information of the continuous casting equipment in the running process in real time, and adjusting the running parameters of the crystallizer and the secondary cooling section in time through a PLC (programmable logic controller) control system to cool each section of the casting blank to a target temperature.
The continuous casting equipment comprises a steel ladle, a tundish, a crystallizer, a secondary cooling section and an air cooling section; the superheat degree of the molten steel in the steel ladle is 10-30 ℃, the superheat degree of the tundish is 20-30 ℃, and the cooling water flow of the crystallizer is 140-150m 3 And h, the moving speed of the casting blank of the secondary cooling section is 25-30cm/s.
The crystallizer is provided with an electromagnetic flow control device for controlling the flow speed of the molten steel, the frequency of the electromagnetic flow control device is 350-450Hz, and the current is 350 +/-150A; when the moving speed of the casting blank is more than 30cm/s, reducing the current of the electromagnetic current control device; and when the moving speed of the casting blank is less than 25cm/s, the current of the electromagnetic current control device is increased.
The casting blank moves between the clamping rollers at two sides of the second cooling section, the second cooling section starts from the outlet of the crystallizer, the front side of the casting blank is sequentially divided into an area a, an area b, an area c, an area g and an area i, and the rear side of the casting blank is correspondingly divided into an area d, an area e, an area f, an area h and an area j; the areas a, b, c, d, e and f are provided with water outlet nozzles, and water is supplied by a first water distribution system in a full-water cooling mode; the g area, the i area, the h area and the j area are provided with high-pressure atomizing nozzles, water is supplied through a second water distribution system, a gas-water cooling mode is adopted, a plurality of air suction channels are further arranged in the h area and the j area in an array mode, and the solidification temperature of the casting blank is controlled in an auxiliary mode through an air suction system.
The air suction system comprises a high-pressure vortex fan and a heat exchange box, wherein an air inlet of the high-pressure vortex fan is connected with the heat exchange box through a first collection air channel, and one end, far away from the first collection air channel, of the heat exchange box is connected with a plurality of air suction air channels of corresponding sections through a second collection air channel; one end of the heat exchange box, which is close to the second air collecting channel, is provided with a heat exchange coil for recovering heat, so that the heat utilization efficiency is increased, and the high-pressure vortex fan is prevented from being damaged by overhigh heat; the first collecting air duct and the second collecting air duct are arranged in the heat exchange box, the first collecting air duct and the second collecting air duct are arranged in the heat exchange box in a staggered mode, the gas-liquid separation effect is achieved, and the liquid discharge pipelines for discharging condensate liquid are arranged at the bottom of the heat exchange box.
The invention has the beneficial effects that:
the method for uniformly regulating the solidification structure of the casting blank is simple, and the front section of the secondary cooling section adopts full water cooling, so that the cooling speed is increased, secondary dendrites are reduced, and the solidification structure of the casting blank is refined; the secondary cooling section h area and the secondary cooling section j area still keep certain spraying strength, the structure air suction system timely removes excessive hot steam, and compared with the independent control of cooling strength, the secondary cooling section h area and the secondary cooling section j area are favorable for reducing the control difficulty, can effectively prevent the surface of a casting blank from generating black marks, and are favorable for keeping the cooling processes of the upper surface and the lower surface of the casting blank in the secondary cooling section consistent, so that the central high-temperature area of the casting blank is positioned in the center of the section, the tempering processes of the upper surface and the lower surface of the casting blank in the air cooling forging process are kept uniform, the generation of internal cracks is reduced, the phenomenon of head splitting of the casting blank in the rolling process is prevented, and the yield of the casting blank is increased.
Drawings
The invention will be further described with reference to the accompanying drawings.
FIG. 1 is a graph of casting slab surface position-temperature in example 2 of the present invention;
FIG. 2 is a graph of surface position-temperature of a cast slab in comparative example 1 of the present invention;
FIG. 3 is a graph of casting slab surface position-temperature in comparative example 2 of the present invention;
FIG. 4 is a schematic view of the construction of the continuous casting apparatus of the present invention;
FIG. 5 is a schematic structural view of a second cooling stage and an air cooling stage of the present invention;
fig. 6 is a schematic structural view of the suction system of the present invention.
In the figure: 1. a ladle; 2. a tundish; 3. a crystallizer; 4. a second cooling section; 5. an air cooling section; 6. a high pressure vortex fan; 7. a water outlet nozzle; 8. a high pressure atomizing nozzle; 9. an air suction duct; 41. a first water distribution system; 61. a first collection duct; 62. a second collection duct; 63. a heat exchange coil; 64. a first baffle plate; 65. a second baffle; 66. a liquid discharge pipeline.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 4-6, the continuous casting equipment includes a ladle 1, a tundish 2, a crystallizer 3, a secondary cooling section 4 and an air cooling section 5, and each section of the continuous casting equipment is provided with a continuous temperature measuring system; the crystallizer 3 is provided with an electromagnetic flow control device for controlling the flow speed of the molten steel; the casting blank moves between the clamping rollers at two sides of the second cooling section 4, the front side of the casting blank is sequentially divided into a region a, a region b, a region c, a region g and a region i from the outlet of the crystallizer 3, and the rear side of the casting blank is correspondingly divided into a region d, a region e, a region f, a region h and a region j.
The areas a, b, c, d, e and f are provided with water outlet nozzles 7, and water is supplied by a first water distribution system 41 in a full-water cooling mode; the g area, the i area, the h area and the j area are provided with high-pressure atomizing nozzles 8, water is supplied through a second water distribution system, and a gas-water cooling mode is adopted; each section is provided with a stop valve for controlling the flow of cooling water, and the j area is also provided with a plurality of air suction ducts 9 in an array manner, and the solidification temperature of the casting blank is controlled in an auxiliary manner through an air suction system.
The air suction system comprises a high-pressure vortex fan 6 and a heat exchange box, wherein an air inlet of the high-pressure vortex fan 6 is connected with the heat exchange box through a first collection air channel 61, and one end, far away from the first collection air channel 61, of the heat exchange box is connected with an air suction air channel 9 of a corresponding section through a second collection air channel 62; one end of the heat exchange box, which is close to the second air collecting duct 62, is provided with a heat exchange coil 63 for recovering heat, so that the heat utilization efficiency is increased, and the high-pressure vortex fan 6 is prevented from being damaged by overhigh heat; a plurality of first baffles 64 and second baffles 65 are arranged at one end of the heat exchange box close to the first air collecting duct 61 in a staggered mode, the first baffles 64 are fixed to the upper portion of the heat exchange box, the second baffles 65 are fixed to the lower portion of the heat exchange box and play a role in gas-liquid separation, and a plurality of liquid drainage pipelines 66 for draining condensate are arranged at the bottom of the heat exchange box.
The continuous casting equipment is in telecommunication connection with a PLC control system, and all parameters are regulated and controlled by the PLC control system.
Example 1
Taking GCr15 steel with the production specification of 180mm multiplied by 220mm as an example, the preset parameters ensure that the superheat degree of the molten steel in a steel ladle 1 is 10-30 ℃, the superheat degree of a tundish 2 is 20-30 ℃, and the cooling water flow of a crystallizer 3 is 140-150m 3 /h。
The crystallizer 3 is provided with an electromagnetic flow control device for controlling the flow speed of molten steel, the moving speed of a casting blank of the secondary cooling section 4 is 25-30cm/s, and when the moving speed of the casting blank is more than 30cm/s, the current of the electromagnetic flow control device is reduced; and when the moving speed of the casting blank is less than 25cm/s, the current of the electromagnetic current control device is increased. The frequency range of the electromagnetic current control device is 350-450Hz, and the current range is 200-500A.
Example 2
Setting target temperatures of the casting blank surfaces of all sections of the second cooling section 4, as shown in table 1:
TABLE 1
According to the preset target temperature, the temperature of each part of the continuous casting equipment is monitored through a continuous temperature measuring system, the operation parameters of the secondary cooling section 4 are adjusted through a PLC control system, so that the actual temperature of each part is close to the target temperature, and the operation parameters mainly comprise the cooling water consumption of each section and the total air quantity of the air suction duct 9, as shown in the table 2:
TABLE 2
And recording the actual surface temperature of each section of the casting blank of the second cooling section 4, and the actual upper surface (marked as m points) temperature and the actual lower surface (marked as n points) temperature of the casting blank of the air cooling section 5 at a distance of 2m from the i area/J area.
Comparative example 1: and (3) cooling the casting blank in the second cooling section 4 according to the cooling strength shown in the table 2, wherein an air suction system is not started, namely the air volume of the air suction ducts 9 in the h area and the j area is 0, and the monitoring shows that black marks appear in the h area and the j area, and the corresponding surface temperature is lower than the target temperature. And recording the actual surface temperature of each section of the casting blank of the second cooling section 4, and the actual upper surface (marked as m point) temperature and the actual lower surface (marked as n point) temperature of the casting blank of the air cooling section 5 at a position 2m away from the i area/J area.
Comparative example 2: the target temperature is preset according to the table 1, an air suction system is not started, namely the air volume of the h-area and j-area air suction duct 9 is 0, the running parameters of the secondary cooling section 4 are adjusted through the PLC control system, so that the actual temperature of each part is close to the target temperature, the difference between the cooling intensity of the h-area and the cooling intensity of the j-area and the difference between the cooling intensity of the corresponding g-area and the cooling intensity of the i-area are increased through monitoring, and the cooling intensity of the h-area and the cooling intensity of the j-area are smaller than the cooling intensity of the corresponding section in the table 2. And recording the actual surface temperature of each section of the casting blank of the second cooling section 4, and the actual upper surface (marked as m point) temperature and the actual lower surface (marked as n point) temperature of the casting blank of the air cooling section 5 at a position 2m away from the i area/J area.
Position-temperature curves are drawn for the actual surface temperatures of the casting blanks in example 2, comparative example 1 and comparative example 2, respectively, corresponding to fig. 1-3 (the areas a, b, c, g, i and m are connected as upper surface curves, and the areas d, e, f, h, j and n are connected as lower surface curves), and each group of casting blanks is monitored by an infrared thermal temperature measurement system.
As can be seen from figure 1, the upper surface curve and the lower surface curve are basically superposed, the infrared temperature measurement shows that the temperature distribution of the upper surface and the lower surface of the casting blank is uniform, the central high-temperature area is positioned at the central position of the section of the casting blank, and the central temperature is about 1500 ℃; as can be seen from FIG. 2, the temperature of the lower surface of the casting blank is lower than that of the upper surface, the infrared temperature measurement shows that the temperature distribution of the upper surface and the lower surface of the casting blank is uneven, the shadow area of the lower surface of the f-region-n point is larger than that of the upper surface of the c-region-m point, and the position of the central high-temperature area is higher; it can be seen from fig. 3 that the return temperature of the casting blank in the air cooling region at the point n is increased, the return temperature at the point m is lower than that at the point n, the infrared temperature measurement shows that the temperature distribution of the upper and lower surfaces of the casting blank is not uniform, the shadow area of the lower surface at the point f-n is smaller than that of the upper surface at the point c-m, and the position of the central high-temperature region is lower.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (5)
1. A method for uniformly regulating and controlling a casting blank solidification structure is characterized by comprising the following steps:
the method comprises the following steps: setting preset parameters and operating continuous casting equipment;
step two: working condition information of continuous casting equipment in the running process is read in real time, and running parameters of a crystallizer (3) and a secondary cooling section (4) are adjusted in time through a PLC control system, so that each section of a casting blank is cooled to a target temperature;
the continuous casting equipment comprises a steel ladle (1), a tundish (2), a crystallizer (3), a secondary cooling section (4) and an air cooling section (5); the superheat degree of the molten steel in the ladle (1) is 10-30 ℃, the superheat degree of the tundish (2) is 20-30 ℃, and the cooling water flow of the crystallizer (3) is 140-150m 3 And h, the moving speed of the casting blank of the secondary cooling section (4) is 25-30cm/s.
2. The method for uniformly regulating and controlling the solidification structure of the casting blank according to claim 1, wherein the crystallizer (3) is provided with an electromagnetic current control device, the frequency of the electromagnetic current control device is 400 +/-50 Hz, and the current is 350 +/-150A.
3. The method for uniformly controlling the solidification structure of a casting blank according to claim 1, wherein the front side of the casting blank of the second cooling section (4) from the outlet of the crystallizer (3) is divided into a region a, a region b, a region c, a region g and a region i in sequence, and the rear side of the casting blank is correspondingly divided into a region d, a region e, a region f, a region h and a region j.
4. The method for uniformly controlling the solidification structure of the casting blank according to claim 3, wherein water outlet nozzles (7) are arranged in the areas a, b, c, d, e and f, and water is supplied by a first water distribution system (41) in a full-water cooling mode.
5. The method for uniformly regulating and controlling the solidification structure of the casting blank according to claim 3, wherein the g area, the i area, the h area and the j area are provided with high-pressure atomizing nozzles (8), water is supplied through a second water distribution system in a gas-water cooling mode, and a plurality of air suction air channels (9) are arranged in the h area and the j area in an array mode and assist in controlling the solidification temperature of the casting blank through an air suction system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211184400.3A CN115608944A (en) | 2022-09-27 | 2022-09-27 | Method for uniformly regulating and controlling solidification structure of casting blank |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211184400.3A CN115608944A (en) | 2022-09-27 | 2022-09-27 | Method for uniformly regulating and controlling solidification structure of casting blank |
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| Publication Number | Publication Date |
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| CN115608944A true CN115608944A (en) | 2023-01-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211184400.3A Withdrawn CN115608944A (en) | 2022-09-27 | 2022-09-27 | Method for uniformly regulating and controlling solidification structure of casting blank |
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| Country | Link |
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| CN (1) | CN115608944A (en) |
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- 2022-09-27 CN CN202211184400.3A patent/CN115608944A/en not_active Withdrawn
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Application publication date: 20230117 |
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