EP3750649A1

EP3750649A1 - Method for controlling structure of solidified cast ingot in continuous casting process and control device thereof

Info

Publication number: EP3750649A1
Application number: EP19777614.9A
Authority: EP
Inventors: Liping Wu; Chang Shen; Biao Sun; Guocai Wang; Qiang Lu
Original assignee: Maanshan Iron and Steel Co Ltd
Current assignee: Maanshan Iron and Steel Co Ltd
Priority date: 2018-03-29
Filing date: 2019-03-15
Publication date: 2020-12-16
Also published as: JP2021516621A; EP3750649A4; WO2019184731A1; CN108672668A; JP7111828B2

Abstract

The present invention discloses a method for controlling the solidification structure of a bloom in a continuous casting process, and the control equipment therefor, and relates to the field of metallurgical continuous casting technologies. According to the method in the present invention, a super strong cooling zone and a heat and slow cooling zone are provided in the range from mould outlet to a solidification end; a continuous casting bloom is first super-cooled in the super strong cooling zone, and then heated and slow-cooled in the heat and slow cooling zone; and cooling intensity of heat and slow cooling is lower than that of air cooling. According to the equipment in the present invention, the super strong cooling zone and the heat and slow cooling zone are provided in the length direction of the continuous casting bloom below the mould; the super strong cooling zone is used to provide water spray cooling to the surface of the bloom; and the heat and slow cooling zone is used to provide heating to the surface of the bloom. According to the present invention, a continuous casting bloom is first super-cooled in the super strong cooling zone, and then heated and slow-cooled in the heat and slow cooling zone. This reduces the columnar crystal spacing and gap, increases the density of the columnar crystals in the subsurface layer of the bloom, and improves the quality of the bloom

Description

TECHNICAL FIELD

The present invention relates to the field of metallurgical continuous casting technologies, and in particular, to a method for controlling the solidification structure of a bloom in a continuous casting process, and a related equipment therefor.

BACKGROUND

In the modern steel continuous casting production technology, the solidification structure and defects of a bloom have been severely affecting the quality of the bloom. Based on the conventional continuous casting cooling mode, the bloom solidification structure usually has insufficient adaptability to casting materials and final products , and inadequacy of control modes and extents results in poor control ability of the solidification structure. Consequently, the increasing material performance requirements, especially the specific personalized requirements, cannot be satisfied. For example, in some cases, the overgrown columnar crystals cause serious center segregation; in some other cases, improper cooling results in coarse crystal grains and crystal boundaries. For another example, the columnar crystals that take priority grow at later stage of solidification are out of control and form a "bridge" at the bloom center, the molten steel in the liquid phase cavity is separated by the "solidified crystal bridge", during solidification shrinkage, the lower structure of the crystal bridge is not supplemented by the upper molten steel, resulting in porosity or shrinkage, and related problems such as center segregation and uneven composition occur. To solve the above-mentioned problems, the low-temperature casting technology, the electromagnetic stirring technology, and the soft reduction or cast-rolling technology at the solidification end have been generated in this field for a long time, but these technologies are still not ideal for the solidification structures of the surface layer, the subsurface layer and the core of the bloom.
Search shows that a method for producing high-carbon chromium bearing steel by a double slow cooling process (publication number: CN101412183A ; publication date: 2009.04.22) has been disclosed. In this technology, the hydrogen content and stress of the slab can be released by slow cooling at high temperature in the slow cooling pit, and then, the rolled products are put into the slow cooling cover to further release the hydrogen and stress in the rolled products. The production method of high carbon chromium bearing steel by twice slow cooling can ensure the low quality of rolled products without white spot cracks. However, it is worth noting that the slow cooling treatment of the existing technology is usually aimed at the solidified bloom, and it is difficult to effectively reduce the columnar crystal spacing and gap, especially to effectively increase the density of the columnar crystals near the surface layer of the bloom.

SUMMARY

1. Technical problems to be solved by the invention

To overcomes the problem that the solidification structure of the surface layer, sub-surface layer and center part of the bloom is still not ideal, the present invention provides a method for controlling the solidification structure of a bloom in a continuous casting process, and a control equipment therefor.
According to the provided method for controlling the solidification structure of a bloom in a continuous casting process, a super cooling zone and a heat and slow cooling zone are arranged between the mould outlet and the end of solidification; a continuous casting bloom is first super-cooled in the super strong cooling zone, and then heated and slow-cooled in the heat and slow cooling zone. This can reduce the columnar crystal spacing and gap, increase the density of the columnar crystals at the subsurface layer of the bloom, and reduce internal cracks.
According to the provided equipment for controlling the solidification structure of a bloom based on heat and slow cooling, a super strong cooling zone and a heat and slow cooling zone are provided in the length direction of a continuous casting bloom at the outlet of mould; the super strong cooling zone is used to provide water spray cooling to the surface of the bloom; the heat and slow cooling zone is used to provide heating to the surface of the bloom. This can reduce the columnar crystal spacing and gap, increase the density of the columnar crystals at subsurface layer of the bloom, and reduce internal cracks.

2. Technical solutions

In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions:
The present invention provides a method for controlling the solidification structure of a bloom in a continuous casting process. A super strong cooling zone and a heat and slow cooling zone are provided in the range from mould outlet to a solidification end. A continuous casting bloom is first super-cooled in the super strong cooling zone, and then heated and slow-cooled in the heat and slow cooling zone. Cooling intensity of heat and slow cooling is lower than that of air cooling.
Preferably, a weak cooling zone is further provided between the super strong cooling zone and the heat and slow cooling zone, and cooling intensity of the weak cooling zone is lower than that of super cooling.
Preferably, water flow density of the super strong cooling zone is Q L/m² and water flow density of the weak cooling zone is q L/m², where Q≥2q.
Preferably, the starting point of super cooling in the super strong cooling zone is located at the mould outlet, and the length of the super strong cooling zone is greater than 12% L, where L represents a total cooling length, and the total cooling length ranges from the mould outlet to the solidification end.
Preferably, the distance between the starting point of heat and slow cooling in the heat and slow cooling zone and the mould outlet is greater than 40% L, where L represents the total cooling length.
Preferably, the water flow density of the super strong cooling zone of the round bloom ≥ 465L/m², or the water flow density of the super strong cooling zone of the rectangular bloom ≥ 490L/m², or the water flow density of the super strong cooling zone of the slab continuous casting bloom ≥ 255L/m².
Preferably, the surface of the bloom is heated in the heat and slow cooling zone, and the heating energy value is greater than 5kW/m².
Preferably, the endpoint of heat and slow cooling in the heat and slow cooling zone is before the solidification end.
The present invention provides the equipment for controlling the solidification structure of a bloom based on heat and slow cooling. A super strong cooling zone and a heat and slow cooling zone are provided in the length direction of a continuous casting bloom below the mould outlet; the super strong cooling zone is used to provide water spray cooling to the surface of the bloom; the heat and slow cooling zone is used to provide heating to the surface of the bloom.
Preferably, the surface of the continuous casting bloom in the heat and slow cooling zone is provided with an electromagnetic heating coil or a heating hood. The heating hood is a steam heating hood, a flammable gas heating hood, or a reflective thermal-insulating self-heating hood.
Preferably, before the heat and slow cooling zone is provided with a weak cooling zone.

3. Beneficial effects

Compared with existing well-known technologies, the technical scheme provided by the invention has the following remarkable effects:

(1) According to the method for controlling the solidification structure of a bloom in a continuous casting process provided in the present invention, the super strong cooling zone and the heat and slow cooling zone are provided in the range from the mould outlet to the solidification endpoint; the continuous casting bloom is first super-cooled in the super strong cooling zone, so as to effectively reduce the primary dendrite spacing and gap, improve the density of columnar crystals in the bloom, and reduce the porosity of columnar crystals; and then the continuous casting bloom is heated and slow-cooled in the heat and slow cooling zone, so as to reduce the temperature gradient in the bloom, reduce the temperature difference between the surface and the interior of the bloom, inhibit the growth of columnar crystals, and avoid the formation of internal cracks in bloom. This reduces the columnar crystal spacing and gap, improves the solidification structures of the subsurface layer and the core of the bloom, increases the density of the columnar crystals in the subsurface layer of the bloom, and reduces internal cracks.
(2) According to the method for controlling the solidification structure of a bloom in a continuous casting process provided in the present invention, the starting point of super cooling in the super strong cooling zone is located at the mould outlet, and the length of the super strong cooling zone is greater than 12% of the total cooling length. If the cooling length is too short, it is impossible to form a sufficiently dense columnar crystal and a maximized thickness of the bloom shell, which is not conducive to the desired weak cooling control at the later stage of solidification.
(3) According to the method for controlling the solidification structure of a bloom in a continuous casting process provided in the present invention, the weak cooling zone is further provided between the super strong cooling zone and the heat and slow cooling zone, and the cooling intensity of the weak cooling zone is lower than that of super cooling, so as to ensure that the weak cooling zone has a sufficient range, to ensure a good transition between the super strong cooling zone and the heat and slow cooling zone in the continuous casting process, and to prevent the continuous casting bloom from being transited directly from the super strong cooling zone to the heat and slow cooling zone. This can avoid causing an excessively high surface temperature rise, thereby reducing the internal cracks in solidification section.
(4) According to the method for controlling the solidification structure of a bloom in a continuous casting process provided in the present invention, the distance between the starting point of heat and slow cooling in the heat and slow cooling zone and the mould outlet is greater than 40% of the total cooling length, and the endpoint of heat and slow cooling in the heat and slow cooling zone precedes the solidification end, that is, the heat and slow cooling zone is located within the range from the position after 40% of the total cooling length to the solidification end. This ensures that there is a sufficient weak cooling zone between the super strong cooling zone and the heat and slow cooling zone, and avoids a sudden temperature rise on the surface of the bloom, thereby reducing the internal cracks in solidification section.
(5) According to the equipment for controlling the solidification structure of a bloom based on heat and slow cooling provided in the present invention, the super strong cooling zone and the heat and slow cooling zone are provided in the length direction of the continuous casting bloom below the mould; the super strong cooling zone is used to provide water spray cooling to the surface of the bloom; the heat and slow cooling zone is used to provide heating to the surface of the bloom. This reduces the columnar crystal spacing and gap, increases the density of the columnar crystals in the subsurface layer of the bloom, and reduces internal cracks, so as to obtain the solidification structures of the bloom meeting the performance requirements of different final products.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic structural diagram of an apparatus for controlling the solidification structure of a bloom based on heat and slow cooling according to the present invention;
FIG. 2 shows an electromagnetic heating coil in the heat and slow cooling zone according to the present invention;
FIG. 3 is a schematic morphological diagram of a micro-structure of a bloom according to

Embodiment 4; and

FIG. 4 is a schematic morphological diagram of a micro-structure of a bloom according to Reference Embodiment 1.

Reference numerals in the accompanying drawings:

100: continuous casting bloom; 110: unsolidified molten steel; 120: solidified bloom shell;
210: super strong cooling zone; 220: weak cooling zone; 230: heat and slow cooling zone;
300: continuous casting crystallizer;
410: columnar crystal zone; 420: equiaxed crystal zone; 430: porosity.

DESCRIPTION OF EMBODIMENTS

In order to further understand the content of the present invention, the present invention is described in detail with reference to accompanying drawings and embodiments.
The structure, scale, size, etc. shown in the drawings of this specification are merely used to cooperate with the content disclosed in the specification for a person skilled in the art to understand and read, and are not restrictions for limiting implementation of the present invention, and therefore have no technically substantial significance. Any modification of the structure, change of a proportional relationship or adjustment of the size shall still fall within the scope that can be covered by the technical content disclosed in the present invention, provided that they do not affect the efficacy that can be generated by the present invention and the purpose that can be achieved by the present invention. In addition, the terms such as "upper", "lower", "left", "right", and "middle" used in this specification are merely intended for clarity of description, but are not intended to limit the scope of implementation. Changes or adjustments in the relative relationship shall be considered to be within the scope of implementation of the present invention, provided that there is no substantial change in the technical content.
As shown in FIG. 1 to FIG. 3, the present invention provides the equipment for controlling the solidification structure of a bloom based on heat and slow cooling. A super strong cooling zone 210 and a heat and slow cooling zone 230 are provided in the length direction of a continuous casting bloom 100 below the mould 300. The exterior of the continuous casting bloom 100 is a solidified bloom shell 120, and the interior of the solidified bloom shell 120 is unsolidified molten steel 110. The super strong cooling zone 210 is used to provide water spray cooling to the surface of the bloom of the solidified bloom shell 120, that is, a nozzle is disposed in the super strong cooling zone 210, and the nozzle is used to provide water spray cooling to the surface of the bloom; the heat and slow cooling zone 230 is used to provide heating to the surface of the bloom, and further perform heat and slow cooling on the surface of the bloom. As shown in FIG. 2, the surface of the continuous casting bloom 100 in the heat and slow cooling zone 230 is provided with an electromagnetic heating coil 231.
Alternatively, as shown in FIG. 3, the surface of the continuous casting bloom 100 in the heat and slow cooling zone 230 is provided with a heating hood 231. The heating hood 231 is a steam heating hood, a flammable gas heating hood, or a reflective thermal-insulating self-heating hood.
As shown in FIG. 3, the front part of the heat and slow cooling zone 230 is provided with a weak cooling zone 220, that is, the weak cooling zone 220 is disposed between the super strong cooling zone 210 and the heat and slow cooling zone 230. A nozzle is provided in the weak cooling zone 220, and the nozzle is used to provide water spray cooling to the surface of the bloom. It is worth noting that water spray cooling can also be water vapor mixing cooling.
According to the method for controlling the solidification structure of a bloom in a continuous casting process provided in the present invention, in the molten steel continuous casting process, super cooling, weak cooling and heat and slow cooling measures are sequentially applied to a specific area of the bloom along the casting direction, thereby improving the solidification structure of the subsurface layer and the core of the bloom, while ensuring that the total amount of energy released in the entire continuous casting process is fixed. Detailed description is as follows: A super strong cooling zone 210 and a heat and slow cooling zone 230 are provided in the range from mould outlet 300 to the solidification end. A continuous casting bloom 100 is first super-cooled in the super strong cooling zone 210, and then heated and slow-cooled in the heat and slow cooling zone 230. Cooling intensity of heat and slow cooling is lower than that of air cooling. Cooling intensity of super cooling is higher than that of air cooling.
To be specific, the starting point of super cooling in the super strong cooling zone 210 is located at the mould 300 outlet, and the length of the super strong cooling zone 210 is greater than 12% L, where L represents a total cooling length, and the total cooling length is the distance from the mould outlet to the solidification end, that is, the super strong cooling zone 210 extends from the mould 300 outlet along the casting direction by more than 12% of the total cooling length. This is because if the length of the super strong cooling zone 210 is less than 12% of the total cooling length, the range of the super strong cooling zone 210 is too short, and consequently, the continuous casting bloom 100 cannot form a sufficiently dense columnar crystal and a maximized thickness of the bloom shell, which is not conducive to the desired weak cooling control at the later stage of solidification. The average cooling intensity of the super strong cooling zone 210 is far higher than the cooling intensity of the existing continuous casting technology. This is because the early cooling has a small specific water flow, which makes the cooling intensity too low. As a result, the heat released by the bloom at the early stage is less, and the bloom shell with an ideal thickness and density cannot be quickly formed. Therefore, it is necessary to strengthen the early cooling of the bloom, so that the total heat of the bloom is released as much as possible at the early stage, and the bloom shell with an ideal thickness and density can quickly formed on the surface of the bloom. Different types of blooms have different super strong cooling intensity, and the cooling intensity can be expressed by water flow density Q L/m². The specific classification is described as follows:

(1) The water flow density of the super strong cooling zone 210 of the round continuous casting bloom 100 is as follows: Q₁≥465L/m².
(2) The water flow density of the super strong cooling zone 210 of the rectangular continuous casting bloom 100 is as follows: Q₂≥490L/m².
(3) The water flow density of the super strong cooling zone 210 of the slab continuous casting bloom 100 is as follows: Q₃≥255L/m² ; and the thickness of the slab continuous casting bloom is not less than 200mm.

After the continuous casting bloom 100 exits the mould 300, super cooling is applied to the continuous casting bloom 100, which can effectively reduce the primary dendrite spacing and gap, improve the density of columnar crystals in the bloom, and reduce the porosity of columnar crystals.
In this embodiment, a weak cooling zone 220 is further provided between the super strong cooling zone 210 and the heat and slow cooling zone 230, and cooling intensity of the weak cooling zone 220 is lower than that of super cooling. After the super cooling, the cooling intensity of the bloom is transited to the weak cooling zone 220, and then to the heat and slow cooling zone 230 after the weak cooling zone 220, where the weak cooling zone 220 uses the conventional cooling intensity of continuous casting. It is worth noting that the cooling intensity of the weak cooling zone 220 is q₁ L/m², and the super strong cooling intensity is Q L/m²; therefore, Q≥2 q₁. For different types of blooms, the cooling intensity of the weak cooling zone 220 is different. In addition, it is worth noting that the cooling intensity of the weak cooling zone 220 is basically the same as the conventional cooling intensity in the continuous casting process. The cooling intensity can be expressed by the water flow density. The specific classification is described as follows:

(1) For round bloom continuous casting, the cooling intensity (water flow density) of this zone needs to be ≥155L/m².
(2) For rectangular bloom continuous casting, the cooling intensity (water flow density) of this zone needs to be ≥245L/m².
(3) For slab bloom continuous casting, the cooling intensity (water flow density) of this zone needs to be ≥85L/m². The bloom first passes through the super strong cooling zone 210 for cooling, and then passes through the weak cooling zone 220 for transition, and then enters the heat and slow cooling zone 230 for heating and slow cooling. This can reduce the temperature transition difference, reduce the temperature gradient in the bloom, reduce the temperature difference between the surface and the interior of the bloom, and inhibit the growth of columnar crystals.

In this embodiment, the distance between the starting point of heat and slow cooling in the heat and slow cooling zone 230 and the mould 300 outlet is greater than 40% of the total cooling length, and the endpoint of heat and slow cooling in the heat and slow cooling zone 230 precedes the solidification end. To be specific, the heat and slow cooling zone 230 starts after extending more than 40% of the total cooling length along the bloom withdrawing direction from the mould 300 outlet, and ends before the endpoint of the cooling length. heat and slow cooling measures are applied to the bloom to reduce the temperature gradient in the bloom, reduce the temperature difference between the surface and the interior of the bloom, inhibit the growth of columnar crystals, and prevent internal cracks in the bloom. The applicant's research and development team found through long-term research and development that, if the heat and slow cooling zone 230 starts at less than 40% of the total cooling length, the conventional cooling zone may be too short to play a good transition role, and the temperature rise on the surface of the bloom is excessively high. As a result, internal cracks appear in the solidification section. Therefore, the applicant creatively proposes that the starting point of heat and slow cooling is located at more than 40% of the total cooling length, and the endpoint of heat and slow cooling precedes the solidification end. In addition, it is worth noting that the endpoint of heat and slow cooling of the heat and slow cooling zone 230 matches the performance of the final product. If the final product has higher requirements for the core of the bloom, the total length of the heat and slow cooling zone 230 needs to match the length of the super strong cooling zone 210 at the early stage, so as to ensure that the total amount of energy released in the entire continuous casting process is fixed. If the length of the super strong cooling zone 210 is longer, the length of the heat and slow cooling zone 230 is longer. In other words, the length of the heat and slow cooling zone 230 is positively correlated with the length of the super strong cooling zone 210, and it is ensured that the total amount of energy released in the continuous casting process is fixed. The heat and slow cooling method provide heating measures to the surface of the bloom, and the heating energy value is greater than 5kW/m².

Embodiment 1

In this embodiment, a 5-stream round bloom continuous casting machine of a certain steel factory is used. The cross-sectional diameter of the bloom is 380mm. During the casting, strong cooling, weak cooling and heat and slow cooling measures are sequentially applied to the bloom along the casting direction. Table 1 shows the length of the super strong cooling zone 210, the water flow density of the cooling in the super strong cooling zone 210, the starting point of heat and slow cooling in the heat and slow cooling zone 230, and the heat provided by heating in the heat and slow cooling zone 230. The super strong cooling zone 210 ranges from the mould 300 outlet to 22% L, and the heat and slow cooling zone 230 ranges from 55% L to the solidification endpoint. After the casting, a macrostructure sample of the bloom is taken to analyze the porosity of columnar crystals of the bloom, and measure the surface temperature when the bloom is completely solidified. Specific parameters and results in the embodiment are shown in Table 1.

Embodiment 2

Basic content of this embodiment is the same as that of Embodiment 1, except that parameters for the water flow density of the cooling in the super strong cooling zone 210, the starting point of heat and slow cooling, and the heat provided by heating in the heat and slow cooling zone 230 are different. Specific parameters are shown in Table 1. After the casting, a macrostructure sample of the bloom is taken to analyze the porosity of columnar crystals of the bloom, and measure the surface temperature when the bloom is completely solidified. Specific parameters and results in the embodiment are shown in Table 1.

Embodiment 3

In this embodiment, a 5-stream round bloom continuous casting machine of a certain steel factory is used. The cross-sectional diameter of the bloom is 700mm. During the casting, strong cooling, weak cooling and heat and slow cooling measures are sequentially applied to the bloom along the casting direction. Table 1 shows the length of the super strong cooling zone 210, the water flow density of the cooling in the super strong cooling zone 210, the starting point of heat and slow cooling in the heat and slow cooling zone 230, and the heat provided by heating in the heat and slow cooling zone 230. The super strong cooling zone 210 ranges from the mould 300 outlet to 17% L, and the heat and slow cooling zone 230 ranges from 55% L to the solidification end. After the casting, a macrostructure sample of the bloom is taken to analyze the porosity of columnar crystals of the bloom, and measure the surface temperature when the bloom is completely solidified. Specific parameters and results in the embodiment are shown in Table 1.

Embodiment 4

Basic content of this embodiment is the same as that of Embodiment 3, except that parameters for the water flow density of the cooling in the super strong cooling zone 210, the starting point of heat and slow cooling, and the heat provided by heating in the heat and slow cooling zone 230 are different. Specific parameters are shown in Table 1. After the casting, a macrostructure sample of the bloom is taken to analyze the porosity of columnar crystals of the bloom, and measure the surface temperature when the bloom is completely solidified. Specific parameters and results in the embodiment are shown in Table 1. FIG. 4 is a diagram of a macrostructure structure of a bloom in Embodiment 4.

Reference Embodiment 1

Basic content of this embodiment is the same as that of Embodiment 4, except that the water flow density of the cooling intensity of the bloom surface is 200 L/m². After the casting, a macrostructure sample of the bloom is taken for macrostructure analysis, so as to analyze the porosity of columnar crystals of the bloom, and measure the surface temperature when the bloom is completely solidified. Specific parameters and results in Reference Embodiment 1 are shown in Table 1. FIG. 4 is a diagram of a low-magnification structure of a bloom in Reference Embodiment 1.

Table 1

	Bloom diameter /mm	Length of super strong cooling zone	Water flow density of cooling in super strong cooling zone	Starting point of heat and slow cooling	Heat provided by heating /kW/m²	Average porosity size of columnar crystals /µm	Surface temperature /°C after complete solidification
Embodiment 1	380	22%L	615	55%L	10	22.1	715
Embodiment 2	380	22%L	570	50% L	28	24.5	726
Embodiment 3	700	17%L	525	60% L	42	26.2	727
Embodiment 4	700	17%L	480	55% L	58	26.0	760
Reference Embodiment 1	700	No other measures are taken in the continuous casting process.				37.2	703

Note: In the table, the unit of the length of the super strong cooling zone 210, and the length of the heat and slow cooling zone 230 is L, and L represents the total cooling length.

It can be seen from the implementation results that the porosity of columnar crystal structure in the solidification structure of the bloom in Embodiments 1-4 is smaller, the average porosity size of columnar crystals is less than 26.0 µm, and the surface temperature of the bloom increases. This can effectively reduce internal cracks and improve the quality of the bloom to satisfy the needs of different products for the solidification structure.
For further analysis, FIG. 3 is a schematic morphological diagram of the micro-structure of a bloom according to Embodiment 4; and FIG. 4 is a schematic morphological diagram of the micro-structure of a bloom according to Reference Embodiment 1. FIG. 3 and FIG. 4 include columnar crystal zones 410, equiaxed crystal zones 420, and porosity holes 430. The domain structure of the columnar crystal zone 410 of the bloom in FIG. 4 is relatively loose, and the columnar crystal zone 410 has porosity holes 430, whereas the domain structure of the columnar crystal zone 410 of the bloom in FIG. 3 is dense and dendrites are fine and tight. The porosity holes 430 in the columnar crystal zone 410 are basically eliminated. In addition, the average porosity size of columnar crystals decreases from 37.2 µm to below 26.0 µm. This reduces the columnar crystal spacing and gap, improves the solidification structures of the subsurface layer and the core of the bloom, increases the density of the columnar crystals near the surface layer of the bloom, and reduces internal cracks. It can be found through further comparison that, compared with Reference Embodiment 1, Embodiment 4 not only reduces the columnar crystal spacing and gap and improves the solidification structures of the subsurface layer and the core of the bloom, but also expands the proportion of the equiaxed crystal zone 420, thereby improving the quality of the bloom.
The present invention has been described in detail above in combination with the specific example embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the present invention as defined by the appended claims. The detailed description and accompanying drawings are to be considered as being illustrative only and not restrictive, and if there are any such modifications and variations, they shall fall within the scope of the present invention described herein. In addition, the background is intended to illustrate the research and development status and significance of the technology, and is not intended to limit the present invention or the present application and application fields of the present invention.

Claims

A method for controlling the solidification structure of a bloom in a continuous casting process, wherein a super strong cooling zone (210) and a heat and slow cooling zone (230) are provided in the range from mould outlet to a solidification end; a continuous casting bloom (100) is first super-cooled in the super strong cooling zone (210), and then heated and slow-cooled in the heat and slow cooling zone (230); and cooling intensity of heat and slow cooling is lower than that of air cooling.
The method for controlling the solidification structure of a bloom in a continuous casting process according to claim 1, wherein a weak cooling zone (220) is further provided between the super strong cooling zone (210) and the heat and slow cooling zone (230), and cooling intensity of the weak cooling zone (220) is lower than that of super cooling.
The method for controlling the solidification structure of a bloom in a continuous casting process according to claim 2, wherein water flow density of the super strong cooling zone (210) is Q L/m², and water flow density of the weak cooling zone (220) is q L/m², wherein Q≥2 q.
The method for controlling the solidification structure of a bloom in a continuous casting process according to claim 1, wherein the starting point of super cooling in the super strong cooling zone (210) is located at the mould outlet, and the length of the super strong cooling zone (210) is greater than 12% L, wherein L represents a total cooling length.
The method for controlling the solidification structure of a bloom in a continuous casting process according to claim 1, wherein the distance between the starting point of heat and slow cooling in the heat and slow cooling zone (230) and the mould outlet is greater than 40% L, wherein L represents a total cooling length.
The method for controlling the solidification structure of a bloom in a continuous casting process according to claim 1, wherein water flow density of the super strong cooling zone (210) of a round continuous casting bloom (100) ≥465L/m², water flow density of the super strong cooling zone (210) of a rectangular continuous casting bloom (100) ≥490L/m², or water flow density of the super strong cooling zone (210) of a slab continuous casting bloom (100) ≥255L/m².
The method for controlling the solidification structure of a bloom in a continuous casting process according to claim 1, wherein the surface of the bloom is heated in the heat and slow cooling zone (230), and the heating energy value is greater than 5kW/m².
The method for controlling the solidification structure of a bloom in a continuous casting process according to any one of claims 1 to 7, wherein the endpoint of heat and slow cooling in the heat and slow cooling zone (230) precedes the solidification end.
The equipmeng for controlling the solidification structure of a bloom based on heat and slow cooling, wherein a super strong cooling zone (210) and a heat and slow cooling zone (230) are provided in the length direction of a continuous casting bloom (100) below the mould (300); the super strong cooling zone (210) is used to provide water spray cooling to the surface of the bloom; and the heat and slow cooling zone (230) is used to provide heating to the surface of the bloom.
The equipment for controlling the solidification structure of a bloom based on heat and slow cooling according to claim 9, wherein the surface of the continuous casting bloom (100) in the heat and slow cooling zone (230) is provided with an electromagnetic heating coil (231) or a heating hood (231); and the heating hood (231) is a steam heating hood, a flammable gas heating hood, or a reflective thermal-insulating self-heating hood.
The apparatus for controlling the solidification structure of a bloom based on heat and slow cooling according to claims 9 and 10, wherein the front part of the heat and slow cooling zone (230) is provided with a weak cooling zone (220).