Continuous casting secondary cooling method for reducing bubble defect of oriented silicon steel

Abstract

The invention relates to the technical field of continuous steel casting in the metallurgical industry, and discloses a continuous casting secondary cooling method for reducing bubble defects of oriented silicon steel. According to the continuous casting secondary cooling method, a continuous casting secondary cooling area is composed of a foot roller area, a vertical area, a bending area, an arc-shaped area, a straightening area and a horizontal area; the secondary cooling specific water flow of the continuous casting secondary cooling area is 0.8-1.2 L / kg; and the proportions of the secondary cooling water in the foot roller area, the vertical area, the bending area, the arc-shaped area, the straightening area and the horizontal area are respectively 22.4 to 22.6 percent, 22.2 to 22.3 percent, 10 to 18 percent, 30 to 36 percent, 3 to 7 percent and 1 to 4 percent. According to the method, the specific water flow of the secondary cooling is limited in a specific range, and the water distribution of the foot roller area, the linear section, the arc-shaped section and the horizontal section is optimized, so that the occurrence rate of microcracks in the oriented silicon steel casting blank can be obviously reduced, and the bubble defect generated in the annealing process of the oriented silicon steel is eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting of steel in the metallurgical industry, and particularly relates to a secondary cooling method for continuous casting to reduce bubble defects in grain-oriented silicon steel. Background Art

[0002] Grain-oriented silicon steel is a key core raw material for modulating voltage equipment such as transformers and reactors. The development of grain-oriented silicon steel bears the green mission of energy conservation and emission reduction. The process flow of grain-oriented silicon steel is: continuous casting billet → hot rolled coil → pickling → acid rolling → decarburization annealing → secondary cold rolling → MgO plating + annealing + small furnace sintering → bell annealing. The quality of the continuous casting billet directly affects the quality of grain-oriented silicon steel.

[0003] Currently, grain-oriented silicon steel continuous casting billets are generally produced by conventional slab continuous casting machines equipped with secondary cooling electromagnetic stirring rolls. The continuous casting billets are hot charged and rolled. There is no method to timely and accurately evaluate the quality of grain-oriented silicon steel. Moreover, some internal defects of the continuous casting billets often only show obvious bubble defects after decarburization annealing. Once bubble defects occur, they often cause batch quality defects and significant economic losses.

[0004] Chinese Patent CN113857449B discloses a preparation method and a billet system for grain-oriented silicon steel continuous casting billets. The preparation method is used for continuous casting treatment of refined molten steel. The continuous casting treatment includes the following steps: performing solidification treatment to cause part of the refined molten steel to solidify into a billet shell; during the solidification treatment, performing electromagnetic stirring to cause the remaining refined molten steel to finally form a continuous casting billet. Among them, the distance between the position of the electromagnetic stirring and the outlet of the mold is 0.3 - 1.5 m, and the current range of the electromagnetic stirring is 0 A - 900 A. The above preparation method adjusts the intensity of the electromagnetic stirring by adjusting the position and current magnitude of the electromagnetic stirring, and then adjusts the generation amount of equiaxed crystals through the intensity of the electromagnetic stirring to expand the range of equiaxed crystal ratio, without mentioning how to solve the problem of bubbles appearing in the annealing process of grain-oriented silicon steel.

[0005] Chinese Patent CN115896602B discloses a production method of grain-oriented silicon steel slab and a grain-oriented silicon steel slab. The method includes the following steps: subjecting hot metal to KR desulfurization treatment and converter smelting to obtain converter hot metal, wherein the carbon content of the converter hot metal is controlled to be 0.02%-0.06%, and the oxygen content is 0.05-0.11%; transferring the converter hot metal to a ladle, and then performing LF refining to obtain refined molten steel, wherein by controlling the addition amount of alloy in the ladle, the slag volume flowing into the ladle during tapping, and the bottom blowing gas flow rate of the LF refining, the surface slag is made to contain less than or equal to 1% FeO; subjecting the refined molten steel to RH refining and continuous casting to obtain a grain-oriented silicon steel slab, wherein the RH refining is controlled by circulation to make inclusions float up sufficiently. The above method significantly reduces inclusions, makes the molten steel cleaner, improves the composition hit rate in the slab, reduces inclusions of MnO, SiO2, Al2O3 and their complexes, makes the slab have better properties, and does not mention how to solve the problem of bubbles appearing in the annealing process of grain-oriented silicon steel.

[0006] It can be seen that the prior art does not solve the problem of bubbles appearing in the annealing process of grain-oriented silicon steel. Therefore, there is an urgent need to provide a new method to reduce the bubble defects of grain-oriented silicon steel and avoid batch quality problems. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problem that the prior art does not solve the problem of bubbles appearing in the annealing process of grain-oriented silicon steel, and provides a continuous casting secondary cooling method for reducing the bubble defects of grain-oriented silicon steel. This method can significantly reduce or even eliminate the bubble defects of the annealed coil of grain-oriented silicon steel, avoid batch quality defects, significantly reduce the quality loss of the continuous casting billet, greatly improve the physical quality of value-added products, bring substantial economic benefits to enterprises, and improve the core competitiveness of enterprises.

[0008] To achieve the above purpose, the present invention provides a continuous casting secondary cooling method for reducing the bubble defects of grain-oriented silicon steel. The continuous casting secondary cooling method includes: performing secondary cooling on the solidified billet shell obtained through mold cooling in the continuous casting secondary cooling zone to obtain a grain-oriented silicon steel continuous casting billet, wherein the continuous casting secondary cooling zone consists of a dummy bar section, a vertical section, a bending section, an arc section, a straightening section and a horizontal section; The specific water ratio of secondary cooling in the continuous casting secondary cooling zone is 0.8-1.2 L / kg; Based on the total water volume of secondary cooling, the proportions of the secondary cooling water volumes in the dummy bar section, vertical section, bending section, arc section, straightening section and horizontal section are 22.4-22.6%, 22.2-22.3%, 10-18%, 30-36%, 3-7%, and 1-4% respectively.

[0009] Preferably, the specific water ratio of secondary cooling in the continuous casting secondary cooling zone is 0.9-1.1 L / Kg.

[0010] Preferably, the total amount of secondary cooling water is 2500 - 3200 L / min.

[0011] Preferably, the amount of secondary cooling water in the foot roll zone is 580 - 720 L / min, the amount of secondary cooling water in the vertical zone is 580 - 710 L / min, the amount of secondary cooling water in the bending zone is 360 - 445 L / min, the amount of secondary cooling water in the arc zone is 870 - 1100 L / min, the amount of secondary cooling water in the straightening zone is 130 - 160 L / min, and the amount of secondary cooling water in the horizontal zone is 60 - 80 L / min.

[0012] Preferably, based on the total amount of secondary cooling water, the proportions of the secondary cooling water in the foot roll zone, vertical zone, bending zone, arc zone, straightening zone, and horizontal zone are 22.5%, 22.3%, 14.1%, 33.6%, 5.0%, and 2.5% respectively.

[0013] Preferably, the arc zone is composed of a total of 6 sector segments, namely sector segment 1, sector segment 2, sector segment 3, sector segment 4, sector segment 5, and sector segment 6 from top to bottom, and is divided into a total of seven secondary cooling control loops for the arc zone, namely loop 1, loop 2, loop 3, loop 4, loop 5, loop 6, and loop 7. Among them, loop 1 controls the cooling water amount of the inner and outer arcs of sector segment 1, loop 2 controls the cooling water amount of the inner arc of sector segment 2, loop 3 controls the cooling water amount of the outer arc of sector segment 2, loop 4 controls the cooling water amount of the inner arcs of sector segments 3 and 4, loop 5 controls the cooling water amount of the outer arcs of sector segments 3 and 4, loop 6 controls the cooling water amount of the inner arcs of sector segments 5 and 6, and loop 7 controls the cooling water amount of the outer arcs of sector segments 5 and 6; among them, the ratio of the cooling water amount of loop 3 to that of loop 2 is 1.3 - 1.5:1, the ratio of the cooling water amount of loop 5 to that of loop 4 is 1.5 - 1.7:1, and the ratio of the cooling water amount of loop 7 to that of loop 6 is 1.7 - 1.9:1.

[0014] Preferably, the straightening zone is composed of a total of 2 sector segments, namely sector segment 7 and sector segment 8 from top to bottom, and is divided into two secondary cooling control loops for the straightening zone, namely loop 8 and loop 9. Among them, loop 8 controls the cooling water amount of the inner arcs of sector segments 7 and 8, and loop 9 controls the cooling water amount of the outer arcs of sector segments 7 and 8; among them, the ratio of the cooling water amount of loop 8 to that of loop 9 is 1.9 - 2.1:1.

[0015] Preferably, indirect cooling is used for the secondary cooling in the horizontal zone.

[0016] Preferably, the process of secondary cooling the solidified billet shell obtained by cooling in the crystallizer in the secondary cooling zone of continuous casting to obtain an oriented silicon steel billet includes: cooling the refined molten steel of oriented silicon steel in the crystallizer to obtain a solidified billet shell, and then casting at a casting speed of 0.8 - 1.4 m / min, and obtaining a solidified casting billet (fully solidified casting billet) after secondary cooling in the secondary cooling zone of continuous casting.

[0017] Preferably, the refined molten steel of oriented silicon steel includes the following chemical components by weight percentage: C: 0.03 - 0.05%, Si: 3.0 - 3.4%, Mn: 0.10 - 0.25%, P: 0.005 - 0.025%, S: 0.004 - 0.015%, Als: 0.0150 - 0.030%, N: 0.0070 - 0.0110%, Cu: 0.40% - 0.60%, and the balance is Fe and unavoidable impurities.

[0018] Preferably, the thickness of the oriented silicon steel billet is 220 - 235 mm, and the width is 1000 - 1400 mm.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: By limiting the secondary cooling water ratio in the secondary cooling zone of continuous casting within a specific range and optimizing the cooling water ratio in the full-roll zone, vertical zone, bending zone, arc zone, straightening zone, and horizontal zone, the present invention can significantly reduce the incidence of microcracks inside the oriented silicon steel billet, and further eliminate the bubble defects generated in the annealing process of the oriented silicon steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the layout of the continuous casting secondary cooling control loop; Figure 2 is a transverse macrostructure diagram of the oriented silicon steel billet prepared in Example 1; Figure 3 is a transverse macrostructure diagram of the oriented silicon steel billet prepared in Example 2; Figure 4 is a transverse macrostructure diagram of the oriented silicon steel billet prepared in Example 3; Figure 5 is a transverse macrostructure diagram of the oriented silicon steel billet prepared in Comparative Example 1; Figure 6 is a transverse macrostructure diagram of the oriented silicon steel billet prepared in Comparative Example 2; Figure 7 is a transverse macrostructure diagram of the oriented silicon steel billet prepared in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustrating and explaining the present invention, and are not used to limit the present invention.

[0022] The endpoints and any values disclosed in this article for a range are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For a numerical range, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0023] The mechanism of the present invention for reducing the bubble defects of grain-oriented silicon steel is as follows: If secondary intergranular microcracks appear inside the slab during the continuous casting process, then the internal defects of the slab will significantly present bubble defects after decarburization annealing. The present invention optimizes the secondary cooling process of continuous casting to reduce the incidence of microcracks inside the grain-oriented silicon steel slab, and thus achieves the purpose of eliminating bubble defects generated in the annealing process of grain-oriented silicon steel.

[0024] As described above, the continuous casting secondary cooling method for reducing the bubble defects of grain-oriented silicon steel provided by the present invention includes: performing secondary cooling on the solidified billet shell obtained after being cooled by the mold in the secondary cooling zone of continuous casting to obtain a grain-oriented silicon steel slab, wherein the secondary cooling zone of continuous casting is composed of a dummy bar section, a vertical section, a bending section, an arc section, a straightening section, and a horizontal section; The specific water ratio of secondary cooling in the secondary cooling zone of continuous casting is 0.8 - 1.2 L / kg; Based on the total water volume of secondary cooling, the proportions of the secondary cooling water volumes in the dummy bar section, vertical section, bending section, arc section, straightening section, and horizontal section are 22.4 - 22.6%, 22.2 - 22.3%, 10 - 18%, 30 - 36%, 3 - 7%, and 1 - 4% respectively.

[0025] In the present invention, the composition of the secondary cooling zone of continuous casting is the same as the common composition method in the prior art, without any special improvement.

[0026] One of the most important improvements of the present invention lies in that the specific secondary cooling water volume in the continuous casting secondary cooling zone is limited to 0.8 - 1.2 L / kg. Limiting the specific secondary cooling water volume within this range can enable the billet to be cooled uniformly, reduce the incidence of cracks, stably improve the quality of the billet, and reduce or even eliminate the bubble defects of grain-oriented silicon steel. When the specific secondary cooling water volume is too low, insufficient cooling causes the solidified shell to bulge between the rolls due to gravity, resulting in crack and segregation porosity defects inside the billet; when the specific secondary cooling water volume is too high, excessive cooling causes the billet to be in a fully solid state when passing through the straightening zone, and under the action of straightening stress, serious internal intermediate crack defects will occur in the billet. Therefore, whether the specific secondary cooling water volume is too high or too low, it will increase the incidence of internal cracks in the billet, leading to bubbles in the grain-oriented silicon steel during the annealing process.

[0027] In order to further reduce or even eliminate the incidence of internal cracks in the billet and eliminate the bubble defects of grain-oriented silicon steel, in some preferred embodiments, the specific secondary cooling water volume in the continuous casting secondary cooling zone can be 0.9 - 1.1 L / Kg, such as 0.9 L / Kg, 1 L / Kg or 1.1 L / Kg.

[0028] Another important improvement of the present invention lies in that the proportion of the secondary cooling water volume in the full-roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone is controlled to be 22.4 - 22.6%, 22.2 - 22.3%, 10 - 18%, 30 - 36%, 3 - 7%, 1 - 4% respectively, which can achieve uniform cooling of the billet and avoid excessive thermal stress caused by uneven cooling and generate intermediate cracks. In a preferred embodiment, the proportion of the secondary cooling water volume in the full-roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone is controlled to be 22.5%, 22.3%, 14.1%, 33.6%, 5.0% and 2.5% respectively.

[0029] In some embodiments, the total secondary cooling water volume can be 2500 - 3200 L / min, that is, the total secondary cooling water volume in the full-roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone is 2500 - 3200 L / min. When the total secondary cooling water volume is too small, the grain-oriented silicon steel billet is prone to bulge, resulting in a significant increase in the probability of intermediate crack occurrence; when the total secondary cooling water volume is too large, the grain-oriented silicon steel billet is prone to excessive straightening stress, resulting in a significant increase in the probability of intermediate crack occurrence. It should be noted that generally, a slab continuous caster has two streams of cooling water, and each stream of cooling water is independently controlled. The "total secondary cooling water volume" described in the present invention refers to the total cooling water volume of each stream.

[0030] In some embodiments, the secondary cooling water volume in the foot roll zone can be 580 - 720 L / min, the secondary cooling water volume in the vertical zone can be 580 - 710 L / min, the secondary cooling water volume in the bending zone can be 360 - 445 L / min, the secondary cooling water volume in the arc zone can be 870 - 1100 L / min, the secondary cooling water volume in the straightening zone can be 130 - 160 L / min, and the secondary cooling water volume in the horizontal zone can be 60 - 80 L / min. As long as the proportion of the secondary cooling water volume in the foot roll zone, vertical zone, bending zone, arc zone, straightening zone, and horizontal zone and the total secondary cooling water volume meet the above ranges.

[0031] In the present invention, as Figure 1 shown, the arc zone is composed of a total of 6 sector segments, namely sector segment 1, sector segment 2, sector segment 3, sector segment 4, sector segment 5, and sector segment 6 from top to bottom, and is divided into seven secondary cooling control loops for the arc zone, namely loop 1, loop 2, loop 3, loop 4, loop 5, loop 6, and loop 7. Among them, loop 1 controls the cooling water volume of the inner and outer arcs of sector segment 1, loop 2 controls the cooling water volume of the inner arc of sector segment 2, loop 3 controls the cooling water volume of the outer arc of sector segment 2, loop 4 controls the cooling water volume of the inner arcs of sector segments 3 and 4, loop 5 controls the cooling water volume of the outer arcs of sector segments 3 and 4, loop 6 controls the cooling water volume of the inner arcs of sector segments 5 and 6, and loop 7 controls the cooling water volume of the outer arcs of sector segments 5 and 6. Compared with the cooling water for the outer arc, the cooling water for the inner arc is prone to accumulate between the rolls, indirectly enhancing the cooling intensity. To effectively reduce the excessive internal stress of the slab caused by uneven cooling of the inner and outer arcs of the slab and control the length of columnar crystals in the inner arc, and further reduce the incidence of internal cracks in the slab, the ratio of the cooling water volume of loop 3 to loop 2 can be controlled to be 1.3 - 1.5:1, the ratio of the cooling water volume of loop 5 to loop 4 can be controlled to be 1.5 - 1.7:1, and the ratio of the cooling water volume of loop 7 to loop 6 can be controlled to be 1.7 - 1.9:1.

[0032] In the present invention, as Figure 1 shown, the straightening zone is composed of a total of 2 sector segments, namely sector segment 7 and sector segment 8 from top to bottom, and is divided into two secondary cooling control loops for the straightening zone, namely loop 8 and loop 9. Among them, loop 8 controls the cooling water volume of the inner arcs of sector segments 7 and 8, and loop 9 controls the cooling water volume of the outer arcs of sector segments 7 and 8. Compared with the cooling water for the outer arc, the cooling water for the inner arc is prone to accumulate between the rolls, indirectly enhancing the cooling intensity. To effectively reduce the excessive internal stress of the slab caused by uneven cooling of the inner and outer arcs of the slab and control the length of columnar crystals in the inner arc, and further reduce the incidence of internal cracks in the slab, the ratio of the cooling water volume of loop 8 to loop 9 can be controlled to be 1.9 - 2.1:1.

[0033] In a preferred embodiment, to avoid the generation of thermal stress-induced microcracks in the middle of the slab due to locally too low surface temperature of the high-temperature oriented silicon steel slab, indirect cooling is adopted for secondary cooling in the horizontal zone, and the cooling water is not directly sprayed onto the surface of the slab.

[0034] In one embodiment, the process of obtaining an oriented silicon steel slab by subjecting the solidified shell obtained through mold cooling to secondary cooling in the continuous casting secondary cooling zone includes: cooling the refined molten steel of oriented silicon steel in the mold to obtain a solidified shell, then casting at a casting speed of 0.8 - 1.4 m / min, and obtaining a solidified slab after secondary cooling in the continuous casting secondary cooling zone. Further, the process of obtaining an oriented silicon steel slab by subjecting the solidified shell obtained through mold cooling to secondary cooling in the continuous casting secondary cooling zone includes: quickly solidifying the molten steel into a solidified shell with a certain thickness around the perimeter in the mold for the refined qualified molten steel of oriented silicon steel, then casting the solidified shell at a casting speed of 0.8 - 1.4 m / min, and gradually solidifying it into a solid high-temperature slab after secondary cooling.

[0035] The method of the present invention is generally applicable to oriented silicon steel containing various chemical components. In a preferred embodiment, the method of the present invention is particularly applicable to the refined molten steel of oriented silicon steel containing the following chemical components by weight percentage: C: 0.03 - 0.05%, Si: 3.0 - 3.4%, Mn: 0.10 - 0.25%, P: 0.005 - 0.025%, S: 0.004 - 0.015%, Als: 0.0150 - 0.030%, N: 0.0070 - 0.0110%, Cu: 0.40% - 0.60%, and the balance is Fe and unavoidable impurities.

[0036] In the method of the present invention, the thickness of the oriented silicon steel slab can be 220 - 235 mm, and the width can be 1000 - 1400 mm. In some embodiments, the size of the oriented silicon steel slab can be 230×1060 mm 2 、230×1100 mm 2 、230×1120 mm 2 .

[0037] The continuous casting secondary cooling method for eliminating bubble defects in oriented silicon steel provided by the present invention can significantly reduce the incidence of internal microcracks in oriented silicon steel and further eliminate bubble defects in oriented silicon steel by optimizing the secondary cooling water ratio, water distribution in the dummy bar section, straight section, arc section and horizontal section, and the water ratio between the inner and outer arcs of the arc section.

[0038] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto. Example 1

[0039] The secondary cooling control circuit of the continuous casting machine is arranged as Figure 1 shown. For example, the equipment accuracy of the arc alignment and roll gap of the continuous casting machine meets the basic requirements (≤0.5 mm), and the casting section is 230×1060 mm 2 (the thickness of the grain-oriented silicon steel slab is 230 mm, and the width is 1060 mm).

[0040] The continuous casting secondary cooling method for reducing the bubble defects of grain-oriented silicon steel includes: Cooling the qualified refined grain-oriented silicon steel molten steel in the mold to obtain a solidified shell, and then pouring it at a casting speed of 1.2 m / min. After secondary cooling in the secondary cooling zone of continuous casting, a completely solidified slab is obtained; The qualified refined grain-oriented silicon steel molten steel includes the following chemical components by weight percentage: C: 0.035%, Si: 3.2%, Mn: 0.15%, P: 0.010%, S: 0.006%, Als: 0.020, N: 0.0090%, Cu: 0.47%; The specific water consumption of secondary cooling in the secondary cooling zone of continuous casting is 0.90 L / Kg; The secondary cooling zone of continuous casting consists of the foot roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone. The total water volume of secondary cooling is 2607 L / min. The secondary cooling water volumes of the foot roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone are 587 L / min, 581 L / min, 368 L / min, 876 L / min, 130 L / min and 65 L / min respectively. That is, based on the total water volume of secondary cooling, the proportions of the secondary cooling water volumes of the foot roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone are 22.5%, 22.3%, 14.1%, 33.6%, 5.0% and 2.5% respectively; The arc zone is composed of a total of 6 fan segments, namely fan segment 1, fan segment 2, fan segment 3, fan segment 4, fan segment 5 and fan segment 6 from top to bottom, and is divided into a total of seven secondary cooling control circuits for the arc zone, namely circuit 1, circuit 2, circuit 3, circuit 4, circuit 5, circuit 6 and circuit 7. Among them, circuit 1 controls the cooling water volume of the inner and outer arcs of fan segment 1, circuit 2 controls the cooling water volume of the inner arc of fan segment 2, circuit 3 controls the cooling water volume of the outer arc of fan segment 2, circuit 4 controls the cooling water volume of the inner arcs of fan segments 3 and 4, circuit 5 controls the cooling water volume of the outer arcs of fan segments 3 and 4, circuit 6 controls the cooling water volume of the inner arcs of fan segments 5 and 6, and circuit 7 controls the cooling water volume of the outer arcs of fan segments 5 and 6. Among them, the ratio of the cooling water volume of circuit 3 to circuit 2 in the arc zone is 1.4:1, the ratio of the cooling water volume of circuit 5 to circuit 4 is 1.6:1, and the ratio of the cooling water volume of circuit 7 to circuit 6 is 1.8:1; The straightening zone consists of two fan-shaped segments, namely fan segment 7 and fan segment 8, from top to bottom, and is divided into two secondary cooling control loops for the straightening zone, namely loop 8 and loop 9. Among them, loop 8 controls the cooling water volume of the inner arcs of fan segment 7 and fan segment 8, and loop 9 controls the cooling water volume of the outer arcs of fan segment 7 and fan segment 8. Among them, the ratio of the cooling water volume of loop 8 to that of loop 9 is 2.0:1; Indirect cooling is adopted for secondary cooling in the horizontal zone.

[0041] Such as Figure 2 shown, the macrostructure inspection results of the grain-oriented silicon steel slab show that there are no center crack defects in the slab; after manual inspection, no bubble defects are found in the decarburization annealing of the slab after rolling. Example 2

[0042] The layout of the secondary cooling control loop of the continuous caster is as Figure 1 shown, such as the equipment accuracy of the alignment and roll gap of the caster meets the basic requirements (≤0.5mm), and the casting section is 230×1100mm 2 (the thickness of the grain-oriented silicon steel slab is 230mm, and the width is 1100mm).

[0043] The continuous casting secondary cooling method for reducing bubble defects in grain-oriented silicon steel includes: Cooling the qualified refined grain-oriented silicon steel molten steel in the mold to obtain a solidified shell, and then casting at a casting speed of 1.1m / min. After secondary cooling in the continuous casting secondary cooling zone, a completely solidified slab is obtained; The qualified refined grain-oriented silicon steel molten steel includes the following chemical components by weight percentage: C: 0.038%, Si: 3.1%, Mn: 0.23%, P: 0.014%, S: 0.008%, ALs: 0.021, N: 0.0095%, Cu: 0.45%; The specific water consumption for secondary cooling in the continuous casting secondary cooling zone is 1.1L / Kg; The continuous casting secondary cooling zone consists of a dummy bar section, a vertical section, a bending section, an arc section, a straightening section and a horizontal section. The total water volume for secondary cooling is 3154 L / min. The water volumes for secondary cooling in the dummy bar section, vertical section, bending section, arc section, straightening section and horizontal section are 710L / min, 703L / min, 444L / min, 1060L / min, 158L / min and 79L / min respectively. That is, based on the total water volume for secondary cooling, the proportions of the water volumes for secondary cooling in the dummy bar section, vertical section, bending section, arc section, straightening section and horizontal section are 22.5%, 22.3%, 14.1%, 33.6%, 5.0% and 2.5% respectively; The arc-shaped area is composed of a total of 6 fan-shaped segments, namely fan-shaped segment 1, fan-shaped segment 2, fan-shaped segment 3, fan-shaped segment 4, fan-shaped segment 5, and fan-shaped segment 6 from top to bottom, and is divided into seven secondary cooling control loops for the arc-shaped area, namely loop 1, loop 2, loop 3, loop 4, loop 5, loop 6, and loop 7. Among them, loop 1 controls the cooling water volume of the inner and outer arcs of fan-shaped segment 1, loop 2 controls the cooling water volume of the inner arc of fan-shaped segment 2, loop 3 controls the cooling water volume of the outer arc of fan-shaped segment 2, loop 4 controls the cooling water volume of the inner arcs of fan-shaped segments 3 and 4, loop 5 controls the cooling water volume of the outer arcs of fan-shaped segments 3 and 4, loop 6 controls the cooling water volume of the inner arcs of fan-shaped segments 5 and 6, and loop 7 controls the cooling water volume of the outer arcs of fan-shaped segments 5 and 6. Among them, the ratio of the cooling water volume of loop 3 to loop 2 in the arc-shaped area is 1.5:1, the ratio of the cooling water volume of loop 5 to loop 4 is 1.7:1, and the ratio of the cooling water volume of loop 7 to loop 6 is 1.9:1; The straightening area is composed of a total of 2 fan-shaped segments, namely fan-shaped segment 7 and fan-shaped segment 8 from top to bottom, and is divided into two secondary cooling control loops for the straightening area, namely loop 8 and loop 9. Among them, loop 8 controls the cooling water volume of the inner arcs of fan-shaped segments 7 and 8, and loop 9 controls the cooling water volume of the outer arcs of fan-shaped segments 7 and 8. Among them, the ratio of the cooling water volume of loop 8 to loop 9 is 2.1:1; Indirect cooling is used for the secondary cooling in the horizontal area.

[0044] As Figure 3 shown, the macrostructure inspection results of the grain-oriented silicon steel slab indicate that there are no intermediate crack defects in the slab; through manual inspection, it is shown that there are no bubble defects after the slab is decarburized and annealed after rolling. Example 3

[0045] The layout of the secondary cooling control loop of the continuous caster is as Figure 1 shown, such as the equipment accuracy of the alignment and roll gap of the caster meets the basic requirements (≤0.5 mm), and the casting section is 230×1120 mm 2 (the thickness of the grain-oriented silicon steel slab is 230 mm and the width is 1120 mm).

[0046] The continuous casting secondary cooling method for reducing the bubble defects of grain-oriented silicon steel includes: Cooling the qualified refined grain-oriented silicon steel molten steel in the mold to obtain a solidified shell, and then casting it at a casting speed of 1.0 m / min, and obtaining a completely solidified slab after secondary cooling in the continuous casting secondary cooling zone; The qualified refined grain-oriented silicon steel molten steel includes the following chemical components by weight percentage: C: 0.04%, Si: 3.3%, Mn: 0.23%, P: 0.017%, S: 0.010%, ALs: 0.025, N: 0.0098%, Cu: 0.50%; The secondary cooling water ratio in the secondary cooling zone of continuous casting is 1.0 L / Kg; The secondary cooling zone of continuous casting consists of a dummy bar section, a vertical section, a bending section, an arc section, a straightening section, and a horizontal section. The total secondary cooling water volume is 2866 L / min. The secondary cooling water volumes in the dummy bar section, vertical section, bending section, arc section, straightening section, and horizontal section are 645 L / min, 639 L / min, 404 L / min, 963 L / min, 143 L / min, and 72 L / min respectively. That is, based on the total secondary cooling water volume, the proportions of the secondary cooling water volumes in the dummy bar section, vertical section, bending section, arc section, straightening section, and horizontal section are 22.5%, 22.3%, 14.1%, 33.6%, 5.0%, and 2.5% respectively; The arc section consists of a total of 6 segment fans, namely segment fan 1, segment fan 2, segment fan 3, segment fan 4, segment fan 5, and segment fan 6 from top to bottom, and is divided into a total of seven secondary cooling control loops for the arc section, namely loop 1, loop 2, loop 3, loop 4, loop 5, loop 6, and loop 7. Among them, loop 1 controls the cooling water volume of the inner and outer arcs of segment fan 1, loop 2 controls the cooling water volume of the inner arc of segment fan 2, loop 3 controls the cooling water volume of the outer arc of segment fan 2, loop 4 controls the cooling water volume of the inner arcs of segment fans 3 and 4, loop 5 controls the cooling water volume of the outer arcs of segment fans 3 and 4, loop 6 controls the cooling water volume of the inner arcs of segment fans 5 and 6, and loop 7 controls the cooling water volume of the outer arcs of segment fans 5 and 6. Among them, the ratio of the cooling water volume of loop 3 to loop 2 in the arc section is 1.3:1, the ratio of the cooling water volume of loop 5 to loop 4 is 1.5:1, and the ratio of the cooling water volume of loop 7 to loop 6 is 1.7:1; The straightening section consists of a total of 2 segment fans, namely segment fan 7 and segment fan 8 from top to bottom, and is divided into two secondary cooling control loops for the straightening section, namely loop 8 and loop 9. Among them, loop 8 controls the cooling water volume of the inner arcs of segment fans 7 and 8, and loop 9 controls the cooling water volume of the outer arcs of segment fans 7 and 8. Among them, the ratio of the cooling water volume of loop 8 to loop 9 is 1.9:1; Indirect cooling is used for secondary cooling in the horizontal section.

[0047] As Figure 4 shown, the macrostructure inspection results of the grain-oriented silicon steel slab indicate that there are no middle crack defects in the slab; after manual inspection, no bubble defects are found in the slab after rolling and decarburization annealing.

[0048] Comparative Example 1 Implemented according to the method of Example 1, the difference is that the proportions of the secondary cooling water volumes in the dummy bar section, vertical section, bending section, arc section, straightening section, and horizontal section are 20%, 24.8%, 14.1%, 28.6%, 10%, and 2.5% respectively.

[0049] As Figure 5As shown, the macrostructure inspection results of the grain-oriented silicon steel slab indicate that there are center crack defects in the slab; through manual inspection, it is found that there are bubble defects after decarburization annealing of the slab after rolling.

[0050] Comparative Example 2 Implemented according to the method of Example 1, except that the specific secondary cooling water ratio in the secondary cooling zone of continuous casting is 1.5 L / kg.

[0051] As Figure 6 As shown, the macrostructure inspection results of the grain-oriented silicon steel slab indicate that there are center crack defects in the slab; through manual inspection, it is found that there are bubble defects after decarburization annealing of the slab after rolling.

[0052] Comparative Example 3 Implemented according to the method of Example 1, except that the specific secondary cooling water ratio in the secondary cooling zone of continuous casting is 0.5 L / kg.

[0053] As Figure 7 As shown, the macrostructure inspection results of the grain-oriented silicon steel slab indicate that there are center crack defects in the slab; through manual inspection, it is found that there are bubble defects after decarburization annealing of the slab after rolling.

[0054] It can be seen from the results of the above examples and comparative examples that by using the method of the present invention for secondary cooling in continuous casting, by limiting the specific secondary cooling water ratio in the secondary cooling zone of continuous casting within a specific range and optimizing the cooling water ratio in the full-roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone, the incidence rate of internal micro-cracks in the grain-oriented silicon steel slab can be significantly reduced, and further the bubble defects generated in the annealing process of the grain-oriented silicon steel can be eliminated.

[0055] It should be understood that the parts not elaborated in detail in this specification all belong to the prior art.

[0056] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A continuous casting secondary cooling method for reducing bubble defects in grain-oriented silicon steel, characterized in that, The continuous casting secondary cooling method includes: performing secondary cooling on the solidified billet shell obtained through mold cooling in the continuous casting secondary cooling zone to obtain an oriented silicon steel casting billet, where the continuous casting secondary cooling zone consists of a dummy bar section, a vertical section, a bending section, an arc section, a straightening section, and a horizontal section; The specific secondary cooling water volume ratio in the continuous casting secondary cooling zone is 0.8 - 1.2 L / kg; Based on the total secondary cooling water volume, the proportions of the secondary cooling water volumes in the dummy bar section, vertical section, bending section, arc section, straightening section, and horizontal section are 22.4 - 22.6%, 22.2 - 22.3%, 10 - 18%, 30 - 36%, 3 - 7%, and 1 - 4% respectively.

2. The continuous casting secondary cooling method according to claim 1, characterized in that, The specific secondary cooling water volume ratio in the continuous casting secondary cooling zone is 0.9 - 1.1 L / Kg.

3. The continuous casting secondary cooling method according to claim 1 or 2, characterized in that, The total secondary cooling water volume is 2500 - 3200 L / min; And / or, the secondary cooling water volume in the dummy bar section is 580 - 720 L / min, the secondary cooling water volume in the vertical section is 580 - 710 L / min, the secondary cooling water volume in the bending section is 360 - 445 L / min, the secondary cooling water volume in the arc section is 870 - 1100 L / min, the secondary cooling water volume in the straightening section is 130 - 160 L / min, and the secondary cooling water volume in the horizontal section is 60 - 80 L / min.

4. The continuous casting secondary cooling method according to claim 1, characterized in that, Based on the total secondary cooling water volume, the proportions of the secondary cooling water volumes in the dummy bar section, vertical section, bending section, arc section, straightening section, and horizontal section are 22.5%, 22.3%, 14.1%, 33.6%, 5.0%, and 2.5% respectively.

5. The continuous casting secondary cooling method according to claim 1, characterized in that, The arc section is composed of a total of 6 segment sectors, namely segment sector 1, segment sector 2, segment sector 3, segment sector 4, segment sector 5, and segment sector 6 from top to bottom, and is divided into a total of seven arc section secondary cooling control loops, namely loop 1, loop 2, loop 3, loop 4, loop 5, loop 6, and loop 7. Among them, loop 1 controls the cooling water volume of the inner and outer arcs of segment sector 1, loop 2 controls the cooling water volume of the inner arc of segment sector 2, loop 3 controls the cooling water volume of the outer arc of segment sector 2, loop 4 controls the cooling water volume of the inner arcs of segment sectors 3 and 4, loop 5 controls the cooling water volume of the outer arcs of segment sectors 3 and 4, loop 6 controls the cooling water volume of the inner arcs of segment sectors 5 and 6, and loop 7 controls the cooling water volume of the outer arcs of segment sectors 5 and 6; Among them, the ratio of the cooling water volume of loop 3 to that of loop 2 is 1.3 - 1.5:1, the ratio of the cooling water volume of loop 5 to that of loop 4 is 1.5 - 1.7:1, and the ratio of the cooling water volume of loop 7 to that of loop 6 is 1.7 - 1.9:

1.

6. The continuous casting secondary cooling method according to claim 1 or 5, characterized in that, The straightening section is composed of a total of 2 segment sectors, namely segment sector 7 and segment sector 8 from top to bottom, and is divided into two straightening section secondary cooling control loops, namely loop 8 and loop 9. Among them, loop 8 controls the cooling water volume of the inner arcs of segment sectors 7 and 8, and loop 9 controls the cooling water volume of the outer arcs of segment sectors 7 and 8; Among them, the ratio of the cooling water volume of loop 8 to that of loop 9 is 1.9 - 2.1:

1.

7. The continuous casting secondary cooling method according to claim 1, characterized in that, The secondary cooling in the horizontal section adopts an indirect cooling method.

8. The continuous casting secondary cooling method according to claim 1, characterized in that, The process of secondary cooling the solidified billet shell obtained by cooling in the mold in the secondary cooling zone of continuous casting to obtain an oriented silicon steel slab includes: cooling the refined molten steel of oriented silicon steel in the mold to obtain a solidified billet shell, and then casting at a casting speed of 0.8 - 1.4 m / min, and obtaining a solidified slab after secondary cooling in the secondary cooling zone of continuous casting.

9. The continuous casting secondary cooling method according to claim 8, characterized in that, The refined molten steel of oriented silicon steel includes the following chemical components by weight percentage: C: 0.03 - 0.05%, Si: 3.0 - 3.4%, Mn: 0.10 - 0.25%, P: 0.005 - 0.025%, S: 0.004 - 0.015%, Als: 0.0150 - 0.030%, N: 0.0070 - 0.0110%, Cu: 0.40% - 0.60%, and the balance is Fe and unavoidable impurities.

10. The continuous casting secondary cooling method according to claim 1, characterized in that, The thickness of the oriented silicon steel slab is 220 - 235 mm, and the width is 1000 - 1400 mm.

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