Secondary cooling method for continuous casting to reduce bubble defects in oriented silicon steel

Abstract

The present invention relates to the field of continuous steel casting technology in the metallurgical industry, and discloses a continuous casting secondary cooling method for reducing bubble defects in oriented silicon steel. The continuous casting secondary cooling method includes: the continuous casting secondary cooling zone is composed of a full roller zone, a vertical zone, a bending zone, an arc zone, a straightening zone and a horizontal zone; the secondary cooling water volume of the continuous casting secondary cooling zone is 0.8-1.2 L / kg; the secondary cooling water volume of the full roller zone, the vertical zone, the bending zone, the arc zone, the straightening zone and the horizontal zone accounts for 22.4-22.6%, 22.2-22.3%, 10-18%, 30-36%, 3-7% and 1-4% respectively. The present invention can significantly reduce the incidence of microcracks inside the oriented silicon steel ingot by limiting the secondary cooling water volume to a specific range and optimizing the water distribution in the full roller zone, the straight section, the arc section and the horizontal section, thereby eliminating the bubble defects generated by the oriented silicon steel during the annealing process.

Description

Technical Field

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

[0002] As the key core raw material for transformers, reactors and other voltage-regulating and transforming equipment, the development of oriented silicon steel carries the green mission of energy conservation and emission reduction. The process flow of oriented silicon steel is ingot casting → hot-rolled coil → pickling → pickling → decarburization annealing → secondary cold rolling → MgO plating + annealing + small furnace sintering → hood annealing. The quality of ingot directly affects the quality of oriented silicon steel.

[0003] At present, oriented silicon steel ingots are generally produced by conventional slab continuous casting machines. The casting machines are equipped with secondary cooling electromagnetic stirring rollers, and the ingots are hot-charged and rolled. There is a method that cannot accurately evaluate the quality of oriented silicon steel in a timely manner. Moreover, some internal defects of the ingots often appear as bubble defects only after decarburization annealing. Once bubble defects appear, they often cause batch quality defects and large economic losses.

[0004] Chinese patent CN113857449B discloses a method and system for preparing oriented silicon steel ingots. This method is used to continuously cast refined molten steel. The continuous casting process includes the following steps: solidification to solidify a portion of the refined molten steel into a shell; and electromagnetic stirring during the solidification process to form the remaining refined molten steel into an ingot. The spacing between the electromagnetic stirring position and the mold outlet is 0.3 to 1.5 meters, and the electromagnetic stirring current range is 0 A to 900 A. This method adjusts the electromagnetic stirring intensity by adjusting the electromagnetic stirring position and current, thereby adjusting the amount of equiaxed crystals generated and expanding the range of equiaxed crystal ratios. However, the method does not address the issue of bubbles in the annealing process of oriented silicon steel.

[0005] Chinese patent CN115896602B discloses a method for producing and processing grain-oriented silicon steel slabs. The method comprises the following steps: subjecting molten iron to KR desulfurization treatment and converter smelting to produce converter iron, wherein the carbon content of the converter iron is controlled to be 0.02%-0.06% and the oxygen content is controlled to be 0.05-0.11%; transferring the converter iron to a ladle and then performing LF refining to produce refined molten steel, wherein the amount of alloy added to the ladle, the amount of slag discharged during tapping, and the bottom-blowing gas flow rate of the LF refining are controlled to ensure that the surface slag contains less than or equal to 1% FeO; and subjecting the refined molten steel to RH refining and continuous casting to produce grain-oriented silicon steel slabs, wherein the RH refining is performed by circulating flow control to ensure that inclusions fully float. The above method significantly reduces inclusions, makes the molten steel cleaner, improves the component hit rate in the slab, reduces the inclusions of MnO, SiO2, Al2O3 and their complexes, and makes the slab have better performance. However, it does not mention how to solve the problem of bubbles appearing in the annealing process of oriented silicon steel.

[0006] It can be seen that the existing technology does not solve the problem of bubbles appearing in the annealing process of oriented silicon steel. Therefore, it is urgent to provide a new method to reduce the bubble defects of 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 existing technology does not solve the problem of bubbles appearing in the annealing process of oriented silicon steel, and to provide a continuous casting secondary cooling method for reducing bubble defects in oriented silicon steel. This method can greatly reduce or even eliminate bubble defects in the annealing rolls of oriented silicon steel, avoid batch quality defects, significantly reduce the quality loss of castings, and greatly improve the physical quality of value-added products, thereby bringing substantial economic benefits to the enterprise and improving the core competitiveness of the enterprise.

[0008] To achieve the above-mentioned object, the present invention provides a continuous casting secondary cooling method for reducing bubble defects in grain-oriented silicon steel. The continuous casting secondary cooling method comprises: subjecting a solidified billet shell obtained by cooling a crystallizer to secondary cooling in a continuous casting secondary cooling zone to obtain a grain-oriented silicon steel billet, wherein the continuous casting secondary cooling zone comprises a foot roll zone, a vertical zone, a bending zone, an arc zone, a straightening zone, and a horizontal zone;

[0009] The secondary cooling water volume of the continuous casting secondary cooling zone is 0.8-1.2 L / kg;

[0010] Taking the total secondary cooling water volume as the benchmark, the secondary cooling water volume of the foot roll area, vertical area, bending area, arc area, straightening area and horizontal area accounts for 22.4-22.6%, 22.2-22.3%, 10-18%, 30-36%, 3-7% and 1-4% respectively.

[0011] Preferably, the secondary cooling water volume of the continuous casting secondary cooling zone is 0.9-1.1 L / Kg.

[0012] Preferably, the total water volume of secondary cooling is 2500-3200 L / min.

[0013] Preferably, the secondary cooling water volume in the foot roll zone is 580-720 L / min, the secondary cooling water volume in the vertical zone is 580-710 L / min, the secondary cooling water volume in the bending zone is 360-445 L / min, the secondary cooling water volume in the arc zone is 870-1100 L / min, the secondary cooling water volume in the straightening zone is 130-160 L / min, and the secondary cooling water volume in the horizontal zone is 60-80 L / min.

[0014] Preferably, based on the total secondary cooling water volume, the secondary cooling water volume in the foot roll area, vertical area, bending area, arc area, straightening area and horizontal area accounts for 22.5%, 22.3%, 14.1%, 33.6%, 5.0% and 2.5% respectively.

[0015] Preferably, the arc zone is composed of 6 sector segments from top to bottom, namely sector 1, sector 2, sector 3, sector 4, sector 5 and sector 6, which are divided into seven arc zone secondary cooling control circuits: 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 1, loop 2 controls the cooling water volume of the inner arc of sector 2, loop 3 controls the cooling water volume of the outer arc of sector 2, and loop 4 controls the cooling water volume of the outer arc of sector 2. Circuit 5 controls the cooling water volume of the inner arc of sector 3 and sector 4, circuit 5 controls the cooling water volume of the outer arc of sector 3 and sector 4, circuit 6 controls the cooling water volume of the inner arc of sector 5 and sector 6, and circuit 7 controls the cooling water volume of the outer arc of sector 5 and sector 6; among them, the cooling water volume ratio of circuit 3 to circuit 2 is 1.3-1.5:1, the cooling water volume ratio of circuit 5 to circuit 4 is 1.5-1.7:1, and the cooling water volume ratio of circuit 7 to circuit 6 is 1.7-1.9:1.

[0016] Preferably, the straightening zone is composed of two sector segments from top to bottom, namely sector 7 and sector 8, and is divided into two straightening zone second cooling control circuits, namely circuit 8 and circuit 9, wherein circuit 8 controls the cooling water volume of the inner arcs of sector 7 and sector 8, and circuit 9 controls the cooling water volume of the outer arcs of sector 7 and sector 8; wherein the cooling water volume ratio of circuit 8 to circuit 9 is 1.9-2.1:1.

[0017] Preferably, the secondary cooling of the horizontal zone adopts indirect cooling.

[0018] Preferably, the solidified shell obtained by cooling the crystallizer is subjected to secondary cooling in the continuous casting secondary cooling zone to obtain the oriented silicon steel ingot. The process includes: cooling the refined oriented silicon steel molten steel in the crystallizer to obtain the solidified shell, then pouring it at a pulling speed of 0.8-1.4m / min, and obtaining the solidified ingot (completely solidified ingot) after secondary cooling in the continuous casting secondary cooling zone.

[0019] Preferably, the refined oriented silicon steel molten steel comprises the following chemical components in weight percentage:

[0020] 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.

[0021] Preferably, the oriented silicon steel ingot has a thickness of 220-235 mm and a width of 1000-1400 mm.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The present invention can significantly reduce the incidence of microcracks inside oriented silicon steel ingots by limiting the secondary cooling water ratio in the continuous casting secondary cooling zone to a specific range and optimizing the cooling water ratio in the foot roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone, thereby eliminating bubble defects generated in oriented silicon steel during the annealing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the layout of the continuous casting secondary cooling control circuit;

[0025] Figure 2 This is a transverse low-magnification image of the oriented silicon steel ingot prepared in Example 1;

[0026] Figure 3 This is a transverse low-magnification image of the oriented silicon steel ingot prepared in Example 2;

[0027] Figure 4 This is a transverse low-magnification image of the oriented silicon steel ingot prepared in Example 3;

[0028] Figure 5 This is a transverse low-magnification image of the oriented silicon steel ingot prepared in Comparative Example 1;

[0029] Figure 6 This is a transverse low-magnification image of the oriented silicon steel ingot prepared in Comparative Example 2;

[0030] Figure 7This is a transverse low-magnification image of the oriented silicon steel ingot prepared in Comparative Example 3. DETAILED DESCRIPTION

[0031] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0032] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0033] The mechanism of reducing bubble defects in oriented silicon steel according to the present invention is that if secondary intergranular microcracks appear inside the ingot during the continuous casting process, then the internal defects of the ingot will obviously appear as bubble defects after decarburization annealing. The present invention reduces the incidence of microcracks inside the oriented silicon steel ingot by optimizing the continuous casting secondary cooling process, thereby achieving the purpose of eliminating bubble defects generated by oriented silicon steel in the annealing process.

[0034] As described above, the continuous casting secondary cooling method for reducing bubble defects in grain-oriented silicon steel provided by the present invention comprises: subjecting the solidified billet shell obtained by cooling the crystallizer to secondary cooling in the continuous casting secondary cooling zone to obtain a grain-oriented silicon steel billet, wherein the continuous casting secondary cooling zone is composed of a foot roll zone, a vertical zone, a bending zone, an arc zone, a straightening zone, and a horizontal zone;

[0035] The secondary cooling water volume of the continuous casting secondary cooling zone is 0.8-1.2L / kg;

[0036] Taking the total secondary cooling water volume as the benchmark, the secondary cooling water volume of the foot roll area, vertical area, bending area, arc area, straightening area and horizontal area accounts for 22.4-22.6%, 22.2-22.3%, 10-18%, 30-36%, 3-7% and 1-4% respectively.

[0037] In the present invention, the composition of the continuous casting secondary cooling zone is the same as the common composition in the prior art, without any special improvement.

[0038] One of the most important improvements of the present invention is that the secondary cooling water ratio of the continuous casting secondary cooling zone is limited to 0.8-1.2 L / kg. Limiting the secondary cooling water ratio to this range can uniformly cool the ingot, reduce the crack incidence, steadily improve the quality of the ingot, and reduce or even eliminate the bubble defects of oriented silicon steel. When the secondary cooling water ratio is too low, insufficient cooling causes the solidified ingot shell to bulge due to gravity between the rollers, resulting in cracks and segregation and loose defects inside the ingot; when the secondary cooling water ratio is too high, excessive cooling will cause the ingot to be in a fully solid state after passing through the straightening zone. Under the action of straightening stress, serious internal intermediate crack defects will occur in the ingot. Therefore, when the secondary cooling water ratio is too high or too low, the incidence of internal cracks in the ingot will increase, thereby causing bubbles to form in the oriented silicon steel during the annealing process.

[0039] In order to further reduce or even eliminate the incidence of internal cracks in the ingot and eliminate bubble defects in oriented silicon steel, in some preferred embodiments, the secondary cooling water volume in the continuous casting secondary cooling zone can be 0.9-1.1 L / Kg, for example, 0.9 L / Kg, 1 L / Kg or 1.1 L / Kg.

[0040] The second most important improvement of the present invention is to control the proportion of secondary cooling water in the foot roll area, vertical area, bending area, arc area, straightening area, and horizontal area to 22.4-22.6%, 22.2-22.3%, 10-18%, 30-36%, 3-7%, and 1-4%, respectively. This achieves uniform cooling of the slab and avoids uneven cooling that causes excessive thermal stress and cracks in the middle. In a preferred embodiment, the proportion of secondary cooling water in the foot roll area, vertical area, bending area, arc area, straightening area, and horizontal area is controlled to 22.5%, 22.3%, 14.1%, 33.6%, 5.0%, and 2.5%, respectively.

[0041] In some embodiments, the total water volume for secondary cooling can be 2500-3200 L / min, that is, the total water volume for secondary cooling in the full roll zone, vertical zone, bending zone, arc zone, straightening zone, and horizontal zone is 2500-3200 L / min. When the total water volume for secondary cooling is too little, the oriented silicon steel ingot is prone to bulging, resulting in a significant increase in the probability of middle cracks; when the total water volume for secondary cooling is too much, the oriented silicon steel ingot is prone to excessive straightening stress, resulting in a significant increase in the probability of middle cracks. It should be noted that a general slab continuous casting machine has two streams of cooling water, and each stream of cooling water is independently controlled. The "total water volume for secondary cooling" described in the present invention refers to the total cooling water volume of each stream.

[0042] In some embodiments, the secondary cooling water volume of the foot roller zone can be 580-720 L / min, the secondary cooling water volume of the vertical zone can be 580-710 L / min, the secondary cooling water volume of the bending zone can be 360-445 L / min, the secondary cooling water volume of the arc zone can be 870-1100 L / min, the secondary cooling water volume of the straightening zone can be 130-160 L / min, and the secondary cooling water volume of the horizontal zone can be 60-80 L / min, as long as the proportion of the secondary cooling water volume of the foot roller zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone and the total secondary cooling water volume meet the above ranges.

[0043] In the present invention, Figure 1 As shown, the arc zone is composed of 6 sector segments from top to bottom, namely sector 1, sector 2, sector 3, sector 4, sector 5 and sector 6, which are divided into seven arc zone two cooling control circuits, namely loop 1, loop 2, loop 3, loop 4, loop 5, loop 6 and loop 7, among which loop 1 controls the cooling water volume of the inner and outer arcs of sector 1 segment, loop 2 controls the cooling water volume of the inner arc of sector 2 segment, loop 3 controls the cooling water volume of the outer arc of sector 2 segment, loop 4 controls the cooling water volume of the inner arcs of sector 3 and sector 4 segments, loop 5 controls the cooling water volume of the outer arc of sector 3 and sector 4 segments, loop 6 controls the cooling water volume of the inner arc of sector 5 and sector 6 segments, and loop 7 controls the cooling water volume of the outer arc of sector 5 and sector 6 segments. Compared with outer arc cooling water, inner arc cooling water is easy to accumulate between the rollers, which indirectly enhances the cooling intensity. In order to effectively reduce the excessive internal stress of the billet caused by uneven cooling of the inner and outer arcs of the billet and control the length of the inner arc columnar crystals, and further reduce the incidence of internal cracks in the billet, the cooling water ratio of loop 3 to loop 2 can be controlled to 1.3-1.5:1, the cooling water ratio of loop 5 to loop 4 can be controlled to 1.5-1.7:1, and the cooling water ratio of loop 7 to loop 6 can be controlled to 1.7-1.9:1.

[0044] In the present invention, Figure 1 As shown, the straightening zone consists of two sectors, sector 7 and sector 8, from top to bottom. These sectors are divided into two cooling control circuits, circuit 8 and circuit 9. Circuit 8 controls the cooling water flow to the inner arcs of sectors 7 and 8, while circuit 9 controls the cooling water flow to the outer arcs of sectors 7 and 8. Compared to the outer arc cooling water, the inner arc cooling water tends to accumulate between the rollers, indirectly enhancing the cooling intensity. To effectively reduce excessive internal stress in the billet caused by uneven cooling of the inner and outer arcs, control the length of columnar crystals in the inner arc, and further reduce the incidence of internal cracks in the billet, the cooling water flow ratio of circuit 8 to circuit 9 can be controlled to 1.9-2.1:1.

[0045] In a preferred embodiment, in order to avoid thermal stress and micro cracks in the middle of the high-temperature oriented silicon steel ingot due to local low temperature on the surface of the ingot, the secondary cooling of the horizontal zone adopts indirect cooling and the cooling water is not directly sprayed onto the ingot surface.

[0046] In one embodiment, the solidified shell obtained by cooling the crystallizer is subjected to secondary cooling in the continuous casting secondary cooling zone to obtain the oriented silicon steel ingot, comprising: cooling the refined oriented silicon steel molten steel in the crystallizer to obtain the solidified shell, then casting at a pulling speed of 0.8-1.4 m / min, and obtaining the solidified ingot after secondary cooling in the continuous casting secondary cooling zone. Further, the solidified shell obtained by cooling the crystallizer is subjected to secondary cooling in the continuous casting secondary cooling zone to obtain the oriented silicon steel ingot, comprising: firstly rapidly solidifying the refined qualified oriented silicon steel molten steel in the crystallizer into a solidified shell with a certain thickness on all sides, then casting the solidified shell at a pulling speed of 0.8-1.4 m / min, and gradually solidifying into a solid high-temperature ingot after secondary cooling.

[0047] The method of the present invention is generally applicable to grain-oriented silicon steels containing various chemical compositions. In a preferred embodiment, the method of the present invention is particularly applicable to refined grain-oriented silicon steel molten steel containing the following chemical compositions in weight percentage:

[0048] 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.

[0049] In the method of the present invention, the thickness of the oriented silicon steel ingot can be 220-235 mm, and the width can be 1000-1400 mm. In some embodiments, the size of the oriented silicon steel ingot can be 230×1060 mm. 2 、230×1100mm 2 、230×1120mm 2 .

[0050] 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 microcracks inside oriented silicon steel by optimizing the water volume of the continuous casting secondary cooling, the water distribution in the full roller area, the straight section, the arc section and the horizontal section, and the water volume ratio of the inner and outer arcs of the arc section, thereby eliminating the bubble defects in oriented silicon steel.

[0051] 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

[0052] The secondary cooling control circuit layout of the continuous casting machine is as follows Figure 1 As shown, the accuracy of the arc and roller slot casting equipment meets the basic requirements (≤0.5mm), and the casting section is 230×1060mm 2 (The thickness of the oriented silicon steel ingot is 230mm and the width is 1060mm).

[0053] The continuous casting secondary cooling method to reduce bubble defects in oriented silicon steel includes:

[0054] The refined qualified oriented silicon steel liquid is cooled in the crystallizer to obtain a solidified shell, which is then cast at a pulling speed of 1.2m / min. After secondary cooling in the continuous casting secondary cooling zone, a fully solidified ingot is obtained.

[0055] The refined qualified oriented silicon steel liquid includes the following chemical components in weight percentage:

[0056] C: 0.035%, Si: 3.2%, Mn: 0.15%, P: 0.010%, S: 0.006%, ALs: 0.020, N: 0.0090%, Cu: 0.47%;

[0057] The secondary cooling water volume in the continuous casting secondary cooling zone is 0.90L / Kg;

[0058] The continuous casting secondary cooling zone consists of a foot roll zone, a vertical zone, a bending zone, an arc zone, a straightening zone and a horizontal zone. The total secondary cooling water volume is 2607 L / min. The secondary cooling water volumes of the foot roll zone, the vertical zone, the bending zone, the arc zone, the straightening zone and the 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 secondary cooling water volume, the secondary cooling water volumes of the foot roll zone, the vertical zone, the bending zone, the arc zone, the straightening zone and the horizontal zone account for 22.5%, 22.3%, 14.1%, 33.6%, 5.0% and 2.5%, respectively.

[0059] The arc zone is composed of 6 sectors from top to bottom, namely sector 1, sector 2, sector 3, sector 4, sector 5 and sector 6, which are divided into seven arc zone secondary cooling control circuits, 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 1, loop 2 controls the cooling water volume of the inner arc of sector 2, loop 3 controls the cooling water volume of the outer arc of sector 2, and loop 4 controls the cooling water volume of the outer arc of sector 2. Control the cooling water volume of the inner arc of sector 3 and sector 4, loop 5 controls the cooling water volume of the outer arc of sector 3 and sector 4, loop 6 controls the cooling water volume of the inner arc of sector 5 and sector 6, and loop 7 controls the cooling water volume of the outer arc of sector 5 and sector 6. Among them, the cooling water volume ratio of loop 3 to loop 2 in the arc area is 1.4:1, the cooling water volume ratio of loop 5 to loop 4 is 1.6:1, and the cooling water volume ratio of loop 7 to loop 6 is 1.8:1;

[0060] The straightening zone is composed of two sectors, sector 7 and sector 8, from top to bottom, and is divided into two straightening zone secondary cooling control circuits, circuit 8 and circuit 9, wherein circuit 8 controls the cooling water volume of the inner arcs of sector 7 and sector 8, and circuit 9 controls the cooling water volume of the outer arcs of sector 7 and sector 8. The cooling water volume ratio of circuit 8 to circuit 9 is 2.0:1.

[0061] The secondary cooling in the horizontal zone adopts indirect cooling method.

[0062] like Figure 2 As shown, the low-magnification inspection results of the oriented silicon steel ingot show that the ingot has no middle crack defects; after manual inspection, the ingot shows no bubble defects after decarburization annealing after rolling. Example 2

[0063] The secondary cooling control circuit layout of the continuous casting machine is as follows Figure 1 As shown, the accuracy of the arc and roller slot casting equipment meets the basic requirements (≤0.5mm), and the casting section is 230×1100mm 2 (The thickness of the oriented silicon steel ingot is 230mm and the width is 1100mm).

[0064] The continuous casting secondary cooling method to reduce bubble defects in oriented silicon steel includes:

[0065] The refined qualified oriented silicon steel liquid is cooled in the crystallizer to obtain a solidified shell, which is then cast at a pulling speed of 1.1m / min. After secondary cooling in the continuous casting secondary cooling zone, a fully solidified ingot is obtained.

[0066] The refined qualified oriented silicon steel liquid includes the following chemical components in weight percentage:

[0067] C: 0.038%, Si: 3.1%, Mn: 0.23%, P: 0.014%, S: 0.008%, ALs: 0.021, N: 0.0095%, Cu: 0.45%;

[0068] The secondary cooling water volume in the continuous casting secondary cooling zone is 1.1L / Kg;

[0069] The continuous casting secondary cooling zone consists of a foot roll zone, a vertical zone, a bending zone, an arc zone, a straightening zone and a horizontal zone. The total secondary cooling water volume is 3154 L / min. The secondary cooling water volumes of the foot roll zone, the vertical zone, the bending zone, the arc zone, the straightening zone and the horizontal zone are 710 L / min, 703 L / min, 444 L / min, 1060 L / min, 158 L / min and 79 L / min, respectively. That is, based on the total secondary cooling water volume, the secondary cooling water volumes of the foot roll zone, the vertical zone, the bending zone, the arc zone, the straightening zone and the horizontal zone account for 22.5%, 22.3%, 14.1%, 33.6%, 5.0% and 2.5%, respectively.

[0070] The arc zone is composed of 6 sectors from top to bottom, namely sector 1, sector 2, sector 3, sector 4, sector 5 and sector 6, which are divided into seven arc zone secondary cooling control circuits, 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 1, loop 2 controls the cooling water volume of the inner arc of sector 2, loop 3 controls the cooling water volume of the outer arc of sector 2, and loop 4 controls the cooling water volume of the outer arc of sector 2. Control the cooling water volume of the inner arc of sector 3 and sector 4, loop 5 controls the cooling water volume of the outer arc of sector 3 and sector 4, loop 6 controls the cooling water volume of the inner arc of sector 5 and sector 6, and loop 7 controls the cooling water volume of the outer arc of sector 5 and sector 6. Among them, the cooling water volume ratio of loop 3 to loop 2 in the arc area is 1.5:1, the cooling water volume ratio of loop 5 to loop 4 is 1.7:1, and the cooling water volume ratio of loop 7 to loop 6 is 1.9:1;

[0071] The straightening zone is composed of two sectors, sector 7 and sector 8, from top to bottom, and is divided into two straightening zone secondary cooling control circuits, circuit 8 and circuit 9, wherein circuit 8 controls the cooling water volume of the inner arcs of sector 7 and sector 8, and circuit 9 controls the cooling water volume of the outer arcs of sector 7 and sector 8. The cooling water volume ratio of circuit 8 to circuit 9 is 2.1:1.

[0072] The secondary cooling in the horizontal zone adopts indirect cooling method.

[0073] like Figure 3 As shown, the low-magnification inspection results of the oriented silicon steel ingot show that the ingot has no middle crack defects; after manual inspection, the ingot shows no bubble defects after decarburization annealing after rolling. Example 3

[0074] The secondary cooling control circuit layout of the continuous casting machine is as follows Figure 1 As shown, the accuracy of the arc and roller slot casting equipment meets the basic requirements (≤0.5mm), and the casting section is 230×1120mm 2 (The thickness of the oriented silicon steel ingot is 230mm and the width is 1120mm).

[0075] The continuous casting secondary cooling method to reduce bubble defects in oriented silicon steel includes:

[0076] The refined qualified oriented silicon steel liquid is cooled in the crystallizer to obtain a solidified shell, which is then cast at a pulling speed of 1.0m / min. After secondary cooling in the continuous casting secondary cooling zone, a fully solidified ingot is obtained.

[0077] The refined qualified oriented silicon steel liquid includes the following chemical components in weight percentage:

[0078] C: 0.04%, Si: 3.3%, Mn: 0.23%, P: 0.017%, S: 0.010%, ALs: 0.025, N: 0.0098%, Cu: 0.50%;

[0079] The secondary cooling water volume in the continuous casting secondary cooling zone is 1.0L / Kg;

[0080] The continuous casting secondary cooling zone consists of a foot roll zone, a vertical zone, a bending zone, an arc zone, a straightening zone and a horizontal zone. The total secondary cooling water volume is 2866 L / min. The secondary cooling water volumes of the foot roll zone, the vertical zone, the bending zone, the arc zone, the straightening zone and the horizontal zone 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 secondary cooling water volumes of the foot roll zone, the vertical zone, the bending zone, the arc zone, the straightening zone and the horizontal zone account for 22.5%, 22.3%, 14.1%, 33.6%, 5.0% and 2.5%, respectively.

[0081] The arc zone is composed of 6 sectors from top to bottom, namely sector 1, sector 2, sector 3, sector 4, sector 5 and sector 6, which are divided into seven arc zone secondary cooling control circuits, 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 1, loop 2 controls the cooling water volume of the inner arc of sector 2, loop 3 controls the cooling water volume of the outer arc of sector 2, and loop 4 controls the cooling water volume of the outer arc of sector 2. Control the cooling water volume of the inner arc of sector 3 and sector 4, loop 5 controls the cooling water volume of the outer arc of sector 3 and sector 4, loop 6 controls the cooling water volume of the inner arc of sector 5 and sector 6, and loop 7 controls the cooling water volume of the outer arc of sector 5 and sector 6. Among them, the cooling water volume ratio of loop 3 to loop 2 in the arc area is 1.3:1, the cooling water volume ratio of loop 5 to loop 4 is 1.5:1, and the cooling water volume ratio of loop 7 to loop 6 is 1.7:1;

[0082] The straightening zone is composed of two sectors, sector 7 and sector 8, from top to bottom, and is divided into two straightening zone secondary cooling control circuits, circuit 8 and circuit 9, wherein circuit 8 controls the cooling water volume of the inner arcs of sector 7 and sector 8, and circuit 9 controls the cooling water volume of the outer arcs of sector 7 and sector 8. The cooling water volume ratio of circuit 8 to circuit 9 is 1.9:1.

[0083] The secondary cooling in the horizontal zone adopts indirect cooling method.

[0084] like Figure 4 As shown, the low-magnification inspection results of the oriented silicon steel ingot show that the ingot has no middle crack defects; after manual inspection, the ingot shows no bubble defects after decarburization annealing after rolling.

[0085] Comparative Example 1

[0086] The method of Example 1 was followed, except that the proportions of secondary cooling water in the foot roll area, vertical area, bending area, arc area, straightening area and horizontal area were 20%, 24.8%, 14.1%, 28.6%, 10% and 2.5%, respectively.

[0087] like Figure 5 As shown in FIG, the low-magnification inspection results of the oriented silicon steel ingot show that there is a middle crack defect in the ingot; after manual inspection, the ingot shows bubble defects after decarburization annealing after rolling.

[0088] Comparative Example 2

[0089] The method of Example 1 was followed, except that the secondary cooling water volume in the continuous casting secondary cooling zone was 1.5 L / kg.

[0090] like Figure 6As shown in FIG, the low-magnification inspection results of the oriented silicon steel ingot show that there is a middle crack defect in the ingot; after manual inspection, the ingot shows bubble defects after decarburization annealing after rolling.

[0091] Comparative Example 3

[0092] The method of Example 1 was followed, except that the secondary cooling water volume in the continuous casting secondary cooling zone was 0.5 L / kg.

[0093] like Figure 7 As shown in FIG, the low-magnification inspection results of the oriented silicon steel ingot show that there is a middle crack defect in the ingot; after manual inspection, the ingot shows bubble defects after decarburization annealing after rolling.

[0094] It can be seen from the results of the above embodiments and comparative examples that by adopting the method described in the present invention for secondary cooling of continuous casting, by limiting the secondary cooling water ratio of the continuous casting secondary cooling zone to a specific range and optimizing the cooling water ratio of the foot roll zone, vertical zone, bending zone, arc zone, straightening zone and horizontal zone, the incidence of microcracks inside the oriented silicon steel ingot can be significantly reduced, thereby eliminating the bubble defects generated in the oriented silicon steel during the annealing process.

[0095] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0096] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A continuous casting secondary cooling method for reducing bubble defects in oriented silicon steel, characterized in that: The continuous casting secondary cooling method comprises: performing secondary cooling on the solidified billet shell obtained by cooling the crystallizer in a continuous casting secondary cooling zone to obtain an oriented silicon steel billet, wherein the continuous casting secondary cooling zone is composed of a foot roll zone, a vertical zone, a bending zone, an arc zone, a straightening zone and a horizontal zone; The secondary cooling water volume of the continuous casting secondary cooling zone is 0.8-1.2 L / kg; Taking the total secondary cooling water volume as the benchmark, the secondary cooling water volume of the foot roll area, vertical area, bending area, arc area, straightening area and horizontal area accounts for 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 secondary cooling water volume of 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 water volume of secondary cooling is 2500-3200 L / min; And / or, the secondary cooling water volume in the foot roll zone is 580-720 L / min, the secondary cooling water volume in the vertical zone is 580-710 L / min, the secondary cooling water volume in the bending zone is 360-445 L / min, the secondary cooling water volume in the arc zone is 870-1100 L / min, the secondary cooling water volume in the straightening zone is 130-160 L / min, and the secondary cooling water volume in the horizontal zone is 60-80 L / min.

4. The continuous casting secondary cooling method according to claim 1, characterized in that: Taking the total secondary cooling water volume as the benchmark, the secondary cooling water volume of the foot roll area, vertical area, bending area, arc area, straightening area and horizontal area accounted for 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 zone is composed of 6 sector segments from top to bottom, namely sector 1, sector 2, sector 3, sector 4, sector 5 and sector 6, and is divided into seven arc zone two cooling control loops, namely loop 1, loop 2, loop 3, loop 4, loop 5, loop 6 and loop 7, wherein loop 1 controls the cooling water volume of the inner and outer arcs of sector 1, loop 2 controls the cooling water volume of the inner arc of sector 2, loop 3 controls the cooling water volume of the outer arc of sector 2, loop 4 controls the cooling water volume of the inner arcs of sector 3 and sector 4, loop 5 controls the cooling water volume of the outer arc of sector 3 and sector 4, loop 6 controls the cooling water volume of the inner arc of sector 5 and sector 6, and loop 7 controls the cooling water volume of the outer arc of sector 5 and sector 6; Among them, the cooling water volume ratio of loop 3 to loop 2 is 1.3-1.5:1, the cooling water volume ratio of loop 5 to loop 4 is 1.5-1.7:1, and the cooling water volume ratio of loop 7 to 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 zone is composed of two sectors, sector 7 and sector 8, from top to bottom, and is divided into two straightening zone secondary cooling control circuits, circuit 8 and circuit 9, wherein circuit 8 controls the cooling water volume of the inner arcs of sector 7 and sector 8, and circuit 9 controls the cooling water volume of the outer arcs of sector 7 and sector 8; Among them, the cooling water volume ratio of loop 8 to 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 of the horizontal zone adopts an indirect cooling method.

8. The continuous casting secondary cooling method according to claim 1, characterized in that: The solidified shell obtained by cooling the crystallizer is subjected to secondary cooling in the continuous casting secondary cooling zone to obtain the oriented silicon steel ingot, which includes: cooling the refined oriented silicon steel molten steel in the crystallizer to obtain the solidified shell, then pouring it at a pulling speed of 0.8-1.4m / min, and obtaining the solidified ingot after secondary cooling in the continuous casting secondary cooling zone.

9. The continuous casting secondary cooling method according to claim 8, characterized in that: The refined oriented silicon steel molten steel includes the following chemical components in 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 oriented silicon steel ingot has a thickness of 220-235 mm and a width of 1000-1400 mm.

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