Manufacturing method for improving cold-rolled edge crack defect of high-silicon phase-change-free electrical steel

Abstract

The invention discloses a manufacturing method for improving the cold-rolled edge crack defect of high-silicon phase-change-free electrical steel, which comprises the following steps: converting molten iron by a converter, transferring to an RH (Ruhrstahl Heraeus) furnace, carrying out vacuum smelting, carrying out alloying treatment, and continuously casting the molten steel with chemical components meeting requirements into a plate blank; the plate blank is hot-rolled into a hot-rolled plate after being heated and subjected to heat preservation; and the hot-rolled plate is subjected to normalizing, acid pickling, cold rolling, continuous annealing and insulating coating coating to prepare a high-silicon phase-change-free electrical steel finished product. In the hot rolling process, the steel plate is transversely rolled through a vertical roller, the vertical roller reduction rate delta B of the vertical roller pass meets the condition that delta B is larger than or equal to 10 * delta h / H inlet and smaller than or equal to 18 * delta h / H inlet, delta h is the thickness difference of the plate blank before and after the pass, and H inlet is the thickness of the plate blank at the pass inlet. Through the process design of the procedures of continuous casting, heating, hot rolling, normalizing, cold rolling and the like, the structure uniformity of the material is improved, especially the structure uniformity in the thickness direction, and the one-time passing rate of cold rolling is 95% or above.

Description

Technical Field

[0001] The invention relates to the technical field of non-oriented electrical steel production, and in particular to a manufacturing method for improving cold-rolled edge crack defects of high-silicon non-phase-change electrical steel. Background Art

[0002] High silicon electrical steel generally refers to iron-based metal materials with a silicon content between 2% and 4%. Due to the high silicon content and low impurity elements such as carbon and nitrogen, the material has a uniform ferrite structure under high temperature and room temperature conditions, and the matrix generally does not undergo a solid phase change process as the temperature changes. High silicon electrical steel is an important soft magnetic material for motor cores in the manufacture of high-efficiency motors, automotive drive motors, compressors and other fields. In order to reduce motor core losses and improve operating efficiency, high silicon electrical steel is generally processed through multiple processes such as hot rolling, cold rolling, and annealing to a finished product with a thickness of 0.15mm to 0.35mm. Affected by material properties and uniformity of organization, the cold rolling production process of high silicon electrical steel is prone to edge cracking and breaking, which increases the difficulty of material production and reduces the product yield.

[0003] The hot-rolled edge microstructure is one of the main reasons for edge cracks and even strip breakage during the cold rolling process. If conventional production processes are used, high-silicon electrical steel is prone to uneven microstructure along the thickness direction due to the lack of phase change and the limitation of thermal conductivity. That is, the surface of the steel plate is partially recrystallized due to thermal deformation and cooling factors, while the center of the steel plate is a deformed banded microstructure. After the uneven microstructure in the hot-rolled state is normalized, the steel plate will have uneven grain sizes along the thickness direction due to the genetic nature of the microstructure, that is, the surface layer is a smaller ferrite microstructure, and the middle part is a coarse ferrite microstructure. After normalization, the uneven ferrite microstructure has different deformation tolerances during the subsequent cold rolling process. The areas with coarse grains and fragile grain boundaries are most likely to form processing cracks during cold rolling deformation. During the cold rolling process, the cracks expand under the action of tensile stress to form edge cracks or even strip breakage.

[0004] In order to improve the edge structure of high-silicon electrical steel, the existing technology mainly relies on edge heaters or local parameter adjustments, but there are still problems such as poor uniformity of structure along the thickness direction and large grain size differences, resulting in low pass rate of one-time cold rolling. For example, the Chinese invention patent document with application number CN202210800762.4 discloses a preparation method for preventing edge damage and cracking of cold-rolled high-grade silicon steel. The material composition used in the invention is C≤0.0030%, Si 2.0%~3.05%, Mn 0.2%~0.6%, Ti≤0.0025%, A1 0.3%~0.8%, S≤0.0020%. Through component optimization (low C, Si, Al, etc.), hot rolling parameter control (furnace entry temperature, final rolling temperature), normalized edge heating and small first pass reduction rate, cold rolling edge damage and cracking are prevented. The invention reduces the break rate, but does not solve the problem of organizational differences along the thickness direction. The Chinese invention application document with application number CN202410658197.1 discloses a method for controlling edge cracks in high-silicon electrical steel. The invention solves the problem of hot-rolled edge cracks in high-silicon electrical steel by controlling the slab width, corner grains and temperature (staged cooling strategy) in the continuous casting stage, combined with heating and rolling processes (rough rolling reduction ratio distribution in the latter stage). The invention avoids using edge heaters to solve the hot-rolled edge crack problem, reducing investment, but does not clarify the improvement effect of cold-rolled edge cracks, and does not solve the problem of organizational differences along the thickness direction.

[0005] Therefore, there is an urgent need to provide a solution to reduce the cold-rolled edge crack defects of high-silicon non-phase change electrical steel, so as to improve the edge organizational state of high-silicon electrical steel, solve the problem of cold-rolled edge cracks, improve the product quality of high-silicon non-phase change electrical steel, increase the yield rate, and provide support for the efficient production of the cold rolling process of high-silicon non-phase change electrical steel. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned technology, the purpose of the present invention is to provide a manufacturing method for improving the cold-rolled edge crack defects of high-silicon non-phase change electrical steel, so as to solve the problem that the high-silicon electrical steel has poor structural uniformity along the thickness direction, which is easy to cause cold-rolled edge cracks.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A manufacturing method for improving the edge crack defect of high silicon non-phase change electrical steel during cold rolling, which is special in that: the method comprises: after molten iron is blown in a converter, it is transferred to an RH furnace for vacuum smelting; after alloying treatment, the molten steel with chemical composition meeting the requirements is continuously cast into a slab with a thickness of 200-250 mm; the slab is heated and heat-insulated, and then hot-rolled into a hot-rolled plate; the hot-rolled plate is subjected to regularization, pickling, cold rolling, continuous annealing, and insulation coating to form a high silicon non-phase change electrical steel finished product; during the hot rolling process, a vertical roller is used to roll the steel plate transversely, and the vertical roller reduction rate ΔB of the vertical roller pass meets the following conditions: 10×Δh / H 入口≤ΔB≤18×Δh / H 入口 , where Δh is the thickness difference of the slab before and after passes, and H 入口 is the thickness of the slab at the entrance of the pass.

[0008] As a preferred solution, during the continuous casting of molten steel, a round-corner mold is used, and the radius R of the round-corner mold meets: 0.25h ≤ R ≤ 0.50h, where h is the slab thickness.

[0009] Furthermore, during the continuous casting of molten steel, electromagnetic stirring is used throughout the mold.

[0010] As a preferred solution, during the slab heating process, the heating temperature is 1020 - 1120°C, and the holding time does not exceed 5h.

[0011] Furthermore, during the hot rolling process, the slab is rough-rolled in 5 passes + finish-rolled in 7 passes to the target thickness. Vertical rolls are used for transverse rolling of the steel plate during both the rough rolling and finish rolling processes.

[0012] Furthermore, during the hot rolling process, the finishing rolling temperature is 850 - 900°C, and the coiling temperature is 550 - 650°C; the thickness of the hot rolled sheet is 1.5 - 2.0mm.

[0013] As a preferred solution, during the hot rolling process, the steel plate rolled to the target thickness is coiled by a coiler after laminar cooling; during the laminar cooling process, the two side edges of the steel plate are protected by C-shaped grooves, and the width L of the steel plate protected by a single-sided C-shaped groove is controlled within: 0.08×hl ≤ L ≤ 0.13×hl, where hl is the distance from the top of the upper water outlet pipe of the laminar cooling to the upper surface of the steel plate.

[0014] As a preferred solution, during the normalizing process, the normalizing temperature is 850 - 950°C, and the normalizing time is 2 - 5min; the strip steel is not trimmed before and after normalizing.

[0015] Furthermore, during the normalizing process, the temperature of the steel plate is raised to above 800°C within 30s.

[0016] As a preferred solution, the cold rolling process uses 5 - 7 passes of single cold rolling; after normalizing, the steel coil is pickled and then cold rolled in a single-stand reciprocating rolling mill in 5 - 7 passes to the target thickness of 0.15 - 0.35mm, and the front tension Kq during passes is controlled within Kq ≤ 1.25×σs×B×H 出口 , where σs is the yield strength of the entrance steel plate, B is the width of the entrance steel plate, and H 出口 is the thickness of the exit steel plate.

[0017] As a preferred solution, during the continuous annealing process, the annealing temperature is 950 - 1050 °C, and the annealing time is 90 - 150 s; the whole process in the furnace is protected by a mixed gas of H2 and N2, and the volume percentage content of H2 is 20% - 50%.

[0018] Furthermore, during the continuous annealing process, the temperature of the steel plate is raised to above 900 °C within 25 s.

[0019] As a preferred solution, the high-silicon non-transforming electrical steel comprises the following chemical components by weight percentage: Si: 2.5% - 4.5%; Als: ≤0.30%; Mn: ≤0.20%; C ≤0.005%; N ≤0.020%, and the remaining components are Fe and inevitable impurity elements.

[0020] The principles of the chemical components and the main processes in the present invention are as follows: Chemical components: Si: It belongs to the alloying element in non-oriented silicon steel. With the increase of Si content, the resistivity increases and the iron loss decreases. At the same time, with the increase of Si content, the solid solution ratio in the steel plate increases, the strength improves, and the brittleness trend increases.

[0021] Als: Similar to Si, adding Al to the steel plate can improve the magnetic properties of silicon steel. However, the addition of Al has an obvious effect on improving the deformation ability of silicon steel, increasing the area of plastic deformation during the subsequent punching process of the steel plate, which is not conducive to reducing the processing stress. At the same time, a relatively high content of aluminum element is likely to reduce titanium in the steel slag during smelting, which has a certain harm to the properties of silicon steel. Therefore, the content of Als should be appropriately controlled.

[0022] Mn: It belongs to the alloying element of silicon steel. The addition of Mn can increase the proportion of favorable textures such as {100} and {110} in the matrix. At the same time, to prevent S from forming low-melting-point FeS with Fe and causing hot brittleness, some Mn also needs to be added to the steel plate to form a solid solution with S, thereby improving the hot deformation ability. However, the addition of Mn can improve the cold deformation ability of silicon steel. Therefore, the content of Mn should be controlled within a certain range.

[0023] N and C: They are harmful elements in silicon steel. N is likely to form second-phase inclusions such as AlN and TiN in silicon steel, strongly hindering grain growth and increasing the resistance to magnetic domain movement, deteriorating the electromagnetic properties. Therefore, the content of N element should be controlled within 0.2%; when the C content exceeds 0.005%, the iron loss increases significantly and magnetic aging is obvious; during the production process, the contents of C and N elements should be strictly controlled. At the same time, reducing the contents of C and N elements reduces the austenite phase at high temperatures, making the material a uniform ferrite structure at both high and normal temperatures.

[0024] Main processes: During the continuous slab casting process, by restricting the mold type and the radius R of the fillet mold to meet the condition: 0.25h ≤ R ≤ 0.50h, the temperature difference between the corner and the middle of the billet can be effectively reduced, and the difference in the microstructure of the hot-rolled plate edge can be effectively minimized. If the fillet radius is too large, the thickness difference between the edge and the middle of the billet will increase. During the subsequent rolling process, the uneven elongation rate between the edge and the middle makes it difficult to control the shape of the steel plate. If the fillet radius is too small, the temperature difference between the corner and the middle of the billet will increase during the cooling and heating processes, resulting in an increase in the microstructure difference during the rolling process. Through full-process electromagnetic stirring, a higher proportion of equiaxed grains can be obtained, improving the hot deformation ability of the material.

[0025] During the hot-rolling heating process, high-temperature heating easily leads to the solid solution of large-sized liquid segregation inclusions. The solid-solved inclusions will form precipitates during the laminar cooling process, hindering the growth of the finished product grains, affecting the movement of magnetic domains, and deteriorating the electromagnetic properties of the product. Therefore, in this invention, a low-temperature heating of 1020 - 1120 °C is adopted to avoid the solid solution of large-sized liquid segregation inclusions in the billet. This invention uses vertical rolls to perform transverse rolling on the steel plate. By suppressing the spread, it guides the coordinated deformation of the edge and the middle, reduces the edge tensile stress, and prevents crack initiation; multiple passes with small reductions are used, and the reduction rate of the vertical roll is controlled to meet the condition: 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 , which can distribute the deformation amount, achieve planned width reduction, improve the rolling stability, and at the same time avoid sudden changes in edge stress, slow down the edge deformation rate, and avoid excessive spread leading to edge tensile stress concentration, thereby reducing the risk of shear damage and tearing, and ensuring that the metal in the middle and edge of the steel plate has the same deformation amount within the rolling mill. The thickness of the hot-rolled plate is selected as the thin gauge target thickness of 1.5 - 2.0 mm to improve the tissue uniformity of the hot-rolled plate along the thickness direction, and the deformation process is mainly placed in the hot-rolling process to reduce the deformation amount of the cold-rolling process. During the laminar cooling process, the two sides of the steel plate are protected by C-shaped grooves, and the width L of the steel plate protected by a single-sided C-shaped groove is controlled within the range of 0.08×hl ≤ L ≤ 0.13×hl, which can ensure that the laminar cooling water does not directly fall on the edge of the steel plate, ensuring consistent cooling of the edge, middle, and thickness direction of the steel plate, and improving the tissue uniformity at different positions. The protection width cannot be too small or too large. If it is too small, the cooling speed of the steel plate edge will be relatively large, and the cooling of the steel plate middle will be relatively small, unable to meet the purpose of consistent cooling of the steel plate edge, middle, and thickness direction. If it is too large, the cooling of the middle area of the steel plate will be restricted and unable to be cooled to the target coiling temperature through laminar cooling. The hot-rolling process uses a low final rolling temperature of 850 - 900 °C to reduce the temperature difference between the surface and the core of the steel plate, so as to improve the tissue difference caused by the temperature difference at different positions during the cooling of the steel plate.

[0026] During the normalizing process, the steel plate is heated to above 800°C within 30 s, the normalizing temperature is 850 - 950°C, and the normalizing time is 2 - 5 min. The normalizing temperature of the present invention is relatively high and the heating rate is relatively fast. By adopting the high-temperature and rapid heating process, the favorable plane textures {100} and {110} in the steel plate can be effectively increased, the proportion of the {111} texture can be reduced, and the electromagnetic properties of the finished product can be effectively improved. At the same time, by adopting the normalizing temperature of the present invention, the average grain size in the steel plate can be increased, and rapid heating can effectively improve the tissue uniformity. The tissue after normalizing can be inherited to the finished product process through cold rolling and annealing processes to increase the grain size of the finished product. The strip steel is not trimmed before and after normalizing, which can avoid introducing deformation internal stress at the strip steel edge due to the shearing process and increase the probability of cracks appearing at the edge during the cold rolling process.

[0027] During the cold rolling process, the front tension Kq per pass is controlled such that Kq ≤ 1.25×σs×B×H 出口 For rolling, if the present invention scheme is not adopted, an excessive front tension before cold rolling will reduce the rolling pressure and the production load of the rolling mill. As the tension increases, the pulling force of the strip steel in the rolling direction increases, and at the same time, the risk of defects and strip breakage at the strip steel edge increases.

[0028] During the annealing process, the annealing temperature is 950 - 1050°C, the annealing time is 90 - 150 s, and the steel plate is heated to above 900°C within 25 s. By adopting the rapid heating combined with high-temperature annealing process, the grain size of the steel plate is fully grown after the annealing process, effectively reducing the hysteresis loss while reducing the deformation ability of the finished steel plate and reducing the introduction of manufacturing stress after punching.

[0029] If there is a too large difference in the grain size of the edge tissue and non-uniform tissue during the hot rolling or normalizing process, edge cracking and strip breakage are likely to occur during the cold rolling process. After edge cracking and strip breakage occur, in the light case, it is necessary to increase the trimming amount and repair, reducing the production line efficiency and the first-pass rate of cold rolling. In the heavy case, it will be scrapped, unable to meet the qualified standard, and reducing the product qualification rate. The high-silicon non-phase-change electrical steel made by the method of the present invention has uniform tissue in the edge tissue after normalizing, the maximum grain size - average grain size ≤ 12 μm, and few edge cracking and strip breakage during cold rolling, and the first-pass rate of cold rolling is more than 95%.

[0030] Compared with the prior art, the beneficial effects of the present invention are: A manufacturing method for improving the cold-rolled edge crack defects of high-silicon non-phase-change electrical steel provided by the present invention. To reduce the cold-rolled edge crack defects of high-silicon non-phase-change electrical steel, through process design of continuous casting, heating, hot rolling, normalizing, cold rolling and other processes, the tissue uniformity of the material is improved, especially the tissue uniformity along the thickness direction. The edge tissue after normalizing the hot rolling raw material is uniform, the grain size distribution is uniform, the maximum grain size - average grain size ≤ 12 μm, and there are few edge cracking and strip breakage during cold rolling, and the first-pass rate of cold rolling is more than 95%. Description of the Drawings

[0031] Figure 1 It is the microstructure distribution diagram along the thickness direction of the high-silicon non-transforming electrical steel in the hot-rolled state of Example 1; Figure 2 It is the microstructure distribution diagram along the thickness direction of the high-silicon non-transforming electrical steel in the normalized state of Example 1; Figure 3 It is the cross-section microstructure distribution diagram of the high-silicon non-transforming electrical steel hot-rolled steel plate in Comparative Example 8; Figure 4 It is the cross-section microstructure distribution diagram of the high-silicon non-transforming electrical steel normalized steel plate in Comparative Example 8. Specific embodiments

[0032] In order to better explain the present invention, the main content of the present invention is further clarified below in conjunction with specific embodiments, but the content of the present invention is not limited to the following embodiments.

[0033] Example 1 A high-silicon non-transforming electrical steel, comprising the following chemical components by weight percentage: Si: 3.30%; Als: 0.10%; Mn: 0.20%; C: 0.0020%; N: 0.010%; the balance being Fe and unavoidable impurity elements.

[0034] A manufacturing method for improving the cold-rolled edge crack defects of the above high-silicon non-transforming electrical steel, comprising the following steps: 1) After the molten iron is blown in the converter, it is transferred to the RH furnace for vacuum smelting. The molten steel after refining and alloying is continuously cast into a slab with a thickness of 210 mm. A fillet mold is used in the continuous casting process, the fillet radius R is 80 mm, electromagnetic stirring is used in the mold during the continuous casting process, and the chemical component weight percentages of the slab are Si: 3.30%; Als: 0.10%; Mn: 0.20%; C: 0.0020%; N: 0.010%; the balance being Fe and unavoidable impurity elements; 2) The slab is heated in a walking beam reheating furnace, the heating temperature is 1050 °C, the holding time is 280 min, and then the steel plate is transversely rolled by vertical rolls. It is rough rolled in 5 passes and finish rolled in 7 passes to a thickness of 2.0 mm. The reduction rate ΔB of the vertical roll in each pass satisfies 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 , the finishing temperature is 860 °C, and it is coiled after laminar cooling to 580 °C. C-shaped grooves are used for protection on both sides during laminar cooling, the unilateral protection width is 120 mm, and hl is 1.1 m; 3) Normalizing and pickling: The normalizing temperature of the hot-rolled plate is 940 °C, the time is 180 s, and the normalized steel coil is surface cleaned in a turbulent acid tank; 4) First cold rolling: The pickled steel plate is cold rolled to a target thickness of 0.25 mm through 6 reciprocating passes. During the rolling process, the front tension of each pass is controlled within 1.25×σs×B×H. 出口 The untrimmed process is adopted from the hot-rolled raw material to before cold rolling. 5) Continuous annealing: The cold-rolled plate is annealed at 980 °C for 150 s. The protective atmosphere in the furnace and its volume percentage content is 30% H2 + 70% N2. 6) Insulating coating application: An insulating coating is applied to the surface of the steel coil and dried and cured.

[0035] As Figures 1-2 shown, for the high-silicon non-phase-change electrical steel manufactured by the above process, the structure is uniform and the grains are equiaxed after normalization of the hot-rolled raw material. The difference between the maximum grain size and the average grain size of the edge structure is 10 μm. It can be cold rolled to the target thickness in one pass without edge crack defects. The first-pass rate of cold rolling is 96%.

[0036] Example 2 A high-silicon non-phase-change electrical steel, including the following chemical components by weight percentage: Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the balance is Fe and inevitable impurity elements.

[0037] A manufacturing method for improving the cold-rolled edge crack defects of the above high-silicon non-phase-change electrical steel, including the following steps: 1) After the hot metal is blown in the converter, it is transferred to the RH furnace for vacuum smelting. The molten steel after refining alloying is continuously cast into a slab with a thickness of 200 mm. During the continuous casting process, a round-corner mold is used, and the radius of the round corner R is 80 mm. Electromagnetic stirring is used in the mold during the continuous casting process. The chemical components of the slab by weight percentage are respectively Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the balance is Fe and inevitable impurity elements. 2) The slab is heated in a walking beam reheating furnace. The heating temperature is 1050 °C and the holding time is 280 min. Then, horizontal rolling is carried out on the steel plate using vertical rolls. After 5 roughing passes and 7 finishing passes, it is rolled to a thickness of 2.0 mm. The reduction rate ΔB of the vertical roll in each pass all satisfies 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 , the finishing temperature is 860 °C, and it is coiled after laminar cooling to 580 °C. During laminar cooling, C-shaped grooves are used for protection on both sides of the edge, the unilateral protection width is 120 mm, and hl is 1.1 m. 3) Normalization and pickling: The normalization temperature of the hot-rolled plate is 920 °C and the time is 180 s. The normalized steel coil is surface cleaned in a turbulent acid tank. 4) First cold rolling: The pickled steel plate is rolled reciprocally through 6 passes to a target thickness of 0.25 mm. During the rolling process, the front tension in each pass is controlled within 1.25×σs×B×H 出口 and the untrimmed process is adopted from the hot-rolled raw material to before cold rolling; 5) Continuous annealing: The cold-rolled sheet is annealed at 980 °C for 150 s, and the protective atmosphere in the furnace is 30% H2 + 70% N2; 6) Insulating coating application: The surface of the steel coil is coated with an insulating coating and dried and cured.

[0038] For the high-silicon non-phase-change electrical steel manufactured by the above process, the difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material is 9 μm. It can be cold-rolled to the target thickness in one pass without edge crack defects. The one-pass cold rolling pass rate is 95%.

[0039] Example 3 A high-silicon non-phase-change electrical steel, comprising the following chemical components by weight percentage: Si: 3.40%; Als: 0.10%; Mn: 0.20%; C: 0.0015%; N: 0.010%; the balance is Fe and unavoidable impurity elements.

[0040] A manufacturing method for improving the cold-rolled edge crack defects of the above high-silicon non-phase-change electrical steel, comprising the following steps: 1) After the hot metal is blown in the converter and transferred to the RH furnace for vacuum smelting, the molten steel after refining alloying is continuously cast into a slab with a thickness of 210 mm. During the continuous casting process, a round-corner mold is used, the round-corner radius R is 100 mm, electromagnetic stirring is used in the mold during the continuous casting process, and the chemical components of the slab by weight percentage are respectively Si: 3.40%; Als: 0.10%; Mn: 0.20%; C: 0.0015%; N: 0.010%; the balance is Fe and unavoidable impurity elements; 2) The slab is heated in a walking beam reheating furnace, the heating temperature is 1100 °C, the holding time is 260 min, and then the steel plate is transversely rolled by vertical rolls. After 5 passes of rough rolling and 7 passes of finish rolling to a thickness of 2.0 mm, the reduction rate ΔB of the vertical rolls in each pass satisfies 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 and the finish rolling temperature is 850 °C. When it is coiled after laminar cooling to 560 °C, C-shaped grooves are used for protection on both sides during laminar cooling, the unilateral protection width is 110 mm, and hl is 1.1 m; 3) Normalizing and pickling: The normalizing temperature of the hot-rolled sheet is 920 °C, the time is 180 s, and the normalized steel coil is surface cleaned in a turbulent acid tank; 4) First cold rolling: The pickled steel plate is rolled reciprocally for 6 passes to a target thickness of 0.20 mm. During the rolling process, the front tension of each pass is controlled within 1.25×σs×B×H. 出口 Before cold rolling, the hot-rolled raw material adopts an untrimmed process. 5) Continuous annealing: The cold-rolled sheet is annealed at 980 °C for 150 s, and the protective atmosphere in the furnace is 30% H2 + 70% N2. 6) Insulating coating application: The surface of the steel coil is coated with an insulating coating and dried and cured.

[0041] For the high-silicon non-phase-change electrical steel manufactured by the above process, the difference between the maximum grain size and the average grain size of the edge structure after normalizing the hot-rolled raw material is 8 μm. It can be cold-rolled to the target thickness in one pass without edge crack defects. The one-pass cold rolling pass rate is 96%.

[0042] Example 4 A high-silicon non-phase-change electrical steel, including the following chemical components by weight percentage: Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the balance is Fe and inevitable impurity elements.

[0043] A manufacturing method for improving the cold-rolled edge crack defects of the above high-silicon non-phase-change electrical steel, including the following steps: 1) After being blown in the converter, the molten iron is transferred to the RH furnace for vacuum smelting. The molten steel after refining and alloying is continuously cast into a slab with a thickness of 200 mm. During continuous casting, a round-corner mold is used, and the round-corner radius R is 100 mm. Electromagnetic stirring is used in the mold during continuous casting. The chemical components of the slab by weight percentage are respectively Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the balance is Fe and inevitable impurity elements. 2) The slab is heated in a walking beam reheating furnace. The heating temperature is 1050 °C, and the holding time is 280 min. Then, horizontal rolling is carried out on the steel plate using vertical rolls. After 5 passes of rough rolling and 7 passes of finish rolling to a thickness of 2.0 mm, the reduction rate ΔB of the vertical roll in each pass satisfies 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 , and the final rolling temperature is 860 °C. It is coiled after laminar cooling to 580 °C. During laminar cooling, C-shaped grooves are used for protection on both sides of the edge, and the single-side protection width is 88 mm, and hl is 1.1 m. 3) Normalizing and pickling: The normalizing temperature of the hot-rolled sheet is 920 °C, and the time is 180 s. The normalized steel coil is surface-cleaned in a turbulent acid tank. 4) First cold rolling: The pickled steel plate is rolled reciprocally for 6 passes to a target thickness of 0.25 mm. During the rolling process, the front tension of each pass is controlled within 1.25×σs×B×H, and the hot-rolled raw material adopts an untrimmed process before cold rolling. 出口 5) Continuous annealing: The cold-rolled sheet is annealed at 980 °C for 150 s, and the protective atmosphere in the furnace is 30% H2 + 70% N2. 6) Insulating coating application: The surface of the steel coil is coated with an insulating paint and dried and cured.

[0044] For the high-silicon non-phase-change electrical steel manufactured by the above process, the difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material is 9 μm. It can be cold-rolled to the target thickness in one pass without edge crack defects. The first-pass rate of cold rolling is 96%.

[0045] Example 5 A high-silicon non-phase-change electrical steel, comprising the following chemical components by weight percentage: Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the balance is Fe and unavoidable impurity elements.

[0046] A manufacturing method for improving the cold-rolled edge crack defects of the above high-silicon non-phase-change electrical steel, comprising the following steps: 1) The molten iron is blown in a converter and then transferred to an RH furnace for vacuum smelting. The molten steel after refining and alloying is continuously cast into a slab with a thickness of 200 mm. During continuous casting, a round-corner mold is used, and the round-corner radius R is 50 mm. Electromagnetic stirring is used in the mold during continuous casting. The chemical components of the slab by weight percentage are respectively Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the balance is Fe and unavoidable impurity elements. 2) The slab is heated in a walking beam reheating furnace, the heating temperature is 1050 °C, and the holding time is 280 min. Then, horizontal rolling is performed on the steel plate using vertical rolls. After 5 passes of rough rolling and 7 passes of finish rolling to a thickness of 2.0 mm, the reduction rate ΔB of the vertical roll in each pass satisfies 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 , the final rolling temperature is 860 °C, and it is coiled after laminar cooling to 580 °C. During laminar cooling, both side edges are protected by C-shaped grooves, the unilateral protection width is 143 mm, and hl is 1.1 m. 3) Normalizing and pickling: The normalizing temperature of the hot-rolled sheet is 920 °C, and the time is 180 s. The normalized steel coil is surface-cleaned in a turbulent acid tank. ​4) First cold rolling: The pickled steel plate is rolled reciprocally for 6 passes to a target thickness of 0.25 mm. During the rolling process, the front tension for each pass is controlled within 1.25×σs×B×H 出口 and the untrimmed process is adopted from the hot-rolled raw material to before cold rolling; 5) Continuous annealing: The cold-rolled sheet is annealed at 980°C for 150 s, and the protective atmosphere in the furnace is 30% H2 + 70% N2; 6) Insulating coating application: The surface of the steel coil is coated with an insulating paint and dried and cured.

[0047] For the high-silicon non-phase-change electrical steel manufactured by the above process, the difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material is 10 μm. It can be cold-rolled to the target thickness in one pass without edge crack defects. The one-pass rate of cold rolling is 97%.

[0048] Comparative Example 1 The difference between this comparative example and Example 1 is that: in the continuous casting process, a conventional right-angle mold is used instead of a rounded-corner mold.

[0049] For the high-silicon non-phase-change electrical steel obtained by this method, the difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material is 15 μm. It can be cold-rolled to the target thickness in one pass, and the one-pass rate of cold rolling is 60%.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that: the radius of the rounded corner R is 120 mm.

[0051] For the high-silicon non-phase-change electrical steel obtained by this method, the difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material is 19 μm. It can be cold-rolled to the target thickness in one pass, and the one-pass rate of cold rolling is 75%.

[0052] Comparative Example 3 The difference between this comparative example and Example 1 is that: in the hot-rolling process, vertical rolls are not used during rolling, and free spread is adopted.

[0053] For the high-silicon non-phase-change electrical steel obtained by this method, the difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material is 20 μm. It can be cold-rolled to the target thickness in one pass, and the one-pass rate of cold rolling is 65%.

[0054] Comparative Example 4 The difference between this comparative example and Example 1 is that: in the hot-rolling process, the reduction rate of the vertical roll in the transverse rolling pass does not satisfy 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 .

[0055] The difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material of the high-silicon non-phase-change electrical steel obtained by this method is 20 μm. It can be cold-rolled to the target thickness in one pass, and the one-pass cold-rolling pass rate is 80%.

[0056] Comparative Example 5 The difference between this comparative example and Example 1 is that edge protection is not used during laminar cooling in the hot-rolling process.

[0057] The difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material of the high-silicon non-phase-change electrical steel obtained by this method is 16 μm. It can be cold-rolled to the target thickness in one pass, and the one-pass cold-rolling pass rate is 80%.

[0058] Comparative Example 6 The difference between this comparative example and Example 1 is that the unilateral protection width L of the edge protection during laminar cooling in the hot-rolling process is 165 mm.

[0059] The difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material of the high-silicon non-phase-change electrical steel obtained by this method is 22 μm. It can be cold-rolled to the target thickness in one pass, and the one-pass cold-rolling pass rate is 85%.

[0060] Comparative Example 7 The difference between this comparative example and Example 1 is that the front tension during the cold-rolling process is controlled to exceed 1.25×σs×B×H 出口 .

[0061] The difference between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material of the high-silicon non-phase-change electrical steel obtained by this method is 11 μm. It can be cold-rolled to the target thickness in one pass, and the one-pass cold-rolling pass rate is 90%.

[0062] Comparative Example 8 A manufacturing method of high-silicon non-phase-change electrical steel includes the following steps: 1) The molten iron is blown in a converter and then transferred to an RH furnace for vacuum smelting. The molten steel after refining alloying is continuously cast into a slab with a thickness of 210 mm. A normal right-angle mold is used during continuous casting, and electromagnetic stirring is used for the mold during continuous casting. The chemical composition weight percentages of the slab are respectively: Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0020%; N: 0.010%; the rest are Fe and inevitable impurity elements; 2) Heat the slab in a walking beam reheating furnace. The heating temperature is 1100 °C and the holding time is 280 min. Then, rough roll it in 5 passes and finish roll it in 7 passes to a thickness of 2.0 mm. Vertical rolls are not used in each pass, and free spread is adopted. The finishing rolling temperature is 860 °C, and coiling is carried out after laminar cooling to 580 °C. Edge protection is not adopted during laminar cooling; 3) Normalizing and pickling: The normalizing temperature of the hot-rolled sheet is 940 °C and the time is 180 s. The normalized steel coil is surface cleaned in a turbulent acid tank; 4) First cold rolling: The pickled steel plate is reciprocally rolled in 6 passes to a target thickness of 0.25 mm. During the rolling process, the front tension in each pass is controlled to exceed 1.25×σs×B×H 出口 .

[0063] In Comparative Example 1 and Comparative Example 2, the mold scheme of the present invention was not adopted. During the hot rolling heating process of the steel billet, the temperature rise at the corners and edges was higher than that in the middle of the slab. The average grain size of the edge structure was larger than that of the middle structure. At the same time, the difference between the surface structure and the middle structure of the steel plate edge along the thickness direction increased, resulting in a large difference between the maximum grain size and the average grain size of the product edge structure and a low primary cold rolling pass rate.

[0064] In Comparative Example 3 and Comparative Example 4, due to the non-adoption of the vertical roll and pass reduction rate control scheme of the present invention, there were differences in the elongation of the metal at the edge and in the middle of the steel plate during the rolling process, resulting in different deformation energy storages at different positions. During the subsequent high-temperature recrystallization process, the tissue uniformity at different positions would be reduced, and the grain size gap of the obtained product would be large, and the primary cold rolling pass rate would be low.

[0065] In Comparative Example 5 and Comparative Example 6, the edge protection and control scheme of laminar cooling of the present invention were not adopted, resulting in uneven cooling of the edge and the middle of the steel plate. The cooling rate at the edge was relatively fast, and there was residual hot-rolled deformation structure. The cooling rate in the middle was slow and it was a recrystallized structure. The grain size gap of the obtained product was relatively large, and the primary cold rolling pass rate was relatively low.

[0066] In Comparative Example 7, the front tension control scheme in the cold rolling pass of the present invention was not adopted. The grain size gap of the obtained product was relatively small, but the primary cold rolling pass rate was slightly low. It can be seen that adopting the conventional scheme - increasing the front tension control, the tensile force on the steel plate along the rolling direction during cold rolling increases, and small cracks or even cracking defects are likely to form at the edge of the steel plate under the action of the tensile force, which may lead to a strip break accident.

[0067] As Figures 3-4As shown, for the high-silicon non-transforming electrical steel manufactured in Comparative Example 8, there is non-uniformity in the structure along the thickness direction in the hot-rolled state of the material. The surface of the steel plate is a partially recrystallized structure, and the central part of the steel plate is a deformed banded structure. After normalizing treatment, there is a problem of uneven grain sizes along the thickness direction of the steel plate. After one-pass rolling in the cold rolling process, large cracks appear at the edges and it is impossible to roll to the target thickness. After normalizing the hot-rolled raw material, the edge structure is non-uniform and the size difference is large. The maximum grain size - average grain size is 35 μm.

[0068] In Examples 1 to 5, for the high-silicon non-transforming electrical steel prepared by the scheme of the present invention, the edge structure is uniform, the difference between the maximum grain size and the average grain size is at most 10 μm, and the occurrence of cracks at the cold-rolled edges is very few. The one-pass cold rolling passing rate is at least 95%.

[0069] From the products of the above examples and comparative examples, it can be seen that in Comparative Examples 1 to 8, in the hot rolling process, since the limiting scheme of the vertical roll and the reduction rate per pass of the present invention is not adopted simultaneously, the edge protection scheme of the present invention is not adopted during laminar flow, and the front tension per pass in cold rolling does not adopt the scheme of the present invention, it is easier for the slab to have edge cracks during cold rolling. Especially in Comparative Example 8, none of the above schemes are adopted, resulting in large edge cracks after one-pass rolling and it is impossible to obtain the target product.

[0070] In the present invention, through process designs such as continuous casting, heating, hot rolling, normalizing, and cold rolling, the uniformity of the material structure is improved. After normalizing the hot-rolled raw material, the edge structure is uniform, the grain sizes are uniform, and the maximum grain size - average grain size ≤ 12 μm; cold rolling can be directly rolled to the target thickness in one pass without edge crack defects, and the one-pass cold rolling passing rate is high, reaching more than 95%.

[0071] Other parts not described belong to the prior art.

Claims

1. A manufacturing method for improving the cold rolling edge crack defects of high-silicon non-phase-change electrical steel, characterized in that: Including: The molten iron is transferred to the RH furnace for vacuum smelting after being blown in the converter. After alloying treatment, the molten steel with qualified chemical composition is continuously cast into slabs; the slabs are hot-rolled into hot-rolled sheets after heating and heat preservation; the hot-rolled sheets are made into finished high-silicon non-phase-change electrical steel after normalizing, pickling, cold rolling, continuous annealing, and insulating coating application; during the hot-rolling process, vertical rolls are used to perform transverse rolling on the steel plate, and the vertical roll reduction rate ΔB of the vertical roll pass meets: 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 , where Δh is the thickness difference of the slab before and after the pass, and H 入口 is the thickness of the slab at the entrance of the pass.

2. The manufacturing method according to claim 1, characterized in that: During the continuous casting of molten steel, a round-corner mold is used, and the radius R of the round-corner mold satisfies: 0.25h ≤ R ≤ 0.50h, where h is the slab thickness.

3. The manufacturing method according to claim 1, characterized in that: During the heating of the slab, the heating temperature is 1020 - 1120 °C, and the holding time does not exceed 5 h.

4. The manufacturing method according to claim 1, characterized in that: During the hot rolling process, the slab is rough rolled in 5 passes and finish rolled in 7 passes to the target thickness. Vertical rolls are used for transverse rolling of the steel plate during both the rough rolling and finish rolling processes.

5. The manufacturing method according to claim 1, characterized in that: During the hot rolling process, the finish rolling temperature is 850 - 900 °C, and the coiling temperature is 550 - 650 °C; the thickness of the hot rolled plate is 1.5 - 2.0 mm.

6. The manufacturing method according to claim 1, wherein: During the hot rolling process, the steel plate rolled to the target thickness is coiled after laminar cooling; during the laminar cooling process, the two side edges of the steel plate are protected by C-shaped grooves, and the width L of the steel plate protected by a single-sided C-shaped groove is controlled within: 0.08×hl ≤ L ≤ 0.13×hl, where hl is the distance from the top of the upper water outlet pipe of the laminar cooling to the upper surface of the steel plate.

7. The manufacturing method according to claim 1, characterized in that: During the normalizing process, the normalizing temperature is 850 - 950 °C, and the normalizing time is 2 - 5 min; the strip steel is not trimmed before and after normalizing.

8. The manufacturing method according to claim 1, characterized in that: The cold rolling process adopts 5 to 7 passes of single cold rolling to a target thickness of 0.15 to 0.35 mm, and the front tension Kq before each pass is controlled such that Kq ≤ 1.25 × σs × B × H 出口 , where σs is the yield strength of the incoming steel plate, B is the width of the incoming steel plate, and H 出口 is the thickness of the outgoing steel plate.

9. The manufacturing method according to any one of claims 1 to 8, characterized in that: During the continuous annealing process, the annealing temperature is 950 - 1050 °C, and the annealing time is 90 - 150 s; the whole process in the furnace is protected by a mixed gas of H2 and N2, and the volume percentage content of H2 is 20% - 50%.

10. The manufacturing method according to claim 9, wherein: The high-silicon non-phase-change electrical steel includes the following chemical components by weight percentage: Si: 2.5% - 4.5%; Als: ≤0.30%; Mn: ≤0.20%; C ≤ 0.005%; N ≤ 0.020%, and the remaining components are Fe and inevitable impurity elements.

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