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

Abstract

The present invention discloses a manufacturing method for improving the edge crack defect of high-silicon non-phase-change electrical steel during cold rolling, comprising: molten iron is blown in a converter and then transferred to an RH furnace for vacuum smelting; after alloying treatment, the molten steel with chemical composition meeting the requirements is continuously cast into slabs; the slabs are heated and kept warm and then hot-rolled into hot-rolled plates; the hot-rolled plates are subjected to regularization, pickling, cold rolling, continuous annealing, and insulation coating to form high-silicon non-phase-change electrical steel products; during the hot rolling process, the steel plates are transversely rolled using vertical rollers, and the vertical roller reduction rate ΔB of the vertical roller passes meets the following requirements: 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, H 入口 The present invention improves the uniformity of material structure, especially the uniformity of structure along the thickness direction, through the process design of continuous casting, heating, hot rolling, normalizing, cold rolling and other processes, and achieves a cold rolling pass rate of more than 95%.

Description

Technical Field

[0001] The present invention relates to the technical field of non-oriented electrical steel production, 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 an iron-based metal material with a silicon content between 2% and 4%. Due to its high silicon content and low levels of impurities such as carbon and nitrogen, the material exhibits a uniform ferrite structure at both high and room temperatures, and the matrix generally does not undergo solid-state phase transformations with temperature changes. High-silicon electrical steel is an important soft magnetic material for motor cores used in the manufacture of high-efficiency motors, automotive drive motors, compressors, and other applications. To reduce motor core losses and improve operational efficiency, high-silicon electrical steel is typically processed through multiple processes, including hot rolling, cold rolling, and annealing, to a finished product thickness of 0.15mm to 0.35mm. Due to the material's properties and structural uniformity, the cold rolling process of high-silicon electrical steel is prone to edge cracking and band breakage, which increases the difficulty of material production and reduces product yield.

[0003] The microstructure of the hot-rolled edge is one of the main causes of edge cracks and even strip breakage during cold rolling. Using conventional production processes, high-silicon electrical steel is prone to structural inhomogeneity along the thickness of the hot-rolled material due to the lack of a phase transformation and limited thermal conductivity. This means that the surface of the steel plate, affected by thermal deformation and cooling, exhibits a partially recrystallized structure, while the center of the plate exhibits a deformed, banded structure. However, after regularization of this hot-rolled inhomogeneous structure, the plate exhibits grain size variations along the thickness due to microstructural heredity, with smaller ferrite at the surface and coarse ferrite in the center. This inhomogeneous ferrite structure after normalization exhibits varying deformation tolerances during subsequent cold rolling. Areas with coarse grains and fragile grain boundaries are most susceptible to machining cracks during cold rolling deformation. These cracks propagate under tensile stress during cold rolling, forming edge cracks and even strip breakage.

[0004] To improve the edge microstructure of high-silicon electrical steel, existing technologies primarily rely on edge heaters or local parameter adjustments. However, these improvements still result in poor microstructure uniformity through the thickness and large grain size variations, leading to low first-pass cold rolling yields. For example, Chinese invention patent application number CN202210800762.4 discloses a method for preventing edge damage and cracking during cold rolling of high-grade silicon steel. The invention utilizes a material composition of C ≤ 0.0030%, Si 2.0%–3.05%, Mn 0.2%–0.6%, Ti ≤ 0.0025%, Al 0.3%–0.8%, and S ≤ 0.0020%. This method prevents edge damage and cracking during cold rolling by optimizing the composition (low C, Si, and Al content), controlling hot rolling parameters (furnace entry temperature, finishing temperature), normalizing edge heating, and reducing the first-pass reduction. This invention reduces the strip break rate but does not address the problem of microstructure variability through the thickness. Chinese invention application document CN202410658197.1 discloses a method for controlling edge cracking in high-silicon electrical steel. This invention addresses the issue of edge cracking during hot rolling of high-silicon electrical steel by controlling slab width, corner grain size, and temperature during the continuous casting stage (a staged cooling strategy), combined with heating and rolling processes (reduction ratio distribution in the latter stages of rough rolling). This invention avoids the use of edge heaters to address hot-rolled edge cracking, reducing investment. However, the invention does not clearly demonstrate the effectiveness of cold-rolled edge cracking mitigation, nor does it address the issue of microstructure variability along the thickness direction.

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

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A manufacturing method for improving edge crack defects during cold rolling of high-silicon non-phase-change electrical steel is characterized in that: molten iron is blown in a converter and then transferred to an RH furnace for vacuum smelting; after alloying, the molten steel having the required chemical composition is continuously cast into slabs with a thickness of 200-250 mm; the slabs are heated and kept warm, and then hot-rolled into hot-rolled plates; the hot-rolled plates are subjected to regularization, pickling, cold rolling, continuous annealing, and insulation coating to produce finished high-silicon non-phase-change electrical steel products; during the hot rolling process, the steel plates are transversely rolled using vertical rollers, and the vertical roller reduction rate ΔB per vertical roller pass meets the following requirements: 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, H 入口 is the slab thickness at the pass entrance.

[0009] As a preferred solution, during the continuous casting of molten steel, a rounded-corner crystallizer is used as the crystallizer, and the radius R of the rounded-corner crystallizer meets the following conditions: 0.25h≤R≤0.50h, where h is the thickness of the slab.

[0010] Furthermore, during the continuous casting of the molten steel, electromagnetic stirring is used in the crystallizer throughout the entire process.

[0011] As a preferred solution, during the slab heating process, the heating temperature is 1020-1120° C., and the insulation time does not exceed 5 hours.

[0012] Furthermore, during the hot rolling process, the slab is subjected to 5 rough rolling passes and 7 finish rolling passes to reach the target thickness, and vertical rollers are used to perform transverse rolling on the steel plate during both the rough rolling and the finish rolling processes.

[0013] Furthermore, during the hot rolling process, the finishing temperature is 850-900° C., the coiling temperature is 550-650° C., and the thickness of the hot rolled plate is 1.5-2.0 mm.

[0014] 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 edges of the steel plate are protected by C-shaped grooves, and the width L of the steel plate protected by the single-sided C-shaped groove is controlled to: 0.08×hl≤L≤0.13×hl, where hl is the distance between the top of the laminar cooling upper outlet pipe and the upper surface of the steel plate.

[0015] As a preferred solution, during the normalizing process, the normalizing temperature is 850-950° C., and the normalizing time is 2-5 minutes; and the strip is not trimmed before and after normalizing.

[0016] Furthermore, during the normalizing process, the temperature of the steel plate is increased to above 800° C. within 30 seconds.

[0017] As a preferred solution, the cold rolling process adopts 5-7 passes of cold rolling; after normalization, the steel coil is pickled and then cold rolled in a single-stand reciprocating rolling mill for 5-7 passes to a target thickness of 0.15-0.35 mm, and the tension Kq before the pass is controlled at Kq≤1.25×σs×B×H 出口 , where σs is the yield strength of the inlet steel plate, B is the width of the inlet steel plate, and H 出口 is the thickness of the exported steel plate.

[0018] As a preferred solution, during the continuous annealing process, the annealing temperature is 950-1050°C, and the annealing time is 90-150s; the furnace is protected by a mixed gas of H2 and N2 throughout the process, and the volume percentage of H2 is 20%-50%.

[0019] Furthermore, during the continuous annealing process, the temperature of the steel plate is increased to above 900° C. within 25 seconds.

[0020] As a preferred solution, the high-silicon non-phase change electrical steel includes the following chemical components in 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 unavoidable impurity elements.

[0021] The chemical composition and main process principles of the present invention are as follows:

[0022] Chemical composition:

[0023] Si: An alloying element in non-oriented silicon steel. As the Si content increases, the resistivity increases and the iron loss decreases. At the same time, as the Si content increases, the solid solution ratio in the steel plate increases, the strength increases, and the brittleness tendency increases.

[0024] Als: Al is similar to Si. Adding Al to steel plates can improve the magnetic properties of silicon steel. However, the addition of Al has a significant effect on improving the deformation capacity of silicon steel, which increases the area of ​​plastic deformation of the steel plate during the subsequent punching process, which is not conducive to reducing processing stress. At the same time, higher aluminum elements can easily cause titanium in the steel slag to be reduced during the smelting process, which has certain harm to the performance of silicon steel. Therefore, the Als content must be properly controlled.

[0025] Mn: It is an alloying element in 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, in order to prevent S and Fe from forming low-melting-point FeS and causing hot brittleness, some Mn 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, so the Mn content should be controlled within a certain range.

[0026] N and C: They are harmful elements in silicon steel. N easily forms second phase inclusions such as AlN and TiN in silicon steel, which strongly hinder grain growth, increase magnetic domain movement resistance, and deteriorate electromagnetic properties. Therefore, the N content should be controlled within the range of 0.2%; when the C content exceeds 0.005%, the iron loss increases significantly and the magnetic aging is obvious; the C and N content should be strictly controlled during the production process. At the same time, the C and N content is reduced, the austenite phase of the material at high temperature is reduced, and the material has a uniform ferrite structure at both high temperature and room temperature.

[0027] Main processes:

[0028] During the continuous casting of slabs, limiting the mold type and fillet radius R to 0.25h ≤ R ≤ 0.50h effectively reduces the temperature difference between the corners and center of the billet, effectively minimizing the microstructural variability at the edge of the hot-rolled plate. Excessively large fillet radii increase the thickness difference between the edges and center of the billet. During subsequent rolling, uneven elongation at the edges and center makes it difficult to control the plate shape. Excessively small fillet radii increase the temperature difference between the corners and center during cooling and heating, further increasing microstructural variability during rolling. Through full-process electromagnetic stirring, a higher proportion of equiaxed grains is achieved, improving the material's thermal deformation capability.

[0029] During the hot rolling heating process, high temperature heating easily produces large-sized liquid inclusions that are dissolved. The dissolved inclusions will form precipitates during the laminar cooling process, hindering the growth of finished grains, affecting the movement of magnetic domains, and deteriorating the electromagnetic properties of the product. Therefore, the heating temperature in the present invention adopts low-temperature heating of 1020~1120℃ to avoid the solid solution of large-sized liquid inclusions in the steel billet. The present invention adopts vertical rollers to perform transverse rolling on the steel plate, and by suppressing the widening, guides the deformation of the edge and the middle to cooperate, reduces the tensile stress of the edge, and prevents the initiation of cracks; adopts multiple passes of small reduction, and controls the reduction rate of the vertical rollers to meet the following requirements: 10×Δh / H 入口 ≤ΔB≤18×Δh / H 入口 , which can distribute deformation, achieve planned widening, and improve rolling stability. At the same time, it avoids sudden stress changes at the edges, slows the deformation rate at the edges, and avoids excessive widening that leads to tensile stress concentration at the edges, thereby reducing the risk of shear damage and tearing, and ensuring that the metal in the middle and edges of the steel plate have the same deformation in the rolling mill. The hot-rolled plate thickness selects a thin target thickness of 1.5-2.0mm to improve the uniformity of the hot-rolled plate along the thickness direction. The deformation process is mainly placed in the hot rolling process to reduce the deformation in the cold rolling process. During the laminar cooling process, the edges of the steel plate are protected by C-shaped grooves, and the width L of the steel plate protected by the single-sided C-shaped groove is controlled within the range of 0.08×hl≤L≤0.13×hl. This ensures that the laminar cooling water does not directly land on the edges of the steel plate, ensuring that the cooling of the edges, center and thickness of the steel plate is consistent, and improving the uniformity of the structure at different locations. The guard width should not be too small or too large. If it is too small, the cooling rate will be higher at the edge of the steel plate and lower in the middle of the steel plate, which will not meet the goal of uniform cooling of the edge and middle of the steel plate and the thickness direction. If it is too large, the cooling of the middle area of ​​the steel plate will be restricted, and it will not be possible to cool to the target coiling temperature through laminar flow. The hot rolling process adopts a low finishing temperature of 850-900℃ to reduce the temperature difference between the surface and the core of the steel plate, thereby improving the structural differences caused by the temperature differences between different positions of the steel plate during the cooling process.

[0030] During the normalizing process, the steel plate is heated to above 800°C within 30 seconds, with a normalizing temperature of 850-950°C and a normalizing time of 2-5 minutes. The present invention utilizes a high normalizing temperature and a rapid heating rate. Using a high-temperature, rapid heating process, the present normalizing temperature effectively enhances the {100} and {110} favorable plane textures in the steel plate, reduces the proportion of {111} texture, and effectively improves the electromagnetic properties of the finished product. Furthermore, the present normalizing temperature increases the average grain size in the steel plate, and rapid heating effectively improves microstructure uniformity. The normalized microstructure can be inherited to the finished product through cold rolling and annealing, thereby increasing the grain size of the finished product. The strip is not trimmed before and after normalizing, avoiding the introduction of deformation stresses at the strip edges during shearing, which increases the likelihood of edge cracking during cold rolling.

[0031] During the cold rolling process, the pre-pass tension Kq is controlled at Kq≤1.25×σs×B×H 出口 During rolling, if the solution of the present invention is not adopted, the tension before cold rolling is too large, which will reduce the rolling pressure and the production load of the rolling mill. As the tension increases, the tensile force of the strip increases along the rolling direction, and the risk of defects and strip breakage along the edges of the strip increases.

[0032] During the annealing process, the annealing temperature is between 950°C and 1050°C for 90 to 150 seconds, with the steel plate temperature rising to above 900°C within 25 seconds. By combining rapid heating with high-temperature annealing, the grain size of the steel plate is fully grown after the annealing process, effectively reducing hysteresis losses, lowering the deformation capacity of the finished steel plate, and minimizing the introduction of manufacturing stress after punching.

[0033] If the grain size disparity and uneven structure of the edge structure during hot rolling or normalizing occurs, edge cracking and band breakage are likely to occur during cold rolling. This can lead to, at best, increased trimming and repairs, reducing production line efficiency and the first-pass cold rolling yield. In severe cases, the steel may be scrapped, failing to meet qualified standards and reducing the product's pass rate. High-silicon, non-phase-change electrical steel produced using the method of the present invention exhibits uniform structure at the edge after normalizing, with a maximum grain size minus the average grain size ≤12μm, minimal cold-rolled edge cracking, and a first-pass cold rolling yield exceeding 95%.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention provides a manufacturing method for improving edge crack defects during cold rolling of high-silicon electrical steel without phase change. In order to reduce edge crack defects during the cold rolling process of high-silicon electrical steel without phase change, the method improves the uniformity of material structure, especially the uniformity of structure along the thickness direction, through the process design of continuous casting, heating, hot rolling, normalizing, cold rolling, etc. After normalizing the hot-rolled raw material, the edge structure is uniform, the grain size distribution is uniform, the maximum grain size minus the average grain size is ≤12μm, and there are few edge cracks during cold rolling, and the first-time pass rate of cold rolling is above 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the microstructure distribution diagram along the thickness direction of the hot-rolled high-silicon non-phase-change electrical steel in Example 1;

[0037] Figure 2 This is the microstructure distribution diagram of the normalized state of the high-silicon non-phase-change electrical steel along the thickness direction in Example 1;

[0038] Figure 3 This is the microstructure distribution diagram along the cross section of the hot-rolled high-silicon electrical steel plate without phase change in Comparative Example 8;

[0039] Figure 4 This is the microstructure distribution diagram along the cross section of the normalized steel plate of high silicon non-phase change electrical steel in comparative example 8. DETAILED DESCRIPTION

[0040] In order to better explain the present invention, the main contents of the present invention are further illustrated below in conjunction with specific examples, but the contents of the present invention are not limited to the following examples.

[0041] Example 1

[0042] A high-silicon non-phase change electrical steel comprises the following chemical components in percentage by weight: Si: 3.30%; Als: 0.10%; Mn: 0.20%; C: 0.0020%; N: 0.010%; the remainder being Fe and unavoidable impurity elements.

[0043] The manufacturing method for improving the above-mentioned cold-rolled edge crack defect of high-silicon non-phase-change electrical steel comprises the following steps:

[0044] 1) After being blown in a converter, the molten iron is transferred to an RH furnace for vacuum smelting. The refined and alloyed molten steel is continuously cast into slabs with a thickness of 210 mm. A rounded mold with a fillet radius R of 80 mm is used in the continuous casting process. Electromagnetic stirring is used in the continuous casting process. The chemical composition of the slabs by weight is Si: 3.30%; Als: 0.10%; Mn: 0.20%; C: 0.0020%; N: 0.010%; the remainder is Fe and unavoidable impurities.

[0045] 2) The slab is heated in a walking beam furnace to 1050°C and held at this temperature for 280 min. The slab is then rolled transversely using vertical rollers for 5 roughing passes and 7 finishing passes to a thickness of 2.0 mm. The vertical roller reduction rate ΔB of each pass meets 10×Δh / H. 入口 ≤ΔB≤18×Δh / H 入口The final rolling temperature is 860℃, and the coiling is done when the laminar cooling reaches 580℃. During the laminar cooling, the edges on both sides are protected by C-shaped grooves, with a single-side protection width of 120mm and a hl of 1.1m.

[0046] 3) Normalizing and pickling: The normalizing temperature of the hot-rolled plate is 940°C for 180 seconds. The surface of the steel coil after normalizing is cleaned in a turbulent acid tank.

[0047] 4) Single cold rolling: The pickled steel plate is cold rolled to the target thickness of 0.25mm by 6 reciprocating rolling passes. The tension before each pass is controlled at 1.25×σs×B×H during the rolling process. 出口 Within, the hot-rolled raw materials are not trimmed before cold rolling;

[0048] 5) Continuous annealing: The cold rolled sheet is annealed at 980℃ for 150s, and the protective atmosphere in the furnace is 30% H2 + 70% N2 by volume;

[0049] 6) Insulation coating: Insulation coating is applied on the surface of the steel coil and dried and cured.

[0050] like Figures 1 and 2 As shown, the high-silicon, non-phase-change electrical steel produced using the above process exhibits uniform microstructure and equiaxed grains after normalization of the hot-rolled raw material. The difference between the maximum grain size and the average grain size at the edge is 10 μm. Cold rolling can be performed in a single pass to the target thickness without edge cracks. The first-pass cold rolling yield is 96%.

[0051] Example 2

[0052] A high-silicon non-phase-change electrical steel comprises the following chemical components in percentage by weight: Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the remainder being Fe and unavoidable impurity elements.

[0053] The manufacturing method for improving the above-mentioned cold-rolled edge crack defect of high-silicon non-phase-change electrical steel comprises the following steps:

[0054] 1) After being blown in a converter, the molten iron is transferred to an RH furnace for vacuum smelting. The refined and alloyed molten steel is continuously cast into 200 mm thick ingots. A rounded mold with an 80 mm radius R is used in the continuous casting process. Electromagnetic stirring is used in the mold during the continuous casting process. The chemical composition of the ingots by weight is Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the remainder is Fe and unavoidable impurities.

[0055] 2) The slab is heated in a walking beam furnace to 1050°C and held at this temperature for 280 min. The slab is then rolled transversely using vertical rollers for 5 roughing passes and 7 finishing passes to a thickness of 2.0 mm. The vertical roller reduction rate ΔB of each pass meets 10×Δh / H. 入口 ≤ΔB≤18×Δh / H 入口 The final rolling temperature is 860℃, and the coiling is done when the laminar cooling reaches 580℃. During the laminar cooling, the edges on both sides are protected by C-shaped grooves, with a single-side protection width of 120mm and a hl of 1.1m.

[0056] 3) Normalizing and pickling: The normalizing temperature of the hot-rolled plate is 920℃ for 180s. The surface of the steel coil after normalizing is cleaned in a turbulent acid tank.

[0057] 4) Primary cold rolling: The pickled steel plate is rolled back and forth for 6 passes to a target thickness of 0.25 mm. During the rolling process, the tension before each pass is controlled at 1.25 × σs × B × H. 出口 Within, the hot-rolled raw materials are not trimmed before cold rolling;

[0058] 5) Continuous annealing: The cold rolled sheet is annealed at 980°C for 150s, and the protective atmosphere in the furnace is 30% H2 + 70% N2;

[0059] 6) Insulation coating: Insulation coating is applied on the surface of the steel coil and dried and cured.

[0060] The high-silicon, non-phase-change electrical steel produced using this process achieves a 9μm difference between the maximum and average grain sizes at the edge of the hot-rolled raw material after normalization. Cold rolling can be performed in a single pass to the target thickness without edge cracks. The first-pass cold rolling yield is 95%.

[0061] Example 3

[0062] A high-silicon non-phase-change electrical steel comprises the following chemical components in percentage by weight: Si: 3.40%; Als: 0.10%; Mn: 0.20%; C: 0.0015%; N: 0.010%; the remainder being Fe and unavoidable impurity elements.

[0063] The manufacturing method for improving the above-mentioned cold-rolled edge crack defect of high-silicon non-phase-change electrical steel comprises the following steps:

[0064] 1) After being blown in a converter, the molten iron is transferred to an RH furnace for vacuum smelting. The refined and alloyed molten steel is continuously cast into slabs with a thickness of 210 mm. A rounded mold with a fillet radius R of 100 mm is used in the continuous casting process. The mold is electromagnetically stirred during the continuous casting process. The chemical composition of the slabs by weight is Si: 3.40%; Als: 0.10%; Mn: 0.20%; C: 0.0015%; N: 0.010%; the remainder is Fe and unavoidable impurities.

[0065] 2) The slab is heated in a walking beam furnace to 1100°C and held at this temperature for 260 minutes. The slab is then rolled transversely using vertical rollers for 5 roughing passes and 7 finishing passes to a thickness of 2.0 mm. The vertical roller reduction rate ΔB of each pass meets 10×Δh / H. 入口 ≤ΔB≤18×Δh / H 入口 The final rolling temperature is 850℃, and the coil is taken up when laminar cooling reaches 560℃. During laminar cooling, the edges on both sides are protected by C-shaped grooves, with a single-side protection width of 110mm and a hl of 1.1m.

[0066] 3) Normalizing and pickling: The normalizing temperature of the hot-rolled plate is 920℃ for 180s. The surface of the steel coil after normalizing is cleaned in a turbulent acid tank.

[0067] 4) Primary cold rolling: The pickled steel plate is rolled back and forth for 6 passes to a target thickness of 0.20 mm. During the rolling process, the tension before each pass is controlled at 1.25 × σs × B × H. 出口 Within, the hot-rolled raw materials are not trimmed before cold rolling;

[0068] 5) Continuous annealing: The cold rolled sheet is annealed at 980°C for 150s in a furnace with a protective atmosphere of 30% H2 + 70% N2;

[0069] 6) Insulation coating: Insulation coating is applied on the surface of the steel coil and dried and cured.

[0070] The high-silicon, non-phase-change electrical steel produced using this process achieves an 8μm difference between the maximum and average grain sizes at the edge of the hot-rolled raw material after normalization. Cold rolling can be performed in a single pass to the target thickness without edge cracks. The first-pass cold rolling yield is 96%.

[0071] Example 4

[0072] A high-silicon non-phase-change electrical steel comprises the following chemical components in percentage by weight: Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the remainder being Fe and unavoidable impurity elements.

[0073] The manufacturing method for improving the above-mentioned cold-rolled edge crack defect of high-silicon non-phase-change electrical steel comprises the following steps:

[0074] 1) After being blown in a converter, the molten iron is transferred to an RH furnace for vacuum smelting. The refined and alloyed molten steel is continuously cast into 200 mm thick ingots. A rounded mold with a corner radius R of 100 mm is used in the continuous casting process. Electromagnetic stirring is used in the continuous casting process. The chemical composition of the ingots by weight is Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the remainder is Fe and unavoidable impurities.

[0075] 2) The slab is heated in a walking beam furnace to 1050°C and held at this temperature for 280 min. The slab is then rolled transversely using vertical rollers for 5 roughing passes and 7 finishing passes to a thickness of 2.0 mm. The vertical roller reduction rate ΔB of each pass meets 10×Δh / H. 入口 ≤ΔB≤18×Δh / H 入口 The final rolling temperature is 860℃, and the coil is taken up when laminar cooling reaches 580℃. During laminar cooling, the edges on both sides are protected by C-shaped grooves, with a single-side protection width of 88mm and a hl of 1.1m.

[0076] 3) Normalizing and pickling: The normalizing temperature of the hot-rolled plate is 920℃ for 180s. The surface of the steel coil after normalizing is cleaned in a turbulent acid tank.

[0077] 4) Primary cold rolling: The pickled steel plate is rolled back and forth for 6 passes to a target thickness of 0.25 mm. During the rolling process, the tension before each pass is controlled at 1.25 × σs × B × H. 出口 Within, the hot-rolled raw materials are not trimmed before cold rolling;

[0078] 5) Continuous annealing: The cold rolled sheet is annealed at 980°C for 150s, and the protective atmosphere in the furnace is 30% H2 + 70% N2;

[0079] 6) Insulation coating: Insulation coating is applied on the surface of the steel coil and dried and cured.

[0080] The high-silicon, non-phase-change electrical steel produced using this process achieves a 9μm difference between the maximum and average grain sizes at the edge of the hot-rolled raw material after normalization. Cold rolling can be performed in a single pass to the target thickness without edge cracks. The first-pass cold rolling yield is 96%.

[0081] Example 5

[0082] A high-silicon non-phase-change electrical steel comprises the following chemical components in percentage by weight: Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the remainder being Fe and unavoidable impurity elements.

[0083] The manufacturing method for improving the above-mentioned cold-rolled edge crack defect of high-silicon non-phase-change electrical steel comprises the following steps:

[0084] 1) After being blown in a converter, the molten iron is transferred to an RH furnace for vacuum smelting. The refined and alloyed molten steel is continuously cast into 200 mm thick ingots. A rounded mold with a corner radius R of 50 mm is used in the continuous casting process. Electromagnetic stirring is used in the continuous casting process. The chemical composition of the ingots by weight is Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0022%; N: 0.015%; the remainder is Fe and unavoidable impurities.

[0085] 2) The slab is heated in a walking beam furnace to 1050°C and held at this temperature for 280 min. The slab is then rolled transversely using vertical rollers for 5 roughing passes and 7 finishing passes to a thickness of 2.0 mm. The vertical roller reduction rate ΔB of each pass meets 10×Δh / H. 入口 ≤ΔB≤18×Δh / H 入口 The final rolling temperature is 860℃, and the coiling is done when the laminar cooling reaches 580℃. During the laminar cooling, the edges on both sides are protected by C-shaped grooves, with a single-side protection width of 143mm and a hl of 1.1m.

[0086] 3) Normalizing and pickling: The normalizing temperature of the hot-rolled plate is 920℃ for 180s. The surface of the steel coil after normalizing is cleaned in a turbulent acid tank.

[0087] 4) Primary cold rolling: The pickled steel plate is rolled back and forth for 6 passes to a target thickness of 0.25 mm. During the rolling process, the tension before each pass is controlled at 1.25 × σs × B × H. 出口 Within, the hot-rolled raw materials are not trimmed before cold rolling;

[0088] 5) Continuous annealing: The cold rolled sheet is annealed at 980°C for 150s, and the protective atmosphere in the furnace is 30% H2 + 70% N2;

[0089] 6) Insulation coating: Insulation coating is applied on the surface of the steel coil and dried and cured.

[0090] The high-silicon, non-phase-change electrical steel produced using this process achieves a 10μm difference between the maximum and average grain sizes at the edge of the hot-rolled raw material after normalization. Cold rolling can be performed in a single pass to the target thickness without edge cracks. The first-pass cold rolling yield is 97%.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 is that a conventional right-angle crystallizer is used instead of a rounded-corner crystallizer during the continuous casting process.

[0093] The high-silicon phase-change-free electrical steel obtained by this method has a difference of 15μm between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material. It can be cold-rolled to the target thickness in one step, and the cold rolling pass rate is 60%.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that the fillet radius R is 120 mm.

[0096] The high-silicon phase-change-free electrical steel obtained by this method has a difference of 19μm between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material. It can be cold-rolled to the target thickness in one step, and the cold rolling pass rate is 75%.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 1 is that vertical rolls are not used during the hot rolling process, and free widening is adopted.

[0099] The high-silicon phase-change-free electrical steel obtained by this method has a difference of 20μm between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material. It can be cold-rolled to the target thickness in one step, and the cold rolling pass rate is 65%.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that the reduction rate of the vertical roll transverse rolling during the hot rolling process does not meet the requirement of 10×Δh / H. 入口 ≤ΔB≤18×Δh / H 入口 .

[0102] The high-silicon phase-change-free electrical steel obtained by this method has a difference of 20μm between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material. It can be cold-rolled to the target thickness in one time, and the cold rolling pass rate is 80%.

[0103] Comparative Example 5

[0104] The difference between this comparative example and Example 1 is that edge protection is not used during laminar cooling during the hot rolling process.

[0105] The high-silicon phase-change-free electrical steel obtained by this method has a difference of 16μm between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material. It can be cold-rolled to the target thickness in one time, and the cold rolling pass rate is 80%.

[0106] Comparative Example 6

[0107] The difference between this comparative example and Example 1 is that the single-side protection width L of the edge protection during laminar cooling in the hot rolling process is 165 mm.

[0108] The high-silicon phase-change-free electrical steel obtained by this method has a difference of 22μm between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material. It can be cold-rolled to the target thickness in one step, and the cold rolling pass rate is 85%.

[0109] Comparative Example 7

[0110] The difference between this comparative example and Example 1 is that the pre-pass tension during the cold rolling process is controlled to be more than 1.25×σs×B×H 出口 .

[0111] The high-silicon phase-change-free electrical steel obtained by this method has a difference of 11μm between the maximum grain size and the average grain size of the edge structure after normalization of the hot-rolled raw material. It can be cold-rolled to the target thickness in one time, and the cold rolling pass rate is 90%.

[0112] Comparative Example 8

[0113] A method for manufacturing high-silicon non-phase-change electrical steel comprises the following steps:

[0114] 1) After being blown in a converter, the molten iron is transferred to an RH furnace for vacuum smelting. The refined and alloyed molten steel is continuously cast into 210 mm thick slabs. A normal right-angle mold is used for continuous casting, and electromagnetic stirring is used for the mold. The chemical composition of the slabs by weight is Si: 3.35%; Als: 0.10%; Mn: 0.20%; C: 0.0020%; N: 0.010%; the remainder is Fe and unavoidable impurities.

[0115] 2) The slab is heated in a walking beam furnace to 1100°C for 280 minutes, and then subjected to 5 rough rolling passes and 7 finish rolling passes to a thickness of 2.0 mm. Vertical rollers are not used in these passes, and free widening is adopted. The final rolling temperature is 860°C. The slab is coiled when cooled to 580°C in a laminar flow process, and no edge protection is used during the laminar flow process.

[0116] 3) Normalizing and pickling: The normalizing temperature of the hot-rolled plate is 940°C for 180 seconds. The surface of the steel coil after normalizing is cleaned in a turbulent acid tank.

[0117] 4) Primary cold rolling: The pickled steel plate is rolled back and forth for 6 passes to a target thickness of 0.25 mm. During the rolling process, the tension before each pass is controlled to be more than 1.25 × σs × B × H. 出口 .

[0118] Comparative Examples 1 and 2 do not adopt the crystallizer scheme of the present invention. During the hot rolling heating process of the steel billet, the temperature of the corners and edges rises higher than that of the middle of the slab, and the average grain size of the edge structure is 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 along the thickness direction increases, resulting in a large difference between the maximum grain size and the average grain size of the edge structure of the product and a low one-time pass rate of cold rolling.

[0119] In Comparative Examples 3 and 4, since the neutral roll and pass reduction rate control scheme of the present invention are not adopted, there is a difference in the extension of the edge metal and the middle metal of the steel plate during the rolling process, resulting in different deformation energy storage at different positions. The subsequent high-temperature recrystallization process will reduce the uniformity of the structure at different positions, the grain size of the obtained products varies greatly, and the cold rolling pass rate is low.

[0120] Comparative Examples 5 and 6 did not adopt the laminar cooling edge protection and control scheme of the present invention, resulting in uneven cooling of the edges and middle of the steel plate. The cooling rate of the edges was faster and hot-rolled deformed structure remained, while the cooling rate of the middle was slow and it was a recrystallized structure. The grain size of the obtained products varied greatly, and the cold rolling pass rate was low.

[0121] Comparative Example 7, which did not employ the present invention's pre-pass tension control scheme for cold rolling, produced a product with smaller grain size variations, but a slightly lower first-pass cold rolling yield. This suggests that the conventional approach of increasing pre-pass tension control increases the tensile force on the steel plate along the rolling direction during cold rolling. This tensile force can easily lead to small cracks or even full-scale cracks on the steel plate edges, potentially causing strip breakage.

[0122] like Figures 3 and 4 As shown, the high-silicon, non-phase-change electrical steel produced in Comparative Example 8 exhibits structural inhomogeneity along the thickness of the hot-rolled material, with a partially recrystallized structure on the surface and a deformed, banded structure in the center. After normalization, the steel exhibits grain size variation along the thickness. Large cracks develop along the edges after a single cold-rolling pass, preventing rolling to the target thickness. After normalization, the hot-rolled raw material exhibits uneven edges with significant size variation, with the maximum grain size minus the average grain size being 35 μm.

[0123] In Examples 1 to 5, the high-silicon phase-change-free electrical steel prepared using the scheme of the present invention has uniform edge structure, the difference between the maximum grain size and the average grain size is at most 10 μm, and cracks on the cold-rolled edges are very rare, and the cold rolling pass rate is at least 95%.

[0124] It can be seen from the products of the above embodiments and comparative examples that the hot rolling processes in comparative examples 1 to 8 do not simultaneously adopt the limiting schemes of the vertical rolls and the pass reduction rate of the present invention, do not adopt the edge protection scheme of the present invention during laminar flow, and do not adopt the scheme of the present invention for the pre-pass tension during cold rolling. As a result, the slabs are more likely to have edge cracks during cold rolling. In particular, in comparative example 8, none of the above schemes were adopted, resulting in large edge cracks after one rolling pass, and the target product could not be obtained.

[0125] The present invention improves the uniformity of material structure through the process design of continuous casting, heating, hot rolling, normalizing, cold rolling and other processes. After the hot-rolled raw material is normalized, the edge structure is uniform, the grain size is uniform, and the maximum grain size minus the average grain size is ≤12μm. The cold rolling can be rolled to the target thickness in one time without edge crack defects, and the cold rolling pass rate is high, reaching more than 95%.

[0126] Other parts not described belong to the prior art.

Claims

1. A method for improving the edge crack defect of cold-rolled high-silicon non-phase-change electrical steel, characterized by: include: After being blown in a converter, the molten iron is transferred to an RH furnace for vacuum smelting. After alloying treatment, the molten steel with the required chemical composition is continuously cast into slabs. The slabs are heated and kept warm before being hot-rolled into hot-rolled plates. The hot-rolled plates are then subjected to regularization, pickling, cold rolling, continuous annealing, and insulation coating to produce high-silicon non-phase-change electrical steel products. During the hot rolling process, vertical rollers are used to roll the steel plates transversely, and the vertical roller reduction rate ΔB per pass meets the following requirements: 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, H 入口 is the thickness of the slab at the entrance of the pass; during the continuous casting of molten steel, a rounded corner crystallizer is used, and the radius R of the rounded corner crystallizer meets the following conditions: 0.25h≤R≤0.50h, where h is the thickness of the slab; during the hot rolling process, the steel plate rolled to the target thickness is coiled after laminar cooling; during the laminar cooling process, the edges of the steel plate are protected by C-shaped grooves, and the width L of the steel plate protected by the single-side C-shaped groove is controlled to be: 0.08×hl≤L≤0.13×hl, where hl is the distance between the top of the laminar cooling upper outlet pipe and the upper surface of the steel plate; during the cold rolling process, the pre-pass tension Kq is controlled to be Kq≤1.25×σs×B×H 出口 , where σs is the yield strength of the inlet steel plate, B is the width of the inlet steel plate, and H 出口 is the thickness of the export steel plate; 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%, the remaining components are Fe and unavoidable impurity elements.

2. The manufacturing method according to claim 1, wherein: During the slab heating process, the heating temperature is 1020-1120° C., and the insulation time does not exceed 5 hours.

3. The manufacturing method according to claim 1, wherein: During the hot rolling process, the slab is subjected to 5 rough rolling passes and 7 finish rolling passes to reach the target thickness. Vertical rollers are used to perform transverse rolling on the steel plate during both the rough rolling and the finish rolling processes.

4. The manufacturing method according to claim 1, wherein: During the hot rolling process, the final rolling temperature is 850-900° C., the coiling temperature is 550-650° C., and the thickness of the hot rolled plate is 1.5-2.0 mm.

5. The manufacturing method according to claim 1, wherein: During the normalizing process, the normalizing temperature is 850-950° C., and the normalizing time is 2-5 minutes; the strip is not trimmed before and after normalizing.

6. The manufacturing method according to claim 1, wherein: The cold rolling process adopts 5 to 7 passes of cold rolling to a target thickness of 0.15 to 0.35 mm.

7. The manufacturing method according to any one of claims 1 to 6, characterized in that: During the continuous annealing process, the annealing temperature is 950-1050° C., and the annealing time is 90-150 seconds. The furnace is protected by a mixed gas of H 2 and N 2 throughout the process, and the volume percentage of H 2 is 20%-50%.

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