A production method for avoiding edge crack of hot-rolled oriented silicon steel
By using a chamfered crystallizer for continuous casting, controlling the billet temperature and heating atmosphere, and optimizing rolling parameters, the problem of edge cracking during hot rolling of grain-oriented silicon steel was solved, improving yield and edge quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN VALIN LIANYUAN IRON & STEEL CO LTD
- Filing Date
- 2024-09-23
- Publication Date
- 2026-06-26
AI Technical Summary
Grain-oriented silicon steel is prone to edge cracking defects during hot rolling, which affects the yield.
Continuous casting is carried out using a chamfered crystallizer, and the surface temperature of the slab is controlled to be no less than 400℃. The slab is heated in a reducing atmosphere in a furnace. By combining a reasonable rolling reduction rate and a furnace heating rate, the shape of the slab is optimized to reduce decarburization and grain coarsening, and to avoid edge cracks.
It effectively reduces edge cracks in hot-rolled coils of oriented silicon steel, improves yield and edge quality, controls grain size to 30-35 micrometers, and increases yield by 0.8%-3%.
Smart Images
Figure CN119056869B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of grain-oriented silicon steel preparation technology, specifically relating to a production method that avoids edge cracking during hot rolling of grain-oriented silicon steel. Background Technology
[0002] Grain-oriented silicon steel possesses excellent magnetic properties and is primarily used in power systems to achieve efficient electromagnetic conversion. It is mainly used in the manufacture of transformer cores, where its excellent soft magnetic characteristics and magnetization properties provide high magnetic flux, thereby enabling efficient electro-magnetic-electric conversion.
[0003] Silicon content has a sensitive effect on the magnetic properties of grain-oriented silicon steel. As silicon content increases, resistivity increases, eddy current loss decreases, and iron loss also decreases. However, with increasing silicon content, grain-oriented silicon steel exhibits characteristics such as low high-temperature strength, high low-temperature strength, low thermal conductivity, and brittleness. During the slab heating process, microcracks easily form at the edges. During hot rolling of grain-oriented silicon steel slabs with microcracks, these microcracks continuously expand under the rolling force, extending towards the surface and eventually leading to edge crack defects. Therefore, improvements are urgently needed. Summary of the Invention
[0004] In view of this, this application provides a production method to avoid edge cracking during hot rolling of grain-oriented silicon steel, aiming to provide a production method that can significantly improve edge cracking defects in the hot rolling process of grain-oriented silicon steel slabs, improve the edge quality of grain-oriented silicon steel, and increase the yield of grain-oriented silicon steel.
[0005] In a first aspect, embodiments of this application provide a production method for avoiding edge cracking during hot rolling of grain-oriented silicon steel, comprising:
[0006] A cast billet is obtained by continuous casting using a chamfered crystallizer;
[0007] The surface temperature of the billet before it enters the heating furnace shall not be lower than 400℃;
[0008] The billet is heated in a heating furnace at a furnace temperature of 1100℃-1330℃ and a reducing atmosphere. The total time in the furnace is 200-330 minutes to obtain a heated slab.
[0009] The heated slab is rolled and coiled to produce oriented silicon steel hot-rolled coils.
[0010] According to an embodiment of one aspect of this application, the billet comprises the following chemical composition by mass fraction: 0.03% ≤ C ≤ 0.07%, 3.0% ≤ Si ≤ 3.60%, 0.05% ≤ Mn ≤ 0.30%, P ≤ 0.03%, S ≤ 0.011%, 0.015% ≤ Als ≤ 0.032%, Cu ≤ 0.6%, with the remainder being iron and unavoidable trace elements.
[0011] According to one embodiment of this application, by allowing the transfer time between the billet and the heating furnace to be 0h to 12h, the surface temperature of the billet before entering the heating furnace is not lower than 400°C.
[0012] According to one embodiment of this application, by placing the billet in a heat-insulating pit with a burner, and transferring it from the heat-insulating pit to the heating furnace in a time of less than 30 minutes, the surface temperature of the billet before entering the heating furnace is not lower than 400°C.
[0013] According to one embodiment of this application, the rolling process includes five roughing passes, wherein the total reduction of the roughing passes is 80%-86%.
[0014] According to one embodiment of this application, the reduction rate per pass of the five-pass roughing is 25%-40%.
[0015] According to one embodiment of this application, the thickness of the cast billet is 200-240 mm.
[0016] According to one embodiment of this application, the thickness of the hot-rolled plate is 1.8-3 mm.
[0017] According to one embodiment of this application, the heating furnace has a heating rate of 6°C-10°C / min; the two side walls along the length direction are subjected to a pressure of 0 to 1000 N by vertical rollers.
[0018] Secondly, embodiments of this application provide a hot-rolled oriented silicon steel coil, which is produced by the production method of the first aspect.
[0019] This application has at least the following beneficial effects:
[0020] The production method provided in this application optimizes the shape of the grain-oriented silicon steel slab by continuously casting in a chamfered crystallizer to prepare the original right-angled slab into a chamfered slab, thereby slowing down heat dissipation at the edges and preventing rapid temperature drop. The surface temperature of the slab before entering the heating furnace is not lower than 400°C. At the same time, by controlling the atmosphere inside the heating furnace, the furnace gas temperature is set at 1100°C-1330°C, the atmosphere inside the furnace is a reducing atmosphere, and the total time in the furnace is 200-330 minutes. This comprehensively reduces the decarburization of the edges and the problem of coarse grains, thereby avoiding edge cracking of the hot-rolled grain-oriented silicon steel coil and improving the product yield. Attached Figure Description
[0021] To more clearly illustrate the technical solutions of the implementation regulations of this application, the drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 An appearance view of the grain-oriented silicon steel billet of Comparative Example 1 of this application is shown.
[0023] Figure 2 An appearance view of the grain-oriented silicon steel billet of Embodiment 1 of this application is shown.
[0024] Figure 3 The image shown is a quality appearance drawing of the hot-rolled edge portion of the grain-oriented silicon steel of Comparative Example 1 of this application.
[0025] Figure 4 The image shows the appearance of the hot-rolled edge of the grained silicon steel according to Embodiment 1 of this application. Detailed Implementation
[0026] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the implementation details described in this specification are merely for illustrative purposes and are not intended to limit the scope of this application.
[0027] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.
[0028] In the description of this application, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.
[0029] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.
[0030] In a first aspect, embodiments of this application provide a production method for avoiding edge cracking in hot-rolled grained silicon steel, the method comprising:
[0031] Molten steel is continuously cast through a beveled crystallizer to obtain a billet;
[0032] The surface temperature of the billet before it enters the heating furnace shall not be lower than 400℃;
[0033] The billet is heated in a heating furnace at a furnace temperature of 1100℃-1330℃ and a reducing atmosphere. The total time in the furnace is 200-330 minutes to obtain a heated slab.
[0034] The heated slab is rolled and coiled to produce oriented silicon steel hot-rolled coils.
[0035] Generally, the silicon content of grain-oriented silicon steel is between 2.5% and 4%. However, with increasing silicon content, it exhibits characteristics such as low high-temperature strength, high low-temperature strength, low thermal conductivity, and brittleness. During the slab heating process, decarburization and grain coarsening are easily observed at the edges, leading to microcracks. During the hot rolling process of grain-oriented silicon steel slabs with microcracks, these microcracks continuously expand under the rolling force, extending towards the surface and eventually resulting in edge crack defects. Edge crack defects are prone to occur during hot rolling.
[0036] Studies have found that grain-oriented silicon steel has a high silicon content. Silicon has a higher solubility in austenite than in ferrite. During the austenite-ferrite transformation, silicon tends to segregate towards grain boundaries, causing grain boundary embrittlement. Furthermore, the temperature at the steel strip edge drops rapidly during rolling, resulting in edge elongation lower than the matrix elongation. Additionally, silicon shrinks the austenite region, easily leading to inhomogeneity in hot-rolled grains. Generally, edge trimming is required after hot rolling. Therefore, minor edge cracks have little impact, but severe edge cracks can lead to excessive trimming and a significant reduction in yield.
[0037] The method of this application reduces heat dissipation and temperature drop by changing the shape of the slab edge from a right angle to a chamfer, thereby reducing decarburization. Furthermore, by selecting a suitable temperature and reducing atmosphere during the heating process, edge cracks are avoided, improving the edge quality of grain-oriented silicon steel, increasing the yield, and reducing hot rolling loss.
[0038] Optimizing the right angles of the slab edges into chamfers transforms heat transfer from three-dimensional to two-dimensional, fundamentally reducing the rapid temperature drop at the edges and decreasing the probability of cracking. When the slab corners are right angles, heat transfer is three-dimensional, resulting in faster heat loss and temperature drop, making cracking more likely. Optimizing them with chamfers slows heat dissipation, reduces the temperature difference between the slab and its interior, and decreases the surface area, making cracking less likely. Furthermore, when the furnace atmosphere is reducing, the reaction between oxygen and carbon in the slab is reduced, thus minimizing decarburization at the corners. The chamfered shape further weakens localized decarburization, further reducing the probability of cracking.
[0039] The above method does not require additional edge heating of the slab, simplifies the complex heating and temperature rise system of the heating furnace, and eliminates the need for edge heating of the hot-rolled plate. By controlling the atmosphere inside the heating furnace, edge decarburization is reduced, further improving the edge quality of grain-oriented silicon steel.
[0040] In some alternative embodiments, the billet comprises the following chemical composition by mass fraction: 0.03% ≤ C ≤ 0.07%, 3.0% ≤ Si ≤ 3.60%, 0.05% ≤ Mn ≤ 0.30%, P ≤ 0.03%, S ≤ 0.011%, 0.015% ≤ Als ≤ 0.032%, Cu ≤ 0.6%, with the remainder being iron and unavoidable trace elements.
[0041] According to the embodiments of this application, by using the above-mentioned elemental composition, on the one hand, it can avoid the elements from causing grain boundary segregation and resulting in grain boundary embrittlement; on the other hand, it is beneficial to further reduce the austenite region, which is prone to causing unevenness of hot-rolled grains, thereby improving the edge quality.
[0042] In some alternative implementations, the surface temperature of the billet before entering the heating furnace is not lower than 400°C by allowing the transfer time between the continuous casting line and the heating furnace to be 0h to 12h.
[0043] In some alternative implementations, the surface temperature of the billet before entering the heating furnace is not lower than 400°C by placing the billet in a heat-insulating pit with a burner and transferring it from the heat-insulating pit to the heating furnace in a time of less than 30 minutes.
[0044] In some alternative embodiments, to reduce edge cracking, the rolling process includes 5 passes of roughing, with a total reduction of 80%-86%. In some alternative embodiments, the rolling process includes 7 passes of finishing.
[0045] In some optional embodiments, the reduction rate per pass of the five-pass rough rolling is 25%-40%. According to embodiments of this application, when the reduction rate is too high, greater than 40%, deformation concentrates in the surface layer of the metal, which may lead to stress concentration and increase the risk of edge cracks. Too low a reduction rate, less than 25%, will result in insufficient metal deformation, potentially requiring greater deformation in subsequent rolling processes, which will also cause edge cracking. A reasonable reduction rate helps the metal deform uniformly, reduces stress concentration, and lowers the risk of edge cracks.
[0046] In some alternative embodiments, the thickness of the cast billet is 200-240 mm.
[0047] In some alternative embodiments, the thickness of the hot-rolled plate is 1.8-3 mm.
[0048] In some optional embodiments, in order to further reduce edge cracks and improve edge quality, the heating furnace has a heating rate of 6°C-10°C / min; the two side walls along the length direction are subjected to a pressure of 0 to 1000N by vertical rollers.
[0049] Oriented silicon steel hot-rolled coil
[0050] Secondly, embodiments of this application provide a hot-rolled oriented silicon steel coil, which is produced by the production method of the first aspect.
[0051] According to the embodiments of this application, the yield of hot-rolled grains of grain-oriented silicon steel is greater than or equal to 96.5%, with better edge quality, and the yield is increased by 0.8%-3%. The edge grain size of the hot-rolled grains of grain-oriented silicon steel is between 30-35 micrometers, which is much smaller than the edge grain size of 55-75 micrometers in the original method, thus avoiding edge cracks caused by coarse grains in the hot-rolled grains of grain-oriented silicon steel.
[0052] Example
[0053] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.
[0054] Example 1
[0055] This application provides a production method for avoiding edge cracking in hot-rolled grained silicon steel, the method comprising:
[0056] The continuous casting process uses a chamfered crystallizer to obtain oriented silicon steel billets with a thickness of 210 mm.
[0057] By making the transfer time between the billet and the heating furnace 4 to 9 hours, the surface temperature of the grain-oriented silicon steel billet before entering the heating furnace is controlled at 460°C.
[0058] The billet was heated in a furnace at a temperature of 1145°C, maintaining a reducing atmosphere, for a total time of 310 minutes.
[0059] Five passes of rough rolling were performed, with a total reduction rate of 81.6%.
[0060] Perform precision rolling and coiling.
[0061] Example 2
[0062] This application provides a production method for avoiding edge cracking in hot-rolled grained silicon steel, the method comprising:
[0063] The continuous casting process uses a chamfered crystallizer to obtain oriented silicon steel billets with a thickness of 232 mm.
[0064] By making the transfer time between the billet and the heating furnace 6h to 11h, the surface temperature of the grain-oriented silicon steel billet before entering the heating furnace is controlled at 413℃.
[0065] The billet was heated in a furnace at a temperature of 1283°C, with the furnace atmosphere maintained as a reducing atmosphere. The total time spent in the furnace was 289 minutes.
[0066] Five passes of rough rolling were performed, with a total reduction rate of 83.8%.
[0067] Perform precision rolling and coiling.
[0068] Example 3
[0069] This application provides a production method for avoiding edge cracking in hot-rolled grained silicon steel, the method comprising:
[0070] The continuous casting process uses a chamfered crystallizer to obtain oriented silicon steel billets with a thickness of 240 mm.
[0071] By making the transfer time between the billet and the heating furnace 3h to 7h, the surface temperature of the grain-oriented silicon steel billet before entering the heating furnace is controlled at 510℃.
[0072] The billet was heated in a furnace at a temperature of 1345°C, maintaining a reducing atmosphere, for a total furnace time of 270 minutes.
[0073] Five passes of rough rolling were performed, with a total reduction rate of 84.2%.
[0074] Perform precision rolling and coiling.
[0075] Example 4
[0076] This application provides a production method for avoiding edge cracking in hot-rolled grained silicon steel, the method comprising:
[0077] The continuous casting process uses a chamfered crystallizer to obtain oriented silicon steel billets with a thickness of 240 mm.
[0078] By making the transfer time between the billet and the heating furnace 2h to 7h, the surface temperature of the grain-oriented silicon steel billet before entering the heating furnace is controlled at 536℃.
[0079] The billet was heated in a furnace at a temperature of 1315℃, and the furnace atmosphere was kept in a reducing atmosphere for a total time of 320 minutes.
[0080] Five passes of rough rolling were performed, with a total reduction rate of 84.2%.
[0081] Perform precision rolling and coiling.
[0082] Example 5
[0083] The difference between this embodiment and Embodiment 1 is that five roughing passes are performed, and the total reduction rate of the roughing is 71.2%.
[0084] Comparative Example 1
[0085] The difference between this comparative example and Example 1 is that continuous casting is performed using a right-angle crystallizer.
[0086] Comparative Example 2
[0087] The difference between this comparative example and Example 1 is that the transfer time between the billet and the heating furnace is 15 hours, and the surface temperature of the grain-oriented silicon steel billet before entering the heating furnace is controlled at 380°C.
[0088] Comparative Example 3
[0089] The difference between this comparative example and Example 1 is that the billet is heated in a heating furnace at a furnace temperature of 1000°C, the furnace atmosphere is kept as an oxidizing atmosphere, and the total time in the furnace is 180 minutes.
[0090] Comparative Example 4
[0091] The difference between this comparative example and Example 2 is that the furnace atmosphere is kept as an oxidizing atmosphere.
[0092] Test section
[0093] The hot-rolled coils prepared in the examples and comparative examples were tested.
[0094] The evaluation criteria for the quality of hot-rolled coils are as follows: those with neat edges and no cracks, and edge cracks less than 2mm deep are considered qualified; those with severe edge defects or edge cracks less than 2mm deep are considered substandard or unqualified.
[0095] The formula for calculating the yield rate is: Yield rate = (Mass of steel after trimming / Mass of steel before trimming) * 100%
[0096] After trimming, the steel edges are neat and free of cracks, with the crack depth less than 2mm.
[0097] Table 1 shows the test results of edge quality and yield of the examples and comparative examples.
[0098]
[0099]
[0100] The performance parameters measured above are taken as average values.
[0101] Figure 1 The image shows the appearance of the grain-oriented silicon steel billet of Comparative Example 1 of this application, illustrating that the grain-oriented silicon steel billet obtained by the right-angle crystallizer used in Comparative Example 1 is right-angled. Heat dissipation is fast at right angles, which can easily cause hot rolling edge cracks.
[0102] Figure 2 The diagram shows the appearance of the grain-oriented silicon steel billet of Embodiment 1 of this application. It illustrates that the grain-oriented silicon steel billet obtained by the chamfered crystallizer used in Comparative Example 1 has a chamfer. The heat dissipation at the chamfer is slower, which is beneficial to reduce the heat dissipation rate and reduce the temperature drop, and can avoid hot rolling edge cracking.
[0103] Figure 3 The image shows the appearance of the hot-rolled edge of the grain-oriented silicon steel of Comparative Example 1 of this application, illustrating that the hot-rolled edge of the grain-oriented silicon steel obtained in Comparative Example 1 has poor quality and obvious cracking.
[0104] Figure 4 The image shows the appearance of the hot-rolled edge of the grain-oriented silicon steel of Example 1 of this application, illustrating that the hot-rolled edge of the grain-oriented silicon steel obtained in Example 1 has good quality, with no obvious cracks or microcracks.
[0105] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any skillful means or substitutions should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A production method for avoiding edge cracking in hot-rolled grained silicon steel, characterized in that, The method includes: Molten steel is continuously cast through a chamfered crystallizer to obtain a billet. The billet contains the following chemical composition by mass fraction: 0.03%≤C≤0.07%, 3.0%≤Si≤3.60%, 0.05%≤Mn≤0.30%, P≤0.03%, S≤0.011%, 0.015%≤Als≤0.032%, Cu≤0.6%, with the remainder being iron and unavoidable trace elements. The surface temperature of the billet before it enters the heating furnace shall not be lower than 400℃; The billet is heated in a heating furnace at a furnace gas temperature of 1100℃-1330℃ and a reducing atmosphere. The total time in the furnace is 270-330 minutes to produce a heated slab. The heating furnace has a heating rate of 6℃-10℃ / min. Pressure of 0 to 1000N is applied to both sides of the length direction by vertical rollers. The heated slab is rolled and coiled to obtain a hot-rolled coil of grain-oriented silicon steel. The rolling process includes five roughing passes, each with a reduction rate of 25%-40%. The edge grain size of the hot-rolled coil of grain-oriented silicon steel is 30-35 micrometers.
2. The production method according to claim 1, characterized in that, By allowing the transfer time between the billet and the heating furnace to be 0h to 12h, the surface temperature of the billet before entering the heating furnace is not lower than 400℃.
3. The production method according to claim 1, characterized in that, By placing the billet in a heat-insulating pit with a burner and transferring it from the heat-insulating pit to the heating furnace in a time of less than 30 minutes, the surface temperature of the billet before entering the heating furnace is not lower than 400°C.
4. The production method according to claim 1, characterized in that, The total reduction rate of the roughing mill is 80%-86%.
5. The production method according to claim 1, characterized in that, The thickness of the cast billet is 200-240 mm.
6. The production method according to claim 1, characterized in that, The thickness of the hot-rolled coil is 1.8-3 mm.
7. A hot-rolled coil of grain-oriented silicon steel, characterized in that, It is obtained by the production method described in any one of claims 1 to 6.