A cubic bi-oriented silicon steel and its preparation method and application

Abstract

The present invention discloses a cubic bi-oriented silicon steel and its preparation method and application, and relates to the field of metallurgical technology. The method comprises the following steps: S1, smelting molten steel with qualified composition; S2, pouring the molten steel into the double rollers of the double-roller thin strip continuous casting machine through the tundish, casting and pressing into a silicon steel thin strip, then cooling with mist water, and coiling after cutting off the head and tail; S3: the steel strip is pickled to remove the oxide layer, and then cold-rolled to the target thickness; S4: coating the cold-rolled plate with a mixed oxide coating, vacuum annealing after drying; S5: decarburization annealing to obtain a cubic bi-oriented silicon steel finished product. The present invention utilizes the rapid solidification characteristics of the double-roller thin strip casting and rolling process, which can greatly shorten the process flow and production time, retain the initial cubic texture of the cast strip, and make the cold-rolled steel plate grow by coarsening the original cubic grains in the vacuum annealing stage and finally obtain cubic bi-oriented silicon steel with excellent magnetic properties.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to cubic bi-oriented silicon steel and a preparation method and application thereof. Background Art

[0002] Electrical steel is an important soft magnetic alloy that is indispensable in the electric power, electronics and military industries. Electrical steel can be divided into two categories according to its performance characteristics and uses. One is non-oriented electrical steel, which is mainly used to make various motors and some small transformers; the other is oriented silicon steel, which is mainly used to make various power transformers, distribution transformers and large generator stators. The grain orientation of non-oriented silicon steel is random, and it has uniform magnetic properties in all directions. It is mainly used in rotating magnetic fields; oriented silicon steel is the easy magnetization direction of the grains. <100> Parallel to the rolling direction, with strong {110} <001> Texture, showing excellent magnetic properties of high magnetic induction and low iron loss only in the rolling direction. However, oriented silicon steel has low magnetic induction and high iron loss in the transverse direction, and is not the most ideal soft magnetic material for oriented magnetic fields. <100> Direction. It can meet the specific needs of transformer cores serving in closed circuits with magnetic circuits perpendicular to each other. Electrical steel sheets have excellent magnetic properties in two perpendicular directions. For a long time, it has been the goal of people to develop, research and explore industrial production.

[0003] Assumus et al. used the surface energy method to prepare cubic textured bi-oriented silicon steel, with the extremely low surface energy advantage of the (100) plane as the driving force. The thinner the steel strip, the more perfect the cubic texture is. This method of preparing cubic textured bi-oriented silicon steel is limited by the surface state of the thin strip, which makes its manufacturing process complicated, the yield rate is low and the cost is high, and the magnetic properties of the final product are not high. Harase Jiro et al. used the cross-cross method to prepare cubic bi-oriented silicon steel, first cold rolling with a 40% reduction rate in the hot rolling direction, and then cold rolling with a 40% reduction rate in the transverse direction, but the processing technology route is too complicated and not suitable for industrial production. Tomita Toshiro et al. used conventional rolling and double annealing methods to prepare a strong rotated cubic texture {100} <011> Silicon steel sheets can also achieve the effect of dual-oriented silicon steel, but the hot-rolled steel sheets need to be thinned to remove a large amount of the surface layer and subsequently demanganized, which complicates the production process and has high requirements on the chemical composition and annealing conditions, making actual production very difficult.

[0004] As an emerging green and environmentally friendly production process technology, the twin-roller thin strip casting and rolling process can significantly reduce energy consumption, reduce construction investment, occupy a small area and have many advantages such as high production efficiency. Since the process completes the process from molten steel to solid thin strip in a very short time, it realizes the preparation from liquid metal to solid thin plate, and does not require traditional hot rolling process to thin the thickness of the ingot. The conventional heating and hot rolling processes can be omitted, which not only shortens the process, but also greatly retains the cubic texture in the thin strip, which is conducive to the development of subsequent annealing cubic texture. Significantly reduce production costs and energy consumption. At present, the main products of this process in China and internationally are low-carbon steel. The twin-roller thin strip casting and rolling process not only has process advantages, but also brings new possibilities for the development of new steel material organizations and properties due to the characteristics of rapid solidification and cooling. The application of twin-roll thin strip casting in silicon steel has a bright future. However, the currently disclosed methods for preparing dual-oriented electrical steel sheets by twin-roll thin strip casting generally go through a conventional long-process steelmaking process, with a large amount of slab reduction, complex processes, and difficult to control the quality of the finished product, and do not have the advantages brought by the short process of twin-roll thin strip casting. Summary of the invention

[0005] The present invention provides a cubic bi-oriented silicon steel and a preparation method and application thereof, in order to shorten the process flow, improve production efficiency, reduce energy consumption, and prepare a cubic bi-oriented silicon steel product with excellent performance by optimizing the composition and utilizing the principle that cubic texture ferrite gradually devours other textures of austenite.

[0006] In order to solve the above technical problems, one of the purposes of the present invention is to provide a method for preparing cubic bi-oriented silicon steel, comprising the following steps:

[0007] S1. Molten steel with qualified smelting composition, the molten steel includes the following components by mass percentage: C: 0.040%-0.080%, Si: 2.0%-3.5%, Mn: 0.50%-1.15%, S: 0.003%-0.005%, P: 0.040%-0.080%, Al: 0.020%-0.040%, N: 0.015%-0.028%, the rest is iron and unavoidable inclusions, and meets 15[C]+[Mn]>0.45[Si];

[0008] S2, pouring molten steel through a tundish into the space between the twin rolls of a twin roll thin strip continuous casting machine, casting and pressing a silicon steel thin strip with a thickness of 1.2-2.5 mm, then controlling the temperature of the silicon steel thin strip to 900-1000° C. for mist cooling, transferring the silicon steel thin strip to a shearing machine through a pulling roller for head and tail cutting, and then coiling at a coiling temperature of 550-700° C. to obtain a steel strip;

[0009] S3: The steel strip is pickled to remove the oxide layer, and then cold rolled to the target thickness to obtain a cold rolled sheet;

[0010] S4: coating the cold-rolled sheet with a mixed oxide coating, the mixed oxide coating comprising MgO, TiO2 and SiO2, and performing vacuum annealing after drying, the vacuum annealing temperature being 1000-1150° C., and maintaining the temperature for 6-8 hours to obtain a vacuum annealed sheet;

[0011] S5: performing decarburization annealing on the vacuum annealed plate, the decarburization temperature is 780-880° C., the decarburization time is 0.5-1.5 h, and a cubic bi-oriented silicon steel product is obtained.

[0012] The present invention makes full use of the technical feature of rapid solidification of the twin-roller thin strip casting and rolling process. With the help of a faster cooling rate, the molten steel can be directly solidified into a thin strip without going through the traditional continuous casting, slab heating, hot rolling, normalization and other processes. It only needs to go through a cold rolling process, which greatly retains the cubic texture. The thinner the thickness of the ingot, the higher the requirements for the twin-roller thin strip continuous casting machine, and the more difficult it is to achieve. The thicker the thickness of the thin strip, the greater the downward pressure and reduction required in the cold rolling stage, which will more easily cause the strip to break. Moreover, if the reduction is too large, it will cause a greater change in the texture of the cast strip. Therefore, a reasonable range of 1.2-2.5mm is selected. The reason for selecting the water mist cooling temperature of 900℃-1000℃ is that too high a temperature water mist cooling will require a higher casting strip temperature, and will cause excessive internal stress in the thin strip. The actual temperature will not be too low. It is a short-process production. With a compact production process, the distance to the water mist cooling will not reduce the casting strip too much. The cold-rolled sheet enters the dual-phase zone when heated at the vacuum annealing temperature. At this time, the cubic ferrite grains are retained due to their lower surface energy, and the non-cubic ferrite is transformed into austenite. As the vacuum annealing proceeds, the surface C, Mn and other elements are removed. Due to the low surface energy of the cubic grains, the surface stable cubic ferrite grains begin to grow until the grains on both sides contact each other. However, the decarburization of the vacuum annealing is not complete. In order to avoid the residual carbon from forming a precipitate phase during the use of the product to increase the iron loss and cause the magnetic aging phenomenon of silicon steel, a subsequent special decarburization annealing treatment is performed to decarburize and demanganese the surface of the steel plate, and the surface cubic ferrite grains gradually grow until the ferrite grains on both sides contact each other to form a strong cubic texture dual-oriented silicon steel. Compared with other dual-oriented silicon steel production, not only the production cost is greatly reduced due to the shortened process and reduced energy consumption, but it is also conducive to the development of cubic texture and the improvement of product magnetic properties.

[0013] In addition, C is an austenite stabilizing element. A certain amount of C element is added to the molten steel to ensure that the steel contains a certain amount of austenite during vacuum annealing. As decarburization occurs, these non-cubic textured austenites will gradually be swallowed up by cubic textured ferrite grains, eventually forming dual-oriented silicon steel. This application avoids excessive C content that makes decarburization difficult.

[0014] Si can increase resistivity, significantly reduce iron loss, promote graphitization of carbon in steel, and reduce bonding and aging phenomena between steel plates. The present application limits the Si content and 15[C]+[Mn]>0.45[Si] to avoid the increase of Si content causing austenite content to decrease during annealing, which is not conducive to the development of cubic texture. At the same time, it avoids the decrease of saturation magnetic induction intensity of dual-oriented silicon steel with increasing Si content, reduces the difficulty of cold working and improves the yield rate of cold-rolled steel plates.

[0015] Al can improve the resistivity of electrical steel and reduce hysteresis loss, but too high Al content will lead to a decrease in the surface processing quality of the steel plate, and will also form AlN precipitation phases with N to pin the grain boundaries, affecting the grain recovery, recrystallization, grain growth and other processes, so that the grains of the steel plate do not grow excessively during the vacuum annealing temperature rise stage. Excessive N will make it difficult to completely remove the N element of the steel plate during vacuum annealing. This application avoids the influence of excessive Al and N content on the magnetic properties of the finished product.

[0016] Mn is an austenite stabilizing element. Adding a certain amount of Mn to molten steel ensures that the steel contains a certain amount of austenite during vacuum annealing. It can also increase the resistivity of electrical steel and reduce hysteresis loss.

[0017] P has obvious solubility in ferrite, and can improve the hardness of the steel plate through solid solution strengthening, which is beneficial to improving the punching performance of the steel plate. The solid-dissolved P can increase the resistivity of ferrite, which is beneficial to reducing eddy current losses. However, P has a significant tendency to segregate at dislocations and grain boundaries. This application avoids excessive P content that affects grain growth and increases hysteresis losses of the steel plate, and improves the magnetic induction of the steel plate.

[0018] Because C and Mn are austenitizing elements, Si and Al are ferritizing elements, Al content is relatively low, and its influence on the phase diagram can be ignored. The influence of C element on the phase diagram is much greater than that of Mn, which needs to be considered. The contents of Si and Mn are relatively high, which needs to be considered. If it is necessary to enter the austenite and ferrite two-phase region at 1000℃-1150℃, the contents of C and Mn need to be controlled to be higher than a certain value of Si. After calculation and measurement, the formula requirements of 15[C]+[Mn]>0.45[Si] are formulated.

[0019] As a preferred solution, in S3, the mixed oxide coating comprises 52%-73% by mass of MgO, 25%-45% by mass of TiO2, and 2%-3% by mass of SiO2.

[0020] By adopting the above scheme, for the finished silicon steel, N, C, S, etc. are all impurity elements, but these elements are inevitable in production. The role of MgO can adsorb impurity elements such as N and S in steel, so that N and S elements can be completely removed after vacuum annealing. Ti02 and SiO2 react with C during vacuum annealing to remove C.

[0021] As a preferred solution, in S1, the molten steel further comprises one or more of 0.01%-0.10% by mass of Sb, 0.01%-0.05% by mass of Bi and 0.01%-0.15% by mass of Sn.

[0022] As a preferred embodiment, in S2, the preheating temperature of the tundish is 1200-1300°C, the superheat is controlled at 30-60°C, the area from the bottom of the tundish to the casting and rolling area is an atmosphere-enclosed area, and the temperature of the silicon steel strip output from the twin-roll thin-strip continuous casting machine is 1300-1400°C through inert gas protection, the pulling speed is controlled at 60-110m / min, and the cooling rate of the mist water cooling is 10-100°C / s.

[0023] As a preferred solution, in S3, the target thickness is 0.15-0.35 mm, and cold rolling is performed using large-diameter working rolls and a pass reduction rate of less than 25%, with a total reduction of not less than 70%.

[0024] As a preferred solution, in S3, the oxide layer is removed by acid washing in 3-6 wt % HCl at 60-80° C. for 0.5-2 min.

[0025] As a preferred solution, in S4, the heating rate of vacuum annealing is 6-12°C / min, then the furnace is cooled to 300°C, taken out and air-cooled to room temperature, and the vacuum degree is 10 -1 -10 -2 pa.

[0026] As a preferred solution, in S5, the heating rate of the decarburization annealing is 20-50°C / s, the atmosphere is wet 70wt%-80wt% H2 and 20wt%-30wt% N2, and the dew point temperature is 30-60°C.

[0027] In order to solve the above technical problems, the second object of the present invention is to provide a method for preparing cubic bi-oriented silicon steel to obtain cubic bi-oriented silicon steel.

[0028] In order to solve the above technical problems, the third object of the present invention provides an application of cubic bi-oriented silicon steel in the field of rotating electrical machinery stator equipment, transformer-type electrical products or electromagnetic materials used in aerospace.

[0029] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0030] 1. The present invention makes full use of the rapid solidification characteristics of the twin-roll thin strip casting and rolling process to make the thin strip blank solidification structure homogeneous and fine. The process can directly solidify the molten steel rapidly, and the conventional slab heating, hot rolling and normalizing processes can be omitted, thus shortening the process, significantly reducing production costs and energy consumption, and can also greatly retain the cubic texture in the thin strip, so that sufficient cubic-oriented ferrite grains grow in the vacuum annealing stage, which is beneficial to improving the magnetic properties.

[0031] 2. The present application adopts twin-roller thin strip casting to produce hot-rolled strips with strong {100} cubic oriented grains on the surface. After cold rolling, the two-phase region is rapidly heated and annealed in a vacuum environment. Under the action of surface energy, the cubic oriented grains with {100} surface on the steel plate surface remain in the ferrite state, while the grains on the non-{100} surface are transformed into austenite. In the subsequent annealing and decarburization process, the cubic oriented ferrite grains with strong {100} surface grow because of their high surface energy and engulf the austenite grains with low surface energy, further exerting the advantage of strong {100} cubic oriented grains in the ferrite region to preferentially grow, and finally forming dual-oriented silicon steel. At this time, the non-{100} surface grains do not have this surface effect, so their grain size will be smaller than the surface grains, providing a driving force for the surface grains to grow inward.

[0032] 3. The annealing temperature in this application is set at 1000-1150℃. The change of austenite content during annealing is as follows: Figure 2 As the temperature increases, the austenite content first increases and then decreases. The temperature range of the dual-phase zone is 580-1400℃. In the early stage of vacuum annealing, the steel plate first completes the primary recrystallization, and coarse cubic ferrite grains are first formed on the surface due to decarburization. After entering the constant temperature zone, the steel plate is required to enter the dual-phase zone. As the ferrite phase zone becomes thicker and the grains coarsen, the ferrite grains on both sides of the steel plate will continue to grow inward and contact each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : A schematic diagram of a process for preparing cubic bi-oriented silicon steel according to the present invention (Note: 1, ladle; 2, tundish; 3, nozzle; 4, casting roll; 5, pinch roll; 6, mist cooling; 7, pulling roll; 8, high-speed flying shear; 9, steering roll; 10, coiler);

[0034] Figure 2 : The alloy property diagram of 3wt%Fe, 0.07wt%Si, 0.08wt%C calculated by thermodynamic software (Note: The curve in the figure shows the relationship between the volume fraction of ferrite BCC and austenite FCC in dual-oriented silicon steel and temperature). DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Embodiment 1

[0037] A cubic bi-oriented silicon steel, wherein the molten steel comprises the following mass components: C: 0.04%, Si: 2.0%, Mn: 0.5%, S: 0.0045%, P: 0.078%, Al: 0.037%, N: 0.028%, Sn: 0.05%, and the rest is iron and inevitable inclusions, and the preparation method thereof is as follows:

[0038] S1: smelting molten steel with qualified composition, pouring the molten steel into the twin rolls of twin-roll thin strip continuous casting machine through tundish, wherein the tundish preheating temperature is 1270℃, and the superheat is controlled at 45℃. The thickness of the produced bi-oriented silicon steel thin strip is 1.7mm, and the temperature of the thin strip billet discharged from the twin-roll continuous casting machine is 1325℃, and the pulling speed is controlled at 72m / min, and then air-cooled to 950℃, wherein inert gas protection is applied throughout the process from the bottom of the tundish to the casting and rolling area, and then the thin strip is mist-cooled, and then transmitted to the shearing machine through the pulling roller for head and tail cutting, and then coiled, and the coiling temperature is 630℃ to obtain the steel strip;

[0039] S2: The steel strip is pickled in 4% HCl at 70°C for 3 minutes to remove the oxide layer, and then the pickled steel strip is cold rolled to 0.15 mm using a large-diameter work roll and a pass reduction rate of less than 25%, with a total reduction of 91.2%, to obtain a cold-rolled sheet;

[0040] S3: The cold rolled sheet is coated with a mixed coating containing 2% SiO2, 25% TiO2 and 73% MgO oxides, and then vacuum annealed after drying; wherein the vacuum annealing process is: heating to 1005°C at a heating rate of 8.5°C / min, keeping the temperature for 6 hours, then cooling the furnace to 300°C, taking it out and air cooling it to room temperature, and the vacuum degree is 10 -2 pa, obtain vacuum annealed plate;

[0041] S4: Decarburization annealing is performed on the vacuum annealed plate, the decarburization temperature is 830° C., the decarburization time is 0.5 h, the atmosphere is wet 80wt% H2+20wt% N2, the dew point temperature is 45° C., and a cubic bi-oriented silicon steel product is obtained.

[0042] Embodiment 2

[0043] A cubic bi-oriented silicon steel, wherein the molten steel comprises the following mass components: C: 0.053%, Si: 2.5%, Mn: 0.75%, S: 0.0041%, P: 0.065%, Al: 0.031%, N: 0.024%, Bi: 0.03%, and the rest is iron and inevitable inclusions, and the preparation method thereof is as follows:

[0044] S1: smelting molten steel with qualified composition, pouring the molten steel into the twin rolls of twin-roll thin strip continuous casting machine through tundish, wherein the tundish preheating temperature is 1255℃, and the superheat is controlled at 41℃. The thickness of the produced bi-oriented silicon steel thin strip is 2.0mm, and the temperature of the thin strip billet discharged from the twin-roll continuous casting machine is 1319℃, and the pulling speed is controlled at 78m / min, and then air-cooled to 950℃, wherein inert gas protection is applied throughout the process from the bottom of the tundish to the casting and rolling area, and then the thin strip is mist-cooled, and then transmitted to the shearing machine through the pulling roller for head and tail cutting, and then coiled, and the coiling temperature is 635℃ to obtain the steel strip;

[0045] S2: The steel strip is pickled in 4% HCl at 70°C for 2 minutes to remove the oxide layer, and then the pickled steel strip is cold rolled with a large-diameter work roll and a pass reduction rate of less than 25% to 0.23 mm, with a total reduction of 88.5%, to obtain a cold-rolled sheet;

[0046] S3: The cold rolled sheet is coated with a mixed coating containing 2% SiO2, 33% TiO2 and 65% MgO oxides, and then vacuum annealed after drying; wherein the vacuum annealing process is: heating to 1050°C at a heating rate of 9.5°C / min, keeping the temperature for 6.5h, then cooling the furnace to 300°C, taking it out and air cooling it to room temperature, and the vacuum degree is 10 -2 pa, obtain vacuum annealed plate;

[0047] S4: Decarburization annealing is performed on the vacuum annealed plate, the decarburization temperature is 855° C., the decarburization time is 0.8 h, the atmosphere is wet 80wt% H2+20wt% N2, the dew point temperature is 50° C., and a cubic bi-oriented silicon steel product is obtained.

[0048] Embodiment 3

[0049] A cubic bi-oriented silicon steel, wherein the molten steel comprises the following mass components: C: 0.065%, Si: 3.0%, Mn: 1.02%, S: 0.0035%, P: 0.054%, Al: 0.025%, N: 0.021%, Sn: 0.04%, Bi: 0.02%, and the rest is iron and inevitable inclusions, and the preparation method thereof is as follows:

[0050] S1: smelting molten steel with qualified composition, pouring the molten steel into the twin rolls of twin-roll thin strip continuous casting machine through tundish, wherein the tundish preheating temperature is 1250℃, and the superheat is controlled at 35℃. The thickness of the produced bi-oriented silicon steel thin strip is 2.3mm, and the temperature of the thin strip billet discharged from the twin-roll continuous casting machine is 1311℃, and the pulling speed is controlled at 82m / min, and then air-cooled to 950℃, wherein the inert gas protection is applied from the bottom of the tundish to the casting and rolling area, and then the thin strip is mist-cooled, and then conveyed to the shearing machine through the pulling roller for head and tail cutting, and then coiled, and the coiling temperature is 600℃ to obtain the steel strip;

[0051] S2: The steel strip is pickled in 4% HCl at 70°C for 2 minutes to remove the oxide layer, and then the pickled steel strip is cold rolled with a large-diameter work roll and a pass reduction rate of less than 25% to 0.27 mm, with a total reduction of 88.3%, to obtain a cold-rolled sheet;

[0052] S3: The cold rolled sheet is coated with a mixed coating containing 3% SiO2, 37% TiO2 and 60% MgO oxides, and then vacuum annealed after drying; wherein the vacuum annealing process is: heating to 1080°C at a heating rate of 10°C / min, keeping the temperature for 7h, then cooling the furnace to 300°C, taking it out and air cooling it to room temperature, and the vacuum degree is 10 -2 pa, obtain vacuum annealed plate;

[0053] S4: Decarburization annealing is performed on the vacuum annealed plate, the decarburization temperature is 845° C., the decarburization time is 1.2 h, the atmosphere is wet 80wt% H2+20wt% N2, the dew point temperature is 50° C., and a cubic bi-oriented silicon steel product is obtained.

[0054] Embodiment 4

[0055] A cubic bi-oriented silicon steel, wherein the molten steel comprises the following mass components: C: 0.08%, Si: 3.5%, Mn: 1.12%, S: 0.0031%, P: 0.045%, Al: 0.022%, N: 0.015%, Sb: 0.05%, and the rest is iron and inevitable inclusions, and the preparation method thereof is as follows:

[0056] S1: smelting molten steel with qualified composition, pouring the molten steel into the twin rolls of the twin-roll thin strip continuous casting machine through the tundish, wherein the preheating temperature of the tundish is 1230℃, and the superheat is controlled at 30℃. The thickness of the produced bi-oriented silicon steel thin strip is 2.5mm, and the temperature of the thin strip billet discharged from the twin-roll continuous casting machine is 1300℃, and the pulling speed is controlled at 85m / min, and then air-cooled to 950℃, wherein the inert gas protection is applied throughout the process from the bottom of the tundish to the casting and rolling area, and then the thin strip is mist-cooled, and then transmitted to the shearing machine through the pulling roller for head and tail cutting, and then coiled, and the coiling temperature is 570℃ to obtain the steel strip;

[0057] S2: The steel strip is pickled in 4% HCl at 70°C for 2 minutes to remove the oxide layer, and then the pickled steel strip is cold rolled to 0.35 mm using a large-diameter work roll and a pass reduction rate of less than 25%, with a total reduction of 86%, to obtain a cold-rolled sheet;

[0058] S3: The cold rolled sheet is coated with a mixed coating containing 3% SiO2, 45% TiO2 and 52% MgO oxides, and then vacuum annealed after drying; wherein the vacuum annealing process is: heating to 1150°C at a heating rate of 12°C / min, keeping the temperature for 8h, then cooling the furnace to 300°C, taking it out and air cooling it to room temperature, and the vacuum degree is 10 -2 pa, obtain vacuum annealed plate;

[0059] S4: Decarburization annealing is performed on the vacuum annealed plate, the decarburization temperature is 860° C., the decarburization time is 1.5 h, the atmosphere is wet 80wt% H2+20wt% N2, the dew point temperature is 50° C., and a cubic bi-oriented silicon steel product is obtained.

[0060] Comparative Example 1

[0061] A cubic bi-oriented silicon steel, wherein each step in the preparation method and the reagents and process parameters used in each step are the same as those in the first embodiment, except that the molten steel comprises the following mass components: C: 0.04%, Si: 2.0%, Mn: 0.3%, S: 0.0045%, P: 0.02%, Al: 0.037%, N: 0.028%, Sn: 0.05%, and the rest are iron and unavoidable inclusions.

[0062] Comparative Example 2

[0063] A cubic bi-oriented silicon steel, wherein each step and the reagents and process parameters used in each step in the preparation method are the same as those in the first embodiment, except that the molten steel comprises the following mass components: C: 0.04%, Si: 3%, Mn: 0.5%, S: 0.0045%, P: 0.078%, Al: 0.037%, N: 0.028%, Sn: 0.05%, and the rest is iron and unavoidable inclusions

[0064] Comparative Example 3

[0065] A cubic bi-oriented silicon steel, wherein each step in the preparation method and the reagents and process parameters used in each step are the same as those in the first embodiment, except that in S3, the mixed coating includes MgO oxide.

[0066] Comparative Example 4

[0067] A cubic bi-oriented silicon steel, wherein each step in the preparation method and the reagents and process parameters used in each step are the same as those in Example 1, except that in S1, the coiling temperature is 450±15°C.

[0068] Performance testing

[0069] 1. Magnetic properties: The standard silicon steel sample of 300mm*30mm silicon steel sheet was used, and the MATS-3000M / k50 silicon steel material measuring device was used to test the transverse and longitudinal magnetic properties respectively, as shown in Table 1 below.

[0070] Table 1 - Magnetic properties of cubic bi-oriented silicon steel in the examples and comparative examples of the present application

[0071]

[0072] Combining the magnetic property test results of Example 1 and Comparative Example 1 in Table 1, it can be seen that the content of P element and Mn is specifically limited in the present invention. Mn can not only expand the austenite region, but also improve the magnetic properties of silicon steel. The present invention requires the cold-rolled steel sheet to enter the austenite phase region during the vacuum annealing stage, and needs to add a sufficient amount of austenitizing element Mn to make the surface (100) surface grains grow during the vacuum annealing stage. P can increase the resistivity, and the solid-solution P can increase the resistivity of ferrite, which is beneficial to reducing eddy current losses. As for magnetic induction, the magnetic induction of steel with a high phosphorus content will increase under weak and medium magnetic fields. The silicon steel product must be packaged through a lamination process. P has obvious solubility in ferrite, and the hardness of the steel plate is improved through solid solution strengthening, which is beneficial to improving the punching performance of the steel plate. However, excessive P has a significant tendency to segregate at dislocations and grain boundaries, which will prevent grain growth, resulting in increased hysteresis losses of the steel plate, and will also affect the evolution process of the steel plate texture and the magnetic induction of the steel plate.

[0073] Combining the magnetic property test results of Example 1 and Comparative Example 3 in Table 1, it can be seen that the mixed coating in S3 is composed of three oxides, with MgO as the main component and TiO2 and SiO2 as the auxiliary components. MgO will form a glass film during vacuum annealing to adsorb impurity elements such as N and S in steel. TiO2 and SiO2 will react with C to achieve the effect of decarburization, and then during the vacuum annealing process, austenite will be transformed into ferrite, thereby improving the magnetic properties of silicon steel.

[0074] Combining the magnetic property test results of Example 1 and Comparative Example 4 in Table 1, it can be seen that the reason why the coiling temperature of the cast steel coil in the present application is required to be between 550-700°C is because stress concentration will occur during the casting and rolling of the steel coil, resulting in cold rolling breakage, and at this temperature, a precipitate phase will be dispersed and precipitated, preventing the grains from growing excessively during the initial recrystallization of the thin strip in the vacuum annealing stage, thereby inhibiting grain boundary migration and preventing grain growth.

[0075] 2. Using the thermodynamic database TCFE4 in the Thermo-Calc analysis software to obtain a property diagram given a given composition, the cold-rolled steel sheet of the present invention has only two phases in the vacuum annealing stage, namely ferrite and austenite. Figure 2 It is the relationship between the volume fraction of ferrite or austenite and temperature drawn by 3% Si, 0.07% C, and 0.8% Mn. For example, at 1150°C, silicon steel enters the single-phase region, that is, the full austenite phase. The present invention requires annealing in the two-phase region, so it is set at 1000-1150°C.

[0076] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing cubic bi-oriented silicon steel, characterized in that: The following steps are involved: S1. Molten steel with qualified smelting composition, the molten steel includes the following components by mass percentage: C: 0.040%-0.080%, Si: 2.0%-3.5%, Mn: 0.50%-1.15%, S: 0.003%-0.005%, P: 0.040%-0.080%, Al: 0.020%-0.040%, N: 0.015%-0.028%, the rest is iron and unavoidable inclusions, and meets 15[C]+[Mn]>0.45[Si]; S2, pouring molten steel through a tundish into the space between the twin rolls of a twin roll thin strip continuous casting machine, casting and pressing a silicon steel thin strip with a thickness of 1.2-2.5 mm, then controlling the temperature of the silicon steel thin strip to 900-1000° C. for mist cooling, transferring the silicon steel thin strip to a shearing machine through a pulling roller for head and tail cutting, and then coiling at a coiling temperature of 550-700° C. to obtain a steel strip; S3: The steel strip is pickled to remove the oxide layer, and then cold rolled to the target thickness to obtain a cold rolled sheet; S4: coating the cold-rolled sheet with a mixed oxide coating, the mixed oxide coating comprising MgO, TiO2 and SiO2, and performing vacuum annealing after drying, the vacuum annealing temperature being 1000-1150° C., and maintaining the temperature for 6-8 hours to obtain a vacuum annealed sheet; S5: Decarburization annealing is performed on the vacuum annealed plate, the decarburization temperature is 780-880°C, and the decarburization time is 0.5-1.5h to obtain a cubic bi-oriented silicon steel product; In S3, the mixed oxide coating comprises 52%-73% by mass of MgO, 25%-45% by mass of TiO2, and 2%-3% by mass of SiO2.

2. The method for preparing cubic bi-oriented silicon steel according to claim 1, characterized in that: In S1, the molten steel further comprises one or more of 0.01%-0.10% by mass of Sb, 0.01%-0.05% by mass of Bi, and 0.01%-0.15% by mass of Sn.

3. The method for preparing cubic bi-oriented silicon steel according to claim 1, characterized in that: In S2, the preheating temperature of the tundish is 1200-1300°C, the superheat is controlled at 30-60°C, the area from the bottom of the tundish to the casting and rolling area is an atmosphere-enclosed area, and the temperature of the silicon steel strip output from the twin-roll thin-strip continuous casting machine is 1300-1400°C through inert gas protection, the pulling speed is controlled at 60-110m / min, and the cooling rate of the mist water cooling is 10-100°C / s.

4. The method for preparing cubic bi-oriented silicon steel according to claim 1, characterized in that: In S3, the target thickness is 0.15-0.35 mm, and cold rolling is performed using large-diameter working rolls and a pass reduction rate of less than 25%, with a total reduction of not less than 70%.

5. The method for preparing cubic bi-oriented silicon steel according to claim 1, characterized in that: In S3, the oxide layer is removed by acid washing in 3-6 wt% HCl at 60-80°C for 0.5-2 min.

6. The method for preparing cubic bi-oriented silicon steel according to claim 1, characterized in that: In S4, the heating rate of vacuum annealing is 6-12℃ / min, then the furnace is cooled to 300℃, taken out and air-cooled to room temperature, and the vacuum degree is 10 -1 -10 -2 pa.

7. The method for preparing cubic bi-oriented silicon steel according to claim 1, characterized in that: In S5, the heating rate of the decarburization annealing is 20-50°C / s, the atmosphere is wet 70wt%-80wt% H2 and 20wt%-30wt% N2, and the dew point temperature is 30-60°C.

8. Cubic bi-oriented silicon steel obtained based on the preparation method of cubic bi-oriented silicon steel according to any one of claims 1 to 7.

9. An application of the cubic bi-oriented silicon steel according to claim 8 in the field of rotating electrical machinery stator equipment, transformer-type electrical products or electromagnetic materials used in aerospace.

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