High-grade non-oriented silicon steel and method for producing the same

Abstract

The application discloses a high-grade non-oriented silicon steel and a production method thereof. The chemical components of the non-oriented silicon steel include, in mass percentage, Si 2.5-3.5%, Al 0.5-1.5%, and Mn 0.2-0.8%. The production method comprises sequentially performed continuous casting, hot rolling, primary cold rolling, primary annealing, secondary cold rolling, and secondary annealing processes. In the continuous casting process, the proportion of columnar crystals in the continuous casting billet obtained in the continuous casting process is controlled to be 50-80%. In the primary cold rolling process, the total reduction rate is controlled to be 90-95%, and the surface roughness of the work rolls in the primary cold rolling is controlled to be 1.5-2.5 μm. In the primary annealing process, the annealing temperature is 930-970 ℃, and the annealing time is 60-180 s. In the secondary cold rolling process, the total reduction rate is 5-10%, and the surface roughness of the work rolls in the secondary cold rolling is 0.2-0.4 μm. In the secondary annealing process, the annealing temperature is 950-1050 ℃, and the annealing time is 50-80 s.

Description

Technical Field

[0001] This application belongs to the field of steel material preparation technology, specifically relating to a high-grade non-oriented silicon steel and its production method. Background Technology

[0002] High-grade non-oriented silicon steel is a key material for manufacturing the cores of various high-efficiency motors and large generator sets. The iron loss of high-grade non-oriented silicon steel is closely related to the operating efficiency of the motor; reducing the iron loss of high-grade non-oriented silicon steel can effectively improve the operating efficiency of the motor.

[0003] Increasing the Si and Al content can effectively reduce the iron loss of non-oriented silicon steel and improve the material resistivity. However, with the increase of Si and Al content, the hot rolling and cold rolling production of high-grade silicon non-oriented silicon steel becomes more difficult, and serrated edge cracks are prone to occur during hot rolling, which in turn cause edge cracks and strip breakage during cold rolling, seriously affecting the continuous and stable production of high-grade non-oriented silicon steel. Summary of the Invention

[0004] The purpose of this application is to provide a high-grade non-oriented silicon steel and a method for producing the same.

[0005] To achieve one of the above-mentioned objectives, one embodiment of this application provides a method for producing high-grade non-oriented silicon steel, wherein the chemical composition of the non-oriented silicon steel, by mass percentage, includes: Si 2.5~3.5%, Al 0.5~1.5%, and Mn 0.2~0.8%; the production method includes sequentially performed continuous casting, hot rolling, primary cold rolling, primary annealing, secondary cold rolling, and secondary annealing processes;

[0006] In the continuous casting process, the proportion of columnar crystals in the continuously cast billet obtained from the continuous casting process is controlled to be 50-80%; In the primary cold rolling process, the total reduction rate is controlled at 90-95%, and the surface roughness of the work rolls in the primary cold rolling process is 1.5-2.5 μm. In the first annealing process, the annealing temperature is 930~970℃ and the annealing time is 60~180s; In the secondary cold rolling process, the total reduction rate is 5~10%, and the surface roughness of the work rolls in the secondary cold rolling process is 0.2~0.4μm. In the secondary annealing process, the annealing temperature is 950~1050℃ and the annealing time is 50~80s.

[0007] As a further improvement of one embodiment of this application, the chemical composition of the high-grade non-oriented silicon steel, by mass percentage, further includes: C≤0.0025%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, N≤0.002%, S≤0.0015%, P 0.03~0.05%, with the remainder being Fe and unavoidable impurities.

[0008] As a further improvement of one embodiment of this application, in the continuous casting process, electromagnetic stirring is controlled at the end of solidification, while electromagnetic stirring is not performed in the crystallizer.

[0009] As a further improvement of one embodiment of this application, in the continuous casting process, the thickness h of the billet shell at the outlet of the crystallizer is controlled to be ≥8Si+10Al+9Mn.

[0010] As a further improvement to one embodiment of this application, in the continuous casting process, the cooling water flow rate of the wide side of the crystallizer is controlled to be 2500~4500 L / min, the cooling water flow rate of the narrow side is controlled to be 400~700 L / min, the crystallizer inlet water temperature is controlled to be 28~35℃, the inlet and outlet water temperature difference is controlled to be 6~10℃, and the average heat flux density of the crystallizer is controlled to be 1200~2000 kW / m³. 2 .

[0011] As a further improvement of one embodiment of this application, the cooling rate of the second cooling zone in the continuous casting process is controlled to gradually decrease along the foot roll section, sector sections 1 to 4, and sector sections 5 to 12. Specifically, the cooling rate of the foot roll section is controlled to be 3 to 10 °C / s, the cooling rate of sector sections 1 to 4 is controlled to be 0.5 to 8 °C / s, and the cooling rate of sector sections 5 to 12 is controlled to be 0.2 to 1.5 °C / s.

[0012] As a further improvement of one embodiment of this application, in the continuous casting process, the specific water volume of the foot roll section is controlled to be 1.2~2.5L / kg, the cooling water volume of the wide face is 260~600L / min, and the cooling water volume of the narrow face is 50~125L / min; The specific water content of the first to fourth fan-shaped sections is controlled at 0.8 to 1.5 L / kg, and the surface temperature of the billet is 1000 to 1100℃; The specific water content of the 5th to 12th segments of the sector is controlled at 0.3 to 0.8 L / kg; Control the straightening temperature to >950℃.

[0013] As a further improvement of one embodiment of this application, in the continuous casting process, the continuous casting speed v, the target thickness δ of the continuous casting billet and the target width w are controlled to satisfy 0.21-0.005×(Si+Al)≤v×δ×w≤0.22-0.003×(Si+Al), and v×δ×w is negatively correlated with Si+Al, where the unit of v is m / min, the unit of δ is m and the unit of w is m.

[0014] As a further improvement of one embodiment of this application, 0.7m / min≤v≤1.2m / min, 0.18m≤δ≤0.25m, and 1.0m≤w≤1.3m.

[0015] As a further improvement of one embodiment of this application, in the hot rolling process, the continuously cast billet obtained from the continuous casting process is heated and then subjected to rough rolling, finish rolling and cooling in sequence; The uniform heating temperature is 1050~1250℃, and the heating time is 180~220min; The reduction rate of each pass in roughing is controlled at 32-38%, and the final rolling temperature of roughing is 950-1000℃; The reduction rate of each pass in the finishing mill is controlled at 30-38%, the finishing temperature is 820-880℃, and the coiling temperature is 600-680℃.

[0016] As a further improvement of one embodiment of this application, the production method further includes a normalizing process performed between the hot rolling and the first cold rolling processes, wherein the normalizing temperature is 920~970℃ and the normalizing time is 2~3min.

[0017] To achieve one of the above-mentioned objectives, one embodiment of this application provides a high-grade non-oriented silicon steel, which is prepared using the production method of high-grade non-oriented silicon steel as described above.

[0018] Compared with the prior art, the beneficial effects of this application include: This application describes a high-grade non-oriented silicon steel and its production method. For high-grade non-oriented silicon steel with high Si and Al content, the proportion of columnar crystals in the continuously cast billet is controlled to 50-80%. Utilizing the high high-temperature strength of columnar crystals along their growth direction, the high-temperature strength of the continuously cast billet is improved, effectively resisting the static pressure of molten steel and reducing the risk of bulging deformation. This, in turn, effectively reduces the occurrence of serrated edge cracks during subsequent hot rolling. Furthermore, a large-roughness work roll and a large reduction are used in the first cold rolling process to induce severe plastic deformation of the columnar crystal structure. Combined with a high-temperature annealing process between the two cold rolling processes, the columnar crystals undergo sufficient recrystallization. Then, in the second cold rolling process, a smaller-roughness work roll and a smaller reduction rate are used for leveling. This allows for adjustment of thickness and strip shape, reduction of surface roughness of the finished strip, and promotion of ferrite grain growth during annealing, eliminating corrugated defects and achieving excellent magnetic properties and surface finish. It also significantly reduces the occurrence of cold-rolled edge cracks and cold-rolled strip breakage. Detailed Implementation

[0019] The present application will be described in detail below with reference to specific embodiments. However, these embodiments do not limit the present application, and structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are all included within the protection scope of the present application.

[0020] This application investigates the fracturing tendency of high-grade non-oriented silicon steel with high Si and Al content during hot rolling. It was found that high Si and Al content significantly reduces the high-temperature thermal conductivity and high-temperature strength of the steel, resulting in slow heat dissipation during solidification. This leads to slow initial shell growth and insufficient strength in the billet during continuous casting, making the billet prone to bulging deformation under the hydrostatic pressure of molten steel. Bulging deformation causes internal stress at the billet edges. During high-temperature heating, this internal stress induces abnormal growth of columnar crystals at the billet edges, resulting in uneven plastic deformation at the billet edges during hot rolling, thus forming serrated edge cracks.

[0021] In view of this, one embodiment of this application provides a method for producing high-grade non-oriented silicon steel and the high-grade non-oriented silicon steel prepared by the method.

[0022] The chemical composition of this high-grade non-oriented silicon steel, by mass percentage, includes: Si 2.5~3.5%, Al 0.5~1.5%, and Mn 0.2~0.8%.

[0023] The production method includes the sequential processes of continuous casting, hot rolling, primary cold rolling, primary annealing, secondary cold rolling, and secondary annealing.

[0024] In the continuous casting process, the proportion of columnar crystals in the continuously cast billet is controlled to be 50-80%. This utilizes the high high-temperature strength of columnar crystals along the growth direction to improve the high-temperature strength of the continuously cast billet, thereby effectively resisting the static pressure of molten steel, reducing the risk of bulging deformation, and thus effectively reducing the occurrence of serrated edge cracks during subsequent hot rolling.

[0025] In the aforementioned cold rolling process, the total reduction rate is controlled at 90-95%, and the surface roughness of the work rolls in the cold rolling process is 1.5-2.5 μm. The high-roughness work rolls generate intense friction with the strip surface during rolling, introducing severe shear plastic deformation into the strip surface layer. This causes the columnar crystal grains to elongate and break up. This, combined with the compressive deformation generated by the overall large reduction, greatly enhances the fragmentation effect on the columnar crystals, thereby forming high-density dislocations and deformation bands, providing sufficient driving force for subsequent recrystallization.

[0026] In the first annealing process, the annealing temperature is 930~970℃ and the annealing time is 60~180s. By performing high-temperature annealing between the two annealing processes, the deformed structure can undergo sufficient recrystallization, forming fine and uniform equiaxed grains, and a large amount of the crystallographic orientation information of the columnar crystals is eliminated.

[0027] In the secondary cold rolling process, the total reduction rate is 5-10%, and the surface roughness of the work rolls in the secondary cold rolling is 0.2-0.4 μm. On the one hand, this can eliminate the strip shape defects that may be generated in the primary cold rolling and primary annealing, and accurately control the thickness tolerance of the finished product. The small roughness of the work rolls can give the finished strip a low-roughness, high-gloss surface. On the other hand, the secondary cold rolling uses a small reduction rate, which results in a lower dislocation density and less energy storage inside the strip after deformation. This leads to a lower recrystallization nucleation rate in the subsequent secondary annealing process, a stronger driving force for grain growth, and thus obtains larger and more uniform ferrite grains. This significantly reduces hysteresis loss and iron loss, and is also conducive to the development of favorable texture and increases magnetic induction intensity.

[0028] In the secondary annealing process, the annealing temperature is 950~1050℃ and the annealing time is 50~80s.

[0029] In summary, this application targets high-grade non-oriented silicon steel with high Si and Al content. It controls the proportion of columnar crystals in the continuously cast billet to 50-80%, utilizing the high-temperature strength of columnar crystals along their growth direction to improve the high-temperature strength of the billet. This effectively resists the static pressure of molten steel, reduces the risk of bulging deformation, and consequently reduces serrated edge cracks during subsequent hot rolling. Furthermore, by using high-roughness work rolls and high reduction during the first cold rolling process, the columnar crystal structure undergoes severe plastic deformation. Combined with a high-temperature annealing process between the two cold rolling steps, the columnar crystals undergo sufficient recrystallization. Then, during the second cold rolling process, lower-roughness work rolls and a smaller reduction rate are used for leveling. This allows for adjustment of thickness and strip shape, reduction of surface roughness of the finished strip, and promotion of ferrite grain growth during annealing, eliminating corrugated defects and achieving excellent magnetic properties and surface finish. It also significantly reduces the occurrence of cold-rolled edge cracks and strip breakage.

[0030] In one embodiment, the chemical composition of the high-grade non-oriented silicon steel, by mass percentage, includes: C≤0.0025%, Si 2.5~3.5%, Al 0.5~1.5%, Mn 0.2~0.8%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, N≤0.002%, S≤0.0015%, P 0.03~0.05%, with the remainder being Fe and unavoidable impurities.

[0031] The role and mechanism of each element in the above chemical composition are introduced below.

[0032] C: In non-oriented silicon steel, C is generally considered to be a harmful element. An increase in C content will lead to fine grains, high iron loss, poor magnetic properties, and magnetic aging problems in the finished product. Therefore, it is generally better to control the C content as low as possible. In this embodiment, the C content is controlled at 0.0025% or below.

[0033] Si is an effective additive element for improving the resistivity of electromagnetic steel sheets and reducing iron loss. It can also effectively improve the strength of steel strips. In this embodiment, the Si content (by mass percentage) is controlled at 2.5-3.5% to effectively reduce iron loss and meet the requirements of high-grade non-oriented silicon steel.

[0034] Al is also an effective additive element for improving the resistivity of electromagnetic steel plates and reducing iron loss. If its content is too high, it will reduce the magnetic induction intensity and significantly increase the brittleness of the steel plate, increasing the difficulty of processing such as cold rolling. If its content is too low, it will lead to excessively low resistivity and fine precipitation of nitrides such as AlN, making it difficult for the grains to grow sufficiently and failing to meet the requirements of low iron loss. Therefore, in this invention, the content of Als (i.e., acid-soluble aluminum) is controlled at 0.5~1.5%.

[0035] Mn can increase the resistivity of materials and reduce iron loss. Mn readily reacts with S to form MnS. Adding an appropriate amount of Mn can suppress the hot brittleness caused by S. In this embodiment, Mn is added and the Mn content (by mass percentage) is controlled to be 0.2-0.8%.

[0036] Nb, V, and Ti: Nb, V, and Ti are carbide and nitride forming elements, and also major impurity elements. Carbides and nitrides in non-oriented silicon steel can form fine precipitates that hinder grain growth during annealing, worsen the magnetic properties of the non-oriented silicon steel, and lead to increased iron loss and decreased magnetic induction. Therefore, their content is controlled to not exceed 0.002%.

[0037] Cr, Ni, Cu: Adding Cr, Ni, and Cu to non-oriented silicon steel can improve its strength, but it will also increase iron loss and reduce magnetic induction. Therefore, their content is controlled to not exceed 0.03%.

[0038] N: It is also an important component of inclusions in steel. The AlN formed in the billet will dissolve in large quantities during the hot rolling process and then disperse and precipitate during the hot working process. It will hinder the growth of grains during the annealing process of the finished product and reduce the magnetism of the finished product. Therefore, its content should be controlled to N≤0.002%.

[0039] S: is a harmful element and an important component of inclusions in steel. In particular, when the billet is heated before hot rolling, a large amount of MnS precipitates in the steel will dissolve and then disperse during the hot working process. This will hinder the growth of grains during the annealing process of the finished product and reduce the magnetism of the finished product. Therefore, an increase in its content will lead to a decrease in magnetic induction intensity and an increase in iron loss. In this embodiment, in order to avoid the precipitation of fine MnS during hot rolling, the content of S (by mass percentage) is controlled to be ≤0.0015%.

[0040] P: It can effectively improve iron loss. Its content can effectively improve the strength of steel strip and improve stamping performance. However, for high-grade non-oriented silicon, P exceeding 0.05% will significantly deteriorate the cold rollability of steel. In this embodiment, in order to further improve the yield strength of non-oriented silicon steel products and meet the actual use requirements of high-speed motors, it is more preferable that the P content is controlled at 0.03~0.05%.

[0041] An embodiment of this application also provides a method for controlling the proportion of columnar crystals in a continuously cast billet.

[0042] The proportion of columnar crystals in the continuously cast billet obtained from the continuous casting process can be controlled to be 50-80% through the method of controlling the proportion of columnar crystals in the continuously cast billet.

[0043] The control method includes: Determine the initial value of electromagnetic stirring intensity at the solidification end of the continuous casting process; Real-time monitoring of the proportion R of columnar crystals in the billet formed at the solidification endpoint during the continuous casting process. m And based on the monitored columnar crystal ratio R m Adjust the intensity of electromagnetic stirring at the end of solidification to reduce the proportion R of columnar crystals in the billet formed at the solidification endpoint. m Adjust to the target value.

[0044] When the electromagnetic stirring intensity at the end of solidification is high, it can interrupt the growth of columnar crystals, break up coarse dendrites and disperse them, making them new equiaxed crystal nuclei, thereby increasing the proportion of equiaxed crystals and decreasing the proportion of columnar crystals; conversely, when the electromagnetic stirring intensity at the end of solidification is low, the proportion of equiaxed crystals decreases and the proportion of columnar crystals increases.

[0045] Thus, by real-time monitoring of the proportion R of columnar crystals in the billet formed at the solidification endpoint during the continuous casting process... m And based on the monitored columnar crystal ratio R m Adjusting the intensity of electromagnetic stirring at the end of solidification can effectively regulate the ratio of columnar crystals and equiaxed crystals in the billet, thereby achieving dynamic adjustment of the proportion of columnar crystals in the billet formed at the end of solidification, so that the proportion of columnar crystals in the billet formed at the end of solidification reaches the target value.

[0046] The electromagnetic stirring intensity parameter includes at least one of the electromagnetic stirring current and the electromagnetic stirring frequency. In other words, the electromagnetic stirring intensity can be adjusted by regulating at least one of the electromagnetic stirring current and the electromagnetic stirring frequency.

[0047] One embodiment of this application also provides a continuous casting apparatus, which includes a continuous casting machine and a control system.

[0048] The continuous casting process is carried out using continuous casting equipment.

[0049] A continuous casting machine includes a rotary table, tundish, crystallizer, sector section, and straightening machine.

[0050] The rotary table can rotate 180 degrees, moving the ladle to the pouring position to enable continuous pouring of multiple heats of molten steel. The tundish, located below the ladle, serves as a crucial transition vessel, buffering the molten steel, stabilizing the flow rate, and providing time for impurities (such as slag) to rise and purify the steel. The crystallizer initially solidifies the molten steel to form a billet shell. The fan-shaped section supports and further cools the billet exiting the crystallizer. The straightening machine pulls out and straightens the billet.

[0051] The fan-shaped section forms the secondary cooling zone in the continuous casting process, meaning that the billet undergoes secondary cooling in the fan-shaped section. The solidification end is part of the secondary cooling zone.

[0052] The sector segment includes the foot roller segment (i.e., sector segment 0) arranged sequentially from the crystallizer to the straightening machine, as well as sector segments 1 to 12.

[0053] The control system is connected to the continuous casting machine and is used to obtain the proportion R of columnar crystals in the billet formed at the monitored solidification endpoint. m And based on the monitored columnar crystal ratio R m Adjust the intensity of electromagnetic stirring at the end of solidification to reduce the proportion R of columnar crystals in the billet formed at the solidification endpoint. m Adjust to the target value.

[0054] In one embodiment, the electromagnetic stirring intensity parameter includes the electromagnetic stirring current.

[0055] The determination of the initial value of the electromagnetic stirring intensity at the solidification end of the continuous casting process includes: Determine the initial value I0 of the electromagnetic stirring current at the solidification end of the continuous casting process.

[0056] The adjustment of the electromagnetic stirring intensity at the solidification end based on the monitored columnar crystal ratio includes: The electromagnetic stirring current I at the end of solidification is adjusted according to the monitored columnar crystal ratio.

[0057] Thus, by adjusting the electromagnetic stirring current I at the end of solidification, the electromagnetic stirring intensity at the end of solidification can be adjusted, thereby achieving dynamic adjustment of the proportion of columnar crystals in the billet formed at the end of solidification, and the adjustment efficiency is relatively high.

[0058] In one embodiment, adjusting the electromagnetic stirring current I at the solidification end according to the monitored columnar crystal ratio includes: Based on the monitored columnar crystal ratio R m The target value of columnar crystal ratio R is used to calculate the adjustment amount ΔI of the electromagnetic stirring current at the end of solidification using a PID algorithm. The electromagnetic stirring current I at the end of solidification is adjusted according to the calculated adjustment amount ΔI.

[0059] Thus, by monitoring the columnar crystal ratio R m Compared with the target value for the proportion of columnar crystals, if R m If the value is lower than the target value, it indicates that the proportion of columnar crystals is insufficient and the proportion of equiaxed crystals is too high. In this case, the electromagnetic stirring current should be reduced to decrease the electromagnetic stirring intensity and promote the development of columnar crystals; if R m If the value is higher than the target value, it indicates that the proportion of columnar crystals is too high. In this case, the electromagnetic stirring current needs to be increased to increase the electromagnetic stirring intensity and promote equiaxed crystal nucleation; if R m If the target value is met, the current electromagnetic stirring parameters are maintained.

[0060] The PID algorithm, namely the proportional-integral-derivative control algorithm, calculates a control output based on the error between the target value and the current value, so as to quickly and stably reach the target value.

[0061] The electromagnetic stirring current regulation amount ΔI at the solidification end is calculated by the PID algorithm based on the monitored columnar crystal ratio R m and the target value R of the columnar crystal ratio, and includes: Based on the monitored columnar crystal ratio R m and the deviation value e(t) from the target value R of the columnar crystal ratio, the electromagnetic stirring current regulation amount ΔI at the solidification end is calculated by the PID algorithm; where, ΔI(t)=K p ·e(t)+K i ·∫e(t)dt+K d ·de(t) / dt, e(t)=R - R m .

[0062] In this way, according to the deviation between the currently monitored columnar crystal ratio R m and the target value R of the columnar crystal ratio, the change of the deviation, and the change rate of the change of the deviation, the electromagnetic stirring current regulation amount ΔI(t) at the solidification end is calculated, so that the electromagnetic stirring current can be adjusted smoothly and stably in the direction of making the columnar crystal ratio reach the target value R.

[0063] In one embodiment, K p = 0.5~1.5, K i = 0.05~0.15, K d = 0.02~0.08.

[0064] ]>In one embodiment, the target value R of the columnar crystal ratio is R1~R2, that is to say, the target value of the columnar crystal ratio is an interval range.

[0065] In this way, when the monitored columnar crystal ratio R m < R1, the target columnar crystal ratio R is calculated based on R1, and e(t)=R1 - R m .

[0066] When the monitored columnar crystal ratio R m > R2, the target columnar crystal ratio R is calculated based on R2, and e(t)=R2 - R m .

[0067] When the monitored columnar crystal ratio R m is within the range of R1~R2, the electromagnetic stirring current at the solidification end remains unchanged.

[0068] That is to say, when the monitored columnar crystal ratio R mWhen outside the target range, the monitored columnar crystal ratio R is used. m The nearest target range endpoint value is used as the target value for calculation and adjustment.

[0069] In one embodiment, the electromagnetic stirring intensity parameter further includes the electromagnetic stirring frequency.

[0070] The determination of the initial value of the electromagnetic stirring intensity at the solidification end of the continuous casting process also includes: The electromagnetic stirring frequency at the end of solidification in the continuous casting process was determined to be 3~7Hz.

[0071] Therefore, there is no need to adjust the electromagnetic stirring frequency at the end of solidification, which simplifies the control method and saves costs.

[0072] In another embodiment, the electromagnetic stirring intensity parameter includes the electromagnetic stirring current.

[0073] The determination of the initial value of the electromagnetic stirring intensity at the solidification end of the continuous casting process includes: Determine the initial value f0 of the electromagnetic stirring frequency at the solidification end of the continuous casting process.

[0074] The proportion R of columnar crystals as monitored m Adjusting the intensity of electromagnetic stirring at the end of solidification includes: Based on the monitored columnar crystal ratio R m Adjust the electromagnetic stirring frequency f at the end of solidification.

[0075] Thus, by adjusting the electromagnetic stirring frequency f at the end of solidification, the intensity of electromagnetic stirring at the end of solidification can be fine-tuned, thereby fine-tuning the proportion of columnar crystals in the billet.

[0076] The initial value f0 of the electromagnetic stirring frequency at the end of solidification is 3~7Hz.

[0077] In one embodiment, determining the initial value I0 of the electromagnetic stirring current at the end of solidification in the continuous casting process includes: The preset value I of the electromagnetic stirring current at the solidification end is calculated based on the alloy element content of the molten steel. y ; Determine the preset value I of the electromagnetic stirring current at the end of solidification. y I0 is the initial value of the electromagnetic stirring current at the end of solidification.

[0078] In this way, the electromagnetic stirring current at the end of solidification can be determined based on the influence of alloying elements in molten steel on columnar and equiaxed crystals during the solidification process of the billet, which is beneficial to control the proportion of columnar crystals in the billet formed at the end of solidification.

[0079] In one embodiment, the preset value I of the electromagnetic stirring current at the solidification end is calculated based on the alloy element content in the molten steel. y include: The preset value of the electromagnetic stirring current I at the end of solidification is calculated based on the Si, Al, and Mn element content in the molten steel. y .

[0080] Since Si and Al significantly reduce the high-temperature thermal conductivity of steel, which is beneficial to the development of columnar crystals during solidification, and Mn can refine the solidification structure and promote the formation of equiaxed crystals, the preset value of the electromagnetic stirring current I at the end of solidification is calculated based on the Si, Al, and Mn element content in the molten steel. y This is to ensure that the proportion of columnar crystals in the billet formed at the solidification endpoint reaches the target value.

[0081] In one embodiment, I y =300 + 30 × Si + 20 × Al + 10 × Mn, where the element symbols represent the mass percentage of the corresponding element. Thus, the influence of Si, Al, and Mn alloying elements on heat transfer efficiency during solidification can be quantified into the control of the electromagnetic stirring current, thereby achieving control over the proportion of columnar crystals.

[0082] In one embodiment, determining the initial value I0 of the electromagnetic stirring current at the solidification end of the continuous casting process further includes: The initial value adjustment amount ΔI0 of the electromagnetic stirring current at the end of solidification is determined based on the fluctuation amount Δv of the continuous casting speed, the fluctuation amount ΔT of the superheat of the molten steel, and the fluctuation amount ΔC of the alloy element content in the molten steel. Determine the preset value I of the electromagnetic stirring current at the end of solidification. y The sum of the initial value adjustment ΔI0 of the electromagnetic stirring current at the end of solidification and the initial value adjustment ΔI0 of the electromagnetic stirring current at the end of solidification is the initial value I0 of the electromagnetic stirring current at the end of solidification.

[0083] Because the temperature and alloy element content of different batches of molten steel will fluctuate during the continuous casting process, and the casting speed will also fluctuate, it is necessary to adjust the initial value of the electromagnetic stirring current at the solidification end according to the different batches of molten steel poured during the continuous casting process and the actual casting speed, so as to make the proportion of columnar crystals in the continuously cast billet reach the target value and have universal applicability.

[0084] In one embodiment, the initial value adjustment amount of the electromagnetic stirring current at the end of solidification is ΔI0=k. v ·Δv+k T ·ΔT+k C ·ΔC; Where, Δv=v m -v0, v m v0 is the measured value of the continuous casting speed, and v0 is the preset value of the continuous casting speed. mBoth v0 and v0 are in m / min. ΔT=T m -T0, T m T0 is the measured value of the superheat of molten steel, and T0 is the preset value of the superheat of molten steel. m The units for T0 are both °C; ΔC=C m -C0,C m C0 is the measured sum of the Si, Al, and Mn element contents in the molten steel, and C0 is the preset sum of the Si, Al, and Mn element contents in the molten steel. m Both C0 and C0 are in units of %.

[0085] In other words, in the above formula, v m v0, T m T0, C m Both C0 and C0 are calculated by substituting the values ​​into the units listed above.

[0086] Where, k v k is the coefficient of variation of continuous casting speed. T k is the coefficient of change in superheat of molten steel. C This is the coefficient of variation of the alloying element content in molten steel.

[0087] k v For 100~200, k T For 8~15, k C It is 20~30.

[0088] In one implementation, k v k T k C The value was determined by linear regression with the electromagnetic stirring current value at the end of solidification.

[0089] In one embodiment, the proportion of columnar crystals in the billet formed at the solidification endpoint during the real-time monitoring of the continuous casting process includes: The proportion of columnar crystals in the billet formed at the solidification endpoint is determined by X-ray detection.

[0090] The solidification structure of the billet formed at the solidification endpoint, i.e., the continuously cast billet, includes a fine-grained surface region, a columnar grain region, and a central equiaxed grain region. Their distribution and morphology determine the internal uniformity and density of the continuously cast billet, directly affecting the material's mechanical properties. Due to their regular crystal structure and consistent grain orientation, the columnar grain region exhibits measurable differences in X-ray scattering and absorption characteristics compared to the equiaxed grain region.

[0091] X-ray inspection technology utilizes the attenuation characteristics of X-rays as they penetrate matter to obtain internal information about the object being inspected. After X-rays penetrate a continuously cast billet, columnar crystal regions, due to their large grain size, low grain boundary density, and strong crystallographic orientation consistency, exhibit relatively high X-ray transmittance and appear as brighter areas on the detector. Conversely, equiaxed crystal regions, with their fine grains, high grain boundary density, and random orientation, experience stronger X-ray scattering and absorption, resulting in relatively lower transmittance and appearing as darker areas. This difference in brightness forms the material basis for distinguishing between columnar and equiaxed crystals.

[0092] In one embodiment, the continuous casting equipment further includes an online X-ray inspection system. The control system is connected to the online X-ray inspection system and is used to obtain the proportion R of columnar crystals in the billet formed at the solidification endpoint detected by the online X-ray inspection system. m .

[0093] X-ray inspection is performed using an online X-ray inspection system.

[0094] The X-ray online inspection system includes: An X-ray source that emits X-rays at an energy of 150-450 kV; A detector array is located on the side of the billet away from the X-ray source to receive transmitted signals; A collimator, placed between the X-ray source and the detector array, collimates the X-rays emitted by the X-ray source to form a narrow beam of scanning rays, thereby reducing scattering interference. The image processing and control system acquires signals received by the detector array in real time, performs image reconstruction and columnar crystal ratio recognition calculation, and transmits the calculation results to the control system to adjust the electromagnetic stirring intensity at the solidification end.

[0095] The energy emitted by the X-ray source can be automatically adjusted according to the thickness of the billet.

[0096] The detector array can employ high-sensitivity linear or area array detectors. For example, amorphous silicon planar detectors, CdTe semiconductor detectors, or CdZnTe semiconductor detectors.

[0097] Specifically, when X-rays pass through a continuously cast billet, their intensity follows the Lambert-Beer attenuation law: .

[0098] Where I is the intensity of the transmitted X-rays, I0 is the intensity of the incident X-rays, and μ is the linear attenuation coefficient, with units of cm. -1 μ reflects the absorption capacity of the medium (such as columnar crystals or equiaxed crystals) for X-rays; x is the path length of X-rays propagating in the medium, in cm.

[0099] A detector array acquires X-ray grayscale images of the cross-section of the continuously cast billet. After filtering, noise reduction, and contrast enhancement, a clear image of the solidification structure is obtained. Edge detection operators such as the Canny and Sobel operators are used to extract grayscale abrupt boundary changes and automatically delineate the inner contour lines of columnar crystal regions, thereby identifying the columnar crystal regions. Then, the pixel area of ​​the columnar crystal region is calculated, and the ratio of the pixel area of ​​the columnar crystal region to the total pixel area of ​​the cross-section is the columnar crystal area ratio R. Based on the low-magnification imaging principle of the solidification structure of the continuously cast billet, the area ratio of the columnar crystal region can be directly equivalent to the volume ratio of the columnar crystals, and is fed back to the control system as a feedback quantity for the image processing and control system.

[0100] In one embodiment, X-ray detection performs cross-sectional scanning and proportion calculation every 5 to 30 seconds to achieve continuous online monitoring of the proportion of columnar crystals in the billet formed at the solidification endpoint.

[0101] Specifically, the X-ray online detection system can use fan-shaped beamline scanning or multi-source array static scanning to perform scanning, with a detection frequency of 5 to 30 seconds per scan.

[0102] In another embodiment, the real-time monitoring of the proportion of columnar crystals in the billet formed at the solidification endpoint during the continuous casting process includes: The proportion of columnar crystals in the billet formed at the solidification endpoint is detected by ultrasonic testing.

[0103] The significant difference in grain size between columnar and equiaxed crystals affects the scattering and attenuation of ultrasound waves. Columnar crystals have large, uniformly oriented grains, resulting in lower ultrasound attenuation, higher echo amplitude, and narrower frequency distribution. In contrast, equiaxed crystals have small, randomly oriented grains, resulting in greater ultrasound attenuation, lower echo amplitude, and wider frequency distribution.

[0104] By propagating ultrasound in the billet, reflection and scattering occur when it encounters the boundary between columnar and equiaxed crystal regions. Based on the echo time-domain signal, the proportion of columnar crystals in the billet formed at the solidification endpoint can be detected.

[0105] In one embodiment, the continuous casting equipment further includes an online ultrasonic detection system. The control system is connected to the online ultrasonic detection system and is used to acquire the proportion R of columnar crystals in the billet formed at the solidification endpoint detected by the online ultrasonic detection system. m .

[0106] Ultrasonic testing is performed using an online ultrasonic testing system.

[0107] The ultrasonic online testing system includes: An electromagnetic ultrasonic transducer (EMAT) includes a high-frequency coil and a bias magnetic field system. The high-frequency coil includes a transmitting coil and a receiving coil.

[0108] An ultrasonic pulse transmitting and receiving system is used to generate high-voltage pulses to excite the EMAT to transmit ultrasonic waves and to receive the echo signals.

[0109] The signal processing unit is used to amplify, filter, perform analog-to-digital conversion, analyze the spectrum, extract features, and classify patterns in the echo signal.

[0110] The control system interface will use the calculated columnar crystal ratio R m Feedback is sent to the control system to adjust the intensity of electromagnetic stirring at the end of solidification.

[0111] Among them, the electromagnetic ultrasonic transducer (EMAT) performs non-contact detection by using non-contact electromagnetic induction to excite and receive ultrasonic transverse waves, which can operate without coupling agent and can operate in high-temperature environments.

[0112] The working principle of EMAT is based on electromagnetic acoustic transduction. When a high-frequency current passes through the high-frequency coil, the resulting alternating magnetic field induces eddy currents on the surface of the billet. The eddy currents interact with the bias static magnetic field to generate Lorentz force, thereby exciting high-frequency elastic waves (transverse or longitudinal waves) inside the billet. The high-frequency elastic waves propagate in the billet and are reflected and scattered when they encounter the microstructure boundaries of columnar and equiaxed crystal regions. The echo signal is received by EMAT.

[0113] An electromagnetic ultrasonic transducer (EMAT) can be installed at the exit of the fan-shaped section of the secondary cooling zone of a continuous casting machine. By installing at least one EMAT probe in the width direction of the billet, the echo signal can be detected.

[0114] In one embodiment, ultrasonic detection performs scanning and proportion calculation every 10 to 20 seconds to achieve continuous online monitoring of the proportion of columnar crystals in the billet formed at the solidification endpoint.

[0115] In one embodiment, the control method further includes: The X-ray or ultrasonic testing is calibrated using a low-magnification acid immersion method.

[0116] Specifically, when changing steel grades or at the beginning of each casting, a sample of the billet at the end of solidification is taken. After low-magnification acid etching, the solidification structure (including fine-grained region, columnar region, and equiaxed region) is observed. By comparing the boundary of the columnar region measured by X-ray detection or ultrasonic detection with the boundary of the columnar region in the low-magnification acid etching photograph, a calibration curve is established to calibrate the X-ray detection or ultrasonic detection.

[0117] In one embodiment, during the continuous casting process, electromagnetic stirring is performed at the end of solidification, while the crystallizer is not subjected to electromagnetic stirring. This avoids the expansion of the equiaxed crystal zone, thus promoting an increase in the proportion of columnar crystals.

[0118] In one embodiment, during the continuous casting process, electromagnetic stirring is not performed in the secondary cooling zone except at the end of solidification, in order to prevent the expansion of the equiaxed crystal zone and thus facilitate an increase in the proportion of columnar crystals.

[0119] In one embodiment, electromagnetic stirring is performed only at the end of the solidification process during continuous casting.

[0120] In high-grade non-oriented silicon steel, Si and Al are the core elements for improving resistivity and reducing iron loss. However, increasing the Si and Al content will significantly reduce the high-temperature thermal conductivity of the molten steel, thereby reducing the initial solidified shell thickness of the continuously cast billet. Mn, on the other hand, affects the width of the solidification two-phase region and the high-temperature strength of the billet shell.

[0121] In one embodiment, during the continuous casting process, the billet shell thickness h at the outlet of the crystallizer is controlled to be ≥8Si+10Al+9Mn. This has several advantages. First, controlling the billet shell thickness at the crystallizer outlet based on the Si, Al, and Mn content not only ensures the initial solidified shell thickness of the continuously cast billet and reduces the bulging on the wide side of the billet, preventing bulging deformation in the secondary cooling zone, thus avoiding abnormal growth of columnar ferrite crystals induced by the internal stress of bulging, thereby reducing serrated edge crack defects in hot-rolled plates, lowering the difficulty of hot rolling, and reducing waste caused by edge trimming, but also lays the foundation for controlling a large proportion of columnar crystals and can address the preparation of non-oriented silicon steel with various compositional variations. Second, this allows for the pre-determination of the minimum required initial solidified shell thickness of the continuously cast billet, enabling targeted adjustment of the crystallizer cooling intensity, such as cooling water flow rate and velocity, to control the initial solidified shell thickness of the continuously cast billet.

[0122] It is understandable that the element symbols in the formula represent the mass percentage of the corresponding element. For example, the mass fraction of Si [Si] means that the mass percentage of Si in molten steel is 2.5%, so the Si in the formula is calculated by substituting 2.5. In addition, the mass percentage of Si, Al, or Mn in the molten steel can be obtained by testing the molten steel poured during continuous casting (or the molten steel at the end of the steelmaking process).

[0123] In one embodiment, during the continuous casting process, the cooling water flow rate of the wide face of the crystallizer is controlled at 2500~4500 L / min, the cooling water flow rate of the narrow face is controlled at 400~700 L / min, the crystallizer inlet water temperature is controlled at 28~35℃, the inlet and outlet water temperature difference is controlled at 6~10℃, and the average heat flux density of the crystallizer is controlled at 1200~2000 kW / m³. 2 By controlling the cooling water flow rate and inlet / outlet water temperature of the crystallizer, the initial solidified shell thickness of the continuously cast billet can be effectively increased.

[0124] In one embodiment, during the continuous casting process, the cooling rate of the secondary cooling zone is controlled to gradually decrease along the foot roll section, sector sections 1-4, and sector sections 5-12. That is, the cooling rate of sector sections 1-4 is lower than that of the foot roll section, and the cooling rate of sector sections 5-12 is lower than that of sector sections 1-4. Thus, using a higher cooling rate in the foot roll section promotes rapid shell thickening and prevents bulging deformation; in sector sections 1-4, the billet still has a relatively thick liquid core, and maintaining a certain cooling rate can maintain a certain cooling intensity to synergistically increase the proportion of columnar crystals; in sector sections 5-12, the billet is about to completely solidify, and appropriately reducing the cooling rate can prevent cracks caused by thermal stress.

[0125] The cooling rate of the foot roller section is controlled at 3~10℃ / s, the cooling rate of the first to fourth fan-shaped sections is 0.5~8℃ / s, and the cooling rate of the fifth to twelfth fan-shaped sections is 0.2~1.5℃ / s.

[0126] Furthermore, the cooling rate of sector segments 1 to 4 gradually decreases from segment 1 to segment 4. Specifically, the cooling rate of sector segment 1 is 2~8℃ / s, and the cooling rate of sector segment 4 is 0.5~3℃ / s.

[0127] In one embodiment, during the continuous casting process, the specific water content of the foot roll section is controlled at 1.2~2.5 L / kg, the cooling water volume of the wide section is 260~600 L / min, and the cooling water volume of the narrow section is 50~125 L / min; the specific water content of the first to fourth fan-shaped sections is controlled at 0.8~1.5 L / kg, and the surface temperature of the billet is controlled at 1000~1100℃; the specific water content of the fifth to 12th fan-shaped sections is controlled at 0.3~0.8 L / kg; and the straightening temperature of the billet at the straightening machine is controlled to be >950℃ to avoid the brittle zone. By controlling these parameters, the cooling rate and cooling rhythm of the secondary cooling zone can be controlled to achieve control over the columnar crystal ratio of the continuously cast billet.

[0128] In one embodiment, during the continuous casting process, the surface cooling rate of the billet along its length is controlled to be <150°C / m.

[0129] In one embodiment, during the continuous casting process, the continuous casting speed v, the target thickness δ of the continuous casting billet, and the target width w are controlled to satisfy 0.21-0.005×(Si+Al)≤v×δ×w≤0.22-0.003×(Si+Al), and v×δ×w is negatively correlated with Si+Al, where the units of v are m / min, δ are m, and w are m.

[0130] Thus, by controlling the continuous casting speed *v*, the initial solidified shell thickness of the continuously cast billet can be increased (i.e., the shell thickness of the billet when it leaves the crystallizer), correspondingly reducing the bulge on the wide side of the billet. This avoids the abnormal growth of columnar ferrite crystals induced by the internal stress of the bulge, thereby reducing the serrated edge crack defect in hot-rolled plates. This production method also avoids a series of derivative problems such as lowering the heating temperature, increasing the difficulty of hot rolling, and waste caused by edge trimming. When the Si+Al content is high, the casting speed is controlled to be lower to prolong the solidification time and promote columnar crystal development.

[0131] Among them, 0.7m / min≤v≤1.2m / min, 0.18m≤δ≤0.25m, and 1.0m≤w≤1.3m.

[0132] In one embodiment, the superheat of the molten steel in the continuous casting process is 10~15°C, thereby controlling the thickness of the billet shell at the outlet of the crystallizer.

[0133] The thickness δ of the continuously cast billet obtained from the continuous casting process is 0.18~0.25m, that is, δ is 180~250mm.

[0134] In the hot rolling process, the continuously cast billet obtained from the continuous casting process is heated and then subjected to rough rolling, finish rolling, and cooling in sequence.

[0135] During heating, the continuously cast billet is fed into a heating furnace. The soaking temperature is 1050~1250℃, and the heating time is 180~220min.

[0136] Roughing is performed using a two-stand mill. The reduction rate for each pass in roughing is controlled at 32-38%, and the final rolling temperature is 950-1000℃. The thickness of the intermediate billet obtained from roughing is 40-45 mm.

[0137] The finishing mill uses a seven-stand mill to produce hot-rolled strip steel with a thickness of 2.0~2.4mm. The reduction rate of each pass in the finishing mill is controlled at 30~38%, the finishing temperature is 820~880℃, and the coiling temperature is 600~680℃.

[0138] The hot-rolled strip obtained from finishing rolling is then subjected to laminar flow cooling.

[0139] In one embodiment, the production method of high-grade non-oriented silicon steel further includes a normalizing process performed between hot rolling and a single cold rolling process. In the normalizing process, the normalizing temperature is 920~970℃, and the normalizing time is 2~3 minutes. High-temperature normalizing can effectively improve the inhomogeneity of the microstructure and texture of the hot-rolled strip, avoiding the λ texture (λ-like texture) caused by a large proportion of columnar crystals on the strip surface after subsequent cold rolling and annealing. <100> / / ND) The corrugated defects that result from the development of the ND.

[0140] In one embodiment, the production method of high-grade non-oriented silicon steel further includes shot blasting and pickling between the normalizing process and a single cold rolling process. Shot blasting and pickling can remove the oxide scale from the surface of the strip steel.

[0141] In one embodiment, during a single annealing process, the annealing is carried out in a protective atmosphere, which is a mixture of 20% H2 and 80% N2.

[0142] In one embodiment, the secondary cold rolling process can be a single-pass rolling process or a two-pass rolling process to obtain cold-rolled strip steel. The specific process can be determined based on the strip steel thickness after the first cold rolling and the target strip steel thickness.

[0143] In one embodiment, the secondary annealing process is carried out in a protective atmosphere, which is a mixture of 20% H2 and 80% N2.

[0144] In one embodiment, the production method of high-grade non-oriented silicon steel further includes a coating process performed after a secondary annealing process. The coating process involves applying an insulating coating to the surface of the cold-rolled strip to obtain the finished non-oriented silicon steel product.

[0145] An embodiment of this application also provides a high-grade non-oriented silicon steel, the chemical composition of which, by mass percentage, further includes: C≤0.0025%, Si 2.5~3.5%, Al 0.5~1.5%, Mn 0.2~0.8%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, N≤0.002%, S≤0.0015%, P0.03~0.05%, with the remainder being Fe and unavoidable impurities.

[0146] This high-grade non-oriented silicon steel is manufactured using the production method for high-grade non-oriented silicon steel as described above. The surface of this non-oriented silicon steel is free of corrugated defects.

[0147] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application, and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.

[0148] The beneficial effects of this application will be further illustrated below through specific embodiments 1-2 and comparative examples 1-5. Both of these embodiments employ the longitudinal thickness fluctuation control method for strip steel described in this application for cold continuous rolling. Of course, these two embodiments are only a part of the numerous variations contained in this application, and not all of them.

[0149] Example 1 The chemical composition of the non-oriented silicon steel in this embodiment, by mass percentage, includes: C ≤ 0.0022%, Si 3.0%, Al 1.0%, Mn 0.5%, Nb 0.0012%, V 0.001%, Ti 0.0011%, Cr 0.016%, Ni 0.005%, Cu 0.02%, N 0.0013%, S 0.0011%, P 0.038%, with the remainder being Fe and unavoidable impurities.

[0150] The production method of this non-oriented silicon steel includes the following steps.

[0151] (1) Continuous casting Molten steel is fed into a continuous casting machine for casting. The superheat of the molten steel is 13°C, and it is continuously cast into a continuous casting billet with a thickness of 220 mm and a width of 1.01 m.

[0152] The cooling water flow rate of the wide face of the crystallizer is 3700 L / min, and the cooling water flow rate of the narrow face is 550 L / min. The inlet water temperature of the crystallizer is 28~35℃, the inlet and outlet water temperature difference is 6~10℃, and the average heat flux density of the crystallizer is 1200~2000 kW / m³. 2 The thickness h of the billet shell at the outlet of the crystallizer is 40 mm.

[0153] The continuous casting speed v is 0.9 m / min.

[0154] Within the second cooling zone, the surface cooling rate of the billet along its length is <150℃ / m. Specifically, the specific water volume of the foot roll section is 1.8L / kg, the wide-face cooling water volume is 420L / min, the narrow-face cooling water volume is 85L / min, and the cooling rate of the foot roll section is 5℃ / s; the specific water volume of sector sections 1-4 is 1.1L / kg, the surface temperature of the billet is 1000~1100℃, and the cooling rate of sector sections 1-4 is 6℃ / s; the specific water volume of sector sections 5-12 is 0.5L / kg, and the cooling rate of sector sections 5-12 is 0.5℃ / s; the straightening temperature of the billet at the tension leveler is 980℃.

[0155] Electromagnetic stirring is performed only at the end of the solidification zone in the secondary cooling zone, while electromagnetic stirring is not performed in the crystallizer, and electromagnetic stirring is not performed in the secondary cooling zone except at the end of the solidification zone.

[0156] First, the initial value of the electromagnetic stirring intensity at the end of solidification was determined to be 410A, and the electromagnetic stirring frequency at the end of solidification was determined to be 7Hz. The proportion R of columnar crystals in the billet formed at the solidification endpoint was monitored in real time using X-rays. m And based on the monitored columnar crystal ratio R m Adjust the intensity of electromagnetic stirring at the end of solidification to reduce the proportion R of columnar crystals in the billet formed at the solidification endpoint. m Adjusted to 68%.

[0157] (2) Hot rolling The continuously cast billet obtained from the continuous casting process is heated and then subjected to rough rolling, finish rolling and cooling in sequence to obtain hot-rolled strip steel with a thickness of 2.3 mm.

[0158] During heating, the continuously cast billet is fed into the heating furnace. The homogenization temperature is 1150℃, and the heating time is 200 minutes.

[0159] Roughing was performed using a two-stand mill. The reduction rate for each pass in roughing was 32-38%, and the final rolling temperature was 975℃. The thickness of the intermediate billet obtained from roughing was 42mm.

[0160] The finishing mill is used for rolling. The reduction rate of each pass in the finishing mill is 30-38%, and the final rolling temperature is 850℃.

[0161] The hot-rolled strip obtained from finishing rolling is then subjected to laminar flow cooling, and the coiling temperature is 640℃.

[0162] (3) Normalization The normalization temperature was 945℃ and the normalization time was 2.5 min.

[0163] (4) Shot blasting and pickling (5) Cold rolling After five rolling passes, the total reduction rate is 90.9%, and the surface roughness of the work rolls is 2.0 μm. The thickness of the strip obtained by one cold rolling is 0.21 mm.

[0164] (6) First annealing The first annealing was carried out in a protective atmosphere, which was a mixture of 20% H2 and 80% N2. The annealing temperature was 950℃ and the annealing time was 120s.

[0165] (7) Secondary cold rolling The total reduction rate was 4.8%, and the surface roughness of the work rolls in the secondary cold rolling was 0.3μm. The thickness of the strip obtained from the secondary cold rolling was 0.20mm.

[0166] (8) Secondary annealing The secondary annealing was carried out in a protective atmosphere, which was a mixture of 20% H2 and 80% N2. The annealing temperature was 980℃ and the annealing time was 60s.

[0167] (9) Coating An insulating coating is applied to the surface of the strip steel to obtain the finished non-oriented silicon steel product.

[0168] In the production process of non-oriented silicon steel in this embodiment, there are no edge cracks during hot rolling, no edge cracks or strip breaks during cold rolling, and the final non-oriented silicon steel product is free of corrugated defects and has a surface roughness Ra of 0.35μm.

[0169] The iron loss and magnetic induction intensity were tested according to the national standard GB / T 3655-2022 "Method for Measuring the Magnetic Properties of Electrical Steel Strips (Sheets) Using Epstein Squares". The iron loss P was measured. 1.5 / 50 =2.05W / kg, magnetic induction B 50 =1.70T.

[0170] Example 2 The chemical composition of the non-oriented silicon steel in this embodiment, by mass percentage, includes: C 0.0020%, Si 2.7%, Al 0.8%, Mn 0.4%, Nb 0.0012%, V 0.0014%, Ti 0.0010%, Cr 0.013%, Ni 0.016%, Cu 0.018%, N 0.0012%, S 0.0011%, P 0.039%, with the remainder being Fe and unavoidable impurities.

[0171] The production method of this non-oriented silicon steel includes the following steps.

[0172] (1) Continuous casting Molten steel is fed into a continuous casting machine for casting. The superheat of the molten steel is 13°C, and it is continuously cast into a continuous casting billet with a thickness of 220 mm and a width of 1.05 m.

[0173] The cooling water flow rate of the wide face of the crystallizer is 3500 L / min, and the cooling water flow rate of the narrow face is 500 L / min. The inlet water temperature of the crystallizer is 28~35℃, the inlet and outlet water temperature difference is 6~10℃, and the average heat flux density of the crystallizer is 1200~2000 kW / m³. 2 The thickness h of the billet shell at the outlet of the crystallizer is 40 mm.

[0174] The continuous casting speed v is 0.87 m / min.

[0175] Within the second cooling zone, the surface cooling rate of the billet along its length is <150℃ / m. Specifically, the specific water volume of the foot roll section is 2.3L / kg, the cooling water volume of the wide face is 420L / min, the cooling water volume of the narrow face is 90L / min, and the cooling rate of the foot roll section is 5℃ / s; the specific water volume of sector sections 1-4 is 1.2L / kg, the surface temperature of the billet is 1000~1100℃, and the cooling rate of sector sections 1-4 is 6.5℃ / s; the specific water volume of sector sections 5-12 is 0.6L / kg, and the cooling rate of sector sections 5-12 is 0.8℃ / s; the straightening temperature of the billet at the tension leveler is 970℃.

[0176] Electromagnetic stirring is performed only at the end of the solidification zone in the secondary cooling zone, while electromagnetic stirring is not performed in the crystallizer, and electromagnetic stirring is not performed in the secondary cooling zone except at the end of the solidification zone.

[0177] First, the initial value of the electromagnetic stirring intensity at the end of solidification was determined to be 415A, and the electromagnetic stirring frequency at the end of solidification was determined to be 7Hz. The proportion R of columnar crystals in the billet formed at the solidification endpoint is monitored in real time using ultrasonic testing. m And based on the monitored columnar crystal ratio R m Adjust the intensity of electromagnetic stirring at the end of solidification to reduce the proportion R of columnar crystals in the billet formed at the solidification endpoint. m Adjusted to 58%.

[0178] (2) Hot rolling The continuously cast billet obtained from the continuous casting process is heated and then subjected to rough rolling, fine rolling, and cooling in sequence to obtain hot-rolled strip steel with a thickness of 2.4 mm.

[0179] During heating, the continuously cast billet is fed into a heating furnace. The homogenization temperature is 1100℃, and the heating time is 190 minutes.

[0180] Roughing was performed using a two-stand mill. The reduction rate for each pass in roughing was 32-38%, and the final rolling temperature was 980℃. The thickness of the intermediate billet obtained from roughing was 42mm.

[0181] The finishing mill is a seven-stand mill. The reduction rate of each pass in the finishing mill is 30-38%, the finishing temperature is 840℃, and the coiling temperature is 620℃.

[0182] The hot-rolled strip obtained from finishing rolling is then subjected to laminar flow cooling.

[0183] (3) Normalization The normalization temperature was 950℃ and the normalization time was 2 min.

[0184] (4) Shot blasting and pickling (5) Cold rolling After five rolling passes, the total reduction rate is 91.25%, and the surface roughness of the work rolls is 2.2μm. The thickness of the strip obtained by one cold rolling is 0.21mm.

[0185] (6) First annealing The first annealing was carried out in a protective atmosphere, which was a mixture of 20% H2 and 80% N2. The annealing temperature was 940℃ and the annealing time was 150s.

[0186] (7) Secondary cold rolling The total reduction rate was 4.8%, and the surface roughness of the work rolls in the secondary cold rolling was 0.3μm. The thickness of the strip obtained from the secondary cold rolling was 0.20mm.

[0187] (8) Secondary annealing The secondary annealing was carried out in a protective atmosphere, which was a mixture of 20% H2 and 80% N2. The annealing temperature was 980℃ and the annealing time was 60s.

[0188] (9) Coating An insulating coating is applied to the surface of the strip steel to obtain the finished non-oriented silicon steel product.

[0189] In the production process of non-oriented silicon steel in this embodiment, there are no edge cracks during hot rolling, no edge cracks or strip breaks during cold rolling, and the final non-oriented silicon steel product is free of corrugated defects and has a surface roughness Ra of 0.38μm.

[0190] The iron loss and magnetic induction intensity were tested according to the national standard GB / T 3655-2022 "Method for Measuring the Magnetic Properties of Electrical Steel Strips (Sheets) Using Epstein Squares". The iron loss P was measured. 1.5 / 50 =2.10W / kg, magnetic induction B 50 =1.68T.

[0191] Comparative Example 1 Comparative Example 1 and Example 1 are identical in all processes except for the continuous casting process, and will not be described again here. The following only introduces the differences.

[0192] In this comparative example, the proportion of columnar crystals in the billet formed at the end of the continuous casting process was 35%, and the proportion of columnar crystals was not monitored and controlled in real time. The proportion of columnar crystals was obtained by testing with the traditional low-magnification acid leaching method after the continuous casting process was completed.

[0193] In this comparative example, the continuously cast billet obtained by continuous casting had severe bulging, and the edge crack rate during hot rolling was as high as 28%, which led to the inability to produce normally in the future.

[0194] Comparative Example 2 Comparative Example 2 is identical to Example 1 except for the continuous casting process, and will not be described again here. The following only introduces the differences.

[0195] In this comparative example, the proportion of columnar crystals in the billet formed at the end of the continuous casting process was 88%, and the proportion of columnar crystals was not monitored and controlled in real time. The proportion of columnar crystals was obtained by testing with the traditional low-magnification acid leaching method after the continuous casting process was completed.

[0196] The comparative example showed no edge cracks during hot rolling, but the final silicon steel product had obvious corrugated defects on its surface, resulting in high iron loss P. 1.5 / 50 =2.28W / kg, magnetic induction B50 =1.61T.

[0197] Comparative Example 3 The difference between Comparative Example 3 and Example 1 lies only in the cold rolling and annealing processes, specifically the process between shot blasting / pickling and coating. All other processes are the same and will not be described further. The following description focuses only on the process from shot blasting / pickling to coating.

[0198] (4) Shot blasting and pickling (5) Cold rolling After five rolling passes, with the surface roughness of the work rolls all at 0.5μm, the thickness of the cold-rolled strip is 0.20mm.

[0199] (6) Annealing Annealing was carried out in a protective atmosphere consisting of a mixture of 20% H2 and 80% N2. The annealing temperature was 980℃ and the annealing time was 60s.

[0200] (7) Coating The comparative example showed no edge cracks during hot rolling, but the final silicon steel product had obvious corrugated defects on the surface, with a surface roughness Ra of 0.6 μm and an iron loss P. 1.5 / 50 =2.25W / kg, magnetic induction B 50 =1.63T.

[0201] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is the single cold rolling process; all other processes are the same and will not be described again here. The following description focuses only on the single cold rolling process.

[0202] (5) Cold rolling After five rolling passes, the total reduction rate is 78.3%, and the surface roughness of the work rolls is 2.0μm. The thickness of the strip obtained by one cold rolling is 0.5mm.

[0203] The comparative example showed no edge cracks during hot rolling, but the final silicon steel product still had corrugated defects on its surface, resulting in iron loss P. 1.5 / 50 =2.20W / kg, magnetic induction B 50 =1.64T.

[0204] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is the single annealing process; all other processes are the same and will not be described again here. The following description focuses solely on the single annealing process.

[0205] (6) First annealing The first annealing was carried out in a protective atmosphere, which was a mixture of 20% H2 and 80% N2. The annealing temperature was 850℃ and the annealing time was 120s.

[0206] The comparative example showed no edge cracks during hot rolling, but the final silicon steel product still had corrugated defects on its surface, resulting in iron loss P. 1.5 / 50 =2.18W / kg, magnetic induction B 50 =1.65T.

[0207] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for producing high-grade non-oriented silicon steel, characterized in that, The chemical composition of the non-oriented silicon steel, by mass percentage, includes: Si 2.5~3.5%, Al 0.5~1.5%, Mn 0.2~0.8%; the production method includes the sequential processes of continuous casting, hot rolling, primary cold rolling, primary annealing, secondary cold rolling, and secondary annealing. In the continuous casting process, the proportion of columnar crystals in the continuously cast billet obtained from the continuous casting process is controlled to be 50-80%; In the primary cold rolling process, the total reduction rate is controlled at 90-95%, and the surface roughness of the work rolls in the primary cold rolling process is 1.5-2.5 μm. In the first annealing process, the annealing temperature is 930~970℃ and the annealing time is 60~180s; In the secondary cold rolling process, the total reduction rate is 5~10%, and the surface roughness of the work rolls in the secondary cold rolling process is 0.2~0.4μm. In the secondary annealing process, the annealing temperature is 950~1050℃ and the annealing time is 50~80s.

2. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, The chemical composition of the high-grade non-oriented silicon steel, by mass percentage, also includes: C≤0.0025%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, Cr≤0.03%, Ni≤0.03%, Cu≤0.03%, N≤0.002%, S≤0.0015%, P 0.03~0.05%, with the remainder being Fe and unavoidable impurities.

3. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, In the continuous casting process, electromagnetic stirring is controlled at the end of solidification, while electromagnetic stirring is not performed in the crystallizer.

4. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, In the continuous casting process, the thickness of the billet shell at the outlet of the crystallizer is controlled to be h≥8Si+10Al+9Mn.

5. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, In the continuous casting process, the cooling water flow rate of the wide face of the crystallizer is controlled at 2500~4500 L / min, the cooling water flow rate of the narrow face is controlled at 400~700 L / min, the crystallizer inlet water temperature is controlled at 28~35℃, the inlet and outlet water temperature difference is controlled at 6~10℃, and the average heat flux density of the crystallizer is controlled at 1200~2000 kW / m³. 2 .

6. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, The cooling rate of the secondary cooling zone in the continuous casting process is controlled to gradually decrease along the foot roll section, sector sections 1-4, and sector sections 5-12. Specifically, the cooling rate of the foot roll section is controlled to be 3-10℃ / s, the cooling rate of sector sections 1-4 is controlled to be 0.5-8℃ / s, and the cooling rate of sector sections 5-12 is controlled to be 0.2-1.5℃ / s.

7. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, In the continuous casting process, the specific water volume of the foot roll section is controlled to be 1.2~2.5L / kg, the cooling water volume of the wide face is 260~600L / min, and the cooling water volume of the narrow face is 50~125L / min; The specific water content of the first to fourth fan-shaped sections is controlled at 0.8 to 1.5 L / kg, and the surface temperature of the billet is 1000 to 1100℃; The specific water content of the 5th to 12th sector segments is controlled at 0.3 to 0.8 L / kg; Control the straightening temperature to >950℃.

8. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, In the continuous casting process, the continuous casting speed v, the target thickness δ of the continuous casting billet, and the target width w are controlled to satisfy 0.21-0.005×(Si+Al)≤v×δ×w≤0.22-0.003×(Si+Al), and v×δ×w is negatively correlated with Si+Al, where the unit of v is m / min, the unit of δ is m, and the unit of w is m.

9. The method for producing high-grade non-oriented silicon steel according to claim 8, characterized in that, 0.7m / min≤v≤1.2m / min, 0.18m≤δ≤0.25m, 1.0m≤w≤1.3m.

10. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, In the hot rolling process, the continuously cast billet obtained from the continuous casting process is heated and then subjected to rough rolling, finish rolling and cooling in sequence; The uniform heating temperature is 1050~1250℃, and the heating time is 180~220min; The reduction rate of each pass in roughing is controlled at 32-38%, and the final rolling temperature of roughing is 950-1000℃; The reduction rate of each pass in the finishing mill is controlled at 30-38%, the finishing temperature is 820-880℃, and the coiling temperature is 600-680℃.

11. The method for producing high-grade non-oriented silicon steel according to claim 1, characterized in that, The production method also includes a normalizing process performed between the hot rolling and the first cold rolling processes, wherein the normalizing temperature is 920~970℃ and the normalizing time is 2~3min.

12. A high-grade non-oriented silicon steel, characterized in that, The high-grade non-oriented silicon steel is prepared by the production method of high-grade non-oriented silicon steel according to any one of claims 1 to 11.