Method for preparing non-oriented silicon steel with improved magnetic properties and non-oriented silicon steel

Abstract

The present application discloses a method for preparing non-oriented silicon steel with improved magnetic properties and non-oriented silicon steel, wherein the non-oriented silicon steel comprises: Si 1.0-3.0%, Mn 0.2-0.5%, Al 0.3~0.6%, N≤0.002%, C≤0.003%, S≤0.003%, and the rest are Fe and impurities; in the preparation method, the ingot heating process includes a heating section and a soaking section, the soaking temperature of the soaking section is T=1050+[Al] / (10×[N])+[Mn] / (10×[S])+10×[Si], the soaking time is t=30+[Al] / (100×[N])+[Mn] / (100×[S])+5×[Si], the unit of T is ℃, and the unit of t is min; in the normalizing process, the normalizing temperature is 860~980℃; in the annealing process, the annealing temperature is 980~990℃, and the annealing time is 150~200s.

Description

Technical Field

[0001] The present application belongs to the technical field of steel smelting, and specifically relates to a method for preparing non-oriented silicon steel with improved magnetic properties, and also relates to non-oriented silicon steel prepared by the non-oriented silicon steel preparation method. Background Art

[0002] Non-oriented silicon steel is the main material for motor and generator rotor cores. When used for motor and generator rotor cores, non-oriented silicon steel is required to have good magnetic properties, including lower iron loss and higher magnetic induction intensity.

[0003] Inclusions are an important factor affecting the magnetic properties of non-oriented silicon steel, especially fine inclusions, that is, inclusions with a diameter of less than 1μm. Their impact on the magnetic properties of silicon steel is mainly to hinder the growth of grains during annealing, increase iron loss, hinder the movement of magnetic domains and domain walls, and deteriorate the magnetic properties. Therefore, it is necessary to control the inclusions in non-oriented silicon steel. Summary of the invention

[0004] The purpose of the present application is to provide a method for preparing non-oriented silicon steel with improved magnetic properties, and a non-oriented silicon steel prepared by the method.

[0005] To achieve one of the above purposes, an embodiment of the present application provides a method for preparing non-oriented silicon steel with improved magnetic properties, wherein the chemical composition of the non-oriented silicon steel comprises, by mass percentage, Si 1.0-3.0%, Mn 0.2-0.5%, Al 0.3-0.6%, N≤0.002%, C≤0.003%, S≤0.003%, and the rest is Fe and unavoidable impurities; the preparation method comprises the steps of heating the ingot, hot rolling, normalizing, pickling, cold rolling, and annealing in sequence;

[0006] The casting heating process includes a heating section and a soaking section, the soaking temperature of the soaking section is T=1050+[Al] / (10×[N])+ [Mn] / (10×[S])+10×[Si], and the soaking time is t=30+[Al] / (100×[N])+ [Mn] / (100×[S])+5×[Si], where T is in °C and t is in min.

[0007] In the normalizing process, the normalizing temperature is 860-980°C;

[0008] In the annealing process, the annealing temperature is 980-990° C. and the annealing time is 150-200 s.

[0009] As a further improvement of an embodiment of the present application, in the ingot heating process, a regenerative walking beam heating furnace is used to heat the ingot, blast furnace gas is used as the combustion medium, and the air-fuel ratio of the soaking section is 0.6~0.8.

[0010] As a further improvement of an embodiment of the present application, the volume fraction of CO in the blast furnace gas is 25-30%, and the calorific value of the blast furnace gas is 3000-4000 kJ / m 3 , pressure is 8~15kPa.

[0011] As a further improvement of one embodiment of the present application, in the casting billet heating process, the length of the casting billet is 7-10 m, the width is 1-2 m, and the height is 0.2-0.3 m.

[0012] As a further improvement of one embodiment of the present application, in the hot rolling process, rough rolling and finish rolling are carried out in sequence and then coiling is performed, the starting rolling temperature of rough rolling is 1040~1080℃, the starting rolling temperature of finish rolling is 950~990℃, the final rolling temperature of finish rolling is 820~860℃, and the coiling temperature is 600~640℃.

[0013] As a further improvement of an embodiment of the present application, in the hot-rolled coil obtained by the hot rolling process, the inclusions include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of the inclusions is 100-150 / mm 2 The equivalent circle diameter of inclusions is 0.3~4μm, and the inclusions with an equivalent circle diameter of less than 1μm account for ≤35%.

[0014] As a further improvement of one embodiment of the present application, in the cold rolling process, a twenty-roll single stand is used to reciprocatingly cold roll the hot-rolled strip after the pickling process to obtain a cold hardened coil with a thickness of 0.5 mm, and the reduction rate of the first pass is controlled to be 30~35%, and the total reduction rate is controlled to be 75~85%.

[0015] As a further improvement of one embodiment of the present application, in the annealing process, the cold hardened coil obtained in the cold rolling process is sent to a continuous annealing furnace for high-temperature annealing to obtain annealed strip steel, and the protective atmosphere adopts a mixed gas of 20% H2+80% N2, or pure N2.

[0016] In order to achieve the above application purpose, an embodiment of the present application further provides a non-oriented silicon steel, which is prepared by the non-oriented silicon steel preparation method as described above.

[0017] As a further improvement of an embodiment of the present application, the thickness of the non-oriented silicon steel is 0.5 mm, and the iron loss P 1.5 / 50 ≤2.78W / kg, magnetic induction intensity B 50It is 1.66~1.72T.

[0018] Compared with the prior art, the beneficial effects of this application are:

[0019] (1) Based on the chemical composition design scheme of non-oriented silicon steel, the present application establishes the relationship between the soaking temperature and soaking time in the heating process of the ingot casting and the chemical elements and their contents. Through this correlation design, the influence of Al, N, Mn, S, and Si elements on the formation and growth behavior of inclusions during hot rolling is controlled to obtain an ideal inclusion precipitation state such as precipitation density and inclusion size. Further combined with the control of normalizing temperature and annealing temperature, the non-oriented silicon steel can obtain excellent magnetic properties. Moreover, the preparation method is applicable to a wide range of Si, Mn, and Al contents, and has universal applicability to the improvement of the magnetic properties of non-oriented silicon steel.

[0020] (2) The non-oriented silicon steel prepared by the above-mentioned non-oriented silicon steel preparation method has an iron loss P of 0.5 mm when the thickness is 0.5 mm. 1.5 / 50 ≤2.78W / kg, magnetic induction intensity B 50 It is 1.66~1.72T, with excellent magnetic induction performance, low iron loss and high magnetic induction. When used in motors and other products, the electromagnetic performance is qualified and can meet the application requirements of motor and generator rotor cores. DETAILED DESCRIPTION

[0021] The present application will be described in detail below in conjunction with specific implementations. However, these implementations do not limit the present application, and any structural, methodological, or functional changes made by a person of ordinary skill in the art based on these implementations are all included in the protection scope of the present application.

[0022] An embodiment of the present application provides a method for preparing non-oriented silicon steel with improved magnetic properties, and non-oriented silicon steel prepared by the method for preparing non-oriented silicon steel, so as to improve the magnetic properties of the non-oriented silicon steel.

[0023] In this embodiment, the chemical composition design of the non-oriented silicon steel is as follows:

[0024] Its chemical composition, in mass percentage, includes: Si 1.0~3.0%, Mn 0.2~0.5%, Al 0.3~0.6%, N≤0.002%, C≤0.003%, S≤0.003%, and the rest is Fe and unavoidable impurities.

[0025] In the chemical composition design scheme of this application, the functions of each chemical component are as follows:

[0026] Si: After solid solution, it can increase the resistivity and help separate the harmful impurity carbon. Si combined with O can be transformed into stable SiO2, thereby avoiding the lattice distortion of iron. Therefore, adding Si can increase the magnetic permeability, reduce the coercive force, and reduce the iron loss. In this application, the Si content is controlled to be 1.0~3.0%.

[0027] Mn: Low content of Mn can improve the strength, hardness and wear resistance of steel, and improve the low-temperature toughness of steel, but too much Mn is easy to form MnS compounds with S during solidification, pinning at the grain boundary is not conducive to grain growth. In this application, the Mn content is controlled to 0.2~0.5%.

[0028] Al: has a similar effect to Si, can increase resistivity and reduce eddy current loss. In this application, the Al content is controlled to be 0.3~0.6%.

[0029] N, C, S: They are harmful elements in non-oriented silicon steel. They generally hinder grain growth and magnetic domain movement by fine precipitation or grain boundary segregation, thereby affecting the organizational state of the material. They also have a very strong impact on the mechanical properties and magnetic properties of non-oriented silicon steel. Therefore, in this application, N≤0.002%, C≤0.003%, and S≤0.003%.

[0030] Based on the above chemical composition design scheme, under the synergistic effect of the aforementioned chemical components and contents, the non-oriented silicon steel can have excellent magnetic and mechanical properties, improve resistivity, and reduce eddy current losses.

[0031] The non-oriented silicon steel preparation method is based on the non-oriented silicon steel chemical composition design scheme, and the relationship between the soaking temperature and soaking time in the billet heating process and the chemical elements and their contents is established. Through this correlation design, the influence of Al, N, Mn, S, and Si elements on the formation and growth behavior of inclusions during hot rolling is controlled to obtain an ideal inclusion precipitation state such as precipitation density and inclusion size, and further combined with the control of normalizing temperature and annealing temperature, the non-oriented silicon steel can obtain excellent magnetic properties. Moreover, the preparation method is applicable to a wide range of Si, Mn, and Al contents, and has universal applicability to the improvement of the magnetic properties of non-oriented silicon steel.

[0032] The preparation method of the non-oriented silicon steel is specifically introduced below, including the steps of heating the ingot, hot rolling, normalizing, pickling, cold rolling and annealing performed in sequence.

[0033] (1) Billet heating process

[0034] The chemical composition of the ingot is substantially the same as the chemical composition of the non-oriented silicon steel finally prepared. That is, the chemical composition of the ingot includes, by mass percentage: Si 1.0-3.0%, Mn 0.2-0.5%, Al 0.3-0.6%, N≤0.002%, C≤0.003%, S≤0.003%, and the rest is Fe and unavoidable impurities.

[0035] In this embodiment, the size of the ingot meets the following requirements: length of 7-10 m, width of 1-2 m, and height of 0.2-0.3 m. Ingots with such sizes can be used to improve the magnetic properties of the non-oriented silicon steel finally prepared by the preparation method of the present application.

[0036] The ingot heating process includes a heating section and a soaking section, the soaking temperature of the soaking section is T=1050+[Al] / (10×[N])+ [Mn] / (10×[S])+10×[Si], the soaking time is t=30+[Al] / (100×[N])+ [Mn] / (100×[S])+5×[Si], the unit of T is ℃, and the unit of t is min.

[0037] Wherein, [Al], [N], [Mn], [S], and [Si] respectively represent the mass percentage values ​​of the corresponding elements. For example, if the Al content in the non-oriented silicon steel is 0.3%, then [Al]=0.3.

[0038] Firstly, Si and Al are the main elements of silicon steel, which can significantly improve the magnetic properties of silicon steel; secondly, the soaking temperature and soaking time during heating of the ingot are closely related to the growth of grains during heating, the solid solution of inclusions, the rolling force required during rolling, the precipitation behavior of inclusions, etc., and these behaviors have an important influence on the magnetic properties of silicon steel; furthermore, the inclusions in silicon steel are mainly AlN inclusions, MnS inclusions and their composite inclusions.

[0039] Therefore, the present application establishes the relationship between the soaking temperature, soaking time and each chemical element and its content. Through this correlation design, the influence of Al, N, Mn, S, and Si elements on the formation and growth behavior of inclusions during hot rolling can be controlled, and the ideal inclusion precipitation state such as precipitation density and inclusion size can be obtained, laying the foundation for non-oriented silicon steel to obtain excellent magnetic properties. Moreover, the above relationship is applicable to a wide range of Si, Mn, and Al contents, and is generally applicable to the improvement of the magnetic properties of non-oriented silicon steel.

[0040] The heating section can make the surface of the ingot reach the preset temperature, while the control of the soaking temperature and soaking time in the soaking section can ensure that the core and surface temperatures of the ingot reach the preset temperature, thereby ensuring the temperature uniformity of the ingot.

[0041] Preferably, a regenerative walking beam heating furnace is used to heat the ingot, blast furnace gas is used as the combustion medium, and the air-fuel ratio in the soaking section is 0.6-0.8, wherein the air-fuel ratio is the volume ratio of air to blast furnace gas.

[0042] By using blast furnace gas as the combustion medium and controlling the air-fuel ratio in the soaking section, the combustion heat can be controlled. The combustion heat is transferred to the ingot by heat transfer and heat radiation, so that the ingot can be heated with better heating quality, which makes it easier to control the soaking temperature and has a better heating effect, which is beneficial to control the precipitation state of inclusions during hot rolling, such as precipitation density and inclusion size.

[0043] Preferably, the volume fraction of CO in the blast furnace gas is 25-30%, and the calorific value of the blast furnace gas is 3000-4000 kJ / m 3 , pressure is 8~15kPa.

[0044] Blast furnace gas includes CO, H2, CH4 and various alkane gases, and the composition of blast furnace gas will change with the change of blast furnace conditions. CO is the most important component in blast furnace gas. The calorific value of blast furnace gas can be guaranteed by controlling the volume fraction, air-fuel ratio and pressure of CO in blast furnace gas. Further, by controlling the calorific value of blast furnace gas, even if a certain heat loss is generated in the process of heat radiation transfer to the ingot, it can still be guaranteed that the ingot reaches the preset temperature, thereby having a better heating effect on the ingot, which is beneficial to control the precipitation state of inclusions during hot rolling, such as precipitation density and inclusion size, so that the finished silicon steel obtains excellent magnetic properties.

[0045] (2) Hot rolling

[0046] The heated ingot is subjected to rough rolling and finish rolling in sequence and then coiled to obtain a hot rolled coil.

[0047] Among them, the starting rolling temperature of rough rolling is 1040~1080℃, the starting rolling temperature of finishing rolling is 950~990℃, the final rolling temperature of finishing rolling is 820~860℃, and the coiling temperature is 600~640℃.

[0048] When the rolling temperature is low, the steel has a large deformation resistance, which requires a high rolling force of the rolling mill, and is conducive to grain refinement, improving strength and plasticity, but grain refinement is not good for magnetic properties. When the rolling temperature is high, the steel has a small deformation resistance and low requirements for the rolling mill. However, more inclusions are dissolved in the heating stage, and a large number of fine and dispersed inclusions will precipitate during the rolling and cooling process, affecting the magnetic properties.

[0049] In the present application, by controlling the rolling temperature and the coiling temperature within this range, the precipitation behavior of inclusions during the hot rolling process can be regulated while regulating the microstructure of the silicon steel.

[0050] In the hot-rolled coil obtained by the hot rolling process, inclusions include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of the inclusions is 100-150 / mm 2 The equivalent circle diameter of inclusions is 0.3~4μm, and the inclusions with an equivalent circle diameter of less than 1μm account for ≤35%.

[0051] Since inclusions affect the magnetic properties of silicon steel by hindering the movement of magnetic domains in the steel, in the present application, the precipitation density of the inclusions is small, the number of inclusions is small, and the size of the inclusions is large, the influence on the magnetic properties is small.

[0052] Hot rolling is completed on a rolling line equipped with a descaling machine, a roughing mill, a finishing mill, a laminar cooling device and a coiling device.

[0053] Among them, the descaling machine descales the ingot, the roughing mill group rough-rolls the ingot, the finishing mill group finish-rolls the intermediate ingot after rough rolling to obtain a steel plate, the laminar cooling device cools the steel plate, and the coiling equipment coils the steel plate to obtain a hot-rolled coil.

[0054] Preferably, the finishing mill adopts a seven-stand finishing mill F1-F7, and its maximum rolling force is 36000 kN.

[0055] (3) Normalization process

[0056] The normalizing temperature is 860~980℃.

[0057] By normalizing the process and controlling the normalizing temperature, not only can the hot-rolled coil be completely recrystallized in the normalizing process, improving the structure and product magnetic properties of the hot-rolled coil, and improving the inconsistency of the magnetic properties at the head, middle and tail, but also the toughness of the steel strip can be improved and the risk of strip breakage during cold rolling can be reduced.

[0058] (4) Pickling process

[0059] The hot rolled coil after the normalizing process is continuously pickled to remove the oxide scale on its surface.

[0060] The acid solution uses hydrochloric acid, the concentration of hydrochloric acid in the acid solution is 140~160g / L, and the pickling temperature is 80~85℃.

[0061] (5) Cold rolling process

[0062] A twenty-roll single stand is used to reciprocate cold rolling the hot-rolled strip after the pickling process to obtain a cold-hardened coil with a thickness of 0.5 mm. The reduction rate of the first pass is controlled at 30-35%, and the total reduction rate is controlled at 75-85%.

[0063] By controlling the large deformation reduction and total reduction rate in the first pass, it can be ensured that the grains are fully broken in the first pass, and the quality of the finished plate shape and thickness accuracy can be guaranteed.

[0064] (6) Annealing process

[0065] The cold-rolled coil obtained in the cold rolling process is sent to a continuous annealing furnace for high-temperature annealing to obtain annealed strip steel, i.e., non-oriented silicon steel, with an annealing temperature of 980-990°C and an annealing time of 150-200s. The annealing process causes the cold-rolled deformed ferrite to recrystallize, thereby improving the magnetic properties of the silicon steel product.

[0066] Among them, the protective atmosphere in the continuous annealing furnace adopts a mixed gas of 20% H2 + 80% N2, or pure N2, which can prevent the strip from forming an inner oxide layer and an inner nitride layer, improve the surface quality of the strip, and further reduce iron loss.

[0067] Furthermore, after the annealing process, the annealed strip is cooled and then coated and finished, so as to evenly coat the upper and lower surfaces of the non-oriented silicon steel with an insulating layer to improve its insulation performance, and then finished.

[0068] The specific operations of coating and finishing can be achieved by using existing feasible coating and finishing technologies, which will not be described in detail here.

[0069] An embodiment of the present application further provides a non-oriented silicon steel, which is prepared by the above-mentioned non-oriented silicon steel preparation method. The thickness of the steel strip of the non-oriented silicon steel is 0.5 mm, and, as mentioned above, its chemical composition includes, by mass percentage: Si 1.0~3.0%, Mn 0.2~0.5%, Al 0.3~0.6%, N≤0.002%, C≤0.003%, S≤0.003%, and the rest is Fe and unavoidable impurities.

[0070] After testing, the non-oriented silicon steel prepared by the above-mentioned non-oriented silicon steel preparation method has an iron loss P 1.5 / 50 ≤2.78W / kg, magnetic induction intensity B 50 It is 1.66~1.72T, with excellent magnetic induction performance, low iron loss and high magnetic induction. When used in motors and other products, the electromagnetic performance is qualified and can meet the application requirements of motor and generator rotor cores.

[0071] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present application should be included in the scope of protection of the present application.

[0072] The beneficial effects of the present application are further illustrated below through 4 embodiments and 2 comparative examples. Of course, these 3 embodiments are only a part of the many varied embodiments contained in the present application, but not all of them.

[0073] Example 1

[0074] The chemical composition of the non-oriented silicon steel includes, by mass percentage, Si 2.48%, Mn 0.49%, Al 0.32%, N 0.0019%, C 0.002%, S 0.0029%, and the rest is Fe and unavoidable impurities.

[0075] (1) Billet heating process

[0076] The chemical composition of the ingot is consistent with the chemical composition of the non-oriented silicon steel finally prepared, and the size of the ingot satisfies: length×width×height is 7m×1.1m×0.22m.

[0077] A regenerative walking beam heating furnace is used to heat the ingot, and blast furnace gas is used as the combustion medium. The heating includes a heating section and a soaking section. The soaking temperature T of the soaking section is 1109°C, the soaking time t is 46min, and the air-fuel ratio of the soaking section is 0.65.

[0078] The volume fraction of CO in the blast furnace gas is 28%, and the calorific value of the blast furnace gas is 3500 kJ / m 3 , the pressure is 10kPa.

[0079] (2) Hot rolling

[0080] After the heated ingot is descaled in the descaling machine, it is sent to the roughing mill for rough rolling, the finishing mill for finishing rolling, the laminar cooling device for cooling, and the coiling equipment for coiling to obtain hot rolled coils. Among them, the finishing mill adopts the seven-stand finishing mill of F1-F7, and its maximum rolling force is 36000kN.

[0081] Among them, the starting rolling temperature of rough rolling is 1050°C, the starting rolling temperature of finish rolling is 965°C, the final rolling temperature of finish rolling is 845°C, and the coiling temperature is 625°C.

[0082] In the obtained hot rolled coil, inclusions include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of inclusions is 130 / mm 2 The equivalent circle diameter of inclusions is 0.3~4μm, and the inclusions with an equivalent circle diameter of less than 1μm account for 30%.

[0083] (3) Normalization process

[0084] The normalizing temperature is 980°C.

[0085] (4) Pickling process

[0086] The hot rolled coil after normalization process is continuously pickled to remove the oxide scale on its surface. The acid solution is hydrochloric acid, the concentration of hydrochloric acid in the acid solution is 140~160g / L, and the pickling temperature is 80~85℃.

[0087] (5) Cold rolling process

[0088] A twenty-roll single stand is used to reciprocate cold rolling the hot-rolled strip after the pickling process to obtain a cold-hardened coil with a thickness of 0.5 mm. The reduction rate of the first pass is controlled to be 35%, and the total reduction rate is controlled to be 75%.

[0089] (6) Annealing process

[0090] The cold-hardened coil obtained in the cold rolling process is sent to a continuous annealing furnace for high-temperature annealing to obtain an annealed strip steel with a thickness of 0.5 mm, that is, non-oriented silicon steel. The annealing temperature is 990° C. and the annealing time is 200 s.

[0091] Among them, the protective atmosphere in the continuous annealing furnace adopts a mixed gas of 20% H2+80% N2.

[0092] Furthermore, after the annealing process, the annealed strip is cooled and then coated and finished.

[0093] The magnetic induction performance of non-oriented silicon steel products was tested according to GB / T3655-2022 standard, and its iron loss P was obtained. 1.5 / 50 is 2.38W / kg, magnetic induction intensity B 50 It is 1.69T.

[0094] Example 2

[0095] The chemical composition of the non-oriented silicon steel includes, by mass percentage, 3% Si, 0.2% Mn, 0.6% Al, 0.0015% N, 0.003% C, 0.0025% S, and the rest is Fe and unavoidable impurities.

[0096] (1) Billet heating process

[0097] The chemical composition of the ingot is consistent with the chemical composition of the non-oriented silicon steel finally prepared, and the size of the ingot satisfies: length×width×height is 7m×1.1m×0.22m.

[0098] The ingot is heated by a regenerative walking beam heating furnace, and blast furnace gas is used as the combustion medium. The heating includes a heating section and a soaking section. The soaking temperature T of the soaking section is 1128°C, the soaking time t is 50min, and the air-fuel ratio of the soaking section is 0.80.

[0099] The volume fraction of CO in the blast furnace gas is 30%, and the calorific value of the blast furnace gas is 4000 kJ / m 3 , the pressure is 8kPa.

[0100] (2) Hot rolling

[0101] After the heated ingot is descaled in the descaling machine, it is sent to the roughing mill for rough rolling, the finishing mill for finishing rolling, the laminar cooling device for cooling, and the coiling equipment for coiling to obtain hot rolled coils. Among them, the finishing mill adopts the seven-stand finishing mill of F1-F7, and its maximum rolling force is 36000kN.

[0102] Among them, the starting rolling temperature of rough rolling is 1080°C, the starting rolling temperature of finish rolling is 990°C, the final rolling temperature of finish rolling is 860°C, and the coiling temperature is 640°C.

[0103] In the obtained hot rolled coil, inclusions include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of inclusions is 100 / mm 2 The equivalent circle diameter of inclusions is 0.3~4μm, and the inclusions with an equivalent circle diameter of less than 1μm account for 33%.

[0104] (3) Normalization process

[0105] The normalizing temperature is 980°C.

[0106] (4) Pickling process

[0107] The hot rolled coil after normalization process is continuously pickled to remove the oxide scale on its surface. The acid solution is hydrochloric acid, the concentration of hydrochloric acid in the acid solution is 140~160g / L, and the pickling temperature is 80~85℃.

[0108] (5) Cold rolling process

[0109] A twenty-roll single stand is used to reciprocate cold rolling the hot-rolled strip after the pickling process to obtain a cold-hardened coil with a thickness of 0.5 mm. The reduction rate of the first pass is controlled to be 35%, and the total reduction rate is controlled to be 75%.

[0110] (6) Annealing process

[0111] The cold-rolled coil obtained in the cold rolling process is sent to a continuous annealing furnace for high-temperature annealing to obtain an annealed strip steel with a thickness of 0.5 mm, that is, non-oriented silicon steel. The annealing temperature is 990° C. and the annealing time is 200 s.

[0112] Among them, the protective atmosphere in the continuous annealing furnace adopts a mixed gas of 20% H2+80% N2.

[0113] Furthermore, after the annealing process, the annealed strip is cooled and then coated and finished.

[0114] The magnetic induction performance of non-oriented silicon steel products was tested according to GB / T3655-2022 standard, and its iron loss P was obtained. 1.5 / 50 is 2.30W / kg, magnetic induction intensity B 50 It is 1.68T.

[0115] Example 3

[0116] The chemical composition of the non-oriented silicon steel includes, by mass percentage, 3% Si, 0.2% Mn, 0.6% Al, 0.0015% N, 0.003% C, 0.0025% S, and the rest is Fe and unavoidable impurities.

[0117] (1) Billet heating process

[0118] The chemical composition of the ingot is consistent with the chemical composition of the non-oriented silicon steel finally prepared, and the size of the ingot satisfies: length×width×height is 7m×1.1m×0.22m.

[0119] The ingot is heated by a regenerative walking beam heating furnace, and blast furnace gas is used as the combustion medium. The heating includes a heating section and a soaking section. The soaking temperature T of the soaking section is 1128°C, the soaking time t is 50min, and the air-fuel ratio of the soaking section is 0.80.

[0120] The volume fraction of CO in the blast furnace gas is 30%, and the calorific value of the blast furnace gas is 4000 kJ / m 3 , the pressure is 8kPa.

[0121] (2) Hot rolling

[0122] After the heated ingot is descaled in the descaling machine, it is sent to the roughing mill for rough rolling, the finishing mill for finishing rolling, the laminar cooling device for cooling, and the coiling equipment for coiling to obtain hot rolled coils. Among them, the finishing mill adopts the seven-stand finishing mill of F1-F7, and its maximum rolling force is 36000kN.

[0123] Among them, the starting rolling temperature of rough rolling is 1080°C, the starting rolling temperature of finish rolling is 990°C, the final rolling temperature of finish rolling is 860°C, and the coiling temperature is 640°C.

[0124] In the obtained hot rolled coil, inclusions include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of inclusions is 100 / mm 2 The equivalent circle diameter of inclusions is 0.3~4μm, and the inclusions with an equivalent circle diameter of less than 1μm account for 33%.

[0125] (3) Normalization process

[0126] The normalizing temperature is 860°C.

[0127] (4) Pickling process

[0128] The hot rolled coil after normalization process is continuously pickled to remove the oxide scale on its surface. The acid solution is hydrochloric acid, the concentration of hydrochloric acid in the acid solution is 140~160g / L, and the pickling temperature is 80~85℃.

[0129] (5) Cold rolling process

[0130] A twenty-roll single stand is used to reciprocate cold rolling the hot-rolled strip after the pickling process to obtain a cold-hardened coil with a thickness of 0.5 mm. The reduction rate of the first pass is controlled to be 35%, and the total reduction rate is controlled to be 75%.

[0131] (6) Annealing process

[0132] The cold-rolled coil obtained in the cold rolling process is sent to a continuous annealing furnace for high-temperature annealing to obtain an annealed strip steel with a thickness of 0.5 mm, that is, non-oriented silicon steel. The annealing temperature is 980° C. and the annealing time is 150 s.

[0133] Among them, the protective atmosphere in the continuous annealing furnace adopts a mixed gas of 20% H2+80% N2.

[0134] Furthermore, after the annealing process, the annealed strip is cooled and then coated and finished.

[0135] The magnetic induction performance of non-oriented silicon steel products was tested according to GB / T3655-2022 standard, and its iron loss P was obtained. 1.5 / 50 is 2.28W / kg, magnetic induction intensity B 50 It is 1.66T.

[0136] Example 4

[0137] The chemical composition of the non-oriented silicon steel includes, by mass percentage, Si 1%, Mn 0.5%, Al 0.3%, N 0.0015%, C 0.003%, S 0.0025%, and the rest is Fe and unavoidable impurities.

[0138] (1) Billet heating process

[0139] The chemical composition of the ingot is consistent with the chemical composition of the non-oriented silicon steel finally prepared, and the size of the ingot satisfies: length×width×height is 7m×1.1m×0.22m.

[0140] The ingot is heated in a regenerative walking beam heating furnace, and blast furnace gas is used as the combustion medium. The heating includes a heating section and a soaking section. The soaking temperature T of the soaking section is 1100°C, the soaking time t is 39 minutes, and the air-fuel ratio of the soaking section is 0.60.

[0141] The volume fraction of CO in the blast furnace gas is 25%, and the calorific value of the blast furnace gas is 3000 kJ / m 3 , the pressure is 15kPa.

[0142] (2) Hot rolling

[0143] After the heated ingot is descaled in the descaling machine, it is sent to the roughing mill for rough rolling, the finishing mill for finishing rolling, the laminar cooling device for cooling, and the coiling equipment for coiling to obtain hot rolled coils. Among them, the finishing mill adopts the seven-stand finishing mill of F1-F7, and its maximum rolling force is 36000kN.

[0144] Among them, the starting rolling temperature of rough rolling is 1040°C, the starting rolling temperature of finish rolling is 950°C, the final rolling temperature of finish rolling is 820°C, and the coiling temperature is 600°C.

[0145] The inclusions in the obtained hot rolled coil include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of the inclusions is 150 / mm 2 The equivalent circle diameter of inclusions is 0.3~4μm, and the inclusions with an equivalent circle diameter of less than 1μm account for 35%.

[0146] (3) Normalization process

[0147] The normalizing temperature is 980°C.

[0148] (4) Pickling process

[0149] The hot rolled coil after normalization process is continuously pickled to remove the oxide scale on its surface. The acid solution is hydrochloric acid, the concentration of hydrochloric acid in the acid solution is 140~160g / L, and the pickling temperature is 80~85℃.

[0150] (5) Cold rolling process

[0151] A twenty-roll single stand is used to reciprocate cold rolling the hot-rolled strip after the pickling process to obtain a cold-hardened coil with a thickness of 0.5 mm. The reduction rate of the first pass is controlled to be 30%, and the total reduction rate is controlled to be 85%.

[0152] (6) Annealing process

[0153] The cold-hardened coil obtained in the cold rolling process is sent to a continuous annealing furnace for high-temperature annealing to obtain an annealed strip steel with a thickness of 0.5 mm, that is, non-oriented silicon steel. The annealing temperature is 990° C. and the annealing time is 200 s.

[0154] Among them, the protective atmosphere in the continuous annealing furnace adopts a mixed gas of 20% H2+80% N2.

[0155] Furthermore, after the annealing process, the annealed strip is cooled and then coated and finished.

[0156] The magnetic induction performance of non-oriented silicon steel products was tested according to GB / T3655-2022 standard, and its iron loss P was obtained. 1.5 / 50 is 2.78W / kg, magnetic induction intensity B 50 It is 1.72T.

[0157] Comparative Example 1

[0158] The only difference between this comparative example and Example 1 is that the equalizing temperature T of the equalizing section in the billet heating process is 1140° C. The remaining processes and parameters are the same and will not be described in detail herein.

[0159] The inclusions in the obtained hot-rolled coil include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of the inclusions is 253 / mm 2 The equivalent circle diameter of inclusions is 0.3~3μm, and the inclusions with an equivalent circle diameter of less than 1μm account for 65%.

[0160] The magnetic induction performance of the final non-oriented silicon steel product was tested according to GB / T3655-2022 standard, and its iron loss P was obtained. 1.5 / 50 is 3.40W / kg, magnetic induction intensity B 50 It is 1.71 T. It can be seen that its iron loss is significantly greater than that of Example 1.

[0161] Comparative Example 2

[0162] The only difference between this comparative example and Example 1 is that the soaking time t of the soaking section in the billet heating process is 60 minutes, and the other processes and parameters are the same and will not be described in detail here.

[0163] The inclusions in the obtained hot rolled coil include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of the inclusions is 220 / mm 2 The equivalent circle diameter of inclusions is 0.3~3.5μm, and the inclusions with an equivalent circle diameter of less than 1μm account for 58%.

[0164] The magnetic induction performance of the final non-oriented silicon steel product was tested according to GB / T3655-2022 standard, and its iron loss P was obtained. 1.5 / 50 is 3.30W / kg, magnetic induction intensity B 50 It is 1.70 T. It can be seen that its iron loss is significantly greater than that of Example 1.

[0165] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0166] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing non-oriented silicon steel with improved magnetic properties, characterized in that: The chemical composition of the non-oriented silicon steel includes, by mass percentage, Si 1.0-3.0%, Mn 0.2-0.5%, Al 0.3-0.6%, N 0.0015-0.002%, C≤0.003%, S 0.0025-0.003%, and the rest is Fe and unavoidable impurities; the preparation method includes the steps of heating the ingot, hot rolling, normalizing, pickling, cold rolling, and annealing in sequence; The casting billet heating process includes a heating section and a soaking section. The casting billet has a length of 7-10 m, a width of 1-2 m, and a height of 0.2-0.3 m. The soaking temperature of the soaking section is T=1050+[Al] / (10×[N])+ [Mn] / (10×[S])+10×[Si], and the soaking time is t=30+[Al] / (100×[N])+ [Mn] / (100×[S])+5×[Si], where T is in °C and t is in min. In the hot rolling process, rough rolling and finish rolling are sequentially performed and then coiled, the starting rolling temperature of the rough rolling is 1040-1080°C, the starting rolling temperature of the finish rolling is 950-990°C, the final rolling temperature of the finish rolling is 820-860°C, and the coiling temperature is 600-640°C; in the obtained hot rolled coil, inclusions include AlN inclusions, MnS inclusions and AlN-MnS inclusions, and the precipitation density of the inclusions is 100-150 pieces / mm 2 , the equivalent circle diameter of inclusions is 0.3~4μm, and the proportion of inclusions with an equivalent circle diameter of less than 1μm is ≤35%; In the normalizing process, the normalizing temperature is 860-980°C; In the annealing process, the annealing temperature is 980-990° C. and the annealing time is 150-200 s.

2. The method for preparing non-oriented silicon steel with improved magnetic properties according to claim 1, characterized in that: In the casting heating process, a regenerative walking beam heating furnace is used to heat the casting, blast furnace gas is used as the combustion medium, and the air-fuel ratio of the soaking section is 0.6-0.

8.

3. The method for preparing non-oriented silicon steel with improved magnetic properties according to claim 2, characterized in that: The volume fraction of CO in the blast furnace gas is 25-30%, and the calorific value of the blast furnace gas is 3000-4000 kJ / m 3 , pressure is 8~15kPa.

4. The method for preparing non-oriented silicon steel with improved magnetic properties according to claim 1, characterized in that: In the cold rolling process, a twenty-roll single stand is used to reciprocate cold rolling the hot-rolled strip after the pickling process to obtain a cold hardened coil with a thickness of 0.5 mm, and the reduction rate of the first pass is controlled to be 30-35%, and the total reduction rate is controlled to be 75-85%.

5. The method for preparing non-oriented silicon steel with improved magnetic properties according to claim 1, characterized in that: In the annealing process, the cold hardened coil obtained in the cold rolling process is sent to a continuous annealing furnace for high temperature annealing to obtain annealed strip steel, and the protective atmosphere adopts a mixed gas of 20% H2+80% N2, or pure N2.

6. A non-oriented silicon steel, characterized in that: The non-oriented silicon steel is prepared by the method for preparing non-oriented silicon steel as described in any one of claims 1 to 5.

7. The non-oriented silicon steel according to claim 6, characterized in that: Its thickness is 0.5mm, and the iron loss P 1.5 / 50 ≤2.78W / kg, magnetic induction intensity B 50 It is 1.66~1.72T.