Production method for non-oriented silicon steel sheets

Abstract

The present invention discloses a non-oriented silicon steel and a method for producing the same. The method includes the steps of producing a slab by making steel with 0.8-1.1% Si and 0.2-0.4% Mn without adding Sn and Sb, heating the slab to 1060-1120°C and holding it for 150 minutes or more, and then rolling it into an intermediate slab with a thickness of 40-45 mm, and then finishing rolling and coiling to obtain a hot rolled coil with a thickness of 3.00±0.25 mm. The rolling start temperature of the finishing rolling is 872°C+1000*(11*[Si]-14*[Mn]+21*[Al] ) or less, the rolling end temperature of the finish rolling is 820°C or less, and the coiling temperature is 560°C or less; normalizing, continuous pickling, and cold rolling are performed to obtain a hard cold-rolled coil having a thickness of 0.500±0.005 mm, the normalizing temperature being 850 to 900°C; and the finish annealing temperature is 820 to 880°C, and after annealing, cooling, painting, and refinement are performed to obtain a non-oriented silicon steel.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a Chinese patent application filed on June 17, 2021, bearing application number 202110670657.9 and entitled "Non-oriented silicon steel and method for producing the same," the entire contents of which are incorporated herein by reference.

[0002] The present invention belongs to the technical field of steel material manufacturing, and relates to non-oriented silicon steel Board Regarding production methods. [Background technology]

[0003] Non-oriented silicon steel is used as the core material for the rotors of electric motors and generators operating in rotating magnetic fields, and its stable quality is crucial for improving the quality of electrical machinery. The silicon content of medium- to low-grade non-oriented silicon steel is controlled to 0.5% to 1.7%. The conventional production process typically involves steelmaking, slab casting, hot rolling, continuous pickling, cold rolling, annealing, painting, and finishing. The hot rolling process produces equiaxed ferrite and deformed ferrite, and the ferrite grain size and proportion are significantly affected by the rolling and coiling temperatures. Furthermore, because heat dissipation is faster at the head and tail ends of a hot-rolled coil, the rolling and coiling temperatures at these ends are lower than at the center. Furthermore, the head and tail ends have finer ferrite grains and a higher proportion of deformed ferrite than the center. Finally, the finished coil made of non-oriented silicon steel has problems such as high iron loss at the leading and trailing ends, low magnetic flux density, and inconsistent magnetic properties throughout the coil.

[0004] To solve the problem of non-uniform magnetic properties throughout the coil of low and medium-grade non-oriented silicon steel, the current approach is to use a slower annealing method at the front and rear ends of the steel coil, in which the roll speed during annealing is slower than the roll speed during annealing the center of the steel coil, so as to improve the uniformity of magnetic properties throughout the coil. However, this method requires adjustment of the roll speed during production, which increases the difficulty of production, reduces production efficiency, and increases the production costs of the annealing process. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a non-oriented silicon steel Board The present invention aims to provide a production method that solves the problem of non-oriented silicon steel coils having non-uniform magnetic properties, on the premise that the demand for medium to low specification non-oriented silicon steel in small and medium-sized electrical machines is met without significantly increasing production costs.

[0006] In order to achieve the object of the invention, one embodiment of the present invention provides a steel sheet having a chemical composition, in mass percent, of C≦0.004%, S≦0.004%, Si: 0.8-1.1%, Mn: 0.2-0.4%, P≦0.03%, Nb≦0.004%, V≦0.006%, Ti≦0.005%, Cr≦0.03%, Ni≦0.03%, Cu≦0.03%, N≦0.004%, Al: 0.15-0.30% or Al≦0.02%, with the balance being Fe and unavoidable impurities, the steel sheet having a thickness of 0.500±0.005 mm, and produced by a process of steelmaking, slab casting, hot rolling, normalizing, continuous pickling and cold rolling, finish annealing, cooling, painting, and finishing, which are carried out in that order; Sn and Sb are not added during the steelmaking process, In the hot rolling process, the slab obtained in the slab casting process is heated to 1060-1120°C and held for 150 minutes or more, then rolled into an intermediate slab with a thickness of 40-45 mm, and the intermediate slab is further subjected to finish rolling and coiling to obtain a hot rolled coil with a thickness of 3.00±0.25 mm. The rolling start temperature of the finish rolling is A r1=872°C + 1000*(11*[Si]-14*[Mn]+21*[Al]) or less, where [Si], [Mn], and [Al] are the mass percentages of Si, Mn, and Al in the slab, respectively; the rolling end temperature of the finish rolling is 820°C or less, and the coiling temperature is 560°C or less; In the normalizing process, the normalizing temperature is 850 to 900°C, The present invention provides a non-oriented silicon steel in which the production is carried out at a constant speed in the final annealing process and the annealing temperature is 820 to 880°C.

[0007] Preferably, the iron loss P of the non-oriented silicon steel 1.5 / 50 When the iron loss P is 4.2W / kg or less, the iron loss P 1.5 / 50 Fluctuation is less than 0.2W / kg, and magnetic flux density B 5000 is 1.72T or more, the magnetic flux density B from the tip to the center and back end 5000 The fluctuation is less than 0.02T.

[0008] Preferably, in the normalizing step, normalizing is carried out in a pure dry N2 atmosphere for 120 to 150 seconds.

[0009] Preferably, in the normalizing step, the normalizing temperature fluctuation is ±10° C. and the production is carried out at a constant rate.

[0010] Preferably, in the annealing step, the annealing time is 50±5 s, the annealing temperature fluctuation is ±10° C., and the annealing production is carried out at a constant speed.

[0011] In order to achieve the above object of the invention, one embodiment of the present invention comprises: 1) producing a slab by steelmaking without adding Sn and Sb, the chemical composition of the slab being, in mass percent, C≦0.004%, S≦0.004%, Si: 0.8-1.1%, Mn: 0.2-0.4%, P≦0.03%, Nb≦0.004%, V≦0.006%, Ti≦0.005%, Cr≦0.03%, Ni≦0.03%, Cu≦0.03%, N≦0.004%, Al: 0.15-0.30% or Al≦0.02%, with the remainder being Fe and unavoidable impurities; 2) The slab is heated to 1060 to 1120°C and held for 150 minutes or more, and then rolled into an intermediate slab having a thickness of 40 to 45 mm. The intermediate slab is then subjected to finish rolling and coiling to obtain a hot-rolled coil having a thickness of 3.00±0.25 mm. r1 =872°C + 1000*(11*[Si]-14*[Mn]+21*[Al]) or less, where [Si], [Mn], and [Al] are the mass percentages of Si, Mn, and Al in the slab, respectively, and the rolling end temperature of the finish rolling is 820°C or less and the coiling temperature is 560°C or less; 3) the hot-rolled coil is subjected to normalization, continuous pickling, and cold rolling in order to obtain a hard cold-rolled coil having a thickness of 0.500±0.005 mm, wherein the normalization temperature is 850 to 900°C; 4) Finish annealing the hard cold-rolled coil at a constant speed in a mixed atmosphere of H2 and N2 using a continuous annealing furnace at a finish annealing temperature of 820 to 880°C, and then cooling, painting, and finishing the annealed steel strip to obtain non-oriented silicon steel.

[0012] Preferably, in step 3, normalization is carried out in a pure dry N2 atmosphere for 120 to 150 seconds.

[0013] Preferably, in step 3, the normalizing temperature variation is ±10° C. and production is carried out at a constant rate.

[0014] Preferably, in step 4, the annealing time is 50±5 s, the annealing temperature fluctuation is ±10°C, and the annealing production is carried out at a constant speed.

[0015] Preferably, the iron loss P of the obtained non-oriented silicon steel 1.5 / 50 When the iron loss P is 4.2W / kg or less, the iron loss P 1.5 / 50 Fluctuation is less than 0.2W / kg, and magnetic flux density B 5000 is 1.72T or more, the magnetic flux density B from the tip to the center and back end 5000 The fluctuation is less than 0.02T.

[0016] In order to achieve the above object of the invention, one embodiment of the present invention comprises: 1) producing a slab by steelmaking with a Si mass percentage of 0.8-1.1% and a Mn mass percentage of 0.2-0.4% among chemical components, without adding Sn and Sb during steelmaking; 2) The slab is heated to 1060 to 1120°C and held for 150 minutes or more, and then rolled into an intermediate slab having a thickness of 40 to 45 mm. The intermediate slab is then subjected to finish rolling and coiling to obtain a hot-rolled coil having a thickness of 3.00±0.25 mm. r1 =872°C + 1000*(11*[Si]-14*[Mn]+21*[Al]) or less, where [Si], [Mn], and [Al] are the mass percentages of Si, Mn, and Al in the slab, respectively, and the rolling end temperature of the finish rolling is 820°C or less and the coiling temperature is 560°C or less; 3) the hot-rolled coil is subjected to normalization, continuous pickling, and cold rolling in order to obtain a hard cold-rolled coil having a thickness of 0.500±0.005 mm, wherein the normalization temperature is 850 to 900°C; 4) Finish annealing the hard cold-rolled coil at a constant speed in a mixed atmosphere of H2 and N2 using a continuous annealing furnace at a finish annealing temperature of 820 to 880°C, and then cooling, painting, and finishing the annealed steel strip to obtain non-oriented silicon steel.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The non-oriented silicon steel finished product with a thickness of 0.500±0.005 mm manufactured by the above production method has an iron loss P 1.5 / 50 is 4.2W / kg or less, and the magnetic flux density B 5000 The magnetic loss coefficient is 1.72T or more, which is excellent in magnetic properties and is almost the same as that of conventional non-oriented silicon steel with an Si content of 1.4 to 1.7%, and can meet the demand for medium and low-grade non-oriented silicon steel in small and medium-sized electrical appliances. The magnetic properties of the entire coil are uniform, and the iron loss P 1.5 / 50Fluctuation is less than 0.2W / kg, and magnetic flux density B 5000 The fluctuation is less than 0.02T.

[0019] (2) By adopting low-temperature rolling and low-temperature coiling processes in the hot rolling process, hot-rolled coils exhibiting a fully deformed ferrite structure can be obtained, and the additional normalizing process ensures that the final non-oriented silicon steel has excellent magnetic properties. At the same time, under conditions where production is carried out at a constant speed in the finish annealing process, the problem of non-oriented silicon steel products having non-uniform magnetic properties from the front end to the center and rear end, which occurs in conventional technology, is resolved, and the situation in which the surface crystal grains of the steel coil grow abnormally compared to the interior during the normalizing process is avoided.

[0020] (3) Despite the addition of the normalizing process, there is no increase in production costs, ensuring low production costs and offering extremely high economic value. Specifically, the combination of hot rolling and normalizing processes fully utilizes the effects of the normalizing process on the structure of the hot-rolled non-oriented silicon steel and the magnetic properties of the finished product. This reduces production costs for the steelmaking, hot rolling, continuous pickling, cold rolling, normalizing, and annealing processes, without increasing the overall cost of the process. In terms of chemical composition in the steelmaking process, the content of Si, which improves magnetic properties, has been reduced from the previous 1.4-1.7% to 0.8-1.1%, and the addition of precious metals Sn and Sb to improve magnetic properties has been eliminated, while the addition of Mn has been reduced. This reduces the cost of the steelmaking alloy while maintaining the same magnetic properties as the previous chemical composition. The adoption of low-temperature rolling and low-temperature coiling processes in the hot rolling process reduces the furnace temperature requirements and allows heating at a lower temperature, thereby reducing energy consumption and production costs compared to conventional hot rolling processes. This also reduces the oxide scale on the hot-rolled coil surface, reducing scale loss and improving yield and production costs. In addition, increasing the thickness of the hot-rolled coil from the conventional 2.0-2.5 mm to 3.00±0.25 mm improves the production speed of the hot-rolling process and reduces overall production costs. In the normalizing process, the adoption of low-temperature rolling and low-temperature coiling processes in hot rolling increases the internal distortion of the hot-rolled coil compared to conventional high-temperature rolling and high-temperature coiling, reducing the difficulty of normalizing and enabling low-temperature, high-speed production in the normalizing process. Furthermore, increasing the thickness of the hot-rolled coil from the conventional 2.0-2.5 mm to 3.00±0.25 mm improves the production speed of the normalizing process and reduces overall production costs. In the continuous pickling cold rolling process, low-temperature rolling and low-temperature coiling processes are used for hot rolling, which makes it easier to remove oxide scale from the steel sheet surface in the continuous pickling cold rolling process compared to conventional technologies. This reduces the difficulty of pickling in the continuous pickling cold rolling process, improving the surface quality and production speed of the product. In addition, by increasing the thickness of the hot-rolled coil from the conventional 2.0-2.5 mm to 3.00±0.25 mm, the production speed of the continuous pickling cold rolling process is improved, and the production costs of the continuous pickling cold rolling process are reduced overall.In the annealing process, the hot rolling process and the normalizing process are combined, so that the structure of the obtained steel coil is uniform from the front end to the middle and rear end, which makes it possible to produce at a constant speed and low temperature in the annealing process, thereby reducing the difficulty of production, improving production efficiency, and further reducing production costs. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a metallographic photograph obtained by detecting the metallographic structure of a hot-rolled coil in Comparative Example 1. [Figure 2] 1 is a metallographic photograph obtained by detecting the metallographic structure of a hot-rolled coil in Comparative Example 2. [Figure 3] 1 is a metallographic photograph obtained by detecting the metallographic structure of a hot-rolled coil in Comparative Example 3. [Figure 4] 1 is a metallographic photograph obtained by detecting the metallographic structure of the hot-rolled coil in Example 1. [Figure 5] 1 is a metallographic photograph obtained by detecting the metallographic structure of the hot-rolled coil in Example 2. [Figure 6] 1 is a metallographic photograph obtained by detecting the metallographic structure of a hot-rolled coil after a normalizing process in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0022] One embodiment of the present invention provides a non-oriented silicon steel and a method for producing the non-oriented silicon steel. The chemical components of the non-oriented silicon steel include a Si content of 0.8-1.1% by mass and a Mn content of 0.2-0.4% by mass. The non-oriented silicon steel is produced by the following steps: steelmaking, slab casting, hot rolling, normalizing, continuous pickling and cold rolling, finish annealing, cooling, painting, and finishing. The production method includes the following steps, which are performed in order: steelmaking, slab casting, hot rolling, normalizing, continuous pickling and cold rolling, finish annealing, cooling, painting, and finishing. The production method is described in detail below.

[0023] In step 1), slabs are produced by steelmaking with a Si mass percentage of 0.8 to 1.1% and a Mn mass percentage of 0.2 to 0.4% among the chemical components, without adding Sn and Sb during steelmaking.

[0024] Step 1 is the steelmaking process and slab casting process.

[0025] The steelmaking process may include processes such as hot metal desulfurization, converter smelting, and RH refining, which are performed in sequence, and can be carried out using conventional process means, so detailed descriptions are omitted here. Here, steel is made with a chemical composition of 0.8-1.1% by mass of Si and 0.2-0.4% by mass of Mn, and Sn and Sb are not added during steelmaking. Accordingly, the chemical compositions of the resulting slab and the final non-oriented silicon steel product are 0.8-1.1% by mass of Si and 0.2-0.4% by mass of Mn, and do not contain Sn or Sb.

[0026] In one embodiment, the chemical compositions of the obtained slab and the finally obtained finished non-oriented silicon steel product include, in mass percent, C≦0.004%, S≦0.004%, Si: 0.8-1.1%, Mn: 0.2-0.4%, P≦0.03%, Nb≦0.004%, V≦0.006%, Ti≦0.005%, Cr≦0.03%, Ni≦0.03%, Cu≦0.03%, N≦0.004%, Al: 0.15-0.30%, and the remainder being Fe and unavoidable impurities. Alternatively, in another embodiment, the chemical compositions of the obtained slab and the finally obtained finished non-oriented silicon steel product include, in mass percent, C≦0.004%, S≦0.004%, Si: 0.8 to 1.1%, Mn: 0.2 to 0.4%, P≦0.03%, Nb≦0.004%, V≦0.006%, Ti≦0.005%, Cr≦0.03%, Ni≦0.03%, Cu≦0.03%, N≦0.004%, Al≦0.02%, and the balance being Fe and unavoidable impurities.

[0027] Preferably, the slab obtained in step 1 has a thickness of ≧200 mm and a length of 10 to 11 m.

[0028] In step 2), the slab obtained in step 1 is heated to 1060 to 1120°C and held for 150 minutes or more, and then rolled into an intermediate slab with a thickness of 40 to 45 mm. The intermediate slab is then finish-rolled and coiled to obtain a hot-rolled coil with a thickness of 3.00±0.25 mm.

[0029] Step 2 is a hot rolling process. Here, the rolling start temperature of the finish rolling is A r1 = 872°C + 1000 * (11 * [Si] - 14 * [Mn] + 21 * [Al]), where [Si], [Mn], and [Al] are the mass percentages of Si, Mn, and Al, respectively, in the slab obtained in step 1. That is, based on the mass percentages of Si, Mn, and Al, [Si], [Mn], and [Al], in the slab obtained in step 1, A r1 = 872 ° C + 1000 * (11 * [Si] - 14 * [Mn] + 21 * [Al]) is calculated, and in step 2, the rolling start temperature of the finish rolling is A r1 The rolling end temperature of the finish rolling is controlled to 820°C or less, and the coiling temperature is controlled to 560°C or less.

[0030] As described above, in this embodiment, the hot rolling process employs a low-temperature rolling and low-temperature coiling process, and all passes of the finish rolling are performed in the ferrite region, with the final rolling pass of the finish rolling being performed in the low-temperature ferrite region. Therefore, there is no γ / α phase change during the finish rolling, and the structure of the obtained hot-rolled coil is a single-phase structure of fully deformed ferrite. Based on this structure, it is possible to ensure structural uniformity even when the heat dissipation rate of the hot-rolled coil is not the same from the front end to the middle and then to the rear end. Furthermore, this lays the foundation for subsequently obtaining a finished non-oriented silicon steel product with uniform magnetic properties throughout the coil.

[0031] In addition, in this embodiment, the hot rolling process employs a low-temperature rolling and low-temperature coiling process, which reduces the requirement for the heating furnace temperature and allows heating to be performed at a low temperature, reducing the dissolution of precipitates from the slab and contributing to the growth of the textured crystal grains. This also ensures excellent magnetic properties of the subsequently obtained non-oriented silicon steel product, and reduces production costs compared to conventional hot rolling processes.

[0032] In step 3), the hot-rolled coil obtained in step 2 is subjected to normalization, continuous pickling, and cold rolling in order to obtain a hard cold-rolled coil having a thickness of 0.500±0.005 mm. The normalization temperature here is 850 to 900°C.

[0033] Step 3 is a normalizing step and a continuous pickling and cold rolling step.

[0034] Typically, the normalizing process is applied to the production of high-grade non-oriented silicon steel, which follows the process path of steelmaking, slab casting, hot rolling, normalizing, continuous pickling, cold rolling, annealing, painting, and finishing. However, adding a normalizing process to the conventional production method of medium- to low-grade non-oriented silicon steel, as in the case of high-grade non-oriented silicon steel, can improve the problem of inconsistent magnetic properties from the front end to the center and rear end to a certain extent, but it also results in abnormal grain growth on the surface of the hot-rolled coil compared to the interior, resulting in poor color evaluation of the steel coil surface after continuous pickling and cold rolling, and increased production costs. In contrast, the production method of this embodiment employs low-temperature rolling and low-temperature coiling processes in the hot rolling process in Step 2, thereby producing a hot-rolled coil exhibiting a fully deformed ferrite structure. This lays the foundation for the normalizing process, thereby avoiding the problem of abnormal grain growth on the surface of the steel coil compared to the interior during the conventional normalizing process. This means that the crystal grains grow uniformly throughout the steel coil after normalizing. Furthermore, the normalizing process also ensures excellent magnetic properties of the final non-oriented silicon steel. Furthermore, the fully deformed ferrite structure of the hot-rolled coil has extremely high storage energy, which reduces the difficulty of normalizing. This allows for low-temperature, high-speed production during the normalizing process, thereby avoiding a significant increase in production costs due to the addition of the normalizing process. Furthermore, the smooth execution of the normalizing process can significantly improve the magnetic properties of the final non-oriented silicon steel. Based on this premise, the present invention reduces the Si content, which improves magnetic properties, from the conventional 1.4-1.7% to 0.8-1.1%, eliminates the addition of the precious metals Sn and Sb, and reduces the addition of Mn, thereby achieving the same magnetic properties as the conventional chemical composition and reducing alloy costs.

[0035] More preferably, in the normalizing step, normalizing is carried out for 120 to 150 seconds in a pure dry N2 atmosphere. Also, preferably, in the normalizing step, the normalizing temperature fluctuation is controlled to ±10°C, i.e., the normalizing temperature is controlled within a fluctuation range of ±10°C, so that the difference between the maximum and minimum temperatures during normalizing does not exceed 20°C, and the normalizing step is carried out at a constant speed, i.e., the roll speed when normalizing the front, middle and rear ends of the steel coil is constant.

[0036] In this embodiment, the low-temperature heating, low-temperature rolling, and low-temperature coiling processes used in the hot rolling process of Step 2 reduce oxide scale on the surface of the hot-rolled coil, thereby reducing scale loss. Furthermore, compared with conventional techniques, the oxide scale on the surface of the steel sheet is easier to remove in the continuous pickling cold rolling process of Step 3, thereby reducing the difficulty of pickling in the continuous pickling cold rolling process and improving the surface quality and production rate of the product. Furthermore, as described above, the low-temperature heating in the hot rolling process of Step 2 contributes to the growth of the textured crystal grains. The addition of the normalizing process allows the thickness of the hot-rolled coil in Step 2 to be increased from the conventional 2.0 to 2.5 mm to 3.00±0.25 mm. The thicker the hot-rolled coil, the greater the amount of steel processed by pickling in the continuous pickling cold rolling process of Step 3 at the same roll speed. This further increases the production rate of the continuous pickling cold rolling process, thereby reducing the overall production cost of the continuous pickling cold rolling process.

[0037] Furthermore, as mentioned above, by combining low-temperature heating and normalizing in the hot rolling process, the thickness of the hot rolled coil can be increased from the conventional 2.0 to 2.5 mm to 3.00±0.25 mm. Increasing the thickness of the hot rolled coil conversely reduces the difficulty of hot rolling in the hot rolling process and improves the production efficiency of the hot rolling process.

[0038] More preferably, in the continuous pickling and cold rolling process of step 3, first, three-stage pickling with HCl is carried out, followed by rinsing, drying and cold rolling to obtain a hard cold-rolled coil.

[0039] In step 4), the hard cold-rolled coil obtained in step 3 is finish-annealed at a constant speed in a mixed atmosphere of H2+N2 using a continuous annealing furnace, the finish-annealing temperature is 820-880°C, and the annealed steel strip is cooled, painted and refined to obtain a finished non-oriented silicon steel product.

[0040] Step 4 includes a finish annealing process, a cooling process, a painting process and a finishing process.

[0041] As can be seen from the above description, in this embodiment, based on the hot rolling process in Step 2 and the normalizing process in Step 3, the structure of the obtained steel coil is uniform from the front end to the middle and to the rear end. Furthermore, in Step 4, the finish annealing process employs low-temperature, constant-speed production. After the normal cooling, coating, and finishing processes, a non-oriented silicon steel having a thickness of 0.500±0.005 mm can be obtained which has excellent magnetic properties and uniform magnetic properties from the front end to the middle and to the rear end. This eliminates the need to employ annealing production with deceleration at the front end and rear end as in the prior art, thereby reducing the difficulty of production and improving production efficiency.

[0042] Here, constant speed production in the finish annealing process means that production is carried out at a constant speed in the finish annealing process, and the roll speed is constant when annealing the front end, center, and rear end of the steel coil.

[0043] More preferably, in the finish annealing step of step 4, the annealing time is 50±5 seconds, the finish annealing temperature fluctuation is ±10°C, and the difference between the maximum and minimum temperatures during the finish annealing does not exceed 20°C.

[0044] More preferably, in the cooling process of step 4, the steel strip after finish annealing is cooled in three stages, which effectively controls the residual stress of the steel strip to 50 MPa or less, thereby contributing to the control of the sheet shape.

[0045] In one embodiment of the present invention, the non-oriented silicon steel is produced by the above production method, and has a thickness of 0.500±0.005 mm. As described above, its chemical composition, in mass percent, includes C≦0.004%, S≦0.004%, Si: 0.8-1.1%, Mn: 0.2-0.4%, P≦0.03%, Nb≦0.004%, V≦0.006%, Ti≦0.005%, Cr≦0.03%, Ni≦0.03%, Cu≦0.03%, N≦0.004%, Al: 0.15-0.30% or Al≦0.02%, and the balance being Fe and unavoidable impurities.

[0046] Iron loss P of the non-oriented silicon steel 1.5 / 50 is 4.2W / kg or less, and the magnetic flux density B 5000 ≧1.72T, which has excellent magnetic properties and is almost the same as that of conventional non-oriented silicon steel with a Si content of 1.4-1.7%, and can meet the demand for medium and low-grade non-oriented silicon steel in small and medium-sized electrical appliances. The magnetic properties of the entire coil are uniform, and the iron loss P 1.5 / 50 Fluctuation is less than 0.2W / kg, and magnetic flux density B 5000 The variation is 0.02T or less, that is, the iron loss P from the tip of the steel coil of the finished non-oriented silicon steel through the center to the rear end 1.5 / 50 The difference between the maximum and minimum values of is 0.2W / kg or less, and the B 5000 The difference between the maximum and minimum values is less than 0.02T.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] (1) The non-oriented silicon steel finished product manufactured by the above production method has excellent magnetic properties, which can meet the demand for medium and low-grade non-oriented silicon steel for small and medium-sized electrical appliances. The magnetic properties of the entire coil are uniform, and the iron loss P from the tip to the center to the rear end is 1.5 / 50 and magnetic flux density B 5000 This reduces the fluctuation in the magnetic properties of the finished non-oriented silicon steel, improving the stability of the magnetic properties.

[0049] (2) By adopting low-temperature rolling and low-temperature coiling processes in the hot rolling process, hot-rolled coils exhibiting a fully deformed ferrite structure can be obtained, and the additional normalizing process ensures that the final non-oriented silicon steel has excellent magnetic properties. At the same time, under conditions where production is carried out at a constant speed in the finish annealing process, the problem of non-oriented silicon steel products having non-uniform magnetic properties from the front end to the center and rear end, which occurs in conventional technology, is resolved, and the situation in which the surface crystal grains of the steel coil grow abnormally compared to the interior during the normalizing process is avoided.

[0050] (3) Despite the addition of the normalizing process, there is no increase in production costs, ensuring low production costs and offering extremely high economic value. Specifically, the combination of hot rolling and normalizing processes fully utilizes the effects of the normalizing process on the structure of the hot-rolled non-oriented silicon steel and the magnetic properties of the finished product. This reduces production costs for the steelmaking, hot rolling, continuous pickling, cold rolling, normalizing, and annealing processes, without increasing the overall cost of the process. In terms of chemical composition in the steelmaking process, the content of Si, which improves magnetic properties, has been reduced from the previous 1.4-1.7% to 0.8-1.1%, and the addition of precious metals Sn and Sb to improve magnetic properties has been eliminated, while the addition of Mn has been reduced. This reduces the cost of the steelmaking alloy while maintaining the same magnetic properties as the previous chemical composition. The adoption of low-temperature rolling and low-temperature coiling processes in the hot rolling process reduces the furnace temperature requirements and allows heating at a lower temperature, thereby reducing energy consumption and production costs compared to conventional hot rolling processes. This also reduces the oxide scale on the hot-rolled coil surface, reducing scale loss and improving yield and production costs. In addition, increasing the thickness of the hot-rolled coil from the conventional 2.0-2.5 mm to 3.00±0.25 mm improves the production speed of the hot-rolling process and reduces overall production costs. In the normalizing process, the adoption of low-temperature rolling and low-temperature coiling processes in hot rolling increases the internal distortion of the hot-rolled coil compared to conventional high-temperature rolling and high-temperature coiling, reducing the difficulty of normalizing and enabling low-temperature, high-speed production in the normalizing process. Furthermore, increasing the thickness of the hot-rolled coil from the conventional 2.0-2.5 mm to 3.00±0.25 mm improves the production speed of the normalizing process and reduces overall production costs. In the continuous pickling cold rolling process, low-temperature rolling and low-temperature coiling processes are used for hot rolling, which makes it easier to remove oxide scale from the steel sheet surface in the continuous pickling cold rolling process compared to conventional technologies. This reduces the difficulty of pickling in the continuous pickling cold rolling process, improving the surface quality and production speed of the product. In addition, by increasing the thickness of the hot-rolled coil from the conventional 2.0-2.5 mm to 3.00±0.25 mm, the production speed of the continuous pickling cold rolling process is improved, and the production costs of the continuous pickling cold rolling process are reduced overall.In the annealing process, the hot rolling process and the normalizing process are combined, so that the structure of the obtained steel coil is uniform from the front end to the middle and rear end, which makes it possible to produce at a constant speed and low temperature in the annealing process, thereby reducing the difficulty of production, improving production efficiency, and further reducing production costs.

[0051] The detailed descriptions listed above are merely specific descriptions of the possible embodiments of the present invention, and are not intended to limit the protection scope of the present invention; any equivalent embodiments or modifications that do not deviate from the technical spirit of the present invention shall be included in the protection scope of the present invention.

[0052] The beneficial effects of the present invention will be further explained below with three comparative examples and two examples. Of course, these two examples are only a part of the many variations included in the present invention, and are not all of them. The three comparative examples and two examples each provide a non-oriented silicon steel. The production methods thereof are specifically as follows:

[0053] Step 1) Steelmaking was then carried out, followed by the production of slabs, whose chemical composition in mass percent is shown in Table 1, whose thickness is also shown in Table 1, and whose length is 10 to 11 m.

[0054] [Table 1] JPEG0007719888000001.jpg50166

[0055] Step 2) The slab obtained in step 1 was heated and then rolled into an intermediate slab, which was then finish-rolled and coiled to obtain a hot-rolled coil. In Examples 1 and 2, the mass percentages of Si, Mn, and Al in the slab obtained in step 1 were calculated based on the mass percentages [Si], [Mn], and [Al] of Si, Mn, and Al. r1 = 872 ° C + 1000 * (11 * [Si] - 14 * [Mn] + 21 * [Al]) is calculated, and in step 2, the rolling start temperature of the finish rolling is A r1In order to obtain a fully deformed structure, the rolling end temperature of the finish rolling was controlled to 820°C or less, and the coiling temperature was controlled to 560°C or less. In contrast, in Comparative Examples 1 to 3, a normal high-temperature final rolling and high-temperature coiling process was adopted in order to obtain as much recrystallized structure as possible.

[0056] The heating temperature, holding time, intermediate slab thickness, finish rolling start temperature, finish rolling end temperature, coiling temperature, and hot-rolled coil thickness for Comparative Examples 1 to 3 and Examples 1 and 2 are as shown in Table 2.

[0057] [Table 2] JPEG0007719888000002.jpg57166

[0058] Here, metallographic microstructure detection was performed on the hot-rolled coils obtained in Comparative Examples 1 to 3 and Examples 1 and 2, respectively, and the detection results obtained are as shown in Figures 1 to 5. As can be seen from the figures, the structures of Comparative Examples 1 to 3 are all composite structures of deformed ferrite and equiaxed ferrite, while the structures of Examples 1 and 2 are all fully deformed ferrite structures and do not contain equiaxed ferrite structures.

[0059] Step 3) The hot-rolled coils obtained in Comparative Example 1 and Comparative Example 3 in Step 2 were directly subjected to continuous pickling and cold rolling to obtain hard cold-rolled coils with a thickness of 0.500±0.005 mm. The hot-rolled coils obtained in Comparative Example 2 and Examples 1 and 2 in Step 2 were then normalized and continuously pickled and cold-rolled to obtain hard cold-rolled coils with a thickness of 0.500±0.005 mm. Here, normalizing was performed in a pure dry N2 atmosphere, and the normalizing temperature was 850 to 900°C.

[0060] Specifically, the main parameters of each comparative example and example, such as normalizing temperature, normalizing time, normalizing temperature fluctuation, pickling rate, hard cold rolled coil thickness and raw material thickness, were as shown in Table 3.

[0061] [Table 3] JPEG0007719888000003.jpg49166

[0062] Here, metallographic microstructures were detected for the hot-rolled coils obtained after the normalizing process in Comparative Example 2 and Examples 1 and 2. The detection results for Comparative Example 2 shown in FIG. 6 show that abnormal grain growth occurred on the surface of the hot-rolled coil after the normalizing process in Comparative Example 2, whereas the structure of the hot-rolled coils obtained after the normalizing process in Examples 1 and 2 was a completely equiaxed ferrite structure and was uniform.

[0063] Furthermore, the surface quality of the hard cold-rolled coils obtained after pickling was good in Comparative Examples 1 to 3 and Examples 1 and 2. As can be seen from this, the thickness of the hot-rolled coils before continuous pickling and cold rolling in Examples 1 and 2, 3.00 mm, is higher than the thickness of 2.50 mm in Comparative Examples 1 to 3, and therefore the actual production efficiency of Examples 1 and 2 is high.

[0064] Step 4) The hard cold-rolled coil obtained in step 3 was finish-annealed in a continuous annealing furnace in a mixed atmosphere of H2 and N2. During finish-annealing, Comparative Example 2 and Examples 1 and 2 were produced at a constant speed throughout the entire procedure, while Comparative Examples 1 and 3 employed production with reduced speed at the front and rear ends to minimize the difference in speed from the front end through the center to the rear end. Here, the annealing temperature fluctuation was ±10°C, i.e., the difference between the maximum and minimum temperatures during finish annealing did not exceed 20°C.

[0065] After annealing, the steel strip is cooled, painted, and refined to obtain the finished non-oriented silicon steel product. In the cooling process, the steel strip after finish annealing is cooled in three stages, which effectively controls the residual stress of the steel strip to 50 MPa or less, contributing to the control of the plate shape.

[0066] Here, the finish annealing temperature, annealing time, annealing speed, annealing time from the front end to the rear end, and annealing speed from the front end to the rear end were as shown in Table 4.

[0067] [Table 4] JPEG0007719888000004.jpg51166

[0068] When the non-oriented silicon steels obtained in Comparative Examples 1 to 3 and Examples 1 and 2 were inspected, the magnetic properties and surface evaluation results were as shown in Table 5.

[0069] [Table 5] JPEG0007719888000005.jpg68166

[0070] As can be seen from Table 5, in Comparative Examples 1 and 3, a normalizing step was not performed, and production was performed by reducing the roll speed at the front and rear end portions during annealing, but the difference in magnetic properties between the front and rear end portions and the center portion could not be completely eliminated. In Comparative Example 2 and Examples 1 and 2, a normalizing step was performed, and production was performed at a constant speed throughout the annealing process, and the difference in magnetic properties between the front and rear end portions and the center portion was small. However, in Comparative Example 2, abnormal crystal grain growth occurred on the surface during normalizing, so the surface quality of the finished product was determined to be poor.

[0071] From the perspective of the entire production process, in Examples 1 and 2, the contents of Si and Mn elements are both significantly lower than in Comparative Example 3, and no Sn is added during steelmaking (the Sn contained in the finished product is inevitably introduced into the molten iron or other alloys). In other words, the cost of steelmaking alloys is reduced, and the increased thickness of the hot-rolled coils improves the speed of hot rolling, normalizing, continuous pickling, and cold rolling, reducing production costs. The annealing process is carried out at a constant speed, improving annealing production efficiency and reducing costs. Thus, on the premise that the overall alloy cost and production cost are low, the resulting non-oriented silicon steel finished product has low iron loss, small variation in iron loss from the front end to the center through to the rear end, and a high magnetic flux density B 5000 The magnetic flux density B from the tip to the center and back end is significantly improved. 5000 The fluctuation is small.

[0072] In summary, as can be seen from Examples 1 and 2 above, when non-oriented silicon steel is produced using one embodiment of the present invention, production efficiency is high and costs are low, and the magnetic properties of the resulting non-oriented silicon steel are higher than those of conventional non-oriented silicon steel with the same Si content (for example, the magnetic properties of the non-oriented silicon steels of Examples 1 and 2 with Si contents of 0.94% and 1.05% and no Sn are higher than the magnetic properties of the non-oriented silicon steel of Comparative Example 3 according to the prior art with a Si content of 1.54% and 0.025% Sn), and annealing production is performed at a constant speed, resulting in high uniformity of magnetic properties from the front end to the center and rear end.

Claims

1. A method for producing a non-oriented silicon steel sheet having an iron loss P1.5 / 50 of 4.2 W / kg or less, an iron loss P1.5 / 50 variation of 0.2 W / kg or less from the front end through the center to the rear end, a magnetic flux density B5000 of 1.72 T or more, and an magnetic flux density B5000 variation of 0.02 T or less from the front end through the center to the rear end, 1) manufacturing steel without adding Sn and Sb to produce a slab, the chemical composition of the slab being, in mass percent, C≦0.004%, S≦0.004%, Si: 0.8-1.1%, Mn: 0.2-0.4%, P≦0.03%, Nb≦0.004%, V≦0.006%, Ti≦0.005%, Cr≦0.03%, Ni≦0.03%, Cu≦0.03%, N≦0.004%, Al: 0.15-0.30% or Al≦0.02%, and the balance being Fe and unavoidable impurities; 2) A step in which the slab is heated to 1060 to 1120°C and held for 150 minutes or more, and then rolled into an intermediate slab having a thickness of 40 to 45 mm, and the intermediate slab is further subjected to finish rolling and coiling to obtain a hot rolled coil having a thickness of 3.00 ± 0.25 mm, wherein the rolling start temperature of the finish rolling is A ｒ１ = 872°C + 1000 * (11 * [Si] - 14 * [Mn] + 21 * [Al]) or less, where [Si], [Mn], and [Al] are the mass percents of Si, Mn, and Al in the slab, respectively, and the rolling end temperature of the finish rolling is 820°C or less and the coiling temperature is 560°C or less; 3) the hot-rolled coil is subjected to normalizing, continuous pickling, and cold rolling in order to obtain a hard cold-rolled coil having a thickness of 0.500±0.005 mm, wherein the normalizing temperature is 850-900°C; 4) The hard cold rolled coil is annealed in a continuous annealing furnace. ２ +N ２ and finishing annealing the steel strip at a constant speed in a mixed atmosphere of 820 to 880°C at a finishing annealing temperature of 820 to 880°C, and cooling, painting and finishing the annealed steel strip to obtain a non-oriented silicon steel sheet.

2. In step 3, pure dry N ２ 2. The method for producing a non-oriented silicon steel sheet according to claim 1, wherein the steel sheet is normalized in an atmosphere for 120 to 150 seconds.

3. 2. The method for producing non-oriented silicon steel sheets according to claim 1, wherein in step 3, the normalizing temperature fluctuation is ±10°C and the production is carried out at a constant speed.

4. 2. The method for producing non-oriented silicon steel sheet according to claim 1, wherein in step 4, the annealing time is 50±5s, the annealing temperature fluctuation is ±10°C, and the production is carried out at a constant speed.

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