Method for producing high-magnetic-induction low-iron-loss non-oriented silicon steel based on thin-strip cast rolling

Abstract

The invention belongs to the technical field of non-oriented electrical steel manufacturing, and relates to a method for producing high-magnetic-induction low-iron-loss non-oriented silicon steel based on thin-strip cast rolling. The low-silicon aluminum-free component design is adopted, the hot-rolled thin substrate with the thickness of 1.60 + / -0.10 mm is directly obtained through thin strip cast rolling, the rolling reduction of hot rolling and cold rolling is greatly reduced, the situation that due to hot rolling and cold rolling with the large compression ratio, alpha and gamma components in a non-oriented silicon steel texture are remarkably improved is avoided, and the magnetic induction of a finished product is improved. The non-oriented silicon steel with the thickness specification of 0.20-0.35 mm is obtained by combining with accurate control of the hot rolling-cold rolling-annealing process, the non-oriented silicon steel has low iron loss and high magnetic induction, the iron loss P1.5 / 50 is 3.3-4.5 W / kg, and the magnetic induction B5000 is 1.78-1.81 T. The double-roller thin-strip continuous casting method is adopted, compared with a conventional process, the processes of hot rolling heating, hot rolling rough rolling, normalizing and the like are omitted, and the double-roller thin-strip continuous casting method is an energy-saving and environment-friendly short-process production technology.

Description

Technical Field

[0001] The invention belongs to the technical field of thin strip casting and rolling, and relates to a method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling. Background Art

[0002] Non-oriented silicon steel, an important soft magnetic material, is primarily used in the manufacture of iron cores for various motors. In 2023, my country's non-oriented silicon steel production reached 12.066 million tons, a year-on-year increase of 1.133 million tons, or 10%, maintaining its position as the world's largest producer and consumer of cold-rolled silicon steel. Of this total, low-silicon non-oriented silicon steel production reached 8.35 million tons, accounting for 69% of all non-oriented silicon steel. Therefore, improving the magnetic properties of low-silicon non-oriented silicon steel can effectively improve motor efficiency, reduce energy consumption, and protect the environment.

[0003] The magnetic properties of non-oriented silicon steel primarily consist of iron loss and magnetic induction. Reducing iron loss can lower motor energy consumption and improve energy conversion efficiency. Improving magnetic induction increases the core's power density, improving operating efficiency. It also reduces the excitation current, lowering copper loss and iron loss, and also helps reduce the core's volume, saving material. The magnetic properties of non-oriented silicon steel directly impact the motor's energy efficiency rating, practicality, and reliability, making improving the steel's magnetic properties particularly important.

[0004] To improve the energy efficiency of motors, non-oriented silicon steel is required to have lower iron loss and higher magnetic induction. The {100} orientation is the most ideal texture type. Because {100}<0vw> is the preferred orientation during the solidification process, it is usually present in large quantities in continuous casting billets. When preparing non-oriented silicon steel through traditional processes, due to the thick billet thickness, hot rolling and cold rolling with a high compression ratio, the α and γ components in the non-oriented silicon steel texture are significantly increased, including {111} <110> 、{111} <112> 、{112} <100> components, forming a stable texture. As a result, the as-cast structure and texture are difficult to retain, and the inheritance of the solidified structure and {100}<0vw> texture is minimized. When preparing non-oriented silicon steel through traditional processes, the structure, texture and magnetic properties of non-oriented silicon steel are regulated by controlling the chemical composition, rolling process and annealing parameters. However, the overall effect is manifested as a reduction in the unfavorable α and γ components in the texture, which cannot change the fact that the solidification texture is severely damaged due to high reduction rate rolling. In fact, traditional processes are essentially unable to achieve the coexistence of high magnetic induction and low iron loss, and can only be adjusted to a limited extent. This is also the fundamental reason why the higher the grade of traditional processes (representing lower iron loss), the lower the magnetic induction. Summary of the Invention

[0005] To address the aforementioned issues with conventional non-oriented silicon steel production processes, the present invention provides a high-magnetic-induction, low-iron-loss non-oriented silicon steel based on thin strip casting and a production method thereof. This process utilizes a low-silicon, aluminum-free design to directly produce a hot-rolled thin base plate through thin strip casting, eliminating the need for continuous casting and heating of the ingot and significantly reducing hot-rolling reduction. Combined with precise control of the hot-rolling, cold-rolling, and annealing processes, the resulting non-oriented silicon steel has a thickness of 0.20-0.35 mm and exhibits both low iron loss and high magnetic induction.

[0006] The present invention specifically adopts the following technical solutions:

[0007] According to a first aspect of the present invention, a method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting is provided, the method comprising the following steps:

[0008] 1) Molten steel smelting

[0009] Molten steel is obtained according to the following composition by mass percentage:

[0010] C: ≤0.0030%, S: ≤0.0030%, Si: 0.40~0.80%, Mn: 0.20~0.60%,

[0011] P: ≤0.03%, Al: ≤0.003%, Nb: ≤0.003%, V: ≤0.003%, Ti: ≤0.003%,

[0012] Cr: ≤0.02%, Ni: ≤0.02%, Cu: ≤0.02%, N: ≤0.0020%, the rest is Fe and unavoidable inclusions;

[0013] 2) Thin strip casting

[0014] The cast strip with a thickness of 2.00±0.20mm is hot rolled in one pass at a reduction rate of 20% to a hot rolled strip with a thickness of 1.60±0.10mm. The range of the final rolling temperature T is controlled as follows:

[0015] T=(Ar1-30)~(Ar1-10)℃,

[0016] Wherein, Ar1 is the γ / α phase transition temperature, unit is °C;

[0017] After hot rolling, the coiling temperature is controlled to be ≥650°C, and the coiling temperature is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 1.60±0.10mm.

[0018] Ar1 is determined according to the following relationship:

[0019] Ar1=872℃+1000(11*[Si]-14*[Mn]+21*[Al]),

[0020] [Si], [Mn], and [Al] in the formula are the mass percentages of Si, Mn, and Al, respectively.

[0021] 3) Acid continuous rolling

[0022] In the pickling continuous rolling process, the pickling adopts hydrochloric acid four-stage pickling, the concentration of the first-stage acid solution is 30-50g / L, the concentration of the second-stage acid solution is 70-90g / L, the concentration of the third-stage acid solution is 100-120g / L, the concentration of the fourth-stage acid solution is 140-160g / L, and the concentration of Fe in the first-stage acid solution is 20-30g / L. 2+ Concentration ≤130g / L, Fe in 2nd grade acid solution 2+ Concentration ≤100g / L, Fe in grade 3 acid solution 2+ Concentration ≤85g / L, Fe in 4-grade acid solution 2+ Concentration ≤ 50g / L, acid solution temperature 75-85℃; rinse water temperature 45-55℃, pickling and rinsing speeds controlled at 150-200mpm, pickling time not less than 45-60s,

[0023] 4) Complete recrystallization annealing + coating + finishing

[0024] The annealing temperature is 850-950°C and the steel plate is kept at this temperature for 60-90 seconds to control the recrystallization of the steel plate. The average recrystallized grain size is 50-80 μm.

[0025] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in the molten steel smelting process, Al and P are not added, and the following control is implemented: P: ≤ 0.03%, Al: ≤ 0.003%.

[0026] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in the molten steel smelting process, 60-80% molten iron + 20-40% scrap steel are used for converter steelmaking, and the converter end point C is 0.020-0.050%, S is ≤0.0025%, and P is ≤0.03%.

[0027] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in the molten steel smelting process, molten steel is obtained according to the following mass percentage components:

[0028] C: ≤0.0030%, S: ≤0.0030%, Si: 0.50~0.70%, Mn: 0.20~0.40%,

[0029] P: ≤0.03%, Al: ≤0.003%, Nb: ≤0.003%, V: ≤0.003%, Ti≤0.003%,

[0030] Cr: ≤0.02%, Ni: ≤0.02%, Cu: ≤0.02%, N: ≤0.0020%, the rest are Fe and inevitable inclusions.

[0031] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in the thin strip casting and rolling process, the starting pouring temperature of the molten steel is 1580-1590°C, the thickness of the cast strip is 2.00±0.20mm, and the continuous casting speed is 60-70m / min.

[0032] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, the acid continuous rolling adopts five-stand continuous rolling.

[0033] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in the acid continuous rolling process, the first pass reduction rate of the continuous rolling is 30-35%, and the last pass reduction rate is not less than 20%.

[0034] According to the second aspect of the present invention, there is provided a non-oriented silicon steel, which is produced by the above method, wherein the thickness of the non-oriented silicon steel is 0.20-0.35 mm, the finished product grain size is 50-80 μm, and the iron loss P is 0. 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.78T.

[0035] According to the non-oriented silicon steel of the present invention, preferably, the thickness of the non-oriented silicon steel is 0.35 mm, the finished grain size is 50-80 μm, and the iron loss P is 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.78T.

[0036] According to the non-oriented silicon steel of the present invention, preferably, the thickness of the non-oriented silicon steel is 0.30 mm, the finished grain size is 50-80 μm, and the iron loss P is 1.5 / 50 ≤4.2W / kg, magnetic induction B 5000 ≥1.78T.

[0037] According to the non-oriented silicon steel of the present invention, preferably, the thickness of the non-oriented silicon steel is 0.25 mm, the finished grain size is 50-80 μm, and the iron loss P is 1.5 / 50 ≤3.9W / kg, magnetic induction B 5000 ≥1.78T.

[0038] According to the non-oriented silicon steel of the present invention, preferably, the thickness of the non-oriented silicon steel is 0.20 mm, the finished grain size is 50-80 μm, and the iron loss P is 1.5 / 50 ≤3.5W / kg, magnetic induction B 5000 ≥1.78T.

[0039] According to a third aspect of the present invention, there is provided a method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling, comprising the following steps:

[0040] (1) Molten steel smelting:

[0041] Use 60-80% molten iron + 20-40% scrap steel for converter steelmaking.

[0042] Converter end point C: 0.020~0.050%, S≤0.0025%, P≤0.03%;

[0043] Then, after vacuum smelting and alloying, molten steel with qualified composition is obtained.

[0044] The percentage by mass is:

[0045] C≤0.0030%, S≤0.0030%, Si: 0.40~0.80%, Mn: 0.20~0.60%,

[0046] P≤0.03%, Al: ≤0.003%, Nb≤0.003%, V≤0.003%, Ti≤0.003%,

[0047] Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, the rest is Fe and unavoidable inclusions;

[0048] (2) Strip casting:

[0049] The twin-roll casting process is used for continuous casting. The starting pouring temperature of the molten steel is controlled at 1580-1590°C. The molten steel is poured through a tundish into a molten pool consisting of rotating steel rolls and side sealing plates. The molten steel rapidly solidifies and forms after contacting the crystallization roll surface of the steel rolls, resulting in a cast strip with a thickness of 2.00±0.20mm. The continuous casting speed is 60-70m / min.

[0050] The cast strip enters the rolling mill through the hot box under the protection of inert gas and is hot rolled into a hot-rolled thin strip with a thickness of 1.60±0.10mm at a reduction rate of 20% in one pass. The final rolling temperature is controlled at T:

[0051] T = (Ar1-30) ~ (Ar1-10) ° C, where Ar1 is the γ / α phase transition temperature, unit: ° C;

[0052] After hot rolling, the coiling temperature is controlled to be ≥650°C, and the coiling temperature is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 1.60±0.10mm.

[0053] The calculation formula of Ar1 is:

[0054] Ar1=872℃+1000(11*[Si]-14*[Mn]+21*[Al]),

[0055] [Si], [Mn], and [Al] in the formula are the mass percentages of Si, Mn, and Al, respectively.

[0056] (3) Acid continuous rolling

[0057] The hot rolled coil obtained by strip casting is pickled and then rolled in five stands to obtain a chilled coil with a thickness of 0.20 to 0.35 mm.

[0058] Use hydrochloric acid four-stage pickling, the concentration of the first-level acid solution is 30-50g / L, the concentration of the second-level acid solution is 70-90g / L, the concentration of the third-level acid solution is 100-120g / L, the concentration of the fourth-level acid solution is 140-160g / L, and the Fe content in the first-level acid solution is 20-30g / L. 2+ Concentration ≤130g / L, Fe in 2nd grade acid solution 2+ Concentration ≤100g / L, Fe in grade 3 acid solution 2+ Concentration ≤85g / L, Fe in 4-grade acid solution 2+ Concentration ≤ 50g / L, acid solution temperature 75-85℃; rinse water temperature 45-55℃, pickling and rinsing speeds controlled at 150-200mpm, pickling time not less than 45-60s; control the first pass reduction rate of continuous rolling to 30-35%, and the last pass reduction rate not less than 20%,

[0059] (4) Complete recrystallization annealing + coating + finishing

[0060] The chilled coil is subjected to complete recrystallization annealing in a 25% H2+75% N2 atmosphere at a temperature of 850-950°C and maintained at this temperature for 60-90 seconds to control the steel plate to complete full recrystallization and an average recrystallized grain size of 50-80 μm. The annealed steel strip is cooled, coated and finished to obtain non-oriented silicon steel.

[0061] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in step 1), the qualified molten steel composition is as follows by mass percentage:

[0062] C≤0.0030%, S≤0.0030%, Si: 0.50~0.70%, Mn: 0.20~0.40%,

[0063] P≤0.03%, Al: ≤0.003%, Nb≤0.003%, V≤0.003%, Ti≤0.003%,

[0064] Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, the rest is Fe and inevitable inclusions.

[0065] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in step 2), the thickness of the cast strip is 1.8-2.0 mm, and the continuous casting speed is 65-70 m / min.

[0066] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in step 3), the first pass reduction rate of the acid continuous rolling is 33%, and the last pass reduction rate is 25%.

[0067] According to the method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling of the present invention, preferably, in step 4), the annealing temperature is 900-950° C. and the holding time is 80-90 seconds.

[0068] The role of each element in the present invention is analyzed as follows:

[0069] C, S, N: C, S, and N are harmful elements in non-oriented silicon steel, which lead to increased iron loss and reduced magnetic induction. In order to meet the requirements of low iron loss and high magnetic induction of the non-oriented silicon steel based on thin strip casting, C≤0.0030%, S≤0.0030%, and N≤0.0020%;

[0070] Si, Al, Mn: Si and Al can increase the resistivity of the steel plate and thus reduce the iron loss of non-oriented silicon steel; Mn forms MnS with S, which affects grain growth but avoids the formation of low-melting-point FeS at the grain boundaries to avoid hot brittleness. Therefore, when preparing non-oriented silicon steel in the traditional process, the Si+Al+Mn design is adopted. However, in the thin strip casting and rolling process of the present invention, the Al2O3 inclusions formed by Al during the steelmaking process will gradually accumulate and form nodules on the side sealing plates of the molten pool. Once the nodules are washed down by the steel flow and enter the casting rollers, it will cause the continuous casting strip to break. Therefore, the present invention strictly controls Al≤0.003%; Si can reduce the iron loss of non-oriented silicon steel, but it will also reduce the magnetic induction. Taking into account that the finished product has both low iron loss and high magnetic induction, as well as rollability, the Si content is controlled between 0.40 and 0.80%, and the Mn content is controlled between 0.20 and 0.60%.

[0071] Nb, V, Ti, Cr, Ni, Cu: Nb, V, Ti, Cr, Ni, and Cu in non-oriented silicon steel will increase iron loss and reduce magnetic induction. Therefore, control Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, and Cu≤0.02%;

[0072] Phosphorus (P) is a residual element that, in conventional processes, can segregate in the core of the ingot, affecting rollability and microstructure uniformity in the finished product. Therefore, P is typically controlled to 0.015% or less, significantly increasing steelmaking costs. However, in the thin strip casting and rolling process of the present invention, P does not segregate due to the high cooling rate of the strip at 1000°C / s. Therefore, the present invention relaxes the P control standard to 0.03% or less, reducing steelmaking costs.

[0073] The core of the present invention is to achieve low silicon content non-oriented silicon steel while meeting the requirements of low iron loss and high magnetic induction through the design of casting and rolling process, acid continuous rolling and annealing process, with the help of means such as organization, texture and resistivity control.

[0074] Beneficial technical effects

[0075] Compared with the prior art, the technical concept and corresponding technical solutions of the present invention can at least achieve the following beneficial technical effects:

[0076] (1) The molten steel is directly cast into a strip with a thickness of 2.00±0.20 mm by two rotating steel rollers. Compared with the conventional process using 220 mm ingot, the subsequent hot rolling and cold rolling reduction is greatly reduced, and the high reduction ratio hot rolling + cold rolling is avoided, which causes a significant increase in the α and γ components in the non-oriented silicon steel texture, including {111} <110> 、{111} <112> 、{112} <100> components; thereby increasing the proportion of the ideal {100}<0vw> texture and improving the magnetic induction of the finished product.

[0077] (2) Hot-rolled coils with a thickness of 1.60±0.10 mm are directly obtained by thin strip casting. Compared with the traditional process of rolling low-silicon non-oriented silicon steel from hot-rolled coils with a thickness of 2.50-2.75 mm to cold-rolled coils with a thickness of 0.50 mm, cold-rolled coils with a thickness of 0.20-0.35 mm can be directly obtained by five-stand continuous rolling, creating conditions for significantly reducing iron loss in the finished product.

[0078] (3) By precisely controlling the hot rolling reduction rate and final rolling temperature, the reduction rate is 20%, and the final rolling temperature T = (Ar1-30) ~ (Ar1-10) ° C, hot rolling is completed in the high-temperature ferrite region. Grain refinement caused by post-rolling phase transformation is avoided. At the same time, with the help of high-temperature coiling and annealing processes, the finished steel plate is controlled to undergo complete recrystallization, with a grain size of 50 to 80 μm; the finished non-oriented silicon steel product with a thickness of 0.20 to 0.35 mm has an iron loss P 1.5 / 50 3.3~4.5W / kg, magnetic induction B 5000 It is 1.78~1.81T.

[0079] (4) The present invention adopts a twin-roller thin strip continuous casting method, which omits hot rolling heating, hot rolling rough rolling, normalizing and other processes compared with conventional processes. It is an energy-saving and environmentally friendly short-process production technology. DETAILED DESCRIPTION

[0080] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0081] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0082] The following are embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments that can be obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention.

[0083] The following 16 examples further illustrate the beneficial effects of this embodiment. Of course, these 16 examples are only a part of the many variations of the present invention, not all of them. The 16 examples each provide a high magnetic induction, low iron loss, non-oriented silicon steel based on thin strip casting, and the specific production method thereof is as follows:

[0084] (1) Molten steel smelting: In Examples 1 to 16, molten iron and scrap steel were used for converter steelmaking. The ratio of molten iron to scrap steel, and the mass percentages of C, S, and P at the converter end point in Examples 1 to 16 are shown in Table 1.

[0085] Table 1 The ratio of molten iron to scrap steel in Examples 1 to 16, and the mass percentage of C, S, and P at the converter end point

[0086] Converter steelmaking parameters Molten iron ratio Scrap steel ratio Converter end point C Converter end point S Converter end point P Examples 1 to 4 68％ 32％ 0.035 0.0015 0.022 Examples 5 to 8 62％ 38％ 0.026 0.0023 0.014 Examples 9 to 12 71％ 29％ 0.041 0.0018 0.021 Examples 13 to 16 74％ 26％ 0.044 0.0022 0.016

[0087] Then, after vacuum smelting and alloying, molten steel with qualified composition is obtained. The chemical compositions of Examples 1 to 16 are shown in Table 2 in terms of mass percentage.

[0088] Table 2 Chemical composition of Examples 1 to 16 (in mass percentage)

[0089]

[0090] (2) Strip Casting: In Examples 1-16, the molten steel obtained in Step 1 was continuously cast using a twin-roll casting process. The molten steel was poured through a tundish into a molten pool consisting of rotating steel rolls and side closure plates. The molten steel rapidly solidified and formed upon contact with the crystallization roll surfaces of the steel rolls to produce a cast strip. The cast strip then passed through a hot box under inert gas protection and into a rolling mill, where it was hot-rolled in a single pass into a hot-rolled strip. The corresponding pouring temperature, continuous casting speed, cast strip thickness, reduction ratio, hot-rolled strip thickness, finishing temperature, coiling temperature, and γ / α phase transition temperature Ar1 for Examples 1-16 are shown in Table 3.

[0091] Table 3 Parameters of pouring temperature, continuous casting speed, etc. of Examples 1 to 16

[0092]

[0093] (3) Acid continuous rolling: In Examples 1 to 16, the hot rolled coil obtained by the thin strip casting in step 2 was pickled and five-stand continuous rolling was carried out in sequence to obtain a chilled coil; a four-stage hydrochloric acid pickling was adopted, with the concentration of the first-stage acid solution being 40 g / L, the concentration of the second-stage acid solution being 82 g / L, the concentration of the third-stage acid solution being 115 g / L, and the concentration of the fourth-stage acid solution being 148 g / L. The concentration of Fe in the first-stage acid solution was 1.3 g / L. 2+ Concentration ≤130g / L, Fe in 2nd grade acid solution 2+ Concentration ≤100g / L, Fe in grade 3 acid solution 2+ Concentration ≤85g / L, Fe in 4-grade acid solution 2+ The concentration is ≤50 g / L, the acid solution temperature is 79°C; the rinse water temperature is 51°C, the pickling and rinsing speeds are controlled at 175 mpm, and the pickling time is 50 s. The pickling rolling procedures, chilled coil thickness, first pass reduction rate, and final pass reduction rate of Examples 1 to 16 are shown in Table 4.

[0094] Table 4 Pickling rolling procedures, chilled coil thickness, first pass reduction and final pass reduction of Examples 1 to 16

[0095]

[0096]

[0097] (4) Complete recrystallization annealing + coating + finishing: Examples 1 to 16: The cold-hardened coils of step 3 are subjected to complete recrystallization annealing in a 25% H2 + 75% N2 atmosphere to control the steel sheets to complete full recrystallization; the annealed steel strips are cooled, coated, and finished to obtain non-oriented silicon steel.

[0098] Annealing temperature, holding time, finished product grain size, iron loss and magnetic induction of Examples 1 to 16 are shown in Table 5.

[0099] Table 5 Annealing temperature, holding time, finished product grain size, iron loss and magnetic induction of Examples 1 to 16

[0100]

[0101] It can be seen that the high magnetic induction and low iron loss non-oriented silicon steel produced by the sequential process of molten steel smelting, thin strip casting and rolling, acid continuous rolling, complete recrystallization annealing + coating + finishing has a finished product thickness of 0.20-0.35mm, a finished product grain size of 50-80μm, and an iron loss P 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.78T. Among them, in Examples 1, 5, 9 and 13, the thickness of the finished product is 0.35mm, and the iron loss of the finished product P 1.5 / 50 ≤4.5W / kg, magnetic induction B5000≥1.78T; Examples 2, 6, 10 and 14, the finished product thickness is 0.30mm, the finished product iron loss P 1.5 / 50 ≤4.2W / kg, magnetic induction B 5000 ≥1.78T; Examples 3, 7, 11 and 15, the finished product thickness is 0.25mm, the finished product iron loss P 1.5 / 50 ≤3.9W / kg, magnetic induction B 5000 ≥1.78T; Examples 4, 8, 12 and 16, the finished product thickness is 0.20mm, the finished product iron loss P 1.5 / 50 ≤3.5W / kg, magnetic induction B 5000 ≥1.78T.

[0102] The above description is only a specific embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, they can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting, characterized in that: The method comprises the following steps: 1) Molten steel smelting Molten steel is obtained according to the following composition by mass percentage: C: ≤0.0030%, S: ≤0.0030%, Si: 0.40~0.80%, Mn: 0.20~0.60%, P: ≤0.03%, Al: ≤0.003%, Nb: ≤0.003%, V: ≤0.003%, Ti: ≤0.003%, Cr: ≤0.02%, Ni: ≤0.02%, Cu: ≤0.02%, N: ≤0.0020%, the rest is Fe and unavoidable inclusions; 2) Thin strip casting The cast strip with a thickness of 2.00±0.20mm is hot rolled in one pass at a reduction rate of 20% to a hot rolled strip with a thickness of 1.60±0.10mm. The range of the final rolling temperature T is controlled as follows: T=(Ar1-30)~(Ar1-10)℃, Wherein, Ar1 is the γ / α phase transition temperature, unit is °C; After hot rolling, the coiling temperature is controlled to be ≥650°C, and the coiling temperature is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 1.60±0.10mm. Ar1 is determined according to the following relationship: Ar1=872℃+1000(11*[Si]-14*[Mn]+21*[Al]), [Si], [Mn], and [Al] in the formula are the mass percentages of Si, Mn, and Al, respectively. 3) Acid continuous rolling In the pickling continuous rolling process, the pickling adopts hydrochloric acid four-stage pickling. The concentration of the first-grade acid solution is 30-50 g / L, the concentration of the second-grade acid solution is 70-90 g / L, the concentration of the third-grade acid solution is 100-120 g / L, and the concentration of the fourth-grade acid solution is 140-160 g / L. 2+ Concentration ≤130g / L, Fe in 2nd grade acid solution 2+ Concentration ≤100g / L, Fe in grade 3 acid solution 2+ Concentration ≤85g / L, Fe in 4-grade acid solution 2+ Concentration ≤ 50g / L, acid temperature 75-85℃; rinse water temperature 45-55℃, pickling and rinsing speeds controlled at 150-200mpm, pickling time not less than 45-60s, 4) Complete recrystallization annealing + coating + finishing The annealing temperature is 850-950°C and the steel plate is kept at this temperature for 60-90 seconds to control the recrystallization of the steel plate. The average recrystallized grain size is 50-80 μm.

2. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 1, characterized in that: During the molten steel smelting process, no Al and P are added, and the following conditions are controlled: P: ≤0.03%, Al: ≤0.003%.

3. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 1, characterized in that: The molten steel smelting process uses 60-80% molten iron + 20-40% scrap steel for converter steelmaking, and the converter end point C is 0.020-0.050%, S is ≤0.0025%, and P is ≤0.03%.

4. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 1, characterized in that: The molten steel smelting process obtains molten steel according to the following mass percentage components: C: ≤0.0030%, S: ≤0.0030%, Si: 0.50~0.70%, Mn: 0.20~0.40%, P: ≤0.03%, Al: ≤0.003%, Nb: ≤0.003%, V: ≤0.003%, Ti≤0.003%, Cr: ≤0.02%, Ni: ≤0.02%, Cu: ≤0.02%, N: ≤0.0020%, the rest are Fe and inevitable inclusions.

5. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 1, characterized in that: In the thin strip casting and rolling process, the starting pouring temperature of the molten steel is 1580-1590°C, the thickness of the cast strip is 2.00±0.20mm, and the continuous casting speed is 60-70m / min.

6. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 1, characterized in that: The acid continuous rolling adopts five-stand continuous rolling.

7. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 1, characterized in that: In the acid continuous rolling process, the reduction rate of the first continuous rolling pass is 30-35%, and the reduction rate of the last continuous rolling pass is not less than 20%.

8. A non-oriented silicon steel, characterized in that: The non-oriented silicon steel is produced by the method according to any one of claims 1 to 7, wherein the thickness of the non-oriented silicon steel is 0.20 to 0.35 mm, the finished product grain size is 50 to 80 μm, and the iron loss P is 0. 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.78T.

9. The non-oriented silicon steel according to claim 8, characterized in that: The thickness of the non-oriented silicon steel is 0.35 mm, the finished grain size is 50 to 80 μm, and the iron loss P 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.78T.

10. The non-oriented silicon steel according to claim 8, characterized in that: The thickness of the non-oriented silicon steel is 0.30 mm, the finished grain size is 50 to 80 μm, and the iron loss P 1.5 / 50 ≤4.2W / kg, magnetic induction B 5000 ≥1.78T.

11. The non-oriented silicon steel according to claim 8, characterized in that: The thickness of the non-oriented silicon steel is 0.25 mm, the finished grain size is 50 to 80 μm, and the iron loss P 1.5 / 50 ≤3.9W / kg, magnetic induction B 5000 ≥1.78T.

12. The non-oriented silicon steel according to claim 8, characterized in that: The thickness of the non-oriented silicon steel is 0.20 mm, the finished grain size is 50 to 80 μm, and the iron loss P 1.5 / 50 ≤3.5W / kg, magnetic induction B 5000 ≥1.78T.

13. A method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting, characterized in that: The following steps are involved: (1) Molten steel smelting: Use 60-80% molten iron + 20-40% scrap steel for converter steelmaking. Converter end point C: 0.020~0.050%, S≤0.0025%, P≤0.03%; Then, after vacuum smelting and alloying, molten steel with qualified composition is obtained. The percentage by mass is: C≤0.0030%, S≤0.0030%, Si: 0.40~0.80%, Mn: 0.20~0.60%, P≤0.03%, Al: ≤0.003%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, the rest is Fe and unavoidable inclusions; (2) Strip casting: The twin-roll casting process is used for continuous casting. The starting pouring temperature of the molten steel is controlled at 1580-1590°C. The molten steel is poured through a tundish into a molten pool consisting of rotating steel rolls and side sealing plates. The molten steel rapidly solidifies and forms after contacting the crystallization roll surface of the steel rolls, resulting in a cast strip with a thickness of 2.00±0.20mm. The continuous casting speed is 60-70m / min. The cast strip enters the rolling mill through the hot box under the protection of inert gas and is hot rolled into a hot-rolled thin strip with a thickness of 1.60±0.10mm at a reduction rate of 20% in one pass. The final rolling temperature is controlled at T: T = (Ar1-30) ~ (Ar1-10) ° C, where Ar1 is the γ / α phase transition temperature, unit: ° C; After hot rolling, the coiling temperature is controlled to be ≥650°C, and the coiling temperature is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 1.60±0.10mm. The calculation formula of Ar1 is: Ar1=872℃+1000(11*[Si]-14*[Mn]+21*[Al]), [Si], [Mn], and [Al] in the formula are the mass percentages of Si, Mn, and Al, respectively. (3) Acid continuous rolling The hot rolled coil obtained by strip casting is pickled and then rolled in five stands in sequence to obtain a chilled coil with a thickness of 0.20 to 0.35 mm. Use hydrochloric acid four-stage pickling, the concentration of the first-level acid solution is 30-50g / L, the concentration of the second-level acid solution is 70-90g / L, the concentration of the third-level acid solution is 100-120g / L, the concentration of the fourth-level acid solution is 140-160g / L, and the Fe content in the first-level acid solution is 20-30g / L. 2+ Concentration ≤130g / L, Fe in 2nd grade acid solution 2+ Concentration ≤100g / L, Fe in grade 3 acid solution 2+ Concentration ≤85g / L, Fe in 4-grade acid solution 2+ Concentration ≤ 50g / L, acid solution temperature 75-85℃; rinse water temperature 45-55℃, pickling and rinsing speeds controlled at 150-200mpm, pickling time not less than 45-60s; control the first pass reduction rate of continuous rolling to 30-35%, and the last pass reduction rate not less than 20%, (4) Complete recrystallization annealing + coating + finishing The chilled coil is subjected to complete recrystallization annealing in a 25% H2+75% N2 atmosphere at a temperature of 850-950°C and maintained at this temperature for 60-90 seconds to control the steel plate to complete full recrystallization and an average recrystallized grain size of 50-80 μm. The annealed steel strip is cooled, coated and finished to obtain non-oriented silicon steel.

14. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 13, characterized in that: In step 1), the qualified molten steel composition is as follows by mass percentage: C≤0.0030%, S≤0.0030%, Si: 0.50~0.70%, Mn: 0.20~0.40%, P≤0.03%, Al: ≤0.003%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, the rest is Fe and inevitable inclusions.

15. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 13, characterized in that: In step 2), the thickness of the cast strip is 1.8 to 2.0 mm, and the continuous casting speed is 65 to 70 m / min.

16. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 13, characterized in that: In step 3), the first pass reduction rate of the acid continuous rolling is 33%, and the last pass reduction rate is 25%.

17. The method for producing high magnetic induction and low iron loss non-oriented silicon steel based on thin strip casting and rolling according to claim 13, characterized in that: In step 4), the annealing temperature is 900-950° C., and the holding time is 80-90 seconds.

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