Low-cost production method of high-performance non-oriented electrical steel

Abstract

The invention discloses a low-cost production method of high-performance non-oriented electrical steel. The high-performance non-oriented electrical steel comprises the following main chemical components: less than or equal to 0.002% of C, 1.0-1.7% of Si, 0.20-0.80% of Mn, 0.01-0.10% of P, less than or equal to 0.001% of S, less than or equal to 0.002% of N, less than or equal to 0.001% of Ti, less than or equal to 0.002% of Nb, less than or equal to 0.002% of V, 0.20-1.0% of Als and 0.10-0.20% of Sb. The resistivity is improved through component adjustment, and the eddy-current loss is reduced; segregation elements are added, and the product texture is optimized; complete recrystallization and grain growth in the non-oriented silicon steel hot rolled plate are realized through controlled rolling and controlled cooling; the recrystallization structure and the texture of a finished product plate are optimized through the continuous annealing process, the magnetic performance is improved to be higher than the level of the same kind of normalized materials, and finally efficient material production of the normalizing removing procedure is achieved; the production efficiency is improved, and the resource consumption is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, is suitable for the production of normalized and efficient products of cold-rolled non-oriented electrical steel, and specifically relates to a low-cost production method for high-performance non-oriented electrical steel. Background Art

[0002] The magnetic properties of non-oriented electrical steel come from the addition of silicon and aluminum elements and the control of microstructure. In order to meet the energy-saving needs, silicon and aluminum elements need to be added to increase resistivity and reduce iron loss. However, since silicon and aluminum reduce magnetic induction at the same time, the amount of addition needs to be determined according to the actual use of the product; after the amount of silicon and aluminum is determined, in order to obtain higher magnetic induction and low iron loss, an equiaxed structure with a larger grain size is required. However, under the existing process conditions, the hot rolling process of medium and high-grade non-oriented silicon steel cannot undergo complete dynamic and static recrystallization, and fine grains and a small amount of deformation structure are retained to room temperature, which affects the subsequent performance. In this case, normalization treatment is often carried out to obtain a microstructure with fully grown grains and increase favorable textures.

[0003] In order to achieve better magnetic properties, non-oriented electrical steel usually needs to be normalized to optimize the structure and coarsen the two-phase particles. As a separate process, normalization increases a lot of energy consumption and reduces production efficiency. If the recrystallization and grain growth can be improved during hot rolling, while the resistivity can be increased and the hysteresis loss can be reduced through composition adjustment and process optimization, it is possible to remove the normalization process of medium and high grades while obtaining the expected magnetic properties, thereby achieving energy conservation and emission reduction. Summary of the invention

[0004] In order to overcome the defects of the above-mentioned prior art, the present invention further improves the resistivity and reduces the eddy current loss by adjusting the composition; achieves organizational homogenization by adding segregated elements; and achieves complete recrystallization and grain growth in the hot-rolled non-oriented silicon steel plate through controlled rolling and controlled cooling during the hot rolling process, thereby improving the magnetic performance level.

[0005] In order to achieve the above-mentioned purpose of the invention, the present invention provides a low-cost production method for high-performance non-oriented electrical steel, which achieves the performance requirements of normalized materials after removing the normalizing process through the process optimization design of smelting composition and each production process.

[0006] The chemical composition (wt%) of the high performance non-oriented electrical steel includes C≤0.0020%, Si: 1.0%-1.7%, Mn: 0.20%-0.80%, P: 0.01%-0.10%, S≤0.0010%, N≤0.0020%, Ti≤0.0010%, Nb≤0.0020%, V≤0.0020%, Als: 0.20%-1.00%, Sb: 0.10%-0.20%, and the rest are Fe and unavoidable residual elements.

[0007] Chemical composition is an effective and necessary approach. Carbon: Since the product does not have a normalization process, it is equivalent to reducing a decarburization process, so the refining process needs to be strictly controlled, so the carbon content is below 0.0020%. Silicon: Considering the performance requirements of the finished product, silicon reduces iron loss while also suppressing magnetic induction B 50 At the same time, due to the normalization, if the silicon content is too high, the product will cause ridge defects due to the hereditary nature of the coarse columnar crystal structure. Therefore, the silicon content is set within the range of 1.0% to 1.7%. Manganese: Manganese has the effect of inhibiting the (111) component and promoting the (100) and (110) components. After adding manganese, B 50 Increased and P 15 Reduce. Phosphorus: One of the important functions of phosphorus is to increase resistivity, thereby reducing eddy current losses. In addition, phosphorus has a significant promoting effect on the occurrence of dynamic recrystallization during hot rolling and finishing. Adding phosphorus to this product can partially make up for the lower silicon content while coarsening the pre-cold rolling structure under the condition of normalization process, but adding phosphorus is prone to cold brittleness, so the phosphorus content should not be too high. Aluminum: The effect of improving the magnetic properties of the product is similar to that of silicon, but due to normalization, the content cannot be set too high. In the present invention, its composition range is set to 0.20% to 1.00%. Antimony: Antimony segregates along the grain boundaries to hinder the nucleation of {111} grains at the grain boundaries of the original hot-rolled plate and promote the nucleation of {110} grains near the deformation band in the cold-rolled plate, further improving the texture. However, as a segregating element, when the antimony content is too high, it hinders grain growth, the grains of the hot-rolled plate and the finished plate are small, and the iron loss increases. Sulfur, nitrogen, titanium, niobium, and vanadium: They are harmful elements to magnetic properties and need to be reduced as much as possible. In addition, if the molten iron is not sufficiently desulfurized and vacuum treated, the number of inclusions such as SiO2 and Mn2SiO4 and the number of MnS and Fe3C precipitates will increase. The added antimony will often concentrate near these precipitates and inclusions and cannot play its beneficial role.

[0008] In order to achieve the magnetic performance requirements under normal conditions, a pure steel production method is required. The specific production process control includes the following steps:

[0009] ① Converter smelting: Converter production requires the use of ultra-low sulfur scrap steel, with an S content of ≤0.005%; converter lime requires an S content of ≤0.01%, with a reference activity of ≥450ml, so as to strictly control the sulfur content, improve the purity of the steel grade, and reduce the loss of magnetic properties caused by the precipitation of the second phase. The first-time hit rate of the composition is ≥95%, reducing the deviation of the composition control caused by subsequent adjustments.

[0010] ②RH refining: remove harmful gases and impurity elements in steel, and complete the adjustment of the main components and segregated element content; the vacuum cycle time is ≥10min. After the RH refining process step is completed, the molten steel calming time is set to 20-35min. This is because extending the calming time is conducive to the full aggregation and floating of dispersed inclusions in the steel, thereby further improving the purity of the molten steel.

[0011] ③Continuous casting: Use continuous casting to cast the molten steel into billets, increase the electromagnetic stirring working current, and increase the electromagnetic stirring working current to above 500A on the basis of normalized varieties and grades, so that the equiaxed crystal rate is ≥60%; use slag baffles when tapping steel to ensure that the ladle slag thickness reaches 50mm~100mm to prevent the molten steel from cooling too quickly and oxidizing.

[0012] ④ Hot rolling: control the heating process, the soaking temperature is controlled at 1150℃~1250℃, the furnace temperature is controlled at 1050℃~1150℃, the final rolling temperature is ≥910℃, water is sprayed 3~6s after the final rolling, the coiling temperature is ≥720℃, and the coil is put into the insulation cover after coiling. Keep warm for more than 24h under the condition of surface temperature ≥500℃ to fully promote the coarsening of the hot rolled coil structure.

[0013] ⑤ Cold rolling: A six-stand continuous rolling unit is used to roll the hot-rolled plate to the finished product thickness. By adjusting the thickness of the hot-rolled material, the total cold rolling reduction rate is controlled in the range of 65% to 80%, of which the first pass reduction rate is ≤32%. By reducing the total cold rolling reduction rate and the reduction rate of each pass, the shear texture strength is weakened, and the subsequent recrystallization nucleation rate is optimized, the average grain size is increased, and the magnetic properties are improved; the steel coil needs to be preheated to above 70°C before rolling to improve rollability.

[0014] ⑥ Annealing: A two-stage annealing furnace is used for annealing. Humidification is added in the front section of the continuous furnace, and the heating temperature is set to 800℃~880℃. The rear section is a dry atmosphere, and high-temperature annealing is adopted, and the heating temperature is set to 900℃~1000℃ to promote full grain growth, optimize texture, and improve magnetic properties.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention establishes the optimal range of main element content by adjusting the composition, further improves the resistivity and reduces the eddy current loss; optimizes the product texture by adding segregated elements to achieve organizational homogenization; achieves complete recrystallization and grain growth in non-oriented silicon steel hot-rolled plates by controlled rolling and controlled cooling during hot rolling to improve the magnetic properties; sets a reasonable continuous annealing process to achieve the optimization of the recrystallization structure and texture of the finished plate, and improves the magnetic properties to above the level of normalized materials of the same category; and finally achieves the production of high-efficiency materials in the denormalization process. The high-performance non-oriented electrical steel produced according to this technical solution has magnetic properties that reach the level of normalized materials of the same category of products. This low-cost production method realizes the non-normalization-free treatment of a series of non-oriented electrical steel grades, and the cost reduction of typical grades is more than 400 yuan / ton, which improves production efficiency, reduces resource consumption and carbon emissions, and has significant economic and social benefits. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0018] The chemical composition mass content of the high performance non-oriented electrical steel is C≤0.0020%, Si: 1.0%-1.7%, Mn: 0.20%-0.80%, P: 0.01%-0.10%, S≤0.0010%, N≤0.0020%, Ti≤0.0010%, Nb≤0.0020%, V≤0.0020%, Als: 0.20%-1.00%, Sb: 0.10%-0.20%, and the rest is Fe and unavoidable residual elements.

[0019] The production method of the high-performance non-oriented electrical steel comprises the following process steps: converter smelting, RH refining, continuous casting, hot rolling, cold rolling, and annealing;

[0020] Wherein, the continuous casting: based on the normalized variety, the electromagnetic stirring working current is increased to above 500A, so that the equiaxed crystal ratio is ≥ 60%;

[0021] The hot rolling: the heating process is controlled, the soaking temperature is controlled at 1150°C to 1250°C, the furnace temperature is controlled at 1050°C to 1150°C, and the final rolling temperature is ≥910°C;

[0022] The cold rolling: preheating the steel coil to above 70°C before rolling;

[0023] The annealing adopts a two-stage annealing furnace, with humidified air added in the front section of the continuous furnace and the heating temperature set to 800°C-880°C; the rear section is a dry atmosphere, high temperature annealing is adopted, and the heating temperature is set to 900°C-1000°C.

[0024] The matters not described in the following embodiments are the same as the description of the above specific implementation methods.

[0025] Example 1

[0026] A low-cost production method for non-oriented electrical steel high-efficiency material, wherein the chemical composition mass content of the non-oriented electrical steel high-efficiency material is C: 0.0017%, Si: 1.65%, Mn: 0.33%, P: 0.06%, S: 0.001%, Als: 0.57%, N: 0.0018%, Ti: 0.0008%, Nb: 0.0014%, V: 0.0019%, Sb: 0.15%, and the rest is iron and unavoidable impurity elements.

[0027] The production method of the above non-oriented electrical steel high-efficiency material comprises the following process steps:

[0028] ① Converter smelting and RH vacuum refining to adjust the main components and segregated element content; converter production uses ultra-low sulfur scrap steel with an S content of 0.003%; converter lime has an S content of 0.007% and an activity of 460ml. The vacuum cycle time is 15 minutes, and the molten steel is calmed for 25 minutes after RH refining.

[0029] ②Continuous casting: The molten steel is cast into billets by continuous casting, and the slab specifications are 230mm*120mm*L. A slag baffle is used during continuous casting to ensure that the ladle slag thickness reaches 60mm.

[0030] ③ Hot rolling: control the heating process, the soaking temperature is 1230℃, the furnace temperature is 1140℃, the final rolling temperature is 930℃, water is sprayed 3s after the final rolling, the coiling temperature is 730℃, and the coiling is put into the insulation cover, and the surface temperature is kept at 550℃ for 30h.

[0031] ④ Cold rolling: total reduction rate is 75%, six-pass rolling is adopted, and the first-pass reduction rate is 28%; a six-stand continuous rolling unit is used to roll the hot-rolled plate into a finished plate with a target thickness of 0.35 mm.

[0032] ⑤ Annealing: two-stage annealing at a speed of 120m / min, the temperature of the first stage is 850℃, the temperature of the second stage is 950℃, and after annealing, an insulating layer is applied to make the finished product.

[0033] The non-oriented electrical steel 35W360 produced in Example 1 was tested according to GB / T 3655-2022 "Method for measuring magnetic properties of electrical steel sheets (strips) using Epstein square rings" to check its P 15 / 50 2.45W / kg, B 5000 (with P 15 / 50 The same standard GB / T3655) is 1.71T; the corresponding grade of the conventional material 35W360 (P 15 / 502.63W / kg, B 5000 For comparison, the iron loss P 15 / 50 The typical value dropped by 0.19W / kg, and the magnetic induction B 5000 The typical value has been increased by 0.01T. At the same time, due to the elimination of the normalization process, the cost is reduced by about 470 yuan / ton compared with the traditional process.

[0034] Example 2

[0035] A low-cost production method for high-performance non-oriented electrical steel, wherein the chemical composition mass content of the high-performance non-oriented electrical steel is C: 0.0019%, Si: 1.36%, Mn: 0.45%, P: 0.08%, S: 0.0015%, Als: 0.49%, N: 0.0013%, Ti: 0.0007%, Nb: 0.0013%, V: 0.0015%, Sb: 0.12%, and the rest is iron and unavoidable impurity elements.

[0036] The production method of the above non-oriented electrical steel high-efficiency material comprises the following process steps:

[0037] ① Converter smelting and RH vacuum refining to adjust the main components and segregated element content; converter production uses ultra-low sulfur scrap steel with a S content of 0.002%; converter lime has a S content of 0.008% and an activity of 480ml. The vacuum cycle time is 12 minutes; after RH refining, the molten steel is calmed for 35 minutes.

[0038] ②Continuous casting: The molten steel is cast into steel billets by continuous casting, with the slab specification of 230mm*1200mm*L; slag baffles are used during continuous casting to ensure that the ladle slag thickness reaches 80mm.

[0039] ③Hot rolling: control the heating process, the soaking temperature is 1250℃, the furnace temperature is 1150℃, the final rolling temperature is 940℃, water spraying is performed 4s after the final rolling, the coiling temperature is 740℃, and the coiling is placed in the insulation cover, and the surface temperature is kept at 570℃ for 24h.

[0040] ④ Cold rolling: total reduction rate is 80%, six-pass rolling is adopted, and the first-pass reduction rate is 30%; a six-stand continuous rolling unit is used to roll the hot-rolled plate into a finished plate with a target thickness of 0.50 mm.

[0041] ⑤ Annealing: two-stage annealing at a speed of 100m / min, the temperature of the first stage is 870℃, the temperature of the second stage is 970℃, and after annealing, an insulating layer is applied to make the finished product.

[0042] The non-oriented electrical steel 50W400 produced in Example 2 was tested according to GB / T 3655-2022 "Method for measuring magnetic properties of electrical steel sheets (strips) using Epstein square rings" to examine its P 15 / 502.87W / kg, B 5000 (with P 15 / 50 The same as GB / T3655) is 1.72T; the corresponding grade of the conventional material 50W400 (P 15 / 50 2.99W / kg, B 5000 For comparison, the iron loss P 15 / 50 The typical value dropped by 0.12W / kg, and the magnetic induction B 5000 The typical value has been increased by 0.01T. At the same time, due to the elimination of the normalization process, the cost is reduced by about 450 yuan / ton compared with the traditional process.

[0043] Example 3

[0044] A low-cost production method for high-performance non-oriented electrical steel, wherein the chemical composition mass content of the high-performance non-oriented electrical steel is C: 0.0013%, Si: 1.13%, Mn: 0.77%, P: 0.10%, S: 0.0012%, Als: 0.28%, N: 0.0011%, Ti: 0.0009%, Nb: 0.0015%, V: 0.0012%, Sb: 0.19%, and the rest is iron and unavoidable impurity elements.

[0045] The production method of the above-mentioned high-performance non-oriented electrical steel comprises the following process steps:

[0046] ① Converter smelting and RH vacuum refining to adjust the main components and segregated element content; converter production uses ultra-low sulfur scrap steel with a S content of 0.001%; ​​converter lime has a S content of 0.01% and an activity of 450ml. The vacuum cycle time is 10 minutes; after RH refining, the molten steel is calmed for 20 minutes.

[0047] ②Continuous casting: The molten steel is cast into steel billets by continuous casting, with the slab specification of 230mm*1200mm*L. A slag baffle is used during continuous casting to ensure that the ladle slag thickness reaches 100mm.

[0048] ③Hot rolling: control the heating process, the soaking temperature is 1150℃, the furnace temperature is 1050℃, the final rolling temperature is 950℃, water spraying is performed 6s after the final rolling, the coiling temperature is 750℃, and the coiling is placed in the insulation cover, and the surface temperature is kept at 575℃ for 24h.

[0049] ④ Cold rolling: total reduction rate is 65%, six-pass rolling is adopted, and the first-pass reduction rate is 32%; a six-stand continuous rolling unit is used to roll the hot-rolled plate into a finished plate with a target thickness of 0.65 mm.

[0050] ⑤ Annealing: two-stage annealing at a speed of 100m / min, the temperature of the first stage is 870℃, the temperature of the second stage is 970℃, and after annealing, an insulating layer is applied to make the finished product.

[0051] The non-oriented electrical steel 65W530 produced in Example 3 was tested according to GB / T 3655-2022 "Method for measuring magnetic properties of electrical steel sheets (strips) using Epstein square rings" to examine its P 15 / 50 3.56W / kg, B 5000 (with P 15 / 50 The same as GB / T3655) is 1.73T; the corresponding grade of the conventional material 65W530 (P 15 / 50 3.87W / kg, B 5000 For comparison, the iron loss P 15 / 50 The typical value dropped by 0.31W / kg, and the magnetic induction B 5000 The typical value has been increased by 0.01T. At the same time, due to the elimination of the normalization process, the cost is reduced by about 410 yuan / ton compared with the traditional process.

[0052] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A low-cost production method for high-performance non-oriented electrical steel, characterized in that: The chemical composition mass content of the non-oriented electrical steel is C≤0.0020%, Si: 1.0%-1.7%, Mn: 0.20%-0.80%, P: 0.01%-0.10%, S≤0.0010%, N≤0.0020%, Ti≤0.0010%, Nb≤0.0020%, V≤0.0020%, Als: 0.20%-1.00%, Sb: 0.10%-0.20%, and the rest are Fe and unavoidable residual elements; The production method of the high-performance non-oriented electrical steel comprises the following process steps: converter smelting, RH refining, continuous casting, hot rolling, cold rolling, and annealing; Wherein, the continuous casting: on the basis of the normalized variety and grade, the electromagnetic stirring working current is increased to above 500A, so that the equiaxed crystal ratio is ≥ 60%; The hot rolling: the heating process is controlled, the soaking temperature is controlled at 1150°C to 1250°C, the furnace temperature is controlled at 1050°C to 1150°C, and the final rolling temperature is ≥910°C; The cold rolling: preheating the steel coil to above 70°C before rolling; The annealing adopts a two-stage annealing furnace, with humidified air added in the front section of the continuous furnace and the heating temperature set to 800°C-880°C; the rear section is a dry atmosphere, high temperature annealing is adopted, and the heating temperature is set to 900°C-1000°C.

2. The production method according to claim 1, characterized in that In the converter smelting step, ultra-low sulfur scrap steel is used in converter production, and the S content is ≤0.005%; the converter lime is required to have an S content of ≤0.01% and an activity of ≥450ml.

3. The production method according to claim 2, characterized in that: For the RH refining, the vacuum cycle time is ≥10 min; after the RH refining is completed, the molten steel calming time is set to 20 to 35 min.

4. The production method according to claim 3, characterized in that: A slag retaining plate is used during the continuous casting to ensure that the ladle slag thickness reaches 50 mm to 100 mm.

5. The production method according to claim 4, characterized in that: The hot rolling is finished by spraying water 3 to 6 seconds after the final rolling, the coiling temperature is ≥720°C, and the coiling is placed in a heat preservation cover, and the surface temperature is ≥500°C and kept warm for more than 24 hours.

6. The production method according to claim 4, characterized in that: The total reduction rate of the cold rolling is 65% to 80%. Six-pass rolling is adopted, and the reduction rate of the first pass is ≤32%.