A low cost production method of high performance non-oriented electrical steel

Abstract

The application discloses a low-cost production method of high-performance non-oriented electrical steel, and the main chemical components of the product are as follows: C is less than or equal to 0.002%, Si is 1.0% to 1.7%, Mn is 0.20% to 0.80%, P is 0.01% to 0.10%, S is less than or equal to 0.001%, N is less than or equal to 0.002%, Ti is less than or equal to 0.001%, Nb is less than or equal to 0.002%, V is less than or equal to 0.002%, Al is 0.20% to 1.0%, and Sb is 0.10% to 0.20%. The resistivity is improved and the eddy current loss is reduced through component adjustment; the product texture is optimized by adding a segregation element; 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 texture of the finished plate are optimized through continuous annealing process, the magnetic property is improved to be higher than that of the normalized material of the same type, and finally the high-efficiency material production without the normalizing process is realized; the production efficiency is improved, and the resource consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metallurgy, and is suitable for the production of cold-rolled non-oriented electrical steel non-normalization high-efficiency products, in particular to a low-cost production method of high-performance non-oriented electrical steel. BACKGROUND

[0002] The magnetic properties of non-oriented electrical steel are derived from the addition of silicon and aluminum elements and microstructure control. To meet the energy-saving needs, silicon and aluminum elements need to be added to increase the resistivity and reduce the iron loss, but since silicon and aluminum also reduce the magnetic induction, 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 a higher magnetic induction and lower iron loss, an equiaxed structure with larger grain size is needed. However, under the existing process conditions, complete dynamic and static recrystallization cannot occur during the hot rolling process of medium and high-grade non-oriented silicon steel, and fine-grained and small amount of deformed structure are retained to room temperature, thereby affecting the subsequent performance. In this case, normalizing treatment is often performed to obtain a microstructure with fully grown grains and increase the beneficial texture.

[0003] In order to achieve better magnetic performance indicators, non-oriented electrical steel usually needs to be normalized to complete the optimization of the structure and the coarsening of the two-phase particles. As a separate process, normalizing increases a large amount of energy consumption and reduces production efficiency. If the recrystallization and grain growth during hot rolling can be improved through composition adjustment and process optimization, while the resistivity is increased and the hysteresis loss is reduced, it is possible to remove the normalizing process of medium and high-grade non-oriented silicon steel under the premise of obtaining the expected magnetic performance level, thereby achieving energy saving and emission reduction. SUMMARY

[0004] To overcome the defects of the prior art, the present application further improves the resistivity and reduces the eddy current loss by adjusting the composition, realizes the uniformization of the structure by adding segregation elements, and realizes complete recrystallization and grain growth in the hot-rolled sheet of non-oriented silicon steel through controlled rolling and controlled cooling during hot rolling, thereby improving the magnetic performance level.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides a low-cost production method of high-performance non-oriented electrical steel, which realizes the requirement that the performance after removing the normalizing process reaches the level of normalized material through the optimization design of smelting composition and process of each production process.

[0006] The chemical composition of the high-performance non-oriented electrical steel (wt%) 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 is Fe and unavoidable residual elements.

[0007] Chemical composition is effective and necessary approach, carbon: because the product non-constant process, equivalent to reduce a decarburization process, so need to strictly control the refining process, so the carbon content is below 0.0020%. Silicon: from the performance requirements of finished product, considering that silicon reduces the iron loss while also inhibits the magnetic induction B 50 Upgrade, while due to non-constant, if the silicon content is too high, it will cause product wa di defect due to the genetic organization of coarse columnar crystal, therefore the silicon content is set to 1.0%~1.7%. Manganese: manganese has the effect of inhibiting (111) component and promoting (100), (110) component, after adding manganese, B 50 Upgrade and P 15 Decrease. Phosphorus: one of the important effects of phosphorus is to improve the resistivity, thereby reducing the eddy current loss, in addition, phosphorus has a significant promoting effect on the occurrence process of dynamic recrystallization during hot rolling and finishing rolling, the addition of phosphorus in the product can partially compensate for the lower silicon content while coarsening the microstructure before cold rolling under the non-constant process conditions, but the addition of 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 non-constant, the content cannot be set too high, in the present invention, the composition interval is set to 0.20%~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 bands in the cold rolled plate, further improving the texture. However, as a segregation element, too high a content of antimony hinders grain growth, resulting in small grains in the hot rolled plate and finished product plate, and high iron loss. Sulfur, nitrogen, titanium, niobium, vanadium: these elements are harmful to magnetic properties and need to be reduced as much as possible. In addition, if the desulfurization of molten iron and vacuum treatment are insufficient, the number of inclusions such as SiO2 and Mn2SiO4, as well as MnS and Fe3C precipitates, increases, and the added antimony often segregates around these precipitates and inclusions, which cannot play its beneficial role.

[0008] To achieve the magnetic performance requirements under non-constant conditions, a clean steel production method is needed, and the specific production process control includes the following steps:

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

[0010] ② RH refining: remove harmful gas and impurity elements in the steel, complete the main component and the content adjustment of segregation elements; vacuum circulation time is greater than or equal to 10 min, after the end of the RH refining process step, the steel setting time is set to 20-35 min, because prolonging the setting time is beneficial to the full aggregation and floating of the dispersed inclusions in the steel, so as to further improve the purity of the molten steel.

[0011] ③ Continuous casting: the molten steel is cast into a billet by adopting continuous casting mode, the electromagnetic stirring working current is improved, the electromagnetic stirring working current is improved to more than 500A based on the normalizing variety, so that the equiaxed crystal rate is greater than or equal to 60%; the slag baffle is used when tapping, the ladle slag thickness is ensured to be 50-100 mm, so as to prevent the molten steel from cooling too fast and oxidizing.

[0012] ④ Hot rolling: the heating process is controlled, the soaking temperature is controlled to be 1150-1250 DEG C, the discharge temperature is controlled to be 1050-1150 DEG C, the finishing temperature is greater than or equal to 910 DEG C, water is sprayed after 3-6 s of finishing, the coiling temperature is greater than or equal to 720 DEG C, the surface temperature is greater than or equal to 500 DEG C after coiling into the heat preservation cover, and the heat preservation is more than 24 h, so as to fully promote the hot rolled coil organization coarsening.

[0013] ⑤ Cold rolling: the hot rolled plate is rolled into a product thickness by adopting a six-stand tandem cold rolling mill, the cold rolling total reduction rate is controlled in the range of 65-80%, wherein the first pass reduction rate is less than or equal to 32%, the shear texture strength is weakened by reducing the cold rolling total reduction rate and each pass reduction rate, then the subsequent recrystallization nucleation rate is optimized, the average value of the grain size is increased, and the magnetic property is improved; the steel coil needs to be preheated to more than 70 DEG C before rolling, so as to improve the rollability.

[0014] ⑥ Annealing: annealing is carried out by adopting a two-stage annealing furnace, humid gas is added in the front stage of the continuous furnace, the heating temperature is set to be 800-880 DEG C, the rear stage is a dry atmosphere, high temperature annealing is adopted, the heating temperature is set to be 900-1000 DEG C, the grain is fully grown, the texture is optimized, and the magnetic property is improved.

[0015] Compared with the prior art, the beneficial effects of the present application are:

[0016] The application establishes the optimal main element content range by adjusting the components, further improves the resistivity and reduces the eddy current loss; the product texture is optimized by adding the segregation element to realize the homogenization of the structure; the complete recrystallization and grain growth in the non-oriented silicon steel hot-rolled plate are realized by controlling the rolling and cooling in the hot rolling process to improve the magnetic performance level; the recrystallization structure and texture of the finished plate are optimized by setting a reasonable continuous annealing process to improve the magnetic performance to the level of the normalizing material of the same type; and the high-efficiency material production without the normalizing process is finally realized. The high-performance non-oriented electrical steel produced according to the technical scheme has the magnetic performance reaching the level of the normalizing material of the same type, the low-cost production method realizes the normalizing-free treatment of the series of non-oriented electrical steel, the cost reduction of the typical grade is more than 400 yuan / ton, the production efficiency is improved, the resource consumption and carbon emission are reduced, and the economic benefit and social benefit are remarkable. DETAILED DESCRIPTION

[0017] The application will be further described below in combination with specific embodiments, but the application is not limited in any way by the embodiments. For the sake of brevity, the raw materials in the following embodiments are all commercially available products if not otherwise specified, and the methods used are all conventional methods if not otherwise specified.

[0018] The chemical component 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 inevitable residual elements.

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

[0020] The continuous casting is to increase the electromagnetic stirring working current to more than 500 A on the basis of the normalizing variety grade to make the equiaxed crystal rate ≥60%;

[0021] The hot rolling controls the heating process, the soaking temperature is controlled at 1150-1250℃, the discharge temperature is controlled at 1050-1150℃, and the finish rolling temperature is ≥910℃;

[0022] The cold rolling preheats the steel coil to more than 70℃ before rolling;

[0023] The annealing adopts a two-stage annealing furnace, the front stage of the continuous furnace is humidified, the heating temperature is set to 800-880℃, the rear stage is a dry atmosphere, high-temperature annealing is adopted, and the heating temperature is set to 900-1000℃.

[0024] The following examples are not described, the same as the description of the above specific embodiments.

[0025] Example 1

[0026] A low-cost production method of non-oriented electrical steel high-efficiency material, 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 inevitable impurity elements.

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

[0028] ① Converter smelting, RH vacuum refining, complete main component and segregation element content adjustment; ultra-low sulfur scrap steel is used in converter production, S content is 0.003%; S content of lime used in converter is 0.007%, and activity is 460ml. The vacuum circulation time is 15min, and the molten steel is settled for 25min after RH refining.

[0029] ② Continuous casting: the molten steel is cast into billets by continuous casting, and the billet specification is 230mm*120mm*L; the slag baffle is used when the molten steel is continuously cast to ensure that the ladle slag thickness reaches 60mm.

[0030] ③ Hot rolling: control the heating process, soaking temperature 1230℃, discharge temperature 1140℃, finishing temperature 930℃, spray after 3s of finishing, coiling temperature 730℃, after coiling, enter the heat preservation cover, and the surface temperature is 550℃ for 30h.

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

[0032] ⑤ Annealing: two-stage annealing at a speed of 120m / min, front-stage temperature 850℃, rear-stage temperature 950℃, after annealing, insulating layer is coated to make finished product.

[0033] The non-oriented electrical steel 35W360 produced in Example 1 is tested according to GB / T 3655-2022 "Method for measuring magnetic properties of electrical steel sheets (strips) with Epstein frame", to test its P 15 / 50 is 2.45W / kg, B 5000 (with P 15 / 50 is 1.71T; and the corresponding brand normalizing material 35W360 produced by the traditional process (P 15 / 502.63 W / kg, B 5000 1.70 T) are compared, the iron loss P 15 / 50 0.19 W / kg, the magnetic induction B 5000 0.01 T, and the cost is reduced by about 470 yuan / ton compared with the traditional process due to the elimination of the normalizing process.

[0034] Example 2

[0035] A low-cost production method of high-performance non-oriented electrical steel, the chemical composition mass content of which 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 inevitable impurity elements.

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

[0037] ① Converter smelting, RH vacuum refining, completing the content adjustment of main components and segregation elements; ultra-low sulfur scrap steel is used in converter production, and the S content is 0.002%; the S content of lime used in converter is 0.008%, and the activity is 480 ml. The vacuum circulation time is 12 min; the molten steel is settled for 35 min after RH refining.

[0038] ② Continuous casting: the molten steel is cast into billets by continuous casting, and the slab specification is 230mm*1200mm*L; a slag baffle is used when the molten steel is continuously cast to ensure that the ladle slag thickness reaches 80mm.

[0039] ③ Hot rolling: control the heating process, soaking temperature 1250℃, discharge temperature 1150℃, finishing temperature 940℃, water spraying after 4s after finishing, coiling temperature 740℃, coiling into a heat preservation cover after coiling, surface temperature 570℃, and heat preservation for 24h under the condition.

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

[0041] ⑤ Annealing: speed 100m / min two-stage annealing, front stage temperature 870℃, rear stage temperature 970℃, after annealing, an insulating layer is coated to make a finished product.

[0042] The non-oriented electrical steel 50W400 produced in Example 2 is tested according to GB / T 3655-2022 "Method for measuring the magnetic properties of electrical steel sheets (strips) with an Epstein frame", to test its P 15 / 502.87 W / kg, B 5000 (With P 15 / 50 1.72 T; compared with the corresponding brand normalized material 50W400 (P 15 / 50 2.99 W / kg, B 5000 1.71 T) produced by the traditional process, the iron loss P 15 / 50 typical value decreased by 0.12 W / kg, the magnetic induction B 5000 typical value increased by 0.01 T, at the same time, due to the elimination of the normalizing process, compared with the traditional process, the cost is reduced by about 450 yuan / ton.

[0043] Example 3

[0044] A low-cost production method of high-performance non-oriented electrical steel, the chemical composition mass content of which 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 inevitable impurity elements.

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

[0046] ① Converter smelting, RH vacuum refining, completing the content adjustment of main components and segregation elements; ultra-low sulfur scrap steel is used in converter production, the S content is 0.001%; the S content of lime used in converter is 0.01%, and the activity is 450 ml. The vacuum circulation time is 10 min; the molten steel is settled for 20 min after RH refining.

[0047] ② Continuous casting: the molten steel is cast into billets by continuous casting, and the slab size is 230mm*1200mm*L; the slag baffle is used when the molten steel is discharged to ensure that the ladle slag thickness reaches 100mm.

[0048] ③ Hot rolling: control the heating process, the soaking temperature is 1150℃, the discharge temperature is 1050℃, the final rolling temperature is 950℃, water is sprayed after 6s after final rolling, the coiling temperature is 750℃, and the surface temperature is 575℃ after coiling into the heat preservation cover, and the temperature is kept for 24h.

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

[0050] ⑤ Annealing: two-stage annealing at a speed of 100m / min, the front stage temperature is 870℃, and the rear stage temperature is 970℃, and the finished product is made after insulating layer coating.

[0051] The non-oriented electrical steel 65W530 produced in Example 3 was tested according to GB / T 3655-2022 "Method of measurement of magnetic properties of electrical steel sheets (strips) with Epstein frame" to verify its P 15 / 50 was 3.56 W / kg, B 5000 (versus P 15 / 50 was 1.73 T; compared with the corresponding grade normalized material 65W530 (P 15 / 50 was 3.87 W / kg, B 5000 was 1.72 T) produced by the conventional process, the iron loss P 15 / 50 decreased by 0.31 W / kg, and the magnetic induction B 5000 increased by 0.01 T, and at the same time, due to the elimination of the normalizing process, the cost was reduced by about 410 yuan / ton compared with the conventional process.

[0052] For any person skilled in the art, many possible variations and modifications, or equivalent embodiments of equivalent changes, can be made to the technical solutions of the present application by using the technical content disclosed above without departing from the scope of the technical solutions of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, which does not depart from the content of the technical solutions of the present application, should still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A low-cost production method for high-performance non-oriented electrical steel, characterized in that, The chemical composition of the non-oriented electrical steel is as follows (mass content): 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%, with the remainder being Fe and unavoidable residual elements. The production method of the above-mentioned high-performance non-oriented electrical steel includes the following process steps: converter smelting, RH refining, continuous casting, hot rolling, cold rolling, and annealing. The production method does not involve normalizing process. The continuous casting process involves increasing the electromagnetic stirring current to over 500A based on the existing grade of the product, thereby achieving an equiaxed crystal ratio of ≥60%. The hot rolling process is controlled with the heating temperature controlled at 1150℃~1250℃, the furnace exit temperature controlled at 1050℃~1150℃, and the final rolling temperature ≥910℃. After the final rolling of the hot rolling process, water is sprayed 3~6s later, the coiling temperature is ≥720℃, and after coiling, the coil is placed in a heat preservation cover and kept at a surface temperature ≥500℃ for more than 24 hours. The cold rolling process involves preheating the steel coil to above 70°C before rolling. The annealing process employs a two-stage annealing furnace. Moisture is added to the front section of the continuous furnace, and the heating temperature is set to 800℃~880℃. The rear section uses a dry atmosphere and employs high-temperature annealing, with the heating temperature set to 900℃~1000℃.

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

3. The production method according to claim 2, characterized in that, The RH refining process involves a vacuum circulation time of ≥10 min; after the RH refining process, the molten steel settling time is set to 20–35 min.

4. The production method according to claim 3, characterized in that, The continuous casting process uses slag baffles to ensure that the slag thickness in the ladle reaches 50mm to 100mm.

5. The production method according to claim 4, characterized in that, The cold rolling process involves a total reduction of 65% to 80%; it employs a six-pass rolling process, with the first pass having a reduction of ≤32%.