CN115233079B - Method for producing non-oriented silicon steel - Google Patents

Method for producing non-oriented silicon steel Download PDF

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CN115233079B
CN115233079B CN202210728811.8A CN202210728811A CN115233079B CN 115233079 B CN115233079 B CN 115233079B CN 202210728811 A CN202210728811 A CN 202210728811A CN 115233079 B CN115233079 B CN 115233079B
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silicon steel
equal
oriented silicon
cold rolling
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CN115233079A (en
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吴圣杰
岳重祥
李化龙
陈爱华
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Zhangjiagang Sino Us Ultra Thin Belt Technology Co ltd
Jiangsu Shagang Group Co Ltd
Jiangsu Shagang Iron and Steel Research Institute Co Ltd
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Zhangjiagang Sino Us Ultra Thin Belt Technology Co ltd
Jiangsu Shagang Group Co Ltd
Jiangsu Shagang Iron and Steel Research Institute Co Ltd
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    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
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    • C21—METALLURGY OF IRON
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1233—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • C21D8/1255—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest with diffusion of elements, e.g. decarburising, nitriding
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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Abstract

The invention belongs to the technical field of metallurgy, and relates to a method for producing non-oriented silicon steel. The method for producing non-oriented silicon steel according to the present invention comprises the steps of: step 1, smelting; step 2, twin-roll thin strip continuous casting; step 3, coiling; step 4, aging treatment; step 5, primary cold rolling; step 6, decarburization annealing treatment; step 7, secondary cold rolling; in the step 8, the step of performing the step, and (5) recrystallization annealing treatment. Through the process, the technical scheme of the invention can obtain the high-grade non-oriented silicon steel finished product.

Description

Method for producing non-oriented silicon steel
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for producing non-oriented silicon steel, in particular to a method for producing non-oriented silicon steel for a new energy drive motor.
Background
With the rapid development of new energy vehicles, the high speed and miniaturization of driving motors become the trend of future development. The maximum rotating speed of the driving motor of the new energy automobile is increased from thousands of revolutions per minute to tens of thousands of revolutions or even up to 20 thousands of revolutions, and the working frequency is increased from 50Hz to hundreds of hertz and thousands of hertz. The non-oriented silicon steel is one of core materials of a driving motor of a new energy automobile, and has the following performance characteristics: the iron loss is low, so that the iron core loss is reduced, and the endurance mileage is improved; high magnetic induction, improved torque when the driving motor is started and accelerated, reduced size and reduced material consumption.
The production process of the traditional low iron loss/high grade non-oriented silicon steel comprises blast furnace molten iron-KR desulfurization-converter steelmaking-RH vacuum refining-slab continuous casting-slab heating-hot rolling-normalizing-cold rolling-annealing coating. The production process has long flow, particularly blast furnace iron making and converter steel making, needs to consume a large amount of iron ore and coke, and has high carbon emission in the process. Therefore, simplifying the production process flow of non-oriented silicon steel is a necessary requirement for the development of green steel in the future.
In addition, the potential of the non-oriented silicon steel produced by the traditional process is almost exploited, and the magnetic induction is continuously reduced while the iron loss is reduced. The development requirements of high rotating speed, high efficiency and miniaturization of the new energy driving motor are difficult to meet. Therefore, the improvement of the magnetic induction intensity of the non-oriented silicon steel is an important requirement of the next generation new energy driving motor on iron core materials.
Disclosure of Invention
According to a first aspect of the present invention, there is disclosed a method of producing non-oriented silicon steel, comprising the steps of:
step 1, smelting:
smelting molten steel, wherein the molten steel comprises the following components in percentage by weight:
c is more than or equal to 0.01 percent and less than or equal to 0.05 percent, si is more than or equal to 2.5 percent and less than or equal to 3.5 percent, mn is more than or equal to 1.5 percent and less than or equal to 3.0 percent, al is less than or equal to 0.003 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.0030 percent, O is less than or equal to 0.0030 percent, N is less than or equal to 0.0020 percent, cu is less than or equal to 0.03 percent, nb is less than or equal to 0.0020 percent, V is less than or equal to 0.0020 percent, al + O + S + N is less than or equal to 0.01 percent, and the balance is Fe and inevitable impurities;
step 2, twin-roll thin strip continuous casting:
transferring the molten steel obtained by the smelting in the step 1 to a pair of counter-rotating casting rolls, cooling and solidifying the molten steel on the casting surfaces of the pair of casting rolls, and passing down through a nip between the pair of casting rolls to form a thin cast strip having a thickness h in the range of 1.4 to 1.8mm,
step 3, coiling:
coiling the thin cast strip at a high temperature to obtain a cast strip coil, wherein the coiling temperature of the thin cast strip is 950-1050 ℃;
step 4, aging treatment:
cooling the coiled cast strip coil for 50-80h at a cooling speed of not higher than 15 ℃/h;
step 5, primary cold rolling:
pickling and cold rolling the aged cast strip coil to form a thin strip coil with the thickness of 0.35-0.50 mm;
step 6, decarburization annealing treatment:
carrying out decarburization annealing treatment on the thin strip coil subjected to the primary cold rolling;
step 7, secondary cold rolling:
the thin strip coil after the decarburization annealing treatment is subjected to secondary cold rolling to form a thin strip coil with the thickness of 0.20-0.30 mm;
and step 8, recrystallization annealing treatment:
and (4) carrying out recrystallization annealing treatment on the thin strip coil after secondary cold rolling.
In a preferred embodiment, in the step 1 smelting process, the molten steel is obtained by using recycled silicon steel waste as smelting raw materials and adopting electric furnace steelmaking-RH vacuum refining-LF external refining.
In a preferred embodiment, the contents of the elemental components contained in the molten steel further satisfy the relationship:
0.25×(Si％)+0.15×(Mn％)+0.3≤lg(C％×10 3 )≤0.25(Si％)+0.15×(Mn％)+0.5。
in a preferred embodiment, in the step 2 twin roll strip casting process, the relation between the temperature T =1607-10 × (Si%) -2 × (Mn%) of the molten steel in the tundish and the strip forming speed v (m/min) and the thin strip thickness h (mm) is v =135-50 × h, and the thickness T (μm) of the deposition film on the surface of the copper casting roll is controlled by a roll brush during the casting process, the thickness T =20-1/3 × Si% -1/2 × Mn%.
In a preferred embodiment, the thin cast strip is not subjected to a hot rolling operation prior to coiling in step 3.
In a preferred embodiment, the dew point in the decarburization annealing treatment of step 6 is from +35 ℃ to +45 ℃ and the protective atmosphere is 20% 2 +80％N 2 ，P H2O /P H2 ＝0.25～0.27，P H2O And P H2 Are respectively H 2 O and H 2 Partial pressure of (c). The soaking temperature T =950-20 (Si%) -500 (C%) of the decarburization annealing, and the soaking time is 3-5 min. Introducing dry H into the cooling section after soaking 2 The dew point is-35 to-45 ℃.
In a preferred embodiment, in the step 5 cold rolling, the surface scale of the cast strip coil is removed by continuous acid cleaning, and then the cast strip coil is subjected to single-stand multi-pass cold rolling, wherein the total reduction of the cold rolling is 70-83%, the first pass reduction of the cold rolling is about 35%, the reduction of the rest passes is controlled to be 20-30%, and the strip thickness of the cold-rolled thin strip coil is in the range of 0.35-0.50 mm.
In a preferred embodiment, in the recrystallization annealing treatment of step 8, the annealing temperature rise rate is 30 to 50 ℃/s, the soaking temperature is 950 to 1050 ℃, the soaking time is 40 to 70s, the atmosphere dew point in the annealing process is-30 to-20 ℃, and the protective atmosphere is 20 percent 2 +80％N 2 (ii) a After soaking, the thin strip coil is cooled to 500 ℃ at a cooling rate of about 10 ℃/s; cooling to room temperature at a cooling speed of 20-30 ℃/s; then on the thin tape rollThe upper and lower surfaces of the thin strip are coated with insulating coatings.
In the preferred embodiment, the non-oriented silicon steel produced by the steps 1-8 meets the following requirements: p 1.5/50 ＝1.9～2.6W/kg，P 1.0/400 ＝11～19W/kg，B 50 ＝1.73～1.79T。
According to a second aspect of the invention, the invention also discloses non-oriented silicon steel produced by the production method.
Specifically, the selection of the content of each element and the selection of the process and the range of the parameters thereof in the smelting process need to consider the following factors:
c: 0.01-0.05%: in the solidification process of the high-grade non-oriented silicon steel, when the carbon content is less than 0.01%, the Si content is more than 2.5%, and no phase change occurs during strip continuous casting. The columnar crystals are over developed, so that the corrugated defects are easily caused on the surface of a cold-rolled finished product, the lamination coefficient of a non-oriented silicon steel finished product is influenced, and the electromagnetic performance of the motor is further influenced. To avoid the corrugated defect, the general practice is: (1) Electromagnetic stirring is added in the solidification process to break the solidified columnar crystals; (2) After hot rolling, a normalizing process is added to improve the structure and texture before cold rolling. The invention adopts the control of phase change in the solidification process to avoid over-development of the solidified columnar crystals. Specifically, the carbon content and the manganese content are increased in the aspect of component design, so that austenite phase change in the continuous casting solidification process is ensured, and the carbon content is correspondingly increased along with the increase of the silicon content. In addition, in the present invention, a very strict regulation is made on the carbon content, that is:
0.25×(Si％)+0.15×(Mn％)+0.3≤lg(C％×10 3 )≤0.25(Si％)+0.15×(Mn％)+0.5，
and the range of the carbon content is limited to 0.01 to 0.05%. This is because carbon is also a magnetic aging element, which leads to an increase in the iron loss of the finished product and deterioration in magnetic properties. In order to avoid the influence of carbon element on the electromagnetic performance of the finished product, a decarburization annealing process is added after one-time cold rolling, and the carbon content of the non-oriented silicon steel finished product is ensured to be less than 0.002%.
Si: 2.5-3.5%: the silicon element can effectively improve the resistivity of the steel plate and reduce the iron loss of a finished product. However, after the silicon content is increased, the thermal conductivity of the material is reduced, and heat transfer is difficult in the process of double-roller thin-strip continuous casting sub-rapid solidification, so that effective banding is difficult. For this reason, the present invention limits the range of silicon content to 2.5 to 3.5%;
mn: 1.5-3.0%: manganese can increase the finished product resistivity, but the manganese contributes 1/2 of the finished product core loss. Manganese can be used as an element for expanding an austenite phase region, and the corrugated defects of a finished product can be effectively improved by controlling the phase change in the solidification process. The Mn content range of the invention is limited to 1.50-3.0%.
Al is less than or equal to 0.003%: the effect of aluminum on magnetic properties is similar to that of silicon, and the resistivity of the steel plate is improved. However, aluminum has strong deoxidizing capacity in the smelting process and is combined with oxygen to form high-melting-point Al 2 O 3 Inclusions of Al having a high melting point due to a small diameter of a casting nozzle for strip casting 2 O 3 The nozzle is easy to block, and the molten steel casting is affected. In the present invention, the upper limit of the Al content is set to 0.003% in order to improve the castability of molten steel.
P is less than or equal to 0.015%: as the Si/Al content increases, phosphorus tends to segregate at the grain boundaries, and manganese in turn promotes phosphorus segregation. The grain boundary segregation of phosphorus element causes the brittleness of silicon steel to increase and the cold rolling rollability to decrease. The upper limit of the P content in the present invention is set to 0.015%.
S is less than or equal to 0.0030%: s is easy to form fine MnS and CuS precipitates with Mn and Cu elements in steel, and the precipitates not only prevent crystal grains from growing in the cold rolling annealing process, but also prevent magnetic domain from rotating in the magnetization process, thereby deteriorating the magnetic performance of finished products. Therefore, the upper limit of the S content in the present invention is set to 0.0030%.
O is less than or equal to 0.003%: oxygen tends to form oxide inclusions with the alloying elements Si/Mn in steel. These inclusions not only plug the casting nozzle, but also affect the purity of the non-oriented silicon steel, leading to a reduction in the electromagnetic properties of the finished product. In the present invention, the upper limit of the O content is set to 0.003%.
N is less than or equal to 0.0020%: n is easy to form TiN and AlN precipitates with Al, ti and other alloy elements in steel, so that crystal grains are prevented from growing in the cold rolling annealing process, and the magnetic performance of a finished product is deteriorated. Therefore, in the present invention, the upper limit of the N content is set to 0.0020%.
Cu is less than or equal to 0.03 percent, and the copper is easy to form fine CuS precipitates by sulfur in steel, and the precipitates not only prevent crystal grains from growing in the annealing process, but also prevent magnetic domain rotation in the magnetizing process and deteriorate the magnetic performance of a finished product. Therefore, the upper limit of the Cu element content in the present invention is set to 0.03%.
The contents of Nb, V and Ti are respectively not higher than 0.0020%: nb/V/Ti forms fine precipitates with C/N atoms in the steel, and the precipitates not only prevent grain growth in the annealing process, but also prevent magnetic domain rotation in the magnetization process, thereby deteriorating the magnetic performance of the finished product. Therefore, the upper limit of the Nb/V/Ti microalloy element content is set to 0.0020% in the invention.
Further, in step 2, since the amount of steel passing through the twin roll strip casting unit time is low, the degree of superheat of molten steel casting is high, but if the degree of superheat of molten steel is too high, the continuous casting process may be interrupted. The temperature of the tundish molten steel is closely related to the components of the Si/Mn alloy, so the tundish temperature of the molten steel is limited by the invention: t =1607-10 × (Si%) -2 × (Mn%).
Further, in step 2, the thin cast strip is formed with a thickness (h) of: 1.4 to 1.8mm, the relationship between the strip speed (v) and the strip thickness being: v =135-50 × h, wherein the casting strip forming speed v is in m/min and the thin casting strip thickness h is in mm.
Further, in step 2, since the silicon content is increased, the heat transfer efficiency of the molten steel is reduced, in order to ensure that the strip is stably and continuously poured in the sub-rapid solidification process of the twin-roll strip casting, the thickness of the oxidized deposition film on the surface of the copper roll needs to be controlled by the roll brush, and the thickness of the deposition film and the Si/Mn content in the molten steel are defined by the following relation: t =20-1/3 × Si% -1/2 × Mn%, wherein the deposited film thickness is in μm units.
Further, in the step 5, surface oxide skin is removed by continuous acid washing, and then the strip is subjected to single-frame multi-pass cold rolling, wherein the total rolling reduction of the cold rolling is 70-83%, the first pass reduction of the cold rolling is 35%, the rest passes are controlled to be 20-30%, and the thickness of the cold-rolled finished thin strip is 0.35-0.50 mm.
Further, in step 6, the decarburization annealing is performed to ensure that the carbon content in the finished non-oriented silicon steel product is less than 0.003%The problem of magnetic aging caused by overhigh carbon content is avoided. The thin strip after cold rolling needs to be subjected to decarburization annealing treatment, the decarburization annealing is mainly carried out by the reaction of water vapor in atmosphere and carbon in steel, and the reaction formula is H 2 O+C→H 2 + CO. In a flowing atmosphere, carbon is continuously diffused from the inside to the outside of the ribbon, and CO is continuously discharged out of the furnace. The main factors influencing the decarburization rate are temperature, time, and atmosphere dew point. As the temperature increases, the diffusion coefficient of carbon increases. However, when the temperature is too high, the oxidation speed is accelerated, and when the oxidation speed is higher than the decarburization speed, dense SiO is formed on the surface of the thin strip 2 Oxide film, which hinders decarburization. To prevent oxidation of the surface of the thin strip, the content of H in the decarburization atmosphere is increased by 20% 2 The decarburization process is maintained in a reducing atmosphere. Dew point of +35 to +45 ℃ in the decarburization annealing process, protective atmosphere of 20% 2 +80％N 2 ，P H2O /P H2 ＝0.25～0.27，P H2O And P H2 Are each H 2 O and H 2 Partial pressure of (c). The soaking temperature T =950-20 (Si%) -500 (C%) of decarburization annealing, and the soaking time is 3-5 min. Introducing dry H into the cooling section after soaking 2 The dew point is-35 to-45 ℃.
Further, in step 7, after the decarburization annealing of the thin strip is completed, the thin strip is cold rolled twice to a thickness of 0.20 to 0.30mm. The thickness of the thin strip is further reduced, so that the eddy current loss of the non-oriented silicon steel can be further reduced, and the electromagnetic performance of a finished product is improved.
Further, in step 8, the thin strip coil after the secondary cold rolling is subjected to final recrystallization annealing treatment, the annealing temperature rise rate is controlled to be 30-50 ℃/s, the soaking temperature is 950-1050 ℃, the soaking time is 40-70 s, the atmosphere dew point in the annealing process is-30-20 ℃, and the protective atmosphere is 20% 2 +80％N 2 . After soaking, the thin strip coil is cooled to 500 ℃ at a cooling speed of about 10 ℃/s and then cooled to room temperature at a cooling speed of 20-30 ℃/s. And then coating insulating coatings on the upper surface and the lower surface to obtain a finished product of the high-grade non-oriented silicon steel.
The finished product of the high-grade non-oriented silicon steel processed by the procedures has the following magnetic properties: p 1.5/50 ＝1.9～2.6W/kg，P 1.0/400 ＝11～19W/kg，B 50 And = 1.73-1.79T. Wherein, P 1.5/50 The iron loss is under the conditions that the magnetic induction intensity is 1.5T and the loading frequency is 50 Hz; p 1.0/400 The iron loss is under the conditions that the magnetic induction intensity is 1.0T and the loading frequency is 400 Hz; b is 50 The magnetic induction intensity is magnetic induction intensity under the magnetic field intensity of 5000A/m.
Advantageous technical effects
The technical scheme of the invention has the following advantages:
(1) The invention changes the production process flow of the traditional high-grade non-oriented silicon steel production, namely, blast furnace molten iron-KR desulfuration-converter steelmaking (BOF) -RH vacuum refining-slab continuous casting-slab heating-hot continuous rolling-normalizing-cold rolling-annealing coating is adopted; the brand-new production process flow of the high-grade non-oriented silicon steel is realized as follows: electric furnace smelting (EAF), vacuum Refining (RH), external refining (LF), thin strip continuous casting, acid pickling cold rolling, decarburization annealing, secondary cold rolling and recrystallization annealing coating;
(2) In addition, the invention greatly simplifies the production process flow of the high-grade non-oriented silicon steel, cancels the hot rolling and normalizing procedures required by the conventional high-grade silicon steel production, reduces the cold rolling reduction, effectively improves the magnetic performance of finished products, and simultaneously reduces the carbon emission in the production process of the non-oriented silicon steel;
(3) According to the invention, by controlling the phase change process of the solidification process, developed columnar crystals in the solidification process are avoided, and the problem of corrugated defects on the surface of high-grade silicon steel is solved. The aim of ultralow carbon of a finished product is achieved through final decarburization annealing, and the problem of magnetic aging caused by high carbon content is solved.
Drawings
In order to more clearly describe the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below. It is to be understood that the drawings in the following description are directed to only some embodiments of the invention and are not limiting of the invention.
FIG. 1 is a schematic illustration of a twin roll caster system of the present invention;
FIG. 2 is an ODF diagram showing the grain orientation distribution of the finished non-oriented silicon steel product produced by the production process of the present invention.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
Referring now to fig. 1, a twin roll caster for continuously casting thin metal strip comprises a pair of counter-rotating casting rolls 1 each having a casting surface 1A forming a nip 2 therebetween. Molten metal (i.e., molten steel) passes from ladle 3 through tundish 4 and then through a refractory outlet shroud to transition ladle 5 and then to distributor 6 positioned between casting rolls 1 above nip 2. The molten metal so delivered forms a molten pool supported above the nip above the casting surfaces 1A of the casting rolls 1.
The casting rolls 1 are internally cooled (e.g., internally water cooled) so that as the casting rolls 1 rotate relative to each other, molten metal in the molten bath rotationally contacts the casting surfaces 1A and cools and solidifies on the casting surfaces 1A. During casting, metal shells that form on the casting surfaces 1A of the casting rolls 1 upon cooling and solidification are brought together at the nip 2 between the casting rolls to form a thin cast strip 8 delivered downwardly from the nip at a cast strip forming speed v (m/min) of the cast strip 8.
In particular, since the heat transfer efficiency of molten steel is lowered due to the increase of silicon content, in order to ensure stable continuous casting of a strip in the sub-rapid solidification process of twin-roll strip casting, the thickness of an oxide deposition film on the surface of a copper roll needs to be controlled by the roll brush 7.
Referring to fig. 2, an ODF diagram of the grain orientation distribution of the non-oriented silicon steel product produced by the process of the present invention is shown, and it can be seen that the non-oriented silicon steel produced by the method of the present invention has a strong {110} <001> goss orientation texture. Because the crystal grains of the finished product have a strong Goss oriented texture, the magnetic induction of the finished product reaches more than 1.73T, and the magnetic permeability has stronger advantages compared with non-oriented silicon steel produced by the conventional process.
Example 1
The embodiment provides a production method of non-oriented silicon steel, which comprises the following steps:
(1) Steel making: the method comprises the following steps of taking recycled silicon steel waste as a smelting raw material, and carrying out electric furnace steelmaking-RH vacuum refining-LF external refining to obtain high-purity smelting molten steel, wherein the components in percentage by weight are as follows: c:0.02%, si:2.5%, mn:1.5%, al:0.0014%, P:0.0012%, S:0.0025%, O:0.0019%, N:0.0014%, cu:0.01%, nb:0.0012%, V:0.0013%, ti:0.0008 percent, and the balance of Fe and inevitable impurities;
(2) Twin-roll thin strip continuous casting: molten steel is passed to a pair of casting rolls of a twin roll caster, the pair of casting rolls rotating in opposition, the molten steel being cooled to solidify on the casting surfaces of the pair of casting rolls and formed into a cast strip as the casting rolls rotate downwardly through the nip between the pair of casting rolls. The temperature of the molten steel in the tundish is 1579 ℃. Thickness (h) of cast strip: 1.8mm, casting strip forming speed (v): 45m/min. In the casting process, the thickness of a deposited film on the surface of the copper casting roller is controlled by the roller brush, and the thickness of the deposited film is ensured to be 18.4 mu m;
(3) Coiling: the cast strip is directly coiled at a high temperature without hot rolling, and the coiling temperature of the cast strip is 1050 ℃.
(4) Aging treatment: keeping the temperature of the cast strip coil coiled at high temperature in an insulation box for 80h, wherein the cooling speed of a thin strip coil in the insulation box is not higher than 15 ℃/h;
(5) Primary cold rolling: pickling and cold rolling the cast strip coil after aging treatment until the thickness of the thin strip is 0.5mm;
(6) Decarburization and annealing: and (3) performing decarburization annealing treatment on the thin strip coil subjected to the primary cold rolling. Dew point of the decarburization annealing process +40 ℃ and protective atmosphere of 20% 2 +80％N 2 ，P H2O /P H2 ＝0.27，P H2O And P H2 Are respectively H 2 O and H 2 Partial pressure of (c). The soaking temperature of decarburization annealing is 890 ℃, and the soaking time is 5min. Introducing dry H into the cooling section after soaking 2 The dew point is-40 ℃;
(7) Secondary cold rolling: carrying out secondary cold rolling on the thin strip coil subjected to decarburization annealing treatment to obtain a thin strip coil with the thickness of 0.30mm;
(8) And (3) recrystallization annealing: and carrying out final recrystallization annealing treatment on the thin strip coil subjected to the secondary cold rolling. The annealing temperature rise speed is controlled to be 35 ℃/s, the soaking temperature is 1050 ℃, the soaking time is 70s, the atmosphere dew point in the annealing process is-30 ℃, the protective atmosphere is 20% 2 +80％N 2 . After soaking, the thin strip coil is slowly cooled to 500 ℃ at the speed of about 10 ℃/s; and then cooled to room temperature at a cooling rate of about 30 ℃/s. And then coating insulating coatings on the upper and lower surfaces of the thin strip to obtain a high-grade non-oriented silicon steel finished product.
The finished product of the high-grade non-oriented silicon steel processed by the procedures has the following magnetic properties: p 1.5/50 ＝2.47W/kg，P 1.0/400 ＝17.62W/kg，B 50 ＝1.784T。
Example 2
The embodiment provides a production method of non-oriented silicon steel, which comprises the following steps:
(1) Steel making: the method comprises the following steps of taking recycled silicon steel waste as a smelting raw material, and carrying out electric furnace steelmaking-RH vacuum refining-LF external refining to obtain high-purity smelting molten steel, wherein the components in percentage by weight are as follows: c:0.03%, si:3.0%, mn:2.5%, al:0.0012%, P:0.0014%, S:0.0021%, O:0.0016%, N:0.0012%, cu:0.011%, nb:0.0008%, V:0.0007%, ti:0.0012%, the balance of Fe and inevitable impurities;
(2) Twin-roll thin strip continuous casting: molten steel is passed to a pair of casting rolls of a twin roll caster, the pair of casting rolls rotating in opposition, the molten steel being cooled to solidify on the casting surfaces of the pair of casting rolls and formed into a cast strip as the casting rolls rotate downwardly through the nip between the pair of casting rolls. The temperature of the molten steel in the tundish is 1572 ℃. Thickness of cast strip (h): 1.5mm, casting strip forming speed (v): 60m/min. In the casting process, the thickness of a deposited film on the surface of the copper casting roller is controlled by the roller brush, and the thickness of the deposited film is ensured to be 17.7 mu m;
(3) Coiling: the cast strip was directly coiled at a high temperature without hot rolling, and the coiling temperature of the cast strip was 1000 ℃.
(4) Aging treatment: keeping the temperature of the cast strip coil after high-temperature coiling in an insulation box for 75h, and controlling the cooling speed of a thin strip coil in the insulation box to be not higher than 15 ℃/h;
(5) Primary cold rolling: pickling and cold rolling the cast strip coil subjected to aging treatment until the thickness of the thin strip is 0.45mm;
(6) Decarburization and annealing: and (3) performing decarburization annealing treatment on the thin strip coil subjected to the primary cold rolling. Dew point of +45 ℃ in the decarburization annealing process, protective atmosphere of 20% 2 +80％N 2 ，P H2O /P H2 ＝0.27，P H2O And P H2 Are respectively H 2 0 and H 2 Partial pressure of (c). The soaking temperature of the decarburization annealing is 875 ℃, and the soaking time is 5min. In the cooling section after soaking, dry H is introduced 2 The dew point is-40 ℃;
(7) Secondary cold rolling: carrying out secondary cold rolling on the thin strip coil subjected to decarburization annealing treatment to obtain a thin strip coil with the thickness of 0.25 mm;
(8) And (3) recrystallization annealing: and (4) carrying out final recrystallization annealing treatment on the thin strip coil subjected to the secondary cold rolling. The annealing temperature rise speed is controlled to be 30 ℃/s, the soaking temperature is 1050 ℃, the soaking time is 70s, the atmosphere dew point in the annealing process is-30 ℃, the protective atmosphere is 20% 2 +80％N 2 . After soaking, the thin strip coil is cooled to 500 ℃ at a speed of about 10 ℃/s; and then cooled to room temperature at a cooling rate of about 30 ℃/s. And then coating insulating coatings on the upper surface and the lower surface of the thin strip to obtain a finished product of the high-grade non-oriented silicon steel.
The finished product of the high-grade non-oriented silicon steel processed by the procedures has the following magnetic properties: p 1.5/50 ＝2.08W/kg，P 1.0/400 ＝12.75W/kg，B 50 ＝1.761T。
Example 3
The embodiment provides a production method of non-oriented silicon steel, which comprises the following steps:
(1) Steel making: the method comprises the following steps of taking recycled silicon steel waste as a smelting raw material, and carrying out electric furnace steelmaking-RH vacuum refining-LF external refining to obtain high-purity smelting molten steel, wherein the components in percentage by weight are as follows: c:0.05%, si:3.5%, mn:3.0%, al:0.0011%, P:0.0013%, S:0.0018%, O:0.0012%, N:0.0011%, cu:0.012%, nb:0.0006%, V:0.0009%, ti:0.0013%, the balance being Fe and inevitable impurities;
(2) Twin-roll thin strip continuous casting: molten steel is passed to a pair of casting rolls of a twin roll caster, the pair of casting rolls rotating in opposition, the molten steel being cooled to solidify on the casting surfaces of the pair of casting rolls and formed into a cast strip as the casting rolls rotate downwardly through the nip between the pair of casting rolls. The temperature of the molten steel in the tundish is 1566 ℃. Thickness (h) of cast strip: 1.4mm, casting strip forming speed (v): 65m/min. In the casting process, the thickness of a deposited film on the surface of the copper casting roller is controlled by the roller brush, and the thickness of the deposited film is ensured to be 17.3 mu m;
(3) Coiling: the cast strip was directly coiled at a high temperature without hot rolling, and the coiling temperature of the cast strip was 950 ℃.
(4) Aging treatment: keeping the temperature of the cast strip coil after high-temperature coiling in an insulation box for 70h, and controlling the cooling speed of a thin strip coil in the insulation box to be not higher than 15 ℃/h;
(5) Primary cold rolling: pickling and cold rolling the aged cast strip coil until the thickness of the strip is 0.40mm;
(6) Decarburization and annealing: and (3) performing decarburization annealing treatment on the thin strip coil subjected to the primary cold rolling. Dew point of the decarburization annealing process +40 ℃ and protective atmosphere of 20% 2 +80％N 2 ，P H2O /P H2 ＝0.26，P H2O And P H2 Are each H 2 O and H 2 Partial pressure of (c). The soaking temperature of the decarburization annealing is 855 ℃, and the soaking time is 5min. Introducing dry H into the cooling section after soaking 2 The dew point is-40 ℃;
(7) Secondary cold rolling: carrying out secondary cold rolling on the thin strip coil subjected to decarburization annealing treatment to obtain a thin strip coil with the thickness of 0.20 mm;
(8) And (3) recrystallization annealing: and (4) carrying out final recrystallization annealing treatment on the thin strip coil subjected to the secondary cold rolling. The annealing temperature rise speed is controlled to be 35 ℃/s, the soaking temperature is 950 ℃, the soaking time is 70s, the atmosphere dew point in the annealing process is-30 ℃, the protective atmosphere is 20% 2 +80％N 2 . After soaking, the thin strip coil is cooled to 500 ℃ at a speed of about 10 ℃/s; cooling to room temperature at a cooling rate of about 30 ℃/s. And then coating insulating coatings on the upper and lower surfaces of the thin strip to obtain a high-grade non-oriented silicon steel finished product.
The finished product of the high-grade non-oriented silicon steel processed by the procedures has the following magnetic properties: p 1.5/50 ＝1.95W/kg，P 1.0/400 ＝11.42W/kg，B 50 ＝1.732T。
Comparative example 1
The comparative example provides a production method of non-oriented silicon steel, and the specific process flow is different from that of example 1 in that the comparative example adopts an ultra-low carbon component design, the carbon content is 0.0020%, and the molten steel is subjected to double-roller thin-strip continuous casting, then is subjected to one-step hot rolling, and is subjected to subsequent non-aging treatment and non-decarburization treatment. The method comprises the following steps:
(1) Steel making: the method comprises the following steps of taking recycled silicon steel waste as a smelting raw material, and carrying out electric furnace steelmaking-RH vacuum refining-LF external refining to obtain high-purity smelting molten steel, wherein the components in percentage by weight are as follows: c:0.0020%, si:2.5%, mn:1.5%, al:0.0025%, P:0.0018%, S:0.0021%, O:0.0011%, N:0.0013%, cu:0.018%, nb:0.0008%, V:0.0012%, ti:0.0014 percent and the balance of Fe;
(2) Strip continuous casting: the molten steel is continuously cast by a twin-roll thin strip to obtain a cast strip, and the temperature of the molten steel in a tundish is 1572 ℃. Thickness of cast strip (h): 1.8mm, casting strip forming speed (v): 45m/min. In the casting process, the thickness of a deposited film on the surface of the copper casting roller is controlled by the roller brush, and the thickness of the deposited film is ensured to be 18.4 mu m;
(3) Hot rolling: hot rolling the cast strip to 1.4mm at 1000 ℃ in one pass, and coiling at 700 ℃;
(4) Cold rolling: pickling and cold rolling the hot rolled thin strip coil to 0.30mm;
(5) And (3) recrystallization annealing: and (4) carrying out recrystallization annealing and coating treatment on the thin strip coil after cold rolling to obtain a finished product coil. The annealing temperature rise speed is controlled to be 35 ℃/s, the soaking temperature is 1050 ℃, the soaking time is 70s, the atmosphere dew point in the annealing process is-30 ℃, the protective atmosphere is 20% 2 +80％N 2 . After soaking, slowly cooling the thin strip to 500 ℃ at a reduced cooling speed of 10 ℃/s;and controlling the cooling section to room temperature at a cooling speed of 30 ℃/s. And then coating insulating coatings on the upper surface and the lower surface to obtain a finished product of the high-grade non-oriented silicon steel.
The finished product of the high-grade non-oriented silicon steel processed by the procedures has the following magnetic properties: p 1.5/50 ＝2.63W/kg，P 1.0/400 ＝19.37W/kg，B 50 =1.774T. And the surface of the finished product has obvious corrugated defects.
Comparative example 2
The comparative example provides a production method for producing high-grade non-oriented silicon steel by adopting a conventional slab continuous casting mode, hot rolling, normalizing, cold rolling and annealing processes, and the production method comprises the following steps:
(1) A pure steel smelting technology is adopted to obtain a continuous casting billet with the thickness of 220mm, and the components of the continuous casting billet are as follows: 0.0013% of C, 3.3% of Si, 1.0% of Al, 0.45% of Mn, 0.016% of P, 0.0011% of S, 0.0015% of N, 0.0013% of Nb, 0.0019% of V, 0.0010% of Ti and the balance of Fe and inevitable impurities.
(2) The heating temperature of the plate blank is 1120 ℃, and the heating time is 240min.
(3) After the continuous casting billet is subjected to rough rolling and finish rolling, the thickness of a finished hot rolled strip steel product is 2.1mm, the finish rolling temperature of hot rolling is 850 ℃, the coiling temperature is 620 ℃, and the convexity C40 of the finished hot rolled product is 45 mu m.
(4) The soaking temperature of the normalizing annealing is 850 ℃, the soaking time is 120s, and the average grain size after normalizing is 76 mu m.
(5) The cold rolling adopts six-roller single-frame reciprocating rolling, and the rolling passes are seven. The thickness of the finished product is 0.30mm. In order to ensure the width direction to be harmoniously deformed and prevent the belt from being broken due to the edge stress concentration, the first-pass pressing rate is 38 percent; the final pressing rate is 28% to ensure the shape of the finished plate. The rolling reduction of the rest intermediate passes is controlled to be 25-35%. In the cold rolling process, in order to reduce rolling load, a small-roll-diameter flat roll is adopted for rolling, and the roll diameter of a working roll is 210mm.
(6) The unit tension of the annealing temperature rising section and the soaking section is controlled to be 4N/mm 2 The annealing temperature rise rate is controlled at 30 ℃/s. The annealing soaking temperature is 1000 ℃, and the soaking time is 60s. To reduce the generation of internal stress during coolingThe force and the cooling rate are controlled within 5 ℃/s. Pure N is adopted in the annealing process 2 Protection, dew point control at-20 ℃. After the strip steel is annealed, the upper surface and the lower surface are uniformly coated with insulating coatings.
The finished product of the high-grade non-oriented silicon steel processed by the procedures has the following magnetic properties: p 1.5/50 ＝2.31W/kg，P 1.0/400 ＝14.32W/kg，B 50 ＝1.662T。
It can be seen from the above examples and comparative examples that the non-oriented silicon steel formed by the process of the present invention can also achieve good product performance under the condition of simplifying the process flow, and effectively avoid the problem of corrugated defects on the surface of the silicon steel, thereby bringing beneficial technical effects.
The above examples are merely illustrative for clarity and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.

Claims (9)

1. A method for producing non-oriented silicon steel, characterized by comprising the steps of:
step 1, smelting:
smelting molten steel, wherein the molten steel comprises the following components in percentage by weight:
c is more than or equal to 0.01 percent and less than or equal to 0.05 percent, si is more than or equal to 2.5 percent and less than or equal to 3.5 percent, mn is more than or equal to 1.5 percent and less than or equal to 3.0 percent, al is less than or equal to 0.003 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.0030 percent, O is less than or equal to 0.0030 percent, N is less than or equal to 0.0020 percent, cu is less than or equal to 0.03 percent, nb is less than or equal to 0.0020 percent, V is less than or equal to 0.0020 percent, al + O + S + N is less than or equal to 0.01 percent, and the balance is Fe and inevitable impurities,
wherein the contents of the element components contained in the molten steel further satisfy the relationship:
0.25×(Si％)+0.15×(Mn％)+0.3≤lg(C％×10 3 )≤0.25(Si％)+0.15×(Mn％)+0.5；
step 2, twin-roll strip casting:
transferring the molten steel obtained by the smelting in the step 1 to a pair of casting rolls rotating relative to each other, cooling and solidifying the molten steel on the casting surfaces of the pair of casting rolls, and passing the molten steel downward through a nip between the pair of casting rolls to form a thin cast strip having a thickness h in the range of 1.4 to 1.8mm,
step 3, coiling:
coiling the thin cast strip at a high temperature to obtain a cast strip coil, wherein the coiling temperature of the thin cast strip is 950-1050 ℃;
step 4, aging treatment:
cooling the coiled cast strip coil for 50-80h at a cooling speed of not higher than 15 ℃/h;
step 5, primary cold rolling:
pickling and cold rolling the aged cast strip coil to form a thin strip coil with the thickness of 0.35-0.50 mm;
step 6, decarburization annealing treatment:
performing decarburization annealing treatment on the thin strip coil subjected to the primary cold rolling;
step 7, secondary cold rolling:
the thin strip coil after the decarburization annealing treatment is subjected to secondary cold rolling to form a thin strip coil with the thickness of 0.20-0.30 mm;
and step 8, recrystallization annealing treatment:
and (4) carrying out recrystallization annealing treatment on the thin strip coil subjected to secondary cold rolling.
2. The method of producing non-oriented silicon steel as claimed in claim 1,
in the smelting process in the step 1, the recycled silicon steel waste is used as a smelting raw material, and electric furnace steelmaking, RH vacuum refining and LF external refining are adopted to obtain the molten steel.
3. The method of producing non-oriented silicon steel as set forth in claim 1,
in the step 2 twin roll strip casting process, the relationship between the temperature T =1607-10 × (Si%) -2 × (Mn%) of the molten steel in the tundish and the thickness h (mm) of the thin cast strip is v =135-50 × h, and the thickness T (μm) of the deposition film on the surface of the copper cast roll is controlled by a roll brush during the casting process, the thickness T =20-1/3 × Si% -1/2 × Mn%.
4. The method of producing non-oriented silicon steel as claimed in claim 1,
the thin cast strip is not subjected to a hot rolling operation prior to coiling in step 3.
5. The method of producing non-oriented silicon steel as set forth in claim 1,
in the decarburization annealing treatment of step 6, the dew point is from +35 ℃ to +45 ℃ and the protective atmosphere is 20% by weight 2 +80％N 2 ，P H2O /P H2 = 0.25-0.27, wherein P H2O And P H2 Are respectively H 2 O and H 2 The partial pressure of the alloy is that the soaking temperature T =950-20 (Si%) -500 (C%) of decarburization annealing is soaked for 3-5 min, and dry H is introduced into a cooling section after soaking 2 The dew point is-35 to-45 ℃.
6. The method of producing non-oriented silicon steel as set forth in claim 1,
in the step 5 of cold rolling, surface scale of the cast strip coil is removed through continuous acid washing, then the cast strip coil is subjected to single-frame multi-pass cold rolling, the total reduction of the cold rolling is 70-83%, the first pass reduction of the cold rolling is 35%, the rest passes are controlled to be 20-30%, and the thickness of a thin strip of the cold-rolled thin strip coil is in the range of 0.35-0.50 mm.
7. The method of producing non-oriented silicon steel as set forth in claim 1,
in the recrystallization annealing treatment of the step 8, the annealing temperature rise speed is 30-50 ℃/s, the soaking temperature is 950-1050 ℃, the soaking time is 40-70 s, the atmosphere dew point in the annealing process is-30 to-20 ℃, the protective atmosphere is 20 percent 2 +80％N 2 (ii) a After soaking, cooling the thin strip coil to 500 ℃ at a cooling speed of 10 ℃/s; then cooling at a rate of 20-30 ℃/sCooling to room temperature; and then applying insulating coatings to the upper and lower surfaces of the thin strip roll.
8. The method of producing non-oriented silicon steel according to any one of claims 1 to 7,
the non-oriented silicon steel produced by the steps 1-8 meets the following performances: p is 1.5/50 ＝1.9～2.6W/kg，P 1.0/400 ＝11～19W/kg，B 50 ＝1.73～1.79T。
9. Non-oriented silicon steel produced by the method for producing non-oriented silicon steel according to any one of claims 1 to 8.
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