High-grade non-oriented silicon steel with low magnetic anisotropy and preparation method thereof

Abstract

The application relates to the technical field of steel production, in particular to a high-grade non-oriented silicon steel with low magnetic anisotropy and a preparation method thereof, wherein the silicon steel comprises 0.4-1.5% of Mn and 0.02-0.10% of Sn in percentage by weight; the preparation method comprises smelting, hot rolling, normalizing, pickling, cold rolling, product annealing, the hot rolling heating temperature is 1120-1160 DEG C; the normalizing temperature is 900-950 DEG C, the normalizing time is 50-70s; the annealing temperature is 950-1050 DEG C, the furnace tension during annealing is less than or equal to 3MPa, and the furnace is cooled to less than or equal to 920 DEG C after annealing, and then the product is discharged and cooled. 1.5 / 50 The high-grade non-oriented silicon steel has low magnetic anisotropy, low iron loss, high magnetic induction, low iron loss P 1.5 / 50 low anisotropy and excellent performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, in particular to a high-grade non-oriented silicon steel with low magnetic anisotropy and a preparation method thereof. BACKGROUND

[0002] With the development of industrial technology, people's consumption of resources is increasing, so energy saving has become a major pursuit of people. Electric appliances are everywhere in modern life, and improving the efficiency of electric appliances can successfully save a large amount of energy. The core material of the motor and transformer applied in various electric appliances is non-oriented electrical steel, and effectively reducing the iron loss and magnetic anisotropy of the non-oriented electrical steel can reduce its energy consumption. For example, some customers have proposed the use of 0.5mm-thick non-oriented silicon steel with iron loss P 1.5 / 50 ≤2.3W / kg, magnetic induction B 5000 ≥1.67T, P 1.5 / 50 anisotropy ≤8% for the stator of a pumped storage generator.

[0003] A means for reducing the magnetic anisotropy of high-grade non-oriented electrical steel is proposed in the prior art, which is to perform electric heating in the high-temperature heating section of the annealing process (normalizing or intermediate annealing) of the steel plate before final cold rolling, so as to achieve the purposes of refining grains, uniformizing the structure, and reducing the magnetic anisotropy. However, electric heating has high requirements for equipment and operation, and it is difficult to achieve in the production and preparation process.

[0004] It is also proposed in the prior art that, under the premise of strictly controlling the purity of high-grade non-oriented silicon steel, the hot rolling heating temperature is appropriately increased to obtain a fully recrystallized hot rolling heating structure, which is beneficial to the random distribution of the texture of the steel and reduces the magnetic anisotropy, and finally obtains non-oriented silicon steel with iron loss P 1.5 / 50 ≤2.4W / kg, P 1.5 / 50 anisotropy ≤10%. However, in this scheme, the lower limit of the Mn content for inhibiting MnS solid solution is too wide under the condition of high hot rolling heating temperature, which causes the iron loss value of the finished product to fluctuate too much, the anisotropy value of the iron loss is not stable and is too high, and the magnetic induction value is also too low. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the defects in the prior art, such as the high iron loss value of high-grade non-oriented silicon steel, high magnetic anisotropy, low magnetic induction, and difficulty in preparing high-grade non-oriented silicon steel with ultra-low iron loss, so as to provide a high-grade non-oriented silicon steel with low magnetic anisotropy and a preparation method thereof.

[0006] To this end, the present application provides the following technical solutions:

[0007] The application provides a preparation method of high-grade non-oriented silicon steel with low magnetic anisotropy, and the chemical composition of the high-grade non-oriented silicon steel with low magnetic anisotropy comprises the following components in percentage by weight: C≤0.005%, Si: 2.8%-3.5%, Mn: 0.4%-1.5%, Al: 0.5%-2.0%, P≤0.05%, S≤0.001%, N≤0.002%, Ti≤0.003%, V≤0.003%, Nb≤0.004%, Sn: 0.02%-0.10%, and the balance is Fe and inevitable impurities; the preparation method comprises the following steps: smelting, hot rolling, normalizing, pickling, cold rolling, and product annealing, wherein the hot rolling heating temperature is 1120-1160 DEG C; the normalizing temperature is 900-950 DEG C, and the normalizing time is 50-70 s; the annealing temperature is 950-1050 DEG C, the furnace tension during annealing is ≤3 MPa, and the furnace is cooled to ≤920 DEG C after annealing, and then the steel is cooled.

[0008] Preferably, the holding time of the hot rolling heating is 0.5-1 h.

[0009] Preferably, the hot final rolling temperature is 800-900 DEG C.

[0010] Preferably, the hot rolling is followed by a coiling step, and the coiling temperature is 580-680 DEG C; the steel coil obtained through coiling is naturally cooled to room temperature.

[0011] Preferably, after normalizing, the step of pickling to clean the surface is included.

[0012] Preferably, the cold rolling reduction is 70%-85%.

[0013] Preferably, the annealing time is 10-60 s.

[0014] Preferably, the annealing is carried out in a mixed gas of H2 and N2 or a full H2 atmosphere.

[0015] Preferably, after annealing, the step of coating and finishing according to a conventional method is included.

[0016] In the preparation method of the high-grade non-oriented silicon steel with low magnetic anisotropy, the smelting process of clean steel is used, so that the inclusions in the silicon steel can be better reduced, the mechanical properties of the silicon steel are improved, and the amount of precipitates such as MnS and AlN in the silicon is at a very low level.

[0017] The application further provides the high-grade non-oriented silicon steel with low magnetic anisotropy prepared by the above preparation method, and the prepared high-grade non-oriented silicon steel with low magnetic anisotropy can be applied to various large motors and high-efficiency motors, such as pumped storage motor.

[0018] The preferred mass percentages of the elements in the steel and the effects of rolling and heat treatment are as follows:

[0019] Sn content is 0.02% to 0.10%, Sn is a key element to be added in the present application, it is generally considered that the addition of Sn element can mainly improve the {100} surface texture strength and improve the magnetic induction, but the addition of Sn element can not only improve the magnetic induction, but also reduce the iron loss and iron loss anisotropy through the improvement of surface texture, especially in the case of relatively high hot rolling heating temperature required by the present application, its effect is more significant, therefore, its content is defined to be above 0.02%; on the other hand, if too much is added, the cost will rise, and it will cause furnace roll nodulation in high temperature annealing, therefore, its upper limit is defined to be 0.10%.

[0020] C content is below 0.005%, C is a component harmful to magnetism, theoretically the lower the better, therefore its content is defined to be below 0.005%, considering its influence on magnetic aging, its content is preferably below 0.003%.

[0021] Si content is defined to be 2.8% to 3.5%, Si is an effective added element to improve resistivity and improve iron loss, for high grade non-oriented silicon steel, if Si content does not reach 2.8%, the required magnetism cannot be obtained, therefore its lower limit is 2.8%; on the other hand, if Si content exceeds 3.5%, its hardness will be very high, and punching processing is prone to occur, therefore its upper limit is defined to be 3.5%.

[0022] Mn content is 0.4% to 1.5%, Mn can improve hot rolling plasticity, high Mn content can improve the solid solution temperature of MnS, correspondingly the casting blank heating temperature can be improved, thereby improving the hot rolling plate structure, and adding Mn can inhibit the hot brittleness caused by S, if Mn content is less than 0.4%, the above effect cannot be achieved; on the other hand, if its content exceeds 1.5%, it will lead to the deterioration of magnetism, therefore its content range is defined to be 0.4% to 1.5%.

[0023] Al content is 0.5 to 2.0%, Al, in addition to the effect of deoxidizing steel, is also an effective element to improve resistivity and improve iron loss as Si, in order to effectively reduce iron loss, its minimum value is limited to 0.5%; on the other hand, if Al content exceeds 2.0%, it will cause the hardness to rise as Si, resulting in the deterioration of processing performance, therefore its upper limit is defined to be 2.0%.

[0024] P content is below 0.05%, P can effectively improve the iron loss, but for high grade non-oriented silicon, more than 0.05% will significantly deteriorate the cold ductility of steel.

[0025] S content is below 0.0010%, S is an important component of inclusions in steel, in the present application, when hot rolling heating temperature is high, MnS precipitates in steel will be dissolved in large amount, and then diffuse in the process of hot working, and further hinder the grain growth in the annealing process of finished product, and reduce the magnetic property of finished product, therefore, its content must be controlled below 0.0010%, preferably below 0.0008%.

[0026] N content is below 0.002%, like S, N is also an important component of inclusions in steel, in the present application, when hot rolling heating temperature is high, AlN precipitates in steel will be dissolved in large amount, and then diffuse in the process of hot working, and hinder the grain growth in the annealing process of finished product, and reduce the magnetic property of finished product, therefore, its content must be controlled below 0.002%, preferably below 0.0015%.

[0027] Ti content is below 0.003%, as the steel with high Al content, TiO in slag will be reduced by Al in the step of adding alloy in the refining process, and Ti enters into the molten steel, therefore, Ti content in steel is relatively high, but as the carbide and nitride forming element, its fine precipitates will hinder the grain growth in the annealing process of finished product, therefore, Ti must be controlled below 0.003%.

[0028] Nb and V contents are below 0.004% and 0.003% respectively, Nb and V are also the key impurity elements in the present application as the carbide and nitride forming elements, and their contents should be below 0.004% and 0.003% respectively.

[0029] Hot rolling heating temperature is 1120-1160°C, high hot rolling heating temperature can make the recrystallization of silicon steel more sufficient, and the randomness of hot rolling texture organization is stronger, too, and low hot rolling heating temperature will increase the rolling pressure of hot rolling, affect the control of hot rolling shape, increase the rolling difficulty, and the fine precipitates of TiN and TiC in steel will hinder the grain growth in the annealing process of finished product, if lower than 1120°C, the recrystallization after hot rolling heating will be insufficient, the fiber texture after hot rolling will be developed, and the anisotropy of finished product will not meet the requirements, and if higher than 1160°C, a small amount of MnS and AlN in steel will also be dissolved and precipitated, and affect the magnetic property of finished product.

[0030] Normalizing temperature is 900-950°C, and normalizing time is 50-70s, normalizing is a necessary process for improving the texture of finished product, when continuous annealing is adopted, the normalizing temperature is controlled at 900-950°C, and the normalizing time is 50-70s, if the temperature is too low, the effect of improving the texture will not be achieved, if the temperature exceeds 950°C, the grains will grow too large, and cold rolling will be difficult, and if the normalizing time is too short, the magnetic property will not be improved, and if the normalizing time is too long, the production efficiency will be low.

[0031] The annealing temperature is 950-1050 DEG C, if the temperature is less than 950 DEG C, the crystal grains cannot grow sufficiently, and the magnetic performance is poor, and if the temperature exceeds 1050 DEG C, the surface of the steel plate is easily oxidized and nodular, etc. The tension in the furnace during annealing is less than or equal to 3 MPa, which can effectively avoid the deformation of the steel strip, because if the tension is too large, the steel strip is deformed along the rolling direction, and there is residual internal stress, and the transverse iron loss is increased. The furnace is cooled to less than or equal to 920 DEG C after annealing, which can reduce the internal stress of the steel plate and reduce the magnetic anisotropy.

[0032] The present application has the following beneficial effects:

[0033] The present application provides a preparation method of high-grade non-oriented silicon steel with low magnetic anisotropy, and the chemical composition includes, in terms of percentage by weight, C≤0.005%, Si: 2.8%-3.5%, Mn: 0.4%-1.5%, Al: 0.5%-2.0%, P≤0.05%, S≤0.001%, N≤0.002%, Ti≤0.003%, V≤0.003%, Nb≤0.004%, Sn: 0.02%-0.10%, and the balance is Fe and inevitable impurities; the preparation method includes smelting, hot rolling, normalizing, pickling, cold rolling, and product annealing, wherein the hot rolling heating temperature is 1120-1160 DEG C; the normalizing temperature is 900-950 DEG C, and the normalizing time is 50-70 s; the annealing temperature is 950-1050 DEG C, the tension in the furnace during annealing is less than or equal to 3 MPa, the furnace is cooled to less than or equal to 920 DEG C after annealing, and the cooling after discharge. The present application can make the random distribution of the texture organization in the high-grade non-oriented silicon steel, reduce the iron loss, reduce the iron loss anisotropy, and increase the magnetic induction of the silicon steel through the cooperation of the chemical composition and the subsequent rolling and heat treatment method, and the finished product iron loss P 1.5 / 50 ≤2.3 W / kg, the magnetic induction B 5000 ≥1.67 T, the iron loss P 1.5 / 50 anisotropy ≤8% of high-grade cold-rolled non-oriented silicon steel. In the present application, the amount of MnS and AlN precipitates in the silicon steel is controlled at a very low level, and the content of Mn element which can inhibit the solid solution of MnS is also appropriately increased, at this time, appropriately increasing the hot rolling heating temperature, the solid solution amount of such precipitates which are not conducive to the magnetic properties will not increase significantly. In the present application, an appropriate amount of Sn element is added, which can enhance the (100) and other beneficial surface textures of the finished product, and can also make the distribution of beneficial texture strength in each direction in the plane more uniform, so as to reduce the iron loss anisotropy of the finished product.

[0034] In the preparation method of high-grade non-oriented silicon steel with low magnetic anisotropy provided by the present application, the cold rolling reduction rate is 70%-85%, which can improve the finished product texture. DETAILED DESCRIPTION

[0035] The following examples are provided to better further understand the present application and are not limited to the best mode contemplated, do not constitute limitations on the scope of the present application, and are not intended to convey any idea of the scope of the present application, and any product identical or similar to the present application obtained by the disclosure of the present application or by combining the present application with other prior art features falls within the scope of the present application.

[0036] When the specific experimental steps or conditions are not indicated in the examples, the operations or conditions can be performed according to the conventional experimental steps described in the literature in the art. When the reagents or instruments are not indicated by the manufacturer, they are conventional reagent products that can be obtained by purchase in the market.

[0037] The smelting method of the silicon steel used in the present application is as follows:

[0038] Converter blowing, refining in RH vacuum, forced desulfurization, deoxidation, degassing, so that the C, P content in the silicon steel reaches the requirements in the present application, and finally continuous casting is obtained. The chemical composition of each slab is shown in Table 1 in terms of weight percentage.

[0039] Table 1

[0040]

[0041] The items with "*" in Table 1 are not within the scope of the present application.

[0042] The preparation method of the high-grade non-oriented silicon steel with low magnetic anisotropy provided by the examples and comparative examples of the present application is as follows:

[0043] (1) The continuous casting billet obtained above is heated to the hot rolling heating temperature and kept for 40 min;

[0044] (2) The heated continuous casting billet is discharged for hot rolling, and hot rolling is performed to 2.1 mm thick steel coil, the hot final rolling temperature is 840℃, the coiling temperature is 650℃, and the coiled steel is naturally cooled to room temperature;

[0045] (3) Normalizing and pickling, normalizing time 60s;

[0046] (4) Cold rolling, cold rolling reduction rate 76.2%, final product thickness 0.5mm;

[0047] (5) Product annealing is performed on the continuous annealing line, annealing time 25s, maintaining a certain furnace tension, furnace cooling, and post-furnace cooling to obtain the high-grade non-oriented silicon steel sample with low magnetic anisotropy.

[0048] For the samples obtained in the examples and comparative examples, an Epstein square test sample is prepared, and the iron loss P 1.5 / 50 , magnetic induction B5000 And calculate P 1.5 / 50 Anisotropy = (P 1.5 / 50横向 -P 1.5 / 50纵向 ) / (P 1.5 / 50横向 +P 1.5 / 50纵向 )×100%.

[0049] The specific steel grades used in each embodiment and comparative example, the hot rolling heating temperature, the normalizing temperature, the annealing temperature, the tapping temperature, the furnace tension, and the P of the obtained samples. 1.5 / 50 B 5000 , and P 1.5 / 50 The anisotropy is shown in Table 2.

[0050] Table 2

[0051]

[0052]

[0053] Items marked with "*" in Table 2 are not within the scope of this invention.

[0054] As shown in Tables 1 and 2, the iron loss P of the high-grade non-oriented silicon steel samples with low magnetic anisotropy, where the chemical composition ratios and heat treatment parameters are within the range specified in this invention, is low. 1.5 / 50 ≤2.3W / kg, magnetic induction B 5000 ≥1.67T, P 1.5 / 50 Anisotropy ≤8%, excellent performance. In contrast, among the samples in Comparative Examples 1 to 8 that were not treated according to the heat treatment methods specified in this invention, and among the samples in Comparative Examples 9 to 15 whose chemical composition ratios were not within the specified range of this invention, Comparative Example 1 achieved an iron loss of 2.27 W / kg, while the iron loss P in the other comparative examples was significantly lower. 1.5 / 50 The lowest is 2.36 W / kg, and the highest is 2.44 W / kg; the magnetic induction B in Comparative Examples 1 and 5 5000 It can reach over 1.67T, but other comparative magnetic induction B 5000 The maximum capacity is only 1.668T; P 1.5 / 50 The anisotropy was as low as 8.4%, and the performance was inferior to that of the samples in the examples. The high-grade non-oriented silicon steel with low magnetic anisotropy prepared according to the present invention has superior performance parameters and can meet the requirements of large motors for high-grade non-oriented silicon steel.

[0055] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for producing a high-grade non-oriented silicon steel having low magnetic anisotropy, characterized by, The chemical composition of the high-grade non-oriented silicon steel with low magnetic anisotropy includes, by weight percentage, C≤0.005%, Si: 2.8%-3.5%, Mn: 0.4%-0.49%, Al: 0.5%-2.0%, P≤0.05%, S≤0.001%, N≤0.002%, Ti≤0.003%, V≤0.003%, Nb≤0.004%, Sn: 0.048%-0.10%, and the balance of Fe and inevitable impurities; P of the high-grade non-oriented silicon steel with low magnetic anisotropy 1.5 / 50 anisotropy ≤ 8%; The preparation method comprises the following steps: hot rolling, normalizing, pickling, cold rolling, and product annealing, wherein, The hot rolling heating temperature is 1120-1160℃; The normalizing temperature is 900-950℃, and the normalizing time is 50-70s; The annealing temperature is 950-1050℃, the furnace tension during annealing is 2.1-3MPa, the furnace is cooled to ≤920℃ after annealing, and the annealing product is cooled outside the furnace.

2. The method of producing a high-grade non-oriented silicon steel with low magnetic anisotropy according to claim 1, characterized by, The hot rolling heating holding time is 0.5-1h; And / or, the hot finish rolling temperature is 800-900℃.

3. The method of producing a high-grade non-oriented silicon steel having low magnetic anisotropy according to claim 1, characterized by, The step of coiling is included after hot rolling, and the coiling temperature is 580-680℃; the steel coil obtained by coiling is naturally cooled to room temperature.

4. The method of producing a high-grade non-oriented silicon steel with low magnetic anisotropy according to claim 1, characterized in that, The step of pickling to clean the surface is included after normalizing.

5. The method of producing a high-grade non-oriented silicon steel with low magnetic anisotropy according to claim 1, characterized in that, The cold rolling reduction is 70%-85%.

6. The method of producing a high-grade non-oriented silicon steel with low magnetic anisotropy according to claim 1, characterized in that, The annealing time is 10-60s.

7. The method of producing a high-grade non-oriented silicon steel with low magnetic anisotropy according to claim 1, characterized in that, The annealing is performed in H2 and N2 mixed gas or full H2 atmosphere.

8. The method of producing a high-grade non-oriented silicon steel with low magnetic anisotropy according to claim 1, characterized in that, The step of coating and finishing by conventional method is included after annealing.

9. A high-grade non-oriented silicon steel with low magnetic anisotropy prepared by the preparation method in any one of claims 1 to 8.

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