Smelting method of non-oriented silicon steel for new energy automobile

Abstract

The invention relates to a smelting method of non-oriented silicon steel for a new energy automobile, which comprises the following steps: smelting desulfurized molten iron in a converter, and tapping to obtain first molten steel; according to the cleanliness grade of a steel ladle where the first molten steel is located, the baking time of the steel ladle and the end point oxygen activity of the first molten steel, the target adding amount of modifier slag is obtained; carrying out top slag modification on the first molten steel by using the modifier slag charge with a target addition amount to obtain second molten steel; the second molten steel is subjected to RH refining, and third molten steel with the set oxygen content and the set sulfur content is obtained; and rare earth alloy powder is injected into the third molten steel, then calcium oxide-containing material powder is injected, and the non-oriented silicon steel for the new energy automobile is obtained. The cleanliness of the non-oriented silicon steel for the new energy automobile is improved.

Description

Technical Field

[0001] The present application relates to the technical field of steelmaking, and in particular to a method for smelting non-oriented silicon steel for new energy vehicles. Background Art

[0002] With the rapid development of new energy vehicles, the motors used in new energy vehicles are required to be efficient, environmentally friendly, and low-noise as their core components, which has become one of the hot spots and difficulties in the development of new energy vehicles. Among them, the core part of the motor is the motor core, and the selection of core materials has a crucial impact on motor performance and manufacturing costs. New energy vehicle motors generally have high speeds and high power, so they put forward higher requirements for magnetic conductive materials: high saturation flux density, high magnetic induction intensity, low loss (especially low iron loss under medium frequency conditions of 400-1500Hz), excellent mechanical properties and fatigue resistance, good processing performance, and high cost performance.

[0003] At present, in addition to the main elements Al and Si, S has a greater influence on the steel loss of non-oriented silicon steel in terms of molten steel composition. It mainly pins grain boundaries and domain walls through nano-scale sulfide precipitates MnS, hindering the magnetization process and leading to increased steel loss of silicon steel. The use of rare earth elements can control the low-melting point MnS to form high-melting point sulfides and improve the texture. The traditional rare earth addition methods mainly include ladle input method, ladle press method, ladle core wire feeding method, die casting injection pipe addition method, die hanging rare earth metal rod method, etc. The ladle top slag modification effect is unstable. The traditional method results in a low or very low effective recovery rate of rare earths, and the rare earth content in steel fluctuates greatly. The subsequent product performance improvement or improvement is extremely unstable, and rare earth treatment is difficult to promote. In order to improve the recovery rate of rare earth alloys under the condition of continuously improving the cleanliness of molten steel, the methods developed later, such as RH vacuum chamber feeding method, feeding rare earth wire in the tundish, feeding rare earth wire in the crystallizer, etc., have greatly improved the recovery rate of rare earth alloys. However, the problems of nozzle and stopper blockage in the continuous casting process have not been solved, and the feeding of rare earth wire in the crystallizer has not solved the problem of uneven distribution of rare earths in the ingot. Summary of the invention

[0004] The present application provides a smelting method for non-oriented silicon steel for new energy vehicles to solve the following technical problem: how to improve the cleanliness of non-oriented silicon steel for new energy vehicles.

[0005] In a first aspect, the present application provides a method for smelting non-oriented silicon steel for new energy vehicles, the method comprising:

[0006] The desulfurized molten iron is subjected to converter smelting and then tapped to obtain the first molten steel;

[0007] Obtaining a target addition amount of the modifier slag according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, and the endpoint oxygen activity of the first molten steel;

[0008] Using the modifier slag material with a target addition amount to perform top slag modification on the first molten steel to obtain a second molten steel;

[0009] The second molten steel is subjected to RH refining to obtain a third molten steel having a set oxygen content and a set sulfur content;

[0010] Rare earth alloy powder is sprayed into the third molten steel, and then calcium oxide-containing material powder is sprayed to obtain non-oriented silicon steel for new energy vehicles.

[0011] Optionally, obtaining a target addition amount of the modifier slag according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, and the oxygen activity of the first molten steel includes:

[0012] If the cleanliness level of the ladle in which the first molten steel is located is Class C, the baking time of the ladle is greater than 25 minutes, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.7kg / t to 2.2kg / t;

[0013] If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is greater than 25 minutes, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.5kg / t to 1.7kg / t;

[0014] If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is ≤25min, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.2kg / t to 1.5kg / t;

[0015] If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is ≤25min, and the endpoint oxygen activity of the first molten steel is 350ppm≤≤500ppm, then the target addition amount of the modifier slag is 1.0kg / t to 1.3kg / t.

[0016] Optionally, the mass fraction of the set oxygen content is ≤0.0010%, and the mass fraction of the set sulfur content is

[0017] ≤0.0015%.

[0018] Optionally, the particle size of the rare earth alloy powder is less than 0.5 mm.

[0019] Optionally, the mass fraction of the rare earth content in the rare earth alloy powder is greater than 0 and not greater than ≤21%.

[0020] Optionally, the mass fraction of the rare earth content in the rare earth alloy powder is 19.5% to 20.5%.

[0021] Optionally, relative to 1 t of the third molten steel, the injection amount of the sprayed rare earth alloy powder is 0.33 kg to 0.54 kg; the injection flow rate of the rare earth alloy powder is 35 kg / min to 40 kg / min.

[0022] Optionally, relative to 1 t of the third molten steel, the injection amount of the calcium oxide-containing material powder is 0.56 kg to 0.70 kg; the injection flow rate of the calcium oxide-containing material powder is 50 kg / min to 55 kg / min.

[0023] Optionally, the process parameters of the steel tapping include: a steel tapping temperature of 1640° C. to 1660° C., and a steel tapping time of ≥5 min.

[0024] Optionally, the method further includes:

[0025] The molten iron is deslagging, and then KR desulfurization and multiple deslagging are performed to make the deslagging bright surface ≥95%, thereby obtaining desulfurized molten iron.

[0026] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0027] The smelting method of the non-oriented silicon steel for new energy vehicles provided in the embodiment of the present application comprises: subjecting desulfurized molten iron to converter smelting, and then tapping to obtain a first molten steel; obtaining a target addition amount of a modifier slag according to the cleanliness level of a ladle in which the first molten steel is located, the baking time of the ladle, and the terminal oxygen activity of the first molten steel; top slag modification of the first molten steel using the modifier slag with the target addition amount to obtain a second molten steel; RH refining of the second molten steel to obtain a third molten steel with a set oxygen content and a set sulfur content; spraying rare earth alloy powder into the third molten steel, and then spraying calcium oxide-containing material powder to obtain non-oriented silicon steel for new energy vehicles. The desulfurized iron water is smelted in a converter and tapped from the converter, and the terminal oxygen activity, composition and slag oxidizability of the desulfurized iron water can be preliminarily controlled to obtain the first molten steel; according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle and the terminal oxygen activity of the first molten steel, the amount of slag modifier added can be dynamically adjusted to achieve relatively accurate control of the slag oxidizability, ensure the stability of the ladle top slag modification effect, and then achieve the stability of subsequent product performance and continuity of casting, thereby reducing the subsequent rare earth treatment and the secondary oxygen transfer of the slag to the molten steel caused by new inclusions. The second molten steel is refined by RH to obtain the third molten steel with set oxygen content and set sulfur content, which can avoid the rare earth from being easily oxidized to generate too much rare earth oxides, thereby ensuring the subsequent sulfur fixation effect of rare earth; spraying rare earth alloy powder into the third molten steel can effectively reduce the local supersaturation after rare earth is added to the molten steel, and generate more rare earth sulfide inclusions; spraying calcium oxide-containing material powder can bring inclusions from the molten steel to the ladle top slag, thereby improving the cleanliness of the molten steel, reducing the subsequent molten steel casting nozzle blockage and improving the quality of the steel billet. In summary, the cleanliness of non-oriented silicon steel for new energy vehicles is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0030] Figure 1 The present invention is a schematic flow chart of a method for smelting non-oriented silicon steel for new energy vehicles according to some embodiments of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0032] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0033] In this application, the terms "include", "comprising", etc. mean "including but not limited to". In this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0034] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] In the first aspect, the present application provides a method for smelting non-oriented silicon steel for new energy vehicles. Figure 1 For a schematic diagram of a smelting method of non-oriented silicon steel for new energy vehicles provided in accordance with some embodiments of the present application, please refer to Figure 1 , the method comprising:

[0036] S1, smelting the desulfurized molten iron in a converter, and then tapping the steel to obtain the first molten steel;

[0037] In some embodiments, the method further comprises:

[0038] The process before step S1 includes: slagging the molten iron, followed by KR desulfurization and multiple slagging, so that the slagging bright surface is ≥95%, and desulfurized molten iron is obtained.

[0039] In some embodiments, the process parameters of the steel tapping include: a steel tapping temperature of 1640° C. to 1660° C., and a steel tapping time of ≥5 min.

[0040] In the embodiment of the present application, when smelting non-oriented silicon steel for new energy, there are a series of requirements for the composition and temperature of molten iron, such as the composition of molten iron (wt%): C>3.8%, 0.25%≤Si≤0.7%, S≤0.035%, Ti≤0.05%, and the initial temperature of molten iron is ≥1300°C. After the composition and temperature of the molten iron are confirmed to be correct, the slag is removed before desulfurization in KR desulfurization, and the KR molten iron desulfurization is carried out after the front slag removal is completed. The stirring time is ≥15min, and the sampling and temperature measurement are immediately carried out after the stirring is completed to ensure that the sulfur content of the molten iron after desulfurization is ≤0.0010%. After sampling, the slag is removed 2 to 3 times, and the subsequent slag is removed after calming for 5 to 7 minutes after each slag removal. The calming time is mainly considered to consider the floating time required for the molten iron desulfurization product. After multiple slag removals, it is mainly considered that after each slag removal, the slag removal plate stirs the slag-iron interface and a small amount of slag will re-enter the molten iron. Therefore, multiple slag removals are carried out to ensure that the slag removal bright surface is ≥95%.

[0041] Since it is necessary to control the final oxygen activity of molten steel, molten steel composition and oxidizability of slag, a converter with good double blowing (bottom blowing) effect is selected for smelting, and a converter with an average carbon oxygen product of ≤0.0020% in the first five furnaces of smelting non-oriented silicon steel for new energy is selected. If the conditions are not met, the smelting is postponed or the bottom of the furnace is operated (to ensure that the bottom blowing hole is exposed). Argon is blown at the bottom of the converter during the whole process of converter blowing, and the converter tapping temperature is controlled at 1640-1660℃. An online turnover ladle is selected to reduce the subsequent RH oxygen blowing temperature rise caused by the low temperature of molten steel. The final oxygen activity of converter blowing is 350ppm≤[O]≤650ppm. When the oxygen is low, the converter is post-blown; when the oxygen is high, the converter is calmed and tapped; the converter final slag TFe≤18% is controlled, and when the converter carbon oxygen product and final oxygen activity are within the above range, the final slag TFe≤18% is naturally completed.

[0042] Before smelting, the tapping port of the converter is checked, and the tapping time of the converter is ≥5min, mainly to reduce the amount of slag before and during the tapping process of the converter, and to reduce the problems of adding more slag modifiers due to the slag of the converter and the low alloy yield caused by the large amount of slag; according to the steel liquid truck scale, when the tapping amount of the converter reaches 1 / 5 to 1 / 4 of the total tapping amount, 2 to 4 kg / t of sintered lime is added, and the total flow rate of the bottom blowing of the ladle is controlled at 300 to 700 L / min before and after the addition of sintered lime; when the tapping is completed, the bottom blowing of the ladle is closed, and after the bottom blowing is closed for 20s, a modifier slag containing 50±3% of metallic aluminum is immediately added to modify the top slag of the ladle. Exemplarily, the above-mentioned tapping temperature can be 1640℃, 1645℃, 1650℃, 1655℃, 1660℃, etc., and the above-mentioned tapping time can be 5min, 6min, 7min, 8min, 9min, etc.

[0043] S2. According to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, and the endpoint oxygen activity of the first molten steel, a target addition amount of the modifier slag is obtained;

[0044] In some embodiments, obtaining the target amount of the modifier slag according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, and the oxygen activity of the first molten steel comprises:

[0045] If the cleanliness level of the ladle in which the first molten steel is located is Class C, the baking time of the ladle is greater than 25 minutes, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.7kg / t to 2.2kg / t;

[0046] If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is greater than 25 minutes, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.5kg / t to 1.7kg / t;

[0047] If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is ≤25min, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.2kg / t to 1.5kg / t;

[0048] If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is ≤25min, and the endpoint oxygen activity of the first molten steel is 350ppm≤≤500ppm, then the target addition amount of the modifier slag is 1.0kg / t to 1.3kg / t.

[0049] S3, using the modifier slag material with a target addition amount to perform top slag modification on the first molten steel to obtain a second molten steel;

[0050] In the embodiment of the present application, the amount of slag modifier added is dynamically adjusted according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle and the endpoint oxygen activity of the first molten steel, so as to achieve relatively accurate control of the oxidizability of the slag, ensure the stability of the slag modification effect on the top of the ladle, and further achieve the stability of subsequent product performance and the continuity of casting, thereby reducing the subsequent rare earth treatment and the secondary oxygen transfer of the slag to the molten steel after the rare earth treatment, causing new inclusions to be generated.

[0051] The cleanliness levels of the above-mentioned ladles are specifically A, B, C, and D. Among them, the ladles determined to be A-level are in a clean state as a whole, the ladles determined to be B-level are in a relatively clean state as a whole, the ladles determined to be C-level are in an unclean state as a whole, and the ladles determined to be D-level are in a very unclean state as a whole. Classify the cleanliness of the ladles: classify the cleanliness of the ladles and take pictures of the ladles at the same time; mainly divided into five items: photos, overall ladle condition, refractory bricks, bottom blowing bricks, and rims. All five items are rated, with the lowest level as the standard. See the table below for details. The correspondence between the image feature information of the ladle picture and the four levels is obtained in the following way. Please refer to the ladle rating conditions shown in Table 1.

[0052] Table 1 Ladle rating conditions

[0053]

[0054]

[0055] Explanation of the ladle rating conditions in Table 1: 1) Explanation of the cleanliness of the ladle: Clean: There is no slag accumulation or slag flow traces at the bottom and upper slag line of the slag flipping side; Relatively clean: There may be a little slag or slag flow traces at the bottom and upper slag line of the slag flipping side; Unclean: There is more slag at the bottom and upper slag line of the slag flipping side; Very unclean: There is a lot of slag at the bottom and upper slag line of the slag flipping side. 2) Explanation of the cleanliness of refractory bricks: Bricks and brick joints are visible: There is no slag covering the surface of refractory bricks and brick joints; Bricks are basically visible: The surface of refractory bricks is covered with a thin layer of slag, and the outline of the bricks is basically visible; Bricks are basically invisible: The surface of refractory bricks is covered with thick slag, and only small areas can see the bricks; Bricks are invisible: The surface of refractory bricks is covered with thick slag, and bricks can only be seen in sporadic small areas; Bricks are invisible: The surface of refractory bricks is covered with thick slag, and bricks cannot be seen as a whole. 3) Description of the visibility of bottom blown bricks: Bottom blown bricks are visible: the arrangement of bottom blown bricks and bottom blowing holes are visible; Bottom blown brick area is visible: there is a small amount of slag at the bottom of the package, but the bottom blown brick area is visible; The outline of the bottom blown brick area is basically visible: there is more slag at the bottom of the package, but the outline of the bottom blown brick area is basically visible; The outline of the bottom blown brick area is not visible: there is a lot of slag at the bottom of the package, and the outline of the bottom blown brick area is not visible.

[0056] S4, performing RH refining on the second molten steel to obtain a third molten steel having a set oxygen content and a set sulfur content;

[0057] In some embodiments, the set oxygen content has a mass fraction of ≤0.0010%, and the set sulfur content has a mass fraction of ≤0.0015%.

[0058] In the embodiment of the present application, after the RH molten steel arrives at the station, the temperature is measured and the oxygen is determined. Whether to blow oxygen for decarburization and blow oxygen for heating is determined according to the results of the temperature measurement and oxygen determination. After the decarburization is completed, the temperature is measured and the oxygen is determined, and the deoxidation and alloying operation is performed. The first batch of RH desulfurizer is added 3 minutes after the deoxidation and alloying operation is completed for desulfurization operation. When multiple batches of RH desulfurizer need to be added, the time interval between each batch is 2 minutes. After the last batch of desulfurizer is added, the molten steel circulates for 5 to 7 minutes for oxygen determination. At the same time, the ladle top slag sample is taken, and the total oxygen of the molten steel is predicted according to the oxygen determination value and the top slag composition. The subsequent rare earth injection is performed according to the total oxygen of the molten steel and the predicted sulfur level after desulfurization, that is, the mass fraction of the oxygen content is set to ≤0.0010%, and the mass fraction of the set sulfur content is set to ≤0.0015%. At this time, the rare earth alloy is added. Rare earth is very easy to oxidize or its reducing ability is very strong. With the increase of oxygen content, the sulfur fixation ability of rare earth elements is weakened. Therefore, the oxygen content needs to be controlled before adding rare earth. If the oxygen content of the third molten steel is too high, the rare earth is easily oxidized to generate too much rare earth oxide, and the amount of rare earth and sulfur combination is reduced, then the control effect of rare earth on MnS becomes worse. At the same time, the oxygen content and sulfur content of the molten steel are too high, which may also lead to a large amount of rare earth alloy added, a large number of inclusions, and an increased probability of nozzle blockage. Exemplarily, the mass fraction of the above-mentioned oxygen content can be 0.0010%, 0.0009%, 0.0008%, etc., and the mass fraction of the above-mentioned sulfur content can be 0.0015%, 0.0013%, 0.0011%, etc.

[0059] S5. Spraying rare earth alloy powder into the third molten steel, and then spraying calcium oxide-containing material powder to obtain non-oriented silicon steel for new energy vehicles.

[0060] In some embodiments, the particle size of the rare earth alloy powder is less than 0.5 mm.

[0061] In the embodiment of the present application, rare earth alloy powder is sprayed by RH top gun, and the particle size of rare earth alloy powder is less than 0.5mm, so as to avoid serious wear of the spray gun due to large particle size, and to avoid high local rare earth supersaturation after spraying into the molten steel due to large particle size, and to avoid the inclusions produced are not the desired inclusions; in addition, the rare earth content of the alloy is much lower than that of high-purity rare earth, which effectively reduces the local supersaturation after rare earth is added to the molten steel, and generates more rare earth sulfide inclusions.

[0062] In some embodiments, the mass fraction of the rare earth content in the rare earth alloy powder is greater than 0 and not greater than ≤21%.

[0063] In some embodiments, the mass fraction of the rare earth content in the rare earth alloy powder is 19.5% to 20.5%.

[0064] In the embodiment of the present application, the mass fraction of the rare earth content in the rare earth alloy powder is greater than 0 and not greater than ≤ 21%. The rare earth alloy is more easily distributed evenly in the molten steel, and more rare earth sulfide inclusions are generated. If high-purity rare earth is used, the local concentration product / supersaturation is too large, and it is easy to produce pure rare earth oxides or sulfides, then the number of effective nuclei is reduced, and the number of dependent nuclei during the precipitation of MnS cannot be guaranteed), and the rest is mainly Fe. Exemplarily, the mass fraction of the rare earth content in the rare earth alloy powder can be 21%, 20%, 19%, 18%, 17%, etc., and further, the mass fraction of the rare earth content in the rare earth alloy powder can be 19.5%, 19.8%, 20%, 20.3%, 20.5%, etc.

[0065] In some embodiments, relative to 1 t of the third molten steel, the injection amount of the sprayed rare earth alloy powder is 0.33 kg to 0.54 kg; the injection flow rate of the rare earth alloy powder is 35 kg / min to 40 kg / min.

[0066] In some embodiments, relative to 1 t of the third molten steel, the injection amount of the calcium oxide-containing material powder is 0.56 kg to 0.70 kg; the injection flow rate of the calcium oxide-containing material powder is 50 kg / min to 55 kg / min.

[0067] In the embodiments of the present application, the rare earth includes at least one of the following: La, Ce; the rare earth is added mainly for sulfur fixation, so the S and O in the molten steel before adding the rare earth are controlled and the ladle top slag is modified. If the injection amount of rare earth is too small, it is difficult to achieve the sulfur fixation effect; if the injection amount is too large, it is easy to cause free rare earth elements in the molten steel, which will have other effects on the performance of the steel and easily cause poor castability of the molten steel. If the injection flow rate of the rare earth alloy powder is too large, it may cause the local rare earth supersaturation of the molten steel to be too large, and the required inclusions cannot be obtained. The sprayed calcium oxide material powder can include one or more of lime powder and raw dolomite powder, which can be used to enter the molten steel for decomposition, release CO2 and form small particles of CaO to combine with rare earth inclusions, and then drive the generated complex rare earth inclusions to float to the ladle top slag, laying the foundation for reducing the total oxygen of the molten steel and the subsequent stable casting of the casting machine. Exemplarily, relative to 1 t of the third molten steel, the injection amount of the rare earth alloy powder is 0.33kg, 0.35kg, 0.37kg, 0.39kg, 0.41kg, 0.43kg, 0.45kg, 0.48kg, 0.5kg, 0.53kg, and 0.54kg; the injection flow rate of the rare earth alloy powder is 35kg / min, 36kg / min, 37kg / min, 38kg / min, 39kg / min, and 40kg / min.

[0068] The injection amount of calcium oxide-containing powder is limited. First, the powder containing calcium oxide is used to generate gas in the molten steel, which stirs the molten steel and the bubbles carry away the rare earth oxides. Second, the CaO produced after the decomposition of the calcium oxide-containing powder can also carry away the rare earth oxides during the floating process (because its density is much smaller than the density of the molten steel, and the density of rare earth inclusions is close to the density of the molten steel, which is difficult to float, or the floating speed is very slow), laying the foundation for reducing the total oxygen of the molten steel and the subsequent stable casting of the casting machine. The injection flow rate of lime powder is limited to avoid excessive injection flow, which requires a large amount of carrier gas, which is easy to cause violent churning of the molten steel, secondary oxidation or easy flipping of the molten steel out of the ladle; at the same time, excessive injection flow is easy to cause incomplete decomposition of lime powder and floating; if the injection flow is too small, the injection time is too long, which is not conducive to cycle control and is easy to cause spray gun blockage. Exemplarily, relative to 1t of the third molten steel, the injection amount of the calcium oxide-containing material powder is 0.56kg, 0.6kg, 0.63kg, 0.65kg, 0.68kg, 0.70kg, etc.; the injection flow rate of the calcium oxide-containing material powder is 50kg / min, 51kg / min, 52kg / min, 53kg / min, 54kg / min, 55kg / min, etc.

[0069] Specifically, after deciding to start spraying rare earth alloy powder, immediately start the bottom blowing of the ladle, and start spraying rare earth alloy powder after blowing argon at a small flow rate of 70-90L / min for 20s. The amount of rare earth sprayed is 0.33-0.54kg / t of molten steel (according to the historical desulfurization data, the sulfur situation at the end of furnace desulfurization is between 6 and 13ppm), and the powder spraying flow rate is controlled at 35-40kg / min. After the powder spraying is completed, the bottom blowing flow rate is maintained within 30s, and then the soft blowing flow rate is switched (40-50L / min, which can be understood as slowly blowing argon). After 3 minutes of soft blowing, limestone powder is sprayed, and the powder spraying flow rate is controlled at 50-55kg / min. The amount of limestone powder sprayed is 0.56-0.70kg / t of molten steel. After the powder spraying is completed, the bottom blowing flow rate is maintained within 15s, and then the soft blowing flow rate is switched. All treatments are completed after 5 minutes of soft blowing. The molten steel is hoisted by the overhead crane, and the ladle is cast on the casting machine. The casting machine is well prepared for full protection casting and covering agent and protective slag selection.

[0070] Through the smelting method of non-oriented silicon steel for new energy vehicles provided in the present application, it is ensured that 3500t (17 furnaces continuous casting) can be continuously cast in one continuous casting, and the high-frequency iron loss of the product is reduced by 0.1-0.2W / kg; precise rare earth treatment can be achieved, the total oxygen of molten steel can be accurately estimated (daily sampling and analysis), and the ladle top slag can be modified to achieve the top slag oxidizability within 2.0%.

[0071] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0072] The embodiment of the present application provides a smelting method of non-oriented silicon steel for new energy vehicles, comprising:

[0073] S11, smelting the desulfurized molten iron in a converter, and then tapping the steel to obtain a first molten steel;

[0074] S21, obtaining a target addition amount of the modifier slag according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, and the endpoint oxygen activity of the first molten steel;

[0075] S31, using the modifier slag material with a target addition amount to perform top slag modification on the first molten steel to obtain a second molten steel;

[0076] S41, performing RH refining on the second molten steel to obtain a third molten steel having a set oxygen content and a set sulfur content;

[0077] S51, spraying rare earth alloy powder into the third molten steel, and then spraying calcium oxide-containing material powder to obtain non-oriented silicon steel for new energy vehicles. For specific process parameter settings, please refer to Table 1.

[0078] Table 1 Smelting process parameters of non-oriented silicon steel for new energy vehicles

[0079]

[0080] Comparative Example 1

[0081] The desulfurized molten iron is smelted in a converter and then tapped to obtain the first molten steel. The tapping temperature of the first molten steel is 1650°C, the tapping time is 6 minutes, the end oxygen is 460ppm, and after tapping, 1.5kg / t of slag modifier is added according to the end oxygen to obtain the second molten steel. The second molten steel is RH refined, and after the RH arrives at the station, temperature measurement and oxygen determination and oxygen blowing decarburization are carried out. After decarburization is completed, temperature measurement and oxygen determination are carried out, and deoxidation and alloying operations are carried out. After the deoxidation and alloying operation is completed, RH desulfurizer is added in batches for desulfurization operation 3 minutes after the deoxidation and alloying operation is completed, and a third molten steel with an oxygen content of 10ppm and a sulfur content of 20ppm is obtained. The third molten steel is subjected to rare earth treatment by adding a rare earth alloy block with a content of 20.5% through a vacuum chamber, and the input amount is 0.35kg / t. After the treatment is completed, it is poured.

[0082] Comparative Example 2

[0083] The desulfurized molten iron is smelted in a converter and then tapped to obtain the first molten steel. The tapping temperature of the first molten steel is 1660°C, the tapping time is 8 minutes, the end oxygen is 380ppm, and after tapping, 1.2kg / t of slag modifier is added according to the end oxygen to obtain the second molten steel. The second molten steel is RH refined, and after the RH arrives at the station, temperature measurement and oxygen determination and oxygen blowing decarburization are carried out. After decarburization, temperature measurement and oxygen determination are carried out, and deoxidation and alloying operations are carried out. After the deoxidation and alloying operations are completed, RH desulfurizer is added in batches for desulfurization operations 3 minutes after the deoxidation and alloying operations are completed, and a third molten steel with an oxygen content of 8ppm and a sulfur content of 26ppm is obtained. The third molten steel is subjected to rare earth treatment by adding a rare earth alloy block with a content of 20.5% through a vacuum chamber, with an input amount of 0.38kg / t, and is poured after the treatment is completed.

[0084] The results of the smelting methods of non-oriented silicon steel for new energy vehicles provided in Examples 1 to 5 and Comparative Example 1 were evaluated. Please see Table 2 for the results.

[0085] Table 2 Results of the smelting method of non-oriented silicon steel for new energy vehicles

[0086]

[0087] As shown in Table 2, Examples 1 to 5 specifically consider the relationship between the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, the terminal oxygen activity of the first molten steel, and the amount of modifier slag added; and spray rare earth alloy powder and calcium oxide-containing material powder into the third molten steel. Finally, the molten steel smelted by the smelting method of non-oriented silicon steel for new energy vehicles provided by Examples 1 to 5 has the advantages of excellent magnetic properties, high cleanliness of the molten steel, and reduced stopper rod clogging problem; while Comparative Examples 1 to 2 do not adopt the scheme of the application embodiment, which to a certain extent causes the results of the smelting method of non-oriented silicon steel for new energy vehicles of Comparative Examples 1 to 2 in Table 1 to be worse than those of Examples 1 to 5.

[0088] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for smelting non-oriented silicon steel for new energy vehicles, characterized in that: The method comprises: The desulfurized molten iron is subjected to converter smelting and then tapped to obtain the first molten steel; Obtaining a target addition amount of the modifier slag according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, and the endpoint oxygen activity of the first molten steel; Using the modifier slag material with a target addition amount to perform top slag modification on the first molten steel to obtain a second molten steel; The second molten steel is subjected to RH refining to obtain a third molten steel having a set oxygen content and a set sulfur content; Rare earth alloy powder is sprayed into the third molten steel, and then calcium oxide-containing material powder is sprayed to obtain non-oriented silicon steel for new energy vehicles.

2. The method according to claim 1, characterized in that The step of obtaining a target amount of the modifier slag to be added according to the cleanliness level of the ladle in which the first molten steel is located, the baking time of the ladle, and the oxygen activity of the first molten steel comprises: If the cleanliness level of the ladle in which the first molten steel is located is Class C, the baking time of the ladle is greater than 25 minutes, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.7kg / t to 2.2kg / t; If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is greater than 25 minutes, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.5kg / t to 1.7kg / t; If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is ≤25min, and the endpoint oxygen activity of the first molten steel is 350ppm<≤650ppm, then the target addition amount of the modifier slag is 1.2kg / t to 1.5kg / t; If the cleanliness level of the ladle in which the first molten steel is located is Class A or Class B, the baking time of the ladle is ≤25min, and the endpoint oxygen activity of the first molten steel is 350ppm≤≤500ppm, then the target addition amount of the modifier slag is 1.0kg / t to 1.3kg / t.

3. The method according to claim 1, characterized in that The mass fraction of the set oxygen content is ≤0.0010%, and the mass fraction of the set sulfur content is ≤0.0015%.

4. The method according to claim 1, characterized in that: The particle size of the rare earth alloy powder is less than 0.5 mm.

5. The method according to claim 1, characterized in that The mass fraction of the rare earth content in the rare earth alloy powder is greater than 0 and not greater than ≤21%.

6. The method according to claim 5, characterized in that The mass fraction of the rare earth content in the rare earth alloy powder is 19.5% to 20.5%.

7. The method according to claim 1, characterized in that The injection amount of the injected rare earth alloy powder is 0.33kg to 0.54kg relative to 1t of the third molten steel; The spraying flow rate of the rare earth alloy powder is 35kg / min to 40kg / min.

8. The method according to claim 1, characterized in that Relative to 1 t of the third molten steel, the injection amount of the calcium oxide-containing material powder is 0.56 kg to 0.70 kg; The injection flow rate of the calcium oxide-containing material powder is 50kg / min to 55kg / min.

9. The method according to claim 1, characterized in that: The process parameters of steel tapping include: a steel tapping temperature of 1640° C. to 1660° C. and a steel tapping time of ≥5 min.

10. The method according to claim 1, characterized in that The method further comprises: The molten iron is deslagging, and then KR desulfurization and multiple deslagging are performed to make the deslagging bright surface ≥95%, thereby obtaining desulfurized molten iron.

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