Low-cost efficient nitrogen-increasing production method of oriented silicon steel and oriented silicon steel

Abstract

The invention provides a low-cost efficient nitrogen-increasing production method of oriented silicon steel and oriented silicon steel. The production method comprises the following steps that nitrogen is blown from the bottom in the whole blowing process of a converter, and the supply strength of the nitrogen blown from the bottom is 0.04-0.08 Nm < 3 > / (min.t); when the blowing end point is reached, top blowing oxygen is switched into top blowing nitrogen, the supply intensity of the top blowing nitrogen is 3.8-4.0 Nm < 3 > / (min.t), the time of the top blowing nitrogen is 1-2 min, and converter molten steel is obtained; the converter molten steel is transferred into a refining furnace, nitrogen is increased in a nitrogen circulation mode, refined molten steel is obtained, the gas supply intensity of nitrogen circulation is 160-200 Nm < 3 > / h, and the nitrogen content in the refined molten steel meets 0.0080%-0.0115%; and the refined molten steel is subjected to continuous casting-rolling, and the oriented silicon steel is obtained. The nitrogen content of the molten steel is controlled by combining converter bottom blowing nitrogen increasing, converter blowing end point top lance high-pressure large-flow nitrogen blowing nitrogen increasing and refining furnace nitrogen circulation nitrogen increasing, the nitrogen increasing method and process for controlling the molten steel in an optimized and perfect mode are provided, the treatment time in the refining stage is shortened, and continuous casting high-pulling-speed production can be effectively matched.

Description

Technical Field

[0001] This application belongs to the field of steel, and particularly relates to a low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel and grain-oriented electrical steel. Background Art

[0002] Grain-oriented electrical steel is the "crown" of steel industry products and is the core material for manufacturing power equipment such as UHV AC / DC transformers, high-efficiency energy-saving distribution transformers, and converter valve saturation reactors.

[0003] In some steel grades, nitrogen is a harmful element. When the nitrogen element content is too high, it will also cause an increase in the iron loss of grain-oriented electrical steel. However, research shows that maintaining a certain amount of nitrogen element in grain-oriented electrical steel is beneficial to improving the performance of grain-oriented electrical steel. This is because the nitrogen element can form fine AlN with the aluminum element to act as an auxiliary inhibitor. In order to reduce the adverse effects on grain-oriented electrical steel, the nitrogen element content in grain-oriented electrical steel is set within the range of 0.006% - 0.012% in the prior art. Usually, a nitrogen addition operation is required during the smelting process of grain-oriented electrical steel.

[0004] In the prior art, there are problems such as low nitrogen addition efficiency, high cost, and long refining furnace treatment time. Summary of the Invention

[0005] The embodiments of this application provide a low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel and grain-oriented electrical steel, which can achieve low-cost smelting, high nitrogen addition efficiency and stable and controllable process during smelting, and at the same time shorten the refining time of the refining furnace.

[0006] In the first aspect, the embodiments of this application provide a low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel, including the following steps: Nitrogen bottom blowing during converter blowing: During the converter blowing process, nitrogen is blown from the bottom throughout the process, and the gas supply intensity of the bottom blowing nitrogen is 0.04 - 0.08 Nm 3 / (min·t); When reaching the blowing end point, switch the top blowing oxygen to top blowing nitrogen, and the gas supply intensity of the top blowing nitrogen is 3.8 - 4.0 Nm 3 / (min·t), and the top blowing nitrogen time is 1 - 2 min to obtain converter molten steel; Nitrogen circulation addition in the refining furnace: Transfer the converter molten steel to the refining furnace and use the nitrogen circulation method for nitrogen addition to obtain refined molten steel. The gas supply intensity of the nitrogen circulation is 160 - 200 Nm 3 / h, and the nitrogen content in the refined molten steel meets 0.0080 - 0.0115%; Carry out continuous casting - rolling on the refined molten steel to obtain grain-oriented electrical steel.

[0007] According to the embodiments of the first aspect of this application, when tapping the converter, the nitrogen content in the converter molten steel meets 0.0040 - 0.0070%.

[0008] According to the embodiment of the first aspect of the present application, bottom blowing of nitrogen is carried out during the entire process of converter smelting.

[0009] According to the embodiment of the first aspect of the present application, during the nitrogen increasing step of converter blowing, the top blowing pressure of top blowing nitrogen is 0.9 Mpa to 1.0 Mpa.

[0010] According to the embodiment of the first aspect of the present application, the gas supply intensity of bottom blowing nitrogen is 0.04 - 0.08 Nm 3 / (min·t).

[0011] According to the embodiment of the first aspect of the present application, the refining furnace smelting stage includes: the first stage, the vacuum degree in the refining furnace is 500 - 700 Pa, and the nitrogen circulation intensity is 180 - 200 Nm 3 / h to add alloy of other elements except nitrogen elements for alloying; the second stage, after alloying is completed, adjust the vacuum degree in the refining furnace to 5.8 - 6.5 Kpa, and the nitrogen circulation intensity is 160 - 180 Nm 3 / h.

[0012] According to the embodiment of the first aspect of the present application, a three - stage vacuum pump is used to maintain nitrogen protection in the first stage, and a four - stage vacuum pump is used to increase nitrogen in the second stage.

[0013] According to the embodiment of the first aspect of the present application, the nitrogen increasing rate in the second stage is 1.6 - 2.4 ppm / min

[0014] According to the embodiment of the first aspect of the present application, the treatment time of the refining furnace smelting stage is 30 min to 35 min.

[0015] In the second aspect, the embodiment of the present application provides an oriented electrical steel, and the oriented electrical steel is prepared by the method provided in the first aspect.

[0016] Compared with the prior art, the embodiment of the present application has at least the following beneficial effects:

[0017] Low-cost and high-efficiency nitrogen-increasing production method for grain-oriented electrical steel in the embodiments of the present application. The design of the nitrogen-increasing process route includes: blowing nitrogen at the bottom of the converter and increasing the gas supply intensity of the bottom-blowing nitrogen in the converter. When reaching the end of the converter blowing, switch the top-blowing oxygen to large-flow top-blowing nitrogen to quickly increase the nitrogen content in the converter molten steel, and carry out large-flow nitrogen circulation nitrogen-increasing in the refining furnace. In the embodiments of the present application, the nitrogen content of the molten steel is controlled by combining bottom-blowing nitrogen-increasing in the converter, high-pressure and large-flow nitrogen blowing by the top lance at the end of the converter blowing, and nitrogen circulation nitrogen-increasing in the refining furnace, providing a nitrogen-increasing method and process for optimizing and improving the control of molten steel in the converter process and the RH refining furnace process for ordinary grain-oriented electrical steel. The production method provided by the present application does not add any nitrogen-containing alloys, smelts at low cost, shortens the treatment time in the refining stage by 10 - 18 minutes, and can effectively match the high casting speed production of continuous casting. The production method of the present application is simple and easy to operate, the nitrogen-increasing is stable and controllable, and the nitrogen content of the molten steel can accurately meet the requirements of the steel grade design. Description of the Drawings

[0018] The features, advantages and technical effects of the exemplary embodiments of the present invention will be described below with reference to the drawings.

[0019] Figure 1 It is a schematic flow chart of the low-cost and high-efficiency nitrogen-increasing production method for grain-oriented electrical steel in the embodiments of the present application. Detailed Embodiments

[0020] The features and exemplary embodiments of various aspects of the present application will be described in detail below. For the purpose of making the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application.

[0021] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, elements defined by the statement "including..." do not exclude the existence of additional identical elements in the process, method, article or device including the elements.

[0022] For grain-oriented electrical steel, an appropriate amount of nitrogen element helps to improve its magnetic properties. For example, it can inhibit the abnormal growth of primary recrystallized grains, improve the magnetic induction intensity of the electrical steel, and the nitrogen content range in the composition of grain-oriented electrical steel can be 0.0080 - 0.0115%. Generally, after melting hot metal and scrap steel into molten steel in a rough melting furnace, secondary refining is carried out in the RH. The conventional production method usually increases nitrogen by adding nitrogen-containing alloys during the tapping process of the rough melting furnace and fine-tuning to reach the nitrogen target composition control requirements by adding nitrogen-containing alloys in the refining furnace; or blowing nitrogen at the bottom of the rough melting furnace and maintaining and increasing nitrogen through nitrogen circulation in the refining furnace until the target nitrogen composition control requirements are reached. However, the inventors of this application noticed in actual production that there are problems with increasing nitrogen by using the alloy nitrogen addition method, such as difficulties in subsequent refining composition fine-tuning due to unstable yield of rough molten steel, inability to stably control the production rhythm, contamination of molten steel by impurity elements brought by alloys, and an increase in cost of 40 - 60 yuan / ton for using argon and nitrogen-containing alloys to increase nitrogen compared with using nitrogen to increase nitrogen; there are problems with increasing nitrogen by introducing nitrogen into molten steel, such as limited nitrogen addition in the rough melting furnace molten steel, low nitrogen addition rate in the refining furnace, resulting in a long refining treatment time for ordinary grain-oriented electrical steel and difficulty in matching the furnace and machine.

[0023] In view of the above problems, the inventors of this application provide a low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel and grain-oriented electrical steel, which can achieve low-cost smelting, high nitrogen addition efficiency and stable and controllable process during smelting, and at the same time shorten the refining time in the refining furnace.

[0024] In the first aspect, an embodiment of this application provides a low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel. Figure 1 The flow of the low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel is shown. Please refer to Figure 1 , the low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel provided by this application includes the following steps:

[0025] S100: Nitrogen addition by converter blowing: Blow nitrogen at the bottom throughout the converter blowing process, and the gas supply intensity of bottom blowing nitrogen is 0.04 - 0.08 Nm 3 / (min·t); when reaching the blowing end point, switch the top blowing oxygen to top blowing nitrogen, and the gas supply intensity of top blowing nitrogen is 3.8 - 4.0 Nm 3 / (min·t), and the time of top blowing nitrogen is 1 - 2 min to obtain converter molten steel;

[0026] S200: Nitrogen addition by nitrogen circulation in the refining furnace: Transfer the converter molten steel to the refining furnace and increase nitrogen by the nitrogen circulation method to obtain refined molten steel. The gas supply intensity of nitrogen circulation is 160 - 200 Nm 3 / h, and the nitrogen content in the refined molten steel meets 0.0080 - 0.0115%;

[0027] S300: Carry out continuous casting - rolling on the refined molten steel to obtain grain-oriented electrical steel.

[0028] Low-cost and high-efficiency nitrogen addition production method for grain-oriented electrical steel according to an embodiment of the present application. The nitrogen addition process path design includes: bottom blowing nitrogen throughout the converter process and increasing the gas supply intensity of bottom blowing nitrogen in the converter, switching the top blowing oxygen to large-flow top blowing nitrogen at the end of the converter blowing process to rapidly increase the nitrogen content in the converter molten steel, and carrying out large-flow nitrogen circulation nitrogen addition in the refining furnace. By combining bottom blowing nitrogen addition in the converter, high-pressure large-flow nitrogen blowing at the top lance at the end of the converter blowing process, and nitrogen circulation nitrogen addition in the refining furnace, the nitrogen content of the molten steel is controlled. A nitrogen addition method and process for optimizing and perfecting the control of molten steel in the converter process and the RH refining furnace process for ordinary grain-oriented electrical steel are provided. The production method provided by the present application does not add any nitrogen-containing alloys, smelts at low cost, shortens the treatment time in the refining stage by 10-18 minutes, and can effectively match the high casting speed production of continuous casting. The production method of the present application is simple and easy to operate, the nitrogen addition is stable and controllable, and the nitrogen content of the molten steel can accurately meet the requirements of the steel grade design.

[0029] [S100]

[0030] In the converter smelting stage of the embodiment of the present application, nitrogen is bottom blown throughout the process, and the gas supply intensity of bottom blowing nitrogen in the converter is increased to 0.04-0.08 Nm3 / (min·t). Nitrogen is used as a nitrogen source and directly contacts the molten steel during the bottom blowing process. As the gas supply intensity is within the range of 0.04-0.08 Nm 3 / (min·t), more nitrogen can be dissolved into the molten steel, thereby increasing the nitrogen content in the molten steel and raising the nitrogen addition upper limit of bottom blowing nitrogen. In addition, the appropriate gas supply intensity can ensure that the molten steel is fully stirred, so that the dissolved nitrogen is more evenly distributed in the molten steel. This helps to avoid the situation of too high or too low local nitrogen content, ensure the uniformity of the entire molten steel composition, and further improve the stability of the final product quality. By adding nitrogen through bottom blowing nitrogen, the use of expensive nitriding alloys to adjust the nitrogen content in the molten steel can be reduced. This not only reduces the alloy cost, but also reduces the impurity elements brought in by the alloy and improves the purity of the steel.

[0031] Operating bottom blowing nitrogen throughout the converter smelting process can improve the nitrogen addition efficiency in the converter smelting stage.

[0032] At the same time, the top lance at the end of the converter blowing uses high-pressure large-flow nitrogen blowing for nitrogen addition at 3.8-4.0 Nm 3 / (min·t), and the time of top blowing nitrogen is 1-2 minutes. On the one hand, it can increase the nitrogen addition upper limit of bottom blowing nitrogen, and on the other hand, it can rapidly increase the nitrogen content in the converter molten steel and reduce the treatment time in the refining furnace.

[0033] At the end of the converter blowing process, the composition and temperature of the molten steel are relatively stable. At this time, using the above high-pressure large-flow nitrogen top blowing can make a large amount of nitrogen quickly contact the molten steel. At 3.8-4.0 Nm 3At a gas supply intensity of / (min·t), nitrogen impacts the surface of the molten steel at a relatively high speed and pressure, forming a large gas-liquid contact area, thereby significantly increasing the dissolution rate of nitrogen atoms into the molten steel and rapidly increasing the nitrogen content in the molten steel within 1 - 2 minutes.

[0034] In the embodiments of the present application, the end point of converter blowing refers to the situation where the target chemical components meet the standards, for example, when the contents of carbon, manganese, silicon, etc. in grain-oriented electrical steel meet the standards.

[0035] In the embodiments of the present application, the specific specifications of the converter are not limited. Exemplarily, the converter is 180 tons to 300 tons. For example, a 210-ton converter is used.

[0036] Exemplarily, the gas supply intensity of bottom-blowing nitrogen is 0.04 Nm 3 / (min.t), 0.042 Nm 3 / (min.t), 0.044 Nm 3 / (min.t), 0.046 Nm 3 / (min.t), 0.048 Nm 3 / (min.t), 0.05 Nm 3 / (min.t), 0.052 Nm 3 / (min.t), 0.054 Nm 3 / (min.t), 0.056 Nm 3 / (min.t), 0.058 Nm 3 / (min.t), 0.06 Nm 3 / (min.t), 0.062 Nm 3 / (min.t), 0.064 Nm 3 / (min.t), 0.066 Nm 3 / (min.t), 0.068 Nm 3 / (min.t), 0.07 Nm 3 / (min.t), 0.072 Nm 3 / (min.t), 0.074 Nm 3 / (min.t), 0.076 Nm 3 / (min.t), 0.078 Nm 3 / (min.t), 0.08 Nm 3 / (min.t) or the range of intervals composed of any two of the above values.

[0037] Exemplarily, the gas supply intensity of top-blowing nitrogen is 3.8 Nm 3 / (min.t), 3.82 Nm 3 / (min.t), 3.84 Nm 3 / (min.t), 3.86 Nm 3 / (min.t), 3.88 Nm 3 / (min.t), 3.90 Nm 3 / (min.t), 3.92 Nm 3 / (min.t), 3.94 Nm 3 / (min.t), 3.96 Nm 3 / (min.t), 3.98 Nm 3 / (min.t), 4.0 Nm 3 / (min.t) or the range formed by any two of the above values.

[0038] Exemplarily, the time for top-blowing nitrogen is 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, 90 s, 95 s, 100 s, 105 s, 110 s, 115 s, 120 s.

[0039] At the end of the converter blowing, top-blowing nitrogen is used to increase nitrogen content. There is no need to add additional complex equipment and process steps, and the operation is simple and fast. The nitrogen-increasing process can be completed within 1 - 2 minutes, without significantly increasing the production cycle of steelmaking, thus improving production efficiency and meeting the requirements of large-scale industrial production.

[0040] In the embodiments of the present application, the method of top-gun high-pressure and large-flow nitrogen blowing is adopted to increase the nitrogen content in the converter molten steel, and the nitrogen content in the converter molten steel is controlled not to exceed the preferred range by controlling the top-blowing time, so as not to affect the performance of grain-oriented silicon steel.

[0041] In some embodiments, when tapping the converter, the nitrogen content in the converter molten steel satisfies 0.0040 - 0.0070%.

[0042] Controlling the nitrogen content within this range when tapping the converter can provide a relatively stable and target-close nitrogen content basis for the refining stage. In the refining stage, there is no need to significantly adjust the nitrogen content, and only fine-tuning is required to reach the nitrogen content range required for the final product. For example, the generally required nitrogen content for grain-oriented silicon steel is generally in the range of 0.0080% - 0.0115%, which makes the regulation of nitrogen content in the refining process more accurate and easier.

[0043] At the same time, since the nitrogen content is within a suitable range when tapping the converter, in the refining stage, there is no need to spend a lot of time and effort to adjust the nitrogen content and deal with problems caused by improper nitrogen content, such as excessive inclusions and uneven composition. Thus, the refining time can be shortened, production efficiency can be improved, the turnover times of equipment can be increased, and production costs can be reduced.

[0044] In addition, an appropriate nitrogen content helps to stabilize the temperature change of the molten steel during the refining stage, making the temperature control during the refining process more stable and easier.

[0045] Exemplarily, when tapping from the converter, the nitrogen content in the converter molten steel is 0.0040%, 0.0045%, 0.0050%, 0.0055%, 0.0060%, 0.0065% or 0.0070%

[0046] In the embodiments of the present application, the air supply intensity of bottom-blowing nitrogen in the converter is increased to 0.04 - 0.08 Nm 3 / (min·t) by blowing nitrogen throughout the process, and at the end of the converter blowing, the top lance adopts high-pressure and large-flow nitrogen blowing with a flow rate of 3.8 - 4.0 Nm 3 / (min·t) to increase nitrogen content, and the time of top-blowing nitrogen is controlled to be 1 - 2 min to control the nitrogen content in the converter molten steel.

[0047] In some embodiments, during the nitrogen-increasing step of converter blowing, the top-blowing pressure of top-blowing nitrogen is 0.9 Mpa - 1.0 Mpa.

[0048] Controlling the top-blowing nitrogen pressure in the range of 0.9 - 1.0 MPa can increase the solubility, expand the nitrogen-increasing potential, provide an ideal intermediate control window for the coordinated nitrogen-increasing of the converter-refining process, and lay a foundation for finally achieving precise nitrogen control of 0.0080 - 0.0115%.

[0049] Exemplarily, during the nitrogen-increasing step of converter blowing, the top-blowing pressure of top-blowing nitrogen is 0.9 Mpa, 0.91 Mpa, 0.92 Mpa, 0.93 Mpa, 0.94 Mpa, 0.95 Mpa, 0.96 Mpa, 0.97 Mpa, 0.99 Mpa, 0.99 Mpa or 1.0 Mpa.

[0050] An appropriate top-blowing pressure can make nitrogen enter the molten steel with appropriate momentum, generating a strong stirring effect, making the distribution of various elements in the molten steel, such as carbon, silicon, manganese, etc. more uniform. This helps to achieve more precise composition control during the blowing process and ensure the stability of the molten steel quality.

[0051] [S200]

[0052] In the refining stage of the refining furnace in the embodiments of the present application, nitrogen circulation is carried out in the refining furnace for nitrogen-increasing: transferring the converter molten steel into the refining furnace, and adopting the nitrogen circulation method for nitrogen-increasing to obtain refined molten steel, and the air supply intensity of nitrogen circulation is 160 - 200 Nm 3 / h, and the nitrogen content in the refined molten steel meets 0.0080 - 0.0115%.

[0053] The magnetic properties and processing properties of grain-oriented electrical steel are closely related to the nitrogen content. Nitrogen can form fine and dispersed nitrides in grain-oriented electrical steel, which can inhibit the abnormal growth of grains, thus facilitating the formation of an ideal grain orientation, improving the magnetic permeability of grain-oriented electrical steel, and reducing iron loss. The nitrogen content can be accurately controlled within the range of 0.0080% - 0.0115% in the nitrogen circulation step of the refining furnace, which can ensure that grain-oriented electrical steel obtains good magnetic properties and processing properties and meets the application requirements in fields such as power transformers.

[0054] In the embodiment of the present application, by controlling the gas supply intensity of nitrogen circulation to be 160 - 200 Nm 3 / h, the nitrogen content in the molten steel can be stabilized within the target range. Compared with the traditional nitrogen addition method, this precise control can reduce the fluctuation of nitrogen content, improve the consistency and stability of product quality, and reduce the defective rate.

[0055] Traditional nitrogen addition methods may need to use nitrogen-containing alloys to increase the nitrogen content in the molten steel, and nitrogen-containing alloys are usually expensive, which will increase production costs. By adopting the nitrogen circulation nitrogen addition method and directly using nitrogen as the nitrogen source, the nitrogen cost is relatively low, avoiding the large use of expensive nitrogen-containing alloys, thus reducing production costs.

[0056] Adopting nitrogen circulation nitrogen addition with a specific gas supply intensity in the refining furnace can make nitrogen fully contact with the molten steel, improve the dissolution rate and absorption efficiency of nitrogen, and achieve uniform nitrogen addition. Compared with other nitrogen addition methods, this method can reach the target nitrogen content in a shorter time, improve production efficiency, and further reduce production costs.

[0057] Exemplarily, the gas supply intensity of nitrogen circulation is 160 Nm 3 / h, 165 Nm 3 / h, 170 Nm 3 / h, 175 Nm 3 / h, 180 Nm 3 / h, 185 Nm 3 / h, 190 Nm 3 / h, 195 Nm 3 / h or 200 Nm 3 / h.

[0058] Exemplarily, the nitrogen content in the refined molten steel is 0.0080%, 0.0085%, 0.0090%, 0.0095%, 0.010%, 0.0105%, 0.0110% or 0.0115%.

[0059] Nitrogen circulation plays a role in stirring the molten steel during the refining process. During the circulation process, the molten steel continuously circulates, enabling various elements in the molten steel to be more evenly distributed and the temperature to be more uniform. This helps to eliminate composition segregation in the molten steel, make the composition of the molten steel more uniform, and improve the quality of the steel.

[0060] While carrying out nitrogen addition through nitrogen circulation in the refining furnace, other refining operations can also be combined, such as adding alloying elements other than nitrogen for alloying. The circulation effect can promote the dissolution and diffusion of alloying elements in the molten steel, making the alloying process more uniform and efficient, and further optimizing the composition and properties of the molten steel.

[0061] Exemplarily, a circulation device such as a circulation pipe or a circulation nozzle can be used to achieve nitrogen circulation. The diameter, length, and shape of the circulation pipe can be optimized according to the size of the refining furnace and the molten steel flow rate to ensure that nitrogen can enter the molten steel evenly and form an effective circulation.

[0062] In some embodiments, the smelting stage of the refining furnace includes: in the first stage, the vacuum degree in the refining furnace is 500 - 700 Pa, and nitrogen circulation intensity is 180 - 200 Nm 3 / h, and alloying is carried out by adding alloys of other elements except nitrogen elements; in the second stage, after alloying is completed, the vacuum degree in the refining furnace is adjusted to 5.8 - 6.5 KPa, and nitrogen circulation intensity is 160 - 180 Nm 3 / h.

[0063] Exemplarily, the RH refining method is adopted for the refining furnace.

[0064] In the first stage, fine adjustment of the element composition is carried out. To preserve nitrogen, the vacuum degree in the refining furnace in this application is 500 - 700 Pa. At this vacuum degree, the nitrogen content in the molten steel will not decrease.

[0065] When the vacuum degree in the refining furnace is controlled within 500 - 700 Pa, although the overall pressure is low, the nitrogen partial pressure in the refining furnace can still be maintained at a certain level at this time. Within this vacuum degree range, the nitrogen partial pressure will not be low enough to cause a large amount of dissolved nitrogen in the molten steel to escape. Because according to Sieverts' law, as long as the nitrogen partial pressure can meet certain conditions, the solubility of nitrogen in the molten steel will not decrease significantly, thus ensuring the relative stability of the nitrogen content.

[0066] Exemplarily, in the first stage, the vacuum degree in the refining furnace is 500 Pa, 550 Pa, 600 Pa, 650 Pa, or 700 Pa.

[0067] Meanwhile, 180 - 200 Nm 3The nitrogen circulation intensity of / h continuously supplies nitrogen to the molten steel. The newly injected nitrogen can replenish the nitrogen lost due to possible minute escapes, and promote sufficient contact between the molten steel and nitrogen, enabling nitrogen to continuously dissolve into the molten steel, further maintaining the dissolution equilibrium of nitrogen in the molten steel and ensuring that the nitrogen content does not decrease.

[0068] Exemplarily, in the first stage, the gas supply intensity of the nitrogen circulation is 180 Nm 3 / h, 185 Nm 3 / h, 190 Nm 3 / h, 195 Nm 3 / h or 200 Nm 3 / h.

[0069] In the embodiments of the present application, the adjustment of other elements except nitrogen in place is the demarcation line between the first stage and the second stage, that is, when other elements except nitrogen are adjusted in place, the first stage ends and the second stage begins.

[0070] After alloying is completed, the vacuum degree is adjusted to 5.8 - 6.5 Kpa, and the nitrogen circulation intensity is 160 - 180 Nm 3 / h for further nitrogen enrichment.

[0071] Adjusting the vacuum degree to 5.8 - 6.5 Kpa will neither be too low to cause a large amount of nitrogen in the molten steel to escape, nor can it provide a relatively low-pressure environment, which is conducive to the formation and rise of nitrogen bubbles in the molten steel, promoting sufficient contact and dissolution between nitrogen and the molten steel. At the same time, an appropriate vacuum degree can also remove some harmful gases and impurities in the molten steel, improve the purity of the molten steel, and further enhance the dissolution ability of the molten steel for nitrogen.

[0072] Exemplarily, after alloying is completed, the vacuum degree is adjusted to 5.8 Kpa, 5.9 Kpa, 6 Kpa, 6.1 Kpa, 6.2 Kpa, 6.3 Kpa, 6.4 Kpa or 6.5 Kpa; the nitrogen circulation intensity is 160 Nm 3 / h, 165 Nm 3 / h, 170 Nm 3 / h, 175 Nm 3 / h or 180 Nm 3 / h.

[0073] In some embodiments, a three-stage vacuum pump is used to maintain nitrogen preservation in the first stage, and a four-stage vacuum pump is used for nitrogen enrichment in the second stage.

[0074] When the vacuum pump is turned on to the first or second stage, due to the high vacuum degree, the nitrogen content in the molten steel will decrease. In the embodiments of the present application, a three-stage vacuum pump is used to maintain an appropriate vacuum degree for nitrogen preservation, and a four-stage vacuum pump is used for nitrogen enrichment.

[0075] In some embodiments, the nitrogen increasing rate in the second stage is 1.6 - 2.4 ppm / min.

[0076] Exemplarily, the nitrogen increasing rate in the second stage is 1.6 ppm / min, 1.7 ppm / min, 1.8 ppm / min, 1.9 ppm / min, 2.0 ppm / min, 2.1 ppm / min, 2.2 ppm / min, 2.3 ppm / min, 2.4 ppm / min, or the range formed by any two of the above values.

[0077] In some embodiments, the treatment time in the refining furnace smelting stage is 30 min to 35 min.

[0078] Using the production method of the embodiments of the present application, the treatment time in the RH refining furnace is shortened by 10 - 18 min, which can effectively match the high casting speed for production. The operation of the present invention is simple and easy, the nitrogen increase is stable and controllable, and the nitrogen content of the molten steel can accurately meet the design requirements of the steel grade.

[0079] [S300]

[0080] The production of the oriented silicon steel by continuous casting - rolling of the refined molten steel can be carried out by the production process in the prior art, which will not be elaborated in the present application.

[0081] In a second aspect, the embodiments of the present application provide an oriented silicon steel, which is obtained by the method provided in the first aspect.

[0082] Embodiment

[0083] The following embodiments more specifically describe the content disclosed in the present application. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the embodiments are commercially available.

[0084] Embodiment 1

[0085] The production method of the oriented silicon steel QX - 1 includes the following steps:

[0086] Converter smelting: Bottom - blowing nitrogen throughout the converter, with a gas supply intensity of 0.06 Nm 3 / (min·t), blowing until the end of the blowing, then switching the top - blowing oxygen to top - blowing nitrogen, with a top - blowing flow rate of 48000 Nm 3 / h, a top - blowing pressure of 0.95 Mpa, blowing nitrogen for 1.25 min and then tapping, and the nitrogen mass percentage of the sample taken at the RH station upon entry is 0.0064%;

[0087] Refining in the refining furnace: The driving gas for RH is nitrogen. In the early stage, the nitrogen circulation is 190 Nm 3 / h. Immediately after the start of RH treatment, it is quickly pumped to the third-stage vacuum pump and maintained. The vacuum degree is 630 Pa. After adjusting other elements to the target composition except for the nitrogen element, it is retreated to the fourth-stage pump, and the nitrogen circulation is adjusted to 160 Nm 3 / h. Nitrogen is increased at a vacuum degree of 6.2 KPa. After retreating to the fourth-stage pump, the treatment time is 12 min, and the mass percentage of nitrogen in the molten steel is 0.0088%. The RH treatment time is 32 min;

[0088] The refined molten steel is subjected to continuous casting-rolling to obtain grain-oriented silicon steel.

[0089] Example 2

[0090] A production method of grain-oriented silicon steel QX-2, comprising the following steps:

[0091] Converter smelting: Nitrogen is blown from the bottom throughout the converter, and the gas supply intensity is 0.06 Nm3 / (min.t). When blowing to the end point, the top blowing oxygen of the converter is switched to top blowing nitrogen, the top blowing flow rate is 50000 Nm3 / h, the top blowing pressure is 0.98 Mpa, and the nitrogen blowing time is 1.2 min before tapping. The mass percentage of nitrogen in the molten steel sampled at the RH station is 0.0068%;

[0092] Refining in the refining furnace: The driving gas for RH is nitrogen. In the early stage, the nitrogen circulation is 190 Nm3 / h. Immediately after the start of RH treatment, it is quickly pumped to the third-stage vacuum pump and maintained. The vacuum degree is 650 Pa. After adjusting other elements to the target composition except for the nitrogen element, it is retreated to the fourth-stage pump, and the nitrogen circulation is adjusted to 160 Nm3 / h. Nitrogen is increased at a vacuum degree of 6.2 KPa. After retreating to the fourth-stage pump, the treatment time is 11 min, and the mass percentage of nitrogen in the molten steel is 0.0091%. The RH treatment time is 32 min;

[0093] The refined molten steel is subjected to continuous casting-rolling to obtain grain-oriented silicon steel.

[0094] Comparative Example 1

[0095] A production method of grain-oriented silicon steel QX-3, comprising the following steps:

[0096] Converter smelting: Nitrogen is blown from the bottom throughout the converter, and the gas supply intensity is 0.04 Nm3 / (min.t). After blowing to the end point, tapping is carried out; the mass percentage of nitrogen in the molten steel sampled at the RH station is 0.0031%;

[0097] Refining in the refining furnace: The driving gas for RH is nitrogen. In the early stage, the nitrogen circulation is 190 Nm3 / h. When the main valve is opened, it is immediately opened to the third-stage vacuum pump and maintained. The vacuum degree is 595 Pa. After adjusting other elements to the target composition except for nitrogen, it is retreated to the fourth-stage pump, and the nitrogen circulation is adjusted to 160 Nm 3 / h, nitrogen addition with a vacuum degree of 6.3 Kpa, post-treatment time of 24 min after retreating to the fourth-stage pump, nitrogen mass percentage in molten steel of 0.0085%. RH treatment time is 46 min.

[0098] In Comparative Example 1, oxygen lance top-blowing nitrogen was not used in the converter smelting stage. The nitrogen content in the molten steel entering RH was low, and the RH treatment time was long. The nitrogen addition rate during the RH nitrogen addition treatment time was 2.25 ppm / min;

[0099] The refined molten steel is subjected to continuous casting-rolling to obtain grain-oriented electrical steel.

[0100] Comparative Example 2

[0101] A production method of grain-oriented electrical steel QX-4, comprising the following steps:

[0102] Converter smelting: Bottom-blowing nitrogen throughout the converter, with a gas supply intensity of 0.04 Nm3 / (min.t), blowing until tapping at the end; Nitrogen mass percentage in the sample taken when entering RH is 0.0034%;

[0103] Refining furnace smelting: Using nitrogen as the driving gas in RH, with a nitrogen circulation of 190 Nm3 / h in the early stage. Immediately after the start of RH treatment, it is quickly pumped to the third-stage vacuum pump and maintained. The vacuum degree is 610 Pa. After adjusting other elements to the target composition except nitrogen, it retreats to the fourth-stage pump, and the nitrogen circulation is adjusted to 160 Nm3 / h. Nitrogen addition is carried out with a vacuum degree of 6.0 Kpa, and the post-treatment time after retreating to the fourth-stage pump is 23 min. The nitrogen content in the molten steel is 0.0084%. RH treatment time is 45 min.

[0104] In Comparative Example 2, oxygen lance top-blowing nitrogen was not used in the converter smelting stage. The nitrogen content in the molten steel entering RH was low, the RH nitrogen addition treatment time was long, and the nitrogen addition rate during the RH nitrogen addition treatment time was 2.17 ppm / min;

[0105] The refined molten steel is subjected to continuous casting-rolling to obtain grain-oriented electrical steel.

[0106] Comparative Example 3

[0107] A production method of grain-oriented electrical steel QX-5, comprising the following steps:

[0108] Converter smelting: Bottom-blowing nitrogen throughout the converter, with a gas supply intensity of 0.06 Nm3 / (min.t), blowing until tapping at the end; Nitrogen mass percentage in the sample taken when entering RH is 0.0036%;

[0109] Refining furnace smelting: The driving gas of RH is nitrogen. In the early stage, the nitrogen circulation rate is 190 Nm3 / h. Immediately after the start of RH treatment, it is quickly pumped to the third-stage vacuum pump and maintained. The vacuum degree is 620 Pa. After adjusting other elements to the target composition except nitrogen, it is retreated to the fourth-stage pump. The nitrogen circulation rate is adjusted to 160 Nm3 / h, and nitrogen is added at a vacuum degree of 6.0 Kpa. After retreating to the fourth-stage pump, the treatment time is 23 min, and the mass percentage of nitrogen in the molten steel is 0.0086%. The RH treatment time is 45 min;

[0110] Continuous casting and rolling the refined molten steel to obtain grain-oriented silicon steel.

[0111] In Comparative Example 3, nitrogen was blown at the bottom throughout the converter smelting stage to increase the gas supply intensity. The converter did not use top blowing nitrogen with an oxygen lance. The increase in the nitrogen content of the molten steel entering the RH station was not obvious, and the RH nitrogen addition treatment time was long. The nitrogen addition rate during the RH nitrogen addition treatment time was 2.17 ppm / min.

[0112] Comparative Example 4

[0113] A production method of grain-oriented silicon steel QX-6, comprising the following steps:

[0114] Converter smelting: Nitrogen is blown at the bottom throughout the converter, and the gas supply intensity is 0.06 Nm3 / (min.t). Blowing until tapping at the end point; The mass percentage of nitrogen in the sample taken when entering the RH station is 0.0038%;

[0115] Refining furnace smelting: The driving gas of RH is nitrogen. In the early stage, the nitrogen circulation rate is 190 Nm3 / h. Immediately after the start of RH treatment, it is quickly pumped to the third-stage vacuum pump and maintained. The vacuum degree is 620 Pa. After adjusting other elements to the target composition except nitrogen, it is retreated to the fourth-stage pump. The nitrogen circulation rate is adjusted to 160 Nm3 / h, and nitrogen is added at a vacuum degree of 6.0 Kpa. After retreating to the fourth-stage pump, the treatment time is 22 min, and the mass percentage of nitrogen in the molten steel is 0.0085 ppm. The RH treatment time is 45 min;

[0116] Continuous casting and rolling the refined molten steel to obtain grain-oriented silicon steel.

[0117] In Comparative Example 4, nitrogen was blown at the bottom throughout the converter to increase the gas supply intensity. The converter did not use top blowing nitrogen with an oxygen lance. The increase in the nitrogen content of the molten steel entering the RH station was also not obvious, and the RH nitrogen addition treatment time was long. The nitrogen addition rate during the RH nitrogen addition treatment time was 2.14 ppm / min.

[0118] Comparing the above data, it can be seen that in Example 1, the bottom blowing gas supply intensity of the converter was increased and high-pressure and large-flow top blowing nitrogen was used after the end of converter smelting. The nitrogen content of the molten steel entering the RH station increased significantly, and the nitrogen addition rate during the nitrogen addition time was 2 ppm / min. Compared with Comparative Example 1, the RH treatment time was shortened by 14 min, and compared with Comparative Example 2, the RH treatment time was shortened by 13 min;

[0119] Example 2 also shows that increasing the bottom blowing gas supply intensity of the converter and using high-pressure and large-flow top blowing nitrogen after the converter end point result in a significant increase in the nitrogen content of the molten steel entering the RH station, and the nitrogen increasing rate is 2.09 ppm / min during the nitrogen increasing time. Compared with Comparative Example 1, the RH treatment time is shortened by 14 minutes, and compared with Comparative Example 2, the RH treatment time is shortened by 13 minutes.

[0120] The above is only the specific implementation manner of the present application. Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working process described above can refer to the corresponding process in the foregoing method embodiment and will not be elaborated here. It should be understood that the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present application.

Claims

1. A low-cost and high-efficiency nitrogen addition production method for grain-oriented silicon steel, characterized in that, It includes the following steps: Nitrogen increase during converter blowing: Nitrogen is blown from the bottom throughout the converter blowing process, and the gas supply intensity of the bottom-blown nitrogen is 0.04 - 0.08 Nm 3 / (min·t); when reaching the blowing end point, the top-blown oxygen is switched to top-blown nitrogen, and the gas supply intensity of the top-blown nitrogen is 3.8 - 4.0 Nm 3 / (min·t), and the time of the top-blown nitrogen is 1 - 2 min to obtain converter molten steel; Nitrogen increase by circulating flow in refining furnace: Transfer the converter molten steel into the refining furnace, and increase nitrogen by means of nitrogen circulating flow to obtain refined molten steel. The gas supply intensity of the nitrogen circulating flow is 160 - 200 Nm 3 / h, and the nitrogen content in the refined molten steel meets 0.0080 - 0.0115%; Continuous casting and rolling the refined molten steel to obtain grain-oriented silicon steel.

2. The low-cost and high-efficiency nitrogen addition production method for grain-oriented silicon steel according to claim 1, wherein When tapping the converter, the nitrogen content in the converter molten steel meets 0.0040 - 0.0070%.

3. The low-cost and high-efficiency nitrogen addition production method of the grain-oriented electrical steel according to claim 1, characterized in that, In the converter blowing nitrogen increasing step, the top blowing pressure of the top blown nitrogen is 0.9 Mpa - 1.0 Mpa.

4. The low-cost and high-efficiency nitrogen increasing production method for grain-oriented silicon steel according to claim 1 or 2, characterized in that, The gas supply intensity of the bottom-blowing nitrogen is 0.04 - 0.06 Nm 3 / (min·t).

5. The low-cost and high-efficiency nitrogen addition production method for grain-oriented silicon steel according to claim 1, characterized in that, The ladle furnace circulating nitrogen increasing includes: In the first stage, the vacuum degree in the refining furnace is controlled to be 500 - 700 Pa, and the gas supply intensity of the nitrogen circulation is 180 - 200 Nm 3 / h, and alloys of other elements except nitrogen are added for alloying; In the second stage, after the alloying is completed, the vacuum degree in the refining furnace is adjusted to 5.8 - 6.5 Kpa, and the nitrogen circulation intensity is 160 - 180 Nm 3 / h.

6. The low-cost and high-efficiency nitrogen increasing production method of the grain-oriented electrical steel according to claim 5, wherein, In the first stage, a three-stage vacuum pump is used to maintain nitrogen protection, and in the second stage, a four-stage vacuum pump is used to increase nitrogen.

7. The low-cost and high-efficiency nitrogen addition production method for grain-oriented silicon steel according to claim 6, wherein The nitrogen increasing rate in the second stage is 1.6 - 2.4 ppm / min.

8. The low-cost and high-efficiency nitrogen increasing production method for oriented silicon steel according to claim 1, characterized in that, The treatment time in the ladle furnace smelting stage is 30 min - 35 min.

9. An oriented silicon steel, characterized in that, The grain-oriented silicon steel is obtained by the production method according to any one of claims 1 to 8.

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