Method for controlling nitrogen content in oriented silicon steel smelting process

Abstract

The invention provides a method for controlling the nitrogen content in the oriented silicon steel smelting process, and relates to the technical field of ferrous metallurgy. Ferro-silicon nitride is added twice in the vacuum treatment stage of RH refining to adjust the nitrogen content of molten steel; the addition amount of the silicon iron nitride for the second time is calculated based on the addition amount of the silicon nitride added for the first time, the increase amount of the nitrogen content in the molten steel after the silicon nitride is added for the first time and the target increase amount of the nitrogen content in the molten steel after the silicon nitride is added for the second time through a preset calculation model; the addition amount of the silicon iron nitride for the second time is obtained on the basis of the yield of the nitrogen element after the silicon nitride is added for the first time in the same furnace, so that the influence of the difference of various process parameters of different furnaces on the yield of the nitrogen element is avoided; the difference between the content of the nitrogen element in the RH refining outbound molten steel and the target nitrogen content of the RH refining outbound molten steel is small, and accurate control over the content of the nitrogen element in the RH refining outbound molten steel is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for controlling nitrogen content in a smelting process of oriented silicon steel. Background Art

[0002] The smelting of oriented silicon steel is a cutting-edge steel grade with high production technology requirements, among which the precise control of nitrogen is the most demanding part of production technology. Since nitrogen itself is a gas element, the nitrogen recovery rate involves many factors, including initial nitrogen content, decomposition pressure, temperature, and the content of other elements. During the RH vacuum smelting process, it is necessary to complete the alloying of nitrogen and other elements under a certain vacuum degree while meeting the production rhythm, and control the temperature to reach the target temperature. At present, it is difficult to achieve precise control of the nitrogen content in the RH refined steel water during the smelting process of oriented silicon steel, resulting in a large difference between the actual nitrogen content of the RH refined steel water and the target nitrogen content of the RH refined steel water. Summary of the invention

[0003] The problem solved by the invention is that it is difficult to achieve accurate control of the nitrogen content in RH refined steel melt during the smelting process of oriented silicon steel.

[0004] In order to solve the above problems, the present invention provides a method for controlling nitrogen content in a smelting process of oriented silicon steel, comprising:

[0005] Step S1, smelting in a converter to obtain primary molten steel;

[0006] Step S2, after the primary molten steel is tapped, it is transferred to an argon station for argon blowing and stirring to obtain a first intermediate molten steel;

[0007] Step S3, after transferring the first intermediate molten steel into the RH refining furnace, adjusting its temperature to a preset temperature, performing vacuum treatment, and obtaining RH refined outlet molten steel; wherein, the vacuum treatment comprises: evacuating to place the RH refining furnace at a preset vacuum degree, maintaining the temperature for a first preset time, adding a first preset additive amount of ferrosilicon nitride, obtaining a second intermediate molten steel after a second preset time, and then adding a second preset additive amount of ferrosilicon nitride after a third preset time, and performing pure degassing treatment; wherein, the second preset additive amount is calculated based on the first preset additive amount, the nitrogen content of the first intermediate molten steel, the nitrogen content of the second intermediate molten steel, and the target nitrogen content of the RH refined outlet molten steel according to a preset calculation model.

[0008] Optionally, in step S3, the preset calculation model is:

[0009]

[0010] Wherein, M is the second preset addition amount, m is the first preset addition amount, and N 目标 is the target nitrogen content of the molten steel out of RH refining, N2 is the nitrogen content of the second intermediate molten steel, N1 is the nitrogen content of the first intermediate molten steel, and K is an empirical constant.

[0011] Optionally, the time of the pure degassing treatment is T minutes, when T≤5, K is 0.9, and when T is greater than 5, K is 0.95.

[0012] Optionally, the N 目标 It is 80-100ppm.

[0013] Optionally, the first preset addition amount is 0.9-1.1 kg / t.

[0014] Optionally, the first preset time is 6-8 minutes, the second preset time is 2-4 minutes, the third preset time is 9-11 minutes, and the time for the pure degassing treatment is 4-6 minutes.

[0015] Optionally, the preset temperature is 1615-1620°C.

[0016] Optionally, the preset vacuum degree is not higher than 267Pa.

[0017] Optionally, in step S2, the argon blowing and stirring time is 5-10 min, and during the argon blowing and stirring process, the bottom blowing argon intensity is 0.09-0.18 m 3 / (h·t).

[0018] Optionally, during the vacuum treatment, circulating nitrogen blowing is performed, and during the circulating nitrogen blowing, the nitrogen supply intensity is 0.7-0.85m 3 / (h·t).

[0019] Compared with the prior art, the present invention adds ferrosilicon nitride twice in the vacuum treatment stage of RH refining to adjust the nitrogen content of molten steel, and the second addition amount of ferrosilicon nitride (the second preset addition amount M) is based on the addition amount of silicon nitride added for the first time (the first preset addition amount m), the increase in nitrogen content in the molten steel after the first addition of silicon nitride (the difference between N2 and N1), and the target increase in nitrogen content in the molten steel after the second addition of silicon nitride (N 目标The difference between N2 and N2) is calculated by a preset calculation model, that is, the amount of silicon nitride added for the second time (M) is obtained based on the nitrogen recovery rate after the first addition of silicon nitride in the same furnace, avoiding the influence of the differences in various process parameters of different furnaces on the nitrogen recovery rate, so that the nitrogen content in the RH refined steel water out of the station is slightly different from the target nitrogen content in the RH refined steel water out of the station, and the precise control of the nitrogen content in the RH refined steel water out of the station is achieved. In addition, the method of the present invention only increases nitrogen during the RH refining process, and the nitrogen increase link is single, which reduces the interference of many external factors and reduces the production difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the method for controlling nitrogen content during the smelting process of oriented silicon steel in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by those skilled in the art to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific implementation methods and are not intended to limit this application;

[0023] The term "including" and its variations used in this article are open inclusions, that is, "including but not limited to"; the term "based on" is "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first" and "second" mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, the meaning of "multiple" is two or more. It should be noted that ppm in the present invention is one part per million, and the nitrogen content N2 of the second intermediate molten steel and the nitrogen content N1 of the first intermediate molten steel are obtained by sampling and detection. Kg / t in the present invention refers to the amount of a substance added per ton of primary molten steel. 3 / (h·t) refers to the flow rate of a certain gas per ton of primary steelmaking liquid.

[0024] like Figure 1 As shown, a method for controlling nitrogen content in a smelting process of oriented silicon steel provided by an embodiment of the present invention comprises:

[0025] Step S1, smelting in a converter to obtain primary molten steel;

[0026] Step S2, after the primary molten steel is tapped, it is transferred to an argon station for argon blowing and stirring to obtain a first intermediate molten steel;

[0027] Step S3, after transferring the first intermediate molten steel into the RH refining furnace, adjusting its temperature to a preset temperature, performing vacuum treatment, and obtaining RH refined outlet molten steel; wherein, the vacuum treatment comprises: evacuating to place the RH refining furnace at a preset vacuum degree, maintaining the temperature for a first preset time, adding a first preset additive amount of ferrosilicon nitride, obtaining a second intermediate molten steel after a second preset time, and then adding a second preset additive amount of ferrosilicon nitride after a third preset time, and performing pure degassing treatment; wherein, the second preset additive amount is calculated based on the first preset additive amount, the nitrogen content of the first intermediate molten steel, the nitrogen content of the second intermediate molten steel, and the target nitrogen content of the RH refined outlet molten steel according to a preset calculation model.

[0028] When adjusting the nitrogen content in molten steel, the amount of ferrosilicon nitride added is generally determined based on the nitrogen recovery rate of the previous furnace. However, nitrogen is a gas element. The nitrogen recovery rate is related not only to the amount of molten steel, but also to the molten steel temperature, the initial nitrogen content of the molten steel, the RH vacuum degree, and the RH vacuum treatment time. However, there are more or less differences in the above parameters between different furnaces, which makes the nitrogen content of the RH refined molten steel out of the station differ greatly from the target nitrogen content of the RH refined molten steel out of the station.

[0029] In the embodiment of the present invention, ferrosilicon nitride is added twice to adjust the nitrogen content of molten steel during the vacuum treatment stage of RH refining, and the amount of ferrosilicon nitride added for the second time (the second preset amount of addition M) is based on the amount of silicon nitride added for the first time (the first preset amount of addition m), the increase in nitrogen content in the molten steel after the first addition of silicon nitride (the difference between N2 and N1), and the target increase in nitrogen content in the molten steel after the second addition of silicon nitride (N 目标 The difference between N2 and N2) is calculated by a preset calculation model, that is, the amount of silicon nitride added for the second time (M) is obtained based on the nitrogen recovery rate after the first addition of silicon nitride in the same furnace, avoiding the influence of the differences in various process parameters of different furnaces on the nitrogen recovery rate, so that the nitrogen content in the RH refined steel water out of the station is slightly different from the target nitrogen content in the RH refined steel water out of the station, and the precise control of the nitrogen content in the RH refined steel water out of the station is achieved. In addition, the method of the embodiment of the present invention only increases nitrogen during the RH refining process, and the nitrogen increase link is single, which reduces the interference of many external factors and reduces the production difficulty.

[0030] In some embodiments of the present invention, in step S3, the preset calculation model is:

[0031]

[0032] Wherein, M is the second preset addition amount, m is the first preset addition amount, and N 目标 is the target nitrogen content of the molten steel out of RH refining, N2 is the nitrogen content of the second intermediate molten steel, N1 is the nitrogen content of the first intermediate molten steel, and K is an empirical constant.

[0033] In some embodiments of the present invention, the time of the pure degassing treatment is T minutes, when T≤5, K is 0.9, and when T is greater than 5, K is 0.95.

[0034] In some embodiments of the present invention, the N 目标 It is 80-100ppm.

[0035] In some embodiments of the present invention, the first preset addition amount is 0.9-1.1 kg / t.

[0036] In order to control the nitrogen content, the vacuum treatment cycle of RH refining is relatively long, generally 50 minutes. For converters above 250 tons, the casting cycle is generally 50 minutes, which can match the vacuum cycle of RH refining. For converters of 200 tons and below, the casting cycle is relatively short, and the casting cycle and RH vacuum cycle cannot match. Generally, the number of continuous casting furnaces is within 4, and the production efficiency is low.

[0037] In some embodiments of the present invention, the first preset time is 6-8 minutes, the second preset time is 2-4 minutes, the third preset time is 9-11 minutes, and the time of the pure degassing treatment is 4-6 minutes. Preferably, the first preset time is 7 minutes, the second preset time is 3 minutes, the third preset time is 10 minutes, and the time of the pure degassing treatment is 5 minutes. In this preferred embodiment, the vacuum treatment cycle of RH refining is 25 minutes. For converters of 200 tons and below, the casting cycle and the RH vacuum cycle can match, and the production efficiency is high.

[0038] In some embodiments of the present invention, the preset temperature is 1615-1620°C.

[0039] In some embodiments of the present invention, the preset vacuum degree is no higher than 267Pa.

[0040] In some embodiments of the present invention, in step S2, the time of argon blowing and stirring is 5-10 minutes, and during the argon blowing and stirring process, the bottom blowing argon intensity is 0.09-0.18m 3 / (h·t).

[0041] In some embodiments of the present invention, during the vacuum treatment, circulating nitrogen blowing is performed, and during the circulating nitrogen blowing, the nitrogen supply intensity is 0.7-0.85m 3 / (h·t).

[0042] The present invention is further described below in conjunction with specific embodiments.

[0043] Example 1: Target nitrogen content (N) of molten steel from RH refining 目标 ) is 95ppm.

[0044] A1. Converter smelting to obtain primary molten steel; during converter smelting, the bottom blowing mode is controlled by conventional nitrogen-argon switching. When the oxygen supply is 75%, the bottom blowing is switched from nitrogen to argon, and the bottom blowing intensity is 2.0m 3 / (h·t), the final converter temperature is 1670°C, the final carbon content is 0.035%, and the final nitrogen content is 20ppm.

[0045] A2. After the primary molten steel is tapped, it is transferred to an argon station for argon blowing and stirring for 5 minutes to obtain the first intermediate molten steel; wherein, during the argon blowing and stirring process, the bottom blowing argon intensity is 0.18m 3 / (h·t), after testing, the temperature of the first intermediate molten steel is 1647°C, the carbon content of the first intermediate molten steel is 0.0315%, and the nitrogen content (N1) of the first intermediate molten steel is 27ppm.

[0046] A3. After the first intermediate molten steel is transferred to the RH refining furnace, its temperature is adjusted to 1617°C, and vacuum treatment is performed to obtain RH refined molten steel; wherein the vacuum treatment comprises: evacuating the RH refining furnace to a preset vacuum degree (89Pa), maintaining it for 7 minutes, adding a first preset addition amount (m) of ferrosilicon nitride, and obtaining a second intermediate molten steel after 3 minutes, and then adding a second preset addition amount (M) of ferrosilicon nitride after 10 minutes, and performing pure degassing treatment for 5 minutes; after testing, the nitrogen content (N2) of the second intermediate molten steel is 67ppm, wherein, during the vacuum treatment, circulating nitrogen blowing is performed, and the nitrogen supply intensity during the circulating nitrogen blowing is 0.74m 3 / (h·t) The first preset addition amount (m) is 1kg / t, and the second preset addition amount (M) is calculated according to the following calculation model:

[0047]

[0048] After calculation, the second preset addition amount (M) = (95-67) ÷ (67-27) × 1 × 0.9 kg / t = 0.63 kg / t.

[0049] Experimental example

[0050] The technical solution of Example 1 was adopted to carry out 30 heats of production, and the actual nitrogen content of the RH refined steel melt of each heat was tested. The results are shown in Table 1. It can be seen from Table 1 that the actual nitrogen content of the RH refined steel melt produced in 30 heats was between 88 and 102 ppm, and the deviation from the target nitrogen content of 95 ppm of the RH refined steel melt was within 7 ppm, indicating that the method of the embodiment of the present invention can achieve accurate control of the nitrogen content in the RH refined steel melt.

[0051] Table 1

[0052]

[0053]

[0054] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for controlling nitrogen content in a smelting process of oriented silicon steel, characterized in that: include: Step S1, smelting in a converter to obtain primary molten steel; Step S2, after the primary molten steel is tapped, it is transferred to an argon station for argon blowing and stirring to obtain a first intermediate molten steel; Step S3, after transferring the first intermediate molten steel into the RH refining furnace, adjusting its temperature to a preset temperature, performing vacuum treatment, and obtaining RH refined outlet molten steel; wherein, the vacuum treatment comprises: evacuating to place the RH refining furnace at a preset vacuum degree, maintaining the temperature for a first preset time, adding a first preset additive amount of ferrosilicon nitride, obtaining a second intermediate molten steel after a second preset time, and then adding a second preset additive amount of ferrosilicon nitride after a third preset time, and performing pure degassing treatment; wherein, the second preset additive amount is calculated based on the first preset additive amount, the nitrogen content of the first intermediate molten steel, the nitrogen content of the second intermediate molten steel, and the target nitrogen content of the RH refined outlet molten steel according to a preset calculation model.

2. The method for controlling nitrogen content in the smelting process of oriented silicon steel according to claim 1, characterized in that: In step S3, the preset calculation model is: Wherein, M is the second preset addition amount, m is the first preset addition amount, and N 目标 is the target nitrogen content of the molten steel out of RH refining, N2 is the nitrogen content of the second intermediate molten steel, N1 is the nitrogen content of the first intermediate molten steel, and K is an empirical constant.

3. The method for controlling nitrogen content in the smelting process of oriented silicon steel according to claim 2, characterized in that: The time of the pure degassing treatment is T minutes. When T≤5, K is 0.9, and when T is greater than 5, K is 0.

95.

4. The method for controlling nitrogen content in the smelting process of oriented silicon steel according to claim 3, characterized in that: The N 目标 It is 80-100ppm.

5. The method for controlling nitrogen content in the smelting process of oriented silicon steel according to claim 3, characterized in that: The first preset addition amount is 0.9-1.1 kg / t.

6. The method for controlling nitrogen content in the smelting process of grain-oriented silicon steel according to claim 3, characterized in that: The first preset time is 6-8 minutes, the second preset time is 2-4 minutes, the third preset time is 9-11 minutes, and the time of the pure degassing treatment is 4-6 minutes.

7. The method for controlling nitrogen content in the smelting process of oriented silicon steel according to claim 1, characterized in that: The preset temperature is 1615-1620°C.

8. The method for controlling nitrogen content in the smelting process of oriented silicon steel according to claim 1, characterized in that: The preset vacuum degree is no higher than 267Pa.

9. The method for controlling nitrogen content in the smelting process of oriented silicon steel according to claim 1, characterized in that: In step S2, the argon blowing and stirring time is 5-10 minutes, and during the argon blowing and stirring process, the bottom blowing argon intensity is 0.09-0.18m 3 / (h·t).

10. The method for controlling nitrogen content in the smelting process of grain-oriented silicon steel according to claim 1, characterized in that: During the vacuum treatment, circulating nitrogen blowing is performed. During the circulating nitrogen blowing, the nitrogen supply intensity is 0.7-0.85m 3 / (h·t).

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