Method for controlling nitrogen content in wheel steel smelting

Abstract

The present invention discloses a method for controlling nitrogen content in the smelting of wheel steel. The wheel steel smelting process includes, in sequence: electric furnace smelting, LF refining, and VD deep vacuum treatment. The method for controlling nitrogen content includes: after the VD breaking vacuum treatment, adding a certain amount of manganese nitride alloy to the molten steel, then blowing nitrogen and stirring for a preset duration, and then entering the next process. Among them, the addition amount of manganese nitride alloy and the nitrogen blowing and stirring duration are related to the finished product nitrogen content range and the content of nitrogen-fixing elements in the molten steel. The method of adding manganese nitride alloy first and then blowing nitrogen and stirring is used for nitrogen increase, and the nitrogen control effect is more stable. And ensuring a certain nitrogen blowing and soft stirring time is beneficial to improving the performance of the finished product. Moreover, the addition amount of manganese nitride alloy and the nitrogen blowing and stirring time can be directly calculated by a formula, greatly reducing the difficulty and cost of the nitrogen control process plan design for wheel steel, and being able to better achieve narrow-range and precise control of nitrogen content composition.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and particularly to a method for controlling nitrogen content in the smelting of wheel steel. Background Art

[0002] In most steel grades, nitrogen is a harmful element. For example, a high nitrogen content in steel can cause stress failure of the steel, reducing the formability, high-temperature toughness, and plasticity of the steel. However, in some austenitic stainless steels, tool steels, die steels, and some high-strength and tough structural steels, it is a beneficial alloying element. The addition of nitrogen can promote the nucleation of intragranular ferrite, effectively refine the grains, improve the strength and toughness of the metal, and nitrogen can also promote the precipitation of carbonitrided vanadium, giving full play to the precipitation strengthening effect of vanadium and greatly increasing the strength of the steel. However, the content of nitrogen in the steel must be controlled within a certain range. Exceeding this range will become a harmful component, resulting in a decline in performance. This requires precise control of nitrogen during the steelmaking process. Especially for heavy-haul railway wheel steel, which has relatively high requirements for the overall performance of the steel and relatively high requirements for the fracture toughness of the steel. At the same time, the upper limit of the N content is specified in its enterprise standard. Therefore, the development of its precise nitrogen control process is of great significance. However, in the current continuous casting process plan for smelting heavy-haul railway wheel steel, in order to ensure that no white spots appear in the finished ingot of the smelted wheel steel, the molten steel needs to be treated under a deep vacuum of 20 - 40 Pa in VD, so that the hydrogen content determined in VD is ≤ 2 ppm. And the denitrification effect is also obvious after the molten steel is treated under a deep vacuum in VD, resulting in greater difficulty in precise nitrogen control.

[0003] Therefore, it is necessary to provide a new method for narrow control of nitrogen content components after high-vacuum deep treatment of heavy-haul railway wheel steel, which can improve its fracture toughness while ensuring that the strength of the wheel steel meets the requirements, and at the same time must meet the requirements for nitrogen content in its industry standard so as not to affect the production of subsequent finished heavy-haul railway wheels. Summary of the Invention

[0004] To solve some or all of the technical problems existing in the above-mentioned prior art, the present invention provides a method for controlling nitrogen content in the smelting of wheel steel. The technical solution is as follows:

[0005] A method for controlling nitrogen content in the smelting of wheel steel is provided. The wheel steel smelting process includes, in sequence: electric furnace smelting, LF refining, and VD deep vacuum treatment. The method for controlling nitrogen content includes: after the VD breaking vacuum treatment, adding a certain amount of manganese nitride alloy to the molten steel, then blowing nitrogen and stirring for a preset duration, and then entering the next process. Among them, the addition amount of the manganese nitride alloy and the blowing nitrogen stirring duration are related to the finished product nitrogen content range and the content of nitrogen-fixing elements in the molten steel.

[0006] In some optional implementation manners, when the median value of the finished product nitrogen content range is less than or equal to the weakly saturated nitrogen content, calculate the addition amount of the manganese nitride alloy and the blowing nitrogen stirring duration according to the following formula:

[0007] N fp = N med = 0.57X + 4.51Y + 10

[0008] In the formula, N fp takes the median value N in the range of the finished product nitrogen content med , X represents the weight of the added manganese nitride alloy, in kg, and Y represents the nitrogen blowing stirring duration, in min;

[0009] The above-mentioned weakly saturated nitrogen content represents the upper limit value of the nitrogen content with high recovery rate of manganese nitride alloy under a certain specific molten steel composition, and its value is related to the content of nitrogen-fixing elements in the molten steel.

[0010] In some alternative implementation manners, according to the following formula, calculate the weakly saturated nitrogen content:

[0011] N ws = 800A + 8B + C + 5

[0012] In the formula, N ws represents the weakly saturated nitrogen content, in ppm, and A, B, and C respectively represent the contents of V, Cr, and Mn in the molten steel as A%, B%, and C%.

[0013] In some alternative implementation manners, when the median value of the finished product nitrogen content range is greater than the weakly saturated nitrogen content, calculate the addition amount of the manganese nitride alloy and the nitrogen blowing stirring duration according to the following formula:

[0014] N fp = 2.1N med - N ws = 0.57X + 4.51Y + 10

[0015] In the formula, N med represents the median value of the finished product nitrogen content range, N ws represents the weakly saturated nitrogen content, X represents the weight of the added manganese nitride alloy, in kg, and Y represents the nitrogen blowing stirring duration, in min.

[0016] In some alternative implementation manners, control the addition amount of the manganese nitride alloy to be above 40 kg and the nitrogen blowing stirring duration to be above 3 min.

[0017] In some alternative implementation manners, the nitrogen flow rate during nitrogen blowing stirring is 260 NL / min.

[0018] In some alternative implementation manners, during electric furnace smelting, control the proportion of the charged hot metal to be 80% - 90%, adopt the operation of leaving steel and slag when tapping from the electric furnace, add coke powder carburizer during tapping, and blow argon for stirring, and then enter the ladle furnace after leaving the station.

[0019] In some alternative implementation manners, after the ladle enters the LF station, the temperature is measured first, power is supplied to raise the temperature, then calcium carbide is added. After argon blowing and stirring, a sample is taken and alloy is added as a supplement according to the target content of the finished product.

[0020] In some alternative implementation manners, after the LF refining and tapping, the weakly saturated nitrogen content is determined according to the contents of V, Cr, and Mn in the molten steel, and the addition amount of manganese nitride alloy and the duration of nitrogen blowing and stirring are determined in combination with the nitrogen content range of the finished product.

[0021] In some alternative implementation manners, during the VD vacuum furnace treatment, it is maintained for 15 min under the condition of a high vacuum degree ≤ 67 Pa. After the components and temperature of the molten steel meet the requirements at the end of the vacuum treatment, wire feeding operation is carried out. After the wire feeding is completed, manganese nitride alloy is added according to the calculated amount and then nitrogen is blown and stirred.

[0022] The main advantages of the technical solution of the present invention are as follows:

[0023] In the method for controlling the nitrogen content in the smelting of the wheel steel of the present invention, nitrogen is increased by the method of adding manganese nitride alloy first and then blowing nitrogen and stirring. The nitrogen control effect is more stable, and ensuring a certain soft nitrogen blowing stirring time is beneficial to improving the performance of the finished product. Moreover, the addition amount of manganese nitride alloy and the nitrogen blowing and stirring time can be directly calculated by formulas, greatly reducing the difficulty and cost of the nitrogen control process scheme design of the wheel steel, and being able to better achieve the narrow-range precise control of the nitrogen content component. Description of the Drawings

[0024] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the attached

[0025] In the figure:

[0026] Figure 1 is a process diagram of the preparation of the wheel steel provided by an embodiment of the present invention. Detailed Embodiments

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] The objective of the present invention is to achieve the narrow-range precise control of the nitrogen content component after the VD deep vacuum treatment in the smelting of the wheel steel, so as to further improve the fracture toughness of the finished wheel and meet the performance requirements of the railway heavy-haul wheels.

[0029] Please refer to the attached Figure 1 , the process route of the wheel steel in the present invention is: electric furnace smelting → LF refining → VD deep vacuum treatment → continuous casting → slow cooling (or annealing) → finishing → inspection and warehousing.

[0030] At present, the main processes for smelting nitrogen-containing steel grades are alloy nitrogen addition method and gas nitrogen addition method. Alloy nitrogen addition mainly adds alloys with high nitrogen content to the molten steel for nitrogen addition, such as manganese nitride, chromium nitride, etc.; the gas nitrogen addition method is to blow nitrogen into the molten steel, and the dispersed nitrogen bubbles can increase the gas / liquid contact area and shorten the atomic diffusion distance. The present invention combines the two methods of adding nitriding alloy and blowing nitrogen smelting to achieve precise control of the nitrogen content of the heavy-haul railway wheel steel.

[0031] The technical solution adopted in the present invention is to add X kg of "manganese nitride" alloy after the VD deep vacuum treatment is completed, that is, after the VD breaks the vacuum, and then blow nitrogen for soft stirring for Y min, with a nitrogen flow rate of 260 NL / min, and then normally enter the next process to continue smelting. When the ability of the molten steel to dissolve nitrogen elements is not limited, theoretically the finished product nitrogen content is N fp (unit: ppm) is directly related to the amount of manganese nitride alloy added and the blowing nitrogen stirring duration. After fitting the test data, the calculation formula for the finished product nitrogen content N fp is as follows:

[0032] N fp = 0.57X + 4.51Y + 10 Formula 1

[0033] The above formula is the calculation formula when the nitrogen addition amount is small and within the dissolution ability range of the molten steel. When the finished product nitrogen content is high and the nitrogen addition amount is large, due to the limitation of the dissolution ability of the molten steel, the recovery rate during nitrogen addition decreases. Based on the above, the present invention proposes a weakly saturated nitrogen content N ws , which represents the upper limit value of the nitrogen content with high recovery rate of "manganese nitride" alloy under a certain specific molten steel composition, unit: ppm. It is mainly affected by the content of nitrogen-fixing elements such as V, Cr, and Mn in the steel. Among them, V, Cr, and Mn are the main influencing elements of the wheel steel. Assuming their contents in the steel are A%, B%, and C% respectively, the weakly saturated nitrogen content N ws corresponding to this molten steel composition can be calculated by the following formula:

[0034] N ws = 800A + 8B + C + 5 Formula 2

[0035] Among them, the coefficients of A, B, and C represent their ability to combine with nitrogen, and 5 is the nitrogen content dissolved by other elements in the steel.

[0036] The present invention needs to complete the calculation of the nitrogen alloy addition amount and the nitrogen blowing duration based on the above two formulas. The complete process is as follows:

[0037] (1) Substitute the contents of elements V, Cr, and Mn in the wheel steel into Formula 2 to calculate the weakly saturated nitrogen content N under this composition ws .

[0038] (2) When the median value N of the finished product target N content range med ≤N ws , assign N fp to N med , calculate a set of X and Y values. At the same time, under the condition of satisfaction, try to make X≥40 and Y≥3.

[0039] (3) When the median value N of the finished product target N content range med >N ws , assign N fp to 2.1N med -N ws , ensure X≥40 and Y≥3, and calculate a set of X and Y values.

[0040] (4) Add X kg of "manganese nitride" alloy after VD breaking the vacuum, then blow nitrogen for soft stirring for Y min, the nitrogen flow rate is 260 NL / min, and then normally enter the next process to continue smelting.

[0041] The present invention obtains Formula 1 and Formula 2 for controlling the nitrogen content of two wheel steels through the fitting analysis of the results of nitrogen control test data of different wheel steels. Through these two formulas, the addition amount of "manganese nitride" alloy and the bottom blowing nitrogen flow rate required to reach the target nitrogen content range can be accurately calculated. Since the alloy nitrogen addition method has a more stable nitrogen control effect than the gas nitrogen addition method, in the selection of the nitrogen control process, the addition amount of "manganese nitride" alloy is preferably ensured to be above 40 kg, that is, ensuring X≥40. However, the price of "manganese nitride" alloy is more expensive than nitrogen, and the alloy recovery rate of nitrogen addition by "manganese nitride" alloy is relatively low. Although the nitrogen addition recovery rate of the "gas nitrogen addition method" is unstable and not conducive to nitrogen control, reducing the nitrogen blowing time will also lead to an increase in nitrogen content segregation, which is not conducive to improving the performance of the finished product. Therefore, it is necessary to appropriately ensure a certain soft nitrogen blowing stirring time, that is, Y≥3. According to the verification of the test results, the final nitrogen control deviation of the present invention is about ±15 ppm. The present invention transforms the nitrogen control process of wheel steel into simple formula calculation, greatly reducing the difficulty and cost of the nitrogen control process plan design of wheel steel, and can better achieve precise control of the nitrogen content component narrowing.

[0042] The following further describes the method for controlling the nitrogen content of the present invention with specific embodiments:

[0043] Example 1:

[0044] Steel grade: Steel for CL60 subway wheels. The tapping volume is 80t, and the requirements for smelting composition are [C]=0.60% - 0.63%, [Si]=0.26% - 0.34%, [Mn]=0.70% - 0.79%, [P]≤0.01%, [S]=0.005 - 0.012%, [V]=0.06 - 0.08%, [Cr]=0.18 - 0.22%, [N]=40 - 70ppm. The specific steps are as follows:

[0045] (1) Electric furnace smelting conditions: The proportion of hot metal charged into the furnace = 83%.

[0046] (2) Electric furnace end point control: End point [C]=0.336%, [P]=0.007%, [S]=0.019%, [Mn]=0.07, [Cr]=0.039; Tapping temperature T = 1677°C.

[0047] (3) Electric furnace tapping: Avoid over-oxidation of the molten steel, and use the operation of leaving steel and slag, and strictly prohibit slagging.

[0048] (4) Addition of carbon powder in the electric furnace: Add a primary coke powder carburizer with a carbon content ≥92% into the ladle during tapping.

[0049] (5) Stirring of the molten steel during tapping: The tapping time is 4.5min, and the bottom blowing Ar is stirred throughout the tapping process. The bottom blowing argon flow rate is controlled at 500Nl / min. After leaving the station, it enters the ladle furnace.

[0050] (6) LF refining: After the ladle enters the LF station, first measure the temperature and send electricity to raise the temperature. The measured temperature is 1565°C, add 220Kg / ladle of calcium carbide, and stir with an argon flow rate of 250 - 300Nl / min for 5 - 8min. Then, take a sample and add alloys according to the finished product target based on its C, Si content, etc. After fine-tuning the components such as C, Si, and Mn in the LF ladle furnace, pure electricity is sent for 10 minutes, and it is stirred with an argon flow rate of 250 - 300Nl / min for 5 - 8min; The white slag holding time is 45 minutes. During refining, add lime at ≤50Kg / batch to maintain the viscosity of the lime-saturated refining slag, and prohibit adding other alloys in the middle and late stages of LF; The final LF tapping composition is shown in Table 1.

[0051] (7) According to the requirements of the smelting composition, taking the target values of V, Cr, and Mn contents, A, B, and C are 0.07, 0.2, and 0.75 respectively, and substituting them into the calculation of the weakly saturated nitrogen content N ws is: N ws =800A + 8B + C + 5 = 63.35(ppm). The median value N med =55 < N ws , so assign N fp as N med , that is, N fp =55, N fp= 0.57X + 4.51Y + 10. Substituting X = 40 gives Y = 4.92. Finally, the nitrogen control process was determined as follows: add 40 kg of "manganese nitride" alloy after VD breaking the vacuum, then perform soft nitrogen stirring for 5 min with a nitrogen flow rate of 260 NL / min.

[0052] (8) VD vacuum furnace treatment: Maintain for 15 min under a high vacuum degree ≤ 67 Pa. After the molten steel composition and temperature meet the requirements (except for the S element) at the end of the vacuum treatment, then perform the wire feeding operation. Wire feeding operation: First, feed CaSi wire (wire diameter Φ13 mm, Ca content about 30%, addition amount 1.4 m / t of steel) into the molten steel in the ladle. Secondly, after soft argon stirring for ≥ 2 minutes, feed the sulfur cored wire; ③ Thirdly, add 40 kg of "manganese nitride" alloy and perform soft nitrogen stirring for 5 minutes. The stirring intensity should be such that the ladle slag surface just starts to wriggle and the slag surface is not blown through. The VD tapping composition is shown in Table 1.

[0053] Table 1 Elemental composition of steel at different smelting stages

[0054] Component / % C Si Mn P S Ni Cr LF tapping 0.605 0.28 0.774 0.009 0.001 0.01 0.22 VD tapping 0.594 0.29 0.762 0.008 0.011 0.01 0.22 Final product 0.605 0.29 0.79 0.008 0.01 0.01 0.21

[0055] Continued Table 1 Elemental composition of steel at different smelting stages

[0056] Component / % Cu Al Mo V Ti B LF tapping 0.01 0.025 0.0096 0.07 0.003 0.0004 VD tapping 0.01 0.009 0.009 0.07 0.0028 0.0004 Final product 0.01 0.007 0.0089 0.07 0.0025 0.0004

[0057] (9) Take a sample from the tundish to measure the finished product melting composition as shown in Table 1, and take a sample from the finished product billet to analyze its nitrogen content as 56 ppm, meeting the target nitrogen content range.

[0058] Example 2:

[0059] Steel grade: Steel for AAR-D heavy-haul railway wheels. The tapping volume is 80 t, and the melting composition requirements are [C] = 0.71% - 0.74%, [Si] = 0.75% - 0.85%, [Mn] = 0.75% - 0.85%, [P] ≤ 0.01%, [S] = 0.008 - 0.015%, [V] = 0.07 - 0.09%, [Cr] = 0.17 - 0.20%, [N] = 40 - 80 ppm. The specific steps are as follows:

[0060] (1) Electric furnace smelting conditions: The proportion of hot metal charged into the furnace = 88%.

[0061] (2) Electric furnace end point control: End point [C] = 0.400%, [P] = 0.006%, [S] = 0.025%, [Mn] = 0.053, [Cr] = 0.046; tapping temperature T = 1645 °C.

[0062] (3) Electric furnace tapping: Avoid overoxidation of the molten steel, and use the operation of retaining steel and slag to strictly prevent slag from flowing into the ladle.

[0063] (4) Addition of electric furnace carbon powder: During tapping, add a primary coke powder carburizer with a carbon content of ≥ 92% into the ladle.

[0064] (5) Stirring of tapped molten steel: The tapping time is 5 min, and the bottom blowing of Ar is carried out throughout the tapping process for stirring. The flow rate of bottom blowing argon is controlled at 500 Nl / min. After tapping, it enters the ladle furnace.

[0065] (6) LF refining: After the ladle enters the LF station, first measure the temperature and send electricity to increase the temperature. The measured temperature is 1541 °C, add 220 Kg / heat of calcium carbide, and stir with an argon flow rate of 250 - 300 Nl / min for 5 - 8 min. Then, take a sample and add alloys according to the finished product target based on its C, Si content, etc. After fine-tuning the components such as C, Si, Mn in the LF ladle furnace, pure electricity is sent for 10 minutes, and stir with an argon flow rate of 250 - 300 Nl / min for 5 - 8 min; the white slag holding time is 45 minutes. During refining, add lime at ≤ 50 Kg / batch to maintain the viscosity of the lime-saturated refining slag, and it is prohibited to add other alloys in the middle and late stages of LF; the final LF tapping composition is shown in Table 2.

[0066] (7) According to the requirements of the melting composition, taking the target values of V, Cr, Mn contents, A, B, C are 0.07, 0.18, 0.8 respectively, and substituting them into the calculation of the weakly saturated nitrogen content N ws is: N ws = 800A + 8B + C + 5 = 63.24 (ppm). Due to the special requirements of the user, the target N content value N med = 70 > N ws , so assign N fp as 2.1N med - N ws , that is, N fp = 83.76, N fp = 0.57X + 4.51Y + 10, substituting X = 45 gives Y = 10.67. Finally, the nitrogen control process is formulated as adding 45 kg of "manganese nitride" alloy after VD breaking the vacuum, and then blowing nitrogen for soft stirring for 10 min, with the nitrogen flow rate of 260 NL / min.

[0067] (8) VD vacuum furnace treatment: Keep it under a high vacuum degree of ≤ 67 Pa for 15 min. After the vacuum treatment ends and the molten steel composition and temperature meet the requirements (except for the S element), then carry out the wire feeding operation. Wire feeding operation: First, feed CaSi wire (wire diameter Φ13 mm, Ca content about 30%, addition amount 1.4 m / t of steel) into the molten steel in the ladle. Secondly, after blowing argon for soft stirring for ≥ 2 minutes, feed the sulfur cored wire; ③ Thirdly, add 45 kg of "manganese nitride" alloy and blow nitrogen for soft stirring for 10 minutes. The stirring intensity should be such that the ladle slag surface just starts to wriggle and the slag surface is not blown through. The VD tapping composition is shown in Table 2.

[0068] Table 2 Elemental composition of steel in different smelting stages

[0069] Component / % C Si Mn P S Ni Cr LF tapping 0.701 0.81 0.814 0.006 0 0.01 0.18 VD tapping 0.71 0.83 0.863 0.006 0.008 0.01 0.19 Final product 0.722 0.8 0.838 0.006 0.009 0.02 0.19

[0070] Continued Table 2 Element Composition Table of Steel in Different Smelting Stages

[0071] Component / % Cu Al Mo V Ti B LF tapping 0.01 0.021 0.0083 0.078 0.0038 0.0005 VD tapping 0.01 0.017 0.0096 0.08 0.0039 0.0006 Final product 0.01 0.01 0.0095 0.079 0.0035 0.0006

[0072] (9) Samples were taken from the tundish to determine the finished product melting composition as shown in Table 2, and samples were taken from the finished product billet to analyze its nitrogen content, which was 72 ppm, meeting the target nitrogen content range.

[0073] It should be noted that in this article, 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 non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. In addition, in this article, "front", "rear", "left", "right", "upper", and "lower" are all referenced based on the placement state shown in the drawings.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for controlling nitrogen content in the smelting of wheel steel, the wheel steel smelting process including, in sequence: electric furnace smelting, LF refining, and VD deep vacuum treatment, Characterized in that, The method for controlling nitrogen content includes: After the VD breaking vacuum treatment, a certain amount of manganese nitride alloy is added to the molten steel, then nitrogen is blown and stirred for a preset duration, and then it enters the next process. Among them, the addition amount of manganese nitride alloy and the nitrogen blowing and stirring duration are related to the finished product nitrogen content range and the content of nitrogen-fixing elements in the molten steel; When the median value of the finished product nitrogen content range is less than or equal to the weakly saturated nitrogen content, calculate the addition amount of manganese nitride alloy and the nitrogen blowing and stirring duration according to the following formula: N fp =N med =0.57X + 4.51Y + 10 Wherein, N fp is the finished product nitrogen content, in ppm, and the value of N fp is taken as the median value N in the range of the finished product nitrogen content med , X represents the weight of the added manganese nitride alloy, in kg, and Y represents the nitrogen blowing and stirring duration, in min; The above-mentioned weakly saturated nitrogen content represents the upper limit value of nitrogen content with high recovery rate of manganese nitride alloy under a certain molten steel composition, and its value is related to the content of nitrogen-fixing elements in the molten steel; Calculate the weakly saturated nitrogen content according to the following formula: N ws = 800A + 8B + C + 5 where N ws represents the weakly saturated nitrogen content in ppm, and A, B, and C represent the contents of V, Cr, and Mn in the molten steel as A%, B%, and C% respectively; When the median value of the finished product nitrogen content range is greater than the weakly saturated nitrogen content, calculate the addition amount of manganese nitride alloy and the nitrogen blowing and stirring duration according to the following formula: N fp = 2.1 N med −N ws = 0.57X + 4.51Y + 10 Where N med represents the median value of the finished product nitrogen content range, N ws represents the weakly saturated nitrogen content, X represents the weight of the added manganese nitride alloy in kg, and Y represents the nitrogen blowing and stirring duration in min; Control the addition amount of manganese nitride alloy to be above 40 kg and the nitrogen blowing and stirring duration to be above 3 min.

2. The method for controlling nitrogen content in the smelting of wheel steel according to claim 1, Characterized in that, The nitrogen flow rate during nitrogen blowing and stirring is 260 NL / min.

3. The method for controlling nitrogen content in the smelting of wheel steel according to claim 2, Characterized in that, During electric furnace smelting, control the proportion of hot metal entering the furnace to be 80%-90%. When tapping from the electric furnace, the operation of leaving steel and slag is adopted. During tapping, coke powder carburizer is added and argon is blown and stirred, and then it enters the ladle furnace after leaving the station.

4. The method for controlling nitrogen content in the smelting of wheel steel according to claim 3, Characterized in that, After the ladle enters the LF station, first measure the temperature and send electricity to raise the temperature, then add calcium carbide. After blowing argon and stirring, sample and add alloy according to the finished product target content.

5. The method for controlling nitrogen content in the smelting of wheel steel according to claim 4, Characterized in that, During VD vacuum furnace treatment, maintain it for 15 min under the condition of high vacuum degree ≤ 67 Pa. After the components and temperature of the molten steel meet the requirements at the end of the vacuum treatment except for S, then carry out the wire feeding operation. After the wire feeding is completed, add manganese nitride alloy according to the calculated amount and then blow nitrogen and stir.

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