Vanadium-nitrogen steel and preparation method thereof

Abstract

The invention provides vanadium-nitrogen steel and a preparation method thereof.The preparation method comprises the following steps that molten iron and a first part of scrap steel are subjected to converter smelting to prepare molten steel, and in the converter smelting process, nitrogen is kept to be introduced from the bottom of a converter all the time; in the tapping process of the molten steel, vanadium-nitrogen alloy is added into the molten steel, then the molten steel is placed in a refining furnace, heating melting treatment and refining treatment are conducted in sequence, and refined molten steel is prepared; in the refining treatment process, nitrogen is introduced from the bottom of the refining furnace; and preparing the refined molten steel into the vanadium-nitrogen steel. According to the preparation method, the effect of accurately increasing the nitrogen content can be achieved, and therefore the mechanical strength performance of the vanadium-nitrogen steel is comprehensively improved.

Description

Technical Field

[0001] The invention relates to the technical field of alloys, and in particular to a vanadium-nitrogen steel and a preparation method thereof. Background Art

[0002] In traditional technology, nitrogen is often introduced into vanadium steel to increase the precipitation strengthening effect of vanadium. Since vanadium preferentially combines with nitrogen, most of it is precipitated in the form of V(CN), which doubles the number of V(CN) precipitation phases, thereby achieving the effect of fine grain strengthening and other effects, thereby improving the performance of steel. Therefore, it is an important way to improve the strength of vanadium steel to change the distribution state of vanadium by adding nitrogen and make full use of the precipitation strengthening effect of vanadium to improve the strength of vanadium steel.

[0003] However, traditional steel production methods encounter many bottlenecks in controlling nitrogen content. On the one hand, the existing nitrogen control methods are relatively single and backward, lacking precise and effective diversified technical support; on the other hand, due to factors such as equipment and process, the overall nitrogen control capacity is very limited. The double dilemma directly leads to the difficulty of stabilizing the nitrogen content in the ideal range during the production of rebar vanadium nitrogen steel. What is more troublesome is that scrap steel, as an important steelmaking raw material, will continuously release the nitrogen element it carries into the molten steel during the smelting process, further aggravating the complexity and difficulty of nitrogen content control, causing the performance of rebar to fluctuate frequently and significantly, and the mechanical quality of the product is greatly reduced, which has become an industry problem that needs to be overcome urgently.

[0004] Therefore, the traditional technology still needs to be improved. Summary of the invention

[0005] Based on this, the present application provides a vanadium-nitrogen steel and a preparation method thereof, which accurately increases the nitrogen content, thereby improving the mechanical properties of the vanadium-nitrogen steel.

[0006] The technical solution of this application is as follows.

[0007] In a first aspect of the present application, a method for preparing vanadium-nitrogen steel is provided, comprising the following steps:

[0008] The molten iron and the first part of the scrap steel are subjected to converter smelting to produce molten steel, and during the converter smelting process, nitrogen is continuously supplied from the bottom of the converter;

[0009] During the steel tapping process, vanadium-nitrogen alloy is added to the molten steel, and then the molten steel is placed in a refining furnace, and subjected to heating and melting treatment and refining treatment in sequence to prepare refined molten steel; during the refining treatment, nitrogen is passed from the bottom of the refining furnace;

[0010] The refined molten steel is made into vanadium-nitrogen steel.

[0011] In the above preparation method, it is creatively proposed to combine the nitrogen blowing mode throughout the converter smelting process with the addition of vanadium-nitrogen alloy refining, and to blow nitrogen from the bottom during the refining process, so that the nitrogen element will be continuously released during the entire smelting and refining process. The synergistic effect can achieve the effect of accurately increasing the nitrogen content, thereby comprehensively improving the mechanical strength performance of the steel.

[0012] In some of the embodiments, in the step of maintaining the nitrogen gas flowing from the bottom of the converter, the flow rate of the nitrogen gas is 300 L / min to 350 L / min.

[0013] The flow rate of nitrogen can be controlled to further improve the stability of the released nitrogen.

[0014] In some of the embodiments, based on the mass of molten steel before tapping, the addition amount of the vanadium-nitrogen alloy is 1 kg / t to 2 kg / t.

[0015] The addition amount of vanadium-nitrogen alloy is controlled to further supplement the appropriate amount of nitrogen element.

[0016] In some of the embodiments, in the step of passing nitrogen from the bottom of the refining furnace, nitrogen is blown into the bottom pipe of the refining furnace at a pressure of ≥1.2 MPa for a blowing time of 0.1 min to 15 min.

[0017] In some of the embodiments, during the temperature rising and melting treatment, a vanadium-nitrogen alloy is added, and based on the mass of the second part of scrap steel and the total mass of the molten steel formed before the temperature rising and melting treatment step, the amount of the vanadium-nitrogen alloy added is 1kg / t to 2.5kg / t.

[0018] "Based on the total mass of the molten steel formed before the step of heating and melting treatment" means the total mass of the molten steel existing in the refining furnace before the step of heating and melting treatment, including the molten steel before tapping, the vanadium-nitrogen alloy added during the tapping process, etc.

[0019] In some of the embodiments, after the step of adding the vanadium-nitrogen alloy and before the step of heating and melting treatment, a second portion of scrap steel is added, and the theoretical maximum volume ratio of the second portion of scrap steel to the ladle of the refining furnace is (0-25):105.

[0020] In some embodiments, the first portion of scrap steel and the second portion of scrap steel are independently selected from at least one of briquetted scrap steel, loose scrap steel, and threaded steel bar grains.

[0021] In some of the embodiments, the nitrogen content in the refined molten steel is 0.01% to 0.019% by mass.

[0022] In some of the embodiments, the vanadium-nitrogen alloy contains 75% vanadium and 16% nitrogen by mass.

[0023] In a second aspect of the present application, a vanadium-nitrogen steel is provided, which is prepared by the method for preparing the vanadium-nitrogen steel as described above.

[0024] The vanadium-nitrogen steel prepared by the above method has excellent and stable mechanical properties. DETAILED DESCRIPTION

[0025] For ease of understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application are provided. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0027] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0028] The "range" disclosed in the present application can be defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and any end value can be included or excluded independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are also listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0029] In this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0030] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0031] As mentioned in the background technology, traditional steel production methods encounter many bottlenecks in nitrogen content control. Single nitrogen control technology is still the mainstream, but the stability is insufficient. After a lot of actual production research, researchers creatively proposed to combine the nitrogen blowing mode of converter smelting throughout the process and add vanadium nitrogen alloy refining, so that nitrogen elements will be continuously released during the entire smelting and refining process, and the synergistic effect can achieve the effect of precise nitrogen control, thereby comprehensively improving the strength index of steel.

[0032] An embodiment of the present application provides a method for preparing vanadium-nitrogen steel, comprising the following steps S10 to S30.

[0033] S10: The molten iron and the first part of scrap steel are subjected to converter smelting to produce molten steel. During the converter smelting process, nitrogen is continuously supplied from the bottom of the converter.

[0034] In some of the embodiments, in the step of maintaining the nitrogen gas flowing from the bottom of the converter, the flow rate of the nitrogen gas is 300 L / min to 350 L / min.

[0035] The flow rate of nitrogen can be controlled to further improve the stability of the released nitrogen.

[0036] In some of the embodiments, during the converter smelting step, oxygen is introduced from the top of the converter.

[0037] The function of oxygen is to react with the carbon, silicon, manganese, phosphorus, sulfur and other elements in the molten iron to reduce these five impurities that are harmful to the composition of the molten steel, and use the chemical heat released during the oxidation reaction and the physical heat of the molten iron as heat sources.

[0038] S20: During the steel tapping process, vanadium-nitrogen alloy is added to the molten steel and then placed in a refining furnace to perform heating and melting treatment and refining treatment in sequence to prepare refined molten steel; during the refining treatment, nitrogen is passed from the bottom of the refining furnace.

[0039] S30: Make refined molten steel into vanadium nitrogen steel.

[0040] In the above preparation method, it is creatively proposed to combine the nitrogen blowing mode throughout the converter smelting process with the addition of vanadium-nitrogen alloy refining, and nitrogen is also blown into the bottom during the refining process, so that the nitrogen element will be continuously released during the entire smelting and refining process. The synergistic effect can achieve the effect of accurately increasing the nitrogen content, thereby comprehensively improving the mechanical strength performance of the steel.

[0041] In some of the embodiments, in the step of adding vanadium-nitrogen alloy to molten steel, the amount of vanadium-nitrogen alloy added is 1kg / t to 2kg / t based on the mass of molten steel before tapping.

[0042] The addition amount of vanadium-nitrogen alloy is controlled to further supplement the appropriate amount of nitrogen element.

[0043] In some of the embodiments, during the tapping process of molten steel smelted in a converter, silicon-manganese alloy is added to the molten steel, and the amount of silicon-manganese alloy added is 9.5kg / t to 10kg / t based on the mass of the molten steel before tapping.

[0044] Silicon-manganese alloy can promote alloying. Manganese and silicon in silicon-manganese alloy have a strong affinity with oxygen and can produce deoxidized products with lower melting points, such as MnSiO3 and Mn 2 SiO 4 These products easily float up and are discharged from the molten steel, thereby achieving a good deoxidation effect, and at the same time as an additive can improve corrosion resistance.

[0045] It should be noted that, with respect to the main technical problem to be solved by this application: precise control of nitrogen content and improvement of mechanical strength, silicon-manganese alloy is not a necessary condition and may not be added.

[0046] In some of the embodiments, in the step of blowing nitrogen from the bottom of the refining furnace, nitrogen is blown into the bottom pipe of the refining furnace at a pressure greater than a pressure ≥ 1.2 MPa, and the blowing time is 0.1 min to 15 min.

[0047] Specifically, the pressure of the nitrogen blowing treatment is 1.2Mpa to 1.5Mpa, and can be optionally 1.2Mpa to 1.4Mpa.

[0048] In some of the embodiments, after the step of adding the vanadium-nitrogen alloy and before the step of heating and melting treatment, a second portion of scrap steel is added, and the theoretical maximum volume ratio of the second portion of scrap steel to the ladle of the refining furnace is (0-25):105.

[0049] It should be noted that the theoretical maximum volume of the ladle of the refining furnace refers to the theoretical volume of the ladle of the refining furnace itself, which essentially refers to the volume ratio of the volume of the second part of scrap steel to the theoretical volume of the ladle of the refining furnace itself. It can also be understood as the ratio of the mass of the second part of scrap steel to the mass of scrap steel that can be accommodated by the theoretical volume of the ladle of the refining furnace itself.

[0050] Furthermore, the mass ratio of the first part of scrap steel to the second part of scrap steel is (1.3-2):1.

[0051] In some of the embodiments, during the temperature rise melting process, a vanadium-nitrogen alloy is added, and based on the total mass of the molten steel formed before the temperature rise melting process, the amount of the vanadium-nitrogen alloy added is 1 kg / t to 2.5 kg / t.

[0052] "Based on the total mass of the molten steel formed before the step of heating and melting treatment" means the total mass of the molten steel existing in the refining furnace before the step of heating and melting treatment, including the molten steel before tapping, the vanadium-nitrogen alloy added during the tapping process, etc.

[0053] Before the refining process, vanadium-nitrogen alloy is added to further supplement the appropriate amount of nitrogen.

[0054] In some of the embodiments, after the step of adding vanadium-nitrogen alloy to the molten steel and placing it in a refining furnace and before the step of adding the second portion of scrap steel, the step of adding refining lime to the molten steel is further included.

[0055] Furthermore, based on the total mass of the molten steel formed before the step of adding the second portion of scrap steel, the amount of refined lime added is 4.5kg / t to 5.5kg / t; for example, before the step of adding the second portion of scrap steel, only vanadium-nitrogen alloy is added during the steel-making process. At this time, the total mass of the molten steel is based on the total mass of the molten steel before steel-making and the vanadium-nitrogen alloy finally added during the steel-making process. If other alloy additives are added during the steel-making process, the mass of the alloy additives must also be added to the total mass of the molten steel.

[0056] In some embodiments, the temperature of the melting treatment can be set to a temperature that can melt the solid raw material; specifically, it can be 1580°C to 1680°C.

[0057] In some of the embodiments, during the process of adding the second portion of scrap steel, argon is blown from the bottom of the refining furnace at a flow rate of 1500 L / min to 2500 L / min.

[0058] In some of the embodiments, the refining process is performed at a temperature of 1550°C to 1600°C.

[0059] In some of the embodiments, the process of refining molten steel to make vanadium-nitrogen steel includes casting and rolling in sequence; further, it may also include processes such as grinding commonly used in the art.

[0060] The casting, rolling and grinding processes may adopt the processes commonly used in the art without any particular limitation.

[0061] In some of the embodiments, the first portion of scrap steel and the second portion of scrap steel can be independently selected from at least one of briquetted scrap steel, loose scrap steel, and threaded steel bar grains.

[0062] In some of the embodiments, the nitrogen content in the refined molten steel is 0.01% to 0.019% by mass.

[0063] In some of the embodiments, the vanadium content in the vanadium-nitrogen alloy is 75% and the nitrogen content is 16% by mass.

[0064] Another embodiment of the present application provides a vanadium-nitrogen steel, which is prepared by the preparation method of vanadium-nitrogen steel as described above.

[0065] The vanadium-nitrogen steel prepared by the above method has excellent and stable mechanical properties and low cost.

[0066] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, technical personnel in the field should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0067] The following are specific embodiments.

[0068] The vanadium content of the vanadium-nitrogen alloy used in each of the examples and comparative examples is 75%, and the nitrogen content is 16%.

[0069] Example 1

[0070] (1) 70 tons of molten iron + the first part of scrap iron (15 tons of briquetted scrap steel + 8 tons of loose scrap steel) are loaded into the converter. Nitrogen is blown from the bottom of the converter at a flow rate of 350 L / min. Oxygen is blown from the top. The scrap steel is melted and dephosphorized to obtain molten steel.

[0071] (2) After smelting, vanadium-nitrogen alloy is added when tapping steel. The amount of addition is 0.2 kg / t based on the mass of molten steel. Then, the steel is transported to the refining furnace for heating. During the heating process, refining lime is added to the refining furnace. Based on the total mass of molten steel in the refining furnace at this time, the amount of refining lime added is 4.6 kg / t. The temperature of the refining furnace is continuously raised to 1601°C. After the ladle car is driven to the bottom of the scrap steel preheating tank, 15 t of threaded steel bar scrap is added to the refining furnace. During the adding process, argon gas is blown from the bottom at a flow rate of 2000 L / min. After the scrap steel is added, the ladle car is driven to the molten steel processing position for power supply and heating to melt the scrap steel. After the temperature rises to 1560°C, samples are taken. According to the sample analysis results, vanadium-nitrogen alloy is added again. Based on the total mass of molten steel in the refining furnace at this time, the amount of addition is 0.22 kg / t. Then, refining is performed: during the refining process, high-pressure bottom blowing of nitrogen is performed at 1.31 MPa for 6 min to obtain refined molten steel. After testing: the nitrogen content in the refined steel water after leaving the station is 0.0152%.

[0072] (3) The refined molten steel is cast and rolled to obtain vanadium-nitrogen steel.

[0073] (4) Testing the performance of vanadium nitrogen steel: Refer to the relevant records in GB 1499.2-2024-Steel for reinforced concrete Part 2: Hot-rolled ribbed steel bars to test and determine the yield strength, tensile strength, elongation, cold bending and welding performance. See Table 1 for specific results.

[0074] Example 2

[0075] (1) 70 tons of molten iron + the first part of scrap iron (15 tons of briquetted scrap steel + 8 tons of loose scrap steel) are loaded into the converter. Nitrogen is blown from the bottom of the converter at a flow rate of 350 L / min. Oxygen is blown from the top. The scrap steel is melted and dephosphorized to obtain molten steel.

[0076] (2) After smelting, vanadium-nitrogen alloy is added when tapping steel. The amount of addition is 0.2 kg / t based on the mass of molten steel. Then, the steel is transported to the refining furnace for heating. Based on the total mass of molten steel in the refining furnace at this time, 4.8 kg / t of refining lime is added to the refining furnace during the heating process, and the temperature of the refining furnace is continuously raised to 1596°C. After the ladle car is driven to the bottom of the scrap steel preheating tank, 15 t of threaded steel bar scrap is added to the refining furnace. During the adding process, argon gas is blown from the bottom at a flow rate of 2000 L / min. After the scrap steel is added, the ladle car is driven to the molten steel processing position to supply power for heating, melt the scrap steel, and take samples after the temperature rises to 1584°C. According to the analysis results of the samples, vanadium-nitrogen alloy is added again. Based on the total mass of molten steel in the refining furnace at this time, the amount of addition is 0.23 kg / t. Then, refining is performed: during the refining process, high-pressure bottom blowing of nitrogen is performed at 1.32 MPa for 7 min to obtain refined molten steel. After testing: the nitrogen content in the refined steel water after leaving the station is 0.0166%.

[0077] (3)~(4): Same as steps (3)~(4) of Example 1. Please see Table 1 for specific results.

[0078] Example 3

[0079] (1) 70 tons of molten iron + the first part of scrap iron (15 tons of briquetted scrap steel + 8 tons of loose scrap steel) were loaded into the converter. Nitrogen was blown from the bottom of the converter at a flow rate of 330 L / min. Oxygen was blown from the top. The temperature was raised to melt the scrap steel and dephosphorize it to obtain molten steel.

[0080] (2) After smelting, vanadium-nitrogen alloy is added when steel is tapped. The amount of addition is 0.2 kg / t steel based on the mass of molten steel. Then the steel is transported to the refining furnace for heating. The total mass of molten steel in the refining furnace is used as the basis. During the heating process, 5.1 kg / t steel of refining lime is added to the refining furnace, and the temperature of the refining furnace is continuously raised to 1620°C. After the ladle car is driven to the bottom of the scrap steel preheating tank, 15 t of threaded steel bar scrap is added to the refining furnace. During the adding process, argon gas is blown from the bottom at a flow rate of 2000 L / min. After the scrap steel is added, the ladle car is driven to the molten steel processing position for power supply and heating to melt the scrap steel. After the temperature rises to 1570°C, samples are taken. According to the analysis results of the samples, vanadium-nitrogen alloy is added. The amount of addition is 0.2 kg / t based on the total mass of molten steel in the refining furnace. Then, refining is performed: during the refining process, high-pressure bottom blowing of nitrogen is performed at 1.32 MPa for 5 min to obtain refined molten steel. After testing: the nitrogen content in the refined steel water after leaving the station is 0.0152%.

[0081] (3)~(4): Same as steps (3)~(4) of Example 1. Please see Table 1 for specific results.

[0082] Comparative Example 1

[0083] (1) 70 tons of molten iron + the first part of scrap iron (15 tons of briquetted scrap steel + 8 tons of scattered scrap steel) were loaded into the converter. During converter smelting, nitrogen was blown for the first 3 minutes, and argon was blown from the bottom for the next 7 minutes. The flow rate was set to 350 L / min. Oxygen was blown from the top throughout the process. The scrap steel was heated to melt and dephosphorized to obtain molten steel.

[0084] (2) After smelting, vanadium-nitrogen alloy is added when tapping steel. The amount of addition is 0.2 kg / t steel based on the mass of molten steel. Then, the steel is transported to the refining furnace for heating. Based on the total mass of molten steel in the refining furnace at this time, 4.4 kg / t steel of refining lime is added to the refining furnace during the heating process, and the temperature of the refining furnace is continuously raised to 1601°C. After the ladle car is driven to the bottom of the scrap preheating tank, 10 t of threaded steel bar scrap and 5 t of scattered scrap are added to the refining furnace. During the adding process, argon gas is blown from the bottom at a flow rate of 2000 L / min. After the scrap is added, the ladle car is driven to the molten steel processing position for power supply and heating to melt the scrap. After the temperature rises to 1555°C, samples are taken. According to the analysis results of the samples, vanadium-nitrogen alloy is added again. Based on the total mass of molten steel in the refining furnace at this time, the amount of addition is 0.19 kg / t. Then, refining is performed: during the refining process, high-pressure bottom blowing of nitrogen is performed at 1.32 MPa for 5 min to obtain refined molten steel. After testing: the nitrogen content in the refined steel water after leaving the station is 0.008%.

[0085] (3)~(4): Same as steps (3)~(4) of Example 1. Please see Table 1 for specific results.

[0086] Table 1

[0087]

[0088] The test results in Table 1 above indicate that the preparation method of the present application can accurately improve the nitrogen content, thereby comprehensively improving the mechanical strength properties of vanadium-nitrogen steel.

[0089] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of this patent shall be subject to the attached claims.

Claims

1. A method for preparing vanadium-nitrogen steel, characterized in that: The steps include: The molten iron and the first part of the scrap steel are subjected to converter smelting to produce molten steel, and during the converter smelting process, nitrogen is continuously supplied from the bottom of the converter; During the steel tapping process, vanadium-nitrogen alloy is added to the molten steel and then placed in a refining furnace to perform heating and melting treatment and refining treatment in sequence to prepare refined molten steel; during the refining treatment, nitrogen is passed from the bottom of the refining furnace; The refined molten steel is made into vanadium-nitrogen steel.

2. The method for preparing vanadium-nitrogen steel according to claim 1, characterized in that: In the step of maintaining the nitrogen gas flowing from the bottom of the converter, the flow rate of the nitrogen gas is 300 L / min to 350 L / min.

3. The method for preparing vanadium-nitrogen steel according to claim 1, characterized in that: Based on the quality of molten steel before tapping, the addition amount of the vanadium-nitrogen alloy is 1kg / t to 2.5kg / t.

4. The method for preparing vanadium-nitrogen steel according to any one of claims 1 to 3, characterized in that: In the step of blowing nitrogen from the bottom of the refining furnace, nitrogen is blown into the bottom pipeline of the refining furnace at a pressure of ≥1.2Mpa for a blowing time of 0.1min to 15min.

5. The method for preparing vanadium-nitrogen steel according to any one of claims 1 to 3, characterized in that: During the temperature rise melting process, a vanadium-nitrogen alloy is added. Based on the total mass of the molten steel formed before the temperature rise melting process, the amount of the vanadium-nitrogen alloy added is 1kg / t to 2.5kg / t.

6. The method for preparing vanadium-nitrogen steel according to any one of claims 1 to 3, characterized in that: After the step of adding the vanadium-nitrogen alloy and before the step of heating and melting treatment, a second portion of scrap steel is added, and the theoretical maximum volume ratio of the second portion of scrap steel to the ladle of the refining furnace is (0-25):

105.

7. The method for preparing vanadium-nitrogen steel according to claim 6, characterized in that: The first part of scrap steel and the second part of scrap steel are independently selected from at least one of briquetted scrap steel, loose scrap steel, and threaded steel bar grains.

8. The method for preparing vanadium-nitrogen steel according to any one of claims 1 to 3, characterized in that: Calculated by mass percentage, the nitrogen content in the refined molten steel is 0.01% to 0.019%.

9. The method for preparing vanadium-nitrogen steel according to any one of claims 1 to 3, characterized in that: Calculated by mass percentage, the vanadium content in the vanadium-nitrogen alloy is 75%, and the nitrogen content is 16%.

10. A vanadium-nitrogen steel, characterized in that: The vanadium-nitrogen steel is prepared by the preparation method of any one of claims 1 to 9.

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