Method for stably controlling nitrogen content in steel by adopting vacuum induction furnace

Abstract

The invention discloses a method for stably controlling nitrogen content in steel by adopting a vacuum induction furnace, which belongs to the technical field of ferrous metallurgy, and is mainly characterized in that the nitrogen content in the steel is stably and accurately controlled by adopting the vacuum induction furnace through stably controlling a smelting process and adding different alloys in combination with the characteristics and yield conditions of different nitrogen-containing alloys. A foundation is laid for accurately ensuring the nitrogen content in the steel.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for stably controlling the nitrogen content in steel by using a vacuum induction furnace. Background Art

[0002] Nitrogen is usually considered as one of the harmful impurities in steel. Although the solubility of nitrogen in liquid steel is very low under normal pressure, this small amount of nitrogen can cause aging embrittlement of steel. Therefore, various secondary refining technologies for reducing nitrogen in liquid steel have been developed and are still being improved. However, in high nitrogen steel, nitrogen as an alloying element can interact with other alloying elements in steel (such as Mn, Cr, V, Nb, Ti, etc.), and give the steel many excellent properties, while reducing the amount of alloying elements added. For example, improving the stability of austenite greatly improves the mechanical properties of steel and improves the corrosion resistance of steel. Although nitrogen can be added to steel in many ways, due to the extremely low limit solid solubility of nitrogen in steel, its addition under conventional smelting processes is limited. At the same time, as the nitrogen content in steel increases, the difficulty of stable control of nitrogen content also increases. Nitrogen in high-nitrogen steel, as one of the important alloying elements, can greatly improve the mechanical properties of steel, such as improving yield strength, tensile strength, wear resistance and corrosion resistance, etc. These beneficial effects all depend on the nitrogen content in steel. There is a lack of effective means for stable control of nitrogen in steels with nitrogen content greater than 100ppm.

[0003] At present, nitrogen-containing steel smelting usually adopts the method of blowing nitrogen and adding alloys to increase nitrogen. Due to the complexity and instability of smelting conditions, the yield of nitrogen in molten steel is difficult to stably control, resulting in a very low control accuracy of nitrogen content in steel. At the same time, due to the characteristics of nitrogen-containing alloys and the fact that the method of adding alloys is mainly affected by the alloy melting effect and the nitrogen yield, the control of nitrogen content in steel is unstable, which poses a problem for accurately controlling nitrogen content in steel. Vacuum induction furnace smelting is a pilot test method for industrial experiments and has certain guiding significance for industrial production. Since the vacuum induction furnace has the characteristics of fast heating speed, good alloy melting effect, high vacuum degree, and simple operation, the present invention combines the characteristics and yield of different nitrogen-containing alloys, adopts a vacuum induction furnace to stably control the smelting process, and adds different alloys, thereby stably and accurately controlling the nitrogen content in steel, laying the foundation for accurately ensuring the nitrogen content in steel.

[0004] A Chinese patent with application number 202210749368.2 discloses a smelting device for improving the control accuracy of the nitrogen content of high nitrogen steel, including a vacuum chamber, an induction furnace crucible, and a steel ingot mold; a sealed steel ring seat is provided on the upper outer periphery of the induction furnace crucible, and a sealing cover is provided above the induction furnace crucible. The sealing cover is driven by a lifting and rotating mechanism and can be sealed and connected with the sealing steel ring seat. A pressure and temperature probe and a signal transmitter are provided on the sealing cover, and a long-term temperature measuring probe is provided on the side wall in the middle of the induction furnace crucible; a breathable brick is provided at the bottom of the induction furnace crucible, and the breathable brick is connected to the nitrogen blowing pipe to accurately control the liquid nitrogen content of the high nitrogen steel.

[0005] The Chinese patent with application number 202210017242.6 discloses a method for controlling the carbon and nitrogen content of high-titanium steel in a vacuum induction furnace. The three elements of carbon, titanium and nitrogen in the molten steel are calculated by mass percentage: carbon 0.4% to 0.5%, titanium 0.5% to 1.45%, and nitrogen ≤ 0.003%. The entire initial melting stage is carried out under vacuum conditions. Industrial pure iron, aluminum particles, and ferrosilicon are loaded into a vacuum induction furnace, vacuumed, and the charge is heated; high-carbon ferromanganese is added for refining; argon is filled into the furnace, the temperature is raised to break the film, and sponge titanium is added. After full melting, it is maintained at a temperature of 1550 to 1600°C for 3 to 6 minutes; the tapping temperature is 1500 to 1520°C, and the casting is carried out with electricity. The advantages are: the C content of the final molten steel using the method of the present invention is 0.4% to 0.5%, and the N content is less than 0.003%; the argon gas filled in the alloying stage can effectively avoid the volatilization of Ti, and the Ti content in the final molten steel is stably controlled at 0.5% to 1.45%.

[0006] The Chinese patent with application number 201910910575.X discloses a method for accurately controlling the nitrogen content of high-nitrogen silicon-containing low-alloy steel at low cost. The method uses a converter blowing process that uses nitrogen to replace Ar gas during the whole converter smelting process. When the converter bottom blowing effect is not good, an oxygen gun is used to blow nitrogen into the molten steel in the post-stirring stage; aluminum and iron are pre-placed at the bottom of the ladle before steel tapping, and nitrogen is blown into the ladle during the steel tapping process to increase nitrogen instead of adding nitrogen-containing alloys to increase nitrogen, and alloys are added during the steel tapping process to fix nitrogen; after steel tapping, nitrogen is continued to be blown to the molten steel to supply nitrogen to ensure that the nitrogen content in the molten steel before entering vacuum refining is greater than 80PPm; in the vacuum process, the method of controlling the nitrogen circulation time is used to achieve accurate nitrogen addition, and the Ar gas is switched to achieve accurate denitrification technology under high vacuum before the end of the treatment, so as to achieve accurate control of the nitrogen content in the molten steel. The method of the present invention is easy to operate, has obvious cost reduction effects, and is suitable for promotion and application in other converter vacuum production lines. Summary of the invention

[0007] The purpose of the present invention is to provide a method for stably controlling the nitrogen content in steel by using a vacuum induction furnace. By combining the characteristics and yields of different nitrogen-containing alloys, a vacuum induction furnace is used to stably control the smelting process and add different alloys, thereby stably and accurately controlling the nitrogen content in steel, laying the foundation for accurately ensuring the nitrogen content in steel.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] The present invention discloses a method for stably controlling the nitrogen content in steel by using a vacuum induction furnace, comprising:

[0010] 1) A 25kg vacuum induction furnace was used to smelt the test steel;

[0011] 2) Use raw materials with similar composition to the target steel grade for smelting to improve the hit rate of the composition and reduce the amount of alloy added;

[0012] 3) Combined with the characteristics of different alloys, accurately test the composition of each element of different nitrogen-containing alloys, accurately set the yield of each element according to the characteristics of the 25kg vacuum induction furnace and the smelting process, and consider the mutual influence of different nitrogen-containing alloys, calculate the addition amount of different alloys, so as to stably and accurately control the nitrogen content in the steel;

[0013] 4) Ensure smelting under vacuum;

[0014] 5) 40-80s after the raw materials are melted, add the calculated alloy;

[0015] 6) After ensuring that all the alloy is melted, cast under vacuum;

[0016] 7) Check the chemical composition of the steel after smelting to ensure that it is basically the same as the target composition.

[0017] Furthermore, the calculated alloy was added 60 s after the raw materials were melted.

[0018] Furthermore, in said 4), the vacuum degree is 80-100 Pa.

[0019] Furthermore, in said 4), the vacuum degree is 90 Pa.

[0020] Furthermore, a 25kg vacuum induction furnace was used to smelt the test steel, and the nitrogen content of the test steel was required to be 0.015%. Raw materials with a composition similar to that of the target steel were used for smelting. In combination with the characteristics of different alloys, the composition of each element of different nitrogen-containing alloys was accurately tested, and the yield of each element was accurately set according to the characteristics of the 5kg vacuum induction furnace and the smelting process. The nitrogen content of the vanadium-nitrogen alloy was 16%, and the addition amount of different alloys was calculated, and 85g of ferromanganese and 27g of vanadium-nitrogen alloy were added. The smelting was carried out in a vacuum state with a vacuum degree of 90pa. 1 minute after the raw materials were melted, ferromanganese and vanadium-nitrogen alloy were added. After heating for 2 minutes, the alloy was ensured to be completely melted and then cast under vacuum. The chemical composition of the smelted steel was tested, and the nitrogen content was 0.0152%, which was basically the same as the target composition.

[0021] Furthermore, a 25kg vacuum induction furnace was used to smelt the test steel, and the nitrogen content of the test steel was required to be 0.017%; raw materials with similar composition to the target steel were used for smelting; the characteristics of different alloys were combined to accurately test the composition of each element of different nitrogen-containing alloys, and the yield of each element was accurately set according to the characteristics of the 25kg vacuum induction furnace and the smelting process. At the same time, the mutual influence of different nitrogen-containing alloys was considered, the nitrogen content of the vanadium-nitrogen alloy was 16%, and the nitrogen content of silicon manganese nitride was 27%. The addition amount of different alloys was calculated, and 85g of ferromanganese, 27g of vanadium-nitrogen alloy, and 11g of silicon manganese nitride were added; smelting was carried out in a vacuum state with a vacuum degree of 90pa; ferromanganese and vanadium-nitrogen alloy were added 1min after the raw materials were melted; after heating for 2min, the alloy was ensured to be completely melted and then cast under vacuum; the chemical composition of the smelted steel was tested, and the nitrogen content was 0.0173%, which was basically the same as the target composition.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are:

[0023] The present invention aims at the technical problems in the background, adopts a vacuum induction furnace to smelt the test steel, calculates the alloy addition amount according to the requirements of different steel grades for nitrogen content and the nitrogen content of different alloys, combines the characteristics of vacuum smelting and the nitrogen recovery rate, and achieves the purpose of stably controlling the nitrogen content in the steel by the vacuum induction furnace, and provides technical support for industrial production to stably control the nitrogen content in the steel. The analysis method is simple and effective, low in cost, and has broad application prospects. DETAILED DESCRIPTION

[0024] Case 1:

[0025] 1. A 25kg vacuum induction furnace is used for smelting of the test steel, and the nitrogen content of the test steel is required to be 0.015%.

[0026] 2. Use raw materials with similar composition to the target steel grade for smelting. The specific composition is shown in the following table.

[0027]

[0028] 3. Combined with the characteristics of different alloys, accurately test the composition of each element of different nitrogen-containing alloys, accurately set the yield of each element according to the characteristics of the 5kg vacuum induction furnace and the smelting process. The nitrogen content of the vanadium-nitrogen alloy is 16%. Calculate the amount of different alloys to be added, add 85g of ferromanganese and 27g of vanadium-nitrogen alloy.

[0029] 4. Ensure that smelting is carried out under vacuum with a vacuum degree of 90pa.

[0030] 5. One minute after the raw materials are melted, add ferromanganese and vanadium-nitrogen alloy.

[0031] 6. After heating for 2 minutes, ensure that the alloy is completely melted and then cast under vacuum.

[0032] 7. The chemical composition of the steel after smelting was checked and the nitrogen content was 0.0152%, which was basically the same as the target composition.

[0033] Case 2:

[0034] 1. A 25kg vacuum induction furnace is used for smelting of the test steel, and the nitrogen content of the test steel is required to be 0.017%.

[0035] 2. Use raw materials with similar composition to the target steel grade for smelting. The specific composition is shown in the following table.

[0036]

[0037] 3. Combined with the characteristics of different alloys, accurately test the composition of each element of different nitrogen-containing alloys, accurately set the yield of each element according to the characteristics of the 5kg vacuum induction furnace and the smelting process, and consider the mutual influence of different nitrogen-containing alloys. The nitrogen content of vanadium-nitrogen alloy is 16%, and the nitrogen content of silicon manganese nitride is 27%. Calculate the addition amount of different alloys, add 85g of ferromanganese, 27g of vanadium-nitrogen alloy, and 11g of silicon manganese nitride.

[0038] 4. Ensure that smelting is carried out under vacuum with a vacuum degree of 90pa.

[0039] 5. One minute after the raw materials are melted, add ferromanganese and vanadium-nitrogen alloy.

[0040] 6. After heating for 2 minutes, ensure that the alloy is completely melted and then cast under vacuum.

[0041] 7. The chemical composition of the steel after smelting was checked and the nitrogen content was 0.0173%, which was basically the same as the target composition.

[0042] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for stably controlling the nitrogen content in steel using a vacuum induction furnace, characterized in that: include: 1) A 25kg vacuum induction furnace was used to smelt the test steel; 2) Use raw materials with similar composition to the target steel grade for smelting to improve the hit rate of the composition and reduce the amount of alloy added; 3) Combined with the characteristics of different alloys, accurately test the composition of each element of different nitrogen-containing alloys, accurately set the yield of each element according to the characteristics of the 25kg vacuum induction furnace and the smelting process, and consider the mutual influence of different nitrogen-containing alloys, calculate the addition amount of different alloys, so as to stably and accurately control the nitrogen content in the steel; 4) Ensure smelting under vacuum; 5) 40-80s after the raw materials are melted, add the calculated alloy; 6) After ensuring that all the alloy is melted, cast under vacuum; 7) Check the chemical composition of the steel after smelting to ensure that it is basically the same as the target composition.

2. The method for stably controlling nitrogen content in steel using a vacuum induction furnace according to claim 1, characterized in that: 60s after the raw materials are melted, add the calculated alloy.

3. The method for stably controlling nitrogen content in steel using a vacuum induction furnace according to claim 1, characterized in that: In the above 4), the vacuum degree is 80-100 Pa.

4. The method for stably controlling nitrogen content in steel using a vacuum induction furnace according to claim 1, characterized in that: In the above 4), the vacuum degree is 90 Pa.

5. The method for stably controlling nitrogen content in steel using a vacuum induction furnace according to claim 1, characterized in that: A 25kg vacuum induction furnace was used to smelt the test steel, and the nitrogen content of the test steel was required to be 0.015%. Raw materials with similar composition to the target steel were used for smelting. In combination with the characteristics of different alloys, the composition of each element of different nitrogen-containing alloys was accurately tested, and the yield of each element was accurately set according to the characteristics of the 5kg vacuum induction furnace and the smelting process. The nitrogen content of the vanadium-nitrogen alloy was 16%, and the addition amount of different alloys was calculated, including 85g of ferromanganese and 27g of vanadium-nitrogen alloy. The smelting was carried out in a vacuum state with a vacuum degree of 90pa. 1 minute after the raw materials were melted, ferromanganese and vanadium-nitrogen alloy were added. After heating for 2 minutes, the alloy was ensured to be completely melted and then cast under vacuum. The chemical composition of the smelted steel was tested, and the nitrogen content was 0.0152%, which was basically the same as the target composition.

6. The method for stably controlling nitrogen content in steel using a vacuum induction furnace according to claim 1, characterized in that: A 25kg vacuum induction furnace was used to smelt the test steel, and the nitrogen content of the test steel was required to be 0.017%. Raw materials with similar composition to the target steel were used for smelting. In combination with the characteristics of different alloys, the composition of each element of different nitrogen-containing alloys was accurately tested, and the yield of each element was accurately set according to the characteristics of the 25kg vacuum induction furnace and the smelting process. At the same time, the mutual influence of different nitrogen-containing alloys was considered. The nitrogen content of the vanadium-nitrogen alloy was 16%, and the nitrogen content of silicon manganese nitride was 27%. The addition amount of different alloys was calculated, and 85g of ferromanganese, 27g of vanadium-nitrogen alloy, and 11g of silicon manganese nitride were added. The smelting was carried out in a vacuum state with a vacuum degree of 90pa. 1 minute after the raw materials were melted, ferromanganese and vanadium-nitrogen alloy were added. After heating for 2 minutes, the alloy was ensured to be completely melted and then cast under vacuum. The chemical composition of the smelted steel was tested, and the nitrogen content was 0.0173%, which was basically the same as the target composition.

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