Method for modifying inclusions in high-nitrogen steel by adopting rare earth cerium element

Abstract

The invention discloses a method for modifying inclusions in high-nitrogen steel by adopting a rare earth cerium element, the inclusions in the high-nitrogen steel are taken as a research basis, a vacuum induction furnace is adopted for smelting the high-nitrogen steel, and the content of rare earth cerium in the high-nitrogen steel is controlled by adding a rare earth cerium iron alloy, and the components, morphology, size and the like of the inclusions in the high-nitrogen steel are modified. It is guaranteed that the inclusions in the high-nitrogen steel are fine and dispersed, and technical support is provided for stable control over the state of the inclusions in the high-nitrogen steel in industrial production. On the premise that the nitrogen content of the high-nitrogen steel is 100-200 ppm, a certain amount of rare earth cerium element is added according to the cerium content condition and the rare earth yield of the rare earth cerium-iron alloy, so that the components, the morphology, the size and the like of inclusions in the high-nitrogen steel are modified, it is guaranteed that the inclusions in the high-nitrogen steel are fine and dispersed, and the problem of control over the inclusions in the high-nitrogen steel is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for modifying inclusions in high nitrogen steel by using rare earth cerium element. Background Art

[0002] At present, high nitrogen steel has been identified as one of the main directions for the development of high-quality metallurgical technology. With people's recognition of the excellent properties of high nitrogen steel, the research and production of high nitrogen steel has been continuously improved and developed. 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.), giving the steel many excellent properties. For example, improving the stability of austenite greatly improves the mechanical properties of steel, improves the corrosion resistance of steel, and so on. The excellent performance of rare earth in steel is due to its unique electronic shell structure, making it an extremely strong purifier and an effective modifier for clean steel inclusions. my country began to study the application of rare earth in steel in the middle of the last century. The United States first discovered the modification effect of rare earth on inclusions in steel. So far, the role of rare earth in steel can be summarized into four aspects, namely purification, modification, grain refinement and microalloying.

[0003] High purity ingot is the basis for producing high quality steel. The purity of ingot is mainly determined by the treatment process before the molten steel enters the crystallizer. The number, size and distribution of inclusions in steel have a great influence on the quality of steel. Controlling non-metallic inclusions in steel is one of the key technologies to improve the quality of steel products and produce clean steel. Non-metallic inclusions in steel directly affect the quality and performance of steel. In order to remove or reduce the number of inclusions entering the crystallizer, in recent years, both at home and abroad, great attention has been paid to the study of the movement and removal of inclusions in the tundish.

[0004] The Chinese patent application number is 201410779570.5. A new type of free-cutting steel material with cerium modified inclusions is composed of the following components in percentage by mass: C: 0.11-0.18, Mn: 0.85-1.45, Si: 0.06-0.15, P≤0.15, S: 0.25-0.35, O: 0.009-0.023, Ce: 0.03-0.09, and the rest is Fe, with a total percentage of 100%. It provides a method for preparing free-cutting steel materials in an economical and superior manner, and improves its cutting performance while ensuring mechanical properties.

[0005] The Chinese patent application number 202111345629.6 discloses a method for refining rare earth inclusions in steel by magnesium pretreatment, which solves the technical problem of large rare earth size when aluminum-deoxidized steel is treated with rare earth. After the aluminum, oxygen, and sulfur content in the refined slag composition and molten steel reach the control target, magnesium pretreatment is first performed to denature large-sized Al 2O3 inclusions into fine and dispersed MgO inclusions, and then rare earth treatment is performed. The rare earth inclusions are transformed from fine and dispersed MgO inclusions, and their size is significantly refined compared to that without magnesium pretreatment. According to Stokes' law, it is easier to float and discharge. The use of magnesium pretreatment can also further improve the cleanliness of the steel. .

[0006] Chinese patent application number 202211144371.8 discloses a method for improving the banded structure of low-carbon gear steel based on oxide metallurgy and low-carbon gear steel. The method for improving the banded structure of low-carbon gear steel based on oxide metallurgy includes the following processes: modification and regulation of inclusions in the smelting process: adding inclusion modifiers when the LF leaves the station, and modifying and metamorphosing to obtain dispersed oxides with a size of 0.5 to 3.0 μm and a number density of 80 to 200 pieces / mm2; controlled rolling and controlled cooling in the rolling process: after the continuous casting billet is heated and kept warm, it is rolled and deformed at 1100 to 1130°C and 920 to 960°C, respectively, and then cooled to room temperature at a rate of 1.0 to 3.0°C / s. The present invention obtains oxides that can induce the nucleation of intragranular ferrite through modification and reforming treatment in the refining process, and exerts the metallurgical effect of oxide inclusions through controlled rolling and controlled cooling in the rolling process, thereby promoting the nucleation and growth of intragranular ferrite during the cooling process, refining the grains, and effectively inhibiting the formation of grain boundary ferrite, thereby achieving the purpose of improving the banded structure. Summary of the invention

[0007] The invention aims to provide a method for modifying inclusions in high nitrogen steel by using rare earth cerium element. The method takes inclusions in high nitrogen steel as the research basis and adopts a vacuum induction furnace to smelt high nitrogen steel. Since the nitrogen content in the steel is 100-200ppm, the composition, morphology and characteristics of the inclusions in the steel are more complicated than those in conventional steel grades, which is not conducive to the floating and removal control of the inclusions in the steel. By adding rare earth cerium iron alloy, the rare earth cerium content in the high nitrogen steel is controlled, the composition, morphology, size and the like of the inclusions in the high nitrogen steel are modified, and the inclusions in the high nitrogen steel are ensured to be fine and dispersed, so as to provide technical support for the stable control of the state of inclusions in the high nitrogen steel in industrial production.

[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 modifying inclusions in high nitrogen steel by using rare earth cerium element, 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 and casting under vacuum;

[0012] 3) Under the premise of ensuring that the nitrogen content of the high nitrogen steel is 100-200ppm, the amount of rare earth ferrocerium alloy to be added is calculated in combination with the cerium content of the rare earth ferrocerium alloy and the rare earth recovery rate, and the calculated alloy is added 0.8-1.2min after the raw materials are melted;

[0013] 4) Analyze the chemical composition of high nitrogen steel to ensure that the nitrogen content is 100-200ppm and the rare earth cerium content is 20-80ppm;

[0014] 5) Use scanning electron microscopy to analyze the composition, morphology and size of inclusions in high nitrogen steel;

[0015] 6) By using the rare earth element cerium to modify the inclusions in the high nitrogen steel, composite inclusions containing rare earth cerium can be formed to refine the inclusions.

[0016] Furthermore, the calculated alloy was added 1 min after the raw materials were melted.

[0017] Furthermore, the nitrogen content of the test steel is required to be 0.015%.

[0018] Furthermore, the nitrogen content of the test steel is required to be 0.017%.

[0019] Furthermore, raw materials with a composition similar to that of the target steel grade are used for smelting and casting under vacuum, and the vacuum degree is 85-95pa.

[0020] Furthermore, the vacuum degree is 90 Pa.

[0021] Furthermore, the target composition of the high nitrogen steel by mass percentage is: C 0.16%, Si 0.20%, Mn 1.30%, N 0.015%, RE 0.0027%, and the rest is Fe and unavoidable impurities.

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

[0023] The present invention adopts a vacuum induction furnace to smelt high nitrogen steel. Under the premise of ensuring that the nitrogen content of the high nitrogen steel is 100-200ppm, a certain amount of rare earth cerium element is added in combination with the cerium content of the rare earth ferrocerium alloy and the rare earth yield rate to modify the composition, morphology, size, etc. of inclusions in the high nitrogen steel, thereby providing technical support for industrial production to stably control the state of inclusions in high nitrogen steel. The analysis method is simple and effective, low in cost, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 The inclusions in the rare earth high nitrogen steel of Example 1;

[0026] Figure 2 This is the inclusion situation in the rare earth high nitrogen steel of Example 2. DETAILED DESCRIPTION

[0027] Embodiment 1:

[0028] 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%.

[0029] 2. Use raw materials with similar composition to the target steel grade to carry out smelting and casting under vacuum, with a vacuum degree of 90 Pa. The raw material composition and target steel grade composition are shown in Table 1.

[0030] Table 1 Raw material composition and target steel grade composition

[0031]

[0032] 3. On the premise of ensuring that the nitrogen content of high nitrogen steel is 100-200ppm, combined with the cerium content of rare earth ferrocerium alloy being 20% ​​and the rare earth recovery rate being 70%, 8g of rare earth ferrocerium alloy is added.

[0033] 4. Analyze the chemical composition of high nitrogen steel, the nitrogen content is 175ppm and the rare earth cerium content is 53ppm.

[0034] 5. Use scanning electron microscopy to analyze the composition, morphology, size, etc. of inclusions in high nitrogen steel. Figure 1 The composition of inclusions in rare earth high nitrogen steel is shown in Table 2.

[0035] Table 2 Composition of inclusions in rare earth high nitrogen steel

[0036] serial number O N Al S Ca Mn Fe Ce 54 18.53 14.41 3.75 2.61 4.89 23.62 23.25 55 5.85 2.51 2.79 1.16 3.01 69.02 6.93 60 16.85 9.77 1.73 3.35 26.20 33.54 61 19.05 11.99 1.36 1.83 22.34 37.45

[0037] 6. The inclusions in high nitrogen steel are modified by using rare earth element cerium. The inclusions are mainly divided into two categories. The first category is oxides of Al, Mn, and Ca, which are modified into rare earth-containing oxides by adding rare earths, with a rare earth content of 23-37%. The second category is mixed inclusions of nitrides and oxides, which are modified into rare earth-containing nitrogen oxides by adding rare earths, with a rare earth content of about 7%. The inclusions in high nitrogen steel are spherical in morphology after modification by adding rare earths, which is conducive to floating removal. At the same time, the size of the modified inclusions is less than 10μm, which has a refining effect on the inclusions.

[0038] Embodiment 2:

[0039] 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%.

[0040] 2. Use raw materials with similar composition to the target steel grade to carry out smelting and casting under vacuum, with a vacuum degree of 90 Pa. The raw material composition and target steel grade composition are shown in Table 1.

[0041] Table 1 Raw material composition and target steel grade composition

[0042]

[0043] 3. On the premise of ensuring that the nitrogen content of high nitrogen steel is 100-200ppm, combined with the cerium content of rare earth ferrocerium alloy being 20% ​​and the rare earth recovery rate being 70%, 3g of rare earth ferrocerium alloy is added.

[0044] 4. Analysis of the chemical composition of high nitrogen steel showed that the nitrogen content was 168ppm and the rare earth cerium content was 21ppm.

[0045] 5. Use scanning electron microscopy to analyze the composition, morphology, size, etc. of inclusions in high nitrogen steel. Figure 1 The composition of inclusions in rare earth high nitrogen steel is shown in Table 2.

[0046] Table 2 Composition of inclusions in rare earth high nitrogen steel

[0047]

[0048] 6. The inclusions in high nitrogen steel are modified by using rare earth element cerium. The inclusions are mainly divided into two categories. The first category is mixed inclusions of nitrides and oxides, which are modified into rare earth-containing nitrogen oxides by adding rare earths, and the rare earth content is about 25%; the second category is oxides of Al, Mn, and Si, which are modified into rare earth-containing oxides by adding rare earths, and the rare earth content is 1-5%; the inclusions in high nitrogen steel are modified into rare earth composite inclusions by adding rare earths, and the size of the modified inclusions is less than 20μm, which has a refining effect on the inclusions.

[0049] 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 modifying inclusions in high nitrogen steel using rare earth cerium, 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 and casting under vacuum; 3) Under the premise of ensuring that the nitrogen content of the high nitrogen steel is 100-200ppm, the amount of rare earth ferrocerium alloy to be added is calculated in combination with the cerium content of the rare earth ferrocerium alloy and the rare earth recovery rate, and the calculated alloy is added 0.8-1.2min after the raw materials are melted; 4) Analyze the chemical composition of high nitrogen steel to ensure that the nitrogen content is 100-200ppm and the rare earth cerium content is 20-80ppm; 5) Use scanning electron microscopy to analyze the composition, morphology and size of inclusions in high nitrogen steel; 6) By using the rare earth element cerium to modify the inclusions in the high nitrogen steel, composite inclusions containing rare earth cerium can be formed to refine the inclusions.

2. The method for modifying inclusions in high nitrogen steel using rare earth cerium according to claim 1, characterized in that: 1 minute after the raw materials are melted, add the calculated alloy.

3. The method of modifying inclusions in high nitrogen steel using rare earth cerium according to claim 1, characterized in that: The nitrogen content of the test steel is required to be 0.015%.

4. The method of modifying inclusions in high nitrogen steel using rare earth cerium element according to claim 1, characterized in that: The nitrogen content of the test steel is required to be 0.017%.

5. The method of modifying inclusions in high nitrogen steel using rare earth cerium element according to claim 1, characterized in that: Raw materials with similar composition to the target steel grade are used for smelting and casting under vacuum state, and the vacuum degree is 85-95pa.

6. The method of modifying inclusions in high nitrogen steel using rare earth cerium element according to claim 5, characterized in that: The vacuum degree is 90pa.

7. The method of modifying inclusions in high nitrogen steel using rare earth cerium element according to claim 1, characterized in that: The target composition of the high nitrogen steel by mass percentage is: C 0.16%, Si 0.20%, Mn 1.30%, N 0.015%, RE 0.0027%, and the rest is Fe and unavoidable impurities.

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