A method for deoxidizing and alloying high cleanliness high carbon silicon manganese steel

Abstract

The application discloses a deoxidation alloying method for high-carbon silicon manganese steel with high cleanliness. The method comprises a technological process of a converter process, an RH process and a square billet continuous casting process; at 1 / 8-1 / 6 of converter tapping, carbon structure alloy balls, ferrochrome and ferrovanadium are added into a ladle to deoxidize and alloy the molten steel, so that the carbon, manganese and silicon elements in the steel are effectively controlled, and the types of inclusions in the steel are controlled; the RH process promotes the floating and removal of inclusions in the steel by controlling process parameters, so that the cleanliness of the molten steel is improved; the carbon structure alloy ball is a double-layer composite structure, wherein the inner layer is ferrosilicon alloy, and the outer layer is a mixture of carbon powder and auxiliary materials. ‑6 wt% or so, and the content of oxide inclusions in the steel is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting and refining technology, and specifically relates to a deoxidation and alloying method for high-purity high-carbon silicon-manganese steel. Background Technology

[0002] The converter steelmaking process is actually a complex metallurgical process involving dephosphorization and decarburization, which requires the injection of large amounts of oxygen into the steel. In recent decades, metallurgists both domestically and internationally have conducted extensive research on reducing the oxygen content at the converter's final stage. However, the oxygen activity at the converter's final stage is generally still 400–800 × 10⁻⁶. -4 For some companies, the percentage is even higher when producing low-carbon steel grades.

[0003] To deoxidize molten steel, the commonly used process involves adding aluminum or aluminum-iron alloys (aluminum-killed steel) or ferrosilicon alloys (silicon-killed steel) to the ladle during the converter tapping process. However, the biggest problem with metal deoxidation is that it leads to the formation of a large number of non-metallic oxide inclusions in the steel, thus degrading its quality. To address this, metallurgists have researched a process where carbonaceous materials are first added to the ladle for deoxidation, followed by the addition of other metal alloys for alloying. However, due to the low density of carbonaceous materials, they often float quickly to the ladle surface and become encapsulated by the ladle slag. This not only fails to effectively deoxidize the steel, but also results in the continuous dissolution of carbon from the ladle slag into the molten steel during the refining-continuous casting process, leading to excessive carbon content in the finished product. Summary of the Invention

[0004] The purpose of this invention is to provide a deoxidation and alloying method for high-purity high-carbon silicon-manganese steel, which can be used for high-quality silicon-manganese deoxidized steel such as heavy rail steel. This method is beneficial for the stable control of inclusions in the steel and the low-cost cleanliness production of the steel.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A deoxidation and alloying method for high-purity high-carbon silicon-manganese steel includes a converter process, an RH process, and a billet continuous casting process. When the steel is tapped from the converter to 1 / 8 to 1 / 6 of its length, carbon structural alloy balls, ferrochrome alloy, and ferrovanadium alloy are added to the ladle to deoxidize and alloy the molten steel, achieving effective control of carbon, manganese, and silicon elements in the steel, as well as the types of inclusions. The RH process, by controlling the processing parameters, promotes the flotation and removal of inclusions in the steel, thereby improving the cleanliness of the molten steel.

[0007] The carbon structural alloy ball has a double-layer composite structure, wherein the inner layer is a silicon-iron alloy and the outer layer is a mixture of carbon powder and auxiliary materials.

[0008] Furthermore, in the above technical solution, during the converter process, the carbon content in the steel is controlled to be 0.3wt% to 0.8×10⁻⁶ after deoxidation and alloying. -4 After tapping, the molten steel is stirred by weak argon blowing, and the diameter of the exposed surface of the molten steel during the argon blowing process is less than 19 cm.

[0009] Furthermore, in the above technical solution, the particle size of the ferrosilicon alloy is 15mm to 45mm, and the composition of the ferrosilicon alloy is: Si: 31wt% to 59wt%, Mn: 31wt% to 59wt%, with the remainder being iron and unavoidable impurities.

[0010] The particle size of the carbon powder is 0.5 mm to 10 mm, the particle size of the auxiliary material is 300 nm to 100 μm, and the mixture of the outer carbon powder and auxiliary material has the following composition: CaO: 3 wt% to 9 wt%, Al2O3: 2 wt% to 6 wt%, C: 80 wt% to 93 wt%, wherein the CaO / Al2O3 ratio is 0.9 to 1.7, and the remainder is unavoidable impurities.

[0011] Furthermore, in the above technical solution, 45 to 70 seconds after the addition of the carbon structural alloy balls, ferrochrome alloy and ferrovanadium alloy are added.

[0012] Furthermore, in the above technical solution, the argon flow rate of the weak argon blowing stirring is 155NL / min to 180NL / min, and the argon blowing time is 5min to 10min.

[0013] Furthermore, in the above technical solution, the RH process parameters are as follows: at the beginning of vacuum treatment, the gas flow rate is increased from 1610 NL / min to 1790 NL / min. When the vacuum level drops to less than 100 Pa, the gas flow rate is reduced to 1200 NL / min to 1380 NL / min, and the cycle is repeated for 8 min to 15 min until the vacuum process ends.

[0014] Furthermore, in the above technical solution, the inner diameter of the carbon structural alloy ball is 15mm to 45mm, and the outer diameter is 25mm to 60mm.

[0015] Furthermore, in the above technical solution, the mass ratio of the inner layer to the outer layer of the carbon structural alloy ball is 2.1:1 to 1:1.8.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention incorporates a double-layered composite carbon alloy into molten steel. Because the inner layer is composed of alloying elements, it is added in spherical form to the molten steel early in the tapping process. This allows the outer layer sufficient time to react with the steel, enabling the carbon to effectively deoxidize the steel. Furthermore, small amounts of ultrafine CaO and Al₂O₃ from the outer layer enter the molten steel. Only after the outer carbon has fully reacted with or melted into the molten steel does the inner silicon-manganese alloy begin to melt. This carbon deoxidation process, occurring during the converter tapping process, can reduce the oxygen content in the steel to 100 × 10⁻⁶. -6 The content of oxide inclusions in the steel is reduced to approximately wt%, significantly decreasing the amount of oxide inclusions. Residual oxygen reacts with ferrosilicon to generate SiO2, which then reacts with CaO and Al2O3 in the steel to form CaO-SiO2-Al2O3 inclusions. These inclusions are more likely to aggregate and float than the CaO-SiO2 or CaO-MnO-SiO2 inclusions produced by the original process, further improving the cleanliness of the steel and resulting in significant economic and social benefits. Attached Figure Description

[0018] Figure 1 The image shows the morphology of inclusions in the RH steel leaving the station in Comparative Example 1.

[0019] Figure 2 The image shows the morphology of inclusions in the RH steel leaving the station in Example 1.

[0020] Figure 3 This is a morphological image of inclusions in the RH steel leaving the station in Example 2;

[0021] Figure 4 This is a schematic diagram of the carbon structure alloy sphere structure of the present invention;

[0022] In the diagram: ① is a silicon-manganese alloy; ② is a mixture of carbon and auxiliary materials. Detailed Implementation

[0023] The following detailed embodiments further illustrate the above-mentioned content of the present invention. Given that those skilled in the art have conducted extensive research in the field of inclusions and accumulated a wealth of theoretical and practical experience, after carefully reading these embodiments and their corresponding analyses, one can certainly, based on other specific conditions, and within the range of the process scheme and alloy composition design ratio proposed in this invention, at most conduct a few limited conventional experiments to specifically select several sets of process technology schemes that meet other conditions, thereby achieving the technical effects described in this invention. Therefore, only some embodiments are given below. However, this should not be construed as limiting the scope of the above-mentioned subject matter of this invention to the following examples; all technologies implemented based on the above-mentioned content of this invention fall within the scope of this invention.

[0024] Comparative Example 1

[0025] The steelmaking process adopts the flow of "converter process - RH process - billet continuous casting process". The product composition is shown in Table 1:

[0026] Table 1 Steel Grade Composition Requirements / wt%

[0027]

[0028]

[0029] Converter process: When the converter has tapped 1 / 2 of the steel, a carburizing agent is added to the ladle. After circulating for 20 seconds, ferrosilicon, ferromanganese, ferrochrome alloy, and ferrovanadium alloy are added to alloy the molten steel. After tapping, the molten steel is stirred by weak argon blowing at a flow rate of 80 NL / min for 5 min. After argon blowing, the concentration of a[O] in the steel is 35 × 10⁻⁶. -4 wt%, [C] 0.65wt%, [Si] 0.62wt%, [Mn] 0.91wt%, [P] 0.017wt%, [S] 0.007wt%, [V] 0.03wt%, [Cr] 0.27wt%.

[0030] RH process: The gas flow rate is increased to 1400 NL / min throughout the vacuum treatment process, and the cycle lasts for 10 minutes before the vacuum process ends.

[0031] The morphology of inclusions in the RH produced in this batch is as follows: Figure 1 As shown.

[0032] Example 1

[0033] The steelmaking process adopts the flow of "converter process - RH process - billet continuous casting process". The product composition is shown in Table 2:

[0034] Table 2 Steel Grade Composition Requirements / wt%

[0035] C Si Mn P S Al V Cr 0.60～0.80 0.50～0.70 0.70～1.20 ≤0.025 ≤0.025 ≤0.004 0.02～0.10 0.25～0.5

[0036] Converter process: When 1 / 8 of the steel is tapped from the converter, carbon structural alloy balls are added to the ladle. 48 seconds after the addition, ferrochrome alloy and ferrovanadium alloy are added to alloy the molten steel. After tapping, the molten steel is stirred by weak argon blowing at a flow rate of 157 NL / min for 8 minutes. After argon blowing, the a[O] content in the steel is 20×10⁻⁶. -4 wt%, [C] 0.69wt%, [Si] 0.62wt%, [Mn] 0.97wt%, [P] 0.016wt%, [S] 0.005wt%, [V] 0.03wt%, [Cr] 0.27wt%;

[0037] RH process: The vacuum treatment begins with a gas flow rate of 1620 NL / min. When the vacuum level drops below 100 Pa, the gas flow rate is reduced to 1360 NL / min. The cycle is repeated for 10 minutes, and the vacuum process ends.

[0038] The composition parameters of the carbon structural alloy balls added in the converter process are shown in Table 3.

[0039] Table 3. Component Indicators of Carbon Structural Alloy Spheres

[0040]

[0041]

[0042] The carbon structural alloy spheres added in the converter process are wrapped with 0.1 to 0.3 mm thick low-carbon steel that does not contain titanium or aluminum between the inner and outer layers and on the surface of the outer layer. The mass ratio of the inner and outer layers is 2.1:1 to 1:1.8.

[0043] The morphology of inclusions in the RH produced in this batch is as follows: Figure 2 As shown.

[0044] Example 2

[0045] The steelmaking process adopts the flow of "converter process - RH process - billet continuous casting process". The product composition is shown in Table 4:

[0046] Table 4 Steel Grade Composition Requirements / wt%

[0047] C Si Mn P S Al V Cr 0.60～0.80 0.50～0.70 0.70～1.20 ≤0.025 ≤0.025 ≤0.004 0.02～0.10 0.25～0.5

[0048] Converter process: When 1 / 6 of the steel has been tapped from the converter, carbon structural alloy balls are added to the ladle. 64 seconds after the addition, ferrochrome alloy and ferrovanadium alloy are added to alloy the molten steel. After tapping, the molten steel is stirred by weak argon blowing at a flow rate of 175 NL / min for 8 minutes. After argon blowing, the concentration of a[O] in the steel is 18 × 10⁻⁶. -4 wt%, [C] 0.63wt%, [Si] 0.55wt%, [Mn] 0.92wt%, [P] 0.016wt%, [S] 0.004wt%, [V] 0.03wt%, [Cr] 0.27wt%;

[0049] RH process: The vacuum treatment begins with a gas flow rate of 1780 NL / min. When the vacuum level drops below 100 Pa, the gas flow rate is reduced to 1200 NL / min. The cycle is repeated for 13 minutes, and the vacuum process ends.

[0050] The specifications of the composite alloys added in the converter process are shown in Table 5.

[0051] Table 5. Component Indicators of Carbon Structural Alloy Spheres

[0052]

[0053]

[0054] The carbon structural alloy spheres added in the converter process are wrapped with 0.1 to 0.3 mm thick low-carbon steel that does not contain titanium or aluminum between the inner and outer layers and on the surface of the outer layer. The mass ratio of the inner and outer layers is 2.1:1 to 1:1.8.

[0055] The morphology of inclusions in the RH produced in this batch is as follows: Figure 3 As shown.

[0056] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A deoxidation and alloying method for high-purity high-carbon silicon-manganese steel, characterized in that: The process flow includes the converter process, the RH process, and the billet continuous casting process. When the steel is tapped from the converter to 1 / 8 to 1 / 6 of its length, carbon structural alloy balls, ferrochrome alloy, and ferrovanadium alloy are added to the ladle in sequence to deoxidize and alloy the molten steel, thereby effectively controlling the carbon, manganese, and silicon elements in the steel as well as the types of inclusions. The RH process promotes the flotation and removal of inclusions in the steel by controlling the process parameters, thereby improving the cleanliness of the molten steel. The carbon structure alloy ball has a double-layer composite structure, wherein the inner layer is a silicon-iron alloy and the outer layer is a mixture of carbon powder and auxiliary materials; The particle size of the carbon powder is 0.5 mm to 10 mm, the particle size of the auxiliary material is 300 nm to 100 μm, and the mixture of the outer carbon powder and auxiliary material has the following composition: CaO: 3 wt% to 9 wt%, Al2O3: 2 wt% to 6 wt%, C: 80 wt% to 93 wt%, wherein the CaO / Al2O3 ratio is 0.9 to 1.7, and the remainder is unavoidable impurities.

2. The deoxidation and alloying method for high-purity high-carbon silicon-manganese steel according to claim 1, characterized in that: In the converter process, after deoxidation and alloying, the carbon content in the steel is controlled to be 0.3wt%~0.8wt%. After tapping, the molten steel is stirred by weak argon blowing. During the argon blowing process, the diameter of the exposed surface of the molten steel is less than 19cm.

3. The deoxidation and alloying method for high-purity high-carbon silicon-manganese steel according to claim 1, characterized in that: The silicon-iron alloy has a particle size of 15mm to 45mm and a composition of: Si: 31wt% to 59wt%, Mn: 31wt% to 59wt%, with the remainder being iron and unavoidable impurities.

4. The deoxidation and alloying method for high-purity high-carbon silicon-manganese steel according to claim 1, characterized in that: After the carbon structural alloy balls are added, add ferrochrome alloy and ferrovanadium alloy 45-70 seconds later.

5. The deoxidation and alloying method for high-purity high-carbon silicon-manganese steel according to claim 2, characterized in that: The argon flow rate for the weak argon blowing stirring is 155 NL / min to 180 NL / min, and the argon blowing time is 5 min to 10 min.

6. The deoxidation and alloying method for high-purity high-carbon silicon-manganese steel according to claim 1, characterized in that: The RH process parameters are as follows: at the start of vacuum treatment, the gas flow rate is 1610NL / min~1790NL / min. When the vacuum level drops to less than 100Pa, the gas flow rate is reduced to 1200NL / min~1380NL / min. The cycle is repeated for 8min~15min, and the vacuum process ends.

7. The deoxidation and alloying method for high-purity high-carbon silicon-manganese steel according to claim 1, characterized in that: The inner diameter of the carbon structural alloy sphere is 15mm~45mm, and the outer diameter is 25mm~60mm.

8. The deoxidation and alloying method for high-purity high-carbon silicon-manganese steel according to claim 1, characterized in that: The mass ratio of the inner and outer layers of the carbon structural alloy sphere is 2.1:1 to 1:1.8.

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