A method for smelting duplex stainless steel in an aod converter with molybdenum alloying

Abstract

The application discloses a duplex stainless steel AOD converter molybdenum alloying smelting method and belongs to the technical field of stainless steel smelting processes. The method comprises the following steps: step one, uniformly stirring 2 tons of molybdenum oxide balls and 2 tons of lime and adding the mixture into a scrap steel hopper; and step two, adding the molybdenum oxide balls into an AOD converter through the scrap steel hopper in the AOD dynamic decarburization period 2. The method uses molybdenum oxide balls to replace part of molybdenum iron, expands the application field of mineral steelmaking in duplex stainless steel, and reduces the production cost. In the method, the molybdenum oxide balls and the lime are uniformly stirred and added into the AOD converter through the scrap steel hopper, MoO3 and CaO are combined to form CaMoO4, the melting point of which is high and the volatilization is not easy; the molybdenum oxide balls are added into the AOD converter through the scrap steel hopper, the molybdenum oxide balls can directly enter the molten steel, and the volatilization in the adding process of the high-position stock bin is reduced; the molybdenum oxide balls are added in the early decarburization period, and the oxygen elements in the molybdenum oxide balls can play a deoxidizing role, so that the overall oxygen blowing amount is reduced.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel smelting technology, specifically relating to a method for smelting duplex stainless steel AOD converter molybdenum alloying. Background Technology

[0002] Duplex stainless steel, combining the advantages of both ferritic and austenitic stainless steels, possesses high strength, toughness, excellent weldability, and corrosion resistance. It is widely used in various industrial sectors, such as pulp and paper, oil and gas, chemical processing, transportation, pharmaceuticals, food processing, and construction. In these applications, duplex stainless steel is considered a cost-effective material, filling the gap between ordinary stainless steel (such as 316L) and high-alloy austenitic stainless steel.

[0003] The addition of molybdenum as a beneficial element in duplex stainless steel can improve its corrosion resistance, specifically as follows: (1) improving resistance to chloride stress corrosion; (2) improving resistance to pitting corrosion. Most manufacturers in the world alloy molybdenum when producing duplex stainless steel, generally by adding ferromolybdenum to the molten steel in an AOD converter. Due to the high price of ferromolybdenum, the smelting cost is high.

[0004] Faced with the steel industry's arduous journey and the shift in market competition to one focused on cost and quality, reducing the production costs of high-value-added products will be the future direction. Direct reduction alloying steelmaking, a process that saves production steps, reduces environmental pollution, and conserves resources and energy, is a highly economically efficient steelmaking technology. Summary of the Invention

[0005] This invention provides a method for molybdenum alloying in an AOD converter for duplex stainless steel, aiming to reduce the production cost of duplex stainless steel and provide a simple, easy-to-operate and controllable method for molybdenum alloying in an AOD converter for duplex stainless steel with low production cost.

[0006] Therefore, the present invention adopts the following technical solution:

[0007] Step 1: Prepare molybdenum oxide balls and lime for the scrap steel hopper. Mix 2 tons of molybdenum oxide balls and 2 tons of lime evenly and add them to the scrap steel hopper.

[0008] Step 2: AOD converter smelting

[0009] a. Adding molten iron: At 1450–1550℃, molten iron with the following chemical composition by mass percentage: C: 3.00–3.50%, Si: 0.20–0.40%, Mn: 0.20–0.30%, P: ≤0.020%, S: ≤0.02%, Cr: 16.50–18.50%, Ni: 5.50–6.50%, Mo: 0.30–0.50% is added to the AOD furnace.

[0010] b. Decarbonization:

[0011] ①Silicon-aluminum oxidation period: Based on the silicon content of 0.20-0.40% in the molten iron, add lime according to the basicity of CaO / SiO2 of 1.40-1.50, without adding lightly calcined dolomite; the oxygen to nitrogen flow ratio is 200-230:30, and the blowing time is 2-3 minutes;

[0012] ② Main decarburization period: No materials are added, and the oxygen to nitrogen flow rate ratio is 200-230:30, with a blowing time of 2-3 minutes;

[0013] ③ Dynamic decarbonization period 1: The oxygen to nitrogen flow rate ratio is 200-230:30, and the blowing time is 3-4 minutes;

[0014] ④ Dynamic decarburization period 2: Oxygen and nitrogen are blown in at a flow ratio of 90:30, and the blowing time is 25-30 minutes; when the carbon content in the molten steel is ≤0.6% and the temperature is ≥1650℃, the scrap steel bucket is hoisted by an overhead crane and added to the AOD converter with evenly mixed molybdenum oxide balls and lime; then 130-170 kg / t of high-carbon ferrochrome and 8-10 kg / t of high-carbon ferrochrome in the high-level silo are added. The high-carbon ferrochrome is added before the end of this stage. The high-carbon ferrochrome and lime are added to the molten steel in batches from the collection silo.

[0015] ⑤ Dynamic decarburization period 3: The oxygen to nitrogen flow rate ratio is 45:90, and the blowing time is 8 to 10 minutes; 30 to 40 kg / t of ferromolybdenum and 1.0 to 1.5 kg / t of lime are added to the high-level silo.

[0016] ⑥ Dynamic decarbonization period 4: Oxygen and nitrogen are blown in at a flow ratio of 30:90, and the blowing time is 6 to 8 minutes respectively;

[0017] ⑦ Dynamic decarbonization period 5: Oxygen and nitrogen are blown in at a flow ratio of 20:90, and the blowing time is 6 to 8 minutes respectively;

[0018] ⑧ Dynamic decarbonization period 6: The flow rate ratio of oxygen to nitrogen is 20:100, and the blowing time is 5 to 6 minutes.

[0019] c. Reduction: When the carbon content drops below 0.010%, the reduction stage begins at a temperature of 1700–1750℃. The slag basicity is controlled at 1.8–2.0. In the AOD furnace, 15–20 kg / t of ferrosilicon, 16–18 kg / t of ferrosilicon-manganese alloy, and 8–10 kg / t of aluminum blocks are added to reduce the residual molybdenum oxide in the slag. The reduction time is 5–6 minutes. At the end of this stage, the slag is dumped to the maximum extent, with a dumping time of 5–6 minutes.

[0020] d. Desulfurization: Add lime to make the slag basicity in the AOD converter 2.1-2.5, and the desulfurization time is 5-6 minutes; take samples to analyze the content of alloying elements in the molten steel, and adjust the Si, Mn, Cr and Ni composition in the molten steel by adding ferrosilicon, silicon-manganese alloy, ferrochrome and metallic nickel according to the test results.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. Mix molybdenum oxide balls and lime evenly and add them to the AOD converter using a scrap steel hopper. MoO3 and CaO combine to form CaMoO4, which has a high melting point and is not easily volatilized.

[0023] 2. Add molybdenum oxide balls to the scrap steel hopper for furnace turning. The molybdenum oxide balls can directly enter the molten steel, reducing volatilization during the high-level silo feeding process;

[0024] 3. In the AOD converter, there are many reducing elements in the molten steel. By utilizing the elements such as C, Si, Mn, and Fe in the molten steel and the good kinetic stirring conditions in the AOD converter, the molybdenum oxide spheres are reduced, achieving rapid reduction of molybdenum oxide and realizing the purpose of direct alloying of molten steel.

[0025] 4. Replacing part of the ferromolybdenum with molybdenum oxide balls can reduce smelting costs and environmental pollution; adding molybdenum oxide balls in the early stage of decarburization can utilize the oxygen element in the molybdenum oxide balls to play a deoxidation role, reducing the overall oxygen blowing amount. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0027] Example 1

[0028] Steel grade: 2205 duplex stainless steel;

[0029] Step 1: Prepare molybdenum oxide balls and lime for the scrap steel hopper. Mix 2 tons of molybdenum oxide balls and 2 tons of lime evenly and add them to the scrap steel hopper.

[0030] The chemical composition of the molybdenum oxide spheres, by mass percentage, is as follows: Mo: 52.0–55.0%, Cu: 0.30–0.40%, P ≤ 0.016%, S ≤ 0.125%.

[0031] The chemical composition range of lime by mass percentage is: CaO ≥ 88.0%, P ≤ 0.01%, S ≤ 0.045%, C 固 ≤0.7%, SiO2≤3.0%, activity≥350ml, raw / overburned ≤7.0%, particle size: 10~100mm≥90%.

[0032] In this embodiment, the commercially available molybdenum oxide spheres have the following composition: 52.68% Mo, 0.317% Cu, 0.016% P, and 0.125% S.

[0033] Step 2: AOD converter smelting

[0034] a. Adding molten iron: At 1450℃, 96.0t of molten iron with the following chemical composition by mass percentage: C: 3.50%, Si: 0.20%, Mn: 0.30%, P: 0.017%, S: 0.02%, Cr: 16.50%, Ni: 5.50%, Mo: 0.30% is added to the AOD furnace.

[0035] b. Decarbonization:

[0036] ①Silicon-aluminum oxidation period: Based on the silicon content of 0.20% in the molten iron, lime is added according to the CaO / SiO2 basicity of 1.40, and lightly calcined dolomite is not added; the oxygen to nitrogen flow ratio is 200:30, and the blowing time is 2 minutes.

[0037] ② Main decarbonization period: No materials are added, oxygen and nitrogen are blown in at a flow ratio of 200:30, and the blowing time is 2 minutes;

[0038] ③ Dynamic decarbonization period 1: Oxygen to nitrogen flow rate ratio is 200:30, blowing time is 3 minutes;

[0039] ④ Dynamic decarburization period 2: Oxygen and nitrogen are blown in at a flow ratio of 90:30 for 25 minutes; when the carbon content in the molten steel is ≤0.6% and the temperature is ≥1650℃, the scrap steel bucket is hoisted by an overhead crane and mixed molybdenum oxide balls and lime are added to the AOD converter; then 170kg / t of high-carbon ferrochrome and 10kg / t of lime are added to the high-level silo. The high-carbon ferrochrome is added before the end of this stage. The high-carbon ferrochrome and lime are added to the molten steel in batches from the collection silo.

[0040] ⑤ Dynamic decarburization period 3: The oxygen to nitrogen flow rate ratio is 45:90, and the blowing time is 8 minutes; 30 kg / t of ferromolybdenum and 1.0 kg / t of lime are added to the high-level silo.

[0041] The chemical composition of ferromolybdenum by mass percentage is: Mo: 62.3%, Cu: 0.2%, P≤0.016%, S≤0.1%.

[0042] ⑥ Dynamic decarbonization period 4: Oxygen and nitrogen are blown in at a flow ratio of 30:90, and the blowing time is 6 minutes each;

[0043] ⑦ Dynamic decarbonization period 5: Oxygen and nitrogen are blown in at a flow ratio of 20:90, and the blowing time is 6 minutes each;

[0044] ⑧ Dynamic decarbonization period 6: Oxygen and nitrogen are blown in at a flow ratio of 20:100, and the blowing time is 5 minutes each;

[0045] c. Reduction: When the carbon content drops below 0.010%, the reduction stage begins at a temperature of 1700℃. The slag basicity is controlled at 1.8. 15 kg / t of ferrosilicon, 16 kg / t of ferromanganese alloy and 8 kg / t of aluminum blocks are added to the AOD furnace to reduce the residual molybdenum oxide in the slag. The reduction time is 5 minutes. At the end of this stage, the slag is dumped to the maximum extent. The slag dumping time is 5 minutes.

[0046] The composition range of ferrosilicon is 72-80% Si, ≤0.030% S, and ≤0.040% P; the composition range of silicon-manganese alloy is 20-25% Si, 60-65% Mn, ≤0.040% P, and ≤0.030% S.

[0047] d. Desulfurization: Add lime to make the slag basicity in the AOD converter 2.1, and the desulfurization time is 5 minutes; take samples to analyze the content of alloying elements in the molten steel, and adjust the Si, Mn, Cr and Ni composition in the molten steel by adding ferrosilicon, ferromanganese silicon alloy, ferrochrome and metallic nickel according to the test results.

[0048] After AOD refining, the amount of molten steel is 110t, and the composition of the molten steel is C: 0.016%, Si: 0.30%, Mn: 1.15%, P: 0.020%, S: 0.0010%, Cr: 22.20%, Ni: 5.15%, N: 0.18%, Mo: 2.90%, and the rest is Fe and residual elements.

[0049] Example 2

[0050] Steel grade: 2205 duplex stainless steel;

[0051] Step 1: Prepare molybdenum oxide balls and lime for the scrap steel hopper. Mix 2 tons of molybdenum oxide balls and 2 tons of lime evenly and add them to the scrap steel hopper.

[0052] The chemical composition of the molybdenum oxide spheres, by mass percentage, is as follows: Mo: 52.68–54.3%, Cu: 0.30–0.40%, P ≤ 0.016%, S ≤ 0.125%.

[0053] The chemical composition range of lime by mass percentage is: CaO ≥ 88.0%, P ≤ 0.01%, S ≤ 0.045%, C 固 ≤0.7%, SiO2≤3.0%, activity≥350ml, raw / overburned ≤7.0%, particle size: 10~100mm≥90%.

[0054] In this embodiment, the commercially available molybdenum oxide spheres have the following composition: 54.3% Mo, 0.30% Cu, 0.015% P, and 0.10% S.

[0055] Step 2: AOD converter smelting

[0056] a. Adding molten iron: At 1500℃, 105.0t of molten iron with the following chemical composition by mass percentage: C: 3.0%, Si: 0.40%, Mn: 0.20%, P: 0.02%, S: 0.015%, Cr: 18.50%, Ni: 6.50%, Mo: 0.50% is added to the AOD furnace.

[0057] b. Decarbonization:

[0058] ①Silicon-aluminum oxidation period: Based on the silicon content of 0.40% in the molten iron, lime is added according to the basicity of CaO / SiO2 of 1.50, and lightly calcined dolomite is not added; the oxygen to nitrogen flow ratio is 230:30, and the blowing time is 3 minutes.

[0059] ② Main decarbonization period: No materials are added, oxygen and nitrogen are blown in at a flow ratio of 230:30, and the blowing time is 3 minutes;

[0060] ③ Dynamic decarbonization period 1: The oxygen to nitrogen flow rate ratio is 230:30, and the blowing time is 4 minutes;

[0061] ④ Dynamic decarburization period 2: Oxygen and nitrogen are blown in at a flow ratio of 90:30 for 30 minutes; when the carbon content in the molten steel is ≤0.6% and the temperature is ≥1650℃, the scrap steel bucket is hoisted by an overhead crane and mixed molybdenum oxide balls and lime are added to the AOD converter; then 130kg / t of high-carbon ferrochrome and 8kg / t of lime are added to the high-level silo. The high-carbon ferrochrome is added before the end of this stage. The high-carbon ferrochrome and lime are added to the molten steel in batches from the collection silo.

[0062] ⑤ Dynamic decarburization period 3: The oxygen to nitrogen flow rate ratio is 45:90, and the blowing time is 10 minutes; 40 kg / t of ferromolybdenum and 1.5 kg / t of lime are added to the high-level silo.

[0063] The chemical composition of ferromolybdenum by mass percentage is: Mo: 56.0%, Cu: 0.2%, P≤0.016%, S≤0.1%.

[0064] ⑥ Dynamic decarbonization period 4: Oxygen and nitrogen are blown in at a flow ratio of 30:90, and the blowing time is 6 minutes each;

[0065] ⑦ Dynamic decarbonization period 5: Oxygen and nitrogen are blown in at a flow ratio of 20:90, and the blowing time is 6 minutes each;

[0066] ⑧ Dynamic decarbonization period 6: Oxygen and nitrogen are blown in at a flow ratio of 20:100, and the blowing time is 5 minutes each;

[0067] c. Reduction: When the carbon content drops below 0.010%, the reduction stage begins at a temperature of 1750℃. The slag basicity is controlled at 2.0. 20 kg / t of ferrosilicon, 18 kg / t of ferromanganese alloy, and 10 kg / t of aluminum blocks are added to the AOD furnace to reduce the residual molybdenum oxide in the slag. The reduction time is 6 minutes. At the end of this stage, the slag is dumped to the maximum extent, and the dumping time is 6 minutes.

[0068] The composition range of ferrosilicon is 72-80% Si, ≤0.030% S, and ≤0.040% P; the composition range of silicon-manganese alloy is 20-25% Si, 60-65% Mn, ≤0.040% P, and ≤0.030% S.

[0069] d. Desulfurization: Add lime to make the slag basicity in the AOD converter 2.5, and the desulfurization time is 6 minutes; take samples to analyze the content of alloying elements in the molten steel, and adjust the Si, Mn, Cr and Ni composition in the molten steel by adding ferrosilicon, ferromanganese silicon alloy, ferrochrome and metallic nickel according to the test results.

[0070] After AOD refining, the amount of molten steel is 115t, and the composition of the molten steel is C: 0.012%, Si: 0.40%, Mn: 1.20%, P: 0.022%, S: 0.0012%, Cr: 22.60%, Ni: 5.25%, N: 0.175%, Mo: 3.15%, and the rest is Fe and residual elements.

[0071] Example 3

[0072] Steel grade: 2205 duplex stainless steel;

[0073] Step 1: Prepare molybdenum oxide balls and lime for the scrap steel hopper. Mix 2 tons of molybdenum oxide balls and 2 tons of lime evenly and add them to the scrap steel hopper.

[0074] The chemical composition of the molybdenum oxide spheres, by mass percentage, is as follows: Mo: 52.68–54.3%, Cu: 0.30–0.40%, P ≤ 0.016%, S ≤ 0.125%.

[0075] The chemical composition range of lime by mass percentage is: CaO ≥ 88.0%, P ≤ 0.01%, S ≤ 0.045%, C 固 ≤0.7%, SiO2≤3.0%, activity≥350ml, raw / overburned ≤7.0%, particle size: 10~100mm≥90%.

[0076] In this embodiment, the commercially available molybdenum oxide spheres have the following composition: 53.4% ​​Mo, 0.34% Cu, 0.010% P, and 0.05% S.

[0077] Step 2: AOD converter smelting

[0078] a. Adding molten iron: At 1500℃, 100.0t of molten iron with the following chemical composition by mass percentage: C: 3.41%, Si: 0.25%, Mn: 0.29%, P: 0.019%, S: 0.018%, Cr: 18.12%, Ni: 5.70%, Mo: 0.40% is added to the AOD furnace.

[0079] b. Decarbonization:

[0080] ①Silicon-aluminum oxidation period: Based on the silicon content of 0.250% in the molten iron, lime is added according to the CaO / SiO2 basicity of 1.50, and lightly calcined dolomite is not added; the oxygen to nitrogen flow ratio is 220:30, and the blowing time is 2 minutes.

[0081] ② Main decarbonization period: No materials are added, oxygen and nitrogen are blown in at a flow ratio of 220:30, and the blowing time is 3 minutes;

[0082] ③ Dynamic decarbonization period 1: The oxygen to nitrogen flow rate ratio is 220:30, and the blowing time is 3 minutes;

[0083] ④ Dynamic decarburization period 2: Oxygen and nitrogen are blown in at a flow ratio of 90:30 for 26 minutes; when the carbon content in the molten steel is ≤0.6% and the temperature is ≥1650℃, the scrap steel bucket is hoisted by an overhead crane and mixed molybdenum oxide balls and lime are added to the AOD converter; then 150kg / t of high-carbon ferrochrome and 9kg / t of lime are added to the high-level silo. The high-carbon ferrochrome is added before the end of this stage. The high-carbon ferrochrome and lime are added to the molten steel in batches from the collection silo.

[0084] ⑤ Dynamic decarburization period 3: The oxygen to nitrogen flow rate ratio is 45:90, and the blowing time is 9 minutes; 35 kg / t of ferromolybdenum and 1.2 kg / t of lime are added to the high-level silo.

[0085] ⑥ Dynamic decarbonization period 4: Oxygen and nitrogen are blown in at a flow ratio of 30:90, and the blowing time is 7 minutes each;

[0086] ⑦ Dynamic decarbonization period 5: Oxygen and nitrogen are blown in at a flow ratio of 20:90, and the blowing time is 7 minutes each;

[0087] ⑧ Dynamic decarbonization period 6: Oxygen and nitrogen are blown in at a flow ratio of 20:100, and the blowing time is 6 minutes.

[0088] c. Reduction: When the carbon content drops below 0.010%, the reduction stage begins at a temperature of 1720℃. The slag basicity is controlled at 1.9. 18 kg / t of ferrosilicon, 17 kg / t of ferromanganese alloy and 9 kg / t of aluminum blocks are added to the AOD furnace to reduce the residual molybdenum oxide in the slag. The reduction time is 6 minutes. At the end of this stage, the slag is dumped to the maximum extent. The slag dumping time is 6 minutes.

[0089] d. Desulfurization: Add lime to make the slag basicity in the AOD converter 2.3, and the desulfurization time is 5 minutes; take samples to analyze the content of alloying elements in the molten steel, and adjust the Si, Mn, Cr and Ni composition in the molten steel by adding ferrosilicon, silicon-manganese alloy, ferrochrome and metallic nickel according to the test results.

[0090] After AOD refining, the amount of molten steel is 112t, and the composition of the molten steel is C: 0.015%, Si: 0.30%, Mn: 1.17%, P: 0.023%, S: 0.0008%, Cr: 22.40%, Ni: 5.21%, N: 0.185%, Mo: 3.02%, and the rest is Fe and residual elements.

Claims

1. A method for molybdenum alloying of duplex stainless steel in an AOD converter, characterized in that, Includes the following steps: Step 1: Prepare molybdenum oxide balls and lime for the scrap steel hopper. Mix the molybdenum oxide balls and lime in a 1:1 mass ratio and add them to the scrap steel hopper. Step 2: AOD converter smelting a. Adding molten iron: At 1450–1550℃, molten iron with the following chemical composition by mass percentage: C: 3.00–3.50%, Si: 0.20–0.40%, Mn: 0.20–0.30%, P: ≤0.020%, S: ≤0.02%, Cr: 16.50–18.50%, Ni: 5.50–6.50%, Mo: 0.30–0.50% is poured into the AOD furnace; b. Decarbonization: ①Silicon-aluminum oxidation period: Based on the silicon content of 0.20-0.40% in the molten iron, add lime according to the basicity of CaO / SiO2 of 1.40-1.50, without adding lightly calcined dolomite; the oxygen to nitrogen flow ratio is 200-230:30, and the blowing time is 2-3 minutes; ② Main decarburization period: No materials are added, and the oxygen to nitrogen flow rate ratio is 200-230:30, with a blowing time of 2-3 minutes; ③ Dynamic decarbonization period 1: The oxygen to nitrogen flow rate ratio is 200-230:30, and the blowing time is 3-4 minutes; ④ Dynamic decarburization period 2: Oxygen and nitrogen are blown in at a flow ratio of 90:30, and the blowing time is 25-30 minutes; when the carbon content in the molten steel is ≤0.6% and the temperature is ≥1650℃, the scrap steel bucket is hoisted by an overhead crane and added to the AOD converter with evenly mixed molybdenum oxide balls and lime; then 130-170 kg / t of high-carbon ferrochrome and 8-10 kg / t of high-carbon ferrochrome in the high-level silo are added. The high-carbon ferrochrome is added before the end of this stage. The high-carbon ferrochrome and lime are added to the molten steel in batches from the collection silo. ⑤ Dynamic decarburization period 3: The oxygen to nitrogen flow rate ratio is 45:90, and the blowing time is 8 to 10 minutes; 30 to 40 kg / t of ferromolybdenum and 1.0 to 1.5 kg / t of lime are added to the high-level silo; ⑥ Dynamic decarbonization period 4: Oxygen and nitrogen are blown in at a flow ratio of 30:90, and the blowing time is 6 to 8 minutes respectively; ⑦ Dynamic decarbonization period 5: Oxygen and nitrogen are blown in at a flow ratio of 20:90, and the blowing time is 6 to 8 minutes respectively; ⑧ Dynamic decarbonization period 6: The oxygen to nitrogen flow rate ratio is 20:100, and the blowing time is 5 to 6 minutes respectively; c. Reduction: When the carbon content drops below 0.010%, the reduction stage begins at a temperature of 1700–1750℃. The slag basicity is controlled at 1.8–2.

0. In the AOD furnace, 15–20 kg / t of ferrosilicon, 16–18 kg / t of ferromanganese alloy, and 8–10 kg / t of aluminum blocks are added to reduce the residual molybdenum oxide in the slag. The reduction time is 5–6 minutes. At the end of this stage, the slag is dumped to the maximum extent, with a dumping time of 5–6 minutes. d. Desulfurization: Add lime to make the slag basicity in the AOD converter 2.1-2.5, and the desulfurization time is 5-6 minutes; take samples to analyze the content of alloying elements in the molten steel, and adjust the Si, Mn, Cr and Ni composition in the molten steel by adding ferrosilicon, silicon-manganese alloy, ferrochrome and metallic nickel according to the test results.

2. The method for molybdenum alloying of duplex stainless steel in an AOD converter according to claim 1, characterized in that, In step one, 2 tons of molybdenum oxide balls and 2 tons of lime are mixed evenly and added to the waste steel hopper.