Smelting method of cobalt-containing steel

Abstract

The invention relates to the field of steelmaking and oxide metallurgy, in particular to a smelting method of cobalt-containing steel. The smelting method mainly solves the problem that the cost is high due to the fact that cobalt-containing steel is alloyed through electrode cobalt and other metal cobalt. After an electric furnace is melted to form a molten pool, cobalt oxide powder is sprayed into the molten pool through a consumable gun, cobalt oxide is reduced through elements such as C, Si and Mn in pre-molten liquid, a reducing agent does not need to be added, oxygen is brought into the cobalt oxide in the smelting process, the oxygen blowing amount can be properly reduced, CO2 gas is selected as blowing carrier gas, the pressure is 0.9-1.0 MPa, the flow is 45-50 Nm < 3 > / min, the cobalt oxide blowing amount of each spraying gun is 80-150 kg / min, and the cobalt oxide powder is sprayed into the molten pool through the consumable gun. Lime is added for slagging in the electric furnace smelting process, an oxygen lance is adopted for spraying Ar gas for stirring for 2-3 min when electric furnace smelting is finished, and molten steel can be continuously cast after smelting is finished to obtain the required steel billet. The cobalt-containing steel is smelted by adopting the method, the sprayed cobalt oxide can increase the contact area of the steel slag, and the reaction speed is increased. And cobalt oxide powder is sprayed for alloying, so that the smelting cost is reduced, and meanwhile, resource consumption and environmental pollution in the electrode cobalt production process are reduced.

Description

Technical Field

[0001] The invention relates to the fields of steelmaking and oxide metallurgy, and in particular to a method for smelting cobalt-containing steel. Background Art

[0002] Cobalt is a metallic element with a hard and brittle texture. Cobalt has many properties. It can maintain high strength at high temperatures, has low thermal conductivity and electrical conductivity, and strong ferromagnetism. Cobalt is an important raw material for the production of heat-resistant alloys, hard alloys, corrosion-resistant alloys, magnetic alloys and various cobalt salts. About 70% of cobalt consumption is metallic cobalt, which is mainly used in super heat-resistant alloys, tool steels, hard alloys, magnetic materials, etc. The consumption in the form of compounds (catalysts, drying materials, reagents, ceramic glazes, etc.) is about 25%, and the rest is about 5%.

[0003] Cobalt-containing steel is a special steel containing cobalt. It has excellent wear resistance and high strength. It is often used to manufacture various high-load and high-strength mechanical parts. The proportion of cobalt is generally between 5% and 30%. Typical cobalt-containing steels include tool steel ASTMT4 (Co: 4.25-5.75%), high-speed steel M35 (W6Mo5Cr4V2Co5, Co: 4.60-5.00%), M36 (W6Mo5Cr4V2Co8, Co: 7.5-8.5%), etc. This type of cobalt-containing steel is generally produced in an electric arc furnace. The smelting process uses electrode cobalt or metal cobalt powder for alloying, which is relatively expensive.

[0004] Cobalt oxide is a product produced by hydrometallurgy, with a cobalt content of 70-75%. It is an important transition metal oxide and is usually used as the main raw material for the production of hard alloys, super heat-resistant alloys, insulating materials and magnetic materials, as well as catalysts and dyes in the chemical industry. Due to its high oxidizability, it is generally used as a raw material in large cobalt production enterprises and then processed deeply to produce electrode cobalt. At present, there is no precedent for the use of cobalt oxide produced by the hydrometallurgical process in steel production enterprises.

[0005] The invention provides a method for producing cobalt-containing steel, wherein the raw material is relatively cheap cobalt oxide, which broadens the access to the raw material for cobalt-containing steel and is beneficial to the competitiveness of enterprises; cobalt oxide is used in the smelting process of the cobalt-containing steel, and elements such as Si, C, and Mn in the premelt can be fully utilized to reduce the cobalt oxide, remove the C and Si elements in the premelt, and reduce the oxygen supply; a spray gun is used to use CO2 gas as a carrier gas to spray cobalt oxide powder into the interior of molten steel, which can increase the contact area between the cobalt oxide and the molten steel, and at the same time, a large flow rate of CO2 gas is sprayed to achieve a strong stirring effect, accelerate the interface mass transfer of the molten steel, promote the reduction of cobalt oxide, and improve the yield of cobalt; the cobalt-containing steel is produced by using cobalt oxide as a raw material, which can replace expensive raw materials such as metal cobalt / electrode cobalt, can significantly reduce the smelting cost of the cobalt-containing steel, and at the same time reduce the resource consumption and environmental pollution in the production process of electrode cobalt. Summary of the invention

[0006] The purpose of the present invention is to provide a method for smelting cobalt-containing steel in view of the above problems.

[0007] The object of the present invention is achieved as follows: A method for smelting cobalt-containing steel comprises the following steps: Step 1: Electric furnace batching: Calculate the required alloy according to the composition of the cobalt-containing steel to be smelted, load the weighed alloy and scrap steel into the electric furnace, and load the cobalt oxide powder into the spray tank, wherein the composition of the cobalt oxide is: Co: 70-75%, O: 23-29%, P≤0.010%, S≤0.010%, and the rest are impurities; Step 2: Electric furnace smelting: Use an oxygen lance to blow oxygen to assist melting and cut the charge, the oxygen pressure is 0.9-1.0Mpa, and the flow rate is 20-50Nm 3 / min, when the furnace charge is melted to form a molten pool, a consumable gun is used to spray cobalt oxide powder into the furnace melt. The carrier gas used is CO2 gas, with a pressure of 0.9-1.0MPa and a flow rate of 45-50Nm 3 / min, each spray gun sprays 80-150kg / min of cobalt oxide; when the melt area increases, double guns are used to spray cobalt oxide powder; oxygen blowing continues during the smelting process for desiliconization, dephosphorization and decarburization, and the oxygen blowing amount is reduced accordingly according to the oxygen content of the added cobalt oxide, O2 reduction = cobalt oxide weight * 25%, lime is added in 4-5 batches during the smelting process to make slag, the amount of lime added is 25-30kg / t, and the slag basicity is controlled at 1.5-1.8. When the smelting temperature and composition are appropriate, steel is tapped, and the tapping adopts a slag-free tapping method, and the tapping temperature is 1630-1650℃; Step 3: The molten steel after tapping enters LF for refining and is cast into qualified ingots.

[0008] The invention has the following beneficial effects: 1. Cobalt oxide powder is sprayed into molten steel by using a spray gun and CO2 gas as a carrier gas, thereby increasing the contact area between cobalt oxide and molten steel, and at the same time, a large flow rate of CO2 gas is sprayed to achieve a strong stirring effect, thereby accelerating the interfacial mass transfer of molten steel, promoting the reduction of cobalt oxide, and improving the yield of cobalt; 2. Cobalt oxide powder is continuously sprayed into an electric furnace, and elements such as Si, C, and Mn in the pre-melted liquid are used to fully reduce the cobalt in the cobalt oxide, while the Si and C elements in the pre-melted liquid are removed, thereby reducing the amount of oxygen blown; 3. Cobalt-containing steel is produced by using cobalt oxide as a raw material, which can replace expensive metal cobalt, electrode cobalt and other precious metal raw materials, and can significantly reduce the smelting cost of cobalt-containing steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will be further described below in conjunction with the accompanying drawings.

[0010] Figure 1 It is a smelting process flow chart of the present invention.

[0011] Figure 2This is the ∆G diagram of the reaction between cobalt oxide and C, Si, Mn, and Fe elements. DETAILED DESCRIPTION

[0012] The present invention proposes a method for smelting cobalt-containing steel using cobalt oxide as raw material. By spraying cobalt oxide powder, the reaction area can be increased and the cobalt recovery rate can be improved. Using cobalt oxide raw material to smelt cobalt-containing steel can make full use of cheap cobalt resources and reduce smelting costs. The present invention loads cobalt oxide powder into a spray tank, charges an electric furnace for smelting, and after a molten pool is formed, a consumable gun is used to spray the cobalt oxide powder into the interior of the electric furnace melt. The spray carrier gas is CO2 gas, the pressure is 0.9-1.0MPa, and the flow rate is 45-50Nm 3 / min, each spray gun sprays 80-150kg / min of cobalt oxide. During the electric furnace smelting process, lime is added in batches to make slag. The amount of lime added is 25-30kg / t. At the end of the electric furnace smelting, an oxygen gun is used to spray Ar gas for stirring for 2-3 minutes. The argon flow rate is 50-55Nm 3 / min.

[0013] The specific technical scheme is as follows: 1. Process route: electric furnace charging smelting - molten steel melts to form a molten pool - spraying cobalt oxide powder - electric furnace melting and cleaning - LF refining - continuous casting.

[0014] 2. Electric furnace burden: calculate the required alloy according to the composition of the cobalt-containing steel to be refined, load the weighed alloy and scrap steel into the electric furnace, and load the cobalt oxide powder into the spray tank. The composition of cobalt oxide is Co: 70-75%, O: 23-29%, P≤0.010%, S≤0.010%, and the rest are impurities.

[0015] 3. Electric furnace power supply smelting, use oxygen lance to blow oxygen to assist melting and cut the charge, the oxygen pressure is 1.0MPa, the flow rate is 20~50Nm 3 / min, when the furnace charge is melted to form a molten pool, a consumable gun is used to spray cobalt oxide powder into the furnace melt. The carrier gas used is CO2 gas, with a pressure of 0.9-1.0MPa and a flow rate of 45-50Nm 3 / min, and the amount of cobalt oxide sprayed by each spray gun is 80-150kg / min. When the melt area increases, double guns are used to spray cobalt oxide powder. The Si, C, Mn, Fe and other elements in the pre-melt are used to reduce cobalt oxide (C+CoO=Co+CO↑; Si+2CoO=2Co+SiO2; Mn+CoO=Co+MnO; Fe+CoO=Co+FeO. The calculation using factsage software shows that the ∆G of the reaction between cobalt oxide and C, Si, Mn, and Fe elements is negative (such as Figure 2), indicating that the reaction can proceed regardless of the temperature), the smelting process continues to blow oxygen for desiliconization, dephosphorization and decarburization, and the amount of oxygen blown is reduced accordingly according to the oxygen content of the added cobalt oxide. During the smelting process, lime is added in batches to make slag, and the amount of lime added is 25-30kg / t. The slag basicity is controlled at 1.5-1.8. When the smelting temperature and composition are appropriate, the steel is tapped. The tapping method is slag-free, and the tapping temperature is 1630-1650℃.

[0016] 4. After LF refining and fine-tuning of the composition, the molten steel is sent to the continuous casting process for continuous casting. Example 1 (90-ton electric furnace spraying cobalt oxide powder to produce M35 steel)

[0017] A 90-ton electric furnace is used to smelt M35 (W6Mo5Cr4V2Co5) steel (composition: C: 0.8-0.9%, Si: 0.2-0.45%, Mn: 0.15-0.40%, P≤0.030%, S≤0.030%, Cr: 3.75-4.5%, V: 1.75-2.25%, Mo: 4.5-5.5%, W: 5.5-6.5%, Co: 4.5-5.5%). The process flow is as follows: electric furnace charging smelting - molten steel melts to form a molten pool - cobalt oxide powder is sprayed - electric furnace melting is completed - LF refining - continuous casting.

[0018] (1) The electric furnace is charged with scrap steel, high carbon ferrochrome, ferromolybdenum and ferrotungsten. The total charge is 90 tons, including 6.5 tons of ferrotungsten, 7.5 tons of ferromolybdenum and 7.6 tons of high carbon ferrochrome. The electric furnace is powered on for melting. Oxygen blowing is performed during the smelting process. The oxygen pressure is 1.0 MPa and the oxygen flow rate is 20-30 Nm 3 / min.

[0019] (2) When the charge of the electric furnace melts to form a molten pool, a consumable gun is used to spray cobalt oxide powder into the molten metal of the electric furnace. The carrier gas used for the spraying is CO2 gas with a pressure of 1.0 MPa and a flow rate of 45-50 Nm 3 / min, each spray gun sprays 100kg / min of cobalt oxide. When the melt area increases, double guns are used to spray cobalt oxide powder. Use Si, C, Mn and other elements in the pre-melt to reduce cobalt oxide (C+CoO=Co+CO↑; Si+2CoO=2Co+SiO2; Mn+CoO=Co+MnO). Oxygen is blown during the smelting process to remove silicon, dephosphorize and decarbonize. The amount of oxygen is reduced according to the oxygen content of the added cobalt oxide. Lime is added in batches to make slag during the smelting process. The amount of lime added is 25-30kg / t. The slag basicity is controlled at 1.5-1.8. (3) When the electric furnace smelting temperature and composition are appropriate, use an oxygen lance to blow Ar gas for strong stirring for 2 to 3 minutes before tapping the steel. The stirring flow rate is 50 to 55 Nm 3 / min, the steel is tapped using a slag-free method, the tapping temperature is 1640℃, ferrosilicon, ferromanganese and ferrovanadium are added to the electric furnace ladle for alloying, and the amount of ferrovanadium added is 3 tons.

[0020] (4) After the electric furnace produces steel, the molten steel is sent to the LF furnace for refining and temperature adjustment, and then hoisted to the continuous casting process for continuous casting.

[0021] The cobalt recovery rate of M35 steel is ≥98.2%, which reduces the cost by RMB 280 / t. Example 2 (160-ton electric furnace spraying cobalt oxide powder to produce ASTM T4 steel)

[0022] A 100-ton electric furnace is used to smelt ASTM T4 steel (composition: C: 0.7-0.8%, Si: 0.2-0.40%, Mn: 0.10-0.40%, P≤0.030%, S≤0.030%, Cr: 3.75-4.5%, V: 0.8-1.20%, Mo: 0.4-1.0%, W: 17.5-19%, Co: 4.25-5.75%). The process flow is as follows: electric furnace charging smelting - molten steel melts to form a molten pool - cobalt oxide powder is sprayed - electric furnace melting is completed - LF refining - continuous casting.

[0023] (1) The electric furnace is charged with scrap steel, high carbon ferrochrome, ferromolybdenum and ferrotungsten. The total charge is 160 tons, including 36 tons of ferrotungsten, 1.6 tons of ferromolybdenum and 13.5 tons of high carbon ferrochrome. The electric furnace is powered on for melting. Oxygen blowing is performed during the smelting process. The oxygen pressure is 1.0 MPa and the oxygen flow rate is 35 Nm 3 / min.

[0024] (2) When the charge of the electric furnace melts to form a molten pool, a consumable gun is used to spray cobalt oxide powder into the molten metal of the electric furnace. The carrier gas used for the spraying is CO2 gas with a pressure of 1.0 MPa and a flow rate of 45-50 Nm 3 / min, each spray gun sprays 150kg / min of cobalt oxide. Double guns are used to spray cobalt oxide powder. Si, C, Mn and other elements in the pre-melt are used to reduce cobalt oxide (C+CoO=Co+CO↑; Si+2CoO=2Co+SiO2; Mn+CoO=Co+MnO). Oxygen is blown during the smelting process to remove silicon, dephosphorize and decarbonize. The amount of oxygen blown is reduced accordingly according to the oxygen content of the added cobalt oxide. Lime is added in batches to make slag during the smelting process. The amount of lime added is 25-30kg / t, and the slag basicity is controlled at 1.6-1.8. (3) When the electric furnace smelting temperature and composition are appropriate, use oxygen lance to blow Ar gas for strong stirring for 3 minutes before tapping the steel. The stirring flow rate is 50-55Nm 3 / min, the steel is tapped using a slag-free method, the tapping temperature is 1640℃, ferrosilicon, ferromanganese and ferrovanadium are added to the electric furnace ladle for alloying, and the amount of ferrovanadium added is 2.4 tons.

[0025] (4) After the electric furnace produces steel, the molten steel is sent to the LF furnace for refining and temperature adjustment, and then hoisted to the continuous casting process for continuous casting.

[0026] The electric furnace sprays cobalt oxide powder to directly alloy and smelt ASTM T4 steel, with a cobalt recovery rate of ≥98.0%, reducing the cost by 260 yuan / t.

[0027] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A method for smelting cobalt-containing steel, characterized in that: The following steps are involved: Step 1: Electric furnace batching: Calculate the required alloy according to the composition of the cobalt-containing steel to be refined, load the weighed alloy and scrap steel into the electric furnace, and load the cobalt oxide powder into the spray tank. The composition of cobalt oxide is: Co: 70-75%, O: 23-29%, P≤0.010%, S≤0.010%, and the rest are impurities; Step 2: Electric furnace smelting: Use oxygen lance to blow oxygen to assist melting and cut the charge. The oxygen pressure is 0.9-1.0Mpa and the flow rate is 20-50Nm 3 / min, when the furnace charge is melted to form a molten pool, a consumable gun is used to spray cobalt oxide powder into the furnace melt. The carrier gas used is CO2 gas, with a pressure of 0.9-1.0MPa and a flow rate of 45-50Nm 3 / min, each spray gun sprays 80-150kg / min of cobalt oxide; when the melt area increases, double guns are used to spray cobalt oxide powder; oxygen blowing continues during the smelting process for desiliconization, dephosphorization and decarburization, and the oxygen blowing amount is reduced accordingly according to the oxygen content of the added cobalt oxide, and the amount of O2 reduction = weight of cobalt oxide * 25%. During the smelting process, lime is added in 4-5 batches to make slag, and the amount of lime added is 25-30kg / t. The basicity of the slag is controlled at 1.5-1.

8. When the smelting temperature and composition are appropriate, the steel is tapped. The steel is tapped in a slag-free manner, and the tapping temperature is 1630-1650℃; Step 3: The molten steel after tapping enters the LF for refining and is cast into qualified ingots.

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