A method for producing low carbon steel by direct top light decarburization process

Abstract

The present application relates to the technical field of metal smelting, and particularly relates to a method for producing low-carbon steel by using straight-up light decarburization process, which comprises the following steps: preparing molten iron, limestone, ore and scrap steel respectively; the composition of limestone requires that CaO content is greater than or equal to 50%, SiO2 content is less than or equal to 5%, SiO2 particle size is 10-20 mm, raw dolomite content is greater than or equal to 20%, raw dolomite particle size is 10-20 mm, and the water content of the above components is less than or equal to 3%; firstly, the first batch of materials is added with light-burned lime, wherein the lime is 1000 kg, the light-burned lime is 800 kg, 500-1000 kg of lump ore is added according to the temperature of the molten iron, 1500-2500 kg of limestone is added, and 1000 kg of raw dolomite is added; the second batch of materials is added with limestone according to the calculated amount of limestone, and the remaining part is divided into not less than 5 batches, 300-500 kg of limestone is added in each batch in the middle period, and 200-300 kg of ore is added in each batch, in the present application, by using the above production process, the production steps are effectively reduced, the production cost is reduced, the carbon content of the steel grade can be effectively ensured to be less than 0.025%, and the steel grade meets the deep drawing requirement.

Description

Technical Field

[0001] The invention relates to the technical field of metal smelting, and in particular to a method for producing low-carbon steel by adopting a direct-up light decarburization process. Background Art

[0002] Traditional processes for producing steel grades with deep drawing requirements such as SPHC or SPHD require lower strength and higher elongation due to deep drawing requirements. LF refining furnaces (VD) and RH vacuum refining furnaces are usually used to meet the requirements of improving molten steel purity and decarburization and desulfurization. The production process is long and costly. Therefore, to address the above issues, a method for producing low-carbon steel using a direct-up light decarburization process is proposed. Summary of the Invention

[0003] The object of the present invention is to provide a method for producing low-carbon steel by adopting a direct-up light decarburization process, thereby realizing stable production of low-carbon steel with a C content of 0.015% to 0.025% at a low cost.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for producing low-carbon steel using a direct-to-light decarburization process comprises the following steps:

[0006] Step 1: Prepare the furnace materials: prepare molten iron, limestone, ore and scrap steel respectively; the limestone composition requirements are CaO content ≥ 50%, SiO2 content ≤ 5%, SiO2 particle size 10-20mm, raw dolomite content ≥ 20%, raw dolomite particle size 10-20mm, and the moisture content of the above materials ≤ 3%;

[0007] Step 2: smelting control: first, the first batch of materials is blown and lime light burning is added in a fixed amount, wherein lime is 1000kg and light burning is 800kg. According to the temperature of the molten iron, 500-1000kg of lump ore, 1500-2500kg of limestone and 1000kg of raw dolomite are added; the second batch of materials is added according to the amount of limestone added calculated by the silicon content of the molten iron, and the remaining part is divided into not less than 5 batches, 300-500kg of limestone per batch in the middle stage, and 200-300kg of follow-up ore per batch. When the temperature is high in the middle and late stages, the remaining raw dolomite is used to adjust the temperature; the end point composition control: C content ≤ 0.05%, P content ≤ 0.015%, S content ≤ 0.015%, and the tapping temperature ≥ 1550°C; the end point slag composition control: FeO content ≤ 18%, CaO content 40-55%, SiO2 ≤ 15%, Al2O3 ≤ 5% and MnO ≤ 5%, and the basicity of the slag is 3.0-4.0;

[0008] Step 3: Argon station operation: After arriving at the argon blowing station, the argon blowing state remains unchanged, and the ladle cover is lowered by winch for insulation and vacuum treatment. After blowing argon for 5 minutes, it is changed to medium blowing, and the flow rate is controlled at 200-300L / min. The temperature is measured and sampled by opening the movable cover of the ladle cover. The molten steel temperature is controlled to be ≥1600℃, the composition C: ≤0.028%, P≤0.015%, S≤0.015%. After the composition is appropriate, aluminum wire is fed to deoxidize the molten steel, and the fixed oxygen is controlled at ≤4ppm. 150kg / t of calcium carbide and 150kg / t of aluminum-calcium balls are added through the chute. Aluminum chips are used for slag adjustment according to the color of the top slag, and FeO+MnO≤2.0%; calcium treatment process: 2m / t of pure calcium wire is fed, and the calcium-aluminum ratio is ≥0.8; the temperature after argon is ≥1575℃.

[0009] Preferably, the composition requirements of the molten iron in step one are: C content ≤ 5.0%, Si content 0.35-0.50%, Mn content 0.30-0.45%, P content ≤ 0.100%, S content ≤ 0.025%, and the molten iron temperature ≥ 1320°C, and the slag content in the molten iron ≤ 4‰.

[0010] Preferably, in step 2, the gun position control and oxygen pressure setting are as follows: the gun position is 1.4 meters when the blowing starts, the working oxygen pressure is 0.80-0.85 MPa, when the blowing reaches 2-3 minutes, the gun position is 1.3 meters, the gun position during the blowing process is 1.2-1.3 meters, when the blowing reaches 11 minutes, the gun is pressed at 1.0 meters to pull carbon, and the gun pressing time is greater than 40 seconds.

[0011] Preferably, in step 2, the tapping time is controlled to be 2.5-4.0 min, the bottom blowing flow rate is controlled to be 500-800 L / min, strong stirring is performed, no alloy is added during the tapping process, 1 kg / t of sintered ore is added in a thin stream, and 500 kg / furnace of white ash is added.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] In the present invention, the above-mentioned production process not only effectively reduces the production steps and thus reduces the production cost, but also effectively ensures that the carbon content of the steel is less than 0.025%, so that it meets the deep drawing requirements. DETAILED DESCRIPTION

[0014] Example 1: The present invention provides a technical solution:

[0015] A method for producing low-carbon steel using a direct-up light decarburization process comprises the following steps:

[0016] Step 1: Prepare the furnace materials: prepare molten iron, limestone, ore and scrap steel respectively; the limestone composition requirements are CaO content ≥ 50%, SiO2 content ≤ 5%, SiO2 particle size 10-20mm, raw dolomite content ≥ 20%, raw dolomite particle size 10-20mm, and the moisture content of the above materials ≤ 3%;

[0017] Step 2: smelting control: first, the first batch of materials is blown and lime light burning is added in a fixed amount, wherein lime is 1000kg and light burning is 800kg. According to the temperature of the molten iron, 500-1000kg of lump ore, 1500-2500kg of limestone and 1000kg of raw dolomite are added; the second batch of materials is added according to the amount of limestone added calculated by the silicon content of the molten iron, and the remaining part is divided into not less than 5 batches, 300-500kg of limestone per batch in the middle stage, and 200-300kg of follow-up ore per batch. When the temperature is high in the middle and late stages, the remaining raw dolomite is used to adjust the temperature; the end point composition control: C content ≤ 0.05%, P content ≤ 0.015%, S content ≤ 0.015%, and the tapping temperature ≥ 1550°C; the end point slag composition control: FeO content ≤ 18%, CaO content 40-55%, SiO2 ≤ 15%, Al2O3 ≤ 5% and MnO ≤ 5%, and the basicity of the slag is 3.0-4.0;

[0018] Step 3: Argon station operation: After arriving at the argon blowing station, the argon blowing state remains unchanged, and the ladle cover is lowered by winch for insulation and vacuum treatment. After blowing argon for 5 minutes, it is changed to medium blowing, and the flow rate is controlled at 200-300L / min. The temperature is measured and sampled by opening the movable cover of the ladle cover. The molten steel temperature is controlled to be ≥1600℃, the composition C: ≤0.028%, P≤0.015%, S≤0.015%. After the composition is appropriate, aluminum wire is fed to deoxidize the molten steel, and the fixed oxygen is controlled at ≤4ppm. 150kg / t of calcium carbide and 150kg / t of aluminum-calcium balls are added through the chute. Aluminum chips are used for slag adjustment according to the color of the top slag, and FeO+MnO≤2.0%; calcium treatment process: 2m / t of pure calcium wire is fed, and the calcium-aluminum ratio is ≥0.8; the temperature after argon is ≥1575℃.

[0019] The composition of the molten iron in step one is required to be: C content ≤5.0%, Si content 0.35-0.50%, Mn content 0.30-0.45%, P content ≤0.100%, S content ≤0.025%, and the molten iron temperature ≥1320℃, and the molten iron slag amount ≤4‰; the ore in step one is mainly block ore and sintered return ore, the weight of the block ore is 10 kg, and the block ore is in a dry state, the SiO2 content of which is <7%, the weight of the sintered return ore is 10-15 kg; the scrap steel is mainly heavy scrap; in step two, the gun position control and oxygen pressure setting: the blowing gun position is 1.4 meters, the working oxygen pressure is 0.80-0.85 MPa, when blowing for 2-3 minutes, the gun position is 1.3 meters, the blowing process gun position is 1.2-1.3 meters, when blowing for 11 minutes, the gun is pressed to 1.0 meter to remove carbon, and the gun pressing time is >40 seconds; the tapping time control in step two is 2.5-4.0 min, the bottom blowing flow rate control is 500-800 L / min, strong stirring is carried out, no alloy is added during tapping, 1 kg / t of sintered ore is added in the form of a fine stream, and 500 kg / ton of lime is added.

[0020] Example table:

[0021] 1. Raw material situation: (molten iron)

[0022] Table 1: Composition of molten iron

[0023]

[0024]

[0025] 2. Loading amount

[0026] Table 2: Loading amount control

[0027]

[0028] 3. End point composition control:

[0029] Table 3: End point composition control results

[0030]

[0031] 4. End point slag control

[0032] Table 4: End point slag control results

[0033]

[0034] 5. Argon blowing station sampling and temperature measurement

[0035] Table 5: Composition and temperature control of argon blowing station

[0036]

[0037] 6. Deoxidation alloying and calcium treatment process

[0038] Table 6 Deoxidation alloying and calcium treatment process

[0039]

[0040]

[0041] 7. Off-site composition and temperature

[0042] Table 7 Off-site composition and temperature control

[0043]

[0044] 8. Continuous casting pouring situation

[0045] Table 8 Continuous casting operation record

[0046]

[0047] 9. Inspection situation

[0048]

[0049] 10. Performance test situation

[0050]

[0051] 11. Process cost comparison

[0052]

[0053] 12. Core index difference

[0054]

[0055] The principles and implementations of the present application are described herein using specific examples. The above examples are only used to help understand the method of the present application and its core idea. The above description is only the preferred embodiments of the present application. It should be noted that due to the limited nature of the language, there are objectively infinite specific structures. For ordinary skilled persons in the technical field, without departing from the principles of the present application, several improvements, refinements or changes can be made, or the above technical features can be combined in an appropriate manner. These improvements, refinements, changes or combinations, or the application of the inventive concept and technical solution to other fields without improvement, shall be considered as the protection scope of the present application.

Claims

1. A method for producing low carbon steel using a direct light decarburization process, characterized in that: The following steps are involved: Step 1: Prepare the furnace materials: prepare molten iron, limestone, ore and scrap steel respectively; the limestone composition requirements are CaO content ≥ 50%, SiO2 content ≤ 5%, SiO2 particle size 10-20mm, raw dolomite content ≥ 20%, raw dolomite particle size 10-20mm, and the moisture content of the above materials ≤ 3%; Step 2: smelting control: first, the first batch of materials is blown and lime light burning is added in a fixed amount, wherein lime is 1000kg and light burning is 800kg. According to the temperature of the molten iron, 500-1000kg of lump ore, 1500-2500kg of limestone and 1000kg of raw dolomite are added; the second batch of materials is added according to the amount of limestone added calculated by the silicon content of the molten iron, and the remaining part is divided into not less than 5 batches, 300-500kg of limestone per batch in the middle stage, and 200-300kg of follow-up ore per batch. When the temperature is high in the middle and late stages, the remaining raw dolomite is used to adjust the temperature; the end point composition control: C content ≤ 0.05%, P content ≤ 0.015%, S content ≤ 0.015%, and the tapping temperature ≥ 1550°C; the end point slag composition control: FeO content ≤ 18%, CaO content 40-55%, SiO2 ≤ 15%, Al2O3 ≤ 5% and MnO ≤ 5%, and the basicity of the slag is 3.0-4.0; Step 3: Argon station operation: After arriving at the argon blowing station, the argon blowing state remains unchanged, and the ladle cover is lowered by winch for insulation and vacuum treatment. After blowing argon for 5 minutes, it is changed to medium blowing, and the flow rate is controlled at 200-300L / min. The temperature is measured and sampled by opening the movable cover of the ladle cover. The molten steel temperature is controlled to be ≥1600℃, the composition C: ≤0.028%, P≤0.015%, S≤0.015%. After the composition is appropriate, aluminum wire is fed to deoxidize the molten steel, and the fixed oxygen is controlled at ≤4ppm. 150kg / t of calcium carbide and 150kg / t of aluminum-calcium balls are added through the chute. Aluminum chips are used for slag adjustment according to the color of the top slag, and FeO+MnO≤2.0%; calcium treatment process: 2m / t of pure calcium wire is fed, and the calcium-aluminum ratio is ≥0.8; the temperature after argon is ≥1575℃.

2. The method for producing low carbon steel using a direct-on light decarburization process according to claim 1, characterized in that: The composition requirements of the molten iron in step 1 are: C content ≤ 5.0%, Si content 0.35-0.50%, Mn content 0.30-0.45%, P content ≤ 0.100%, S content ≤ 0.025%, and the molten iron temperature ≥ 1320°C, and the slag content in the molten iron ≤ 4‰.

3. The method for producing low carbon steel using a direct-on light decarburization process according to claim 1, characterized in that: In step 2, the gun position control and oxygen pressure setting are as follows: the gun position is 1.4 meters when the blowing starts, the working oxygen pressure is 0.80-0.85 MPa, when the blowing reaches 2-3 minutes, the gun position is 1.3 meters, the gun position during the blowing process is 1.2-1.3 meters, when the blowing reaches 11 minutes, the gun is pressed to 1.0 meters to pull carbon, and the gun pressing time is greater than 40 seconds.

4. The method for producing low carbon steel using a direct-on light decarburization process according to claim 1, characterized in that: In step 2, the tapping time is controlled to be 2.5-4.0 min, the bottom blowing flow rate is controlled to be 500-800 L / min, strong stirring is performed, no alloy is added during the tapping process, 1 kg / t of sintered ore is added in a thin stream, and 500 kg / furnace of white ash is added.

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