Molten steel deoxidation method for converter tapping

Abstract

The invention discloses a molten steel deoxidation method for converter tapping, and mainly solves the technical problem of high molten steel deoxidation cost of converter tapping of steel with the upper limit of w [C] larger than 0.03% in the prior art. According to the technical scheme, w [C] in the steel grade is larger than 0.03%, and the molten steel deoxidation method for converter tapping comprises the steps that (1) converter blowing is conducted, specifically, a top-bottom combined blowing converter is adopted to smelt molten steel, and the end point of w [C] in the molten steel at the converter blowing end point is controlled to be 0.03%-0.07%; (2) converter tapping: when the amount of molten steel tapped by the converter reaches 20-25% of the total amount of the molten steel, adding a silicon-containing alloy into the molten steel in a steel ladle at one time for pre-deoxidation of the molten steel; after the silicon-containing alloy is added for 20-40 seconds, aluminum alloy and alloy for alloying are added into the molten steel in the steel ladle at a time for molten steel final deoxidation and molten steel alloying; and (3) steel tapping is finished. According to the method, silicon pre-deoxidation of the steel grade with the silicon upper limit mass percentage content larger than or equal to 0.03% is achieved, and the molten steel deoxidation cost is reduced by 1.84 yuan per ton of steel or above.

Description

Technical Field

[0001] The present invention relates to a deoxidation technology for molten steel in converter smelting, and particularly to a method for deoxidizing molten steel during tapping from a converter. Specifically, it relates to a deoxidation process for molten steel tapped from a converter with a carbon mass percentage content of the steel grade > 0.03%, belonging to the technical field of iron and steel metallurgy. Background Art

[0002] During the converter smelting process, under equilibrium conditions, the product of the carbon content and the oxygen content in the molten steel in the converter bath is a constant. As the blowing progresses, the carbon content gradually decreases, and the free oxygen content in the molten steel also gradually increases. When reaching the end of blowing, the free oxygen content in the molten steel is usually relatively high, generally above 0.03%. To avoid a large number of porosity and other defects in the casting billet, it is necessary to deoxidize the molten steel.

[0003] Common deoxidizing elements include carbon, aluminum, and silicon. Among them, carbon has the lowest deoxidation cost, but the deoxidation speed is slow and the deoxidation ability is limited; aluminum has the strongest deoxidation ability, but the deoxidation cost is the highest, and a large amount of Al2O3 generated is not conducive to the cleanliness of the molten steel and continuous casting pouring; the deoxidation ability of silicon is weaker than that of aluminum but stronger than that of carbon, and the deoxidation cost is only 1 / 3 of that of ferrosilicon alloy.

[0004] At present, silicon-containing alloys have been used for deoxidizing molten steel during the tapping process of a converter. Most of them are only applied to silicon-containing steel grades, with a narrow range of use. At the same time, only ferrosilicon or silicomanganese alloy is used as a single source of silicon element, and there is no dynamic selection of ferrosilicon or silicomanganese alloy according to the designed composition of the steel grade and the change of alloy price. Therefore, the cost advantage of silicon deoxidation has not been fully exerted.

[0005] The Chinese patent application document with the application publication number CN105714010A discloses a converter silicon deoxidation method for IF steel and ultra-low carbon steel. For IF steel and ultra-low carbon steel, when the oxygen content of the molten steel at the end point ≥ 0.0600%, ferrosilicon is used to replace aluminomanganese iron for pre-deoxidation during tapping from the converter. The dosage of ferrosilicon ≤ 2 kg / t of steel, and for every 0.0025% increase in the oxygen content of the molten steel, the dosage of ferrosilicon increases by 0.01 - 0.15 kg / t of steel. Ferrosilicon is added when the tapping is 1 / 4 - 1 / 3, and the finished silicon content is controlled at 0.005 - 0.012%. This technology is only applicable to ultra-low carbon steel and is not applicable to non-ultra-low carbon steel with a carbon mass percentage content > 0.03%; moreover, only ferrosilicon is used as the alloy for silicon deoxidation, and the deoxidation cost of the molten steel cannot meet the industry's requirement for extreme cost reduction.

[0006] The Chinese patent application document with the publication number CN112553410A discloses a silicon deoxidation process for RH quality steel. When the final oxygen content ≥ 0.045%, aluminum deoxidation and alloying are not carried out during the tapping process, and ferrosilicon is used for deoxidation, which is added when the tapping reaches 1 / 4 - 1 / 2. The addition amount is as follows: based on the final oxygen content of 0.045%, 0.26 kg of ferrosilicon is added per ton of steel, and for every 0.01% increase in the final oxygen content, 0.13 kg of ferrosilicon is added per ton of steel. In this technology, final aluminum deoxidation is not carried out during the tapping process, and silicon deoxidation is only adopted when the final oxygen content in the converter ≥ 0.045%. There is no need to deal with the problem of synergistic deoxidation of ferrosilicon and aluminum alloy, and only ferrosilicon is used as the alloy for silicon deoxidation, so the cost advantage of silicon deoxidation is not fully exploited.

[0007] The Chinese patent application document with the publication number CN110117696A discloses a silicon deoxidation process for silicon-containing steel grades. Ferrosilicon is added when the tapping reaches 1 / 5, and ferraluminum is added when the tapping reaches 2 / 3. For steel grades with a silicon content ≥ 0.10%, the addition amount of ferrosilicon deoxidizer is 0.571 kg per ton of steel, and the addition amount of ferraluminum is 0.571 - 1.143 kg per ton of steel. For steel grades with a silicon content of 0.06 - 0.10% and a manganese content < 1.00%, the addition amount of ferrosilicon is 0.171 kg per ton of steel, and the addition amount of ferraluminum is 1.143 - 1.714 kg per ton of steel. At the same time, during the refining desulfurization process, the addition amount and addition timing of slag-making aluminum are controlled to control the silicon return. This technology is only applicable to silicon-containing steel grades with a silicon content requirement ≥ 0.06%, and is not applicable to non-silicon-containing steel grades. The addition timing of ferrosilicon is too early, resulting in a lower yield, while the addition of other alloys is too late, there is a problem that the alloy is not easy to melt. At the same time, only ferrosilicon is used as the alloy for silicon deoxidation, so the cost advantage of silicon deoxidation is not fully exploited.

[0008] Therefore, the source of the existing molten steel silicon deoxidation alloy is relatively single, and no silicon deoxidation solution with better cost is provided according to the change of alloy price and the requirements of steel grade composition. Although the cost of molten steel deoxidation has been reduced to a certain extent, it is still relatively high and cannot meet the needs of iron and steel enterprises for extreme cost reduction. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for deoxidizing molten steel during the tapping of a converter, mainly solving the technical problem of high cost of deoxidizing molten steel during the tapping of a converter for steel grades with w[C] > 0.03%. The method of the present invention reduces the cost of molten steel smelted in the converter.

[0010] The technical idea of the present invention is to use one of ferrosilicon and silicomanganese alloy as the source of silicon element to pre-deoxidize molten steel. The specific selection of which silicon-containing alloy is determined based on the principle that the composition of molten steel does not exceed the standard and the pre-deoxidation benefit is maximized; when tapping steel from the converter, control the addition timing of the silicon-containing alloy for pre-deoxidizing molten steel and the aluminum alloy for final deoxidizing molten steel, and keep a certain time interval between the two, so as to exert the deoxidation effect of silicon element, reduce the consumption of aluminum alloy, and reduce the smelting cost of the converter.

[0011] The technical solution adopted by the present invention is a method for deoxidizing molten steel during tapping from a converter. In the steel grade, w[C]>0.03%, and it includes the following steps:

[0012] 1) Converter blowing, using a top-bottom combined blown converter to smelt molten steel, and controlling w[C] in the molten steel at the end of converter blowing 终点 to be 0.03% - 0.07% and the temperature of the molten steel at the end of converter blowing ≥ 1600°C;

[0013] 2) Tapping from the converter, when the molten steel covers the bottom of the ladle, add metallurgical lime. When the amount of molten steel tapped from the converter reaches 20% - 25% of the total amount of molten steel, add the silicon-containing alloy for pre-deoxidizing the molten steel into the molten steel in the ladle at one time for pre-deoxidizing the molten steel; 20 - 40 s after adding the silicon-containing alloy, add the aluminum alloy and the alloy for alloying into the molten steel in the ladle at one time for final deoxidizing the molten steel and alloying the molten steel, and adjust the composition of the molten steel after tapping to the set value; the determination method of the silicon-containing alloy includes the following steps:

[0014] 2.1) Collect data. After the converter heat starts, collect the designed composition of the steel grade, the deoxidation method of the converter, and the refining method of the molten steel for the current heat.

[0015] 2.2) Determine the added mass m of silicon element for pre-deoxidizing molten steel Si , m Si According to the upper limit mass percentage w[Si] of silicon in the steel grade 上限 and the refining method of the molten steel, it is divided into six intervals. When w[Si] 上限 <0.03%, m Si is 0 kg / t of steel, that is, silicon pre-deoxidation is not adopted; when the molten steel is not treated by an LF ladle refining furnace and w[Si] 上限 is 0.03 - 0.05%, m Si is 0.25 - 0.32 kg / t of steel; when the molten steel is not treated by an LF ladle refining furnace and w[Si] 上限 >0.05%, m Si is 0.54 - 0.66 kg / t of steel; when the molten steel is treated by an LF ladle refining furnace and w[Si] 上限 ≤0.05%, m Si0 kg / ton steel, that is, no silicon pre-deoxidation is used; when LF ladle refining furnace is used to treat molten steel and w[Si] 上限 In the range of (0.05%, 0.1%), m Si 0.25~0.32 kg / ton steel; when LF ladle refining furnace is used to treat molten steel and w[Si] 上限 When >0.1%, m Si 0.54-0.66 kg / ton of steel;

[0016] 2.3) Calculate the reduced mass Δm of aluminum alloy used for final deoxidation of molten steel Al , Δm Al Calculated by formula 1,

[0017]

[0018] In formula 1, Δm Al is the mass reduction of aluminum alloy, in kg / ton steel, m Si is the mass of silicon added for pre-deoxidation of molten steel, in kg / ton of steel, α is the proportion of silicon used for deoxidation, α is 50% to 55%, β is the proportion of aluminum used for deoxidation, β is 75% to 85%, and w[Al] is the mass percentage of aluminum in the aluminum alloy;

[0019] 2.4) Precalculate the added mass m of ferrosilicon SiFe And silicon manganese alloy added mass m SiMn , ferrosilicon or silicon manganese alloy is used to provide silicon element, pre-deoxidize the molten steel, m SiFe Calculated by formula 2, m SiMn Calculated by formula 3,

[0020]

[0021]

[0022] In formulas 2 and 3, m SiFe The mass of ferrosilicon added when all silicon elements are provided by ferrosilicon, in kg / ton steel, m SiMn The mass of silicon-manganese alloy added when all silicon-manganese alloy is used to provide silicon elements, in kg / ton steel, m Si The mass of silicon added for pre-deoxidation of molten steel, expressed in kg / ton of steel, w[Si] SiFe w[Si] is the mass percentage of silicon in ferrosilicon. SiMn is the mass percentage of silicon element in silicon-manganese alloy;

[0023] 2.5) Calculate the benefit EP1 when using ferrosilicon pre-deoxidation. EP1 is calculated by formula 4.

[0024] EP1=Δm Al ×p Al -m SiFe ×p SiFe Formula 4;

[0025] In formula 4, EP1 is the silicon iron pre-deoxidation benefit, the unit is yuan / ton steel, p Al is the price of aluminum alloy, in yuan / kg, p SiFe is the price of ferrosilicon, in yuan / kg;

[0026] 2.6) Calculate the benefits of using silicon-manganese alloy pre-deoxidation. After silicon-manganese alloy pre-deoxidation, the manganese content of molten steel will increase, which can reduce the addition of other ferromanganese alloys. If the reduced ferromanganese alloy is high-carbon ferromanganese, the silicon-manganese alloy pre-deoxidation benefit EP2 is calculated by formula 5. If the reduced ferromanganese alloy is medium-carbon ferromanganese, the silicon-manganese alloy pre-deoxidation benefit EP3 is calculated by formula 6.

[0027]

[0028]

[0029] In formulas 5 and 6, EP2 is the pre-deoxidation benefit of silicon-manganese alloy when the ferromanganese alloy is high carbon ferromanganese, and the unit is yuan / ton steel; EP3 is the pre-deoxidation benefit of silicon-manganese alloy when the ferromanganese alloy is medium carbon ferromanganese, and the unit is yuan / ton steel. HCM is the price of high carbon ferromanganese, in yuan / kg, p MCM is the price of medium carbon ferromanganese, in yuan / kg, p SiMn is the price of silicon manganese alloy, in yuan / kg, w[Mn] SiMn w[Mn] is the mass percentage of manganese in silicon-manganese alloy. HCM w[Mn] is the mass percentage of manganese in high carbon ferromanganese. MCM is the mass percentage of manganese in medium carbon ferromanganese, r1 is the manganese recovery rate during pre-deoxidation of silicon manganese alloy, r1 is 80% to 85%, r2 is the manganese recovery rate during alloying of high carbon ferromanganese or medium carbon ferromanganese, when the molten steel deoxidation method is semi-deoxidation, r2 is 80% to 85%, when the molten steel deoxidation method is full deoxidation, r2 is 89% to 96%;

[0030] 2.7) Determine the type and mass of silicon-containing alloy for pre-deoxidation of molten steel. Ferrosilicon is used as the silicon-containing alloy for pre-deoxidation of molten steel, and the mass added is m SiFe ; Use formulas 7 to 8 to calculate the mass percentage of manganese in the molten steel after pre-deoxidation when the manganese recovery rate in the silicon-manganese alloy is 100% w[Mn] max The carbon content w[C] in the molten steel after pre-deoxidation when the carbon recovery rate in the silicon-manganese alloy is 100% max ,

[0031]

[0032]

[0033] In Formulas 7-8, w[Mn] max is the mass percentage of manganese in the molten steel after pre-deoxidation when the manganese recovery rate in ferrosilicon-manganese alloy is 100%, and w[C] max is the mass percentage of carbon in the molten steel after pre-deoxidation when the carbon recovery rate in ferrosilicon-manganese alloy is 100%, and w[Mn] 终点 is the mass percentage of manganese in the molten steel at the end of converter blowing, and w[C] SiMn is the mass percentage of carbon element in ferrosilicon-manganese alloy, and w[C] 终点 is the mass percentage of carbon in the molten steel at the end of converter blowing;

[0034] When EP1 < EP2 and w[Mn] max < the upper limit of manganese mass percentage of the steel grade w[Mn] 上限 and w[C] max < the upper limit of carbon mass percentage of the steel grade w[C] 上限 at this time, the silicon-containing alloy for pre-deoxidizing the molten steel adopts ferrosilicon-manganese alloy, and the added mass is m SiMn ;

[0035] When EP1 < EP3 and w[Mn] max < the upper limit of manganese mass percentage of the steel grade w[Mn] 上限 and w[C] max < the upper limit of carbon mass percentage of the steel grade w[C] 上限 and the mass of high-carbon ferromanganese that can be added at this time, the silicon-containing alloy for pre-deoxidizing the molten steel adopts ferrosilicon-manganese alloy, and the added mass is m SiMn ;

[0036] 3) At the end of tapping, when the slag detector detects that a large amount of slag is entrained in the molten steel stream, tapping ends; then ladle slag deoxidizer is added to the ladle for top slag deoxidation of the ladle.

[0037] Furthermore, in step 2) of the present invention, the mass percentage of the chemical composition of the ferrosilicon is: Si: 73% - 76%, and the balance is iron and impurities; the mass percentage of the chemical composition of the ferrosilicon-manganese alloy is: Mn: 64% - 67%, Si: 16% - 20%, and the balance is iron and impurities.

[0038] Basis for selecting process parameters of the method of the present invention:

[0039] 1. Determination of silicon-containing alloy for pre-deoxidizing molten steel from converter tapping

[0040] In step 2.2), mSi Determination: According to the molten steel refining method and the upper limit mass percentage content of silicon in the steel grade, the added mass m of silicon element used for pre-deoxidizing the molten steel tapped from the converter Si is divided into six intervals. This is because the equilibrium concentration of silicon and oxygen is higher than that of aluminum. After pre-deoxidizing with silicon, part of the silicon alloy will be alloyed into the molten steel, increasing the mass percentage content of silicon in the molten steel and increasing with the increase of the deoxidation depth. At the same time, when using the LF ladle refining furnace to treat the molten steel, part of the SiO2 in the ladle slag will be reduced to Si, increasing the mass percentage content of silicon in the molten steel. Therefore, for steel grades with an upper limit mass percentage content of silicon < 0.03% and steel grades with an upper limit mass percentage content of silicon ≤ 0.05% treated with the LF ladle refining furnace, no silicon pre-deoxidation is carried out to avoid the mass percentage content of silicon in the molten steel exceeding the upper limit; for furnace heats not treated with the LF ladle refining furnace, it is further divided into two intervals with the upper limit mass percentage content of silicon of 0.05% as the boundary. The purpose of this is to enable silicon pre-deoxidation for steel grades without silicon and at the same time increase the consumption of silicon alloy for pre-deoxidizing steel grades with a higher upper limit mass percentage content of silicon. The dosage of silicon element for pre-deoxidation is determined according to the condition that the mass percentage content of silicon in the molten steel does not exceed the upper limit mass percentage content of silicon in the steel grade under the condition of 75% alloying of silicon element, which can avoid the problem that the mass percentage content of silicon in the molten steel exceeds the upper limit caused by the wrong operation of adding silicon alloy for pre-deoxidation and silicon alloy for alloying at the same time; the maximum dosage of silicon element for pre-deoxidation is controlled below 0.66 kg / t of steel. This is because on the one hand, the deoxidation depth of silicon is limited. When the dosage of silicon alloy is relatively high and continues to increase, the amount of oxygen that can be removed by unit silicon alloy will decrease, increasing the deoxidation cost. On the other hand, it is necessary to ensure a relatively high ratio of the mass percentage content of manganese to the mass percentage content of silicon in the molten steel, so that the deoxidation product is in the liquid inclusion range, avoiding the clogging of the nozzle during the continuous casting process.

[0041] Determination of α and β in step 2.3): Since the silicon-containing alloy and aluminum alloy cannot be fully used for deoxidation after being added to the molten steel, part of the silicon element will participate in the alloying of the molten steel and be burned, and part of the aluminum element will be burned. Therefore, the added silicon-containing alloy and aluminum alloy will not all participate in deoxidation. The proportion α of silicon element used for deoxidation and the proportion β of aluminum element used for deoxidation can be obtained by statistical analysis of a large amount of on-site production data and calculated according to the added amount of silicon-containing alloy, the added amount of aluminum alloy, the reduction amount of the mass percentage content of free oxygen in the molten steel, and the mass of the molten steel.

[0042] Determination of the manganese element recovery rates r1 and r2 in step 2.6): The manganese element recovery rate r1 during pre-deoxidation with ferrosilicon manganese and the manganese element recovery rate r2 during alloying with high-carbon ferromanganese or medium-carbon ferromanganese should be considered separately. This is because when adding ferrosilicon manganese for pre-deoxidation, the mass percentage content of free oxygen in the molten steel at this time ≥ 0.01%, which is usually greater than the mass percentage content of free oxygen in the molten steel during alloying with high-carbon ferromanganese or medium-carbon ferromanganese. Therefore, the manganese element recovery rate r1 during pre-deoxidation with ferrosilicon manganese adopts the manganese element recovery rate during semi-deoxidation.

[0043] Step 2.7) Determination of the type of silicon-containing alloy for pre-deoxidation of molten steel during converter tapping. The selection criteria for using ferrosilicon or silicomanganese alloy for pre-deoxidation are given, where w[Mn] max <The upper limit of manganese mass percentage content w[Mn] of the steel grade 上限 and w[C] max <The upper limit of carbon mass percentage content w[C] of the steel grade 上限 respectively indicate that even if 100% of the manganese and carbon in the silicomanganese alloy enter the molten steel, the composition of the molten steel will not exceed the upper limit. These are two prerequisites for using silicomanganese alloy for pre-deoxidation. When both conditions are met, then by comparing the benefits of pre-deoxidation with silicomanganese alloy and ferrosilicon and the amount of high-carbon ferromanganese used during alloying, it is determined whether silicomanganese alloy can be used for pre-deoxidation. When the benefit of pre-deoxidation with silicomanganese alloy when the reduced ferromanganese alloy is high-carbon ferromanganese is greater than the benefit of pre-deoxidation with ferrosilicon, that is, EP1 < EP2, it means that even if all the low-cost high-carbon ferromanganese is replaced after pre-deoxidation with silicomanganese alloy, more benefits can be generated than pre-deoxidation with ferrosilicon. At this time, the silicon-containing alloy is selected as silicomanganese alloy; when the benefit of pre-deoxidation with silicomanganese alloy when reducing the amount of medium-carbon ferromanganese is greater than the benefit of pre-deoxidation with ferrosilicon and the calculated amount of high-carbon ferromanganese used during alloying is less than half of the amount of high-carbon ferromanganese that can be reduced by the silicomanganese alloy, that is, when EP1 < EP3 and It means that the amount of high-carbon ferromanganese that can be used for manganese alloying of this steel grade is very small, and more expensive other high-grade ferromanganese alloys need to be added for manganese alloying. When using silicomanganese alloy for pre-deoxidation, the amount of medium-carbon ferromanganese and even more expensive low-carbon ferromanganese can be reduced. At this time, the silicon-containing alloy is selected as silicomanganese alloy.

[0044] In step 3), the timing of adding the silicon-containing alloy is determined. When 20 - 25% of the molten steel has been tapped, the silicon-containing alloy is added for pre-deoxidation. This is because if the silicon alloy is added too early, the amount of molten steel in the ladle is small at this time, and the silicon deoxidation effect cannot be maximally exerted. If the silicon alloy is added too late, it will cause the subsequent alloys for final deoxidation and alloying to be too late to be added, affecting alloy melting and tapping.

[0045] 2. Determination of the process parameters for final deoxidation of molten steel during converter tapping

[0046] In step 3), the timing of adding aluminum alloy is determined. Other alloys such as aluminum alloy are added 20 - 40 s after adding the silicon-containing alloy. This is because the binding ability of aluminum with oxygen is stronger than that of silicon. If the aluminum alloy and the silicon alloy are added simultaneously, aluminum will react with oxygen preferentially, and silicon will mainly alloy into the molten steel and cannot play the role of silicon deoxidation. Therefore, the silicon alloy should be added first, and then other alloys such as aluminum alloy should be added. There should be a certain time interval between the two to allow silicon to fully react with the oxygen in the molten steel, but the time interval cannot be too long, otherwise it may cause other alloys such as aluminum alloy to be too late to be added.

[0047] The present invention has the following positive effects compared with the prior art: 1. In step 2) of the method of the present invention, starting from the dosage of silicon element for preliminary deoxidation, the appropriate dosage of silicon element for preliminary deoxidation of molten steel tapped from the converter is determined according to the deoxidation method of molten steel, the refining method of molten steel and the upper limit mass percentage of silicon in the steel grade, realizing the silicon preliminary deoxidation of steel grades without silicon and containing silicon with the upper limit mass percentage of silicon ≥ 0.03%; Ferrosilicon or silicomanganese alloy is used for preliminary deoxidation of molten steel and the corresponding selection criteria are given, realizing the diversification of the source of silicon element for preliminary deoxidation of molten steel. More economical silicon-containing alloys for preliminary deoxidation can be dynamically selected according to the price changes of aluminum alloy, ferrosilicon, silicomanganese alloy, high-carbon ferromanganese, medium-carbon ferromanganese, etc., reducing the deoxidation cost of converter molten steel by more than 1.84 yuan per ton of steel. 2. In step 2) of the method of the present invention, there is a certain time interval between the addition time of the silicon-containing alloy for preliminary deoxidation of molten steel and the aluminum alloy for final deoxidation of molten steel, which can give full play to the deoxidation effect of silicon element and reduce the mass percentage of silicon in molten steel. For steel grades with the upper limit mass percentage of silicon between 0.03% and 0.05%, the mass percentage of silicon in the molten steel in the ladle can be controlled below 0.02%. For steel grades with the upper limit mass percentage of silicon > 0.05%, the mass percentage of silicon in the molten steel in the ladle can be controlled below 0.035%, ensuring that the composition of molten steel meets the requirements. Detailed implementation manners

[0048] The present invention will be further described below in conjunction with Examples 1 to 7. The chemical compositions of the alloys used in the examples, the dosage of silicon element for preliminary deoxidation, the reduction amount of aluminum alloy for final deoxidation, the dosage of silicon-containing alloy, the dosage of high-carbon ferromanganese or medium-carbon ferromanganese that can be reduced by silicomanganese alloy, the deoxidation benefits of ferrosilicon and silicomanganese alloy, the selection parameters of the types of silicon-containing alloys for preliminary deoxidation, the preliminary deoxidation process and effects of molten steel tapped from the converter are shown in Tables 1 to 9.

[0049] In the embodiment of the present invention, 250-ton top-bottom combined blowing converter is used to smelt molten steel. The ferrosilicon used during the tapping process of the converter in the embodiment is 75 ferrosilicon; the grade of silicomanganese alloy is Mn65Si17; the aluminum alloy is aluminum-manganese-calcium.

[0050] A method for deoxidizing molten steel for tapping from a converter, with w[C] > 0.03% in the steel grade, comprising the following steps:

[0051] 1) Converter blowing, using a top-bottom combined blowing converter to smelt molten steel, controlling w[C] in the molten steel at the end of converter blowing 终点 to be 0.03% - 0.07% and the temperature of the molten steel at the end of converter blowing ≥ 1600°C;

[0052] 2) Tapping the converter, after the molten steel covers the bottom of the ladle, add metallurgical lime. When the amount of molten steel tapped from the converter reaches 20% - 25% of the total amount of molten steel, add the silicon-containing alloy for preliminary deoxidation of the molten steel into the molten steel in the ladle at one time for preliminary deoxidation of the molten steel; after 20 - 40 s of adding the silicon-containing alloy, add aluminum alloy and alloy for alloying into the molten steel in the ladle at one time for final deoxidation and alloying of the molten steel, and adjust the composition of the molten steel after tapping to the set value; the determination method of the silicon-containing alloy includes the following steps:

[0053] 2.1) Collect data. After the converter heat starts, collect the designed composition of the steel grade, the deoxidation method of the converter, and the refining method of the molten steel for the current heat.

[0054] 2.2) Determine the mass m of silicon element added for preliminary deoxidation of the molten steel Si , m Si According to the upper limit mass percentage content w[Si] of silicon in the steel grade 上限 and the refining method of the molten steel, it is divided into six intervals. When w[Si] 上限 < 0.03%, m Si is 0 kg / t of steel, that is, silicon preliminary deoxidation is not adopted; when the molten steel is not treated by LF ladle refining furnace and w[Si] 上限 is 0.03 - 0.05%, m Si is 0.25 - 0.32 kg / t of steel; when the molten steel is not treated by LF ladle refining furnace and w[Si] 上限 > 0.05%, m Si is 0.54 - 0.66 kg / t of steel; when the molten steel is treated by LF ladle refining furnace and w[Si] 上限 ≤ 0.05%, m Si is 0 kg / t of steel, that is, silicon preliminary deoxidation is not adopted; when the molten steel is treated by LF ladle refining furnace and w[Si] 上限 is in the interval (0.05%, 0.1%], m Si is 0.25 - 0.32 kg / t of steel; when the molten steel is treated by LF ladle refining furnace and w[Si] 上限 > 0.1%, m Si is 0.54 - 0.66 kg / t of steel;

[0055] 2.3) Calculate the reduced mass Δm of aluminum alloy for final deoxidation of the molten steel Al , Δm Al is calculated by formula one,

[0056]

[0057] In formula one, Δm Al is the reduced mass of aluminum alloy, with the unit of kg / t of steel, m SiThe mass of silicon element added for pre-deoxidation of molten steel, in kg / t of molten steel. α is the proportion of silicon element used for deoxidation, where α is 50% - 55%. β is the proportion of aluminum element used for deoxidation, where β is 75% - 85%. w[Al] is the mass percentage of aluminum element in the aluminum alloy.

[0058] 2.4) Pre-calculate the mass of ferrosilicon added, m SiFe and the mass of silicomanganese alloy added, m SiMn . Ferrosilicon or silicomanganese alloy is used to provide silicon element for pre-deoxidation of molten steel. m SiFe is calculated by Formula 2, and m SiMn is calculated by Formula 3.

[0059]

[0060]

[0061] In Formulas 2 - 3, m SiFe is the mass of ferrosilicon added when all silicon elements are provided by ferrosilicon, in kg / t of molten steel. m SiMn is the mass of silicomanganese alloy added when all silicon elements are provided by silicomanganese alloy, in kg / t of molten steel. m Si is the mass of silicon element added for pre-deoxidation of molten steel, in kg / t of molten steel. w[Si] SiFe is the mass percentage of silicon element in ferrosilicon. w[Si] SiMn is the mass percentage of silicon element in silicomanganese alloy.

[0062] 2.5) Calculate the benefit EP1 when using ferrosilicon for pre-deoxidation. EP1 is calculated by Formula 4

[0063] EP1 = Δm Al × p Al - m SiFe × p SiFe Formula 4;

[0064] In Formula 4, EP1 is the benefit of ferrosilicon pre-deoxidation, in yuan / t of molten steel. p Al is the price of aluminum alloy, in yuan / kg. p SiFe is the price of ferrosilicon, in yuan / kg.

[0065] 2.6) Calculate the benefit when using silicomanganese alloy for pre-deoxidation. After pre-deoxidation with silicomanganese alloy, the mass percentage of manganese in molten steel will increase, which can reduce the mass of other ferromanganese alloys added. If the ferromanganese alloy reduced is high-carbon ferromanganese, the benefit of silicomanganese alloy pre-deoxidation, EP2, is calculated by Formula 5. If the ferromanganese alloy reduced is medium-carbon ferromanganese, the benefit of silicomanganese alloy pre-deoxidation, EP3, is calculated by Formula 6.

[0066]

[0067]

[0068] In formulas 5 and 6, EP2 is the pre-deoxidation benefit of silicon-manganese alloy when the ferromanganese alloy is high carbon ferromanganese, and the unit is yuan / ton steel; EP3 is the pre-deoxidation benefit of silicon-manganese alloy when the ferromanganese alloy is medium carbon ferromanganese, and the unit is yuan / ton steel. HCM is the price of high carbon ferromanganese, in yuan / kg, p MCM is the price of medium carbon ferromanganese, in yuan / kg, p SiMn is the price of silicon manganese alloy, in yuan / kg, w[Mn] SiMn w[Mn] is the mass percentage of manganese in silicon-manganese alloy. HCM w[Mn] is the mass percentage of manganese in high carbon ferromanganese. MCM is the mass percentage of manganese in medium carbon ferromanganese, r1 is the manganese recovery rate during pre-deoxidation of silicon manganese alloy, r1 is 80% to 85%, r2 is the manganese recovery rate during alloying of high carbon ferromanganese or medium carbon ferromanganese, when the molten steel deoxidation method is semi-deoxidation, r2 is 80% to 85%, when the molten steel deoxidation method is full deoxidation, r2 is 89% to 96%;

[0069] 2.7) Determine the type and mass of silicon-containing alloy for pre-deoxidation of molten steel. Ferrosilicon is used as the silicon-containing alloy for pre-deoxidation of molten steel, and the mass added is m SiFe ; Use formulas 7 to 8 to calculate the mass percentage of manganese in the molten steel after pre-deoxidation when the manganese recovery rate in the silicon-manganese alloy is 100% w[Mn] max The carbon content w[C] in the molten steel after pre-deoxidation when the carbon recovery rate in the silicon-manganese alloy is 100% max ,

[0070]

[0071]

[0072] In formulas 7 and 8, w[Mn] max w[C] is the mass percentage of manganese in the molten steel after pre-deoxidation when the manganese recovery rate in the silicon-manganese alloy is 100%. max w[Mn] is the mass percentage of carbon in the molten steel after pre-deoxidation when the carbon recovery rate in the silicon-manganese alloy is 100%. 终点 w[C] is the mass percentage of manganese in molten steel at the end of converter blowing, SiMn is the mass percentage of carbon in silicon-manganese alloy, w[C] 终点 The carbon content of molten steel at the end of converter blowing is expressed as a percentage by mass.

[0073] When EP1<EP2 and w[Mn] max<Upper limit of manganese mass percentage in steel grade w[Mn] 上限 and w[C] max <Upper limit of carbon mass percentage in steel grade w[C] 上限 When, the silicon-containing alloy for preliminary deoxidation of molten steel uses ferrosilicon-manganese alloy, and the added mass is m SiMn ;

[0074] When EP1 < EP3 and w[Mn] max <Upper limit of manganese mass percentage in steel grade w[Mn] 上限 and w[C] max <Upper limit of carbon mass percentage in steel grade w[C] 上限 and the mass of high-carbon ferromanganese that can be added When, the silicon-containing alloy for preliminary deoxidation of molten steel uses ferrosilicon-manganese alloy, and the added mass is m SiMn ;

[0075] 3) At the end of tapping, when the slag entrainment detector detects a large amount of slag in the molten steel stream, tapping ends; then ladle slag deoxidizer is added to the ladle for ladle top slag deoxidation.

[0076] Table 1 Chemical compositions of alloys used in the examples of the present invention, unit: mass percentage.

[0077]

[0078]

[0079] Note: "-" in Table 1 indicates that no requirement is made for this element.

[0080] Table 2 Process parameters of silicon element dosage for preliminary deoxidation of molten steel during converter tapping in the examples of the present invention

[0081]

[0082] Table 3 Data of reduction amount of aluminum alloy for final deoxidation of molten steel during converter tapping in the examples of the present invention

[0083]

[0084] Table 4 Dosage data of using ferrosilicon or ferrosilicon-manganese alloy as the source of silicon element in the examples of the present invention

[0085]

[0086] Table 5 Dosage data of high-carbon ferromanganese or medium-carbon ferromanganese that can be reduced by ferrosilicon-manganese alloy in the examples of the present invention

[0087]

[0088]

[0089] Table 6 Data on the pre-deoxidation benefits of ferrosilicon and the pre-deoxidation benefits of silicomanganese alloy in the embodiments of the present invention

[0090]

[0091] Table 7 Selection condition parameters of silicon-containing alloy types for pre-deoxidizing molten steel during converter tapping in the embodiments of the present invention

[0092]

[0093] Table 8 Pre-deoxidation process of molten steel during converter tapping in the embodiments of the present invention

[0094]

[0095] Table 9 Pre-deoxidation effect of molten steel during converter tapping in the embodiments of the present invention

[0096]

[0097]

[0098] In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A molten steel deoxidation method for converter tapping, where w[C] > 0.03% in the steel grade, characterized in that, The method described above includes the following steps: 1) Converter blowing, using a top-bottom combined blowing converter to smelt molten steel, controlling the w[C] in the molten steel at the end of converter blowing 终点 to be 0.03% - 0.07%, and the temperature of the molten steel at the end of converter blowing ≥ 1600 °C; 2) Tapping the converter. After the molten steel covers the bottom of the ladle, metallurgical lime is added. When the amount of molten steel tapped from the converter reaches 20% - 25% of the total amount of molten steel, a silicon-containing alloy for preliminary deoxidation is added to the molten steel in the ladle at one time for preliminary deoxidation of the molten steel. 20 - 40 s after the addition of the silicon-containing alloy, an aluminum alloy and an alloy for alloying are added to the molten steel in the ladle at one time for final deoxidation and alloying of the molten steel, and the composition of the molten steel after tapping is adjusted to the set value. The method for determining the silicon-containing alloy includes the following steps: 2.1) Collecting data. After the converter heat starts, collect the designed composition of the steel grade, the deoxidation method of the converter, and the refining method of the molten steel for the current heat. 2.2) Determine the mass m of silicon element added for preliminary deoxidation of molten steel Si , m Si According to the upper limit mass percentage w[Si] of silicon in the steel grade 上限 and the molten steel refining method, it is divided into six intervals. When w[Si] 上限 <0.03%, m Si is 0 kg / t of steel, that is, silicon preliminary deoxidation is not adopted; when the molten steel is not treated by LF ladle refining furnace and w[Si] 上限 is 0.03 - 0.05%, m Si is 0.25 - 0.32 kg / t of steel; when the molten steel is not treated by LF ladle refining furnace and w[Si] 上限 >0.05%, m Si is 0.54 - 0.66 kg / t of steel; when the molten steel is treated by LF ladle refining furnace and w[Si] 上限 ≤0.05%, m Si is 0 kg / t of steel, that is, silicon preliminary deoxidation is not adopted; when the molten steel is treated by LF ladle refining furnace and w[Si] 上限 is in the interval (0.05%, 0.1%], m Si is 0.25 - 0.32 kg / t of steel; when the molten steel is treated by LF ladle refining furnace and w[Si] 上限 >0.1%, m Si is 0.54 - 0.66 kg / t of steel; 2.3) Calculate the reduced mass Δm of the aluminum alloy used for final deoxidation of the molten steel Al , Δm Al is calculated by Formula 1 In Formula 1, Δm Al is the mass reduction of aluminum alloy, with the unit of kg / t steel, m Si is the added mass of silicon element used for pre-deoxidation of molten steel, with the unit of kg / t steel, α is the proportion of silicon element used for deoxidation, α is 50% - 55%, β is the proportion of aluminum element used for deoxidation, β is 75% - 85%, and w[Al] is the mass percentage of aluminum element in the aluminum alloy; 2.4) Pre-calculate the mass m of ferrosilicon added SiFe and the mass m of silicomanganese alloy added SiMn , where ferrosilicon or silicomanganese alloy is used to provide silicon elements for pre-deoxidizing the molten steel, and m SiFe is calculated by Formula 2, and m SiMn is calculated by Formula 3 In Formulas (2) to (3), m SiFe is the mass of ferrosilicon added when all the silicon element is provided by ferrosilicon, with the unit of kg / t of molten steel, m SiMn is the mass of ferrosilicon manganese alloy added when all the silicon element is provided by ferrosilicon manganese alloy, with the unit of kg / t of molten steel, m Si is the mass of silicon element added for pre-deoxidation of molten steel, with the unit of kg / t of molten steel, w[Si] SiFe is the mass percentage of silicon element in ferrosilicon, w[Si] SiMn is the mass percentage of silicon element in ferrosilicon manganese alloy; 2.5) Calculating the benefit EP1 when ferrosilicon is used for preliminary deoxidation, and EP1 is calculated by Formula Four. EP1 = Δm Al × p Al - m SiFe × p SiFe Equation Four; In Formula 4, EP1 is the pre-deoxidation benefit of ferrosilicon, with the unit of yuan / ton of steel, p Al is the price of aluminum alloy, with the unit of yuan / kg, p SiFe is the price of ferrosilicon, with the unit of yuan / kg; 2.6) Calculating the benefit when silicomanganese alloy is used for preliminary deoxidation. After preliminary deoxidation with silicomanganese alloy, the mass percentage of manganese in the molten steel will increase, and the addition mass of other ferromanganese alloys can be reduced. If the reduced ferromanganese alloy is high-carbon ferromanganese, the benefit EP2 of preliminary deoxidation with silicomanganese alloy is calculated by Formula Five; if the reduced ferromanganese alloy is medium-carbon ferromanganese, the benefit EP3 of preliminary deoxidation with silicomanganese alloy is calculated by Formula Six. In Formulas 5 to 6, EP2 is the pre-deoxidation benefit of silicomanganese alloy when the reduced ferromanganese alloy is high-carbon ferromanganese, with the unit of yuan / ton of steel. EP3 is the pre-deoxidation benefit of silicomanganese alloy when the reduced ferromanganese alloy is medium-carbon ferromanganese, with the unit of yuan / ton of steel. p HCM is the price of high-carbon ferromanganese, with the unit of yuan / kg. p MCM is the price of medium-carbon ferromanganese, with the unit of yuan / kg. p SiMn is the price of silicomanganese alloy, with the unit of yuan / kg. w[Mn] SiMn is the mass percentage of manganese element in silicomanganese alloy. w[Mn] HCM is the mass percentage of manganese element in high-carbon ferromanganese. w[Mn] MCM is the mass percentage of manganese element in medium-carbon ferromanganese. r1 is the recovery rate of manganese element during the pre-deoxidation of silicomanganese alloy, and r1 is 80% - 85%. r2 is the recovery rate of manganese element during the alloying of high-carbon ferromanganese or medium-carbon ferromanganese. When the deoxidation method of molten steel is semi-deoxidation, r2 is 80% - 85%. When the deoxidation method of molten steel is full-deoxidation, r2 is 89% - 96%. 2.7) Determine the type and addition mass of the silicon-containing alloy for pre-deoxidizing molten steel. It is preset to use ferrosilicon as the silicon-containing alloy for pre-deoxidizing molten steel, and the addition mass is m SiFe ; Use Formulas 7-8 to calculate the mass percentage content w[Mn] of manganese in the molten steel after pre-deoxidation when the manganese recovery rate in the silicomanganese alloy is 100% max and the mass percentage content w[C] of carbon in the molten steel after pre-deoxidation when the carbon recovery rate in the silicomanganese alloy is 100% max , In Formulas Seven to Eight, w[Mn] max is the mass percentage of manganese in the molten steel after pre-deoxidation when the manganese recovery rate in ferrosilicon manganese alloy is 100%, w[C] max is the mass percentage of carbon in the molten steel after pre-deoxidation when the carbon recovery rate in ferrosilicon manganese alloy is 100%, w[Mn] 终点 is the mass percentage of manganese in the molten steel at the end of converter blowing, w[C] SiMn is the mass percentage of carbon element in ferrosilicon manganese alloy, w[C] 终点 is the mass percentage of carbon in the molten steel at the end of converter blowing; When EP1 < EP2 and w[Mn] max <Upper limit of manganese mass percentage w[Mn] for steel grade 上限 and w[C] max <Upper limit of carbon mass percentage w[C] for steel grade 上限 at that time, ferrosilicon manganese alloy is used for pre-deoxidation of molten steel, and the added mass is m SiMn ; When EP1 < EP3 and w[Mn] max <Upper limit of manganese mass percentage w[Mn] for steel grade 上限 and w[C] max <Upper limit of carbon mass percentage w[C] for steel grade 上限 and the mass of ferromanganese with high carbon that can be added When, the silicon-manganese alloy is used as the silicon-containing alloy for preliminary deoxidation of molten steel, and the added mass is m SiMn ; 3) Ending the tapping. When the slag detector detects that a large amount of slag is entrained in the steel stream, the tapping ends; then a ladle slag deoxidizer is added to the ladle for deoxidizing the top slag of the ladle.

2. The molten steel deoxidation method for converter tapping according to claim 1, characterized in that, The mass percentage of the chemical composition of the ferrosilicon is: Si: 73% - 76%, and the balance is iron and impurities.

3. The molten steel deoxidation method for converter tapping as claimed in claim 1, characterized in that, The mass percentage of the chemical composition of the silicomanganese alloy is: Mn: 64% - 67%, Si: 16% - 20%, and the balance is iron and impurities.

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