CN109868336B - Method for controlling manganese content in molten steel - Google Patents
Method for controlling manganese content in molten steel Download PDFInfo
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Abstract
The invention provides a method for controlling the manganese content in molten steel, which comprises the following steps: (1) adding low-phosphorus manganese-rich ore fine powder and low-phosphorus iron ore fine powder in the process of blending the sinter to obtain the sinter; (2) smelting the manganese-rich molten iron by using sintered ores to obtain the manganese-rich molten iron with the manganese content of 15-25%, the carbon content of 3-5%, the iron content of 70-80%, the P content of less than or equal to 0.07% and the S content of less than 0.03%; (3) adding molten iron with conventional components into a converter, controlling the blowing end temperature of the molten steel to be more than or equal to 1670 ℃, and controlling the phosphorus content of the molten steel to be less than or equal to 0.017 percent at the blowing end; (4) before tapping of a converter, adding manganese-rich molten iron into an empty ladle; (5) and when the steel is tapped to 1/2-3/4, adding silicon alloy into the molten steel, and supplementing manganese alloy or carbon powder. The molten steel obtained by the method has high purity, the cost and energy are greatly saved compared with the existing method, and the recovery rate of manganese in manganese ore can reach more than 80%.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for controlling manganese content in molten steel.
Background
Manganese is an alloy element with the widest consumption in the existing steel, the proper amount of manganese can effectively improve the strength of the steel, eliminate the influence of sulfur on the hot brittleness of the steel, improve the hot workability of the steel, and simultaneously, the plasticity and the impact toughness of the steel are not remarkably reduced, and the content of manganese in the common carbon steel is about 0.3-1.5%. At present, the manganese content in the deformed steel with the largest steel grade yield is 1.0-1.5 percent generally.
At present, the manganese content in molten steel is controlled by adding ferromanganese and silicon-manganese into the molten steel, the price of high-carbon ferromanganese containing 64% of manganese is about 7000 yuan/ton, the price of silicon-manganese containing 64% of manganese is about 8000 yuan/ton, the price is high, the consumption of manganese alloy is a large part of the alloy cost of a steel mill, and the average amount of manganese added to 1% of molten steel is about 120 yuan/ton. The price of manganese ore is very cheap at present, and the price of manganese ore containing 50% of manganese is about 1500 yuan/ton at present. Compared with ferromanganese, the cost for increasing manganese of molten steel by adopting manganese ore can be reduced by 70%. At present, the conventional manganese increasing mode of a steel mill is to transport hot manganese alloy (silicon manganese alloy, high-carbon ferromanganese alloy, medium-carbon ferromanganese alloy, low-carbon ferromanganese alloy and the like) to the steel mill after cooling, wherein the manganese alloy is high in price and alloy cost, and the heat of the hot manganese alloy is lost, so that energy waste is caused.
However, if the manganese ore is directly added into molten steel in the converter smelting process, the recovery rate of manganese is low, most of manganese enters the slag in the form of MnO, and the recovery rate of manganese is about 10-30%. The invention patent with application number 201310478304.4 (a smelting method for improving the manganese content of molten steel at the end point of a small converter) provides a process which can effectively and directly add manganese ore on the small converter aiming at the characteristics of the small converter. However, according to the technology disclosed in the patent, the recovery rate of Mn in manganese ore can only reach 37%, and the recovery rate of Mn is still low.
Disclosure of Invention
Aiming at the problems, the invention provides a method for controlling the manganese content in molten steel, which can increase manganese in the molten steel at low cost.
A method for controlling the content of manganese in molten steel comprises the following steps,
(1) adding low-phosphorus manganese-rich ore fine powder and low-phosphorus iron ore fine powder into the sintered ore, wherein the mass percentage of the low-phosphorus manganese-rich ore fine powder in the sintered ore is 15-25%;
(2) smelting the manganese-rich molten iron by using the sintered ore in blast furnace production to obtain the manganese-rich molten iron with the manganese content of 15-25%, the carbon content of 3-5%, the iron content of 70-80%, the P content of less than or equal to 0.07% and the S content of less than 0.03%, wherein the temperature of the manganese-rich molten iron is more than or equal to 1500 ℃ when the blast furnace is tapped;
(3) before converter blowing, adding molten iron with conventional components into a converter, blowing the molten iron according to a converter steelmaking process in the converter blowing process, controlling the blowing end temperature of the molten steel to be more than or equal to 1670 ℃, and controlling the phosphorus content of the blowing end of the molten steel to be less than or equal to 0.017% to obtain the molten steel;
(4) before tapping of the converter, adding the manganese-rich molten iron obtained in the step (2) into an empty ladle, calculating the adding amount of the manganese-rich molten iron according to carbon and manganese components in steel, and then opening a ladle bottom argon blowing system;
(5) and adjusting the bottom argon blowing valve of the ladle to the maximum opening degree in the tapping process of the converter, forcibly stirring the molten steel, and adding silicon alloy and supplementing carbon powder or manganese alloy into the molten steel when the tapping reaches 1/2-3/4.
When a steel plant produces the molten iron rich in manganese, a small blast furnace with low yield is selected to produce the molten iron rich in manganese, and the total yield of steel products is not greatly influenced.
Preferably, the sintered ore also comprises 57-67% by mass of low-phosphorus iron ore fine powder; lime with the mass fraction of 4-6%, dolomite with the mass fraction of 7-9%, and coke powder or anthracite with the mass fraction of 4-5%.
Preferably, the preparation process of the low-phosphorus manganese-rich ore fine powder in the step (1) comprises the following steps: grinding the low-phosphorus manganese-rich ore to the granularity of less than or equal to 0.038mm in the ore dressing process, separating phosphate particles from manganese ore particles in the low-phosphorus manganese ore, and then carrying out magnetic separation to obtain the low-phosphorus manganese ore fine powder with the Mn of more than or equal to 50%, the P of less than or equal to 0.040% and the S of less than or equal to 0.3%.
Preferably, the process for preparing the low-phosphorus iron ore concentrate powder in the step (1) comprises the following steps: grinding the low-phosphorus iron ore concentrate to a granularity of less than or equal to 0.038mm in the ore dressing process, separating phosphate particles from iron mineral particles in the low-phosphorus iron ore concentrate, and then carrying out magnetic separation to obtain the low-phosphorus iron ore fine powder with Fe of more than or equal to 62%, P of less than or equal to 0.07% and S of less than or equal to 0.3%.
Preferably, the opening degree of the bottom-blown gas flow control valve of the bottom-blown argon system in the step (4) is controlled to be 20-30% of the maximum valve opening degree.
Preferably, the method for calculating the blending amount of the manganese-rich molten iron in the step (4) comprises the following steps: calculating the amount of ferromanganese-rich water which is required to be added to the target carbon content according to the carbon content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the carbon content of the ferromanganese-rich molten iron and the target carbon content of the steel grade, and recording as X1; calculating the manganese-rich molten iron amount which is required to be added to the target manganese content according to the manganese content, the weight of the molten steel, the manganese content of the manganese-rich molten iron and the target manganese content of the steel grade in the smelting end point of the converter, and marking as X2; and the smaller value of the actual adding amount of the manganese-rich molten iron is X1 or X2.
The specific calculation formula of the amount of the ferromanganese-rich water X1 to be added is as follows: x1 ═ target carbon content of steel grade-carbon content in molten steel composition at the end of converter smelting) × molten steel weight/(carbon content of manganese-rich molten iron-target carbon content of steel grade);
the specific calculation formula of the amount of the ferromanganese-rich water X2 to be added is as follows: x2 ═ target manganese content of steel grade-manganese content in molten steel composition at the end of converter smelting) × molten steel weight/(manganese content of manganese-rich molten iron-target manganese content of steel grade).
In order to avoid the manganese content or the carbon content in the molten steel from exceeding the target component requirement, the smaller value of X1 and X2 is taken as the actual adding amount of the manganese-rich molten iron. And (3) after the manganese-rich molten iron is added, for the carbon content or the manganese content which still cannot meet the component requirement of the target molten steel, adding carbon powder or manganese alloy into the molten steel when the steel is tapped to 1/2-3/4 in the step (5).
Further preferably, when X1 is less than X2, the manganese alloy needs to be supplemented, and the calculation method of the weight of the manganese alloy needs to be supplemented comprises the following steps: calculating the weight of the manganese alloy to be supplemented according to the difference between X2 and X1, the manganese content of the manganese-rich molten iron, the mass percentage of manganese in the manganese alloy and the recovery rate of manganese in the manganese alloy adding process, wherein the specific calculation formula is as follows: the manganese alloy weight is (X2-X1) × manganese content of the manganese-rich molten iron/(manganese content in the manganese alloy × recovery rate of manganese in the process of adding the manganese alloy);
when X1 is more than X2, the carbon powder needs to be supplemented, and the weight of the carbon powder needs to be supplemented is calculated by the following method: calculating the weight of the carbon powder to be supplemented according to the difference value of X1 and X2, the carbon content of the manganese-rich molten iron and the recovery rate in the carbon powder adding process, wherein the specific calculation formula is as follows: the carbon powder weight is (X1-X2) × the carbon content of the manganese-rich molten iron/(the recovery rate of carbon in the process of adding the carbon powder).
Preferably, in the step (3), the actual charging amount of the molten iron is reduced by a smaller one of the values of X1 and X2 calculated in the previous heat of the same steel grade than the standard charging amount before converter blowing.
And (5) in the converter tapping process, part of carbon and manganese in the manganese-rich molten iron are consumed in the deoxidation reaction, and the rest carbon and manganese play an alloying role.
The contents of the components in the invention are mass percent except for special specification.
The invention has the beneficial effects that:
1. the price of manganese ore is far lower than that of ferromanganese, and by adopting the technology provided by the application, the recovery rate of manganese in the manganese ore can reach more than 80%, and the manganese-rich molten iron can be obtained at low cost. In the converter tapping process, manganese is added to molten steel by utilizing manganese-rich molten iron, and the cost of 1% of manganese in the molten steel is increased by 30-50 yuan per ton of steel; if manganese is added to the molten steel by the ferromanganese alloy, the cost required for increasing 1% of manganese in the molten steel is 110-130 yuan per ton of steel; the manganese alloy cost can be reduced by about 70% by adopting the manganese-rich molten iron to add manganese to the molten steel.
2. The recovery rate of manganese in the method can reach more than 80 percent, and is obviously improved compared with the prior method of directly adding manganese ore into molten steel.
3. The manganese-rich molten iron contains 3-5% of carbon, the carbon plays the role of a deoxidizer and a carbon alloy, the consumption of the deoxidizer can be reduced, the deoxidized product is gaseous CO, and the gaseous CO is combusted at the temperature of molten steel (about 1600 ℃) to generate CO2When entering the air, the deoxidizer will not remain in the molten steel, and the molten steel has high purity.
4. The conventional manganese increasing mode is as follows: the alloy plant produces the thermal manganese alloy, then transports the thermal manganese alloy to the steel plant after cooling for supplying molten steel to add manganese, under this mode, the heat loss of thermal manganese alloy causes the waste of energy. The temperature of the liquid iron rich in manganese is 1300-1500 ℃ when the liquid iron rich in manganese is conveyed to a converter area (the temperature of the liquid iron rich in manganese is more than 1500 ℃ when a blast furnace is discharged, and part of heat is dissipated in the processes of discharging and conveying), and the temperature of the liquid steel is reduced due to the fact that the liquid iron rich in manganese is used for increasing the manganese of the liquid steel in a hot state.
5. At present, 10 blast furnaces are commonly used in large-scale iron and steel enterprises, and the blast furnace with the lowest scale is taken out and is specially used for producing the molten manganese-rich iron, and the molten manganese-rich iron is finally converted into steel without influencing the total yield of the steel.
Detailed Description
The method for controlling the manganese content in the molten steel comprises the following steps:
1. a small-sized blast furnace with low yield is selected in a steel plant to produce the manganese-rich molten iron, the low-phosphorus manganese-rich ore fine powder and the low-phosphorus iron ore fine powder are added into the sintered ore used by the blast furnace in the material blending process, the mass percentage of the low-phosphorus manganese-rich ore fine powder in the sintered ore is 15-25%, and the mass percentage of the low-phosphorus iron ore fine powder in the sintered ore is 57-67%.
The manufacturing process of the low-phosphorus manganese ore fine powder comprises the following steps: grinding the low-phosphorus manganese-rich ore to the granularity of less than or equal to 0.038mm in the ore dressing process, separating phosphate particles from manganese ore particles in the low-phosphorus manganese ore, and then carrying out magnetic separation to obtain the low-phosphorus manganese ore fine powder with the Mn of more than or equal to 50%, the P of less than or equal to 0.040% and the S of less than or equal to 0.3%.
The manufacturing process of the low-phosphorus iron ore fine powder comprises the following steps: grinding the low-phosphorus iron ore concentrate to a granularity of less than or equal to 0.038mm in the ore dressing process, separating phosphate particles from iron mineral particles in the low-phosphorus iron ore concentrate, and then carrying out magnetic separation to obtain the low-phosphorus iron ore fine powder with Fe of more than or equal to 62%, P of less than or equal to 0.07% and S of less than or equal to 0.3%.
The sintering ore raw material also comprises 4-6% by mass of lime, 7-9% by mass of dolomite and 4-5% by mass of coke powder or anthracite.
2. In the blast furnace production, the sintered ore is used for smelting molten iron to obtain manganese-rich molten iron with the manganese content of 15-25%, the carbon content of 3-5%, the iron content of 70-80%, the P content of less than or equal to 0.07% and the S content of less than 0.03%, and the temperature of the molten iron is more than or equal to 1500 ℃.
3. Before converter blowing, adding molten iron with common conventional components into a converter, blowing the molten iron according to a converter steelmaking process in the converter blowing process, controlling the blowing end temperature of the molten steel to be more than or equal to 1670 ℃, and controlling the phosphorus content of the blowing end of the molten steel to be less than or equal to 0.017% to obtain the molten steel.
4. Before tapping of a converter, adding a part of manganese-rich molten iron into an empty ladle, calculating the adding amount of the manganese-rich molten iron according to carbon and manganese components in steel, and then opening a ladle bottom argon blowing system to control the opening degree of a bottom blowing gas flow control valve to be 20-30%.
The method for calculating the adding amount of the manganese-rich molten iron in the step 4 comprises the following steps: calculating the amount of ferromanganese-rich water which is required to be added to the target carbon content according to the carbon content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the carbon content of the ferromanganese-rich molten iron and the target carbon content of the steel grade, and recording as X1; and calculating the amount of the ferromanganese-rich water required to be added to the target manganese content according to the manganese content, the weight of the molten steel, the manganese content of the ferromanganese-rich water and the target manganese content of the steel grade at the smelting end point of the converter, and marking the amount as X2, wherein the actual adding amount of the ferromanganese-rich water is the smaller one of the X1 value and the X2 value.
5. And (3) adjusting the bottom argon blowing valve of the ladle to the maximum during the tapping process of the converter, carrying out strong stirring on the molten steel, adding silicon alloy into the molten steel when the tapping is carried out to 1/2-3/4, and supplementing manganese alloy or carbon powder. In the converter tapping process, part of carbon and manganese in the manganese-rich molten iron are consumed in the deoxidation reaction, and the rest carbon and manganese play an alloying role.
The molten iron added with conventional components in the step (3) refers to the actual addition amount of the molten iron, and the standard addition amount of the molten iron is (the nominal tonnage of the converter/the recovery rate of the iron and steel materials in the smelting process of the converter) -the addition amount of scrap steel.
In the step 3, before the converter is blown, the actual charging amount of the molten iron is reduced by a smaller value of X1 and X2 compared with the standard charging amount, and the values of X1 and X2 of the current heat cannot be calculated yet when the molten iron is added. Because the actual charging amount of the molten iron is not required to be accurate, and the normal smelting of the converter cannot be influenced by controlling the charging amount of the molten iron within the error of 5%, the actual charging amount of the molten iron of the current furnace is guided by using the values of the manganese-rich molten iron adding amount X1 and X2 calculated in the previous furnace of the same steel type. If the steel grade is smelted for the first time, the amount of molten iron added during the smelting of a converter can be referred to similar steel grades, wherein the target composition difference of carbon in molten steel is less than 0.05 percent and the target composition difference of manganese is less than 0.3 percent.
The actual charging amount of the molten iron of the furnace is guided by using the values of the molten iron adding amount X1 and X2 calculated by the previous furnace of the same steel grade, so that the phenomenon that the molten iron is added too much, and the molten steel smelted by a converter is too much and exceeds the capacity of a steel ladle to cause the overflow of the molten steel is avoided.
Mineral separation and phosphorus reduction: the mineral and phosphorus in the ore are quite complicated in intercalation relationship, the forms of phosphorus existing in the ore are various, but the intercalation relationship of phosphorus and iron minerals can be summarized into two types, one type is that phosphorus and iron both appear as independent minerals, the other type is that phosphorus exists in an iron mineral in an ion adsorption state, and for phosphorus existing in the first type, metal minerals and phosphorus ore substances can be completely dissociated by fine grinding, and then the metal minerals and the phosphorus ore substances are separated by a magnetic separation method. And grinding the low-phosphorus manganese-rich ore and the low-phosphorus iron ore to the granularity of less than 0.035mm, separating the phosphate ore particles existing in the first form from the metal mineral particles, and after magnetic separation, the phosphate ore particles enter tailings, wherein the phosphorus removal rate can reach 40-50%.
Controlling the content of phosphorus in molten steel: the phosphorus content in the iron-making raw materials is limited, the phosphorus content range in the manganese-rich molten iron is less than or equal to 0.07 percent, the manganese content range is 15-25 percent, and through calculation, if 0.5-1.5 percent of manganese is added to the molten steel by the manganese-rich molten iron, 0.0014-0.007 percent of phosphorus is correspondingly added to the molten steel. Under the condition that P in molten steel is controlled to be less than or equal to 0.017 percent before converter tapping, after the molten steel is added with the manganese-rich molten iron, the phosphorus content in the molten steel is as follows: p is more than or equal to 0.0184 percent and less than or equal to 0.024 percent, the phosphorus content in the composition range can meet the requirements of HRB 400-HRB 600 deformed steel, Q345B, 45 steel, 50 steel, 65Mn and 45Mn, and the steel with partial marks is the steel with the maximum output at present and accounts for more than 60 percent of the total amount of the steel.
Controlling the temperature of molten steel: the content of manganese in the manganese-rich molten iron is 15-25%, and if the manganese is increased by 0.5-1.5% of the molten steel by the manganese-rich molten iron, the adding amount of the manganese-rich molten iron is 2-10% of the weight of the molten steel by calculation. The temperature of the manganese-rich molten iron is about 1300-1500 ℃, the temperature of the molten steel is about 1550-1650 ℃, the temperature of the molten steel can be reduced by 5-20 ℃ after the manganese of the molten steel is increased by adopting the manganese-rich molten iron, and the temperature drop caused by the manganese increase of the molten steel by adopting the manganese-rich molten iron can not reduce the temperature of the molten steel.
And (3) deoxidation effect: the manganese-rich molten iron contains 3-5% of carbon, and the oxygen content balanced with 3-5% of C in a carbon-oxygen balance reaction formula is less than 10ppm, so the manganese-rich molten iron can exert a great deoxidation effect, and the consumption of deoxidation alloy can be saved by more than 50%.
Carbon powder consumption: the manganese-rich molten iron contains 3-5% of carbon, and if the adding amount of the manganese-rich molten iron is 2-10% of the weight of the molten steel, the carbon content of the molten steel can be increased by 0.06-0.5%, the carbon content requirement of most steel grades can be met, and the adding amount of carbon powder is saved.
Setting the manganese-carbon ratio in the manganese-rich molten iron: manganese in the manganese-rich molten iron: 15-25%, carbon: 3 to 5% of WMn/WC3 to 8, wherein WMn/WCThe mass ratio of manganese to carbon in molten iron or molten steel components is that W in the components of HRB 400-HRB 600 deformed steel, Q345B, 45 steel, 50 steel, 65Mn and 45Mn of common steel grades containing higher manganese at presentMn/WCThe value of (a) is basically 3-8, and manganese-rich molten iron is adoptedCan directly complete the operations of manganese increasing and carbon increasing on the steel grade at the same time.
The present invention will be described in further detail with reference to examples. The invention is not limited to the examples given.
Example 1
1. The total energy of a certain steel plant is 1200 ten thousand tons of steel per year, and 13 blast furnaces are used in total, wherein one blast furnace with the minimum size of 750m is selected3The blast furnace is specially used for producing the manganese-rich molten iron, the low-phosphorus manganese-rich ore fine powder and the low-phosphorus iron ore fine powder are added into the sintered ore used by the blast furnace in the proportioning process, and the low-phosphorus manganese-rich ore fine powder accounts for 15 percent of the mass of the sintered ore. The mass percentage of the low-phosphorus iron ore fine powder in the sintered ore is 67%. The sintered ore also comprises 5 mass percent of lime, 8 mass percent of dolomite and 5 mass percent of the sintered ore. The manufacturing process of the low-phosphorus manganese ore fine powder comprises the following steps: grinding the low-phosphorus manganese-rich ore to the granularity of less than or equal to 0.035mm in the ore dressing process, separating phosphate particles from manganese ore particles in the low-phosphorus manganese ore, and then carrying out magnetic separation to obtain the low-phosphorus manganese ore fine powder with the Mn of more than or equal to 50%, the P of less than or equal to 0.040% and the S of less than or equal to 0.3%.
The manufacturing process of the low-phosphorus iron concentrate powder comprises the following steps: grinding the low-phosphorus iron ore to the granularity of less than or equal to 0.035mm in the ore dressing process to separate phosphate particles and iron mineral particles in the low-phosphorus iron ore, and then carrying out magnetic separation to obtain the low-phosphorus iron ore concentrate powder with the Fe content of more than or equal to 62%, the P content of less than or equal to 0.07% and the S content of less than or equal to 0.3%
2. The sintered ore is used for smelting molten iron in blast furnace production to obtain manganese-rich molten iron with the manganese content of 15 percent, the carbon content of 3 percent, the iron content of 80 percent, the P content of less than or equal to 0.07 percent and the S content of less than 0.03 percent, and the temperature of the molten iron is more than or equal to 1500 ℃.
3. Smelting HRB 400-grade deformed steel by using a converter with nominal tonnage of 80 tons, adding 81 tons of molten iron and 8 tons of scrap steel (the molten iron is low-sulfur molten iron, and the property data of the molten iron are shown in table 2) which are common and conventional components into the converter before converting, converting the molten iron according to a converter steelmaking process in the converter converting process, controlling the converting end point temperature of the molten steel to be more than or equal to 1670 ℃, controlling the converting end point phosphorus content of the molten steel to be less than or equal to 0.017% and obtaining the molten steel; the properties of the converter steel are shown in Table 1.
4. Before tapping of a converter, 4.3 tons of manganese-rich molten iron is added into an empty ladle, the adding amount of the manganese-rich molten iron is calculated according to carbon and manganese components in steel, then a ladle bottom argon blowing system is opened, and the opening degree of a bottom blowing gas flow control valve is controlled to be 20-30%.
The method for calculating the adding amount of the manganese-rich molten iron comprises the following steps: calculating the amount of ferromanganese-rich water which is required to be added to the target carbon content and is marked as X1 according to the carbon content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the carbon content of the ferromanganese-rich molten iron and the target carbon content of the steel grade,
the calculation process is as follows: the carbon content in the molten steel at the smelting end point of the converter is 0.10 percent, the weight of the molten steel is 80 tons, the carbon content of the manganese-rich molten iron is 3 percent, and the target carbon content of the steel grade is 0.25 percent.
X1 ═ 80 ton × 0.25-80 ton × 0.1)/(3-0.25)
X1 t 4.3 ton
And calculating the manganese-rich molten iron amount which needs to be added to the target manganese content according to the manganese content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the manganese content of the manganese-rich molten iron and the target manganese content of the steel grade, and recording as X2.
The calculation process is as follows: the manganese content in the molten steel component at the smelting end point of the converter is 0.07 percent, the weight of the molten steel is 80 tons, the manganese content of the manganese-rich molten iron is 15 percent, and the target manganese content of the steel grade is 1.2 percent.
X2 ═ 80 ton × 1.2-80 ton × 0.07)/(15-1.2)
X2 ═ 6.5 ton
The smaller value of the actual adding amount of the manganese-rich molten iron X1 and X2 is that: the actual adding amount of the manganese-rich molten iron is 4.3 tons.
According to calculation, the actual charging amount of the molten iron needs to be reduced by 4.3 tons compared with the standard charging amount before the converter is blown, and the actual charging amount of the molten iron needs to be reduced by 4.3 tons compared with the standard charging amount when the manganese-rich molten iron is used for carrying out the manganese increasing operation on the molten steel to produce the HRB400 steel grade in the later furnace.
5. And in the process of converter tapping, the argon blowing valve at the bottom of the ladle is adjusted to the maximum, the molten steel is strongly stirred, and 188kg of silicon-iron alloy (FeSi75) and 607kg of silicon-manganese alloy (FeMn64Si18) are added into the molten steel when the steel is tapped to 1/2-3/4.
The amount of silicon-manganese alloy added (X2-X1) × manganese content of manganese-rich molten iron/(manganese content in manganese alloy × recovery rate of manganese during addition of manganese alloy) (6.5 ton-4.3 ton) × 0.15/(0.64 × 0.85) × 607 kg.
The ferrosilicon addition amount (weight of molten steel × silicon content in the target component of molten steel — silicon-manganese alloy addition amount × silicon content in the ferrosilicon-manganese alloy × recovery rate of silicon in the process of adding the ferrosilicon) (80 tons × 0.0025-607kg × 0.18 × 0.8)/(0.75 × 0.8) — 188 kg.
In the converter tapping process, part of carbon and manganese in the manganese-rich molten iron are consumed in the deoxidation reaction, and the rest carbon and manganese play an alloying role.
The mass percent of silicon in the supplemented silicon-manganese alloy is 18 percent, and the mass percent of manganese is 64 percent.
The property data of the HRB400 molten steel which is qualified by 85 tons is shown in the table 3, the molten steel meets the national standard requirements, and the manganese alloy cost is reduced by 50 yuan/ton steel by calculation because the manganese-rich molten iron plays a role in increasing 0.75 percent of manganese in the molten steel and increasing 0.15 percent of carbon in the molten steel.
Example 2
1. The total energy of a certain steel plant is 1200 ten thousand tons of steel per year, and 13 blast furnaces are used in total, wherein one minimum furnace is selected to be 750m3The blast furnace is specially used for producing the manganese-rich molten iron, the sintered ore used by the blast furnace is added with the low-phosphorus manganese-rich ore fine powder and the low-phosphorus iron ore fine powder in the proportioning process, the mass percent of the low-phosphorus manganese-rich ore fine powder in the sintered ore is 25%, and the mass percent of the low-phosphorus iron ore fine powder in the sintered ore is 57%. The sinter also comprises 9 percent of lime to obtain dolomite and 5 percent of coke powder by mass percent of 4 percent.
The manufacturing process of the low-phosphorus manganese ore fine powder comprises the following steps: grinding the low-phosphorus manganese-rich ore to the granularity of less than or equal to 0.035mm in the ore dressing process, separating phosphate particles from manganese ore particles in the low-phosphorus manganese ore, and then carrying out magnetic separation to obtain the low-phosphorus manganese ore fine powder with the Mn of more than or equal to 50%, the P of less than or equal to 0.040% and the S of less than or equal to 0.3%.
The manufacturing process of the low-phosphorus iron concentrate powder comprises the following steps: grinding the low-phosphorus iron ore to the granularity of less than or equal to 0.035mm in the ore dressing process to separate phosphate particles and iron mineral particles in the low-phosphorus iron ore, and then carrying out magnetic separation to obtain the low-phosphorus iron ore concentrate powder with the Fe content of more than or equal to 62%, the P content of less than or equal to 0.07% and the S content of less than or equal to 0.3%
2. In the blast furnace production, the sintered ore is used for smelting molten iron to obtain manganese-rich molten iron with the manganese content of 25 percent, the carbon content of 5 percent, the iron content of 69 percent, the P content of less than or equal to 0.07 percent and the S content of less than 0.03 percent, and the temperature of the molten iron is more than or equal to 1500 ℃.
3. Smelting 65 Mn-brand high-carbon steel by using a converter with nominal tonnage of 120 tons, adding 122 tons of molten iron and 10 tons of scrap steel (the molten iron is low-sulfur molten iron, and the property data of the molten iron are shown in table 2) which are common and conventional components into the converter before converting, converting the molten iron according to a converter steelmaking process in the converter converting process, controlling the converting end point temperature of the molten steel to be more than or equal to 1670 ℃, controlling the converting end point phosphorus content of the molten steel to be less than or equal to 0.017% and obtaining the molten steel; the properties of the converter steel are shown in Table 1.
4. Before tapping of a converter, 4.55 tons of manganese-rich molten iron is added into an empty ladle, the adding amount of the manganese-rich molten iron is calculated according to carbon and manganese components in steel, then a ladle bottom argon blowing system is opened, and the opening degree of a bottom blowing gas flow control valve is controlled to be 20-30%.
The method for calculating the adding amount of the manganese-rich molten iron in the step 4 comprises the following steps: calculating the amount of ferromanganese-rich water which is required to be added to the target carbon content and is marked as X1 according to the carbon content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the carbon content of the ferromanganese-rich molten iron and the target carbon content of the steel grade,
the calculation process is as follows: the carbon content in the molten steel at the smelting end point of the converter is 0.15 percent, the weight of the molten steel is 120 tons, the carbon content of the manganese-rich molten iron is 5 percent, and the target carbon content of the steel grade is 0.65 percent.
X1 ═ 120 ton X0.65-120 ton X0.15)/(5-0.65)
X1 ═ 13.8 ton
And calculating the manganese-rich molten iron amount which needs to be added to the target manganese content according to the manganese content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the manganese content of the manganese-rich molten iron and the target manganese content of the steel grade, and recording as X2.
The calculation process is as follows: the manganese content in the molten steel component at the smelting end point of the converter is 0.09%, the weight of the molten steel is 120 tons, the manganese content of the manganese-rich molten iron is 25%, and the target manganese content of the steel grade is 1.0%.
X2 ═ 120 ton × 1.0-120 ton × 0.09)/(25-1.0)
X2-4.55 ton
The smaller value of the actual adding amount of the manganese-rich molten iron X1 and X2 is that: the actual charging amount of the manganese-rich molten iron is 4.55 tons.
According to calculation, the actual charging amount of the molten iron needs to be reduced by 4.55 tons compared with the standard charging amount before the converter is blown, and the actual charging amount of the molten iron needs to be reduced by 4.55 tons compared with the standard charging amount when the manganese increasing operation is carried out on the molten steel by using the manganese-rich molten iron in the later furnace to produce 65Mn steel grade.
5. During the tapping process of the converter, the argon blowing valve at the bottom of the ladle is adjusted to the maximum, the molten steel is strongly stirred, and 420kg of silicon alloy (FeSi75B) and 661kg of carbon powder are added into the molten steel when the steel is tapped to 1/2-3/4. In the converter tapping process, part of carbon and manganese in the manganese-rich molten iron are consumed in the deoxidation reaction, and the rest carbon and manganese play an alloying role.
The specific calculation formula is as follows: the carbon content of the carbon powder (X1-X2) × manganese-rich molten iron/(the recovery rate of carbon in the process of adding the carbon powder) (13.8-4.55 ton) × 0.05/0.7 (661 kg);
the amount of ferrosilicon added (weight of molten steel × silicon content in the target component of molten steel)/(silicon content in ferrosilicon × recovery rate of silicon in the course of ferrosilicon addition) (120 ton × 0.002)/(0.75 × 0.8) (400 kg).
Finally, 125 tons of qualified 65Mn molten steel is prepared, the property data of the molten steel is shown in a table 3, the molten steel meets the national standard requirements, and the manganese-rich molten iron plays a role in increasing 0.91% of manganese in the molten steel, so that the manganese alloy cost is reduced by 70 yuan per ton of steel through calculation.
Example 3
1. The total energy of a certain steel plant is 1200 ten thousand tons of steel per year, and 13 blast furnaces are used in total, wherein one minimum furnace is selected to be 750m3The blast furnace is specially used for producing the manganese-rich molten iron, the sintered ore used by the blast furnace is added with the low-phosphorus manganese-rich ore fine powder and the low-phosphorus iron ore fine powder in the proportioning process, and the mass percentage of the low-phosphorus manganese-rich ore fine powder in the sintered ore is20 percent. The low-phosphorus iron ore fine powder accounts for 62 percent of the mass of the sinter. The sintered ore also comprises 5 mass percent of lime, 9 mass percent of dolomite and 4 mass percent of anthracite.
The manufacturing process of the low-phosphorus manganese ore fine powder comprises the following steps: grinding the low-phosphorus manganese-rich ore to the granularity of less than or equal to 0.035mm in the ore dressing process, separating phosphate particles from manganese ore particles in the low-phosphorus manganese ore, and then carrying out magnetic separation to obtain the low-phosphorus manganese ore fine powder with the Mn of more than or equal to 50%, the P of less than or equal to 0.040% and the S of less than or equal to 0.3%.
The manufacturing process of the low-phosphorus iron concentrate powder comprises the following steps: grinding the low-phosphorus iron ore to the granularity of less than or equal to 0.035mm in the ore dressing process, separating phosphate particles from iron mineral particles in the low-phosphorus iron ore, and then carrying out magnetic separation to obtain the low-phosphorus iron ore concentrate powder with the Fe content of more than or equal to 62%, the P content of less than or equal to 0.07% and the S content of less than or equal to 0.3%.
2. In the blast furnace production, the sintered ore is used for smelting molten iron to obtain manganese-rich molten iron with the manganese content of 20 percent, the carbon content of 4 percent, the iron content of 75 percent, the P content of less than or equal to 0.07 percent and the S content of less than 0.03 percent, and the temperature of the molten iron is more than or equal to 1500 ℃.
3. Smelting 45-grade high-quality carbon steel by using a converter with nominal tonnage of 100 tons, adding 103 tons of molten iron and 9 tons of scrap steel (the molten iron is low-sulfur molten iron, and the property data of the molten iron are shown in table 2) which are common and conventional components into the converter before converting, converting the molten iron according to a converter steelmaking process in the converter converting process, controlling the converting end point temperature of the molten steel to be more than or equal to 1670 ℃, controlling the converting end point phosphorus content of the molten steel to be less than or equal to 0.017% and obtaining the molten steel; the properties of the converter steel are shown in Table 1.
4. Before tapping of a converter, 3.2 tons of manganese-rich molten iron is added into an empty ladle, the adding amount of the manganese-rich molten iron is calculated according to carbon and manganese components in steel, then a ladle bottom argon blowing system is opened, and the opening degree of a bottom blowing gas flow control valve is controlled to be 20-30%.
The method for calculating the adding amount of the manganese-rich molten iron in the step 4 comprises the following steps: calculating the amount of ferromanganese-rich water which is required to be added to the target carbon content and is marked as X1 according to the carbon content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the carbon content of the ferromanganese-rich molten iron and the target carbon content of the steel grade,
the calculation process is as follows: the carbon content in the molten steel at the smelting end point of the converter is 0.12 percent, the weight of the molten steel is 100 tons, the carbon content of the manganese-rich molten iron is 4 percent, and the target carbon content of the steel grade is 0.45 percent.
X1 ═ 100 ton × 0.45-100 ton × 0.12)/(4-0.45)
X1 ═ 9.5 ton
And calculating the manganese-rich molten iron amount which needs to be added to the target manganese content according to the manganese content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the manganese content of the manganese-rich molten iron and the target manganese content of the steel grade, and recording as X2.
The calculation process is as follows: the manganese content in the molten steel component at the smelting end point of the converter is 0.08 percent, the weight of the molten steel is 100 tons, the manganese content of the manganese-rich molten iron is 20 percent, and the target manganese content of the steel grade is 0.7 percent.
X2 ═ 100 ton × 0.7-100 ton × 0.08)/(20-0.7)
X2 ═ 3.2 ton
The smaller value of the actual adding amount of the manganese-rich molten iron X1 and X2 is that: the actual adding amount of the manganese-rich molten iron is 3.2 tons.
According to calculation, the actual charging amount of the molten iron needs to be reduced by 3.2 tons compared with the standard charging amount before the converter is blown, and the actual charging amount of the molten iron needs to be reduced by 3.2 tons compared with the standard charging amount when the manganese increasing operation is carried out on the molten steel by using the manganese-rich molten iron in the later furnace to produce 65Mn steel grade.
5. During the tapping process of the converter, the argon blowing valve at the bottom of the ladle is adjusted to the maximum, the molten steel is strongly stirred, and 333kg of silicon alloy (FeSi75B) and 360kg of carbon powder are added into the molten steel when the steel is tapped to 1/2-3/4. In the converter tapping process, part of carbon and manganese in the manganese-rich molten iron are consumed in the deoxidation reaction, and the rest carbon and manganese play an alloying role.
The specific calculation formula is as follows: the carbon content of the carbon powder (X1-X2) multiplied by the manganese-rich molten iron/(the recovery rate of carbon in the carbon powder adding process) is (9.5 ton-3.2 ton) multiplied by 0.04/0.7 is 360 kg;
the amount of ferrosilicon added (weight of molten steel × silicon content in the target component of molten steel)/(silicon content in ferrosilicon × recovery rate of silicon in the course of ferrosilicon addition) (100 ton × 0.002)/(0.75 × 0.8) — 333 kg.
103 tons of qualified molten steel with the mark number of 45 are finally prepared, the property data of the molten steel are shown in a table 3, the molten steel meets the national standard requirements, and the manganese-rich molten iron plays a role of increasing 0.62 percent of manganese in the molten steel, so that the manganese alloy cost is reduced by 40 yuan per ton of steel through calculation.
TABLE 1 data of properties of molten steel in converter in examples
TABLE 2 data on the properties (wt%) of the low-sulfur molten iron used in the examples
TABLE 3 Property data (wt%) of molten steel prepared in example
Claims (7)
1. A method for controlling the content of manganese in molten steel is characterized by comprising the following steps,
(1) adding low-phosphorus manganese-rich ore fine powder and low-phosphorus iron ore fine powder into the sintered ore, wherein the mass percentage of the low-phosphorus manganese-rich ore fine powder in the sintered ore is 15-25%;
(2) smelting the manganese-rich molten iron by using the sintered ore in blast furnace production to obtain the manganese-rich molten iron with the manganese content of 15-25%, the carbon content of 3-5%, the iron content of 70-80%, the P content of less than or equal to 0.07% and the S content of less than 0.03%, wherein the temperature of the manganese-rich molten iron is more than or equal to 1500 ℃ when the blast furnace is tapped;
(3) before converter blowing, adding molten iron with conventional components into a converter, blowing the molten iron according to a converter steelmaking process in the converter blowing process, controlling the blowing end temperature of the molten steel to be more than or equal to 1670 ℃, and controlling the phosphorus content of the blowing end of the molten steel to be less than or equal to 0.017% to obtain the molten steel;
(4) before tapping of the converter, adding the manganese-rich molten iron obtained in the step (2) into an empty ladle, calculating the adding amount of the manganese-rich molten iron according to carbon and manganese components in steel, and then opening a ladle bottom argon blowing system;
(5) and adjusting the bottom argon blowing valve of the ladle to the maximum opening degree in the tapping process of the converter, forcibly stirring the molten steel, and adding silicon alloy and supplementing carbon powder or manganese alloy into the molten steel when the tapping reaches 1/2-3/4.
2. The method for controlling the manganese content in molten steel according to claim 1, wherein the manufacturing process of the low-phosphorus manganese-rich ore fine powder in the step (1) is as follows: grinding the low-phosphorus manganese-rich ore to the granularity of less than or equal to 0.038mm in the ore dressing process, separating phosphate particles from manganese ore particles in the low-phosphorus manganese ore, and then carrying out magnetic separation to obtain the low-phosphorus manganese ore fine powder with the Mn of more than or equal to 50%, the P of less than or equal to 0.040% and the S of less than or equal to 0.3%.
3. The method for controlling the manganese content in the molten steel according to claim 1, wherein the manufacturing process of the low-phosphorus iron ore concentrate powder in the step (1) is as follows: grinding the low-phosphorus iron ore concentrate to a granularity of less than or equal to 0.038mm in the ore dressing process, separating phosphate particles from iron mineral particles in the low-phosphorus iron ore concentrate, and then carrying out magnetic separation to obtain the low-phosphorus iron ore fine powder with Fe of more than or equal to 62%, P of less than or equal to 0.07% and S of less than or equal to 0.3%.
4. The method for controlling the manganese content in the molten steel according to claim 1, wherein the method for calculating the adding amount of the manganese-rich molten iron in the step (4) comprises the following steps: calculating the amount of ferromanganese-rich water which is required to be added to the target carbon content according to the carbon content in the molten steel components at the smelting end point of the converter, the weight of the molten steel, the carbon content of the ferromanganese-rich molten iron and the target carbon content of the steel grade, and recording as X1; calculating the manganese-rich molten iron amount which is required to be added to the target manganese content according to the manganese content, the weight of the molten steel, the manganese content of the manganese-rich molten iron and the target manganese content of the steel grade in the smelting end point of the converter, and marking as X2; and the smaller value of the actual adding amount of the manganese-rich molten iron is X1 or X2.
5. The method of controlling manganese content in molten steel according to claim 4,
the specific calculation formula of the amount of the ferromanganese-rich water X1 to be added is as follows: x1 ═ target carbon content of steel grade-carbon content in molten steel composition at the end of converter smelting) × molten steel weight/(carbon content of manganese-rich molten iron-target carbon content of steel grade);
the specific calculation formula of the amount of the ferromanganese-rich water X2 to be added is as follows: x2 ═ target manganese content of steel grade-manganese content in molten steel composition at the end of converter smelting) × molten steel weight/(manganese content of manganese-rich molten iron-target manganese content of steel grade).
6. The method for controlling the manganese content in the molten steel according to claim 5, wherein the carbon powder or the manganese alloy is supplemented in the step (5) in the following weight ratio:
when X1 is less than X2, manganese alloy needs to be supplemented, and the added weight of the manganese alloy is (X2-X1) multiplied by the manganese content of the manganese-rich molten iron/(the manganese content in the manganese alloy multiplied by the recovery rate of manganese in the adding process of the manganese alloy);
and when X1 is more than X2, replenishing carbon powder, wherein the added weight of the carbon powder is (X1-X2) multiplied by the carbon content of the manganese-rich molten iron/(the carbon recovery rate in the carbon powder adding process).
7. The method of claim 4, wherein in the step (3), the actual charge amount of the molten iron is reduced from the standard charge amount by the smaller one of the X1 and X2 values in the previous heat before the converter blows.
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