KR20000042514A - Method of refining electric furnace to upturn terminal carbon - Google Patents

Abstract

The present invention relates to a method for refining a converter for upgrading the end point carbon, the purpose of which is the injection timing of the molten lime and light dolomite (CaO · MgO) and sintered ore as a blowing pattern or an auxiliary raw material in the converter operation of the molten iron and scrap metal By controlling the amount appropriately, the carbon, manganese, and slag in molten steel are effectively controlled, and the phosphorus content in molten iron is stably moved to the slag side during removal so that the phosphorus content is less than 0.025% by weight at the end of the converter while the carbon concentration is not less than 0.04% by weight. It is to provide a converter refining method to maintain the high.

In order to achieve the above object, the present invention adds 8-13 kg of green dolomite (mainly CaCO ₃ and MgCO ₃ ) to 1 ton of the total charge in the converter which left 20-35% of the slag of the previous operation. After slagging the furnace body 3-4 times, slag is coated on the furnace wall, and then 13-20 kg of the furnace body quicklime is charged and charged with scrap metal. After charging the molten iron, the molten iron in the furnace is ignited by Songsan. In the operation method of batch-feeding sintered ore, and splitting the quicklime, light dolomite and sintered ore at 30-70% of total blowing time, and adding a small amount of quicklime and light dolomite at around 80% of the blowdown, the end carbon is increased. The quicklime and sintered ore which is added when ignited by is added to the total amount of tonnes of 25kg or less (including the furnace protection quicklime) and 3-15kg of sintered ore alone or in combination. At least one kind of quicklime, light bovine dolomite and sintered ore injected at 30-70% of the time is selectively added.For 1 ton of full-load, quicklime less than 15kg, light bovine dolomite is divided into 5-15kg, and sintered ore is less than 30kg. At the time of 80-85% of the total blowing time, 1 to 4 kg of quicklime, light micro dolomite, and sintered ore are selectively added to each ton of 1 ton of charge, refining the converter for increasing the end point carbon. Let that point be about.

Description

Converter refining method to raise the end point carbon

The present invention relates to a refining method of raising the converter end carbon in the manufacture of low-lin (P) carbon steel, and more specifically to the method of inputting the quick-burning lime or light dolomite or coolant, which is a blowing pattern or an auxiliary material, in a converter operation using molten iron and scrap metal. The present invention relates to a converter refining method for maintaining a high carbon concentration of at least 0.04% by weight while changing the phosphorus content in molten iron to be slag side while removing it to ensure that the phosphorus content is less than 0.025% by weight at the end of the converter.

In general, the converter works by charging hot metals and scraps, which are the main raw materials, into the converters and at the same time as the Songsan, the molten irons and ignition at the same time. When the phenomenon is called ignition), the main raw material is quicklime (mainly calcium oxide, CaO), light dolomite (mainly calcium oxide and magnesium oxide, CaO · MgO) and sintered ore (main component is iron oxide), fluorite (main component is Calcium fluoride, CaF ₂ ), etc., in order to oxidize carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), titanium (Ti), etc. Collectively referred to as a series of operations to remove.

The molten steel obtained through such converter operation usually requires a phosphorus content of 0.025% by weight or less. Conventionally, carbon has been decarburized from 4.5 wt% to 0.04 wt% (usually 0.025-0.035 wt%) in molten iron (collectively referred to as molten iron and molten steel) to obtain molten steel having a phosphorus content of 0.025 wt% or less.

On the other hand, in general, it is known that the end point of the converter (which refers to the point at which the transfer operation is completed) increases the manganese and phosphorus content as the carbon concentration increases in the carbon range of 0.04% by weight or more. .

However, when the converter terminal carbon is blown at 0.04% by weight or less, there are the following problems.

Valuable metals such as iron and manganese are excessively oxidized in the molten iron, and the amount of slag increases due to the increase of iron oxide and coral manganese in the slag in the form of oxide. As a result, the dissolved oxygen in molten steel rises with excessive loss of converter refractory. In addition, the molten steel in the converter thus made must be re-injected as much as it is oxidized and removed in order to meet the target molten steel composition at the time of tapping, and at this time, the error rate of various ferroalloys is low due to excessive oxygen dissolved in the molten steel. In addition, oxides produced by reacting with dissolved oxygen in ferroalloy and molten steel become inclusions and cause deterioration of the quality of molten steel, and cause various nozzle clogging during the secondary refining and continuous casting process. This leads to deterioration in productivity as well as workability, and there is a problem that causes various defects in products.

On the other hand, in order to efficiently remove phosphorus content in molten iron at 0.025% by weight or less in the converter operation, impurity elements such as carbon, silicon, and manganese in molten iron and calcium oxide (CaO), magnesium oxide (MgO), and silicon oxide in slag ( Stable control of oxide concentrations such as SiO ₂ ), manganese oxide (MnO), and iron oxide (FeO) must be solved essentially.

For example, steels that need to manufacture medium carbon steel (target carbon 0.08-0.30% by weight) and steels that need to be depressurized and refined in the secondary refining process are preferred to raise the converter endpoint carbon, which is the end point for converter operations. Since the oxygen is lowered and the iron oxide content in the slag is reduced, the slag generation amount is reduced. Of course, it is possible to contribute greatly to the steelmaking industry, such as the deoxidation material, carbonaceous material and ferroalloy, the error rate is increased, the generation amount of inclusions is reduced and the quality is improved, thereby greatly reducing cost and stabilizing molten steel quality. In addition, converter refractories have an increased lifespan and a better exit condition, making the operator stable.

Looking at this through the chemical reaction for Tallinn (P) is as follows.

4 (CaO) + 2 [P] + 5 [O] = (4CaO · P ₂ O ₅ )

Here, K is the equilibrium constant of the chemical equation, only depends on the temperature, T is the absolute temperature, a _i means the activity of the i component in the molten iron. In order to remove the phosphorus ([P]) in the molten steel from the reaction equation (1) and the equation (1), the problem of how to effectively react and move the phosphorus in the molten iron to the slag layer during the blowing, and once the slag is moved and slag Phosphorus entering the bed leaves the inevitable task of not allowing it to enter the molten metal until the smelting is completed, which is impossible according to the converter reconstruction theory known to date.

In general, in the case of converter operation using general molten iron, it is known that when the end carbon is high, molten steel of 0.025% by weight or less at the end cannot be stably produced.

If the carbon in the molten iron is high, the blowing time is shortened, and the quicklime effect is insufficient. Therefore, carbon and phosphorus in the molten iron are processed by the opposite metallurgical reaction characteristics, so that the phosphorus concentration of 0.025% by weight or less is satisfied. Many difficulties are involved in manufacturing molten steel.

Manganese in molten iron during melting is a representative element that causes uplift (phenomena in which manganese concentration in molten iron rises due to reduction of manganese oxide in slag of decarburized strong carbon during blowing), which is caused only by oxidation reaction and becomes carbon monoxide. Unlike, it is an element that causes oxidation and reduction at the same time.

Therefore, even under the same blowing pattern conditions, a technique for properly controlling the component behavior of manganese in accordance with the amount of feedstock and the timing is essential. In conclusion, the phosphorus in the molten iron should be present to the slag side stably by the above reaction (1). With this in mind, it is possible to adjust the method of inputting subsidiary materials to slag goods in the course of pretreatment, that is, the type, timing and amount of subsidiary materials during the pretreatment.

Accordingly, the present invention is to realize the above-mentioned possibility, and its purpose is to appropriately adjust the timing and amount of the blowing pattern or auxiliary raw material such as quicklime, hard bovine dolomite (CaO · MgO) and sintered ore in the converter operation mainly using molten iron and scrap metal. By effectively controlling carbon, manganese and slag in molten steel, the phosphorus in molten iron is stably moved to the slag side during removal to remove the phosphorus content so that the phosphorus content is less than 0.025% by weight at the end of the converter while keeping the carbon concentration higher than 0.04% by weight. To provide converter refining methods.

1 is a process diagram of the converter operation

Figure 2 is a graph showing the converter blow pattern and the secondary raw material input method of the invention example and comparative example

3 is a graph showing the component behavior of molten iron during the blowing of the invention example and comparative example

4 is a graph showing the correlation between the carbon content and the phosphorus content in molten steel at the time of completion of blowing of the invention and comparative examples

The present inventors try to solve the above problems in two aspects. First of all, it is necessary to fully understand the various applications of theoretical aspects and various ways of using the actual industry, and secondly, it is impossible to understand the metallurgical reactions that occur during refining. The idea was to converge through various applications such as the input method of materials, the optimization of blow patterns, and the understanding of the operation results for the post-treatment steel grades.

First of all, in the theoretical approach, there is nothing other than lowering a _P in Equation (1). That is, the method of lowering a _P increases the activity of calcium oxide and molten oxygen in slag, and lowers the reaction temperature (T). A detailed review of this suggests that the following conditions must be met:

First, how to manage slag temperature during blowing while inducing the same end temperature.

Second, how to increase the basicity ((CaO wt%) / (SiO ₂ wt%)) in the slag.

Third, how to maintain high iron oxide content in the slag to lead to the end point.

Fourth, how to maintain high Oxygen Potential among slag in blow steam (decarbonation vigor).

Fifth, how to keep manganese with strong affinity with molten iron during the drilling low?

However, a method of increasing the basicity by adding a large amount of quicklime to satisfy the above conditions is not preferable. Rather, the direction is approached by converging ideas to achieve a desired purpose while reducing the amount of quicklime by securing an appropriate base.

The reason is that the input of large amount of quicklime during the blow job operation causes various problems. For example, quicklime has a melting point of 2570 ° C (usually in the furnace at a temperature of 1200-1730 ° C) and is therefore a high melting point oxide, which makes it difficult to premature slag regeneration (phenomena of slag injected subsidiary materials). To solve this problem, a large amount of fluorspar is used. However, even if the high base also secures slag, the amount of slag is increased, and the slag is generated during the tapping, and the slag overflows from the furnace, causing the fugitive or flowing down into the furnace and causing fire and disaster. On the other hand, if the slag layer is delayed due to excessive input of quicklime in the early stage of blowing, spitting (splitting molten iron by Songsan Jet) may cause deterioration of workability due to the attachment of lances and furnaces, in particular 33% or At 67% of the time, there is a high risk of workability and pollution problems due to slinging (slag in the converter into the furnace).

The present inventors have proposed the present invention in consideration of the above circumstances, and the present invention applies five conditions for lowering a _P to remove phosphorus in the molten steel, and also provides an instantaneous violent chemical reaction phenomenon in an actual converter operation. The idea is to use it effectively.

The present invention proposed by such an idea is that 8-13 kg of green dolomite (mainly composed of CaCO ₃ and MgCO ₃ ) is added to 1 ton of total charge in a converter that leaves 20-35% of the slag of the previous operation. Later, the slab is coated on the furnace wall by tilting the furnace body 3-4 times, and then 13-20 kg of the furnace quicklime for protection of the furnace is charged, and then the scrap iron is charged. Then, after the molten iron is ignited by Songshan, the lime is burnt. In the operation method of batching and sintered ore, and adding calcite, light dolomite and sintered ore at 30-70% of total blowing time, and adding small amount of quicklime and light dolomite at 80-85% of blowing,

The quicklime and sintered ore which are added when complexed by the pine acid are separately or mixed with 25kg or less (including protective quicklime) and 3-15kg of sintered ore with respect to 1 ton of total charge, and the total blowing time is 30-70% At least one type of quicklime, light bovine dolomite and sintered ore is selectively inputted.For 1 ton of charged lime, quicklime less than 15kg, light bovine dolomite is divided into 5-15kg, and sintered ore is 30kg or less. At 80-85%, the present invention relates to a converter refining method for increasing the end point carbon, characterized in that 1-4 kg of quicklime, light small dolomite, and sintered ore are selectively added to each ton of 1 ton of charge.

Hereinafter, the present invention will be described.

In general, the converter operation consists of (preparation stage for the preparation work) → (charging stage) → (treatment work) → (learning stage) → (discharge stage). A schematic working flowchart thereof is shown in FIG. 1. The converter operation consists of a repeated operation as shown in FIG. 1 each time.

In the present invention, 20-35% by weight relative to the total slag operated in the preparation step of the blow job, and the raw dolomite (caCO ₃ · MgCO ₃ is the main component) for the purpose of preventing the cooling of the slag in the converter and erosion of the refractory. 8-13kg is added to the total amount (the weight of molten iron and scrap metal), and the slab is coated on the furnace wall three to four times, and the slag is coated on the furnace wall. For protection, the quicklime is charged with 13-20 kg per 1 ton of full charge.

In the present invention, injecting fresh dolomite into the slag in the converter of the last operation is to make the slag coating in a short time because the slag mixing and cooling ability is excellent by the endothermic reaction during pyrolysis and carbon dioxide generation at the same time. That is, a chemical reaction of CaCO ₃ MgCO ₃ → CaO MgO + CO ₂ (gas) occurs.

In addition, in the present invention, when the main raw material is charged into the furnace in the main raw material charging step, and after stirring the furnace body about two times, the molten iron is charged into the converter, and then blows pure oxygen while the lance for transpiration is blown to start drilling.

In the present invention, after charging the main raw material in the furnace, when the molten iron is ignited by starting the transmission in the blow operation stage, the quicklime lime and / or sintered ore is injected in a batch, each input amount is 0-25kg and 3-15kg range for 1 ton total charge It is preferable to inject as, for the following reason.

When the quicklime is molten silicon (Si) is 0.2% by weight or less, when added in addition to the initial slag basicity of brittle meteorite and protective quicklime added only for the preparation of the furnace wall slag coating in the preparatory stage, even if the initial slag basicity is secured, the lance by spitting In this case, it may not be added in this case because the adhesion problem occurs, and when it is added in excess of 25kg, the problem of slitting occurs due to poor flammability, and the workability worsens. In addition, when the sintered ore is less than 3 kg, the iron oxide concentration in the initial slag is insufficient to induce low melting point slag of high oxygen potential, and when the amount of the sintered ore is more than 15 kg, the slag cooling is severe and the risk of causing the slope is implied. . In this way, when the quicklime and sintered ore are put in the appropriate range after ignition, the slag is lowered and the goods are promoted at the same time, so that the proper slag basicity is secured. Lose.

In addition, in the present invention, during the blowing period (30-70% of the time point), the quick loading of 0-15kg of quicklime and 7-15kg of light dolomite is divided into 1 ton of total charge, and the sintered ore is 0-30kg. One or more types must be selectively added to each other, and it is required to input each set range.

The reason for this is that phosphorus and manganese in the molten iron obtained in the quick lime and sintered ore input range described above are effectively removed so that they can be continuously present as stable phosphorus compounds and manganese oxide in the slag. When the slag layer is put into the furnace so that the slag layer iron oxide is not reduced by the carbon monoxide (CO) produced, the quicklime, light dolomite, and sintered ore particles are incorporated into the slag by the Songsan jet, so that they are fixed or supplied with oxygen potential, Reduction of iron oxide and manganese oxide is suppressed, and a phosphorus compound exists as a stable compound. When all of the quicklime, light dolomite, and sintered ore are not added or lower than the lower limit, the slag viscosity becomes too low due to the high temperature of the slag, so that iron oxide and manganese oxide in the slag are reacted at the interface between carbon monoxide and slag / molten iron (that is, FeO + CO = Fe + CO ₂ , MnO + CO = Mn + CO ₂ ) due to the instability of the phosphorus compound and lack of the proper oxygen potential has a problem that occurs phenol and fugan manganese phenomenon. On the other hand, if the quicklime, light dolomite, and sintered ore are added above the upper limit, the slag ash rate caused by excessive input of the subsidiary materials is caused to spall the lance now due to spitting, which impairs workability. When it comes to lack of heat source, there is a problem in securing the appropriate carbon at the completion of the blow.

On the other hand, for the quicklime, light and small dolomite and sintered ore injected at 30-70% of the time point of blowing, the input method is important. In other words, the quicklime and light calcined dolomite are preferably divided into 2-3 kg per 1 ton, and the sintered ore is divided into 3-7 kg per minute. The reason is that when quicklime is added too quickly, quick phosphorus and manganese oxide cannot be stably fixed in the initial slag, and if it is added too fast, the slag temperature is too low to be effective for slag formation. It is difficult to induce a reaction. In addition, when the sintered ore is excessively input, there is a problem in that the tapping yield is lowered due to the excessive presence of iron oxide in the slag as well as the end point temperature control due to the low temperature.

In the present invention, at least one type of quicklime, light calcinal dolomite, and sintered ore is selectively added at the end of the blow (80-85% of the blowing time), and the dose is in the range of 1 to 4% by weight based on 1 ton of total charge. It is preferable to inject.

The reason for this is that if these auxiliary materials are not added at this point, iron oxide and manganese oxide are generated in slag after 80-85% of the blown, and the phosphorus compounds produced by the reaction formula (1) cannot be stably fixed. Therefore, there is a problem that causes extraneous blood intermittently, if there is an excessive input there is a problem that does not contribute to the metallurgical reaction characteristics do not become a good within a short time.

On the other hand, in the present invention, when the molten iron in the furnace is ignited by the acid in the blowing operation step, immediately followed by quicklime, sintered ore. At 85-90% of the blowing time, a sublance is used to predict the carbon content in the molten steel, and the target end temperature is adjusted by measuring the temperature. .

After the completion of the drill, the steel is pulled out and the deoxidizer, ferroalloy, and charcoal ash for adjustment of molten steel composition are put in. When the tapping is completed, the disposal of 65-80% of the slag remaining in the furnace is completed.

In the above-mentioned drilling work, it is very important to add the appropriate amount of subsidiary materials at the proper input time through the whole process.

On the other hand, the present invention as described above is characterized by the method of adding the subsidiary materials during refining, such features are best seen in 300 tons composite converter operation, but is not limited thereto.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

The total amount of slag (40-45 tons) in the previous operation, which is 20-35% by weight of total charge (the combined weight of scrap metal and molten iron), was put into the furnace of 7 to 15 kg of raw dolomite for 1 ton. The slag was coated on the furnace wall by repeatedly tilting 3-4 times, and 13-14 kg of quicklime was added into the furnace. Subsequently, after charging 15 weight% of total amount of scrap iron which is a main raw material, and stirring a furnace body twice, 85 weight% of molten iron which has the component of Table 1 were charged.

carbon silicon manganese sign brimstone titanium 4.4-4.6 0.15-0.67 0.23-0.52 0.075-0.125 0.003-0.025 0.035-0.083

Then, the lance descends from the upper portion of the converter, and the delivery begins. At this time, when the molten iron was ignited by pine acid, the quicklime was charged at 0-15 kg per 1 ton of charged content and the sintered ore was charged at 6-12 kg.

In the middle of drilling, quicklime of quicklime, dimineral dolomite and sintered ore is divided into appropriate amounts. At 80%, 2-3kg of quicklime, dimineral dolomite and sintered ore are selected and added in batches according to the conditions of the furnace. At 85-90% of the blowing time, the sublance was used to estimate the temperature of the molten iron and the carbon content, and when the temperature was high, an appropriate amount of coolant was added.

Compositional analysis values for the various subsidiary materials used in this example are shown in Table 2 below.

division Calcium oxide Magnesium oxide iron content Manganese oxide Silicon oxide Aluminum oxide Titanium oxide Calcium fluoride carbon brimstone quicklime 92.50 2.20 0.39 - 0.92 0.30 - - - - Saint Dolomite 30.73 20.99 - - 0.58 0.17 - - - - Minor Dolomite 56.16 38.80 0.60 - 1.40 0.51 - - - - fluorite - - - - 13.54 - - 83.86 - - Sintered ore 8.42 1.24 48.294 0.42 4.54 1.56 0.17 - 2.60 0.034

In the comparative example of the conventional method when the quicklime and sintered ore are added in Table 2, when molten iron is ignited in the furnace, all of the quicklime is immediately added to the molten iron regardless of the silicon content of the molten iron. .

In the case of the invention example which is the method of the present invention, the amount to be added according to the silicon content in the molten iron as soon as the vessel is ignited is 5 kg of quicklime and 1 to 3 kg of sintered ore and 3-15 kg of sintered ore. Light dolomite was not added immediately after ignition, but the proper amount was effectively injected at 30-70% and 80% of the time of blowing.

Figure 2 shows the timing and the amount of quicklime, light dolomite and sintered ore of the present invention and the comparative example according to the blowing pattern and the blowing time for the blow rate of the present embodiment, the lance height.

While refining by the method as described above, Table 3 below measures the change in the composition of the molten steel according to the input time and the amount of the auxiliary material, the results are shown in Table 3 below. Inventive example of Table 3 is the result of the irradiation of the quicklime immediately after the ignition of Comparative Example 3 is the same as the input amount and the sintered ore when the sintered ore is changed only the input time. In the comparative example, the total amount of quicklime is added at the beginning of the blow operation and the amount of quicklime is changed, and only the sintered ore is interlocked in the blowdown period.

division number Subsidiary input time and quantity (kg / ton) Molten steel component (wt%) Immediately after ignition 30-70% 80% blow 80% blow Termination quicklime Sintered ore Sintered ore Sintered ore carbon sign carbon sign Comparative example One 0 - 20 - 0.35 0.036 0.031 0.016 2 5 - 20 - 0.26 0.035 0.025 0.021 3 10 - 20 - 0.39 0.038 0.033 0.016 4 15 - 20 - 0.42 0.039 0.055 0.023 5 20 - 20 - 0.29 0.032 0.037 0.015 6 25 - 20 - 0.40 0.027 0.021 0.014 Inventive Example 1-1 5 3 15 2 0.33 0.021 0.056 0.011 1-2 5 6 13 2 0.52 0.015 0.067 0.013 1-3 5 9 10 2 0.63 0.017 0.095 0.015 1-4 5 12 7 3 0.35 0.025 0.053 0.009 1-5 5 14 5 3 0.43 0.018 0.132 0.015 1-6 5 15 3 3 0.58 0.021 0.083 0.014

As can be seen in Table 3, the results of the comparative example shows that phosphorus is high at 0.027-0.039% by weight when the carbon is 0.26-0.42% by weight at 80% time point, and phosphorus content is 0.021-0.055% by weight when the carbon is low at the end point. It can be seen that the anxiety is 0.015-0.023% by weight. This makes it difficult to stably produce when the content of the required steel grade of the demanded steel grade is less than 0.025% by weight, in consideration of the bokrin (typically 0.002-0.004% by weight) by the converter slag during the tapping. On the other hand, the result of the invention example shows that the carbon concentration ranges from 0.33 to 0.63% by weight at 80% blowing time, while the phosphorus is stable at 0.015-0.025% by weight, similar to the comparative example. Phosphorus can be confirmed that even more stable at 0.009-0.015% by weight. As described above, the invention example was able to confirm that the stable production is easy even when considering the lean (normally 0.001-0.002% by weight increase) during the tapping by controlling the stable phosphorus content.

Example 2

This embodiment is the same as the converter operation method of Example 1, and when the injection amount and the injection time of the same sintered ore at the time of blowing as the embodiment of the invention example, the molten steel component when only the amount of quicklime is changed. The results are as shown in Table 4 below.

division number Subsidiary input time and quantity (kg / ton) Molten steel component (wt%) Immediately after ignition 30-70% 80% blow 80% blow Termination quicklime Sintered ore quicklime Sintered ore Sintered ore carbon sign carbon sign Inventive Example 2-1 25 10 5 10 3 0.35 0.023 0.082 0.008 2-2 20 8 2 0.43 0.016 0.128 0.013 2-3 15 8 2 0.33 0.013 0.057 0.009 2-4 15 12 2 0.49 0.012 0.134 0.009 2-5 10 13 2 0.45 0.014 0.159 0.011 2-6 10 13 One 0.40 0.015 0.078 0.007 2-7 5 15 One 0.38 0.015 0.095 0.012

As can be seen in Table 4, when the amount of quicklime was changed, that is, 0-25 (kg) was added immediately after ignition of quicklime for 1 ton of total charge, and 5-15kg at 30-70% of the blowing time. At 80% of the blowing time, the phosphorus was stable at 0.012-0.016% by weight despite being 0.33-0.48% by weight, and at the termination point of the phosphorus, phosphorus was very stable at 0.008-0.013% by weight even in the area of 0.057-0.159% by weight It was confirmed that it is.

Example 3

This embodiment is the same as the converter operation method of Example 1, and as the embodiment of the present invention immediately after ignition, the method of applying quicklime and sintered ore is applied in the same way, light and dolomite and The molten steel component was investigated by changing the input amount of sintered ore and changing the light dolomite input amount at 80% of the blowing time. The results are summarized in Table 5 below.

division number Subsidiary input time and quantity (kg / ton) Molten steel component (wt%) Immediately after ignition 30-70% 80% blow 80% blow Termination quicklime Sintered ore Dolomite Sintered ore Dolomite carbon sign carbon sign Inventive Example 3-1 10 10 5 15 One 0.52 0.020 0.162 0.016 3-2 7 30 2 0.43 0.015 0.092 0.013 3-3 10 8 4 0.32 0.012 0.075 0.011 3-4 12 20 3 0.29 0.014 0.061 0.009 3-5 13 25 2 0.45 0.020 0.055 0.010 3-6 15 10 One 0.33 0.016 0.068 0.012 3-7 18 5 3 0.55 0.017 0.077 0.015 3-8 20 3 One 0.42 0.018 0.127 0.013

As can be seen in Table 5, immediately after ignition, 10 kg of quicklime and sintered ore were charged per ton of total charge. At 30-70% of the blowing time, 5-20 kg of light calcined dolomite and 3-30 kg of sintered ore were added. As a result, phosphorus was stabilized as low as 0.012-0.020% by weight even though carbon was 0.29-0.55% by weight at 80% blowing time, and phosphorus was 0.009-0.016% by 0.055-0.162% by weight at the end point. Could confirm.

Example 4

As a result of the irradiation in Example 1-3, the effect on the method of adding quicklime and sintered ore immediately after ignition was confirmed. As a result, the correlation between the phosphorus content by carbon concentration at 80% of the time point and the end point of blowing was proved to be superior to the comparative example.

Therefore, the present embodiment and the converter operation method is basically the same in the present embodiment, and the molten steel component when the amount of quick lime, light dolomite, and sintered ore input method is appropriately selected and applied to each step of blowing time. Investigate. The results are summarized in Table 6 below.

division number Subsidiary input time and quantity (kg / ton) Molten steel component (wt%) Immediately after ignition 30-70% 80% blow 80% blow Termination quicklime Sintered ore quicklime Dolomite Sintered ore quicklime Dolomite Sintered ore carbon sign carbon sign Inventive Example 4-1 3 5 15 7 10 3 2 3 0.44 0.020 0.055 0.007 4-2 5 8 12 7 5 2 2 2 0.39 0.015 0.078 0.013 4-3 8 6 12 15 - 2 - - 0.37 0.014 0.132 0.011 4-4 12 8 9 13 - 3 - 2 0.52 0.017 0.214 0.012 4-5 15 10 4 10 - 2 - 3 0.44 0.015 0.085 0.008 4-6 3 12 3 8 - 3 - - 0.39 0.014 0.065 0.007 4-7 8 12 8 15 - 2 3 - 0.56 0.012 0.148 0.014 4-8 12 15 - 10 25 One - One 0.45 0.013 0.129 0.010 4-9 15 3 3 12 15 2 One - 0.56 0.014 0.093 0.011 4-10 20 8 - 10 30 - - 2 0.49 0.015 0.152 0.013

In Table 6, the method of inputting quicklime, light dolomite and sintered ore during the treatment is as follows. Immediately after ignition, 3-20 kg of quicklime and 3-15 kg of sintered ore are added to 1 ton of charged content, and 3-15 kg of quicklime, 7-15 kg of light and small dolomite, and 0-30 kg of sintered ore are selectively added for 30-70% of the blowing time. Divided input. At 80 points of time, 1-3 kg of quicklime, light and small dolomite, and sintered ore were selectively added to 1 ton of charged content.

According to the analysis results of molten steel component of Table 6, the carbon at the time of 80% of the blowing time is low in the high carbon region of 0.37-0.56% by weight of phosphorus 0.012-0.020% by weight, the carbon 0.055-0.214 at the end of the blowing It was confirmed that phosphorus was very stable at 0.007-0.014% in the weight% region.

In Example 1-4, the method for adding quicklime, light bovine dolomite and sintering holes to be injected at 30-70% of the blowing time is 1-4 kg at a time with respect to 1 ton of full charge. , Sintered ore is recommended to interlock 3-7kg per minute. However, at least one kind of quicklime, light dolomite and sintered ore must be added.

As demonstrated in Examples 1-4 above, in any case, the method of injecting the present invention can obtain stable phosphorus behavior and reproducible end phosphorus regardless of the carbon concentration range at 80% of the blowing time and the end point compared to the comparative example. Confirmed. Because of this, even if the end point carbon is higher than that of the comparative example, the end point phosphorus is obtained lower than that of the prior art, and it has been proved that the end point carbon can be increased during the converter blow.

In the above Example 1-4, the molten iron sample was collected according to the blowing time by using a sub lance, and the typical molten iron behavior according to the blowing time of the comparative example and the inventive example was analyzed in FIG. Shown. Carbon concentration is shown in FIG. 3 (a), manganese concentration in FIG. 3 (b), and phosphorus concentration in FIG. 3 (c). Here, the behavior of each component with respect to the change over time during the blowing of the invention example and the comparative example appeared as shown in Figure 3 almost the same tendency.

As shown in FIG. 3 (a), the comparative example is high up to 70% of the blownability, and then the invention is high, and the comparative example is high up to 75% of the manganese (Fig. 3b), and then the invention is high. On the other hand, phosphorus (Fig. 3c) the case of the invention shows a low value in the entire process of blowing. In the case of the present invention, carbon and manganese concentrations are low from the start of the blow to 70-75% of the time, the lower the amount of the initial quicklime is added to the slag than the comparative example, the slagization rate is increased, and the sintered ore, which is the source of oxygen, is decarburized by the batch injection. And demanganese reaction is promoted. That is, compared with the invention example, the comparative example is remarkable in the manganese phenomenon from 20% of the time of blowing, and this effect is advantageous for the Tallinn reaction. As described above, in the case of the present invention, the phosphorus content can be controlled to 0.025% or less within 30% of the blowing time.

As shown in FIG. 3, the case of the invention demonstrates that the behavior of phosphorus in molten iron can be controlled in the high-carbon region with little or no abdominal phenomenon, whereas the comparative example shows the abdominal phenomenon between 30% and 70% of blowing. It has been proven that it is impossible to control the phosphorus low while keeping the endpoint carbon high. As a result, in the case of the invention example, it is possible to stably manufacture molten steel having a phosphorus content of 0.025% by weight or less regardless of the carbon concentration during the blowing.

In view of the above, according to the present invention, according to the proper supply of quicklime, light bovine dolomite, and sintered ore as raw materials, the slag temperature is lowered up to -70%, and the iron oxide content and basicity of the slag are kept high. As a result, the oxygen potential of the slag is increased to stably exist the phosphorus compound already produced in the slag, thereby stably producing molten steel with a carbon content of 0.04 wt% or more while maintaining a phosphorus content of less than 0.025 wt%.

Figure 4 shows the correlation between the carbon content of the molten steel and the phosphorus at the blowing point obtained in Example 1-4, in the case of the comparative example the phosphorus increases as the carbon content is higher, the phosphorus content in the same carbon content compared to the comparative example The case of invention example is remarkably low. This reflects the result of the slag crystallization rate of slaked lime which has been added stably along with the blowing time due to the quickening effect of quicklime and sintered ore into which phosphate produced by reacting with phosphorus in molten iron is removed. have. In addition, after 30% of blowing, the slag layer was lowered by the quick-lime lime, light dolomite, and sintered ore in which phosphate and manganese oxide, which were initially produced, were stably fixed and stabilized by ensuring proper basicity as well as maintaining proper oxygen potential. Therefore, the case of the invention example proves that it provides the conditions which can significantly reduce phosphorus content even in the same blowing end carbon content compared with the comparative example.

On the other hand, as shown in Fig. 3, the result obtained by controlling the stable phosphorus content of 0.025% by weight or less after 30% of blowing as shown in Fig. 3, in the case of the invention example, 0.025% by weight even in the carbon region of 0.04% by weight or more. It is proved that molten steel which has the following phosphorus contents can be manufactured stably.

Therefore, the converter operation can move stably in the slag side to the slag side by utilizing the shape of the converter itself, the blowing pattern (Lance height and Songsan pattern), and the previous operation conditions that can be thought of in the whole process of drilling. It is confirmed that the cargo can be effectively sustained to the end point. In particular, the combined smelting furnace has a stronger stirring power than that of the smelting furnace, so the behavior of carbon, phosphorus, and manganese in the molten iron, as well as the characteristics of the iron oxide in the slag in the furnace, is completely different from the smelting converter.

As described above, the present invention can maintain the slag ash rate of molten iron and slag and the slag ash content of molten lime and slag by deriving appropriate input time, amount, and method of quicklime, hard borosilicate and sintered ore for each stage of blowing. As the temperature of the heavy slag can be controlled to lower the activity of the calcium oxide, the end point oxygen is lowered as the carbon of the phosphorous content of 0.025% by weight or less is stably manufactured together with the increase of the end point carbon. In addition, when the end point carbon is raised, the end point oxygen is lowered and the iron oxide concentration in the slag is reduced, thereby reducing slag generation, improving the yield rate of the tap, improving the life of converter refractory, reducing the amount of aluminum, carbonaceous and ferroalloys used during tapping, and high molten steel. There are effects such as productivity improvement and quality improvement of molten steel by the increase of cleanliness and lead casting ratio. Compared with the conventional operation of the comparative example, the operation of the present invention improves the reflow rate of the added raw materials, thus reducing the input amount of quicklime, light dolomite, forming, sedative, etc. It also has an extended effect.

Claims (2)

The slag is coated on the furnace wall by slagging the slag 3-4 times, and then applying slag to the furnace wall to the furnace with 20-35% of the slag of the previous operation. After inputting 13-20kg, load the scrap metal, and then charge the molten iron, and when the internal molten iron is ignited by Songshan, the quicklime and sintered ore are put in a batch, and the quickening time is 30-70%. In the operation method of splitting and raising the end point carbon by adding a small amount of quicklime and light small dolomite at around 80% of blowing, The quicklime and sintered ore which are added when complexed by the pine acid are separately or combined with 25 kg or less (including the furnace protection quicklime) and 3-15kg of sintered ore with respect to 1 ton of total charge, and the total blowing time is 30-70%. At least one type of quicklime, light bovine dolomite and sintered ore can be selectively added, and for each ton of charged tonnes, quicklime less than 15kg, light bovine dolomite is divided into 5-15kg, and sintered ore is 30kg or less. At 80-85% of the blowing time, the converter refining method for raising the end point carbon, characterized in that 1 to 4 kg of quicklime, light small dolomite, and sintered ore are selectively added to 1 ton of charged content. The method of claim 1, The quicklime and light dolomite at 30-70% of the total blowing time are divided into 2-3 kg per 1 ton of full charge and the sintered ore is 3-7 kg per minute with respect to 1 ton of full charge. Converter refining method to raise the end point carbon