Smelting method for reducing cost of 10B21 steel and controlling nitrogen

Abstract

The invention discloses a smelting method for reducing the cost of 10B21 steel and controlling nitrogen. The method comprises the steps that black sticky slag is smelted on the surface of molten steel in the earlier stage of converter smelting and LF furnace refining so as to prevent nitrogen in air from entering the molten steel, aluminum wires are added in the later stage of LF furnace refining so that the black sticky slag can be converted into white diluted slag so as to remove oxygen and sulfur in the molten steel, and then the components of the molten steel are adjusted according to the steel grade component requirements. In the converter tapping process, bottom blowing argon of a steel ladle is adjusted to be in a soft blowing state, sampling is carried out after tapping to an argon station, aluminum wires are not fed to prepare acid-soluble aluminum, molten steel is fed to an LF furnace, slag charge is added, and then electric slag feeding is carried out. After slag is molten in the LF furnace, aluminum wires are added to be matched with acid-soluble aluminum for desulfurization and deoxidation, then the components of the molten steel are adjusted according to the steel grade component requirements, in this way, consumption of slag charge, alloy and electric quantity can be reduced, and meanwhile the nitrogen control effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a smelting method for reducing the cost of 10B21 steel and controlling nitrogen. Background Art

[0002] 10B21 is a cold heading steel wire rod, mainly used to manufacture bolts, nuts and other parts. It has a stable composition and a large market demand. It is widely used in construction engineering, machinery manufacturing, automotive parts and other fields. Since aluminum nitride, boron nitride and other precipitates hinder the movement of grain boundaries during the thermal deformation of steel, thus generating stress, in order to reduce the nitrogen content, the cost will increase. 10B21 ingots are prone to surface cracks during hot delivery, which seriously affects the processing performance, resulting in unqualified products when 10B21 ingots are processed into products, and the product yield is low. In actual use, the product will have serious surface wear and a short service life. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the above technical background and provide a smelting method for reducing the cost of 10B21 steel and controlling nitrogen.

[0004] The embodiment of the present invention provides a smelting method for reducing the cost of 10B21 steel and controlling nitrogen, which mainly includes: in the early stage of converter smelting and LF furnace refining, black viscous slag is melted on the surface of molten steel to prevent nitrogen in the air from entering the molten steel, in the late stage of LF furnace refining, aluminum wire is added to transform the black viscous slag into white diluted slag to remove oxygen and sulfur in the molten steel, and then the composition of the molten steel is adjusted according to the composition requirements of the steel grade.

[0005] The present invention has the following beneficial effects.

[0006] The present invention provides a smelting method for reducing the cost of 10B21 steel and controlling nitrogen, which comprises: adjusting the argon gas blowing at the bottom of the ladle to a soft blowing state during the converter tapping process, and switching the aluminum wire feeding time from the argon station to after the LF furnace slag is completed. Through the above improvements, the nitrogen increase of molten steel is effectively controlled while reducing the slag consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0008] Figure 1 This is the appearance of the slag in the LF furnace before feeding the aluminum wire;

[0009] Figure 2This is the appearance of the slag after feeding aluminum wire in the LF furnace. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0011] A smelting method for reducing the cost of 10B21 steel and controlling nitrogen provided by an embodiment of the present invention is described in detail below.

[0012] The embodiment of the present invention provides a smelting method for reducing the cost of 10B21 steel and controlling nitrogen, which mainly includes: adjusting the argon blowing at the bottom of the ladle to a soft blowing state during the converter tapping process, and switching the aluminum wire feeding timing from the argon station to after the LF furnace slag is completed.

[0013] The embodiment of the present invention provides a smelting method for reducing the cost of 10B21 steel and controlling nitrogen, which mainly includes: in the early stage of converter smelting and LF furnace refining, black viscous slag is melted on the surface of molten steel to prevent nitrogen in the air from entering the molten steel, in the late stage of LF furnace refining, aluminum wire is added to transform the black viscous slag into white diluted slag to remove oxygen and sulfur in the molten steel, and then the composition of the molten steel is adjusted according to the composition requirements of the steel grade.

[0014] In some optional implementations, it mainly includes: adjusting the argon blowing at the bottom of the ladle to a soft blowing state during the converter steel tapping process, and switching the aluminum wire feeding timing from the argon station to after the LF furnace slag is completed.

[0015] In some optional implementation methods, it mainly includes: after the alloy and slag are added during the steel production from the converter, the argon blowing at the bottom of the ladle is adjusted to a soft blowing state; sampling is performed after the steel is produced and arrives at the argon station, and no aluminum wire is fed to prepare acid-soluble aluminum; after the molten steel arrives at the LF furnace, slag is added, electricity is supplied until the slag is melted, and then aluminum wire is fed to convert the black viscous slag into white diluted slag; after sampling the molten steel, alloy is added according to the sampling results to adjust the composition of the molten steel.

[0016] In some optional embodiments, the converter tapping includes: before the converter tapping, controlling the end point carbon to be 0.07%-0.10%. In theory, the higher the end point carbon is, the lower the cost will be. However, the phosphorus content of the 10B21 finished product is required to be within 0.020%, and the carbon content is 0.19%-0.21%. The end point oxygen content and the end point phosphorus content are generally inversely proportional, and the end point oxygen content and the end point carbon content are also inversely proportional. Therefore, when the carbon is higher, the end point oxygen content will be lower, and the phosphorus content will be higher. If you want to keep a high carbon content and remove phosphorus to a qualified range, then the amount of lime, iron ore and other slag materials added to the converter in the early stage will be relatively large, and it can only be completed under the condition of relatively high iron and steel, which is not conducive to cost control.

[0017] In some optional embodiments, when the steel output reaches 1 / 3, 500 kg of lime per 120 tons of steel, 290-310 kg of aluminum iron per 120 tons of steel and 1100-1200 kg of high manganese per 120 tons of steel are added. After the addition, the argon blowing at the bottom of the ladle is adjusted to a soft blowing state.

[0018] When the converter is tapping steel, when the steel output reaches 1 / 3, that is, more than 40 tons, 500 kg of lime / 120 tons of steel, 290-310 kg of aluminum iron / 120 tons of steel and 1100-1200 kg of high manganese / 120 tons of steel are added. After the slag and alloy are added, the argon gas is turned down to soft argon blowing. Compared with the original method of using large argon gas to stir and promote alloy melting, turning down the bottom blowing argon gas flow rate can reduce the nitrogen absorption of molten steel. According to statistics, this method takes gas samples after the steel is tapped, and the nitrogen content of the molten steel is 22-35ppm. The nitrogen increase in the steel tapping process is less. The disadvantage is that the alloy and slag are not melted, forming a thick and hard slag covering the surface of the molten steel.

[0019] In some optional embodiments, sampling is performed after the steel is discharged from the converter to the argon station, and no aluminum wire is fed into the argon station for acid-dissolving aluminum.

[0020] Compared with the need to feed aluminum wire to the argon station for acid-dissolving aluminum before the improvement, the embodiment of the present invention provides a solution, that is, after the improvement, sampling is performed after the converter is finished and arrives at the argon station, and aluminum wire is not fed for acid-dissolving aluminum. The disadvantage is poor deoxidation and increased deoxidation pressure of the LF furnace, and the advantage is effective control of nitrogen increase in molten steel in the early stage of the LF furnace. Because the conditions for nitrogen increase in molten steel in the early stage of the LF are that the slag is not well oxidized, the molten steel is low in oxygen and sulfur, and the electrode ionizes the nitrogen in the air when power is supplied, which is due to the poor ability to prevent the ionized nitrogen in the air from entering the molten steel. After the improvement, due to poor deoxidation after the converter is finished, and the argon station does not feed aluminum wire for deoxidation and acid-dissolving aluminum, when the molten steel arrives at the LF furnace, the oxygen and sulfur in the molten steel will be relatively high when the LF is electrified and slag is oxidized in the early stage of the LF, and both oxygen and sulfur can hinder the molten steel from absorbing nitrogen, so when slag is oxidized before the LF, the nitrogen absorption of the molten steel is reduced from 12-22ppm to 4-9ppm.

[0021] In some optional embodiments, after the molten steel arrives at the LF furnace, adding slag to the molten steel includes: after the molten steel arrives at the LF furnace, adding slag stone 300-330 kg / 120 tons of steel, fluorite 100-120 kg / 120 tons of steel, aluminum slag 130-160 kg / 120 tons of steel and synthetic slag 500-550 kg / 120 tons of steel to the molten steel.

[0022] In some optional implementations, the electroslag-forming time is 5-7 minutes.

[0023] In some optional embodiments, after the molten steel arrives at the LF furnace, slag is added, electricity is supplied until the slag is melted, and then aluminum wire is fed to convert the black viscous slag into white diluted slag, including: after the molten steel arrives at the LF furnace, slag is added to the molten steel to form black viscous slag on the surface of the molten steel, and then aluminum wire is fed to acid-dissolve aluminum in the molten steel to 0.060-0.070%, and electricity is continued to be supplied until the temperature rises to 1580-1600°C, so that the black viscous slag is converted into white diluted slag.

[0024] After the molten steel arrives at the LF furnace, slag is added in the early stage to send electricity, and before the aluminum wire is fed after the slag is melted, during this period of time, since this type of steel does not add ferrosilicon, the silicon dioxide in the slag is 1.2%-3.5%, and the converter only adds aluminum iron once, so the aluminum oxide in the slag is low, only 3%-4%. At this time, the slag looks like pebbles on the road, one piece after another, and the slag stuck together with a rod is black and thick. Figure 1 As shown in the figure, it is very difficult to desulfurize such slag. If the sulfur content of molten steel sampled by argon sampling is 0.018%, the original method requires the addition of 550-600 kg of lime and fluorite. After the improvement, the aluminum wire is fed after the LF slag is slag-treated. After the aluminum oxide reaction, the generated aluminum oxide will enter the slag. The aluminum oxide can quickly increase from 3%-4% to 27-33%. Therefore, after a period of time after feeding the aluminum wire, the slag will become white and thin. Figure 2 As shown, the slag has a strong desulfurization ability. After the improvement, if the sulfur content of the argon station sample is 0.027% or less, add 300-330 kg of lime, and basically remove it to 0.010% or less at the time of LF sampling. Through the above improvements, the nitrogen increase of molten steel is effectively controlled while reducing the slag consumption.

[0025] In some optional embodiments, adding alloys to adjust the composition of steel includes: first matching the carbon and acid-soluble aluminum in the molten steel according to the analysis results of the molten steel sampling, then raising the temperature to the temperature required before soft blowing of the calcium line + 5°C, adjusting the argon gas to soft blowing argon gas, adding chromium and titanium alloys to adjust the chromium and titanium content in the molten steel, and then adding ferroboron alloy to adjust the boron content in the molten steel, and soft blowing the calcium line out of the station.

[0026] In some optional embodiments, the following steps are included: according to the results of molten steel sampling and analysis, the carbon and acid-soluble aluminum of the molten steel are first added, and then the temperature is increased to the temperature required before soft blowing of the calcium line + 5°C, the argon gas is adjusted to the soft blowing state, and then 140 kg of ferrochrome and 165 kg of ferrotitanium are added, and after adding, wait for 2-3 minutes before adding ferroboron, and after adding ferroboron, the calcium line is soft-blown out of the station.

[0027] Since 10B21 steel contains chromium, titanium, boron, and acid-soluble aluminum, among which titanium, aluminum, and boron are easily oxidized and nitrided elements, and the formed nitrides have an impact on the quality of molten steel, so compared with the original, we have the following optimizations: Originally, we allocated the components to the range based on the molten steel sample and then used the calcium line for soft blowing. In this way, we found that the yields of ferrochrome, ferrotitanium, and ferroboron were low, so we now first allocate the carbon and acid-soluble aluminum to the molten steel, and then adjust the molten steel temperature to 1590℃, that is, the temperature required before calcium line soft blowing +5℃, adjust the argon to soft blowing argon, with a flow rate of 10 cubic meters / hour, and add 140 kg of ferrochrome and 165 kg of 30 ferrotitanium. After adding, wait for 2-3 minutes before adding ferroboron. After adding ferroboron, use the calcium line for soft blowing out of the station. Compared with the original operation, this operation can reduce the burning loss of titanium and boron, improve the alloy recovery rate, and the composition is stable and accurate. At the same time, the molten steel is firstly mixed with acid to dissolve aluminum to generate aluminum nitride, then ferrotitanium is added to generate titanium nitride, and finally ferroboron is added to generate boron nitride. Compared with the original method, which can generate a variety of alloys, add ferroboron, ferrotitanium, and feed aluminum wire, etc., so as to generate disorderly nitrides, the improved method will be better for the quality of molten steel. After the improvement, an average of 165 kg of ferrotitanium, 12 kg of ferroboron, and 140 kg of ferrochromium are added to each furnace of steel.

[0028] In some optional embodiments, the flow rate of argon in the soft blowing state is 5-10 cubic meters per hour.

[0029] The present invention will be further described below in conjunction with the embodiments.

[0030] Example 1

[0031] 1. Before tapping the converter, the final carbon content is 0.07%. When tapping, when the tapping volume reaches 1 / 3, that is, more than 40 tons, add 500 kg of lime, 310 kg of aluminum iron, and 1200 kg of high manganese. After adding, turn down the argon gas to soft blowing argon gas with a flow rate of 10 cubic meters / hour. Take a gas sample after tapping, and the nitrogen content of the molten steel is 35ppm.

[0032] 2. After the steel is discharged to the argon station, sampling is performed without feeding aluminum wire to dissolve the aluminum in acid. The nitrogen absorption of molten steel is reduced from 12-22ppm to 9ppm.

[0033] 3. After the molten steel arrives at the LF furnace, add 330 kg of slag stone, 120 kg of fluorite, 160 kg of aluminum slag and 550 kg of synthetic slag. After 7 minutes, it has basically been fused to form fine slag, which can effectively isolate the ionized nitrogen in the air from entering the molten steel. Only then start feeding aluminum wire and adjust the acid-soluble aluminum to 0.070%. Continue to send power to 1600℃ for sampling.

[0034] 4. According to the sampling results, first add carbon and acid-soluble aluminum to the molten steel, then adjust the molten steel temperature to 1590℃, that is, the temperature required before soft blowing of the calcium line +5℃, adjust the argon to soft blowing argon, with a flow rate of 10 cubic meters / hour, and add 140 kg of ferrochrome and 165 kg of 30 titanium iron. After adding, wait for 3 minutes before adding ferroboron. After adding ferroboron, the calcium line is soft-blown out of the station.

[0035] Example 2

[0036] 1. Before tapping the converter, the final carbon content is 0.08%. When tapping, when the tapping volume reaches 1 / 3, that is, more than 40 tons, add 500 kg of lime, 310 kg of aluminum iron, and 1200 kg of high manganese. After adding, turn down the argon gas to soft blowing argon gas with a flow rate of 10 cubic meters / hour. Take a gas sample after tapping, and the nitrogen content of the molten steel is 32ppm.

[0037] 2. After the steel is discharged to the argon station, sampling is performed without feeding aluminum wire to dissolve the aluminum in acid. The nitrogen absorption of molten steel is reduced from 12-22ppm to 8ppm.

[0038] 3. After the molten steel arrives at the LF furnace, add 330 kg of slag stone, 120 kg of fluorite, 150 kg of aluminum slag and 550 kg of synthetic slag. After 7 minutes, it has basically been molten to form fine slag, which can effectively isolate the ionized nitrogen in the air from entering the molten steel. Only then start feeding aluminum wire and adjust the acid-soluble aluminum to 0.068%. Continue to send power to 1600℃ for sampling.

[0039] 4. According to the sampling results, first add carbon and acid-soluble aluminum to the molten steel, then adjust the molten steel temperature to 1590℃, that is, the temperature required before soft blowing of the calcium line +5℃, adjust the argon to soft blowing argon, with a flow rate of 10 cubic meters / hour, and add 140 kg of ferrochrome and 165 kg of 30 titanium iron. After adding, wait for 3 minutes before adding ferroboron. After adding ferroboron, the calcium line is soft-blown out of the station.

[0040] Example 3

[0041] 1. Before tapping the converter, the final carbon content is 0.09%. When tapping, when the tapping volume reaches 1 / 3, that is, more than 40 tons, add 500 kg of lime, 300 kg of aluminum iron, and 1150 kg of high manganese. After adding, turn down the argon gas to soft blowing argon gas with a flow rate of 10 cubic meters / hour. Take a gas sample after tapping, and the nitrogen content of the molten steel is 28ppm.

[0042] 2. After the steel is discharged to the argon station, sampling is performed without feeding aluminum wire to dissolve the aluminum in acid. The nitrogen absorption of molten steel is reduced from 12-22ppm to 6ppm.

[0043] 3. After the molten steel arrives at the LF furnace, add 320 kg of slag stone, 110 kg of fluorite, 140 kg of aluminum slag and 500 kg of synthetic slag. After 6 minutes, it has been basically fused to form fine slag, which can effectively isolate the ionized nitrogen in the air from entering the molten steel. Only then start feeding aluminum wire and adjust the acid-soluble aluminum to 0.065%, and continue to send power to 1600℃ for sampling.

[0044] 4. According to the sampling results, first add carbon and acid-soluble aluminum to the molten steel, then adjust the molten steel temperature to 1590℃, that is, the temperature required before soft blowing of the calcium line +5℃, adjust the argon to soft blowing argon, with a flow rate of 10 cubic meters / hour, and add 140 kg of ferrochrome and 165 kg of 30 titanium iron. After adding, wait for 2 minutes before adding ferroboron. After adding ferroboron, the calcium line is soft-blown out of the station.

[0045] Example 4

[0046] 1. Before tapping the converter, the final carbon content is 0.10%. When tapping, when the tapping volume reaches 1 / 3, that is, more than 40 tons, add 500 kg of lime, 290 kg of aluminum iron, and 1100 kg of high manganese. After adding, turn down the argon gas to soft blowing argon gas with a flow rate of 10 cubic meters / hour. Take a gas sample after tapping, and the nitrogen content of the molten steel is 22ppm.

[0047] 2. After the steel is discharged to the argon station, sampling is performed without feeding aluminum wire to dissolve the aluminum in acid. The nitrogen absorption of molten steel is reduced from 12-22ppm to 4ppm.

[0048] 3. After the molten steel arrives at the LF furnace, add 300 kg of slag stone, 100 kg of fluorite, 130 kg of aluminum slag and 500 kg of synthetic slag. After 5 minutes, it has basically been fused to form fine slag, which can effectively isolate the ionized nitrogen in the air from entering the molten steel. Then start feeding aluminum wire and adjust the acid-soluble aluminum to 0.060%. Continue to send power to 1600℃ for sampling.

[0049] 4. According to the sampling results, first add carbon and acid-soluble aluminum to the molten steel, then adjust the molten steel temperature to 1590℃, that is, the temperature required before soft blowing of the calcium line +5℃, adjust the argon to soft blowing argon, with a flow rate of 10 cubic meters / hour, and add 140 kg of ferrochrome and 165 kg of 30 titanium iron. After adding, wait for 2-3 minutes before adding ferroboron. After adding ferroboron, the calcium line is soft-blown out of the station.

[0050] The following table shows the consumption of slag, alloy and electricity in Examples 1-4 and Comparative Example 1.

[0051]

[0052]

[0053] Comparative Example 1

[0054] The converter produces an average of 131 tons of molten steel. When tapping, 500 kg of lime, 290-340 kg of aluminum and iron for alloy, and 1100-1200 kg of high manganese are added. During the tapping process, large argon gas stirring is used to promote the melting of all alloys and slag. After tapping, samples are taken at the argon station, and then the acid-soluble aluminum in the molten steel is adjusted to 0.030-0.060% before leaving the station. After the molten steel arrives at the LF furnace, 300-800 kg of lime, 100-150 kg of fluorite, 150 kg of aluminum slag, and 550 kg of synthetic slag are added. After power is supplied for heating for 10-15 minutes, samples are taken, alloys are added according to the components, and samples are taken again until the components are adjusted within the range, and then the temperature is adjusted and the calcium line is soft-blown before leaving the station.

[0055] After the above operations, we have statistically analyzed the quality and cost as follows: after the converter produces steel, the nitrogen content of the molten steel is 35-48ppm, and the LF furnace has relatively fixed usage, such as an average of 565 kg of lime, 201 kg of fluorite, 550 kg of synthetic slag, 156 kg of aluminum slag, 180 kg of 30 titanium iron, 15 kg of ferroboron, and 195 kg of ferrochrome. The relatively unstable ferromanganese and aluminum wire will have different effects with the oxygen content and residual manganese in the converter molten steel. The aluminum wire is 160-350 meters / furnace, and the high manganese is 160-250 kg / furnace. The average power consumption per furnace of steel is 6446 kWh.

[0056] We found that, first, after the steel is produced from the converter, the nitrogen content of the molten steel is 35-48ppm higher, that is, 0.0035-0.0048%. After passing through the LF furnace and continuous casting, the nitrogen content of the molten steel can easily exceed the range of 0.006% or 60ppm. Second, the slag making dosage and power consumption of the LF furnace are higher than those of SWRCH22A steel with the same composition. SWRCH22A steel has 0.20-0.22% carbon, ≤0.08% silicon, 0.75-0.85% manganese, ≤0.022%, ≤0.010% phosphorus, ≤0.010% sulfur, 0.025-0.040% acid-soluble aluminum, an average of 333 kg of lime, 120 kg of fluorite, 400 kg of synthetic slag, and 111 kg of aluminum slag. The average power consumption per furnace of steel is 5,885 kWh.

[0057] Comparative Example 2

[0058] The steps are similar to those in Example 1, except that the final carbon control of the converter is not 0.07%-0.10%, but 0.04%-0.06% to ensure that the dephosphorization is within the qualified range. That will cause high oxygen in the molten steel and increase the cost of aluminum deoxidation. In addition, as the carbon content of the molten steel is low, the oxygen blown into the converter reacts less with carbon, and the carbon monoxide generated is also less, which reduces the emission of carbon monoxide that hinders the molten steel from absorbing nitrogen, and also increases the molten steel's nitrogen absorption.

[0059] Comparative Example 3

[0060] The steps are similar to those in Example 1, except that slag is added early or late during the steel tapping process. Theoretically, the advantage of adding slag and alloy when 15 tons of steel is tapping is that a layer of slag surface is formed as early as possible to protect the molten steel from being exposed and reduce nitrogen absorption; the disadvantage is that there is less molten steel in the early stage, the slag is difficult to melt, and it is difficult to form a slag layer that can protect the molten steel from being exposed. However, the slag and alloy are added only when 70 tons of steel is tapped. The advantage is that the alloy yield can be improved and the slag can be ensured to melt quickly, but the disadvantage is that the molten steel absorbs nitrogen for a long time in the early stage and the molten steel increases nitrogen a lot. Therefore, under the same bottom blowing, the same tapping temperature and other same conditions, on the basis of ensuring that the slag alloy can melt quickly, adding it as early as possible is the best value to reduce the nitrogen absorption of molten steel. The ladle size, tapping steel flow size, ladle bottom blowing method, and alloy feeding equipment of each steel plant are different, so the timing of controlling the addition of slag and alloy is different.

[0061] Comparative Example 4

[0062] The steps are similar to those in Example 1, except that after the steel is discharged, the molten steel is fed with aluminum wire instead of aluminum wire in the argon station to remove oxygen completely. In theory, oxygen and sulfur in the molten steel are beneficial to preventing the molten steel from absorbing nitrogen. If the argon station removes all oxygen, the molten steel will absorb more nitrogen during the early power supply process of the LF furnace.

[0063] Comparative Example 5

[0064] The steps are similar to those in Example 1, except that the LF furnace starts feeding aluminum wire 5-7 minutes after slagging, and changes to 13-15 minutes before feeding aluminum wire to reduce nitrogen absorption by molten steel in the early stage. This will reduce the time for removing aluminum oxide from molten steel, resulting in quality problems of molten steel. Because aluminum oxide has a high melting point and is difficult to remove, it needs to be removed as soon as possible to ensure the quality of molten steel. In the present invention, it is necessary not only to remove aluminum oxide from molten steel, but also to control the increase of nitrogen in molten steel. Therefore, we studied the time required for removing aluminum oxide. As long as the time is greater than 15 minutes after the LF furnace is equipped with aluminum to 0.060%, and calcium wire is fed for soft blowing for 12 minutes, aluminum oxide can be removed to within the qualified range. The LF furnace has a steel processing cycle of 35 minutes, and the removal time of alumina is 27 minutes, which is only 8 minutes. Therefore, the LF furnace is required to melt the slag in the first 5-7 minutes. After forming a layer of protective slag, it starts to feed aluminum wire to 0.060% aluminum. This can ensure the effective removal of alumina in the molten steel and control the nitrogen absorption of the molten steel.

[0065] Comparative Example 6

[0066] The steps are similar to those in Example 1, except that: the power is supplied to 1590°C, which is the temperature required before the calcium wire soft blowing + 5°C, and then ferrochrome, ferrotitanium, and ferroboron are added, and the power is supplied to 1560°C instead. After the above alloys are added, the power is supplied to 1585°C for the calcium wire soft blowing. In terms of operation, the power supply time and cost are not affected, but the alloy consumption is affected. During the power supply process, the bottom blowing of argon is relatively large, which will burn part of the boron, titanium, and chromium.

[0067] Comparative Example 7

[0068] The steps are similar to those in Example 1, except that the LF furnace process needs to feed aluminum wire, add ferrochrome, ferrotitanium, and ferroboron, and the order of adding alloys is changed. In terms of quality control, we studied the influence of nitrides on molten steel, and the order from largest to smallest is boron nitride, titanium nitride, and aluminum nitride. Therefore, we added ferroboron, which has the greatest influence on quality, last, in order to reduce the generation of boron nitride as much as possible.

[0069] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A smelting method for reducing the cost of 10B21 steel and controlling nitrogen, characterized in that: It includes: In the early stage of converter smelting and LF furnace refining, black viscous slag is melted on the surface of molten steel to prevent nitrogen in the air from entering the molten steel. In the later stage of LF furnace refining, aluminum wire is added to transform the black viscous slag into white diluted slag to remove oxygen and sulfur in the molten steel, and then the composition of the molten steel is adjusted according to the composition requirements of the steel grade.

2. The smelting method according to claim 1, characterized in that: Mainly include: During the steel-making process of the converter, the argon blowing at the bottom of the ladle is adjusted to a soft blowing state, and the timing of feeding the aluminum wire is transferred from the argon station to after the slag-making of the LF furnace is completed.

3. The smelting method according to claim 1, characterized in that: The following steps are involved: After the alloy and slag are added during the steel production from the converter, the argon blowing at the bottom of the ladle is adjusted to a soft blowing state; after the steel is discharged to the argon station, sampling is taken without feeding aluminum wire to prepare acid-soluble aluminum; after the molten steel reaches the LF furnace, slag is added and electricity is supplied until the slag is completely melted, and then aluminum wire is fed to convert the black viscous slag into white diluted slag; after sampling the molten steel, alloys are added according to the sampling results to adjust the composition of the molten steel.

4. The smelting method according to claim 3, characterized in that: The converter steel tapping includes: before the converter steel tapping, controlling the end point carbon to be 0.07%-0.10%.

5. The smelting method according to claim 4, characterized in that: When the output of steel reaches 1 / 3, add 500 kg of lime / 120 tons of steel, 290-310 kg of aluminum iron / 120 tons of steel and 1100-1200 kg of high manganese / 120 tons of steel. After adding, adjust the argon blowing at the bottom of the ladle to the soft blowing state.

6. The smelting method according to claim 2, characterized in that: After the molten steel arrives at the LF furnace, slag is added to the molten steel, including: 300-330 kg / 120 tons of steel slag stone, 100-120 kg / 120 tons of steel fluorite, 130-160 kg / 120 tons of steel aluminum slag and 500-550 kg / 120 tons of steel synthetic slag.

7. The smelting method according to claim 2, characterized in that: The time for delivering electrochemical slag is 5-7 minutes, and sampling is carried out.

8. The smelting method according to claim 3, characterized in that: After the molten steel arrives at the LF furnace, slag is added and electricity is supplied until the slag is completely melted, and then aluminum wire is fed to convert the black viscous slag into white diluted slag, including: after the molten steel arrives at the LF furnace, slag is added to the molten steel to form black viscous slag on the surface of the molten steel, and then aluminum wire is fed to acid-dissolve aluminum in the molten steel to 0.060-0.070%, and electricity is continued to be supplied until the temperature rises to 1580-1600℃, so that the black viscous slag is converted into white diluted slag.

9. The smelting method according to claim 3, characterized in that: Adjusting the composition of molten steel includes: firstly adjusting the carbon and acid-soluble aluminum in the molten steel according to the analysis results of the molten steel sampling, then raising the temperature to the temperature required before soft blowing of the calcium line + 5°C, adjusting the argon gas to soft blowing argon gas, adding chromium and titanium alloy to adjust the chromium and titanium content in the molten steel, and then adding ferroboron alloy to adjust, and after adding the boron content in the molten steel, the calcium line soft blowing station is completed.

10. The smelting method according to claim 9, characterized in that: The following steps are involved: According to the results of molten steel sampling and analysis, first add carbon and acid-soluble aluminum to the molten steel, then raise the temperature to the temperature required before soft blowing of the calcium line + 5°C, adjust the argon to the soft blowing state, and then add 140 kg of ferrochrome and 165 kg of ferrotitanium. After adding, wait for 2-3 minutes before adding ferroboron. After adding ferroboron, the calcium line is soft-blown out of the station.

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