A method for handling abnormalities in molten steel in a LF furnace

Abstract

The present invention discloses a method for handling abnormalities in LF furnace molten steel, which belongs to the field of metallurgical technology. The method for handling abnormalities in LF furnace molten steel provided by the present invention comprises: after the LF furnace cover slag falls into the molten steel, the subsequent process path of the molten steel, the LF smelting moment, the area of ​​the furnace cover slag and the type of steel used in smelting the molten steel are quickly identified; according to the above characteristics, a slag surface deoxidizer is added, and the bottom blowing argon flow rate and the calcium wire feeding speed and feeding amount are adjusted to reduce the secondary oxidation degree of the molten steel and prevent nozzle nodules. The present invention quickly identifies the relevant characteristics of the LF furnace cover slag falling into the molten steel, and adopts corresponding measures such as adding a slag surface deoxidizer, blowing argon gas at the bottom of the ladle for strong deoxidation, and then feeding calcium wire for weak supplementary deoxidation, thereby reducing the secondary oxidation of the molten steel and preventing nozzle nodules.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a method for handling abnormalities in molten steel in an LF furnace. Background Art

[0002] LF refining is a widely used method for purifying molten steel. The LF furnace cover plays a crucial role in creating a reducing atmosphere, reducing molten steel aspiration, and minimizing dust outflow during the refining process. However, due to its harsh environment, slag easily adheres to the inside of the cover, adversely affecting cleaning difficulty, molten steel quality, and the frequency of cover leaks. To reduce slag adhesion to the cover, two common methods are: spraying the cover with a spray coating of appropriate properties to reduce slag adhesion and minimize the chance of adhesion; and: controlling the ladle headroom and bottom blowing air flow rate to minimize slag adhesion. However, these methods can only reduce (minor) cover slag, but cannot completely eliminate it. Furthermore, at certain times or during certain operations, such as occasional or when raising or lowering the cover, highly oxidizing cover slag may fall into the molten steel. If not promptly addressed, this can cause secondary oxidation of the molten steel, impacting its quality, particularly in the "primary furnace + LF + CC" process. At present, there are few cases of furnace cover slag falling and no abnormal disposal measures have been found.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for handling abnormalities in molten steel in an LF furnace.

[0005] The present invention solves the technical problem by adopting the following technical solutions.

[0006] The present invention provides a method for handling abnormalities in molten steel in an LF furnace, comprising: after LF furnace cover slag falls into the molten steel, quickly identifying the subsequent process path of the molten steel, the LF smelting time, the area of ​​the furnace cover slag, and the steel type of the molten steel; according to the above characteristics, adding a slag surface deoxidizer, and adjusting the bottom blowing argon flow rate and the calcium wire feeding speed and feeding amount to reduce the oxidation degree of the molten steel and prevent nozzle nodules.

[0007] The present invention has the following beneficial effects:

[0008] The present invention provides a method for handling abnormalities in molten steel in an LF furnace, comprising: after LF furnace cover slag falls into the molten steel, quickly identifying the subsequent process path of the molten steel, the LF smelting time, the area of ​​the furnace cover slag, and the type of steel being smelted in the molten steel; based on the aforementioned characteristics, adding a slag surface deoxidizer; and adjusting the bottom blowing argon flow rate and the calcium wire feed speed and feed amount to reduce the degree of secondary oxidation of the molten steel and prevent nozzle nodules. The present invention takes appropriate measures to deal with LF furnace cover slag falling into the molten steel, thereby reducing the secondary oxidation caused by the highly oxidizing furnace cover slag falling into the molten steel, minimizing the impact of the abnormal situation on the quality of the molten steel, and improving the quality of the molten steel. DETAILED DESCRIPTION

[0009] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0010] The following is a detailed description of a method for handling abnormalities in molten steel in an LF furnace provided by an embodiment of the present invention.

[0011] Note: The smelting process of LF of molten steel can generally be divided into the following steps:

[0012] 1. Early smelting.

[0013] 2. Mid-term smelting.

[0014] 3. Later smelting.

[0015] 4. (After feeding calcium line) soft blowing. (This step is generally only for molten steel in the path of primary refining furnace + LF + CC. For molten steel in the path of primary refining furnace + LF + RH + CC, there is generally no soft blowing step after calcium treatment in LF furnace)

[0016] 5. When leaving the LF station, go to the next process. (such as CC pouring, RH further processing, etc.)

[0017] The embodiment of the present invention provides a method for handling abnormalities in molten steel in an LF furnace. Before handling, the following judgments are made:

[0018] S1: After the LF furnace cover slag falls into the molten steel, the subsequent process path of the molten steel in this furnace is A or B. (A: primary furnace + LF + CC, B: primary furnace + LF + RH + CC)

[0019] S2: Identify the LF smelting moment after the LF furnace cover slag falls into the molten steel. (There are 3 cases for path A and 2 cases for path B)

[0020] S3: Identify the area M of the LF furnace cover slag after it falls into the molten steel. (The unit of M is dm 2 )

[0021] S4: After the LF furnace cover slag falls into the molten steel, it is determined whether the molten steel is aluminum deoxidized steel or silicon manganese deoxidized steel.

[0022] After determining the time, area, steel type and smelting route of the LF furnace cover slag falling into the molten steel, different disposal measures are adopted. The specific methods are as follows:

[0023] If it is path A: primary furnace + LF + CC.

[0024] For case A1: the slag from the furnace cover falls before, during and after LF smelting. Add 2.5kg / dm2 of deoxidizer to the slag surface by shoveling. 2 -5kg / dm 2 Aluminum granules (for aluminum-deoxidized steel) or 5kg / dm 2 -7.5kg / dm 2 Ferrosilicon powder (for silicon-manganese deoxidized steel) is deoxidized, and the ladle bottom blowing flow rate is controlled at 30-60Nm 3 / h, and conduct strong stirring and deoxidation for ≥2 minutes. (Make the slag fluctuate violently and deoxidize quickly)

[0025] Because of timely disposal, the above emergency treatment of the LF furnace can basically eliminate the adverse effects of oxidizing furnace cover slag. However, for the sake of insurance, the calcium treatment amount of the LF furnace is the normal process feed amount + 20m3 / 130-140t of molten steel. (Weak supplementary deoxidation)

[0026] The speed of the calcium feeding line is the normal process, generally 150-250m / min.

[0027] For situation A2: the furnace cover slag falls within 2 minutes before the calcium line is fed. Aluminum pellets are added in a whole bag at 1.25 kg / dm 2 -3.75kg / dm 2 (For aluminum deoxidized steel) or add magnesium particles 1.25kg / dm 2 -3.75kg / dm 2 (For silicon-manganese deoxidized steel) After covering the furnace cover slag drop position, the ladle bottom blowing flow rate is controlled at 20-30Nm 3 / h, after sending electricity for medium stirring deoxidation for 0-2 minutes, feed calcium line for medium supplementary deoxidation. (make the steel slag medium volatile and weakly deoxidized)

[0028] (Note: The aluminum / magnesium granules are 3-6kg / bag. Compared with shoveling in, only by throwing in the whole bag can there be a greater impact force to break through the slag layer, so that the deoxidizer can reach the side of the steel-slag interface close to the molten steel. Otherwise, if the air blowing at the bottom of the ladle is not strong, the shoveled in deoxidizer will only float on the side of the steel-slag interface close to the steel slag, that is, float on the slag surface, and the deoxidation capacity will be limited).

[0029] The density of molten steel is generally 6.8-7.2g / cm 3 , while the density of steel slag is 2.4-3.4g / cm 3 The density of aluminum is 2.7g / cm 3 , the density of magnesium is 1.7g / cm 3 .

[0030] Because the treatment is late, the above emergency treatment of the LF furnace can eliminate most of the adverse effects of the oxidizing furnace cover slag. Therefore, the calcium treatment amount of the LF furnace is the normal process feed amount + 30-50m3 / 130-140t of molten steel.

[0031] (Medium Supplemental Deoxygenation)

[0032] The speed of the calcium feeding wire is 80-150m / min to avoid excessive fluctuation of the slag surface caused by splashing of molten steel.

[0033] For situation A3: the furnace cover slag falls after the calcium wire is fed normally and the soft blowing starts or after a period of soft blowing. 2 -3.75kg / dm 2 (For aluminum deoxidized steel) or add magnesium particles 1.25kg / dm 2 -3.75kg / dm 2 (For silicon-manganese deoxidized steel) After covering the slag drop position of the furnace cover, the ladle bottom blowing flow rate is controlled at 5-20Nm 3 / h (soft blowing) after weak stirring diffusion deoxidation, then feed calcium line for strong supplementary deoxidation (no power supply during this period). (Make the steel slag slightly fluctuate and diffuse deoxidation)

[0034] Because the treatment is very late, the above emergency treatment of the LF furnace can partially eliminate the adverse effects of the oxidizing furnace cover slag. Therefore, the calcium treatment amount is (normal process feed amount, generally 0m) 60-90m3 / 130-140t molten steel. (Strong supplementary deoxidation)

[0035] The speed of the calcium feeding wire is ≤80m / min to avoid excessive fluctuation of the slag surface caused by splashing of molten steel, so as to make the slag surface crust as soon as possible, reduce the oxygen transfer of furnace cover slag into the molten steel, and reduce the slag being drawn into the deep of the molten steel.

[0036] For case B1: the slag from the furnace cover falls before, during and after LF smelting. Add 2.5kg / dm2 of deoxidizer to the slag surface by shoveling. 2 -5kg / dm 2 Aluminum granules (for aluminum-deoxidized steel) or 5kg / dm 2 -7.5kg / dm 2 Ferrosilicon powder (for silicon-manganese deoxidized steel) is deoxidized, and the ladle bottom blowing flow rate is controlled at 30-60Nm 3 / h, and conduct strong stirring and deoxidation for ≥2 minutes. (Make the slag fluctuate violently and deoxidize quickly)

[0037] Because of timely disposal, the above emergency treatment of the LF furnace can basically eliminate the adverse effects of oxidizing furnace cover slag. However, for the sake of insurance, the calcium treatment amount of the RH furnace is the normal process feed amount + 20m3 / 130-140t of molten steel. (Weak supplementary deoxidation)

[0038] The speed of the calcium feeding line is the normal process, generally 150-250m / min. (Basically the same as the above A1 situation, the main difference is that the calcium feeding line is fed in the RH furnace)

[0039] For case B2: the slag from the furnace cover falls within 2 minutes before the molten steel leaves the LF station. In this case, the LF shall be taken and steel samples shall be taken immediately to confirm the Als and Si contents in the molten steel. Then, aluminum pellets (1.25 kg / dm2) shall be added to the whole package. 2 -3.75kg / dm 2 (For aluminum deoxidized steel) or add magnesium particles 1.25kg / dm 2 -3.75kg / dm 2 (For silicon-manganese deoxidized steel) After covering the furnace cover slag drop position, the ladle bottom blowing flow rate is controlled at 20-30Nm 3 / h, after the power is supplied for medium stirring and deoxidation for 0-2 minutes, the calcium line is fed for 20-40m / 130-140t (under normal circumstances, the molten steel on this path does not need to be fed with calcium line, which is for the first medium supplementary deoxidation), and finally the molten steel leaves the LF station;

[0040] The speed of the calcium feeding wire is 80-150m / min to avoid excessive fluctuation of the slag surface caused by splashing of molten steel.

[0041] After the molten steel reaches the RH furnace, observe the location of the remaining furnace cover slag on the molten steel surface. Lift the steel away from the furnace cover slag to prevent it from rising through the immersion tube into the RH vacuum tank. Immediately after the molten steel reaches the RH furnace, sample the steel to confirm the Als and Si contents. These values ​​are then compared with the Als and Si contents of the steel sample taken during the LF process. If the ΔAls loss is ≥0.004% (for aluminum-deoxidized steels) or the ΔSi loss is ≥0.02% (for silicon-manganese-deoxidized steels), alloying is performed according to the upper limits of the Als and Si content for that steel type, respectively, to prevent the finished continuous casting product from falling below the specified composition. Furthermore, after the RH vacuum is terminated, an additional 10-30 m / 130-140 t of molten steel is fed to the pure calcium line (second weak supplemental deoxidation).

[0042] The speed of the calcium feeding wire is 80-150m / min to avoid excessive fluctuation of the slag surface caused by splashing of molten steel.

[0043] The composition and particle size of the aluminum or magnesium particles used above are as follows:

[0044] Aluminum particle parameters: composition Al ≥ 99.5%; particle size 5mm ≤ ≤ 10mm.

[0045] Magnesium particle parameters: composition Mg ≥ 99.5%; particle size 5mm ≤ ≤ 10mm.

[0046] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0047] Before technical reform, Example 1

[0048] In the 408460 heat of SWRCH6A steel (aluminum steel, i.e. aluminum deoxidized steel) in the “primary furnace + LF + CC” route, in the late smelting period, the LF furnace master found a piece of about 7dm on the slag surface 3 minutes before preparing to feed the Ca line. 2 After the furnace cover slag was removed, no corresponding measures were taken. After normal power supply for 2 minutes and a 1-minute wait, the Ca wire was fed at a feed speed of 220m / min for 170m (the normal Ca processing capacity for this steel grade). After 15 minutes of soft blowing, temperature measurement, sampling, and exiting the station, it was found that the Ca content in the molten steel leaving the LF station was only 8ppm (normally about 20ppm). During subsequent pouring of molten steel from this furnace, the stopper rod curve rose significantly, about 7mm (normally ≤0.5mm), the crystallizer liquid level fluctuated frequently, and subsequent continuous casting was stopped unplanned. (Situation A1 before implementation, aluminum-deoxidized steel)

[0049] Before technical reform, Example 2

[0050] 408991 heat "primary furnace + LF + CC" route 20 steel (not including aluminum steel, i.e. silicon manganese deoxidized steel), 2 minutes before the molten steel was ready to feed the Ca line, the LF furnace master found a piece of about 5dm on the slag surface. 2After the furnace cover slag was removed, no corresponding measures were taken. Normal power was supplied for 1 minute, and after waiting for 1 minute, 80 meters of Ca wire was fed at a feed speed of 220m / min (the normal Ca processing capacity for this steel grade). After 15 minutes of soft blowing, temperature measurement, sampling, and exiting the station, it was found that the Ca content in the molten steel leaving the LF station was only 7ppm (normally about 13ppm). During subsequent pouring of molten steel from this furnace, the stopper rod curve rose significantly, about 4mm (normally ≤0.5mm), and the crystallizer liquid level fluctuated frequently. (Before implementation of Case A2, silicon-manganese deoxidized steel)

[0051] Before technical reform, Example 3

[0052] In the 408843 heat of SWRCH6A steel (aluminum steel, i.e. aluminum deoxidized steel) in the “primary furnace + LF + CC” route, after 1 minute of soft blowing, the LF furnace master observed the size of the bright surface of the slag during the soft blowing and found a piece of about 5dm on the slag surface. 2 After the furnace cover slag was removed, no corresponding measures were taken. After continuing the soft blowing for 14 minutes, temperature measurement, sampling, and exiting the station, it was found that the Ca content in the molten steel leaving the LF station was only 6ppm (normally about 20ppm). During subsequent pouring of molten steel from this furnace, the stopper rod curve rose significantly, about 9mm (normally ≤0.5mm), and the crystallizer liquid level fluctuated frequently, resulting in unplanned casting stops. (Situation A3 before implementation, aluminum-deoxidized steel)

[0053] Before technical reform, Example 4

[0054] 408952 heat of SWRCH6A steel (aluminum steel, i.e. aluminum deoxidized steel) in the “primary furnace + LF + CC + RH” route. 2 minutes before the molten steel was ready to leave the station, the LF furnace master found a piece of about 7dm on the slag surface. 2 After the slag from the furnace cover was detected, samples were taken immediately (the Als was measured to be 0.045%). No corresponding measures were taken subsequently. After normal power supply for 1 minute and waiting for 1 minute, temperature measurement, sampling, and exiting the station were carried out. After the molten steel reached RH, temperature measurement and sampling were carried out (the Als was measured to be 0.037%). After normal high vacuum treatment, the Ca wire was fed for 170m at a feeding speed of 220m / min (the normal Ca treatment amount for this type of steel). After soft blowing for 15 minutes, temperature measurement, sampling, and exiting the station were carried out. It was found that the Ca content in the molten steel leaving the RH station was only 10ppm (normally about 20ppm). When the molten steel from this furnace was subsequently poured, the stopper rod curve rose significantly, about 5mm (normally ≤0.5mm), the liquid level of the crystallizer fluctuated frequently, and the continuous casting was subsequently stopped unplanned. (Before the implementation of Situation B2, aluminum-deoxidized steel)

[0055] Before the technical transformation, cases 1-4 showed the occurrence of furnace cover slag falling, which was the result of not adopting the method used in the present invention. It can be seen that the Ca content of LF or RH outlet was lower than that in normal situation, indicating that the furnace cover slag oxidized the molten steel and increased the inclusions, which eventually led to frequent fluctuations in the crystallizer liquid level, even serious blockage of the water nozzle and unplanned suspension of continuous casting.

[0056] Example 1

[0057] In the process of SWRCH6A steel (aluminum steel, i.e. aluminum deoxidized steel) in the “primary furnace + LF + CC” process, in the late stage of smelting, the LF furnace master found a piece of about 7dm on the slag surface 3 minutes before preparing to feed the Ca line. 2 After the furnace cover slag is removed, add 25kg (3.5kg / dm2) of aluminum granules as a deoxidizer to the slag surface immediately by shoveling it in. 2 *7dm 2 = 25kg) for deoxidation, and the ladle bottom blowing flow rate is controlled at 50Nm 3 / h, and carry out power supply strong stirring deoxidation for 2 minutes to make the slag fluctuate violently and deoxidize quickly. After stopping power supply and waiting for 1 minute, feed the Ca wire for 190m at a feeding speed of 220m / min (the normal Ca processing capacity of this steel type is 170m+20m). After soft blowing for 15 minutes, measure the temperature, take samples, and leave the station. It was found that the Ca content in the LF molten steel leaving the station was 16ppm (normally about 20ppm, originally 8ppm). When the molten steel of this furnace was poured later, the stopper rod curve did not rise obviously, about 2mm (normally ≤0.5mm, originally 7mm), and the liquid level in the crystallizer fluctuated 5mm once.

[0058] Different from Example 1 before the technical transformation, the above emergency treatment of the LF furnace can eliminate most of the adverse effects of the oxidizing furnace cover slag due to timely disposal.

[0059] Example 2

[0060] In the “primary furnace + LF + CC” route for 20 steel (aluminum-free steel, i.e. silicon-manganese deoxidized steel), 2 minutes before the molten steel was ready to feed the Ca line, the LF furnace master found a piece of about 5dm on the slag surface. 2 After removing the furnace cover slag, put magnesium particles 2kg / dm in a whole bag. 2 (2kg / dm 2 *5dm 2 =10kg) to cover the falling position of the furnace cover slag and then deoxidize, while the ladle bottom blowing flow rate is controlled at 20Nm 3 / h, and carry out medium stirring deoxidation for 1 minute to make the slag moderately fluctuate and deoxidize quickly. After stopping power supply and waiting for 1 minute, feed the Ca line for 120m at a feeding speed of 120m / min (the normal Ca processing capacity of this steel type is 80m+40m). After soft blowing for 15 minutes, measure the temperature, take samples, and leave the station. It was found that the Ca content in the LF molten steel leaving the station was 11ppm (normally about 13ppm, originally 7ppm). When the molten steel of this furnace was poured later, the stopper rod curve did not rise significantly, about 1.5mm (normally ≤0.5mm, originally 4mm), and the liquid level in the crystallizer fluctuated 3mm once.

[0061] Different from Example 2 before the technical transformation, the above emergency treatment of the LF furnace can eliminate most of the adverse effects of the oxidizing furnace cover slag due to timely disposal.

[0062] Example 3

[0063] In the process of “primary furnace + LF + CC”, SWRCH6A steel (aluminum steel, i.e. aluminum deoxidized steel) was blown for 1 minute. When the LF furnace master observed the size of the bright surface of the slag during the soft blowing, he found a piece of about 5dm on the slag surface. 2 After removing the slag from the furnace cover, add aluminum particles 2kg / dm in a whole bag. 2 (2kg / dm 2 *5dm 2 =10kg) to cover the slag drop position of the furnace cover and then deoxidize, while the ladle bottom blowing flow rate is controlled at 8Nm 3 / h, making the slag fluctuate slightly for diffusion deoxidation, and then feeding the Ca line for 80m at a feeding speed of 80m / min. After continuing soft blowing for 14min, temperature measurement, sampling, and exiting the station, it was found that the Ca content in the molten steel leaving the LF station was 14ppm (normally about 20ppm, originally 6ppm). When the molten steel of this furnace was subsequently poured, the stopper rod curve did not rise significantly, about 2mm (normally ≤0.5mm, originally 9mm), and the liquid level in the crystallizer fluctuated by 5mm twice.

[0064] Different from Example 3 before the technical transformation, the above emergency treatment of the LF furnace can eliminate most of the adverse effects of the oxidizing furnace cover slag due to timely disposal.

[0065] Example 4

[0066] In the “primary furnace + LF + CC + RH” path, SWRCH6A steel (aluminum steel, i.e. aluminum deoxidized steel) was produced. 2 minutes before the molten steel was ready to leave the station, the LF furnace master found a piece of about 7dm on the slag surface. 2 After the furnace cover slag is removed, a sample is taken immediately (the Als is measured to be 0.045%), and then 2 kg / dm of aluminum particles are added in a whole bag. 2 (2kg / dm 2 *5dm 2 =10kg) to cover the falling position of the furnace cover slag and then deoxidize, while the ladle bottom blowing flow rate is controlled at 20Nm 3 / h, and conduct medium stirring deoxidation for 1 minute at the power supply to make the slag moderately fluctuate and deoxidize quickly and strongly. After stopping the power supply and waiting for 1 minute, feed the Ca wire for 30m at a feeding speed of 120m / min for medium supplementary deoxidation (under normal circumstances, the LF station does not need to feed the Ca wire for this steel). After the molten steel reaches the RH, measure the temperature and take samples (the Als is measured to be 0.042%). After normal high vacuum treatment, feed the Ca wire for 200m at a feeding speed of 120m / min (the normal Ca treatment capacity of this steel is 170m+30m). After soft blowing for 15 minutes, measure the temperature, take samples, and leave the station. It was found that the Ca content in the molten steel leaving the RH station was 16ppm (normally about 20ppm, originally 10ppm). When the molten steel from this furnace was subsequently poured, the stopper rod curve did not rise significantly, about 1.5mm (normally ≤0.5mm, originally 5mm), and the liquid level in the crystallizer fluctuated 3mm once.

[0067] After the technical transformation, Examples 1-4 showed that the furnace cover slag fell. The results of the method used in the present invention showed that the Ca content of LF or RH at the outlet increased compared with the case without treatment, and the rising amplitude of the stopper rod and the frequency of crystallizer liquid level fluctuations decreased, indicating that the corresponding method of the present invention can basically eliminate the adverse effects of the furnace cover slag.

[0068] Taking Example 3 as an example, the influence of changes in various key parameters on the final results (such as the rise of the stopper rod and the frequency of crystallizer liquid level fluctuation) is explained.

[0069] Comparative Example 1

[0070] The steps are similar to those in Example 3, except that the amount of aluminum pellets used as deoxidizer is less, and the aluminum pellets are added in a package at 1 kg / dm 2 (1kg / dm 2 *5dm 2 =5kg) was added to cover the fallen slag from the furnace roof, and then deoxidation was performed. Temperature measurement, sampling, and exit were performed. The Ca content in the molten steel exiting the LF was found to be 8ppm (normally about 20ppm, 14ppm in Example 3). During subsequent pouring of molten steel from this furnace, the stopper curve rose significantly, by about 6mm (normally ≤0.5mm, 2mm in Example 3), and the mold liquid level fluctuated by 5mm five times.

[0071] This indicates that when the amount of deoxidizer aluminum particles is too little, the oxidizing hazards of the furnace cover slag are mostly not eliminated, more inclusions are generated, and the rise of the stopper rod and the frequency of the crystallizer liquid level fluctuations are still relatively high.

[0072] Comparative Example 2

[0073] The steps are similar to those in Example 3, except that more aluminum particles are added as deoxidizer, and 4 kg / dm2 of aluminum particles are added as a whole bag. 2 (4kg / dm2 *5dm 2 =20kg) was added to cover the fallen slag from the furnace roof, and then deoxidation was performed. Temperature measurement, sampling, and exit were performed. The Ca content in the molten steel exiting the LF was found to be 10 ppm (normally about 20 ppm, 14 ppm in Example 3). During subsequent pouring of molten steel from this furnace, the stopper curve rose significantly, by about 4 mm (normally ≤ 0.5 mm, 2 mm in Example 3), and the mold level fluctuated by 5 mm four times.

[0074] This shows that when the amount of deoxidizer aluminum particles is too high, the oxidizing hazard of the furnace cover slag has been partially eliminated. However, since too many aluminum particles are added, the part of aluminum particles that have not reacted with the furnace cover slag is easily oxidized by the air, resulting in the formation of more inclusions, and the rise of the stopper rod and the frequency of fluctuation of the crystallizer liquid level are still relatively high.

[0075] Comparative Example 3

[0076] The steps are similar to those in Example 3, except that the ladle bottom blowing flow rate is too large and is controlled at 30 Nm 3 / h. Temperature measurement, sampling, and exit were performed. It was later discovered that the Ca content in the molten steel exiting the LF was 7 ppm (normally about 20 ppm, 14 ppm in Example 3). During subsequent pouring of molten steel from this furnace, the stopper curve rose significantly, reaching about 5.5 mm (normally ≤ 0.5 mm, 2 mm in Example 3), and the mold liquid level fluctuated by 5 mm five times.

[0077] This indicates that when the ladle bottom blowing flow rate is too large, the slag fluctuates greatly, and the oxidizing property of the furnace cover slag is easily transferred to the lower and upper layers of the molten steel, resulting in more molten steel being oxidized and more inclusions being produced. The stopper rod rises and the crystallizer liquid level fluctuates frequently.

[0078] Comparative Example 4

[0079] The steps were similar to those in Example 3, except that the Ca feed line speed was too high and was controlled at 160 m / min. Temperature measurement, sampling, and exit were performed. The Ca content in the molten steel exiting the LF was found to be 6 ppm (normally about 20 ppm, 14 ppm in Example 3). During subsequent pouring of molten steel from this furnace, the stopper curve rose significantly, reaching approximately 6.5 mm (normally ≤ 0.5 mm, 2 mm in Example 3). The mold level fluctuated by 5 mm six times.

[0080] This indicates that when the Ca feeding linear velocity is too high, more calcium vapor is generated per unit time, the slag mixing is strong, and the slag fluctuation is large. Similarly, the oxidizing property of the furnace cover slag is easily transferred to the lower and upper layers of the molten steel, resulting in more molten steel being oxidized and more inclusions being produced. The rise of the stopper rod and the frequency of fluctuations in the crystallizer liquid level are still relatively high.

[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for handling abnormalities in molten steel in an LF furnace, characterized in that: include: After the LF furnace cover slag falls into the molten steel, the subsequent process path of the molten steel, the LF smelting time, the area of ​​the furnace cover slag and the steel type of the smelting molten steel are quickly identified. According to the above characteristics, a slag surface deoxidizer is added, and the bottom blowing argon flow rate and the calcium wire feeding speed and feeding amount are adjusted to reduce the secondary oxidation degree of the molten steel and prevent nozzle nodules. Among them: When the smelting path of molten steel is primary furnace + LF + CC, the area unit of furnace cover slag is dm 2 During the smelting process, if the furnace cover slag falls before, during or after the LF smelting, add additional deoxidizer to the slag surface by shoveling, and adjust the argon flow rate at the bottom of the ladle to carry out strong stirring and deoxidation by power transmission, and then feed the calcium line for weak supplementary deoxidation; if the furnace cover slag falls within 2 minutes before the calcium line is fed, add the slag surface deoxidizer by adding the whole bag, and adjust the argon flow rate at the bottom of the ladle to carry out medium stirring and deoxidation by power transmission, and then feed the calcium line for medium supplementary deoxidation; if the furnace cover slag falls after the calcium line is fed normally and soft blowing begins or after soft blowing for a period of time, add the slag surface deoxidizer by adding the whole bag, and adjust the argon flow rate at the bottom of the ladle to carry out weak stirring and diffusion deoxidation, and then feed the calcium line for strong supplementary deoxidation; When the smelting path of molten steel is primary furnace + LF + RH + CC, the area of ​​furnace cover slag is in dm 2 When the molten steel is discharged from the LF furnace, if the slag falls before, during or after the LF smelting, an additional slag surface deoxidizer is added by shoveling, and the argon flow rate of the ladle bottom blowing is adjusted to carry out strong stirring deoxidation, and then the calcium wire is fed for weak supplementary deoxidation; if the slag falls within 2 minutes before the molten steel leaves the LF station, the LF furnace immediately takes a steel sample to confirm the Als and Si content in the molten steel, adds the slag surface deoxidizer by adding the whole bag, and adjusts the argon flow rate of the ladle bottom blowing to carry out medium stirring deoxidation, and then the calcium wire is additionally fed for the first medium supplementary deoxidation, and finally the molten steel from the LF furnace leaves the station; after the molten steel reaches the RH furnace, the position of the remaining slag on the molten steel surface is observed, and the jacking is carried out to avoid the position of the slag to prevent the slag from being lifted into the RH vacuum tank through the immersion pipe; after the molten steel reaches the RH furnace, the Als and Si content in the molten steel is immediately sampled to confirm the Als and Si content in the molten steel, and then compared with the Als and Si content in the steel sample taken from the LF furnace, the alloy composition is adjusted, and after the RH vacuum is ended, additional pure calcium wire is required to be fed for a second weak supplementary deoxidation.

2. The method for handling abnormality of molten steel in a LF furnace according to claim 1, wherein: When the smelting path of molten steel is primary furnace + LF + CC, the area unit of furnace cover slag is dm 2 If the furnace cover slag falls before, during or after LF smelting, for aluminum deoxidized steel, add additional aluminum particles 2.5kg / dm by shoveling. 2 -5kg / dm 2 For deoxidation, or for silicon-manganese deoxidized steel, add 5kg / dm of ferrosilicon powder by shoveling 2 -7.5kg / dm 2 Deoxidation is carried out, and the ladle bottom blowing flow rate is controlled at 30-60Nm 3 / h, supply power for strong stirring and deoxidation for ≥2 minutes, and then feed the calcium wire.

3. The method for handling abnormality of molten steel in LF furnace according to claim 2, characterized in that: The calcium processing capacity of the LF furnace is the normal process feed amount + 20m3 / 130-140t molten steel.

4. The method for handling abnormality of molten steel in a LF furnace according to claim 2, wherein: The calcium feeding line speed of the LF furnace is 150-250m / min.

5. The method for handling abnormality of molten steel in LF furnace according to claim 1, characterized in that: When the smelting path of molten steel is primary furnace + LF + CC, the area unit of furnace cover slag is dm 2 If the furnace cover slag falls within 2 minutes before the calcium line is ready to be fed, for aluminum deoxidized steel, add aluminum particles 1.25kg / dm in the form of a whole bag. 2 -3.75kg / dm 2 After covering the fallen position of the furnace cover slag, or for silicon-manganese deoxidized steel, add magnesium particles 1.25kg / dm in the form of a whole bag. 2 -3.75kg / dm 2 After covering the falling position of the furnace cover slag, the ladle bottom blowing flow rate is controlled at 20-30Nm 3 / h, after power supply and medium stirring and deoxidation for 0-2 minutes, feed the calcium wire.

6. The method for handling abnormality of molten steel in LF furnace according to claim 5, characterized in that: The calcium processing capacity of the LF furnace is the normal process feed amount + 30-50m3 / 130-140t of molten steel.

7. The method for handling abnormality of molten steel in a LF furnace according to claim 5, characterized in that: The speed of the calcium wire feeding the LF furnace is 80-150m / min.

8. The method for handling abnormality of molten steel in a LF furnace according to claim 1, characterized in that: When the smelting path of molten steel is primary furnace + LF + CC, the area unit of furnace cover slag is dm 2 When the furnace cover slag is fed with calcium wire normally, it starts to be soft blown or falls off after being soft blown for a period of time. For aluminum deoxidized steel, aluminum particles 1.25kg / dm are added in a whole package. 2 -3.75kg / dm 2 Or for silicon-manganese deoxidized steel, add magnesium particles 1.25kg / dm2 in the whole package 2 -3.75kg / dm 2 After covering the falling position of the furnace cover slag, the ladle bottom blowing flow rate is controlled at 5-20Nm 3 / h later, the calcium line is fed, and no power is supplied during the bottom blowing of argon and the feeding of the calcium line.

9. The method for handling abnormality of molten steel in a LF furnace according to claim 8, characterized in that: The calcium processing capacity of the LF furnace is 60-90m3 / 130-140t of molten steel.

10. The method for handling abnormality of molten steel in a LF furnace according to claim 8, characterized in that: The speed of feeding calcium wire to LF furnace is ≤80m / min.

11. The method for handling abnormality of molten steel in a LF furnace according to claim 1, characterized in that: When the smelting path of molten steel is primary furnace + LF + RH + CC, the area of ​​furnace cover slag is in dm 2 The furnace cover slag is dropped before, during and after LF smelting. For aluminum deoxidized steel, additional aluminum particles 2.5kg / dm are added by shoveling. 2 -5kg / dm 2 For deoxidation, or for silicon-manganese deoxidized steel, add 5kg / dm of ferrosilicon powder by shoveling 2 -7.5kg / dm 2 Deoxidation is carried out, and the ladle bottom blowing flow rate is controlled at 30-60Nm 3 / h, and carry out power supply, strong stirring and deoxidation for ≥2min.

12. The method for handling abnormality of molten steel in an LF furnace according to claim 11, characterized in that: The calcium processing capacity of the RH furnace is the normal process feed amount + 20m3 / 130-140t molten steel.

13. The method for handling abnormality of molten steel in an LF furnace according to claim 11, characterized in that: The speed of feeding calcium wire to RH furnace is 150-250m / min.

14. The method for handling abnormality of molten steel in an LF furnace according to claim 1, characterized in that: When the smelting path of molten steel is primary furnace + LF + RH + CC, the area of ​​furnace cover slag is in dm 2 If the slag from the furnace cover falls within 2 minutes before the molten steel leaves the LF station, the LF furnace will immediately take a steel sample to confirm the Als and Si content in the molten steel. For aluminum deoxidized steel, add aluminum particles 1.25kg / dm2 in the form of a whole package. 2 -3.75kg / dm 2 Or for silicon-manganese deoxidized steel, add magnesium particles 1.25kg / dm in the form of a whole package 2 -3.75kg / dm 2 After covering the slag drop position of the furnace cover, control the air blowing flow rate of the ladle bottom to 20-30Nm 3 / h, after power supply and medium stirring and deoxidation for 0-2 minutes, the calcium line is fed, and finally the molten steel leaves the LF station.

15. The method for handling abnormality of molten steel in an LF furnace according to claim 14, characterized in that: The calcium processing capacity of the LF furnace is 20-40m3 / 130-140t of molten steel for weak supplementary deoxidation.

16. The method for handling abnormality of molten steel in an LF furnace according to claim 14, characterized in that: The speed of the LF furnace calcium line is 80-150m / min.

17. The method for handling abnormality of molten steel in an LF furnace according to claim 1, characterized in that: When the smelting path of molten steel is primary furnace + LF + RH + CC, the area of ​​furnace cover slag is in dm 2 When the molten steel reaches the RH furnace, if the furnace cover slag falls within 2 minutes before the molten steel leaves the LF station, after the molten steel reaches the RH furnace, observe the position of the furnace cover slag remaining on the molten steel surface at this time, avoid the position of the furnace cover slag for jacking, and prevent the furnace cover slag from being lifted into the RH vacuum tank through the immersion tube; after the molten steel reaches the RH furnace, immediately take samples to confirm the Als and Si contents in the molten steel, and then compare them with the Als and Si contents in the steel samples taken from the aforementioned LF furnace. For aluminum-deoxidized steel, if the △Als loss is ≥0.004%, or for silicon-manganese-deoxidized steel, if the △Si loss is ≥0.02%, then add alloy according to the upper limit requirements of the Als and Si contents of this steel composition to prevent the composition of the continuous casting product from being lower than the requirement; in addition, after the RH vacuum ends, additional pure calcium wire needs to be fed, and finally the molten steel leaves the RH station.

18. The method for handling abnormality of molten steel in an LF furnace according to claim 17, characterized in that: The calcium treatment capacity of the RH furnace is the normal process feed rate + 10-30m3 / 130-140t of molten steel for strong supplementary deoxidation.

19. The method for handling abnormality of molten steel in an LF furnace according to claim 17, characterized in that: The speed of the RH furnace calcium line is 80-150m / min.

20. The method for handling abnormality of molten steel in an LF furnace according to any one of claims 2 to 16, characterized in that: The parameters of aluminum particles are as follows: composition Al ≥ 99.5%; particle size 5mm ≤ ≤ 10mm.

21. The method for handling abnormality of molten steel in an LF furnace according to any one of claims 5-10 and 14-16, characterized in that: The parameters of magnesium particles are as follows: composition Mg ≥ 99.5%; particle size 5mm ≤ ≤ 10mm.