Ladle refining furnace and method for reducing electrode consumption in molten steel refining and smelting process

Abstract

The invention discloses a ladle refining furnace and a method for reducing electrode consumption in the molten steel refining and smelting process, and belongs to the technical field of metallurgy. The ladle refining furnace comprises an electrode clamp and a gas blowing device arranged below the electrode clamp. According to the gas injection device of the ladle refining furnace, the gas wall is formed below the electrode to prevent the air from being in contact with the electrode, so that the electrode consumption in the molten steel refining and smelting process is reduced. Moreover, when the ladle refining furnace is used for refining and smelting the molten steel, the process is simple and easy to operate, the overall cost is remarkably reduced, and the ladle refining furnace is suitable for large-scale industrial production. In addition, the method solves the problems of high electrode consumption and short service life in the refining process caused by serious air oxidation after the electrode is electrified in the molten steel refining and smelting process, reduces the oxygen concentration on the surface of a steel ladle after refining and smelting, reduces the oxygen uptake in the slag forming process, and improves the molten steel quality.

Description

Technical Field

[0001] The present invention relates to the field of metallurgical technology, and in particular, to a ladle refining furnace and a method for reducing electrode consumption during the refining process of molten steel. Background Art

[0002] Molten steel, as an intermediate product in the steelmaking process, is closely related to the application fields and development challenges of the steel industry. After solidification and shaping, molten steel can be transformed into various types of steel and has been widely used. In the field of construction and infrastructure, it can be used for high-rise buildings, bridges, roads, or seismic structures; in the field of transportation, it can be used for automobile manufacturing, ships, rail transit, or aerospace; in the field of machinery manufacturing, it can be used for industrial equipment, tools, and die manufacturing; in the field of energy and power, it can be used for power equipment, nuclear power, and wind power; in the field of household appliances and consumer goods, it can be used for the outer shells of household appliances or daily necessities, etc.; in other emerging fields, it can be used for 3D printing or green energy equipment. However, the production of molten steel also faces many challenges, such as environmental protection and carbon emission pressure, resource constraint pressure, high costs, and the need for technological upgrading.

[0003] The LF (Ladle Furnace) refining process is an important secondary refining technology in iron and steel metallurgy, mainly used for adjusting the composition of molten steel, controlling the temperature, desulfurization, deoxidation, and removing inclusions. At present, the main research and development fields of the LF refining process lie in its green and efficient development. The green and efficient development of the LF refining process is mainly reflected in the development of energy-saving and consumption-reducing technologies, such as developing an efficient electrode system to reduce oxidation loss; promoting waste heat recovery technology to preheat scrap steel or generate electricity using the flue gas of the LF furnace; carrying out environmental protection upgrades, such as developing an integrated dust removal system to capture dust and harmful gases (such as CO, fluorides), and promoting low-fluoride / fluoride-free environmentally friendly slag systems to reduce environmental pollution; promoting intelligent and digitalization, such as applying artificial intelligence (AI) to predict the composition and temperature of molten steel, optimizing the refining path, or combining with the industrial Internet of Things (IIoT) to achieve remote monitoring and fault diagnosis.

[0004] In order to improve the quality of molten steel and reduce production costs, molten steel is generally smelted through the LF refining process after being smelted in a converter or electric furnace, so as to adjust the composition, reduce impurities in the steel, and improve the quality of molten steel. The LF refining and smelting process mainly uses three electrodes for heating and slag removal. During the smelting process, the electrodes are consumed quickly due to factors such as slag scouring, erosion, and oxidation in a high-temperature hot state, resulting in a large consumption of electrodes, which significantly increases production costs. Specifically, the cost of electrode materials is high: LF furnace electrodes are usually made of high-purity graphite materials, which are expensive (accounting for 15%-30% of the refining cost). Excessive consumption directly increases the cost per ton of steel and reduces profits; energy waste: excessive consumption of electrodes may be accompanied by a decrease in the utilization rate of electrical energy, resulting in an increase in additional electricity costs; increased loss of auxiliary materials: frequent replacement of electrodes may increase the maintenance costs of auxiliary components such as electrode holders and cooling water systems. Moreover, the large consumption of electrodes will also reduce production efficiency, which is reflected in the frequent shutdown to replace electrodes: the electrode consumption is too fast and the production needs to be interrupted for replacement, resulting in reduced equipment utilization and affecting the production rhythm; the process cycle is extended: abnormal electrode consumption may lead to reduced heating efficiency, extended refining time (such as difficulty in heating molten steel), and disrupt the connection of subsequent processes such as continuous casting machines. In addition, the large consumption of electrodes will also lead to the risk of fluctuations in the quality of molten steel, which is reflected in unstable temperature control: abnormal electrode consumption may lead to arc instability, affect the uniformity of molten steel temperature, lead to overcooling or overheating, and then affect the refining effects such as desulfurization and deoxidation; poor composition uniformity: discontinuous heating may weaken the stirring effect of argon blowing at the bottom of the ladle, cause composition segregation or incomplete removal of inclusions, and reduce the mechanical properties of steel; electrode shedding and contamination of molten steel: excessive consumption of electrodes may produce graphite particles due to fracture or peeling, which are mixed into the molten steel to form inclusion defects. In addition, the large consumption of electrodes may also cause problems such as aggravated lining erosion, damage to the pole clamping system, and load fluctuations in the electrical system, resulting in a shortened equipment life and even further safety hazards and environmental problems. In short, excessive electrode consumption will form a chain reaction of "high cost → low efficiency → quality fluctuation → equipment loss → safety risk", which seriously affects the comprehensive benefits of LF refining process. Therefore, it is necessary to reduce electrode consumption and ensure production stability and economy by optimizing arc control, improving electrode quality, and strengthening equipment maintenance.

[0005] In order to reduce electrode consumption, most steel mills currently tend to reduce the oxidizability of slag and adjust power supply parameters during refining and smelting. However, after the power is turned on, the electrodes are prone to react with oxygen in the air under high temperature and heat, resulting in severe oxidation of the surface electrodes and reduced electrode surface strength. As a result, during the next smelting, the erosion of the electrodes by the slag is seriously aggravated, resulting in still high electrode consumption.

[0006] Therefore, it is of great significance to research and develop a new method for reducing electrode consumption during LF refining and smelting processes. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a ladle refining furnace and a method for reducing electrode consumption during molten steel refining and smelting processes. Using the ladle refining furnace for molten steel refining and smelting can reduce electrode consumption and the production cost of steel.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a ladle refining furnace, including an electrode clamp and a gas injection device arranged below the electrode clamp.

[0010] Preferably, the gas injection device is annular and a Laval nozzle is arranged below it.

[0011] The present invention can install protective materials on the adjacent sides of the gas injection device and the Laval nozzle and the electrode.

[0012] The present invention does not limit the number of Laval nozzles.

[0013] Preferably, the included angle between the Laval nozzle and the central horizontal line of the gas injection device is 85° - 88°.

[0014] Preferably, the distance between each nozzle of the Laval nozzle is 80 - 100 mm.

[0015] Preferably, the opening and closing of the gas injection device are controlled by the lifting position of the electrode of the ladle refining furnace.

[0016] The above control by the lifting position of the electrode of the ladle refining furnace is specifically as follows: After the electrode is energized, when the electrode rises to the specified position, the gas injection device switch automatically opens and injects gas according to a certain injection time and injection flow rate, thereby forming a gas wall to prevent air from contacting the electrode and reducing electrode consumption during molten steel refining and smelting processes.

[0017] Preferably, the injection time and injection flow rate after the gas injection device is opened are controlled by a set model. The present invention improves the ordinary ladle refining furnace by installing a gas injection device below the electrode clamp (electrode holder) of the ladle refining furnace.

[0018] The electrode consumption of the ladle refining furnace (LF) mainly comes from the oxidation of the electrode in contact with air at high temperature and hot state, as well as the oxidation and erosion of the slag during power-on.

[0019] The present invention uses the improved ladle refining furnace described above to refine molten steel, which can reduce the electrode consumption caused by the oxidation of the electrode under high temperature and hot state due to the contact between the electrode and air, and thus achieve the purpose of reducing the electrode consumption during the refining of molten steel.

[0020] The present invention also provides a method for reducing electrode consumption during the refining of molten steel, including the following steps:

[0021] After the electrodes of the above ladle refining furnace are energized, gas is blown downward along the electrodes through the gas injection device to form a gas wall to prevent air from contacting the electrodes, thereby reducing the electrode consumption during the refining of molten steel.

[0022] The blown gas in the above method includes but is not limited to inert gas.

[0023] Preferably, the gas in the present invention is selected from nitrogen or argon; more preferably nitrogen.

[0024] The blowing time (s) of the gas in the present invention is related to the electrode energizing time (s) of the ladle refining furnace.

[0025] Preferably, the blowing time (s) model of the gas in the present invention is shown in the following table:

[0026] Power-on time, s Blow time, s ≤60 60 90 60.9 120 62.1 150 63.6 180 65.4 210 67.5 240 69.9 270 72.6 300 75.6 330 78.9 360 82.5 390 86.4 420 90.6 450 95.1 480 99.9 。

[0027] The blowing flow rate (m 3 ) of the gas in the present invention is related to the electrode power consumption (Kwh) and the electrode diameter (mm) of the ladle refining furnace.

[0028] Preferably, the blowing flow rate (m3) model of the gas in the present invention is shown in the following table:

[0029]

[0030] In the blowing flow rate (m 3 ) model table of the above gas, the data in the first row from top to bottom is the power consumption, the data in the first column from left to right is the electrode diameter, and the remaining data are all the blowing flow rate (m 3 ) of the gas.

[0031] After tapping the molten steel from the converter and the molten steel enters the refining position for refining and the electrodes are energized, the gas injection device is started to blow the gas downward along the electrodes according to the blowing model, and the blowing of the gas is stopped according to the control nodes of the blowing model.

[0032] When the gas injection device blows the gas downward along the electrodes, a gas wall will be formed to prevent air from contacting the electrodes, reduce the oxidation degree of the electrodes under high temperature and hot state, and thus reduce the consumption of the refining electrodes and extend the service life of the electrodes.

[0033] Compared with the prior art, the ladle refining furnace provided by the present invention includes an electrode clamp and a gas injection device disposed below the electrode clamp. The gas injection device of the ladle refining furnace forms a gas wall below the electrode to prevent air from contacting the electrode, thereby reducing the electrode consumption during the refining process of molten steel. Moreover, when using the ladle refining furnace of the present invention for the refining of molten steel, the process is simple and easy to operate, the overall cost is significantly reduced, and it is suitable for large-scale industrial production. In addition, the method solves the problems of high electrode consumption and short service life during the refining process of molten steel caused by serious oxidation of the electrode by air after power-on, reduces the oxygen concentration on the surface of the ladle after refining, reduces the oxygen absorption amount during the slag formation process, and improves the quality of molten steel. Detailed Description of the Invention

[0034] To further illustrate the present invention, the following describes in detail a kind of ladle refining furnace provided by the present invention and a method for reducing electrode consumption during the refining process of molten steel in combination with embodiments.

[0035] The ladle refining furnace provided by the present invention includes an electrode clamp and a gas injection device disposed below the electrode clamp.

[0036] Preferably, the gas injection device is annular and a Laval nozzle is disposed below it.

[0037] The present invention can be provided with a protective material on the adjacent side of the gas injection device and the Laval nozzle to the electrode.

[0038] The present invention does not limit the number of Laval nozzles.

[0039] Preferably, the included angle between the Laval nozzle and the central horizontal line of the gas injection device is 85° - 88°.

[0040] Preferably, the distance between the nozzles of the Laval nozzle is 80 - 100 mm.

[0041] Preferably, the opening and closing of the gas injection device are controlled by the lifting position of the electrode of the ladle refining furnace.

[0042] The above control by the lifting position of the electrode of the ladle refining furnace is specifically as follows: after the electrode is powered on and rises to a specified position, the gas injection device switch automatically opens to inject gas according to a certain injection time and injection flow rate, thereby forming a gas wall to prevent air from contacting the electrode and reducing the electrode consumption during the refining process of molten steel.

[0043] Preferably, the injection time and injection flow rate after the gas injection device is opened are controlled by a set model. The present invention improves a common ladle refining furnace by installing a gas injection device below the electrode clamp (electrode holder) of the ladle refining furnace.

[0044] The electrode consumption of the ladle furnace (LF) mainly comes from the oxidation of the electrode at high temperature in contact with air and the oxidation and erosion of the slag during power-on.

[0045] The present invention uses the improved ladle furnace described above for refining molten steel, which can reduce the electrode consumption caused by the oxidation of the electrode at high temperature in contact with air, and thus achieve the purpose of reducing the electrode consumption during the refining of molten steel.

[0046] The present invention also provides a method for reducing the electrode consumption during the refining of molten steel, including the following steps:

[0047] After the electrode is powered on in the above ladle furnace, gas is blown downward along the electrode through the gas injection device to form a gas wall to prevent air from contacting the electrode, thereby reducing the electrode consumption during the refining of molten steel.

[0048] The blown gas in the above method includes but is not limited to inert gas.

[0049] Preferably, the gas in the present invention is selected from nitrogen or argon; more preferably nitrogen.

[0050] The blowing time (s) of the gas in the present invention is related to the electrode power-on time (s) of the ladle furnace.

[0051] Preferably, the blowing time (s) model of the gas in the present invention is as shown in the following table:

[0052] Power-on time, s Blow time, s ≤60 60 90 60.9 120 62.1 150 63.6 180 65.4 210 67.5 240 69.9 270 72.6 300 75.6 330 78.9 360 82.5 390 86.4 420 90.6 450 95.1 480 99.9 。

[0053] The blowing flow rate (m 3 ) of the gas in the present invention is related to the electrode power consumption (Kwh) and the electrode diameter (mm) of the ladle furnace.

[0054] Preferably, the blowing flow rate (m 3 ) model of the gas in the present invention is as shown in the following table:

[0055]

[0056] In the blowing flow rate (m 3 ) model table of the above gas, the data in the first row from top to bottom is the power consumption, the data in the first column from left to right is the electrode diameter, and the remaining data are all the blowing flow rate (m 3 ).

[0057] After the molten steel is tapped from the converter and enters the refining position for refining and the electrodes are energized, the gas injection device is started to inject gas downward along the electrodes according to the injection model, and the gas injection is stopped according to the control node of the injection model.

[0058] When the gas injection device injects gas downward along the electrodes, an air wall will be formed to prevent air from contacting the electrodes, reducing the oxidation degree of the electrodes in the high-temperature hot state, thereby reducing the consumption of the refining electrodes and prolonging the service life of the electrodes.

[0059] Example 1

[0060] The 150t ladle furnace (LF) smelting control is adopted, specifically by using the method of reducing the electrode consumption in the LF refining process, including the following steps:

[0061] When smelting HRB600E, after the molten steel is tapped from the converter, the weight of the molten steel is 150 tons. The ladle runs to the refining position for refining, and the temperature of the molten steel is measured at 1538 °C. The electrode is lowered to the working position for energized smelting. During the smelting process, 400 kg of lime, 100 kg of calcium carbide, and 60 kg of fluorite are added. The energizing time is 420 seconds. After the power consumption reaches 2000 kwh, the power supply is stopped. When the electrode is lifted to 300 mm, the injection device is started to inject nitrogen. The set nitrogen injection volume is 32 m 3 , the injection time is 90.6 seconds. During the injection process, the temperature of the molten steel is measured at 1560 °C, meeting the tapping requirements. All the chemical components of the molten steel meet the requirements of the steel grade. The refining is completed, and the molten steel is taken out of the refining position for soft blowing operation. The injection device stops injecting after injecting according to the set parameters.

[0062] Using this method for 100 furnaces of molten steel refining, the amount of molten steel is 15000 tons, the electrode energizing time is 42000 minutes, the power consumption is 200000 kwh, and the electrode consumption is 0.145 kg / t of molten steel.

[0063] Comparative Example 1

[0064] The 150t ladle LF refining furnace smelting control is adopted, specifically by using the method of ordinary electrode energization:

[0065] When smelting HRB600E, after the molten steel is tapped from the converter, the weight of the molten steel is 150 tons. The ladle runs to the refining position for refining, and the temperature of the molten steel is measured at 1538 °C. The electrode is lowered to the working position for energized smelting. During the smelting process, 400 kg of lime, 100 kg of calcium carbide, and 60 kg of fluorite are added. The energizing time is 420 seconds. After the power consumption reaches 2000 kwh, the power supply is stopped. The temperature of the molten steel is measured at 1560 °C, meeting the tapping requirements. All the chemical components of the molten steel meet the requirements of the steel grade. The refining is completed, and the molten steel is taken out of the refining position for soft blowing operation.

[0066] The present method is used for refining molten steel in 100 furnaces, with a molten steel volume of 15,000 tons, an electrode energization time of 42,000 minutes, an electricity consumption of 200,000 kwh, and an electrode consumption of 0.20 kg / t of molten steel.

[0067] The electrode consumption, nitrogen injection, injection operation cost, and production cost in the examples and comparative examples were statistically analyzed, and the results are shown in Table 1.

[0068] Table 1 Comparison data table of electrode consumption, nitrogen injection, injection operation cost, and production cost in examples and comparative examples (data of 100 furnaces)

[0069]

[0070]

[0071] Example 2

[0072] The refining of 220t ladle refining furnace (LF) is used for smelting control. Specifically, the method of reducing the electrode consumption in the LF refining process is adopted, including the following steps:

[0073] When smelting Q355C, after the converter tapping is completed, the weight of the molten steel is 220 tons. The ladle runs to the refining position for refining. The temperature of the molten steel is measured at 1548 °C, and the electrode is lowered to the working position for energized smelting. During the smelting process, 800 kg of lime, 200 kg of calcium carbide, and 100 kg of fluorite are added. After the energization time of 420 seconds and the electricity consumption of 3200 kwh, the power supply is stopped. When the electrode is lifted to 300 mm, the blowing device is started for argon blowing. The set argon blowing volume is 43.2 m 3 , and the blowing time is 90.6 seconds. During the blowing process, the temperature of the molten steel is measured at 1550 °C, meeting the tapping requirements. The chemical composition of the molten steel fully meets the requirements of the steel grade. The refining is completed, and the molten steel is taken out of the refining position for soft blowing operation. After the blowing device blows according to the set parameters, the blowing stops.

[0074] The present method is used for refining molten steel in 100 furnaces, with a molten steel volume of 22,000 tons, an electrode energization time of 42,000 minutes, an electricity consumption of 320,000 kwh, and an electrode consumption of 0.135 kg / t of molten steel.

[0075] Comparative Example 2

[0076] The refining of 220t ladle LF refining furnace is used for smelting control. Specifically, the method of ordinary electrode energization is adopted:

[0077] When smelting Q355C, after the converter tapping is completed, the weight of the molten steel is 220 tons. The ladle runs to the refining position for refining. The temperature of the molten steel is measured at 1548 °C, and the electrode Lower to the working position for energized smelting. During the smelting process, 1000 kg of lime, 200 kg of calcium carbide, and 100 kg of fluorite are added. The energizing time is 420 seconds. After the power consumption reaches 3200 kwh, the power supply is stopped. The molten steel temperature is measured at 1550 °C, meeting the tapping requirements. The composition of the molten steel fully meets the requirements of the steel grade. The refining is completed, and the molten steel is discharged from the refining position for soft blowing operation.

[0078] Using this method for molten steel refining for 100 furnaces, the amount of molten steel is 22000 tons, the electrode energizing time is 42000 minutes, the power consumption is 320000 kwh, and the electrode consumption is 0.20 kg / t of molten steel.

[0079] The electrode consumption, nitrogen injection, injection operation cost, and production cost in the examples and comparative examples are statistically analyzed, and the results are shown in Table 2.

[0080] Table 2 Comparison data table of electrode consumption, nitrogen injection, injection operation cost, and production cost in examples and comparative examples (data of 100 furnaces)

[0081]

[0082] The results show that after using the method described in the present invention, the electrode erosion rate slows down, the electrode consumption decreases, and the production cost decreases.

[0083] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A ladle refining furnace, characterized in that, It includes an electrode clamp and a gas blowing device arranged below the electrode clamp.

2. The ladle refining furnace according to claim 1, characterized in that, The gas blowing device is annular and a Laval nozzle is arranged below it.

3. The ladle refining furnace according to claim 2, characterized in that, The included angle between the Laval nozzle and the central horizontal line of the gas blowing device is 85° - 88°.

4. The ladle refining furnace according to claim 2, characterized in that, The distance between each nozzle of the Laval nozzle is 80 - 100 mm.

5. The ladle refining furnace according to claim 1, characterized in that, The opening and closing of the gas blowing device are controlled by the lifting position of the electrode of the ladle refining furnace.

6. The ladle refining furnace according to claim 1, characterized in that, The blowing time and blowing flow rate after the gas blowing device is opened are controlled by a set model.

7. A method for reducing the electrode consumption in the refining process of molten steel, characterized in that, It includes the following steps: After the electrode of the ladle refining furnace described in any one of claims 1 - 6 is electrified, gas is blown downward along the electrode through the gas blowing device to form a gas wall to prevent air from contacting the electrode and reduce the electrode consumption during the molten steel refining process.

8. The method according to claim 7, wherein The gas is selected from nitrogen or argon.

9. The method according to claim 8, characterized in that, The blowing time (s) model of the gas is shown in the following table: 。 10. The method according to claim 9, characterized in that The blowing flow rate (m 3 ) of the gas is as shown in the following table:

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