Bottom blowing gas control method and method for LF refining
By adding carbonized rice husks after powering on or feeding in the inclusion-modifying line in the bottom-blowing control method, and adjusting the bottom-blowing parameters, the problems of steel slag crusting and poor inclusion removal were solved, achieving more efficient steel slag spreading and inclusion removal, and improving production stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SGIS SONGSHAN CO LTD
- Filing Date
- 2024-07-31
- Publication Date
- 2026-07-03
Smart Images
Figure CN119433144B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of iron and steel metallurgy technology, and more specifically, to a bottom blowing gas control method and an LF refining method. Background Technology
[0002] In the field of iron and steel metallurgy, bottom blowing (argon) gas control in steel ladles plays a crucial role in slag formation and inclusion removal. Existing bottom blowing (argon) gas control methods are mainly divided into the following two types: changing the layout of bottom blowing (side blowing) holes and blowing (argon) gas method in steel ladles, and using certain monitoring methods to monitor the fluctuation of the molten steel surface in real time so as to dynamically adjust the bottom blowing parameters to achieve the appropriate effect.
[0003] Current technologies for real-time monitoring of molten steel surface fluctuations to facilitate dynamic adjustment of bottom blowing parameters do not address the various conditions necessary for effective monitoring. If the molten steel surface consists only of steel slag, even if the slag is of higher fluidity (low basicity or acidic nature, with a binary basicity ≤ 2), after a period of bottom blowing, certain areas of the slag, such as weakly affected areas far from the bottom blowing holes, will inevitably develop large crusts (due to the poor spreadability of pure steel slag). In such cases, the monitored area and radius become meaningless and will affect the direction of subsequent bottom blowing parameter adjustments.
[0004] In view of this, the present invention is proposed. Summary of the Invention
[0005] The purpose of this invention is to provide a bottom blowing gas control method and a refining method.
[0006] This invention is implemented as follows:
[0007] In a first aspect, the present invention provides a bottom blowing air control method, comprising:
[0008] Power is supplied to heat the molten steel, and carbonized rice husks are added to the molten steel after the power supply is completed.
[0009] Soft blowing involves soft blowing the molten steel after adding carbonized rice husks. During the soft blowing process, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0-1.5 m / s and t is 0-1.2 s. Specifically, v and t are defined as follows: the middle of the exposed area on the steel slag is taken as the monitoring point. Under the condition of bottom blowing gas, ripples will continuously spread outward from the monitoring point. The propagation rate of the ripples is v, and the time interval between adjacent ripples is t.
[0010] In an optional implementation, when the equivalent diameter of the largest slag agglomeration on the surface of molten steel within the monitoring range is ≤10cm, the values of v and t are measured.
[0011] In an optional implementation, the power supply time is greater than 15 seconds.
[0012] In an optional embodiment, carbonized rice husks are added to the molten steel within 25 seconds after the power supply is completed.
[0013] In an optional embodiment, after the power supply is completed, a modified wire containing impurities can be fed first, and carbonized rice husks can be added to the molten steel within 25 seconds after the modified wire containing impurities is fed.
[0014] In an optional embodiment, 0.3 to 0.7 kg of carbonized rice husks are added per ton of molten steel.
[0015] In an optional embodiment, when the carbonized rice husks accumulate on the surface of the molten steel, the coupling head is inserted into the accumulated carbonized rice husks to cause the carbonized rice husks to splash.
[0016] In an optional implementation, the soft blowing includes a soft blowing phase and a soft blowing mid-to-late phase: in the soft blowing phase, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0.4 to 1.5 m / s and t is 0 to 0.6 s.
[0017] In an optional implementation, the soft blowing includes a soft blowing pre-stage and a soft blowing mid-to-late stage: during the soft blowing mid-to-late stage, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0-0.4 m / s and t is 0.6-1.2 s.
[0018] Secondly, the present invention provides a method for LF refining, including the bottom blowing gas control method described in any of the foregoing embodiments.
[0019] The present invention has the following beneficial effects:
[0020] In this embodiment of the invention, before monitoring the liquid level to control bottom blowing, power is supplied or an inclusion deformation line is fed in to obtain steel slag with good initial fluidity. After power supply or feeding of the inclusion deformation line, carbonized rice husks are added to the molten steel, which helps to further improve the spreadability of the steel slag. At the same time, since power supply or feeding of the inclusion deformation line is performed before adding the carbonized rice husks, the added carbonized rice husks can quickly combine with the steel slag with good fluidity.
[0021] After adjusting the steel slag to have good ductility, the flow rate and pressure of the bottom blowing air are controlled so that v is 0-1.5 m / s and t is 0-1.2 s. This makes the monitoring results of the propagation rate v and time interval t more accurate, which is more conducive to reducing inclusions in molten steel, reducing the rise of the tundish stopper rod, and improving the stability of production. Attached Figure Description
[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is a schematic diagram illustrating the monitoring principle of propagation rate v and time interval t. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0025] This invention provides a bottom blowing air control method, comprising:
[0026] Power is supplied to heat the molten steel. After the power supply is completed, carbonized rice husks are added to the molten steel or carbonized rice husks are added after the inclusions have been fed into the deformation line.
[0027] Soft blowing involves soft blowing the molten steel after adding carbonized rice husks. During the soft blowing process, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0-1.5 m / s and t is 0-1.2 s. Specifically, v and t are defined as follows: the middle of the exposed area on the steel slag (usually the center point) is taken as the monitoring point. Under the condition of bottom blowing gas, ripples will continuously spread outward from the monitoring point. The propagation rate of the ripples is v, and the time interval between adjacent ripples is t.
[0028] In this embodiment of the invention, before monitoring the liquid level to control bottom blowing, power is supplied or an inclusion deformation line is fed in to obtain steel slag with good initial fluidity. After power supply or feeding of the inclusion deformation line, carbonized rice husks are added to the molten steel, which helps to further improve the spreadability of the steel slag. At the same time, since power supply or feeding of the inclusion deformation line is performed before adding the carbonized rice husks, the added carbonized rice husks can quickly combine with the steel slag with good fluidity.
[0029] After adjusting the steel slag to have good ductility, the flow rate and pressure of the bottom blowing air are controlled so that v is 0-1.5 m / s and t is 0-1.2 s. This makes the monitoring results of the propagation rate v and time interval t more accurate, which is more conducive to reducing inclusions in molten steel and improving the stability of production.
[0030] Specifically, such as Figure 1As shown, when monitoring v and t, the center of the exposed area on the steel slag can be taken as the starting point for monitoring, such as... Figure 1 Point B in the diagram, under the condition of bottom blowing air, will have ripples that continuously spread outward from the monitoring starting point. Any point along the ripple propagation path can be selected as the monitoring endpoint, such as... Figure 1 Points O1 or O2 in the monitoring system are used to calculate the propagation rate v of the same ripple by observing the time and distance it takes for the ripple to travel from the monitoring start point to the monitoring end point. The time interval between adjacent ripples at the monitoring start point or the monitoring end point is measured and is called t. It should be noted that the monitoring start point in this embodiment is usually the center of the bottom blow hole, and the monitoring end point can be any point in the area that the ripple can reach. However, if the distance from the monitoring start point is too far, it may be greatly affected by interference from other bottom blow holes. To avoid the influence of other bottom blow holes, the distance between the monitoring start point and the monitoring end point should not be too large. That is, choosing O1 as the monitoring end point is more conducive to reducing errors than O2. However, if the distance between the monitoring start point and the monitoring end point is too small, the time taken for the ripple to propagate will be shortened, and the calculation error of the propagation rate v will increase. Therefore, those skilled in the art can choose the distance between the monitoring start point and the monitoring end point according to the actual situation.
[0031] It should be noted that bottom blowing (argon) gas is present throughout the power transmission and soft blowing processes. Furthermore, slag-reducing agents such as fluorite balls can be added to improve the fluidity and spreadability of the steel slag, in conjunction with the power transmission and carbonization of rice husks. However, since monitoring has not yet begun during the power transmission process, the size of the bottom blowing gas only needs to be 20-60 Nm. 3 / h is sufficient.
[0032] In an optional implementation, when the equivalent diameter of the largest slag agglomeration on the surface of molten steel within the monitoring range is ≤10cm, the values of v and t are measured.
[0033] After the addition of carbonized rice husks, as bottom blowing proceeds, the surface of the steel slag or the mixture of steel slag and carbonized rice husks develops certain cracks and agglomerates. When the equivalent diameter of the largest agglomerate of steel slag on the molten steel surface within the monitoring range is ≤10cm, the ripples and their movement trajectory can be more clearly monitored, allowing for the monitoring of the ripple propagation rate and time interval. In this embodiment, the monitoring range refers to the area between the monitoring start point and the monitoring end point.
[0034] In an optional implementation, the power supply time is greater than 15 seconds, which is long enough to ensure that the steel slag has good fluidity and spreadability from the beginning.
[0035] In an optional embodiment, carbonized rice husks are added to the molten steel within 25 seconds after the power supply is completed. The carbonized rice husks are added to the molten steel when the steel slag has good fluidity and spreadability, so that the carbonized rice husks can quickly combine with the steel slag.
[0036] In an optional embodiment, after the power supply is completed, a modified wire for feeding inclusions can be performed first. Within 25 seconds after the modified wire for feeding inclusions is completed, carbonized rice husks are added to the molten steel. The modified wire for feeding inclusions includes Ca wire, Si-Ca wire, etc.
[0037] In an optional embodiment, 0.3 to 0.7 kg of carbonized rice husks are added per ton of molten steel.
[0038] In an optional embodiment, when the carbonized rice husks accumulate on the surface of the molten steel, the coupling head is inserted into the accumulated carbonized rice husks to cause the carbonized rice husks to splash.
[0039] It is worth mentioning that carbonized rice husks are generally added manually in whole bundles (approximately 7 kg / bundle, and quite large in volume), often resulting in small piles, which affects the rapid spreading of steel slag (and carbonized rice husks). Furthermore, when using a toothed ladle cover device for direct-flow continuous casting in an LF furnace (where carbonized rice husks can only be manually added at the LF furnace processing position), the obstruction of the LF furnace cover and the small gaps near the observation doors and electrodes make it very difficult to quickly distribute the whole bundle of carbonized rice husks to every part of the circular slag surface. This easily leads to small piles, hindering the rapid spreading of the steel slag. Therefore, a "directional splashing method" is used for dispersion and spreading. That is, during sampling, temperature measurement, hydrogen determination, and oxygen determination, the characteristic of the moisture trapped in the emulsion head filler exploding and splashing in a large area (forward) when it encounters high-temperature molten steel (slag) is fully utilized to splash the piled-up carbonized rice husks to the target area, achieving rapid spreading. It should be noted that residual thermocouples after use (such as sampling, temperature measurement, hydrogen determination, oxygen determination, etc.) must not be thrown onto the steel slag surface, so as not to affect the subsequent judgment of the bottom blowing status.
[0040] In an optional implementation, the soft blowing includes a soft blowing phase and a soft blowing mid-to-late phase: in the soft blowing phase, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0.4 to 1.5 m / s and t is 0 to 0.6 s.
[0041] In an optional implementation, the soft blowing includes a soft blowing pre-stage and a soft blowing mid-to-late stage: during the soft blowing mid-to-late stage, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0-0.4 m / s and t is 0.6-1.2 s.
[0042] The soft blowing process is divided into early, middle and late stages. In the early stage, the flow rate of the bottom blowing gas is relatively fast (larger flow rate), and the generated bubbles are relatively large. In the middle and late stages, the flow rate of the bottom blowing gas is relatively slow (smaller flow rate), and the generated bubbles are relatively small, which helps to reduce inclusions in the molten steel.
[0043] The embodiments also provide a method for LF refining, including the bottom blowing gas control method described in any of the foregoing embodiments.
[0044] The features and performance of the present invention will be further described in detail below with reference to the LF furnace smelting examples of non-aluminum 45 steel for industrial wire drawing.
[0045] Example 1
[0046] This embodiment provides a bottom blowing control method, including:
[0047] Power on, start bottom blowing, and adjust the bottom blowing air flow rate to 30 Nm. 3 At a pressure of 1.4 MPa, the molten steel is energized for 30 seconds. Within 25 seconds after the energization ends, carbonized rice husks are added to the molten steel at a rate of 0.5 kg per ton of molten steel. The carbonized rice husks accumulate on the surface of the molten steel. The coupling head is inserted into the accumulated carbonized rice husks to cause the carbonized rice husks to splash, thereby achieving rapid bonding and spreading of the carbonized rice husks and steel slag.
[0048] Soft blowing involves applying soft blowing pressure to molten steel after the addition of carbonized rice husks. This soft blowing process includes an early stage and a later stage: in the early stage, the flow rate and pressure of the bottom blowing gas are adjusted to achieve a velocity (v) of 1.1 m / s and a t of 0.4 s; in the later stage, the flow rate and pressure are adjusted to achieve a velocity (v) of 0.2 m / s and a t of 0.8 s, ultimately resulting in a stopper rod rise of -0.1 mm (i.e., a stopper rod descent of 0.1 mm). Specifically, v and t are defined as follows: when the equivalent diameter of the largest slag agglomeration on the molten steel surface within the monitoring range is ≤10 cm, the center of the exposed area on the slag is taken as the monitoring point. Under the condition of bottom blowing gas, ripples will continuously spread outward from the monitoring point; the propagation rate of these ripples is v, and the time interval between adjacent ripples is t.
[0049] Example 2
[0050] This embodiment provides a bottom blowing control method, including:
[0051] Power on, start bottom blowing, and adjust the bottom blowing air flow rate to 30 Nm. 3 At a pressure of 1.4 MPa, the molten steel is energized for 30 seconds. After the energization is completed, 15m of pure Ca wire with inclusion modification is fed. Within 25 seconds after feeding the pure Ca wire, carbonized rice husks are added to the molten steel at a rate of 0.5kg per ton of molten steel. The carbonized rice husks accumulate on the surface of the molten steel. The coupling head is inserted into the accumulated carbonized rice husks to cause the carbonized rice husks to splash, thereby achieving rapid bonding and spreading of the carbonized rice husks with the steel slag.
[0052] Soft blowing involves applying soft blowing pressure to molten steel after the addition of carbonized rice husks. This soft blowing process includes an early stage and a later stage: In the early stage, the flow rate and pressure of the bottom blowing gas are adjusted to achieve a velocity (v) of 1.1 m / s and a t of 0.4 s; in the later stage, the flow rate and pressure are adjusted to achieve a velocity (v) of 0.2 m / s and a t of 0.8 s. Ultimately, the tundish stopper rises by -0.3 mm (i.e., the stopper descends by 0.3 mm). Specifically, v and t are defined as follows: when the equivalent diameter of the largest slag agglomeration on the molten steel surface within the monitoring range is ≤10 cm, the center of the exposed area on the slag is taken as the monitoring point. Under the condition of bottom blowing gas, ripples will continuously spread outward from the monitoring point. The propagation rate of these ripples is v, and the time interval between adjacent ripples is t.
[0053] Comparative Example 1
[0054] This comparative example provides a bottom-blowing air control method, which differs from Example 1 only in that no power is supplied before adding carbonized rice husks to the molten steel; the final rise of the tundish stopper rod is 0.8 mm (i.e., the stopper rod rises by 0.8 mm).
[0055] Comparative Example 2
[0056] This comparative example provides a bottom-blowing air control method, which differs from Example 1 only in that carbonized rice husks are not added; the final rise of the intermediate bag stopper rod is 1.5 mm (i.e., the stopper rod rises 1.5 mm).
[0057] Comparative Example 3
[0058] This comparative example provides a bottom-blowing air control method, which differs from Example 1 only in that the coupling head is not inserted into the piled carbonized rice husks, allowing the carbonized rice husks to spread slowly without human intervention; the final rise of the intermediate packing stopper rod is 0.7 mm (i.e., the stopper rod rises by 0.7 mm).
[0059] Comparative Example 4
[0060] This comparative example provides a bottom blowing air control method, which differs from Example 1 only in that the flow rate and pressure of the bottom blowing air are adjusted in the early stage of the soft blowing so that v is 0.6m / s and t is 0.6s; and the final rise of the intermediate burlap stopper rod is 0.4mm (i.e., the rise stroke of the stopper rod is 0.4mm).
[0061] Comparative Example 5
[0062] This comparative example provides a bottom blowing air control method, which differs from Example 1 only in that the flow rate and pressure of the bottom blowing air are adjusted in the early stage of the soft blowing so that v is 1.5m / s and t is 0.1s; and the final rise of the intermediate burlap stopper rod is 0.1mm (i.e., the rise stroke of the stopper rod is 0.1mm).
[0063] Comparative Example 6
[0064] This comparative example provides a bottom blowing air control method, which differs from Example 1 only in that the flow rate and pressure of the bottom blowing air are adjusted in the middle and later stages of the soft blowing process so that v is 0.1m / s and t is 1.2s; the final rise of the intermediate burlap stopper rod is 0.2mm (i.e., the rise stroke of the stopper rod is 0.2mm).
[0065] Comparative Example 7
[0066] This comparative example provides a bottom blowing air control method, which differs from Example 1 only in that the flow rate and pressure of the bottom blowing air are adjusted in the middle and later stages of the soft blowing process so that v is 0.4 m / s and t is 0.6 s; the final rise of the intermediate burlap stopper rod is 0.3 mm (i.e., the rise stroke of the stopper rod is 0.3 mm).
[0067] The increase in the tundish stopper rod of the above embodiments and comparative examples is shown in Table 1.
[0068] Table 1
[0069]
[0070]
[0071] As can be seen from Example 1, under suitable parameters, the stopper rod of the tundish experiences a slight decrease (-0.1 mm). In Example 2, based on Example 1, the stopper rod experiences a further slight decrease (-0.3 mm). This is the effect of the fed pure Ca wire on the erosion of the stopper rod, which is a normal phenomenon.
[0072] As can be seen from Example 1 and Comparative Examples 1, 2, and 3, the absence of carbonized rice husks in Comparative Example 2 had the greatest impact, as the adsorption capacity of steel slag for inclusions decreased, resulting in the largest increase in stopper rod height (1.5 mm). The lack of power supply in Comparative Example 1 and the poor spreadability of steel slag in Comparative Example 3 also affected the adsorption of inclusions, with significant increases in stopper rod height (0.8 mm and 0.7 mm, respectively).
[0073] As shown in Example 1 and Comparative Example 4, when the propagation speed slows down and the interval time becomes longer (low frequency) in the early stage of soft blowing, the further spreading speed of the steel slag slows down, the adsorption capacity of inclusions weakens, and the stopper rod rises more significantly (0.4 mm). As shown in Example 1 and Comparative Example 5, when the propagation speed speed increases and the interval time becomes shorter (high frequency) in the early stage of soft blowing, although the further spreading speed of the steel slag increases, the fluctuation of the molten steel surface is larger at this time. The steel slag close to the molten steel and the already adsorbed inclusions are easily re-entered into the molten steel and become sources of inclusions, and the stopper rod rises slightly more significantly (0.1 mm).
[0074] As shown in Example 1 and Comparative Example 6, when the propagation speed slows down and the interval time becomes longer (low frequency) in the middle and late stages of soft blowing, the mass transfer from the slag near the molten steel to the surface slag slows down, the adsorption capacity of inclusions weakens, and the stopper rod rises slightly more (0.2 mm). As shown in Example 1 and Comparative Example 7, when the propagation speed speed increases and the interval time becomes shorter (high frequency) in the middle and late stages of soft blowing, although the mass transfer from the slag near the molten steel to the surface slag becomes faster, the liquid surface fluctuation is also larger at this time. The slag and the already adsorbed inclusions are easily re-entered into the molten steel and become a source of inclusions, and the stopper rod rises more significantly (0.3 mm).
[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for controlling bottom blowing air, characterized in that, include: Power is supplied to heat the molten steel, and carbonized rice husks are added to the molten steel after the power supply is completed. Soft blowing involves soft blowing the molten steel after adding carbonized rice husks. During the soft blowing process, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0~1.5m / s and t is 0~1.2s. Specifically, v and t are defined as follows: the middle of the exposed area on the steel slag is taken as the monitoring point. Under the condition of bottom blowing gas, ripples will continuously spread outward from the monitoring point. The propagation rate of the ripples is v, and the time interval between adjacent ripples is t. The soft blowing includes a soft blowing phase and a soft blowing mid-to-late phase: in the soft blowing phase, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0.4~1.5m / s and t is 0~0.6s; in the soft blowing mid-to-late phase, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0~0.4m / s and t is 0.6~1.2s. When the carbonized rice husks accumulate on the surface of the molten steel, the coupling head is inserted into the accumulated carbonized rice husks to cause the carbonized rice husks to splash. The power supply time is greater than 15 seconds; Within 25 seconds after the power supply is completed, carbonized rice husks are added to the molten steel; after the power supply is completed, a modified wire containing inclusions is fed, and within 25 seconds after the modified wire containing inclusions is fed, carbonized rice husks are added to the molten steel. When the equivalent diameter of the largest slag agglomeration on the surface of molten steel within the monitoring range is ≤10cm, the values of v and t are measured.
2. The bottom blowing air control method according to claim 1, characterized in that, 0.3-0.7 kg of carbonized rice husks are added to each ton of molten steel.
3. A method for refining LF, characterized in that, The method includes the bottom blowing air control method according to any one of claims 1-2.