Bottom blowing control method and LF refining method

Abstract

The invention discloses a bottom blowing control method and an LF refining method.The bottom blowing control method comprises the steps that molten steel is subjected to power transmission and temperature rise, and carbonized rice husks are added into the molten steel after power transmission is finished or carbonized rice husks are added after inclusion denaturation lines are fed; the molten steel is subjected to soft blowing, the flow and pressure of bottom blowing air are adjusted in the soft blowing process so that v can be 0-1.5 m / s, t can be 0-1.2 s, v is the propagation rate of corrugations, namely v, and t is the time interval generated by adjacent corrugations. The carbonized rice husks are added, and power transmission is carried out before the carbonized rice husks are added, so that the added carbonized rice husks can be rapidly combined with the steel slag with good fluidity. After the steel slag is adjusted to have good ductility, the flow and pressure of bottom blowing gas are controlled, so that the monitoring results of the propagation rate v and the time interval t are more accurate, inclusions in molten steel are more favorably reduced, and the rising amplitude of a tundish stopper rod is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a bottom blowing gas control method and a LF refining method. Background Art

[0002] In the field of iron and steel metallurgy, ladle bottom blowing (argon) gas control plays a vital role in slag making, inclusion removal, etc. The existing bottom blowing (argon) gas control methods are mainly divided into the following two types: changing the layout of the ladle bottom blowing (side blowing) holes and the (argon) gas blowing method, and using certain monitoring methods to monitor the fluctuation of the steel liquid level in real time so as to dynamically adjust the bottom blowing parameters to the appropriate effect.

[0003] When the existing technology monitors the fluctuation of the steel liquid level in real time so as to dynamically adjust the bottom blowing parameters to the appropriate effect, it does not mention the various conditions that need to be met for monitoring. If there is only slag on the steel liquid level, even if the slag is a low-basicity slag or acidic slag (its binary basicity is ≤2) with better fluidity, after a period of bottom blowing, some parts of the slag, such as the weakly affected area far away from the bottom blowing hole, will definitely (largely) crust (pure slag has poor spreadability). In this case, the so-called area, radius, etc. monitored are not representative, which will affect the subsequent bottom blowing parameter control direction.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a bottom blowing gas control method and a refining method.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a bottom blowing control method, comprising:

[0008] Power transmission is used to heat the molten steel, and after the power transmission is completed, carbonized rice husk is added to the molten steel;

[0009] Soft blowing is performed on the molten steel after adding carbonized rice husk. 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, wherein v and t are specifically: the middle of the exposed area on the slag is taken as the monitoring point. Under the condition of the presence of bottom blowing gas, ripples will continuously diffuse 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 embodiment, when the equivalent diameter of the largest agglomerate of slag on the surface of molten steel within the monitoring range is ≤10 cm, the values ​​of v and t are determined.

[0011] In an optional implementation, the power delivery 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 transmission is completed.

[0013] In an optional embodiment, after the power transmission is completed, the inclusion feeding and modification line may be first performed, and the carbonized rice husk is added to the molten steel within 25 seconds after the inclusion feeding and modification line is completed.

[0014] In an optional embodiment, 0.3-0.7 kg of the carbonized rice husk is added per ton of the molten steel.

[0015] In an optional embodiment, when the carbonized rice husk is accumulated on the surface of the molten steel, the doll head is inserted into the accumulated carbonized rice husk to cause the carbonized rice husk to splash.

[0016] In an optional embodiment, the soft blowing includes an early stage of soft blowing and a middle and late stage of soft blowing: in the early stage of soft blowing, the flow rate and pressure of the bottom blowing air are adjusted so that v is 0.4-1.5 m / s and t is 0-0.6 s.

[0017] In an optional embodiment, the soft blowing includes an early stage of soft blowing and a middle and late stage of soft blowing: in the middle and late stage of soft blowing, the flow rate and pressure of the bottom blowing air are adjusted so that v is 0-0.4 m / s and t is 0.6-1.2 s.

[0018] In a second aspect, the present invention provides a method for LF refining, comprising the bottom blowing gas control method described in any one of the aforementioned embodiments.

[0019] The present invention has the following beneficial effects:

[0020] In the embodiment of the present invention, before the liquid level is monitored to control the bottom blowing, power is supplied or an inclusion modification line is fed to obtain steel slag with good initial fluidity. After the power is supplied or the inclusion modification line is fed, carbonized rice husk is added to the molten steel, which is beneficial to further improve the spreadability of the steel slag. At the same time, since power is supplied or the inclusion modification line is fed before the carbonized rice husk is added, the added carbonized rice husk can be quickly combined 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 gas are controlled so that v is 0-1.5m / s and t is 0-1.2s, making the monitoring results of the propagation velocity v and the time interval t more accurate, which is more conducive to reducing inclusions in the molten steel and reducing the rise of the tundish plug rod, and at the same time helping to improve production stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 Schematic diagram of the monitoring principle of propagation rate v and time interval t. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0025] An embodiment of the present invention provides a bottom blowing control method, comprising:

[0026] Power transmission is performed to heat the molten steel, and after power transmission is completed, carbonized rice husk is added to the molten steel or the carbonized rice husk is added after the inclusion modification line is fed;

[0027] Soft blowing is performed on the molten steel after adding carbonized rice husk. 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, wherein v and t are specifically: the middle of the exposed area on the slag (generally the center point) is taken as the monitoring point. Under the condition of the presence of bottom blowing gas, ripples will continuously diffuse outward from the monitoring point. The propagation rate of the ripples is v, and the time interval between adjacent ripples is t.

[0028] In the embodiment of the present invention, before the liquid level is monitored to control the bottom blowing, power is supplied or an inclusion modification line is fed to obtain steel slag with good initial fluidity. After the power is supplied or the inclusion modification line is fed, carbonized rice husk is added to the molten steel, which is beneficial to further improve the spreadability of the steel slag. At the same time, since power is supplied or the inclusion modification line is fed before the carbonized rice husk is added, the added carbonized rice husk can be quickly combined 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 gas are controlled so that v is 0-1.5m / s and t is 0-1.2s, making the monitoring results of the propagation velocity v and the time interval t more accurate, which is more conducive to reducing inclusions in the molten steel and improving the stability of production.

[0030] Specifically, Figure 1As shown in Figure 2, when monitoring v and t, the center of the exposed area on the slag can be taken as the monitoring starting point, as shown in Figure 2. Figure 1 At point B in the figure, under the condition of bottom blowing, ripples will continue to spread outward from the monitoring starting point. Any point on the ripple propagation path is selected as the monitoring end point, such as Figure 1 Point O1 or O2 in the monitoring data is used to calculate the propagation rate of the ripples by observing the time and distance that the same ripples travel from the monitoring start point to the monitoring end point, which is v; the time interval between adjacent ripples generated at the detection start point or the detection end point is t. It should be noted that the monitoring start point in the embodiment of the present invention is usually the center of the bottom blowing hole, and the monitoring end point can be a point on any area that the ripples can reach. However, if the distance from the detection start point is too far, it may be greatly interfered by other bottom blowing holes. In order to avoid the influence of other bottom blowing 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 used for the ripples to propagate is shortened, and the calculation error of the propagation rate v will increase. Therefore, the distance between the monitoring start point and the monitoring end point can be selected by technicians in this field according to actual conditions.

[0031] It should be noted that in the power transmission and soft blowing steps, bottom blowing (argon) gas is always present, and when improving the fluidity and spreadability of the steel slag, slag-removing agents such as fluorite balls can also be added to cooperate with the power transmission and the addition of carbonized rice husks. However, since monitoring has not yet begun during the power transmission process, the size of the bottom blowing gas at this time only needs to meet 20-60Nm 3 / h.

[0032] In an optional embodiment, when the equivalent diameter of the largest agglomerate of slag on the surface of molten steel within the monitoring range is ≤10 cm, the values ​​of v and t are determined.

[0033] After the carbonized rice husk is added, as the bottom blowing proceeds, the surface of the steel slag or the mixture of steel slag and carbonized rice husk has certain cracks and agglomerates. When the equivalent diameter of the largest agglomerate of steel slag on the surface of the molten steel within the monitoring range is ≤10 cm, the ripples and their movement trajectories can be more clearly monitored, so as to monitor the propagation rate and time interval of the ripples. In this embodiment, the monitoring range refers to the range between the monitoring start point and the monitoring end point.

[0034] In an optional embodiment, the power supply time is greater than 15 seconds, and the power supply time is long enough to allow the steel slag to have good fluidity and spreadability from the beginning.

[0035] In an optional embodiment, the carbonized rice husk is added to the molten steel within 25 seconds after the power transmission is completed, and the carbonized rice husk is added to the molten steel when the steel slag has good fluidity and spreadability so that the carbonized rice husk can be quickly combined with the steel slag.

[0036] In an optional embodiment, after the power transmission is completed, the inclusion feeding modification line can be first performed, and carbonized rice husks are added to the molten steel within 25 seconds after the inclusion feeding modification line is completed, wherein the inclusion feeding modification line includes Ca wire, Si-Ca wire, etc.

[0037] In an optional embodiment, 0.3-0.7 kg of the carbonized rice husk is added per ton of the molten steel.

[0038] In an optional embodiment, when the carbonized rice husk is accumulated on the surface of the molten steel, the doll head is inserted into the accumulated carbonized rice husk to cause the carbonized rice husk to splash.

[0039] It is worth mentioning that carbonized rice husks are usually put into the LF furnace in whole packages (about 7kg / package, and the volume is large), and there is a situation that the carbonized rice husks are piled up into small hills, which will affect the rapid spreading of steel slag (and carbonized rice husks). In addition, for the molten steel casted directly on the LF furnace and the use of the slotted ladle capping device (at this time, the carbonized rice husks can only be thrown into the LF furnace processing position by hand), due to the obstruction of the LF furnace cover and the small gap between the observation door on the furnace cover and the electrode, it is very difficult to quickly throw the whole package of carbonized rice husks to each part of the circular slag surface steel slag, so it is extremely easy to pile up into small hills, which is not conducive to the rapid spreading of steel slag. Therefore, the "directional splashing method" is used for dispersion and spreading. That is, when sampling, measuring temperature, determining hydrogen and oxygen, the water mixed in the even-head filler is fully utilized. When encountering high-temperature molten steel (steel slag), it will explode and splash in a large range (forward), so that the carbonized rice husk piled into a small hill will splash to the target area to achieve the purpose of rapid spreading. It should be noted that the residual heads after use (such as sampling, temperature measurement, hydrogen determination, oxygen determination, etc.) are prohibited from being thrown onto the surface of the slag, so as not to affect the subsequent judgment of the bottom blowing status.

[0040] In an optional embodiment, the soft blowing includes an early stage of soft blowing and a middle and late stage of soft blowing: in the early stage of soft blowing, the flow rate and pressure of the bottom blowing air are adjusted so that v is 0.4-1.5 m / s and t is 0-0.6 s.

[0041] In an optional embodiment, the soft blowing includes an early stage of soft blowing and a middle and late stage of soft blowing: in the middle and late stage of soft blowing, the flow rate and pressure of the bottom blowing air are adjusted so that v is 0-0.4 m / s and t is 0.6-1.2 s.

[0042] The soft blowing steps are divided into early, middle and late stages. The flow rate of the bottom blowing gas in the early stage is relatively fast (large flow rate), and the bubbles generated are relatively large. The flow rate of the bottom blowing gas in the middle and late stages is relatively slow (small flow rate), and the bubbles generated are relatively small, which is beneficial to reducing inclusions in the molten steel.

[0043] An embodiment further provides a method for LF refining, comprising the bottom blowing gas control method described in any one of the aforementioned embodiments.

[0044] The features and performances of the present invention are further described in detail below in conjunction with an example of smelting industrial wire drawing material non-aluminum-containing 45 steel in an LF furnace.

[0045] Example 1

[0046] This embodiment provides a bottom blowing control method, including:

[0047] Turn on the power, turn on the bottom air blowing, and adjust the bottom air blowing flow rate to 30Nm 3 / h, pressure 1.4MPa, power is supplied to the molten steel for 30s, carbonized rice husk is added to the molten steel within 25s after power supply is completed, 0.5kg of carbonized rice husk is added per ton of molten steel, the carbonized rice husk is accumulated on the surface of the molten steel, a doll head is inserted into the accumulated carbonized rice husk to make the carbonized rice husk splash, thereby realizing rapid combination and spreading of the carbonized rice husk and steel slag;

[0048] Soft blowing, soft blowing is performed on the molten steel after adding carbonized rice husk, and the soft blowing includes the early stage of soft blowing and the middle and late stages of soft blowing: in the early stage of soft blowing, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 1.1m / s and t is 0.4s; in the middle and late stages of soft blowing, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0.2m / s and t is 0.8s, and finally the rise amplitude of the tundish plug rod is -0.1mm (i.e. the plug rod descends by 0.1mm). Among them, v and t are specifically: when the equivalent diameter of the largest agglomerate of slag on the surface of the molten steel within the monitoring range is ≤10cm, the center of the exposed area on the slag is taken as the monitoring point, and under the condition of the presence of bottom blowing gas, ripples will continuously spread outward from the monitoring point, and the propagation rate of the 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] Turn on the power, turn on the bottom air blowing, and adjust the bottom air blowing flow rate to 30Nm 3 / h, pressure 1.4MPa, power is supplied to the molten steel for 30s, after power supply is completed, 15m of pure Ca wire with inclusion modification wire is fed, carbonized rice husk is added to the molten steel within 25s after feeding the pure Ca wire, 0.5kg of carbonized rice husk is added per ton of the molten steel, the carbonized rice husk is accumulated on the surface of the molten steel, and a doll head is inserted into the accumulated carbonized rice husk to make the carbonized rice husk splash, thereby realizing rapid combination and spreading of the carbonized rice husk and the steel slag;

[0052] Soft blowing, soft blowing is performed on the molten steel after adding carbonized rice husk, and the soft blowing includes the early stage of soft blowing and the middle and late stages of soft blowing: in the early stage of soft blowing, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 1.1m / s and t is 0.4s; in the middle and late stages of soft blowing, the flow rate and pressure of the bottom blowing gas are adjusted so that v is 0.2m / s and t is 0.8s, and finally the rise amplitude of the tundish plug rod is -0.3mm (i.e. the plug rod descends by 0.3mm). Among them, v and t are specifically: when the equivalent diameter of the largest agglomerate of slag on the surface of the molten steel within the monitoring range is ≤10cm, the center of the exposed area on the slag is taken as the monitoring point, and under the condition of the presence of bottom blowing gas, ripples will continuously spread outward from the monitoring point, and the propagation rate of the ripples is v, and the time interval between adjacent ripples is t.

[0053] Comparative Example 1

[0054] This comparative example provides a bottom blowing control method, which is different from Example 1 only in that no power is supplied before adding carbonized rice husks to the molten steel; and finally the rise amplitude of the tundish stopper rod is 0.8 mm (i.e. the rise stroke of the stopper rod is 0.8 mm).

[0055] Comparative Example 2

[0056] This comparative example provides a bottom blowing air control method, which is different from Example 1 only in that no carbonized rice husk is added; and finally the rise amplitude of the tundish stopper rod is 1.5 mm (ie, the rise stroke of the stopper rod is 1.5 mm).

[0057] Comparative Example 3

[0058] This comparative example provides a bottom blowing control method, which is different from Example 1 only in that the doll head is not inserted into the accumulated carbonized rice husks, so that the carbonized rice husks are slowly spread without human intervention; and finally the rise amplitude of the tundish stopper rod is 0.7 mm (i.e., the rise stroke of the stopper rod is 0.7 mm).

[0059] Comparative Example 4

[0060] This comparative example provides a bottom blowing gas control method, which is different from Example 1 only in that the flow rate and pressure of the bottom blowing gas are adjusted in the early stage of soft blowing so that v is 0.6m / s and t is 0.6s; and finally the rise amplitude of the tundish 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 gas control method, which is different from Example 1 only in that the flow rate and pressure of the bottom blowing gas are adjusted in the early stage of soft blowing so that v is 1.5m / s and t is 0.1s; and finally the rise amplitude of the tundish 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 gas control method, which is different from Example 1 only in that the flow rate and pressure of the bottom blowing gas are adjusted in the middle and late stages of the soft blowing so that v is 0.1 m / s and t is 1.2 s; and finally the rise amplitude of the tundish stopper rod is 0.2 mm (i.e., the rise stroke of the stopper rod is 0.2 mm).

[0065] Comparative Example 7

[0066] This comparative example provides a bottom blowing gas control method, which is different from Example 1 only in that the flow rate and pressure of the bottom blowing gas are adjusted in the middle and late stages of the soft blowing so that v is 0.4 m / s and t is 0.6 s; and finally the rise amplitude of the tundish stopper rod is 0.3 mm (i.e., the rise stroke of the stopper rod is 0.3 mm).

[0067] The results of comparing the increase in the tundish plug rod of the above embodiment and the comparative example are shown in Table 1.

[0068] Table 1

[0069]

[0070]

[0071] It can be seen from Example 1 that when the relevant parameters are appropriate, the tundish stopper rod has a slight decrease (-0.1 mm), and on the basis of Example 1, the stopper rod in Example 2 further decreases slightly (-0.3 mm). This is the effect of the pure Ca wire fed on the erosion of the stopper rod, which is a normal phenomenon.

[0072] Through Example 1 and Comparative Examples 1, 2 and 3, it can be seen that the absence of carbonized rice husk in Comparative Example 2 has the greatest impact, because the adsorption capacity of steel slag for inclusions is poor, so the increase in the stopper rod is the largest (1.5 mm), while the absence of power supply in Comparative Example 1 and the poor spreading of steel slag in Comparative Example 3 will also affect the adsorption of inclusions, and the increase in the stopper rod is also large (0.8 mm and 0.7 mm respectively).

[0073] It can be seen from Example 1 and Comparative Example 4 that when the propagation speed in the early stage of soft blowing becomes slower and the interval time becomes longer (the frequency is low), because the further spreading speed of the slag becomes slower, the adsorption capacity of inclusions becomes weaker, and the rise of the stopper rod is larger (0.4 mm); It can be seen from Example 1 and Comparative Example 5 that when the propagation speed in the early stage of soft blowing becomes faster and the interval time becomes shorter (the frequency is high), although the further spreading speed of the slag becomes faster, the steel liquid level fluctuates greatly at this time, the slag close to one side of the molten steel and the inclusions that have been adsorbed are easily re-involved in the molten steel to become the source of inclusions, and the rise of the stopper rod is slightly larger (0.1 mm).

[0074] It can be seen from Example 1 and Comparative Example 6 that when the propagation speed becomes slower and the interval time becomes longer (the frequency is low) in the middle and late stages of soft blowing, the mass transfer from the slag close to the molten steel side to the surface slag becomes slower, the adsorption capacity of inclusions becomes weaker, and the rise of the stopper rod is slightly larger (0.2 mm); It can be seen from Example 1 and Comparative Example 7 that when the propagation speed becomes faster and the interval time becomes shorter (the frequency is high) in the middle and late stages of soft blowing, although the mass transfer from the slag close to the molten steel side to the surface slag becomes faster, the liquid level fluctuates greatly at this time, the slag and the inclusions that have been adsorbed are easily re-involved in the molten steel and become the source of inclusions, and the rise of the stopper rod is larger (0.3 mm).

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A bottom blowing control method, characterized in that: include: Power transmission is used to heat the molten steel, and after the power transmission is completed, carbonized rice husk is added to the molten steel; Soft blowing is performed on the molten steel after adding carbonized rice husk. 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, wherein v and t are specifically: the middle of the exposed area on the slag is taken as the monitoring point. Under the condition of the presence of bottom blowing gas, ripples will continuously diffuse outward from the monitoring point. The propagation rate of the ripples is v, and the time interval between adjacent ripples is t.

2. The bottom blowing control method according to claim 1, characterized in that: When the equivalent diameter of the largest agglomerate of slag on the surface of molten steel within the monitoring range is ≤10 cm, the values ​​of v and t are determined.

3. The bottom blowing control method according to claim 1, characterized in that: The power transmission time is greater than 15s.

4. The bottom blowing control method according to claim 1, characterized in that: After the power transmission is completed, the carbonized rice husk is added to the molten steel within 25 seconds.

5. The bottom blowing control method according to claim 1, characterized in that: After the power transmission is completed, an inclusion feeding and modification line is also carried out, and carbonized rice husks are added to the molten steel within 25 seconds after the inclusion feeding and modification line is completed.

6. The bottom blowing control method according to claim 1, characterized in that: 0.3-0.7 kg of the carbonized rice husk is added per ton of the molten steel.

7. The bottom blowing control method according to claim 1, characterized in that: When the carbonized rice husks are accumulated on the surface of the molten steel, the coupler head is inserted into the accumulated carbonized rice husks to make the carbonized rice husks splash.

8. The bottom blowing control method according to claim 1, characterized in that: The soft blowing includes an early stage of soft blowing and a middle and late stage of soft blowing: in the early stage of soft blowing, the flow rate and pressure of the bottom blowing air are adjusted so that v is 0.4-1.5 m / s and t is 0-0.6 s.

9. The bottom blowing control method according to claim 1, characterized in that: The soft blowing includes an early stage of soft blowing and a middle and late stage of soft blowing: in the middle and late stage of soft blowing, the flow rate and pressure of the bottom blowing air are adjusted so that v is 0-0.4 m / s and t is 0.6-1.2 s.

10. A method for LF refining, characterized in that: The invention comprises the bottom blowing gas control method as described in any one of claims 1 to 9.

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