Method for removing inclusions in heavy rail steel

Abstract

The present application relates to the field of steel smelting, and discloses a method for removing inclusions in steel, comprising the following steps: S1, bottom argon blowing is performed on molten steel in a ladle at a first argon blowing flow rate; S2, power ultrasound is applied to the molten steel at a first frequency to refine argon bubbles; S3, power ultrasound is applied to the molten steel at a second frequency lower than the first frequency to promote diffusion of the refined argon bubbles; and S4, bottom argon blowing is performed on the molten steel at a second argon blowing flow rate lower than the first argon blowing flow rate. By refining the size of the argon bubbles and changing the motion trajectory of the argon bubbles, the present application improves the contact probability of the argon bubbles and non-metallic inclusions in the molten steel, and strengthens the removal effect of the non-metallic inclusions by the ladle bottom argon blowing process.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and specifically to a method for removing inclusions from steel. Background Technology

[0002] Argon bubbles in bottom-blown argon ladles play a crucial role in the transport and removal of inclusions. In the refining of heavy rail steel, bottom-blown argon is a vital method for removing non-metallic inclusions and improving the cleanliness of molten steel. By agitating the molten steel with bottom-blown argon, a circulating flow is created, accelerating mass transfer, homogenizing temperature, promoting slag-metal interface reactions, and facilitating the flotation and removal of inclusions within the molten steel.

[0003] Current research on bottom-blowing argon in molten steel mainly focuses on optimizing the flow and temperature fields within the ladle by adjusting bottom-blowing argon parameters, thereby promoting the flotation and removal of inclusions. However, due to the relatively large size of the argon bubbles formed by bottom-blowing argon in the molten steel, its effect on the aggregation and flotation removal of small-sized non-metallic inclusions is weak. Related studies indicate that the flotation and removal of small-sized non-metallic inclusions is closely related to the size of the argon bubbles. Therefore, it is urgent to optimize the bottom-blowing argon process in molten steel to refine the argon bubble size and efficiently remove small-sized inclusions from the molten steel. Summary of the Invention

[0004] The main objective of this invention is to provide a method for removing inclusions from steel, thereby solving the technical problem of how to enhance the removal effect of the bottom blowing argon process on inclusions in steel ladles.

[0005] According to one aspect of the present invention, a method for removing inclusions in steel is provided, comprising the following steps: S1, bottom blowing argon into molten steel in a ladle at a first argon flow rate; S2, applying power ultrasound to the molten steel at a first frequency to refine argon bubbles; S3, applying power ultrasound to the molten steel at a second frequency lower than the first frequency to promote diffusion of the refined argon bubbles; S4, bottom blowing argon into the molten steel at a second argon flow rate lower than the first argon flow rate.

[0006] According to one embodiment of the present invention, in step S1, the first argon blowing flow rate is 100~120 NL / min, and the argon blowing time is 3~5 min.

[0007] According to one embodiment of the present invention, in steps S2 and S3, power ultrasound is applied by a power ultrasound sensor inserted into the molten steel.

[0008] According to one embodiment of the present invention, in step S2, the height of the probe of the power ultrasonic sensor from the bottom of the ladle is 1 / 4 to 1 / 2 of the total height of the ladle.

[0009] According to one embodiment of the present invention, in step S2, the first frequency is 300~500kHz, the vibration mode of the power ultrasound is continuous vibration, the power range is 48~120kW, and the action time is 2~4min.

[0010] According to one embodiment of the present invention, in step S3, the height of the probe of the power ultrasonic sensor from the bottom of the ladle is 1 / 4 to 3 / 4 of the total height of the ladle.

[0011] According to one embodiment of the present invention, in step S3, the second frequency is 24~100kHz, the vibration mode of the power ultrasound is intermittent vibration, the power range is 48~120kW, and the action time is 1~3min.

[0012] According to one embodiment of the present invention, in steps S2 and S3, the probe of the power ultrasonic sensor and the center of the bottom-blown argon nozzle at the bottom of the ladle are located on the same longitudinal axis.

[0013] According to one embodiment of the present invention, in step S4, the second argon blowing flow rate is 50~70 NL / min, and the argon blowing time is 3~5 min.

[0014] According to one embodiment of the present invention, step S2 is started after a stable flow field is formed in the ladle in step S1; steps S2 to S4 are performed sequentially.

[0015] In the technical solution of this invention, step S1 involves bottom blowing with argon at a relatively high flow rate to form a large number of argon bubbles and a stable circulating field in the molten steel. Then, step S2 applies high-frequency power ultrasound, utilizing its cavitation effect to break large bubbles into smaller bubbles, significantly increasing the contact area between the bubbles and inclusions in the molten steel, thereby enhancing the ability to capture small-sized non-metallic inclusions. Next, step S3 applies low-frequency power ultrasound, utilizing its acoustic flow effect to rapidly disperse the refined bubbles throughout the ladle, preventing small bubbles from re-aggregating and growing, and extending the residence time of the bubbles in the molten steel. Finally, step S4 uses soft blowing with a low flow rate to gently push the bubbles carrying inclusions to the slag layer, while simultaneously preventing secondary oxidation of the molten steel. Through the synergistic effect of the above steps, this invention can effectively remove small-sized non-metallic inclusions and significantly improve the cleanliness of the molten steel. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating a method for removing inclusions in steel according to an embodiment of the present invention is shown; Figure 2 Showing through Figure 1 A schematic diagram illustrating the method for enhancing the removal of inclusions in steel. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0019] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0020] The inventors recognized that the cavitation, acoustic flow, and overheating phenomena generated by power ultrasound propagation in melt make it widely applicable in the metallurgical field. Combining power ultrasound with bottom-blowing argon in a ladle can break up argon bubbles, forming smaller argon bubbles, accompanied by the generation of cavitation bubbles. The acoustic flow effect alters the propagation path of the argon bubbles, prolonging their residence time in the molten steel. Furthermore, the acoustic flow rapidly diffuses the formed small argon bubbles into the surrounding molten steel, reducing aggregation and engulfment caused by agglomeration, and enhancing the flotation and removal of non-metallic inclusions.

[0021] As mentioned above, power ultrasound has been continuously explored, developed, and applied in metallurgical processes such as promoting material diffusion in molten steel, refining grains, and removing inclusions using cavitation effects. Inspired by the widespread application of power ultrasound technology, the inventors developed a method for refining argon bubbles to promote the flotation and removal of non-metallic inclusions in molten steel, proposing a method using power ultrasound to refine argon bubbles and enhance the removal of inclusions in heavy rail steel. The cavitation effect of power ultrasound can refine argon bubbles, and combined with the acoustic flow effect, disperses the refined argon bubbles, reducing their aggregation and growth, and increasing the contact probability between argon bubbles and non-metallic inclusions. Furthermore, the cavitation effect of power ultrasound excites cavitation bubbles in the molten steel, which, together with the refined argon bubbles, can effectively capture small-sized non-metallic inclusions, promoting their aggregation and flotation for removal. The method of this invention will be described in detail below.

[0022] refer to Figure 1 This invention proposes a method for removing inclusions from steel, comprising the following steps: S1, bottom blowing argon into the molten steel in the ladle is performed at the first argon blowing flow rate; S2, apply power ultrasound to the molten steel at the first frequency to refine the argon bubbles; S3, applying power ultrasound to the molten steel at a second frequency lower than the first frequency to promote the diffusion of refined argon bubbles; S4, bottom blowing argon is performed on the molten steel at a second argon flow rate lower than the first argon flow rate.

[0023] refer to Figure 2 In the technical solution of this invention, step S1 involves bottom blowing with argon at a relatively high flow rate to form a large number of argon bubbles and a stable circulating field in the molten steel. Then, step S2 applies high-frequency power ultrasound, utilizing its cavitation effect to break large bubbles into smaller bubbles, significantly increasing the contact area between the bubbles and inclusions in the molten steel, thereby enhancing the ability to capture small-sized non-metallic inclusions. Next, step S3 applies low-frequency power ultrasound, utilizing its acoustic flow effect to rapidly disperse the refined bubbles throughout the ladle, preventing small bubbles from re-aggregating and growing, and extending the residence time of the bubbles in the molten steel. Finally, step S4 uses soft blowing at a low flow rate to gently push the bubbles carrying inclusions to the slag layer, while avoiding secondary oxidation of the molten steel. Through the synergistic effect of the above steps, this invention can effectively remove small-sized non-metallic inclusions and significantly improve the cleanliness of the molten steel.

[0024] Step S1 is the bottom-blowing argon hard blowing stage of the ladle. After the ladle enters the refining process, bottom-blowing argon is performed. An argon inlet is provided at the bottom of the ladle, and a bottom-blowing argon nozzle is installed at the argon inlet for bottom-blowing argon. The argon inlet can be located at the center of the bottom of the ladle, so that the argon rises along the central axis of the ladle, driving the molten steel to form a symmetrical and stable circulation, ensuring uniform composition and temperature of the molten steel. In other embodiments, the argon inlet can also be located at other positions as needed. In some embodiments, in step S1, the first argon blowing flow rate is 100~120 NL / min, and the blowing time is 3~5 min. Through high-flow-rate bottom-blowing argon, a macroscopic circulation and stable flow field are quickly formed in the ladle, providing a sufficient source of argon bubbles for subsequent power ultrasonic treatment.

[0025] Step S2 is the high-frequency power ultrasound stage. After a stable flow field is formed in the ladle during the bottom-blowing argon hard-blowing stage of step S1, an immersion power ultrasound sensor is inserted into the molten steel to apply power ultrasound. Step S2 can be performed in the middle or late stage of step S1. The height of the power ultrasound sensor probe from the bottom of the ladle is 1 / 4 to 1 / 2 (e.g., 1 / 3) of the total height of the ladle, ensuring that the probe is located in the bubble-rich area formed by bottom-blowing argon, so as to efficiently break up argon bubbles using the cavitation effect of high-frequency ultrasound. The probe can be set on the central axis of the ladle so that the ultrasonic energy is symmetrically distributed radially along the ladle. In other embodiments, the probe can also be set in other positions as needed. The center of the probe and the bottom-blowing argon nozzle are located on the same longitudinal axis so that the ultrasonic energy and the argon bubble upflow interact in the same direction, thereby maximizing the cavitation effect on bubble breaking efficiency. In some embodiments, in step S2, the first frequency is 300~500kHz, the vibration mode of the power ultrasound is continuous vibration, the power range is 48~120kW, and the action time is 2~4min. High-frequency continuous vibration ultrasound is used to efficiently break large bubbles formed by bottom-blown argon into micron-sized fine bubbles by utilizing its strong cavitation effect.

[0026] Step S3 is the low-frequency power ultrasound stage. After step S2, the power ultrasound sensor is switched to low-frequency operating mode, utilizing the acoustic flow effect of low-frequency power ultrasound to quickly disperse the small argon bubbles. The height of the power ultrasound sensor probe from the bottom of the ladle can be adjusted at different heights, for example, within the range of 1 / 4 to 3 / 4 of the total ladle height. This allows for targeted dispersion of the refined argon bubbles to different depths within the ladle based on the actual circulation state of the molten steel. In some embodiments, in step S3, the second frequency is 24-100 kHz, the power ultrasound vibration mode is intermittent vibration with a time interval of 2-4 seconds, the power range is 48-120 kW, and the duration is 1-3 minutes. Through low-frequency intermittent vibration ultrasound, the argon bubbles refined in step S2 are uniformly dispersed throughout the ladle using its acoustic flow effect. The probe can be positioned on the central axis of the ladle or at other locations as needed. The center of the probe and the bottom-blowing argon nozzle can be located on the same longitudinal axis, so that the acoustic flow generated by low-frequency ultrasound gives the refined argon bubbles a vertical downward velocity, changes the propagation path of the argon bubbles, and prolongs the residence time of the argon bubbles in the molten steel.

[0027] Step S4 is the bottom argon blowing stage of the ladle. After the power ultrasonic treatment ends, bottom argon blowing of the ladle continues. In some embodiments, in step S4, the second argon blowing flow rate is 50~70 NL / min, which is suitable when the refining slag on the upper surface of the molten steel is agitated but the molten steel is not exposed, and the argon blowing time is 3~5 min until the refining process is completed.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention refines argon bubbles by using the cavitation effect of high-frequency power ultrasound. It takes advantage of the fact that small-sized argon bubbles can easily capture small-sized non-metallic inclusions in molten steel. By combining reasonable bottom-blowing argon parameters, the floating and removal of small-sized inclusions are enhanced.

[0029] (2) The present invention places the center of the power ultrasonic probe and the bottom blowing argon nozzle on the same longitudinal axis, and uses the acoustic flow effect of low frequency power ultrasound to quickly disperse the refined argon bubbles. On the one hand, it reduces the possibility of the refined argon bubbles growing due to aggregation. On the other hand, the vertically downward acoustic flow gives the refined argon bubbles a vertically downward speed, changes the propagation path of the argon bubbles, prolongs the residence time of the argon bubbles in the molten steel, and increases the probability of contact between the argon bubbles and non-metallic inclusions.

[0030] (3) The present invention places the center of the power ultrasonic probe and the bottom blowing argon nozzle on the same longitudinal axis. Compared with the traditional bottom blowing argon process, it can reduce the direct impact of the bottom blowing argon gas flow on the refining slag, reduce the slag hole area formed by the bottom blowing argon gas, and reduce the secondary oxidation of the molten steel.

[0031] (4) The present invention utilizes the acoustic flow effect of low-frequency power ultrasound to disperse refined argon bubbles into the surrounding molten steel. Compared with the traditional bottom blowing argon process, it can reduce the proportion of dead zone in the ladle and improve the mixing efficiency to a certain extent.

[0032] The following description is based on specific embodiments.

[0033] Example 1 A method for removing inclusions in heavy rail steel using power ultrasonic refining argon bubble strengthening includes the following steps: Step 1: Bottom blowing of argon into the ladle, hard blowing stage.

[0034] After the ladle enters the refining process, bottom blowing argon operation is performed. The argon inlet is located at the center of the bottom of the ladle, the bottom blowing argon flow rate is controlled at 100 NL / min, and the blowing time is 4 min.

[0035] Step 2: Apply high-frequency power ultrasound to the molten steel to refine the argon bubbles.

[0036] Position of the power ultrasonic sensor: Insert the immersion power ultrasonic sensor into the molten steel, with the sensor probe located on the central axis of the ladle and at 1 / 3 of the height from the bottom of the ladle; High-frequency power ultrasound parameters: Set the power ultrasound vibration mode to continuous vibration, the frequency to 400kHz, the power to 72kW, and the duration to 2min.

[0037] Step 3: Apply low-frequency power ultrasound to the molten steel to promote the diffusion of refined argon bubbles.

[0038] Position of the power ultrasonic sensor: Power ultrasound converts high frequency to low frequency, utilizing the acoustic flow effect of low-frequency power ultrasound to rapidly disperse tiny argon bubbles. The sensor probe is located on the central axis of the ladle, at a distance of 1 / 3 of the ladle's height from the bottom. Low-frequency power ultrasound parameters: The power ultrasound vibration mode is set to intermittent vibration, with a time interval of 3 seconds, a frequency of 24 kHz, a power of 48 kW, and an action time of 1 minute.

[0039] Step 4: Bottom blowing of argon into the ladle, soft blowing stage.

[0040] After the power ultrasound treatment ends, continue to blow argon into the bottom of the ladle, with the flow rate controlled at 50 NL / min and the blowing time at 3 min.

[0041] According to the test and analysis, the removal rate of non-metallic inclusions was 96.37%. The rating results of Class B and C non-metallic inclusions in the molten steel are shown in Table 1.

[0042] Table 1. Rating of Class B and C Non-metallic Inclusions in Molten Steel

[0043] Example 2 A method for removing inclusions in heavy rail steel using power ultrasonic refining argon bubble strengthening includes the following steps: Step 1: Bottom blowing of argon into the ladle, hard blowing stage.

[0044] After the ladle enters the refining process, bottom blowing argon operation is performed. The argon inlet is located at the center of the bottom of the ladle, the bottom blowing argon flow rate is controlled at 120 NL / min, and the blowing time is 4 min.

[0045] Step 2: Apply high-frequency power ultrasound to the molten steel to refine the argon bubbles.

[0046] Position of the power ultrasonic sensor: Insert the immersion power ultrasonic sensor into the molten steel, with the sensor probe located on the central axis of the ladle and at 1 / 3 of the height from the bottom of the ladle; High-frequency power ultrasound parameters: Set the power ultrasound vibration mode to continuous vibration, the frequency to 400kHz, the power to 96kW, and the duration to 2min.

[0047] Step 3: Apply low-frequency power ultrasound to the molten steel to promote the diffusion of refined argon bubbles.

[0048] Position of the power ultrasonic sensor: Power ultrasound converts high frequency to low frequency, utilizing the acoustic flow effect of low-frequency power ultrasound to rapidly disperse tiny argon bubbles. The sensor probe is located on the central axis of the ladle, at a distance of 2 / 3 of the ladle's height from the bottom. Low-frequency power ultrasound parameters: The power ultrasound vibration mode is set to intermittent vibration, with a time interval of 3 seconds, a frequency of 24 kHz, a power of 96 kW, and an action time of 1 minute.

[0049] Step 4: Bottom blowing of argon into the ladle, soft blowing stage.

[0050] After the power ultrasound treatment ends, continue to blow argon from the bottom of the ladle, with the flow rate controlled at 70 NL / min and the blowing time at 3 min.

[0051] According to the test and analysis, the removal rate of non-metallic inclusions was 97.10%. The rating results of B and C class non-metallic inclusions in molten steel are shown in Table 2.

[0052] Table 2 Rating of Class B and C Non-metallic Inclusions in Molten Steel

[0053] Example 3 A method for removing inclusions in heavy rail steel using power ultrasonic refining argon bubble strengthening includes the following steps: Step 1: Bottom blowing of argon into the ladle, hard blowing stage.

[0054] After the ladle enters the refining process, bottom blowing argon operation is performed. The argon inlet is located at the center of the bottom of the ladle, the bottom blowing argon flow rate is controlled at 100 NL / min, and the blowing time is 5 min.

[0055] Step 2: Apply high-frequency power ultrasound to the molten steel to refine the argon bubbles.

[0056] Position of the power ultrasonic sensor: Insert the immersion power ultrasonic sensor into the molten steel, with the sensor probe located on the central axis of the ladle and at 1 / 3 of the height from the bottom of the ladle; High-frequency power ultrasound parameters: Set the power ultrasound vibration mode to continuous vibration, the frequency to 400kHz, the power to 120kW, and the duration to 4min.

[0057] Step 3: Apply low-frequency power ultrasound to the molten steel to promote the diffusion of refined argon bubbles.

[0058] Position of the power ultrasonic sensor: Power ultrasound converts high frequency to low frequency, utilizing the acoustic flow effect of low-frequency power ultrasound to rapidly disperse tiny argon bubbles. The sensor probe is located on the central axis of the ladle, at a distance of 1 / 3 of the ladle's height from the bottom. Low-frequency power ultrasound parameters: Set the power ultrasound vibration mode to intermittent vibration, with a time interval of 3 seconds, a frequency of 24 kHz, a power of 120 kW, and an action time of 2 minutes.

[0059] Step 4: Bottom blowing of argon into the ladle, soft blowing stage.

[0060] After the power ultrasound treatment ends, continue to blow argon into the bottom of the ladle, with the flow rate controlled at 50 NL / min and the blowing time at 5 min.

[0061] According to the test and analysis, the removal rate of non-metallic inclusions was 98.24%. The rating results of B and C class non-metallic inclusions in the molten steel are shown in Table 3.

[0062] Table 3. Rating of Class B and C Non-metallic Inclusions in Molten Steel

[0063] In summary, this invention proposes a method for refining argon bubbles using power ultrasound to enhance the removal of inclusions in heavy rail steel. The power ultrasound frequency range is 24–500 kHz, and the power range is 48–120 kW. This method enhances the removal of small inclusions by refining argon bubbles and promoting their diffusion and mass transfer. The cavitation effect of power ultrasound refines the argon bubbles, enhancing their ability to capture small non-metallic inclusions in the molten steel. The acoustic flow effect of power ultrasound rapidly diffuses the refined argon bubbles, reducing their aggregation and growth; furthermore, it alters the argon bubble trajectory, prolonging their residence time in the molten steel and increasing the probability of contact between the argon bubbles and non-metallic inclusions. The combined effect of cavitation and acoustic flow refines the argon bubbles, thus enhancing the removal of inclusions in heavy rail steel.

[0064] This invention can achieve a non-metallic inclusion removal rate of ≥96.37% in molten steel, with over 97.5% of Class B inclusions having a rating ≤0.5, over 98.8% of Class C inclusions having a rating ≤0.5, over 95.37% of inclusions having a rating ≤0.5 for both Class B and Class C inclusions, and over 55.75% of inclusions having a rating of 0 for both Class B and Class C inclusions. Compared to conditions without power ultrasound, the non-metallic inclusion removal rate is increased by 12.95%, and the proportion of inclusions with a rating ≤0.5 for both Class B and Class C inclusions is increased by nearly 10%. Power ultrasound effectively enhances the removal of inclusions in molten steel and improves the inclusion rating level of rails.

[0065] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for removing inclusions from steel, characterized in that, Includes the following steps: S1, bottom blowing argon into the molten steel in the ladle is performed at the first argon blowing flow rate; S2, apply power ultrasound to the molten steel at the first frequency to refine the argon bubbles; S3, apply power ultrasound to the molten steel at a second frequency lower than the first frequency to promote the diffusion of refined argon bubbles; S4, perform bottom blowing of argon onto the molten steel at a second argon flow rate lower than the first argon flow rate.

2. The method according to claim 1, characterized in that, In step S1, the first argon blowing flow rate is 100~120 NL / min, and the argon blowing time is 3~5 min.

3. The method according to claim 1, characterized in that, In steps S2 and S3, power ultrasound is applied by a power ultrasound sensor inserted into the molten steel.

4. The method according to claim 3, characterized in that, In step S2, the height of the probe of the power ultrasonic sensor from the bottom of the ladle is 1 / 4 to 1 / 2 of the total height of the ladle.

5. The method according to claim 1, characterized in that, In step S2, the first frequency is 300~500kHz, the vibration mode of the power ultrasound is continuous vibration, the power range is 48~120kW, and the action time is 2~4min.

6. The method according to claim 3, characterized in that, In step S3, the height of the probe of the power ultrasonic sensor from the bottom of the ladle is 1 / 4 to 3 / 4 of the total height of the ladle.

7. The method according to claim 1, characterized in that, In step S3, the second frequency is 24~100kHz, the vibration mode of the power ultrasound is intermittent vibration, the power range is 48~120kW, and the action time is 1~3min.

8. The method according to claim 3, characterized in that, In steps S2 and S3, the probe of the power ultrasonic sensor and the center of the bottom-blown argon nozzle at the bottom of the ladle are located on the same longitudinal axis.

9. The method according to claim 1, characterized in that, In step S4, the second argon blowing flow rate is 50~70 NL / min, and the argon blowing time is 3~5 min.

10. The method according to claim 1, characterized in that, After a stable flow field is formed in the ladle in step S1, step S2 is started; steps S2 to S4 are performed sequentially.

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