CN109732072B - Method for applying same-polarity charges to inhibit inner wall accretion of submerged nozzle - Google Patents
Method for applying same-polarity charges to inhibit inner wall accretion of submerged nozzle Download PDFInfo
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- CN109732072B CN109732072B CN201910205858.4A CN201910205858A CN109732072B CN 109732072 B CN109732072 B CN 109732072B CN 201910205858 A CN201910205858 A CN 201910205858A CN 109732072 B CN109732072 B CN 109732072B
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Abstract
The invention belongs to the field of metallurgical continuous casting, and particularly relates to a method for inhibiting inner wall accretion of an immersion nozzle by applying same-polarity charges. The technical scheme of the invention is as follows: a method for applying same-polarity charges to inhibit the inner wall of a submerged nozzle from nodulation is characterized in that a stable forward current is applied to the inner wall of the submerged nozzle, so that the sintering and adhesion behaviors of impurities on the inner wall of the submerged nozzle are limited, and the nozzle nodulation is further inhibited. The method for applying the charges with the same polarity to inhibit the nodulation of the inner wall of the submerged nozzle can effectively inhibit the nodulation of the inner wall of the submerged nozzle through the acting force of the repulsion of the charges with the same polarity.
Description
Technical Field
The invention belongs to the field of metallurgical continuous casting, and particularly relates to a method for inhibiting inner wall accretion of an immersion nozzle by applying same-polarity charges.
Background
Compared with the obvious improvement of the thermal shock resistance of the nozzle material, the problems of nodulation and blockage, slag adhering and slag line erosion of the nozzle material become common service failure problems of the submerged nozzle in the service process. Severe nozzle clogging behavior can even lead to complete blockage of submerged entry nozzles, which in turn leads to production accidents with interrupted continuous casting.
The effective control and prevention of the problem of the nodulation of the submerged entry nozzle during the continuous casting process has been the subject of continuous exploration and improvement in the continuous casting process. At present, the main method for controlling the nozzle nodulation is generally to control the generation amount of deoxidation product alumina; the deoxidation product is made to form a low-melting-point compound which is easy to float upwards as much as possible by means of calcium treatment and the like; blowing and stirring are carried out moderately to accelerate the floating of the deoxidation product alumina inclusion; the problem of accretion of the submerged nozzle controlled by the ways of supplying oxygen to molten steel through the nozzle refractory material, changing and optimizing the structure and the material of the inner wall of the nozzle and the like is solved.
However, in the actual production process, the production cost is seriously increased due to the large process change of the several nozzle nodulation modes. And when the steel with more aluminum content in the steel is processed, the control effect of the nozzle nodulation is not improved ideally. Therefore, it is important to develop a technology for preventing the clogging of the submerged nozzle reasonably and conveniently.
Although the formation of nozzle nodules is a complex physicochemical process, many factors and conditions are involved and affect each other. However, related researches find that a certain potential difference exists between the inner wall of the water gap and molten steel in the casting process, and the value of the potential difference is positively correlated with the casting speed. And proves that during the casting process, alumina inclusions flowing through the water openings generate certain transient positive charges due to high-speed friction behavior.
Disclosure of Invention
The invention provides a method for applying charges with the same polarity to inhibit the nodulation of the inner wall of an immersion nozzle, which can effectively inhibit the nodulation of the inner wall of the immersion nozzle through the acting force of the repulsion of the charges with the same polarity.
The technical scheme of the invention is as follows:
a method for applying the same-polarity charge to suppress the nodulation of the inner wall of a submerged nozzle applies a stable forward current to the inner wall of the submerged nozzle, so that the sintering and adhering actions of the impurities on the inner wall of the submerged nozzle are limited, the nodulation of the nozzle is further suppressed, and the quantity of the impurities in steel is improved.
Further, the method for applying the same-polarity charges to inhibit the nodulation of the inner wall of the submerged nozzle comprises the following specific steps: forming a groove on the surface of an original aluminum-carbon submerged nozzle, putting a metal wire into the groove, and sealing the groove by using high-temperature cement and refractory cotton; the width of the groove is 2-3cm, and the exposed end of the metal wire is connected with a direct current power supply.
Further, the method for applying the same-polarity charges to inhibit the nodulation of the inner wall of the submerged nozzle is characterized in that the metal wire is a steel wire, a molybdenum wire or a tungsten wire and has certain high-temperature resistance.
Further, the method for applying the same-polarity charges to inhibit the inner wall of the submerged nozzle from nodulation is characterized in that the metal wire is a pure molybdenum wire with the diameter of 0.8-1.5 mm.
Further, the method for applying the same-polarity charges to inhibit the inner wall of the submerged nozzle from nodulation comprises the step of preheating and baking the submerged nozzle at high temperature for 2 hours before casting.
Further, the method for applying the same polarity charges to inhibit the inner wall accretion of the submerged nozzle is described, wherein the current of the DC power supply is controlled within 2-5A, the casting speed is controlled within 2.1m/min, and the casting temperature is between 1540-1560 ℃.
The invention has the beneficial effects that:
1. the invention applies a stable direct current on the wall surface of the water gap to form a stable electric field, so that the inclusion particles which generate transient charges due to friction can not be adhered to the inner wall of the water gap to form adhered slag and nodules due to the action of repulsion; but also can not react with the slag line interlayer on the wall surface of the water gap and the material of the water gap. The nozzle material is protected while the nozzle nodulation is inhibited, so that the continuous casting production process can be safely, stably and efficiently carried out. Even if the normal casting operation is carried out for more than 12 hours, the slag line on the inner wall of the water gap is still relatively intact; the number of casting furnaces can be increased completely, and the single casting yield can be continuously enlarged. Meanwhile, due to the effect that like charges generate repulsion force, the inclusions flowing through the water gap cannot be contacted with each other, further aggregation cannot be achieved, and the growth cannot be achieved, so that the size of the inclusions in the final casting blank is relatively small, the number of the whole inclusions in the casting blank can be reduced to a certain extent, and the effect of improving the quality of the casting blank is achieved finally.
2. In the casting process, stable direct current is applied to the submerged nozzle through a direct current power supply, and the current can be controlled between 2 and 5A according to the content of alumina inclusions in steel.
3. By the method, the thickness of the nozzle nodule can be reduced by more than 12%, and the unreacted slag line layer of the nozzle can be improved by more than 140%; although the thickness reduction effect of nozzle nodules is not obvious, it can be seen from the comparison of the overall profile of the nozzle that the material of the nozzle itself is substantially severely eroded, but untreated nozzles are severely eroded. By the method, the newly generated surface nodulation of the water gap is more stable in property, the density is improved to a certain extent, and the size and the number of the inclusions are improved to different degrees.
Drawings
FIG. 1 is a cross-sectional comparison of an aluminum killed steel 10B21 submerged entry nozzle; wherein, (a) contrast immersion nozzle, (b) test immersion nozzle that lets in direct current;
FIG. 2 is a cross-sectional comparison of 35K submerged nozzle made of aluminum killed steel; wherein, (a) contrast immersion nozzle, (b) the experimental immersion nozzle that lets in direct current.
FIG. 3 is a comparison of the microscopic morphology of an aluminum killed steel 10B21 submerged nozzle; wherein, (a) contrast immersion nozzle, (b) the experimental immersion nozzle that lets in direct current.
FIG. 4 is a microscopic comparison of the aluminum killed steel 35K submerged nozzle; wherein, (a) contrast immersion nozzle, (b) the experimental immersion nozzle that lets in direct current.
Detailed Description
A method for applying same-polarity charges to inhibit the inner wall of a submerged nozzle from nodulation comprises the following specific operation methods:
step 1: slotting on the surface of an aluminum-carbon original submerged nozzle, burying a metal wire into the submerged nozzle, and sealing by using high-temperature cement and refractory cotton to prevent the metal wire from being oxidized in the pouring process; the metal wire extends to a far position outside for connecting a direct current power supply; the metal wire is a pure molybdenum wire with the diameter of more than 1 mm.
Step 2: before casting, the submerged nozzle is baked at high temperature for 2 hours, and then the formal casting process is carried out.
And step 3: in the casting process, stable direct current is applied to the submerged nozzle through a direct current power supply, and the current is controlled to be 2-5A according to the content of alumina inclusions in steel; the casting speed is controlled within 2.1m/min, and the casting temperature is 1540-1560 ℃.
And 4, step 4: and after the casting is finished, closing the direct current power supply.
Example 1
The test was carried out by selecting the aluminum killed steel 10B21 as the casting object. The experiment is carried out on a continuous casting machine in an eight-flow casting mode, one flow is selected to carry out direct current application treatment on the submerged nozzle, and the other flow corresponding to the normal casting flow is used as a comparison experiment.
Before casting, grooving on the surface of an original aluminum-carbon submerged nozzle, then embedding a metal molybdenum wire with the diameter of 1.5mm into the submerged nozzle, and sealing the submerged nozzle by using high-temperature cement and refractory cotton to prevent the molybdenum wire from being oxidized in the casting process. And the outer part extends to a far position for connecting a direct current power supply. And after sealing is finished, preheating and baking the water gap at high temperature for 2 hours before casting. And (3) carrying out formal casting after baking is finished, applying stable direct current to the submerged nozzle through a direct current generator in the casting process, wherein the direct current intensity is controlled to be about 5A according to the content of alumina inclusions in steel. The casting speed was 2.0m/min and the casting temperature was 1550 ℃. After the casting is completed (12 furnaces, about 12 hours), the direct current power supply is turned off, and the corresponding lead is removed. Then taking out the water gap and analyzing the effect of controlling the nodulation of the water gap, wherein the results of slag adhering and original size change of the corresponding water gap are shown in the table 1; the accretion on the innermost layer of the nozzle is shown in figure 1.
TABLE 1 comparison of the variation of the slag adhering to the nozzle and the original size/mm
It can be seen from table 1 that, after the protection of the direct current, the nodulation behavior of the wall surface of the nozzle and the nozzle are both protected. The surface slag adhering thickness and the intermediate nodulation layer thickness of 10B21 are respectively reduced by 13% and 48.45%, the total nodulation thickness is reduced by 38.10%, and the unreacted layer and the original layer of the nozzle are improved by 231.12% and 24.02%.
And the statistics of the inclusions in the same field of view before and after the direct current technology is adopted under an OLYMPUS-DSX500 metallographic microscope shows that the inclusions with large sizes are obviously refined and reduced after the direct current treatment. The quantity of large-size inclusions exceeding 10 mu m in the casting blank is reduced by more than 50 percent. Further, the solidification proceeds early on the edge side of the nozzle, and it is extremely difficult to form large-sized inclusions exceeding 10 μm on the edge portion.
Example 2
The test was carried out by selecting an aluminum killed steel SWRCH35K as a casting object. The experiment is carried out on a continuous casting machine in an eight-flow casting mode, one flow is selected to carry out direct current application treatment on the submerged nozzle, and the other flow corresponding to the normal casting flow is used as a comparison experiment.
Before casting, grooving on the surface of an original aluminum-carbon submerged nozzle, then embedding a metal molybdenum wire with the diameter of 1.5mm into the submerged nozzle, and sealing the submerged nozzle by using high-temperature cement and refractory cotton to prevent the molybdenum wire from being oxidized in the casting process. And the outer part extends to a far position for connecting a direct current power supply. And after sealing is finished, preheating and baking the water gap at high temperature for 2 hours before casting. And (3) carrying out formal casting after baking is finished, and applying stable direct current to the submerged nozzle through a direct current generator in the casting process, wherein the direct current intensity is controlled to be about 3A. The casting speed was 2.0m/min and the casting temperature was 1550 ℃. After the casting was completed (10 furnaces, about 10 hours), the dc power was turned off and the corresponding wires were removed. Then taking out the water gap and analyzing the effect of controlling the nodulation of the water gap, wherein the results of slag adhering of the corresponding water gap and the change of the original size are shown in a table 2; the accretion on the innermost layer of the nozzle is shown in figure 2.
TABLE 2 comparison of nozzle slagging and original size change/mm
It can be seen from table 2 that, after the dc current protection, the nodulation behavior of the nozzle wall surface and the nozzle itself are both protected. The surface slag adhering thickness, the middle nodulation layer thickness and the bottom nodulation layer thickness of the nozzle of the SWRCH35K are respectively reduced by 27.66%, 5.51% and 37.77%, the total nodulation thickness of the inner wall of the nozzle is reduced by 12.79%, and the unreacted layer and the original layer of the nozzle are improved by 141.07% and 30.00%.
And the statistics of the inclusions in the same field of view before and after the direct current technology is adopted under an OLYMPUS-DSX500 metallographic microscope shows that the overall number of the inclusions tends to be stable and is greatly reduced after the direct current treatment. The reduction range of the inclusions in the steel reaches 85.33 percent. Further, the solidification proceeds early on the edge side of the nozzle, and it is extremely difficult to form large-sized inclusions exceeding 10 μm on the edge portion.
Claims (4)
1. A method for applying like electric charge to inhibit the inner wall of the submerged nozzle from nodulating is characterized in that a stable forward current is applied to the inner wall of the submerged nozzle, so that inclusion particles which generate transient electric charge due to friction cannot adhere to the inner wall of the submerged nozzle to form adhered slag and nodulation due to the action of repulsion force, and any chemical reaction cannot occur between the inclusion particles and a slag line interlayer of the wall surface of the submerged nozzle and the material of the submerged nozzle, so that the sintering and adhering actions of the inclusions on the inner wall of the submerged nozzle are limited, the nozzle nodulation is further inhibited, the newly generated nodulation on the surface layer of the submerged nozzle is more stable in property, the density is also improved to a certain extent, and the quantity of the inclusions in steel is improved; the method comprises the following specific steps: forming a groove on the surface of an original aluminum-carbon submerged nozzle, putting a metal wire into the groove, and sealing the groove by using high-temperature cement and refractory cotton; the width of the groove is 2-3cm, and the exposed end of the metal wire is connected with a direct current power supply; the current of the direct current power supply is controlled to be between 2 and 5A, the casting speed is controlled to be within 2.1m/min, and the casting temperature is between 1540 and 1560 ℃.
2. The method for suppressing the inner wall accretion of a submerged nozzle according to claim 1, wherein said metal wire is a steel wire, a molybdenum wire or a tungsten wire, having a certain high temperature resistance.
3. The method of applying a uniform electrical charge to suppress the formation of nodules on the inner wall of a submerged nozzle as claimed in claim 2, wherein said metal wire is a pure molybdenum wire having a diameter of 0.8-1.5 mm.
4. The method of claim 1, wherein the submerged nozzle is baked at a high temperature for 2 hours before casting.
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| CN112658241B (en) * | 2020-12-10 | 2022-11-08 | 东北大学 | Method for preventing decarburization and reaction behavior of rare earth steel nozzle by applying interface electric field |
| CN115717210B (en) * | 2022-11-08 | 2023-11-24 | 北京科技大学 | Method for inhibiting titanium-containing steel-bonded fish phenomenon by using pulse current |
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