Method for effectively removing inclusions in steel

Abstract

The invention relates to the technical field of metallurgical continuous casting, in particular to a method for effectively removing inclusions in steel, which comprises the following steps of: before molten steel is cast, inserting a plurality of electrified rod bodies into molten steel in a tundish, and arranging the electrified rod bodies on a circumference taking a stopper rod as a circle center or a circumference taking a long nozzle as a circle center; or arranged between the long nozzle and the stopper rod in a whole row in the direction perpendicular to the length direction of the tundish; the electrified rod bodies are parallel to the stopper rod; the number of the charged rod bodies is not less than 4 and is an even number; the stopper rod or the long nozzle or the stopper rod and the long nozzle are connected with the position with the potential being zero through a conductive material; after the liquid level of the tundish is stable, direct current is supplied to the electrified rod body, and positive electricity and negative electricity are alternately arranged on the electrified rod body. According to the method, a plurality of electrified rod bodies are arranged in the tundish, and inclusions in steel are enriched on the electrified rod bodies, so that the purposes of purifying molten steel and preventing water gap flocculation are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical continuous casting, and particularly to a method for effectively removing inclusions in steel. Background Art

[0002] With the continuous improvement of people's requirements for steel quality, at present, almost all steel grades require secondary refining. In order to control the free oxygen content in steel, a large amount of deoxidizing alloy is generally added during the refining process for deep deoxidation, and a large amount of oxides are correspondingly generated. Among these oxides, most can be removed by floating up into the slag from the molten steel during the steel water calming, but a part of them will still remain in the molten steel in the form of oxide inclusions. During the continuous casting process, when the molten steel flows from the ladle through the long nozzle into the tundish or from the tundish through the submerged nozzle into the mold, these oxide inclusions will adhere and accumulate on the inner surface of the nozzle, thereby blocking the continuous casting nozzle. In particular, the alumina inclusions formed in aluminum-deoxidized steel are more likely to block the nozzle. The nozzle blockage will cause the problem of turbulent flow of the continuous casting nozzle, which has an adverse impact on both the continuity of continuous casting and the cleanliness of steel.

[0003] In order to reduce the blockage of the continuous casting nozzle during the continuous casting process, a variety of methods have been studied and developed at present, such as: using a composite nozzle, using a new material, using a wire feeding technology, etc. In addition, there are also technologies and methods such as improving the nozzle structure, strictly controlling the continuous casting operation process, and using a nozzle thermal insulation sleeve to reasonably control the superheat degree. Although many continuous casting nozzle anti-blocking technologies have been developed, in the actual use process, the blockage of the continuous casting nozzle still occurs frequently.

[0004] The utility model patent with the publication number of CN 2496580 Y discloses a tundish adsorber, which is composed of several columns. The columns are arranged in a staggered manner, and the spacing between them is 10-20 mm, and the diameter is 30-70 mm. The adsorber has a simple structure and is easy to install. The active surface area in contact with the molten steel is large, and the ability to adsorb inclusions is stronger. It can reduce the content of oxides in steel by 30%-55%, and reduce the large particle inclusions in steel by more than 50%. However, this adsorber is not charged and has no remote adsorption ability for inclusions. It only relies on the natural adhesion of inclusions on the adsorber when the molten steel flows through the adsorber to achieve the purpose of adsorbing and removing inclusions. Therefore, the effect of adsorbing and removing inclusions is general.

[0005] At present, it is generally believed that the non-metallic inclusions in molten steel are electrically neutral, that is, the inclusions in molten steel do not carry any charge themselves. However, during the continuous casting process, due to the flow of molten steel, the inclusions in steel will be charged due to the friction between the molten steel and them. Therefore, the charge characteristics of inclusions can be utilized to study the removal path of inclusions in steel. Summary of the Invention

[0006] To overcome the deficiencies of the prior art, the technical problem solved by the present invention is to provide a method for effectively removing inclusions in steel. This method arranges several charged rod bodies in the tundish. By utilizing the property that inclusions in the molten steel will be charged due to the friction between the molten steel and them during the flow of the molten steel, the inclusions in the steel are enriched on the charged rod bodies, so as to achieve the purpose of purifying the molten steel and preventing nozzle flocculation.

[0007] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0008] A method for effectively removing inclusions in steel, comprising the following steps:

[0009] Before the molten steel is poured, several charged rod bodies are inserted into the molten steel in the tundish and arranged on a circumference centered on the stopper rod, or arranged on a circumference centered on the long nozzle, or arranged in a whole row perpendicular to the length direction of the tundish between the long nozzle and the stopper rod; the charged rod bodies are all parallel to the stopper rod; the number of charged rod bodies ≥ 4;

[0010] Connect the stopper rod or the long nozzle or both to a part with zero potential using a conductive material; after the tundish liquid level is stable, pass direct current through the charged rod bodies, and positive and negative charges are alternately arranged on the charged rod bodies.

[0011] The energization voltage is 20 - 50V, and the current is 1 - 10A.

[0012] The diameter range of the circumference is all 450 - 800mm.

[0013] When arranged in a whole row, the distance L between the charged rod bodies: 100mm ≤ L ≤ 300mm.

[0014] The material of the charged rod body is Al 2 O 3 -C, Al 2 O 3 -ZrO 2 -C, ZrO 2 -C or Al 2 O 3 -SiC-C.

[0015] The charged rod body is a cylinder, with a diameter of 150 - 500mm and a length ≥ 2000mm.

[0016] The depth of the charged rod body inserted into the molten steel ≥ 500mm.

[0017] The number of charged rod bodies is an even number.

[0018] The several charged rod bodies are inserted into the molten steel in the tundish and are evenly arranged on a circumference centered on the stopper rod.

[0019] The plurality of charged rod bodies are inserted into the molten steel in the tundish and are uniformly arranged on a circumference centered on the long nozzle.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1) Since in the process of molten steel flowing, inclusions in the steel will be charged due to the friction between the molten steel and them, some are positively charged and some are negatively charged. According to the principle that opposite charges attract each other, after the charged rod bodies are electrified, the inclusions in the steel will move towards the charged rod bodies, and then gradually accumulate on the charged rod bodies, achieving the purpose of removing inclusions and preventing nozzle clogging.

[0022] 2) Arranging the charged rod bodies in the circumferential direction centered on the stopper rod or the long nozzle is beneficial to adsorbing inclusions in multiple directions, uniformly removing inclusions in the molten steel, and avoiding clogging of the upper nozzle, lower nozzle and submerged nozzle in the tundish; arranging the charged rod bodies in a whole row perpendicular to the length direction of the tundish between the long nozzle and the stopper rod is beneficial to the molten steel passing through the charged rod bodies uniformly during casting to achieve comprehensive adsorption of inclusions and reduce the inclusion content in the molten steel.

[0023] 3) Connecting the stopper rod or the long nozzle or both to a part with zero potential to keep the stopper rod or the long nozzle or both at zero potential, avoiding the stopper rod or the long nozzle or both being charged, eliminating the migration and accumulation of inclusions in the steel towards the surface and bottom of the stopper rod or the long nozzle or both, and preventing the influence on the flow control of the stopper rod and the use effect of the long nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0025] Figure 1 It is a schematic structural principle diagram of Embodiment 1 of the present invention.

[0026] Figure 2 It is a top view of the schematic structural principle of Embodiment 1 of the present invention.

[0027] Figure 3 It is a schematic structural principle diagram of Embodiment 2 of the present invention.

[0028] Figure 4 It is a top view of the schematic structural principle of Embodiment 2 of the present invention.

[0029] Figure 5 It is a schematic structural principle diagram of Embodiment 3 of the present invention.

[0030] Figure 6 It is a top view of the schematic structural principle of Embodiment 3 of the present invention.

[0031] Description of the reference numerals:

[0032] In the figure: 1 - tundish; 2 - molten steel; 3 - stopper rod; 4 - charged rod body; 5 - upper nozzle of the tundish; 6 - lower nozzle of the tundish; 7 - submerged nozzle; 8 - long nozzle Specific embodiments

[0033] The following further describes the specific embodiments of the present invention with reference to the accompanying drawings:

[0034] Example 1

[0035] The present invention provides a method for effectively removing inclusions in steel, comprising the following steps:

[0036] Before the pouring of molten steel, several charged rod bodies are inserted into the molten steel 2 in the tundish 1 and are evenly arranged on a circumference with the stopper rod 3 as the center, as Figure 1 shown. The charged rod bodies 4 are all parallel to the stopper rod 3 and perpendicular to the liquid surface of the molten steel 2. The number of the charged rod bodies 4 is 4, and the included angle between the connecting lines of two adjacent charged rod bodies 4 and the center of the circle is 90 degrees. The stopper rod 3 is connected to a part with zero potential using a conductive material. After the liquid level of the tundish 1 is stable, direct current is applied to the charged rod bodies 4, and positive and negative charges are alternately arranged on the charged rod bodies 4, as Figure 2 shown. The applied voltage is 20V and the current is 3A.

[0037] The circumferential diameter range is 450 mm. The material of the charged rod body 4 is Al 2 O 3 -ZrO 2 -C. The charged rod body 4 is a cylinder with a diameter of 200 mm and a length of 2000 mm. The depth of the charged rod body 4 inserted into the molten steel is 500 mm.

[0038] After continuous casting, samples are taken from the billet and the inclusions are analyzed. The results are as follows:

[0039]

[0040]

[0041] The nozzle flocculation conditions of the upper nozzle 5 of the tundish, the lower nozzle 6 of the tundish, and the submerged nozzle 7 are as follows:

[0042]

[0043] Example 2

[0044] Before the pouring of molten steel, several charged rod bodies are inserted into the molten steel 2 in the tundish 1 and are arranged in a whole row perpendicular to the length direction of the tundish between the long nozzle 8 and the stopper rod 3, as Figure 3 and 4As shown. The charged rod bodies 4 are all parallel to the stopper rod 3 and perpendicular to the molten steel 2 liquid surface. The number of charged rod bodies 4 is 6, and the distance L between two adjacent charged rod bodies 4 is 150 mm. Connect the stopper rod 3 to the part with zero potential using a conductive material. After the tundish 1 liquid surface is stable, pass direct current through the charged rod bodies 4, and the positive and negative charges are alternately arranged on the charged rod bodies 4. The energization voltage is 30 V and the current is 5 A.

[0045] The material of the charged rod body 4 is Al 2 O 3 -SiC-C. The charged rod body 4 is a cylinder, with a diameter of 150 mm and a length of 2500 mm. The depth of the charged rod body 4 inserted into the molten steel is 600 mm.

[0046] After continuous casting is completed, samples are taken from the billet and the inclusions are analyzed. The results are as follows:

[0047]

[0048] The nozzle flocculation conditions of the tundish upper nozzle 5, tundish lower nozzle 6, and submerged entry nozzle 7 are as follows:

[0049]

[0050] Example 3

[0051] Before pouring the molten steel, several charged rod bodies are inserted into the molten steel 2 in the tundish 1 and are evenly arranged on the circumference with the long nozzle 8 as the center, as Figure 5 and 6 shown. The charged rod bodies 4 are all parallel to the stopper rod 3 and perpendicular to the molten steel 2 liquid surface. The number of charged rod bodies 4 is 8, and the included angle between the connecting lines of two adjacent charged rod bodies 4 and the center of the circle is 45 degrees. Connect both the stopper rod 3 and the long nozzle 8 to the part with zero potential using a conductive material. After the tundish 1 liquid surface is stable, pass direct current through the charged rod bodies 4, and the positive and negative charges are alternately arranged on the charged rod bodies 4. The energization voltage is 50 V and the current is 10 A.

[0052] The circumferential diameter range is 800 mm. The material of the charged rod body 4 is Al 2 O 3 -C. The charged rod body 4 is a cylinder, with a diameter of 250 mm and a length of 2200 mm. The depth of the charged rod body 4 inserted into the molten steel is 700 mm.

[0053] After continuous casting is completed, samples are taken from the billet and the inclusions are analyzed. The results are as follows:

[0054]

[0055] The nozzle flocculation conditions of the tundish upper nozzle 5, tundish lower nozzle 6, and submerged entry nozzle 7 are as follows:

[0056]

[0057] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention. In addition, it should be noted that in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. In addition, any combination can be made between the various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for effectively removing inclusions in steel, characterized in that: The steps include: Before the molten steel is poured, several charged rods are inserted into the molten steel in the tundish and arranged on a circle with the stopper rod as the center, or arranged on a circle with the long shroud as the center, or arranged in a row perpendicular to the length direction of the tundish between the long shroud and the stopper rod; the charged rods are parallel to the stopper rod; the number of charged rods is ≥4; Use conductive materials to connect the stopper rod or the long water nozzle or both to a position with zero potential; after the liquid level in the tundish is stable, direct current is passed through the charged rod body, and positive and negative electricity are alternately arranged on the charged rod body.

2. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The power-on voltage is 20-50V, and the current is 1-10A.

3. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The circumferential diameter ranges from 450 to 800 mm.

4. A method for effectively removing inclusions in steel according to claim 1, characterized in that: When the charged rods are arranged in a row, the distance L between them is 100 mm ≤ L ≤ 300 mm.

5. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The charged rod is made of one of Al2O3-C, Al2O3-ZrO2-C, ZrO2-C or Al2O3-SiC-C.

6. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The charged rod is a cylinder with a diameter of 150-500 mm and a length of ≥2000 mm.

7. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The charged rod is inserted into the molten steel to a depth of ≥500mm.

8. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The number of the charged rods is an even number.

9. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The several charged rods are inserted into the molten steel in the tundish and are evenly arranged on a circle with the stopper rod as the center.

10. A method for effectively removing inclusions in steel according to claim 1, characterized in that: The several charged rods are inserted into the molten steel in the tundish and are evenly arranged on a circle with the long shroud as the center.

Images