Method for removing inclusions and entrapped slag in steel in crystallizer

Abstract

The invention relates to a method for removing inclusions and entrapped slag in steel in a crystallizer. The method comprises the steps that S1, electromagnetic devices are arranged on the outer sides of copper plates on the front side and the rear side of the crystallizer; s2, after continuous casting is started and the state of the molten steel in the crystallizer is stable, an electromagnetic device is started to treat the molten steel in the crystallizer until casting is finished; and S3, after the casting blank is taken out of the crystallizer, the surfaces of the front side and the rear side of the casting blank are subjected to online scaling treatment or scaling treatment is conducted after the casting blank is taken out of the crystallizer. The electromagnetic device is arranged on the outer side of the wide face of the crystallizer, in the continuous casting process of molten steel, inclusions and involved casting powder are charged due to friction in the flowing process of the molten steel, and charged particles are subjected to the action characteristic of Lorentz force when moving in a magnetic field; and after the casting blank is discharged from the crystallizer, the narrow surface of the casting blank is subjected to scaling treatment, and finally, the pure high-quality casting blank is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of steel continuous casting, and in particular to a method for removing inclusions and slag rolls in steel in a crystallizer. Background Art

[0002] Removing inclusions from steel is a constant pursuit and endeavor for metallurgists. While it's impossible to completely eliminate inclusions, it's only possible to minimize them. Inclusions in steel are detrimental and a key factor limiting the production of high-quality steel. They represent a bottleneck in the production of deep-drawing and ultra-deep-drawing steels, which have particularly stringent inclusion requirements. Furthermore, during the continuous casting process, inclusions can easily accumulate and adhere to the inner wall of the nozzle, causing blockage, disrupting continuous casting, and in severe cases, interrupting casting, leading to serious production accidents.

[0003] Furthermore, mold slag entrainment in the molten steel during the continuous casting process, resulting in slag entrainment, is a common problem encountered in continuous casting production. This often results in surface quality defects in the finished steel, severely impacting both user experience and the company's image. Mold slag plays a vital role in the continuous casting process, crucial for improving product quality and production efficiency, and is a crucial guarantee for producing high-quality continuous cast ingots. Mold slag plays a crucial role in continuous casting, providing insulation, preventing oxidation of the molten steel, absorbing inclusions, controlling heat transfer between the mold and the ingot, and providing lubrication. Therefore, the performance of the mold slag is crucial to its effectiveness. Poor mold slag performance or unstable production control, resulting in an unstable mold level (large level fluctuations), can cause liquid mold slag to be entrained in the molten steel. If the entrained mold slag does not have time to float up or is captured by the solidifying shell, slag entrainment can result, impacting the surface and internal quality of the finished steel and causing significant quality defects.

[0004] However, inclusions and entangled slag in steel are usually unavoidable, especially inclusions in steel, which can only be reduced as much as possible but not completely removed. Therefore, how to remove or reduce inclusions and entangled protective slag in steel is an important issue that needs to be solved urgently. This is crucial to ensure the smooth progress of steel continuous casting production and product quality.

[0005] At present, there are many methods for removing inclusions in steel, but they are all based on the treatment methods before the continuous casting process, such as the LF refining process inclusion removal method, the tundish metallurgical method for removing inclusions, the ladle bottom blowing stirring and calming treatment method for removing inclusions, etc. The method based on removing inclusions in the crystallizer of the continuous casting process mainly relies on the natural floating of inclusions and their removal by adsorption by the protective slag. There is currently no better solution for removing the protective slag entangled in the crystallizer, and it can only rely on its natural floating and removal by adsorption. Removing inclusions and entangled protective slag in steel in the crystallizer is the last process in steel production where measures can be taken. The treatment method and effect of this process are crucial and are an important link in ensuring the production of high-quality continuous casting billets. Therefore, it is of great significance to research and develop a solution that can effectively remove inclusions and entangled protective slag in steel in the crystallizer. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for removing inclusions and slag coils in steel in a crystallizer. By arranging an electromagnet or a permanent magnet on the outside of the wide surface of the crystallizer, during the continuous casting of molten steel, the inclusions and the entangled protective slag are charged due to friction during the flow of molten steel. When the charged particles move in the magnetic field, they are affected by the Lorentz force, which promotes the inclusions and slag coils to gather on the narrow surface of the crystallizer or the liquid protective slag above. The narrow surface of the ingot is then peeled after the ingot leaves the crystallizer, and finally a pure, high-quality ingot is obtained.

[0007] The technical solution adopted in the present invention is as follows: The present invention proposes a method for removing inclusions and slag entanglement in steel in a crystallizer, which specifically comprises the following steps: S1. An electromagnetic device is installed on the outer sides of the copper plates on both sides of the crystallizer; S2. After continuous casting starts and the molten steel in the mold stabilizes, the electromagnetic device is turned on to treat the molten steel in the mold until the casting is completed; S3. After the billet leaves the crystallizer, the front and rear surfaces of the billet are peeled online or after the billet is off the line.

[0008] Furthermore, when the crystallizer is a slab crystallizer, the electromagnetic device is arranged on the outside of the two wide copper plates of the slab crystallizer; when the crystallizer is a square billet crystallizer, the electromagnetic device is arranged on the outside of the copper plates on both sides of the square billet crystallizer parallel to the immersion water outlet.

[0009] Furthermore, the electromagnetic device is an electromagnet or a permanent magnet.

[0010] Furthermore, the width of the electromagnetic device is greater than or equal to the width of the copper plate of the crystallizer; the length of the electromagnetic device is 1 / 3 to 2 / 3 of the length of the copper plate; and the upper edge of the electromagnetic device is flush with the upper edge of the crystallizer.

[0011] Furthermore, the electromagnet is powered by direct current, the electromagnets on both sides of the crystallizer are N poles and S poles respectively, and the electrical properties and magnetic poles remain unchanged during the entire casting process.

[0012] Furthermore, the current in the electromagnet is 100-500A.

[0013] Furthermore, the magnetic field strength of the permanent magnet is 0.5~1T.

[0014] Furthermore, the peeling amount of the peeling process is 2~6mm.

[0015] Furthermore, the peeling treatment method is flame cleaning peeling or grinding peeling.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention effectively removes inclusions and entrapped mold slag from steel during the final step of continuous steel casting, effectively reducing the risk of inclusions and entrapped slag entering the continuous cast strand as the molten steel cools and solidifies, leading to excessive inclusions and entrapped slag defects. This method maximizes the removal of inclusions and entrapped mold slag from the steel, encouraging them to gather in the newly formed solidified strand shell or float to the mold slag layer. This achieves pollution-free removal of inclusions and entrapped slag from the steel without adding any raw materials. Furthermore, this method is simple to operate and low-cost, making it suitable for widespread application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the main structure of the relative positions of the slab crystallizer and the electromagnetic device; Figure 2 It is a side view structural diagram of the relative positions of the slab crystallizer and the electromagnetic device; Figure 3 It is a schematic diagram of the main structure of the relative positions of the square billet crystallizer and the electromagnetic device. DETAILED DESCRIPTION

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] See attached Figures 1-3 The present invention proposes a method for removing inclusions and slag entanglements in steel in a crystallizer, which specifically comprises the following steps: S1. An electromagnetic device is installed on the outer sides of the copper plates on both sides of the crystallizer; Wherein, when the crystallizer is a slab crystallizer, the electromagnetic device is arranged on the outside of the two wide copper plates of the slab crystallizer; when the crystallizer is a billet crystallizer, the electromagnetic device is arranged on the outside of the copper plates on both sides of the billet crystallizer parallel to the outlet of the immersion nozzle; The electromagnetic device is an electromagnet or a permanent magnet, and the width of the electromagnetic device is greater than or equal to the width of the wide copper plate of the slab crystallizer or the width of the copper plates on both sides (inner and outer arc sides) of the billet crystallizer parallel to the immersion nozzle outlet; 1 / 3 of the copper plate length is less than or equal to 2 / 3 of the copper plate length; the upper edge of the electromagnetic device is flush with the upper edge of the crystallizer; The width of the electromagnetic device is ≥ the width of the wide copper plate of the slab crystallizer or the width of the copper plates on both sides of the outlet of the submerged nozzle (on both sides of the inner and outer arcs) of the billet crystallizer. The purpose of this design is to ensure that magnetic flux lines pass through the entire width of the crystallizer; the length of the electromagnetic device is ≥ 1 / 3 of the copper plate length. The purpose of designing the electromagnetic device is to ensure that all magnetic flux lines pass through the molten steel discharged from the submerged nozzle outlet, and the length of the electromagnetic device is ≤ 2 / 3 of the copper plate length. The purpose of designing the electromagnetic device is to ensure that no magnetic flux lines pass through the molten steel in the crystallizer below the lower 1 / 3 of the length of the crystallizer, thereby preventing inclusions or slag coils in the molten steel below the lower 1 / 3 of the crystallizer from being moved to the narrow shell of the slab or the shells on both sides of the vertical submerged nozzle outlet (on both sides of the inner and outer arcs) of the billet due to the Lorentz force and adhering to them. The solidified shell here is thicker, and if inclusions or slag coils adhere to it, the amount of skin removed by subsequent skinning is too large, resulting in high iron loss and high processing cost.

[0020] S2. After continuous casting starts and the molten steel in the mold stabilizes, the electromagnetic device is turned on to treat the molten steel in the mold until the casting is completed; When the electromagnetic device adopts an electromagnet, the electromagnet is energized in the form of direct current, the electromagnets on both sides are respectively N-pole and S-pole, and the electrical properties and magnetic poles remain unchanged during the entire casting process; The current in the electromagnet is 100~500A; the purpose of setting the current is to ensure that the electromagnet has a high magnetic induction intensity, so that the inclusions or slag in the steel have sufficient Lorentz force, which prompts the inclusions or slag to gather towards the solidified shell or float to the protective slag liquid slag layer for removal.

[0021] When the electromagnetic device uses a permanent magnet, the magnetic field strength of the permanent magnet is 0.5~1T.

[0022] S3. After the billet leaves the crystallizer, the narrow side surface of the slab billet or the billet surface on both sides of the vertical submerged nozzle outlet of the square billet is peeled online or peeled after the billet is off the line; the peeling method is flame cleaning peeling or grinding peeling, and the peeling amount is 2~6mm.

[0023] By peeling, the surface of the ingot with a large amount of inclusions or slag can be removed, thereby ultimately removing the inclusions or slag in the steel.

[0024] The present invention will be further described below by means of specific embodiments: Example 1: A method for removing inclusions and slag from steel in a crystallizer, the specific implementation process is as follows: In slab continuous casting production, the produced steel type is IF steel, the ingot size is 230*1650mm, the crystallizer width is 1670mm and the length is 900mm.

[0025] S1. An electromagnet is installed outside the wide copper plate of the crystallizer; The width of the electromagnet is 1680mm, the length of the electromagnet is 450mm, and the upper edge of the electromagnet is flush with the upper edge of the crystallizer; S2. After the molten steel in the continuous casting mold is stable, the electromagnet system is turned on to process the molten steel in the mold until the casting is completed; The electromagnet system is powered by direct current with a current of I=100A. The electromagnet on the outer arc side is N-pole, and the electromagnet on the inner arc side is S-pole. The electrical and magnetic properties remain unchanged during the entire casting process. S3. After the slab leaves the crystallizer, the narrow side of the slab is subjected to online peeling treatment. The peeling treatment method adopts flame cleaning, and the peeling amount is 2mm.

[0026] After continuous casting, samples were taken from the ingot at 1 / 4 of its width and 1 / 4 of its thickness. The samples were analyzed for inclusions using an optical microscope. The results are as follows:

[0027] No slag defects or large-particle inclusions were found in the steel, and the inclusion ratings were all below level 0.5, indicating that the steel had a high degree of purity.

[0028] Example 2: A method for removing inclusions and slag from steel in a crystallizer, the specific implementation process is as follows: In the continuous casting production of square billets, the steel type produced is heavy rail steel, the billet size is 280*380mm, the crystallizer width is 400mm and the length is 850mm.

[0029] S1. Electromagnets are installed on the outer sides of the copper plates on both sides of the crystallizer parallel to the outlet of the immersion nozzle (both sides of the inner and outer arcs); The width of the electromagnet is 420mm, the length of the electromagnet is 560mm, and the upper edge of the electromagnet is flush with the upper edge of the crystallizer; S2. After the molten steel in the continuous casting mold is stable, the electromagnet system is turned on to process the molten steel in the mold until the casting is completed; The electromagnet system is powered by direct current with a current of I=500A. The electromagnet on the outer arc side is N-pole, and the electromagnet on the inner arc side is S-pole. The electrical and magnetic properties remain unchanged during the entire casting process. S3. After the slab leaves the crystallizer, the narrow side of the slab is subjected to online peeling treatment. The peeling treatment method adopts flame cleaning, and the peeling amount is 6.0mm.

[0030] After continuous casting, samples were taken from the ingot at 1 / 4 of its width and 1 / 4 of its thickness. The samples were analyzed for inclusions using an optical microscope. The results are as follows:

[0031] No slag defects or large-particle inclusions were found in the steel, and the inclusion ratings were all below level 0.5, indicating that the steel had a high degree of purity.

[0032] Example 3: A method for removing inclusions and slag from steel in a crystallizer, the specific implementation process is as follows: In slab continuous casting production, the steel type produced is ship plate steel, the slab size is 200*1950mm, the crystallizer width is 1970mm and the length is 900mm.

[0033] S1. A permanent magnet is placed outside the wide copper plate of the crystallizer; The width of the permanent magnet is 1970 mm, the length of the permanent magnet is 600 mm, and the upper edge of the permanent magnet is flush with the upper edge of the crystallizer; S2. After the molten steel in the continuous casting mold is stable, the permanent magnet system is turned on to treat the molten steel in the mold until the casting is completed; The magnetic induction intensity of the permanent magnet in the permanent magnet system is 1T, the permanent magnet on the outer arc side is the N pole, and the permanent magnet on the inner arc side is the S pole, and the magnetism and magnetic pole remain unchanged during the entire casting process; S3. After the slab leaves the crystallizer, the narrow side of the slab is peeled offline. The peeling treatment method is grinding and cleaning, and the peeling amount is 4.0mm.

[0034] After continuous casting, samples were taken from the ingot at 1 / 4 of its width and 1 / 4 of its thickness. The samples were analyzed for inclusions using an optical microscope. The results are as follows:

[0035] No slag defects or large-particle inclusions were found in the steel, and the inclusion ratings were all below level 0.5, indicating that the steel had a high degree of purity.

[0036] Matters not described in detail in this invention are all known technologies.

[0037] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for removing inclusions and slag from steel in a crystallizer, characterized in that: The method comprises the following steps: S1. An electromagnetic device is installed on the outer sides of the copper plates on both sides of the crystallizer; S2. After continuous casting starts and the molten steel in the mold stabilizes, the electromagnetic device is turned on to treat the molten steel in the mold until the casting is completed; S3. After the billet leaves the crystallizer, the front and rear surfaces of the billet are subjected to online peeling treatment or the billet is peeled off after it leaves the production line; When the crystallizer is a slab crystallizer, the electromagnetic device is arranged on the outside of the two wide copper plates of the slab crystallizer; when the crystallizer is a square billet crystallizer, the electromagnetic device is arranged on the outside of the copper plates on both sides of the square billet crystallizer parallel to the immersion water outlet.

2. The method for removing inclusions and slag entanglement in steel in a crystallizer according to claim 1, characterized in that: The electromagnetic device is an electromagnet or a permanent magnet.

3. A method for removing inclusions and slag entanglement in steel in a crystallizer according to claim 1 or 2, characterized in that: The width of the electromagnetic device is greater than or equal to the width of the copper plate of the crystallizer; the length of the electromagnetic device is 1 / 3 to 2 / 3 of the length of the copper plate; and the upper edge of the electromagnetic device is flush with the upper edge of the crystallizer.

4. The method for removing inclusions and slag entanglement in steel in a crystallizer according to claim 2, wherein: The electromagnet is powered by direct current, and the electromagnets on both sides of the mold are N-pole and S-pole respectively, and the electrical properties and magnetic poles remain unchanged during the entire casting process.

5. The method for removing inclusions and slag entanglement in steel in a crystallizer according to claim 4, characterized in that: The current in the electromagnet is 100-500A.

6. The method for removing inclusions and slag entanglement in steel in a crystallizer according to claim 2, wherein: The magnetic field strength of the permanent magnet is 0.5-1T.

7. The method for removing inclusions and slag entanglement in steel in a crystallizer according to claim 1, wherein: The peeling amount of the peeling process is 2 to 6 mm.

8. The method for removing inclusions and slag entanglement in steel in a crystallizer according to claim 1, wherein: The peeling treatment method is flame cleaning peeling or grinding peeling.

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