A method for removing inclusions and skull from steel in a crystallizer

Abstract

The present application relates to a kind of methods for removing inclusions and slag entrapment in steel in crystallizer, comprising S1, the outside of copper plate of the front and rear sides of crystallizer is provided with electromagnetic device;S2, after continuous casting and the molten steel state in crystallizer is stable, electromagnetic device is opened to the molten steel in crystallizer is treated, until pouring is finished;S3, after the cast blank is out of crystallizer, the surface of the front and rear sides of cast blank is treated or the cast blank is taken off line after skinning treatment is carried out.The present application is by the outside of the wide face of crystallizer is provided with electromagnetic device, in the continuous casting process of molten steel, using inclusion and the protective slag entrapment in molten steel flows in the process of flow due to friction and has electric charge, when charged particle moves in magnetic field, will receive the action characteristics of Lorentz force, promote inclusion and slag entrapment to the narrow face of crystallizer or the liquid protective slag on top gathers, again through the cast blank is out of crystallizer, the narrow face of cast blank is treated, finally obtains the cast blank of high quality of purity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of continuous casting of steel, and particularly relates to a method for removing inclusions and slag entrapment in a crystallizer. BACKGROUND

[0002] It is an eternal work and pursuit of metallurgical workers to remove inclusions in steel, but the inclusions in steel cannot be completely removed and can only be reduced as much as possible. The inclusions in steel have a hundred harms and no benefits, and are a key factor limiting the production of high-quality steel and a bottleneck for the production of deep-drawing steel and ultra-deep-drawing steel and other steel grades with particularly strict requirements for inclusions. In addition, the inclusions in steel are easily adsorbed on the inner wall of the nozzle during continuous casting of molten steel, causing nozzle clogging, affecting the smooth progress of continuous casting production, and even causing a serious production accident.

[0003] In addition, in the continuous casting process, the protective slag is entrapped in the molten steel to cause the slag entrapment defect of the casting blank, which is also a common problem in continuous casting production, and usually causes surface quality defects of the finished plate, seriously affecting the use of users and the image of enterprises. The protective slag plays an important role in the continuous casting production of steel and is crucial to improving product quality and production efficiency, and is an important guarantee for the production of high-quality continuous casting blanks. The protective slag plays an important role in heat insulation, oxidation prevention, inclusion absorption, heat conduction control between the crystallizer and the casting blank, and lubrication in continuous casting, and therefore the performance of the protective slag is crucial to the effect of its use. If the performance of the protective slag is poor or the production control is unstable, the liquid level of the crystallizer is unstable (the liquid level fluctuates greatly), and the liquid protective slag is entrapped in the molten steel, and if the entrapped protective slag cannot float up or is captured by the solidified shell, the slag entrapment defect will be caused, affecting the surface quality and internal quality of the steel product, and causing large quality defects of the steel product.

[0004] However, the inclusions in steel and the slag entrapment are usually unavoidable, especially the inclusions in steel, which can only be reduced as much as possible but cannot be completely removed, and therefore how to remove or reduce the inclusions in steel and the entrapped protective slag is an important problem to be solved at present, which is crucial to ensuring the smooth progress of the continuous casting production of steel and the product quality.

[0005] At present, there are many methods for removing inclusions in steel, but they are all based on the treatment method before the continuous casting process, such as the method for removing inclusions in LF refining process, the method for removing inclusions in tundish metallurgy, the method for removing inclusions by ladle bottom stirring and static treatment, etc. The method for removing inclusions in the crystallizer mainly relies on the natural floating of inclusions and the adsorption removal by the protective slag. At present, there is no good solution for the removal of the protective slag involved in the crystallizer, and it can only rely on the natural floating and adsorption removal. The removal of inclusions in steel and the protective slag involved in the crystallizer is the last process that can be taken in steel production, and the treatment method and effect of this process are crucial, which is an important link to ensure the production of high-quality continuous casting billets. Therefore, it is of great significance to research and develop a scheme for effectively removing inclusions in steel and the protective slag involved in the crystallizer. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a method for removing inclusions in steel and slag in a crystallizer, by arranging electromagnets or permanent magnets outside the wide faces of the crystallizer. During the continuous casting process of molten steel, the inclusions and the protective slag involved are charged due to friction during the flow in the molten steel. When the charged particles move in the magnetic field, they will be affected by the Lorentz force, which promotes the aggregation of inclusions and slag involved to the narrow face or the upper liquid protective slag of the crystallizer. After the casting billet is discharged from the crystallizer, the skin of the casting billet is treated, and finally the pure high-quality casting billet is obtained.

[0007] The technical scheme adopted by the present application is as follows:

[0008] The method for removing inclusions in steel and slag in a crystallizer proposed by the present application specifically comprises the following steps:

[0009] S1, electromagnet devices are arranged outside the copper plates on both sides of the crystallizer;

[0010] S2, after the continuous casting is started and the state of the molten steel in the crystallizer is stable, the electromagnet devices are turned on to treat the molten steel in the crystallizer until the casting is finished;

[0011] S3, after the casting billet is discharged from the crystallizer, the surface of the casting billet on both sides is treated online or after the casting billet is discharged.

[0012] Further, when the crystallizer is a slab crystallizer, the electromagnet devices are arranged outside the copper plates on both wide faces of the slab crystallizer; when the crystallizer is a square billet crystallizer, the electromagnet devices are arranged outside the copper plates on both sides of the outlet of the submerged entry nozzle parallel to the crystallizer.

[0013] Further, the electromagnet devices are electromagnets or permanent magnets.

[0014] Further, 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 / 3-2 / 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.

[0015] Further, the electromagnetic device is powered by direct current, the electromagnetic devices on the two sides of the crystallizer are N-pole and S-pole respectively, and the electrical property and magnetic pole remain unchanged during the entire casting process.

[0016] Further, the current in the electromagnetic device is 100-500 A.

[0017] Further, the magnetic induction intensity of the permanent magnet is 0.5-1 T.

[0018] Further, the amount of skinning in the skinning treatment is 2-6 mm.

[0019] Further, the skinning treatment is flame cleaning skinning or grinding skinning.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application can effectively remove inclusions and protective slag entrained in molten steel in the last process of continuous casting of molten steel, effectively reduce the occurrence of defects such as excessive inclusions and slag entrapment in the continuous casting billet caused by the continuous casting and solidification of inclusions and slag entrained in molten steel. The method can maximize the removal of inclusions and protective slag entrained in molten steel, promote the aggregation or floating of inclusions and protective slag entrained in molten steel to the newly formed solid shell, and realize the pollution-free removal of inclusions and slag in molten steel without adding any raw materials to the molten steel. At the same time, the method is simple in operation and low in cost, and is therefore beneficial to popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 It is a front view structural schematic diagram of the relative position of the slab crystallizer and the electromagnetic device.

[0023] Fig. 2 It is a side view structural schematic diagram of the relative position of the slab crystallizer and the electromagnetic device.

[0024] Fig. 3 It is a front view structural schematic diagram of the relative position of the bloom crystallizer and the electromagnetic device. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0026] Referring to the drawings Figs. 1-3 The method for removing inclusions and slag inclusions in a crystallizer, specifically comprises the following steps:

[0027] S1, setting electromagnetic devices on the outer side of the copper plate on both sides of the crystallizer;

[0028] When the crystallizer is a slab crystallizer, the electromagnetic devices are arranged on the outer side of the wide face copper plate of the slab crystallizer; when the crystallizer is a square billet crystallizer, the electromagnetic devices are arranged on the outer side of the copper plate parallel to the two sides of the outlet of the submerged nozzle of the square billet crystallizer;

[0029] 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 face copper plate of the slab crystallizer or the width of the copper plate parallel to the two sides (the inner and outer arc sides) of the outlet of the submerged nozzle of the square billet crystallizer; the length of the electromagnetic device is greater than or equal to 1 / 3 of the length of the copper plate and less than or equal to 2 / 3 of the length of the copper plate; the upper edge of the electromagnetic device is flush with the upper edge of the crystallizer.

[0030] The width of the electromagnetic device is greater than or equal to the width of the wide face copper plate of the slab crystallizer or the width of the copper plate parallel to the two sides (the inner and outer arc sides) of the outlet of the submerged nozzle of the square billet crystallizer, which is designed to make the magnetic induction lines pass through the entire width direction of the crystallizer; the length of the electromagnetic device is greater than or equal to 1 / 3 of the length of the copper plate, which is designed to ensure that the molten steel discharged from the outlet of the submerged nozzle passes through the magnetic induction lines; and the length of the electromagnetic device is less than or equal to 2 / 3 of the length of the copper plate, which is designed to make the molten steel in the lower 1 / 3 of the crystallizer not pass through the magnetic induction lines, so as to avoid the inclusions or slag inclusions in the molten steel in the lower 1 / 3 of the crystallizer from moving to the narrow face shell of the slab or the vertical submerged nozzle outlet two sides (the inner and outer arc sides) shell of the square billet due to the action of the Lorentz force, and then adhering to the thick solidified shell, and then the inclusions or slag inclusions are removed by skinning, which results in too large skinning amount and high iron loss, and the processing cost is high.

[0031] S2, after the continuous casting is started and the molten steel in the crystallizer is stable, the electromagnetic devices are turned on to treat the molten steel in the crystallizer until the casting is completed;

[0032] When the electromagnetic device is an electromagnet, the power supply of the electromagnet is direct current, and the two electromagnets are N-pole and S-pole respectively, and the electrical properties and magnetic poles remain unchanged during the entire casting process;

[0033] The current in the electromagnet is 100-500 A, which is designed to ensure that the electromagnet has high magnetic induction strength, so that the inclusions or slag inclusions in the steel have sufficient Lorentz force to promote the inclusions or slag inclusions to gather to the solidified shell or float to the protective slag layer to be removed.

[0034] When the electromagnetic device adopts a permanent magnet, the magnetic induction intensity of the permanent magnet is 0.5-1T.

[0035] S3, after the casting blank exits the crystallizer, the narrow side surface of the slab casting blank or the casting blank surface on both sides of the vertical submerged nozzle outlet of the square casting blank is subjected to on-line skinning treatment or skinning treatment after the casting blank is taken offline; the skinning treatment mode is flame cleaning skinning or grinding skinning, and the skinning amount is 2-6mm.

[0036] Through the skinning treatment, the casting blank skin gathering a large number of inclusions or slag inclusions can be removed, and finally the inclusions or slag inclusions in the steel can be removed.

[0037] The application will be further described below through specific examples:

[0038] Example 1:

[0039] A method for removing inclusions and slag inclusions in a crystallizer, the specific implementation process is as follows:

[0040] In the slab continuous casting production, the production steel grade is IF steel, the casting blank size is 230*1650mm, the crystallizer width is 1670mm, and the length is 900mm.

[0041] S1, an electromagnet is arranged outside the copper plate of the wide face of the crystallizer;

[0042] The electromagnet width is 1680mm, the electromagnet length is 450mm, and the upper edge of the electromagnet is flush with the upper edge of the crystallizer;

[0043] S2, after the molten steel in the crystallizer is stable, the electromagnet system is turned on to treat the molten steel in the crystallizer until the casting is completed;

[0044] The electromagnet system is powered by direct current, the current size is I=100A, the outer arc side electromagnet is N pole, the inner arc side electromagnet is S pole, and the electrical property and magnetic pole remain unchanged during the entire casting process;

[0045] S3, after the casting blank exits the crystallizer, the narrow side of the slab casting blank is subjected to on-line skinning treatment, the skinning treatment mode adopts flame cleaning, and the skinning amount is 2mm.

[0046] After the continuous casting is completed, the casting blank is sampled, the sampling position is the 1 / 4 of the casting blank in the transverse direction and the 1 / 4 of the thickness, and the optical microscope inclusion evaluation analysis is performed on the sample, and the results are as follows:

[0047]

[0048] No slag inclusion defects and large particle inclusions are found in the steel, the inclusion rating is below 0.5 level, and the steel purity is high.

[0049] Example 2:

[0050] A method for removing inclusions and slag entrapment in a crystallizer, the specific implementation process is as follows:

[0051] In the production of square billet continuous casting, the produced steel grade is heavy rail steel, the size of the casting blank is 280*380mm, the width of the crystallizer is 400mm, and the length is 850mm.

[0052] S1, the electromagnet is arranged outside the copper plate parallel to the two sides (the inner and outer arc sides) of the outlet of the submerged entry nozzle of the crystallizer;

[0053] 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;

[0054] S2, after the molten steel in the crystallizer is stable, the electromagnet system is turned on to treat the molten steel in the crystallizer until the casting is completed;

[0055] The electromagnet system is powered by direct current, the current is I=500A, the outer arc side electromagnet is N pole, the inner arc side electromagnet is S pole, and the electrical property and magnetic pole remain unchanged during the entire casting process;

[0056] S3, after the casting blank exits the crystallizer, the narrow side of the slab blank is treated by online skinning, the skinning treatment method adopts flame cleaning, and the skinning amount is 6.0mm.

[0057] After the continuous casting is completed, the casting blank is sampled, the sampling position is the transverse 1 / 4 and the thickness 1 / 4 of the casting blank, and the optical microscope inclusion evaluation analysis is carried out on the sample, and the results are as follows:

[0058]

[0059] No slag entrapment defects and large particle inclusions are found in the steel, the inclusion rating is below 0.5 level, and the steel purity is high.

[0060] Example 3:

[0061] A method for removing inclusions and slag entrapment in a crystallizer, the specific implementation process is as follows:

[0062] In the production of slab continuous casting, the produced steel grade is ship plate steel, the size of the casting blank is 200*1950mm, the width of the crystallizer is 1970mm, and the length is 900mm.

[0063] S1, a permanent magnet is arranged outside the wide face copper plate of the crystallizer;

[0064] The width of the permanent magnet is 1970mm, the length of the permanent magnet is 600mm, and the upper edge of the permanent magnet is flush with the upper edge of the crystallizer;

[0065] S2, after the molten steel in the continuous casting starting crystallizer is stable, the permanent magnet system is opened to treat the molten steel in the crystallizer until the casting is finished;

[0066] The magnetic induction intensity of the permanent magnet in the permanent magnet system is 1T, the outer arc side permanent magnet is N pole, the inner arc side permanent magnet is S pole, and the magnetism and the magnetic pole remain unchanged during the whole casting process;

[0067] S3, after the casting blank is out of the crystallizer, the line is scraped to the narrow side of the slab blank, the scraping treatment mode adopts grinding cleaning, and the scraping amount is 4.0mm.

[0068] After the continuous casting is finished, the casting blank is sampled, the sampling position is the transverse 1 / 4 and the thickness 1 / 4 of the casting blank, the optical microscope inclusion evaluation analysis is carried out on the sample, and the results are as follows:

[0069]

[0070] No slag inclusion defect and large particle inclusion is found in the steel, the inclusion rating is below 0.5 level, and the steel purity is high.

[0071] The details of the application are all known technology.

[0072] The above-described embodiments are only used to describe the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements of the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application should fall within the protection scope of the present application.

Claims

1. A method for removing inclusions and slag from steel in a crystallizer, characterized in that, The method includes the following steps: S1. An electromagnetic device is installed on the outer side of the copper plates on both the front and rear sides of the crystallizer. S2. After continuous casting begins and the molten steel in the crystallizer is stable, the electromagnetic device is activated to process the molten steel in the crystallizer until casting is completed. S3. After the billet exits the crystallizer, the front and rear surfaces of the billet are peeled online or after the billet is removed from the production line. When the crystallizer is a slab crystallizer, the electromagnetic device is located 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 located on the outside of the two copper plates parallel to the immersion nozzle outlet of the square billet crystallizer.

2. The method for removing inclusions and slag from 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 from 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; the upper edge of the electromagnetic device is flush with the upper edge of the crystallizer.

4. The method for removing inclusions and slag from steel in a crystallizer according to claim 2, characterized in that: The electromagnet is energized with direct current, and the electromagnets on both sides of the crystallizer are the N pole and the S pole, respectively, and the electrical and magnetic poles remain unchanged throughout the casting process.

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

6. A method for removing inclusions and slag from steel in a crystallizer according to claim 2, characterized in that: The magnetic flux density of the permanent magnet is 0.5~1T.

7. The method for removing inclusions and slag from steel in a crystallizer according to claim 1, characterized in that: The amount of skin removed during the peeling process is 2~6mm.

8. The method for removing inclusions and slag from steel in a crystallizer according to claim 1, characterized in that: The peeling process is carried out by flame cleaning or grinding.

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