Preparation method of electrical steel and electrical steel

Abstract

The invention discloses a preparation method of electrical steel and the electrical steel, and the preparation method of the electrical steel comprises the steps that tundish molten steel passes through a chamfering crystallizer at the speed of 1.2-1.5 m / min for continuous casting to obtain a continuous casting billet; wherein the step of continuously casting the tundish molten steel through the chamfering crystallizer at the speed of 1.2-1.5 m / min comprises the following steps: cooling the molten steel in the chamfering crystallizer, and cooling by adopting first cooling water in a first direction and second cooling water in a second direction; the flow of the first cooling water is 4200 L / min to 4900 L / min, and the flow of the second cooling water is 580 L / min to 650 L / min. By means of the method, the point-shaped peeling phenomenon of the edges of the electrical steel can be greatly improved, the yield of the electrical steel is increased, and the comprehensive performance of the electrical steel is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of steel plate smelting, and specifically relates to a preparation method of electrical steel and electrical steel. Background Art

[0002] The occurrence of spot peeling on the edge of electrical steel has a serious impact on the performance of electrical steel and also affects the yield rate of electrical steel. For example, the occurrence of spot peeling on the edge of electrical steel may expose the base material. The damage of the surface oxide layer or coating will affect the iron loss characteristics of the electrical steel, leading to magnetic flux leakage or increased magnetic loss, affecting the electromagnetic performance. The spot peeling phenomenon may cause uneven edge defects, which may cause magnetic discontinuity and increase eddy current loss: due to the damage of the coating or the exposure of the base material in the peeling area, it may cause an increase in local eddy currents, affecting high frequency and reducing the magnetic permeability of the material.

[0003] The performance of electrical steel with spot peeling on the edge mainly depends on the range, depth and area of ​​the peeling. Therefore, improvement is urgently needed. Summary of the invention

[0004] In view of this, the present application provides a method for preparing electrical steel and electrical steel, aiming to provide a method that can significantly improve the spot peeling phenomenon on the edge of electrical steel, improve the yield rate of electrical steel, and improve the comprehensive performance of electrical steel.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing electrical steel, comprising:

[0006] The molten steel in the tundish is continuously cast through the chamfered crystallizer at a speed of 1.2 to 1.5 m / min to obtain a continuously cast billet;

[0007] The method of continuously casting the molten steel in the chamfered crystallizer at a speed of 1.2 to 1.5 m / min includes: cooling the molten steel in the chamfered crystallizer, wherein the cooling includes using first cooling water in a first direction and second cooling water in a second direction;

[0008] The flow rate of the first cooling water is 4200 L / min to 4900 L / min, and the flow rate of the second cooling water is 580 L / min to 650 L / min.

[0009] According to an embodiment of one aspect of the present application, the flow rate of the first cooling water is 8.5m / s-9.5m / s.

[0010] According to an embodiment of one aspect of the present application, the distance between one end of the submerged water inlet of the chamfered crystallizer immersed in the molten steel and the surface of the molten steel is 120mm-130mm.

[0011] According to an embodiment of one aspect of the present application, when the width of the electrical steel is 1220 to 1250 mm, the taper coefficient of the chamfered crystallizer is 1.4%-1.6%.

[0012] According to an embodiment of one aspect of the present application, the superheat degree of the molten steel in the tundish is 25°C to 35°C.

[0013] According to an embodiment of one aspect of the present application, the pouring temperature of the molten steel in the tundish is 1552°C to 1564°C.

[0014] According to an embodiment of one aspect of the present application, the tundish molten steel includes, by mass percentage: C≤0.0025%, Si: 1.2%-1.5%, Mn: 0.25%-0.35%, Al: 0.2%-0.3%, and the remainder is iron and unavoidable impurity elements.

[0015] According to an embodiment of one aspect of the present application, the liquidus temperature of the molten steel in the tundish is 1527°C to 1529°C.

[0016] According to an embodiment of one aspect of the present application, the method also includes: slab heating, high-pressure water dephosphorization, hot rolling, laminar cooling, coiling and packaging into a furnace, the slab heating temperature is 1150±20°C, the slab heating time is 110-130min, and the slab heated out of the furnace temperature is 1030-1070°C; hot rolling includes finish rolling, and the final rolling temperature of the finish rolling is 900±15°C.

[0017] In a second aspect, an embodiment of the present application provides an electrical steel produced by the preparation method of the first aspect.

[0018] This application has at least the following beneficial effects:

[0019] The method provided in the present application, under a suitable continuous casting speed and in combination with a suitable cooling water flow rate, can promote the rapid solidification of molten steel on the meniscus of the chamfered crystallizer during the preparation process of electrical steel, ensure sufficient strength of the solidified billet shell, avoid the leakage of molten steel causing small steel particles on the chamfered edge of the electrical steel and spot peeling during the hot rolling process, thereby reducing the occurrence of spots on the edge of the electrical steel, improving the edge quality of the electrical steel and improving the yield rate of the electrical steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the implementation regulations of this application, the following is a brief introduction to the drawings required for use in the embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 A schematic diagram of the structure of molten steel and protective slag in a chamfered crystallizer according to an embodiment of the present application is shown.

[0022] Figure 2 The figure shows the appearance of peeling at the chamfer of the electrical steel billet of comparative example 1 of the present application.

[0023] Figure 3 The appearance of the chamfered corner of the electrical steel billet of Example 1 of the present application is shown.

[0024] Among them, 1. chamfered crystallizer; 2. glass slag layer; 3. crystallized slag layer; 4. liquid slag layer; 5. solidified billet shell; 6. submerged nozzle. DETAILED DESCRIPTION

[0025] In order to make the application purpose, technical solution and beneficial technical effect of this application clearer, the application is further described in detail below in conjunction with the embodiments. It should be understood that the implementation regulations described in this specification are only for explaining this application, not for limiting this application.

[0026] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0027] In the description of the present application, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number, and the “multiple” in “one or more” means two or more than two.

[0028] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided through a series of embodiments, and these implementation regulations can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0029] During the solidification and forming process of molten steel, the connection between the wide surface and the chamfered surface of the crystallizer is often insufficient due to factors such as excessive corner gap, weak cooling water volume of the crystallizer, and unreasonable setting of the crystallizer taper. This often leads to quality problems such as small steel particles or infiltrated steel (see the figure below). When the amount of infiltrated steel is serious or the amount of burnt loss in the heating furnace is small, edge defects such as edge scarring and spot peeling will appear during the hot rolling process. The product quality does not meet the judgment requirements, and the edge trimming is outsourced, resulting in certain economic losses and seriously affecting the fulfillment of product orders.

[0030] In view of this, an embodiment of the present application provides a method for preparing electrical steel to solve the above problems.

[0031] Method for preparing electrical steel

[0032] In a first aspect, an embodiment of the present application provides a method for preparing electrical steel, comprising:

[0033] The molten steel in the tundish is continuously cast through the chamfered crystallizer at a speed of 1.2 to 1.5 m / min to obtain a continuously cast billet;

[0034] The method of continuously casting the molten steel in the chamfered crystallizer at a speed of 1.2 to 1.5 m / min includes: cooling the molten steel in the chamfered crystallizer, wherein the cooling includes using first cooling water in a first direction and second cooling water in a second direction;

[0035] The flow rate of the first cooling water is 4200 L / min to 4900 L / min, and the flow rate of the second cooling water is 580 L / min to 650 L / min.

[0036] Optionally, the molten steel in the tundish is continuously cast through the chamfered crystallizer at a speed of 1.20 m / min, 1.25 m / min, 1.30 m / min, 1.35 m / min, 1.40 m / min, 1.45 m / min, or 1.50 m / min. This speed can be understood as the pulling speed of continuous casting.

[0037] Optionally, the flow rate of the first cooling water can be any value among 4200L / min, 4250L / min, 4300L / min, 4350L / min, 4400L / min, 4450L / min, 4500L / min, 4550L / min, 4600L / min, 4650L / min, 4700L / min, 4750L / min, 4800L / min, 4850L / min, 4900L / min or any range of their combinations.

[0038] Optionally, the flow rate of the first cooling water can be any value among 580 L / min, 590 L / min, 600 L / min, 610 L / min, 620 L / min, 630 L / min, 640 L / min, 650 L / min, or a range of their combinations.

[0039] It can be understood that: the first direction can be the wide surface direction of the crystallizer or the length direction of the continuous casting billet; the second direction can be the narrow surface direction of the crystallizer or the width direction of the continuous casting billet.

[0040] In the embodiment of the present application, the molten steel in the middle package is continuously cast through the chamfered crystallizer at a speed of 1.2 to 1.5 m / min. With the appropriate cooling water flow rate, the rapid solidification of the molten steel on the meniscus of the chamfered crystallizer can be promoted, sufficient strength of the solidified billet shell can be ensured, and the seepage of molten steel can be avoided, thereby improving the apparent quality of the corner area of ​​the chamfered continuous casting billet of electrical steel, reducing the rework rate of its hot-rolled coil, improving the comprehensive yield rate, and saving production costs.

[0041] In addition, the first cooling water flow in the first direction is greater than the second cooling water flow in the second direction, which can further increase the shrinkage of the solidified shell, especially the shrinkage of the initial solidified shell in the meniscus area, enhance the strength of the solidified shell and avoid the seepage of molten steel.

[0042] In some optional embodiments, the flow rate of the first cooling water is 8.5m / s-9.5m / s. The flow rate of the first cooling water is within the above range, which matches the flow rate of the first cooling water, can promote the rapid solidification of the molten steel on the meniscus of the chamfered crystallizer, ensure sufficient solidified billet shell strength, further improve the apparent quality of the corner area of ​​the electrical steel continuous casting billet, and further reduce the rework rate.

[0043] In some optional embodiments, the distance between one end of the immersion nozzle of the chamfered crystallizer immersed in the molten steel and the surface of the molten steel is 120mm-130mm. The distance between one end of the immersion nozzle immersed in the molten steel and the surface of the molten steel can be understood as the insertion depth of the immersion nozzle. Within the above range, the overall heat of the molten steel reflow zone in the chamfered crystallizer can be moved upward, effectively promoting the melting of the protective slag, improving the solidification heat conductivity, facilitating the rapid formation or thickening of the solidified billet shell, and enhancing the strength of the solidified billet shell, reducing the molten steel seepage, thereby improving the apparent quality of the corner area of ​​the electrical steel continuous casting billet, reducing the rework rate, improving the comprehensive yield rate, and saving production costs.

[0044] In addition, the distance between one end of the submerged nozzle immersed in the molten steel and the surface of the molten steel is within the above-mentioned range, which will not obviously cause the risk of slag rolling of the crystallizer protective slag, and can make the flow rate of the molten steel surface in the crystallizer within a reasonable range, which is conducive to normal continuous casting.

[0045] In some optional embodiments, when the width of the electrical steel is 1220 to 1250 mm, the taper coefficient of the chamfered crystallizer is 1.4%-1.6%.

[0046] It can be understood that: mold taper coefficient = mold taper / steel width

[0047] When the taper coefficient of the chamfered crystallizer is within the above range, it can provide sufficiently strong support to avoid the phenomenon of insufficient support for the solidified shell on the narrow surface of the crystallizer, thereby preventing the solidified shell from losing support and leaking molten steel after shrinking, improving the apparent quality of the corner area of ​​the electrical steel continuous casting billet, reducing the rework rate, improving the comprehensive yield rate, and saving production costs.

[0048] In some optional embodiments, the superheat of the molten steel in the middle package is 25° C. to 35° C. Controlling the superheat of the molten steel in the middle package within the above range is conducive to promoting the rapid melting of the protective slag in the crystallizer, improving lubrication, and allowing the liquid protective slag to flow between the solidified shell and the crystallization wall, which improves the heat conduction effect compared with air heat conduction, is conducive to the rapid formation or thickening of the solidified shell, and enhances the strength of the solidified shell, reduces the molten steel seepage, thereby improving the apparent quality of the corner area of ​​the electrical steel continuous casting billet, reducing the rework rate, improving the comprehensive yield rate, and saving production costs.

[0049] Figure 1 The schematic diagram of the structure of molten steel and protective slag in the chamfered crystallizer of the embodiment of the present application is shown. Figure 1 The chamfered crystallizer 1 contains molten steel, and the container wall of the chamfered crystallizer 1 is formed by a glass slag layer 2 and a crystal slag layer 3 in sequence. The molten steel between the molten steel and the crystal slag layer 3 begins to cool to form a solidified shell 5. The protective slag liquefies under high temperature and becomes liquefied protective slag. The liquefied protective slag flows between the solidified shell 5 and the crystal slag layer 3 to form a liquid slag layer 4, which is also conducive to the formation of the solidified shell 5 and enhances the strength of the solidified shell 5. The molten steel enters the chamfered crystallizer 1 through the submerged nozzle 6.

[0050] In some optional embodiments, the pouring temperature of the molten steel in the middle ladle is 1552° C. to 1564° C. The pouring temperature of the molten steel in the middle ladle is within the above range, which can promote the rapid melting of the protective slag in the crystallizer, improve lubrication, facilitate the rapid formation or thickening of the solidified shell, enhance the strength of the solidified shell, and reduce the seepage of molten steel.

[0051] In some optional embodiments, the middle molten steel includes, by mass percentage, C≤0.0025%, Si: 1.2%-1.5%, Mn: 0.25%-0.35%, Al: 0.2%-0.3%, and the remainder is iron and unavoidable impurity elements. The middle molten steel with this composition is prone to edge spot peeling during the hot rolling process. The above method can improve the edge peeling phenomenon of electrical steel after hot rolling.

[0052] The liquidus temperature of the molten steel in the middle package of this composition is within a certain range, and the superheat of the molten steel in the middle package can be controlled, thereby achieving the purpose of reducing the seepage of molten steel.

[0053] In some optional embodiments, the liquidus temperature of the molten steel in the middle package is 1527° C. to 1529° C. When the liquidus temperature of the molten steel in the middle package is within the above range, the pouring temperature can be controlled to reduce the molten steel seepage during the continuous casting process, thereby improving and enhancing the surface quality of the continuous casting billet.

[0054] In some optional embodiments, the method also includes: slab heating, high-pressure water dephosphorization, hot rolling, laminar cooling, coiling and packaging into a furnace, the slab heating temperature is 1150±20°C, the slab heating time is 110-130min, and the heated slab furnace outlet temperature is 1030-1070°C; hot rolling includes finish rolling, and the final rolling temperature of finish rolling is 900±15°C.

[0055] In some optional embodiments, the coiling temperature is 725±18°C

[0056] In the second aspect, the embodiment of the present application provides an electrical steel, which is prepared by the preparation method of the first aspect. The electrical steel prepared by the above method has good edge quality, especially good edge quality at the chamfer, so that the surface quality of the continuous casting billet and the electrical steel after hot rolling is improved and enhanced.

[0057] Example

[0058] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations may be made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0059] Example 1

[0060] This embodiment provides a method for preparing electrical steel, comprising the following steps:

[0061] The molten steel in the middle package is continuously cast through a chamfered crystallizer at a speed of 1.3 m / min to obtain a continuously cast billet, wherein the molten steel in the middle package includes, by mass percentage, C≤0.0025%, Si: 1.3%, Mn: 0.30%, Al: 0.25%, and the remainder is iron and unavoidable impurity elements;

[0062] The method of continuously casting the molten steel in the tundish through the chamfering crystallizer at a speed of 1.3 m / min includes: cooling the molten steel in the chamfering crystallizer, wherein the cooling includes using first cooling water in a first direction and second cooling water in a second direction;

[0063] The flow rate of the first cooling water is 4200L / min, and the flow rate of the first cooling water is 8.91m / s; the flow rate of the second cooling water is 610L / min. Among them, the insertion depth of the immersion nozzle is 120mm. The width of the electrical steel is 1230mm, and the taper coefficient of the chamfered crystallizer is 1.5%. The superheat of the molten steel in the middle package is 31℃, the pouring temperature of the molten steel in the middle package is 1552℃, and the liquidus temperature of the molten steel in the middle package is 1521℃.

[0064] Then the continuous casting billet is subjected to slab heating, high-pressure water dephosphorization, hot rolling, laminar cooling, coiling and packing into a furnace to produce electrical steel. The slab heating temperature is 1150±20℃, the slab heating time is 110-130min, and the slab temperature out of the furnace is 1030-1070℃; hot rolling includes finishing rolling, and the final rolling temperature of finishing rolling is 900±15℃.

[0065] Example 2

[0066] The difference between this embodiment and embodiment 1 is that the flow rate of the first cooling water is 4900 L / min and the flow rate of the second cooling water is 650 L / min.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that the flow rate of the first cooling water is 4600 L / min, the flow velocity of the first cooling water is 8.93 m / s; the flow rate of the second cooling water is 580 L / min.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that the taper coefficient of the chamfered crystallizer is 1.6%.

[0071] Example 5

[0072] The difference between this embodiment and embodiment 1 is that the superheat of the molten steel in the middle package is 35°C, the pouring temperature of the molten steel in the middle package is 1556°C, and the liquidus temperature of the molten steel in the middle package is 1521°C.

[0073] Example 6

[0074] The difference between this embodiment and embodiment 1 is that the insertion depth of the submerged nozzle is increased from 155 mm.

[0075] Example 7

[0076] The difference between this embodiment and embodiment 1 is that the taper coefficient of the chamfered crystallizer is 1.3%.

[0077] Example 8

[0078] The difference between this embodiment and embodiment 1 is that the superheat of the molten steel in the middle package is 20°C, the pouring temperature of the molten steel in the middle package is 1541°C, and the liquidus temperature of the molten steel in the middle package is 1521°C.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is that the molten steel in the tundish is continuously cast through the chamfered crystallizer at a speed of 1.8 m / min.

[0081] Comparative Example 2

[0082] The difference between this comparative example and Example 1 is that the flow rate of the first cooling water on the narrow surface of the chamfered crystallizer is 7.60 m / s, and the flow rate of the first cooling water is 3580 L / min.

[0083] Test Section

[0084] The peeling condition of the edges of the electrical steel coils prepared in the examples and comparative examples was tested, and the peeled parts of the edges of the steel coils were trimmed. The peeling position of the edges was generally located at 35-45mm in the wide width direction of the steel coil. The steel coils with peeling on the edges were trimmed, and the remaining steel coils were unqualified.

[0085] Trimming rate = the mass of the peeled steel coil cut off / the mass of the steel coil not trimmed

[0086] Yield rate = quality of qualified steel coils / quality of untrimmed steel coils

[0087] Table 1 Test results of electrical steel of embodiments and comparative examples.

[0088]

[0089]

[0090] The above measured performance parameters are taken as average values.

[0091] The spot peeling phenomenon at the chamfer of the chamfered electrical steel in Comparative Example 1 is as follows Figure 2 As shown; in Example 1, the chamfered electrical steel has less spot peeling at the chamfer, such as Figure 3 shown. Figure 2 and Figure 3 The comparison shows that the method of the embodiment of the present application can effectively reduce the spot peeling at the chamfer of the chamfered electrical steel and improve the surface quality of the electrical steel.

[0092] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto, and any familiarity with the present technology or replacement should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing electrical steel, characterized in that: include: The molten steel in the tundish is continuously cast through the chamfered crystallizer at a speed of 1.2 to 1.5 m / min to obtain a continuously cast billet; The method of continuously casting the molten steel in the chamfered crystallizer at a speed of 1.2 to 1.5 m / min includes: cooling the molten steel in the chamfered crystallizer, wherein the cooling includes using first cooling water in a first direction and second cooling water in a second direction; The flow rate of the first cooling water is 4200 L / min to 4900 L / min, and the flow rate of the second cooling water is 580 L / min to 650 L / min.

2. The preparation method according to claim 1, characterized in that: The flow rate of the first cooling water is 8.5m / s-9.5m / s.

3. The preparation method according to claim 1, characterized in that: The distance between one end of the submerged water inlet of the chamfered crystallizer immersed in the molten steel and the surface of the molten steel is 120mm-130mm.

4. The preparation method according to claim 1, characterized in that: When the width of the electrical steel is 1220 to 1250 mm, the taper coefficient of the chamfered crystallizer is 1.4% to 1.6%.

5. The preparation method according to claim 1, characterized in that: The superheat degree of the molten steel in the tundish is 25°C to 35°C.

6. The preparation method according to claim 1, characterized in that: The pouring temperature of the molten steel in the tundish is 1552°C to 1564°C.

7. The preparation method according to claim 1, characterized in that: The tundish molten steel comprises, by mass percentage, C≤0.0025%, Si: 1.2%-1.5%, Mn: 0.25%-0.35%, Al: 0.2%-0.3%, and the remainder is iron and inevitable impurity elements.

8. The preparation method according to claim 1, characterized in that: The liquidus temperature of the molten steel in the tundish is 1527°C to 1529°C.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The method also includes: slab heating, high-pressure water dephosphorization, hot rolling, laminar cooling, coiling and packing into a furnace, the slab heating temperature is 1150±20°C, the slab heating time is 110-130min, and the slab out-of-furnace temperature is 1030-1070°C; the hot rolling includes finish rolling, and the final rolling temperature of the finish rolling is 900±15°C.

10. An electrical steel, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

Images