Processing technology of grain-oriented silicon steel and grain-oriented silicon steel

Abstract

The application discloses a processing technology of oriented silicon steel and the oriented silicon steel. The processing technology comprises the following steps: providing a continuous casting slab of the oriented silicon steel; heating the continuous casting slab; hot continuous rolling the continuous casting slab, and the final rolling temperature is 890 DEG C to 970 DEG C; the hot continuous rolling comprises the following steps: rough rolling the heated continuous casting slab, adjusting the temperature difference between the upper surface and the lower surface of the steel plate to be less than or equal to 30 DEG C, and obtaining a rough-rolled steel plate; finish rolling the rough-rolled steel plate, and obtaining a finish-rolled steel plate; and super-fast cooling and laminar cooling the finish-rolled steel plate in sequence, so as to reduce the oxidation of the steel plate. The processing technology of the oriented silicon steel adjusts the temperature difference between the upper surface and the lower surface of the steel plate to be less than or equal to 30 DEG C in the rough rolling process, and performs super-fast cooling and laminar cooling on the steel plate after the finish rolling, so as to reduce the thickness of the oxidation layers on the upper surface and the lower surface of the steel plate, and solve the problem that the thicknesses of the oxidation layers on the upper surface and the lower surface of the oriented silicon steel are inconsistent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel smelting, and particularly relates to a processing technology of oriented silicon steel and the oriented silicon steel. BACKGROUND

[0002] The oriented silicon steel is an important soft magnetic functional material and is mainly used as the iron core of various transformers. The production of the oriented silicon steel comprises the following procedures: steelmaking, hot rolling, pickling, cold rolling, annealing and the like.

[0003] A large amount of iron oxide scale is generated in the hot rolling process, which affects the pickling efficiency and quality. The hot rolling process comprises the following procedures: heating, rough rolling, finish rolling and coiling. The whole process is carried out at high temperature and in the state of contacting with air, and the surface of the steel plate is extremely easy to be oxidized to form an oxide layer. The silicon content of the oriented silicon steel is high, generally more than 3.0%, and the silicon is easy to be oxidized to form silicon dioxide and iron silicate in the high-temperature heating process, so that the oxide layer structure of the oriented silicon steel is more complex. The bonding force between the iron silicate and the matrix is strong, so that the oxide layer is more difficult to be removed compared with other steel types. SUMMARY

[0004] The embodiment of the application provides a processing technology of oriented silicon steel. The temperature difference between the upper surface and the lower surface of the steel plate is controlled through rough rolling, and the measures of super-fast cooling and laminar cooling of the steel plate in the finish rolling process are taken, so that the thickness of the hot rolling oxide layer can be effectively reduced, and the uniformity of the thickness of the oxide layers on the upper surface and the lower surface of the steel plate can be improved.

[0005] In a first aspect, the embodiment of the application provides a processing technology of oriented silicon steel, and the method comprises the following steps.

[0006] A continuous casting slab of the oriented silicon steel is provided.

[0007] The continuous casting slab of the oriented silicon steel is heated.

[0008] The heated continuous casting slab is subjected to hot continuous rolling, and the finish rolling temperature is 890 DEG C to 970 DEG C. The hot continuous rolling comprises the following steps.

[0009] The heated continuous casting slab is subjected to rough rolling, and the temperature difference between the upper surface and the lower surface of the steel plate is adjusted to be less than or equal to 30 DEG C in the process of the rough rolling, so as to obtain a steel plate subjected to rough rolling.

[0010] The steel plate subjected to rough rolling is subjected to finish rolling, so as to obtain a steel plate subjected to finish rolling.

[0011] The steel plate subjected to finish rolling is subjected to super-fast cooling first, and then subjected to laminar cooling, so as to reduce the oxidation of the surface of the steel plate.

[0012] In an embodiment, the composition and content of the oriented silicon steel are as follows in percentage by mass: C: 0.03wt%-0.09wt%; Si: 2.8wt%-4.4wt%; Als: 0.013wt%-0.030wt%; N: 0.0050wt%-0.0120wt%; Mn: 0.1wt%-0.4wt%; Cu: 0.05wt%-0.60wt%; S: 0.001wt%-0.03wt%, and the rest is Fe and inevitable impurities; wherein the content of the impurities is <0.1wt%.

[0013] In an embodiment, the heating temperature of the continuous casting slab of the oriented silicon steel in the heating step is 1150°C-1300°C.

[0014] In an embodiment, the heating temperature of the continuous casting slab of the oriented silicon steel in the heating step is 1150°C-1280°C.

[0015] In an embodiment, the hot continuous rolling of the heated continuous casting slab further comprises:

[0016] The heated continuous casting slab is subjected to descaling treatment using high-pressure fluid to remove the oxide layer on the surface of the continuous casting slab. The scale is the flaky oxide layer on the surface of the continuous casting slab.

[0017] In an embodiment, the high-pressure fluid is water or inert gas, which can be nitrogen or argon.

[0018] In an embodiment, the pressure of the high-pressure fluid is 100MPa-300MPa.

[0019] In an embodiment, in the rough rolling of the heated continuous casting slab, a circulation fan or air blowing is arranged under the rough rolling table to cool the steel plate, so that the temperature difference between the upper surface and the lower surface of the steel plate is ≤30°C.

[0020] In an embodiment, in the step of first subjecting the finished steel plate to ultrafast cooling and then to laminar cooling to reduce the oxidation of the steel plate, the finished steel plate is subjected to ultrafast cooling at the finishing mill outlet, and the cooling rate of the ultrafast cooling is >150°C / s.

[0021] In an embodiment, in the step of first subjecting the finished steel plate to ultrafast cooling and then to laminar cooling to reduce the oxidation of the steel plate, the finished steel plate is subjected to ultrafast cooling at the finishing mill outlet, and the cooling rate of the ultrafast cooling is >200°C / s or 250°C / s.

[0022] In an embodiment, the processing technology of the oriented silicon steel of the present application further comprises:

[0023] The steel plate after the laminar cooling is coiled and cooled to obtain an oriented silicon steel coil with a desired shape.

[0024] In one embodiment, in the step of coiling and cooling the steel plate after the laminar cooling to obtain an oriented silicon steel coil with a desired shape, the hot coiling temperature of the steel plate is 500-700℃.

[0025] In one embodiment, the step of coiling and cooling the steel plate after the laminar cooling to obtain an oriented silicon steel coil with a desired shape comprises:

[0026] The coiled oriented silicon steel coil is cooled in a protective atmosphere to avoid further oxidation of the surface of the coil during the cooling process and reduce the thickness of the oxidation layer.

[0027] In one embodiment, the step of cooling the coiled oriented silicon steel coil in a protective atmosphere comprises:

[0028] The coiled oriented silicon steel coil is placed in a protective cover for cooling, and inert gas is introduced into the protective cover, the flow rate of the inert gas being >5Nm 3 / h. The protective atmosphere formed by the inert gas protects the coil from oxidation during the cooling process and reduces the oxidation layer.

[0029] In one embodiment, the inert gas is nitrogen or argon or other inert gas that does not react with the oriented silicon steel.

[0030] In one embodiment, in the step of placing the coiled oriented silicon steel coil in a protective cover for cooling, a water cooling pipe is arranged in the protective cover to cool the oriented silicon steel coil, and the temperature of the inner wall of the protective cover is maintained at <80℃ to accelerate the rapid cooling of the coil.

[0031] In one embodiment, the water cooling pipe can be a copper pipe or an iron pipe to quickly transfer and dissipate the heat in the protective cover and accelerate the cooling of the coil.

[0032] In a second aspect, the embodiments of the present application also provide an oriented silicon steel prepared according to the above-mentioned processing technology of oriented silicon steel, which has the advantages of a small and relatively uniform oxidation layer thickness.

[0033] The processing technology of the oriented silicon steel of the embodiments of the present application heats the provided oriented silicon steel plate to hot continuous rolling; in the process of the hot continuous rolling, the temperature difference between the upper and lower surfaces of the steel plate is adjusted to be not more than 30℃ in the rough rolling process, so that the oxidation layer thickness of the upper and lower surfaces of the steel plate is uniform; and after the finish rolling, the steel plate after the finish rolling is subjected to ultra-fast cooling and laminar cooling in sequence to reduce the oxidation layer on the upper and lower surfaces of the steel plate, thereby solving the problems of easy formation of an oxidation layer on the surface of the oriented silicon steel and inconsistent thickness of the oxidation layer. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart illustrating the processing technology of oriented silicon steel according to an embodiment of this application.

[0036] Figure 2 This paper shows a graph illustrating the trend of different oxide contents in the oxide layer of an embodiment of the present application as a function of temperature.

[0037] Figure 3 The cross-section of the oxide layer and the oxide content of different layers are shown;

[0038] Figure 4 The diagram shows the effect of the cooling rate at the finishing mill exit on the oxide layer thickness. Detailed Implementation

[0039] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0040] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0041] The primary goal of hot rolling process control for silicon steel is to ensure performance. The process window is narrow, leaving little room for adjustments to reduce the oxide layer. Reducing the thickness of the hot-rolled oxide layer is mainly achieved through adjustments to the hot rolling process.

[0042] In the process of obtaining the processing technology of the oriented silicon steel of the embodiments of the present application, the inventors find that

[0043] The oxidation layer of the oriented silicon steel is different from other steel products: first, the performance of the finished product is greatly affected by the heating and process control parameters of hot rolling, and the optimization of the hot rolling process to reduce the thickness of the oxidation layer must first consider the impact on the performance of the finished oriented silicon steel; second, due to the different working conditions of the upper and lower surfaces of the steel plate, the temperatures of the upper and lower surfaces are different, and the thicknesses of the oxidation layers of the upper and lower surfaces are different.

[0044] In order to solve the problems in the prior art, the embodiments of the present application provide a processing technology of oriented silicon steel. First, the processing technology of oriented silicon steel provided by the embodiments of the present application will be introduced.

[0045] Figure 1 The flowchart of the processing technology of oriented silicon steel provided by some embodiments of the present application is shown.

[0046] As Figure 1 shown, the processing technology of oriented silicon steel provided by some embodiments of the present application includes:

[0047] S1, the molten iron or steelmaking raw material is sequentially subjected to converter blowing, refining, and continuous casting to obtain and provide a continuous casting slab of oriented silicon steel having the following components and contents: in terms of mass percentage, C: 0.03wt%~0.09wt%; Si: 2.8wt%~4.4wt%; Als: 0.013wt%~0.030wt%; N: 0.0050wt%~0.0120wt%; Mn: 0.1wt%~0.4wt%; Cu: 0.05wt%~0.60wt%; S: 0.001wt%~0.03wt%, the rest being Fe and unavoidable impurities; wherein the impurity content is <0.1wt%.

[0048] S2, the continuous casting slab of oriented silicon steel is heated, and the end point temperature of the heating is 1150℃~1300℃;

[0049] S3, the heated continuous casting slab is subjected to hot continuous rolling, and the hot continuous rolling includes:

[0050] S30, the heated continuous casting slab is subjected to descaling treatment using high-pressure water with a pressure of 200MPa~300MPa to remove the oxidation layer on the surface of the continuous casting slab;

[0051] S31. After heating and removing the surface oxide layer, the continuously cast slab at a temperature of 1150℃~1280℃ is rough rolled using a single-stand or double-stand reversible rolling mill to produce hot-rolled strip steel with a thickness of 2.0~3.0mm. During the rough rolling process, the lower surface of the steel plate is cooled by circulating fans or by blowing air under the rough rolling roller table to ensure that the temperature difference between the upper and lower surfaces of the steel plate is ≤30℃.

[0052] Table 1. Effect of temperature difference between the upper and lower surfaces of the steel plate on oxide layer thickness.

[0053]

[0054]

[0055] During the roughing process of steel plates, the space below the roughing roller table is relatively enclosed, which prevents timely heat exchange. This results in the lower surface temperature of the steel plate being more than 100°C higher than the upper surface temperature, causing the oxide layer on the lower surface to be generally thicker than that on the upper surface.

[0056] As shown in Table 1, compared to the 40%-200% difference in oxide layer thickness between the upper and lower surfaces of the steel plates in Comparative Examples 1-3, the processing technology of the grain-oriented silicon steel in this application, by controlling the temperature difference between the upper and lower surfaces of the steel plate within 30°C during the rough rolling stage, can reduce the oxide layer thickness between the upper and lower surfaces of the steel plate from 6 μm to 0.5 μm, with the difference in oxide layer thickness not exceeding 30%. Therefore, by reducing the temperature difference between the upper and lower surfaces, the difference in oxide layer thickness between the upper and lower surfaces of the steel plate can be effectively reduced.

[0057] S32. The steel plate that has completed rough rolling is then finished rolled to obtain a finished steel plate. The final rolling temperature is 890℃~970℃.

[0058] S33. The finished rolled steel plate is first rapidly cooled, then laminar flow cooled to 500℃~700℃ before being coiled to obtain the desired shape of grain-oriented silicon steel coil; the rapid cooling rate is >150℃ / s; such as Figure 4 As shown, when the cooling rate after exiting the rolling mill is less than 150℃ / s, the oxide layer thickness also decreases with increasing cooling rate, but the decrease is not significant. When the cooling rate is higher than 150℃ / s, the oxide layer thickness decreases rapidly with increasing cooling rate. When the cooling rate reaches 200℃ / s, the oxide layer thickness can reach 4.25μm to 4.30μm. When the cooling rate further reaches 250℃ / s, the oxide layer thickness drops to about 4μm.

[0059] S34. After removing the grain-oriented silicon steel coil from the coiler, place it inside a protective cover. Pour N2 into the protective cover to create a protective atmosphere for cooling the coil. The N2 flow rate is > 6 Nm³. 3 / h; and a plurality of water-cooled copper pipes are arranged in the protective cover to improve the cooling speed and reduce the temperature in the protective cover;

[0060] Table 2 Influence of cooling mode of the steel coil after coiling on the thickness of the oxide layer

[0061]

[0062]

[0063] As shown in Table 2, taking Comparative Examples 1-3 as examples, when the steel coil is not cooled in the protective cover, the average thickness of the oxide layer can reach 6.5 μm to 9 μm, and the thickest part can even reach 18 μm. When cooled in a N2 protective atmosphere, the thickness of the oxide layer is significantly reduced, but when the nitrogen flow is less than 5 Nm 3 / h, the thickness reduction effect of the oxide layer is not ideal, and is still more than 6 μm; when the nitrogen flow is more than 5 Nm 3 / h, the average thickness of the oxide layer is reduced to 3 μm to 3.5 μm, and a significant effect of reducing the oxide layer is achieved.

[0064] There are three types of oxides generated on the surface of the steel: ferrous oxide (FeO), ferric oxide (Fe2O3), and magnetite (Fe3O4). Among the three oxides, ferrous oxide has the lowest oxygen content and is in the innermost layer of the oxide. When the temperature is lower than 570°C, ferrous oxide is in an unstable state, and the content of ferrous oxide in the oxide layer increases with the increase of the surface temperature of the billet. Magnetite is in the middle layer of the oxide layer. Ferric oxide is in the outermost layer of the oxide layer, which is usually formed at a temperature higher than 800°C and exists at high temperature. The content of various oxides in the oxide layer of the steel plate at different temperatures is shown in Table 1. Figure 2

[0065] The oriented silicon steel has a high silicon content, and silicon is more likely to be oxidized to form silicon dioxide. Therefore, a layer of fayalite (Fe2SiO4) is formed on the interface between the base and the oxide layer of the oriented silicon steel. Therefore, the typical oxidation structure layer of the oriented silicon steel is shown in Table 2, which is Fe2SiO4, FeO, Fe3O4, and Fe2O3 from the inside to the outside. Figure 3

[0066] Among the four layers of the oxide layer, the iron silicate has high viscosity and strong bonding force with the base layer, and is the most difficult to remove, and its thickness is mainly affected by the heating temperature and the time in the furnace. The higher the temperature and the longer the time in the furnace, the thicker the iron silicate layer, but reducing the heating temperature and shortening the time in the furnace will significantly affect the magnetic properties of the finished oriented silicon steel. Among the three iron oxides, the ferrous oxide layer is the most easily decomposed by acid, the magnetite layer is the second, and the ferric oxide layer is the most difficult to be decomposed by acid.

[0067] From​​Figure 2 As can be seen, the steel sheet is in a high temperature zone of 900°C or more before the finish rolling is completed, and a large amount of ferrous oxide is generated. The difficult-to-pickling ferric oxide and magnetite are mainly formed after the finish rolling is completed, and thus the steel sheet should be rapidly cooled after the finish rolling to reduce the generation of new ferrous oxide and ferric oxide. A large amount of ferrous oxide is converted into the difficult-to-pickling ferric oxide and magnetite during the cooling process of coiling at 650°C or less, and the generation of ferric oxide can be effectively prevented by cooling in a protective atmosphere after coiling.

[0068] It should be noted that the present application is not limited to the specific configurations and processes described above and illustrated in the drawings. For the sake of brevity, detailed descriptions of known methods are omitted. In the above-described embodiments, several specific steps are described and illustrated as examples. However, the method processes of the present application are not limited to the specific steps described and illustrated, and one skilled in the art can make various changes, modifications and additions, or change the order of the steps, after understanding the spirit of the present application.

[0069] The above describes only specific implementation of the present application, and those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, modules and units can refer to the corresponding processes in the foregoing method embodiments, which will not be described here. It should be understood that the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed in the present application, and these modifications or replacements should be covered within the protection scope of the present application.

Claims

1. A process for working an oriented silicon steel, characterized in that, The application provides a processing method of oriented silicon steel. The oriented silicon steel comprises the following components and contents in percentage by mass: C: 0.03wt%-0.09wt%; Si: 2.8wt%-4.4wt%; Als: 0.013wt%-0.030wt%; N: 0.0050wt%-0.0120wt%; Mn: 0.1wt%-0.4wt%; Cu: 0.05wt%-0.60wt%; S: 0.001wt%-0.03wt%, and the rest is Fe and inevitable impurities; wherein the content of the impurities is less than 0.1wt%. The heated continuous casting slab is subjected to hot continuous rolling, and the final rolling temperature is 890-970 DEG C. The heated continuous casting slab is subjected to rough rolling, and the temperature difference between the upper surface and the lower surface of the steel plate is adjusted to be less than or equal to 30 DEG C during the rough rolling to obtain a rough-rolled steel plate. The rough-rolled steel plate is subjected to finish rolling to obtain a finish-rolled steel plate. The finish-rolled steel plate is subjected to ultra-fast cooling at a cooling rate greater than 250 DEG C / s, and then subjected to laminar cooling to reduce the oxidation of the surface of the steel plate. The heating temperature of the heated continuous casting slab is 1150-1300 DEG C. The heated continuous casting slab is subjected to descaling treatment to remove the oxide layer on the surface of the continuous casting slab.

2. The process for working an oriented silicon steel according to claim 1, characterized in that, The finish-rolled steel plate is coiled and cooled to obtain an oriented silicon steel coil with a required shape.

3. The process for working oriented silicon steel according to claim 1, characterized in that, The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape.

4. The process for working an oriented silicon steel according to claim 1, characterized in that, The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape.

5. The process for working oriented silicon steel according to claim 4, characterized in that, The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape.

6. The process for working oriented silicon steel according to claim 4, characterized in that, The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape.

7. The processing of oriented silicon steel of claim 6, wherein, The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The finished coiled oriented silicon steel coil is placed in a protective cover for cooling, inert gas is passed in the protective cover, the flow rate of the inert gas > 5 Nm 3 / h.

8. The process for working oriented silicon steel according to claim 7, characterized in that, The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape.

9. An oriented silicon steel characterized by, The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. The coiled and cooled steel plate is subjected to laminar cooling to obtain an oriented silicon steel coil with a required shape. 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