An oriented silicon steel pickling coil and a preparation method thereof, and an oriented silicon steel finished product

Abstract

The present application belongs to the technical field of oriented silicon steel production, and particularly relates to an oriented silicon steel pickling coil, a preparation method thereof and an oriented silicon steel finished product. The preparation method comprises the following steps: heating a continuous casting slab, and performing dephosphorization treatment on the heated continuous casting slab; performing hot continuous rolling on the dephosphorized continuous casting slab to obtain a hot-rolled coil; cooling the hot-rolled coil in a protective atmosphere to obtain a strip, and performing shot blasting treatment on the strip; and performing pickling on the shot-blasted strip in an acid solution added with a pickling promoter. During the pickling process, the pickling time of the head of the strip is 90-100s, and the pickling time of the tail of the strip is 110-120s. The pickling promoter comprises a complexing agent composed of a sulfite and a furan dione derivative containing a carbon-carbon double bond. The oriented silicon steel pickling coil prepared by the method has clean pickling of the surface scale, and the surface of the strip after decarburization annealing is metallic luster. The silicon steel finished product prepared from the pickling coil has excellent magnetic properties and coating adhesion.

Description

Technical Field

[0001] This invention belongs to the field of grain-oriented silicon steel production technology, specifically relating to a grain-oriented silicon steel pickled coil and its preparation method, and a grain-oriented silicon steel finished product. Background Technology

[0002] Grain-oriented silicon steel is an energy-saving soft magnetic alloy material with low iron loss and high magnetic induction, widely used in the manufacture of various transformer cores, reactors, instrument transformers, and large motors. The production process of high-temperature grain-oriented silicon steel is lengthy, generally involving molten iron → steelmaking → continuous casting → hot rolling → pickling → primary cold rolling → decarburization annealing → secondary cold rolling → MgO coating → high-temperature annealing → stretching annealing → scoring → slitting. Due to equipment limitations, most private enterprises lack steel processing facilities and hot rolling mills, possessing only downstream processing equipment. Furthermore, due to environmental pressures, they often lack pickling lines, typically outsourcing the processing of hot-rolled raw materials or directly purchasing pickled grain-oriented silicon steel coils for subsequent cold rolling, decarburization annealing, and high-temperature annealing.

[0003] In subsequent production processes, decarburization annealing is particularly important. Decarburization annealing ensures a sufficient number of primary grains (secondary nuclei) in the matrix, along with a primary recrystallization texture and microstructure conducive to their growth. Simultaneously, it reduces the carbon content in the steel to below 30 ppm, guaranteeing a single α-phase during subsequent high-temperature annealing, fostering a well-developed secondary recrystallization microstructure, removing sulfur and nitrogen from the steel, and eliminating magnetic aging in the product. However, in actual decarburization annealing production, a blackening phenomenon is frequently encountered on the strip surface after decarburization annealing. The main reason is incomplete cleaning of the iron oxide scale on the surface of the hot-rolled raw material during pickling. Surface blackening affects the decarburization effect, hindering the diffusion of Fe atoms from the matrix to the surface to react with water vapor, resulting in a thinner oxide layer. This affects the formation of the subsequent glass underlayer, impacting the magnetic properties of the final product, and may even cause gold leakage on the finished product surface. Therefore, surface quality control after decarburization annealing is crucial.

[0004] The iron oxide scale formed during hot rolling mainly consists of Fe3O4, Fe2O3, and FeO. Fe2O3 (reddish-brown) forms the outermost layer, followed by Fe3O4 (black), and then FeO (black) on the innermost layer. Research shows that when the final rolling temperature is between 700 and 900°C, the formed iron oxide scale contains 80-90% FeO and 10-20% Fe3O4. When the final rolling temperature exceeds 900°C, iron rapidly oxidizes to Fe3O4, forming Fe2O3 on the outermost layer. During high-temperature coiling, the fullerite FeO transforms into Fe3O4. Therefore, under the high-temperature conditions of 930-980°C final rolling temperature for grain-oriented silicon steel, the easily cleanable FeO fullerite content on the innermost layer is 10%, the difficult-to-clean Fe3O4 content in the middle layer is 70-80%, and the Fe2O3 content on the outermost layer is 10-20%. Given that the heating furnace temperature and final rolling temperature of oriented silicon steel have a significant impact on magnetic properties, it is impossible to reduce the content of surface iron oxide scale through optimization of the hot rolling process. Furthermore, the furnace atmosphere in the decarburization annealing process is a humid atmosphere with a low content of reducing atmosphere, making it difficult to remove surface iron oxide scale through the decarburization annealing process. Therefore, the only way to improve the pickling effect of surface iron oxide scale is to optimize the pickling process.

[0005] To improve the pickling effect of grain-oriented silicon steel, the prior art "CN117867506A" proposes a pickling method for grain-oriented silicon steel. This method uses a two-stage pickling process. Although it does not change the pickling process, the two-stage pickling increases production costs and reduces production efficiency. Moreover, the pickled coil after the two-stage pickling has a distinct silver-gray color, which meets the requirements of subsequent production processes. However, this invention does not address whether the finished product produced from this pickled coil has excellent performance. The prior art "CN116875987A" proposes a continuous pickling method for ordinary grain-oriented silicon steel. This method uses the pressure rollers of an uncoiler to roll the strip steel, causing micro-cracks in the iron oxide scale on the surface of the strip steel. Then, the surface of the strip steel is ground and brushed, mainly using physical rust removal. However, the iron oxide scale on the surface of the strip steel may not be cleaned evenly. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing pickling methods for grain-oriented silicon steel, which result in uneven removal of iron oxide scale from the strip surface and low production efficiency. Therefore, this invention proposes a pickled grain-oriented silicon steel coil, its preparation method, and the finished grain-oriented silicon steel product. The preparation method of this invention first involves rapidly cooling the strip surface to a certain temperature using an inert gas after hot rolling to prevent the formation of Fe3O4. Simultaneously, a specific type of pickling accelerator is added during the pickling process to promote the thorough removal of iron oxide scale from the hot-rolled strip surface. This synergistic control of the pickling time ensures consistent pickling quality across the entire coil. The grain-oriented silicon steel pickled coil prepared using this method has a clean iron oxide scale surface. After decarburization and annealing, the strip surface exhibits a metallic luster without blackening or darkening defects. Furthermore, the finished grain-oriented silicon steel product produced from the pickled coil raw material possesses excellent magnetic properties and superior coating adhesion.

[0007] The first aspect of this invention provides a method for preparing pickled coils of grain-oriented silicon steel, the method comprising the following steps:

[0008] Step S1: Heating the continuous casting slab and descaling the heated slab. Then, hot rolling the descaled slab to obtain a hot-rolled coil.

[0009] Step S2: Cool the hot-rolled coil in a protective atmosphere to obtain strip steel, and then perform shot blasting on the strip steel.

[0010] Step S3: Pickling the shot-blasted strip in an acid solution with added pickling accelerator. During the pickling process, the pickling time for the head of the strip is 90-100s, and the pickling time for the tail of the strip is 110-120s. The pickling accelerator includes a complexing agent composed of sulfite and furan dione derivatives containing carbon-carbon double bonds.

[0011] Preferably, the sulfite is ammonium sulfite hydrate or sodium sulfite; the furanyl dione derivative containing carbon-carbon double bonds is an organic compound in which the two ends of an alkane are respectively replaced by carbon-carbon double bonds and furanyl dione.

[0012] More preferably, the furanedione derivative containing a carbon-carbon double bond is 3-octadecane-dihydro-2,5-furanedione.

[0013] More preferably, based on the total mass of the pickling accelerator as 100%, the content of ammonium sulfite hydrate or sodium sulfite is ≥30%, and the content of 3-octadecane-dihydro-2,5-furandione is ≤5%.

[0014] More preferably, based on the total mass of the pickling accelerator as 100%, the content of ammonium sulfite hydrate or sodium sulfite is 30-35%, and the content of 3-octadecane-dihydro-2,5-furandione is 3-5%.

[0015] More preferably, in the acid solution with added pickling accelerator, the concentration of the pickling accelerator is 0.3-0.5%; the acid solution is hydrochloric acid, the concentration of hydrochloric acid is 150-200 g / L, and the temperature of hydrochloric acid is 85-90°C.

[0016] Preferably, the pressure of the dephosphorization water used in the dephosphorization treatment is ≥200 bar; in the shot blasting treatment, the shot blasting speed is 60-80 m / s.

[0017] Preferably, the chemical composition of the continuously cast slab, by weight percentage, includes: C: 0.030–0.045%, Si: 3.05–3.30%, Mn: 0.15–0.25%, Als: 0.015–0.025%, N: 0.0080–0.0100%, S: 0.0050–0.0100%, Cu: 0.45–0.60%, P: ≤0.020%, Ti: ≤0.003%, with the remainder being Fe and unavoidable impurities.

[0018] A second aspect of the present invention provides an oriented silicon steel pickled coil obtained according to the preparation method described above.

[0019] The third aspect of the present invention provides a finished grain-oriented silicon steel product, which is obtained by the pickling of grain-oriented silicon steel coils as described above, followed by a first cold rolling, decarburization annealing, a second cold rolling, and coating.

[0020] The pickled coil of grain-oriented silicon steel, its preparation method, and the finished grain-oriented silicon steel product described in this invention have at least the following beneficial effects:

[0021] (1) In this invention, the surface of the strip steel is first cooled to a certain temperature by inert gas after hot rolling and coiling to prevent the formation of Fe3O4. At the same time, pickling accelerator is added during the pickling process to promote the cleaning of iron oxide scale on the surface of the hot-rolled strip steel. The pickling time of the strip steel is controlled in a coordinated manner to ensure the consistency of pickling quality of the entire strip steel surface. The iron oxide scale on the surface of the pickled silicon steel produced is cleaned by pickling. After decarburization and annealing, the surface of the strip steel has a metallic luster and no defects such as blackening or darkening. The finished oriented silicon steel produced using pickled coil raw materials has excellent magnetic properties and excellent coating adhesion.

[0022] (2) Under preferred conditions, select appropriate types and amounts of pickling accelerators, and reasonably control the relevant parameters in the preparation process of the oriented silicon steel pickling coil. The final oriented silicon steel pickling coil has a thickness of 2.3 to 2.6 mm, and the whiteness of the strip surface is above 65. After decarburization annealing in the subsequent process, the strip surface has a metallic luster and no defects such as blackening or darkening. Using this oriented silicon steel pickling coil, oriented silicon steel products of different thicknesses can be produced. Among them, the 0.27 mm thickness is graded 27Q095 to 110, the 0.23 mm thickness is graded 23Q085 to 100, and the 0.20 mm thickness is graded 20Q080 to 090. The coating adhesion of the oriented silicon steel products is grade 1, which meets the requirements of excellent magnetic properties and excellent coating adhesion of oriented silicon steel products. Attached Figure Description

[0023] Figure 1 This is a photograph of the pickled oriented silicon steel coil prepared in Example 1 of this invention.

[0024] Figure 2 The oriented silicon steel finished product prepared from the pickled coil of oriented silicon steel obtained in Example 1 in this invention;

[0025] Figure 3 This is a photograph of the pickled oriented silicon steel coil prepared in Comparative Example 1 of this invention.

[0026] Figure 4 The oriented silicon steel finished product prepared from the pickled coil of oriented silicon steel obtained in Comparative Example 1 in this invention;

[0027] Figure 5 This is a physical image of the pickled silicon steel coil prepared in Comparative Example 2 of this invention. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0029] Since iron oxide scale (FeO) has a fusiform structure, it is easy to clean. However, at temperatures of 350–570°C, fusiform FeO is unstable and will transform into Fe3O4, which is difficult to clean. Therefore, in order to reduce the possibility of FeO transforming into Fe3O4, hot-rolled coils are rapidly cooled in a protective atmosphere after coiling to quickly lower the temperature of the coil to below 350°C, which can effectively prevent the formation of difficult-to-clean Fe3O4.

[0030] To ensure thorough cleaning of the iron oxide scale on the strip surface, the pickling speed is determined based on the length of the pickling tank, ensuring a pickling time of no less than 90 seconds. To prevent over-pickling, an inhibitor is added to the acid solution, and the pickling time is required to be no more than 120 seconds. Because the outer ring of the strip cools faster after hot rolling and coiling than the inner ring, and spends more time in the high-temperature zone, the inner ring generally shows more severe oxidation than the outer ring. Therefore, to ensure consistent pickling quality across the entire strip coil, the pickling time at the strip head can be controlled at 90–100 seconds, and the pickling time at the strip tail can be controlled at 110–120 seconds. In this article, the strip head refers to the section from the beginning to one-third of the strip's length, and the strip tail refers to the section from two-thirds of the strip's length to the end.

[0031] To facilitate the removal of iron oxide scale from the surface of hot-rolled strip steel, a pickling accelerator is added to the acid solution during the pickling process. A complexing agent composed of sulfite and furan diketone derivatives containing carbon-carbon double bonds is used as a reducing agent. This complexing agent reacts with Fe3O4 and Fe2O3 on the outside of the iron oxide scale, which are difficult to clean, to generate Fuji body structure FeO, which is easy to pickle, thus promoting the removal of iron oxide scale.

[0032] The first aspect of this invention provides a method for preparing pickled coils of grain-oriented silicon steel, the method comprising the following steps:

[0033] Step S1: Heating the continuous casting slab and descaling the heated slab. Then, hot rolling the descaled slab to obtain a hot-rolled coil.

[0034] Step S2: Cool the hot-rolled coil in a protective atmosphere to obtain strip steel, and then perform shot blasting on the strip steel.

[0035] Step S3: Pickling the shot-blasted strip in an acid solution with added pickling accelerator to obtain a pickled plate. During the pickling process, the pickling time for the head of the strip is 90-100s, and the pickling time for the tail of the strip is 110-120s. The pickling accelerator includes a complexing agent composed of sulfite and furan dione derivatives containing carbon-carbon double bonds.

[0036] In a specific embodiment of the preparation method described in this invention, molten steel is continuously cast into a slab with a thickness of 200-230 mm.

[0037] In a specific embodiment of the preparation method described in this invention, the chemical composition of the continuously cast slab, by weight percentage, includes: C: 0.030–0.045%, for example, 0.030%, 0.035%, 0.037%, 0.038%, 0.039%, 0.040%, or 0.045%; Si: 3.05–3.30%, for example, 3.05%, 3.10%, 3.16%, 3.25%, or 3.30%; Mn: 0.15–0.25%, for example, 0.15%, 0.19%, 0.20%, or 0.25%; Als: 0.015–0.025%, for example, 0.015%, 0.020%, 0.023%, or 0.025%; N: 0.0080–0.0100%, For example, it can be 0.0080%, 0.0085%, 0.0090%, 0.0095%, or 0.0100%; S: 0.0050–0.0100%, for example, 0.0050%, 0.0055%, 0.0060%, 0.0065%, 0.0070%, 0.0080%, 0.0090%, or 0.0100%; Cu: 0.45–0.60%, for example, 0.45%, 0.48%, 0.49%, 0.50%, or 0.60%; P: ≤0.020%, for example, 0.013%, 0.014%, or 0.015%; Ti: ≤0.003%, for example, 0.0013%, 0.0018%, or 0.0020%; the remainder is Fe and unavoidable impurities.

[0038] In continuously cast slabs, a carbon content of less than 0.030% reduces the amount of γ-phase, or even eliminates phase transformation, while making hot rolling and cold rolling difficult, and hot-rolled plates are prone to transverse cracks. A carbon content greater than 0.045% leads to difficulties in decarburization during the decarburization process, increases the solution temperature of MnS, and requires higher heating temperatures for the slab. A silicon content of less than 3.05% reduces the magnetic properties of the finished product. Although a certain amount of Si can improve magnetic properties, when the silicon content is greater than 3.30%, the inhibitory effect weakens, which is detrimental to the development of secondary recrystallization. Furthermore, excessively high Si content hinders dynamic recrystallization during hot rolling, resulting in uneven microstructure and composition in the hot-rolled plate. For MnS, an inhibitor, a manganese content of less than 0.15% leads to a decrease in the amount of MnS, resulting in insufficient inhibitory effect; a manganese content greater than 0.25% leads to excessive MnS inhibitory effect, which is detrimental to secondary recrystallization. For Als (acid-soluble aluminum), an important inhibitor, a content of less than 0.015% leads to insufficient AlN, reducing... Low inhibition capacity: A content of acid-soluble aluminum greater than 0.025% can lead to surface quality problems such as gold leakage in the bottom layer of the finished product; a nitrogen content less than 0.0080% can lead to insufficient AlN inhibitors, while a nitrogen content greater than 0.0100% can easily cause bubble defects in the finished product; a sulfur content less than 0.0050% can lead to a reduction in MnS and insufficient inhibition capacity, while a sulfur content greater than 0.0100% can lead to difficulties in desulfurization during high-temperature purification; Cu2S, as an inhibitor in ordinary grain-oriented silicon steel, can also expand the γ phase region. A copper content less than 0.45% will reduce the number of Cu2S inhibitors, while a copper content greater than 0.60% will lead to the appearance of CuO in the oxide layer on the substrate surface, affecting decarburization efficiency; a phosphorus content greater than 0.020% can lead to uneven distribution of MnS in hot-rolled plates, reducing the magnetic properties of the finished product; as an impurity element, a titanium content greater than 0.003% can form TiN with nitrogen, reducing the nitrogen content, and at the same time forming stable carbides, hindering decarburization.

[0039] In a specific embodiment of the preparation method described in this invention, the continuously cast slab is directly loaded into a heating furnace for heating, the temperature of the soaking zone of the heating furnace is controlled at 1270-1320℃, and the total heating time is 250-300 min.

[0040] In a specific embodiment of the preparation method described in this invention, in order to reduce the content of iron oxide scale before rough rolling, the pressure of the dephosphorizing water used in the dephosphorization treatment is ≥200 bar. When the pressure of the dephosphorizing water is less than 200 bar, the iron oxide scale on the surface of the strip steel will not be completely removed, the subsequent pickling will be incomplete, the decarburization effect will be hindered, and the magnetic properties of the finished product will be affected.

[0041] In a specific embodiment of the preparation method described in this invention, the continuously cast slab after dephosphorization treatment is subjected to hot continuous rolling, wherein the hot continuous rolling includes rough rolling and finish rolling. Specifically, the continuously cast slab after dephosphorization treatment is rough rolled to an intermediate slab of 40-50 mm at a rough rolling temperature of 1070-1140°C, and then the intermediate slab is finish rolled to a strip of 2.2-2.6 mm thickness at a final rolling temperature of 940-970°C and a coiling temperature of 540-570°C.

[0042] In the actual operation of cooling the hot-rolled coil in a protective atmosphere, N2 cooling can be stopped when the strip temperature drops below 350°C, and air cooling can be selected instead.

[0043] In a specific embodiment of the preparation method described in this invention, the shot blasting speed is 60-80 m / s, for example, 60 m / s, 65 m / s, 70 m / s or 80 m / s. When the shot blasting speed is less than 60 m / s, the iron oxide scale on the strip surface is not completely broken up. When the shot blasting speed is greater than 80 m / s, pits are easily formed on the strip surface. The increased roughness leads to an increase in rolling force during the cold rolling process, and the rolling force is unstable.

[0044] In a specific embodiment of the preparation method described in this invention, the sulfite is ammonium sulfite hydrate or sodium sulfite; the furanyl dione derivative containing a carbon-carbon double bond is an organic compound in which the two ends of an alkane are respectively replaced by a carbon-carbon double bond and a furanyl dione; preferably, the alkane furanyl dione derivative containing a carbon-carbon double bond is 3-octadecane-dihydro-2,5-furanyl dione. In this document, the pickling accelerator further includes a surfactant, a stabilizer, and water, wherein the surfactant is sodium alkylbenzene sulfonate and / or sodium dodecylbenzene sulfonate, and the stabilizer is 1,4-butynediol.

[0045] In a specific embodiment of the preparation method described in this invention, based on the total mass of the pickling accelerator (100%), the content of ammonium sulfite hydrate or sodium sulfite is ≥30%. If the content of ammonium sulfite hydrate or sodium sulfite is less than 30%, the iron oxide scale on the strip surface will not be properly pickled. The content of 3-octadecane-dihydro-2,5-furandione is ≤5%. In a preferred embodiment, based on the total mass of the pickling accelerator (100%), the content of ammonium sulfite hydrate or sodium sulfite is 30-35%, for example, 30%, 31%, 32%, 33%, 34%, or 35%; the content of 3-octadecane-dihydro-2,5-furandione is 3-5%, for example, 3%, 4%, or 5%.

[0046] In a preferred embodiment of the preparation method of the present invention, the concentration of the pickling accelerator in the acid solution containing the pickling accelerator is 0.3 to 0.5%, for example, 0.3%, 0.4% or 0.5%. When the concentration of the pickling accelerator is less than 0.3%, the iron oxide scale on the surface of the strip steel will not be properly pickled.

[0047] In a specific embodiment of the preparation method described in this invention, the acid solution is hydrochloric acid, the concentration of hydrochloric acid is 150-200 g / L, and the temperature of hydrochloric acid is 85-90°C.

[0048] In a specific embodiment of the preparation method described in this invention, the silicon content in oriented silicon steel is high, and the weld is prone to breakage during continuous production. Therefore, the quality of the weld is very important during continuous production. To reduce the impact of pickling accelerator on weld quality, the shear blades of the crescent shears at the head and tail of the strip are coated with oil. At the same time, to reduce the contact time between the pickling accelerator and the weld, the strip speed is increased when the weld enters the acid solution, and then returned to normal speed when the weld exits the acid solution. Taking a domestic continuous rolling mill with a pickling tank length of 120m as an example, when the weld enters the acid tank, the pickling speed is increased from 60m / min to 80m / min, and when the weld exits the acid tank, the pickling speed is restored from 80m / min to 60m / min.

[0049] In a specific embodiment of the preparation method described in this invention, the pickled plate is cleaned in a rinsing tank and then dried, with the rinsing temperature being 50–90°C.

[0050] A second aspect of the present invention provides an oriented silicon steel pickled coil obtained according to the preparation method described above.

[0051] The third aspect of this invention provides a finished grain-oriented silicon steel product, which is obtained by first cold rolling, decarburization annealing, second cold rolling, and coating of the grain-oriented silicon steel pickled coil described above. The specific operation process is as follows: the grain-oriented silicon steel pickled coil is sequentially subjected to first cold rolling, decarburization annealing, second cold rolling, magnesium oxide coating, high-temperature annealing, tensile annealing, scoring, and slitting. In this document, the detailed operation processes of first cold rolling, decarburization annealing, second cold rolling, magnesium oxide coating, high-temperature annealing, tensile annealing, scoring, and slitting are all conventional technical means in the art.

[0052] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0053] Example 1

[0054] A method for preparing pickled coils of grain-oriented silicon steel, the method comprising the following steps:

[0055] Step S1: Molten steel is continuously cast into a continuous casting slab with a thickness of 230mm. The chemical composition of the continuous casting slab, by weight percentage, includes: C: 0.038%, Si: 3.25%, Mn: 0.20%, Als: 0.023%, N: 0.0095%, S: 0.0065%, Cu: 0.50%, P: 0.013%, Ti: 0.0013%, with the remainder being Fe and unavoidable impurities. The continuous casting slab is directly loaded into a heating furnace. The temperature of the soaking zone of the heating furnace is 1295℃, and the total heating time is 280min. After heating, the continuous casting slab is dephosphorized under a dephosphorizing water pressure of 210bar. The dephosphorized continuous casting slab is then rough-rolled to 42mm at 1110℃ to obtain an intermediate slab. The intermediate slab is then finish-rolled to a thickness of 2.3mm at a final rolling temperature of 955℃ and a coiling temperature of 550℃ to form a hot-rolled coil.

[0056] Step S2: After the hot-rolled coil is rolled, it is first cooled to 350°C in N2, and then air-cooled to obtain strip steel. The strip steel is then shot-blasted at a shot blasting speed of 65m / s.

[0057] Step S3: The shot-blasted steel strip is pickled in hydrochloric acid with added pickling accelerator. The concentration of hydrochloric acid is 180 g / L, and the temperature is 85°C. The pickling accelerator consists of 33% ammonium sulfite hydrate, 5% 3-octadecane-dihydro-2,5-furandione, 3% sodium dodecylbenzenesulfonate (surfactant), 3% 1,4-butynediol (stabilizer), and 56% water. The concentration of the pickling accelerator in the acid solution is 0.4%. The tank is 120m long. During the pickling process, the pickling speed from the head to 1 / 3 of the strip is 70m / min, and the pickling speed from 2 / 3 to the tail is 60m / min. During continuous production, the shear blade of the crescent shear at the weld of the strip is coated with oil. When the weld enters the pickling tank, the pickling speed is 80m / min. When the weld exits the pickling tank, the pickling speed returns to 70m / min. After pickling, the pickled plate is obtained. The pickled plate is cleaned in a rinsing tank and then dried. The rinsing temperature is 60℃ to obtain grain-oriented silicon steel pickled coil A1.

[0058] The surface whiteness of the pickled steel strip A1 is 65; the production success rate of grade 27Q095 using pickled steel strip A1 is over 50%, grade 23Q090 is over 50%, and grade 20Q085 is over 40%, with coating adhesion at level 1.

[0059] Example 2

[0060] A method for preparing pickled coils of grain-oriented silicon steel, the method comprising the following steps:

[0061] Step S1: Molten steel is continuously cast into a continuous casting slab with a thickness of 230mm. The chemical composition of the continuous casting slab, by weight percentage, includes: C: 0.037%, Si: 3.16%, Mn: 0.19%, Als: 0.020%, N: 0.0090%, S: 0.0060%, Cu: 0.48%, P: 0.015%, Ti: 0.0018%, with the remainder being Fe and unavoidable impurities. The continuous casting slab is directly loaded into a heating furnace. The temperature of the soaking zone of the heating furnace is 1280℃, and the total heating time is 280min. After heating, the continuous casting slab is dephosphorized under a dephosphorizing water pressure of 210bar. The dephosphorized continuous casting slab is then rough rolled to 45mm at 1100℃ to obtain an intermediate slab. The intermediate slab is then finish rolled to a thickness of 2.3mm at a final rolling temperature of 948℃ and a coiling temperature of 548℃ to form a hot-rolled coil.

[0062] Step S2: After the hot-rolled coil is rolled, it is first cooled to 350°C in N2, and then air-cooled to obtain strip steel. The strip steel is then shot-blasted at a shot blasting speed of 65m / s.

[0063] Step S3: The shot-blasted steel strip is pickled in hydrochloric acid with added pickling accelerator. The concentration of hydrochloric acid is 165 g / L, and the temperature is 84°C. The pickling accelerator consists of 30% sodium sulfite, 4% 3-octadecane-dihydro-2,5-furandione, 3% sodium alkylbenzene sulfonate (surfactant), 3% 1,4-butynediol (stabilizer), and 60% water. The concentration of the pickling accelerator in the acid solution is 0.3%. The acid tank length is... The pickling speed is 120m. During the pickling process, the pickling speed from the head to 1 / 3 of the strip is 75m / min, and the pickling speed from 2 / 3 to the tail is 65m / min. During continuous production, the shear blade of the crescent shear at the weld of the strip is coated with oil. When the weld enters the pickling tank, the pickling speed is 80m / min. When the weld exits the pickling tank, the pickling speed returns to 65m / min. After pickling, the pickled plate is obtained. The pickled plate is cleaned in a rinsing tank and then dried. The rinsing temperature is 60℃ to obtain the grain-oriented silicon steel pickled coil A2.

[0064] The surface whiteness of the pickled steel strip A2 is 63; the production success rate of grade 27Q095 using pickled steel strip A2 is over 45%, grade 23Q090 is over 45%, and grade 20Q085 is over 35%, with coating adhesion at level 1.

[0065] Example 3

[0066] A method for preparing pickled coils of grain-oriented silicon steel, the method comprising the following steps:

[0067] Step S1: Molten steel is continuously cast into a continuous casting slab with a thickness of 230mm. The chemical composition of the continuous casting slab, by weight percentage, includes: C: 0.039%, Si: 3.10%, Mn: 0.20%, Als: 0.020%, N: 0.0085%, S: 0.0065%, Cu: 0.49%, P: 0.014%, Ti: 0.0020%, with the remainder being Fe and unavoidable impurities. The continuous casting slab is directly loaded into a heating furnace. The temperature of the soaking zone of the heating furnace is 1285℃, and the total heating time is 280min. After heating, the continuous casting slab is dephosphorized under a dephosphorizing water pressure of 205bar. The dephosphorized continuous casting slab is then rough-rolled to 42mm at 1085℃ to obtain an intermediate slab. The intermediate slab is then finish-rolled to a thickness of 2.3mm at a final rolling temperature of 945℃ and a coiling temperature of 545℃ to form a hot-rolled coil.

[0068] Step S2: After the hot-rolled coil is rolled, it is first cooled to 350°C in N2, and then air-cooled to obtain strip steel. The strip steel is then shot-blasted at a shot blasting speed of 65m / s.

[0069] Step S3: The shot-blasted steel strip is pickled in hydrochloric acid with added pickling accelerator. The concentration of hydrochloric acid is 155 g / L, and the temperature is 86°C. The pickling accelerator consists of 30% sodium sulfite, 3% 3-octadecane-dihydro-2,5-furandione, 3% sodium alkylbenzene sulfonate (surfactant), 3% 1,4-butynediol (stabilizer), and 61% water. The concentration of the pickling accelerator in the acid solution is 0.25%. The acid tank length is... The pickling speed is 120m. During the pickling process, the pickling speed from the head to 1 / 3 of the strip is 80m / min, and the pickling speed from 2 / 3 to the tail is 65m / min. During continuous production, the shear blade of the crescent shear at the weld of the strip is coated with oil. When the weld enters the pickling tank, the pickling speed is 80m / min. When the weld exits the pickling tank, the pickling speed returns to 65m / min. After pickling, the pickled plate is obtained. The pickled plate is cleaned in a rinsing tank and then dried. The rinsing temperature is 60℃ to obtain the grain-oriented silicon steel pickled coil A3.

[0070] The surface whiteness of the pickled steel strip A3 is 60; the production success rate of grade 27Q095 using pickled steel strip A3 is over 40%, grade 23Q090 is over 40%, and grade 20Q085 is over 30%, with coating adhesion at level 1.

[0071] Comparative Example 1

[0072] A method for preparing pickled coils of grain-oriented silicon steel, the method comprising the following steps:

[0073] Step S1: Molten steel is continuously cast into a continuous casting slab with a thickness of 230mm. The chemical composition of the continuous casting slab, by weight percentage, includes: C: 0.038%, Si: 3.25%, Mn: 0.20%, Als: 0.023%, N: 0.0095%, S: 0.0065%, Cu: 0.50%, P: 0.013%, Ti: 0.0013%, with the remainder being Fe and unavoidable impurities. The continuous casting slab is directly loaded into a heating furnace. The temperature of the soaking zone of the heating furnace is 1270℃, and the total heating time is 280min. After heating, the continuous casting slab is dephosphorized under a dephosphorizing water pressure of 190bar. The dephosphorized continuous casting slab is then rough rolled to 42mm at 1070℃ to obtain an intermediate slab. The intermediate slab is then finish rolled to a thickness of 2.3mm at a final rolling temperature of 955℃ and a coiling temperature of 550℃ to form a hot-rolled coil.

[0074] Step S2: After the hot-rolled coil is rolled, it is first cooled to 350°C in N2, and then air-cooled to obtain strip steel. The strip steel is then shot-blasted at a shot blasting speed of 55m / s.

[0075] Step S3: Pickle the shot-blasted strip in hydrochloric acid with a concentration of 140 g / L and a temperature of 85°C. The length of the pickling tank is 120 m, and the pickling speed of the strip is 70 m / min. After pickling, a pickled plate is obtained. The pickled plate is then cleaned in a rinsing tank and dried. The rinsing temperature is 60°C to obtain pickled coil B1 of oriented silicon steel.

[0076] The surface whiteness of the pickled steel strip B1 of oriented silicon steel is 45. The production of grade 27Q095 using pickled steel strip B1 has a hit rate of over 20%, grade 23Q090 has a hit rate of over 10%, and grade 20Q085 has a hit rate of over 20%. The coating adhesion is grade 2-3, and the coating adhesion is unqualified.

[0077] Comparative Example 2

[0078] A method for preparing pickled coils of grain-oriented silicon steel, the method comprising the following steps:

[0079] Step S1: Molten steel is continuously cast into a continuous casting slab with a thickness of 230mm. The chemical composition of the continuous casting slab, by weight percentage, includes: C: 0.038%, Si: 3.13%, Mn: 0.20%, Als: 0.020%, N: 0.0083%, S: 0.0065%, Cu: 0.49%, P: 0.015%, Ti: 0.0020%, with the remainder being Fe and unavoidable impurities. The continuous casting slab is directly loaded into a heating furnace. The temperature of the soaking zone of the heating furnace is 1285℃, and the total heating time is 280min. After heating, the continuous casting slab is dephosphorized under a dephosphorizing water pressure of 190bar. The dephosphorized continuous casting slab is then rough-rolled to 42mm at 1085℃ to obtain an intermediate slab. The intermediate slab is then finish-rolled to a thickness of 2.3mm at a final rolling temperature of 945℃ and a coiling temperature of 545℃ to form a hot-rolled coil.

[0080] Step S2: The hot-rolled coil is air-cooled after being rolled to obtain strip steel, and the strip steel is shot-blasted at a shot blasting speed of 50m / s.

[0081] Step S3: The shot-blasted strip steel is pickled in hydrochloric acid with added pickling accelerator. The concentration of hydrochloric acid is 140 g / L, and the temperature of hydrochloric acid is 85℃. The pickling accelerator consists of 15% sodium sulfite, 1% 3-octadecane-dihydro-2,5-furandione, 3% sodium alkylbenzene sulfonate (surfactant), 3% 1,4-butynediol (stabilizer), and 75% water. The concentration of the pickling accelerator in the acid solution is 0.15%. The length of the acid tank is 120 m, and the pickling speed of the strip steel is 120 m / min. During continuous production, the shear blade of the crescent shear at the weld seam of the strip steel is coated with oil. After pickling, a pickled plate is obtained. The pickled plate is cleaned in a rinsing tank and then dried. The rinsing temperature is 60℃ to obtain pickled coil B2 of oriented silicon steel.

[0082] The surface whiteness of pickled steel strip B2 is 55, and the surface is dark. Using pickled steel strip B2, the success rate of producing grade 27Q095 is over 30%, grade 23Q090 is over 30%, grade 20Q085 is over 30%, and the pass rate of coating adhesion grade 1 is 70%.

[0083] Test case

[0084] The pickled coils A1 to A3 and B1 to B2 of grain-oriented silicon steel are sequentially subjected to one cold rolling, decarburization annealing, two cold rolling, MgO coating, high temperature annealing, stretching annealing, scoring and slitting to obtain the finished grain-oriented silicon steel products A1 to A3 and B1 to B2, respectively.

[0085] The magnetic properties of the oriented silicon steel products A1-A3 and B1-B2 were tested using the GB / T 3655 method. The test results are shown in Table 1.

[0086] Table 1 shows the test results (mean values) of the magnetic induction performance of A1~A3 and B1~B2.

[0087]

[0088] According to the results in Table 1, the iron loss P of oriented silicon steel products of different thicknesses prepared from pickled coils A1 to A3 of oriented silicon steel is... 1.7 / 50 Both the magnetic properties of the B8 and B1-B2 pickled silicon steel coils produced by this invention are superior to those of the finished oriented silicon steel products. This is because, in the process of preparing the pickled silicon steel coils, the surface of the strip is first rapidly cooled to a certain temperature using inert gas after hot rolling to prevent the formation of Fe3O4. At the same time, a specific type of pickling accelerator is added during the pickling process to promote the cleaning of iron oxide scale on the surface of the hot-rolled strip. The pickling time of the strip is also controlled to ensure the consistency of the pickling quality of the entire coil. Therefore, the finished oriented silicon steel products produced using the pickled silicon steel coils obtained by this invention have excellent magnetic properties, which is of great significance in reducing energy consumption, improving equipment efficiency, and enhancing equipment stability.

[0089] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing pickled coils of grain-oriented silicon steel, characterized in that, The preparation method includes the following steps: Step S1: Heating the continuous casting slab and descaling the heated slab. Then, hot rolling the descaled slab to obtain a hot-rolled coil. Step S2: Cool the hot-rolled coil in a protective atmosphere to obtain strip steel, and then perform shot blasting on the strip steel. Step S3: Pickling the shot-blasted strip in an acid solution with added pickling accelerator. During the pickling process, the pickling time for the head of the strip is 90-100 s and the pickling time for the tail of the strip is 110-120 s. The pickling accelerator includes a complexing agent composed of sulfite and furan dione derivatives containing carbon-carbon double bonds. In the above steps, the sulfite is ammonium sulfite hydrate or sodium sulfite; the furanedione derivative containing a carbon-carbon double bond is 3-octadecane-dihydro-2,5-furanedione. Based on the total mass of the pickling accelerator as 100%, the content of ammonium sulfite hydrate or sodium sulfite is ≥30%, and the content of 3-octadecane-dihydro-2,5-furandione is ≤5%; In the acid solution with added pickling accelerator, the concentration of the pickling accelerator is 0.3~0.5%; the acid solution is hydrochloric acid, the concentration of hydrochloric acid is 150~200 g / L, and the temperature of hydrochloric acid is 85~90 ℃.

2. The method for preparing pickled silicon steel coils according to claim 1, characterized in that, Based on the total mass of the pickling accelerator as 100%, the content of ammonium sulfite hydrate or sodium sulfite is 30-35%, and the content of 3-octadecane-dihydro-2,5-furandione is 3-5%.

3. The method for preparing pickled coils of grain-oriented silicon steel according to claim 1, characterized in that, The chemical composition of the continuously cast slab, by weight percentage, includes: C: 0.030~0.045%, Si: 3.05~3.30%, Mn: 0.15~0.25%, Als: 0.015~0.025%, N: 0.0080~0.0100%, S: 0.0050~0.0100%, Cu: 0.45~0.60%, P: ≤0.020%, Ti: ≤0.003%, with the remainder being Fe and unavoidable impurities.

4. The method for preparing pickled coils of grain-oriented silicon steel according to claim 1, characterized in that, In the above steps, the pressure of the dephosphorization water used in the dephosphorization treatment is ≥200 bar; in the shot blasting treatment, the shot blasting speed is 60~80 m / s.

5. An oriented silicon steel pickled coil obtained by the preparation method according to any one of claims 1 to 3.

6. A finished grain-oriented silicon steel product, characterized in that, The finished grain-oriented silicon steel is obtained by the pickling of the grain-oriented silicon steel coil described in claim 4, followed by one cold rolling, decarburization annealing, a second cold rolling, and coating.

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