Method for improving bottom layer quality of copper-containing oriented silicon steel and copper-containing oriented silicon steel

Abstract

The invention discloses a method for improving the bottom layer quality of copper-containing oriented silicon steel and the copper-containing oriented silicon steel, and belongs to the technical field of electrical steel manufacturing. The method for improving the quality of the copper-containing oriented silicon steel bottom layer comprises the steps that molten steel with specific components is smelted and then subjected to continuous casting to form a blank, then the plate blank is subjected to heating, hot rolling and acid pickling and then subjected to primary cold rolling to obtain a primary cold-rolled plate, then the primary cold-rolled plate is subjected to intermediate annealing and secondary cold rolling to obtain a secondary cold-rolled plate, and the secondary cold-rolled plate is subjected to hot rolling and acid pickling to obtain the copper-containing oriented silicon steel bottom layer. And after decarburization annealing is conducted on the secondary cold-rolled sheet, the secondary cold-rolled sheet is coated with a separant, then high-temperature annealing and purification annealing are conducted in sequence, and finally uncoiling, flat stretching annealing and insulating coating coating are conducted to obtain the copper-containing oriented silicon steel. According to the method, the machining stress of secondary rolling is eliminated, the situation that the oxidation film is broken due to the too large pressing rate is avoided, the glass film bottom layer good in quality is obtained, the magnetic performance of a product is improved, and iron loss is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical steel manufacturing, and in particular relates to a method for improving the quality of a bottom layer of copper-containing oriented silicon steel and the copper-containing oriented silicon steel. Background Art

[0002] Oriented silicon steel consists of a single Goss orientation ({110} <001> ) grain composition, has the characteristics of high magnetic induction and low iron loss when magnetized along the rolling direction, so it is mainly used to produce transformer cores. For ordinary oriented silicon steel and high magnetic induction oriented silicon steel with MnS as an inhibitor, decarburization annealing will be carried out in a humid nitrogen and hydrogen atmosphere at around 830℃ after cold rolling to the final thickness, and an oxide layer mainly composed of SiO2 will be formed. During the high-temperature annealing process, SiO2 reacts with MgO coated on the surface in the range of 900~1100℃ to form a magnesium silicate bottom layer. The quality of the magnesium silicate bottom layer not only affects the adhesion of the surface insulating coating, but also affects the tension effect of the insulating coating, thereby affecting the magnetic properties of the product. Studies have shown that the quality of the magnesium silicate bottom layer depends largely on whether the quality of the SiO2 layer formed during the decarburization process is good.

[0003] In the 1970s and 1980s, the Novolipetsk Plant and the Verkhniy Isetsky Plant in the Soviet Union developed Cu-containing oriented silicon steel, which has low C content and high Mn content. At the same time, about 0.5% Cu is added, with Cu2S (ε-Cu) and AlN as inhibitors. Its main production process is: ironmaking → desulfurization → converter or electric furnace steelmaking → refining → continuous casting → hot rolling → pickling → primary cold rolling → decarburization annealing → secondary cold rolling → recovery treatment (can be omitted) → MgO coating → high temperature annealing → flat stretching annealing → insulation coating. By adopting the above process, the hot rolling heating temperature can be reduced to 1250~1300 ℃, and normalization treatment is not required. The secondary cold rolling method is adopted. In addition, due to the low carbon content, decarburization annealing is carried out after the first rolling. The Cu-containing oriented silicon steel is completely decarburized in the moist nitrogen and hydrogen atmosphere of the intermediate annealing, and an oxide layer is formed on the surface, thereby greatly simplifying the production process. However, the oxide layer of the intermediate annealed sheet may crack or peel off during the secondary cold rolling process with a reduction rate of about 70%. Since the secondary cold rolled sheet is often coated with MgO directly or after low temperature recovery, the damaged oxide layer cannot be regenerated, which will deteriorate the quality of the magnesium silicate base layer and reduce the magnetic properties of the product.

[0004] How to obtain Cu-containing oriented silicon steel products with good bottom layer quality is still a problem that needs to be solved urgently in this field. Researchers have proposed a variety of methods to improve the bottom layer quality, but there are problems such as poor improvement effect or high cost. It is still necessary to propose a new method to improve the bottom layer quality of Cu-containing oriented silicon steel while saving production costs. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for improving the quality of the bottom layer of copper-containing oriented silicon steel and copper-containing oriented silicon steel. The present invention eliminates the processing stress of the secondary rolling through intermediate annealing after the primary cold rolling and decarburization annealing after the secondary cold rolling, and simultaneously coordinates the control of other process parameters, thereby avoiding the rupture of the oxide film caused by excessive pressing rate, obtaining a glass film bottom layer of good quality, improving the magnetic properties of the product, and reducing the iron loss.

[0006] The technical solution of the present invention is as follows: The present invention firstly protects a method for improving the quality of the bottom layer of copper-containing oriented silicon steel, the method comprising the following steps: S1: smelting molten steel and then continuously casting it into billets.

[0007] S2: After heating, hot rolling and pickling the slab, cold rolling is performed once to obtain a primary cold-rolled sheet.

[0008] S3: intermediate annealing is performed on the primary cold rolled sheet.

[0009] S4: Then, secondary cold rolling is performed to obtain a secondary cold rolled sheet.

[0010] S5: After the secondary cold rolled sheet is decarburized and annealed, a release agent is coated on the surface.

[0011] S6: The plate coated with the release agent is subjected to high temperature annealing and purification annealing in sequence, and then unrolled, flattened and stretched for annealing, and coated with an insulating coating to obtain copper-containing oriented silicon steel.

[0012] In step S1, the molten steel includes the following components, by mass percentage: C 0.01-0.04%, Si 2.8-3.4%, Mn 0.10-0.35%, S 0.01-0.03%, Als 0.005-0.04%, N 0.005-0.015%, Cu 0.4-0.6%, O<0.004%, P<0.01%, and the balance is Fe.

[0013] In step S3, the intermediate annealing is performed in an atmosphere of pure dry argon or pure dry nitrogen, at a temperature of 800-900° C., for a time of 3-10 min.

[0014] In step S4, the thickness of the secondary cold-rolled sheet is 0.20-0.23 mm.

[0015] In step S5, the decarburization annealing is performed at a temperature of 800-900°C and for a time of 3-10 minutes.

[0016] In step S6, the high temperature annealing atmosphere is a mixed atmosphere of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 70-80%.

[0017] Preferably, in step S2, the thickness of the primary cold-rolled sheet is 0.6-0.7 mm.

[0018] Preferably, in step S5, the decarburization annealing atmosphere is a mixed atmosphere of hydrogen and nitrogen, and the atmosphere dew point is 20-50° C.; and the volume percentage of hydrogen in the mixed atmosphere is 40-60%.

[0019] Preferably, in step S5, the isolation agent includes a magnesium oxide isolation agent.

[0020] Preferably, in step S6, the specific process of high temperature annealing and purification annealing is: heating the plate coated with the isolation agent to 780-830°C, then heating to 1180-1250°C at 10-30°C / h to complete high temperature annealing, and then keeping it at the same temperature for 20-22h to complete purification annealing.

[0021] Preferably, the atmosphere of the purification annealing is a pure hydrogen atmosphere.

[0022] The second aspect of the present invention protects a copper-containing oriented silicon steel prepared by the method described in the first aspect.

[0023] The beneficial technical effects of the present invention are: The present invention adopts intermediate annealing instead of decarburization annealing after sequential cold rolling, and performs decarburization annealing after secondary cold rolling, so as to eliminate the processing stress of the secondary rolling, ensure the formation of a uniform oxide layer mainly composed of SiO2, and fundamentally avoid the oxide layer from cracking and peeling due to rolling deformation, resulting in the magnesium silicate bottom layer formed by the reaction with magnesium oxide in the high-temperature annealing stage being not dense and having uneven thickness, thereby resulting in poor bottom layer adhesion of the oriented silicon steel finished product, and ultimately affecting the magnetic properties of the product, thereby obtaining a glass film bottom layer of good quality.

[0024] The main process of decarburization is the diffusion of carbon atoms. The thicker the steel strip is, the farther the carbon atoms inside the steel strip diffuse, and the longer the decarburization time is. The present invention further limits the thickness of the primary cold-rolled sheet to 0.60-0.70 mm, and the thickness of the secondary cold-rolled sheet to 0.20-0.23 mm. The thickness is relatively small, and decarburizing the secondary cold-rolled sheet can significantly reduce the decarburization load of the production line, thereby ensuring the decarburization effect.

[0025] The manufacturing method of the present invention is an improvement based on the existing process, and the preparation is simple and effective without adding additional costs. At the same time, it has the characteristics of being easy to control and can be better used in actual production improvements. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a schematic diagram of the manufacturing process of the copper-containing oriented silicon steel.

[0027] Figure 2Surface morphology of silicon steel prepared in Examples 1-3 of the present invention and Comparative Example 2.

[0028] Figure 2 In the figure: (a) is Example 1; (b) is Example 2; (c) is Example 3; (d) is Comparative Example 2. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0030] In the preparation of copper-containing oriented silicon steel, it generally undergoes a process of primary cold rolling, decarburization annealing, secondary cold rolling, and high-temperature annealing. Among them, the main purpose of decarburization annealing after primary rolling is: (1) to complete the primary recrystallization so that the copper-containing oriented silicon steel matrix contains a sufficient amount of Gaussian texture; (2) to remove carbon from the steel to a specific range to ensure that the high-temperature annealing is in a single phase region, preparing for the secondary recrystallization to form a Gaussian texture; (3) to obtain a good SiO2 layer on the surface of the steel plate, and finally obtain a good magnesium silicate bottom layer on the surface of the steel plate after high-temperature annealing. After applying an insulating coating on this basis, a good finished product insulation layer effect can be obtained. However, after a primary cold rolling and then decarburization annealing, the SiO2 layer generated on the surface cracks and peels off as the secondary rolling proceeds, thereby affecting the quality of the final surface layer and causing surface damage, shedding and other problems.

[0031] The present invention adopts intermediate annealing after the first cold rolling, and the intermediate annealing is carried out under dry 100% nitrogen or dry 100% hydrogen. After the second cold rolling, decarburization is carried out to obtain an oxide layer mainly composed of SiO2, which fundamentally avoids the SiO2 layer from being easily damaged due to the rolling pressure and roller friction during the second rolling process, resulting in the magnesium silicate bottom layer formed by the reaction with magnesium oxide in the high-temperature annealing stage being not dense and having uneven thickness, thereby resulting in poor bottom layer adhesion of the oriented silicon steel finished product, which ultimately affects the magnetic properties of the product. At the same time, the present invention can eliminate the processing stress of the second rolling and avoid the complete disappearance of the Gaussian texture caused by excessive pressure reduction through intermediate annealing after the first cold rolling. At the same time, a sufficient number of Gaussian structures are obtained through intermediate annealing, which eliminates the stress for the second cold rolling process and forms the first crystal grains.

[0032] The first aspect of the present invention provides a method for improving the quality of the bottom layer of copper-containing oriented silicon steel, such as Figure 1 As shown, the following steps are included: S1: smelting molten steel and continuously casting it into billets; S2: After heating, hot rolling and pickling the slab, cold rolling is performed once to obtain a cold-rolled sheet; S3: intermediate annealing of the primary cold rolled sheet; S4: then performing secondary cold rolling to obtain a secondary cold rolled sheet; S5: After decarburization annealing of the secondary cold rolled sheet, a release agent is coated on the surface; S6: The plate coated with the release agent is subjected to high temperature annealing and purification annealing in sequence, and then unrolled, flattened and stretched for annealing, and coated with an insulating coating to obtain copper-containing oriented silicon steel.

[0033] In some embodiments, in step S1, the molten steel includes the following components, by mass percentage: C 0.01-0.04%, Si 2.8-3.4%, Mn 0.10-0.35%, S 0.01-0.03%, Als 0.005-0.04%, N 0.005-0.015%, Cu 0.4-0.6%, O<0.004%, P<0.01%, and the balance is Fe.

[0034] It can be understood that the heating, hot rolling, pickling, etc. in step S2 of the present invention are conventional technical processes in the field, and the present invention is not limited to this. The process methods and conditions that can achieve the purpose of the present invention are within the protection scope of the present invention.

[0035] It is understood that in step S2, heating is heating the ingot to 1250-1300° C. The temperature of hot rolling is 1120-1140° C. The temperature of pickling is 85-90° C., and the reagent used for pickling includes hydrochloric acid. Preferably, the pickling reagent is hydrochloric acid with a mass concentration of 25-31%.

[0036] In some embodiments, in step S3, the intermediate annealing atmosphere is argon or nitrogen. Preferably, the intermediate annealing atmosphere is dry 100% argon or dry 100% nitrogen.

[0037] In some embodiments, the intermediate annealing temperature is 800-900°C, including but not limited to 800°C, 820°C, 840°C, 860°C, 880°C, 900°C; the time is 3-10 min, including but not limited to 3 min, 5 min, 7 min, 9 min, 10 min.

[0038] It can be understood that, in the present invention, by limiting the annealing after the first cold rolling to intermediate annealing rather than decarburization annealing, and combining the control of the annealing time, the completion of decarburization is ensured, while the damage to the surface caused by the secondary cold rolling is avoided.

[0039] In some embodiments, in step S2, the thickness of the primary cold-rolled sheet is 0.6-0.7 mm, including but not limited to 0.60 mm, 0.62 mm, 0.64 mm, 0.68 mm, and 0.70 mm.

[0040] In some embodiments, in step S4, the thickness of the secondary cold rolled sheet is 0.20-0.23 mm, including but not limited to 0.20 mm, 0.21 mm, 0.22 mm, and 0.23 mm.

[0041] It is understandable that the change in the crystal structure of the steel in the secondary cold rolling will be different if the thickness of the primary cold rolled sheet is different. The present invention ensures that the secondary cold rolling has no effect on the crystal structure of the steel surface by limiting the thickness of the primary cold rolled sheet, thereby improving the quality of the steel surface. In addition, the main process of decarburization is the diffusion of carbon atoms. The thicker the steel strip is, the farther the carbon atoms inside the steel strip diffuse, and the longer the time required for decarburization. The present invention can significantly reduce the decarburization load of the production line when decarburizing the secondary cold rolled sheet by limiting the thickness of the primary cold rolling and the secondary cold rolling, thereby ensuring the decarburization effect.

[0042] In some embodiments, in step S5, the temperature of decarburization annealing is 800-900°C, including but not limited to 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, and the time is 3-10 min, including but not limited to 3 min, 5 min, 7 min, 8 min, 9 min, 10 min.

[0043] In some embodiments, in step S5, the atmosphere of the decarburization annealing is a mixed atmosphere of hydrogen and nitrogen, and the atmosphere dew point is 20-50°C, including but not limited to 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C.

[0044] In some embodiments, the volume percentage of hydrogen in the mixed atmosphere is 40-60%, including but not limited to 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, and 60%.

[0045] In some embodiments, in step S5, the release agent includes a magnesium oxide release agent.

[0046] In some embodiments, in step S6, the specific process of high temperature annealing and purification annealing is: heating the plate coated with the release agent to 780-830°C, then heating to 1180-1250°C at 10-30°C / h to complete high temperature annealing, and then keeping at the same temperature for 20-22h to complete purification annealing. It is understood that heating to 780-830°C includes but is not limited to 780°C, 790°C, 800°C, 810°C, 820°C, and 830°C. Heating to 1180-1250°C at 10-30°C / h includes but is not limited to heating to 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, 1230°C, 1240°C, or 1250°C at 10°C / h, 15°C / h, 20°C / h, 25°C / h, or 30°C / h.

[0047] In some embodiments, the atmosphere for high temperature annealing is a mixed atmosphere of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 70-80%, including but not limited to 70%, 72%, 74%, 76%, 78%, and 80%.

[0048] In some embodiments, the atmosphere of the purification annealing is a pure hydrogen atmosphere.

[0049] It can be understood that the high temperature annealing and purification annealing process of the present invention can utilize secondary recrystallization to form a single Goss texture; a glass film bottom layer is formed by the reaction of magnesium oxide with silicon dioxide in the surface oxide film; in addition, sulfur and nitrogen in the steel can be removed, and at the same time, the secondary grains are swallowed up and dispersed by the participating primary grains, so that the secondary grain structure is more complete and the grain boundaries are straighter.

[0050] The second aspect of the present invention protects a copper-containing oriented silicon steel prepared by the method of the first aspect. The prepared oriented silicon steel has better bottom layer quality, low iron loss, and higher magnetic induction.

[0051] The present invention is further described below by way of examples etc. It should be understood that the following contents are further descriptions of the present invention and cannot be regarded as limitations of the present invention. Example 1

[0052] The method for improving the quality of the bottom layer of copper-containing oriented silicon steel comprises the following steps: S1: Molten steel is smelted according to the set composition to obtain a continuous casting billet; wherein the molten steel containing Cu-oriented silicon steel comprises the following components by mass percentage (recorded as: component 1): C 0.03%, Si 3.1%, Mn 0.20%, S 0.02%, Als 0.02%, N0.01%, Cu 0.5%, O<0.004%, P<0.01%, and the balance is Fe.

[0053] S2: After heating the slab to 1300°C, hot rolling is performed at 1120°C to obtain a hot-rolled plate. The hot-rolled plate is pickled with 25% by mass hydrochloric acid to remove surface iron oxide scale, and then cold rolled to 0.6 mm to obtain a primary cold-rolled plate.

[0054] S3: intermediate annealing is performed at a temperature of 830°C for 6 minutes in an annealing atmosphere of dry 100% argon.

[0055] S4: The steel sheet after intermediate annealing is subjected to secondary cold rolling, and the intermediate annealing sheet is cold rolled to 0.2 mm to obtain a secondary cold rolled sheet.

[0056] S5: Decarburization annealing is then performed at a temperature of 830°C for 6 minutes in an annealing atmosphere of 50% hydrogen, 50% nitrogen and water vapor with an atmosphere dew point of 37°C. Subsequently, MgO isolating agent is applied on the surface of the decarburization annealed plate.

[0057] S6: The plate coated with MgO insulating agent is heated to 800°C, and then the temperature is increased to 1200°C at a rate of 15°C / h to complete high temperature annealing, and then kept at 1200°C for 20 hours to complete purification annealing, and finally uncoiling, flattening and stretching annealing and MgO insulation layer coating are performed to make Cu-containing oriented silicon steel, wherein the atmosphere of high temperature annealing is a mixed atmosphere of hydrogen and nitrogen, and the volume percentage of hydrogen is 75%; the atmosphere of purification annealing is a pure hydrogen atmosphere.

[0058] like Figure 2 As shown in Figure (a), the glass film of the copper-containing oriented silicon steel product is uniform without cracking or peeling; the magnetic induction B8 is 1.91T; the iron loss P of the finished product is 17 / 50 0.94W / kg; thickness 0.20mm. Comparative Example 1

[0059] The composition of the molten steel is the same as that of Example 1, and the preparation method is basically the same as that of Example 1, except that a steel plate with a different composition is used. The composition of the molten steel is as follows in mass percentage: C 0.04%, Si 3.0%, Mn 0.01%, S 0.05%, Als0.02%, N 0.02%, O<0.004%, P<0.01%, and the balance is Fe.

[0060] The preparation method of Comparative Example 1 is the same as that of Example 1. The glass film of the oriented silicon steel product obtained is not damaged; the magnetic induction B8 of the finished product is 1.85T; the iron loss P 17 / 50 It is 1.29W / kg.

[0061] By comparing Example 1 and Comparative Example 1, it can be seen that the inhibitor affects the final magnetic properties of the finished product. Mn and Cu are the main components of the inhibitor. Because the content of Mn and Cu is reduced under this composition, the composition of the inhibitor is reduced, which increases the iron loss. Example 2

[0062] The method for improving the quality of the bottom layer of copper-containing oriented silicon steel comprises the following steps: S1: Molten steel is smelted according to the set composition to obtain a continuous casting billet; wherein the molten steel containing Cu-oriented silicon steel comprises the following components in percentage by mass (recorded as: component 2): C 0.01%, Si 2.8%, Mn 0.2%, S 0.025%, Als 0.03%, N0.01%, Cu 0.52%, O<0.004%, P<0.01%, and the balance is Fe.

[0063] S2: The slab is heated and hot-rolled to obtain a hot-rolled plate, the hot-rolled plate is pickled to remove the surface iron oxide scale, and then cold-rolled to 0.65 mm to obtain a primary cold-rolled plate.

[0064] S3: perform intermediate annealing at a temperature of 840° C. for 6 min in an annealing atmosphere of pure dry nitrogen.

[0065] S4: The intermediate annealed sheet is subjected to secondary cold rolling to obtain a secondary cold rolled sheet to a thickness of 0.23 mm.

[0066] S5: Decarburization annealing is then performed at a temperature of 830°C for 6 minutes in an annealing atmosphere of 50% hydrogen, 50% nitrogen and water vapor, with an atmosphere dew point of 37°C, and then MgO is coated on the surface of the decarburization annealed plate.

[0067] S6: The MgO-coated plate is heated to 800°C, and then the temperature is increased to 1200°C at a rate of 15°C / h to complete high temperature annealing, and then kept at 1200°C for 20 hours to complete purification annealing, and finally uncoiling, flattening and stretching annealing and insulating layer coating are performed to make Cu-containing oriented silicon steel, wherein the atmosphere of the high temperature annealing is a mixed atmosphere of hydrogen and nitrogen, and the volume percentage of hydrogen is 75%; the atmosphere of the purification annealing is a pure hydrogen atmosphere.

[0068] The magnetic induction B8 of the obtained copper-containing oriented silicon steel is 1.89T; Figure 2 As shown in Figure (b), the finished glass film is uniform without cracks or peeling; the iron loss of the finished product is P 17 / 50 0.96W / kg; thickness 0.23mm. Comparative Example 2

[0069] The composition of the molten steel is the same as that in Example 2, and the preparation method is basically the same as that in Example 2. The difference is that in the experiment, decarburization annealing is carried out after the first cold rolling, the decarburization annealing temperature is 840°C, and the time is 6 minutes. Subsequently, secondary cold rolling, 550°C recovery and MgO coating are carried out after high-temperature annealing to obtain copper-containing oriented silicon steel, wherein the thickness of the steel plate obtained by the secondary cold rolling is 0.23 mm, the temperature of the recovery treatment is 580°C, and the time is 6 minutes, and the coating of magnesium oxide and the subsequent processes are the same as in Example 2.

[0070] like Figure 2 As shown in Figure (d), the glass film of the oriented silicon steel product obtained in Comparative Example 2 is damaged in some areas; the magnetic induction B8 is 1.88T; the iron loss P 17 / 50 It is 1.07W / kg. Example 3

[0071] The method for improving the quality of the bottom layer of copper-containing oriented silicon steel comprises the following steps: S1: Molten steel is smelted according to the set composition to obtain a continuous casting billet; wherein the molten steel containing Cu-oriented silicon steel comprises the following components by mass percentage (recorded as: component 3): C 0.032%, Si 3.0%, Mn 0.25%, S 0.02%, Als 0.035%, N0.01%, Cu 0.45%, O<0.004%, P<0.01%, and the balance is Fe.

[0072] S2: The slab is heated and hot-rolled to obtain a hot-rolled plate, the hot-rolled plate is pickled to remove the surface iron oxide scale, and then cold-rolled to 0.65 mm to obtain a primary cold-rolled plate.

[0073] S3: perform intermediate annealing at a temperature of 830° C. for 8 min in an annealing atmosphere of pure dry nitrogen.

[0074] S4: The steel sheet after intermediate annealing is subjected to secondary cold rolling, and the intermediate annealed sheet is cold rolled to 0.20 mm to obtain a secondary cold rolled sheet.

[0075] S5: Then decarburization annealing is performed at a temperature of 840°C for 5 minutes in an annealing atmosphere of 50% hydrogen, 50% nitrogen and water vapor, and then MgO is coated on the surface of the decarburization annealed plate.

[0076] S6: The MgO-coated plate is heated to 800°C, and then the temperature is increased to 1200°C at a rate of 15°C / h to complete high temperature annealing, and then kept at 1200°C for 20 hours to complete purification annealing, and finally uncoiling, flattening and stretching annealing and insulating layer coating are performed to make Cu-containing oriented silicon steel, wherein the atmosphere of the high temperature annealing is a mixed atmosphere of hydrogen and nitrogen, and the volume percentage of hydrogen is 75%; the atmosphere of the purification annealing is a pure hydrogen atmosphere.

[0077] like Figure 2 As shown in Figure (c), the glass film of the copper-containing oriented silicon steel product is uniform without cracking or peeling; the magnetic induction B8 of the copper-containing oriented silicon steel is 1.90T; the iron loss P 17 / 50 1.05W / kg; thickness 0.20mm. Comparative Example 3

[0078] The composition of the molten steel is the same as that of Example 3, and the preparation method is basically the same as that of Example 3, except that decarburization annealing is performed after the first cold rolling, the temperature of the decarburization annealing is 840°C, the time is 6 minutes, and then the second cold rolling is performed, the second cold rolled sheet is recovered at 500°C, and then MgO is coated and high temperature annealing is performed to obtain copper-containing oriented silicon steel, wherein the thickness of the steel sheet obtained by the second cold rolling is 0.23mm, the recovery treatment time is 3-10 minutes, and the coating of magnesium oxide and the subsequent processes are the same as those of Example 3. The glass film of some areas of the product obtained in this comparative example is damaged; the magnetic induction B8 of the finished product is 1.87T; the iron loss P 17 / 50It is 1.14W / kg. Example 4

[0079] The composition of the molten steel of the Cu-containing oriented silicon steel in Example 4 is the same as that in Example 1, and the manufacturing method is basically the same as that in Example 1, except that: the atmosphere during the intermediate annealing is pure dry nitrogen, the intermediate annealing temperature is 825°C, the intermediate annealing time is 8 minutes, the decarburization annealing temperature is 835°C, and the decarburization annealing time is 4 minutes.

[0080] The glass film of the copper-containing oriented silicon steel product obtained in this embodiment is complete and uniform; the magnetic induction B8 of the product is 1.92T; the iron loss P 17 / 50 It is 0.97W / kg. Example 5

[0081] The composition of the molten steel of the Cu-containing oriented silicon steel in Example 5 is the same as that in Example 2, and the manufacturing method is basically the same as that in Example 2, except that the dew point during decarburization annealing is 37° C., the decarburization annealing temperature is 840° C., and the annealing time is 8 min.

[0082] The glass film of the copper-containing oriented silicon steel product obtained in this embodiment is complete and uniform; the magnetic induction B8 of the product is 1.92T; the iron loss P 17 / 50 It is 0.97W / kg. Example 6

[0083] The molten steel composition of the Cu-containing oriented silicon steel of Example 6 is the same as that of Example 3, and the manufacturing method is basically the same as that of Example 3, except that the dew point of the atmosphere in the decarburization annealing is different, the dew point is 45°C, the decarburization annealing temperature is 825°C, and the annealing time is 6 minutes.

[0084] The finished copper-containing oriented silicon steel glass film obtained in this embodiment is complete and uniform; the magnetic induction B8 of the finished product is 1.91T; the iron loss P 17 / 50 It is 0.98W / kg. Test Case

[0085] The surface morphology, coating adhesion and magnetic properties of the copper-containing oriented silicon steel prepared in the examples and comparative examples were tested, and the results are shown in Table 1.

[0086] The coating adhesion is tested according to GB / T2522 standard. The magnetic performance data is obtained by using a single-piece test method on a MATS-2010M magnetic performance tester.

[0087] Table 1. Comparison of surface and performance of oriented silicon steel products in different embodiments

[0088] Note: The surface is graded by naked eye observation: Grade I: the surface color is uniform, the gloss is good, there is no exposed crystals, poor bottom layer, blackening, etc.; Grade II: the surface color is relatively uniform, the bottom layer is good; Grade III: the surface has color difference, poor gloss, and a little exposed crystals.

[0089] As can be seen from Table 1, the embodiment of the present invention adopts intermediate annealing after the first cold rolling and performs decarburization annealing after the second cold rolling, which improves the bottom layer quality of the copper-containing oriented silicon steel and the surface adhesion of the coating, and at the same time, improves the magnetic induction of the copper-containing oriented silicon steel and reduces the iron loss.

[0090] The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A method for improving the quality of copper-containing oriented silicon steel bottom layer, characterized in that: The method comprises the following steps: S1: smelting molten steel and continuously casting it into billets; S2: After heating, hot rolling and pickling the slab, cold rolling is performed once to obtain a cold-rolled sheet; S3: intermediate annealing of the primary cold rolled sheet; S4: then performing secondary cold rolling to obtain a secondary cold rolled sheet; S5: After decarburization annealing of the secondary cold rolled sheet, a release agent is coated on the surface; S6: performing high temperature annealing and purification annealing on the plate coated with the release agent in sequence, then uncoiling, flattening and stretching annealing, and coating an insulating coating to obtain copper-containing oriented silicon steel; In step S1, the molten steel comprises the following components by mass percentage: C 0.01-0.04%, Si 2.8-3.4%, Mn 0.10-0.35%, S 0.01-0.03%, Als 0.005-0.04%, N 0.005-0.015%, Cu 0.4-0.6%, O<0.004%, P<0.01%, and the balance is Fe; In step S3, the intermediate annealing is performed in an atmosphere of pure dry argon or pure dry nitrogen, at a temperature of 800-900° C., for a time of 3-10 min; In step S4, the thickness of the secondary cold-rolled sheet is 0.20-0.23 mm; In step S5, the decarburization annealing is performed at a temperature of 800-900°C and a time of 3-10 minutes; In step S6, the high temperature annealing atmosphere is a mixed atmosphere of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 70-80%.

2. The method according to claim 1, characterized in that In step S2, the thickness of the primary cold-rolled sheet is 0.6-0.7 mm.

3. The method according to claim 1, characterized in that In step S5, the decarburization annealing atmosphere is a mixed atmosphere of hydrogen and nitrogen, and the atmosphere dew point is 20-50° C.; and the volume percentage of hydrogen in the mixed atmosphere is 40-60%.

4. The method according to claim 1, characterized in that: In step S5, the isolation agent includes a magnesium oxide isolation agent.

5. The method according to claim 1, characterized in that: In step S6, the specific process of high temperature annealing and purification annealing is: heat the plate coated with the isolation agent to 780~830℃, then increase the temperature to 1180~1250℃ at 10~30℃ / h to complete high temperature annealing, and then keep it at the same temperature for 20~22h to complete purification annealing.

6. The method according to claim 5, characterized in that The atmosphere of the purification annealing is a pure hydrogen atmosphere.

7. A copper-containing oriented silicon steel prepared by the method according to any one of claims 1 to 6.

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