High-heat-resistance-grade non-oriented silicon steel and production method thereof

Abstract

The invention discloses high-heat-resistance-grade non-oriented silicon steel and a production method thereof. According to the non-oriented silicon steel, the surface of strip steel coated with insulating paint for the first time is coated with water-based secondary paint. According to the high-heat-resistance-grade non-oriented silicon steel, the magnetic performance meets the conditions that the iron loss P1.5 / 50 is smaller than or equal to 3.0 W / Kg, the magnetic induction B5000 is larger than or equal to 1.66 T, the highest heat resistance grade can reach 190 DEG C * 48 h, the coating pencil hardness is 6-8 H, the coating adhesive force is 1 grade, the coating film weight is 6-8 g / m < 2 >, the interlayer resistance is larger than or equal to 20000 omega.mm < 2 > / piece, and the high-heat-resistance-grade non-oriented silicon steel has the beneficial effects of being high in heat resistance grade, high in interlayer resistance, excellent in corrosion resistance, excellent in magnetic performance, excellent in coating adhesive force and the like; and the requirements of the large generator field on the magnetic performance of the silicon steel, the insulation performance between the silicon steel sheets and the H-level (180 DEG C * 48 hours) of the high-temperature-resistant grade are met.

Description

Technical Field

[0001] The invention relates to the technical field of non-oriented silicon steel production, and in particular to high heat-resistant grade non-oriented silicon steel and a production method thereof. Background Art

[0002] Silicon steel is the raw material for the production of various rotating motors, transformers, generators, etc. It is an important soft magnetic alloy material in electricity, electronics, military industry and transportation. In the above applications, the coating on the surface of non-oriented silicon steel can play an insulating role to prevent short circuits between core laminations and increase eddy current losses, thereby preventing deterioration of electromagnetic performance. For general small and medium-sized motors, compressors, industrial motors and other industries, the requirements for insulating coatings on the surface of silicon steel are relatively low. The thickness of the semi-organic coating on the surface of non-oriented silicon steel produced by mainstream steel mills is 0.5-1.0μm, and the interlayer resistance is generally 200Ω·mm 2 / pieces, which can meet the requirements of related fields.

[0003] However, in the field of large-scale generators such as hydropower, thermal power, and nuclear power, in order to reduce the eddy current loss of the core of large-scale generators, the insulation performance of silicon steel materials is required to be higher, and the interlayer resistance is generally required to be greater than 10000Ω·mm 2 / sheet, the existing magnesium chromate coating is difficult to meet the use requirements, and C5 thick coating or ultra-thick coating is generally used, or users use secondary painting on the silicon steel surface before use to increase the interlayer resistance of the silicon steel sheet. At the same time, due to the high ambient temperature of the large motor field, the interlayer resistance of the non-oriented silicon steel surface is required to be high, and the highest heat resistance grade is required to reach H grade (180℃×48h).

[0004] In order to improve the interlayer resistance of silicon steel materials, the document with Chinese patent application number 201410163551.X discloses the production of extremely thick insulating coatings for electrical steel with good film-forming properties. The coating product obtained by forming a layer of hollow oxide film of a certain thickness on the surface of the steel plate, and then applying an extremely thick insulating coating and then baking and curing it has excellent film-forming properties. This patent is to obtain a coating film product by applying an extremely thick insulating coating and then baking and curing the surface of the steel plate after surface treatment in an annealing furnace. Since it is difficult to treat the surface of the steel plate by controlling the dew point, the oxide film is prone to unevenness, resulting in unstable surface coating performance, and the oxide film on the surface of the steel plate also has a negative impact on the magnetic properties of non-oriented electrical steel products. The document with Chinese patent application number 201811523645.8 discloses a method for treating non-oriented electrical steel materials. After coating the non-oriented electrical steel strip with a water-soluble insulating coating, a coating film with a single-sided dry film thickness of 0.3 to 10 μm is formed on the surface, and the coating adhesion, pencil hardness, and scratch resistance are excellent. However, the interlayer resistance of the coating was not disclosed, and the heat resistance level was unknown. The document with Chinese patent application number 202310806855.2 discloses a production method of non-oriented silicon steel for improving the insulation of the iron core of large generators and the products obtained therefrom. The method uses an oily secondary paint applied on the surface of the primary paint. Although the interlayer resistance is improved, the oily secondary paint is limited by the characteristics of its coating composition. The heat resistance level is generally only Class F (155℃×48h), which is relatively low and cannot meet the higher heat resistance level requirements of large generators. In addition, due to severe environmental pollution, the oily secondary paint is difficult to meet the "low carbon" requirements. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned technology, the present invention provides a high heat-resistant grade non-oriented silicon steel and a production method thereof, which solves the problems of low heat resistance, interlayer resistance and corrosion resistance of the existing non-oriented silicon steel. It has the characteristics of high heat resistance and large interlayer resistance, and meets the performance requirements of large generators for non-oriented silicon steel with high heat resistance, high interlayer resistance and excellent corrosion resistance.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for producing high heat-resistant grade non-oriented silicon steel comprises coating a water-based secondary coating on the surface of a strip steel coated with an insulating coating once.

[0008] Preferably, the solid content of the water-based secondary paint is ≥70%, the curing temperature is 250-300° C., and the curing time is 40-60 seconds.

[0009] Preferably, the water-based secondary paint comprises 20-25% by mass of BaSO4, 15-25% by mass of ZnSO4 and 10-15% by mass of CaSO4.

[0010] Preferably, the water-based secondary paint further comprises 10-15% by mass of water-based acrylic resin and 5-10% by mass of nano-SiO2 sol, and the rest are additives and deionized water.

[0011] Further preferably, the additive comprises the following components, calculated by mass fraction in the water-based secondary paint: 0.1-0.5% dispersant, 0.1-0.5% defoamer, and 0.1-0.5% leveling agent.

[0012] Further preferably, the dispersant includes an organic synthetic polyether dispersant; the defoamer includes diethylhexanol; and the leveling agent includes polyether-modified polysiloxane.

[0013] Preferably, the production method comprises the following steps:

[0014] 1) Take molten steel and continuously cast it into a slab with a thickness of 200 to 230 mm;

[0015] 2) directly loading the slab into a heating furnace for heating, wherein the temperature of the heating furnace is 1150-1250° C. and the total heating time is 210-230 min;

[0016] 3) finishing rolling the slab to a hot rolled plate with a thickness of 2.2 to 2.4 mm, with a final rolling temperature of 860 to 920° C. and a coiling temperature of 650 to 700° C.;

[0017] 4) After shot blasting and pickling, the hot rolled plate is normalized at 850-900° C. to obtain a normalized plate;

[0018] 5) cold rolling the normalized sheet to a target thickness of 0.50 mm, using a rough roll as the rolling roller, and the surface roughness of the cold rolled sheet after cold rolling is Ra≥0.8 μm;

[0019] 6) After alkali washing, the cold-rolled sheet is continuously annealed. The atmosphere in the furnace is dry atmosphere. The temperature of the soaking section of the annealing furnace is 950-1000°C. The total annealing time is 240-480s.

[0020] 7) The strip steel after continuous annealing is coated with a semi-organic zinc chromate insulating coating through a coating roller, and then cured at 500-600° C. after coating;

[0021] 8) After the first coating is cured, a water-based secondary coating is applied, and after coating, it is cured at 250-300°C for 40-60s.

[0022] Preferably, in the step 2), the chemical composition of the slab includes, by weight percentage: C≤0.003%, Si: 2.8-3.4%, Mn: 0.15-0.45%, Als: 0.5-1.0%, S≤0.003%, N≤0.003%, Ti≤0.003%, and the rest is Fe and unavoidable impurities.

[0023] Preferably, in step 6), the atmosphere in the furnace is a mixture of hydrogen and nitrogen, with the ratio of H2 to N2 being 4:6.

[0024] Preferably, the semi-organic zinc chromate insulating coating comprises 0.5-2.0% H3BO3, 5-10% CrO3, 5-10% ZnO, 10-20% propylene organic resin, and 3-8% glycerol in mass fraction; the solid content of the semi-organic zinc chromate insulating coating is ≥20%.

[0025] Preferably, the semi-organic zinc chromate insulating coating further comprises 3-5% by mass of polyethylene resin powder, and the rest is deionized water.

[0026] The present invention also provides a non-oriented silicon steel produced by the production method, wherein the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤3.0W / Kg, magnetic induction B 5000 ≥1.66T, heat resistance level reaches 190℃×48h, coating pencil hardness 6~8H, coating adhesion is level 1, coating film weight 6~8g / m 2 , interlayer resistance ≥ 20000Ω·mm 2 / piece.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a high heat-resistant grade non-oriented silicon steel and a production method thereof to improve the heat-resistant grade of non-oriented silicon steel and increase the interlayer resistance. The surface of the strip steel is coated with a water-based secondary paint on the surface of the original zinc-based chromate coating, and the magnetic properties meet the iron loss P 1.5 / 50 ≤3.0W / Kg, magnetic induction B 5000 ≥1.66T, the highest heat resistance level can reach 190℃×48h, the coating pencil hardness is 6~8H, the coating adhesion is level 1, and the coating film weight is 6~8g / m 2 , interlayer resistance ≥ 20000Ω·mm 2 / piece, with the characteristics of high heat resistance, high interlayer resistance, excellent corrosion resistance, excellent magnetic properties, and excellent coating adhesion, it meets the insulation performance between silicon steel sheets in the field of large-scale generators, as well as the high heat resistance grade H (180℃×48h), and can reach a maximum heat resistance grade of 190℃×48h. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the surface morphology of the water-based secondary paint in Example 1 after curing at 270°C × 50s;

[0030] Figure 2 This is a schematic diagram of the surface corrosion of the water-based secondary paint in Example 1 under the conditions of 5% NaCl solution and 35°C for 5h;

[0031] Figure 3 This is the surface morphology of the water-based secondary paint in Comparative Example 2 after curing at 230°C × 50s;

[0032] Figure 4 This is the surface morphology of the water-based secondary paint in Comparative Example 3 after curing at 330℃×30s. DETAILED DESCRIPTION

[0033] In order to better explain the present invention, the main contents of the present invention are further explained below in combination with specific embodiments and drawings, but the contents of the present invention are not limited to the following embodiments.

[0034] Example 1

[0035] A high heat-resistant grade non-oriented silicon steel and a production method thereof, specifically comprising the following steps:

[0036] 1) The molten steel refined in the RH furnace is continuously cast into a slab with a thickness of 210 mm. The chemical composition percentages by weight of the slab are C: 0.003%; Si: 2.80%; Mn: 0.15%; Als: 0.60%; S: 0.003%, N: 0.003%, Ti: 0.003%, and the rest are Fe and unavoidable impurity elements.

[0037] 2) The slab is directly loaded into the heating furnace for heating. The temperature of the heating furnace is 1180°C and the heating and holding time is 210 minutes;

[0038] 3) The slab is hot rolled to a hot rolled plate with a thickness of 2.4 mm, the final rolling temperature is controlled at 920°C, and the coiling temperature is 670°C;

[0039] 4) The hot rolled plate is shot blasted and pickled and then normalized at 900°C;

[0040] 5) The normalized plate is cold rolled to a target thickness of 0.50 mm using a roughing roll, and the surface roughness of the strip after cold rolling is Ra=0.82 μm;

[0041] 6) After the cold-rolled sheet is washed with an aqueous solution of disodium hydrogen phosphate and sodium hydroxide, it is continuously annealed in a continuous annealing furnace, wherein the atmosphere in the continuous annealing furnace is a mixture of hydrogen and nitrogen with a H2 content of 40%. The temperature of the soaking section of the annealing furnace is 950° C., and the total annealing time is 240 seconds.

[0042] 7) After the strip is annealed, the first insulating coating is applied by a coating roller. The coating is a semi-organic zinc chromate insulating coating with a solid content of 22%. The insulating coating is cured at 500°C. In the semi-organic zinc chromate insulating coating, the mass fraction of H3BO3 is 1.0%, the mass fraction of CrO3 is 7.0%, the mass fraction of ZnO is 6.5%, the mass fraction of propylene organic resin is 15.0%, the mass fraction of glycerol is 4.0%, the mass fraction of polyethylene resin powder is 3.5%, and the rest is deionized water;

[0043] 8) After the first coating of the steel strip is cured, a water-based secondary coating is applied. The solid content of the water-based secondary coating is 72%. The strip is cured at 250°C for 50 seconds. After curing, the surface of the steel strip is dark gray. Figure 1 In the water-based secondary coating, the mass fraction of BaSO4 is 22.0%, the mass fraction of ZnSO4 is 20.0%, the mass fraction of CaSO4 is 13.0%, the mass fraction of water-based acrylic resin is 13.0%, the mass fraction of nano-SiO2 sol is 8.0%, and the rest is 0.2% of organic synthetic polyether dispersant, 0.3% of diethylhexanol defoamer, 0.2% of polyether modified polysiloxane leveling agent and deionized water.

[0044] The iron loss P of the finished non-oriented electrical steel manufactured by the above process is 1.5 / 50 2.70W / Kg, magnetic induction B 5000 1.68T, coating film weight 7.5g / m 2 , pencil hardness is 7H, coating adhesion is level 1, interlayer resistance is 22000Ω·mm 2 / piece, heat resistance level is 190℃×48h, corrosion resistance is good, 5% NaCl solution, 35℃×5h conditions, surface corrosion conditions are as follows Figure 2 As shown, the surface corrosion area is less than 10%.

[0045] Example 2

[0046] A non-oriented silicon steel for reducing eddy current loss in a large generator core and a production method thereof, specifically comprising the following steps:

[0047] 1) The molten steel refined in the RH furnace is continuously cast into a slab with a thickness of 230 mm. The chemical composition of the slab is C: 0.002%; Si: 3.0%; Mn: 0.3%; Als: 1.0%; S: 0.002%, N: 0.002%, Ti: 0.002%, and the rest is Fe and unavoidable impurity elements.

[0048] 2) The slab is directly loaded into the heating furnace for heating. The temperature of the heating furnace is 1150°C and the heating and holding time is 220 minutes;

[0049] 3) The slab is hot rolled to a hot rolled plate with a thickness of 2.2 mm, the final rolling temperature is controlled at 900°C, and the coiling temperature is 700°C;

[0050] 4) The hot rolled plate is shot blasted and pickled and then normalized at 880°C;

[0051] 5) The normalized plate is cold rolled to a target thickness of 0.50 mm using a roughing roll, and the surface roughness of the strip after cold rolling is Ra=0.85 μm;

[0052] 6) After the cold-rolled sheet is washed with an aqueous solution of disodium hydrogen phosphate and sodium hydroxide, it is continuously annealed in a continuous annealing furnace, wherein the atmosphere in the continuous annealing furnace is a mixture of hydrogen and nitrogen with a H2 content of 40%. The temperature of the soaking section of the annealing furnace is 980° C., and the total annealing time is 280 seconds.

[0053] 7) After the strip is annealed, the first insulating coating is applied by a coating roller. The coating is a semi-organic zinc chromate insulating coating with a solid content of 21%. The insulating coating is cured at 550° C. The semi-organic zinc chromate insulating coating contains 0.5% by mass of H3BO3, 7.5% by mass of CrO3, 7.0% by mass of ZnO, 12.0% by mass of propylene organic resin, 4.0% by mass of glycerol, 3.5% by mass of polyethylene resin powder, and the rest is deionized water.

[0054] 8) After the primary paint of the steel strip is cured, a water-based secondary paint is applied, the solid content of the water-based secondary paint is 73%, and the paint is cured at 280°C for 60 seconds. In the water-based secondary paint, the mass fraction of BaSO4 is 24.0%, the mass fraction of ZnSO4 is 23.0%, the mass fraction of CaSO4 is 12.0%, the mass fraction of water-based acrylic resin is 12.0%, the mass fraction of nano-SiO2 sol is 7.0%, and the rest is 0.3% of organic synthetic polyether dispersant, 0.2% of diethylhexanol defoamer, 0.3% of polyether modified polysiloxane leveling agent and deionized water.

[0055] The iron loss P of the finished non-oriented electrical steel manufactured by the above process is 1.5 / 50 2.45W / Kg, magnetic induction B 5000 1.67T, coating film weight 8.0g / m 2 , pencil hardness is 7H, coating adhesion is level 1, interlayer resistance is 25000Ω·mm 2 / piece, heat resistance grade is 190℃×48h, 5% NaCl solution, 35℃×5h, surface corrosion area is <10%.

[0056] Example 3

[0057] A non-oriented silicon steel for reducing eddy current loss in a large generator core and a production method thereof, specifically comprising the following steps:

[0058] 1) The molten steel refined in the RH furnace is continuously cast into a slab with a thickness of 200 mm. The chemical composition percentages by weight of the slab are C: 0.002%; Si: 3.4%; Mn: 0.45%; Als: 0.50%; S: 0.002%, N: 0.002%, Ti: 0.002%, and the rest are Fe and unavoidable impurity elements.

[0059] 2) The slab is directly loaded into the heating furnace for heating. The temperature of the heating furnace is 1250℃ and the heating and insulation time is 230min.

[0060] 3) The slab is hot rolled to a hot rolled plate with a thickness of 2.2 mm, the final rolling temperature is controlled at 860°C, and the coiling temperature is 680°C;

[0061] 4) The hot rolled plates are shot blasted and pickled and then normalized at 850°C.

[0062] 5) The normalized plate is cold rolled with a roughing roll to a target thickness of 0.50 mm, and the surface roughness of the strip after cold rolling is Ra=0.89 μm.

[0063] 6) After the cold-rolled sheet is washed with an aqueous solution of disodium hydrogen phosphate and sodium hydroxide, it is continuously annealed in a continuous annealing furnace, wherein the atmosphere in the continuous annealing furnace is a mixture of hydrogen and nitrogen with a H2 content of 40%. The soaking zone temperature of the annealing furnace is 1000° C., and the total annealing time is 320 seconds.

[0064] 7) After the strip is annealed, the first insulating coating is applied by a coating roller. The coating is a semi-organic zinc chromate insulating coating with a solid content of 21%. The insulating coating is cured at 580° C. In the semi-organic zinc chromate insulating coating, the mass fraction of H3BO3 is 0.6%, the mass fraction of CrO3 is 8.0%, the mass fraction of ZnO is 6.0%, the mass fraction of propylene organic resin is 13.0%, the mass fraction of glycerol is 4.5%, the mass fraction of polyethylene resin powder is 4.0%, and the rest is deionized water.

[0065] 8) After the primary paint of the steel strip is cured, a water-based secondary paint is applied, the solid content of the water-based secondary paint is 70%, and the paint is cured at 300°C for 60 seconds. In the water-based secondary paint, the mass fraction of BaSO4 is 21.0%, the mass fraction of ZnSO4 is 18.0%, the mass fraction of CaSO4 is 13.0%, the mass fraction of water-based acrylic resin is 11.0%, the mass fraction of nano-SiO2 sol is 9.0%, and the rest is 0.1% of organic synthetic polyether dispersant, 0.2% of diethylhexanol defoamer, 0.35% of polyether modified polysiloxane leveling agent and deionized water.

[0066] The iron loss P of the finished non-oriented electrical steel manufactured by the above process is 1.5 / 50 2.40W / Kg, magnetic induction B 5000 1.66T, coating film weight 6.1g / m 2 , pencil hardness is 8H, coating adhesion is level 1, interlayer resistance is 20000Ω·mm 2 / piece, heat resistance grade is 190℃×48h, 5% NaCl solution, 35℃×5h, surface corrosion area is <10%.

[0067] Comparative Example 1

[0068] A non-oriented silicon steel and a production method thereof, specifically comprising the following steps:

[0069] 1) The molten steel refined in the RH furnace is continuously cast into a slab with a thickness of 210 mm. The chemical composition of the slab is C: 0.003%; Si: 2.8%; Mn: 0.15%; Als: 0.6%; S: 0.003%, N: 0.003%, Ti: 0.003%, and the rest is Fe and unavoidable impurity elements.

[0070] 2) The slab is directly loaded into the heating furnace for heating. The temperature of the heating furnace is 1180°C and the heating and holding time is 210 minutes;

[0071] 3) The slab is hot-rolled to a hot-rolled plate with a thickness of 2.4 mm, a final rolling temperature of 920°C, and a coiling temperature of 670°C;

[0072] 4) The hot rolled plate is shot blasted and pickled and then normalized at 900°C;

[0073] 5) The normalized plate is cold rolled to a target thickness of 0.50 mm using a flat roll, and the surface roughness of the strip after cold rolling is Ra = 0.30 μm;

[0074] 6) After conventional alkali washing, the cold-rolled sheet is continuously annealed in a continuous annealing furnace, wherein the atmosphere in the continuous annealing furnace is a mixture of hydrogen and nitrogen with a H2 content of 40%. The temperature of the soaking section of the annealing furnace is 950° C. and the annealing time is 240 seconds.

[0075] 7) After the strip is annealed, the first insulating coating is applied by a coating roller. The coating is a semi-organic zinc chromate insulating coating with a solid content of 20%. The insulating coating is cured at 500°C. In the semi-organic zinc chromate insulating coating, the mass fraction of H3BO3 is 1.0%, the mass fraction of CrO3 is 7.0%, the mass fraction of ZnO is 6.5%, the mass fraction of propylene organic resin is 15.0%, the mass fraction of glycerol is 4.0%, the mass fraction of polyethylene resin powder is 3.5%, and the rest is deionized water;

[0076] 8) After the primary paint of the steel strip is cured, a water-based secondary paint is applied, the solid content of the water-based secondary paint is 72%, and the paint is cured at 250° C. for 50 seconds. In the water-based secondary paint, the mass fraction of BaSO4 is 15.0%, the mass fraction of ZnSO4 is 12.0%, the mass fraction of CaSO4 is 8.0%, the mass fraction of water-based acrylic resin is 9.0%, the mass fraction of nano-SiO2 sol is 8.0%, and the rest is 0.1% of organic synthetic polyether dispersant, 0.1% of diethylhexanol defoamer, 0.2% of polyether modified polysiloxane leveling agent and deionized water.

[0077] The iron loss P of the finished non-oriented electrical steel manufactured by the above process is 1.5 / 50 2.70W / Kg, magnetic induction B 5000 1.68T, coating film weight 5.4g / m 2 , pencil hardness is 7H, coating adhesion is level 2, interlayer resistance is 9000Ω·mm 2 / piece, heat resistance level is 185℃×48h. Although the product has excellent magnetic properties, the secondary paint coating has poor adhesion and low interlayer resistance, which does not meet the interlayer resistance requirements of large generators.

[0078] Comparative Example 2

[0079] A non-oriented silicon steel and a production method thereof, specifically comprising the following steps:

[0080] 1) The molten steel refined in the RH furnace is continuously cast into a slab with a thickness of 230 mm. The chemical composition percentages by weight of the slab are C: 0.003%; Si: 2.3%; Mn: 0.10%; Als: 0.45%; S: 0.003%, N: 0.003%, Ti: 0.003%, and the rest are Fe and unavoidable impurity elements.

[0081] 2) The slab is directly loaded into the heating furnace for heating. The temperature of the heating furnace is 1160°C and the heating and holding time is 220 minutes;

[0082] 3) The slab is hot-rolled to a hot-rolled plate with a thickness of 2.2 mm, a final rolling temperature of 920°C, and a coiling temperature of 700°C;

[0083] 4) The hot rolled plate is shot blasted and pickled and then normalized at 930°C;

[0084] 6) The normalized plate is cold rolled to a target thickness of 0.50 mm using a roughing roll, and the surface roughness of the strip after cold rolling is Ra=0.83 μm;

[0085] 7) After conventional alkali washing, the above-mentioned cold-rolled sheet is continuously annealed in a continuous annealing furnace. The atmosphere in the continuous annealing furnace is a mixture of hydrogen and nitrogen with an H2 content of 40%. The temperature of the annealing furnace soaking section is 930°C, and the annealing time is 280s. After the strip is annealed, the first insulating coating is applied by a coating roller. The coating is a semi-organic zinc chromate insulating coating with a solid content of 19.5%. The insulating coating is cured at 500°C. In the zinc chromate coating, the mass fraction of H3BO3 is 0.5%, the mass fraction of CrO3 is 7.5%, the mass fraction of ZnO is 7.0%, the mass fraction of propylene organic resin is 12.0%, the mass fraction of glycerol is 4.0%, the mass fraction of polyethylene resin powder is 3.5%, and the rest is deionized water;

[0086] 8) After the primary paint of the steel strip is cured, a water-based secondary paint is applied, the solid content of the water-based secondary paint is 72%, and the paint is cured at 230° C. for 50 seconds. In the water-based secondary paint, the mass fraction of BaSO4 is 23.0%, the mass fraction of ZnSO4 is 20.0%, the mass fraction of CaSO4 is 12.0%, the mass fraction of water-based acrylic resin is 12.0%, the mass fraction of nano-SiO2 sol is 7.0%, and the rest is 0.2% of organic synthetic polyether dispersant, 0.2% of diethylhexanol defoamer, 0.3% of polyether modified polysiloxane leveling agent and deionized water.

[0087] The iron loss P of the finished non-oriented electrical steel manufactured by the above process is 1.5 / 50 3.20W / Kg, magnetic induction B 5000 1.70T, coating film weight 7.5g / m 2 , pencil hardness is 5H, coating adhesion is level 3, interlayer resistance is 10000Ω·mm 2 / piece, heat resistance level is 165℃×48h. The magnetic properties of the product are poor, and the secondary paint is not solidified. The surface falls off after being wiped with alcohol. Figure 3 At the same time, the coating has poor adhesion and low heat resistance, which does not meet the requirements of large generators for the magnetic properties and high heat resistance of silicon steel sheets.

[0088] Comparative Example 3

[0089] A non-oriented silicon steel and a production method thereof, specifically comprising the following steps:

[0090] 1) The molten steel refined in the RH furnace is continuously cast into a slab with a thickness of 230 mm. The chemical composition percentages by weight of the slab are C: 0.002%; Si: 3.0%; Mn: 0.30%; Als: 1.0%; S: 0.002%, N: 0.002%, Ti: 0.002%, and the rest are Fe and unavoidable impurity elements.

[0091] 2) The slab is directly loaded into the heating furnace for heating. The temperature of the heating furnace is 1150°C and the heating and holding time is 230 minutes;

[0092] 3) The slab is hot-rolled to a hot-rolled plate with a thickness of 2.2 mm, a final rolling temperature of 900°C, and a coiling temperature of 700°C;

[0093] 4) The hot rolled plate is shot blasted and pickled and then normalized at 880°C;

[0094] 6) The normalized plate is cold rolled to a target thickness of 0.50 mm using a roughing roll, and the surface roughness of the strip after cold rolling is Ra=0.85 μm;

[0095] 7) After the above cold-rolled sheet is washed with an aqueous solution of disodium hydrogen phosphate and sodium hydroxide, it is continuously annealed in a continuous annealing furnace. The atmosphere in the continuous annealing furnace is a mixture of hydrogen and nitrogen with an H2 content of 40%. The temperature of the annealing furnace soaking section is 980°C, and the annealing time is 280s. After the strip is annealed, the first insulating coating is applied by a coating roller. The coating is a semi-organic zinc chromate insulating coating with a solid content of 18.5%. The insulating coating is cured at 550°C. In the zinc chromate coating, the mass fraction of H3BO3 is 0.6%, the mass fraction of CrO3 is 8.0%, the mass fraction of ZnO is 6.0%, the mass fraction of propylene organic resin is 13.0%, the mass fraction of glycerol is 4.5%, the mass fraction of polyethylene resin powder is 4.0%, and the rest is deionized water;

[0096] 8) After the primary paint of the steel strip is cured, a water-based secondary paint is applied, the solid content of the water-based secondary paint is 73%, and the paint is cured at 330° C. for 30 seconds. In the water-based secondary paint, the mass fraction of BaSO4 is 21.0%, the mass fraction of ZnSO4 is 16.0%, the mass fraction of CaSO4 is 13.0%, the mass fraction of water-based acrylic resin is 14.0%, the mass fraction of nano-SiO2 sol is 6.0%, and the rest is 0.4% of organic synthetic polyether dispersant, 0.2% of diethylhexanol defoamer, 0.1% of polyether modified polysiloxane leveling agent and deionized water.

[0097] The iron loss P of the finished non-oriented electrical steel manufactured by the above process is 1.5 / 50 2.45W / Kg, magnetic induction B 5000 1.67T, coating film weight 6.0g / m 2 , pencil hardness is 5H, coating adhesion is level 3, interlayer resistance is 8500Ω·mm 2 / piece, heat resistance level is 160℃×48h. Although the magnetic properties of the product are excellent, the secondary paint is over-burned and the surface is dark yellow. Figure 4 As shown. This results in poor coating adhesion and low heat resistance.

Claims

1. A method for producing high heat-resistant grade non-oriented silicon steel, characterized in that: A water-based secondary paint is applied to the surface of the strip coated with insulating paint once.

2. The production method according to claim 1, characterized in that: The solid content of the water-based secondary paint is ≥70%, the curing temperature is 250-300° C., and the curing time is 40-60 seconds.

3. The production method according to claim 1, characterized in that: The water-based secondary paint comprises 20-25% by mass of BaSO4, 15-25% by mass of ZnSO4 and 10-15% by mass of CaSO4.

4. The production method according to claim 3, characterized in that: The water-based secondary paint also includes 10-15% by mass of water-based acrylic resin and 5-10% by mass of nano-SiO2 sol, and the rest is auxiliary agent and deionized water.

5. The production method according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) Take molten steel and continuously cast it into a slab with a thickness of 200 to 230 mm; 2) directly loading the slab into a heating furnace for heating, wherein the temperature of the heating furnace is 1150-1250° C. and the total heating time is 210-230 min; 3) finishing rolling the slab to a hot rolled plate with a thickness of 2.2 to 2.4 mm, with a final rolling temperature of 860 to 920° C. and a coiling temperature of 650 to 700° C.; 4) After shot blasting and pickling, the hot rolled plate is normalized at 850-900° C. to obtain a normalized plate; 5) cold rolling the normalized sheet to a target thickness of 0.50 mm, using a rough roll as the rolling roller, and the surface roughness of the cold rolled sheet after cold rolling is Ra≥0.8 μm; 6) After alkali washing, the cold-rolled sheet is continuously annealed. The atmosphere in the furnace is dry atmosphere. The temperature of the soaking section of the annealing furnace is 950-1000°C. The total annealing time is 240-480s. 7) The strip steel after continuous annealing is coated with a semi-organic zinc chromate insulating coating through a coating roller, and then cured at 500-600° C. after coating; 8) After the first coating is cured, a water-based secondary coating is applied, and after coating, it is cured at 250-300°C for 40-60s.

6. The production method according to claim 5, characterized in that: In the step 2), the chemical composition of the slab includes, by weight percentage: C≤0.003%, Si: 2.8-3.4%, Mn: 0.15-0.45%, Als: 0.5-1.0%, S≤0.003%, N≤0.003%, Ti≤0.003%, and the rest is Fe and unavoidable impurities.

7. The production method according to claim 5, characterized in that: In the step 6), the atmosphere in the furnace is a mixture of hydrogen and nitrogen, with the ratio of H2 to N2 being 4:

6.

8. The production method according to claim 5, characterized in that: The semi-organic zinc chromate insulating coating comprises 0.5-2.0% H3BO3, 5-10% CrO3, 5-10% ZnO, 10-20% propylene organic resin and 3-8% glycerol in mass fraction; the solid content of the semi-organic zinc chromate insulating coating is ≥20%.

9. The production method according to claim 8, characterized in that: The semi-organic zinc chromate insulating coating also includes polyethylene resin powder with a mass fraction of 3-5%, and the rest is deionized water.

10. Non-oriented silicon steel produced by the production method according to any one of claims 1 to 9, characterized in that: The iron loss P of the non-oriented silicon steel 1.5 / 50 ≤3.0W / Kg, magnetic induction B 5000 ≥1.66T, heat resistance level reaches 190℃×48h, coating pencil hardness 6~8H, coating adhesion is level 1, coating film weight 6~8g / m 2 , interlayer resistance ≥ 20000Ω·mm 2 / piece.

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