High heat-resistant non-oriented silicon steel and its production method

Abstract

This invention discloses a high heat-resistant grade non-oriented silicon steel and its production method. The non-oriented silicon steel is produced by coating a strip of steel with an insulating coating in the first stage with a water-based secondary coating. The high heat-resistant grade non-oriented silicon steel provided by this invention has the following magnetic properties: iron loss P... 1.5 / 50 ≤3.0W / Kg, Magnetic induction B 5000 ≥1.66T, maximum heat resistance up to 190℃×48h, coating pencil hardness 6~8H, coating adhesion grade 1, coating film weight 6~8g / m³ 2 Interlayer resistance ≥20000Ω·mm 2 The sheet has the characteristics of high heat resistance, high interlayer resistance, excellent corrosion resistance, excellent magnetic properties, and excellent coating adhesion, which meet the requirements of large generator field for silicon steel magnetic properties, silicon steel sheet insulation performance, and high heat resistance grade H (180℃×48h).

Description

Technical Field

[0001] This invention relates to the field of non-oriented silicon steel production technology, specifically to a high heat-resistant non-oriented silicon steel and its production method. Background Technology

[0002] Silicon steel is a raw material for producing various rotating electric machines, transformers, generators, etc., and is an important soft magnetic alloy material in the power, electronics, military, and transportation industries. In these applications, the coating on the surface of non-oriented silicon steel acts as insulation to prevent short circuits between the core laminations, which would increase eddy current losses and thus prevent deterioration of electromagnetic performance. For industries such as general small and medium-sized motors, compressors, and industrial motors, the requirements for the insulating coating on the silicon steel surface are relatively low. Currently, mainstream steel mills produce non-oriented silicon steel with a semi-organic coating thickness of 0.5–1.0 μm and an interlayer resistance typically around 200 Ω·mm². 2 The film / video is capable of meeting the requirements of relevant fields.

[0003] However, for large generator applications such as hydropower, thermal power, and nuclear power, in order to reduce eddy current losses in the generator core, the insulation performance of silicon steel materials is required to be high, and the interlayer resistance is generally required to be greater than 10000 Ω·mm. 2 For single sheets, existing magnesium-based chromate coatings are insufficient to meet application requirements. Generally, a C5 thick coating or an extremely thick coating is used, or users apply a second coat of paint to the silicon steel surface before use to increase the interlayer resistance of the silicon steel sheets. At the same time, due to the high operating temperature in the field of large motors, the requirements for the interlayer resistance of the non-oriented silicon steel surface are high, requiring the highest heat resistance rating to reach H class (180℃×48h).

[0004] To improve the interlayer resistance of silicon steel, Chinese patent application No. 201410163551.X discloses the production of an extremely thick insulating coating for electrical steel with good film-forming properties. This method involves forming a porous oxide film of a certain thickness on the steel plate surface, then applying an extremely thick insulating coating and baking to cure it, resulting in a coating product with excellent film-forming properties. This patent involves surface treatment of the steel plate surface in an annealing furnace, followed by applying an extremely thick insulating coating and baking to cure it. However, controlling the dew point for steel plate surface treatment is difficult, and the oxide film is prone to unevenness, leading to unstable surface coating performance. Furthermore, the oxide film on the steel plate surface also negatively affects the magnetic properties of non-oriented electrical steel products. Chinese patent application No. 201811523645.8 discloses a method for processing 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 0.3–10 μm is formed on the surface, exhibiting excellent coating adhesion, pencil hardness, and scratch resistance. However, the interlayer resistance of the coating is not disclosed, and the heat resistance rating is unknown. Chinese patent application number 202310806855.2 discloses a method for producing non-oriented silicon steel to improve the insulation of large generator cores and the resulting product. This method involves applying an oil-based secondary coating to the surface of a primary coating. While this increases the interlayer resistance, the oil-based secondary coating, due to the limitations of its coating composition, generally only has a heat resistance rating of F (155℃×48h), which is low and cannot meet the higher heat resistance requirements of large generators. Furthermore, due to severe environmental pollution, the oil-based secondary coating is unlikely to meet the "low carbon" requirement. Summary of the Invention

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

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

[0007] A method for producing high heat-resistant non-oriented silicon steel involves coating the surface of a strip steel that has been coated with an insulating coating in the first stage with a water-based secondary coating.

[0008] Preferably, the water-based secondary coating has a solid content of ≥70%, a curing temperature of 250-300℃, and a curing time of 40-60s.

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

[0010] Preferably, the water-based secondary coating further includes 10-15% by mass of water-based acrylic resin and 5-10% by mass of nano-SiO2 sol, with the remainder being additives and deionized water.

[0011] More preferably, the additives, by mass fraction in the water-based secondary coating, comprise the following components: 0.1-0.5% dispersant, 0.1-0.5% defoamer, and 0.1-0.5% leveling agent.

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

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

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

[0015] 2) The slab is directly loaded into a heating furnace for heating. The temperature of the heating furnace is 1150-1250℃, and the total heating time is 210-230 min.

[0016] 3) The slab is finished rolled into a hot-rolled plate with a thickness of 2.2 to 2.4 mm at a final rolling temperature of 860 to 920°C and a coiling temperature of 650 to 700°C;

[0017] 4) The hot-rolled plate is shot-blasted and pickled, then normalized at 850-900℃ to obtain a normalized plate;

[0018] 5) The normalized plate is cold-rolled to a target thickness of 0.50 mm using coarse rolls, and the surface roughness Ra of the cold-rolled plate is ≥0.8 μm;

[0019] 6) After the cold-rolled sheet is alkali washed, it is subjected to continuous annealing treatment. The atmosphere in the furnace is dry, the temperature of the soaking zone of the annealing furnace is 950-1000℃, and 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℃.

[0021] 8) After the first coat has cured, apply a second coat of water-based paint. After the second coat is applied, cure at 250-300℃ for 40-60 seconds.

[0022] Preferably, in step 2), the chemical composition of the slab, by weight percentage, includes: 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%, with the remainder being Fe and unavoidable impurities.

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

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

[0025] Preferably, the semi-organic zinc-based chromate insulating coating further includes 3-5% polyethylene resin powder by mass, with the remainder being deionized water.

[0026] The present invention also provides a non-oriented silicon steel produced by the above-described 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 up to 190℃×48h, coating pencil hardness 6~8H, coating adhesion grade 1, coating film weight 6~8g / m 2 Interlayer resistance ≥20000Ω·mm 2 / piece.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention aims to improve the heat resistance of non-oriented silicon steel and increase its interlayer resistance. It provides a high-heat-resistant non-oriented silicon steel and its production method. The strip surface is coated with a water-based secondary coating on top of the existing zinc-based chromate coating. The magnetic properties meet the iron loss P... 1.5 / 50 ≤3.0W / Kg, Magnetic induction B 5000 ≥1.66T, maximum heat resistance up to 190℃×48h, coating pencil hardness 6~8H, coating adhesion grade 1, coating film weight 6~8g / m³ 2 Interlayer resistance ≥20000Ω·mm 2 The sheet has the characteristics of high heat resistance, high interlayer resistance, excellent corrosion resistance, excellent magnetic properties, and excellent coating adhesion. It meets the requirements of large generator field for insulation performance between silicon steel sheets and high heat resistance grade H (180℃×48h), and can reach the highest heat resistance grade of 190℃×48h. Attached Figure Description

[0029] Figure 1 This is a surface morphology image of the water-based secondary coating after curing at 270℃ for 50s in Example 1;

[0030] Figure 2 This is a schematic diagram of the surface corrosion of the water-based secondary coating in Example 1 under conditions of 5% NaCl solution and 35℃×5h.

[0031] Figure 3 The image shows the surface morphology of the water-based secondary coating in Comparative Example 2 after curing at 230℃ for 50 seconds.

[0032] Figure 4 The image shows the surface morphology of the water-based secondary coating in Comparative Example 3 after curing at 330℃ for 30s. Detailed Implementation

[0033] To better explain the present invention, the main contents of the present invention are further illustrated below with reference to specific embodiments and accompanying drawings, but the contents of the present invention are not limited to the following embodiments.

[0034] Example 1

[0035] A high heat-resistant non-oriented silicon steel and its production method, specifically including the following steps:

[0036] 1) The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 210 mm. The chemical composition of the slabs by weight percentage is C: 0.003%; Si: 2.80%; Mn: 0.15%; Als: 0.60%; S: 0.003%; N: 0.003%; Ti: 0.003%; with the remainder being 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℃, and the heating and holding time is 210min.

[0038] 3) Hot-rolled slabs are hot-rolled to a thickness of 2.4 mm, with the final rolling temperature controlled at 920℃ and the coiling temperature at 670℃.

[0039] 4) The above-mentioned hot-rolled plates are shot-blasted, pickled, and then normalized at 900℃;

[0040] 5) The above-mentioned normalized plate is cold rolled to the target thickness of 0.50 mm using rough rolls, and the surface roughness of the strip after cold rolling is Ra = 0.82 μm;

[0041] 6) After cleaning the above-mentioned cold-rolled sheet with an aqueous solution of disodium hydrogen phosphate and sodium hydroxide, it is continuously annealed in a continuous annealing furnace. The atmosphere inside the continuous annealing furnace is a mixture of hydrogen and nitrogen, with an H2 content of 40%. The temperature of the soaking zone of the annealing furnace is 950℃, and the total annealing time is 240s.

[0042] 7) After annealing, the strip steel is coated with the first insulating coating using a coating roller. The coating is a semi-organic zinc-based chromate insulating coating with a solid content of 22%, and is cured at 500℃. The semi-organic zinc-based chromate insulating coating contains 1.0% H3BO3, 7.0% CrO3, 6.5% ZnO, 15.0% acrylic organic resin, 4.0% glycerol, 3.5% polyethylene resin powder, and the remainder is deionized water.

[0043] 8) After the first coat of paint on the strip steel has cured, a second coat of water-based paint is applied. The water-based second coat has a solid content of 72%, and is cured at 250℃ for 50 seconds. After curing, the surface of the strip steel is dark gray. Figure 1 As shown. 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 remainder consists of 0.2% organic synthetic polyether dispersant, 0.3% diethylhexanol defoamer, 0.2% polyether-modified polysiloxane leveling agent, and deionized water.

[0044] The non-oriented electrical steel manufactured using the above process has a finished product iron loss P. 1.5 / 50 It is 2.70W / Kg, magnetic induction B 5000 The coating weight is 1.68T, and the coating film weight is 7.5g / m³. 2 The pencil hardness is 7H, the coating adhesion is grade 1, and the interlayer resistance is 22000 Ω·mm. 2 / piece, heat resistance rating is 190℃×48h, good corrosion resistance, surface corrosion condition under 5% NaCl solution, 35℃×5h conditions is as follows. Figure 2 As shown, the surface corrosion area is <10%.

[0045] Example 2

[0046] A non-oriented silicon steel for reducing eddy current losses in the core of a large generator and its production method, specifically including the following steps:

[0047] 1) The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 230 mm. The chemical composition of the slabs by weight percentage is C: 0.002%; Si: 3.0%; Mn: 0.3%; Als: 1.0%; S: 0.002%; N: 0.002%; Ti: 0.002%; with the remainder being 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℃, and the heating and holding time is 220min.

[0049] 3) Hot-rolled slabs are hot-rolled to a thickness of 2.2 mm, with the final rolling temperature controlled at 900℃ and the coiling temperature at 700℃;

[0050] 4) The above-mentioned hot-rolled plates are shot-blasted and pickled, and then normalized at 880℃;

[0051] 5) The above-mentioned normalized plate is cold rolled to the target thickness of 0.50 mm using rough rolls, and the surface roughness of the strip after cold rolling is Ra = 0.85 μm;

[0052] 6) After cleaning the above-mentioned cold-rolled sheet with an aqueous solution of disodium hydrogen phosphate and sodium hydroxide, it is continuously annealed in a continuous annealing furnace. The atmosphere inside the continuous annealing furnace is a mixture of hydrogen and nitrogen, with an H2 content of 40%. The temperature of the soaking zone of the annealing furnace is 980℃, and the total annealing time is 280s.

[0053] 7) After annealing, the strip steel is coated with the first insulating coating using a coating roller. The coating is a semi-organic zinc-based chromate insulating coating with a solid content of 21%, and is cured at 550℃. The semi-organic zinc-based chromate insulating coating contains 0.5% H3BO3, 7.5% CrO3, 7.0% ZnO, 12.0% acrylic organic resin, 4.0% glycerol, and 3.5% polyethylene resin powder, with the remainder being deionized water.

[0054] 8) After the first coating of the above-mentioned steel strip is cured, a second water-based coating is applied. The solid content of the second water-based coating is 73%, and it is cured at 280℃ for 60 seconds. In the second water-based coating, the mass fractions of BaSO4 are 24.0%, ZnSO4 are 23.0%, CaSO4 is 12.0%, water-based acrylic resin is 12.0%, nano-SiO2 sol is 7.0%, and the remainder consists of 0.3% organic synthetic polyether dispersant, 0.2% diethylhexanol defoamer, 0.3% polyether-modified polysiloxane leveling agent, and deionized water.

[0055] The non-oriented electrical steel manufactured using the above process has a finished product iron loss P. 1.5 / 50 It is 2.45W / Kg, magnetic induction B 5000 It has a thickness of 1.67T and a coating film weight of 8.0g / m³. 2 The pencil hardness is 7H, the coating adhesion is grade 1, and the interlayer resistance is 25000 Ω·mm. 2 / piece, heat resistance rating is 190℃×48h, 5% NaCl solution, 35℃×5h conditions, surface corrosion area <10%.

[0056] Example 3

[0057] A non-oriented silicon steel for reducing eddy current losses in the core of a large generator and its production method, specifically including the following steps:

[0058] 1) The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 200 mm. The chemical composition of the slabs by weight percentage is C: 0.002%; Si: 3.4%; Mn: 0.45%; Als: 0.50%; S: 0.002%; N: 0.002%; Ti: 0.002%; with the remainder being 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 holding time is 230min.

[0060] 3) Hot-rolled slabs are hot-rolled to a thickness of 2.2 mm, with the final rolling temperature controlled at 860℃ and the coiling temperature at 680℃;

[0061] 4) The above-mentioned hot-rolled plates are shot-blasted and pickled, and then normalized at 850℃.

[0062] 5) The above-mentioned normalized plate is cold rolled to the target thickness of 0.50 mm using rough rolls, and the surface roughness of the strip after cold rolling is Ra = 0.89 μm.

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

[0064] 7) After annealing, the strip steel is coated with the first insulating coating using a coating roller. The coating is a semi-organic zinc-based chromate insulating coating with a solid content of 21%, and is cured at 580℃. The semi-organic zinc-based chromate insulating coating contains 0.6% H3BO3, 8.0% CrO3, 6.0% ZnO, 13.0% acrylic organic resin, 4.5% glycerol, and 4.0% polyethylene resin powder, with the remainder being deionized water.

[0065] 8) After the first coating of the above-mentioned steel strip is cured, a second water-based coating is applied. The solid content of the second water-based coating is 70%, and it is cured at 300℃ for 60 seconds. In the second water-based coating, the mass fractions of BaSO4 are 21.0%, ZnSO4 is 18.0%, CaSO4 is 13.0%, water-based acrylic resin is 11.0%, nano-SiO2 sol is 9.0%, and the remainder consists of 0.1% organic synthetic polyether dispersant, 0.2% diethylhexanol defoamer, 0.35% polyether-modified polysiloxane leveling agent, and deionized water.

[0066] The non-oriented electrical steel manufactured using the above process has a finished product iron loss P. 1.5 / 50 It is 2.40W / Kg, magnetic induction B 5000 It has a strength of 1.66T and a coating film weight of 6.1g / m³. 2 The pencil hardness is 8H, the coating adhesion is grade 1, and the interlayer resistance is 20000 Ω·mm. 2 / piece, heat resistance rating is 190℃×48h, 5% NaCl solution, 35℃×5h conditions, surface corrosion area <10%.

[0067] Comparative Example 1

[0068] A non-oriented silicon steel and its production method, specifically including the following steps:

[0069] 1) The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 210 mm. The chemical composition of the slabs by weight percentage is C: 0.003%; Si: 2.8%; Mn: 0.15%; Als: 0.6%; S: 0.003%; N: 0.003%; Ti: 0.003%; with the remainder being 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℃, and the heating and holding time is 210min.

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

[0072] 4) The above-mentioned hot-rolled plates are shot-blasted, pickled, and then normalized at 900℃;

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

[0074] 6) After the above-mentioned cold-rolled sheet is subjected to conventional alkaline washing, it is continuously annealed in a continuous annealing furnace. The atmosphere inside the continuous annealing furnace is a mixture of hydrogen and nitrogen, with an H2 content of 40%. The temperature of the soaking zone of the annealing furnace is 950℃, and the annealing time is 240s.

[0075] 7) After annealing, the strip steel is coated with the first insulating coating using a coating roller. The coating is a semi-organic zinc-based chromate insulating coating with a solid content of 20%, and is cured at 500℃. The semi-organic zinc-based chromate insulating coating contains 1.0% H3BO3, 7.0% CrO3, 6.5% ZnO, 15.0% acrylic organic resin, 4.0% glycerol, 3.5% polyethylene resin powder, and the remainder is deionized water.

[0076] 8) After the first coating of the above-mentioned steel strip is cured, a second water-based coating is applied. The solid content of the second water-based coating is 72%, and it is cured at 250℃ for 50 seconds. In the second water-based coating, the mass fractions of BaSO4 are 15.0%, ZnSO4 are 12.0%, CaSO4 is 8.0%, water-based acrylic resin is 9.0%, nano-SiO2 sol is 8.0%, and the remainder consists of 0.1% organic synthetic polyether dispersant, 0.1% diethylhexanol defoamer, 0.2% polyether-modified polysiloxane leveling agent, and deionized water.

[0077] The non-oriented electrical steel manufactured using the above process has a finished product iron loss P. 1.5 / 50 It is 2.70W / Kg, magnetic induction B 5000 The coating weight is 1.68T, and the coating film weight is 5.4g / m³. 2 The pencil hardness is 7H, the coating adhesion is grade 2, and the interlayer resistance is 9000 Ω·mm. 2 / piece, heat resistance rating is 185℃×48h. Although the product has excellent magnetic properties, the adhesion of the secondary paint coating is poor and the interlayer resistance is low, which does not meet the interlayer resistance requirements of large generators.

[0078] Comparative Example 2

[0079] A non-oriented silicon steel and its production method, specifically including the following steps:

[0080] 1) The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 230 mm. The chemical composition of the slabs by weight percentage is C: 0.003%; Si: 2.3%; Mn: 0.10%; Als: 0.45%; S: 0.003%; N: 0.003%; Ti: 0.003%; with the remainder being 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℃, and the heating and holding time is 220min.

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

[0083] 4) The above-mentioned hot-rolled plates are shot-blasted and pickled, and then normalized at 930℃;

[0084] 6) The above-mentioned normalized plate is cold rolled to the target thickness of 0.50 mm using rough rolls, and the surface roughness of the strip after cold rolling is Ra = 0.83 μm;

[0085] 7) After conventional alkaline washing, the cold-rolled strip is continuously annealed in a continuous annealing furnace. The atmosphere inside the furnace is a mixture of hydrogen and nitrogen, with an H2 content of 40%. The soaking temperature in the annealing furnace is 930℃, and the annealing time is 280s. After annealing, the strip is coated with a first insulating coating using a coating roller. The coating is a semi-organic zinc-based chromate insulating coating with a solid content of 19.5%, and it is cured at 500℃. In the zinc-based chromate coating, the mass fractions of H3BO3 are 0.5%, CrO3 is 7.5%, ZnO is 7.0%, acrylic organic resin is 12.0%, glycerol is 4.0%, polyethylene resin powder is 3.5%, and the remainder is deionized water.

[0086] 8) After the first coating of the above-mentioned steel strip is cured, a second water-based coating is applied. The solid content of the second water-based coating is 72%, and it is cured at 230℃ for 50 seconds. In the second water-based coating, the mass fractions of BaSO4 are 23.0%, ZnSO4 are 20.0%, CaSO4 is 12.0%, water-based acrylic resin is 12.0%, nano-SiO2 sol is 7.0%, and the remainder consists of 0.2% organic synthetic polyether dispersant, 0.2% diethylhexanol defoamer, 0.3% polyether-modified polysiloxane leveling agent, and deionized water.

[0087] The non-oriented electrical steel manufactured using the above process has a finished product iron loss P. 1.5 / 50 It is 3.20W / Kg, magnetic induction B 5000 It has a capacity of 1.70T and a coating film weight of 7.5g / m³. 2 The pencil hardness is 5H, the coating adhesion is grade 3, and the interlayer resistance is 10000 Ω·mm. 2 / piece, heat resistance rating 165℃×48h. The product has poor magnetic properties, and the second coating was not fully cured; the surface peeled off after being wiped with alcohol. Figure 3 As shown. Meanwhile, the coating has poor adhesion and low heat resistance, failing to 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 its production method, specifically including the following steps:

[0090] 1) The molten steel refined in the RH furnace is continuously cast into slabs with a thickness of 230 mm. The chemical composition of the slabs by weight percentage is C: 0.002%; Si: 3.0%; Mn: 0.30%; Als: 1.0%; S: 0.002%; N: 0.002%; Ti: 0.002%; with the remainder being 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℃, and the heating and holding time is 230min.

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

[0093] 4) The above-mentioned hot-rolled plates are shot-blasted and pickled, and then normalized at 880℃;

[0094] 6) The above-mentioned normalized plate is cold rolled to the target thickness of 0.50 mm using rough rolls, and the surface roughness of the strip after cold rolling is Ra=0.85μm;

[0095] 7) After cleaning the above-mentioned cold-rolled strip with an aqueous solution of disodium hydrogen phosphate and sodium hydroxide, it is continuously annealed in a continuous annealing furnace. The atmosphere inside the continuous annealing furnace is a mixture of hydrogen and nitrogen, with an H2 content of 40%. The soaking temperature of the annealing furnace is 980℃, and the annealing time is 280s. After annealing, the strip is coated with a first insulating coating using a coating roller. The coating is a semi-organic zinc-based chromate insulating coating with a solid content of 18.5%, and is cured at 550℃. In the zinc-based chromate coating, the mass fractions of H3BO3 are 0.6%, CrO3 is 8.0%, ZnO is 6.0%, acrylic organic resin is 13.0%, glycerol is 4.5%, polyethylene resin powder is 4.0%, and the remainder is deionized water.

[0096] 8) After the first coating of the above-mentioned steel strip is cured, a second water-based coating is applied. The solid content of the second water-based coating is 73%, and it is cured at 330℃ for 30 seconds. In the second water-based coating, the mass fractions of BaSO4 are 21.0%, ZnSO4 is 16.0%, CaSO4 is 13.0%, water-based acrylic resin is 14.0%, nano-SiO2 sol is 6.0%, and the remainder consists of 0.4% organic synthetic polyether dispersant, 0.2% diethylhexanol defoamer, 0.1% polyether-modified polysiloxane leveling agent, and deionized water.

[0097] The non-oriented electrical steel manufactured using the above process has a finished product iron loss P. 1.5 / 50 It is 2.45W / Kg, magnetic induction B 5000 It has a weight of 1.67T and a coating film weight of 6.0g / m³. 2 The pencil hardness is 5H, the coating adhesion is grade 3, and the interlayer resistance is 8500 Ω·mm. 2 / piece, heat resistance rating 160℃×48h. Although the product has excellent magnetic properties, the second coating was overheated, resulting in a dark yellow surface. Figure 4 As shown, this results in poor coating adhesion and a low heat resistance rating.

Claims

1. A method for producing high heat-resistant non-oriented silicon steel, characterized in that: A water-based secondary coating is applied to the surface of a steel strip that has been initially coated with an insulating coating; the production method includes the following steps: 1) Take molten steel and continuously cast it into slabs with a thickness of 200~230mm; 2) The slab is directly loaded into the heating furnace for heating. The temperature of the heating furnace is 1150~1250℃, and the total heating time is 210~230min. 3) The slab is finished rolled into a hot-rolled plate with a thickness of 2.2~2.4mm at a final rolling temperature of 860~920℃ and a coiling temperature of 650~700℃; 4) The hot-rolled plate is shot-blasted and pickled, then normalized at 850~900℃ to obtain a normalized plate; 5) The normalized plate is cold-rolled to a target thickness of 0.50 mm using coarse rolls, and the surface roughness Ra of the cold-rolled plate is ≥0.8 μm; 6) After the cold-rolled sheet is alkali washed, it is subjected to continuous annealing treatment. The atmosphere in the furnace is dry, the temperature of the soaking zone of the annealing furnace is 950~1000℃, and the total annealing time is 240~480s. 7) The continuously annealed steel strip is coated with a semi-organic zinc-based chromate insulating coating using a coating roller, and then cured at 500~600℃. The semi-organic zinc-based chromate insulating coating comprises 0.5~2.0% H3BO3, 5~10% CrO3, 5~10% ZnO, 10~20% acrylic organic resin, and 3~8% glycerol by mass fraction; the solid content of the semi-organic zinc-based chromate insulating coating is ≥20%. 8) After the first coat has cured, apply a second coat of water-based paint. After the second coat is applied, cure at 250~300℃ for 40~60 seconds.

2. The production method according to claim 1, characterized in that: The water-based secondary coating has a solid content of ≥70%, a curing temperature of 250~300℃, and a curing time of 40~60s.

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

4. The production method according to claim 3, characterized in that: The water-based secondary coating also includes 10-15% water-based acrylic resin and 5-10% nano-SiO2 sol by mass, with the remainder being additives and deionized water.

5. The production method according to claim 1, characterized in that: In step 2), the chemical composition of the slab, by weight percentage, includes: 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%, with the remainder being Fe and unavoidable impurities.

6. The production method according to claim 1, characterized in that: In step 6), the atmosphere inside the furnace is a mixture of hydrogen and nitrogen, with a ratio of H2 to N2 of 4:

6.

7. The production method according to claim 1, characterized in that: The semi-organic zinc-based chromate insulating coating also includes 3-5% polyethylene resin powder by mass, with the remainder being deionized water.

8. A non-oriented silicon steel produced by the production method according to any one of claims 1 to 7, 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 up to 190℃×48h, coating pencil hardness 6~8H, coating adhesion grade 1, coating film weight 6~8g / m³ 2 Interlayer resistance ≥20000Ω·mm 2 / piece.

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