Normalizing-free method for producing high-grade non-oriented electrical steel

Abstract

The invention discloses a normalizing-free method for producing high-grade non-oriented electrical steel, and belongs to the technical field of steel rolling. In order to solve the problem in non-normalizing production of high-grade non-oriented electrical steel with high silicon and high aluminum, the invention provides a method for producing the high-grade non-oriented electrical steel without normalizing, the high-grade non-oriented electrical steel contains 2.8-3.2 wt% of Si and 0.2-1 wt% of Al, and a hot rolling process, an acid pickling process and a cold rolling process are adopted, the hot rolling process adopts low-temperature plate blank heating, width fixing, rough rolling, finish rolling and high-temperature coiling heat treatment, and the cold rolling process adopts primary cold rolling, intermediate annealing, secondary cold rolling and finished product annealing. Under the condition of no special normalizing production line for the electrical steel, the hot rolling reduction rate and the coiling temperature are adjusted, the heat preservation pit is additionally arranged, hot rolling waste heat self-annealing is used for replacing normalizing, and the reduction rate and the annealing temperature of primary cold rolling and secondary cold rolling are reasonably distributed; and the high-efficiency non-oriented electrical steel with excellent large grain size and excellent magnetic performance is successfully developed.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel rolling, and specifically relates to a method for producing high-grade non-oriented electrical steel without normalization, which is used to prepare finished non-oriented electrical steel sheets with a thickness of 0.35 mm and excellent magnetic properties on a normalization production line dedicated to non-oriented electrical steel. Background Art

[0002] High-grade non-oriented silicon steel is primarily used in the cores of large steam turbines and hydroelectric generators, as well as high-efficiency, energy-saving home appliances, electric vehicles, and brushless DC and AC induction motors. High-grade non-oriented electrical steel boasts high magnetic permeability, low coercivity, and high resistivity, effectively reducing hysteresis and eddy current losses. Stringent performance requirements are imposed on this steel, with low iron loss being a key quality indicator. The lower the iron loss, the higher the product grade and quality. High magnetic induction strength is also crucial. Under the same magnetic field, high-magnetic-induction silicon steel sheets can make motor or transformer cores smaller and lighter, saving material.

[0003] During the steelmaking process, high-grade non-oriented electrical steel strictly limits the presence of impurities. Conventional harmful impurities such as carbon, sulfur, nitrogen, and oxygen must be extremely low. Magnetic detrimental elements such as titanium, vanadium, zirconium, niobium, arsenic, and copper must also be controlled within certain limits. Phosphorus forms iron phosphide at grain boundaries, which improves punchability, inhibits the nucleation and growth of unfavorably oriented grains, and increases magnetic induction intensity. During the hot rolling process, optimized heat treatment processes are required, with strict requirements for slab heating and finishing temperatures. When the hot rolling heating temperature is below the MnS solution temperature, MnS coarsens, which benefits magnetic properties. However, when the temperature exceeds the solution temperature, MnS dissolves and disperses, degrading magnetic properties. Therefore, the slab heating temperature must be properly controlled. A low slab heating temperature prevents the re-solution of MnS second-phase particles, ensuring their precipitation in the appropriate state during hot rolling and subsequent heat treatment, thereby avoiding deterioration of the finished product's iron loss. A properly set finishing temperature promotes the coarsening and aggregation of second-phase particles, promoting grain growth and improving iron loss.

[0004] Normalizing is an important step in the production of non-oriented electrical steel. By annealing the hot-rolled plate, the steel structure is homogenized, the residual stress generated during the hot rolling process is eliminated, the grains are refined, and a good organizational foundation is provided for subsequent cold rolling and annealing processes.

[0005] CN102634729A discloses a method for preparing a non-oriented electrical steel with low iron loss, high magnetic induction and high grade. The ingot is subjected to hot rolling, normalizing, pickling, primary cold rolling, intermediate annealing, secondary cold rolling and coating annealing to prepare a non-oriented electrical steel with low iron loss and high magnetic induction. CN103882291B discloses a high-silicon cold-rolled non-oriented electrical steel and a method for preparing the same. The steel comprises smelting, continuous casting, hot rolling, normalizing, primary cold rolling, two-stage annealing and finished product annealing. The steel adopts a low-silicon and high-aluminum composition system to achieve a high silicon effect and avoids the addition of rare earth elements. CN104073715A discloses a high-magnetic induction non-oriented electrical steel and a method for manufacturing the same. The steel is smelted with molten iron, steel is made in a converter, RH refining and desulfurization, continuous casting and rolling of thin slabs, normalizing, primary cold rolling and annealing. The finished product can meet the requirements of high-magnetic induction electrical steel for high-efficiency motors and variable frequency motor cores, and has low energy consumption and noise. CN110565022A discloses a method for manufacturing high-grade non-oriented electrical steel, which includes molten iron pretreatment, converter steelmaking, RH refining, continuous casting, hot rolling, normalizing, cold rolling and annealing. It adds online trimming to the cold rolling step of traditional electrical steel production, improves the risk of strip breakage caused by cold rolling edge cracking, improves production efficiency and meets the product thickness requirement of 0.5mm.

[0006] However, the normalizing process is typically reserved for dedicated electrical steel production lines, which require significant investment and are expensive. Omitting the normalizing process can reduce energy consumption in heating furnaces and other equipment, lowering production costs without compromising product performance. This allows the production of high-grade non-oriented electrical steel using conventional hot-rolling lines.

[0007] CN118756039A discloses an efficient method for preparing non-oriented silicon steel for refrigeration compressors. The chemical composition of the non-oriented silicon steel, measured in mass percentage, includes: C ≤ 0.0025%, Si 0.7-1.5%, Mn 0.20-0.40%, P ≤ 0.09%, S ≤ 0.007%, Al 0.2-0.5%, Ni 0.02-0.05%, Cr 0.02-0.05%, Ti ≤ 0.002%, with the remainder being Fe and unavoidable impurities. The preparation method includes continuous casting, heating, hot rolling, pickling, cold rolling, recrystallization annealing, and coating with an insulating coating. However, the product of this method is low-silicon medium-grade steel, and the upper limit of silicon content is 1.5%; although it does not require normalization, due to the low silicon content, the hot rolling heat treatment process will be very different from that of high-silicon steel, so its hot rolling heat treatment process is not suitable for high-grade; in addition, the cold rolling of this method is 5-pass cold rolling, which is not suitable for the production of high-grade silicon steel; at the same time, the thinner the silicon steel, the higher the performance and the greater the difficulty. The finished product thickness of this method is 0.5mm, which is not suitable for the production of thinner high-grade silicon steel.

[0008] CN115198203A discloses a non-oriented electrical steel sheet exempt from normalizing intermediate annealing, wherein the mass percentage of each chemical element is as follows: 0<C≤0.004%, Si: 1.0~2.6%, Mn: 0.2~1.0%, Al: 0.2~1.6%, Ca: 0.0003%~0.0035%, the balance being Fe and other inevitable impurities, as well as Si+Al: 1.4~3.2%, Si2 / Mn: 0.017~0.17, and among other inevitable impurities: S≤0.0040%, O≤0.003%, N≤0.003%, P≤0.2 %, Nb≤0.001%, V≤0.001%, Ti≤0.001%, and further satisfying: Nb+V+Ti≤0.0025%, 0.11≤C≤0.71, wherein R=Ca / (O+1 / 2S), and the Ca content is 0.0005%~0.0025%; the manufacturing method comprises the following steps: (1) smelting and continuous casting, (2) hot rolling, which includes: rough rolling, finishing rolling, coiling and heat preservation; wherein the temperature of the intermediate billet after rough rolling and before finishing rolling is controlled to be ≥950℃; (3) directly cold rolling without normalizing intermediate annealing or bell furnace intermediate annealing after the above hot rolling step; (4) continuous annealing. However, the product of this method is medium-low silicon medium grade steel, and the upper limit of silicon content is 2.6%. The invention discloses the hot rolling and hot rolling coiling process, but does not disclose the subsequent specific cold rolling process, annealing process and finished product thickness, and is not suitable for the production of thinner high-grade silicon steel. Summary of the Invention

[0009] In order to solve the problems caused by normalization in the prior art, the present invention develops a method for producing high-grade non-oriented electrical steel with high silicon and high aluminum without normalization. In the absence of a dedicated normalization production line for electrical steel, the method adjusts the hot rolling reduction rate, the opening degree of hot rolling laminar cooling water, and adds a heat preservation pit. The hot rolling coiling temperature is increased and the hot rolling waste heat self-annealing method is used to replace the traditional normalization step. The method further performs staged cold rolling and intermediate annealing to perform secondary cold rolling of 2.0-2.5 mm hot-rolled electrical steel to a finished product thickness of 0.15-0.65 mm. By rationally allocating the reduction rate and annealing temperature of the primary and secondary cold rolling, high-efficiency non-oriented electrical steel with fine grain size and excellent magnetic properties is successfully developed.

[0010] To achieve the above object, the present invention provides a method for producing high-grade non-oriented electrical steel without normalization, wherein the chemical smelting composition of the high-grade non-oriented electrical steel is C: ≤0.003wt%, Si: 2.8~3.2wt%, Mn: 0.2~1wt%, Al: 0.2~1wt%, Cr: 0.005~0.05wt%, Cu: 0.03~0.1wt%, P: 0.008~0.015wt%, S: ≤0.003wt%, N: ≤0.003wt%, Sb: 0.01~0.08wt%, Ti: ≤0.003wt%, V: ≤0.001wt%, and the remainder is Fe and unavoidable impurities; The process comprises the following steps: hot rolling process → pickling process → cold rolling process → insulating coating process to obtain a high-grade non-oriented electrical tube with a thickness of 0.15-0.65 mm; Hot rolling process: The steel billet adopts the process of low temperature slab heating → width setting → rough rolling → finishing rolling → high temperature coiling heat treatment; During the width setting process, the width setting machine applies a side pressure of 6 to 10 mm on both sides of the billet before rough rolling; In the rough rolling, the starting temperature of the rough rolling is 1100-1150° C., the reduction rate of the final rough rolling pass is controlled to be below 30%, the cumulative reduction rate of the rough rolling is above 80%, and the thickness of the intermediate billet is 40-45 mm; In the finishing rolling, the starting temperature of the finishing rolling is 950-1000° C., the cumulative reduction rate of the remaining passes except the last three passes is greater than 70%, the cumulative reduction rate of the last three passes is less than 30%, and the finishing temperature of the finishing rolling is 850-900° C. to obtain a hot rolled coil with a thickness of 2.0-2.5 mm; During the high-temperature coiling heat treatment, the laminar cooling water spray time is delayed for 1 to 3 seconds, or the laminar cooling water is not turned on and air cooling is used to perform high-temperature coiling, and the coiling temperature is controlled to be above 710°C. After coiling, the coiling is cooled to room temperature in a slow cooling pit. Pickling process: Use hydrochloric acid aqueous solution with HCl concentration of 60~70g / L and pickling accelerator mass fraction of 0.2~1% as the pickling medium; Cold rolling process: adopt the process of primary cold rolling → intermediate annealing → secondary cold rolling → finished product annealing; In the first cold rolling, the cumulative reduction rate of the first cold rolling is controlled to be 25-35%, and the first cold rolling temperature is above 50°C; In the secondary cold rolling, the cumulative reduction rate of the secondary cold rolling is controlled to be 75-85%, and the secondary cold rolling temperature is above 50°C.

[0011] Wherein, in the above method, the thickness of the steel ingot is 200~300mm.

[0012] Wherein, in the above method, during the low-temperature slab heating, the heating temperature of the steel slab is 1050~1150℃, and the holding time is 60~120min.

[0013] Among them, in the above method, in the rough rolling, a reciprocating 5-pass rough rolling process is performed on a single-stand rolling mill, and the 1st, 3rd and 5th passes are opened for high-pressure descaling water descaling treatment.

[0014] Wherein, in the above method, in the finishing rolling, 6 to 7 stands of finishing rolling are performed by a hot continuous finishing rolling mill group.

[0015] Wherein, in the above method, during the high-temperature coiling heat treatment, the slow cooling pit cooling time is 48 to 72 hours.

[0016] Wherein, in the above method, in the pickling process, the pickling speed is controlled at 60-80 m / min and the pickling temperature is 70-80°C.

[0017] Among them, in the above method, in the intermediate annealing, the once cold-rolled strip is subjected to intermediate annealing at 850~950℃×1~2min, the dew point is 0~-20℃, and the atmosphere is 10~20% H2+90~80% N2 by volume.

[0018] Among them, in the above method, in the finished product annealing, the secondary cold-rolled strip steel is subjected to finished product annealing at 900~950℃×1~2min, the dew point in the furnace is 0~-20℃, and the atmosphere is 10%~20% H2+90~80% N2 in a volume ratio.

[0019] Wherein, in the above method, the thickness of the obtained high-grade non-oriented electrical tube is 0.15mm, 0.20mm, 0.27mm, 0.50mm, 0.35mm or 0.65mm.

[0020] Beneficial effects of the present invention: In order to solve the problems caused by normalization in the prior art, the present invention develops a method for producing high-grade non-oriented electrical steel without normalization. In the absence of a dedicated normalization production line for electrical steel, the method adjusts the hot rolling reduction rate, the opening degree of hot rolling laminar cooling water, and adds a holding pit. The hot rolling coiling temperature is increased and the hot rolling waste heat self-annealing method is used to replace the traditional normalization step. Cold rolling is carried out in stages, and intermediate annealing is used to perform secondary cold rolling of 2.0-2.5 mm hot-rolled electrical steel to a finished product thickness of 0.15-0.65 mm. By rationally allocating the reduction rate and annealing temperature of the primary and secondary cold rolling, high-efficiency non-oriented electrical steel with excellent large grain size and excellent magnetic properties is successfully developed. The present invention reduces the normalization process, shortens the production cycle, enables the product to enter the next process more quickly, and improves overall production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the metallographic structure diagram of the finished product of Example 3.

[0022] Figure 2 This is the metallographic structure diagram of the finished product of Comparative Example 3. DETAILED DESCRIPTION

[0023] Specifically, a method for producing high-grade non-oriented electrical steel without normalization, wherein the chemical smelting composition of the high-grade non-oriented electrical steel is C: ≤0.003wt%, Si: 2.8-3.2wt%, Mn: 0.2-1wt%, Al: 0.2-1wt%, Cr: 0.005-0.05wt%, Cu: 0.03-0.1wt%, P: 0.008-0.015wt%, S: ≤0.003wt%, N: ≤0.003wt%, Sb: 0.01-0.08wt%, Ti: ≤0.003wt%, V: ≤0.001wt%, and the remainder is Fe and unavoidable impurities; The process comprises the following steps: hot rolling process → pickling process → cold rolling process → insulating coating process to obtain a high-grade non-oriented electrical tube with a thickness of 0.15-0.65 mm; Hot rolling process: The steel billet adopts the process of low temperature slab heating → width setting → rough rolling → finishing rolling → high temperature coiling heat treatment; During the width setting process, the width setting machine applies a side pressure of 6 to 10 mm on both sides of the billet before rough rolling; In the rough rolling, the starting temperature of the rough rolling is 1100-1150° C., the reduction rate of the final rough rolling pass is controlled to be below 30%, the cumulative reduction rate of the rough rolling is above 80%, and the thickness of the intermediate billet is 40-45 mm; In the finishing rolling, the starting temperature of the finishing rolling is 950-1000° C., the cumulative reduction rate of the remaining passes except the last three passes is greater than 70%, the cumulative reduction rate of the last three passes is less than 30%, and the finishing temperature of the finishing rolling is 850-900° C. to obtain a hot rolled coil with a thickness of 2.0-2.5 mm; During the high-temperature coiling heat treatment, the laminar cooling water spray time is delayed for 1 to 3 seconds, or the laminar cooling water is not turned on and air cooling is used to perform high-temperature coiling, and the coiling temperature is controlled to be above 710°C. After coiling, the coiling is cooled to room temperature in a slow cooling pit. Pickling process: Use hydrochloric acid aqueous solution with HCl concentration of 60~70g / L and pickling accelerator mass fraction of 0.2~1% as the pickling medium; Cold rolling process: adopt the process of primary cold rolling → intermediate annealing → secondary cold rolling → finished product annealing; In the first cold rolling, the cumulative reduction rate of the first cold rolling is controlled to be 25-35%, and the first cold rolling temperature is above 50°C; In the secondary cold rolling, the cumulative reduction rate of the secondary cold rolling is controlled to be 75-85%, and the secondary cold rolling temperature is above 50°C.

[0024] Hereinafter, the reasons for selecting the components of the base steel plate and limiting the range thereof in the present invention will be explained.

[0025] Carbon: is a harmful element. Residual carbon will worsen iron loss, cause magnetic aging, form fine carbides, increase hysteresis loss, and reduce magnetic induction intensity. Its influence on magnetic properties varies with its content and form. The non-oriented silicon steel of the present invention requires C: ≤0.003wt%.

[0026] Silicon: significantly reduces eddy current loss and total core loss; increases the critical temperature of A3 and A4 lines in the phase diagram, so that the high silicon silicon steel sheet has uniform structure, coarsened grains, and inclusions aggregate after high temperature annealing; reduces crystal anisotropy, reduces magnetic resistance, alleviates the harm of other impurities, deoxidizes and reduces magnetic aging. Silicon allows ferrite to exist stably at higher temperatures, which is beneficial for inhibiting the formation of austenite. Properly increasing the silicon content can increase the resistivity, reduce classical eddy current loss, and improve magnetic permeability. However, a silicon content exceeding 2% will deteriorate the processing performance. If a single cold rolling method is used, a normalization step must be performed. The present invention belongs to a high-grade electrical steel with a high silicon and high aluminum component system, with a silicon content Si: 2.8~3.2wt%. The steel has high strength and hardness. Therefore, the present invention performs intermediate annealing + secondary cold rolling to overcome the problems that may be caused by excessively high silicon content.

[0027] Manganese: increases the electrical resistance of steel and reduces iron loss; increases the occupancy of (100) and (110) surface textures in the strip structure and reduces the occupancy of (111) surface texture, improving magnetic properties; forms MnS to prevent hot brittleness caused by FeS. The addition amount of Mn in the present invention is 0.2~1wt%.

[0028] Aluminum: Similar to silicon, it has beneficial effects on magnetic properties, increasing electrical resistance, reducing the austenite phase, and promoting grain growth. However, it can make the steel brittle, but still offers greater plasticity than silicon. Aluminum's effects are affected by nitrogen content. It forms AlN precipitates with nitrogen, pinning grain boundaries, hindering grain growth and increasing iron loss. The addition level in this invention is controlled at 0.2-1 wt% Al.

[0029] Chromium: Cr can combine with N to form Cr2N, which can effectively reduce the magnetic damage to steel. When the Cr content in steel is less than 0.005%, the Cr element has a poor effect on fixing N, so 0.005% or more of Cr should be added to the steel. However, when the Cr content exceeds 0.2%, it will cause abnormal grain refinement. In order to meet the electromagnetic performance requirements, the Cr content is precisely controlled within a range close to the lower limit to avoid performance degradation due to other factors. The addition amount of the present invention is controlled at Cr: 0.005~0.05wt%.

[0030] Copper: Combined with S to form Cu x S inhibits MnS precipitation, improves the magnetic properties of the finished product, enhances the corrosion resistance and edge crack resistance of the hot-rolled plate, and improves the punching performance of the cold-rolled finished product. However, a copper content exceeding 0.2% by mass is not conducive to pickling. Based on cost considerations, the present invention adds 0.03-0.1 wt% Cu.

[0031] Phosphorus improves the magnetic properties of iron-silicon alloys, strengthens ferrite in low-carbon electrical steel, increases hardness, and improves punching performance. As a grain-boundary active element, it segregates at grain boundaries to form iron phosphide, leading to grain boundary embrittlement and cold brittleness. However, it can hinder the nucleation and growth of unfavorable (111)-oriented recrystallized grains, improve magnetic induction intensity, increase resistance, and reduce iron loss. Therefore, the phosphorus content can be added in appropriate amounts. The present invention controls the addition amount to be 0.008-0.015wt%.

[0032] Sulfur and nitrogen: They form fine particles that inhibit domain wall movement and degrade magnetic properties. Nitrogen forms harmful AIN precipitates, increasing iron loss. Sulfur exists as MnS microparticles in the matrix and as free S at grain boundaries. Reducing sulfur content can significantly reduce iron loss. The present invention strictly limits sulfur and nitrogen contents to ≤0.003wt% for S and ≤0.003wt% for N.

[0033] Tin and Antimony: Trace amounts of tin and antimony within certain limits promote the formation of favorable textures, increase magnetic induction intensity, and reduce iron losses. They can segregate at the interface between second-phase particles and the matrix, preventing their growth and enhancing the ability to suppress normal grain growth, acting as a secondary inhibitor. Sn and Sb have similar mechanisms of action on non-oriented electrical steel. Because the alloying element tin is more expensive than antimony, 0.01-0.08wt% Sb is added for cost considerations, while Sn is omitted. This can reduce the {111} texture component in the final annealed texture and increase the {100} texture component, thereby improving magnetic permeability.

[0034] Titanium, vanadium, zirconium, and niobium form fine particles that precipitate, raising the recrystallization temperature, delaying recrystallization and grain growth, and promoting the development of unfavorable {111} textures. Arsenic promotes the precipitation of sulfides such as MnS, affecting performance. Electrical steel requires high cleanliness, and the contents of these conventional harmful impurities and magnetic elements must be kept as low as possible. Since vanadium-titanium magnetite is used to smelt molten steel, the present invention controls the addition levels to ≤0.003wt% for Ti and ≤0.001wt% for V. Nb and Zr are omitted. Furthermore, the Ti and Nb contents are minimized, and can be set to zero.

[0035] The present invention adopts the process means of avoiding normalization and secondary cold rolling and the distribution of reduction rates of hot rolling and cold rolling in a high-silicon and high-aluminum component system to realize a method for producing high-grade non-oriented electrical steel.

[0036] In the present invention, the steel ingot used in the hot rolling process can be prepared using conventional processes in the art to ensure that the steel ingot meets the composition requirements of the present invention. The general process for smelting and continuous casting to obtain the steel ingot may include: blast furnace molten iron → molten iron pretreatment → converter smelting → RH refining → continuous casting, to obtain a steel ingot with a thickness of 200-300 mm and meeting the above-mentioned composition requirements, which then enters the non-normalization production process of the present invention. Of course, the present invention is not limited to the aforementioned smelting and continuous casting processes.

[0037] The present invention adopts a low-temperature slab heating + high-temperature coiling heat treatment process, the thickness of the steel ingot is 200-300mm, the slab temperature is controlled at 1050-1150°C, and the holding time is 60-120min; before rough rolling, the width setting machine applies a side pressure of 6-10mm on both sides of the ingot; then a reciprocating 5-pass rough rolling process is performed on a single-stand rolling mill, the rough rolling start temperature is 1100-1150°C, high-pressure descaling water is used for 3 passes, and high-pressure descaling water is used for descaling in passes 1, 3 and 5. The final rough rolling reduction rate is controlled to be less than 30%, the cumulative rough rolling reduction rate is more than 80%, and the intermediate billet thickness is controlled to be 40-45mm; then the intermediate billet is subjected to flying shearing and fine descaling treatment, and then the intermediate billet is subjected to hot rolling. The finishing rolling mill group performs 6~7 stands of finishing rolling, the finishing rolling start temperature is 950~1000℃, the cumulative reduction rate of the remaining passes (the first three passes or the first four passes) of the hot rolling finishing rolling except the last three passes is greater than 70%, and the cumulative reduction rate of the last three passes is less than 30%, the finishing rolling temperature is controlled to 850~900℃, the temperature difference between the finishing rolling entrance temperature and the final rolling temperature is controlled within 200℃, and the final hot rolling thickness is 2.0~2.5mm; in order to omit the hot rolling normalizing annealing, the laminar cooling water spray time is delayed by 1~3s, or the laminar cooling water is not turned on and air cooling is used. Finally, high-temperature coiling is adopted, and the coiling temperature is controlled to above 710℃ to achieve residual heat self-annealing. After hot rolling coiling, it enters the slow cooling pit and cools to room temperature for 48~72h.

[0038] While ensuring production efficiency and pickling surface quality, the pickling speed is controlled to 60-80 m / min and the pickling temperature is 70-80° C. In particular, the present invention uses a hydrochloric acid aqueous solution with an HCl concentration of 60-70 g / L and a pickling accelerator mass fraction of 0.2-1% as the pickling medium, in order to reduce the generation of surface iron oxide scale and provide a good foundation for subsequent cold rolling.

[0039] Cold rolling process: adopt primary cold rolling + intermediate annealing + secondary cold rolling + finished product annealing, reasonably distribute the reduction ratio of primary cold rolling and secondary cold rolling to obtain the ideal recrystallization structure and texture, among which the secondary cold rolling reduction ratio is kept at 75~85%, and then the primary cold rolling reduction ratio is calculated according to the thickness of the hot-rolled product and the thickness of the cold-rolled product. A smaller primary cold rolling reduction is conducive to the production of coarse grains during the intermediate annealing process, and a larger secondary cold rolling reduction ratio is conducive to promoting the transformation of {111} texture ({111} is an unfavorable texture) during the subsequent annealing process, which is conducive to the formation of strong {100} and the high magnetic flux density B of the finished product. 50 .

[0040] Single cold rolling: The hot-rolled pickled coil is reciprocatingly cold rolled on a 20-roll Sendzimir mill, and the cumulative cold rolling reduction is controlled at 25-35%. The 2.0-2.5mm hot-rolled pickled plate is cold rolled to a certain thickness. The thermal effect generated by the cold rolling deformation is used to heat the strip. The injection flow and temperature of the cold rolling emulsion are controlled to keep the cold rolling temperature above 50°C.

[0041] Intermediate annealing: The cold-rolled strip is annealed in a continuous furnace at 850~950℃×1~2min, with a dew point of 0℃~-20℃ and an atmosphere of 10~20% H2+90~80% N2 by volume. The purpose of the intermediate annealing step is to soften the metal that has been hardened by high cold working and form a primary recrystallization.

[0042] Secondary cold rolling: The intermediate annealed strip is subjected to a second reciprocating cold rolling on a 20-roll Sendzimir rolling mill. The cold rolling temperature is above 50°C, the cumulative reduction rate is controlled at 75~85%, and the thickness of the rolled product is 0.15~0.65mm.

[0043] Finished product annealing: The secondary cold-rolled strip undergoes finished product annealing in a continuous furnace at 900~950℃×1~2min. The dew point in the furnace is 0℃~-20℃, and the atmosphere is 10~20% H2+90~80% N2 by volume. After applying the insulating coating, the strip passes through the dryer and coiler to complete the production.

[0044] More specifically, the thickness of the high-grade non-oriented electrical tube obtained in the present invention is 0.15 mm, 0.20 mm, 0.27 mm, 0.50 mm, 0.35 mm or 0.65 mm.

[0045] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0046] Example 1 Step 1: The chemical smelting composition of the rolled steel ingot includes, by weight percentage, C: 0.003%, Si: 2.8%, Mn: 0.2%, Al: 0.3%, Cr: 0.03%, Cu: 0.05%, P: 0.01%, S: 0.003%, N: 0.0015%, Sb: 0.03%, Ti: 0.003%, V: 0.001%, and the rest is Fe and unavoidable impurity elements.

[0047] Step 2: Low-temperature slab heating: The steel slab thickness is 250 mm and the slab length is 8.5 m; the heating temperature is 1130° C. and the slab holding time is 90 min.

[0048] Step 3: High temperature hot rolling: The width setting machine applies 6mm side pressure to both sides of the ingot to give the edge deformation to achieve the purpose of refining the edge grain of the slab to control the hot rolling edge cracking phenomenon; then the single stand rolling mill performs a reciprocating 5-pass rough rolling process, the rough rolling start temperature is 1100℃, high pressure water descaling is performed for 3 passes, and high pressure water descaling is performed for 1, 3 and 5 passes. The final rough rolling reduction rate is controlled below 30%, the cumulative rough rolling reduction rate is above 80%, and the intermediate billet thickness is controlled at 40 mm; then the intermediate billet is subjected to flying shearing and fine descaling treatments, and then is subjected to 7-stand finishing rolling by a hot continuous rolling finishing mill. The finishing rolling start temperature is 1000°C, and the cumulative reduction rate of the first four finishing passes is controlled to be greater than 70%, and the cumulative reduction rate of the last three finishing passes is less than 30%. The finishing final rolling temperature is controlled at 880°C, and the finishing outlet plate thickness is 2.5mm; after finishing rolling, the laminar cooling water is delayed for 3s, and the coiling temperature is controlled to 750°C by the rear-stage cooling method, and then it enters the slow cooling pit to cool to room temperature for 72h.

[0049] Step 4: Pickling: In order to ensure the surface quality of the cold-rolled steel base, 0.3% mass fraction of pickling accelerator (QUAKER INHIBITOR 8905) is added to the hot-rolled plate for pickling. The pickling medium is HCl, the concentration is 70g / L, the pickling speed is 60m / min, and the pickling tank temperature is 80℃.

[0050] Step 5: Primary cold rolling: The hot-rolled pickled coil is reciprocatingly cold rolled on a 20-roll Sendzimir mill, and the cumulative cold rolling reduction is controlled at 30%. The 2.5mm hot-rolled pickled plate is cold rolled to 1.75mm. The thermal effect generated by the cold rolling deformation is used to heat the strip, and the injection flow and temperature of the cold rolling emulsion are controlled to keep the cold rolling temperature above 50°C.

[0051] Step 6: Intermediate annealing: The cold-rolled strip is annealed in a continuous furnace at 950°C for 1 minute, with a dew point of -20°C and an atmosphere of 10% H₂O₂ by volume. 2+ 90%N2.

[0052] Step 7: Secondary cold rolling: The intermediate annealed strip with a thickness of 1.75 mm is subjected to a second reciprocating cold rolling on a 20-roll Sendzimir rolling mill. The cold rolling temperature is above 50°C, the cumulative reduction rate is controlled to be 80%, and the thickness of the rolled product is 0.35 mm.

[0053] Step 8: The secondary cold rolled strip is annealed in a continuous furnace at 950°C for 2 minutes. The dew point in the furnace is -20°C and the atmosphere is 10% H2O by volume. 2+ 90% N2, after applying the insulating coating, the strip passes through the dryer and coiler to complete the production.

[0054] Example 2 Step 1: The chemical smelting composition of the rolled steel ingot includes, by weight percentage, C: 0.003%, Si: 3.0%, Mn: 0.2%, Al: 0.5%, Cr: 0.03%, Cu: 0.04%, P: 0.01%, S: 0.003%, N: 0.0015%, Sb: 0.03%, Ti: 0.003%, V: 0.001%, and the rest are Fe and unavoidable impurity elements.

[0055] Step 2: Low-temperature slab heating: The steel slab thickness is 250 mm and the slab length is 8.5 m; the heating temperature is 1120° C. and the slab holding time is 90 min.

[0056] Step 3: High temperature hot rolling: The width setting machine applies 6mm side pressure to both sides of the ingot to give the edge deformation to achieve the purpose of refining the edge grain of the slab to control the hot rolling edge cracking phenomenon; then the single stand rolling mill performs a reciprocating 5-pass rough rolling process, the rough rolling start temperature is 1100℃, high pressure water descaling is performed for 3 passes, and high pressure water descaling is performed for 1, 3 and 5 passes. The final rough rolling reduction rate is controlled below 30%, the cumulative rough rolling reduction rate is above 80%, and the intermediate billet thickness is controlled at 4 0mm; then the intermediate billet is subjected to flying shearing and fine descaling treatment, and then the 7-stand finishing rolling is carried out by the hot continuous rolling finishing mill. The finishing rolling start temperature is 1000℃, and the cumulative reduction rate of the first four finishing passes is controlled to be greater than 70%, and the cumulative reduction rate of the last three finishing passes is less than 30%. The finishing rolling final temperature is controlled at 880℃, and the finishing rolling outlet plate thickness is 2.5mm; after rolling, the laminar cooling water is delayed for 3s, and the coiling temperature is controlled to 750℃ by the rear cooling method, and then it enters the slow cooling pit to cool to room temperature for 72h.

[0057] Step 4: Pickling: In order to ensure the surface quality of the cold-rolled steel base, 0.3% mass fraction of pickling accelerator (QUAKER INHIBITOR 8905) is added to the hot-rolled plate for pickling. The pickling medium is HCl, the concentration is 70g / L, the pickling speed is 60m / min, and the pickling tank temperature is 80℃.

[0058] Step 5: Primary cold rolling: The hot-rolled pickled coil is reciprocatingly cold rolled on a 20-roll Sendzimir mill, and the cumulative cold rolling reduction is controlled at 30%. The 2.5mm hot-rolled pickled plate is cold rolled to 1.75mm. The thermal effect generated by the cold rolling deformation is used to heat the strip, and the injection flow and temperature of the cold rolling emulsion are controlled to keep the cold rolling temperature above 50°C.

[0059] Step 6: Intermediate annealing: The cold-rolled strip is annealed in a continuous furnace at 950°C for 1 minute, with a dew point of -20°C and an atmosphere of 10% H₂O₂ by volume. 2+ 90%N2.

[0060] Step 7: Secondary cold rolling: The intermediate annealed strip with a thickness of 1.75 mm is subjected to a second reciprocating cold rolling on a 20-roll Sendzimir rolling mill, with the cumulative reduction rate controlled at 80%, and the thickness of the rolled product is 0.35 mm.

[0061] Step 8: The secondary cold rolled strip is annealed in a continuous furnace at 950°C for 2 minutes. The dew point in the furnace is -20°C and the atmosphere is 10% H2O by volume. 2+ 90% N2, after applying the insulating coating, the strip passes through the dryer and coiler to complete the production.

[0062] Example 3 Step 1: The chemical smelting composition of the rolled steel ingot includes, by weight percentage, C: 0.003%, Si: 3.2%, Mn: 0.2%, Al: 0.7%, Cr: 0.03%, Cu: 0.05%, P: 0.01%, S: 0.003%, N: 0.0015%, Sb: 0.03%, Ti: 0.003%, V: 0.001%, and the rest are Fe and unavoidable impurity elements.

[0063] Step 2: Low-temperature slab heating: The steel slab thickness is 250 mm and the slab length is 8.5 m; the heating temperature is 1130° C. and the slab holding time is 90 min.

[0064] Step 3: High temperature hot rolling: The width setting machine applies 6mm side pressure on both sides of the ingot to give the edge deformation to achieve the purpose of refining the edge grain of the slab to control the hot rolling edge cracking phenomenon; then the single stand rolling mill performs a reciprocating 5-pass rough rolling process, the rough rolling start temperature is 1150℃, high pressure water descaling is performed for 3 passes, and high pressure water descaling is performed for 1, 3 and 5 passes. The final rough rolling reduction rate is controlled below 30%, the cumulative rough rolling reduction rate is above 80%, and the intermediate billet thickness is controlled at 4 0mm; then the intermediate billet is subjected to flying shearing and fine descaling treatment, and then the 7-stand finishing rolling is carried out by the hot continuous rolling finishing mill. The finishing rolling start temperature is 1000℃, and the cumulative reduction rate of the first three finishing passes is controlled to be greater than 70%, and the cumulative reduction rate of the last three finishing passes is less than 30%. The finishing temperature is controlled at 880℃, and the finishing outlet plate thickness is 2.5mm; after rolling, the laminar cooling water is delayed for 3s, and the coiling temperature is controlled to 750℃ by the rear cooling method, and then it enters the slow cooling pit to cool to room temperature for 72h.

[0065] Step 4: Pickling: In order to ensure the surface quality of the cold-rolled steel base, 0.3% mass fraction of pickling accelerator (QUAKER INHIBITOR 8905) is added to the hot-rolled plate for pickling. The pickling medium is HCl, the concentration is 70g / L, the pickling speed is 60m / min, and the pickling tank temperature is 80℃.

[0066] Step 5: One-time cold rolling: The hot-rolled pickled coil is reciprocatingly cold rolled on a 20-roll Sendzimir mill, and the cumulative cold rolling reduction is controlled at 30%. The 2.5mm hot-rolled pickled plate is cold rolled to 1.75mm. The cold rolling temperature is kept above 50°C by controlling the thermal effect generated by deformation and the injection flow and temperature of the cold rolling emulsion.

[0067] Step 6: Intermediate annealing: The cold-rolled strip is annealed in a continuous furnace at 950°C for 1 minute, with a dew point of -20°C and an atmosphere of 10% H₂O₂ by volume. 2+ 90%N2.

[0068] Step 7: Secondary cold rolling: The intermediate annealed strip with a thickness of 1.75 mm is subjected to a second reciprocating cold rolling on a 20-roll Sendzimir rolling mill, with the cumulative reduction rate controlled at 80%, and the thickness of the rolled product is 0.35 mm.

[0069] Step 8: The secondary cold rolled strip is annealed in a continuous furnace at 950°C for 2 minutes. The dew point in the furnace is -20°C and the atmosphere is 10% H2O by volume. 2+ 90% N2, after applying the insulating coating, the strip passes through the dryer and coiler to complete the production.

[0070] Comparative Example 1 The difference from the embodiment is that the steel base uses a low-silicon, low-aluminum alloy composition and no Sb element is added. The specific steps are as follows: Step 1: The chemical smelting composition of the rolled steel ingot includes, by weight percentage, C: 0.003%, Si: 1.7%, Mn: 0.2%, Al: 0.3%, Cr: 0.03%, Cu: 0.04%, P: 0.01%, S: 0.003%, N: 0.0015%, Ti: 0.003%, V: 0.001%, and the rest is Fe and unavoidable impurity elements.

[0071] Step 2: Low-temperature slab heating: The steel slab thickness is 250 mm and the slab length is 8.5 m; the heating temperature is 1200°C and the slab holding time is 90 min.

[0072] Step 3: High temperature hot rolling: The width setting machine applies 6mm side pressure on both sides of the ingot to give the edge deformation to achieve the purpose of refining the edge grain of the slab to control the hot rolling edge cracking phenomenon; then the single stand rolling mill performs a reciprocating 5-pass rough rolling process, the rough rolling start temperature is 1150℃, high pressure water descaling is performed for 3 passes, and high pressure water descaling is performed for 1, 3 and 5 passes. The final rough rolling reduction rate is controlled below 30%, the cumulative rough rolling reduction rate is above 80%, and the intermediate billet thickness is controlled at 4 5mm; then the intermediate billet is subjected to flying shearing and fine descaling treatment, and then to 7-stand finishing rolling by hot continuous rolling finishing mill, the finishing rolling start temperature is 1000℃, and the cumulative reduction rate of the first four finishing passes is controlled to be less than 40%, and the cumulative reduction rate of the last three finishing passes is greater than 60%, the finishing temperature is controlled at 880℃, and the finishing outlet plate thickness is 2.5mm; after rolling, the laminar cooling water is delayed for 3s, and the coiling temperature is controlled to 750℃ by the back-stage cooling method, and then it enters the slow cooling pit to cool to room temperature for 72h.

[0073] Step 4: Pickling: In order to ensure the surface quality of the cold-rolled steel base, 0.2% mass fraction of pickling accelerator (QUAKER INHIBITOR 8905) is added to the hot-rolled plate for pickling. The pickling medium is HCl with a concentration of 70g / L, the pickling speed is 60m / min, and the pickling tank temperature is 80℃.

[0074] Step 5: One-time cold rolling: The hot-rolled pickled coil is reciprocatingly cold rolled on a 20-roll Sendzimir mill, and the cumulative cold rolling reduction is controlled at 30%. The 2.5mm hot-rolled pickled plate is cold rolled to 1.75mm. The cold rolling temperature is kept above 50°C by controlling the thermal effect generated by deformation and the injection flow and temperature of the cold rolling emulsion.

[0075] Step 6: Intermediate annealing: The cold-rolled strip is annealed in a continuous furnace at 950°C for 1 minute, with a dew point of -20°C and an atmosphere of 10% H₂O₂ by volume. 2+ 90%N2.

[0076] Step 7: Secondary cold rolling: The intermediate annealed strip with a thickness of 1.75 mm is subjected to a second reciprocating cold rolling on a 20-roll Sendzimir rolling mill, with the cumulative reduction rate controlled at 80%, and the thickness of the rolled product is 0.35 mm.

[0077] Step 8: The secondary cold rolled strip is annealed in a continuous furnace at 950°C for 2 minutes. The dew point in the furnace is -20°C and the atmosphere is 10% H2O by volume. 2+ 90% N2, after applying the insulating coating, the strip passes through the dryer and coiler to complete the production.

[0078] Comparative Example 2 The difference from the embodiment is that the thickness of the finished product is the same but the reduction ratio distribution of the secondary cold rolling is different.

[0079] Step 1: The chemical smelting composition of the rolled steel ingot includes, by weight percentage, C: 0.003%, Si: 3.2%, Mn: 0.2%, Al: 0.5%, Cr: 0.03%, Cu: 0.05%, P: 0.01%, S: 0.003%, N: 0.0015%, Sb: 0.03%, Ti: 0.003%, V: 0.001%, and the rest are Fe and unavoidable impurity elements.

[0080] Step 2: Low-temperature slab heating: The steel slab thickness is 250 mm and the slab length is 8.5 m; the heating temperature is 1130° C. and the slab holding time is 90 min.

[0081] Step 3: High temperature hot rolling: The width setting machine applies 6mm side pressure on both sides of the ingot to give the edge deformation to achieve the purpose of refining the edge grain of the slab to control the hot rolling edge cracking phenomenon; then the single stand rolling mill performs a reciprocating 5-pass rough rolling process, the rough rolling start temperature is 1150℃, high pressure water descaling is performed for 3 passes, and high pressure water descaling is performed for 1, 3 and 5 passes. The final rough rolling reduction rate is controlled below 30%, the cumulative rough rolling reduction rate is above 80%, and the intermediate billet thickness is controlled at 4 0mm; then the intermediate billet is subjected to flying shearing and fine descaling treatment, and then the 7-stand finishing rolling is carried out by the hot continuous rolling finishing mill. The finishing rolling start temperature is 1000℃, and the cumulative reduction rate of the first four finishing passes is controlled to be greater than 70%, and the cumulative reduction rate of the last three finishing passes is less than 30%. The finishing rolling final temperature is controlled at 880℃, and the finishing rolling outlet plate thickness is 2.5mm; after rolling, the laminar cooling water is delayed for 3s, and the coiling temperature is controlled to 750℃ by the rear cooling method, and then it enters the slow cooling pit to cool to room temperature for 72h.

[0082] Step 4: Pickling: In order to ensure the surface quality of the cold-rolled steel base, 0.2% mass fraction of pickling accelerator (QUAKER INHIBITOR 8905) is added to the hot-rolled plate for pickling. The pickling medium is HCl with a concentration of 70g / L, the pickling speed is 60m / min, and the pickling tank temperature is 80℃.

[0083] Step 5: One-time cold rolling: The hot-rolled pickled coil is reciprocatingly cold rolled on a 20-roll Sendzimir mill, and the cumulative cold rolling reduction is controlled at 60%. The 2.5mm hot-rolled pickled plate is cold rolled to 1mm. The cold rolling temperature is kept above 50°C by controlling the thermal effect generated by deformation and the injection flow and temperature of the cold rolling emulsion.

[0084] Step 6: Intermediate annealing: The cold-rolled strip is annealed in a continuous furnace at 950°C for 1 minute, with a dew point of -20°C and an atmosphere of 10% H₂O₂ by volume. 2+ 90%N2.

[0085] Step 7: Secondary cold rolling: The intermediate annealed strip with a thickness of 1 mm is subjected to a second reciprocating cold rolling on a 20-roll Sendzimir rolling mill, with the cumulative reduction rate controlled at 65%, and the thickness of the rolled product is 0.35 mm.

[0086] Step 8: The secondary cold rolled strip is annealed in a continuous furnace at 950°C for 2 minutes. The dew point in the furnace is -20°C and the atmosphere is 10% H2O by volume. 2+ 90% N2, after applying the insulating coating, the strip passes through the dryer and coiler to complete the production.

[0087] Comparative Example 3 The difference from the embodiment is that the hot rolling coiling temperature is low and hot rolling residual heat self-annealing is not used instead of normalizing.

[0088] Step 1: The chemical smelting composition of the rolled steel ingot includes, by weight percentage, C: 0.003%, Si: 3.0%, Mn: 0.2%, Al: 0.7%, Cr: 0.03%, Cu: 0.04%, P: 0.01%, S: 0.005%, N: 0.0015%, Sb: 0.03%, Ti: 0.003%, V: 0.001%, and the rest are Fe and unavoidable impurity elements.

[0089] Step 2: Low-temperature slab heating: The steel slab thickness is 250 mm and the slab length is 8.5 m; the heating temperature is 1120° C. and the slab holding time is 90 min.

[0090] Step 3: High temperature hot rolling: The width setting machine applies 6mm side pressure to both sides of the ingot to give the edge deformation to achieve the purpose of refining the edge grain of the slab to control the hot rolling edge cracking phenomenon; then the single stand rolling mill performs a reciprocating 5-pass rough rolling process, the rough rolling start temperature is 1100℃, high pressure water descaling is performed for 3 passes, and the 1st, 3rd and 5th passes are opened for high pressure water descaling. The final rough rolling reduction rate is controlled below 30%, the rough rolling cumulative reduction rate is above 80%, and the intermediate The thickness of the billet is controlled at 40mm; then the intermediate billet is subjected to flying shearing and fine descaling treatment, and then subjected to 7-stand finishing rolling by the hot continuous rolling finishing mill. The finishing rolling start temperature is 1000℃, and the cumulative reduction rate of the first four finishing passes is controlled to be greater than 70%, and the cumulative reduction rate of the last three finishing passes is less than 30%. The finishing rolling final temperature is controlled at 880℃, and the finishing rolling outlet plate thickness is 2.5mm; after rolling, the laminar cooling water is turned on, the coiling temperature is controlled to 620℃, and then it enters the slow cooling pit to cool to room temperature for 72h.

[0091] Step 4: Pickling: In order to ensure the surface quality of the cold-rolled steel base, 0.2% mass fraction of pickling accelerator (QUAKER INHIBITOR 8905) is added to the hot-rolled plate for pickling. The pickling medium is HCl with a concentration of 70g / L, the pickling speed is 60m / min, and the pickling tank temperature is 80℃.

[0092] Step 5: Primary cold rolling: The hot-rolled pickled coil is reciprocatingly cold rolled on a 20-roll Sendzimir mill, and the cumulative cold rolling reduction is controlled at 30%. The 2.5mm hot-rolled pickled plate is cold rolled to 1.75mm. The thermal effect generated by the cold rolling deformation is used to heat the strip, and the injection flow and temperature of the cold rolling emulsion are controlled to keep the cold rolling temperature above 50°C.

[0093] Step 6: Intermediate annealing: The cold-rolled strip is annealed in a continuous furnace at 950°C for 1 minute, with a dew point of -20°C and an atmosphere of 10% H₂O₂ by volume. 2+ 90%N2.

[0094] Step 7: Secondary cold rolling: The intermediate annealed strip with a thickness of 1.75 mm is subjected to a second reciprocating cold rolling on a 20-roll Sendzimir rolling mill, with the cumulative reduction rate controlled at 80%, and the thickness of the rolled product is 0.35 mm.

[0095] Step 8: The secondary cold rolled strip is annealed in a continuous furnace at 950°C for 2 minutes. The dew point in the furnace is -20°C and the atmosphere is 10% H2O by volume. 2+ 90% N2, after applying the insulating coating, the strip passes through the dryer and coiler to complete the production.

[0096] The test results are shown in Table 1. It can be seen that the embodiments can obtain non-oriented electrical steel products with high magnetic induction and low iron loss.

[0097] Table 1 Composition and performance differences between examples and comparative examples Figure 1 This is the metallographic structure diagram of the finished product of Example 3, the average grain size is 130 μm, Figure 2 The metallographic structure of the finished product of comparative example 3 is shown in FIG. 1 , wherein the average grain size is 105 μm. Figure 1 and Figure 2 It can be seen that the finished product of Comparative Example 3 has not been subjected to high-temperature coiling, and its grain size is significantly smaller, which does not meet the large grain size requirement of non-oriented silicon steel.

[0098] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0099] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for producing high-grade non-oriented electrical steel without normalization, characterized in that: The chemical smelting composition of the high-grade non-oriented electrical steel is C: ≤0.003wt%, Si: 2.8~3.2wt%, Mn: 0.2~1wt%, Al: 0.2~1wt%, Cr: 0.005~0.05wt%, Cu: 0.03~0.1wt%, P: 0.008~0.015wt%, S: ≤0.003wt%, N: ≤0.003wt%, Sb: 0.01~0.08wt%, Ti: ≤0.003wt%, V: ≤0.001wt%, and the rest is Fe and unavoidable impurities; The process comprises the following steps: hot rolling process → pickling process → cold rolling process → insulating coating process to obtain a high-grade non-oriented electrical tube with a thickness of 0.15-0.65 mm; Hot rolling process: The steel billet adopts the process of low temperature slab heating → width setting → rough rolling → finishing rolling → high temperature coiling heat treatment; During the width setting process, the width setting machine applies a side pressure of 6 to 10 mm on both sides of the billet before rough rolling; In the rough rolling, the starting temperature of the rough rolling is 1100-1150° C., the reduction rate of the final rough rolling pass is controlled to be below 30%, the cumulative reduction rate of the rough rolling is above 80%, and the thickness of the intermediate billet is 40-45 mm; In the finishing rolling, the starting temperature of the finishing rolling is 950-1000° C., the cumulative reduction rate of the remaining passes except the last three passes is greater than 70%, the cumulative reduction rate of the last three passes is less than 30%, and the finishing temperature of the finishing rolling is 850-900° C. to obtain a hot rolled coil with a thickness of 2.0-2.5 mm; During the high-temperature coiling heat treatment, the laminar cooling water spray time is delayed for 1 to 3 seconds, or the laminar cooling water is not turned on and air cooling is used to perform high-temperature coiling, and the coiling temperature is controlled to be above 710°C. After coiling, the coiling is cooled to room temperature in a slow cooling pit. Pickling process: Use hydrochloric acid aqueous solution with HCl concentration of 60~70g / L and pickling accelerator mass fraction of 0.2~1% as the pickling medium; Cold rolling process: adopt the process of primary cold rolling → intermediate annealing → secondary cold rolling → finished product annealing; In the first cold rolling, the cumulative reduction rate of the first cold rolling is controlled to be 25-35%, and the first cold rolling temperature is above 50°C; In the secondary cold rolling, the cumulative reduction rate of the secondary cold rolling is controlled to be 75-85%, and the secondary cold rolling temperature is above 50°C.

2. The method according to claim 1, wherein: The thickness of the steel ingot is 200-300 mm.

3. The method according to claim 1, wherein: In the low-temperature slab heating, the heating temperature of the steel slab is 1050-1150° C., and the holding time is 60-120 minutes.

4. The method according to claim 1, wherein: In the rough rolling, a reciprocating 5-pass rough rolling process is performed on a single-stand rolling mill, and the 1st, 3rd and 5th passes are opened for high-pressure descaling water descaling treatment.

5. The method according to claim 1, wherein: In the finishing rolling, 6 to 7 stands of finishing rolling are performed by a hot continuous finishing rolling mill group.

6. The method according to claim 1, wherein: During the high-temperature coiling heat treatment, the slow cooling pit cooling time is 48 to 72 hours.

7. The method according to claim 1, wherein: In the pickling process, the pickling speed is controlled at 60-80 m / min and the pickling temperature is 70-80°C.

8. The method according to claim 1, wherein: In the intermediate annealing, the cold-rolled steel strip is subjected to intermediate annealing at 850-950° C.×1-2 min, with a dew point of 0-20° C. and an atmosphere of 10-20% H 2 + 90-80% N 2 by volume.

9. The method according to claim 1, wherein: In the finished product annealing, the secondary cold rolled strip steel is subjected to finished product annealing at 900-950° C.×1-2 min, the dew point in the furnace is 0-20° C., and the atmosphere is 10%-20% H2+90-80% N2 in a volume ratio.

10. The method according to any one of claims 1 to 9, characterized in that: The obtained high-grade non-oriented electrical tube has a thickness of 0.15 mm, 0.20 mm, 0.27 mm, 0.50 mm, 0.35 mm or 0.65 mm.

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