Preparation method of non-oriented electrical steel 50W800 and non-oriented electrical steel 50W800

Abstract

The invention provides a preparation method of non-oriented electrical steel 50W800 and the non-oriented electrical steel 50W800. The preparation method comprises the steps that molten iron is pretreated, smelted in a converter and refined, and refined molten steel is obtained; thin slab continuous casting and rolling: the refined molten steel is injected into a tundish for continuous casting to form a continuous casting slab; the continuous casting billet is heated in a furnace, discharged out of the furnace, rolled and taken to obtain a steel coil; annealing: carrying out annealing, coating and cooling on the steel coil to obtain the non-oriented electrical steel 50W800; the annealing temperature is 930 DEG C to 1000 DEG C; the non-oriented electrical steel 50W800 comprises the following chemical components in percentage by weight: less than or equal to 0.0030% of C, more than or equal to 0.35% and less than or equal to 0.48% of Si, more than or equal to 0.20% and less than or equal to 0.30% of Mn, more than or equal to 0.075% and less than or equal to 0.095% of P, less than or equal to 0.0045% of S, more than or equal to 0.20% and less than or equal to 0.40% of Al, less than or equal to 0.0030% of N, less than or equal to 0.0020% of Ti, more than or equal to 0.0015% and less than or equal to 0.0035% of Ca, less than or equal to 0.010% of C + S + N + Ti and the balance of iron and inevitable trace elements The method is long in continuous casting furnace, high in pulling speed, high in production efficiency and low in production cost, and the obtained product is low in iron loss and high in magnetic induction intensity.

Description

Technical Field

[0001] The present application belongs to the field of steel, and specifically relates to a preparation method of non-oriented electrical steel 50W800 and non-oriented electrical steel 50W800. Background Art

[0002] The main component of non-oriented electrical steel 50W800 is ferrosilicon alloy, which is easy to cut and punch, and the slice size is high, which is conducive to improving its processing efficiency and product quality. In addition, the volume and weight of the motor or transformer core made of it are relatively small, which is conducive to saving materials and reducing costs. Therefore, it is widely used in motors, generators, transformers, chokes, electromagnetic mechanisms, relays and measuring instruments, especially in large AC generators, motors, and large, medium and small AC and DC motors.

[0003] Compared with the traditional thick slab process, the thin slab continuous casting and rolling technology has the following process characteristics: short process flow, thin slab, fast cooling speed, developed columnar crystals, fast production rhythm, fast slab entering the furnace and small heat loss. Therefore, this process is also widely used in the production of non-oriented electrical steel.

[0004] Thin slab continuous casting and rolling technology involves multiple complex process steps and equipment, such as the design of the crystallizer, the use of protective slag and the continuous casting and rolling process, which increases the complexity of the technology and the difficulty of operation, affects the efficiency of thin slab continuous casting and rolling production, and the quality of the product, such as poor stability and poor surface quality. Summary of the invention

[0005] The present application provides a preparation method of non-oriented electrical steel 50W800 and non-oriented electrical steel 50W800, aiming to improve the efficiency of producing non-oriented electrical steel 50W800 by continuous casting and rolling of thin slabs, and the obtained non-oriented electrical steel 50W800 has low cost, low iron loss, high magnetic induction intensity and good surface quality.

[0006] The first aspect of the present application provides a method for preparing non-oriented electrical steel 50W800, comprising:

[0007] Pre-treating molten iron, smelting in a converter, and refining to obtain refined molten steel;

[0008] Thin slab continuous casting and rolling: pouring refined molten steel into a tundish and continuously casting to obtain a continuous casting slab; heating the continuous casting slab in a furnace, taking it out of the furnace, rolling it, and coiling it to obtain a steel coil;

[0009] Annealing: annealing, coating and cooling the steel coil to obtain non-oriented electrical steel 50W800; the annealing temperature is 930℃~1000℃;

[0010] Non-oriented electrical steel 50W800, based on the total mass content of 100%, includes the following chemical compositions in weight percentage: C≤0.0030%, 0.35%≤Si≤0.48%, 0.20%≤Mn≤0.30%, 0.075%≤P≤0.095%, S≤0.0045%, 0.20%≤Al≤0.40%, N≤0.0030%, Ti≤0.0020%, 0.0015%≤Ca≤0.0035%, C+S+N+Ti≤0.010%, and the rest are iron and inevitable trace elements.

[0011] In a feasible implementation manner of the first aspect of the present application, in the annealing step, the annealing temperature is 930° C. to 940° C., the holding time is 1 min to 2 min, and the annealing speed is 130 m / min to 150 m / min.

[0012] In a feasible implementation manner of the first aspect of the present application, in the steps of continuous casting and rolling of thin slabs, the furnace entry temperature of the continuously cast slabs is 800°C to 900°C, the heating temperature of the continuously cast slabs is 1130°C to 1170°C, the furnace time is 10min to 35min, and the furnace exit temperature of the continuously cast slabs is 1010°C to 1080°C.

[0013] In a feasible implementation manner of the first aspect of the present application, in the steps of continuous casting and rolling of thin slabs, the rolling includes hot rolling, the final rolling temperature of the hot rolling is 890°C to 930°C, and the coiling temperature is 740°C to 780°C.

[0014] In a feasible implementation manner of the first aspect of the present application, in the steps of continuous casting and rolling of thin slabs, rolling includes hot rolling and cold rolling, the temperature of the steel coil before cold rolling after hot rolling is ≥200°C, and the relative reduction rate of cold rolling is 75% to 85%.

[0015] In a feasible implementation manner of the first aspect of the present application, the steps of continuous casting and rolling of thin slabs include: injecting refined molten steel into a tundish, continuously casting, and casting a continuously cast billet with a thickness of 55mm to 75mm, and adopting light liquid core pressure in the first section of the continuous casting sector during billet drawing, and controlling the liquid core pressure to be 3mm to 7mm, and adopting strong cooling method for the liquid core sections 1 to 4, and the specific water volume of the secondary cooling water is 2.2L / kg to 2.4L / kg.

[0016] In a feasible implementation manner of the first aspect of the present application, in the steps of continuous casting and rolling of thin slabs, the pulling speed of the cast slab is 5.5 m / min to 5.8 m / min, and the superheat of the tundish is 15° C. to 35° C.

[0017] In a feasible implementation manner of the first aspect of the present application, in the steps of continuous casting and rolling of thin slabs, the number of continuous casting furnaces is ≥25.

[0018] In a feasible implementation of the first aspect of the present application, in the step of pre-treating molten iron, smelting in a converter, and refining to obtain refined molten steel, the mass content of the molten iron pre-treated at the outlet [S] is controlled to be ≤0.0015%, and the outlet temperature is controlled to be ≥1300°C

[0019] In a feasible implementation manner of the first aspect of the present application, in the steps of pretreating molten iron, smelting in a converter, and refining to obtain refined molten steel, the mass content of the steel-tapping end point [C] of the molten steel smelted in the converter is controlled at 0.035% to 0.055%, the mass content of the steel-tapping end point [O] is controlled at 0.06% to 0.080%, and the converter end point temperature is controlled at 1660°C to 1700°C.

[0020] In a feasible implementation manner of the first aspect of the present application, in the steps of pre-treating molten iron, smelting in a converter, and refining to obtain refined molten steel, the refining includes: degassing, decarburizing, adding aluminum blocks for deoxidation and alloying, adding ferrosilicon alloy, and vacuum circulating the molten steel for 8 minutes to 12 minutes to obtain refined molten steel, and the ferrosilicon alloy includes the following chemical components in weight percentage: C≤0.25%, 72%≤Si≤80%, Ti≤0.2%, 1.0%≤Ca≤4.0%, and the rest is Fe and unavoidable trace elements.

[0021] In a second aspect of the present application, there is provided a non-oriented electrical steel 50W800, which comprises the following composition in weight percentage, based on the total mass content of the non-oriented electrical steel 50W800 being 100%: C≤0.0030%, 0.35%≤Si≤0.48%, 0.20%≤Mn≤0.30%, 0.075%≤P≤0.095%, S≤0.0045%, 0.20%≤Al≤0.40%, N≤0.0030%, Ti≤0.0020%, 0.0015%≤Ca≤0.0035%, C+S+N+Ti≤0.010%, and the rest being iron and inevitable trace elements; the thickness of the non-oriented electrical steel 50W800 is 0.3 mm to 0.8 mm.

[0022] In a feasible implementation manner of the second aspect of the present application, the iron loss P of the non-oriented electrical steel 50W800 is 1.5 / 50 =4.74W / kg~5.0W / kg, magnetic induction intensity B 50 =1.737T~1.743T. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the process of continuous casting and rolling of thin slabs;

[0024] Figure 2 It is a process diagram of pickling and cold rolling;

[0025] Figure 3 It is a schematic diagram of the continuous annealing coating process. DETAILED DESCRIPTION

[0026] In order to make the invention purpose, technical scheme and beneficial technical effect of the present application clearer, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application, not for limiting the present application.

[0027] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0028] In the description herein, when a composition is described as containing, comprising or including specific components, or when a process is described as containing, comprising or including specific process steps, it is expected that the composition of the present application also consists essentially of or consists of the components, and the process of the present application also consists essentially of or consists of the process steps.

[0029] The use of the terms "including," "comprising," "containing," and "having" should generally be interpreted as open ended and non-limiting unless expressly stated otherwise.

[0030] In the description of this article, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number itself, and the “multiple” in “one or more” means more than two.

[0031] The above-mentioned summary of the invention of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0032] The production process of thin slab continuous casting and rolling technology (CPS for short) includes obtaining blast furnace molten iron, KR pretreatment of the blast furnace molten iron, converter smelting and RH refining, obtaining refined molten steel, continuous casting of the refined molten steel, continuous rolling after continuous casting, and annealing and coating process to obtain non-oriented electrical steel 50W800.

[0033] like Figure 1 and Figure 2 As shown, the continuous casting and rolling process of CPS starts with transferring the refined molten steel into the ladle, forming the ingot in the crystallizer and the fan-shaped segment, heating it through the cutting shear and the swing tunnel heating furnace, accidentally shearing it into the corresponding size, and then passing through the high-pressure water dephosphorization machine, the finishing mill, and the laminar cooling device to obtain the steel coil. Among them, rolling generally includes hot rolling and cold rolling. Cold rolling includes cooling the hot-rolled steel coil, welding, straightening and descaling, trimming and continuous rolling of the rack to obtain the steel coil, and then the steel coil is annealed and coated. Figure 3 Schematic diagram of the annealing coating process.

[0034] Since the thin slab continuous casting and rolling technology involves multiple complex process steps and equipment, the technical complexity and operation difficulty are high, the product quality is uncontrollable, which affects the stability and surface quality of the product. In addition, the thin slab continuous casting and rolling technology has short continuous casting furnaces and low pulling speed, and the production efficiency is low.

[0035] The inventors found through in-depth research that by selecting a suitable non-oriented electrical steel 50W800 low-Si, low-Al and low-alloy cost component system, matching a suitable annealing process, and a reasonable configuration of the secondary cooling water strength of the continuous casting liquid core part, and / or the billet reduction control technology to obtain a suitable slab furnace entry temperature, and / or calculating the phase change temperature according to the component system and formulating a suitable hot rolling temperature system, and / or a steel coil storage process system from hot rolling to cold rolling, a preparation method of non-oriented electrical steel 50W800 and non-oriented electrical steel 50W800 are proposed, which can improve the efficiency of thin slab continuous casting and rolling to produce non-oriented electrical steel 50W800, and the obtained non-oriented electrical steel 50W800 has low cost, low iron loss, high magnetic induction intensity and good surface quality, and good stability in the same batch.

[0036] In an embodiment of the first aspect of the present application, a method for preparing non-oriented electrical steel 50W800 is provided, comprising:

[0037] Pre-treating molten iron, smelting in a converter, and refining to obtain refined molten steel;

[0038] Thin slab continuous casting and rolling: pouring refined molten steel into a tundish and continuously casting to obtain a continuous casting slab; heating the continuous casting slab in a furnace, taking it out of the furnace, rolling it, and coiling it to obtain a steel coil;

[0039] Annealing: annealing, coating and cooling the steel coil to obtain non-oriented electrical steel 50W800; the annealing temperature is 930℃~1000℃;

[0040] Non-oriented electrical steel 50W800, based on the total mass content of 100%, includes the following chemical compositions in weight percentage: C≤0.0030%, 0.35%≤Si≤0.48%, 0.20%≤Mn≤0.30%, 0.075%≤P≤0.095%, S≤0.0045%, 0.20%≤Al≤0.40%, N≤0.0030%, Ti≤0.0020%, 0.0015%≤Ca≤0.0035%, C+S+N+Ti≤0.010%, and the rest are iron and inevitable trace elements.

[0041] In some embodiments of the present application, the design ideas of the components in the non-oriented electrical steel 50W800 are as follows:

[0042] Carbon C: Carbon content increases, iron loss P 1.5 / 50 The value increases, so the carbon content in the finished product is required to be as low as possible. This product requires the carbon content to be controlled below 0.0030%.

[0043] Silicon Si: The influence of silicon is mainly decisive for the organization, texture and magnetic properties of non-oriented electrical steel. With the increase of silicon content, the resistivity increases, the austenite phase area shrinks, the eddy current loss decreases, the grains coarsen, the hysteresis loss decreases, the iron loss value decreases and the magnetic induction value also decreases; silicon can reduce the harm of impurity elements in steel, graphitize carbon, and reduce the harmful effect of carbon on magnetic properties; silicon has an affinity with oxygen, plays a deoxidation role, and forms silicon nitride with nitrogen, reducing the solubility of nitrogen in steel. Taking all the influencing factors into consideration, the silicon content of this product is designed to be 0.35-0.48%.

[0044] Manganese Mn: Manganese and sulfur form MnS inclusions to prevent hot brittleness caused by low-melting-point FeS along the grain boundaries and improve the thermoplasticity of the material. At the same time, manganese expands the austenite phase region and promotes the growth of MnS inclusions, which is beneficial to the subsequent grain growth. The manganese content is designed to be 0.20-0.30%.

[0045] Sulfur S: Sulfur can form MnS inclusions that will hinder grain growth and increase iron loss. The main effect of S is that the harmful effect of sulfur on magnetic properties in electrical steel is related to the presence of fine particles of manganese sulfide in the matrix and free sulfur on the grain boundaries. The influence of Mn and S is mainly because the supersaturated Mn and S in the steel will disperse and precipitate in the form of MnS particles, causing an increase in iron loss, so the sulfur content is required to be ≤0.0045%.

[0046] Phosphorus P: Phosphorus increases ρ, shrinks the γ zone, promotes grain growth, and reduces iron loss. Phosphorus segregates along the grain boundary to increase the (100) component and reduce the (111) component. Phosphorus significantly increases hardness and improves punchability. The phosphorus content of this product is designed to be controlled at 0.075-0.095%.

[0047] Aluminum Al: Aluminum has similar effects to silicon, increasing resistivity, reducing austenite phase area and promoting grain growth. When its content reaches a certain amount, it can form coarse AlN, improve texture, reduce iron loss and reduce anisotropy. When the aluminum content reaches a certain amount, it will coarsen steel and promote carbon graphitization. The aluminum content of this product is designed to be 0.20-0.40%.

[0048] Titanium Ti: When the titanium content exceeds a certain amount, the precipitated Ti (CN) will pin the grain boundary, hindering the growth of grains, making the grains finer, increasing iron loss, and reducing magnetic induction. This product requires titanium to be controlled within 0.0020%.

[0049] Nitrogen N: Nitrogen tends to form fine AlN particles to inhibit grain growth. An important purpose of the heating, hot rolling and annealing process is to prevent the precipitation of fine AlN or to coarsen the existing AlN in the steel. This product requires nitrogen to be controlled within 0.0030%.

[0050] Calcium Ca: Ca can denature inclusions, which can solve the problems of tundish plug rod rise and nozzle nodules caused by inclusions, which eventually lead to ladle dead flow and production interruption, and ensure the castability of thin slab continuous casting; at the same time, the calcium element in the molten steel inhibits the growth of second phase precipitates such as MnS and AlN in the steel, which is beneficial to improve the magnetic properties of the product. The calcium content of this product is designed to be controlled at 0.0015~0.0035%.

[0051] Impurity elements C, S, N, and Ti are not conducive to reducing iron loss, causing serious lattice distortion and large internal stress. The finished product requires that such elements should be as low as possible. They have a very bad effect on grain growth and texture components, especially fine dispersed precipitates such as MnS, AlN, Ti (CN), etc., which obviously hinder the grain growth during annealing. In some embodiments of the present application, it is required to control C+S+N+Ti within 0.010%.

[0052] The present application selects a suitable non-oriented electrical steel 50W800 low Si, low Al and low alloy cost composition system, the ingot thickness is 55mm-75mm, the suitable combination of beneficial elements Si, Mn, P and Al can make the grain growth during annealing have sufficient driving energy, low C, S, N and Ti, pure steel and suitable alloy cost, meet the magnetic property requirements, and the annealing temperature is 930℃-1000℃. Within this temperature range, the cold-rolled strip can eliminate the strain generated by the cold rolling process and promote grain growth through recrystallization, so that the steel plate can be fully recrystallized to obtain excellent magnetic properties.

[0053] The continuous casting number of the thin slab continuous casting and rolling production of non-oriented electrical steel 50W800 can be ≥25 furnaces, and the casting speed can reach 5.5m / min-5.8m / min, the production efficiency is significantly improved, and the production cost is also reduced. In addition, the non-oriented electrical steel 50W800 obtained has low iron loss, P1.5 / 50 4.74W / kg~5.0W / kg, high magnetic induction intensity, B 50 =1.737T~1.743T and the surface quality is good and the stability in the same batch is good.

[0054] In some embodiments, in the annealing step, the annealing temperature is 930° C. to 940° C., the holding time is 1 min to 2 min, and the annealing speed is 130 m / min to 150 m / min.

[0055] The inventors have found through research that the annealing process will affect the production of non-oriented electrical steel 50W800. The low Si, low Al and low alloy cost component system of the present application, combined with the above-mentioned process with high annealing temperature and fast annealing speed, can eliminate the strain generated by the cold rolling process and promote grain growth through recrystallization of the cold-rolled strip, so that the steel plate can be fully recrystallized, which can not only improve the quality of the obtained non-oriented electrical steel 50W800, but also improve production efficiency and reduce production costs.

[0056] In some embodiments, in the step of continuous casting and rolling of thin slabs, the furnace entry temperature of the continuous casting slab is 800°C to 900°C, the heating temperature of the continuous casting slab is 1130°C to 1170°C, the furnace time is 10min to 35min, and the furnace exit temperature of the continuous casting slab is 1010°C to 1080°C.

[0057] In some embodiments, the selection of the furnace entry temperature, heating temperature, furnace time and furnace exit temperature of the above-mentioned continuous casting slab of the present application can make the interior of the slab fully austenitized, with appropriate grain size and uniform structure, so as to obtain a good steel microstructure, which is beneficial to improving product quality and reducing defects such as grain boundary melting and loose structure in the product.

[0058] In some embodiments, in the step of continuous casting and rolling of thin slabs, the rolling includes hot rolling, the final rolling temperature of the hot rolling is 890°C to 930°C, and the coiling temperature is 740°C to 780°C.

[0059] The main purpose of hot rolling is to allow the precipitates of the slab to fully precipitate and grow. In some embodiments of the present application, the above-mentioned heating temperature, a higher final rolling temperature and a higher coiling temperature are used to ensure that the precipitates grow further after coiling to form a better organizational structure.

[0060] In some embodiments, in the step of continuous casting and rolling of thin slabs, rolling includes hot rolling and cold rolling, the temperature of the steel coil after hot rolling and before cold rolling is ≥200°C (or the hot rolled coil out-of-warehouse temperature is ≥200°C, which can be 250°C~300°C), and the relative reduction rate of cold rolling is 75%~85%.

[0061] In some embodiments of the present application, the slow cooling mode is adopted after hot rolling and before cold rolling, and the pickling cold rolling is performed. The temperature of the steel coil after hot rolling is required to be ≥200℃ before cold rolling (or the temperature of the hot rolled coil out of the warehouse is ≥200℃, which can be 250℃~300℃). The main purpose of pickling is to remove the iron scale on the surface of the steel plate while rolling the thicker hot rolled plate into a thinner cold rolled plate. The relative reduction rate of cold rolling in the above range of the steel type of the present application is conducive to reducing the iron loss of the finished product.

[0062] In some embodiments, the steps of continuous casting and rolling of thin slabs include: injecting refined molten steel into a tundish, continuously casting, and casting a continuous casting billet with a thickness of 55 mm to 75 mm, using light liquid core pressure in the first section of the continuous casting sector during billet drawing, controlling the liquid core pressure to be 3 mm to 7 mm, and using strong cooling for the liquid core sections 1 to 4, and the specific water volume of the secondary cooling water is 2.2 L / kg to 2.4 L / kg.

[0063] The secondary cooling water strength of the continuous casting liquid core part of the present application is reasonably configured, which can control the dendrite growth rate inside the ingot and prevent the center segregation caused by the gravity segregation caused by crystal precipitation, thereby forming a good steel structure.

[0064] In some embodiments, in the step of continuous casting and rolling of thin slabs, the pulling speed of the cast slab is 5.5 m / min to 5.8 m / min, and the superheat of the tundish is 15° C. to 35° C.

[0065] In some implementations of the present application, the pulling speed is fast, and more products can be produced per unit time, thereby improving production efficiency and output.

[0066] In some embodiments, in the step of continuous casting and rolling of thin slabs, the number of continuous casting furnaces is ≥ 25.

[0067] In some embodiments, in the step of pre-treating molten iron, smelting in a converter, and refining to obtain refined molten steel, the mass content of the molten iron [S] out of the pre-treated molten iron is controlled to be ≤ 0.0015%, and the out-station temperature is controlled to be ≥ 1300°C.

[0068] In some embodiments, in the steps of pretreating molten iron, smelting in a converter, and refining to obtain refined molten steel, the mass content of the steel-tapping end point [C] of the molten steel smelted in the converter is controlled at 0.035% to 0.055%, the mass content of the steel-tapping end point [O] is controlled at 0.06% to 0.080%, and the converter end point temperature is controlled at 1660°C to 1700°C.

[0069] In some embodiments, in the steps of pretreating molten iron, smelting in a converter, and refining to obtain refined molten steel, the refining includes: degassing, decarburizing, adding aluminum blocks for deoxidation and alloying, adding ferrosilicon alloy, and vacuum circulating the molten steel for 8 minutes to 12 minutes to obtain refined molten steel, wherein the ferrosilicon alloy includes the following chemical components in weight percentage: C≤0.25%, 72%≤Si≤80%, Ti≤0.2%, 1.0%≤Ca≤4.0%, and the rest are Fe and unavoidable trace elements.

[0070] The RH refining process stage can include: after the converter taps out steel, the ladle containing qualified molten steel is driven to the processing station by the ladle car for the first time to measure temperature and determine oxygen sampling to determine the incoming steel conditions; after the ladle car top is raised to the right position to ensure the appropriate insertion depth of the insertion tube, the vacuum pump circulation system is turned on to evacuate the vacuum; after 6 to 7 minutes, the vacuum degree reaches the ultimate vacuum (≤133Pa); degassing, decarburization, temperature adjustment, temperature measurement sampling, oxygen determination, final deoxidation, alloying, and composition uniformity are carried out according to the initial composition, inlet temperature and oxygen content of the incoming molten steel; after the RH treatment is completed, the vacuum chamber is finally sampled, temperature measured and oxygen determined before re-pressurization, and the qualified refined molten steel is transported to the continuous casting and rolling. After decarburization, when the carbon content in the molten steel reaches the requirement, aluminum blocks are added for deoxidation and alloying; after the ultimate vacuum cycle is ≥4 minutes, special ferrosilicon, metallic manganese and other alloys are added; after all alloys are added, they are circulated for 8-12 minutes under the ultimate vacuum degree to break the air out of the station.

[0071] In an embodiment of the second aspect of the present application, there is provided a non-oriented electrical steel 50W800, which comprises the following composition in weight percentage based on the total weight content of the non-oriented electrical steel 50W800 as 100%: C≤0.0030%, 0.35%≤Si≤0.48%, 0.20%≤Mn≤0.30%, 0.075%≤P≤0.095%, S≤0.0045%, 0.20%≤Al≤0.40%, N≤0.0030%, Ti≤0.0020%, 0.0015%≤Ca≤0.0035%, C+S+N+Ti≤0.010%, and the remainder is iron and inevitable trace elements; the thickness of the non-oriented electrical steel 50W800 is 0.3 mm to 0.8 mm.

[0072] In some embodiments, the iron loss P of non-oriented electrical steel 50W800 is 1.5 / 50 =4.74W / kg~5.0W / kg, magnetic induction intensity B 50 =1.737T~1.743T.

[0073] Example

[0074] The following examples more specifically describe the disclosure of the present application, which are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0075] Example 1

[0076] The corresponding relationship between the product codes in each process is as follows:

[0077]

[0078] ①Chemical composition (furnace number 23222241)

[0079] C: 0.0025Wt%; Si: 0.41Wt%; Mn: 0.24Wt%; P: 0.081Wt%; S: 0.0036Wt%; Al: 0.20Wt%; N: 0.0016%; Ti: 0.0018%; Ca: 0.0025%; C+S+N+Ti: 0.0095%; the rest are Fe and inevitable trace elements.

[0080] The composition design follows three principles: appropriate beneficial elements Si, Mn, P, and Al to ensure the driving energy of grain growth during annealing, low C, S, N, and Ti, pure steel and appropriate alloy cost, and meeting the magnetic property requirements. Considering the poor continuous casting and rolling of thin slabs, without increasing the calcium treatment process, Ca-containing ferrosilicon alloy is used to replace the calcium treatment process to ensure a certain Ca content in the steel to ensure continuous casting.

[0081] ②Process parameters

[0082] Converter steelmaking: endpoint C is 0.045%; temperature is 1675°C, endpoint [O] content is 0.0697%, 100kg of modifier (comprising the following chemical components in weight percentage: Al: 40%, Al2O3: 16%, CaO: 22%, MgO: 6%, SiO2: 4%, the rest being Fe and unavoidable trace elements, the components of the modifier involved in the following embodiments or comparative examples are the same) and 300kg of lime are added during steelmaking.

[0083] RH molten steel refining treatment: molten steel inlet temperature is 1618℃, inlet [O] content is 0.060%, decarburization end point [O] is 0.035%, the time interval for adding aluminum block and ferrosilicon alloy (also known as calcium ferrosilicon alloy) is 4min, ferrosilicon alloy includes the following chemical components in weight percentage: C: 0.24%, Si: 75%, Ti: 0.1%, Ca: 1.8%, the rest are Fe and unavoidable trace elements, the net circulation time of molten steel after alloying is 8min, and the molten steel treatment cycle is 26min.

[0084] Continuous casting: pouring order 8 furnaces, liquid core pressure reduction of 5mm, tundish superheat of 25℃, casting speed of 5.6m / min, secondary cooling water ratio controlled at 2.25L / kg. Use special protective slag for electrical steel (including the following chemical components in weight percentage: Al2O3: 6%, CaO: 34%, MgO: 7%, SiO2: 27%, F: 10%, the rest is Fe and inevitable trace elements), the special protective slag for electrical steel used in the following examples and comparative examples is the same as that in this example.

[0085] CSP line hot rolling is as follows:

[0086]

[0087] The main purpose of hot rolling is to make the precipitates in the slab fully precipitate and grow, so a low heating temperature is used and a higher coiling temperature is used to ensure that the precipitates grow further after coiling.

[0088] Pickling and cold rolling are as follows:

[0089]

[0090]

[0091] The main purpose of pickling is to remove the iron oxide scale on the surface of the steel plate and roll the thicker hot-rolled plate into a thinner cold-rolled plate. The setting of the reduction rate is mainly determined by the rolling mill capacity. For this type of steel, a larger reduction rate is conducive to reducing the iron loss of the finished product.

[0092] Continuous furnace annealing coating is as follows:

[0093] Pickling Roll No. Annealing temperature Insulation time Annealing speed, m / min A301517500 930℃ 1.5min 133 A301517400 930℃ 1.5min 133 A301517300 930℃ 1.5min 135 A301517200 930℃ 1.5min 135 A301517100 930℃ 1.5min 135

[0094] The main purpose of annealing is to eliminate the strain caused by the cold rolling process and promote grain growth through recrystallization of the cold rolled strip, so that the steel plate can be fully recrystallized to ensure that the magnetic properties meet the required conditions.

[0095] Magnetic property test: The annealed coated electrical steel sample was processed into a 0.5mm×500mm×500mm sample, and the sample was placed in a magnetic property tester. The transverse and longitudinal magnetic properties were measured respectively, and the average value was taken as the test value. The test results are shown in the following table.

[0096] Finished product roll number Iron loss, W / Kg Magnetic induction, T A301517500 4.87 1.737 A301517400 4.88 1.737 A301517300 4.74 1.739 A301517200 4.96 1.737 A301517100 4.94 1.737

[0097] Example 2

[0098] The corresponding relationship between the product codes in each process is as follows:

[0099]

[0100]

[0101] ①Chemical composition (furnace number 23222242)

[0102] C: 0.0020Wt%; Si: 0.44Wt%; Mn: 0.22Wt%; P: 0.078Wt%; S: 0.0035Wt%; Al: 0.23Wt%; N: 0.0018%; Ti: 0.0015%; Ca: 0.0020%; C+S+N+Ti: 0.0088%; the rest are Fe and inevitable trace elements.

[0103] The composition design follows three principles: appropriate beneficial elements Si, Mn, P, and Al to ensure the driving energy of grain growth during annealing, low C, S, N, and Ti, pure steel and appropriate alloy cost, and meeting the magnetic property requirements. Considering the poor continuous casting and rolling of thin slabs, without increasing the calcium treatment process, Ca-containing ferrosilicon alloy is used to replace the calcium treatment process to ensure a certain Ca content in the steel to ensure continuous casting.

[0104] ②Process parameters

[0105] Converter steelmaking: end point C is 0.040%; temperature is 1680°C, end point [O] content is 0.075%, and 100kg modifier and 300kg lime are added during steelmaking.

[0106] RH molten steel refining treatment: molten steel inlet temperature 1628℃, inlet [O] content 0.065%, decarburization end point [O] 0.040%, time interval for adding aluminum block and ferrosilicon alloy 4min, ferrosilicon alloy includes the following chemical components in weight percentage: C: 0.20%, Si: 76%, Ti: 0.08%, Ca: 1.5%, the rest are Fe and unavoidable trace elements. The net circulation time of molten steel after alloying is 10min, and the molten steel treatment cycle is 28min.

[0107] Continuous casting: Casting sequence 26 furnaces, liquid core pressure reduction of 5mm, tundish superheat of 30℃, casting speed of 5.8m / min, secondary cooling water volume controlled at 2.36L / kg. Special protective slag for electrical steel was used.

[0108] CSP line hot rolling is as follows:

[0109]

[0110] Pickling and cold rolling are as follows:

[0111] Pickling Roll No. Reduction rate A301517600 82％ A301517700 82％ A301659200 82％ A301517800 82％ A301578500 82％

[0112] Continuous furnace annealing coating is as follows:

[0113] Pickling Roll No. Annealing temperature Insulation time Annealing speed, m / min A301517600 935℃ 2min 135 A301517700 934℃ 2min 135 A301659200 935℃ 2min 136 A301517800 933℃ 2min 136 A301578500 934℃ 2min 135

[0114] Magnetic property test: The annealed coated electrical steel sample was processed into a 0.5mm×500mm×500mm sample, and the sample was placed in a magnetic property tester. The transverse and longitudinal magnetic properties were measured respectively, and the average value was taken as the test value. The test results are shown in the following table.

[0115] Finished product roll number Iron loss, W / Kg Magnetic induction, T A301517600 4.96 1.74 A301517700 4.85 1.744 A301659200 4.82 1.744 A301517800 4.87 1.744 A301578500 4.85 1.738

[0116] Example 3

[0117] The corresponding relationship between the product codes in each process is as follows:

[0118]

[0119]

[0120] ①Chemical composition (furnace number 23222246)

[0121] C: 0.0018Wt%; Si: 0.36Wt%; Mn: 0.28Wt%; P: 0.091Wt%; S: 0.0030Wt%; Al: 0.30Wt%; N: 0.0018%; Ti: 0.0019%; Ca: 0.0033%; C+S+N+Ti: 0.0085%; the rest are Fe and inevitable trace elements.

[0122] ②Process parameters

[0123] Converter steelmaking: end point C is 0.035%; temperature is 1695°C, end point [O] content is 0.073%, and 100kg modifier and 300kg lime are added during steelmaking.

[0124] RH molten steel refining treatment: molten steel inlet temperature is 1630℃, inlet [O] content is 0.062%, decarburization end point [O] is 0.038%, the time interval between adding aluminum block and ferrosilicon alloy is 4min, ferrosilicon alloy includes the following chemical composition in weight percentage: C: 0.15%, Si: 75%, Ti: 0.12%, Ca: 3%, the rest is Fe and unavoidable trace elements, the net circulation time of molten steel after alloying is 10min, and the molten steel treatment cycle is 28min.

[0125] Continuous casting: pouring sequence 20 furnaces, liquid core pressure reduction of 5mm, tundish superheat of 32℃, casting speed of 5.8m / min, secondary cooling water ratio controlled at 2.39L / kg. Use special protective slag for electrical steel.

[0126] CSP line hot rolling is as follows:

[0127]

[0128] Pickling and cold rolling are as follows:

[0129]

[0130]

[0131] Continuous furnace annealing coating is as follows:

[0132] Pickling Roll No. Annealing temperature Insulation time Annealing speed, m / min A301518400 935℃ 1.5min 131 A301518500 935℃ 1.5min 130 A301518800 935℃ 1.5min 132 A301518700 935℃ 1.5min 132 A301518600 935℃ 1.5min 132

[0133] Magnetic property test: The annealed coated electrical steel sample was processed into a 0.5mm×500mm×500mm sample, and the sample was placed in a magnetic property tester. The transverse and longitudinal magnetic properties were measured respectively, and the average value was taken as the test value. The test results are shown in the following table.

[0134] Finished product roll number Iron loss, W / Kg Magnetic induction, T A301518400 4.93 1.742 A301518500 4.85 1.741 A301518800 4.89 1.738 A301518700 4.84 1.743 A301518600 5.0 1.738

[0135] Comparative Example 1

[0136] The corresponding relationship between the product codes in each process is as follows:

[0137]

[0138]

[0139] Chemical composition (furnace number 23350841)

[0140] C: 0.0035Wt%; Si: 0.75Wt%; Mn: 0.25Wt%; P: 0.035Wt%; S: 0.0054Wt%; Al: 0.28Wt%; N: 0.003%; Ti: 0.0021%; the rest are Fe and inevitable trace elements.

[0141] Process parameters

[0142] Converter steelmaking: end point C is 0.045%; temperature is 1660°C, end point [O] content is 0.075%, and 100kg modifier and 300kg lime are added during steelmaking.

[0143] RH molten steel refining treatment: molten steel inlet temperature 1615℃, inlet [O] content 0.055%, decarburization end point [O] 0.035%, time interval for adding aluminum block and ferrosilicon alloy 3min, ferrosilicon alloy includes the following chemical composition in weight percentage: C: 0.23%, Si: 75%, Ti: 0.15%, Ca: 0.02%, the rest is Fe and unavoidable trace elements, the net circulation time of molten steel after alloying is 6min, and the molten steel treatment cycle is 30min.

[0144] Continuous casting: Casting order 10th furnace, tundish superheat 30℃, casting speed 5.0m / min, secondary cooling water volume controlled at 1.6L / kg. Use special protective slag for electrical steel.

[0145] CSP line hot rolling is as follows:

[0146]

[0147] Pickling and cold rolling are as follows:

[0148]

[0149]

[0150] Continuous furnace annealing coating is as follows:

[0151] Pickling Roll No. Annealing temperature Insulation time Annealing speed, m / min A308383810 835℃ 1.5min 60 A307894010 835℃ 1.5min 60 A307893820 835℃ 1.5min 60 A307894210 835℃ 1.5min 60 A307894110 835℃ 1.5min 60 A307893920 835℃ 1.5min 60

[0152] Magnetic property test: The annealed coated electrical steel sample was processed into a 0.5mm×500mm×500mm sample, and the sample was placed in a magnetic property tester. The transverse and longitudinal magnetic properties were measured respectively, and the average value was taken as the test value, as shown in the following table.

[0153] Finished product roll number Iron loss, W / Kg Magnetic induction, T A308383810 5.09 1.727 A307894010 4.965 1.727 A307893820 5.072 1.726 A307894210 5.005 1.729 A307894110 4.926 1.727 A307893920 5.084 1.73

[0154] Comparative Example 2

[0155] The corresponding relationship between the product codes in each process is as follows:

[0156]

[0157]

[0158] Chemical composition (furnace number 23350851)

[0159] C: 0.0030Wt%; Si: 0.65Wt%; Mn: 0.20Wt%; P: 0.030Wt%; S: 0.0050Wt%; Al: 0.26Wt%; N: 0.0018%; Ti: 0.0022%; the rest are Fe and inevitable trace elements.

[0160] Process parameters

[0161] Converter steelmaking: end point C is 0.035%; temperature is 1680°C, end point [O] content is 0.063%, and 100kg modifier and 300kg lime are added during steelmaking.

[0162] RH molten steel refining treatment: molten steel inlet temperature 1625℃, inlet [O] content 0.065%, decarburization end point [O] 0.038%, time interval for adding aluminum block and ferrosilicon alloy 3min, ferrosilicon alloy includes the following chemical composition in weight percentage: C: 0.20%, Si: 76%, Ti: 0.20%, Ca: 0.03%, the rest is Fe and unavoidable trace elements, the net circulation time of molten steel after alloying is 7min, and the molten steel treatment cycle is 28min.

[0163] Continuous casting: Casting order 15th furnace, tundish superheat 25℃, casting speed 5.2m / min, secondary cooling water volume controlled at 1.8L / kg. Use special protective slag for electrical steel.

[0164] CSP line hot rolling is as follows:

[0165]

[0166] Pickling and cold rolling are as follows:

[0167]

[0168]

[0169] Continuous furnace annealing coating is as follows:

[0170] Pickling Roll No. Annealing temperature Insulation time Annealing speed, m / min A309177720 825℃ 2min 65 A307896120 825℃ 2min 65 A307896010 825℃ 2min 65 A307895910 825℃ 2min 65 A307895820 825℃ 2min 65 A307896210 825℃ 2min 65

[0171] Magnetic property test: The annealed coated electrical steel sample was processed into a 0.5mm×500mm×500mm sample, and the sample was placed in a magnetic property tester. The transverse and longitudinal magnetic properties were measured respectively, and the average value was taken as the test value, as shown in the following table.

[0172] Finished product roll number Iron loss, W / Kg Magnetic induction, T A309177720 5.1 1.73 A307896120 4.916 1.731 A307896010 5.029 1.73 A307895910 5.029 1.728 A307895820 5.1 1.722 A307896210 5.011 1.73

[0173] From the table data, it can be seen that compared with the comparative example, the iron loss of the non-oriented electrical steel 50W800 obtained in the embodiment is lower, P1.5 / 50 4.74W / kg~5.0W / kg, the magnetic induction intensity is higher, B 50 =1.737T~1.743T, good stability in the same batch, continuous casting furnaces can be ≥25 furnaces, casting speed reaches 5.5m / min~5.8m / min, production efficiency is significantly improved, and production costs are also reduced.

[0174] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing non-oriented electrical steel 50W800, characterized in that: include: Pre-treating molten iron, smelting in a converter, and refining to obtain refined molten steel; Thin slab continuous casting and rolling: the refined molten steel is poured into a tundish and continuously cast to obtain a continuously cast slab; The continuous casting billet is heated in a furnace, taken out of the furnace, rolled, and coiled to obtain a steel coil; Annealing: annealing, coating, and cooling the steel coil to obtain non-oriented electrical steel 50W800; the annealing temperature is 930° C. to 1000° C.; The non-oriented electrical steel 50W800, based on a total mass content of 100%, comprises the following chemical components in weight percentage: C≤0.0030%, 0.35%≤Si≤0.48%, 0.20%≤Mn≤0.30%, 0.075%≤P≤0.095%, S≤0.0045%, 0.20%≤Al≤0.40%, N≤0.0030%, Ti≤0.0020%, 0.0015%≤Ca≤0.0035%, C+S+N+Ti≤0.010%, and the rest are iron and inevitable trace elements.

2. The method for preparing non-oriented electrical steel 50W800 according to claim 1, characterized in that: In the annealing step, the annealing temperature is 930° C. to 940° C., the holding time is 1 min to 2 min, and the annealing speed is 130 m / min to 150 m / min.

3. The method for preparing non-oriented electrical steel 50W800 according to claim 1, characterized in that: In the step of continuous casting and rolling of thin slabs, the furnace entry temperature of the continuously cast slabs is 800°C to 900°C, the heating temperature of the continuously cast slabs is 1130°C to 1170°C, the furnace time is 10min to 35min, and the furnace exit temperature of the continuously cast slabs is 1010°C to 1080°C.

4. The method for preparing non-oriented electrical steel 50W800 according to claim 1, characterized in that: In the step of continuous casting and rolling of thin slabs, the rolling includes hot rolling, the final rolling temperature of the hot rolling is 890°C to 930°C, and the coiling temperature is 740°C to 780°C.

5. The method for preparing non-oriented electrical steel 50W800 according to claim 4, characterized in that: In the step of continuous casting and rolling of thin slabs, the rolling includes hot rolling and cold rolling, the temperature of the steel coil before cold rolling after hot rolling is ≥200°C, and the relative reduction rate of the cold rolling is 75% to 85%.

6. The method for preparing non-oriented electrical steel 50W800 according to claim 1, characterized in that: The steps of continuous casting and rolling of thin slabs include: injecting the refined molten steel into a tundish, continuously casting, and casting a continuous casting billet with a thickness of 55mm to 75mm; during billet drawing, light liquid core pressure is adopted in the first section of the continuous casting sector, and the liquid core pressure is controlled to be 3mm to 7mm; the liquid core section 1 to 4 is subjected to strong cooling, and the specific water volume of the secondary cooling water is 2.2L / kg to 2.4L / kg.

7. The method for preparing non-oriented electrical steel 50W800 according to claim 1, characterized in that: In the step of continuous casting and rolling of thin slabs, the pulling speed of the cast slab is 5.5 m / min to 5.8 m / min, and the superheat of the tundish is 15° C. to 35° C.

8. The method for preparing non-oriented electrical steel 50W800 according to claim 1, characterized in that: In the step of continuous casting and rolling of thin slabs, the number of continuous casting furnaces is ≥25.

9. The method for preparing non-oriented electrical steel 50W800 according to any one of claims 1 to 8, characterized in that: In the steps of pre-treating the molten iron, smelting in a converter, and refining to obtain refined molten steel, the mass content of the outlet [S] of the molten iron pre-treated is controlled at ≤0.0015%, and the outlet temperature is controlled at ≥1300°C.

10. The method for preparing non-oriented electrical steel 50W800 according to any one of claims 1 to 8, characterized in that: In the steps of pretreating the molten iron, smelting in a converter, and refining to obtain refined molten steel, the mass content of the steel tapping end point [C] of the molten steel smelted in the converter is controlled at 0.035% to 0.055%, the mass content of the steel tapping end point [O] is controlled at 0.06% to 0.080%, and the converter end point temperature is controlled at 1660°C to 1700°C.

11. The method for preparing non-oriented electrical steel 50W800 according to any one of claims 1 to 8, characterized in that: In the steps of pretreating molten iron, smelting in a converter, and refining to obtain refined molten steel, the refining includes: degassing, decarburizing, adding aluminum blocks for deoxidation and alloying, adding ferrosilicon alloy, and vacuum circulating for 8 minutes to 12 minutes to obtain the refined molten steel, wherein the ferrosilicon alloy includes the following chemical components in weight percentage: C≤0.25%, 72%≤Si≤80%, Ti≤0.2%, 1.0%≤Ca≤4.0%, and the rest are Fe and inevitable trace elements.

12. A non-oriented electrical steel 50W800, characterized in that: Taking the total mass content of non-oriented electrical steel 50W800 as 100% as a benchmark, the steel comprises the following compositions in weight percentage: C≤0.0030%, 0.35%≤Si≤0.48%, 0.20%≤Mn≤0.30%, 0.075%≤P≤0.095%, S≤0.0045%, 0.20%≤Al≤0.40%, N≤0.0030%, Ti≤0.0020%, 0.0015%≤Ca≤0.0035%, C+S+N+Ti≤0.010%, and the rest are iron and inevitable trace elements; the thickness of the non-oriented electrical steel 50W800 is 0.3mm-0.8mm.

13. The non-oriented electrical steel 50W800 according to claim 12, characterized in that: The iron loss P of the non-oriented electrical steel 50W800 is 1.5 / 50 =4.74W / kg~5.0W / kg, magnetic induction intensity B 50 =1.737T~1.743T.

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