A near-net-shape manufacturing method for ultra-thin high-silicon steel strips

Abstract

This invention discloses a near-net-shape manufacturing method for ultra-thin high-silicon steel strip, comprising the following steps: melting raw materials into molten steel; injecting the molten steel into a nozzle ladle, spraying the molten steel through the nozzle onto the surface of the main crystallizing roll and casting and solidifying it into strip; after the strip leaves the molten pool, subjecting the strip on the main crystallizing roll to gas protection until the strip detaches from the main crystallizing roll, thus obtaining ultra-thin high-silicon steel strip. This invention lowers the melting point and reduces the wetting angle with the crystallizing roll by adding boron and scientifically matching its content with silicon, achieving close contact with the roll. Simultaneously, by improving the cooling effect, it achieves the effects of eliminating the need for pickling, leveling, and specialized annealing, resulting in superior product performance. The ultra-thin high-silicon steel product manufactured by this invention has a B800 of 1.29~1.69T and a P1.0 / 400 ≤ 3.6w / kg.

Description

Technical Field

[0001] This invention relates to the field of electrical steel, and more particularly to a near-net-shape manufacturing method for ultrathin strips of high-silicon steel. Background Technology

[0002] Non-oriented electrical steel, possessing magnetic isotropic properties, is widely used in the manufacture of rotating electric motor cores. As the operating frequencies of electric motors increase, the iron loss of non-oriented electrical steel at high frequencies is primarily eddy current loss. Eddy current loss is directly proportional to the operating frequency and the square of the steel plate thickness; therefore, reducing the thickness is an important means of reducing core losses. Thus, researching how to develop thin strips (0.35 mm and below) or ultra-thin strips (0.20 mm and below) of non-oriented electrical steel has significant practical and economic value.

[0003] Existing methods for producing non-oriented electrical steel strips primarily involve one or two rolling processes. The disadvantages of this process are: complex production procedures, high rolling difficulty, and very high costs; especially when the silicon content reaches 3.5% or higher, direct cold rolling is practically impossible; furthermore, due to the initial billet thickness of 230-250 mm, work hardening is severe when preparing strips with a thickness of 0.20 mm or less, leading to significant deterioration of the original texture and making it difficult to obtain good performance. Existing technology discloses a short-process, high-efficiency cold-rolling method for preparing high-silicon steel strips. This method prepares high-silicon steel strips through rapid solidification, then reduces their thickness (to a minimum thickness of 0.02 mm) through cold rolling, improving surface quality and enhancing high-frequency magnetic properties. However, this method requires cold rolling, making mass production difficult. Existing technology discloses a high-magnetic-induction, high-silicon non-oriented silicon steel sheet and its preparation method. This method significantly improves the magnetic induction intensity of the high-silicon non-oriented silicon steel sheet by adding the micro-alloying element Ce and employing a matching manufacturing process combining casting, hot rolling, and warm rolling. However, the process is lengthy, costly, and difficult to produce. Existing technology also discloses a method for preparing high-silicon non-oriented electrical thin strip steel based on a three-roll continuous casting machine. This method involves casting thin strip steel using a three-roll continuous casting machine, followed by leveling, cooling, automatic peeling, and automatic coiling to obtain non-oriented electrical thin strip steel with excellent magnetic properties. This solves the problems of complex production processes, high rolling difficulty, and high costs in the current preparation of non-oriented electrical steel thin strip steel. However, this method involves pressure spraying, requires leveling, and due to the high annealing temperature, an isolation coating is needed before annealing to prevent adhesion. Furthermore, the finished product has poor magnetic properties; after annealing, the minimum loss P of a 0.05mm thick product is low. 1.0 / 400 =5.2w / kg. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a near-net-shape manufacturing method for ultra-thin high-silicon steel strips, thereby solving the technical problems of long preparation process and the need to improve magnetic properties in the existing technology for ultra-thin high-silicon steel strips.

[0005] This invention provides a near-net-shape manufacturing method for ultra-thin high-silicon steel strips, comprising the following steps:

[0006] The raw materials are smelted into molten steel. The composition of the raw materials, by mass percentage, is as follows: C≤2.50%, Si:0.95%~6.75%, B:0.05%~2.75%, P:0.010%~0.025%, Mn≤0.35%, S≤0.006%, Cu≤0.50%, Al≤0.1%, with the balance being Fe and unavoidable impurities. Among them, the weight percentage of boron and silicon meets the following conditions: B=3.00-(0.25~0.29)×Si, and 3.5≤B+Si≤8.5.

[0007] Molten steel is injected into the nozzle, and the molten steel is sprayed through the nozzle onto the surface of the main crystallizing roll and cast and solidified into strip.

[0008] After the strip leaves the molten pool, the strip on the main crystallizing roll is protected by gas until the strip leaves the main crystallizing roll, resulting in a high-silicon steel ultrathin strip.

[0009] Compared with the prior art, the beneficial effects of the present invention include:

[0010] This invention lowers the melting point and reduces the wetting angle with the crystallizing roller by adding boron and scientifically matching its content with silicon, achieving close contact with the roller. Simultaneously, by improving cooling efficiency, it achieves the effects of eliminating the need for pickling, leveling, and specialized annealing, resulting in superior product performance. The high-silicon steel ultra-thin product manufactured by this invention has B... 800 =1.29~1.69T, P 1.0 / 400 ≤3.6w / kg. Attached Figure Description

[0011] Figure 1 This is a process flow diagram of one embodiment of the near-net-shape manufacturing method for ultra-thin high-silicon steel strips provided by the present invention;

[0012] Figure 2 This is a process flow diagram of another embodiment of the near-net-shape manufacturing method for ultra-thin high-silicon steel strips provided by the present invention;

[0013] Figure 3 This is a schematic diagram of the process equipment of one embodiment of the near-net-shape manufacturing apparatus for ultra-thin high-silicon steel strips provided by the present invention.

[0014] Figure 4 This is a schematic diagram of the gas protection system for the near-net-shape manufacturing apparatus for ultra-thin high-silicon steel strips provided by the present invention.

[0015] Figures 3-4In the middle, 1. Strip preparation unit, 11. Melting equipment, 12. Nozzle pack, 13. Nozzle, 14. Crystallizing roller group, 141. Main crystallizing roller, 142. Secondary crystallizing roller, 143. Stripping roller, 15. Directing roller, 16. Pinch roller, 17. Thickness gauge, 18. First coiler, 2. High silicon steel ultra-thin strip. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] Please see Figure 1 This invention provides a near-net-shape manufacturing method for ultra-thin high-silicon steel strips, comprising the following steps:

[0018] S1. The raw materials are smelted into molten steel. The composition of the raw materials by mass percentage is as follows: C≤2.50%, Si:0.95%~6.75%, B:0.05%~2.75%, P:0.010%~0.025%, Mn≤0.35%, S≤0.006%, Cu≤0.50%, Al≤0.1%, with the balance being Fe and unavoidable impurities. Among them, the weight percentage of boron and silicon meets the following conditions: B=3.00-(0.25~0.29)×Si, and 3.5≤B+Si≤8.5.

[0019] S2. The molten steel is injected into the nozzle, and the molten steel is sprayed through the nozzle onto the surface of the main crystallizing roll and cast and solidified into strip.

[0020] S3. After the strip leaves the molten pool, the strip on the main crystallizing roll is protected by gas until the strip leaves the main crystallizing roll, resulting in a high-silicon steel ultra-thin strip.

[0021] In the raw materials used in this invention, sulfur (S) is an element that is harmful to magnetic properties. Therefore, this invention specifies that S ≤ 0.006%.

[0022] Si: The most effective element for reducing iron loss. Specifically, considering the magnetic performance requirements and production methods of the products in this invention, the Si content is specified as 0.95% to 6.75%. If Si < 0.95%, it is difficult to reduce the iron loss of the finished product; if Si > 6.75%, it is not conducive to improving magnetic induction.

[0023] B: Boron atoms have a small atomic radius and tend to agglomerate at grain boundaries, forming trace amounts of borides (such as Fe2B). These borides pin grain boundary movement, hindering abnormal grain growth and thus achieving grain refinement. The refined grain structure reduces the obstruction of grain boundaries to magnetic domain wall movement, while simultaneously improving the material's plasticity and toughness, alleviating the brittleness problem caused by the high silicon content in high-silicon steel. Furthermore, boron can purify grain boundaries, reducing the scattering of electrons by impurity atoms, which is beneficial for texture development, making it easier for high-silicon steel to reach saturation during magnetization, thus improving both initial and maximum permeability. Considering that boron is mainly sourced from ferroborone or borax, which is costly, this invention controls the boron and silicon content within the range specified in the above formula, resulting in relatively low cost and optimal magnetic properties.

[0024] Mn: It mainly plays a role in sulfur fixation by generating MnS. This invention has a high requirement for sulfur, that is, S≤0.006%. Increasing Mn will increase the production cost, so Mn≤0.35% is sufficient.

[0025] P: It tends to segregate at grain boundaries, causing brittleness, which is detrimental to processing and is a harmful element in high silicon steel; if the restriction is too strict, the smelting difficulty will increase, so this invention specifies 0.010%≤P≤0.025%.

[0026] Cu promotes favorable {110} textures, suppresses unfavorable {111} textures, and improves magnetic induction (B50), but it has a certain impact on iron loss and is relatively expensive. Therefore, this invention specifies Cu≤0.50%.

[0027] Al: It is easily oxidized and is a strong deoxidizing element, which is beneficial for reducing oxygen content. However, this invention specifies Al ≤ 0.1%, mainly because Al easily generates Al2O3, which floats on the molten steel along with other steel slag. Because the nozzle orifice is small, impurities can easily clog it, which is not good for continuous spraying.

[0028] In some specific embodiments of the present invention, the composition of the raw materials by mass percentage is as follows: C≤0.050%, Si:2.95%~6.65%, B:1.25%~2.25%, P:0.010%~0.017%, Mn:0.12%~0.18%, S≤0.005%, Cu≤0.045%, Al≤0.045%, with the balance being Fe element and unavoidable impurities.

[0029] This invention does not limit the raw materials used in the production of high-silicon steel ultrathin strips. Those skilled in the art can select materials according to actual conditions, as long as the final product meets the above-mentioned composition requirements. For example, it may include at least one of the following: converter steel, industrial pure iron, silicon steel scrap, metallic silicon, ferroborone, borax, etc.

[0030] In this embodiment, the melting temperature in step S1 is 1300~1680℃. This invention does not limit the equipment used in the melting process; those skilled in the art can select appropriate equipment based on actual conditions, such as a vacuum furnace or a medium-frequency furnace.

[0031] In this embodiment, in step S2, molten steel is injected into a nozzle preheated to 1000~1350°C.

[0032] In this invention, it should be noted that the method of spraying is not limited. Those skilled in the art can choose according to the actual situation, such as pressure spraying or gravity spraying. The gas used for pressure spraying is a non-oxidizing gas (including but not limited to argon, nitrogen, etc.). This invention preferably adopts gravity spraying, which has the advantages of simple equipment requirements, continuous spraying, high operating rate, high yield, and strong performance stability.

[0033] In this embodiment, during step S2, when the molten steel is sprayed onto the surface of the main crystallizing roller through the nozzle, the superheat of the molten steel at the start of casting is 7~50°C, preferably 25~45°C, and further preferably 30~45°C.

[0034] In this embodiment, during step S2, when molten steel is sprayed onto the surface of the main crystallizing roll through the nozzle, the gap between the nozzle and the main crystallizing roll is 0.20~1.0mm, including but not limited to 0.20mm, 0.40mm, 0.60mm, 0.80mm, 1.0mm, etc.

[0035] In this embodiment, in step S2, after casting begins, CO gas is sprayed around the molten pool. This heats the nozzles to prevent them from clogging the gate due to low temperature, and also consumes the surrounding oxygen to protect the molten pool from oxidation and improve the surface quality of the strip.

[0036] Preferably, the CO pressure is 0.05~0.20MPa, including but not limited to 0.05MPa, 0.10MPa, 0.15MPa, 0.20MPa, etc.

[0037] In this embodiment, in step S3, the cooling length of the main crystallizing roller is ≥1.5m. By controlling the cooling length of the main crystallizing roller within the above range, this invention can increase the cooling time, improve the microstructure of the strip, and enhance the surface quality and strip-making stability of the strip.

[0038] In this invention, it should be noted that the cooling length of the main crystallizing roll refers to the continuous arc length of the roll surface from when the molten steel is sprayed from the nozzle and contacts the surface of the main crystallizing roll until the strip solidifies and naturally separates or peels off from the main crystallizing roll, during which the strip maintains close contact with the surface of the main crystallizing roll and undergoes the main heat exchange.

[0039] Preferably, the main crystallizing roll is reversed to ensure that the angle of the ultra-thin strip wrapping roll during casting solidification is ≥180°. In this way, the cooling length exceeds half the arc length of the main crystallizing roll, far exceeding the cooling length when the crystallizing roll rotates forward (about 1 / 8 of the arc length of the crystallizing roll), ensuring that the strip can still obtain the required solidification cooling length even when using a small radius roll.

[0040] In this embodiment, in steps S2 and S3, the surface temperature of the main crystallizing roller, the secondary crystallizing roller, and the stripping roller is 25~35℃.

[0041] In this embodiment, in steps S2 and S3, the linear speed of the main crystallizing roller is ≥20 m / s. By controlling the linear speed within the above range, the present invention can obtain a cast strip that meets the thickness requirements of this application. If the linear speed is too low, the cast strip will be too thick.

[0042] In some specific embodiments of the present invention, the linear speed of the main crystallizing roller is 20~30m / s.

[0043] In this embodiment, in steps S2 and S3, the linear velocity of the secondary crystallizer roller is 98% to 102% of the linear velocity of the primary crystallizer roller.

[0044] In this embodiment, in steps S2 and S3, the linear speed of the stripping roller is 100% to 105% of the linear speed of the main crystallizing roller.

[0045] The high-silicon steel ultra-thin strip of this invention is manufactured using a three-roll continuous casting machine. The main crystallizing roll plays a primary role in solidification; molten steel is sprayed onto the surface of the main crystallizing roll through a nozzle and instantly solidifies on the surface, forming the initial thin strip. The secondary crystallizing roll is parallel to the main crystallizing roll and further cools the initially solidified strip to improve internal density and promote uniform heat dissipation on both sides. The peeling roll stably and continuously peels the fully solidified strip, which has reached a certain strength, from the surface of the main crystallizing roll and guides it to the subsequent coiler. The main crystallizing roll, secondary crystallizing roll, and peeling roll work closely together to achieve rapid solidification and continuous forming of the metal strip.

[0046] In this embodiment, in step S3, after the strip leaves the molten pool by 50~100mm, the strip on the main crystallizing roller is protected by gas.

[0047] In this embodiment, during step S3, the gas pressure is 0.3~3.5 MPa. This invention uses gas protection to enhance cooling and prevent high-temperature oxidation of the strip. The atmosphere used for gas protection in this invention includes, but is not limited to, nitrogen, argon, and compressed air. It should be noted that if the strip temperature is high, a non-oxidizing atmosphere should be used; if the strip temperature drops to a level where oxidation does not occur, compressed air can be used to reduce costs.

[0048] In this embodiment, in step S3, the strip outlet temperature (i.e., the bottom outlet of the main crystallizing roller) is 100~200℃, including but not limited to 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, etc. An excessively high strip outlet temperature indicates insufficient cooling of the steel strip.

[0049] In this embodiment, the thickness of the high-silicon steel ultrathin strip is 0.015~0.150mm, including but not limited to 0.015mm, 0.03mm, 0.05mm, 0.08mm, 0.100mm, 0.120mm, 0.150mm, etc.

[0050] In this embodiment, the finished thickness of the high-silicon steel ultrathin strip is 0.018~0.050mm, and the magnetic induction B... 800 =1.29~1.69T, further to 1.55~1.65T, iron loss P 1.0 / 400 ≤3.6w / kg, further to 2.5~3w / kg, P 1.0 / 1K =8.50~9.85kg, P 0.1 / 10K =3.00~4.00kg, high-frequency loss is close to that of amorphous alloy strip.

[0051] Please see Figure 2 In this embodiment, the above-mentioned near-net-shape manufacturing method for ultra-thin high-silicon steel strips further includes:

[0052] S4. Post-processing: The high-silicon steel ultra-thin strip is cleaned, dried, coated with an insulating layer, and then dried.

[0053] The high-silicon steel ultrathin strip of the present invention can have its magnetic properties further enhanced after being coated with an insulating layer.

[0054] Preferably, the high-silicon steel ultrathin strip is wound into a coil after leaving the main crystallizing roll, and unwound before the post-processing process. Specifically, a coiler is used to wind the strip into a coil; the linear speed of the coiler is 100% to 105% of the linear speed of the main crystallizing roll; the winding temperature is <200℃.

[0055] Preferably, the cleaning process involves cleaning with an alkaline solution and water. The alkaline solution can be a 2%–4% sodium hydroxide solution, etc.

[0056] Preferably, the coating used in the process of applying the insulating layer is a T4 coating. This invention does not limit the use of a T4 coating; any conventional T4 coating in the art can be selected.

[0057] Preferably, the coating thickness is 0.50~2.5μm.

[0058] Preferably, the drying temperature is 200~750℃, more preferably 200~400℃; the drying time is 30~36000s, more preferably 50~75s.

[0059] Preferably, after drying, the process further includes: winding up the ultra-thin high-silicon steel strip.

[0060] Please see Figures 3-4 The apparatus used in the above-mentioned near-net-shape method for ultra-thin high-silicon steel strip includes: a strip preparation unit 1; wherein, the strip preparation unit 1 includes: a smelting device 11, a nozzle 12, a nozzle 13, and a crystallizing roller group 14; the outlet of the smelting device 11 is connected to the inlet of the nozzle 12 for conveying molten steel to the nozzle 12; the nozzle 13 is provided at the bottom of the nozzle 12, and the nozzle 13 is located on the upstream side of the crystallizing roller group 14 to spray molten steel onto the roller surface of the crystallizing roller group 14; the crystallizing roller group 14 is used to rapidly cool the molten steel sprayed onto it and form a strip.

[0061] In this embodiment, the crystallization roller group 14 includes a main crystallization roller 141, a secondary crystallization roller 142, and a stripping roller 143. The main crystallization roller 141 and the secondary crystallization roller 142 are arranged in parallel and rotate relative to each other to form a roller gap for cooling the strip. The stripping roller 143 is located on the strip exit side of the main crystallization roller 141 or the secondary crystallization roller 142 and is used to strip and export the solidified thin strip.

[0062] Preferably, the diameter of the main crystallizing roller is 0.4~1m.

[0063] In this embodiment, the crystallizing roller assembly 14 is cooled by compressed air and / or internal water cooling.

[0064] In this embodiment, the strip preparation unit 1 further includes: a guide roller 15, a pinch roller 16, a thickness gauge 17, and a first winding machine 18. The guide roller 15, the pinch roller 16, and the thickness gauge 17 are disposed between the crystallizing roller group 14 and the first winding machine 18 to guide the strip from the crystallizing roller group 14 to the first winding machine 18. The first winding machine 18 is disposed on the downstream side of the crystallizing roller group 14 to wind up the cooled strip.

[0065] Specifically, there are two pinch rollers 16.

[0066] In this embodiment, the above-mentioned device includes: a strip post-processing unit (not shown in the figure), and the strip post-processing unit includes: an uncoiler, a cleaning mechanism, a first drying oven, a coating mechanism, a second drying oven, and a second winding machine arranged in sequence.

[0067] The principles of this application will be explained below with reference to the accompanying drawings:

[0068] Please see Figures 1-4This invention uses converter steel, industrial pure iron, or silicon steel scrap as the main raw materials, supplemented with appropriate amounts of silicon steel or metallic silicon, ferroborone, or borax as auxiliary materials. The steel is smelted in a medium-frequency furnace (or vacuum furnace). After melting, the molten steel is injected into a nozzle preheated to 1000-1350℃. The gap between the nozzle and the main crystallizing roller is 0.20-1.0mm. The molten steel flows out from the nozzle gap and is cast flatly to the top of the main crystallizing roller. Before casting, the superheat of the molten steel at the start of casting is controlled to be 7-50℃. After casting begins, CO gas is sprayed around the molten pool. This serves two purposes: first, to heat the nozzle and prevent it from clogging the nozzle nozzle due to low temperature; second, to purify the surrounding area of ​​the molten pool with CO. Oxygen combustion is consumed to protect the molten pool from oxidation; the cooling length of the crystallizing roller is controlled to be ≥1.5m to improve the microstructure and properties of the strip, and enhance its surface quality and stability; after the cast strip leaves the molten pool by 50~100mm, the strip on the main crystallizing roller is protected by gas until it leaves the main crystallizing roller, and the gas pressure is controlled to be 0.3~3.5MPa; the strip is output from the bottom of the main crystallizing roller, and the strip outlet temperature is 100~200℃; an automatic winding device is used to wind the cast strip with a thickness of 0.015~0.150mm into a roll; before coating the insulating layer, the surface of the high silicon steel ultrathin strip is unwound, cleaned, and dried, and then dried after coating the insulating layer. The high-silicon steel ultra-thin strip of the present invention has no surface oxidation, and does not require pickling or surface rust removal, nor does it require leveling, cold rolling or other processing steps. The high-silicon steel ultra-thin strip of the present invention does not require special annealing treatment to achieve good performance. After coating with an insulating layer, the insulating layer is dried in a drying oven at 200~750℃, which can further improve the performance.

[0069] Examples 1-6

[0070] (1) Using industrial pure iron as the main raw material, the steel is smelted in a medium frequency furnace. The composition by mass percentage is: C≤0.050%, Si:2.95%~6.65%, B:1.25%~2.25%, Mn:0.12%~0.18%, P:0.010%~0.017%, S≤0.005%, Cu≤0.045%, Al≤0.045%, with the balance being Fe element and unavoidable impurities. The steel smelting temperature is 1630℃.

[0071] (2) The qualified molten steel is injected into the nozzle ladle with a preheating temperature of 1100~1350℃. Before casting, the superheat of the molten steel at the start of casting should be controlled to be 25~45℃. The gap (shortest distance) between the nozzle and the main crystallizing roller should be 0.40mm. The molten steel flows out from the nozzle gap and is cast in a plane to the top of the main crystallizing roller. After casting, CO gas is sprayed around the molten pool at a pressure of 0.05MPa. The main crystallizing roller is reversed so that the roll angle of the cast and solidified ultra-thin strip is ≥180°. The linear velocity of the main crystallizing roller is 22~29m / s, and the cooling length of the main crystallizing roller is about 1.6m.

[0072] (3) Gas protection: When the strip leaves the molten pool by 50~100mm, nitrogen protection is applied to the strip on the main crystallizing roller. The protection zone is maintained until the strip leaves the main crystallizing roller. The nitrogen pressure is controlled at 0.3~3.5MPa. The strip is quickly output from the bottom of the main crystallizing roller. The strip outlet temperature is 120~200℃.

[0073] (4) Winding: The cast strip with a thickness of 0.018~0.050mm is wound into a coil using an automatic winding device. The linear speed of the main crystallizing roller is controlled to be synchronized with that of the auxiliary crystallizing roller, the stripping roller and the winding machine. The steel strip winding temperature is <200℃.

[0074] (5) Coating: Before coating, the surface of the ultra-thin strip is cleaned, dried, coated and baked. The coating thickness is controlled to be 0.50~2.5μm, the drying temperature is 200~400℃, and the drying time is 50~75s.

[0075] Comparative Example 1

[0076] The only difference from Example 1 is that the boron content is 1.05%.

[0077] Comparative Example 2

[0078] The only difference from Example 6 is that the boron content is 0.36%.

[0079] Comparative Example 3

[0080] Compared to Example 2, a forward spray belt is used, and the cooling length of the main crystallizing roller is approximately 0.40m.

[0081] Based on the above-described method for manufacturing ultrathin high-silicon steel strips, the present invention further illustrates the composition and preparation parameters of the embodiments and comparative examples in conjunction with the following three tables.

[0082] Table 1. List of component values ​​(wt%) for Examples 1-6 and Comparative Examples 1-3 of the present invention

[0083]

[0084] Table 2. List of main process parameters for Examples 1-6 and Comparative Examples 1-3 of the present invention (I)

[0085]

[0086] (Note: T in Table 2) 液 =1538- ), where k i To reduce the melting point of element i, w i This represents the mass fraction of the element.

[0087] Table 3. List of main process parameters for Examples 1-6 and Comparative Examples 1-3 of the present invention (II)

[0088]

[0089] Performance testing

[0090] The high-silicon steel ultrathin strips prepared in the above embodiments and comparative examples were made into ring samples with a diameter of Ф40mm×Ф32mm×10mm. The samples were tested according to GB / T3658-2022 Method for measuring the magnetic properties of soft magnetic metal materials and powder metallurgy materials in the frequency range of 20Hz to 100kHz and GB / T13012-2008 Method for measuring the DC magnetic properties of soft magnetic materials. The magnetic properties were measured using a single-chip permeameter. The test results are shown in Table 4.

[0091] Table 4. Performance test results of Examples 1-6 and Comparative Examples 1-3 of the present invention

[0092]

[0093] (Where, nominal density = 7.865 - 0.065 × (Si + Al × 1.7); the results in Examples 1-6 and Comparative Examples 1-3 are all test results without coating).

[0094] Please refer to Tables 1-4. As can be seen from Tables 1-4, in embodiments 1-6 of this invention, the finished product thickness is 0.018-0.050 mm, and the magnetic induction B... 800 =1.55~1.65T, iron loss P 1.0 / 400 =2.76~2.98W / kg, R m =485~548MPa, A=2.56%~3.86%, indicating that by using the method of the present invention, the cast thin strip can achieve near-net-shape forming of ultra-thin strips of super high silicon steel without argon protection, rolling or leveling, pickling or special annealing treatment. This can shorten the process flow, reduce production costs, energy consumption and waste gas emissions, and improve magnetic properties.

[0095] Compared to Example 1, in Comparative Example 1, the silicon content was 2.95% and the boron content was 1.05%. Although it could form a strip, the quality of the strip was poor and it was prone to curling. This indicates that when the boron and silicon content does not meet the formula requirements of this application, although it can form a strip, it has an adverse effect on the quality of the ultra-thin strip (thickness 0.03 mm). Compared to Example 6, in Comparative Example 2, the silicon content was 6.65% and the boron content was 0.36%. The strip did not stick to the roller and was fragmented, making it impossible to form a strip. This indicates that when the boron and silicon content does not meet the formula requirements of this application, it is impossible to obtain an ultra-thin strip with a higher thickness (thickness ≥ 0.05 mm). Compared to Example 2, in Comparative Example 3, a forward spraying method was used, resulting in a shorter cooling length and extremely poor strip quality with severe curling. This indicates that the cooling length is less than the range of this application, which also has an adverse effect on the quality of the ultra-thin strip.

[0096] Compared with existing methods, the beneficial effects of the present invention include:

[0097] (1) This invention directly casts alloy steel into an extremely thin strip of 0.015~0.150mm without leveling or rolling deformation, breaking through many key technical bottlenecks of high silicon steel strips, which have high hardness, high brittleness and are difficult to roll. The process is short, the yield is high, and the production cost, energy consumption and exhaust emissions are significantly reduced.

[0098] (2) This invention improves the surface quality of the strip and the stability of the sprayed strip by adding boron and increasing the cooling length. The molten steel solidifies quickly and is thin. The {001} texture in the thin strip can be retained during coating drying, which improves the magnetic properties. No rolling and annealing treatment is required, which completely subverts the production process of silicon steel.

[0099] (3) The casting strip of the present invention adopts atmosphere protection during the production process, the surface is free from oxidation, the surface quality is good, and there is no need to go through the pickling process, thus eliminating the pollution of acid liquid and acid mist.

[0100] (4) This invention is a true near-net-shape manufacturing process. It does not require an annealing process. The purpose of annealing can be achieved through the drying process after coating, without the need for an additional annealing process.

[0101] (5) The present invention can achieve rapid strip formation, automatic peeling and automatic winding. After coating, a high silicon steel ultra-thin strip product with excellent magnetic properties can be obtained.

[0102] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A near-net-shape manufacturing method for ultra-thin high-silicon steel strips, characterized in that, Includes the following steps: The raw materials are smelted into molten steel. The composition of the raw materials, by mass percentage, is as follows: C≤0.050%, Si:2.95%~6.65%, B:1.25%~2.25%, P:0.010%~0.017%, Mn:0.12%~0.18%, S≤0.005%, Cu≤0.045%, Al≤0.045%, with the balance being Fe and unavoidable impurities. The weight percentages of boron and silicon meet the following conditions: B=3.00-(0.25~0.29)×Si, and 3.5≤B+Si≤8.

5. The molten steel is injected into the nozzle, and the molten steel is sprayed through the nozzle onto the surface of the main crystallizing roll and cast and solidified into strip. After the strip leaves the molten pool, it is protected with gas on the main crystallizing roll until it detaches from the roll, resulting in a high-silicon steel ultrathin strip. The cooling length of the main crystallizing roll is ≥1.5m, and the roll is reversed to ensure that the angle of the solidified ultrathin strip wrapping around the roll is ≥180°. .

2. The near-net-shape manufacturing method for ultra-thin high-silicon steel strips according to claim 1, characterized in that, The melting temperature is 1300~1680℃; The molten steel is injected into a nozzle preheated to 1000~1350℃.

3. The near-net-shape manufacturing method for ultra-thin high-silicon steel strips according to claim 1, characterized in that, During the process of the molten steel being sprayed onto the surface of the main crystallizing roller through the nozzle, when casting begins, the superheat of the molten steel is 7~50℃, and the gap between the nozzle and the main crystallizing roller is 0.20~1.0mm; after casting begins, CO gas is sprayed around the molten pool.

4. The near-net-shape manufacturing method for ultra-thin high-silicon steel strips according to claim 1, characterized in that, The surface temperature of the main crystallizing roller, the auxiliary crystallizing roller, and the stripping roller is 25~35℃. The linear speed of the main crystallizing roller is ≥20m / s, the linear speed of the auxiliary crystallizing roller is 98%~102% of the linear speed of the main crystallizing roller, and the linear speed of the stripping roller is 100%~105% of the linear speed of the main crystallizing roller.

5. The near-net-shape manufacturing method for ultra-thin high-silicon steel strips according to claim 1, characterized in that, During the gas protection process, the gas pressure is 0.3~3.5MPa; The strip exit temperature is 100~200℃.

6. The near-net-shape manufacturing method for ultra-thin high-silicon steel strips according to claim 1, characterized in that, The thickness of the high-silicon steel ultrathin strip is 0.015~0.150mm.

7. The near-net-shape manufacturing method for ultra-thin high-silicon steel strips according to claim 1, characterized in that, Also includes: The post-processing process includes: cleaning, drying, coating with an insulating layer, and drying the high-silicon steel ultrathin strip.

8. The near-net-shape manufacturing method for ultra-thin high-silicon steel strips according to claim 7, characterized in that, The high-silicon steel ultra-thin strip is detached from the main crystallizing roll, wound into a coil, and unwound before the post-processing step. The drying temperature is 200~750℃, and the drying time is 30~36000s; After drying, the process further includes: winding up the high-silicon steel ultrathin strip.

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