Production method for reducing edge cracks of high-magnetic-induction oriented silicon steel

Abstract

The invention discloses a production method for reducing edge cracks of high-magnetic-induction oriented silicon steel, and relates to the technical field of oriented silicon steel production and manufacturing, and the production method comprises the following steps: S1, carrying out normalizing treatment, acid pickling and cold rolling on a hot rolled steel coil to obtain a cold-rolled steel plate; s2, carrying out decarburization annealing and nitriding treatment on the cold-rolled steel sheet, extruding the cold-rolled steel sheet, coating a magnesium oxide coating, and carrying out high-temperature annealing to obtain an annealed steel coil; and S3, the annealed steel coil is subjected to stretching flattening annealing and laser nicking treatment, and the high-magnetic-induction oriented silicon steel is obtained. According to the production method disclosed by the invention, the cracking occurrence rate of the edge part of the steel coil after high-temperature annealing is greatly reduced through a low-cost production method.

Description

Technical Field

[0001] The invention belongs to the technical field of oriented silicon steel production and manufacturing, and in particular is a production method for reducing edge cracks of high magnetic induction oriented silicon steel. Background Art

[0002] During the high temperature annealing process, the high magnetic induction oriented silicon steel coil needs to be kept at a temperature of about 1200℃ for a long time, and the total processing time exceeds 150 hours. Since the weight of the silicon steel coil is usually between 15 and 25 tons, during high temperature annealing, due to the influence of high temperature creep and thermal expansion and contraction, the edges of the steel coils close to the furnace bottom plate are prone to cracks and poor plate shape defects. These defects are manifested as cracks along the length of the steel coil edge, forming obvious cracks.

[0003] The main reasons for these defects include: the bottom of the silicon steel coil undergoes high-temperature creep under the combined effect of the support force of the furnace bottom plate and its own gravity, resulting in obvious wrinkles on the edge; during the heating process, the steel coil expands outward; and during the cooling stage, the steel coil shrinks inward. During this process, the bottom of the steel coil and the furnace bottom plate are subjected to intense friction, especially the outer ring of the steel coil, which suffers the most severe friction damage due to the largest displacement. If the levelness or flatness of the furnace table or furnace bottom plate is not good, the support force of the furnace bottom plate is unevenly distributed, and the friction force on the local part of the steel coil will increase sharply, resulting in edge cracks in the silicon steel coil.

[0004] Edge cracks in high magnetic induction oriented silicon steel can lead to a series of problems: after high temperature annealing, the edges of the steel coils tend to stick together, resulting in more scrap when unwinding; during stretching and flattening annealing, the edges of the steel coils tend to crack, resulting in product breakage and production stoppages; during laser scoring, the steel plate has a large amplitude of vibration and the plate surface is uneven, resulting in uneven scoring and poor scoring effect. Ultimately, these defects must be removed in the shearing and packaging stage before the product can be shipped as a qualified product, which will result in a significant loss in yield.

[0005] In order to reduce the occurrence of these defects, the existing technology usually controls the related defects through the following methods: adjusting the high-temperature annealing cooling rate, strengthening the quality maintenance of the high-temperature annealing furnace bottom plate, adjusting the strip tension in the annealing furnace of the stretching and flattening production line, and other parameters. However, these methods have limited effects on the one hand, and on the other hand may lead to a significant increase in production costs, reduced production efficiency, and even a negative impact on the magnetic level of the product. Therefore, it is necessary to find more effective solutions to reduce these defects in order to improve production efficiency and product quality. Summary of the invention

[0006] The present invention overcomes the defects of the above-mentioned background technology, and thus provides a production method for reducing edge cracks of high magnetic induction oriented silicon steel. The edge crack defects of high magnetic induction oriented silicon steel can be effectively controlled through a low-cost process.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] The present invention discloses a production method for reducing edge cracks of high magnetic induction oriented silicon steel, comprising the following steps:

[0009] S1. The hot-rolled steel coil is normalized and cold-rolled to obtain a cold-rolled steel sheet;

[0010] S2. The cold-rolled steel sheet is subjected to decarburization annealing and nitriding treatment, and then the cold-rolled steel sheet is extruded, coated with a magnesium oxide coating and then annealed at high temperature to obtain an annealed steel coil;

[0011] The extrusion position is the upper and lower surfaces within a width range of 0 to 20 mm from the edge of the steel coil;

[0012] The extrusion pressure is 60-480 MPa;

[0013] S3. The annealed steel coil is subjected to stretching flattening annealing and laser scoring treatment to obtain high magnetic induction oriented silicon steel.

[0014] In S1, the hot rolled steel coil comprises the following elements in percentage by mass:

[0015] C: 0.040% to 0.080%, Si: 3.0% to 3.60%, Mn: 0.05% to 0.30%, Als: 0.0230% to 0.0310 %, N: 0.006%~0.009%, Sn: ≤0.10%, Cr: ≤0.20%, P: ≤0.050%, S: 0.003~0.016%.

[0016] In S1, the hot-rolled steel coil is composed of the following elements in mass percentage: C: 0.040% to 0.080%, Si: 3.0% to 3.60%, Mn: 0.05% to 0.30%, Als: 0.0230% to 0.0310%, N: 0.006% to 0.009%, Sn: ≤0.10%, Cr: ≤0.20%, P: ≤0.050%, S: 0.003 to 0.016%; the rest is Fe and unavoidable impurities.

[0017] In S2, the extrusion position is the upper and lower surfaces within a width range of 0 to 15 mm from the edge of the steel plate.

[0018] In S2, the extrusion pressure is 80-450 MPa, preferably 100-445 MPa. The extrusion causes slight plastic deformation of the edge of the steel plate.

[0019] In S2, the diameter of the steel rollers on both sides of the strip used for extrusion is 50-100 mm, preferably 60-100 mm.

[0020] In S2, the coating of the magnesium oxide coating is a conventional process in the art, and the main component of the magnesium oxide coating is magnesium oxide.

[0021] In S1, the normalization process includes:

[0022] The heating temperature of the first normalization stage is 1000-1120°C, and the holding time is 1-3 minutes;

[0023] The heating temperature of the second normalization stage is 900-950°C, and the holding time is 1-3 minutes.

[0024] In S1, the normalizing treatment further includes a pickling process, and the pickling may be a conventional process in the art.

[0025] In S1, the cold rolling method is a single cold rolling method.

[0026] In S1, the thickness of the cold-rolled steel sheet is 0.18-0.30 mm.

[0027] In S2, the temperature of the decarburization annealing is 800-900°C, and the time of the decarburization annealing is 100-200s.

[0028] In S2, the decarburization annealing further includes a nitriding operation.

[0029] Furthermore, the nitriding temperature is 780-920°C.

[0030] Furthermore, the nitriding time is 10 to 60 seconds.

[0031] Furthermore, the nitriding gas is a mixed gas of N2, H2 and NH3.

[0032] In S2, the high temperature annealing process includes a first stage of high temperature annealing with a temperature rise and a second stage of high temperature annealing.

[0033] Furthermore, the first high-temperature annealing: heating from room temperature to 550-750°C and keeping the temperature, the heating rate is 20-50°C / h, the holding time is 20-40h, the atmosphere is a mixture of N2 and H2, the proportion of H2 in the mixture is 20-80%; wherein the room temperature is 15-30°C;

[0034] The second high temperature annealing: the temperature is raised to 1150-1250°C and kept at this temperature for 20-40 hours, the heating rate is 5-20°C / h, the heating atmosphere is a mixture of N2 and H2, and the atmosphere during the holding stage is pure hydrogen. The room temperature is 15-30°C.

[0035] In S2, after the high temperature annealing, the grain size within a width range of 0 to 15 mm from the edge of the steel plate is 100 to 2500 μm.

[0036] In S3, the stretching and flattening annealing is a conventional process in this field.

[0037] In S3, the laser scribing is a conventional process in the art.

[0038] In the present invention, the number of cracks with a depth of ≥2 mm in the high magnetic induction oriented silicon steel is 0 to 0.5 per meter.

[0039] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention causes slight plastic deformation of the edge of the steel plate by extruding the edge, thereby increasing deformation energy storage; during high-temperature annealing, this part undergoes recrystallization in advance, and when secondary recrystallization occurs in other parts, the coarse Gaussian grains cannot swallow up the recrystallized grains formed in the extruded part, which ultimately leads to a significantly finer grain size in the extruded part than in the normal part, thereby achieving the effect of improving the toughness of the edge structure, thereby effectively preventing the occurrence of edge cracks.

[0042] 2. The present invention can significantly reduce the incidence of cracks at the edge of the steel coil after high-temperature annealing through a low-cost production method. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a diagram of the edge of the high magnetic induction oriented silicon steel of Example 1.

[0044] Figure 2 This is the edge diagram of the high magnetic induction oriented silicon steel of comparative example 1. DETAILED DESCRIPTION

[0045] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0046] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0047] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] If not otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0050] If not otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0051] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0052] If not specifically stated, in the present invention, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0053] The hot rolled steel coils of the following examples and comparative examples are composed of the following elements in percentage by mass:

[0054] C: 0.060%, Si: 3.25%, Mn: 0.12%, Als: 0.0285%, N: 0.0077%, Sn: 0.043%, Cr: ≤0.0342%, P: ≤0.0212%, S: 0.0064%; the rest are Fe and unavoidable impurities.

[0055] Example 1

[0056] The production method for reducing edge cracks of high magnetic induction oriented silicon steel of this embodiment comprises the following steps:

[0057] (1) The hot-rolled steel coil is kept at 1100°C for 3 minutes, then kept at 930°C for 2 minutes for normalization treatment, and then pickled;

[0058] (2) A cold-rolled steel sheet with a thickness of 0.17 mm is obtained by a single cold rolling method;

[0059] (3) The cold-rolled steel sheet was decarburized and annealed at 800°C for 110 seconds;

[0060] (4) nitriding treatment was performed at 800°C for 20 seconds, and the gas used for nitriding was a mixture of N2, H2 and NH3;

[0061] (5) A steel roller with a diameter of 61 mm is used on both sides of the strip to squeeze the upper and lower surfaces of the edge of the cold-rolled steel plate within a width range of 0 to 15 mm, and the extrusion pressure is 445 MPa;

[0062] (6) applying a magnesium oxide coating and drying;

[0063] (7) High temperature annealing: The first stage of high temperature annealing is to heat the steel coil from room temperature (20°C) to 650°C at a heating rate of 30°C / h and then keep it at that temperature for 25 hours; the second stage of high temperature annealing is to heat the steel coil from room temperature (20°C) to 1120°C at a heating rate of 10°C / h and then keep it at that temperature for 30 hours to obtain the annealed steel coil; wherein, the atmosphere during the heating process is a mixture of N2 and H2, and the atmosphere during the holding stage is pure hydrogen; after high temperature annealing, the grain size within a width range of 0 to 15 mm from the edge of the steel coil is 100 to 2500 μm;

[0064] (8) The annealed steel coil is stretched, flattened, annealed and laser scored, sheared and packaged, and the fine grains at the edge are cut off to obtain high magnetic induction oriented silicon steel. See the edge diagram of high magnetic induction oriented silicon steel for details. Figure 1 , Figure 1 The surface coating and magnesium silicate bottom layer are removed to expose the matrix grains.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is:

[0067] This comparative example does not include the extrusion process in step (5), and the other steps and parameters are the same as those in Example 1.

[0068] See the edge diagram of high magnetic induction oriented silicon steel for details. Figure 2 , Figure 2 After removing the surface coating and magnesium silicate bottom layer, the matrix grains are exposed.

[0069] Example 2

[0070] The difference between this embodiment and embodiment 1 is that:

[0071] In step (2), the thickness of the cold-rolled steel plate is 0.19 mm.

[0072] In step (5), a steel roller with a diameter of 70 mm is used to extrude the upper and lower surfaces of the edge of the cold-rolled steel plate within a width range of 0 to 12 mm, and the extrusion pressure is 400 MPa.

[0073] In step (7), after high temperature annealing, the grain size within a width range of 0 to 13 mm from the edge of the steel coil is 800 to 2000 μm.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 2 is that:

[0076] This comparative example does not include the extrusion process in step (5), and the other steps and parameters are the same as those in Example 1.

[0077] Example 3

[0078] The difference between this embodiment and embodiment 1 is that:

[0079] In step (2), the thickness of the cold-rolled steel plate is 0.22 mm.

[0080] In step (5), a steel roller with a diameter of 80 mm is used to extrude the upper and lower surfaces of the edge of the cold-rolled steel plate within a width range of 0 to 9 mm, and the extrusion pressure is 300 MPa.

[0081] In step (7), after high temperature annealing, the grain size within a width range of 0 to 8 mm from the edge of the steel coil is 300 to 1000 μm.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 3 is that:

[0084] This comparative example does not include the extrusion process in step (5), and the other steps and parameters are the same as those in Example 1.

[0085] Example 4

[0086] The difference between this embodiment and embodiment 1 is that:

[0087] In step (2), the thickness of the cold-rolled steel plate is 0.26 mm.

[0088] In step (5), a steel roller with a diameter of 90 mm is used to extrude the upper and lower surfaces of the edge of the cold-rolled steel plate within a width range of 0 to 7 mm, and the extrusion pressure is 200 MPa.

[0089] In step (7), after high temperature annealing, the grain size within a width range of 0 to 5 mm from the edge of the steel coil is 200 to 900 μm.

[0090] Comparative Example 4

[0091] The difference between this comparative example and Example 4 is that:

[0092] This comparative example does not include the extrusion process in step (5), and the other steps and parameters are the same as those in Example 1.

[0093] Example 5

[0094] The difference between this embodiment and embodiment 1 is that:

[0095] In step (2), the thickness of the cold-rolled steel plate is 0.285 mm.

[0096] In step (5), a steel roller with a diameter of 100 mm is used to extrude the upper and lower surfaces of the edge of the cold-rolled steel plate within a width range of 0 to 3 mm, and the extrusion pressure is 100 MPa.

[0097] In step (7), after high temperature annealing, the grain size within a width range of 0 to 3 mm from the edge of the steel coil is 1500 to 2500 μm.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 5 is:

[0100] This comparative example does not include the extrusion process in step (5), and the other steps and parameters are the same as those in Example 1.

[0101] The above embodiment n reduces the waste cutting by more than 120kg compared with the comparative example n, wherein n=1-5; the edge of the steel coil is not easy to crack during the stretching and flattening annealing, and the product breakage is greatly reduced; the steel plate vibration amplitude is reduced during the laser scoring process, the plate surface is smoother, the scoring is more uniform, and the scoring effect is improved; the fine grain area at the edge is cut off in the final shearing and packaging stage, but the cutting width is significantly smaller than that of conventional products, and the yield rate is increased by more than 0.24%.

[0102] The apparent defect statistics first use the visual method to count the number and distribution of cracks, and then use the non-contact scanning method or other measuring tools to determine the specific crack depth and width and other data. The apparent defect statistics results of the above embodiments and comparative examples are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods. The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A production method for reducing edge cracks in high magnetic induction oriented silicon steel, characterized in that: The following steps are involved: S1. The hot-rolled steel coil is normalized and cold-rolled to obtain a cold-rolled steel sheet; S2. The cold-rolled steel sheet is subjected to decarburization annealing and nitriding treatment, and then the cold-rolled steel sheet is extruded, coated with a magnesium oxide coating and then annealed at high temperature to obtain an annealed steel coil; The extrusion position is the upper and lower surfaces within a width range of 0 to 20 mm from the edge of the steel coil; The extrusion pressure is 60-480 MPa; S3. The annealed steel coil is subjected to stretching, flattening annealing and laser scoring to obtain high magnetic induction oriented silicon steel.

2. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: The hot-rolled steel coil comprises the following elements in mass percentage: C: 0.040% to 0.080%, Si: 3.0% to 3.60%, Mn: 0.05% to 0.30%, Als: 0.0230% to 0.0310%, N: 0.006% to 0.009%, Sn: ≤0.10%, Cr: ≤0.20%, P: ≤0.050%, S: 0.003 to 0.016%.

3. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: The extrusion position is the upper and lower surfaces within a width range of 0 to 15 mm from the edge of the steel plate; And / or, the extrusion pressure is 80-450 MPa; And / or, the diameter of the steel rollers on both sides of the strip steel used for extrusion is 50-100 mm.

4. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: The process of normalization treatment includes: The heating temperature of the first normalization stage is 1000-1120°C, and the holding time is 1-3 minutes; The heating temperature of the second normalization stage is 900-950°C, and the holding time is 1-3 minutes; And / or, the normalizing treatment further includes a pickling process.

5. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: The cold rolling method is a single cold rolling method; And / or, the thickness of the cold-rolled steel plate is 0.18-0.30 mm.

6. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: The temperature of the decarburization annealing is 800-900°C, and the time of the decarburization annealing is 100-200s; And / or, the decarburization annealing further includes a nitriding operation.

7. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: The nitriding temperature is 780-920°C; And / or, the nitriding time is 10 to 60 seconds.

8. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: The high temperature annealing process includes a first stage of high temperature annealing with a rising temperature and a second stage of high temperature annealing.

9. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 8, characterized in that: The first high temperature annealing: heating from room temperature to 550-750°C and keeping the temperature, the heating rate is 20-50°C / h, the holding time is 20-40h, the atmosphere is a mixture of N2 and H2, and the proportion of H2 in the mixture is 20-80%; The second stage of high temperature annealing: heating to 1150-1250°C and keeping warm for 20-40h, heating rate 5-20°C / h, heating atmosphere is a mixture of N2 and H2, and the atmosphere in the keeping stage is pure hydrogen.

10. The production method for reducing edge cracks of high magnetic induction oriented silicon steel according to claim 1, characterized in that: After the high temperature annealing, the grain size within a width range of 0 to 15 mm from the edge of the steel plate is 100 to 2500 μm.

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