A production method for reducing edge cracking of high magnetic induction oriented silicon steel

Abstract

The application 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 comprises the following steps: S1, normalizing, pickling and cold rolling a hot-rolled steel coil to obtain a cold-rolled steel plate; S2, decarburizing annealing and nitriding treatment are performed on the cold-rolled steel plate, then the cold-rolled steel plate is extruded, a magnesium oxide coating is coated, and high-temperature annealing is performed to obtain an annealed steel coil; and S3, the annealed steel coil is subjected to tensile flattening annealing and laser marking treatment to obtain high-magnetic-induction oriented silicon steel. According to the production method, the occurrence rate of cracks in the edge part of the steel coil after high-temperature annealing is greatly reduced by means of a low-cost production method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oriented silicon steel production and manufacturing, and specifically relates to a production method for reducing edge cracks of high-magnetic-induction oriented silicon steel. BACKGROUND

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

[0003] The main reasons for these defects include: high-temperature creep of the bottom of the silicon steel coil under the combined action of the support force of the furnace bottom plate and its own gravity, resulting in obvious wrinkles in the edge; during the heating process, the steel coil expands outward; and during the cooling stage, the steel coil shrinks inward, and during this process, the bottom of the steel coil rubs against the furnace bottom plate violently, especially the outer circle of the steel coil, which is subjected to the most serious friction damage due to the largest displacement. If the levelness or flatness of the furnace table or furnace bottom plate is poor, the support force of the furnace bottom plate is unevenly distributed, and the friction force on the local steel coil is sharply increased, thereby causing the silicon steel coil to crack.

[0004] The edge cracks of the high-magnetic-induction oriented silicon steel can cause a series of problems: the edge of the steel coil is prone to sticking after high-temperature annealing, resulting in an increase in scrap cutting during uncoiling; the edge of the steel coil is prone to cracking during tensile leveling annealing, resulting in product breakage and production stoppage; the steel plate jumps with a large amplitude and the plate surface is uneven during laser marking, resulting in uneven marking and poor marking effect. Finally, at the stage of shearing and packaging, these defects must be removed before the product can be shipped as a qualified product, which can cause a substantial loss of yield.

[0005] In order to reduce the occurrence of these defects, the prior art usually controls the relevant defects by adjusting the high-temperature annealing cooling speed, strengthening the quality maintenance of the high-temperature annealing furnace bottom plate, and adjusting the steel strip tension parameters in the tensile leveling production line annealing furnace. However, these methods have limited effect on one hand, and on the other hand, can cause a substantial increase in production cost, a decrease in production efficiency, and even a negative impact on the magnetic level of the product. Therefore, a more effective solution is needed to reduce these defects in order to improve production efficiency and product quality. SUMMARY

[0006] The present application overcomes the defects of the prior art, and therefore provides a production method for reducing edge cracks of high-magnetic-induction oriented silicon steel, which can effectively control the edge crack defects of the high-magnetic-induction oriented silicon steel through a low-cost process.

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

[0008] This invention discloses a production method for reducing edge cracking in high-magnetic-induction grain-oriented silicon steel, comprising the following steps:

[0009] S1. Hot-rolled steel coils are normalized and then cold-rolled to obtain cold-rolled steel sheets;

[0010] S2. The cold-rolled steel sheet is decarburized and nitrided, then extruded, coated with magnesium oxide, and then annealed at high temperature to obtain annealed steel coil.

[0011] The extrusion location 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. Annealed steel coils are subjected to stretching, leveling, annealing, and laser scoring to obtain high magnetic orientation silicon steel.

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

[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 by mass percentage: C: 0.040%–0.080%, Si: 3.0%–3.60%, Mn: 0.05%–0.30%, Als: 0.0230%–0.0310%, N: 0.006%–0.009%, Sn: ≤0.10%, Cr: ≤0.20%, P: ≤0.050%, S: 0.003–0.016%; the remainder is Fe and unavoidable impurities.

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

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

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

[0020] In S2, the coating 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 process of the normalizing treatment comprises:

[0022] The heating temperature of the first normalizing is 1000-1120℃, and the holding time is 1-3min.

[0023] The heating temperature of the second normalizing is 900-950℃, and the holding time is 1-3min.

[0024] In S1, the process after the normalizing treatment further comprises pickling, which can be a conventional process in the art.

[0025] In S1, the cold rolling method is a one-time cold rolling method.

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

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

[0028] In S2, the process after the decarburization annealing further comprises nitriding.

[0029] Further, the temperature of the nitriding is 780-920℃.

[0030] Further, the time of the nitriding is 10-60s.

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

[0032] In S2, the process of the high-temperature annealing comprises a first high-temperature annealing and a second high-temperature annealing.

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

[0034] The second high-temperature annealing is: from room temperature to 1150-1250℃, the holding time is 20-40h, the heating rate is 5-20℃ / h, the atmosphere of the heating is a mixed gas of N2 and H2, and the atmosphere of the holding stage is pure hydrogen. The room temperature is 15-30℃.

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

[0036] In S3, the stretch leveling annealing is a conventional process in the art.

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

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

[0039] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining various preferred examples of the present application.

[0040] Compared with the prior art, the present application has the following advantages:

[0041] 1. The present application can effectively prevent the occurrence of edge cracks by slightly deforming the edge of the steel plate through extrusion, increasing the deformation energy storage, and causing recrystallization in the extruded part in advance during high-temperature annealing, so that the coarse Goss grains cannot engulf the recrystallized grains formed in the extruded part, thereby finally resulting in a significant refinement of the grain size in the extruded part compared with the normal part, and achieving the effect of improving the toughness of the edge structure.

[0042] 2. The present application can significantly reduce the occurrence rate of cracks in the edge of the steel coil after high-temperature annealing by a low-cost production method. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 Figure for the edge of the high-magnetic-induction oriented silicon steel of Example 1.

[0044] Figure 2 Figure for the edge of the high-magnetic-induction oriented silicon steel of Comparative Example 1. DETAILED DESCRIPTION

[0045] In order to facilitate the understanding of the present application, the following will describe the present application more comprehensively and in detail in combination with preferred examples, but the protection scope of the present application is not limited to the following specific examples.

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

[0047] The ranges disclosed herein are intended to be "open" ranges, unless expressly specified otherwise. For example, a range of "1 to 10" is intended to include all whole numbers and fractions within this range, e.g., 1, 1.1, 1.2.,..., 10. Similarly, a range of "5-10" is intended to include, 5, 5.1, 5.2,..., 10. Also, the ranges disclosed herein are intended to be "inclusive" of the minimum and maximum values, unless specifically indicated otherwise. For example, a range of "between 1 and 10" is intended to include the values of 1 and 10. Also, when referring to a parameter as being an integer, it is understood that the parameter can be, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0049] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0050] All steps of the present application can be performed in sequence or randomly, preferably in sequence, unless otherwise specified. For example, the method comprises steps (a) and (b) indicates that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) indicates that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0051] "Include" and "contain" mentioned in the present application means open or closed, unless otherwise specified. For example, "include" and "contain" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0052] If not otherwise specifically defined, the term "or" in this disclosure is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0053] The hot-rolled steel coils of the following examples and comparative examples are composed of the following mass percentages of elements:

[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 is Fe and inevitable impurities.

[0055] Example 1

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

[0057] (1) normalizing the hot-rolled steel coil at 1100°C for 3 min, and then at 930°C for 2 min, and then pickling;

[0058] (2) using one-step cold rolling method to obtain a cold-rolled steel plate with a thickness of 0.17 mm;

[0059] (3) decarburizing annealing the cold-rolled steel plate at 800°C for 110 s;

[0060] (4) nitriding treatment at 800°C for 20 s, using a mixed gas of N2, H2 and NH3 for nitriding;

[0061] (5) using steel rollers with a diameter of 61 mm to extrude the upper and lower surfaces of the cold-rolled steel plate within a width range of 0-15 mm from the edges of the strip, with an extrusion pressure of 445 MPa;

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

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

[0064] (8) annealing the steel coil to perform a tension levelling annealing and a laser marking treatment, shearing, packaging and removing the small grains at the edge of the high magnetic induction oriented silicon steel to obtain a high magnetic induction oriented silicon steel, and the edge of the high magnetic induction oriented silicon steel is shown in FIG. 2. Figure 1 , Figure 1 The surface coating and the magnesium silicate layer are removed in the high magnetic induction oriented silicon steel of FIG. 2 to expose the base grains.

[0065] Comparative Example 1

[0066] The difference between the present comparative example and Example 1 is that:

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

[0068] The edge of the high magnetic induction oriented silicon steel is shown in FIG. 2. Figure 2 , Figure 2 The surface coating and the magnesium silicate layer are removed in the high magnetic induction oriented silicon steel of FIG. 2 to expose the base grains.

[0069] Example 2

[0070] The difference between the present example and Example 1 is that:

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

[0072] In step (5), the upper and lower surfaces of the cold-rolled steel sheet in a width range of 0-12 mm from the edge of the steel sheet are extruded by a steel roller with a diameter of 70 mm, and the extrusion pressure is 400 MPa.

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

[0074] Comparative Example 2

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

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

[0077] Example 3

[0078] The difference between the present example and Example 1 is that:

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

[0080] In step (5), the upper and lower surfaces of the cold-rolled steel sheet in a width range of 0-9 mm from the edge of the steel sheet are extruded by a steel roller with a diameter of 80 mm, and the extrusion pressure is 300 MPa.

[0081] In step (7), the grain size in the width range of 0 to 8 mm from the edge of the steel coil after high temperature annealing 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 process of extrusion 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 example and Example 1 is that:

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

[0088] In step (5), the upper and lower surfaces in the width range of 0 to 7 mm from the edge of the cold-rolled steel sheet are extruded using a steel roller with a diameter of 90 mm, and the extrusion pressure is 200 MPa.

[0089] In step (7), the grain size in the width range of 0 to 5 mm from the edge of the steel coil after high temperature annealing 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 process of extrusion 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 example and Example 1 is that:

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

[0096] In step (5), the upper and lower surfaces in the width range of 0 to 3 mm from the edge of the cold-rolled steel sheet are extruded using a steel roller with a diameter of 100 mm, and the extrusion pressure is 100 MPa.

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

[0098] Comparative Example 5

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

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

[0101] The cutting waste of the above embodiment n compared to the comparative example n is reduced by 120 kg or more, wherein n = 1-5; the edge of the steel is not prone to cracking during the stretch leveling annealing, and the product belt breaking condition is greatly reduced; the amplitude of the steel plate jumping is reduced during the laser marking treatment, the plate surface is more flat, the marking is more uniform, and the marking effect is improved; the edge fine grain zone is cut off during the final shearing and packaging stage, but the cutting width is significantly smaller than that of the conventional product, and the yield is increased by 0.24% or more.

[0102] The apparent defect statistics are first visually counted for the number and distribution of cracks, and then the non-contact scanning method or other measuring tools are used to measure the specific crack depth and width data. The apparent defect statistics of the above examples and comparative examples are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] Unless otherwise specifically indicated, all of the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods. The above specific examples further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included within the scope of protection of the present application.

Claims

1. A production method for reducing edge cracking in high-magnetic-induction grain-oriented silicon steel, characterized in that, Includes the following steps: S1. Hot-rolled steel coils are normalized and then cold-rolled to obtain cold-rolled steel sheets; S2. The cold-rolled steel sheet is decarburized and nitrided, then extruded, coated with magnesium oxide, and then annealed at high temperature to obtain annealed steel coil. The extrusion location is the upper and lower surfaces within a width range of 0~20mm from the edge of the steel coil; The extrusion pressure is 60~480 MPa; The diameter of the steel rollers on both sides of the strip used for extrusion is 50~100mm; S3. Annealed steel coils are subjected to stretching, leveling, annealing, and laser scoring to obtain high magnetic orientation silicon steel.

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

3. The production method for reducing edge cracks in high-magnetic-induction grain-oriented silicon steel as described in claim 1, characterized in that, The extrusion location is the upper and lower surfaces within a width range of 0~15mm from the edge of the steel plate; And / or, the pressure of the extrusion is 80~450 MPa.

4. The production method for reducing edge cracks in high-magnetic-induction grain-oriented silicon steel as described in claim 1, characterized in that, The normalization process includes: The heating temperature for the first stage of normalization is 1000~1120℃, and the holding time is 1~3 minutes; The heating temperature for the second stage of normalization is 900~950℃, and the holding time is 1~3 minutes; And / or, the normalization process may further include an acid washing process.

5. The production method for reducing edge cracks in high-magnetic-induction grain-oriented silicon steel as described in claim 1, characterized in that, The cold rolling method is a single-stage cold rolling method; And / or, the thickness of the cold-rolled steel sheet is 0.18~0.30mm.

6. The production method for reducing edge cracks in high-magnetic-induction grain-oriented silicon steel as described in claim 1, characterized in that, The decarburization annealing temperature is 800~900℃, and the decarburization annealing time is 100~200s; And / or, the decarburization annealing process further includes a nitriding operation.

7. The production method for reducing edge cracks in high-magnetic-induction grain-oriented silicon steel as described in claim 1, characterized in that, The nitriding temperature is 780~920℃; And / or, the nitriding time is 10~60s.

8. The production method for reducing edge cracks in high-magnetic-induction grain-oriented silicon steel as described in claim 1, characterized in that, The high-temperature annealing process includes a first stage of high-temperature annealing heating and a second stage of high-temperature annealing.

9. The production method for reducing edge cracks in high-magnetic-induction grain-oriented silicon steel as described in claim 8, characterized in that, The first stage of high-temperature annealing involves heating from room temperature to 550~750℃ and holding at that temperature for 20~50℃ / h for 20~40h in an atmosphere of N2 and H2, with H2 comprising 20~80% of the mixture. The second stage of high-temperature annealing: the temperature is raised to 1150~1250℃ and held for 20~40h, the heating rate is 5~20℃ / h, the heating atmosphere is a mixture of N2 and H2, and the holding atmosphere is pure hydrogen.

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

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