CN117821724A - High-temperature annealing process and manufacturing method for high-magnetic-induction oriented silicon steel and high-magnetic-induction oriented silicon steel - Google Patents
High-temperature annealing process and manufacturing method for high-magnetic-induction oriented silicon steel and high-magnetic-induction oriented silicon steel Download PDFInfo
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Abstract
The invention discloses a high-temperature annealing process for high-magnetic induction oriented silicon steel, which is characterized in that a steel coil is placed in an annealing furnace in a horizontal posture, and an inner sleeve is arranged at the core part of the steel coil so as to perform high-temperature annealing; wherein during the high temperature annealing: in the first stage, the steel coil enters an annealing furnace with the furnace temperature of 600-800 ℃ and is kept for 5-30 hours; in the second stage, the annealing furnace temperature is increased to 900-1000 ℃ at a heating rate of 5-30 ℃/h; in the third stage, the annealing furnace temperature is raised to 1150-1250 ℃ at a heating rate of more than 5 ℃/h; in the fourth stage, the steel coil is at least insulated for 15 hours at 1150-1250 ℃; wherein the atmosphere of high temperature annealing is dry atmosphere with dew point less than-10 ℃. Correspondingly, the invention also discloses a manufacturing method for the high-magnetic induction oriented silicon steel, which comprises the following steps: smelting and casting, slab heating, hot rolling, normalizing, pickling, cold rolling, decarburization annealing, nitriding treatment, coating an annealing separator and the high-temperature annealing process.
Description
Technical Field
The invention relates to a high-temperature annealing process of steel, in particular to a high-temperature annealing process of oriented silicon steel.
Background
As is well known, the current application of oriented silicon steel is very wide, and oriented silicon steel is mainly used as various transformer cores and is an important soft magnetic alloy indispensable in the power, electronics and military industries. The oriented silicon steel specifically consists of Goss texture crystal grains, wherein {110} crystal faces are parallel to a rolling plane, and easy magnetization direction <001> crystal directions are parallel to a rolling direction, so that the oriented silicon steel has very excellent magnetic performance when magnetized along the rolling direction.
In order to obtain strict Goss texture grains, inhibitors play an important role in the production of oriented silicon steel, which acts as follows: preventing the primary grains from growing normally and ensuring the Goss texture grains to grow abnormally during the secondary recrystallization.
In the process of preparing the oriented silicon steel, the production process of the oriented silicon steel is generally classified into a high temperature process, a medium temperature process and a low temperature process according to different slab heating temperatures. The high-temperature process needs to heat the slab to the maximum 1400 ℃, so that the slab is burnt, the energy consumption is high, the utilization rate of a heating furnace is low, the service life is short, the hot-rolled edge is severe, and the yield is low. The slab heating temperature of the low-temperature process is controlled between 1100 ℃ and 1250 ℃, and the means for preparing the oriented silicon steel by the low-temperature process is popularized by various large manufacturers in consideration of the advantages of manufacturing cost and yield.
In order to achieve the purposes of high efficiency, low power consumption, small volume and light weight of the transformer, the oriented silicon steel generally requires the product to have iron core loss (the iron loss guarantee value is generally P 17/50 ) Low magnetic induction (magnetic induction guarantee value is generally B 8 ) High performance, good punching performance, smooth and flat surface and good insulating film performance.
The good magnetic performance requires the oriented silicon steel to form an accurate Goss texture, so the oriented silicon steel has strict requirements on components, and the manufacturing process flow is long, so the factors influencing the performance and quality of the product are many. Taking low temperature process for manufacturing oriented silicon steel as an example, the manufacturing process generally comprises: smelting, secondary refining and alloying, continuous casting, slab heating, hot rolling, normalizing, pickling, cold rolling, decarburization annealing, nitriding of a steel plate, coating of an annealing isolating agent, high-temperature annealing, hot stretching and leveling annealing and coating of an insulating coating. In the low-temperature process, the adopted high-temperature annealing is a core flow in the production process of oriented silicon steel, secondary recrystallization can be carried out on the product in the high-temperature annealing process, purification annealing is carried out to remove S and N in steel, and meanwhile, secondary grains swallow and disperse residual primary grains, so that the Goss texture is more complete.
It should be noted that, in the high-temperature annealing step of the low-temperature process, the highest temperature adopted in the high-temperature annealing is generally about 1200 ℃, in order to avoid the collapse of the horizontal steel coil caused by softening at high temperature, the steel coil needs to be turned over after the decarburization annealing process is completed, and the high-temperature annealing is performed in the vertical coil direction, while the vertical coil annealing still has some unavoidable problems:
in the vertical coil annealing process, the temperature difference of different positions of the steel coil is larger in the high-temperature annealing temperature rising process, the temperature rising speed is the fastest at the position close to the outer ring of the upper end face, the heat conduction efficiency of the isolating agent with MgO as a main component is much lower than that of the steel plate, the temperature rising speed of the middle part of the steel coil is the slowest, and the temperature difference of the isolating agent and the steel plate can exceed 300 ℃. The temperature difference causes the evolution of the inner ring inhibitor and the outer ring inhibitor of the whole steel coil and the secondary recrystallization to be different, and finally causes the magnetic property of the steel coil to be different in the length and width ranges. In addition, due to the fact that the thermal expansion coefficients of the steel coil and the bottom plate are different, relative displacement exists between the steel coil and the bottom plate in the heating and cooling processes, and creep deformation of the steel coil caused by uneven dead weight of temperature can cause deformation of the strip steel edge of the contact area between the lower part of the annealed steel coil and the bottom plate, and the strip steel edge is generally called as an 'elephant foot', so that the yield of a final product is low. In addition, the residual stress of the inner ring of the steel coil before being fed into the furnace is larger, the inner convex defect is generated after the steel coil is released after high-temperature annealing, the production of the subsequent process is influenced, and the yield of products is influenced by the treatment of the inner convex defect.
Aiming at the technical problems existing in the vertical coil annealing, the production method of the high-temperature high-magnetic induction oriented silicon steel is also optimized by the technicians in the field:
for example: the Chinese patent literature with publication number of CN108004376A and publication date of 2018, 5 months and 8 days, named as a production method of low-temperature high-magnetic induction oriented silicon steel with uniform longitudinal magnetic property, discloses a production method of low-temperature high-magnetic induction oriented silicon steel with uniform longitudinal magnetic property, which is characterized in that when a steel coil is 50X (170-Alr) less than or equal to L less than or equal to 50X (200-Alr) from a strip tail in a decarburization annealing procedure, the process is adjusted and kept to the next strip head, so that the primary recrystallization grain sizes of an outer ring and an inner ring of the steel coil can be properly adjusted to cope with the deterioration effect of inhibitors caused by the temperature difference of the inner ring and the outer ring in the annealing temperature rising process, so that the secondary recrystallization temperature of the inner ring and the outer ring of the steel coil is basically the same, and finally the magnetic property is basically the same. However, in such a technical scheme, the difficulty of online process adjustment operation of the decarburization annealing unit at a relatively accurate position is great, and the accuracy of the adjustment parameters is difficult to grasp.
Also for example: the Chinese patent literature with publication number CN107858494A and publication date of 2018, 3 months and 30 days, named as "production method of high-temperature high-magnetic induction oriented silicon steel" discloses a production method of low-temperature high-magnetic induction oriented silicon steel, which is characterized in that P is measured on line through decarburization annealing procedure 13/50 To predict the secondary recrystallization starting temperature T of the steel coil TS And at T TS Preserving heat for at least 10 hours at the temperature to ensure the temperature of the whole steel coil to be uniform, and accelerating T in order to ensure the whole production efficiency not to be reduced TS Heating speed before and after heat preservation. The technical scheme is helpful for stabilizing the iron loss at the rear part of the steel coil, but the improvement degree is very limited.
For another example: chinese patent document with publication number CN103667874a, publication date 2014, 3 months and 26 days, entitled "production method of oriented silicon steel during high temperature annealing to shorten the time in a furnace", discloses a production method of oriented silicon steel during high temperature annealing to shorten the time in a furnace, which homogenizes the internal temperature of a steel coil by providing two steps at the low heat-preserving stage of high temperature annealing. However, the technical scheme does not disclose parameters such as temperature rising speed and the like, the problem of temperature difference inside the steel coil after a low heat preservation stage cannot be solved, and the performance of the finally obtained product is not excellent.
In addition, the inventors have found that, at high magnetic inductionIn the preparation process of the oriented silicon steel, in order to prevent strip steel from being bonded in the high-temperature annealing process, the traditional oriented silicon steel is coated with an annealing isolating agent which takes MgO as a main component before high-temperature annealing, and the MgO isolating agent and SiO in a surface oxide film are coated in the high-temperature annealing process 2 Chemically reacts to form Mg 2 SiO 4 A glass membrane bottom layer to promote desulfurization and denitrification reactions. However, because the magnesium silicate bottom layer has high hardness, the magnesium silicate bottom layer can cause poor punching performance of the oriented silicon steel; moreover, the rough interface of the underlayer and the matrix has an impeding effect on the movement of the magnetic domains, which is also disadvantageous for reducing the core loss.
Therefore, in order to improve the processing performance of the oriented silicon steel and further reduce the iron core loss, the non-bottom oriented silicon steel is developed, and the production method is roughly divided into: no underlayer is produced at the time of production or removed at a later stage.
For example: chinese patent document with publication No. CN102453793a, publication No. 2012, 5-16, entitled "annealing separator for mirror-oriented silicon steel production with excellent magnetic properties", discloses an annealing separator for mirror-oriented silicon steel production with excellent magnetic properties, which comprises the following components in percentage by weight: al (Al) 2 O 3 77-98% of powder, 1-8% of alkaline earth metal oxide powder, and 1-15% of alkali metal chloride or/and alkaline earth metal chloride. According to the annealing isolating agent in the technical scheme, the surface of the oriented silicon steel plate does not form a glass film bottom layer in the high-temperature annealing process, and meanwhile, the embedded oxide on the near surface of the substrate is removed by utilizing the corrosion reaction of the chloride, so that a product with smooth surface and stable magnetic performance is obtained.
For another example: the Chinese patent literature with publication number of CN101643881A and publication date of 2012, 2 and 10, named as "method for producing copper-containing oriented silicon Steel", discloses a method for producing copper-containing oriented silicon Steel, which strictly controls the thickness of oxide film after decarburization annealing, and the isolating agent adopts Al 2 O 3 、SiO 2 Or ZrO 2 Ceramic fines or a combination of both to not react with surface oxides during high temperature annealing to form a glass film.
The two technical schemes do not generate bottom layer during production; in some other embodiments, it is still necessary to prepare the glass film underlayer during production and remove the glass film underlayer at a later stage. The conventional method for removing the bottom layer of the glass film in the later stage is acid washing removal, which has high manufacturing cost and has great problems in aspects of medicament management, environmental pollution and the like, so that other methods for removing the bottom layer have appeared in recent years.
For example: chinese patent document with publication number of CN113211325A, publication day 2021, 8 and 6 discloses a method for preparing a non-bottom raw material of an oriented silicon steel thin strip by removing a bottom layer of a glass film in a physical sand blasting mode. Chinese patent document publication No. CN113215374a, publication No. 2021, 8 and 6 discloses a method for producing non-bottom oriented silicon steel by removing the bottom layer of glass film by laser scoring. The research shows that the non-bottom oriented silicon steel not only has excellent magnetic property and processing property, but also can be used as a base material for further preparing the extremely thin oriented silicon steel, thereby having great potential market demands and good development prospects.
However, because the magnesium silicate bottom layer is relatively hard in a high-temperature state, the bottomless product does not generate a bottom layer in a high-temperature annealing stage or the generated bottom layer is very thin for convenient removal, the deformation degree of the edge of the strip steel is more serious after the vertical coil high-temperature annealing is finished, edge cracks are easy to form, and the yield of the bottomless product is greatly influenced.
Therefore, in order to solve the problems in the manufacturing process of the high magnetic induction oriented silicon steel designed in the prior art, the invention provides a novel high-temperature annealing process for the high magnetic induction oriented silicon steel, and the high-temperature annealing process heats the steel coil in a horizontal form, so that the temperature uniformity in the steel coil can be improved, the problems of uneven color, uneven color and the like on the surface of the steel plate can be favorably solved, the magnetic performance in the width direction of the steel plate is more uniform, the defects of plate shapes caused by high temperature such as elephant feet and the like and gravity factors can be relieved, the problem of collapse of the horizontal steel coil can be solved, the problem of protrusion of the steel coil before and/or after high-temperature annealing is solved, the problem of transverse movement of the steel coil during uncoiling after high-temperature annealing is effectively solved, and the high-temperature annealing oriented silicon steel has wide application prospect.
Disclosure of Invention
The invention aims to provide a high-temperature annealing process for high-magnetic induction oriented silicon steel, which heats a steel coil in a horizontal form, can improve the temperature uniformity in the steel coil, is favorable for solving the problems of uneven oxidation color, uneven color and the like of the surface of a steel plate, ensures that the magnetic performance along the width direction of the steel plate is more uniform, can relieve some plate-shaped defects caused by high temperature such as elephant feet and the like and gravity factors, can solve the problem of coil collapse of a horizontal steel coil, also solves the problem of protrusion of the inner coil of the steel coil before and/or after high-temperature annealing, effectively solves the problem of transverse movement of the steel coil during uncoiling after high-temperature annealing, and has wide application prospect.
In order to achieve the above object, the present invention provides a high temperature annealing process for high magnetic induction oriented silicon steel, which places a steel coil in a horizontal posture in an annealing furnace, and sets an inner sleeve in a core of the steel coil to perform high temperature annealing; wherein during the high temperature annealing:
in the first stage, the steel coil enters an annealing furnace with the furnace temperature of 600-800 ℃ and is kept for 5-30 hours;
in the second stage, the annealing furnace temperature is raised to 900-1000 ℃ at a heating rate of 5-30 ℃/h;
In the third stage, the annealing furnace temperature is raised to 1150-1250 ℃ at a heating rate of more than 5 ℃/h;
in the fourth stage, the steel coil is at least insulated for 15 hours at 1150-1250 ℃;
wherein the atmosphere of high temperature annealing is dry atmosphere with dew point less than-10 ℃.
In the high-temperature annealing process for the high-magnetic induction oriented silicon steel, in order to prevent the horizontal steel coil from softening and collapsing at high temperature, the inventor sets and installs the high-temperature resistant steel inner sleeve on the core of the steel coil when coiling in the decarburization annealing process, the radius of the inner sleeve is not larger than that of the steel coil, in certain embodiments, the inner sleeve can be specifically controlled to be prepared by using the high-temperature resistant steel with the thickness of 5-30 mm, and the inner sleeve is not extruded and deformed due to the softening of the steel coil after the high-temperature annealing.
Because the heat conduction efficiency of the high magnetic induction oriented silicon steel strip is far higher than that of the annealing isolating agent, the steel coil is annealed in a horizontal coil, the steel coil can transfer heat through the strip steel at the two ends simultaneously, the two ends of the horizontal coil are exposed in inner cover gas, and the inner cover gas can also permeate into the steel coil from the two ends simultaneously through gaps in the isolating agent for heating, so that the overall heat conduction efficiency of the steel coil is obviously improved. Through comparison measurement, the whole temperature difference of the steel coil can be reduced to 1/4-1/2 of that of the traditional high-temperature annealing process by using the high-temperature annealing process designed by the invention under the same temperature rising speed. And the two ends of the steel coil are heated simultaneously, so that the problem of inconsistent transverse magnetic properties caused by asynchronous secondary recrystallization within the width range of the strip steel is solved.
In addition, H in the inner cover atmosphere during the high-temperature annealing of the horizontal steel coil 2 The two ends of the steel coil can be penetrated into the steel coil through gaps in the annealing isolating agent to be fully contacted with the surface of the strip steel, the speed of decomposing the inhibitor at the beginning of secondary recrystallization can be ensured, and the Goss crystal grains with accurate orientation can be fully utilized with H under the state of low inhibition force 2 The surface energy advantage of the contact brings about a driving force that rapidly grows and establishes the advantage.
In addition, in the high-temperature annealing process, the temperature range of 900-1150 ℃ is the temperature range of secondary recrystallization development, and when the temperature rising speed is less than 5 ℃/h, the production efficiency is affected, and the manufacturing cost of the product is improved.
By adopting the high-temperature annealing process designed by the invention, goss grains of the high-magnetic induction oriented silicon steel product prepared after the secondary recrystallization is finished are often particularly coarse and are usually more than 100mm, and the deviation angle is usually less than 3 degrees, so that the high-magnetic induction oriented silicon steel product with excellent magnetic induction can be obtained, and the final magnetic induction B of the high-magnetic induction oriented silicon steel product is obtained 8 > 1.96T. Although the vertical coil annealing has similar benefits in reducing the temperature rising speed at the secondary recrystallization development temperature, the Goss crystal grains grow to the inside of the steel coil because the temperature difference between the inside and outside of the vertical coil is overlarge and the inhibitor is decomposed slowly, so that the resistance of the Goss crystal grains to the growth of the inside of the steel coil is large, and the crystal grains grow Slow, and do not fully develop the dimensional advantage.
In addition, as the uncoated oriented silicon steel product does not generate a magnesium silicate bottom layer or the bottom layer is very thin in the high-temperature annealing process, the magnesium silicate bottom layer can prevent the decomposition of the inhibitor and the steel plate and H to a certain extent 2 Therefore, the method adopts a horizontal mode to carry out high-temperature annealing on the steel coil, and is more suitable for producing the oriented silicon steel without the bottom layer in the aspect of improving the magnetic performance of the product.
Correspondingly, when the high-temperature annealing process designed by the invention is actually adopted, water in the annealing isolating agent can be discharged through two ends of the steel coil, the water discharging efficiency is far higher than that of the traditional vertical high-temperature annealing method, and free water and combined water in the coating can be completely discharged through shorter low-temperature-keeping time. Therefore, the additional oxidation of the steel plate caused by water remained in the coating layer can not occur in the high-temperature annealing, and the defects of watermarks, oxidation colors and the like which are difficult to avoid in the conventional oriented silicon steel production process are overcome. In addition, the high-temperature annealing process can better control the surface oxide layer of the bottomless oriented silicon steel product, prevent the oxide layer from reacting with chemical substances in the coating due to the excessive thickness, and finally obtain excellent magnetic performance.
Because the high-temperature annealing process designed by the invention carries out high-temperature annealing on the oriented silicon steel after the inner sleeve is arranged on the core part in the horizontal steel coil, the strip steel cannot be pressed by the end part of the steel coil, and thus, the defects of elephant feet cannot be generated even if the steel plate is softened in a high-temperature environment.
In addition, as the inner ring of the steel coil has residual stress in the coiling process of the coating and annealing isolating agent, the residual stress is released after high-temperature annealing to generate inward convex defects, the production of the subsequent procedures is influenced, and the treatment of the inward convex defects is difficult and the yield of products is influenced. Meanwhile, the steel coil becomes soft and loose after high-temperature annealing, and transverse movement between steel coil layers frequently occurs in the production process of the later working procedure, so that the production needs to be slowed down and even shutdown is carried out. In order to reduce the transverse movement probability of the steel coil, the coiling tension is usually increased after the annealing isolating agent is coated or the film thickness of the isolating agent is thinned to enable the steel coil to be tighter, the coiling tension is increased to enable the inward bulge to be more serious, the drainage efficiency of the steel coil in the high-temperature annealing process is also affected, and the film thickness of the isolating agent is thinned to generate the bonding risk of the steel coil. However, when the high-temperature annealing process designed by the invention is used, the rigid inner sleeve can effectively solve the inward convex defect, and the efficiency of simultaneously draining the two end surfaces of the steel coil can also compensate the influence caused by the increase of coiling tension. Therefore, the high-temperature annealing is performed by using the technical scheme designed by the invention, and the coiling tension is properly increased in the coiling process of the steel coil on the premise of ensuring the annealing isolating agent with a certain thickness, so that the probability of transverse movement of the steel coil in the subsequent working procedure is reduced. However, it should be noted that too much coiling tension also affects the drainage efficiency of the horizontal steel coil during high-temperature annealing.
In the high-temperature annealing process for the high-magnetic induction oriented silicon steel, the steel coil is annealed at a high temperature in a horizontal mode, so that the overall heat transfer efficiency of the steel coil is greatly improved, and the moisture in the isolating agent can be discharged from two ends simultaneously, so that only a short time is needed in a low heat preservation stage of a high-temperature annealing process.
In the high temperature annealing process, the atmosphere of the first stage and the second stage of the high temperature annealing may preferably use pure N 2 Or N 2 /H 2 Mixture gas (N therein 2 The proportion is not less than 50 percent), which is to ensure that the inhibition force is not weakened due to the precipitation of N element in the heating process, and the condition of lower internal temperature of the steel coil still occurs when the heating speed is more than 30 ℃/h, so that when the secondary recrystallization of the outer part of the steel coil in the third stage is started, the temperature of the central part of the steel coil is lower and does not reach the secondary recrystallization temperature, namely, the atmosphere is switched, the inhibition force is weakened along with the precipitation of N, S and other elements, and the secondary recrystallization is imperfect; when the temperature rising speed is less than 5 ℃/h, the manufacturing efficiency is reduced, and non-Goss grains slowly grow up in the temperature rising process, so that the Goss grains are difficult to form advantages in secondary recrystallization, and the product performance is poor.
In addition, in the high-temperature annealing process designed by the invention, the third stage is the temperature range of secondary recrystallization development, and when the temperature rising speed is less than 5 ℃/h, the production efficiency is affected.
Further, in the present inventionIn the high temperature annealing process, the atmospheres of the first stage, the second stage, the third stage and the fourth stage are all N 2 And H 2 At least one of them.
Further, in the high temperature annealing process of the present invention, the atmosphere of the first stage and the second stage is pure N 2 Or N 2 /H 2 A mixed gas; the atmosphere of the third stage is N 2 /H 2 A mixed gas; the atmosphere of the fourth stage is pure H 2 。
Further, in the high temperature annealing process of the present invention, when the atmosphere of the first stage and the second stage is N 2 /H 2 In the case of a mixture, N is 2 Not less than 50% by volume; and/or N of the third stage 2 /H 2 H in the mixed gas 2 The volume ratio of (2) is not less than 50%.
Further, in the high-temperature annealing process, when the steel coil is placed in the annealing furnace in a horizontal posture, an arc-shaped lifting plate is adopted to lift the outer circumferential wall of the steel coil.
In the technical scheme of the invention, when the steel coil is placed in the annealing furnace in a horizontal posture, the arc-shaped lifting plate can be specifically adopted to lift the outer circumferential wall of the steel coil so as to replace the traditional hearth plate and supporting device steel.
In some embodiments, the lifting plate can be designed into an arc shape, the radius of the arc shape can be controlled to be larger than the maximum steel coil diameter/2, the width of the steel plate for preparing the lifting plate can be controlled to be larger than the maximum steel coil width, and the angle of the lifting plate can be controlled to be 15-45 degrees.
It should be noted that in the high temperature annealing process designed by the invention, 2-3 layers of backing plates coated with annealing isolating agents can be arranged between the lifting device and the steel coil, so that the deformation defect of the steel coil caused by different thermal expansion coefficients of the steel coil and the lifting device can be eliminated by sliding of the isolating agents in the backing plates in the high temperature annealing and temperature raising process.
Accordingly, another object of the present invention is to devise a new manufacturing method for high magnetic induction oriented silicon steel, which can effectively use the above-mentioned designed high temperature annealing process of the present invention, and can effectively prepare high magnetic induction oriented silicon steel with good magnetic properties.
In order to achieve the above object, the present invention provides a manufacturing method for high magnetic induction oriented silicon steel, comprising the steps of: smelting and casting, slab heating, hot rolling, normalizing, pickling, cold rolling, decarburization annealing, nitriding treatment, coating with an annealing separator, and high-temperature annealing process as described above in the present invention.
The manufacturing method for the high-magnetic-induction oriented silicon steel designed by the invention comprises the following specific steps: smelting and casting, slab heating, hot rolling, normalizing, pickling, cold rolling, decarburization annealing, nitriding treatment, coating an annealing separator and high-temperature annealing.
It should be noted that the bottomless oriented silicon steel produced by the invention can be further rolled at the user to obtain the extremely thin oriented silicon steel. Therefore, the non-bottom layer high magnetic induction oriented silicon steel formed after high-temperature annealing can be coated with an insulating coating for delivery to users, and can also be directly delivered to users or delivered to users after cleaning and slitting.
That is, in some embodiments, after the high temperature annealing, the high magnetic induction oriented silicon steel after the high temperature annealing may be further subjected to an insulating coating and a leveling annealing to apply the insulating coating after uncoiling and a hot stretching leveling annealing. In other embodiments, after the high-temperature annealing is completed, in order to facilitate the detection of the performance of the high-magnetic-induction oriented silicon steel, the performance detection may be performed after the cleaning spacer is unwound in a later process.
Further, in the production method according to the present invention, in the decarburization annealing step, the decarburization annealing atmosphere is controlled So as to control the oxygen content in the steel plate after decarburization annealing and nitriding treatment to be less than 500ppm, thereby obtaining the oriented silicon steel without the bottom layer in the high-temperature annealing step.
Further, in the production method according to the present invention, in the decarburization annealing step, the decarburization annealing atmosphere is controlledSo as to control the oxygen content in the steel plate after decarburization annealing and nitriding treatment to be more than or equal to 500ppm, and obtain the oriented silicon steel with the bottom layer in the high-temperature annealing step.
In the manufacturing method designed by the invention, the high-temperature annealing isolating agent with the conventional MgO as the main component can be specifically adopted to produce the conventional oriented silicon steel product. In this case, it is necessary to adjust the annealing atmosphereSo as to control the oxygen content in the steel plate after decarburization annealing and nitriding treatment to be more than or equal to 500ppm, and further removing magnesium oxide, coating an insulating coating and delivering to users after hot stretch annealing.
When producing non-underlayer oriented silicon steel, it is necessary to control the oxygen content in the steel sheet to be in the range of < 500ppm after the decarburization annealing and nitriding treatment are completed, because an excessively thick surface oxide layer of the strip steel affects the properties of the non-underlayer product and there is a risk of reacting with the annealing separator at high temperature.
Accordingly, when conventional oriented silicon steel is produced, it is necessary to control the oxygen content in the steel sheet to be in the range of 500ppm or more after the decarburization annealing and nitriding treatment are completed, because it is necessary that an oxide layer on the surface of a strip steel having a certain thickness reacts with MgO to form a magnesium silicate underlayer.
Further, in the production method of the present invention, in the step of applying the annealing separator, the annealing separator is applied so that the sum of film thicknesses of the annealing separator on the upper and lower surfaces of the strip steel is 5.0 to 16.0g/m 2 And/or the unit tension A of the strip steel coiling after the release agent is coated is controlled as follows: 0.8× [ 50+M/(0.35+T)]＜A＜1.4×[50+M/(0.35+T)]Wherein A represents the unit tension of strip steel coiling, and the unit parameter is N/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the T represents the thickness of the strip steel without film thickness, and the unit parameter of the thickness is mm; m represents a tapeThe unit parameter of the sum of film thickness of the annealing isolating agent on the upper surface and the lower surface of steel is g/m 2 。
Further, in the production method of the present invention, in the decarburization annealing step, the decarburization annealing temperature is 800 to 880 ℃ and the decarburization annealing time is 75 to 150 seconds.
Further, in the production method of the present invention, the nitrogen content in the steel sheet after nitriding treatment is 150 to 300ppm.
Further, in the manufacturing method according to the present invention, in the slab heating step, the heating temperature is 1100 to 1200 ℃.
Further, in the manufacturing method of the present invention, in the normalizing step, a two-stage normalizing process is adopted: the hot rolled plate is heated to 1050-1150 ℃, then cooled to 850-950 ℃ and kept for 10-60 s.
Further, in the manufacturing method of the present invention, the slab is rolled to a thickness of 2.0 to 3.0mm through a hot rolling step.
Further, in the manufacturing method of the present invention, the strip steel is rolled to a thickness of 0.18 to 0.35mm through a cold rolling step.
Correspondingly, the invention further aims to provide the high-magnetic induction oriented silicon steel which has very excellent quality, higher magnetic induction, B8 of which is more than 1.96T, typical secondary grain size of 100-300 mm and very wide application prospect.
In order to achieve the above object, the present invention provides a high magnetic induction oriented silicon steel, which is manufactured by the manufacturing method of the present invention, wherein the high magnetic induction oriented silicon steel contains Fe and unavoidable impurities, and the following chemical elements by mass percent:
C：0.03～0.08％，Si：2.5～3.8％，Mn：0.10～0.25％，S：0.005～0.015％，Als：0.015～0.035％，N：0.004～0.010％。
further, in the high magnetic induction oriented silicon steel, the mass percentage of each chemical element is as follows:
c:0.03 to 0.08 percent, si:2.5 to 3.8 percent, mn:0.10 to 0.25 percent, S: 0.005-0.015%, als:0.015 to 0.035 percent, N: 0.004-0.010%, and the balance of Fe and unavoidable impurities.
In the high-magnetic induction oriented silicon steel designed by the invention, the chemical element components are as follows:
c: in the high-magnetic induction oriented silicon steel designed by the invention, the C element can keep gamma phase when the silicon steel is normalized by a hot rolled plate, and the solid solubility of the N element in the gamma phase is far higher than that of the N element in the alpha phase. When the mass percentage of the C element in the steel is less than 0.03%, the gamma formed by the silicon steel during the normalizing of the hot rolled plate is too small; and when the mass percentage of the C element in the steel is more than 0.08%, the subsequent decarburization annealing is difficult to remove, which can cause the magnetic aging of the finished product. Based on the above, in the invention, the mass percentage of the C element is specifically controlled to be between 0.03 and 0.08 percent.
Si: in the high-magnetic-induction oriented silicon steel designed by the invention, si element can improve the resistivity of steel and reduce the iron loss. When the mass percentage of Si element in the steel is less than 2.5%, the eddy current loss of the oriented silicon steel cannot be effectively reduced; when the content of Si element in steel is more than 3.8% by mass, the brittleness of the steel sheet is increased, the rolling ability is deteriorated, and the magnetic induction of the finished product is reduced. Based on this, in the present invention, the mass percentage of Si element is controlled to be 2.5 to 3.8%.
Mn: in the high-magnetic induction oriented silicon steel designed by the invention, mn element can be matched with S element to form an important inhibitor MnS of the oriented silicon steel. When the mass percentage of Mn element in the steel is less than 0.10%, the formed MnS inhibitor is too little, which can lead to imperfect secondary recrystallization; when the mass percentage of Mn element in the steel is more than 0.25%, the formed MnS inhibitor is too coarse, and the effect of the inhibitor is weakened. Based on this, in order to exert the beneficial effect of the Mn element, in the present invention, the mass percentage content of the Mn element is controlled to be between 0.10 and 0.25%.
S: in the high-magnetic induction oriented silicon steel designed by the invention, S element can be matched with Mn element to form an important inhibitor MnS of the oriented silicon steel. When the mass percentage of S element in the steel is less than 0.005%, the formed MnS inhibitor is too little, so that secondary recrystallization is imperfect; when the mass percentage of S element in the steel is more than 0.015%, the high-temperature purification annealing desulfurization is difficult, and the magnetic aging of the finished product is initiated. Based on this, in order to exert the beneficial effect of the S element, in the present invention, the mass percentage of the S element is controlled to be between 0.005 and 0.015%.
Als: in the high-magnetic induction oriented silicon steel designed by the invention, als element can be matched with N element to form an important inhibitor AlN of the oriented silicon steel. When the mass percentage of Als element in the steel is less than 0.015%, the AlN inhibitor formed by the coordination of Als element is too little, which can lead to imperfect secondary recrystallization; when the mass percentage of Als element in the steel is more than 0.035%, the AlN inhibitor is too coarse and its inhibitor effect is weakened. Based on this, in order to exert the beneficial effect of the Als element, in the present invention, the mass percentage of the Als element is controlled to be between 0.015 and 0.035%.
N: in the high-magnetic induction oriented silicon steel designed by the invention, N element can be matched with Als element to form an important inhibitor AlN of the oriented silicon steel. When the mass percentage of N element in the steel is less than 0.004%, alN inhibitor formed by the combination of the N element and Als element is too little, and primary recrystallization is too coarse; and when the mass percentage of N element in the steel is more than 0.010%, the cold-rolled steel plate is easy to generate bubble defects. Therefore, in order to exert the beneficial effect of the N element, the mass percentage of the N element is controlled to be 0.004-0.010 percent in the invention.
Further, in the high magnetic induction oriented silicon steel, the magnetic induction B8 is more than 1.96T.
Further, in the high magnetic induction oriented silicon steel of the present invention, the typical secondary grain size is 100-300 mm.
Compared with the prior art, the high-temperature annealing process and the manufacturing method for the high-magnetic induction oriented silicon steel have the following beneficial effects that compared with the prior art:
the invention provides a novel high-temperature annealing process for high-magnetic induction oriented silicon steel and a corresponding manufacturing method thereof, wherein the manufacturing method is very suitable for manufacturing of non-bottom oriented silicon steel, and the product yield is high. The manufacturing method with the high-temperature annealing process designed by the invention can effectively obtain the high-magnetic induction oriented silicon steel, wherein the typical magnetic induction B8 of the high-magnetic induction oriented silicon steel product is more than 1.96T, and the typical secondary grain size is 100-300 mm.
(1) According to the high-temperature annealing process, the vertical steel coil is changed into the horizontal steel coil, so that the heat conduction mechanism in the steel coil can be changed, the Goss grain boundary is promoted to grow in the heat flow direction, the size advantage is obtained, and the accuracy of the Goss orientation of a finished product is improved.
(2) The high-temperature annealing process changes the vertical steel coil into the horizontal steel coil, and can promote the inside of the steel coil and H 2 The protective gases are fully contacted, so that H in the annealing isolating agent is quickened 2 O is removed, and the temperature uniformity in the steel coil is improved, so that the magnetic performance along the width direction of the steel plate is more uniform.
(3) The high-temperature annealing process changes a vertical steel coil into a horizontal steel coil through reasonable design, and can relieve some plate-shaped defects caused by high temperature such as elephant feet and the like and gravity factors.
(4) The high-temperature annealing process changes the vertical steel coil into the horizontal steel coil, thereby accelerating H in the annealing isolating agent 2 O is removed, the temperature uniformity in the steel coil is improved, and the problems of oxidation color, uneven color and the like on the surface of the steel plate are solved.
(5) The high-temperature annealing process designed by the invention is characterized in that an inner sleeve is additionally arranged during design, so that the problem of collapse of the horizontal steel coil is solved, and the problem of protrusion of the inner coil before and/or after high-temperature annealing of the steel coil is also solved. Compared with the original scheme without an inner sleeve, the scheme with the inner sleeve can further increase the coiling tension of the steel coil before high-temperature annealing, so that the problem of transverse movement of the steel coil when the coil is uncoiled after high-temperature annealing can be solved.
Drawings
Fig. 1 schematically shows a structural diagram of a heating mode of vertical high-temperature annealing in the process of preparing oriented silicon steel according to the conventional technology.
Fig. 2 schematically shows a distribution diagram of the internal temperature of a steel coil during a temperature rising stage of vertical coil high temperature annealing in the conventional art.
Detailed Description
The high temperature annealing process, the manufacturing method and the high magnetic induction oriented silicon steel for the high magnetic induction oriented silicon steel according to the present invention will be further explained and illustrated with reference to the accompanying drawings and specific examples, however, the explanation and illustration do not constitute undue limitations on the technical scheme of the present invention.
At present, when the oriented silicon steel is prepared by adopting the traditional technology, the high-temperature annealing furnace of the oriented silicon steel is mainly divided into a bell-type furnace, an annular furnace and a tunnel furnace, and is characterized in that a heating device (a burner or electric heating) is arranged on the inner wall of a hearth to heat the steel coil as far as possible, then the vertical steel coil is placed on a furnace chassis with a supporting structure, a metal inner cover is buckled on the whole, and then the steel coil enters the hearth to be heated, and sealing sand is buried at the root of the metal inner cover to isolate gas in the hearth of the annealing furnace from gas in the inner cover, as shown in figure 1.
Fig. 1 schematically shows a structural diagram of a heating mode of vertical high-temperature annealing in the process of preparing oriented silicon steel according to the conventional technology.
As shown in fig. 1, when the oriented silicon steel is annealed and heated at high temperature in fig. 1, the oriented silicon steel is specifically provided with a furnace wall 1, a burner 2, an inner cover 3, a steel coil 4, a bottom plate 5, a supporting device 6 and sealing sand 7. Wherein, a plurality of burners 2 are arranged on the inner wall of the furnace wall 1 for heating; the steel coil 4 is arranged on the bottom plate 5 in a vertical mode through the supporting device 6, and the whole steel coil can be heated in the hearth after being buckled with the inner cover 3; and, seal sand 7 is buried at the root of the inner cover 3 for isolating the gas in the hearth of the annealing furnace from the gas in the inner cover.
The heating sequence of the traditional vertical high-temperature annealing heating method is as follows: heating by a heating device, heating gas in a hearth, heating a metal inner cover, heating gas in the inner cover, directly heating the upper end and the inner and outer rings of the steel coil by the gas of the inner cover, and heating the steel coil by the chassis after the gas heats the chassis at the lower part of the steel coil. The temperature field in the coil of steel during the temperature rise phase of this conventional vertical coil high temperature anneal can be further referred to below in fig. 2.
Fig. 2 schematically shows a distribution diagram of the internal temperature of a steel coil during a temperature rising stage of vertical coil high temperature annealing in the conventional art.
As shown in fig. 2, the supporting device 6 is correspondingly connected with the bottom plate 5, and the bottom plate 5 is provided with a vertical steel coil.
In the high-temperature annealing heating mode, annealing isolating agents are required to be coated between layers of the steel coil before high-temperature annealing, the heat conduction efficiency of the annealing isolating agents is often far lower than that of the steel coil, and inner cover gas can permeate into the steel coil from the upper end of the steel coil through the annealing isolating agents to heat the steel coil, so that the fastest heating direction of the whole steel coil is only that the upper end face of the steel coil is downwards heated, and the upward heat transfer of the lower end of the steel coil is greatly reduced due to the influence of the chassis and the supporting device of the chassis. This makes the temperature of the middle lower position of the whole steel coil lowest (E is the lowest temperature position shown in fig. 2) and the temperature difference between the upper temperature position (F is the highest temperature position shown in fig. 2) can exceed 300 ℃ at maximum. The temperature difference can cause the asynchronism of the upper end and the lower end of the steel coil due to secondary recrystallization, and the magnetic property transverse uniformity of the finally prepared oriented silicon steel strip steel is poor.
In addition, when the high-temperature annealing reaches the secondary recrystallization temperature, H in the high-temperature annealing atmosphere 2 Tends to have lower surface energies than {100} and {110} grains, making the driving force for Goss grain growth stronger. Steel plate in middle of vertical coiled steel coil and H in protective atmosphere 2 Insufficient contact, weak driving force for Goss grain growth, and failure to contact H 2 The adequate contact makes the coarsening and decomposing speed of the inhibitor slower, so that the inhibiting force is still kept stronger when the secondary recrystallization in the middle of the steel coil begins. Therefore, the Goss crystal grains with accurate orientation in the middle of the steel coil can not fully utilize the advantages of the surface energy to grow up and establish advantages, the crystal grains with larger deviation angle with the Goss crystal grains can also grow up abnormally at the same time, and the Goss crystal grains after secondary recrystallization have small size and are usually < ">
50mm and deviate fromThe angle is larger, the magnetic induction of the finally prepared oriented silicon steel product is lower, and the magnetic induction B thereof 8 Typically not exceeding 1.94T.
In addition, in such vertical high temperature annealing process, both the conventional oriented silicon steel and the non-bottom oriented silicon steel require draining water (including free water and combined water) in the annealing separator before the annealing separator reacts with the strip steel. For the traditional oriented silicon steel, the water in the annealing isolating agent is not removed cleanly, so that the strip steel is over-oxidized, the bottom oxidation color and watermark defects occur, and the magnetic property is poor. For non-bottom layer oriented silicon steel products, the oxide layer on the surface of the strip steel after decarburization annealing is usually required to be strictly controlled so as to ensure that no bottom layer is formed at high temperature or is easy to remove later, and the non-discharged water in the oriented silicon steel isolating agent reacts with the strip steel at high temperature to damage the strictly controlled oxide layer structure. The lower end of the steel coil in the vertical high-temperature annealing mode is blocked by the chassis, and water in the annealing isolating agent can only be discharged through the upper end of the steel coil. If the chassis is arranged to be a porous structure which is easy to drain, not only the mechanical property of the steel coil at high temperature cannot be ensured, but also the edge deformation of the softened lower end of the steel coil at high temperature is more serious. Therefore, considering the temperature difference inside the steel coil, the traditional high-temperature annealing generally sets a long-time heat preservation at 600-800 ℃ and generally over 20 hours to ensure the water discharge effect in the isolating agent, and the production efficiency of the oriented silicon steel is affected to a certain extent.
In summary, in order to solve the defects of the vertical high-temperature annealing in the conventional technical scheme, the inventor designs and invents a method for horizontal coil high-temperature annealing.
According to the horizontal high-temperature annealing process for the high-magnetic-induction oriented silicon steel, a steel coil is placed in an annealing furnace in a horizontal posture, and an inner sleeve is arranged at the core part of the steel coil so as to perform high-temperature annealing; wherein, in the high temperature annealing process:
in the first stage, the steel coil enters an annealing furnace with the furnace temperature of 600-800 ℃ and is kept for 5-30 hours;
in the second stage, the annealing furnace temperature is raised to 900-1000 ℃ at a heating rate of 5-30 ℃/h;
in the third stage, the annealing furnace temperature is raised to 1150-1250 ℃ at a heating rate of more than 5 ℃/h;
in the fourth stage, the steel coil is at least insulated for 15 hours at 1150-1250 ℃;
wherein the atmosphere of high temperature annealing is dry atmosphere with dew point less than-10 ℃.
When the steel coil is placed in the annealing furnace in a horizontal posture, an arc-shaped lifting plate can be adopted to lift the outer circumferential wall of the steel coil; in the high-temperature annealing process, the atmosphere of the first stage and the second stage can be specifically selected as pure N 2 Or N 2 /H 2 A mixed gas; the atmosphere in the third stage can be specifically selected as N 2 /H 2 A mixed gas; the atmosphere in the fourth stage is pure H 2
It should be noted that in the high temperature annealing process, when the atmosphere of the first stage and the second stage is N 2 /H 2 When mixed gas is used, N 2 Not less than 50% by volume; and at the same time it can also control N of the third stage 2 /H 2 H in the mixed gas 2 The volume ratio of (2) is not less than 50%.
Correspondingly, the horizontal high-temperature annealing process designed by the invention can be used for effectively preparing the high-magnetic induction oriented silicon steel by being matched with other manufacturing processes, and the manufacturing method of the high-magnetic induction oriented silicon steel can comprise the following process steps:
(1) Smelting and casting.
(2) And (3) heating a plate blank: the heating temperature is controlled to be 1100-1200 ℃.
(3) And (3) hot rolling: and hot rolling the slab to a thickness of 2.0-3.0 mm.
(4) Normalizing: and (3) adopting two-stage normalizing treatment, heating the hot rolled plate to 1050-1150 ℃, cooling to 850-950 ℃ and preserving heat for 10-60 s.
(5) And (5) acid washing.
(6) Cold rolling: the cold rolling step rolls the strip steel to a thickness of 0.18-0.35 mm.
(7) Decarburization annealing: in the decarburization annealing step, P of the decarburization annealing atmosphere is controlled H2O /P H2 The oxygen content in the steel plate after decarburization annealing and nitriding treatment is controlled to be less than 500ppm, so that the oriented silicon steel without the bottom layer can be obtained; the oxygen content in the steel plate after decarburization annealing and nitriding treatment is controlled to be more than or equal to 500ppm, so that oriented silicon steel with a bottom layer can be obtained; wherein the decarburization annealing temperature can be specifically controlled between 800 and 880 ℃, and the decarburization annealing time can be controlled between 75 and 150 seconds.
(8) Nitriding: after nitriding treatment, the nitrogen content in the steel plate is 150-300 ppm.
(9) And (3) coating an annealing isolating agent: coating annealing separator to make the sum of film thickness of annealing separator on upper and lower surfaces of strip steel be 5.0-16.0 g/m 2 And/or the unit tension A of the strip steel coiling after the release agent is coated is controlled as follows: 0.8× [ 50+M/(0.35+T)]＜A＜1.4×[50+M/(0.35+T)]Wherein A represents the unit tension of strip steel coiling, and the unit parameter is N/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the T represents the thickness of the strip steel without film thickness, and the unit parameter of the thickness is mm; m represents the film thickness of the annealing separator, and the unit parameter is g/M 2 。
(10) And (3) a high-temperature annealing process: the high-temperature annealing process designed by the invention is adopted to carry out high-temperature annealing treatment so as to correspondingly obtain the high-magnetic induction oriented silicon steel.
In the manufacturing process according to the present invention, the annealing separator may be specifically selected from non-hydrated Al during the process of applying the annealing separator in step (9) 2 O 3 High temperature annealing isolating agent with low activity MgO or conventional MgO as main component.
The technical scheme of the scheme is further described by adopting specific embodiment data, and the beneficial effects brought by the high-temperature annealing process designed by the invention are proved:
table 1 shows the composition ratios of the chemical elements used for the oriented silicon steel sheets of examples 1 to 25 and comparative examples 1 to 20.
Table 1 (wt.%), balance Fe and other unavoidable impurity elements
Examples 1 to 6 and comparative examples 1 to 6
In the present invention, the high magnetic induction oriented silicon steel sheets of examples 1 to 6 and comparative examples 1 to 6 were each produced by the following steps:
(1) Smelting and casting were performed according to the chemical compositions shown in the above table 1 to obtain cast slabs corresponding to each example and comparative example.
(2) And (3) heating a plate blank: the heating temperature of the plate blank is controlled to be 1180 ℃.
(3) And (3) hot rolling: the slab was hot rolled to obtain a hot rolled plate having a thickness of 2.8 mm.
(4) Normalizing: the hot rolled plate was heated to 1080 ℃, then cooled to 920 ℃ and incubated for 15s.
(5) Acid washing: and (5) carrying out acid washing treatment on the plate.
(6) Cold rolling: cold rolling is carried out, and a cold-rolled sheet with the finished thickness of 0.25mm is obtained after cold rolling.
(7) Decarburization annealing and nitriding treatment: the decarburization annealing temperature was controlled to 810 c and the decarburization annealing time was controlled to 120s, and the oxygen content in the steel sheet after the decarburization annealing and nitriding treatment was controlled depending on whether or not it was an underlying product, as shown in table 2, with the nitrogen content being controlled to be between 250 and 300 ppm.
(8) Coating an annealing isolating agent and coiling the strip steel: the main components of the annealing isolating agent are shown in table 2, and the sum M of the film thicknesses of the annealing isolating agent on the upper surface and the lower surface of the strip steel is controlled to be 11-13 g/M 2 Between the two, the unit tension A of the strip steel coiling is controlled to be 80N/mm 2 。
(9) High-temperature annealing: the annealing form of the steel coil is shown in table 2, the introduced atmosphere of high-temperature annealing is dry atmosphere with dew point less than-10 ℃, and in the first stage, the steel coil enters an annealing furnace with furnace temperature of 600 ℃ and is kept for 25 hours; in the second stage, the furnace temperature is increased to 900 ℃ at a heating rate of 30 ℃/h; in the third stage, the furnace temperature is increased to 1180 ℃ at 15 ℃/h; in the fourth stage, the incubation was carried out at 1180deg.C for 18h. And the atmosphere of the first stage and the second stage is pure N2; the atmosphere in the third stage was switched to 30% n2+65% h 2 A mixed gas; atmosphere switching in the fourth stage to pure H 2 Subsequently switching atmosphere coolingTo the tapping temperature.
(10) Insulating coating and leveling annealing: and (3) after uncoiling, coating an insulating coating, and performing hot stretching, leveling and annealing to obtain the corresponding high-magnetic-induction oriented silicon steel.
In the invention, the chemical element components and the related processes of the high magnetic induction oriented silicon steel plates in the embodiments 1 to 6 all meet the design requirements of the invention; while the chemical element components of the high magnetic induction oriented silicon steel sheets of comparative examples 1 to 6 satisfy the design requirements of the present invention, the manufacturing process adopted by the same had contents that did not satisfy the requirements of the present invention.
Table 2 shows specific processes of the main components of the release agent, the oxygen content after decarburization annealing and nitriding treatment, and the form of high-temperature annealing used in the above processes for the high-magnetic-induction oriented silicon steel sheets of examples 1 to 6 and comparative examples 1 to 6.
Table 2.
Accordingly, regarding the high magnetic induction oriented silicon steel sheets of the prepared final products examples 1 to 6 and comparative examples 1 to 6, the degree of defects of the elephant foot, the degree of inward convexity and the degree of oxidation/watermarking of the underlying layer were judged by means of manual observation and recording, and the magnetic induction B8 of the high magnetic induction oriented silicon steel sheets of each example and comparative example was tested by using the method of measuring the magnetic properties of electrical steel sheets (tapes) with Epstein square rings by GB/T3655-2008, and the results of the related tests are listed in the following Table 3.
Table 3 shows the results of the magnetic induction performance test analysis of the quality of the high magnetic induction oriented silicon steel sheets of examples 1 to 6 and comparative examples 1 to 6.
Table 3.
As can be seen from the above Table 3, compared with comparative examples 1 to 3, the high magnetic induction oriented silicon steel sheets of examples 1 to 6 were produced by horizontal coil high temperature annealing, which solved the defects of elephant feet, inward protrusions and watermarks, and the magnetic induction of the products was excellent, and the magnetic induction advantage of the non-bottom oriented silicon steel products obtained in examples in which the oxygen content in the steel sheets after decarburization annealing and nitriding treatment was less than 500ppm was more remarkable than that of the conventional oriented silicon steel.
Comparative examples 4 to 5 use non-hydrated Al 2 O 3 And the low-activity MgO is used for producing a bottomless product, and the performance of the bottomless product can be influenced by the excessively high oxygen content in the steel plate after decarburization annealing and nitriding treatment; comparative example 6 was produced with the conventional MgO, and the steel sheet after decarburization annealing and nitriding treatment had too low oxygen content, which resulted in poor defects of the underlayer, and affected the magnetic induction of the product to some extent, but not to a great extent.
Examples 7 to 12 and comparative examples 7 to 10
In the present invention, the high magnetic induction oriented silicon steel sheets of examples 7 to 12 and comparative examples 7 to 10 were each produced by the following steps:
(1) Smelting and casting were performed according to the chemical compositions shown in the above table 1 to obtain cast slabs corresponding to each example and comparative example.
(2) And (3) heating a plate blank: the heating temperature of the slab is controlled to be 1100 ℃.
(3) And (3) hot rolling: the slab was hot rolled to obtain a hot rolled plate having a thickness of 2.2 mm.
(4) Normalizing: the hot rolled plate was heated to 1150 c, then cooled to 860 c, and kept at the temperature for 40s.
(5) Acid washing: and (5) carrying out acid washing treatment on the plate.
(6) Cold rolling: cold rolling to obtain cold-rolled sheet with thickness of 0.20 mm.
(7) Decarburization annealing and nitriding treatment: the decarburization annealing temperature is controlled to 850 ℃, the decarburization annealing time is controlled to 75 seconds, the oxygen content in the steel plate after the decarburization annealing and nitriding treatment is controlled to be 600-700 ppm, and the nitrogen content is controlled to be 150-200 ppm.
(8) Coating an annealing isolating agent and coiling the strip steel: coating an annealing isolating agent with conventional MgO as a main component, and controlling the annealing isolation of the upper surface and the lower surface of the strip steelThe sum of the film thickness of the release agent is 14-16 g/m 2 Between the two, the unit tension A of the strip steel coiling is controlled to be 90N/mm 2 。
(9) High-temperature annealing: the annealing form of the steel coil is shown in table 4, and the introduced atmosphere of high-temperature annealing is dry atmosphere with dew point of < -10 ℃; in the first stage, the steel coil enters an annealing furnace with the furnace temperature of 680 ℃ and is insulated, and the insulation time is shown in table 4; in the second stage, the annealing furnace temperature is increased to 930 ℃ at a heating rate of 5 ℃/h; in the third stage, the annealing furnace temperature is increased to 1220 ℃ at 20 ℃/h; in the fourth stage, the incubation was carried out at 1220℃for 25h. Correspondingly, the atmosphere of the first stage and the second stage is 50% N 2 +50％H 2 A mixed gas; third stage, atmosphere is switched to 20% N 2 +80％H 2 A mixed gas; fourth stage, atmosphere is switched to pure H 2 The method comprises the steps of carrying out a first treatment on the surface of the The atmosphere is then switched to cool to tapping temperature.
(10) Insulating coating and leveling annealing: and (5) after uncoiling, coating an insulating coating, and performing hot stretching, leveling and annealing to obtain the high-magnetic induction oriented silicon steel.
In the invention, the chemical element components and the related processes of the high magnetic induction oriented silicon steel plates of the embodiments 7 to 12 all meet the design requirements of the invention; while the chemical element components of the high magnetic induction oriented silicon steel sheets of comparative examples 7 to 10 satisfy the design requirements of the present invention, the manufacturing process adopted therein does not satisfy the requirements of the present invention.
Table 4 shows specific processes of the high temperature annealed forms and the low holding times employed in the above processes for the high magnetic induction oriented silicon steel sheets of examples 7 to 12 and comparative examples 7 to 10.
Table 4.
Accordingly, regarding the prepared high magnetic induction oriented silicon steel sheets of the final examples 7 to 12 and comparative examples 7 to 10, the degree of oxidation/watermarking of the underlayer of the high magnetic induction oriented silicon steel sheets of each example and comparative example was judged by means of manual observation recording, and the magnetic induction B8 of the high magnetic induction oriented silicon steel sheets of each example and comparative example was tested by means of epstein square ring measurement of the magnetic properties of electrical steel sheets (tapes) using GB/T3655-2008, and the results of the related tests are listed in table 5 below.
Table 5 shows the quality and magnetic induction performance test analysis results of the high magnetic induction oriented silicon steel sheets of examples 7 to 12 and comparative examples 7 to 10.
Table 5.
As can be seen from the above Table 5, compared with comparative examples 7-10, the high magnetic induction oriented silicon steel sheets of examples 7-12 were produced by horizontal coil high temperature annealing in the production process, and the degree of oxidation/watermarking and magnetic induction B8 of the bottom layer of the finished oriented silicon steel product were not significantly changed after the heat preservation time of the first stage was reduced. And in comparative examples 7-10 adopting the vertical coil high-temperature heating mode, after the heat preservation time in the first stage is lower than 20 hours, the oxidation color/watermark degree and the magnetic induction B8 performance of the bottom layer of the finished oriented silicon steel product are obviously deteriorated.
Examples 13 to 15 and comparative examples 11 to 14
In the present invention, the high magnetic induction oriented silicon steel sheets of examples 13 to 15 and comparative examples 11 to 14 were each produced by the following steps:
(1) Smelting and casting were performed according to the chemical compositions shown in the above table 1 to obtain cast slabs corresponding to each example and comparative example.
(2) And (3) heating a plate blank: the heating temperature of the plate blank is controlled to be 1200 ℃.
(3) And (3) hot rolling: the slab was hot rolled to obtain a hot rolled plate having a thickness of 2.5 mm.
(4) Normalizing: the hot rolled plate was heated to 1110 ℃, then cooled to 940 ℃ and kept at the temperature for 50s.
(5) Acid washing: and (5) carrying out acid washing treatment on the plate.
(6) Cold rolling: cold rolling to obtain cold-rolled sheet with thickness of 0.30 mm.
(7) Decarburization annealing and nitriding treatment: the decarburization annealing temperature is controlled to 880 ℃, the decarburization annealing time is controlled to 100s, the oxygen content in the steel plate after the decarburization annealing and nitriding treatment is controlled to be 200-300 ppm, and the nitrogen content is controlled to be 200-250 ppm.
(8) Coating an annealing isolating agent and coiling the strip steel: coated with non-hydrating Al 2 O 3 The annealing isolating agent is used as the main component, and the sum of the film thickness of the annealing isolating agent on the upper surface and the lower surface of the strip steel is controlled to be 9-11 g/m 2 Controlling the coiling unit tension of the strip steel to be 85N/mm 2 。
(9) High-temperature annealing: carrying out high-temperature annealing by using a horizontal coil, wherein the introduced atmosphere of the high-temperature annealing is a dry atmosphere with a dew point of < -10 ℃; in the first stage, the steel coil enters an annealing furnace with the furnace temperature of 750 ℃ and is kept for 10 hours; in the second stage, the temperature rising speed is shown in Table 6, and the temperature rises to 980 ℃; in the third stage, the temperature rising speed is 10 ℃/h and rises to 1250 ℃; and in the fourth stage, the temperature is kept at 1250 ℃ for 22h. Correspondingly, the atmosphere of the first stage and the second stage is 75% N 2 +25％H 2 A mixed gas; third stage, atmosphere is switched to 10% N 2 +50％H 2 A mixed gas; a fourth stage, wherein the atmosphere is switched to pure H2; the atmosphere is then switched to cool to tapping temperature.
(10) And (5) cleaning the release agent to obtain the corresponding high-magnetic-induction oriented silicon steel plate.
In the invention, the chemical element components and the related processes of the high magnetic induction oriented silicon steel plates in the embodiments 13 to 15 all meet the design requirements of the invention; while the chemical element components of the high magnetic induction oriented silicon steel sheets of comparative examples 11 to 14 satisfy the design requirements of the present invention, the manufacturing process adopted therein had contents that did not satisfy the requirements of the present invention.
Table 6 shows specific processes of the high magnetic induction oriented silicon steel sheets of examples 13 to 15 and comparative examples 11 to 14 at the heating rate of the third stage of the high temperature annealing in the above-mentioned processes.
Table 6.
Accordingly, for the prepared high magnetic induction oriented silicon steel sheets of the final examples 13 to 15 and comparative examples 11 to 14, the magnetic induction B8 of the high magnetic induction oriented silicon steel sheets of each example and comparative example was tested by the method of measuring the magnetic properties of the electrical steel sheet (tape) with epstein square coil using GB/T3655-2008, and the results of the related tests are listed in the following table 7.
Table 7 shows the results of magnetic induction performance test analysis of the high magnetic induction oriented silicon steel sheets of examples 13 to 15 and comparative examples 11 to 14.
Table 7.
As can be seen from Table 7, the high magnetic induction oriented silicon steel sheets of examples 13 to 15 were excellent in magnetic induction performance in the final oriented silicon steel products by using a heating rate of 5 to 30 ℃/h in the second stage of high temperature annealing, as compared with comparative examples 11 to 14. In comparative examples 11 to 14, the magnetic induction performance of the oriented silicon steel product tends to be deteriorated after the temperature rising rate in the second stage exceeds 5 to 30 ℃/h designed by the invention.
Examples 16 to 25 and comparative examples 15 to 20
In the present invention, the high magnetic induction oriented silicon steel sheets of examples 16 to 25 and comparative examples 15 to 20 were each produced by the following steps:
(1) Smelting and casting were performed according to the chemical compositions shown in the above table 1 to obtain cast slabs corresponding to each example and comparative example.
(2) And (3) heating a plate blank: the heating temperature of the plate blank is controlled to be 1160 ℃.
(3) And (3) hot rolling: the slab was hot rolled to obtain a hot rolled plate having a thickness of 3.0 mm.
(4) Normalizing: the hot rolled plate was heated to 1050 ℃, then cooled to 900 ℃ and kept at the temperature for 25s.
(5) Acid washing: and (5) carrying out acid washing treatment on the plate.
(6) Cold rolling: cold rolling to obtain cold-rolled sheet with thickness of 0.35 mm.
(7) Decarburization annealing and nitriding treatment: the decarburization annealing temperature is controlled to 830 ℃, the decarburization annealing time is controlled to 150s, the oxygen content in the steel plate after the decarburization annealing and nitriding treatment is controlled to be 180-280 ppm, and the nitrogen content is controlled to be 180-230 ppm.
(8) Coating an annealing isolating agent and coiling the strip steel: the annealing separator containing MgO having low activity as a main component was coated, and the film thickness control and the strip coiling unit tension were as shown in Table 8 below.
(9) High-temperature annealing: carrying out high-temperature annealing by using a horizontal coil, wherein the introduced atmosphere of the high-temperature annealing is a dry atmosphere with a dew point of < -10 ℃; in the first stage, the steel coil enters an annealing furnace with the furnace temperature of 800 ℃ and is kept for 15 hours; in the second stage, the annealing furnace temperature is increased to 1000 ℃ at a heating rate of 20 ℃/h; in the third stage, the annealing furnace temperature is increased to 1150 ℃ at a speed of 5 ℃/h; and a fourth stage, wherein the temperature is maintained at 1150 ℃ for 15 hours. Correspondingly, the atmosphere of the first stage and the second stage is 85% N 2 +15％H 2 A mixed gas; third stage, atmosphere is switched to 10% N 2 +90％H 2 The method comprises the steps of carrying out a first treatment on the surface of the Fourth stage, atmosphere is switched to pure H 2 The method comprises the steps of carrying out a first treatment on the surface of the The atmosphere is then switched to cool to tapping temperature.
(10) And (3) after the separating agent is uncoiled and cleaned in the later working procedure, the corresponding high magnetic induction oriented silicon steel plate can be obtained.
In the invention, the chemical element components and the related processes of the high magnetic induction oriented silicon steel plates of the embodiments 16 to 25 all meet the design requirements of the invention; while the chemical element components of the high magnetic induction oriented silicon steel sheets of comparative examples 15 to 20 satisfy the design requirements of the present invention, the manufacturing process adopted therein does not satisfy the requirements of the present invention.
Table 8 shows the thickness of the release agent, the coiling tension of the strip and the post-process production conditions in the above-mentioned processes for the high magnetic induction oriented silicon steel sheets of examples 16 to 25 and comparative examples 15 to 20.
Table 8.
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Note that: in the present invention, 0.8× [ 50+M/(0.35+T)]＜A＜1.4×[50+M/(0.35+T)]Wherein A represents the unit tension of strip steel coiling, and the unit parameter is N/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the T represents the thickness of the strip steel without film thickness, and the unit parameter of the thickness is mm; m represents the sum of the film thickness of the upper surface annealing isolating agent and the lower surface annealing isolating agent, and the unit parameter is g/M 2 。
Accordingly, for the prepared high magnetic induction oriented silicon steel sheets of the final examples 16 to 25 and comparative examples 15 to 20, the magnetic induction B8 of the high magnetic induction oriented silicon steel sheets of each example and comparative example was tested by using the method of measuring magnetic properties of electric steel sheets (tapes) with epstein square coil in GB/T3655 to 2008, and the results of the related tests are listed in the following table 9.
Table 9 shows the magnetic induction performance test analysis results of the high magnetic induction oriented silicon steel sheets of examples 16 to 25 and comparative examples 15 to 20.
Table 9.
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As can be seen from Table 9, the high magnetic induction oriented silicon steel sheets of examples 16 to 25 used an appropriate strip coiling tension A in a suitable annealing separator film thickness range, compared with comparative examples 15 to 16, and the subsequent process production was substantially normal.
The strip steel coiling tension A adopted in the comparative examples 15-16 is too low, and the strip steel transverse movement in the subsequent process is serious; the annealing separator used in comparative examples 17-18 had a film thickness that was too low, which resulted in adhesion of the strip; the annealing separator used in comparative examples 19-20 was too thick in film thickness, resulting in severe lateral movement of the coil during subsequent process production.
It should be noted that the prior art part in the protection scope of the present invention is not limited to the embodiments set forth in the present application, and all prior art that does not contradict the scheme of the present invention, including but not limited to the prior patent document, the prior publication, the prior disclosure, the use, etc., can be included in the protection scope of the present invention.
In addition, the combination of the features described in the present application is not limited to the combination described in the claims or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradiction occurs between them.
It should also be noted that the above-recited embodiments are merely specific examples of the present invention. It is apparent that the present invention is not limited to the above embodiments, and similar changes or modifications will be apparent to those skilled in the art from the present disclosure, and it is intended to be within the scope of the present invention.
Claims (19)
1. A high-temperature annealing process for high-magnetic induction oriented silicon steel is characterized in that:
placing the steel coil in an annealing furnace in a horizontal posture, and arranging an inner sleeve at the core part of the steel coil to perform high-temperature annealing; wherein during the high temperature annealing:
in the first stage, the steel coil enters an annealing furnace with the furnace temperature of 600-800 ℃ and is kept for 5-30 hours;
in the second stage, the annealing furnace temperature is raised to 900-1000 ℃ at a heating rate of 5-30 ℃/h;
in the third stage, the annealing furnace temperature is raised to 1150-1250 ℃ at a heating rate of more than 5 ℃/h;
in the fourth stage, the steel coil is at least insulated for 15 hours at 1150-1250 ℃;
wherein the atmosphere of high temperature annealing is dry atmosphere with dew point less than-10 ℃.
2. The high temperature annealing process according to claim 1, wherein,the atmosphere of the first stage, the second stage, the third stage and the fourth stage is N 2 And H 2 At least one of them.
3. The high temperature annealing process according to claim 2, wherein the atmosphere of the first stage and the second stage is pure N 2 Or N 2 /H 2 A mixed gas; the atmosphere of the third stage is N 2 /H 2 A mixed gas; the atmosphere of the fourth stage is pure H 2 。
4. The high temperature annealing process according to claim 3, wherein when the atmosphere of the first stage and the second stage is N 2 /H 2 In the case of a mixture, N is 2 Not less than 50% by volume; and/or N of the third stage 2 /H 2 H in the mixed gas 2 The volume ratio of (2) is not less than 50%.
5. The high temperature annealing process according to claim 1, wherein when the steel coil is placed in the annealing furnace in a horizontal posture, an arc-shaped lifting plate is used to lift the outer circumferential wall of the steel coil.
6. The manufacturing method for the high-magnetic-induction oriented silicon steel is characterized by comprising the following steps of: smelting and casting, slab heating, hot rolling, normalizing, pickling, cold rolling, decarburization annealing, nitriding, applying an annealing separator, and a high temperature annealing process according to any one of claims 1 to 5.
7. The method according to claim 6, wherein in the decarburization annealing step, the decarburization annealing atmosphere is controlled So as to control the oxygen content in the steel plate after decarburization annealing and nitriding treatment to be less than 500ppm, thereby obtaining the oriented silicon steel without the bottom layer in the high-temperature annealing step.
8. The method according to claim 6, wherein in the decarburization annealing step, the decarburization annealing atmosphere is controlledSo as to control the oxygen content in the steel plate after decarburization annealing and nitriding treatment to be more than or equal to 500ppm, and obtain the oriented silicon steel with the bottom layer in the high-temperature annealing step.
9. The method according to claim 6, wherein in the step of applying the annealing separator, the annealing separator is applied so that the sum of film thicknesses of the annealing separator on the upper and lower surfaces of the steel strip is 5.0 to 16.0g/m 2 And/or the unit tension A of the strip steel coiling after the release agent is coated is controlled as follows: 0.8× [ 50+M/(0.35+T)]＜A＜1.4×[50+M/(0.35+T)]Wherein A represents the unit tension of strip steel coiling, and the unit parameter is N/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the T represents the thickness of the strip steel without film thickness, and the unit parameter of the thickness is mm; m represents the film thickness of the annealing separator, and the unit parameter is g/M 2 。
10. The method according to claim 6, wherein in the decarburization annealing step, the decarburization annealing temperature is 800 to 880℃and the decarburization annealing time is 75 to 150 seconds.
11. The method according to claim 6, wherein the nitrogen content of the steel sheet after nitriding is 150 to 300ppm.
12. The method according to claim 6, wherein in the slab heating step, the heating temperature is 1100 to 1200 ℃.
13. The method of manufacturing according to claim 6, wherein in the normalizing step, a two-stage normalizing process is used: the hot rolled plate is heated to 1050-1150 ℃, then cooled to 850-950 ℃ and kept for 10-60 s.
14. The method according to claim 6, wherein the slab is rolled to a thickness of 2.0 to 3.0mm by the hot rolling step.
15. The method of manufacturing according to claim 6, wherein the strip is rolled to a thickness of 0.18 to 0.35mm by a cold rolling step.
16. A high magnetic induction oriented silicon steel prepared by the manufacturing method according to any one of claims 6 to 15, wherein the high magnetic induction oriented silicon steel contains Fe and unavoidable impurities, and the following chemical elements in percentage by mass:
C：0.03～0.08％，Si：2.5～3.8％，Mn：0.10～0.25％，S：0.005～0.015％，Als：0.015～0.035％，N：0.004～0.010％。
17. the high magnetic induction oriented silicon steel as set forth in claim 16, wherein the mass percentages of the chemical elements are:
c:0.03 to 0.08 percent, si:2.5 to 3.8 percent, mn:0.10 to 0.25 percent, S: 0.005-0.015%, als:0.015 to 0.035 percent, N: 0.004-0.010%, and the balance of Fe and unavoidable impurities.
18. The high magnetic induction grain-oriented silicon steel according to claim 16 or 17, characterized in that the magnetic induction B8 is > 1.96T.
19. High induction oriented silicon steel according to claim 16 or 17, characterized in that its typical secondary grain size is 100-300 mm.
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