Manufacturing method of low-temperature high-magnetic-induction oriented silicon steel with nitride as inhibitor

Abstract

The invention discloses a low-temperature high-magnetic-induction oriented silicon steel manufacturing method with nitride as an inhibitor, and belongs to the field of high-magnetic-induction oriented silicon steel manufacturing. According to the invention, a high-temperature annealing process is adjusted, high-temperature annealing is set as a three-section heating and heat preservation system, and particularly, the heating speed, the heat preservation temperature and the heat preservation time in high-temperature annealing are adjusted in a targeted manner according to the N content of the steel plate after nitriding and the thickness of the steel plate after cold rolling; therefore, decomposition of nitrogen in high-temperature annealed steel, diffusion of nitrogen in the plate thickness direction, precipitation and decomposition of a nitride inhibitor and the like are effectively controlled, the secondary recrystallization process of oriented silicon steel is regulated and controlled, and secondary recrystallization grains with high-orientation Gaussian orientation are obtained. And finally, the magnetic performance of the low-temperature high-magnetic-induction oriented silicon steel with the nitride as the inhibitor is improved, the process is good in repeatability, the magnetism of the steel plate can be stably controlled, and batch industrial production is facilitated.

Description

Technical Field

[0001] The invention belongs to the field of high magnetic induction oriented silicon steel manufacturing, and specifically relates to a method for manufacturing low-temperature high magnetic induction oriented silicon steel using nitride as an inhibitor. Background Art

[0002] High magnetic induction oriented silicon steel is an important soft magnetic material, which is widely used in power transmission and transformation industries such as large transformers. There are generally two production methods for high magnetic induction oriented silicon steel: one production method is called high temperature high magnetic induction oriented silicon steel manufacturing method, in which the inhibitor starts from steelmaking. In order to fully dissolve the inhibitor, the billet is heated to 1360-1400℃ before rolling. Due to the high heating temperature of the billet, a series of problems such as high energy consumption, low yield rate and poor productivity are prone to occur. At present, another method is mainly used to produce high magnetic induction oriented silicon steel, which makes the heating temperature of the billet lower than 1200℃ and has good productivity. The inhibitor is obtained by nitriding after decarburization annealing, which is an acquired inhibitor. The oriented silicon steel produced by this method is called low temperature high magnetic induction oriented silicon steel.

[0003] Oriented silicon steel is formed by secondary recrystallization during the high temperature annealing stage to form a single {110} <001> Texture, thereby improving the magnetic properties of the steel sheet. Since low-temperature, high-magnetic induction oriented silicon steel uses nitrides as inhibitors, the diffusion of nitrogen in the steel sheet, the precipitation and decomposition of nitride inhibitors will affect the secondary recrystallization process of the oriented silicon steel, thereby affecting the magnetic properties of the steel sheet, especially the magnetic induction. Therefore, the control of the diffusion, precipitation and decomposition of nitrides during high-temperature annealing is a key issue affecting secondary recrystallization, and is also the top priority in the entire production process of low-temperature, high-magnetic induction oriented silicon steel. Domestic and foreign scholars have conducted a lot of research on the high-temperature annealing process.

[0004] Chinese invention patent CN109402513A discloses a method for producing high magnetic induction oriented silicon steel, wherein the steel coil is subjected to high temperature annealing, including: first heating to 600-750°C, keeping warm for 10-20 hours; second heating to the lower limit temperature T of the secondary recrystallization starting temperature min ; The third heating to the upper limit temperature T of the secondary recrystallization starting temperature max ; The fourth temperature is raised to 1170-1220°C and kept warm for 20-30 hours; the annealed steel coil is stretched and flattened to obtain the high magnetic induction oriented silicon steel; the lower limit temperature T min From the remaining aluminum Al r and the iron loss value P of the decarburized plate 13 / 50 The maximum value P 13max Determine that the upper limit temperature T max From the remaining aluminum Al r and the iron loss value P of the decarburized plate 13 / 50 The minimum value P 13minAccording to the iron loss value P of the steel strip 13 / 50 and residual aluminum r , the furnace temperature range for the start of secondary recrystallization can be obtained, thereby improving the performance of the steel coil. Patent CN107988472A proposes an energy-saving high magnetic induction oriented silicon steel production method, which is based on the composition and the iron loss value P of the steel strip after decarburization and nitriding. 13 / 50 To define the secondary recrystallization temperature T0 of the product, to increase the secondary recrystallization heating rate and atmosphere conversion control, to shorten the high-temperature annealing heating process time, and to improve the secondary recrystallization development of the product by increasing the insulation time in the secondary recrystallization temperature area and maintaining the inhibitor effect through the atmosphere. The high-temperature annealing process proposed in patent CN110066908A adopts a two-stage insulation process, and improves the state of the grains and magnetic uniformity in the width direction of the steel strip by controlling the gas flow rate and heating rate. The processes used in the above methods are consistent with the finished product P 13 The iron loss value P of the steel strip head and tail is 13 / 50 The fluctuations are originally large, which is not conducive to the setting of the steel strip process. It is difficult to achieve precise control in the production process, and it is still not conducive to obtaining low-temperature and high-magnetic induction oriented silicon steel with excellent magnetic properties.

[0005] Chinese patent CN107858494A discloses a method for producing low-temperature high-magnetic induction oriented silicon steel, wherein in the high-temperature annealing stage, from low temperature to high temperature, it includes a primary heating section, a low insulation section, a secondary heating section, a high-temperature insulation section and a cooling section in sequence, and the secondary heating section includes an initial heating section, an insulation platform TS section and a later heating section. r The content Ts is estimated and the high-temperature annealing process is adjusted to stabilize the iron loss curve at the rear of the steel coil. Compared with the conventional preparation method, the iron loss in the length direction of the steel coil in the prepared 0.2-0.3mm specification products is ≤0.03W / kg, which improves the uniformity of the iron loss at the head and tail of the steel coil. However, this method needs to measure the size of the primary recrystallized grains. The size of the primary recrystallized grains in the head and tail of the steel coil fluctuates greatly, which will affect the setting of the high-temperature annealing process and is not conducive to obtaining low-temperature and high magnetic induction oriented silicon steel with excellent magnetic properties. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for manufacturing low-temperature and high-magnetic induction oriented silicon steel with nitride as an inhibitor in view of the shortcomings of the prior art, so as to obtain secondary recrystallized grains with high orientation Gaussian orientation, thereby obtaining a low-temperature and high-magnetic induction oriented silicon steel product with excellent magnetic properties.

[0007] In order to solve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0008] Provided is a method for manufacturing low-temperature high-magnetic induction oriented silicon steel using nitride as an inhibitor, wherein the molten steel is smelted in a converter and continuously cast, the ingot is heated, and after conventional hot rolling, normalized pickling is performed, and then cold rolling is performed to a finished steel plate thickness h, where h is 0.20-0.3 mm; decarburization and nitriding annealing is performed, and after nitriding, the steel plate has a nitrogen content [N] of 250-500 ppm, and then a magnesium oxide annealing separator is applied, and high-temperature annealing is performed, and after applying an insulating coating liquid, flattening and stretching annealing is performed, wherein: the high-temperature annealing system after applying the magnesium oxide annealing separator is a three-stage heating and insulation system:

[0009] First, pure nitrogen is introduced to enter the first heating stage, the heating rate V1: 50-70℃ / h, the temperature is raised to temperature T1, and the first insulation stage is entered. At this time, it is switched to a nitrogen-hydrogen mixed atmosphere and kept warm for a period of time t1.

[0010] After switching to nitrogen-hydrogen mixed atmosphere for heat preservation, NH3 formed by the reaction of N2 and H2 adsorbed on the surface of the steel plate is decomposed to penetrate N into the steel, forming a nitride inhibitor in the steel, and the inhibition is further enhanced with the steel plate nitriding process. It is conducive to the recrystallization of grains in the Gauss orientation and improves the magnetic properties of the steel plate.

[0011] The relationship between the holding temperature T1, the N content [N] in the steel plate, and the finished steel plate thickness h is as follows:

[0012] 400+[N]×h ≤ T1 ≤ 650 (1)

[0013] The relationship between the holding time t1 and the N content [N] in the steel plate and the thickness h of the steel plate is as follows:

[0014] [N]×e h / 30 < t1 < [N]×e h / 20 (2)

[0015] Wherein t1 represents the holding time of the first stage, measured in h; [N] represents the N content in the steel, measured in ppm; h represents the finished steel plate thickness, measured in mm.

[0016] In the first heating and insulation stage, the insulation temperature T1 and the insulation time t1 are regulated in combination with the N content [N] in the steel plate and the thickness h of the steel plate, and a certain heating rate V1 is used to regulate the N decomposition on the surface of the steel strip and the diffusion of N into the interior, so as to achieve better surface N decomposition and uniform and sufficient diffusion of N into the interior, and avoid the precipitation of hydrogen nitride on the steel plate surface when it is not completely decomposed and / or the decomposed N is not fully diffused into the interior, thereby affecting the content of nitride inhibitors in the steel, weakening the inhibition force, causing the secondary recrystallization to deviate from the Gaussian texture and affecting the magnetic properties of the steel plate. Among them:

[0017] The higher the N content in the steel plate and the thicker the steel plate, the slower the speed of N nitriding into the steel in the atmosphere, the higher the required insulation and the longer the insulation time, which is more conducive to accelerating the speed of N nitriding into the steel plate in the atmosphere and improving the inhibitory power of the inhibitor in the steel.

[0018] The insulation temperature T1 is regulated to satisfy the relationship (1) with the nitrogen content in the steel plate and the thickness of the steel plate, wherein: if the insulation temperature T1 is too low, the nitrogen on the steel plate surface is not completely decomposed and cannot be nitrided into the steel, affecting the magnetic properties of the steel coil; if the temperature is too high, the decomposed nitrogen will precipitate before being fully diffused into the interior, affecting the magnetic properties of the steel coil.

[0019] The holding time t1 is regulated to satisfy the relationship (2) with the N content in the steel plate and the thickness of the steel plate to avoid the situation where the N on the surface of the steel plate is not evenly diffused along the thickness direction of the steel plate during the holding time is too short, which affects the magnetic properties of the steel coil. If the holding time is too long, the inhibitor formed will grow and coarsen, and fine inhibitors cannot be formed, which weakens the inhibitory force.

[0020] The appropriate heating rate can avoid uneven surface temperature and affect the decomposition and diffusion rate of nitrogen on the steel strip surface.

[0021] Then, the second heating and holding stage is entered in the same nitrogen-hydrogen mixed atmosphere, and the heating rate V2 of the second heating stage is controlled. In this temperature stage, the inhibitor is gradually decomposed, and the grain growth of the secondary recrystallization occurs at the same time.

[0022] The heating rate V2 in the second heating stage has the following relationship with the N content in the steel plate and the thickness h of the steel plate:

[0023] [N]×e h / 50 <V2 < [N]×e h / 25 (3)

[0024] Wherein V2 represents the heating rate in the second heating stage, measured in °C / h; [N] represents the N content in the steel, measured in ppm; and h represents the thickness of the steel plate, measured in mm.

[0025] The temperature rises to the second stage insulation temperature T2, and the insulation is continued for a period of time t2. The insulation temperature T2 has the following relationship with the nitrogen content [N] in the steel plate and the thickness h of the steel plate:

[0026] 800+[N]×h ≤ T2 ≤ 1050 (4)

[0027] Where T2 represents the second stage insulation temperature, measured in °C; [N] represents the nitrogen content in the steel, measured in ppm; h represents the thickness of the steel plate, measured in mm.

[0028] The relationship between the holding time t2 and the N content and thickness h of the steel plate is as follows:

[0029] [N] × h / 6 ≤ t2 ≤ [N] × h / 5 (5)

[0030] Wherein t2 represents the second stage holding time, measured in h; [N] represents the N content in the steel, measured in ppm; h represents the steel plate thickness, measured in mm.

[0031] In the second heating and holding stage, the heating rate V2, holding temperature T2 and holding time t2 are regulated in combination with the N content [N] and the thickness h of the steel plate, so as to coordinately control the decomposition of the nitride inhibitor and the growth of the secondary recrystallization, thereby ensuring that the nitride inhibitor in the steel is completely decomposed, and that the grain size generated by the secondary recrystallization is appropriate and uniform, with a high Gauss orientation degree and improved magnetic properties of the steel plate.

[0032] During this heating stage, the higher the N content in the steel and the thicker the steel plate, the faster the heating rate V2 should be, which is beneficial to accelerate the decomposition of the inhibitor and avoid the inhibition of nitrides on the Gaussian grains in the secondary recrystallization process, resulting in too small grains.

[0033] During this holding stage, the nitride inhibitor in the steel decomposes, the inhibitory force gradually weakens, and the grains in the steel grow, that is, secondary recrystallization occurs. The higher the N content in the steel and the thicker the steel plate, the higher the holding temperature T2 should be, and the longer the holding time t2 should be, which is more conducive to promoting the decomposition of the inhibitor, accelerating the growth of the secondary recrystallization grains, and ensuring that the secondary recrystallization along the thickness direction occurs completely.

[0034] However, if the heating rate V2 is too fast, it is easy to cause uneven heating of the steel plate along the thickness direction, resulting in incomplete decomposition of the nitride inhibitor in the steel, affecting the size and orientation of the recrystallized grains. If the heating rate V2 is too slow, the inhibitor decomposition is completed, but at the same time, due to the rapid disappearance of the inhibitor, the grains in all directions in the steel grow, the Gauss orientation of the secondary grains is poor, and the magnetic properties are reduced. If the holding temperature T2 is too high and the holding time t2 is too long, the secondary recrystallized grains are too large. If the holding temperature T2 is too low and the holding time t2 is too short, the secondary recrystallized grains are too small, reducing the magnetic properties of the steel plate. Therefore, according to the N content [N] in the steel plate and the thickness h of the steel plate, the heating rate V2, the holding temperature T2 and the holding time t2 are respectively adjusted according to the relationship (3)-(5), so as to ensure that the nitride inhibitor in the steel is completely decomposed and the grain size formed by the secondary recrystallization is appropriate and uniform, and the grain Gauss orientation is high.

[0035] Then, the third heating stage is entered in the same nitrogen-hydrogen mixed atmosphere, at a V3 speed of 15-30°C / h. After reaching T3: 1150-1230°C, it is switched to pure H2 atmosphere and enters the third insulation stage. The insulation time is t3: 15-25h. In this stage, steel purification is mainly carried out.

[0036] The appropriate setting of heating speed and heating time can completely remove nitrogen from the steel, achieve good steel purification effect, and avoid incomplete removal of nitrogen from the finished steel, which affects the purity of the steel plate and reduces the magnetic properties of the steel strip.

[0037] Finally, it enters the cooling stage and is cooled to below 250℃ before being taken out of the furnace.

[0038] According to the above scheme, the components and weight percentages of the applicable steel are: C: 0.04%-0.08%, Si: 3.0%-3.4%, Mn: 0.06%-0.12%, S: 0.01%-0.03%, Als: 0.02%-0.03%, N: 0.006%-0.01%, and the balance is Fe and unavoidable impurities.

[0039] According to the above scheme, the volume ratio of H2 and N2 in the nitrogen-hydrogen mixed atmosphere is (2-4):1.

[0040] According to the above scheme, the specific cooling process in the cooling stage is: switch to a mixed atmosphere of H2+N2, cool to 750-600°C, then switch to pure nitrogen and cool to below 250°C before exiting the furnace. Preferably, in the mixed atmosphere of H2+N2, H2:N2=(2-4):1.

[0041] According to the above scheme, the ingot is heated to 1100-1250°C.

[0042] According to the above scheme, the process of flat stretching annealing is: 820-920℃, keeping warm for 3-10min.

[0043] Provided is a low-temperature high-magnetic induction oriented silicon steel manufactured by the manufacturing method.

[0044] According to the above scheme, the magnetic induction B of the low temperature high magnetic induction oriented silicon steel 800 ≥1.92T, iron loss P 17 / 50 ≤0.9w / kg.

[0045] Beneficial effects of the present invention:

[0046] The present invention provides a method for manufacturing low-temperature high-magnetic induction oriented silicon steel with nitride as an inhibitor. The method adjusts the high-temperature annealing process, sets the high-temperature annealing as a three-stage insulation system, and particularly adjusts the heating rate, insulation temperature and insulation time in the high-temperature annealing according to the N content of the steel plate after nitriding and the thickness of the steel plate after cold rolling, thereby effectively controlling the decomposition of nitrogen in the high-temperature annealed steel, the diffusion of nitrogen along the plate thickness direction, and the precipitation and decomposition of the nitride inhibitor, and regulating the secondary recrystallization process of the oriented silicon steel, obtaining secondary recrystallized grains with a high orientation degree Gaussian orientation, and finally improving the magnetic properties of the low-temperature high-magnetic induction oriented silicon steel with nitride as an inhibitor. The process has good repeatability, can stably control the magnetic properties of the steel plate, and is conducive to mass industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the recrystallized grain diagram of the oriented silicon steel obtained in Example 1.

[0048] Figure 2 This is the recrystallized grain diagram of the oriented silicon steel obtained in Comparative Example 1. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] The embodiment of the present invention provides a method for manufacturing low-temperature high magnetic induction oriented silicon steel using nitride as an inhibitor, comprising the following steps:

[0051] The molten steel is smelted in a converter and continuously cast, and the ingot is heated to 1100-1250°C. After conventional hot rolling, it is normalized and pickled, and then cold rolled to the finished steel plate thickness h, h is 0.20-0.3mm;

[0052] Decarburization and nitriding annealing are performed. After nitriding, the steel plate has a nitrogen content [N] of 250-500ppm, and then a magnesium oxide annealing separator is applied;

[0053] High temperature annealing is performed, and flat stretching annealing is performed after applying the insulating coating liquid, wherein: the high temperature annealing system after applying the magnesium oxide annealing isolation agent is a three-stage heating and insulation system:

[0054] First, pure nitrogen is introduced to enter the first heating stage, the heating rate V1: 50-70℃ / h, the temperature is raised to temperature T1, and then the first insulation stage is entered. At this time, it is switched to a nitrogen-hydrogen mixed atmosphere (H2:N2=(2-4):1) and kept warm for a period of time t1.

[0055] The relationship between the insulation temperature T1 and the nitrogen content [N] in the steel plate and the thickness h of the steel plate is as follows:

[0056] 400+[N]×h ≤ T1 ≤ 650 (1)

[0057] The relationship between the holding time t1 and the N content [N] in the steel plate and the thickness h of the steel plate is as follows:

[0058] [N]×e h / 30 < t1 < [N]×e h / 20 (2)

[0059] Then, in the same H2+N2 mixed atmosphere (H2:N2=(2-4):1), the second heating stage is entered, and the heating rate V2 of the second heating stage is controlled.

[0060] The heating rate V2 in the second heating stage has the following relationship with the N content in the steel plate and the thickness h of the steel plate:

[0061] [N]×e h / 50 <V2 < [N]×e h / 25 (3)

[0062] The temperature rises to the second stage insulation temperature T2, and the insulation is continued for a period of time t2. The insulation temperature T2 has the following relationship with the nitrogen content [N] in the steel plate and the thickness h of the steel plate:

[0063] 800+[N]×h ≤ T2 ≤ 1050 (4)

[0064] The relationship between the holding time t2 and the N content and thickness h of the steel plate is as follows:

[0065] [N] × h / 6 ≤ t2 ≤ [N] × h / 5 (5)

[0066] In the above relationship equations (1)-(5), T1, t1, V2, T2, t2, h and [N] are unitless and represent specific values; wherein T1 and T2 represent the insulation temperatures of the first and second stages respectively, in units of °C; t1 and t2 represent the insulation time of the first and second stages respectively, in units of h; V2 represents the heating rate of the second heating stage, in units of °C / h; [N] represents the nitrogen content in the steel, in units of ppm; h represents the finished steel plate thickness, in units of mm.

[0067] Then, the third heating stage is entered in the same nitrogen-hydrogen mixed atmosphere, at a V3 speed of 15-30°C / h. After reaching T3: 1150-1230°C, it is switched to pure H2 atmosphere and enters the third insulation stage. The insulation time is t3: 15-25h. In this stage, steel purification is mainly carried out.

[0068] Finally, it enters the cooling stage, switching to a mixed atmosphere of H2+N2, H2:N2=(2-4):1, cooling to about 750-600°C, and then switching to pure nitrogen to cool to below 250°C before leaving the furnace.

[0069] In one of the embodiments, the components and weight percentages of the steel are: C: 0.04%-0.08%, Si: 3.0%-3.4%, Mn: 0.06%-0.12%, S: 0.01%-0.03%, Als: 0.02%-0.03%, N: 0.006%-0.01%, and the balance is Fe and unavoidable impurities.

[0070] In one embodiment, the flattening stretching annealing process is: 820-920°C, keeping warm for 3-10 minutes.

[0071] The following are specific embodiments.

[0072] Example 1

[0073] A method for manufacturing low-temperature high magnetic induction oriented silicon steel using nitride as an inhibitor is provided, comprising the following steps:

[0074] The composition content is: C: 0.06%, Si: 3.3%, Mn: 0.08%, S: 0.01%, Als: 0.02%, N: 0.006%, the balance is Fe and inevitable impurities. The molten steel is smelted in a converter and continuously cast. The ingot is heated to 1250°C, and after conventional hot rolling, it is normalized and pickled, and then cold rolled to a finished product thickness of 0.20mm; decarburization and nitriding annealing are performed, and the N content of the steel plate after nitriding is: 250ppm. Then, magnesium oxide annealing separator is applied.

[0075] A three-stage insulation system is used for high temperature annealing: first, enter the first heating stage, introduce 100% nitrogen, the heating rate V1: 50℃ / h, rise to T1: 450℃, enter the first insulation stage, at this time, introduce 75% H2+25% N2 atmosphere, insulation time t1: 11h. Then enter the second heating stage in a mixed atmosphere of 75% H2+25% N2, the heating rate V2 is 6.2℃ / h, rise to the second insulation temperature T2: 850℃, insulation time t2: 10h. Then at V3 rate of 15℃ / h, rise to T3: 1150℃, enter the third insulation stage, insulation time t3: 15h, the atmosphere of this insulation stage is pure H2. After the insulation is completed, enter the cooling stage, after power off, switch to 75% H2+25% N2 to cool to about 700℃, and then switch to pure nitrogen to cool to below 250℃ before leaving the furnace.

[0076] After the steel plate was coated with the insulating coating, it was kept at 900°C for 5 minutes for flattening and stretching annealing. The magnetic induction intensity and iron loss value of the finished steel plate were tested, as shown in Table 3.

[0077] The secondary recrystallized grains in this embodiment are analyzed. Figure 1 As shown in Figure 2, the secondary recrystallization is complete and the grain size is relatively uniform.

[0078] Embodiment 2-8

[0079] The composition of the molten steel and the specific operation are the same as those in Example 1, wherein the main process parameters are shown in Tables 1 and 2, and the magnetic induction intensity and iron loss value of the tested finished steel plate are shown in Table 3.

[0080] Comparative Examples 1-3

[0081] The composition of the molten steel and the specific operation are the same as those in Example 1, wherein the main process parameters are shown in Tables 1 and 2, and the magnetic induction intensity and iron loss value of the tested finished steel plate are shown in Table 3.

[0082] Table 1. Main process parameters of various embodiments of the present invention and comparative examples

[0083]

[0084]

[0085] Table 2. Annealing atmosphere at different annealing stages in the examples and comparative examples

[0086]

[0087]

[0088] Table 3. Magnetic properties and iron loss of steel sheets obtained in Examples and Comparative Examples

[0089] <![CDATA[B 800 (T)]]> <![CDATA[P 17 / 50 (w / kg)]]> Example 1 1.920 0.881 Example 2 1.920 0.878 Example 3 1.922 0.887 Example 4 1.920 0.882 Example 5 1.921 0.895 Example 6 1.920 0.890 Example 7 1.922 0.891 Example 8 1.921 0.896 Comparative Example 1 1.87 1.09 Comparative Example 2 1.88 1.11 Comparative Example 3 1.88 1.12

[0090] It can be seen from Table 2 that when the high temperature annealing process meets the scope of the technical solution of the present invention, the magnetic induction intensity B of the finished steel plate can be obtained. 800 Reaching 1.920T or above, the iron loss value P 17 / 50 Also lower.

[0091] In Comparative Example 1, the holding time t1 of the first heating stage of high temperature annealing does not satisfy the relationship (2) proposed in the present invention, the holding time t1 is too short, the holding temperature T1 of the first heating stage does not satisfy the relationship (1) proposed in the present invention, the holding temperature T2 of the second stage does not satisfy the relationship (4) proposed in the present invention, the N on the surface of the steel plate is not evenly diffused along the thickness direction of the steel plate, and the nitride is not completely decomposed, resulting in low magnetic properties of the finished steel plate, B 800 Only 1.87T, P 17 / 50 The secondary recrystallized grains in this embodiment are analyzed. Figure 2The secondary recrystallization is complete, but the grain size is uneven and the grains are too large, resulting in reduced magnetic properties.

[0092] In Comparative Example 2, the heating rate V2, the holding temperature T2, and the holding time t2 of the second heating stage of high temperature annealing do not meet the requirements of the present invention. The heating rate V2 is too fast, the holding temperature T2 is too low, and the holding time t2 is too short, which leads to the incomplete precipitation of the nitride inhibitor in the steel, reduces the strength of the inhibitor, and thus affects the grain size and orientation of the secondary recrystallization, resulting in low magnetic properties of the finished steel plate. 800 Only 1.88T, P 17 / 50 It is 1.11w / kg.

[0093] In Comparative Example 3, the heating rate V2, the holding temperature T2, and the holding time t3 of the third stage of the second heating stage of high temperature annealing do not meet the requirements of the present invention. The heating rate V2 is too slow, the holding temperature T2 is too low, the precipitated nitrides are not completely decomposed, and the secondary recrystallization is still inhibited, affecting the grain size and orientation of the secondary recrystallization. The holding time t3 is too short, which affects the purification effect of the steel quality, resulting in lower magnetic properties of the finished steel plate. 800 Only 1.88T, P 17 / 50 It is 1.12w / kg.

[0094] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for manufacturing low-temperature high magnetic induction oriented silicon steel using nitride as an inhibitor, characterized in that: The molten steel is smelted in a converter and continuously cast, and the ingot is heated. After conventional hot rolling, it is subjected to normal pickling, and then cold rolled to the finished steel plate thickness h, where h is 0.20-0.3 mm; decarburization and nitriding annealing are performed, and after nitriding, the steel plate contains N [N] of 250-500 ppm, and then a magnesium oxide annealing separator is applied, and high-temperature annealing is performed. After applying an insulating coating liquid, a flat stretching annealing is performed, wherein: the high-temperature annealing system after applying the magnesium oxide annealing separator is a three-stage heating and insulation system: First, pure nitrogen is introduced to enter the first heating stage, the heating rate V1: 50-70℃ / h, the temperature is raised to temperature T1, and the first insulation stage is entered. At this time, it is switched to a nitrogen-hydrogen mixed atmosphere and kept warm for a period of time t1; The relationship between the holding temperature T1, the N content [N] in the steel plate, and the finished steel plate thickness h is as follows: 400+[N]×h ≤ T1 ≤ 650 (1) The relationship between the holding time t1, the N content [N] in the steel plate, and the finished steel plate thickness h is as follows: [N]×e h / 30 < t1 < [N]×e h / 20 (2) Then, the second heating and insulation stage is entered in the same nitrogen-hydrogen mixed atmosphere, and the heating rate V2 in the second heating stage is controlled. The relationship between V2 and the N content in the steel plate and the finished steel plate thickness h is as follows: [N]×e h / 50 <V2 < [N]×e h / 25 (3) Rise to the second insulation stage insulation temperature T2, insulation period t2: The relationship between the holding temperature T2, the N content [N] in the steel plate, and the finished steel plate thickness h is as follows: 800+[N]×h ≤ T2 ≤ 1050 (4) The relationship between the holding time t2, the N content in the steel plate and the finished steel plate thickness h is as follows: [N] × h / 6 ≤ t2 ≤ [N] × h / 5 (5) In the above equations (1) to (5), T1, t1, V2, T2, t2, h and [N] are unitless and represent specific values; among which t1 and t2 are expressed in h; V2 is expressed in °C / h; T1 and T2 are expressed in °C; [N] is expressed in ppm; and h is expressed in mm. Then, the third heating stage is entered in the same nitrogen-hydrogen mixed atmosphere, at a speed of V3: 15-30°C / h, and the temperature is raised to T3: 1150-1230°C, and then it is switched to pure H2 atmosphere and enters the third heating stage, with a heating time of t3: 15-25h; Finally, it enters the cooling stage and is cooled to below 250℃ before being taken out of the furnace.

2. The manufacturing method according to claim 1, characterized in that: The components and weight percentages of the applicable steel are: C: 0.04%-0.08%, Si: 3.0%-3.4%, Mn: 0.06%-0.12%, S: 0.01%-0.03%, Als: 0.02%-0.03%, N: 0.006%-0.01%, and the balance is Fe and unavoidable impurities.

3. The manufacturing method according to claim 1, characterized in that: In the nitrogen-hydrogen mixed atmosphere, the volume ratio of H2 and N2 is (2-4):

1.

4. The manufacturing method according to claim 1, characterized in that: The specific cooling process in the cooling stage is: switching to a mixed atmosphere of H2+N2, cooling to 750-600°C, and then switching to pure nitrogen to cool to below 250°C before taking out of the furnace.

5. The manufacturing method according to claim 4, characterized in that: In the mixed atmosphere of H2+N2, the volume ratio of H2 and N2 is (2-4):

1.

6. The manufacturing method according to claim 1, characterized in that: The cast strand is heated to 1100-1250°C.

7. The manufacturing method according to claim 1, characterized in that: The process of flat stretching annealing is: 820-920℃, keeping warm for 3-10min.

8. A low-temperature and high-magnetic-induction oriented silicon steel manufactured by the manufacturing method according to any one of claims 1 to 7.

9. The low temperature and high magnetic induction oriented silicon steel according to claim 8, characterized in that: The magnetic induction B of the low temperature high magnetic induction oriented silicon steel 800 ≥1.92T, iron loss P 17 / 50 ≤0.9w / kg.

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