A high temperature annealing method for low temperature and high magnetic induction oriented silicon steel

Abstract

The present invention discloses a high-temperature annealing method for low-temperature and high-magnetic induction oriented silicon steel, and the specific steps are as follows: obtain a steel strip with a finished thickness through smelting, continuous casting, heating, hot rolling, normalizing, and cold rolling processes; decarburization annealing the steel strip, coating the annealed steel strip with magnesium oxide, and coiling it into a steel coil; sampling and testing to obtain the data average of [C], [N], [O] and grain size; and high-temperature annealing is performed by calculating the high-temperature annealing parameters according to a given formula. The present invention provides a high-temperature annealing method for low-temperature and high-magnetic induction oriented silicon steel, which determines the heating rate and furnace atmosphere during the high-temperature annealing process by the composition and oxygen, nitrogen and primary recrystallization grain size in the steel after decarburization annealing, thereby achieving the purpose of improving magnetic properties and facilitating the precise control of the high-temperature annealing process.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and in particular relates to a high-temperature annealing method for low-temperature and high-magnetic-induction oriented silicon steel. Background Art

[0002] Silicon alloy steel with a silicon content of 1.0-4.5% and a carbon content of less than 0.08% is called silicon steel. It has the characteristics of high magnetic permeability, low coercive force, and large resistivity, so the hysteresis loss and eddy current loss are small. It is mainly used as a magnetic material in motors, transformers, electrical appliances, and electrical instruments. In order to meet the needs of punching and shearing when manufacturing electrical appliances, a certain degree of plasticity is also required. In order to improve the magnetic induction performance and reduce the hysteresis loss, the content of harmful impurities is required to be as low as possible, and the plate shape is required to be flat and the surface quality is good.

[0003] The production process of low-temperature high-magnetic induction oriented silicon steel mainly includes smelting, hot rolling, normalizing, cold rolling, decarburization, nitriding, high-temperature annealing and stretching and leveling. The processes of each process are interrelated and affect each other. The recrystallization that occurs during decarburization annealing is called primary recrystallization, and the abnormal growth of GOSS grains during high-temperature annealing is called secondary recrystallization. In the production of high-magnetic induction oriented silicon steel, the grain size of the primary recrystallization has an important influence on the secondary recrystallization. When the primary recrystallization grains are fine, the driving force for the secondary recrystallization of the grains becomes larger, and the secondary recrystallization temperature decreases; when the primary recrystallization grains are larger, the driving force for the secondary recrystallization of the grains becomes smaller, and the secondary recrystallization temperature increases. Under certain inhibitor conditions, both situations are prone to imperfect secondary recrystallization. In addition, during high-temperature annealing, the atmosphere in the furnace has an important influence on the secondary recrystallization. Inappropriate furnace atmosphere will cause imperfect secondary recrystallization or even failure. Therefore, different composition control and primary recrystallization grain size require a suitable high-temperature annealing atmosphere and heating rate to ensure the perfection of secondary recrystallization.

[0004] The Chinese patent document of Chinese invention patent 201910938854.7 discloses "a method for preparing high magnetic induction oriented silicon steel", and the Chinese patent document of patent application number 200910273458.3 discloses "a method for preparing high magnetic induction oriented silicon steel". The above documents both elaborate on the high temperature annealing of oriented silicon steel in detail. However, they only determine the range of atmosphere and heating rate, and fail to establish the corresponding relationship between the main influencing factors, which is not conducive to the precise control of the high temperature annealing process.

[0005] To this end, we propose a high temperature annealing method for low temperature and high magnetic induction oriented silicon steel. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a high temperature annealing method for low temperature and high magnetic induction oriented silicon steel.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A high temperature annealing method for low temperature and high magnetic induction oriented silicon steel, the high temperature annealing method has the following specific steps:

[0009] (S1), smelting according to the set composition and obtaining a billet through a continuous casting process, and obtaining a steel strip of finished thickness after heating, hot rolling, normalizing, and cold rolling of the billet;

[0010] (S2), decarburizing and annealing the cold-rolled steel strip, coating the annealed steel strip with magnesium oxide, and then coiling it into a steel coil;

[0011] (S3) After decarburization annealing, the steel strip is sampled and tested for [C], [N], [O] and grain size;

[0012] (S4) performing high temperature annealing on the steel coil after decarburization annealing.

[0013] Preferably, the finished thick steel strip obtained in the step (S1) has the following chemical compositions in terms of mass percentage: C: 0.05-0.09%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030%; S: 0.005-0.010%; Als: 0.02-0.035%; N: 0.0060-0.011%; Sn: 0.05-0.10%; Cr: ≤0.30%; Cu: ≤0.60%; and the rest are Fe and unavoidable impurity elements.

[0014] Preferably, the process flow in the step (S1) is billet→heating→hot rolling→normalizing→cold rolling, wherein the heating temperature of the billet is 1120-1200°C, the final rolling temperature of hot rolling is 900-1000°C, the normalizing adopts a two-stage normalizing of 1100°C+900°C, and the total deformation rate of one cold rolling is 86-90%.

[0015] Preferably, in the steel after decarburization annealing in the step (S2), [C]: ≤30ppm; [N]: 150-300ppm; [O]: 450-1200ppm, and the primary recrystallization grain size is detected at the same time.

[0016] Preferably, in the step (S3), samples are taken at the head, middle and tail of each roll of steel strip, and then the average values ​​of [C], [N], [O] and grain size are determined by detection.

[0017] Preferably, in the step (S4), the steel coil is subjected to high temperature annealing at N 2 Raise the temperature to 650-750℃ in the atmosphere and keep it for 20-30h. 2 and H2 The temperature was raised to 1200℃ at a certain heating rate in the atmosphere, where H 2 The percentage of the temperature is calculated according to formula (1), the heating rate of the 650-1000℃ heating section is calculated according to formula (2), and the heating rate of the 1000-1200℃ heating section is calculated according to formula (3). 2 Keep warm in N atmosphere for 20-30h, then 2 Cool with the furnace under atmosphere.

[0018]

[0019]

[0020]

[0021] Where A: H in nitrogen-hydrogen mixture 2 percentage of

[0022] d: Primary recrystallization grain size.

[0023] v 1 , v 2 : Heating rate;

[0024] [Als], [N], [O]: The unit is ppm.

[0025] The design basis of the present invention is:

[0026] (1) The main inhibitor of low-temperature high-magnetic induction oriented silicon steel is AlN. Its size and quantity have an important influence on the perfection of secondary recrystallization. Its size and quantity need to be guaranteed by reasonable composition control, hot rolling and normalizing process. The inhibitor's inhibitory ability directly affects the starting temperature of secondary recrystallization. Therefore, the formulation of high-temperature annealing process needs to consider the influence of the inhibitor's inhibitory ability. When the inhibitor's inhibitory force is large, GOSS grains and other oriented grains will be restricted. Therefore, it is necessary to accelerate the decomposition of the inhibitor to a certain extent through the atmosphere in the furnace. On the contrary, when the inhibitor's inhibitory ability is weak, it is necessary to slow down the decomposition of the inhibitor by adjusting the atmosphere in the furnace. Therefore, with the increase of [Als], [N], and [O], the proportion of hydrogen in the atmosphere during high-temperature annealing should be increased.

[0027] (2) The size of the primary recrystallization grains is affected by factors such as composition, hot rolling process, normalizing process, cold rolling deformation and annealing process, so its size cannot always remain stable. In order to make the secondary recrystallization develop and improve, when the primary recrystallization grains are smaller, the secondary recrystallization temperature is reduced, and high-temperature annealing needs to accelerate the decomposition of inhibitors, weaken the inhibitor's inhibitory effect on Goss grains, and promote the development and improvement of secondary recrystallization. On the contrary, it is necessary to slow down the decomposition of inhibitors to ensure that the inhibitor has an inhibitory effect on other oriented grains during secondary recrystallization. Therefore, as the size of the primary recrystallization grains increases, the proportion of hydrogen in the high-temperature annealing atmosphere should be reduced.

[0028] (3) At about 1000°C, the secondary recrystallization temperature range is entered. In order to prevent the inhibitor from coarsening prematurely, a higher heating rate is used below 1000°C, and a lower heating rate is used above 1000°C.

[0029] Compared with the prior art, the high temperature annealing method of low temperature and high magnetic induction oriented silicon steel according to the present invention has the following beneficial effects:

[0030] The present invention discloses a high-temperature annealing method for low-temperature and high-magnetic induction oriented silicon steel, which determines the heating rate and furnace atmosphere during the high-temperature annealing process by the composition and oxygen, nitrogen and primary recrystallization grain size in the steel after decarburization annealing, thereby achieving the purpose of improving the magnetic properties and facilitating the precise control of the high-temperature annealing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall process of the present invention.

[0032] Figure 2 Schematic diagram of high temperature annealing of the present invention DETAILED DESCRIPTION

[0033] The following is combined with Figure 1-2 , further illustrating a specific implementation of a high temperature annealing method of low temperature and high magnetic induction oriented silicon steel of the present invention. A high temperature annealing method of low temperature and high magnetic induction oriented silicon steel of the present invention is not limited to the description of the following embodiments.

[0034] Embodiment 1:

[0035] A high temperature annealing method for low temperature and high magnetic induction oriented silicon steel. The specific steps of the high temperature annealing method are as follows:

[0036] (S1) Obtaining finished steel strip with a thickness of:

[0037] The process flow is smelting → continuous casting → heating → hot rolling → normalizing → cold rolling. Its composition by mass percentage is: C: 0.058%; Si: 3.11%; Mn: 0.13%; P: 0.012%; S: 0.008%; Als: 0.023%; N: 0.0075%; Sn: 0.060%; Cr: 0.21%; Cu: 0.02%; the rest is Fe and unavoidable impurity elements. The heating temperature of the billet is 1158℃, the final rolling temperature of hot rolling is 953℃, the normalizing adopts 1100℃+900℃ two-stage normalizing, and the total deformation rate of one cold rolling is 89.5%.

[0038] (S2) Decarburizing and annealing the cold-rolled steel strip, and then coiling it into a steel coil after magnesium oxide coating and sampling.

[0039] (S3) Samples are taken from the beginning, middle and end of each roll to test [C], [N], [O] and grain size d, and the average values ​​are: [C]: 13.6ppm, [N]: 230ppm, [O]: 511ppm, and the primary recrystallization grain size is d = 21.2μm.

[0040] (S4) The steel coil is subjected to high temperature annealing at N 2 Raise the temperature to 650-750℃ in the atmosphere and keep it for 20-30h. 2 and H 2 The temperature was raised to 1200℃ at a certain heating rate in the atmosphere, where H 2 The percentage A is calculated according to formula (1), and the heating rate v in the 700-1000℃ heating section is 1 According to formula (2), the heating rate V in the 1000-1200℃ heating stage is 2 Calculate according to formula (3). Then in pure H 2 Keep warm in N atmosphere for 20-30h, then 2 Cool with the furnace under atmosphere.

[0041]

[0042]

[0043]

[0044] Substituting the data into formula (1), H in nitrogen-hydrogen mixture 2 The percentage of A = 52%, that is, the mixed gas uses 48% N 2 +52%H 2 .

[0045] Substituting the data into formula (2), the heating rate v in the 700~1000℃ heating stage is 1 =18℃ / h.

[0046] Substituting the data into formula (3), the heating rate v in the 1000~1200℃ heating stage is 2 =10℃ / h.

[0047] Embodiment 2:

[0048] A high temperature annealing method for low temperature and high magnetic induction oriented silicon steel. The specific steps of the high temperature annealing method are as follows:

[0049] (S1) Obtaining finished steel strip with a thickness of:

[0050] The process flow is smelting → continuous casting → heating → hot rolling → normalizing → cold rolling. Its composition by mass percentage is: C: 0.053%; Si: 3.09%; Mn: 0.14%; P: 0.010%; S: 0.007%; Als: 0.029%; N: 0.0079%; Sn: 0.061%; Cr: 0.22%; Cu: 0.02%; the rest is Fe and unavoidable impurity elements. The heating temperature of the billet is 1153℃, the final rolling temperature of hot rolling is 956℃, the normalizing adopts 1100℃+900℃ two-stage normalizing, and the total deformation rate of one cold rolling is 89.5%.

[0051] (S2) Decarburizing and annealing the cold-rolled steel strip, and then coiling it into a steel coil after magnesium oxide coating and sampling.

[0052] (S3) Samples are taken from the beginning, middle and end of each roll to test [C], [N], [O] and grain size d, and the average values ​​are: [C]: 13.6ppm, [N]: 230ppm, [O]: 511ppm, and the primary recrystallization grain size is d = 21.2μm.

[0053] (S4) The steel coil is subjected to high temperature annealing at N 2 Raise the temperature to 700℃ in the atmosphere and keep it for 20-30h. 2 and H 2 The temperature was raised to 1200℃ at a certain heating rate in the atmosphere, where H 2 The percentage A is calculated according to formula (1), and the heating rate v in the 700-1000℃ heating section is 1 According to formula (2), the heating rate V in the 1000-1200℃ heating stage is 2 Calculate according to formula (3). Then in pure H 2 Keep warm in N atmosphere for 20-30h, then 2 Cool with the furnace under atmosphere.

[0054]

[0055]

[0056]

[0057] Substituting the data into formula (1), H in nitrogen-hydrogen mixture 2 The percentage of A = 76%, that is, the mixed gas uses 24% N 2 +76% H 2 .

[0058] Substituting the data into formula (2), the heating rate v in the 700~1000℃ heating stage is 1 =17℃ / h.

[0059] Substituting the data into formula (3), the heating rate v in the 1000~1200℃ heating stage is 2 =8℃ / h.

[0060] Comparative Example

[0061] The process control results before high temperature annealing of Comparative Example 1 are completely consistent with those of Example 1.

[0062] The process control results before high temperature annealing of Comparative Example 2 are completely consistent with those of Example 2.

[0063] Comparative Example High Temperature Annealing Process: 2 The temperature was raised to 700 °C in an atmosphere and kept at this temperature for 25 h. Then, the temperature was raised to 1200 °C at a rate of 17 °C / h in an ammonia decomposition atmosphere. Then, the temperature was heated to 700 °C in an atmosphere of pure H 2 Keep warm for 25 hours and then cool in the furnace.

[0064] After warm annealing, flat stretching and sampling inspection are carried out. The inspection results are shown in Table 1.

[0065] <![CDATA[P 1.7 / 50 (W / kg)]]> <![CDATA[B 800 (T)]]> Example 1 1.05 1.89 Comparative Example 1 1.28 1.86 Example 2 0.93 1.92 Comparative Example 2 1.12 1.89

[0066] The present invention discloses a high-temperature annealing method for low-temperature and high-magnetic induction oriented silicon steel, which determines the heating rate and furnace atmosphere during the high-temperature annealing process by the composition and oxygen, nitrogen and primary recrystallization grain size in the steel after decarburization annealing, thereby achieving the purpose of improving the magnetic properties and facilitating the precise control of the high-temperature annealing process.

[0067] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A high temperature annealing method for low temperature and high magnetic induction oriented silicon steel, Features: The specific steps of the high temperature annealing method are as follows: (S1), smelting according to the set composition and obtaining a billet through a continuous casting process, and obtaining a steel strip of finished thickness after the billet is heated, hot-rolled, normalized, and cold-rolled; wherein the mass percentage of the smelting composition is: C: 0.05-0.09%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030%; S：0 .005～0 .010％； Als: 0.02~0.035%; N：0 .0060 ～0 .011％； Sn: 0.05~0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest are Fe and inevitable impurity elements; the heating temperature of the billet is 1120~1200℃; the final rolling temperature of hot rolling is 900~1000℃; the normalization adopts 1100℃+900℃ two-stage normalization; the total deformation rate of one cold rolling is 86~90%; (S2), decarburizing and annealing the cold-rolled steel strip, coating the annealed steel strip with magnesium oxide, and then coiling it into a steel coil; (S3) After decarburization annealing, the steel strip should meet the following conditions: [C] ≤ 30ppm; [N] 150-300ppm; [O] 450-1200ppm; samples should be taken from the head, middle and tail of each roll of steel strip to obtain the average values ​​of [C], [N], [O] and grain size; (S4) High temperature annealing is performed on the steel coil, firstly, the temperature is raised to 700°C in a N2 atmosphere and kept at this temperature for 20 to 30 hours, then the temperature is raised to 1200°C at a certain heating rate in an atmosphere of a mixture of N2 and H2 in a certain proportion, then the temperature is kept at this temperature for 20 to 30 hours in a pure H2 atmosphere, and then the steel coil is cooled with the furnace in a N2 atmosphere; at the same time, the component proportion of the mixed gas and the heating rate are carried out according to the following contents; First: the proportion of the components of the mixed gas; The nitrogen and hydrogen mixed gas used for high temperature annealing is H 2 The percentage ratio is calculated as follows: ； A: H in nitrogen-hydrogen mixture 2 Percentage; [Als], [N], [O]: mass fraction, unit is ppm; d: primary recrystallization grain size; e: natural constant; Second: heating rate; The heating rate in the 650-1000℃ heating stage is calculated as follows: ; V1: heating rate; d: primary recrystallization grain size; The heating rate in the 1000-1200℃ heating stage is calculated as follows: ； V2: heating rate; d: primary recrystallized grain size; [Als] and [N]: mass fraction, in ppm.

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