Design method of oriented silicon steel decarburization annealing process

Abstract

The invention relates to a decarburization annealing process for oriented silicon steel, which comprises the following steps: by taking decarburization annealing heating temperature, # imgabs 0 # partial pressure ratio in annealing atmosphere and decarburization annealing time as design parameters, introducing the decarburization annealing heating temperature, # imgabs 1 # partial pressure ratio in the annealing atmosphere and the decarburization annealing time into a decarburization dynamic process; carbon concentrations of all points of the steel plates with different thickness specifications at different time are obtained, so that the optimal matching relation of the decarburization annealing heating temperature, the # imgabs2 # partial pressure ratio in the annealing atmosphere and the decarburization annealing time is obtained when the decarburization requirement is met, and then the optimal value of a third variable is obtained through calculation when any two parameters are fixed; the decarburization annealing heating temperature is 800-860 DEG C, the decarburization annealing time is 40-80 seconds, and the partial pressure ratio # imgabs3 # ranges from 0.25 to 0.50; according to the method, decarburization annealing is accurately controlled, and a basis is provided for designing decarburization annealing process parameters for research and development of new oriented silicon steel varieties.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a decarburization annealing process design method for oriented silicon steel. Background Art

[0002] The production process of oriented silicon steel is long and difficult. Energy-saving and consumption-reducing technologies in the production process of oriented silicon steel can significantly reduce production costs and improve economic benefits. Improving process speed is a necessary condition for improving production efficiency. Decarburization annealing is a key process for oriented silicon steel to obtain a suitable primary recrystallization structure. It is also a key process for decarburization to avoid magnetic aging of finished products, obtain sufficient acquired inhibitors and oxide layer formation. However, as the process speed increases, the oxide layer of the annealed steel plate will become thinner, and the decarburization and nitriding effects will also be affected. At the same time, the primary recrystallization structure will change, thereby affecting the magnetic properties of the finished product. Therefore, satisfying the matching relationship between temperature, time and partial pressure ratio is the key to ensuring smooth decarburization and nitriding and achieving efficient production.

[0003] The Chinese patent with publication number CN113832322B discloses a high-efficiency decarburization annealing process for high-magnetic induction oriented silicon steel. The main process flow is: steelmaking and continuous casting → hot rolling → pickling and normalizing → cold rolling → decarburization and primary recrystallization annealing → nitriding treatment (low-temperature HiB) → coating of magnesium oxide isolation agent → high-temperature annealing → stretching and flattening annealing → coating of insulating coating → finishing. The process flow of low-temperature HiB is different from that of high-temperature HiB mainly in that a nitriding section is added after decarburization annealing. Under the premise of ensuring that the physical quality of the product is not lower than the existing level (domestic leading level), this invention makes the annealing efficiency of Hi-B steel reach the world's leading level and significantly reduces the manufacturing cost. However, the patent only designs the process for the physical quality after adding the nitriding function to the decarburization annealing, and does not propose an efficient decarburization design method.

[0004] The Chinese patent with publication number CN113249554A discloses a decarburization annealing process for high magnetic induction oriented silicon steel. First, the silicon steel coil is unwound, looped, and cleaned; then the silicon steel is decarburized and nitrided. The ammonia flow rate is 6-20m 3 / h, humidification tank temperature 30-70℃, decarburization temperature 780-880℃, unit speed 45-75m / min, hydrogen ratio 20%-60%, nitrogen ratio 40%-80% in the atmosphere, and then cooled to room temperature; looping the silicon steel; and then coating the silicon steel with magnesium oxide, the coating amount is 4-10g / m 2; Finally, the silicon steel is dried and rolled into a silicon steel coil; The decarburization annealing process of high magnetic induction oriented silicon steel is optimized and designed through the present invention, and the parameters such as ammonia flow rate, atmosphere, and humidification tank water temperature in the decarburization annealing process are adjusted, and the contents of carbon, nitrogen and oxygen in the high magnetic induction oriented silicon steel are optimized, so that the high magnetic induction oriented silicon steel can achieve stable performance, and the magnetic induction reaches 1.92T; However, the patent optimizes the decarburization annealing atmosphere to ensure good control indicators of carbon, nitrogen and oxygen elements and achieve stable performance, and no efficient decarburization technology and method are proposed.

[0005] The present invention provides a method for designing a decarburization annealing process for oriented silicon steel, which adjusts the decarburization annealing heating temperature, the annealing atmosphere, The partial pressure ratio and decarburization annealing time are taken as design parameters. By introducing the above three parameters into the decarburization kinetics, the decarburization annealing heating temperature, the annealing atmosphere and the decarburization kinetics of different thickness specifications of steel plates are obtained when the decarburization requirements are met. The optimal matching relationship between the partial pressure ratio and the decarburization annealing time is obtained, and then when any two of the parameters are fixed, the optimal value of the third variable is obtained by calculation, so as to achieve precise control of decarburization annealing, and provide a basis for designing decarburization annealing process parameters for the development of new oriented silicon steel varieties.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A decarburization annealing process design method for oriented silicon steel, which adjusts the decarburization annealing heating temperature, the annealing atmosphere The partial pressure ratio and decarburization annealing time are used as design parameters. The partial pressure ratio and decarburization annealing time are introduced into the decarburization kinetics process to obtain the carbon concentration of each point at different times in steel plates of different thickness specifications. This results in the decarburization annealing heating temperature and the annealing atmosphere when the decarburization requirements are met. The best matching relationship between the partial pressure ratio and the decarburization annealing time, and then when any two of the parameters are fixed, the best value of the third variable is obtained by calculation;

[0008] Among them, the decarburization annealing process parameters of oriented silicon steel are required: decarburization annealing heating temperature 800℃~860℃, decarburization annealing time 40s~80s, partial pressure ratio Range: 0.25~0.50.

[0009] Furthermore, the decarburization annealing heating temperature and the annealing atmosphere are The partial pressure ratio and decarburization annealing time are introduced into the decarburization kinetics process to obtain the carbon concentration of each point at different times in steel plates of different thickness specifications. This results in the decarburization annealing heating temperature and the annealing atmosphere when the decarburization requirements are met. The optimal matching relationship between the partial pressure ratio and the decarburization annealing time specifically includes the following steps:

[0010] S1, decarburization annealing heating temperature T, annealing atmosphere The three decarburization annealing parameters of partial pressure ratio and decarburization annealing time t are introduced into the decarburization kinetic process, and the steel plate is divided into i nodes along the thickness direction according to the step length Δx, and the surface starting node is recorded as 0; the decarburization annealing time is divided into j nodes according to the time step Δt, and the starting time node is 0; C(i,j) is the carbon concentration at the node i at the time j, and the carbon content calculation equation at any position and time is obtained:

[0011]

[0012] Where k is the reaction rate kinetic constant of the surface decarburization reaction,

[0013] θ'0 is the oxygen coverage on the reaction surface of the steel strip, which decays exponentially with the decarburization time;

[0014] S2, when the decarburization value of the surface layer and the core layer of the strip is equal and less than or equal to 20ppm, that is When the decarburization annealing heating temperature and the annealing atmosphere are less than or equal to 20ppm, the decarburization annealing heating temperature and the annealing atmosphere are obtained by calculating the decarburization kinetic process. The best matching relationship between partial pressure ratio and decarburization annealing time.

[0015] Furthermore, when any two parameters are fixed, the optimal value of the third variable is obtained by calculation, which specifically includes the following contents:

[0016] Set the decarburization annealing heating temperature T and When the partial pressure ratio is , the optimal decarburization annealing time t is calculated according to the carbon content calculation equation at any position and time;

[0017] When setting the decarburization annealing heating temperature T and decarburization annealing time t, the optimal value is calculated according to the carbon content calculation equation at any position and time. Voltage divider ratio;

[0018] Set the decarburization annealing time t and When the partial pressure ratio is , the optimal decarburization annealing heating temperature T is calculated according to the carbon content calculation equation at any position and time.

[0019] Furthermore, the oxygen coverage on the reaction surface of the steel strip, which shows an exponential decay as the decarburization time decays, is:

[0020]

[0021] Wherein, t is the decarburization time, θ0 is the initial coverage, when t=0, θ'0=θ0, and C1 is the coverage attenuation constant.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] Decarburization annealing heating temperature, The partial pressure ratio and decarburization annealing time are the key design parameters. The carbon concentration of each point in the steel strip at different times is obtained by the decarburization kinetics of high magnetic induction oriented silicon steel. The optimal temperature and atmosphere required for decarburization of steel plates of different thicknesses under high-speed decarburization conditions are obtained. The partial pressure ratio can achieve precise control of decarburization annealing, provide a basis for designing decarburization annealing process parameters for the development of new varieties of oriented silicon steel, obtain stable electromagnetic properties and effectively increase production, and at the same time provide a basis for designing decarburization annealing process parameters for new varieties of oriented silicon steel. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are further described below:

[0025] The present invention provides a method for designing a decarburization annealing process for oriented silicon steel, wherein the decarburization annealing heating temperature, The partial pressure ratio and decarburization annealing time are the design parameters. The carbon concentration of each point in the steel strip at different times is obtained through the decarburization kinetics of high magnetic induction oriented silicon steel, and the optimal decarburization annealing heating temperature and atmosphere required for decarburization of steel plates of different thickness specifications are obtained. The partial pressure ratio is as follows: the decarburization annealing process parameters of oriented silicon steel are as follows: the decarburization annealing heating temperature is 800℃~860℃, the decarburization annealing time is 40s~80s, the partial pressure ratio is Range: 0.25~0.50.

[0026] S1, decarburization annealing heating temperature T, annealing atmosphere The three decarburization annealing parameters of partial pressure ratio and decarburization annealing time t are introduced into the decarburization kinetic process, and the steel plate is divided into i nodes along the thickness direction according to the step length Δx, and the surface starting node is recorded as 0; the decarburization annealing time is divided into j nodes according to the time step Δt, and the starting time node is 0; C(i,j) is the carbon concentration at the node i at the time j, and the carbon content calculation equation at any position and time is obtained:

[0027]

[0028] Where: k is the reaction rate kinetic constant of the surface decarburization reaction,

[0029] θ0 is the coverage of oxygen on the reaction surface of the steel strip, K0 is a function of the decarburization annealing heating temperature, lnK0 = 3020 / T-1.16;

[0030] θ'0 is the oxygen coverage on the steel strip reaction surface that decays exponentially with the decarburization annealing time. C1 is the coverage decay constant; the reaction rate kinetic constant k, the coverage of oxygen on the reaction surface of the steel strip θ0, and the coverage of oxygen on the reaction surface of the steel strip θ'0 which decays exponentially with the decarburization annealing time are collectively referred to as the reaction kinetic coefficient;

[0031] At the beginning of the decarburization reaction, the carbon content in the thickness direction of the steel strip is evenly distributed, that is, the carbon concentration in the thickness direction at t = 0 is C0, from which the initial conditions for the decarburization reaction of the steel strip are obtained as follows:

[0032] C(i,0)=C0 (4)

[0033] From this, the interface conditions on the steel strip surface at any time can be obtained:

[0034]

[0035] Since the steel strip is decarburized from both the upper and lower surfaces, the carbon concentration in the center of the steel strip with a thickness of S is:

[0036]

[0037] Combined with the boundary conditions of formula (4), the decarburization conditions are set, and the carbon concentration of each point on the steel strip at different times is iteratively calculated;

[0038] S2, when the decarburization value of the surface and core of the strip steel Through the calculation of decarburization kinetics, the decarburization annealing heating temperature and the annealing atmosphere are obtained. The best matching relationship between partial pressure ratio and decarburization annealing time.

[0039] Set the decarburization annealing heating temperature T and When the partial pressure ratio is , the optimal decarburization annealing time t is calculated according to the carbon content calculation equation at any position and time;

[0040] When setting the decarburization annealing heating temperature T and decarburization annealing time t, the optimal value is calculated according to the carbon content calculation equation at any position and time. Voltage Divider Ratio

[0041] Set the decarburization annealing time t and When the partial pressure ratio is , the optimal decarburization annealing heating temperature T is calculated according to the carbon content calculation equation at any position and time.

[0042] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0043] [Example 1]

[0044] A method for designing a decarburization annealing process for oriented silicon steel comprises the following steps:

[0045] S1. Select oriented silicon steel with an initial carbon content of 490ppm and a thickness of 0.27mm.

[0046] S2. Design decarburization annealing process parameters according to the technical solution: set the decarburization annealing heating temperature to 840°C and the decarburization annealing time to 60s.

[0047] S3. From the known parameters, the reaction rate kinetic constant k of the surface decarburization reaction can be obtained as 0.00295 cm / s and the oxygen coverage on the steel strip reaction surface θ'0=0.36, which decays exponentially with the decarburization annealing time.

[0048] S4. Substitute the reaction rate kinetic constant k and the oxygen coverage rate θ'0 on the steel strip reaction surface, which decays exponentially with the decarburization annealing time, into formula (3), set the step size Δx = 0.05 mm, △t = 10 s, and perform iterative calculation to obtain: Under the condition of 840℃×60s, the partial pressure ratio that best matches the decarburization process should be set to

[0049] S5. After the decarburization annealing, the oriented silicon steel is subjected to conventional high temperature annealing and hot stretching and flattening annealing in the post-process. The magnetic properties are tested and the results are as follows: magnetic property iron loss P 1.7 =0.98W / kg, magnetic performance, magnetic induction B8 =1.917T, reaching the level of 27AG100.

[0050] The embodiment shows that: by using the decarburization process design model proposed in the present invention to calculate the change of carbon concentration at each point of the steel strip over time, it is possible to obtain the decarburization annealing heating temperature, decarburization annealing time and the decarburization temperature required for decarburization of steel plates of different thickness specifications under decarburization conditions. The best matching relationship enables precise control of decarburization annealing and further increases production on the basis of stable magnetic properties.

[0051] [Example 2-5]

[0052] S1. When the surface carbon content is equal to the core carbon content and is less than 20ppm, set the decarburization annealing time and decarburization annealing heating temperature, and calculate The calculation results of the embodiment are shown in Table 1. The annealing treatment is carried out in the decarburization annealing production line according to the parameters designed by the model. The oriented silicon steel product is subsequently made into a finished product through nitriding, high temperature annealing and hot stretching flattening processes. The carbon content of the annealed plate and the magnetic properties of the finished product are tested by sampling as shown in Table 2.

[0053] Table 1 Design of partial pressure ratio in decarburization atmosphere using decarburization kinetic process

[0054]

[0055] Table 2 Magnetic properties of examples

[0056]

[0057] S2: When the surface carbon content is equal to the core carbon content and is less than 20ppm, set the decarburization annealing time and partial pressure ratio The calculation results of the embodiment for calculating the decarburization annealing heating temperature are shown in Table 3. The annealing treatment is carried out in the decarburization annealing production line according to the parameters designed by the model, and the oriented silicon steel product is subsequently made into a finished product through nitriding, high temperature annealing and hot stretching flattening process. The carbon content of the annealed plate and the magnetic properties of the finished product are tested by sampling as shown in Table 4.

[0058] Table 3 Design of decarburization annealing heating temperature using decarburization kinetics process

[0059]

[0060] Table 4 Magnetic properties of the examples

[0061]

[0062] S3: When the surface carbon content is equal to the core carbon content and is less than 20ppm, set the partial pressure ratio The calculation results of the embodiment of the decarburization annealing heating temperature are shown in Table 5. The annealing treatment is carried out on the decarburization annealing production line according to the parameters designed by the model, and then the oriented silicon steel product is made into a finished product through nitriding, high temperature annealing and hot stretching flattening process. The carbon content of the annealed plate and the magnetic properties of the finished product are tested by sampling as shown in Table 6.

[0063] Table 5 Decarburization annealing time designed using decarburization kinetics

[0064]

[0065] Table 6 Magnetic properties of the examples

[0066]

[0067] S4. It can be seen from the magnetic properties of the embodiment that the method of the present invention can achieve effective decarburization on the basis of stable magnetic properties, greatly improve the unit output, and can meet the electromagnetic performance level above AG100. The process design method provided by the present invention can provide a basis for the research and development of new oriented silicon steel decarburization annealing process parameter design.

Claims

1. A method for designing a decarburization annealing process for oriented silicon steel, characterized in that: The decarburization annealing heating temperature and the annealing atmosphere The partial pressure ratio and decarburization annealing time are used as design parameters. The partial pressure ratio and decarburization annealing time are introduced into the decarburization kinetics process to obtain the carbon concentration of each point at different times in steel plates of different thickness specifications. This results in the decarburization annealing heating temperature and the annealing atmosphere when the decarburization requirements are met. The best matching relationship between the partial pressure ratio and the decarburization annealing time, and then when any two of the parameters are fixed, the best value of the third variable is obtained by calculation; Among them, the decarburization annealing process parameters of oriented silicon steel are required: decarburization annealing heating temperature 800℃~860℃, decarburization annealing time 40s~80s, partial pressure ratio Range: 0.25~0.

50.

2. A method for designing a decarburization annealing process for oriented silicon steel according to claim 1, characterized in that: The decarburization annealing heating temperature, the annealing atmosphere The partial pressure ratio and decarburization annealing time are introduced into the decarburization kinetics process to obtain the carbon concentration of each point at different times in steel plates of different thickness specifications. This results in the decarburization annealing heating temperature and the annealing atmosphere when the decarburization requirements are met. The optimal matching relationship between the partial pressure ratio and the decarburization annealing time specifically includes the following steps: S1, decarburization annealing heating temperature T, annealing atmosphere The three decarburization annealing parameters of partial pressure ratio and decarburization annealing time t are introduced into the decarburization kinetic process, and the steel plate is divided into i nodes along the thickness direction according to the step length Δx, and the surface starting node is recorded as 0; the decarburization annealing time is divided into j nodes according to the time step Δt, and the starting time node is 0; C(i,j) is the carbon concentration at the node i at the time j, and the carbon content calculation equation at any position and time is obtained: Where k is the reaction rate kinetic constant of the surface decarburization reaction, θ'0 is the oxygen coverage on the reaction surface of the steel strip, which decays exponentially with the decarburization time; S2, when the decarburization value of the surface layer and the core layer of the strip is equal and less than or equal to 20ppm, that is When the decarburization annealing heating temperature and the P content in the annealing atmosphere are calculated by the decarburization kinetic process, the H2O / P H2 The best matching relationship between partial pressure ratio and decarburization annealing time.

3. A method for designing a decarburization annealing process for oriented silicon steel according to claim 2, characterized in that: When any two parameters are fixed, the optimal value of the third variable is obtained by calculation, which specifically includes the following contents: Set the decarburization annealing heating temperature T and When the partial pressure ratio is , the optimal decarburization annealing time t is calculated according to the carbon content calculation equation at any position and time; When setting the decarburization annealing heating temperature T and decarburization annealing time t, the optimal value is calculated according to the carbon content calculation equation at any position and time. Voltage divider ratio; Set the decarburization annealing time t and When the partial pressure ratio is , the optimal decarburization annealing heating temperature T is calculated according to the carbon content calculation equation at any position and time.

4. A method for designing a decarburization annealing process for oriented silicon steel according to claim 2, characterized in that: The oxygen coverage on the reaction surface of the steel strip, which shows an exponential decay as the decarburization time decays, is: Among them, t is the decarburization time, θ0 is the initial coverage, and when t=0, C1 is the coverage attenuation constant.

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