Nitriding process for preparing oriented silicon steel and continuous annealing furnace

Abstract

The invention discloses a nitriding process for preparing oriented silicon steel, a continuous annealing furnace is adopted, the continuous annealing furnace comprises soaking two-section equipment and soaking three-section equipment, the continuous annealing furnace further comprises intermediate equipment, and the nitriding process can utilize the continuous annealing furnace to carry out low-temperature nitriding treatment and high-temperature nitriding treatment; the low-temperature nitriding treatment comprises the steps that soaking is kept on the decarbonized strip steel through soaking two-section equipment, then the strip steel is conveyed to intermediate equipment to be cooled, and then the strip steel is conveyed to soaking three-section equipment to be subjected to low-temperature nitriding; the high-temperature nitriding treatment comprises the steps that soaking is kept on the decarburized strip steel through soaking two-section equipment, then the strip steel is conveyed to intermediate equipment for high-temperature nitriding, and then the strip steel is conveyed to soaking three-section equipment for cooling. According to the nitriding process, low-temperature nitriding treatment and high-temperature nitriding treatment can be carried out by adopting one production line, so that the production line of the nitriding process is simplified, and the production cost is reduced. The invention further discloses the continuous annealing furnace.

Description

Technical Field

[0001] The invention relates to the field of manufacturing oriented silicon steel, and in particular to a nitriding process and a continuous annealing furnace for preparing oriented silicon steel. Background Art

[0002] Grain-oriented silicon steel, also known as cold-rolled transformer steel, is an extremely low carbon silicon-iron alloy material with grains arranged in the same direction. It is mainly used in the transformer (iron core) manufacturing industry. According to the strength of magnetic induction, oriented silicon steel can be divided into general oriented silicon steel (CGO) and high magnetic induction oriented silicon steel (HiB). Among them, high magnetic induction oriented silicon steel has lower iron loss performance. When used as a transformer core, it can reduce the loss in the energy conversion process.

[0003] The manufacturing process of oriented silicon steel mainly includes decarburization and nitriding processes, among which the nitriding process is a chemical heat treatment process that allows nitrogen atoms to penetrate into the surface of the workpiece in a certain medium at a certain temperature. At present, oriented silicon steel manufacturers carry out this nitriding process at low temperature or high temperature according to their own production know-how. The corresponding production equipment on the market is also designed in a single way according to low-temperature nitriding treatment or high-temperature nitriding treatment. Therefore, a continuous treatment furnace can only be used for low-temperature nitriding treatment or high-temperature nitriding treatment, and cannot be used for both low-temperature nitriding treatment and high-temperature nitriding treatment. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a nitriding process and a continuous annealing furnace for preparing oriented silicon steel.

[0005] In a first aspect, an embodiment of the present invention discloses a nitriding process for preparing oriented silicon steel, which is carried out by a continuous annealing furnace, wherein the continuous annealing furnace comprises a 2-stage soaking device and a 3-stage soaking device, and the continuous annealing furnace further comprises an intermediate device, wherein the intermediate device is located between the 2-stage soaking device and the 3-stage soaking device along the conveying direction of the strip steel, and the intermediate device comprises: an electric heating module, which is used to heat the strip steel on the strip steel conveying channel; a cooling unit, which is used to cool the strip steel on the strip steel conveying channel; and an air jet unit, which is used to jet the strip steel on the strip steel conveying channel;

[0006] The nitriding process can utilize the continuous annealing furnace to perform low-temperature nitriding treatment and high-temperature nitriding treatment; the low-temperature nitriding treatment includes: using the two-stage heat-saturating equipment to keep the decarburized strip heated, then transporting the strip to the intermediate equipment for cooling, and then transporting it to the three-stage heat-saturating equipment for low-temperature nitriding; the high-temperature nitriding treatment includes: using the two-stage heat-saturating equipment to keep the decarburized strip heated, then transporting the strip to the intermediate equipment for the high-temperature nitriding, and then transporting it to the three-stage heat-saturating equipment for cooling.

[0007] By adopting the above technical solution, one production line can be used for both low-temperature nitriding treatment and high-temperature nitriding treatment, which simplifies the production line of the nitriding process. There is no need to use two production lines specifically for low-temperature nitriding treatment and high-temperature nitriding treatment, which greatly reduces production costs.

[0008] According to another specific embodiment of the present invention, in the low-temperature nitriding treatment, the soaking temperature is 850-870°C, and the cooling is to 700-750°C.

[0009] According to another specific embodiment of the present invention, the low-temperature nitriding is carried out in a nitriding atmosphere of ammonia, nitrogen and hydrogen at a nitriding temperature of 700-750° C., and the proportion of ammonia in the nitriding atmosphere is 5-20% by volume.

[0010] According to another specific embodiment of the present invention, in the high temperature nitriding treatment, the soaking temperature is 890-920°C, and the cooling temperature is 830-850°C.

[0011] According to another specific embodiment of the present invention, the high temperature nitriding is carried out in a nitriding atmosphere of ammonia, nitrogen and hydrogen at a nitriding temperature of 890-920° C., and the proportion of ammonia in the nitriding atmosphere is 5-20% by volume.

[0012] According to another specific embodiment of the present invention, the jet unit includes a nozzle, and the distance between the nozzle and the strip along the height direction of the intermediate equipment is 100 to 200 mm, and / or the jetting direction of the nozzle and the conveying direction of the strip form an angle of 30° to 45°.

[0013] According to another specific embodiment of the present invention, the intermediate device further comprises a humidifier, the humidifier is connected to the nozzle, and the temperature of the humidifier is 60-90°C.

[0014] According to another specific embodiment of the present invention, along the conveying direction of the steel strip, a sealed door is provided between the intermediate equipment and the three-stage equalizing equipment, so that the atmosphere of the intermediate equipment is not connected to the atmosphere of the three-stage equalizing equipment.

[0015] In a second aspect, an embodiment of the present invention discloses a continuous annealing furnace for performing a nitriding process as in any embodiment of the first aspect, wherein the continuous annealing furnace comprises a 2-stage soaking device and a 3-stage soaking device, and the continuous annealing furnace further comprises an intermediate device, wherein the intermediate device is located between the 2-stage soaking device and the 3-stage soaking device along the conveying direction of the strip, and the intermediate device comprises: an electric heating module for heating the strip on the strip conveying channel; a cooling unit for cooling the strip on the strip conveying channel; and an air jet unit for jetting the strip on the strip conveying channel;

[0016] The continuous annealing furnace is capable of performing the low-temperature nitriding treatment and the high-temperature nitriding treatment; when performing the low-temperature nitriding treatment, the 2-stage equalizing device is used to maintain the equalizing of the decarburized strip, and after the intermediate equipment receives the strip from the 2-stage equalizing device for the cooling, the 3-stage equalizing device receives the strip from the intermediate equipment for the low-temperature nitriding; when performing the high-temperature nitriding treatment, the 2-stage equalizing device is used to maintain the equalizing of the decarburized strip, and after the intermediate equipment receives the strip from the 2-stage equalizing device for the high-temperature nitriding, the 3-stage equalizing device receives the strip from the intermediate equipment for the cooling.

[0017] By adopting the above technical solution, the present invention only needs to use one set of continuous annealing furnace to perform low-temperature nitriding treatment or high-temperature nitriding treatment. Compared with the prior art, the present invention does not need to use two sets of continuous annealing furnaces to design a single production line for low-temperature nitriding treatment or a single production line for high-temperature nitriding treatment, which greatly reduces the production cost.

[0018] According to another specific embodiment of the present invention, along the conveying direction of the steel strip, a sealed door is provided between the intermediate equipment and the three-stage equalizing equipment, so that the atmosphere of the intermediate equipment is not connected to the atmosphere of the three-stage equalizing equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram showing the composition of a conventional continuous annealing furnace along the conveying direction of the strip steel;

[0020] Figure 2 A schematic cross-sectional view of the intermediate device of the present invention along the width direction of the intermediate device Figure 1 ;

[0021] Figure 3 A schematic cross-sectional view of the intermediate device of the present invention along the width direction of the intermediate device Figure 2 ;

[0022] Figure 4 A partial cross-sectional schematic diagram showing the intermediate device of the present invention along the conveying direction of the strip steel;

[0023] Figure 5 Show Figure 4 A partial enlarged schematic diagram of

[0024] Figure 6 A schematic diagram showing the structure of a humidifying device according to an embodiment of the present invention is shown;

[0025] Figure 7 The temperature variation curves of low temperature nitriding treatment and high temperature nitriding treatment in the embodiment of the present invention are shown.

[0026] 0. Intermediate equipment, 1. Cooling unit, 1a. First cooling radiation tube, 1b. Second cooling radiation tube, 2. Strip steel, 3. Electric heating module, 4. Exhaust pipe, 5. Shell, 6. Nozzle, 61. Upper nozzle, 62. Lower nozzle, 7. Inlet pipe, 71. Mixed atmosphere pipe, 72. Ammonia pipe, 8. Humidifier, 81. Mixer, 82. Hot water tank

[0027] x. The width direction of the intermediate equipment, y. The height direction of the intermediate equipment, a. The conveying direction of the strip, z. The spraying direction, β. The angle DETAILED DESCRIPTION

[0028] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this implementation. On the contrary, the purpose of introducing the invention in conjunction with the implementation is to cover other options or modifications that may extend based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0029] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0030] The terms “first”, “second”, etc. are only used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0031] In the description of this embodiment, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this embodiment can be understood according to specific circumstances.

[0032] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] In the prior art, such as Figure 1 As shown, the continuous annealing furnace includes an inlet sealing door, a heating section 1 device, a soaking section 1 device, a sealing door #1, a heating section 2 device, a soaking section 2 device, a cooling section 1 device, a sealing door #2, a soaking section 3 device, a sealing door #3, a cooling section 2 device, a sealing door #4, a fast cooling section device, an outlet sealing door and an air cooling section device in the conveying direction of the strip. In the prior art, the continuous annealing furnace for preparing oriented silicon steel can only perform low-temperature nitriding treatment or high-temperature nitriding treatment. Therefore, two production lines need to be set up for low-temperature nitriding treatment and high-temperature nitriding treatment respectively.

[0034] First, as Figure 2-7 As shown, the embodiment of the present invention discloses a nitriding process for preparing oriented silicon steel, which is carried out by a continuous annealing furnace, the continuous annealing furnace includes a 2-stage soaking device and a 3-stage soaking device, and the continuous annealing furnace also includes an intermediate device 0, which is arranged along the conveying direction of the strip (for example Figure 4 The a direction shown in the figure is located between the soaking stage 2 equipment and the soaking stage 3 equipment, that is, the intermediate equipment 0 is used to replace the cooling stage 1 equipment in the continuous annealing furnace of the prior art.

[0035] Among them, the intermediate device 0 includes an electric heating module 3, a cooling unit 1 and an air jet unit. Specifically, the electric heating module 3 is used to heat the strip steel 2 on the strip steel conveying channel; the cooling unit 1 is used to cool the strip steel 2 on the strip steel conveying channel; and the air jet unit is used to jet the strip steel 2 on the strip steel conveying channel. That is to say, the intermediate device 0 of the present invention has the functions of cooling, heating and atmosphere ventilation, and can thus perform cooling and high-temperature nitriding. Specifically, in the low-temperature nitriding treatment, the intermediate device 0 is used for cooling; in the high-temperature nitriding treatment, the intermediate device 0 is used for high-temperature nitriding. As a result, the intermediate device 0 can be used for both low-temperature nitriding treatment and high-temperature nitriding treatment, so that the continuous annealing furnace equipped with the intermediate device 0 of the present invention can also be used for both low-temperature nitriding treatment and high-temperature nitriding treatment.

[0036] Furthermore, the nitriding process in the embodiment of the present invention can use a continuous annealing furnace to perform low-temperature nitriding treatment and high-temperature nitriding treatment. Specifically, the low-temperature nitriding treatment includes: using a 2-stage soaking device to keep the decarburized steel strip 2 soaked, then transporting the steel strip 2 to the intermediate device 0 for cooling, and then transporting it to the 3-stage soaking device for low-temperature nitriding; the high-temperature nitriding treatment includes: using a 2-stage soaking device to keep the decarburized steel strip 2 soaked, then transporting the steel strip 2 to the intermediate device 0 for high-temperature nitriding, and then transporting it to the 3-stage soaking device for cooling.

[0037] In some other possible embodiments provided by the present invention, refer to Figure 2 , Figure 3 and Figure 4 The intermediate device 0 further includes a housing 5, the jet unit includes a nozzle 6, and the cooling unit 1, the electric heating module 3 and the nozzle 6 are arranged in the housing 5. The cooling unit 1 is arranged along the width direction of the intermediate device (for example Figure 2 The number of cooling units 1 is multiple, and the multiple cooling units 1 extend along the conveying direction of the strip (for example, Figure 4 The cooling units 1 are arranged at intervals along the conveying direction of the strip (in the direction a shown in the figure), and the distance between adjacent cooling units 1 along the conveying direction of the strip is 0.5 to 0.9 m. The cooling unit 1 includes a first cooling radiant tube 1a and a second cooling radiant tube 1b. The first cooling radiant tube 1a extends from the outside of the shell 5 into the inside of the shell 5 along the width direction of the intermediate device, and the second cooling radiant tube 1b extends from the outside of the shell 5 into the inside of the shell 5 in the opposite direction of the width direction of the intermediate device. The nozzle 6 extends along the width direction of the intermediate device (for example Figure 2 The number of the nozzles 6 is multiple, and the multiple nozzles 6 extend in the conveying direction of the strip (for example, Figure 4 The distance between adjacent nozzles 6 along the conveying direction of the strip steel is 2.8 to 3.2 m. The nozzle 6 includes an upper nozzle 61 and a lower nozzle 62. The first cooling radiation tube 1a, the upper nozzle 61, the lower nozzle 62, the second cooling radiation tube 1b and the electric heating module 3 are arranged in the height direction of the intermediate equipment (e.g. Figure 2 The upper nozzle 61 and the lower nozzle 62 are arranged in sequence, and a conveying channel for the strip steel 2 is formed between the upper nozzle 61 and the lower nozzle 62. The electric heating module 3 is arranged on the inner wall of the shell 5. In one or more embodiments, the first cooling radiation tube 1a and the upper nozzle 61 can be located at approximately the same height, and the second cooling radiation tube 1b and the lower nozzle 62 can be located at approximately the same height. The shell 5 is provided with heat-insulating refractory heat-insulating materials.

[0038] Among them, the first cooling radiation tube 1a and the second cooling radiation tube 1b can be type I. The first cooling radiation tube 1a and the second cooling radiation tube 1b both include an inner sleeve and an outer sleeve, the outer sleeve is sleeved on the inner sleeve, the inner sleeve extends from the outside of one side of the shell 5 into the shell 5 and extends to the other side of the shell 5 along the width direction of the intermediate device. The inner sleeve is used to pass the cooling gas into the shell 5, the outer sleeve is connected to the exhaust pipe 4, and the outer sleeve is used to flow out the heated cooling gas. A regulating valve is provided at one end of the inner sleeve located outside the shell 5, which is used to adjust the flow rate of the cooling gas passed in to achieve adjustable cooling rate.

[0039] In some other possible embodiments provided by the present invention, there are multiple electric heating modules 3, and the multiple electric heating modules 3 are arranged at intervals along the width direction of the intermediate equipment to avoid mutual interference, facilitate independent control of each electric heating module 3, and facilitate better regulation of the temperature of the strip steel 2 during the transportation process of the intermediate equipment 0.

[0040] By adopting the above technical scheme, the intermediate equipment 0 is arranged between the 2nd and 3rd soaking equipment along the conveying direction of the steel strip through the present invention, and the intermediate equipment 0 with cooling, heating and atmosphere ventilation functions can be effectively used for both low-temperature nitriding treatment and high-temperature nitriding treatment. Therefore, the present invention only needs to set up a production line with an intermediate equipment 0 and the intermediate equipment 0 is arranged between the 2nd and 3rd soaking equipment along the conveying direction of the steel strip, so as to carry out low-temperature nitriding treatment, or adjust the production mode to carry out high-temperature nitriding treatment. Compared with the prior art, the present invention simplifies the production line of the nitriding process, and there is no need to use two production lines to carry out a single design for low-temperature nitriding treatment or high-temperature nitriding treatment, which greatly reduces the production cost and is also conducive to the technicians to accurately control the nitriding process according to the needs of different stages. In addition, the above intermediate equipment 0 is conducive to better regulating the process conditions during the nitriding process, and is conducive to ensuring the uniformity and stability of the nitriding of the steel strip 2.

[0041] It should be noted that, in the embodiments of the present invention, high temperature nitriding or low temperature nitriding refers to a process in which active N atoms decomposed from ammonia enter the surface layer of the steel strip and react with Si and Al in the steel to generate Si3N4 and AlN inhibitors.

[0042] In some other possible embodiments provided by the present invention, the low-temperature nitriding treatment includes: using a 2-stage soaking device to soak the decarburized steel strip 2, then transporting the steel strip 2 to an intermediate device 0 for cooling, and then transporting it to a 3-stage soaking device for low-temperature nitriding. Specifically, the soaking temperature is controlled to be 850-870°C, and cooled to 700-750°C. Through the soaking step and the cooling step, it is beneficial to form a fine grain structure, which is beneficial to the adsorption and diffusion of nitrogen atoms, improves the nitriding effect, and finally improves the magnetic properties of the oriented silicon steel.

[0043] Furthermore, a three-stage soaking device is used to perform low-temperature nitriding in a nitriding atmosphere of ammonia, nitrogen and hydrogen at a nitriding temperature of 700-750°C, and the proportion of ammonia in the nitriding atmosphere is 5-20% by volume. Thus, by controlling the amount of ammonia in the nitriding process, the unevenness of the N content in the surface layer of the steel strip 2 can be reduced, and nitrogen atoms can be effectively promoted to penetrate into the surface layer of the steel strip 3 to form fine and evenly distributed nitride inhibitors, which are very important for controlling the formation of an accurately oriented Gossian texture during the recrystallization annealing process, thereby directly affecting the magnetic properties of the oriented silicon steel.

[0044] In some other possible embodiments provided by the present invention, the high-temperature nitriding treatment includes: using a 2-stage equalizing device to equalize the decarburized strip steel 2, then transporting the strip steel 2 to the intermediate device 0 for high-temperature nitriding, and then transporting it to a 3-stage equalizing device for cooling. Specifically, controlling the equalizing temperature to 890-920°C is conducive to the adsorption and diffusion of nitrogen atoms and improving the nitriding effect. Cooling to 830-850°C, more specifically, cooling refers to natural cooling to 830-850°C. As a result, natural cooling helps to release internal stress and prevent uneven distribution of nitrides and grain growth due to rapid cooling. Controlling the cooling to 830-850°C ensures that the grains grow uniformly at this temperature, optimizes the magnetic permeability of silicon steel, reduces hysteresis loss and eddy current loss, and thus improves the overall performance of oriented silicon steel.

[0045] Further, the intermediate device 0 is used to perform high temperature nitriding in a nitriding atmosphere of ammonia, nitrogen and hydrogen at a nitriding temperature of 890-920° C., and the ammonia ratio in the nitriding atmosphere is 5-20% by volume. Thus, high temperature nitriding can increase the nitrogen content in the steel strip 3, which helps to form a nitrided layer.

[0046] In some other possible embodiments provided by the present invention, the continuous annealing furnace further includes a cooling 2-stage device, a rapid cooling stage device and an air cooling stage device, and the nitriding process further includes: after receiving the strip steel 2 from the soaking 3 stage, the strip steel 2 is slowly cooled by the cooling 2-stage device, and then the strip steel 2 is transported to the rapid cooling stage device for rapid cooling, and then transported to the air cooling stage device for air cooling, which helps to eliminate the residual stress in the strip steel 2, stabilize its organizational structure, and ensure the stability of the silicon steel during subsequent processing and use. Specifically, the slow cooling is controlled to 600-650°C, and the rapid cooling is controlled to 90-120°C.

[0047] The inventors also considered that the strip steel 2 with low carbon content is more conducive to the absorption and diffusion of nitrogen atoms, that is, during the nitriding process of the strip steel 2 after decarburization, nitrogen atoms can penetrate deeper into the interior of the steel to form a stable nitride layer. And because decarburization needs to be carried out in an oxidizing atmosphere. In theory, the higher the dew point, the easier it is to decarburize, but when the oxidation rate is greater than the decarburization rate, the dense oxide film will affect the further progress of the decarburization reaction. Therefore, in an embodiment of the present invention, the continuous annealing furnace also includes a soaking 1-stage device, and the nitriding process also includes using a soaking 1-stage device to carry out a decarburization reaction. The decarburization reaction includes: controlling the decarburization to be carried out in a decarburization atmosphere, the decarburization atmosphere is a mixed atmosphere of nitrogen and hydrogen, and the hydrogen ratio is 25-75% by volume, and the decarburization temperature is controlled to be 850-870°C, and the carbon content in the strip steel 2 after decarburization is ≤30ppm. When the H2 content is too low, excessive water vapor will accelerate the oxidation of the steel surface; when the content is too high, since H2 is a reducing gas, it is not conducive to the decarburization reaction. Thus, a more reasonable surface oxide layer structure can be obtained while ensuring good decarburization effect. Thus, a large number of fine dispersed grains, also called primary grains, and some coarse Gaussian oriented grains are formed. These coarse grains are the initial nuclei of secondary recrystallization during high temperature annealing and are the basis of Gaussian structure.

[0048] Specifically, the continuous annealing furnace further includes a heating stage 1 device, and before the decarburization reaction, the step of heating the pickled and hot-rolled strip steel 2 using the heating stage 1 device is performed, wherein the heating temperature is controlled to be greater than 835°C.

[0049] In some other possible embodiments provided by the present invention, combined with Figure 2 and Figure 3 As shown, the intermediate device 0 also includes an air inlet pipe 7, and the air inlet pipe 7 is connected to the nozzle 6. That is to say, the gas in the air inlet pipe 7 passes through the nozzle 6 to reach the surface of the steel strip 2. The air inlet pipe 7 includes a mixed atmosphere pipe 71 and an ammonia pipe 72, wherein the mixed atmosphere pipe 71 is used to introduce a mixed gas of nitrogen and hydrogen, and the ammonia pipe 72 is used to introduce ammonia. Further, the distance between the nozzle 6 and the steel strip 2 along the height direction of the intermediate device is 100 to 200 mm. Since the nitriding time is limited, it can be avoided that the ammonia is too far away from the surface of the steel strip 2 and there is no time for nitriding; it can also be avoided that the ammonia is too far away from the surface of the steel strip 2 and there is no time for the ammonia to decompose, and the undecomposed ammonia directly reacts with the steel strip 3.

[0050] Furthermore, combined with Figure 4 and Figure 5As shown, the angle between the spray direction of the nozzle 6 and the conveying direction of the steel strip is 30° to 45°. Thus, sufficient NH3 is evenly decomposed on the surface of the steel strip 2, so that the AlN content in the steel plate after nitriding is increased, the precipitated phase is finely and evenly distributed, and the nitriding layer is deepened, so as to increase the effective inhibitor content formed in the final high-temperature annealing process, thereby improving the magnetic properties of the oriented silicon steel. For example, the spray direction of the upper nozzle 61 (for example Figure 5 The z direction shown in FIG. 1 ) forms an angle with the conveying direction of the strip (e.g. Figure 5 The angle β shown is 30° to 45°.

[0051] In some other possible embodiments provided by the present invention, combined with Figure 2 , Figure 3 and Figure 6 As shown, the intermediate device 0 also includes a humidifier 8, which is connected to the air inlet pipe 7, and the temperature of the humidifier 8 is 60-90°C. Specifically, the intermediate device 0 also includes a humidifying device, which includes a humidifier 8, a mixer 81 and a hot water tank 82. The mixer 81 and the hot water tank 82 are respectively connected to the humidifier 8, and the humidifier 8 is connected to the ammonia pipe 72 and then to the nozzle 6. The mixer 81 is used to form a mixed gas of N2 and H2, and the hot water tank 82 is used to adjust the temperature of the humidifier 8. Therefore, by controlling the temperature of the humidifier 8, the dew point of the decarburizing atmosphere and the nitriding atmosphere is controlled to ensure the stability of humidification, which is conducive to promoting the decarburizing effect and the nitriding effect.

[0052] In another embodiment of the present invention, the continuous annealing furnace further includes a 2-stage heating device, wherein the 2-stage heating device and the 2-stage soaking device are sequentially arranged along the conveying direction of the steel strip.

[0053] In some other possible embodiments provided by the present invention, a sealed door is provided between the intermediate device 0 and the three-stage soaking device along the conveying direction of the steel strip, so that the atmosphere of the intermediate device 0 is not connected to the atmosphere of the three-stage soaking device. Thus, the atmosphere of the intermediate device 0 and the atmosphere of the three-stage soaking device are prevented from affecting each other.

[0054] In a second aspect, an embodiment of the present invention discloses a continuous annealing furnace for performing a nitriding process as in any embodiment of the first aspect, wherein the continuous annealing furnace comprises a 2-stage soaking device and a 3-stage soaking device, and the continuous annealing furnace comprises an intermediate device 0, wherein the intermediate device 0 is located between the 2-stage soaking device and the 3-stage soaking device along the conveying direction of the strip, and the intermediate device 0 comprises: an electric heating module 3 for heating the strip 2 on the strip conveying channel; a cooling unit 1 for cooling the strip 2 on the strip conveying channel; and an air jet unit for jetting the strip 2 on the strip conveying channel;

[0055] The continuous annealing furnace is capable of performing low-temperature nitriding treatment and high-temperature nitriding treatment; when performing low-temperature nitriding treatment, the 2-stage soaking equipment is used to keep the decarburized strip 2 evenly heated, and after the intermediate equipment 0 receives the strip 2 from the 2-stage soaking equipment for cooling, the 3-stage soaking equipment receives the strip from the intermediate equipment 0 for low-temperature nitriding; when performing high-temperature nitriding treatment, the 2-stage soaking equipment is used to keep the decarburized strip 2 evenly heated, and after the intermediate equipment 0 receives the strip 2 from the 2-stage soaking equipment for high-temperature nitriding, the 3-stage soaking equipment receives the strip 2 from the intermediate equipment 0 for cooling.

[0056] By adopting the above technical solution, the present invention only needs to use one set of continuous annealing furnace to perform low-temperature nitriding treatment or high-temperature nitriding treatment. Compared with the prior art, the present invention does not need to use two sets of continuous annealing furnaces to perform low-temperature nitriding treatment and high-temperature nitriding treatment respectively, which greatly reduces the production cost.

[0057] Among them, along the conveying direction of the strip, a sealed door is provided between the intermediate equipment 0 and the 3-stage soaking equipment, so that the atmosphere of the intermediate equipment is not connected with the atmosphere of the 3-stage soaking equipment, avoiding mutual influence, which is conducive to improving production efficiency. Further, along the conveying direction of the strip, a first sealed door is provided between the 1-stage soaking equipment and the 2-stage heating equipment, so that the atmosphere of the 1-stage soaking equipment is not connected with the atmosphere of the 2-stage heating equipment; a third sealed door is provided between the 3-stage soaking equipment and the 2-stage cooling equipment, so that the atmosphere of the 3-stage soaking equipment is not connected with the atmosphere of the 2-stage cooling equipment; an outlet sealed door is provided between the fast cooling equipment and the air cooling equipment to prevent external air from entering the continuous annealing furnace.

[0058] The following will provide a further detailed description in conjunction with more specific implementation methods.

[0059] Example 1: Low temperature nitriding treatment is carried out using a continuous annealing furnace, and the temperature variation curve is as follows: Figure 7 As shown, the following equipment and steps are included:

[0060] Heating stage 1 equipment: heating the pickled and hot-rolled strip steel 2 to a temperature greater than 835°C;

[0061] Soaking stage 1 equipment: decarburization reaction of the steel strip 2 is carried out in a decarburization atmosphere of nitrogen and hydrogen and a decarburization temperature of 850-870°C. After decarburization, the carbon content of the steel strip 2 is ≤30ppm, and the hydrogen ratio is 25-75% by volume;

[0062] The first sealing door: to prevent the atmosphere of the first stage of equalization from being connected to the atmosphere of the second stage of heating equipment;

[0063] Heating 2-stage equipment: heating the decarburized strip steel 2 to 850-870°C;

[0064] 2-stage soaking equipment: maintain the soaking temperature at 850-870℃;

[0065] Intermediate equipment 0: Cooling to 700-750°C;

[0066] Sealed door: This prevents the atmosphere of the intermediate device 0 from being connected to the atmosphere of the 3-stage equalizing device;

[0067] Three-stage soaking equipment: low-temperature nitriding is carried out in a nitriding atmosphere of ammonia, nitrogen and hydrogen and a nitriding temperature of 700-750°C. The proportion of ammonia in the nitriding atmosphere is 5-20% by volume.

[0068] The third sealing door: It prevents the atmosphere of the equipment in the third stage of equalization from being connected to the atmosphere of the equipment in the second stage of cooling;

[0069] Cooling 2-stage equipment: slowly cool the strip 2 to 600-650°C;

[0070] Rapid cooling equipment: Rapidly cool the strip steel 2 to 90-120°C;

[0071] Exit sealing door: prevents external air from entering the continuous annealing furnace;

[0072] Air cooling section equipment: air is sprayed on the surface of the strip 2 for cooling.

[0073] Example 2: High temperature nitriding treatment is carried out using a continuous annealing furnace, and the temperature variation curve is as follows: Figure 7 As shown, the following equipment and steps are included:

[0074] Heating stage 1 equipment: heating the pickled and hot-rolled strip steel 2 to a temperature greater than 835°C;

[0075] Soaking stage 1 equipment: decarburization reaction of the steel strip 2 is carried out in a decarburization atmosphere of nitrogen and hydrogen and a decarburization temperature of 850-870°C. After decarburization, the carbon content of the steel strip 2 is ≤30ppm, and the hydrogen ratio is 25-75% by volume;

[0076] The first sealing door: to prevent the atmosphere of the first stage of equalization from being connected to the atmosphere of the second stage of heating equipment;

[0077] Heating 2-stage equipment: heating the decarburized strip steel 2 to 890-920°C;

[0078] 2-stage soaking equipment: maintain soaking temperature at 890-920℃;

[0079] Intermediate equipment 0: high temperature nitriding is carried out in a nitriding atmosphere of ammonia, nitrogen and hydrogen and a nitriding temperature of 890 to 920°C, and the proportion of ammonia in the nitriding atmosphere is 5 to 20% by volume;

[0080] Sealed door: This prevents the atmosphere of the intermediate device 0 from being connected to the atmosphere of the 3-stage equalizing device;

[0081] 3-stage heat-averaging equipment: Natural cooling to 830-850℃.

[0082] The third sealing door: It prevents the atmosphere of the equipment in the third stage of equalization from being connected to the atmosphere of the equipment in the second stage of cooling;

[0083] Cooling 2-stage equipment: slowly cool the strip 2 to 600-650°C;

[0084] Rapid cooling equipment: Rapidly cool the strip steel 2 to 90-120°C;

[0085] Exit sealing door: prevents external air from entering the continuous annealing furnace;

[0086] Air cooling section equipment: air is sprayed on the surface of the strip 2 for cooling.

[0087] Although the present invention has been illustrated and described with reference to certain preferred embodiments of the present invention, it should be understood by those skilled in the art that the above is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. Those skilled in the art may make various changes in form and details, including making several simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A nitriding process for preparing oriented silicon steel, which is carried out using a continuous annealing furnace, wherein the continuous annealing furnace comprises a 2-stage soaking device and a 3-stage soaking device, characterized in that: The continuous annealing furnace further comprises an intermediate device, which is located between the second-stage soaking device and the third-stage soaking device along the conveying direction of the steel strip, and comprises: an electric heating module for heating the steel strip on the steel strip conveying channel; a cooling unit for cooling the steel strip on the steel strip conveying channel; and an air jet unit for jetting the steel strip on the steel strip conveying channel; The nitriding process can utilize the continuous annealing furnace to perform low-temperature nitriding treatment and high-temperature nitriding treatment; the low-temperature nitriding treatment includes: using the two-stage heat-saturating equipment to keep the decarburized strip heated, then transporting the strip to the intermediate equipment for cooling, and then transporting it to the three-stage heat-saturating equipment for low-temperature nitriding; the high-temperature nitriding treatment includes: using the two-stage heat-saturating equipment to keep the decarburized strip heated, then transporting the strip to the intermediate equipment for the high-temperature nitriding, and then transporting it to the three-stage heat-saturating equipment for cooling.

2. The nitriding process according to claim 1, characterized in that: In the low temperature nitriding treatment, the soaking temperature is 850-870°C, and the cooling is to 700-750°C.

3. The nitriding process according to claim 2, characterized in that: The low-temperature nitriding is performed in a nitriding atmosphere of ammonia, nitrogen and hydrogen at a nitriding temperature of 700-750° C., and the proportion of ammonia in the nitriding atmosphere is 5-20% by volume.

4. The nitriding process according to claim 1, characterized in that: In the high temperature nitriding treatment, the soaking temperature is 890-920°C, and the cooling temperature is 830-850°C.

5. The nitriding process according to claim 4, characterized in that: The high temperature nitriding is carried out in a nitriding atmosphere of ammonia, nitrogen and hydrogen at a nitriding temperature of 890 to 920° C., and the proportion of ammonia in the nitriding atmosphere is 5 to 20% by volume.

6. The nitriding process according to claim 1, characterized in that: The jet unit comprises a nozzle, the distance between the nozzle and the strip along the height direction of the intermediate equipment is 100-200 mm, and / or the jet direction of the nozzle forms an angle with the conveying direction of the strip, and the angle is 30°-45°.

7. The nitriding process according to claim 6, characterized in that: The intermediate device further comprises a humidifier, the humidifier is connected to the spray pipe, and the temperature of the humidifier is 60-90°C.

8. The nitriding process according to claim 1, characterized in that: Along the conveying direction of the steel strip, a sealed door is provided between the intermediate equipment and the three-stage equalizing equipment, so that the atmosphere of the intermediate equipment is not connected to the atmosphere of the three-stage equalizing equipment.

9. A continuous annealing furnace for carrying out the nitriding process according to any one of claims 1 to 7, the continuous annealing furnace comprising a 2-stage soaking device and a 3-stage soaking device, characterized in that: The continuous annealing furnace further comprises an intermediate device, which is located between the second-stage soaking device and the third-stage soaking device along the conveying direction of the strip steel, and comprises: an electric heating module for heating the strip steel on the strip steel conveying channel; a cooling unit for cooling the strip steel on the strip steel conveying channel; and an air jet unit for jetting the strip steel on the strip steel conveying channel; The continuous annealing furnace is capable of performing the low-temperature nitriding treatment and the high-temperature nitriding treatment; when performing the low-temperature nitriding treatment, the 2-stage equalizing device is used to maintain the equalizing of the decarburized strip, and after the intermediate equipment receives the strip from the 2-stage equalizing device for the cooling, the 3-stage equalizing device receives the strip from the intermediate equipment for the low-temperature nitriding; when performing the high-temperature nitriding treatment, the 2-stage equalizing device is used to maintain the equalizing of the decarburized strip, and after the intermediate equipment receives the strip from the 2-stage equalizing device for the high-temperature nitriding, the 3-stage equalizing device receives the strip from the intermediate equipment for the cooling.

10. The continuous annealing furnace according to claim 9, characterized in that: Along the conveying direction of the steel strip, a sealed door is provided between the intermediate equipment and the three-stage equalizing equipment, so that the atmosphere of the intermediate equipment is not connected to the atmosphere of the three-stage equalizing equipment.

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