Method for cold rolling of very thin silicon steel

Abstract

The present application belongs to the field of plate strip rolling, and relates to a method for cold rolling of very thin silicon steel. The method for cold rolling of very thin silicon steel comprises a preparation stage and a cold rolling stage. The preparation stage comprises obtaining raw materials, processing the raw materials according to the steps of smelting, casting, hot rolling, normalizing and pickling to obtain a first strip, i.e. quantitative analysis of many process parameters of the five links of smelting, casting, hot rolling, normalizing and pickling in the preparation stage is completed, which provides a basis for the guarantee of product quality; the cold rolling stage comprises adjusting the reduction rate, lubrication parameters, tensile stress and plate difference to thin the first strip, and controlling the plate difference of the thinned first strip within the range of ±3 µm to obtain a target strip, i.e. in the cold rolling stage, a large reduction rate, a lubrication scheme of high oil temperature and low oil quantity, and a large tension rolling process are adopted, the minimum rollable thickness limit is broken through, and the requirement of high plate difference is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of plate rolling, and particularly relates to a cold rolling method of extremely thin silicon steel. BACKGROUND

[0002] The extremely thin silicon steel is an important soft magnetic alloy indispensable for the electric power, electronic and military industries, and is also the largest production of metal functional materials, which is mainly used for manufacturing various electric machines, transformers, mutual inductors, relays and household appliances. At present, China cannot realize the independent production of the steel grade, and there are the following obvious disadvantages in the actual production-research process:

[0003] (1) The process research and development lacks integrity. At present, the research on the rolling of the extremely thin silicon steel by colleges and universities, research institutes and production enterprises is mainly anchored to a certain technical link, which causes the process research and development to be not smooth due to the lack of integrity, and when the product has a problem, the specific process corresponding to the cause cannot be investigated, which greatly limits the development of the silicon steel technology, and causes the final product to be unable to meet the terminal requirements in terms of the magnetic properties.

[0004] (2) The equipment research and development lacks systematization. At present, the domestic silicon steel production machines are mainly six-roller rolling mills or Sendzimir mills. The six-roller rolling mill can only produce slightly thick silicon steel, and the product thickness is relatively large, which causes the iron loss to be high and affects the magnetic properties. The Sendzimir mill can produce relatively thin strips, but due to the limited opening degree of the equipment and the hard and brittle characteristics of the product, once the strip breaks during the rolling process, it is extremely difficult to clean the broken strip residues. SUMMARY

[0005] The present application aims to provide a cold rolling method of extremely thin silicon steel to overcome the above technical defects.

[0006] In order to solve the above technical problems, the present application provides a cold rolling method of extremely thin silicon steel, which comprises:

[0007] Step 100, material preparation stage;

[0008] Obtaining raw materials, processing the raw materials according to the steps of smelting, casting, hot rolling, normalizing and pickling to obtain a first strip;

[0009] Step 200, cold rolling stage;

[0010] In the cold rolling stage, the reduction rate, lubrication parameters, tensile stress and plate difference are adjusted to thin the first strip, and the plate difference of the thinned first strip is controlled within the range of ±3µm to obtain a target strip.

[0011] According to the cold rolling method of extremely thin silicon steel, the smelting step comprises: in the smelting link, controlling the mass fraction of silicon element of the raw material to be 3.4%-3.6% to reduce the iron loss and maintain the magnetic properties, and preparing a casting blank.

[0012] According to the cold rolling method of the ultra-thin silicon steel, the casting step comprises: using a continuous casting process to slow cool and keep the temperature of the casting blank to prevent the generation of invisible cracks and coarse grains.

[0013] According to the cold rolling method of the ultra-thin silicon steel, the hot rolling step comprises:

[0014] The heating temperature is adjusted to 1250-1350 degrees Celsius to control the solid solution degree of the inhibitor in the casting blank;

[0015] The finishing temperature is adjusted to 850-950 degrees Celsius to control the precipitation of the inhibitor in the casting blank;

[0016] The coiling temperature is adjusted to 550-650 degrees Celsius to control the generation of iron oxide scale.

[0017] According to the cold rolling method of the ultra-thin silicon steel, the normalizing step comprises: controlling the normalizing temperature to 1000-1100 degrees Celsius, the holding time to 2-3 minutes, and the water spray rapid cooling to improve the magnetism and reduce the iron loss, to obtain the hot rolled strip.

[0018] According to the cold rolling method of the ultra-thin silicon steel, the pickling step comprises a shot blasting pretreatment link and an official pickling link;

[0019] In the shot blasting pretreatment link, the shot blasting flow is 800-1000 kg / min, the shot blasting particles are 1.0 mm steel particles, and the shot blasting is used to remove the iron oxide scale on the surface of the hot rolled strip;

[0020] In the official pickling link, hydrochloric acid is selected as the acid solution, the mass fraction of hydrochloric acid in the acid solution is 3%, and the pickling temperature is 75 degrees Celsius, to obtain the first strip.

[0021] According to the cold rolling method of the ultra-thin silicon steel, in the cold rolling stage, the reduction rate, the lubrication parameter, the tensile stress, and the same plate difference are adjusted to thin the first strip, and the same plate difference of the thinned first strip is controlled within ±3µm, to obtain the target strip, comprising the following steps:

[0022] The reduction rate is maintained above 85% to generate a large amount of deformation heat;

[0023] The temperature of the lubricating medium is controlled to 55 degrees Celsius, and the amount of lubricating oil is 12000 ml / min, to maximize the reduction of the heat of the first strip taken away by the lubricating medium by using the lubrication scheme of high oil temperature and low oil amount;

[0024] The tensile stress of the first strip is adjusted to 40% of the current pass yield limit;

[0025] The first strip is introduced into the cold rolling production system of the ultra-thin silicon steel, the cold rolling production system of the ultra-thin silicon steel is used to eliminate the wedge-shaped plate shape and control the same plate difference of the thinned first strip within the range of ±3µm, and the target strip is obtained.

[0026] According to the cold rolling method of the ultra-thin silicon steel, the cold rolling production system of the ultra-thin silicon steel comprises:

[0027] a frame;

[0028] a tower-shaped roller system, which is composed of an upper roller system and a lower roller system, and the upper roller system and the lower roller system are both installed in the frame;

[0029] a servo oil cylinder, which is arranged below the lower roller system, and the servo oil cylinder controls the overall lifting of the lower roller system to change the rolling mill opening, and the rolling mill opening is suitable for the strip rolling and strip breaking treatment of the ultra-thin silicon steel and the residue cleaning.

[0030] According to the cold rolling method of the ultra-thin silicon steel, the upper roller system and the lower roller system both comprise ten rollers;

[0031] The ten rollers are arranged in a tower shape, the innermost circle is a work roller, and the outermost circle is a support roller;

[0032] The support roller is four;

[0033] The four support rollers are arranged in a fan shape, and the center of the fan points to the work roller;

[0034] Each of the support rollers comprises at least a shaft, and a plurality of thick wall bearings are sleeved on the shaft;

[0035] The four support rollers arranged in a fan shape are composed of two intermediate support rollers and two side support rollers, the number of thick wall bearings on the two intermediate support rollers is the same, the number of thick wall bearings on the two side support rollers is the same, and the number of thick wall bearings on the side support rollers is one more than that on the intermediate support rollers.

[0036] According to the cold rolling method of the ultra-thin silicon steel, the upper roller system can be lifted as a whole;

[0037] During rolling production, the upper roller system is in a locked state;

[0038] During non-rolling production, the lifting height of the upper roller system is adjusted to keep the rolling line at a preset position, wherein the non-rolling production includes roller replacement, rolling line calibration or regrinding.

[0039] The frame comprises at least an operation side rack and a transmission side rack;

[0040] The extension and retraction amount of the servo oil cylinder can make the lower roller system be in an inclined state along the operation side or the transmission side, so as to eliminate the wedge-shaped plate shape and control the same plate difference of the first strip within the range of ±3µm.

[0041] Wherein, the operation side is the side where the operation side rack is located, and the transmission side is the side where the transmission side rack is located.

[0042] The beneficial effects of the present application are as follows:

[0043] (1) The present application researches and develops the whole process flow affecting the quality of silicon steel, proposes an extremely thin silicon steel cold rolling method, and divides it into a material preparation stage and a cold rolling stage. Quantitative analysis is completed on many process parameters of five links such as smelting, casting, hot rolling, normalizing and pickling in the material preparation stage, which provides a basis for the protection of product quality; in the cold rolling stage, a large reduction rate, a high oil temperature and a low oil amount lubrication scheme, and a large tension rolling process are adopted, the minimum rollable thickness limit is broken through, and the high same plate difference requirement is realized.

[0044] (2) According to the process characteristics of the cold rolling stage, an extremely thin silicon steel cold rolling production system with large opening degree and high roller system stiffness is developed. The arrangement of the tower-shaped roller system not only meets the small roller diameter required for rolling the extremely thin silicon steel strip, but also ensures the overall rigidity of the roller system; the overall lifting of the lower roller system driven by the servo oil cylinder meets the requirement of large opening degree in the conditions such as threading and maintenance, and the great in-machine space arrangement provides convenience for the treatment of accidents such as strip breakage.

[0045] In order to make the above content of the present application more obvious and easy to understand, the preferred embodiments are described in detail below, and the drawings are combined as follows. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a flow chart of the extremely thin silicon steel cold rolling method.

[0047] Figure 2 is a sectional view of the extremely thin silicon steel cold rolling production system.

[0048] Figure 3 is a structural diagram of the extremely thin silicon steel cold rolling production system.

[0049] Figure 4 is an arrangement diagram of the upper roller system and the lower roller system.

[0050] Figure 5 is a thick wall bearing distribution diagram of the supporting roller.

[0051] Explanation of reference signs:

[0052] A. archway; B. upper roller system; C. lower roller system; D. servo oil cylinder;

[0053] 1. operating side frame; 2. drive side frame; 3. upper cross beam; 4. lower cross beam. DETAILED DESCRIPTION

[0054] The present application will be described with respect to the following specific embodiments, which are intended to illustrate the present application and not to limit the scope of the application. The skilled person can easily understand other advantages and effects of the present application from the disclosure of the present specification.

[0055] It should be noted that in the present application, the up, down, left and right in the figures are considered as the up, down, left and right of the cold rolling method of the ultra-thin silicon steel described in the specification.

[0056] Exemplary embodiments of the present application will now be described with reference to the accompanying drawings, which are intended to illustrate the present application and not to limit the scope of the application. The present application can be implemented in many different forms and is not limited to the embodiments described herein, which are provided to fully and completely disclose the present application and to fully convey the scope of the present application to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not limiting of the present application. In the drawings, the same elements / elements are denoted by the same reference numerals.

[0057] Unless otherwise defined, the terms used herein (including technical and scientific terms) have the meanings commonly understood by one of ordinary skill in the art. In addition, it is to be understood that the terminology used herein is to be interpreted in accordance with the ordinary meanings of the terms, and should not be interpreted in an idealized or overly formal sense.

[0058] The present embodiment relates to a cold rolling method of ultra-thin silicon steel, please refer to Figure 1 , which includes a preparation stage and a cold rolling stage, which will be described in detail below.

[0059] Step 100, preparation stage.

[0060] Only when the influencing factors such as elemental composition, microstructure and geometric size of the raw material are strictly controlled within a certain range in the preparation stage, the ferromagnetic properties of the product can be maximized to avoid edge cracks or to provide guarantee for the thickness difference accuracy and the same plate difference accuracy of the cold rolling stage.

[0061] According to the sequence of production procedures, the preparation stage at least includes obtaining raw materials, processing the raw materials according to the steps of smelting, casting, hot rolling, normalizing and pickling, and obtaining the first strip.

[0062] The smelting step includes: in the smelting link, controlling the mass fraction of silicon element of the raw material to be 3.4%-3.6% to reduce the iron loss and maintain the ferromagnetic properties, and preparing the casting blank.

[0063] Specifically, the mass fraction of silicon element is kept at about 3.5% in the smelting step, so as to reduce the iron loss and maintain high mechanical properties. This is because the increase of silicon content in a certain range can reduce the eddy current loss and coercivity, but when the mass fraction of silicon element exceeds 3.5%, the yield strength and elongation will decrease, and the disadvantage of coarse grain will be caused. On the contrary, if the mass fraction of silicon element is too low, the magnetic induction will be seriously affected due to the increase of iron loss. Therefore, the content of silicon element is the key to the mechanical properties and ferromagnetic characteristics of the final product.

[0064] The casting step includes: using continuous casting process, slow cooling and heat preservation of the casting blank to prevent the generation of invisible cracks and coarse grains.

[0065] Slow cooling refers to placing the steel material at high temperature in a slow cooling environment to achieve the required microstructure and mechanical properties. Heat preservation refers to controlling the temperature change of the steel material during rolling to ensure that it maintains an appropriate temperature range during processing, thereby ensuring product quality, performance and production efficiency.

[0066] The casting step uses continuous casting technology, and the slow cooling and heat preservation technology for the casting blank can prevent the generation of cracks and coarse grains. The surface defects of the ingot (i.e. the casting blank obtained in the smelting step) are many and the yield rate is low, so the continuous casting method is used. Through the synergistic effect of casting speed and molten steel, the slow cooling and heat preservation technology effectively controls the grain size of the casting blank and avoids the spread of invisible cracks, while also reducing the oxidation of the molten steel, which lays the foundation for the subsequent process steps without porosity and edge cracks.

[0067] The hot rolling step includes: adjusting the heating temperature to 1250-1350 degrees Celsius to control the solid solution degree of the inhibitor in the casting blank; adjusting the finishing temperature to 850-950 degrees Celsius to control the precipitation of the inhibitor in the casting blank; adjusting the coiling temperature to 550-650 degrees Celsius to control the generation of iron oxide scale.

[0068] The hot rolling step effectively controls the microstructure and properties and the iron oxide scale through the organic coordination of the heating temperature, the finishing temperature and the coiling temperature. The heating temperature is about 1250-1350 degrees Celsius, preferably 1300 degrees Celsius, and the solid solution degree of the inhibitor in the casting blank is controlled by controlling the heating temperature; the finishing temperature is about 850-950 degrees Celsius, preferably 900 degrees Celsius, and the precipitation of the inhibitor is effectively controlled by controlling the finishing temperature; the coiling temperature is about 550-650 degrees Celsius, preferably 600 degrees Celsius, and the generation of iron oxide scale and the difficulty of pickling can be reduced by controlling the coiling temperature.

[0069] The normalizing step includes: controlling the normalizing temperature to be 1000-1100 degrees Celsius, the holding time to be 2-3 minutes, and spraying water to rapidly cool to increase the magnetism and reduce the iron loss, so as to obtain the hot-rolled strip.

[0070] The normalizing step controls the secondary recrystallization and the inhibitor precipitation through the overall control of the normalizing temperature and the holding time, so as to reduce the occurrence of the problems such as brittle fracture or crack in the cold rolling stage. The normalizing temperature is about 1000-1100 degrees Celsius, preferably 1050 degrees Celsius, and the holding time is about 2-3 minutes, and then the water is sprayed to rapidly cool to increase the magnetism and reduce the iron loss.

[0071] The pickling step includes the shot blasting pretreatment step and the formal pickling step.

[0072] (1) In the shot blasting pretreatment step, the shot blasting process is adopted, the shot blasting flow is 800-1000 kg / min, the steel shot is 1.0 mm, and the shot blasting is used to remove the oxide scale on the surface of the hot-rolled strip.

[0073] (2) In the formal pickling step, hydrochloric acid is selected as the acid solution, the mass fraction of hydrochloric acid in the acid solution is about 3%, and the pickling temperature is 75 degrees Celsius, so as to obtain the first strip.

[0074] The pickling step includes the shot blasting pretreatment and the formal pickling. In the shot blasting pretreatment, the shot blasting process is adopted, the shot blasting capacity is 800-1000 kg / min, the steel shot size is about 1.0 mm, the dust, powder and slag generated are removed by the dust removal device, the shot blasting pretreatment is used to damage and clean the oxide scale on the surface of the hot-rolled strip, which reduces the difficulty of acid corrosion in the subsequent formal pickling step. In the formal pickling step, hydrochloric acid is used as the acid solution, the mass fraction of hydrochloric acid in the acid solution is about 3%, and the pickling temperature is about 75 degrees Celsius. The high acid solution temperature helps to speed up the pickling speed and greatly improve the overall production rhythm.

[0075] Step 200, cold rolling stage.

[0076] The main process parameters of the cold rolling stage include the reduction rate, lubrication parameters, tensile stress and plate difference, etc. Through the cold rolling stage, the strip is not only thinned to obtain the required thickness, but also creates favorable conditions for obtaining ideal primary recrystallization structure and texture, so the cold rolling stage is a decisive stage affecting the product quality. The proposal and effective control of the key process parameters are the key to guarantee the comprehensive quality of the product.

[0077] Specifically, in the cold rolling stage, the reduction rate, lubrication parameters, tensile stress and plate difference are adjusted to thin the first strip, and the plate difference of the thinned first strip is controlled within the range of ±3 µm to obtain the target strip.

[0078] Please continue to read Figure 1In the cold rolling stage, the reduction, lubrication parameters, tension stress, and strip thickness difference are adjusted to thin the first strip, and the thickness difference of the thinned first strip is controlled within a range of ±3 pm to obtain a target strip, including the following steps:

[0079] The reduction is maintained above 85% to generate a large amount of deformation heat.

[0080] The cold rolling stage adopts a large reduction process route, and the total reduction is maintained above about 85% to obtain good high magnetic induction. A large reduction can generate a large amount of deformation heat, and the use of a fast rolling production rhythm can further increase the temperature of the strip, that is, fast rolling can prevent heat loss to keep the strip at a high temperature to prevent strip breakage.

[0081] The large amount of deformation heat generated by the large reduction can keep the silicon steel strip at a high temperature to resist its own hard and brittle characteristics and prevent strip breakage.

[0082] The temperature of the lubricating medium is controlled at 55°C, and the amount of lubricating oil is 12000 ml / min, so that the high oil temperature and low oil amount lubrication scheme can maximize the reduction of the heat of the first strip taken away by the lubricating medium.

[0083] The lubricating oil temperature is 55°C, and the amount of lubricating oil is 12000 ml / min, which can be considered as high oil temperature and low oil amount. The high oil temperature and low oil amount lubrication scheme can maximize the reduction of the heat of the steel plate (i.e. the first strip) taken away by the lubricating medium under the premise of meeting the lubrication requirements. The above measures not only reduce the risk of strip edge cracking and brittle fracture, but also improve the pinning dislocation ability of the steel strip (i.e. the first strip), hinder the dislocation movement, change the cold rolling texture, and further reduce the iron loss. This has a positive effect on improving the toughness of the steel strip (i.e. the first strip), reducing rolling strip breakage, and improving the yield.

[0084] The tension stress of the first strip is adjusted to 40% of the current pass yield limit.

[0085] The cold rolling stage adopts a large tension rolling process, and the strip tension stress is about 40% of the current pass yield limit. A large tension stress helps to break through the minimum rollable thickness bottleneck. When the product thickness is thin, simply increasing the rolling pressure only causes elastic deformation of the rollers and housings, but the outlet thickness of the strip cannot be further thinned. Especially when the end of the roller is pressed, the increase of the rolling force can even cause irreversible damage to the mechanical, electrical and hydraulic equipment (i.e. mechanical equipment, electrical equipment and hydraulic equipment). At this time, only by increasing the tension stress of the strip can the thickness limit be broken, and further thinning of the strip thickness can reduce the iron loss of the product and improve its magnetic properties.

[0086] The first strip is introduced into the cold rolling production system of the ultra-thin silicon steel, the cold rolling production system of the ultra-thin silicon steel is used to eliminate the wedge-shaped shape and control the same plate difference of the thinned first strip within the range of ±3μm, and the target strip is obtained.

[0087] The roll inclination technology is adopted in the cold rolling stage, the technology can effectively compensate and inhibit the wedge-shaped shape, and through the comprehensive use of the shape system and the thickness control system, the same plate difference of the strip can be controlled within the range of ±3μm, the high same plate difference is helpful to improve the lamination coefficient and increase the punching property, which is very favorable for reducing the iron loss and enhancing the magnetic induction intensity.

[0088] At present, there are three contradictory technical requirements when rolling the ultra-thin and hard and brittle silicon steel strip:

[0089] Small roll diameter requirement: In order to reduce the rolling deformation resistance and contact arc length, and realize the rolling of ultra-thin specifications, it is necessary to use a very small diameter (such as 80mm) work roll.

[0090] High stiffness requirement: The rolling of ultra-thin silicon steel requires huge rolling force, and the small diameter work roll is prone to deflection, vibration and flattening under high pressure, and must be supported by a high stiffness roll system to ensure the shape and thickness accuracy.

[0091] Large opening requirement: Due to the hard and brittle characteristics of silicon steel, "strip breaking" is prone to occur during rolling, and after breaking, it is scattered in the form of fragments. At the same time, it is difficult to pass through the small roll diameter. Therefore, the rolling mill must have a large enough opening to facilitate the threading operation and thoroughly clean the broken strip residues, otherwise the remaining debris will damage the expensive bearings and other components.

[0092] The dilemma of the prior art is that the traditional six-high rolling mill cannot meet the requirements of small roll diameter and high stiffness, and the Sendzimir type multi-roll rolling mill (tower-shaped roll system) which can meet the requirements of small roll diameter and high stiffness has a compact structure and a very small inherent opening, which cannot meet the requirements of ultra-thin silicon steel strip breaking and large space threading. In other words, under the framework of the prior art, the three goals of "small roll diameter", "high stiffness" and "large opening" are mutually exclusive and difficult to achieve.

[0093] The cold rolling production system of the ultra-thin silicon steel realizes the above three contradictory goals through the collaborative configuration of "tower-shaped roll system" and "servo oil cylinder driven lower roll system lifting".

[0094] The "tower-shaped roll system" mainly solves the contradiction between "small roll diameter" and "high stiffness". The multi-layer support structure ensures the vertical and horizontal stability of the small diameter work roll when bearing huge rolling force, and the roll system stiffness is increased to 5 times of the same specification six-high rolling mill.

[0095] The "overall lifting of the lower roller system driven by servo oil cylinders" mainly solves the contradiction between "high rigidity and compact structure" and "large opening degree". By lifting the entire lower tower-shaped roller system as a rigid unit by servo oil cylinders, a huge opening degree (up to 90mm) far exceeding that of traditional Sendzimir rolling mills (e.g. up to 12 times) is achieved without damaging the internal precision structure of the tower-shaped roller system.

[0096] What is particularly critical is that the combination of these two features produces a synergistic effect:

[0097] It is precisely because the tower-shaped roller system itself is a high-rigidity whole that it can be stably and accurately lifted as a whole unit by servo oil cylinders. If the rigidity of the roller system is insufficient, overall lifting will cause the roller system to deform, which cannot guarantee the rolling precision.

[0098] On the other hand, the precise and stable large-stroke lifting provided by the servo oil cylinders enables this high-rigidity tower-shaped roller system to have unprecedented process flexibility, enabling it to handle both high-precision ultra-thin rolling and quickly switch to a maintenance-friendly accident handling mode.

[0099] This synergistic effect enables the ultra-thin silicon steel cold rolling production system to combine the high-rigidity advantage of Sendzimir rolling mills and the large-opening advantage of six-high rolling mills, successfully breaking through the minimum rollable thickness limit of ultra-thin silicon steel, and solving the industry problem of strip breakage handling, which cannot be achieved by any single type of rolling mill.

[0100] In detail, please refer to Figure 2 , the ultra-thin silicon steel cold rolling production system includes a housing A and a tower-shaped roller system.

[0101] The tower-shaped roller system is composed of an upper roller system B and a lower roller system C. The upper roller system B and the lower roller system C are both installed in the housing A, and both are tower-shaped roller systems. The structure of the upper roller system B and the lower roller system C is basically symmetrical, and the arrangement of the tower-shaped roller system greatly improves the overall rigidity, so that the device can still maintain a very small spring value when subjected to a large rolling pressure, and the arrangement can make the work roll diameter smaller.

[0102] Please continue to refer to Figure 2 , the upper roller system B and the lower roller system C are both composed of ten rollers, which are arranged in a tower shape. The innermost circle is the work roll for contacting the ultra-thin silicon steel strip, and the outermost circle is the backup roll.

[0103] Among them, the diameter of the work roll is 79-81mm to reduce the contact arc length of the work roll in the rolling deformation.

[0104] In some embodiments, the diameter of the work roll is 80 mm, or about 80 mm, and the size of the work roll in direct contact with the very thin silicon steel strip is set to be about 80 mm. A smaller diameter can make the contact arc length of the roll in the rolling deformation smaller and greatly reduce the deformation resistance required for strip thinning.

[0105] Small work roll diameter and large roll system stiffness are one of the decisive factors to break through the thickness limit of silicon steel. In the present embodiment, the arrangement of the tower-shaped roll system meets the small roll diameter required for rolling very thin silicon steel strip and ensures the overall roll system stiffness.

[0106] The roll system stiffness of the present embodiment is about 5 times that of a six-high rolling mill of the same specification. The small work roll diameter can reduce the elastic flattening of the corresponding roll under huge rolling pressure. The tower-shaped arrangement of the upper roll system B and the lower roll system C can improve the vertical stability of the work roll in direct contact with the strip, and can prevent the lateral movement of the work roll when using a large tension rolling process. In addition, this arrangement can transmit the lateral force and vertical force to the corresponding equipment in a dispersed manner. This arrangement solves the contradiction between small work roll diameter and large roll system stiffness, and provides a device foundation for successfully breaking through the minimum rollable thickness of silicon steel.

[0107] The support roll at least includes a core shaft, and a plurality of thick wall bearings are sleeved on the core shaft. Specifically, the core shaft is a stringing of a plurality of thick wall bearings, and the outer ring of the thick wall bearing directly serves as the support roll, as shown in Figure 5 The reason for adopting this arrangement is that the width of a single thick wall bearing is not large, so the stiffness is relatively large.

[0108] The outermost circle of the ten rolling rolls is four support rolls, and the four support rolls are arranged in a fan shape with the center of the fan pointing to the work roll. Each support roll at least includes a core shaft, and a plurality of thick wall bearings are sleeved on the core shaft. The four support rolls arranged in a fan shape are composed of two intermediate support rolls and two side support rolls. The number of thick wall bearings on the two intermediate support rolls is the same, the number of thick wall bearings on the two side support rolls is the same, and the number of thick wall bearings on the side support roll is one more than the number of thick wall bearings on the intermediate support roll. The number of thick wall bearings on the side support roll is different from the number of thick wall bearings on the intermediate support roll mainly to prevent the gap between adjacent thick wall bearings from being indirectly transmitted to the strip surface and leaving a mark. The arrangement can be seen from Figure 5 , Figure 5 It is shown that the gaps of the thick wall bearings of the intermediate support roll (for example, B3) and the side support roll (for example, B4) in the same roll system (the upper roll system B or the lower roll system C) are staggered, that is, the gap between the two adjacent thick wall bearings on the intermediate support roll B3 is directly opposite the outer surface of the thick wall bearing of the side support roll B4.

[0109] In the present embodiment, the diameter of the work roll is 80 mm, or about 80 mm, and the size of the work roll in direct contact with the very thin silicon steel strip is set to be about 80 mm. A smaller diameter can make the contact arc length of the roll in the rolling deformation smaller and greatly reduce the deformation resistance required for strip thinning. Figure 4The outermost circle of the upper roller system B is taken as an example, the four supporting rollers are numbered as B1-B4 in clockwise direction, wherein the number of the thick-wall bearings of the middle supporting rollers B2 and B3 is the same, and is a positive integer n, such as Figure 5 In the example shown in FIG. 6, the number of the thick-wall bearings of the middle supporting rollers B2 and B3 is 8, i.e. n=8, and the number of the thick-wall bearings of the side supporting rollers B1 and B4 is the same, and is a positive integer n-1 or n+1, such as Figure 5 In the example shown in FIG. 6, the number of the thick-wall bearings of the middle supporting rollers B2 and B3 is 8, i.e. n=8, and the number of the thick-wall bearings of the side supporting rollers B1 and B4 is the same, and is a positive integer n-1 or n+1, such as

[0110] In the example shown in FIG. 6, the number of the thick-wall bearings of the middle supporting rollers B2 and B3 is 8, i.e. n=8, and the number of the thick-wall bearings of the side supporting rollers B1 and B4 is the same, and is a positive integer n-1 or n+1, such as Figure 4 The lower roller system C is taken as an example, the four supporting rollers of the outermost circle are numbered as C1-C4 in counterclockwise direction, wherein the number of the thick-wall bearings of the middle supporting rollers C2 and C3 is the same, and is a positive integer m, such as Figure 5 In the example shown in FIG. 7, the number of the thick-wall bearings of the middle supporting rollers C2 and C3 is 7, i.e. m=7, and the number of the thick-wall bearings of the side supporting rollers C1 and C4 is the same, and is a positive integer m+1 or m-1, such as Figure 5 In the example shown in FIG. 7, the number of the thick-wall bearings of the middle supporting rollers C2 and C3 is 7, i.e. m=7, and the number of the thick-wall bearings of the side supporting rollers C1 and C4 is the same, and is a positive integer m+1 or m-1, such as

[0111] It is worth mentioning that m=n, or m-n=±1.

[0112] That is, in order to prevent the gap of adjacent thick-wall bearings from being indirectly transmitted to the strip surface and leaving a mark, in the present embodiment, it is required that the number of the thick-wall bearings of the middle supporting rollers of the same roller system differs from the number of the thick-wall bearings of the side supporting rollers by one.

[0113] In order to further solve the problem of strip marking, in the present embodiment, two kinds of roller system configurations will be provided according to the width of the strip, since the plate shape problem of wide strip is more prominent, therefore, the upper and lower asymmetric roller system configuration is more adopted for wider strip, and the upper and lower symmetric roller system configuration is more adopted for narrower strip. Here, the wide strip and the narrow strip are relative, without specific numerical requirements.

[0114] Asymmetric roll system configuration, specifically refers to: the number of intermediate support roll thick wall bearings of the upper roll system and the lower roll system is not the same (that is, m-n=±1), for example, the number of intermediate support roll thick wall bearings of the upper roll system is 8, the number of two side support roll thick wall bearings of the upper roll system is 7, the number of intermediate support roll thick wall bearings of the lower roll system is 7, and the number of two side support roll thick wall bearings of the lower roll system is 8, in this example, B2=B3=C1=C4=8, here B2, B3, C1, C4 refers to the number of thick wall bearings on the corresponding support roll, B1=B4=C2=C3=7, here B1, B4, C2, C3 refers to the number of thick wall bearings on the corresponding support roll. That is, the number of thick wall bearings on the intermediate support roll B2, the intermediate support roll B3, the side support roll C1 and the side support roll C4 is 8, and the number of thick wall bearings on the side support roll B1, the side support roll B4, the intermediate support roll C2 and the intermediate support roll C3 is 7.

[0115] Symmetric roll system configuration, specifically refers to: the number of intermediate support roll thick wall bearings of the upper roll system and the lower roll system is the same (that is, m=n), and the number of intermediate support roll thick wall bearings is one more or one less than the number of two side support roll thick wall bearings, for example, the number of intermediate support roll thick wall bearings of the upper roll system and the lower roll system is 8 (that is, B2=B3=C2=C3=8, here B2, B3, C2, C3 refers to the number of thick wall bearings on the corresponding support roll), and the number of two side support roll thick wall bearings of the same roll system is 7 or 9 (that is, B1=B4=C1=C4=7, or B1=B4=C1=C4=9, or B1=B4=7 and C1=C4=9, or B1=B4=9 and C1=C4=7, here B1, B4, C1, C4 refers to the number of thick wall bearings on the corresponding support roll).

[0116] It needs to be specially pointed out that considering the different space required by different width strips, the present embodiment proposes a thick wall bearing configuration scheme from another angle: the upper roll system and the lower roll system can adopt the same or different thick wall bearing configuration scheme.

[0117] The same thick wall bearing configuration scheme refers to: the number of intermediate thick wall bearings of the upper roll system = the number of intermediate support roll thick wall bearings of the lower roll system, and the number of side support roll thick wall bearings of the upper roll system = the number of side support roll thick wall bearings of the lower roll system; while the different thick wall bearing configuration scheme contains asymmetric roll system configuration, and also contains the number of intermediate thick wall bearings of the upper roll system = the number of intermediate support roll thick wall bearings of the lower roll system, and the number of side support roll thick wall bearings of the upper roll system and the number of side support roll thick wall bearings of the lower roll system are not the same, for example, the number of intermediate thick wall bearings of the upper roll system = the number of intermediate support roll thick wall bearings of the lower roll system = 8, but the number of side support roll thick wall bearings of the upper roll system is 7, and the number of side support roll thick wall bearings of the lower roll system is 9.

[0118] Due to the large equipment space corresponding to the wide strip, space can be provided for asymmetric roll system configuration, so different thick wall bearing configuration schemes can be adopted.

[0119] The number of thick wall bearings of the middle support roll of the same roll system differs by one from the number of thick wall bearings of the two side support rolls. Such arrangement can ensure the stability of the equipment along the transverse and vertical directions to ensure the continuous rolling, while compensating for the influence of the axial discrete area between the thick wall bearings on the strip, weakening the strip stress distribution along the width direction, and improving the flatness and microstructure performance.

[0120] The ultra-thin silicon steel cold rolling production system also includes a servo oil cylinder D, please refer to Figure 2 Or Figure 3 The servo oil cylinder D is arranged below the lower roll system C, and the servo oil cylinder D controls the overall lifting of the lower roll system C to change the rolling mill opening, which is suitable for the strip rolling and strip breaking treatment and residue cleaning of the ultra-thin silicon steel.

[0121] That is, the overall lifting of the lower roll system C is driven by the servo oil cylinder D, and the lifting distance directly affects the roll gap size and product thickness, and the guide precision is ensured by the operation side rack 1 and the transmission side rack 2.

[0122] The overall lifting of the lower roll system C driven by the servo oil cylinder D meets the requirements of large opening for strip threading and maintenance, so that the rolling mill opening in the embodiment can reach 90mm, which is about 12 times of the same specification of the Sun Kim mill, and the large opening arrangement can provide convenience for the threading of thin silicon steel. This arrangement specifically solves the problems of strip breaking and cleaning of hard and brittle silicon steel, and cooperates with the large internal space to conveniently clean the broken strip residues in the form of fragments, and avoids the bearing burning problem caused by incomplete residue cleaning.

[0123] The upper roll system B can be lifted as a whole, and has ten built-in rollers, of which the upper work roll has a diameter of about 80mm.

[0124] During rolling production, the upper roll system B is in a locked state, and during non-rolling production, the lifting height of the upper roll system B is adjusted to keep the rolling line at a preset position, wherein the non-rolling production includes roll replacement, roll line calibration or regrinding.

[0125] That is, the upper roll system B is in a locked state during normal production, and is adjusted only during roll replacement, roll line calibration or regrinding to keep the rolling line at a fixed position.

[0126] Please refer to Figure 3The frame A of the cold rolling production system of the ultra-thin silicon steel at least comprises an operation side rack 1 and a transmission side rack 2, and the operation side rack 1 and the transmission side rack 2 are both made of cast steel. The operation side rack 1 and the transmission side rack 2 made of cast steel are main bearing units of rolling pressure.

[0127] Please continue to refer to Figure 3 The frame A further comprises two cross beams, i.e., an upper cross beam 3 and a lower cross beam 4, which are installed between the operation side rack 1 and the transmission side rack 2. The frame A is assembled by the two racks and the two cross beams to reduce the machining difficulty and manufacturing cycle of a single part and provide convenience for inspection and detection.

[0128] The extension and retraction amount of the servo oil cylinder D can make the lower roller system C be in an inclined state along the operation side or the transmission side to eliminate the wedge-shaped plate shape and control the same plate difference of the first strip within the range of ±3µm. The operation side is the side where the operation side rack 1 is located, and the transmission side is the side where the transmission side rack 2 is located. The ultra-thin silicon steel refers to the target strip which is flat and does not have a wedge-shaped plate shape.

[0129] Specifically, the servo oil cylinder D is located in the operation side rack 1 and the transmission side rack 2, and the position control precision of the servo oil cylinder D is ±0.5µm. The servo oil cylinder D is a core component of the thickness control system, and its response speed, precision and synchronicity have a direct impact on the roll gap, thus directly determining the thickness difference and quality of the product. Through the control of the extension and retraction amount of the servo oil cylinder D, the lower roller system C can be in an inclined state along the operation side or the transmission side, which can effectively control the wedge-shaped plate shape and greatly improve the same plate difference, thereby directly affecting the key indicators such as the lamination coefficient of the silicon steel product.

[0130] The present application has researched the whole process that may affect the quality of silicon steel, and then proposed an ultra-thin silicon steel cold rolling method, which is divided into a material preparation stage and a cold rolling stage. Quantitative analysis of many process parameters in the five links of smelting, casting, hot rolling, normalizing and pickling in the material preparation stage is completed, which provides a basis for the protection of product quality. In the cold rolling stage, through the research and development of large tension rolling process and the precise control of oil temperature and oil quantity, the minimum rollable thickness limit is broken through, and the high same plate difference requirement is realized.

[0131] According to the process characteristics of the above-mentioned ultra-thin silicon steel cold rolling method, an ultra-thin silicon steel cold rolling system with large opening degree and high roller system stiffness is developed. The arrangement of the tower-shaped roller system not only meets the small roller diameter required for rolling the ultra-thin silicon steel strip, but also ensures the overall roller system stiffness. The overall lifting of the lower roller system driven by the servo oil cylinder meets the requirement of large opening degree in the conditions of threading and maintenance, and the large internal space greatly facilitates the treatment of accidents such as strip breakage.

[0132] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the present application, and various changes can be made in form and details in practical application without departing from the spirit and scope of the present application.

Claims

1. A method for cold rolling of extra thin silicon steel, characterized by, Comprise: Step 100, preparation stage; Obtain raw materials, process the raw materials according to the steps of smelting, casting, hot rolling, normalizing, pickling to obtain the first strip; Step 200, cold rolling stage; In the cold rolling stage, the reduction, lubrication parameters, tensile stress and plate difference are adjusted to thin the first strip, and the plate difference of the thinned first strip is controlled within ±3µm to obtain the target strip, comprising the following steps: Keep the reduction rate above 85% to generate a large amount of deformation heat; Control the temperature of the lubricating medium to 55 degrees Celsius, and the amount of lubricating oil to 12000ml / min, so as to maximize the reduction of the heat of the first strip taken away by the lubricating medium with the lubrication scheme of high oil temperature and low oil amount; Adjust the tensile stress of the first strip to 40% of the current pass yield limit; Introduce the first strip into the ultra-thin silicon steel cold rolling production system, use the ultra-thin silicon steel cold rolling production system to eliminate the wedge-shaped plate shape and control the plate difference of the thinned first strip within ±3µm to obtain the target strip.

2. The method of cold rolling an extra thin silicon steel as claimed in claim 1, wherein, The smelting step comprises: in the smelting link, controlling the mass fraction of silicon element in the raw material to be 3.4%-3.6% to reduce the iron loss and maintain the ferromagnetic properties to prepare the casting blank.

3. The method of cold rolling an extra thin silicon steel as claimed in claim 2, wherein, The casting step comprises: using continuous casting process to slow cool and keep the casting blank to prevent the generation of invisible cracks and coarse grains.

4. The method of cold rolling an extra thin silicon steel as claimed in claim 3, wherein, The hot rolling step comprises: Adjusting the heating temperature to 1250-1350 degrees Celsius to control the solid solution degree of the inhibitor in the casting blank; Adjusting the finishing temperature to 850-950 degrees Celsius to control the precipitation of the inhibitor in the casting blank; Adjusting the coiling temperature to 550-650 degrees Celsius to control the generation of iron oxide scale.

5. The method of cold rolling an extra thin silicon steel as claimed in claim 4, wherein, The normalizing step comprises: controlling the normalizing temperature to 1000-1100 degrees Celsius, the holding time to 2-3 minutes, and the water spray rapid cooling to improve the magnetism and reduce the iron loss to prepare the hot rolled strip.

6. The method of cold rolling an extra thin silicon steel of claim 5, wherein, The pickling step comprises a shot blasting pretreatment link and an official pickling link; In the shot blasting pretreatment link, the shot blasting flow is 800-1000kg / min, the shot blasting particles are 1.0mm steel particles, and the shot blasting is used to remove the iron oxide scale on the surface of the hot rolled strip; In the official pickling link, hydrochloric acid is selected as the acid solution, the mass fraction of hydrochloric acid in the acid solution is 3%, and the pickling temperature is 75 degrees Celsius to prepare the first strip.

7. The method of cold rolling of an extra thin silicon steel as claimed in claim 1, wherein, The ultra-thin silicon steel cold rolling production system comprises: A housing (A); A tower-shaped roller system composed of an upper roller system (B) and a lower roller system (C), both of which are installed in the housing (A); A servo oil cylinder (D) arranged below the lower roller system (C), which controls the overall lifting of the lower roller system (C) to change the rolling mill opening, which is suitable for the strip rolling and strip breaking treatment of ultra-thin silicon steel and residue cleaning.

8. The method of cold rolling an extra thin silicon steel of claim 7, wherein, Both the upper roller system (B) and the lower roller system (C) are composed of ten rollers; The ten rollers are arranged in a tower shape, with the innermost circle being the working roller and the outermost circle being the support roller; The support roller is four; The four support rollers are arranged in a fan shape, with the fan center pointing to the working roller; Each of the support rollers comprises at least a mandrel, on which a plurality of thick-wall bearings are sleeved; The four support rollers arranged in a fan shape are composed of two middle support rollers and two side support rollers, the number of thick-wall bearings on the two middle support rollers is the same, the number of thick-wall bearings on the two side support rollers is the same, and the number of thick-wall bearings on the side support rollers is one more than that on the middle support rollers.

9. The method of cold rolling an extra thin silicon steel of claim 7, wherein, The upper roller system (B) can be lifted as a whole; During rolling production, the upper roller system (B) is in a locked state; During non-rolling production, the lifting height of the upper roller system (B) is adjusted to keep the rolling line at a preset position, wherein the non-rolling production includes roll replacement, roll line calibration or regrinding; The housing (A) comprises at least an operation side rack (1) and a transmission side rack (2); The extension and retraction amount of the servo oil cylinder (D) can make the lower roller system (C) be in an inclined state along the operation side or the transmission side, so as to eliminate the wedge-shaped plate shape and control the same plate difference of the first strip within the range of ±3µm; Wherein, the operation side is the side where the operation side rack (1) is located, and the transmission side is the side where the transmission side rack (2) is located.

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