A method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel

Abstract

The present invention belongs to the field of metallurgy technology, and in particular to a method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel. The production process includes steelmaking-hot rolling-normalizing-cold rolling-annealing. A micro-reduction deformation process is set after the normalizing process. The strip is micro-deformed by micro-reduction with a reduction rate of 0.1% to 1% by utilizing the residual heat of normalization. The strip after micro-deformation is preheated at low temperature and then cold-rolled or directly cold-rolled. When 3.5%≤Si+Als≤4.6%, low-temperature preheating is performed after the micro-reduction deformation process, and the temperature of the low-temperature preheating is 60 to 70°C. The present invention can eliminate the preheating preparation unit in the existing process or reduce the temperature of the preheating unit, reduce energy consumption, and achieve energy saving under the premise of ensuring smooth cold rolling production. At the same time, it optimizes production logistics, reduces production difficulty, and can effectively reduce the comprehensive production cost of the product.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel. Background Art

[0002] To ensure good electromagnetic properties, the total silicon and aluminum content of non-oriented silicon steel used in new energy vehicle drive motors and other low-loss demanding occasions exceeds 3.2% during the composition design process. The higher the grade, the greater the total amount of silicon and aluminum needs to be to further reduce eddy current losses. High silicon and high aluminum increase the brittleness and hardness of the material, resulting in greater difficulties in the cold processing process.

[0003] The fundamental process of rolling deformation is the movement and proliferation of internal dislocations in the steel strip under the forces applied by the rolls. The force required for plastic deformation overcomes the resistance encountered during the generation, proliferation, and movement of dislocations. For the first cold rolling pass, since dislocations are relatively few and stable before rolling begins, rolling at room temperature necessitates greater rolling forces to activate these dislocations, which in turn increases the likelihood of significant stress concentration, leading to brittle fracture and edge cracking. Therefore, to improve the rollability of the material in the first cold rolling pass, a preparation unit is typically installed after normalization and before cold rolling. This unit preheats the steel coil to be rolled, increasing the toughness of the strip and reducing the difficulty of rolling. After preheating, the first rolling pass begins. The heating temperature of the preparation unit is typically above 100°C, and cold rolling production must resume as soon as possible after the preparation unit is removed from the production line.

[0004] Steel used in new energy vehicle drive motors is typically rolled using a 20-high Sendzimir mill. Preheating the strip before rolling can effectively reduce the strip breakage rate. Preheating methods include water bath heating, induction heating, and flame heating. However, all methods share common challenges: They require dedicated space for the equipment; heating requires significant energy input; and continuous production logistics are required. This increases energy costs, reduces production efficiency, and places strain on production logistics, leading to higher overall costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel, making full use of the existing equipment of the normalizing production line, and causing micro-deformation of the strip after normalizing without making major changes, thereby achieving the rollability of the strip and reducing production costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel, the production process includes steelmaking-hot rolling-normalizing-cold rolling-annealing, after the normalizing process, a slight reduction deformation process is provided, the normalizing waste heat is utilized, and a reduction rate of 0.1% to 1% is used to cause slight deformation of the steel strip, and the slightly deformed steel strip is preheated at low temperature and then cold rolled or directly cold rolled.

[0008] The mass fraction of chemical components in the high-silicon and high-aluminum non-oriented silicon steel satisfies: 2.0%≤Si+Als≤4.6%.

[0009] The normalizing process is as follows: the strip steel is heated in a normalizing annealing furnace, and the furnace temperature is controlled at 300-350°C.

[0010] When 3.5%≤Si+Als≤4.6%, low-temperature preheating is performed after the slight reduction deformation process, and the low-temperature preheating temperature is 60-70°C.

[0011] The cold rolling process adopts 5 rolling passes, with the total reduction rate controlled at 75% to 90%, and the reduction rate of each pass decreasing step by step. The reduction rate of the first two passes is 30% to 35%, and the reduction rate of the last three passes is gradually reduced to 5% to 10%. The thickness tolerance is controlled within ±0.02mm, the rolling speed is 100 to 300m / min, the front tension is 10 to 30kN, the rear tension is 5 to 15kN, the cooling water temperature is 20 to 30℃, and spray cooling is adopted.

[0012] The micro-deformation is achieved by applying pressure via a sealing roller at the outlet of the normalizing annealing furnace, or by providing a roller pressing device after the normalizing process.

[0013] Compared with the existing technology, the beneficial effects of the present invention are:

[0014] The present invention utilizes the residual heat of the steel strip after normalizing, and sets a micro-reduction deformation process after normalizing to cause the steel strip to undergo micro-deformation. After micro-reduction deformation, the average grain size of the steel strip is refined from 90 to 120 μm after normalizing to 80 to 110 μm, the grain size distribution is more uniform, and the shape tends to be equiaxed. This helps to improve the plasticity and toughness of the material. The proportion of subgrained structure increases from 5% to 15% after normalizing to 10% to 20%, which makes the deformation coordination of the material better and the rollability significantly improved. At the same time, in this process, the micro-plastic deformation causes the internal dislocations of the steel strip to deviate from the mechanically stable configuration, increases the number of active dislocations and slip cores, and because the amount of plastic deformation is very small, dislocation entanglement has not yet occurred on a large scale, and work hardening can be ignored, which also reduces the brittleness of the steel plate and improves the rollability.

[0015] The present invention can eliminate the preheating preparation unit in the existing process or lower the temperature of the preheating unit, reduce energy consumption, achieve energy saving while ensuring smooth cold rolling production, and at the same time optimize production logistics, reduce production difficulty, and effectively reduce the comprehensive production cost of the product. DETAILED DESCRIPTION

[0016] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein in the specification of the application are for the purpose of describing specific embodiments only and are not intended to limit this application. Mentioning "embodiments" herein means that the specific features, structures or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0017] A method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel, wherein the mass fraction of chemical components in the steel satisfies: 2.0%≤Si+Als≤4.6%.

[0018] The production process includes steelmaking, hot rolling, normalizing, cold rolling, and annealing. The hot-rolled strip is heated in a normalizing annealing furnace, with the exit temperature controlled at 300-350°C. Following the normalizing process, a micro-reduction deformation process is performed. This utilizes the residual heat from normalizing to flatten the dislocations at a small reduction rate, causing micro-deformation of the strip. The reduction rate is controlled at 0.1%-1%, and the strip after micro-deformation is directly cold-rolled.

[0019] When 3.5%≤Si+Als≤4.6%, low-temperature preheating is carried out after the slight reduction deformation process. The low-temperature preheating temperature is 60-70°C, and the preheated strip is cold rolled.

[0020] The cold rolling process utilizes five passes, with a total reduction controlled between 75% and 90%. The reduction decreases gradually with each pass, starting with a higher reduction of approximately 30% to 35% in the first two passes and gradually decreasing to 5% to 10% in the final three passes. This ensures uniform strip deformation and a thickness tolerance within ±0.02mm. The rolling speed ranges from 100 to 300m / min, with a front tension of 10 to 30kN and a rear tension of 5 to 15kN, dynamically adjusted to ensure strip stability and shape. A high-efficiency emulsion is used, with flow and pressure adjusted according to the number of passes and thickness. The cooling water temperature is 20 to 30°C, and spray cooling is employed to ensure uniform strip temperature.

[0021] The outlet temperature of the normalizing annealing furnace is above 300°C. A pressure device is added to the sealing roller at the outlet of the normalizing annealing furnace. The surface roughness index of the sealing roller at the outlet of the normalizing annealing furnace is 0.5-6.0μm. Appropriate surface roughness of the sealing roller can effectively reduce the risk of scratches on the strip when passing through the sealing roller, and at the same time provide sufficient friction to ensure smooth operation of the strip.

[0022] By utilizing the residual heat of the strip after normalization, a certain pressure is applied to the strip, causing it to undergo micro-deformation, with a reduction ratio of 0.1% to 1%. During this process, the tiny plastic deformation causes dislocations within the strip to break away from their mechanically stable configuration, increasing the number of active dislocations and slip cores. At the same time, because the plastic deformation is so small, dislocation entanglement has not yet occurred on a large scale, and work hardening can be ignored, thereby reducing the brittleness of the steel plate and improving its rollability.

[0023] A pair of small hydraulic cylinders are added to the normalizing annealing furnace outlet sealing rollers as pressure devices. If it is difficult to add a pressure device to the normalizing annealing furnace outlet sealing rollers due to the layout of the normalizing unit and other reasons, a pair of leveling roller pressing devices can also be set at any position after the strip is discharged from the furnace to perform micro-deformation control on the strip.

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0025] Example:

[0026] The chemical composition of the steel is shown in Table 1;

[0027] Table 1: Chemical composition (%)

[0028]

[0029] The production process includes steelmaking, hot rolling, normalizing, slight reduction deformation (pressurizing the sealed rollers at the outlet of the normalizing annealing furnace), and cold rolling. The production process is shown in Table 2.

[0030] Table 2: Process parameters

[0031]

[0032] Examples 1 to 4 show that the method of the present invention can eliminate the preheating preparation unit in the existing process or reduce the temperature of the preheating unit, thereby reducing energy consumption. At the same time, the performance of the finished product produced is consistent with the performance of the product output by the process before optimization, thereby reducing the production cost of high-silicon and high-aluminum steel for new energy vehicle drive motors.

[0033] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and basic spirit of the invention, and the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel, the production process comprising steelmaking - hot rolling - normalizing - cold rolling - annealing, characterized in that: After the normalizing process, a slight reduction deformation process is set up, using the residual heat of normalizing with a reduction rate of 0.1% to 1% to cause slight deformation of the strip. The slightly deformed strip is preheated at low temperature and then cold rolled or directly cold rolled.

2. The method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel according to claim 1, characterized in that: The mass fraction of chemical components in the high-silicon and high-aluminum non-oriented silicon steel satisfies: 2.0%≤Si+Als≤4.6%.

3. The method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel according to claim 1, characterized in that: The normalizing process is as follows: the strip steel is heated in a normalizing annealing furnace, and the furnace temperature is controlled at 300-350°C.

4. The method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel according to claim 1, characterized in that: When 3.5%≤Si+Als≤4.6%, after the slight reduction deformation process, low-temperature preheating is carried out, and the temperature of the low-temperature preheating is 60-70℃.

5. The method for reducing the production cost of high-silicon and high-aluminum non-oriented silicon steel according to claim 1, characterized in that: The cold rolling process adopts 5 rolling passes, with the total reduction rate controlled at 75% to 90%, and the reduction rate of each pass decreasing step by step. The reduction rate of the first two passes is 30% to 35%, and the reduction rate of the last three passes is gradually reduced to 5% to 10%. The thickness tolerance is controlled within ±0.02mm, the rolling speed is 100 to 300m / min, the front tension is 10 to 30kN, the rear tension is 5 to 15kN, the cooling water temperature is 20 to 30℃, and spray cooling is adopted.

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