Grain-Oriented Silicon Steel Single Cold Rolling Process
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Solution Overview
Problem
High-temperature grain-oriented silicon steel production faces issues such as high energy consumption, severe edge cracking, and high production costs due to the need for special-purpose furnaces and complex processes, while low-temperature methods struggle with controlling crystal grain growth and nitridation stability.
Innovation Solution
A method involving single cold rolling with controlled normalization and cooling processes to form (Al, Si)N inclusions, utilizing nitrogen absorption during decarburizing annealing and low-temperature holding, which refrains primary recrystallization and facilitates stable secondary recrystallization, eliminating the need for ammonia nitridation and optimizing crystal texture and inhibitor formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature heating (1400°C) is used to solid dissolve inclusions and form inhibitors, then the magnetism and orientation of grain-oriented silicon steel are improved, but energy consumption increases and heating furnace utility decreases
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature (1400°C) heating to low-temperature (900-1100°C) heating combined with controlled cooling. This parameter change allows the formation of favorable inclusions and inhibitors without requiring excessive energy input, thus resolving the contradiction between achieving good magnetism/orientation and reducing energy consumption
Solution Approach 2:
The patent performs preliminary action by controlling the cooling process after hot rolling to precipitate favorable inclusions (Al, Si)N and inhibitors before the annealing stage. This preliminary formation of inhibitors eliminates the need for high-temperature heating to dissolve inclusions, thereby reducing energy consumption while maintaining the required magnetism and orientation properties
2Manufacturing precision
If high-temperature heating (1400°C) is used to form inhibitors, then the microstructure and texture control is improved, but the heating furnace requires frequent repair and production practicality deteriorates
Solution Approach 1:
The patent changes the heating temperature parameter to a lower range (900-1100°C) that is within the capability of ordinary heating furnaces, eliminating the need for special-purpose high-temperature furnaces. This makes the production process more practical and easier to manufacture while still achieving precise control of microstructure and texture through controlled cooling and annealing
Solution Approach 2:
The patent replaces expensive, specialized high-temperature heating furnaces with ordinary, readily available heating furnaces. This substitution of equipment reduces capital investment and maintenance costs, improving production practicality while achieving the same microstructure control through process optimization
3Reliability
If high-temperature heating is used, then inhibitor formation is improved, but burning loss increases and production cost rises
Solution Approach 1:
The patent changes the temperature parameter from high (1400°C) to low (900-1100°C) heating, which significantly reduces burning loss and energy consumption. The inhibitor formation is maintained through controlled cooling that precipitates favorable inclusions, achieving the same reliability in inhibitor formation with much lower energy loss
4Stability of the object's composition
If high-temperature heating is used, then inclusions are solid dissolved, but severe edge cracking occurs and cold rolling becomes difficult
Solution Approach 1:
The patent changes the heating temperature to a lower range (900-1100°C) that avoids the edge cracking problem associated with high-temperature heating. The inclusion distribution is controlled through the cooling process rather than high-temperature dissolution, maintaining compositional stability while improving edge strength and cold rolling performance
5Reliability
If conventional high-temperature process is used, then grain-oriented silicon steel with high orientation is produced, but the process is complicated and technicality is high
Solution Approach 1:
The patent changes the temperature parameter to a lower, more controllable range and shifts the control mechanism from high-temperature dissolution to controlled cooling precipitation. This simplifies the production process and reduces technical complexity while maintaining high orientation through the optimized cooling and annealing parameters
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces energy consumption and production costs, enhances production flexibility, and ensures stable magnetism and a good glass film underlying layer, overcoming the limitations of high-temperature methods and improving the quality of grain-oriented silicon steel.
Implementation Method 1
utilizing nitrogen absorption by slab during decarburizing annealing and low-temperature holding of high-temperature annealing
Implementation Method 2
The inclusions function to refrain primarily recrystallized grains, and thus the primary recrystallization microstructure of steel sheet is controlled effectively
Implementation Method 3
the sheet is decarburizing annealed to lower [C] in the steel sheet to a level not influencing the magnetism of the final product
Implementation Method 4
the sheet is decarburizing annealed and high-temperature annealed, during which nitridation is carried out once secondary recrystallization begins
Implementation Method 5
physical and chemical changes such as secondary recrystallization, formation of Mg 2 SiO 4 underlying layer
Data Source
Figure 1~2
Figure 3
AI summary
The invention provides a method for producing grain-oriented silicon steel with single cold rolling, comprising: 1) smelting, refining and continuous casting to obtain a casting blank; 2) hot rolling; 3) normalization, i.e, normalizing annealing and cooling; 4) cold-rolling, i.e. single cold rolling at a cold rolling reduction rate of 75-92%; 5) decarburizing annealing at 780-880°C for 80-350s in a protective atmosphere having a due point of 40-80°C, wherein the total oxygen [O] in the surface of the decarburized sheet: 171/t≤ [O]≤ 313/t (t represents the actual thickness of the steel sheet in mm), the amount of absorbed nitrogen: 2-10ppm; 6) high temperature annealing, wherein the dew point of the protective atmosphere: 0-50°C, the temperature holding time at the first stage: 6-30h, the amount of absorbed nitrogen during high-temperature annealing: 10-40ppm; 7) hot-leveling annealing. The invention may control the primary recrystallization microstructure of steel sheet effectively by controlling the normalization process of hot rolled sheet to form sufficient favorable (Al, Si)N inclusions from nitrogen absorbed by slab during decarburizing annealing and low-temperature holding of high-temperature annealing, facilitating the generation of stable, perfect secondary recrystallization microstructure of the final products. In addition, the invention avoids the impact of nitridation using ammonia on the underlying layer in prior art, and thus the formation of a good glass film underlying layer is favored.