Oriented Si Steel Decarburization and Surface Quality Control
Solution Overview
Problem
The production of grain-oriented silicon steel at medium temperature faces challenges such as incomplete decarburization, damage to the oxide layer during cold rolling, poor surface quality, and increased iron loss due to the formation of an underlying layer, which affects magnetic domain activity and stamping performance.
Innovation Solution
A method involving secondary refining and continuous casting of molten steel, followed by hot rolling, acid washing, primary cold rolling, and decarburizing annealing in a protective atmosphere to reduce carbon content, with shot blasting and acid washing to remove iron oxides, and high-temperature annealing using a zirconia, alumina, or silicon dioxide separator to prevent glass film formation and ensure a mirror-like surface without an underlying layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If decarburizing annealing is carried out at medium temperature to reduce carbon content, then carbon reduction is achieved, but the oxide layer on the surface is damaged during subsequent cold rolling
Solution Approach 1:
The patent applies preliminary action by forming a protective oxide layer before cold rolling through controlled decarburizing annealing. The oxide layer is formed in advance to protect the surface during subsequent cold rolling operations, preventing surface quality degradation while maintaining the carbon reduction benefit.
Solution Approach 2:
The oxide layer acts as an intermediary protective barrier between the steel substrate and the cold rolling process. This intermediate layer prevents direct contact and potential damage to the surface during rolling, while still allowing the carbon reduction objective to be achieved through the annealing process.
2Reliability
If an underlying layer is formed during high-temperature annealing to ensure tension effect and insulating effect, then magnetic domain activity is improved, but stamping performance deteriorates
Solution Approach 1:
The patent extracts or removes the underlying layer formation process from the high-temperature annealing stage. By eliminating the underlying layer, the patent resolves the conflict between magnetic domain activity and stamping performance, achieving both improved magnetic properties and enhanced stamping performance without the compromising effects of an underlying layer.
Solution Approach 2:
Instead of forming an underlying layer to achieve tension and insulating effects, the patent inverts the approach by creating a mirror-like surface without an underlying layer. This inverted approach achieves the desired tension effect and insulating effect through alternative mechanisms, simultaneously improving both magnetic domain activity and stamping performance.
3Manufacturing precision
If strict control of decarburizing annealing conditions is implemented to form appropriate oxide layer, then surface quality is improved, but production complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the decarburizing annealing conditions to form an appropriate oxide layer through controlled temperature, atmosphere composition, and time parameters. These parameter adjustments enable surface quality improvement while maintaining manageable process control complexity through well-defined processing windows.
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 method enhances decarburization efficiency, improves surface quality, reduces iron loss, and stabilizes magnetic performance, achieving superior electromagnetic properties and cost-effectiveness by eliminating the need for strict control of decarburizing annealing conditions and recovery annealing.
Implementation Method 1
the steel sheet is decarburized and annealed at 840-890°C in a protective atmosphere of wet nitrogen and hydrogen containing ammonia
Implementation Method 2
high-temperature annealing
Implementation Method 3
the steel sheet is subjected to high-temperature annealing
Implementation Method 4
After an oxide layer comprising silicon oxide as the main component is formed on the steel sheet surface
Data Source
AI summary
A method of manufacturing oriented Si steel containing Cu with high electric-magnetic property comprises: hot rolling slab; after first cold rolling, heating it to 800°C or higher temperature and performing intermediate decarburization annealing in a protective atmosphere with PH2O/PH2 of 0.50∼0.88 for 3-8 minutes, to decrease carbon content of the steel plate to less than 30ppm; then peening and acid-pickling to remove oxide of Fe on surface and to control oxygen content to lower than 500ppm; secondary cold rolling to final thickness and coating separation agent in water-slurry form; drying to decrease water content to lower than 1.5%; high-temperature annealing in a protective atmosphere containing hydrogen with oxidation degree (PH2O/PH2) of 0.0001-0.2; finally applying a tension coating and leveling tension annealing.