Nucor has filed a patent for a method of manufacturing electrical steel. The process involves hot rolling a steel slab into a sheet, annealing the sheet, and cold rolling it. The sheet is then stamped into a part and annealed again. The method aims to produce electrical steel with similar or better magnetic properties compared to traditional processing methods. The stamped part has specific composition requirements and must meet certain permeability and core loss criteria. GlobalData’s report on Nucor gives a 360-degree view of the company including its patenting strategy. Buy the report here.
According to GlobalData’s company profile on Nucor, Structure Building Framework was a key innovation area identified from patents. Nucor's grant share as of September 2023 was 55%. Grant share is based on the ratio of number of grants to total number of patents.
Method of manufacturing electrical steel without intermediate annealing steps
A recently filed patent (Publication Number: US20230290549A1) describes a method for manufacturing electrical steel with improved properties. The method involves several steps, including hot rolling, annealing, cold rolling, stamping, and annealing again.
In the method, a steel slab is hot rolled into a steel sheet, which is then annealed in a batch annealing process at a temperature of 1550 degrees Fahrenheit or higher. After annealing, the steel sheet undergoes cold rolling. The steel sheet is then stamped into a stamped part, and without any intermediate annealing process, it is annealed again after stamping. The annealing after stamping is performed at a temperature of 1550 degrees Fahrenheit or higher.
The stamped part, when annealed at a temperature of 1550 degrees Fahrenheit or higher, has specific composition requirements. It must contain silicon (Si) equal to or greater than 2.0% weight, aluminum (Al) in the range of 0.15-1% weight, manganese (Mn) in the range of 0.005-1% weight, carbon (C) less than or equal to 0.04% weight, and antimony (Sb) or tin (Sn) less than or equal to 0.1% weight. The remaining composition of the stamped part consists of unavoidable impurities and iron.
The stamped part manufactured using this method exhibits desirable properties. It has a permeability greater than or equal to 1400 G/Oe and a core loss less than or equal to 1.8 W/lb in all directions.
Additional steps can be performed in the method, such as tension leveling, coating, or rough rolling on the steel sheet after cold rolling and before stamping and annealing after stamping. Pickling of the steel sheet can also be done after hot rolling and before annealing after hot rolling.
The patent also provides variations in the method, such as different post hot rolling annealing temperatures (greater than or equal to 1700 degrees Fahrenheit) and post stamping annealing temperatures (greater than or equal to 1700 degrees Fahrenheit). The silicon content in the stamped part can also be increased to 2.2%, 2.6%, or 3.0% weight.
Overall, this patent presents a method for manufacturing electrical steel with improved properties, offering potential benefits in various applications that require high permeability and low core loss.