Cobalt & Nickel Annealing Process
Wed March 17, 2021
In mission critical applications such as high frequency and high rpm motors for aerospace, engineers are specifying annealed cobalt iron and nickel iron alloys for motor laminations to achieve increased performance and higher efficiencies. The raw materials on their own don’t have the ideal electrical properties until they’re heat treated and insulated.
Annealing is a heat treating process that results in improved magnetic properties, especially for high frequency applications. Once a lamination is stamped or laser cut, it loses some of its magnetic properties from the stress of the production process. Annealing gets the part back to its optimal magnetic or mechanical state.
Laser Technologies' NADCAP Certified annealing process is tailored to meet the customers desired mechanical and electrical specifications. We implement the use of batch annealing furnaces that operate with inert gas, typically hydrogen. The box furnace is sealed, all the air is replaced with hydrogen, once the oxygen is removed, the parts undergo the heat treat process tailored to a specific receipt implementing time and temperature conditions. Special considerations need to be implemented in lamination design and fixturing when tolerances are critical to offset any thermal expansion that will occur at high temperatures. All conditions are monitored and recorded to assure the integrity of the annealing cycle was properly achieved. Typically parts undergo the annealing process for 24-36 hours. However, some customers provide specific instructions on the amount of time and temperature, and inert gas they want to process the parts at.
After the annealing process, a secondary operation is sometimes required to insulate the parts and minimize eddy current loss. This could involve creating an oxide layer on the surface of the lamination or physically coating the parts with a thin insulator such as C-5 coating. The oxide coating insulation involves a secondary annealing process at a lower temperature in an air atmosphere to develop an oxide layer film coating on the surface of the parts. The alternative way to insulate the surface of parts incorporates roll coating a C5 insulation at a controlled thickness over both surfaces of lamination, then curing the insulation at a low temperature for a specific period of time.