Forming and Annealing Parameters for Moly and Its Alloys
Industrial molybdenum rolling presents unusually complex challenges, especially in comparison with the rolling of non-ferrous metals such as aluminum, copper, zinc, and titanium. This complexity is largely due to Molybdenum’s unique properties, including high, hot working temperatures; increased susceptibility to oxidation at elevated temperatures; pronounced low-temperature brittleness; swift thermal conductivity; substantial tensile strength which increases as temperature decreases; and a consistent reduction in ductile-to-brittle transition temperature (DBTT).
Molybdenum rolling, especially into molybdenum sheets, is an intricate process requiring exceptional knowledge and meticulous attention to detail. Beginning as an initial slab or billet, moly or its alloyed metal must undergo several operations to attain a prescribed gauge. These include pre-form rolling; hot, warm, and cold rolling; intermediate and final annealing; and surface descaling. Highly skilled mill operators adjust moly’s process parameters—total and pass deformations and rolling directions and rolling and annealing temperatures—to meet exacting customer specifications.
Formation in molybdenum rolling
The pre-form rolling stage is the beginning of plastic deformation and work hardening of the workpiece under the rolling force. It then undergoes molybdenum hot and warm rolling stages, each of which typically involves multiple passes, and each triggering strain hardening, which is in turn counterbalanced by concurrent recrystallization softening. These two simultaneous, countervailing mechanisms, known as “dynamic recovery” and “dynamic recrystallization,” are pivotal to the successful molybdenum rolling process.
Annealing in molybdenum rolling
Following the hot and warm rolling stages, the workpiece undergoes heat retention, cold rolling, annealing, and quenching treatments. Static recovery and recrystallization predominantly take place during the cold rolling stage of molybdenum rolling. These processes help to reduce dislocation density and stored energy within the metal(s) that has increased due to deformation.
Molybdenum rolling’s finished components or workpieces, often destined for subsequent operations such as drawing, stamping, and other forming processes, demand careful planning and management of process parameters at every stage. This attention to detail is pivotal in determining the intrinsic quality, mechanical properties, and potential applications of the sheet material. The knowledge and expertise required to meet the unique challenges of molybdenum rolling are essential to producing high-quality components with this unique metal and its various alloys.