Differences Between Cold Rolling And Hot Rolling in Processing Techniques

Hot rolling and cold rolling of nickel-based alloys are two important rolling processes, both serving their plastic processing. They differ significantly in terms of process and product characteristics, and their functions are complementary.

Hot rolling is performed above the recrystallization temperature (1000-1200°C). Using cast billets or forged billets as raw materials, it undergoes processes such as homogenizing annealing, heating, multi-pass rolling (with a single pass reduction of 10%-30% and a speed of 1-5 m/s), rapid cooling, and descaling. Its purpose is to eliminate casting defects, refine grains, and roll the billets into thicker products (≥3mm) such as medium and heavy plates and strip billets. It has the advantages of enabling large deformation and improving the mechanical properties of the alloy. However, it has poor surface quality and dimensional accuracy (with a tolerance of ±0.5mm) and low cost, making it suitable for scenarios such as thick-walled tube billets of nuclear power plant steam generators.

Cold rolling is carried out below the recrystallization temperature (room temperature - 200°C). Using hot-rolled strips or thin plates as billets, after surface treatment, it undergoes multi-pass rolling (with a single pass reduction of 5%-20%, requiring multiple intermediate annealings to restore plasticity), followed by finish rolling, straightening, and possible final heat treatment. Its aim is to reduce thickness, improve dimensional accuracy (with a tolerance up to ±0.005mm) and surface quality, and enhance strength through work hardening. It can produce thin plates and ultra-thin strips (≤3mm). With high cost, it is suitable for precision components such as high-temperature gaskets of aero-engines.