Process Differences Between Hot Forging and Cold Forging

Process Differences Between Hot Forging and Cold Forging

Hot forging and cold forging are two core processes in metal forging. Both realize plastic deformation of metals through pressure to optimize the mechanical properties of parts. However, they differ significantly in processing temperature, forming principles, process characteristics and application scenarios. Reasonable process selection according to the working conditions, accuracy and strength requirements of products can effectively improve the quality of forgings and control production costs, serving as a key basis for type selection in industrial forging production.

Processing temperature is the fundamental difference between the two processes. Hot forging is carried out above the metal recrystallization temperature. The blanks are heated to a high temperature in a furnace to weaken the bonding force of internal metal grains, greatly improve metal plasticity and reduce deformation resistance. In contrast, cold forging is completed at room temperature without heating treatment. Metal blanks are directly formed under high equipment pressure with a simpler processing flow and no high-temperature operation.

In terms of process performance and forming effect, hot forging features outstanding plasticity and good metal fluidity. It is suitable for processing large-size, large-deformation and complex-structured heavy forgings, which can completely eliminate internal defects such as pores and shrinkage porosity and refine grain structures to greatly enhance the strength and toughness of forgings. Nevertheless, high-temperature processing easily produces oxide scales, resulting in high surface roughness and relatively ordinary dimensional accuracy, requiring subsequent finishing processes such as polishing and heat treatment.

Benefiting from room-temperature forming, cold forging causes no oxidation loss, delivering forgings with high surface finish and excellent dimensional accuracy. It can realize near-net shaping with minimal machining allowance and effectively save raw materials. Meanwhile, room-temperature processing generates no thermal stress, ensuring high dimensional stability and consistency of products. However, cold forging features high metal deformation resistance and extremely high requirements for equipment pressure, which is only applicable to small, simple-structured and small-deformation precision parts.

The two processes have distinct application scenarios. Hot forging focuses on the processing of heavy-load and high-strength large parts, widely used in core accessories for mining, wind power and heavy machinery. Cold forging is dedicated to the mass production of precision small parts such as automotive fasteners and precision transmission components. With respective advantages, the two processes can be applied reasonably in industrial production to balance the strength, accuracy and production efficiency of forgings and meet the part manufacturing needs of various industries.