Hot Working
Hot working is a metal deformation process performed above the material's recrystallization temperature, allowing plastic flow while new grains form during deformation. This reduces strain hardening, keeps ductility high, and requires less forming force, making it ideal for primary shaping operations like forging, rolling, extrusion, and hot drawing. In CNC manufacturing, hot working is typically upstream of machining, establishing rough form and microstructure before final tolerance work.
In a manufacturing cell, hot working begins by heating a billet, slab, or bar to its specified forming range, then transferring it quickly to a press, mill, or forge before it cools below the workable window. Operators and process engineers watch temperature closely because flow stress changes rapidly with heat; uneven temperature can create scale, inconsistent deformation, or dimensional drift. For CNC shops, the usual workflow is to rough-form hot, allow controlled cooling or heat treatment as required, then machine critical faces, bores, datums, and tolerance features after the material is stable. This sequencing matters because thermal history changes hardness, residual stress, and machinability. Machining after thermal processing prevents distortion caused by later stress relief or hardening shifts. Hot working thus acts as an upstream bulk-shaping step, while CNC operations deliver final accuracy, surface finish, and proof of geometry.
Why is hot working preferred for large shape changes?
Because above recrystallization temperature the metal can keep deforming without accumulating the strain hardening that would otherwise make further forming difficult.
Is hot working the same as heat treatment?
No. Hot working is a forming process; heat treatment is a property-modifying thermal cycle used to alter hardness, strength, ductility, toughness, or residual stress.
Why do precision shops often machine after hot working?
Because final machining after the thermal cycle helps control distortion and allows the shop to hold tighter tolerances on features that would otherwise move as the part cools or is later heat treated.