Stay Updated with WXING's News and Innovations.
In the mass production of standard fasteners such as bolts, flange nuts, and profiled rivets, cold heading and hot heading are the two mainstream plastic forging and forming processes. Distinguished primarily by processing temperature, they differ significantly in forming principle, equipment investment, finished product quality, production cost, and applicable product specifications.
Cold heading is a chipless or low-chip metal pressure working process that leverages the plastic deformation of metal at room temperature, applying force through dies to achieve extrusion, heading, or forming. It is widely used for mass-producing standard fasteners including bolts, nuts, screws, and rivets.
Hot heading is a metal plastic forming process. It heats metal raw materials above the recrystallization temperature, then performs extrusion or forging forming with dies.
|
Comparison Item |
Cold Heading |
Hot Heading |
|
Forming Temperature |
Room temperature (20–25°C), below the recrystallization temperature |
800–1200°C, above the recrystallization temperature |
|
Deformation Resistance |
High resistance, relying on high-rigidity cold heading equipment to apply pressure |
Extremely low resistance; metal softens at high temperature for easy forming |
|
Core Deformation Mechanism |
Plastic deformation via room-temperature extrusion, with inherent work hardening |
Plastic deformation via high-temperature recrystallization, eliminating work hardening |
|
Core Supporting Equipment |
Fully automatic multi-station cold heading machines, precision forming dies |
Heating furnaces, hot forging presses, high-temperature resistant forging dies |
Cold heading applies to materials with good ductility, such as low- and medium-carbon steels, stainless steel, copper, aluminum, and aluminum alloys.
Hot heading can process high-hardness, difficult-to-form materials including titanium alloys, superalloys, high-alloy steels, and heat-resistant steels.
Cold heading is performed at room temperature; a single machine can process hundreds of parts per minute, making it suitable for high-volume, automated assembly line operations.
For hot heading, the workpiece must be heated above the recrystallization temperature; the heating and handling stages increase the processing time per unit, resulting in a production speed significantly lower than that of cold heading.
Cold heading achieves a notably higher material utilization rate than hot heading. The material utilization of the cold heading process generally reaches 80%–90%, while that of hot heading is usually around 50%–70% due to heating, oxidation, and large subsequent machining allowance.
Products manufactured by cold heading feature high dimensional accuracy and smooth surfaces. Hot-headed products have lower accuracy and carry oxide scale on the surface.
1. High dimensional accuracy: easy tolerance control and excellent surface finish.
2. Extremely high production efficiency: strong process continuity, ideal for mass production of standard fasteners.
3. Cost and material saving: chipless or low-chip processing with high comprehensive material utilization.
1. Strict requirements for equipment and dies: high metal deformation resistance subjects dies to extreme stress, which easily causes die wear or even cracking.
2. Limited material processability: only compatible with materials with good plasticity and low deformation resistance (e.g., low carbon steel, medium carbon steel, copper, aluminum).
3. High internal stress: residual stress remains inside the formed product, which sometimes requires subsequent stress relief annealing.
1. Low deformation resistance: when heated above the recrystallization temperature, the metal softens and undergoes plastic deformation very easily.
2. Wide application scope: capable of processing large and extra-long workpieces, as well as hard materials that are difficult to deform at room temperature, such as high-strength alloy steel and stainless steel.
3. Longer die service life: softened material greatly reduces the pressure and impact force borne by the die.
4. No work hardening: intact internal metal flow lines make it highly suitable for subsequent heat treatment to eliminate residual stress.
1. Low accuracy and poor surface quality: heating tends to form an oxide scale, resulting in high surface roughness; thermal expansion and contraction also make precise control of dimensional tolerances difficult.
2. High energy consumption and low efficiency: requires supporting heating equipment (such as medium-frequency induction heating furnaces), with slow production rhythm and relatively harsh working environment.
The core equipment of the cold heading process is the cold heading machine, a dedicated device designed for mass production of fasteners such as nuts and bolts. It works by using coiled wire or straight bar stock to produce bolts with various head types and mechanical parts through multiple heading operations.
Cold heading machines have evolved from single-stroke to double-stroke, and from single-station to multi-station designs. Modern multi-station cold heading machines can perform multiple processes including cutting, pre-heading, forming, and punching on a single machine, realizing highly automated continuous production.
For fastener manufacturers, the selection of cold heading machines directly determines production efficiency, product quality, and cost control capability. A high-performance cold heading machine, matched with precise die design, can deliver high-speed output of hundreds of pieces per minute while ensuring accuracy.
