Comparison Between Cold Heading Process and Cold Extrusion Process

Cold heading and cold extrusion are essentially deformation processes under similar conditions, but they differ in their operational methods. Cold heading is a forging deformation process typically used for smaller workpieces and is commonly employed in the fastener industry. In contrast, cold extrusion involves the extrusion deformation of larger workpieces and has a broader range of applications.

Cold extrusion is a processing method in which a metal blank is placed in a cold extrusion die cavity, and at room temperature, a fixed punch on a press applies pressure to the blank, causing plastic deformation of the metal to produce parts. Clearly, cold extrusion relies on dies to control metal flow and involves substantial transfer of metal volume to form parts. In terms of extrusion equipment, China has the capability to design and manufacture extrusion presses of various tonnage levels. In addition to using universal mechanical presses, hydraulic presses, and cold extrusion presses, friction screw presses and high-speed, high-energy equipment have also been successfully employed for cold extrusion production.

If the blank is extruded without heating, the process is called cold extrusion. Cold extrusion is one of the chip-less or minimal-chip machining processes, making it an advanced method in metal plastic processing. If the blank is heated to a temperature below the recrystallization temperature before extrusion, the process is called warm extrusion. Warm extrusion still retains the advantages of minimal or no chip production.

Cold extrusion technology is an advanced production process characterized by high precision, efficiency, quality, and low consumption. It is widely used in the large-scale production of small and medium-sized forged parts. Compared to hot forging and warm forging processes, it can save 30% to 50% in materials and 40% to 80% in energy, while also improving the quality of forged parts and enhancing the working environment.

Currently, cold extrusion technology has found extensive application in industries such as fasteners, machinery, instruments, electrical appliances, light industry, aerospace, shipbuilding, and military manufacturing. It has become an indispensable important processing method in metal plastic volume forming technology. With technological advancements and increasing technical requirements for products in industries such as automobiles, motorcycles, and household appliances, cold extrusion production technology has gradually become the development direction for the refined production of small and medium-sized forged parts.

Cold extrusion can also be classified into forward extrusion, backward extrusion, compound extrusion, and radial extrusion.

Cold heading is one of the new chip-less or minimal-chip metal forming processes. It is a processing method that utilizes the plastic deformation of metal under external force, redistributing and transferring the metal volume with the aid of dies to form the desired parts or blanks. Cold heading is most suitable for producing standard fasteners such as bolts, screws, nuts, rivets, and pins. The equipment commonly used for cold heading is specialized cold heading machines. If the production volume is relatively low, crank presses or friction screw presses can be used as alternatives.

Due to its high productivity, excellent product quality, significant material savings, reduced production costs, and improved working conditions, cold heading is increasingly widely applied in mechanical manufacturing, particularly in the production of standard fasteners. Among these applications, the most representative products manufactured using multi-station cold heading machines are bolts, screws, and nuts.

Cold heading and cold extrusion are essentially deformation processes under similar conditions, but they differ in their operating methods. Cold heading is a forging deformation typically used for smaller workpieces and is commonly employed in the fastener industry. In contrast, cold extrusion involves the extrusion deformation of larger workpieces and has a broader range of applications. Cold heading can be considered a branch of cold extrusion.  

To put it simply, in the bolt manufacturing process:  
- The formation of the hex head is achieved through cold heading.  
- The reduction of the shank diameter is accomplished by cold extrusion (forward extrusion).  

For example, trimless hex flange bolts (formed through multi-station processes) involve both cold heading and cold extrusion. In the manufacturing of hex nuts, the initial shaping stage involves only cold heading, while the subsequent hole extrusion step utilizes cold extrusion (both forward and backward extrusion).