The cold forging manufacturing process is performed at room temperature. The workpiece is squeezed between two dies until it has assumed their shape. To deliver a finished, ready to fit component, the technique includes rolling, drawing, pressing, spinning, extruding and heading. Cold forging extrusion is one of the most common manufacturing techniques, widely used in the production of automotive components.
Cold Forged Components
Manufacturers may prefer cold over hot forging process; since cold forged parts require very little or no finishing work. Since all bars are annealed before being forged, there is no need for a secondary heat treatment prior to machining. Another significant advantage is the material savings achieved through near net shapes. The initial weight of the workpiece equals the final weight of the cold forged component. Cold forged parts offer a good level of attainable dimensional accuracy and excellent surface quality.
The economic advantages combined with high production rates and long die life are more than enough to convince many manufacturers that cold forging is the best option for them.
Depending on the manufacturer’s requirements, some of the cold forging characteristics may turn out disadvantages; e.g. only simple shapes in high volumes can be shaped. The achievable deformation levels and shaping grade are much more limited compared to stamping. Therefore, if the customer is searching for a specific customized component, cold forging won’t be the best alternative.
A second more significant disadvantage is that cold forged metals are less ductile, which makes them inappropriate for certain configurations. Also, because of the grain structure that gives the material its strength, residual stress may occur.
It is important to mention that cold forging extrusion for example requires also a heat treatment to eliminate possible cracks, creeks hardening or rafters.
As a consequence of the above statements, cold forging cannot be used on every steel grade, particularly on those with low ductility or sensitivity to strain hardening. For instance, low alloy steel with carbon content higher than 0,05% is not appropriate for cold forging.