Forging is a manufacturing process, which shapes a workpiece by applying compressive forces on it. According to the temperature at which is performed, forging is classified in “hot”, “warm” and “cold”. The most common configurations use hammers or presses to squeeze and deform the material into high strength parts.
It is essential to note that the forging manufacturing process is completely different from the casting one, where the molten material is poured into a mold. Another significant difference to the other manufacturing methods as casting and machining is that forging improves the mechanical properties of the material by refining its grain structure and making it tougher and stronger.
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.
Manufacturers may prefer cold over hot forging process; since cold forged parts require very little or no finishing work, which saves cost. The second significant advantage is the material savings achieved through precision shapes. 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. 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.
The hot forging manufacturing process is performed at extreme high temperature (up to 1150 °C for steel, 360 to 520 °C for al-alloys, 700 to 800 °C for cu-alloys). This temperature is necessary in order to avoid strain hardening of the metal during deformation.
Hot forged components possess increased ductility which makes them desirable for many configurations. Also, as a technique hot forging is more flexible than cold forging, since customized parts can be manufactured. The excellent surface quality allows a wide range of finishing work as polishing, coating or painting, tailored to customers’ specific needs.
Less precise dimensional tolerance is a possible disadvantage of hot forged components compared to the cold forged ones. The cooling process should be also performed under special conditions; otherwise there is a risk of warping. Also, the grain structure of forged metals may vary and there is always a possibility of reactions between the atmosphere and the workpiece.
The main difference between hot and cold forging may be summarized as follows: The cold forging manufacturing process increases the strength of a metal through strain hardening at a room temperature. On the contrary the hot forging manufacturing process keeps materials from strain hardening at high temperature, which results in optimum yield strength, low hardness and high ductility.
Finally, a manufacturer would choose one process over the other because of economic and not quality reasons. The decision is based on the required functions of the desired component, the industry and if it’s a mass production or a low volume of customized parts.
Setforge provides cold and hot forging, both performed in excellent conditions with state-of-the-art machinery for perfect results. We work close with our customers to understand their specific needs and find the best possible solution.