1. Free Forging: Valve blanks can be machined by the free forging method. This method requires a spherical hammer or mould, on which the metal blank is placed, forged and shaped under force. Free forging can achieve large deformations, but accuracy and surface quality are relatively poor.
2. Die forging: Die forging is a method of machining a goal blank using a special die. The die can be closed or semi-closed and is capable of forging to a predetermined shape and size. Die forging can provide higher accuracy and surface quality than free forging.
3. Hot Forging: Hot forging is a forging process carried out at high temperatures. By heating the metal billet it can be made more plastic and easy to shape. Hot forging can be used in the machining of valve blanks to obtain better shape control and mechanical properties.
4. Precision Forging: Precision forging is a high precision forging method usually used for machining more demanding valve blanks. This method combines die forging and hot forging with advanced CNC equipment and process control to achieve greater accuracy and reliability.