Forging :Forging is the process by which a metallic part is deformed to a final shape with the application of pressure and with or without the application of heat. Forging processes can broadly be classified as follows.

Open die forging : The workpiece is compressed between two flat dies facilitating lateral flow of material without constraint.

Impression die forging : The workpiece is compressed between two dies with a cavity or impression that is imparted to the workpiece. The metal flow is constrained within the impression of the dies. However, the excess material remains as flash.

Hence, the correct option is (D).