Open Die Forging
Also known as smith forging, hand forging or hammer forging, open die forging involves the use of flat dies with little shape. This method creates parts by the manipulation of the metal through the die into the required shape. The open die forging process allows for larger products to be forged and can offer a wider variety of mechanical products than closed-die or other types of forging. Typically used for small quantities, common shapes that are formed during open die forging include spindle forgings, hub forgings, simple pancake forgings, mandrel forgings, pierced blanks and hexagons. Some of the benefits of open die forgings includes a long service life, decreased porosity, fine grain structure and provides addtional strength. Open die forging is ideal for materials such as Inconel®, carbon steel, stainless steel, copper alloys, nickel alloys, aluminum steel and titanium. Industries that benefit from open die forgings include aerospace, automotive, material handling, marine, military, industrial, cement, electronics and home appliances.
Open die forging is performed horizontally between two flat dies, or a flat die and an operator's hands, which do not have impressions made in them. The dies or hands do not fully cover the material to be worked, or the workpiece; this allows for areas of the workpiece to move from direct contact with the hot die to open and cooler areas. To begin open die forging, the workpiece is heated to above its recrystallization temperature. Throughout the open die forging process, the workpiece is rotated and moved around so that every area of the workpiece is forged. During this repositioning the workpiece begins to cool below its recrystallization point when out of contact with the die, thus the workpiece must be reheated to continue to he forging process. This heating, cooling and reheating of the workpiece creates a discontinuous material flow, which is different than other deformations methods which offer a continuous flow of material. Open die forging typically is used to forge larger products as well as products that require mechanical properties of the worked metal that cannot be forged using closed die forging.