It is distinct from closed-die forging, in which the dies fully enclose the workpiece when they are brought together. The open die forging process allows for larger products to be forged than other types of forging – up to 150 tons and 80 feet long or more.
Open die forging is used most often to produce round, square, rectangular, and hexagonal bars, beams and other basic shapes. Other common products formed using open die forging include spindles, hubs, mandrels, step shafts, metal shells, simple pancake forgings and pierced blanks. Since tooling tends to be simpler and lower in cost for open die forges than for closed die forges, open die forging is better suited for lower volume production runs and for creating unique forged items.
The pressure applied during the forging process gives metal improved grain structure, higher density, decreased porosity and therefore additional strength and longer service life as compared to cast metal products. Open die forging works well with any metal, including carbon steel, stainless steel, copper, nickel, aluminum and titanium.
Industries that benefit from open die forgings include aerospace, automotive, material handling, marine, military, cement, electronics and home appliances.
In open die forging, a metal workpiece, usually heated above its re-crystallization temperature, rests on a stationary anvil and is struck on the opposite side by a hammer or press, so that it is compacted and conforms to the shape of the anvil and hammer dies. The dies can be flat, concave or convex, or may include a tool to form holes or to shear.
The product usually requires numerous strikes or presses to take on its intended shape, so an operator must repeatedly reposition and orient the workpiece so that the die will fall successively on the next side or sections of the workpiece. Multiple open die forging processes can be combined to create a final product. In some cases open die forging can also be a pre-forming process for subsequent operations using other forging methods or various machining processes.
The whole forging process can be customized to attain the optimal grain structure and ensure the best-performing final product possible. Open die forging is the most common method of forging utilized to produce simple forms and small production runs, offering many possibilities for creating high strength metal pieces.