Large forgings are generally made through the process of open-die forging. Called open-die because the metal is not laterally confined during forging, as it is during impression or closed-die forging, this process continuously works the starting stock until it reaches its desired shape and proportions, most commonly between flat-faced dies.
The many process variations in open die forging make it possible for it to accommodate a broad range of shapes and sizes. The sheer size capability of this type of forging makes it the go-to choice over non-forging when a design requires optimum structural integrity for a large metal part. With this process, the only limit to large forgings is the size of the starting stock. Though often associated with simpler large items, such as bars and rings, open-die forging can in fact produce many custom options without sacrificing structural integrity.
As technology has grown, so have the forging possibilities and capabilities. With the help of advanced computer modeling, many companies can forge incredibly complex shapes. Also, hydraulic presses, weighing upwards of 10,000 tons, can be incorporated into the process to create very large forgings.
Need for large forgings in the U.S. increased in earnest starting in the 1880’s and 1890’s, when the American government wanted to switch to large, ironclad ships. The defense industry continues to be a market for large forgings, for large weaponry, aerospace technology and the like.
Another fairly early market for large forgings was the electric power industry, which developed after WWII, when the demand for commercial items like wind turbines and generator shafts increased. Currently, among others, large forgings have a strong customer base in industrial equipment and machinery building, mining, commercial nuclear, capital goods such as columns and rams, offshore oil and gas and power generation.