features high productivity of forging. However small single reductions of a work piece restricted by the design of these machines lead to localization of strains mainly in surface zones of the work piece while metal in the core zone remains unworked. In 80-90s hydro-mechanical and hydraulic radial forging machines appeared that do not have the disadvantages inherent to mechanical RFM. Nevertheless, radial forging machines are very specific and very expensive equipment in comparison with multipurpose forging presses. The application of such machines at enterprises with a wide range of forgings manufactured is economically disadvantageous and inexpedient. The problem of manufacturing long-axis forgings by radial forging method in open-die hydraulic forging presses can be solved with use of multi-die forging devices. First such devices different in design and principle of operation appeared in the 1980s. At present, the most widespread and famous is the four-die forging device of the above described design engineered by Ukrainian and Russian scientists. The four-die forging devices have no analogues in the world now. They are successfully used at works in Russia, Ukraine, Spain, China and Germany. Advantages of Forging with Four-Die Forging Device The use of four-die forging devices in hydraulic forging presses provides for the following advantages in comparison with conventional methods of forging by two dies: Capability of forging low-ductility and hard-to-deform steels and alloys due to favourable stress and strain state of metal in the zone of deformation Increase in the forging process productivity at the average by 2 times due to the absence of lateral spread of metal and consequently the lower number of press strokes required to obtain the forging of the required size and shape Electric power saving because of lower press running time as well as lower consumption of energy carriers required to reheat metal between forging passes and lower metal loss during reheating Higher dimensional accuracy of forgings after sizing in the device allowing to decrease forging tolerances by 2-2.5 times and forging allowances by 1.5 time for further machining Higher metal yield by 10-12% High flexibility in operation and fast adjustment of equipment to varying range of forging stock Relatively low cost, low operating expenses and high reliability of the four-die forging device proven by many years of its industrial operation. See also Viktor Lazorkin, Yuriy Melnykov. New Technologies of Forging of Ingots and Blanks by Four Dies in Open-Die Forging Presses. Proc. 18th IFM 2011,