Theory and Approach to the Less-loading Closed Die Forging

The needed load for closed die forging is maximum in plastic forming.Moreover,the load should be increased with the strength of the forging material and the forging dimension.Former Soviet Union built the 750 MN hydraulic closed die forging press in 1967,even now it is the biggest one used in the world.Also a proposal to build the 2 000 MN die forging press is proposed in the same year.In America,The character of that press in design and the difficulties to manufacture it are described.Besides,the factors influencing load of the closed die forging and the approach of decreasing its value are also mentioned.It is shown that the load of closed die forging can be decreased by minimizing the material flow stress and decreasing the pressure at the flash gate.For example,flow stress can be minimized by using the isothermal die forging and super-plastic forging process invented by American in 1970s.Thus,the existing press can meet the demand of new material with greater strength and dimensions.So,to construct the 2 000 MN hydraulic die forging press became then un-stringency.As an example,the same front frame forging of the truck has been manufactured both in the 25 MN high energy screw press and in the 120 MN wedge press,but in the perform for screw press process is provided by precise roll forging,its final forging flash volume is much less than in later case.So,the less-loading forming concept is very important.