For the structural parts of the aircraft manufacturing, the main frame of the fuselage is the most important, the most time-consuming, and also the most expensive parts, which is the key factors that limits the production capacity and performance life of fighter.
The main frame on the high performance fighter must rely on the basic shape by forging formed in the mold under great pressure. Under the great pressure with long time, the metal blank is softening by high temperature like kneading dough vigorously, the inner loose organization, internal bubbles, cracks and other defects would all be eliminated compaction. However, there are hundreds of hours needed to remove the excess part on the primary forged products in order to fully meet the design shape requiring. Then through the subsequent heat treatment process and quality inspection, the production is finished.
Before 2013 in domestic, there was only a 30 thousand tons forging press could be put into use. Its maximum projected area of aluminum alloy material is not more than 2 square meters, and the projection area of titanium alloy is not more than 1.2 square meters as well. Cause of this restriction, the titanium alloy large frame on J-20 has to be divided into several forging in the design and forging respectively, by using electron beam welding into a whole finally.
In April 10, 2013, the world’s largest 80 thousand tons die forging machine developed by Chinese Double Group successfully achieved trial production. That means that China has made a breakthrough in the manufacturing capacity of large aerospace forgings, reaching the world’s top level. For the J-20, which means that it can be used to form a complete titanium alloy frame, its life will be a huge breakthrough.