Abstract: The paper briefly describes the geometric structure characteristics of large wing with thin webs, and the possibility of isothermal forging technology of wing is used in 5 × 104 kN hydraulic press. The technological parameters of isothermal forging such as its deformation temperature, strain rate and so on are introduced. The paper also analyses the causes of defects in detail such as pierce rib, strinkage cavity, lap and crack, and so on. The practical methods to remove these defects by lots of technological tests are given. Meanwhile, it points out that in order to avoid or reduce the defects, it is important to determine the die structure, optimum shapes and size of blank in the small serial production with the help of CAD. The suitable equivalent height blank and the practical and inexpensive holes for excess metal in dies cavity can be obtained.

Key words: the wing of aluminium alloy, isothermal forging, defects analysis