Triangular inner hole crude type structure preparation method for aluminum alloy die forging

The invention relates to a triangular inner hole crude type structure preparation method for an aluminum alloy die forging. The method includes: manufacturing a similar punch tooling according to the shape and size of an inner hole before forging, wherein the shape of the inner hole is triangular, and the shape of the punch tooling is trapezoidal; pre-forging a bar or slab into a final crude type structure having a middle size, performing punching by using a trapezoidal punch; expanding the forging according to the size of the trapezoidal inner hole by using a pressing plate and a square expanding bar after punching; and expanding the inner hole of the forging to meet the triangular-shape demand desired by the final crude type structure. The method can save raw materials, can reduce the production cost of products, and can avoid the problem that the mechanical performance is lowered and the fatigue life of the forging is shortened due to the fact that small deformation is passed down to the forging when the i