A new machining method of niobium alloy special-shaped hollow forgings is presented. The process steps are as follows: first, the niobium alloy bar blank is forged on the hollow special-shaped die, then the solid special-shaped blank is obtained after demoulding, and then the special-shaped hollow forgings are obtained by reaming along the hole with a punch. The invention adopts H13 steel with quenched hardness of HRC40 ~ 45 to make hollow shaped mold, and designs the inclination Angle of 2° ~ 4° for the large diameter end of the mold, so as to realize the smooth demoulding of the material after forming, and can be applied to mass production. At the same time, the hot working die steel 5CrNiMo with quench hardness of HRC50 ~ 55 is selected as the punch material, so as to prevent the fracture during the instant forging impact and avoid the deformation problem with the depth of the punch.
Taking niobium metal as matrix, adding tungsten, molybdenum and zirconium and other high melting point metal elements, through solid solution strengthening and precipitation strengthening typical strengthening methods significantly improve the high temperature mechanical properties of metal niobium, and stable performance, uniform composition of high temperature high specific strength niobium alloy (grade Nb521) bar, its tensile strength at 1400°C up to 190MPa, Nearly 4 times higher than that of C103 alloy; The tensile strength reaches more than 70MPa at 1600°C and remains more than 50MPa at 1800°C. The new niobium alloy can increase the working temperature of aerospace heat-resistant structural materials by more than 200°C. However, the niobium alloy bar has the following technical defects in the processing of the hollow forgings: 1. It can not guarantee the stiffness of the die in forging impact and realize the problem of material withdrawal after forming; 2. Can not prevent the punch in the instant forging impact occurred fracture and deformation with the depth of the punch.
A new machining method of niobium alloy special-shaped hollow forging is presented. The process steps are as follows: first, the niobium alloy bar blank is forged on the hollow special-shaped mold, then the solid special-shaped blank is obtained after demoulding, then the hole is drilled, and the final special-shaped hollow forging product is obtained by reaming the hole with a punch.
The hollow shaped mold is made of H13 steel with quenched hardness of HRC40 ~ 45, and the large diameter end of the mold is designed with an inclination Angle of 2° ~ 4°, so as to realize the smooth demoulding of the material after molding, and it can be used in mass production. At the same time, the hot working die steel 5CrNiMo with quench hardness of HRC50 ~ 55 is selected as the punch material, so as to prevent the fracture during the instant forging impact and avoid the deformation problem with the depth of the punch.
