Isothermal Forging of Titanium Alloys Using Large Precision-Cast Dies.

Abstract : The technology of isothermal forging of titanium alloys in large precision-cast dies was established. Twelve forging die castings were produced in the range of 200 to 1400 lb per die half. MAR-M 200 and IN-100 nickel-base superalloys were selected as die materials on the basis of their hot hardness, high-temperature strength, oxidation resitance, and castability. A molding system was devised which utilized a ceramic molding process and allowed for the production of dies having a high degree of precision, good surface finish, casting integrity, and fine grain structure in the die cavity. Induction heating systems were developed to heat the dies in the forging press to 1800F. A series of over 200 Ti-6Al-6V-2Sn alloy forgings were produced, representing typical airframe structural shapes having plan areas 10 to 55 sq in. and nose wheel forgings having plan areas up to 110 sq in. and thinnest section of 0.12 in. The majority of the forings were produced by the isothermal creep forging technique in which the load is maintained at a preselected low value and the press speed is automatically regulated by the resistance to deformation of the forging blank. With this technique a complete forging cycle takes place in about 5 min with the resulting press speed of about 0.1 ipm in the final stages of forging. Die-workpiece temperatures ranged from 1600 to 1800F. (Author)