High strength fastener stock of wrought titanium alloy and method of manufacturing the same

Abstract

This invention generally relates to the field of nonferrous metallurgy, namely to titanium alloy materials with specified mechanical properties for manufacturing the aircraft fasteners. A stock for high strength fastener is manufactured from wrought titanium alloy containing, in weight percentages, 5.5 to 6.5 Al, 3.0 to 4.5 V, 1.0 to 2.0 Mo, 0.3 to 1.5 Fe, 0.3 to 1.5 Cr, 0.05 to 0.5 Zr, 0.15 to 0.3 O, 0.05 max. N, 0.08 max. C, 0.25 max. Si, balance titanium and inevitable impurities, having the value of aluminum structural equivalent [Al] eq in the range of 7.5 to 9.5, and the value of molybdenum structural equivalent [Mo] eq in the range of 6.0 to 8.5, where the equivalents are defined by the following equations: [Al] eq=[Al]+[O]×10+[Zr]/6; [Mo] eq=[Mo]+[V]/1.5+[Cr]×1.25+[Fe]×2.5. A manufacturing method for a stock for high strength fastener includes melting of titanium alloy ingot, production of forged billed from ingot at beta and/or alpha-beta phase field temperatures, hot rolling at a heating temperature of beta and/or alpha-beta phase field to produce a round stock, subsequent annealing of a rolled stock at a temperature of 550° C. to 705° C. (1022° F. to 1300° F.) for at least 0.5 hour followed by drawing to produce a wire with diameter up to 10 mm (0.394 inches) and subsequent annealing at a temperature of 550° C. to 705° C. (1022° F. to 1300° F.) for at least 0.5 hour. A technical result is production of a titanium alloy stock for high strength fastener having high ultimate tensile strength and double shear strength while maintaining a high level of plastic properties in the annealed condition.