Research On Ti-1023Titanium Alloy Large Diameter Bar

Ti-1023titanium alloy has high specific strength, good fracture toughness, largequenching cross-section, small anisotropy and strong stress corrosion resistance and aseries of advantages, to meet the design requirements to the aircraft of high structureefficiency, high reliability and low manufacturing cost. It is one of high strength andtoughness titanium alloys which currently with largest application in the aerospaceindustry. Therefore it has important practical significance to develop the titanium alloylarge size bars.This text closely connect the China aviation industry demand, has pertinence tocarry out the development of Ti-1023titanium alloy bars with large-size Ф350mm,mainly determine the melting process of Φ720mm large ingots, forging process ofФ350mm large-size bars and heat treatment process of finished products, also researchthe alloying method of Ti-1023alloy and ultrasonic detection method of bars.The research results show that:(1) Using the low current melting process and reasonable alloying method is aneffective way to control the iron segregation. According to this technology successfullydeveloped Φ720mm ingots, the metallurgical quality of the ingots meet therequirements of N/BS5313and AMS4986.(2)The process that forging the ingot to blank using3150T and2500T hydraulicpress, the forging of middle billet and finished products are performed in α+β phasezone, and perform β homogenizing treatment in twice, it determined the Ti-1023alloyΦ350mm bars could be forged according to the method of “small deformation, multipleheating, high-low-high”. (3) Through the test to get the optimum heat treatment range of Ti-1023alloyΦ350mm bars is750-760℃/2h.WC+530-540℃/8h.AC.(4) Using the Semi acoustic method to perform the ultrasonic detection of Φ350㎜Ti-1023bars, it could reduce the assessment of noise to flaw and improve thesignal-to-noise ratio, the noise level is Ф2.0-9dB～-12dB.(5)The technical indicators of tensile properties, fracture toughness, microstructureµstructure, NDT and others of the developed Φ350mm bars all reached thetechnical requirements of N/BS5313and AMS4986.