3.2 Titanium for aircraft engines
Figure 4 shows examples of titanium alloy applications for the V2500 engine employed by Airbus A320. The V2500 engine is manufactured by International Aero Engines, an international joint venture that includes Japanese enterprises. Nippon Steel & Sumitomo Metal has a dependable record delivering titanium alloys to the company over more than 25 years. Materials produced are mainly bars for the forging of fan case, low-pressure compressor blades, low-pressure compressor stator vanes, and the like. Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloys are most commonly used, and effective production technologies of such materials have been put into practice, providing high quality in a wide range of sizes, from 30mm diameter small bars to billets exceeding 300mm. Since foreign substances can be introduced into the material during the ingot manufacturing process, which can then be the origin of the fatigue fracture during operations,5) contamination prevention for aircraft engines is crucial.
At Nippon Steel & Sumitomo Metal, contamination prevention is achieved with thorough equipment cleaning control, for which the company has obtained high praise from customers. Furthermore, Nippon Steel & Sumitomo Metal acquired certification under the international special process accreditation program (Nadcap), as well as the qualifications of General Electric, Rolls-Royce and domestic heavy industry manufacturers in the fields of nondestructive testing, such as ultrasonic testing, and material testing (conducted by Nippon Steel & Sumikin Technology Co., Ltd.), thereby meeting their demand for high quality.
On the other hand, while ensuring quality in the titanium ingot forging process, it is also important to determine a forging schedule for the most efficient operation.6) Finite Element Method analysis is applied as a tool for studying optimization of the forging ratio, the amount of forging reduction, the amount of feeding in forging, forging speed, and the like. Technologies for quicker and more accurate analysis have been established by applying a deformation resistance model obtained through high temperature compression testing of materials actually applied to titanium forgings. Figure 5 shows an example of forging analysis. Quality stabilization and cost reduction can be promoted by selecting the forging schedule that produces optimum surface strain and center strain.