Standardization of high-quality titanium alloy raw materials and forgings

Over the years, China has made significant progress in equipment capabilities and technological processes related to the melting, forging, heat treatment, and mechanical processing of titanium alloys, providing excellent equipment conditions and technological foundations for the production of large titanium alloy aircraft frames, beams, landing gear components, and aircraft engine discs, blades, and casing forgings. The safe use of aircraft and aircraft engines is largely dependent on the metallurgical quality, microstructure, micro-texture, and mechanical properties of raw materials and forgings. In addition to being limited by manufacturing processes and equipment conditions, the quality control of raw materials and forgings mainly relies on establishing corresponding material and forging standards, thermal processes, and inspection standards.

During the transition from the research stage to the production stage of aviation titanium alloy materials in China, corresponding different levels of material standards and process specifications have been gradually established, such as enterprise standards, model standards, aviation standards, and military standards, serving as the basis for material or forging production and acceptance. The majority of in-service titanium alloy materials in China are mainly imported brands. Therefore, when formulating material standards and forging standards, the main approach is to refer to or equivalently adopt the technical requirements and regulations of relevant foreign standards.

When applying material or forging standards, it is often encountered that there are misunderstandings and ambiguities in the understanding and actual operation of provisions such as the control of chemical composition range, the control of impurity element content, thermal process systems, high and low-magnification microstructures, ultrasonic testing, and mechanical performance indicators requirements.

With the construction of China's aviation equipment, the titanium alloy forgings used tend to be larger in size, more integrated, more precise, and more cost-effective. Corresponding raw material specifications and sizes also keep increasing. Some specifications, sizes, and weights have exceeded the limits of the current standards.

For example, the φ 500mm titanium alloy large billet being produced by a certain factory, while the maximum size of the large specification billet stipulated in the current standard is only φ 350mm; the weight of a certain type of titanium alloy fan disk forging is close to 500kg, with a large size, thick section, and has greatly exceeded the specifications of the titanium alloy disk forgings produced in the past.

Therefore, for such ultra-large-sized titanium alloy billets and ultra-large-sized titanium alloy forgings, how to scientifically, reasonably, and appropriately stipulate technical requirements such as high-magnification microstructure, mechanical properties, and ultrasonic testing for these materials and forgings, still requires targeted research efforts, data accumulation, experience accumulation, and continuous improvement, supplementation, and revision of material and forging standards.