Development status of titanium alloy precision casting technology
Titanium alloy precision casting technology has the characteristics of high forming accuracy, short production cycle and good dimensional flexibility. It can be well adapted to the development of high-precision and complex thin-walled titanium alloy components. Among them, graphite casting and investment precision casting are widely used in the aerospace field, mainly for the development of impellers, cabins, and casings.
At present, international head manufacturers are very mature in medium temperature and medium strength titanium alloy precision casting technology, and the main alloy grades are Ti-6-4 and BT20. The precision casting of high-temperature and high-strength titanium alloys mainly involves grades such as β-21S, BT35, Ti1100, IMI834, but the casting process still has disadvantages such as low casting performance, difficult welding, and high cracking tendency of castings.
The development needs of large, complex precision structures and high performance of titanium alloy castings in the aerospace field have rapidly promoted the application and development of new technologies and processes such as magnetic levitation melting, 3D printing, computer numerical simulation, and hot isostatic pressure densification in the field of precision casting .
At present, 3D printing technology can achieve the production of 1800 mm×1000 mm×700 mm integral casting shells or cores, and its accuracy can be controlled within 0.3 mm. Representative manufacturers include German ExOne, Voxeljet Company, American SolidScape, 3DSystem the company.
In addition, numerical simulation technology has been widely used in casting mold filling, solidification, shrinkage porosity and shrinkage cavity prediction, stress distribution prediction and other processes, which can effectively guide the casting process and improve the accuracy and quality of castings. At present, mainstream numerical simulation software vendors include American Procast, Japanese Soldia, German Magma Soft, China Huazhu CAE, etc.
In terms of performance improvement, hot isostatic pressing densification technology has been widely used in the post-processing of castings, which can cause metallurgical closure of defects, eliminate shrinkage porosity and shrinkage cavities, improve component segregation, and effectively improve the microstructure and mechanics of castings Performance, but still need to pay attention to and solve the problems of structure coarsening, phase change and deformation control of castings during hot isostatic pressing. At present, with the progress of a variety of process technologies, titanium alloy precision casting technology has shown a development trend of diversification, crossover, and universalization of technology types. Large-scale titanium alloy castings with a diameter of 2m can be produced with casting tolerances. It can reach ±0.13 mm, and the minimum wall thickness can be controlled at 1.0 mm.