R. Gerke-Cantow, Titan-Aluminium-Feinguss GmbH, Bestwig, Germany
The term casting often suggests products with properties generally inferior to wrought products. This is not true with titanium cast parts.
The main reason is the β to α+ β phase transformation at a temperature of about 1000 °C, which changes the cast structure completely, leading to an α+ β lamellar structure, which is also typical of β processed wrought alloy.
To reduce the material costs recycling of solid scrap and turnings as well as cold-hearth melting processes for the production of ingots are established in the industry. With this the titanium consumption of foundries related to their casting weight produced (buy-to-fly) can be reduced to values well below 2 (depending on the parts to be produced).
The increasing demand for titanium products in the past led to a substantial increase in the price for the metal. Consequently, old and new designs are considered for a casting solution as the leading near-net-shape technology available. This in turn indicates that for geometrically complex parts with a high amount of human labour in production, casting is a cost effective alternative to milled products due to reduced material and lower machining costs.
Also the reduction of the well known casting factor is once again a topic on customers’ agendas. The investigations performed in TITAL show that the investment casting process is also in terms of process variability (coefficient of variation) on a level playing field with its wrought products competition.
In addition, the advantages of investment castings are the realization of complex structures, run through of load path, reduction of part numbers, minimized assembly, less milling, less drawing expenditure…
Summary: Titanium castings have the same strenght level compared to wrought products. Using the casting technology the buy to fly ratio can be reduced to values below 2. Although a high ammount of human labour is necessary in producing castings it is a cost effective alternative due to reduced material and lower machining cost. Proof of process investigations for casting factor reduction programs show that casting is on a level playing field with its wrought products competition.
