Titanium investment castings save costs and resources
The use of titanium investment castings in aircraft construction not only saves weight and fuel during flights, but is already very energy efficient, economical and environmentally friendly in the production process, with significant advantages in terms of CO2 emissions. The Federal Environment Ministry funded on a pro-rata basis a project at TITAL which allows an innovative, material-efficient production of large titanium components using the titanium investment casting process. As part of the project an analysis was completed to investigate the resource and energy efficiency of titanium investment cast parts in comparison to titanium parts machined from solid material. TITAL has produced a report about this in conjunction with the University of Hanover (Center for Production Technology - PZH).
According to the study, waste material per kilogram of finished titanium parts in the aviation business is more than 10 kg when the components are manufactured by machine processes. Through the investment casting process waste material can be reduced to just 2 kg per kg. Depending on the complexity of the product being manufactured, the energy consumption in the machining process is 1,090 kWh per kg and is approximately four times higher than the energy used in the casting process at 266 kWh per kg. The CO2 emissions for a machined component are 650 kg per kg and are also four times higher than a component produced by the casting process at 127 kg per kg. The expected production output for the TITAL site in Bestwig, Germany is 30,000 kg which generates a CO2 emission reduction of 15,690 tons per year.
In 2009, TITAL began production with their newly installed titanium casting furnace which is capable of pouring 1.5 m (60") diameter parts weighing 300 kg (660 lbs). A condition of the 10 million Euro investments in 2007 and 2008 was the guarantee that the gravity casting process for titanium would be successful. The previous titanium castings were manufactured using a centrifugal casting process which produced components up to a maximum diameter of 600 mm (24") and a maximum part weight of 40 kg (88 lbs). TITAL's new large titanium casting furnace makes them one of only three suppliers world wide that can offer components of this size.
The background to this is the growth of the lightweight construction philosophy for large aircrafts. CFRP (carbon fiber reinforced plastic), which is ideal for use with titanium, is used more frequently in this field. New aircraft lines such as the A380, the Airbus A350XWB and Boeings Dreamliner 787, are relying on lightweight parts for more of the aircraft's components. The disadvantage: CFRP components cause corrosion problems when used with aluminum alloys. With titanium, this physical problem does not exist. Due to its corrosion resistance, titanium is the preferred choice of manufacturers in this area. Therefore specialists expect that the use of titanium in aircraft construction will continue to increase. Titanium makes up 3% of the total material mix in the Airbus A320. The new A380 contains more than 10% titanium and the newest Airbus plane, the A350XWB, scheduled for its first flight in 2012, will contain approx. 14% titanium structural components - this with a CFRP proportion that already exceeds 50%, and with a fuel consumption of considerably less than 3 liters of kerosene per passenger kilometer flown.
Typically a large percentage of metal components for aircraft construction are still produced using metal-cutting and machining techniques. When using titanium materials this results in high machining costs as the cutting tools dull quickly and need to be replaced often. This leads to a short lifespan of the already expensive machine cutting tools. For years TITAL has been successfully promoting the investment casting technology for titanium and aluminum aerospace components and the aerospace industry has been utilizing TITAL's patented HERO-Premium-Casting® process for aluminum components which has a casting factor of 1.0.
The study from TITAL and PZH shows that typical geometries used in the aviation industry lead to a 90% loss of material when producing titanium components by milling or other machining processes. The report continues that "in addition to the material waste, the machine tools used for milling have to be continually sharpened and charged with cooling lubricants in order to extend their durability." TITAL GmbH has also developed a process for the recycling of internal scrap. The total material consumption per pound of produced titanium castings were cut in half by this new process.