Titanium Alloys Used To Make Car Parts--II
Using titanium alloy to manufacture automobile valves can reduce quality, prolong service life, also can improve reliability and save fuel. Early use of a costly titanium alloy, and later the use of γ-Ti Al alloy, the engine Max speed increased by about 10%. In recent years, some titanium manufacturers have developed a number of cheaper titanium alloys for engine valves, and some of them have entered the mass production stage. It is a key technology to improve the wear resistance of titanium alloy used in valve.It is one of the effective processes to improve the surface hardness and wear resistance to oxidize the surface even if the solid solution in titanium is as much oxygen as possible.
The V-8 cylinder made by Del West in the United States has been widely used for inlet and exhaust valves. Ti-6Al-4V is used for inlet valves and Ti-6Al-2Sn-4Zr-2Mo alloy is used for exhaust valves. The weight of each valve is about 50g lighter than the stainless steel, and the service life is extended by 2 to 3 times. The Ti-5Al-2Cr-1Fe alloy intake valve prepared by Hitachi, has been widely used. The R382 and R380 racing cars of Nissan Motor Company equipped with this kind of intake valve have achieved excellent results in many races. The mass of steel valve used in the past is 90g, while that of titanium alloy valve is only 55g, which is reduced by about 40%, and the performance is improved by 10% ~ 15%.
In 1998, the Toyota Motor Company's two-door sedan and Honda Motor Company's Altezza, used powder metallurgy Ti-6Al-4V/TiB alloy intake valve, exhaust valve is made of heat-resistant Ti-Al-Sn-Zr-Mo-Nb-Si/ Tib alloy. The former engine displacement of 2000 ml, equipped with a 27g intake valve and 8--24g exhaust valve, a car with a total of titanium 408g, the car's valve spring is also made of titanium alloy, its mass decreased from 43g to 36g, down by 16.3%.
The exhaust valve has high working temperature, and can be made of high temperature titanium alloy Ti-6Al-2Sn-4Zr-2Mo-0.1Si (6242S). But the motorcycle valve is more likely to be exposed to high temperature for a long time, so it is appropriate to choose the more heat-resistant TIMETAL-1100 (Ti-2.7Sn-4Zr-0.4Mo-0.45Si) alloy, it is one of the best heat-resistant titanium alloy, the working temperature is about 600℃, the exhaust valve of two wheels motorcycle is best made of titanium alloy, which can work for a long time at 800℃. At the same time, the alloy should have high damage resistance and tolerance, so researchers hope to develop Al-Ti3 and AITI based intermetallic compound new titanium alloy, and achieved certain results, the representative alloy is: Ti-14Al-21Nb, Ti-14Al-21Nb-3V-2Mo, Ti-24Al-10Nb, Ti-25Al-8Nb-2Mo-2TA, Ti-25Al-10Nb-3V-1Mo, and Ti-22AI-27Nb, but they're not cheap.
The 746-kW V-16 engine of the General Motors Cadillac Model 16, uses a wide range of light metals. The cylinder body and cylinder head are made of aluminum alloy, while the valve springs and some parts are made of titanium alloy. It has a fuel economy of 7.23 km/L.
