Application of titanium alloy in manufacturing automobile parts

Titanium is widely used in automobile exhaust pipe. In the past, ordinary steel, aluminum alloy and fiber reinforced plastic (FRP) were mostly used for exhaust pipes and silencers. Exhaust temperature > 400 ℃, the heat resistance of titanium is much higher than that of aluminum alloy, and the strength is higher than that of steel. The manufacturing of exhaust pipe and muffler must go through various forming processes such as bending and cold pressing, and the materials are required to have good cold forming properties. In addition, the muffler is an external part of the car body, which is made of titanium alloy, which is more novel and fashionable.

In addition to heat resistance and wear resistance, the exhaust valve shall be free of lead and cobalt. American automobile companies mostly use titanium alloy to make inlet and exhaust valves. TC4 is used for inlet valves and ti-6al-2sn-4zr-2mo alloy is used for exhaust valves. The valve seats of Japanese automobile companies are generally made of TC4 alloy and ti-5al-2cr-1fe alloy. The exhaust pipe adopts titanium alloy tail nozzle / return pipe component, which can not be corroded by chlorine salt and sulfur-containing waste gas, and even the weld will not be corroded. It is 8.2kg lighter than the traditional stainless steel exhaust system, which improves the fuel efficiency, speeds up the speed-up capacity and shortens the braking distance.

The mass of titanium alloy muffler is only 5kg ~ 6kg, which is much lighter than that made of stainless steel. Almost all silencers of Japanese cars have been titanium alloyed. The mass of titanium muffler and exhaust pipe system of General Motors (GM) Chevrolet is only 11.8kg, 41% lighter than 20kg of stainless steel, and the strength is higher. Ti-33.5al-1nb-0.5cr-0.5si alloy developed by Datong iron and Steel Company of Japan is a good material for manufacturing engine exhaust valve. It has good oxidation resistance and creep resistance. Compared with martensitic heat-resistant steel and nickel alloy traditionally used for exhaust valve, titanium alloy has the following outstanding characteristics: low density, good heat resistance and higher strength above 540 ℃, Moreover, the creep resistance is higher than that of nickel alloy, and has good wear resistance.

The actual use shows that the service life of the titanium alloy exhaust system is the same as that of the vehicle, which is 12-14 years, and the service life of the stainless steel device is only 8 years. Therefore, it is more cost-effective to use titanium. The mass of titanium alloy muffler is generally less than 12g, which is more than 40% lighter than that of stainless steel, which helps to improve the performance of the vehicle, and the service life of the muffler is semi permanent. Titanium and titanium alloys are completely inert, can be completely recovered without reducing the grade, and will not bring any harmful by-products in the production process.

Valve seat rings are widely used in racing cars and sports cars. In 2020, the world output is estimated to exceed 600000 pieces. They are usually made of TC4 alloy and can be made by mechanical cutting method. The processing cost is not high, and there is no need for special surface treatment. Mitsubishi Corporation of Japan uses ti-5al-2cr-1fe alloy to make valve seat rings.

Considering the strength, density and elastic modulus, titanium alloy is a good material for making springs. TC4 alloy was used to make springs for Porsche 917 racing cars nearly 20 years ago; Ford Motor Company uses RMI in racing β The spring made of C alloy replaces the steel spiral suspension spring in the past, and the quality is reduced by 53%, but the high production cost limits its wide application. Later, titanium metal company (timet) developed a new ti-4.5fe-6.8mo-1.5al alloy mainly composed of Fe and Mo, called low cost β Titanium alloy LCB (low cost beta) maintains β C alloy has the advantages of reasonable price. It is used to manufacture springs. It can be processed with the original steel spring production equipment and supported by Volkswagen. The manufactured springs are 1 / 3 lighter than steel and better than the original ones β The price of titanium alloy has decreased by 50%. What's more valuable is that the height of titanium alloy spring is 50% ~ 80% lower than that of steel spring, which means that more riding and loading space can be obtained. Titanium alloy spring has another outstanding advantage - high corrosion resistance. In the standard salt spray corrosion fatigue test, the fatigue life of steel spring is 50% lower than that in air, while the fatigue life of titanium alloy spring is only 4%. In addition, titanium alloy spring does not need protective surface treatment.