Astm B265 Gr2 titanium alloy in automotive lightweight manufacturing applications
Titanium and titanium alloys are characterized by low density, excellent mechanical properties, good biocompatibility, corrosion resistance, high temperature resistance, low temperature toughness, etc., and have been widely used in automobile manufacturing field. Titanium alloy density is only 60% of steel, and the strength can reach more than 800MPa, in 500 ℃ or so still maintain good mechanical properties, and welding and molding performance is better, in more than 20 years ago has been used in the manufacture of racing cars, greatly reducing the quality of the racing car engine, at the same time improve the performance of the engine.
At present, the titanium alloy parts used in automobile manufacturing are mainly distributed in the automobile exhaust system, engine system, transmission and vibration damping system and body frame parts.
1. Exhaust system
Automotive exhaust system materials are required to have good high-temperature mechanical properties and corrosion resistance to S, Cl elements. Traditionally, exhaust components have been made of stainless steel, but titanium alloys have been found to be more suitable in terms of performance.
The titanium return pipe used in the new Chevrolet Corvette Z206 automobile effectively avoids pitting and weld corrosion problems that occur in stainless steel pipes, and at the same time improves fuel combustion efficiency and acceleration, and shortens braking distance.
Timet, the largest titanium manufacturer in the U.S., has been committed to the research and development and manufacture of titanium alloy exhaust systems, a number of Japanese companies have also carried out related research and development work, and at present, Fuji Heavy Industries Co., Ltd. has produced a limited number of 440 sets of titanium alloy exhaust pipes for cars.
2. Engine system
Automobile engine system is the most used titanium alloy parts in the automobile field, titanium alloy in the engine system is mainly used in valves, connecting rods, crankshafts, valve seats and other parts.
Japan's Honda Motor Company used forged titanium connecting rods in the NSX racing V-6 engine; Mitsubishi Motors Corporation manufactured high-capacity, four-cylinder engine using titanium valve spring seat, Porsche cars also use titanium connecting rods.
(1) Valves
Titanium alloy valves, the United States and Japan have carried out a lot of research work, the United States is now common use of Ti-6Al-4V alloy manufacturing intake valves, the use of Ti-6Al-2Sn-4Zr-2Mo alloy manufacturing exhaust valves; and Toyota Japan is the use of Ti-6Al-4V/Ti B alloy preparation of intake valves, the use of Ti-Al-Zr-Sn-Mo-Nb- Si/Ti B alloy to prepare exhaust valves. These types of titanium alloys have better high-temperature mechanical properties, oxidation and creep resistance, effectively improving the engine performance and increasing the speed of the automobile.
(2) Valve seat
Titanium alloy valve seat has been widely used in racing cars and sports cars, the annual production of more than 250,000 sets, mainly using Ti-6Al-4V or Ti-5Al-2Cr-1Fe alloy preparation, due to the shape of the valve seat is relatively simple, so in the machining requirements are not high, and do not need a special surface treatment, the cost is cheaper, and in the automobile weight reduction effect is obvious.
(3) Connecting rod
The use of titanium connecting rods can effectively reduce the quality of the engine and improve the performance of the car. At present, the main preparation material is Ti-6Al-4V alloy. Ltd. is currently developing a two-phase titanium alloy, Ti-3Al-2V-0.5V.
Ti-3Al-2V-0.2Si-0.47Ce-0.27La, the alloy has good machinability, mechanical properties, fatigue properties and corrosion resistance are also excellent, is expected to be used in the engine acceleration, deceleration of the connecting rod components.
(4) Crankshaft
Titanium alloy crankshaft is not widely used at present, but Japan's specially developed Ti-3Al-2.5V alloy has been verified in the Honda racing car above, in the effective reduction of quality at the same time, the engine speed increased by 700r/min, proving the superiority of titanium alloy crankshaft. At the same time, Japan has been in the trial production of Ti-5Al-2Cr-Fe alloy crankshaft, expect titanium alloy in the crankshaft components to be more widely used.
3. Damping systems
The core component of automobile vibration-damping suspension system is the suspension spring. Titanium alloy has higher specific strength, lower shear modulus and higher fatigue strength than general steel for automotive springs, which makes it more suitable for manufacturing automotive vibration damping springs. Since the spring deflection and the number of coils are proportional to each other, and the shear modulus of the material is inversely proportional to each other, titanium alloy springs require fewer coils than steel springs to achieve the same spring response, which effectively reduces the quality of springs and saves space.
At the same time, titanium alloy springs can also effectively increase the resonance frequency of the spring and improve its service life. At present, most of the titanium alloy springs are prepared with single-phase β-titanium alloy. Germany Volkswagen has used Lupo FSI titanium gear springs in some of its cars, with a usage of about 3,500 cars.
4. Body Frame
For body frame components, titanium alloy's high specific strength, low density and good corrosion resistance indicate that it is a good material for the preparation of body frames. Currently, some automobile companies are using titanium alloys for components such as gear brackets and brake caliper pistons. Transmission components, Japan is currently developing a high spin molding method for the preparation of titanium alloy shell process, compared with steel shell, titanium alloy shell better reduce the impact of the flywheel, better cushioning effect.
In addition, titanium alloy is also used in automobile fasteners and other components, with the continuous development of titanium alloy preparation process and the automobile industry, titanium alloy will be used in automobile parts and components.
5. The significance of titanium alloy for automobile lightweighting
Foreign research institutes have found that when the overall quality of automobile decreases by 10%, the fuel consumption can be reduced by 6%~8%. There are also studies that show that for every 91kg of weight reduction in a car, the average fuel per liter can be driven 0.43km more. Therefore, with the continuous development of China's economy and the increasing number of automobile ownership, automobile lightweighting has become one of the most important ways to reduce energy consumption and air pollution.
Titanium and titanium alloy materials have been used in a large number of automobile parts due to their excellent physical and chemical properties. The use of titanium materials not only effectively improve the performance of the car and the safety coefficient, but also play an important role in automotive lightweighting, effectively reducing the overall mass of the car, reducing fuel consumption.
Automobile exhaust system using titanium tailpipe - return pipe assembly compared to the traditional stainless steel system, can be about 8.2 kg weight reduction, and engine parts in the valve, connecting rod and other components using titanium alloy products instead of the traditional steel and cast iron materials can effectively reduce the quality of the engine.
According to the Japanese automobile industry research, automobile power valve using about 0.8kg of titanium parts equivalent to 20kg of steel parts to achieve the effect; each titanium valve seat compared to steel valve seat can reduce the quality of about 10g; connecting rod and crankshaft used in titanium alloy, the most effective in reducing engine quality.
Above the damping system, each titanium alloy spring can reduce the quality of steel springs by more than 60%, 4 suspension springs per vehicle calculation, after the replacement of titanium alloy springs, each vehicle can reduce weight by 9~13.6 kg. In addition, the quality of titanium alloy muffler is only 5~6 kg, which is 40% lighter than that of stainless steel muffler.
Take an ordinary medium-sized sedan for example, if the existing titanium alloy auto parts to replace the traditional parts, the car's overall quality will be about 1500kg from the original weight reduction to about 1000kg, the weight loss rate of up to 30%, the overall fuel consumption can be reduced by more than 20%, which will greatly reduce the world's fuel consumption, and effectively alleviate the problem of energy scarcity and environmental pollution.
The above data show that the use of titanium alloy in automobile lightweight effect is obvious, in the modern automobile industry, should continue to develop titanium and titanium alloy in the application of automobile parts and components technology, to increase the proportion of titanium alloy in the application of automobiles.
At present, the application of titanium alloy in China's automobile industry is still only in the trial stage. The main problem is that the cost of titanium alloy material is too high, and the parts are not easy to process.
Therefore, the main task in the future should be to reduce the price of titanium alloy parts through the development of cheap titanium alloy materials, reduce the production cost of titanium alloy raw materials, etc., and improve the processing efficiency of titanium alloy parts by improving the processing technology.
