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The application of titanium alloy in lightweight manufacturing of automobiles

Titanium and titanium alloys have the characteristics of low density, excellent mechanical properties, good biocompatibility, corrosion resistance, high temperature resistance, and good low-temperature toughness. They have been widely used in the field of automotive manufacturing.

Titanium alloy has a density of only 60% of steel, but its strength can reach over 800MPa. It still maintains good mechanical properties at around 500 ℃, and has good welding and forming properties. It has been used in the manufacturing of racing cars for more than 20 years, greatly reducing the quality of racing engines and improving engine performance.

At present, titanium alloy components used in automobile manufacturing are mainly distributed in the exhaust system, engine system, transmission and damping system, as well as the body frame.

1. Exhaust system

Automotive exhaust system materials are required to have good high-temperature mechanical properties and corrosion resistance to S and Cl elements. Traditional exhaust valve components are made of stainless steel, but it has been found that titanium alloy is more suitable as an exhaust valve material in terms of performance.

The titanium return pipe used in the new Chevrolet Corvette Z206 car effectively avoids issues such as pitting and weld rust on stainless steel pipes, while also improving fuel combustion efficiency and acceleration ability, and shortening braking distance.

The largest titanium manufacturer in the United States, Timet, has been committed to the research and manufacturing of titanium alloy exhaust systems, and several Japanese companies have also carried out related research and development work. Currently, Fuji Heavy Industries Co., Ltd. has limited the production of 440 sets of titanium alloy automotive exhaust pipes.

2. Engine system

The automotive engine system is the component that uses titanium alloy the most in the automotive industry. The main applications of titanium alloy in engine systems include valves, connecting rods, crankshafts, valve seats, and other components.

Honda Motor Company of Japan used forged titanium connecting rods in the NSX racing V-6 engine; The high-capacity, four cylinder engines manufactured by Mitsubishi Motors use titanium valve spring seats, and Porsche cars also use titanium connecting rods.

(1) Valve

In terms of titanium alloy valves, both the United States and Japan have conducted extensive research work. Currently, the United States generally uses Ti-6Al-4V alloy to manufacture intake valves and Ti-6Al-2Sn-4Zr-2M o alloy to manufacture exhaust valves; Toyota, on the other hand, uses Ti-6Al-4V/Ti B alloy to prepare intake valves and Ti Al Zr Sn Mo Nb Si/Ti B alloy to prepare exhaust valves. These types of titanium alloys all have good high-temperature mechanical properties, oxidation resistance, and creep resistance, effectively improving engine performance and increasing car speed.

(2) Valve seat

Titanium alloy valve seats have been widely used in racing and sports cars, producing over 250000 sets annually. They are mainly made of Ti-6Al-4V or Ti-5Al-2Cr-1Fe alloy. Due to the relatively simple shape of the valve seat, there are no high requirements for mechanical processing, and no special surface treatment is required. The cost is relatively low, and the effect on weight reduction in automobiles is significant.

(3) Connecting rod

The use of titanium alloy connecting rods can effectively reduce the weight of the engine and improve car performance. At present, the main preparation material is Ti-6Al-4V alloy. Japan's Datong Corporation is currently developing a two-phase titanium alloy Ti-3Al-2V-0.2Si-0.47Ce-0.27La, which has good machinability, excellent mechanical properties, fatigue performance, and corrosion resistance. It is expected to be used in connecting rod components for rapid acceleration and deceleration of engines.

(4) Crankshaft

Although titanium alloy crankshafts have not been widely used, the Ti-3Al-2.5V alloy specially developed by Japan has been validated on Honda racing cars, effectively reducing weight while increasing engine speed by 700r/min, proving the superiority of titanium alloy crankshafts. At the same time, Japan has been trial producing Ti-5Al-2Cr Fe alloy crankshafts, hoping that titanium alloys will be more widely used in crankshaft components.

3. Vibration damping system

The core component of a car suspension system is the suspension spring. Compared to steel used for general automotive springs, titanium alloy has higher specific strength and lower shear modulus, as well as higher fatigue resistance, making it more suitable for manufacturing automotive damping springs. Due to the fact that the deflection of the spring is directly proportional to the number of turns and inversely proportional to the shear modulus of the material, titanium alloy springs require fewer turns than steel springs to achieve the same spring response, effectively reducing spring mass and saving space.

At the same time, titanium alloy springs can effectively increase the resonance frequency of the spring and improve its service life. Currently, most titanium alloy springs are single-phase β Preparation of titanium alloys. Volkswagen has already used Lupo FSI titanium alloy gear springs in some cars, with a usage of approximately 3500 vehicles.

4. Vehicle frame

In terms of body frame components, the high specific strength, low density, and good corrosion resistance of titanium alloy all indicate that it is a good material for preparing body frames. At present, some car companies have used titanium alloy on components such as gear brackets, brake calipers, and pistons. In terms of transmission components, Japan is currently developing a high spin forming process to prepare titanium alloy casings. Compared with steel casings, titanium alloy casings better reduce the impact of the flywheel and provide better cushioning effects.

In addition, titanium alloys have also been applied in automotive fasteners and other components. With the continuous development of titanium alloy preparation processes and the automotive industry, titanium alloys will inevitably be more widely used in automotive components.

5. The significance of titanium alloy for automotive lightweighting

Foreign research institutions have found that when the curb weight of a car decreases by 10%, fuel consumption can be reduced by 6% to 8%. There are also studies showing that for every 91kg of weight lost in a car, the average fuel consumption per liter can increase by 0.43km. Therefore, with the continuous development of China's economy and the increasing number of automobiles, vehicle lightweighting has become one of the important ways to reduce energy consumption and air pollution.

Titanium and titanium alloy materials have been widely used in automotive components due to their excellent physical and chemical properties. The use of titanium materials not only effectively improves the performance and safety factor of automobiles, but also plays an important role in automobile lightweighting, effectively reducing the curb weight of automobiles and reducing fuel consumption.

Compared to traditional stainless steel systems, the titanium tailpipe return pipe component used in the automotive exhaust system can reduce weight by approximately 8.2kg. The use of titanium alloy products instead of traditional steel and cast iron materials in engine components such as valves and connecting rods can effectively reduce engine weight.

According to research in the Japanese automotive industry, the use of approximately 0.8kg of titanium material parts in automotive power valves is equivalent to the effect achieved by 20kg of steel parts; Each titanium valve seat can reduce the weight by about 10g compared to steel valve seats; The connecting rod and crankshaft are made of titanium alloy, which is most effective in reducing engine weight.

On the vibration reduction system, each titanium alloy spring can reduce the weight by more than 60% compared to steel springs. Calculated with 4 suspension springs per vehicle, after replacing with titanium alloy springs, each vehicle can reduce weight by 9-13.6kg. In addition, the mass of titanium alloy silencers is only 5-6kg, which is 40% lighter than stainless steel silencers.

Taking ordinary medium-sized sedans as an example, if traditional parts are replaced with existing titanium alloy car parts, the curb weight of the car will be reduced from about 1500kg to about 1000kg, with a weight reduction rate of up to 30% and a comprehensive fuel consumption reduction of over 20%. This will greatly reduce fuel consumption worldwide, effectively alleviate energy scarcity and environmental pollution problems.

The above data shows that the use of titanium alloy has a significant effect on automotive lightweighting. In modern automotive industry, it is necessary to continuously develop the application technology of titanium and titanium alloy in automotive components, and increase the proportion of titanium alloy application in automobiles.

At present, the application of titanium alloys in China's automotive industry is only in the experimental stage. The main problems are the high cost of titanium alloy materials and the difficulty in processing components.

Therefore, the main task in the future should be to develop low-cost titanium alloy materials, reduce the production cost of titanium alloy raw materials, and lower the price of titanium alloy components, and improve the processing efficiency of titanium alloy components by improving the processing technology.

Foreign experience has shown that only by combining automotive design and manufacturing companies with titanium alloy development companies can we provide higher quality titanium alloy materials for automobiles.

I believe that with the continuous deepening of research and development work, titanium and titanium alloys will play an increasingly important role in China's modern automotive industry, promoting the continuous development of the automotive industry.

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