Prospect and practical application of titanium and titanium alloy in automotive
lightweight research and development
The application of new materials such as light weight materials, metal matrix composites and ceramics determines the development trend of automobile to a certain extent. Titanium and titanium alloy, as structural functional materials, are ideal materials for realizing lightweight, high performance and high function. With the development of titanium industry, titanium material will occupy an important position in the field of automobile. Automobile titanium market potential is not to be underestimated.
The advantages of titanium alloys
I. Titanium alloy has excellent comprehensive performance, low density and high specific strength. Titanium has a density of 4.51g/cm3, between aluminum (2.7g/cm3) and iron (7.6g/cm3).The specific strength of titanium alloy is higher than that of aluminum alloy and steel. Titanium and titanium alloy corrosion resistant performance is good, better than stainless steel, especially the resistance to chloride ion erosion in the Marine atmosphere environment and good corrosion resistance under oxidizing atmosphere, with wider working temperature of titanium alloy, the titanium alloy at low temperature in 253 ℃ can keep good plasticity, and heat resistant titanium alloy working temperature can reach 550 ℃, its heat resistance is significantly higher than aluminum and magnesium alloys .
At the same time with good processing, welding performance.
AApplication of titanium alloy in automobile
Although titanium alloys have been widely used in aerospace, petrochemical and ship industries, their applications in the automotive industry have developed slowly. From 1956 when the first all-titanium automobile was successfully developed by general motors of the United States, the titanium auto parts did not reach the level of mass production until the 1980s. In the 1990s, with the increasing demand for luxury cars, sports cars and racing cars, the titanium auto parts developed rapidly.
The USES of titanium in automobiles fall into two main categories:
The first is to reduce the mass of reciprocating parts in an internal combustion engine.
The second is to reduce the total mass of the car. According to the design and material characteristics, titanium is mainly distributed in the engine components and chassis parts of the new generation of cars. In the engine system, titanium can make valve, valve spring, valve spring bearing and connecting rod and other parts; The main components in the chassis are springs, exhaust systems, half-shafts and fasteners.
At present, there are several parts of titanium alloy
1. Engine connecting rod
Titanium alloy is an ideal material for connecting rod. The connecting rod of the engine has strict requirements on the strength, fatigue performance, rigidity (especially the big end) and wear-resisting performance of the material. The reduction of the quality of the titanium connecting rod, combined with the lightweight piston and piston pin, can significantly reduce the noise, vibration and body jumping, and improve the working performance of the engine. At the same time, these parts, if made of titanium, can also increase the working temperature of the engine. The piston pin requires the material to have a certain strength, wear resistance, high stiffness and high temperature resistance. At present, the best choice is the intermetallic compound -- with low density, high temperature strength and relatively low production cost. For higher speed engines, the valve drive mechanism is also appropriate to use creep resistance, oxidation resistance of titanium. In particular, the use of gamma - aluminum titanium valve spring, in addition to reducing the mass, but also can increase the engine speed by 10%.
2. Engine valve
Automobile engine valves made of titanium alloy can not only reduce quality and prolong service life, but also reduce fuel consumption and improve automobile reliability. Compared with the steel valve, the quality of titanium valve can be reduced by 30% ~ 40%, and the limit speed of engine can be increased by 20%.For current applications, Ti-6AL-4V is the main material for the intake valve, and Ti-6242 is the main material for the exhaust valve. Usually Sn and Al are added together to obtain lower brittleness and higher strength. The addition of Mo can improve the heat treatment performance of titanium alloy, strengthen the strength of quenching and aging titanium alloy, and increase the hardness.
3, valve spring seat
High strength and fatigue resistance is the valve spring seat must have the performance, titanium alloy is heat treatment alloy, can get high strength through solid solution aging treatment, the corresponding suitable materials are Ti-15V-3Cr-3AL-3Sn and Ti-15Mo-3AL-2.7 Nb-0.2 Si. Mitsubishi motors USES Ti-22V-4AL titanium alloy valve spring seat in its large-scale production vehicles, which reduces 42% of the mass compared with the original steel lock, reduces 6% of the inertial mass of the valve mechanism, and increases the maximum engine speed by 300r/min.
4, titanium alloy spring
(10) titanium and its alloys have low modulus of elasticity relative to steel and have high value of s/E. Compared with the steel car spring, the titanium spring is only 40% of the height and 30% ~ 40% of the mass of the steel spring under the premise of the same elastic work, which is convenient for the car body design. In addition, excellent fatigue performance and corrosion resistance of titanium alloy can improve the service life of the spring. At present, Ti-4.5 Fe-6.8 Mo-1.5 AL and Ti-13V-11C-3AL are titanium alloy materials that can be used to make automotive springs.
Turbochargers can improve engine combustion efficiency and enhance engine power and torque. Turbocharger turbine rotor need to work for a long time in more than 850 ℃ high temperature exhaust gas, so demand has very good heat resistance. Traditional light metals such as Aluminium alloys are not usable because of their low melting point. Although ceramic materials are used in turbine rotors due to their light weight and high temperature resistance, their applications are limited due to high cost and shape optimization. In order to solve these problems, Tetsui et al. developed the rotor of the capital turbine, which has been tested and verified for many times. It not only has good durability and efficiency, but also can improve the acceleration of the engine. The design has been successfully commercialized in the Mitsubishi Lancer Evolution series.
6. Exhaust system and muffler
Titanium is widely used in automobile exhaust system. Exhaust systems made of titanium and its alloys not only improve reliability, life and appearance, but also reduce quality and improve fuel combustion efficiency. The titanium exhaust system has a mass reduction of about 40% compared to the steel exhaust system. In Go1f series cars, the quality of titanium exhaust system can be reduced by 7 ~ 9kg. At present, the titanium used in the exhaust system is mainly pure industrial titanium.
The quality of titanium muffler is only 5 ~ 6kg, which is lighter than stainless steel muffler. The 2000 Chevrolet CorvetteZ06 replaces the 20kg stainless steel system with an 11.8kg titanium muffler and exhaust pipe system, resulting in a 41% reduction in mass. The replacement system has the same strength, and makes the car faster, more flexible and fuel saving. Muffler USES titanium material is also mainly pure industrial titanium.
7. Body frame part
In order to improve the safety and reliability of automobile, the design and manufacturing aspects, especially the manufacturing materials, need to be considered. Titanium is a good material used to make the frame of the car body. It is not only higher than the strength, but also has good toughness. In Japan, car manufacturers choose pure titanium welded tubes as the body frame, which can make drivers feel safe when driving.
8. Other titanium alloy parts
In addition to the above components, titanium is also used in engine rocker arm, suspension spring, engine piston pin, automotive fasteners, lug nut, car door protruding beam, car block support, brake caliper piston, pin , pressure plate, speed change button and car clutch circular plate and other auto parts.