The present situation and prospect of titanium and titanium alloy for automobile
Today, the automobile has more than a hundred years of history, is an important means of transportation in our lives.Titanium’s lightweight, high-strength properties have long attracted the attention of carmakers.Titanium has been used in racing cars for many years, and almost all current cars are made of it.But general motors is a growing market for titanium.
The advantages of titanium as automobile parts materials are: high strength, small density, elastic modulus is about half of steel, low coefficient of thermal expansion, about half of stainless steel and aluminum, non-magnetic, low thermal conductivity, no pollution to the environment and so on.In addition, the use of titanium in the automotive industry can greatly reduce the weight of the car, reduce its fuel consumption, improve the efficiency of the car, reduce the noise.
- Application of titanium alloy in automobile
Typical titanium alloy parts on the automobile include: rotor blade of turbine charger, connecting rod and valve made of ti-6a1-4v alloy, etc.In order to realize low cost, ti-6a1-4sn-4zr-1nb-1mo-0.2si-0.3c alloy matrix with TiB particle dispersion was added into the ti-6a1-4sn-4zr-1nb-1mo-0.2si-0.3c alloy matrix by powder metallurgy method to manufacture the engine valve.Connecting rod and engine valve, TIMETAL LCB low cost titanium alloy suspension spring.Recently, progress has been made in the development of low-cost titanium alloys for engine valves and exhaust.In particular, the demand for titanium alloy on motorcycle exhaust system (muffler) is increasing, so the development of low cost alloy for exhaust system is more prevalent.
In 1956, general motors (GM) and its suppliers assembled an ideal exhibition car with an all-titanium body.Since then, GM has wanted to use titanium in engines, including exhaust valves and connecting rods.Some carmakers already use small amounts of titanium in some models.For example, in 1994, Honda motor company of Japan used forged titanium connecting rod in the NSX (parameter | picture) racing car 3.0 L24 valve v-6 engine.The high-capacity, four-cylinder engines made by mitsubishi motors use titanium valve spring sockets;Titanium links are also used in porsche cars.With the development of titanium, it has been widely used as advanced car parts for special purposes.
1.1 the valve
The automobile valve made of titanium alloy can not only reduce the weight and prolong the service life, but also have high reliability and save fuel.Exhaust valve in addition to the requirements of heat, wear resistance, but also free of lead and cobalt.It is common for American manufacturers to make intake and exhaust valves with titanium alloy. The intake valve USES ti-6a1-4v alloy, while the exhaust valve USES ti-6a1-2sn-4zn-2mo alloy.The sintered intake valves made by Hitachi have been supplied to the Japanese automobile industry.
Howmet foundry USES a continuous casting process to produce valves that weigh a quarter of their weight in titanium, with an estimated potential market of 200 million valves per year for new vehicles and 80 million valve replacements per year.
1.2 valve seat
In racing cars and sports cars, the most widely used titanium components are valve seats produced more than 250,000 per year, generally made of ti-6a1-4v alloy, and ti-5a1-2cr-1fe alloy is also used in Japan.Because of its simple shape and small size, it is easy to manufacture and cheap to produce.It doesn’t have to be treated with a special finish. It’s 10 to 12 grams lighter than a steel valve seat.
1.3 connecting rod
Titanium alloy connecting rod is the most effective to reduce the weight of the engine and can greatly improve the performance.The materials used for connecting rod are mainly ti-6a1-4v. Other materials such as ti-4a1-2sn-4mn and ti-7a1-4mo are also under development.
1.4 crankshaft and other engine components
Japan is trial-producing ti-5a1-2cr-fe alloy crankshaft, which has not yet been put into practical use due to the need for anti-bonding treatment.Other engine components such as rocker arm, valve spring and lower bolt of connecting rod can also be made of ti-6a1-4v alloy.
The free cutting ti-3a1-2.5v alloy crankshaft specially developed in Japan has been used in the Honda 280 HP 3.o liter V6NSX luxury racing car. Compared with the steel crankshaft with the same fatigue strength, the weight is reduced by 30% and the engine speed is increased by 700r/min.The results of these applications show that titanium has been accepted in racing cars and has been used in larger quantities.
Using titanium tail nozzle/muffler components are not affected by chlorine salt and waste gas in the sulfur corrosion, pitting the exhaust system won’t appear, also won’t appear rust in welding place, even compared with the traditional stainless steel exhaust system can reduce 40% of the weight, improved fuel economy at the same time, has fast speed ability and shorter braking distance.Because of the high cost of titanium, Timet has developed a special surface treatment method to produce parts that can help meet automakers’ cost standards.The new Chevrolet Corvette Z06 has a titanium muffler.
1.6 suspension spring
Compared with steel springs used in ordinary automobiles, titanium springs have light weight, good corrosion resistance and low shear modulus (which can reduce the steering of the spring coil).Timet has developed a titanium alloy to meet the cost and component assembly requirements of automotive suspension spring manufacturers. This material retains the excellent performance of aerospace titanium alloy springs and greatly reduces costs.The initial production usage was small and used in the gear suspension spring of Volkswagen’s new Lupo FSI car in Europe.Timet and Volkswagen announced in January 2001 the use of titanium suspension springs in the Lupo FSI 2001 model, which is expected to produce 3500 units.
Springs made of titanium weigh 60-70% less than those made of steel.In a typical five – to six-seat family car made in the United States, weight can be reduced by between 9kg and 13.6kg per vehicle by using four suspension springs.
The titanium muffler is only 5-6kg, much lighter than the stainless steel muffler and easy to operate.The demand for titanium in Japan’s automotive sector (actual demand reached 457t in 1999) is almost entirely for silencer, mainly used in large vehicles (900cc +).Japan’s Honda, suzuki and other four larger manufacturers have used titanium mufflers.Titanium mufflers are mainly used in large cars and some medium cars.
In the 2000 Chevrolet Corvette 206, GM has replaced the 20kg stainless steel system with an 11.8kg titanium muffler and tailpipe system.It is 4l % lighter, faster, more flexible and fuel-efficient.
1.8 body and other parts
Timet believes titanium can be used in other forms of home vehicle components to significantly reduce weight and improve durability, including engine components, drive gear parts, suspension systems and structural components.For example, shock absorber center rod, lug nut and bolt, control rod, fastener, driven shaft, car block bracket, door protruder beam, brake caliper piston, engine connecting rod, pin pin bolt, valve, valve spring and socket, etc.
Titanium alloy ti-6a1-4v is used to manufacture clutch plate, pressure plate and other transmission parts. Recently, titanium alloy housing has been made by high spinning molding. Compared with steel housing, it can reduce the impact damage of flywheel and make buffering easier.A new type of combined sliding die was designed by Japanese scholars and another type of automobile sprocket was developed by using push-down forming.
1.8 Titanium alloy bolts and nuts
With the popularity of cars, the automobile repacking market is also booming. More and more car enthusiasts can’t help thinking about how to make their cars more personalized and ultimate. EnergyTi came up with the perfect answer – change the bolt.
Thousands of bolts spread over the whole car seems unremarkable, but is known as the “rice of industry”, the United States New York times weekly has listed the bolt as one of the most important inventions in the past one thousand years.Bolts play a decisive role in the performance and driving control of the car, and the excellent bolts, not only its mechanical strength, fatigue, corrosion resistance to reach the standard, but also to achieve enough light.
Automobile lightweight has become the trend of the world’s automobile development.The results show that if the vehicle weight is reduced by 10%, the fuel efficiency can be improved by 6%~8%.For every 100 kg reduction in vehicle quality, the fuel consumption of 100 km can be reduced by 0.3~0.6 liters, and the carbon dioxide emission can be reduced by about 5 g/km. 1% reduction in vehicle weight results in 0.7% reduction in fuel consumption.The lightweight unsprung mass can improve the damping efficiency, improve the road holding, reduce the inertia and improve the handling, improve the acceleration performance, and reduce the braking distance.
Hub bolts as the most important parts of the car, in the premise of ensuring strength and toughness, of course, the lighter the better.Compared with the original bolts, the weight of titanium alloy wheel hub bolts is reduced by more than 45%, and the strength is increased by more than 125%.It is the first titanium alloy automobile wheel bolts reaching the standards of 8.8, 9.8 and 10.9grade.
Not all titanium alloys can be used as the original material of hub bolts, because the hub bolts are required to be “tough” due to the high shear, heavy load bearing and long period fretting wear.Toughness represents the ability of a material to absorb energy during deformation and fracture.The better the toughness, the less the possibility of brittle fracture, the higher the safety.In general, the higher the strength of the same material, the lower the toughness, and vice versa.For example, a certain GR5 titanium alloy currently on the market is prone to brittle fracture due to its high strength but low toughness.Thanks to the in-depth study and mastery of material application science, We have formed a unique titanium alloy material system and standards, and cooperated with well-known aviation enterprises to develop special titanium alloy materials. Both strength and toughness indexes have comprehensively surpassed the traditional steel bolts and common titanium alloy bolts.
- Research status of titanium and its alloys for automotive applications
2.1 the U.S.
The countries that use the most titanium in cars are the United States and Japan.First of all, the United States attaches great importance to the application of titanium in automobiles. For example, Timet has set up a special automobile factory to develop automobile parts for titanium.The United States has produced titanium intake valves, exhaust valves, valve retainers and connecting rods for racing cars, and up to 50t of titanium is used exclusively for cars each year.1996 titanium in Las Vegas at the international association for exhibition shows the Timet made of pure titanium titanium auto exhaust system, Chrysler and GM company created the commercial pure titanium and exhaust system prototype, large-scale production assessment is ongoing: GM also in Timetal – 62 – s and Timetal – LCB shaft, and is considering the alloy into mass production.In addition, the American high-performance car NSX (parameter | picture) Acura also USES titanium connecting rods, which is an example of mass production of titanium used in automobile connecting rods.Ford motor company has confirmed that several titanium alloy parts suitable for automobiles are ti-3a1-8v-6cr-4mo-4zr spring, ti-6a1-4v inlet valve and valve retainer, ti-6a1-2sn-4zr-2mo, ti-6a1-2sn-4zr-2mo-0.1 Si exhaust valve.Its 1989 titanium springs weighed a third as much as their steel counterparts and were smaller and more compact.The production of intake and exhaust valves can extend a car’s mileage by 3-4% per gallon.The valve is combined with a titanium spring to reduce the fuel consumption of the engine.
The United States has developed a series of low-cost titanium alloys.For example, Timetal 62S (ti-6a1-2fe-0.1 Si) alloy developed by Timet and GM is used in automobile engine parts. Its performance is better than ti-6a1-4v, and its cost is 15% ~ 25% lower than ti-6a1-4v.Timetal exhausting XT, a new titanium alloy developed by Timet company for motorcycle and automobile Exhaust systems, is a ti-fe-si-o alloy. The maximum quality score of alloy elements is 0.5% Fe.0.6% Si;0.15% O.The company produced 3.2t flat ingot by a single melting of electron beam, and rolled it into coil with the specification of 1.65 ~ 0.91mm after hot rolling.
Timetal1100 (ti-6al-2.7 sn-4zr-0.4 mo-0.45 Si) alloy exhaust valve was developed by American titanium smelting company, which has creep strength and oxidation resistance at 6000 ℃.Timet Timetal of LCB (Fe Ti – 4.5-6.8 Mo – 1.5 A1) alloy, its comprehensive performance is excellent, especially the anti-fatigue performance is better than that of any other titanium alloy, Timetal LCB metastable beta titanium alloy is a kind of low cost, the main alloying element is low Fe – Mo alloy, yield strength is higher than 900 mpa, elongation rate is about 18%, performance as high strength steel, compared with using aluminum molybdenum intermediate alloy, using molybdenum iron can cut costs by 25% ~ 33%.LCB suspension springs have been used in off-road racing trucks. In addition to reducing vehicle weight, they have two advantages: a faster response rate than steel springs and thus a smoother ride;Weight reduction of 60%, volume reduction of 25%, life more than 4 times the steel spring.
2.2 the Japanese
Japan used titanium for racing cars and some sports cars 20 years ago.For example, nissan R382 won the Japan competition because of the use of titanium alloy valve.At present, the applications of titanium and its alloys in automobiles mainly include engine parts, springs, rods, connecting rods, standard parts, wheels, power valves, etc.According to the experience of Japan, the use of 0.8 ~ 0.9 kg of titanium in the automobile power valve is equivalent to a weight loss of 20kg/unit.
Japan has done a lot of research on the application of titanium in automobiles.Future technology research institute has developed SAT64AW, SAT64HM, SAT325HM, ti-20v-4a1-lsn and other automotive titanium alloys.AT64HM, SAT325HM alloy has good thermal processing, drilling and anti-fatigue performance, or do more drilling links and other parts, cutting cost is low.The ti-2v-4a1 alloy developed by mitsubishi motors of Japan has good cold working performance and is suitable for manufacturing valve rods.The intake valve and exhaust valve made by the ti-6al-4v made by Japan’s toda manufacture company have improved the performance of the engine and increased the speed of the vehicle by 10-15%.It is worth mentioning that at the 29th international automobile exhibition held in Tokyo, Japan in 1992, a titanium body plate and a titanium energy-saving low-pollution engine car were exhibited for the first time, which attracted the attention of all the participants.In 1996, titanium was used in the structural parts of the solar car made in Japan, which won a place in the fourth world solar car competition.Titanium was first used in mass production of the premium NSX v-6 and then in the valves of the Toyota convertible coupe, which won an award in Japan in 1998.Ti-6a1-4v /TiB alloy was used for the intake valve and ti-al-zr-sn-nb-mo-si /TiB alloy with heat resistance was used for the exhaust valve.The engine of this car is 2000cc, using 1 279 intake valve and 8 exhaust valve of 249, a total of 408g of titanium material for a car.When the raw materials are steel, their respective weights are 40.Og and 44.6g, and the total weight of valves is more than twice that of titanium.The car also USES titanium in its valve springs, which are reduced in weight from 43g to 36g.Toyota initially built 4, 000 of the new models, half of them made of titanium.
Datong iron & steel co., ltd. of Japan has developed a new type of titanium aluminum alloy, which can be applied to the exhaust valve of automobile engine and greatly improve the performance of the engine.The composition of this new titanium aluminum alloy is ti-33.5 a1-1nb-0.5 cr-0.5 Si(wt %), in which Nb and Si are added to improve the antioxidant performance and creep resistance.Compared with the martensitic heat resistant steel and nickel-based alloy commonly used in exhaust valves, this alloy is characterized by its small specific gravity (only half that of martensitic heat resistant steel) and good thermal conductivity.Japan metal material research institute and Korea metal research institute cooperate, use element mixing method to alloy powder and strengthen powder uniform mixing, vacuum sintering, thermal isostatic pressure into two kinds of low-cost alloy, with excellent tensile, creep and fatigue properties, is expected to be made into auto parts.
The required characteristics of titanium alloy for automobile exhaust system must conform to the following four points:
(1) it has enough strength at the high temperature above 600℃, and the strength will decrease after a long time use.
(2) the reduction of wall thickness caused by oxidation is very small at the high temperature above 700℃.
(3) at room temperature, it has the same formability as JIS 2 and ASTMGr.2 pure titanium (hereinafter referred to as gr.2) (bending property, bulging property, deep impact property, etc.).
(4) excellent creep resistance at temperatures above 600℃.
Ti-lcu and ti-1cu-0.5 Nb for automobile exhaust system developed by Nippon steel corporation of Japan have the design concept and excellent characteristics (room temperature formability, high temperature strength, oxidation resistance and creep resistance).These alloys have achieved low oxidation through the addition of Cu and necessary addition of Nb, and new ideas have been born. For example, super-tix 10CU and super-tix 1OCUNB have been widely used as exhaust materials of automobiles.For example, super-tix 10CU has been used in the heat resistant parts of suzuki GSX series mufflers since 2007.The nissan gt-rspec-v and gt-r EGOIST silencers from 2009 and 2010 show a weight reduction of about 30% compared to stainless steel.Akrapovic, Europe’s largest manufacturer of exhaust system components, is used not only on motorcycles but also on parts of the muffler of cars.