Abstract China's high-speed rail exports are of extraordinary significance, not just the “out of the sea†of individual industries, but the “going out†of the entire industrial chain. At present, the market size is small, but once it is recognized by overseas markets, it will reshape...
China's high-speed rail exports are of extraordinary significance, not just the “out of the sea†of individual industries, but the “going out†of the entire industrial chain. Although the market size is small, once it is recognized by overseas markets, it will reshape the global brand image made in China and drive the development of the upstream and downstream segments of the industry chain. Today, the straw will take you to see the materials on the high-speed rail ~~~ For high-speed railways, higher requirements are imposed on the strength, fatigue performance, light weight, and processability of new materials. The application of new materials is mainly in the following aspects.
Railway vehicle body
stainless steel
Stainless steel mainly uses nickel-chromium austenitic stainless steel. Due to its high corrosion resistance and aesthetic characteristics, it is widely used in Japan, the United States, and the former Soviet Union. Under the premise of ensuring strength and rigidity, the thickness of the skeleton such as beams and columns is The 3.2-6.0mm of ordinary steel is reduced to 1.0-1.5 mm, which can reduce the weight by about 40%. In the early 1960s, Japan took the lead in the development of stainless steel vehicles, which were lightweight, energy-saving, and did not need to be painted. They produced significant economic benefits. At present, there are more than 5,000 stainless steel vehicles, accounting for more than 10% of all passenger cars.
Main application: stainless steel car body is not easy to solve the problem of airtightness of the car body. It is only used to manufacture the car body of 20km/h speed class, and the bearing and decoration parts in the car.
Aluminum alloy
The density of aluminum is small, only 2.7 (light metal), about 1/3 of steel. Since the surface of aluminum is easily oxidized to form a dense and stable oxide film, corrosion resistance is good. Aluminum has good castability. Because of its low melting temperature and good fluidity, aluminum is easy to manufacture parts with complex shapes. The aluminum alloy still maintains the light weight characteristics, but the mechanical properties are significantly improved.
Main applications: First, as a force member; second, as a door, window, tube, cover, shell and other materials; third, as a decorative and thermal insulation material. The aluminum alloy is easy to process and has a high heat dissipation.
In particular, the engine part of the vehicle is particularly suitable for use with aluminum alloy materials. It is almost entirely a world of aluminum alloy. In addition, the processing technology of aluminum alloys is diverse. Strong versatility.
In the long run, aluminum alloys are moderately priced. The higher price of aluminum makes the cost of vehicle manufacturing increase. However, due to the lightweighting of aluminum alloys, the weight reduction of vehicles brings about an increase in energy consumption, a reduction in energy consumption, and a reduction in maintenance costs. According to statistics, fuel consumption can be saved by 8% for every 10% reduction in vehicle weight. In the case of scrap recycling, aluminum profiles can be 100% recycled, and recycled aluminum profiles can reduce energy consumption by 95%.
As early as the 1950s, some of the more developed countries in the world began to use aluminum profiles to manufacture railway vehicles, including the United States, Canada, Japan, Russia, Germany and France. At present, domestic high-speed train cars have used aluminum alloy materials in large quantities. . Experts in the industry pointed out that the high-speed train body with a speed of more than 300 kilometers per hour must be made of lightweight aluminum alloy material. All the train cars of more than 350 kilometers use aluminum profiles except the chassis. At present, among the four types of CRHI, CRH2, CRH3, and CRH5 adopted by the China Railway Passenger Dedicated Line EMU, except for the CRHI type body, which is made of stainless steel, the other three types of EMUs are made of aluminum alloy.
In recent years, foreign attempts have been made to manufacture car body skeletons from aerospace materials such as magnesium alloys and alloys. The weight of the car body is only 66% of that of aluminum alloy, and the weight reduction effect is obvious. But still in the test.
Composite material
Composite materials have been used in vehicles and their use has increased, representing a future trend. Fiber reinforced resin matrix composites (FRF) have been applied to non-structures in the 1960s because of their high specific strength (stiffness), fatigue resistance, corrosion resistance, heat insulation, flame retardancy, and designability. It is now increasingly used in a variety of structural parts, such as the front and rear of the car and the front end of the front with FRP, aramid fiber reinforced epoxy resin. At present, in Western Europe, among the composite materials used in the manufacture of railway vehicles, glass fiber accounts for 58% according to the type of fiber. Aramid fiber accounts for 20%, carbon fiber accounts for 20%, and other accounts for 2%. According to the type of resin, Polyester accounts for 35%, vinylate accounts for 22%, epoxy resin accounts for 21%, phenolic resin accounts for 15%, modified acrylic resin accounts for 4%, and others account for 3%.
Bogie
The bogie frame is a particularly important high-strength component that is related to overall vehicle safety. The rotating frame must meet the requirements of safety, running comfort, wear resistance and easy maintenance.
Most of them are made of high-quality carbon steel, low-alloy low-carbon high-strength steel and weather-resistant steel. Recently, research hotspots have been fabricated for polymer composites and aluminum alloys.
Vehicle interior and equipment
The interior and equipment of the vehicle mainly include decorative panels, toilets, toilet rooms, seats and water tanks. The main components are aluminum alloy and polymer materials. For example, the decorative panels are made of aluminum alloy and laminated with a layer of non-combustible fiber reinforced plastic. The toilet, the seat and the water tank should also be considered for hygiene and corrosion resistance, and also for non-combustibility.
In addition to having sufficient strength, toughness and wear resistance, the wheel and rail materials of the wheel-rail system must also have the characteristics of scratch resistance and peeling resistance.
As far as the line is concerned, the main characteristics of the high-speed railway are that the curvature radius is large, the strain rate is high, the axle weight is light and the traction is large, the rail wear is small, and the fatigue damage is relatively prominent. Therefore, the selection of the rail material is more demanding. high.
For rail materials, European railways have been studied on alloy rails. For example, non-heat-treated Cr-Mo, alloy rails have better cyclic softening resistance, and also have better ability to resist short-wave wear. One of the key selection objects for the material. In addition, efforts should be made to strengthen and toughen rail steels, and to develop full-length heat-treated rails, rare earth rails and new rails for noise reduction and vibration reduction.
At present, the anti-peeling performance of bainitic steels studied abroad is better than that of pearlitic steels, but it is still in the experimental stage. In order to reduce weight, Germany is studying the combination of wheels, that is, the wheel center uses FRP, and then the steel wheel and the wheel.
Ballastless track
The ballastless track is the trend and direction of current and future world railway construction development. The rails of the ballastless track itself are made of concrete, and the roadbed does not use gravel, which can reduce maintenance, reduce dust and beautify the environment. Rails and sleepers are laid directly on the concrete road, and many joint measures are taken between the cement pillow and the rail. The train can reach speeds of over 200km.
The joint between the high-speed rail cement pillow, the rail and the foundation is filled and sealed with polyurethane elastomer. One makes the connection stable and does not shift due to climate change. The other can prevent earthquake and eliminate noise, and increase passengers' ride. comfortability.
Polyurethane sleeper
In order to meet the speed-up requirements of high-speed trains, the development of polyurethane sleepers to replace or partially replace concrete sleepers will be the future development trend. In Western Europe, the technology has more mature development and application experience; in Japan, polyurethane sleepers have been applied in the high-speed train Shinkansen track. Polyurethane sleepers have superior durability and lower cycle costs compared to other materials.
Polyurethane adhesive
The demand for the use of polyurethane adhesives in the production of high-speed trains has also increased significantly. Polyurethanes bear all kinds of essential functions such as glass bonding, floor bonding, caulking filling, sealing and waterproofing on vehicles. According to the CRH3 of the EMU, the polyurethane glue for a single car is about 84.07L, which is about 103.9kg. It is mainly used for the sealing and sealing of window glass and the sealing of partial filling parts.
Polyurea elastomer coating
Because the high-speed rail adopts the ballastless track, the protective layer is required to have not only the basic performances of waterproofing, anti-seepage and anti-cracking, but also the high-speed, heavy-load, alternating impact and the like brought by the high-speed train. Polyurea coating has no joints and strong adhesion. It is truly waterproof. It also has excellent wear resistance, impact resistance, crack resistance, UV resistance and high and low temperature resistance, which can meet the special requirements of high iron.
Pantograph skateboards currently used in high-speed railways are mainly copper and silver (0.15% - 0.18% Ag), copper cadmium (0.7% - 1.3% Cd) or copper-tin alloy (0.3% Sn). With the speed of the train. The development of new composite wires with high wire tension and light weight (ie, copper on the outside and steel on the core) is a development trend.
The pantograph skateboard is an important collector component of the locomotive power supply system. It usually has carbon skateboards, metal skateboards, metal-impregnated carbon skateboards and powder metallurgy skateboards. Carbon skateboards are used in various countries. Such as German ICE and French TGV. The metal-impregnated carbon skateboard has the self-lubricating properties of carbon materials, and has the characteristics of high concentration, strength and impact resistance of metal materials. It has become the most ideal skateboard material, and has been in the industrialization stage in recent years. Foreign countries are currently strengthening the research of carbon fiber metal matrix composite skateboards, which will surpass the existing skateboards in terms of current collection, self-lubrication and impact resistance.
At present, the metal-impregnated carbon slides studied at home and abroad have entered a practical stage. It mainly utilizes the porous nature of carbon slide materials to immerse high-conductivity metals such as molten copper or copper alloys under high temperature and high pressure. The carbon skateboard base body has the characteristics of self-lubrication and arc resistance of the carbon material, and has the characteristics of high current collection, high strength and strong impact force of the metal material, and becomes the most ideal skateboard material.
At the same time, research on carbon fiber-metal composite skateboards should be strengthened. Such skateboards will surpass existing metal skateboards, carbon skateboards, metal-impregnated carbon skateboards and powder metallurgy skateboards in terms of current collection, lubrication and impact performance. The application prospects are very broad.
Brake Friction System Brake Friction System requires friction material with high and stable friction coefficient, better heat dissipation and wear resistance, high enough impact strength and shear strength, no abnormal wear on the grinding parts and other Formal damage, less brake sparks, cheaper, and lighter weight.
Brake discs used to use alloy cast iron for a long time, but high-speed trains require high-strength anti-thermal cracking alloy forged steel, such as Ni-Cr-Mo or Cr-Mo-V alloy steel, and also developed metal-based composite materials and CC composite materials. Moving plate. Japan's heat-resistant crack brake disc developed in 1997. It can last for more than 20 years; Germany's carbon fiber composite discs are of good quality at a high speed of 250 km/h and have passed the bench test of 400 km/h.
Currently commonly used friction materials can be divided into phosphorus-containing cast iron, powder metallurgy materials and synthetic materials. High-speed trains such as the French TGV-A and the Japanese Shinkansen have adopted powder metallurgy brakes and are generally copper-based materials. For iron-based and aluminum-based materials, Japan, Europe, and the United States have recently made new materials, such as ceramics or short fibers, to make composite materials. In the synthetic friction material, the aluminum alloy disc/synthesis brake disc was installed on the German ICE train, which achieved good results. At present, the successful development and application of fiber reinforced composite materials in friction braking materials has attracted much attention, and has become a research hotspot. For example, in 1997, the brakes developed by the mouth of the mouth were made of phenolic resin, graphite, synthetic rubber and carbon fiber.
Vibration and noise reduction materials
The impact of high-speed shock, vibration and noise is enhanced by the use of vibration-damping and noise-reducing components, such as rubber components with excellent elastic properties, fatigue resistance and aging resistance, to ensure safe and comfortable ride.
Rubber components have been widely used in high-speed trains for anti-vibration, cushioning, sound insulation, sealing, insulation, and elastic couplings and air rubber springs, especially for vibration and noise reduction, and for the comfort and stability of high-speed trains. A replaceable role.
The most eye-catching application of rubber components is the six-link rubber joint on the bogie. In the early 1950s, rubber materials were used as rail pads in foreign countries. In the 70s, with the increase of train speed, elastomers such as natural rubber, neoprene and urethane rubber were used as rail clamps and pads in the track structure. And cushions for sleepers; in the 1980s, low-foam polyurethane elastic materials have been widely used in track structural materials. Japan's screening of more than 100 kinds of elastic materials suggests that low-foamed polyurethane materials produced by reaction injection molding are most suitable for use as high-speed rail materials.
The high-speed rail industry represents the level of a country's high-end manufacturing. China's high-speed rail going abroad means the global market's affirmation of Chinese manufacturing. China's Zhongwang and other domestic aluminum profile leading enterprises, with strong technical research and development and product production strength, may usher in more development opportunities and market space.
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