The comparison between titanium bicycle frames and other frames has its own advantages and disadvantages for several known types of frame materials:
At present, steel is the most widely used and longest-used material in the bicycle manufacturing industry. The technology of steel frames is quite mature. Through the optimization of composition, advanced heat treatment process, and processing technology, the pipe wall of steel pipe can reach the ideal thickness under the premise of ensuring performance. The advantages of steel frames are (1) good processing performance and mature technology. The steel frame is the frame with the longest history of research, and its technology in all aspects is better than other materials. Therefore, there are relatively few difficulties in design and manufacturing. (2) Good welding performance. Compared with titanium, aluminum, and other light alloy materials, steel welding has relatively low requirements for a protective atmosphere. After welding, it is generally unnecessary to eliminate the defects in the welding process through heat treatment, which reduces the investment in equipment. (3) Good shock absorption performance. (4) Price advantage: compared with other materials, steel materials have an unshakable cost advantage in terms of manufacturer quantity, product quantity, processing technology, and application range. Disadvantages of steel frame: (1) easy to rust. The steel pipe with the thin wall is used in the current application. If the surface anti-corrosion treatment is not applied, the corrosion will be small in time, and the impact on the mechanical properties of the frame will also be very large. Therefore, the anti-corrosion treatment of the steel frame before delivery has to be considered. (2) Metal fatigue caused by stress concentration. The influence of this factor mainly lies in the welding heat-affected zone. The residual stress and component segregation produced during the welding process will affect the mechanical properties of the material to a certain extent; In addition, if impurities enter the weld during welding, stress concentration will occur around the impurities. (3) Frame weight. Although the weight of the steel frame is decreasing and the thickness of the steel pipe wall used as the frame is almost reaching the limit, there is still a certain gap between the steel frame and some light frames (especially carbon fiber frames) in the application field.
Aluminum itself has the advantages of low density, good plasticity, corrosion resistance, and so on. After alloying with other metals, the mechanical properties will be significantly improved. Most aluminum alloys used in bicycles are 6000 series (Al-Mg-Si) and 7000 series (Al-Zn-Mg-Cu). Aluminum materials are usually heated before use to improve their performance to meet the needs of practical applications. Advantages of aluminum alloy frame: (1) It can be made into a light frame. (2) Good corrosion resistance in atmospheric environments. Aluminum itself is a metal that is easily corroded. It will be oxidized immediately when placed in the air and form a very thin oxide film. However, when this layer of oxide film accumulates to a certain extent, it will protect the body from further corrosion. Disadvantages of aluminum alloy frame: (1) The elastic modulus and rigidity of aluminum are low. Generally, methods such as enlarging the outer diameter of the pipe, using a flat pipe, or carrying out heat treatment on the aluminum pipe are adopted to minimize the impact of lower elastic modulus on the performance of the frame and adapt to the change of stress during use. (2) Heat treatment is required. Most aluminum alloys must undergo heat treatment before use (except 7075 aluminum alloy pipe), otherwise, the strength is difficult to meet the requirements, and the purchase of heat treatment equipment will lead to increased production costs to a certain extent.
CFRP material means that carbon fiber is added to the resin matrix as a reinforcing phase to form a composite. Due to the anisotropy of carbon fibers, the arrangement and overlapping direction of carbon fibers should be considered during the composite process. Compared with other materials, carbon fiber composites have the following advantages: (1) high strength and lightweight. The tensile strength of carbon fiber is higher than that of steel, but the density of the composite material is far lower than that of aluminum alloy. Such properties are undoubtedly expected by both manufacturers and users. (2) Good shock absorption. With its excellent performance of absorbing impact, it can be used to make bicycles without shock absorbers. (3) Integral molding. The basic forming method of a CFRP frame is to pour the resin into the mold paved with carbon fiber for integral forming, so the connection between frames is not considered. Disadvantages of carbon fiber frame: (1) Complex stress calculation. The shear strength of carbon fiber is not very good. Therefore, complex stress calculations should be carried out during processing, and carbon fibers should be arranged according to the results in order to obtain a good combination of properties. (2) The size cannot be changed after processing and molding, and only the corresponding model of the mold can be produced. Every time a new model is developed, another mold must be designed and manufactured. (3) Aging of the resin matrix. (4) The price is high.
Titanium alloy is a high-performance material used in aerospace products and has excellent metal material properties. It is currently internationally recognized as the most advanced and ideal material for producing high-grade bicycles for various sports and leisure purposes. The outstanding characteristics of titanium alloy are lightweight, high strength, good elasticity, impact resistance, good fatigue performance, corrosion resistance, and never rust. Bicycles, especially racing cars, require light weight, good rigidity, and good impact performance. Light weight can improve speed and reduce physical consumption during long-distance sports; The bicycle frame with good rigidity is conducive to the conversion of the driving force and improves the handling performance; The bicycle frame with good impact absorption can better reduce the impact from the road, thus reducing the fatigue of the driver. Advantages of titanium frame: (1) low density and high specific strength. The weight of titanium alloy is only 50% of that of steel, and its strength-to-weight ratio is 28.4% higher than that of chromium-molybdenum steel. The fatigue limit of titanium alloy is twice that of steel, and aluminum alloy bicycles can not be compared with titanium alloy bicycle frames in this respect after a long time of use. As a high-strength and low-density titanium alloy material applied to bicycle frames, it will not only make bicycle frames light and strong, but also make bicycle frames more durable. (2) No rust. Titanium will not corrode in the general environment, so when it is used as a structural material, no additional anti-corrosion treatment is required.
lightweight
With low density and high specific strength, the weight of titanium alloy is only 50% of that of steel.
Corrosion resistance
Titanium is more corrosion resistance than stainless steel and no need to do anti-corrosion treatment
Disadvantages of titanium frame: (1) High price. In nature, titanium can be found as titanium dioxide. The refining and processing process is complex, and the technical requirements are high and time-consuming, so the cost is high. (2) The welding cost is high. Due to the high affinity between titanium and oxygen, titanium dioxide quickly turns into titanium dioxide upon contact with air. Titanium dioxide is brittle and hard, and as a result, the strength of this component will continue to deteriorate. Therefore, inert gas-shielded welding must be used for the welding of titanium frames. The common method is TIG welding (TIG: abbreviation for tungsten and inert gas): tungsten electrode is used for welding under argon protection, and the welding cost is high. For the manufacture of bicycle frames, among many metal materials, titanium alloy meets the above requirements at the same time, so it is a very ideal material for making frames. Titanium alloy has excellent corrosion resistance, longer service life than other metal and non-metallic materials, and it is durable without aging, wear, and scratch. As a bicycle frame, its surface does not need painting protection, because it will not rust or corrode like iron and aluminum frames, and can resist acid rain, ultraviolet rays, moisture, and other erosion, so you do not have to worry about its metal surface will form pits and rust due to exposure in the air. The bicycle frame made of titanium alloy material makes the rider feel safer and more reliable. It will not break suddenly. When it breaks, it will start from a small crack, which will be noticed at this time; Even if accidental collisions and fractures occur, the unique toughness of the metal will protect the user from injury.
