Pure titanium is an off-white light metal with a low density of 4.54 sm3, which is between Al and Fe, and has a high melting point of about 1668°C. It is higher than iron, and has a small thermal expansion coefficient and poor thermal conductivity.
Pure titanium plasticity, low strength, easy processing and forming, can be made of filaments and flakes. The strength of titanium alloy is very high. It can reach as high as 1400MPa in 0h, similar to some high-strength alloy steels, and also has good low-temperature mechanical properties. Ti has excellent corrosion resistance in the atmosphere and seawater, and is stable in sulfuric acid, hydrochloric acid, nitric acid, sodium oxynitride and other media. Ti has better oxidation resistance than most austenitic stainless steels.
Ti has an isomeric transition in the solid state: a close-packed hexagonal lattice at 882.5°C and a-Ti; and a melting point of body-centered cubic lattice at 882.5°C or more, called β-Ti; occurs at 882.5°C. The isomerization transition is a-Tiâ†â†’β-Ti, which is of great significance for strengthening.
Industrial pure titanium contains H, C, 0, Fe, Mg and other impurity elements. A small amount of impurities can significantly increase the strength and hardness of titanium, and significantly reduce the plasticity and toughness. Industrial pure titanium is divided into TA1, TA2, TA3 and other three types according to the impurity content (according to 15-1). The larger the number, the more impurities, and the parts that work below 350°C and do not require high strength can be produced.
The alloying element dissolves into a-Ti, forms a solid solution, dissolves into the knife-Ti to form β solid solution. Al, C, NO, "B", etc. increase the transition temperature of a-Ti-Ti-Ti, which is called a stabilizing element. Fe, Mo. Mg, Cr, Mn, V, etc., lower the homo-isomerization transition temperature, and are called The β-stabilizing element, Sn.Zr, etc. have no obvious effect on the transition temperature and are called neutral elements.
According to the phase structure after annealing, the titanium alloys can be classified into three types: a titanium alloy, 18 titanium alloy, and ((a + beta) titanium alloy. The grades are TA, TB, TC and numbering. The grades and uses of the grades are shown in Table 15-1. a. titanium alloy titanium is alloyed with Al, B, etc. to obtain a titanium alloy, which has a room temperature strength lower than that of β titanium alloy and (a+β) titanium alloy, but The high temperature (500-600°C) is stronger than them, and the structure is stable, the oxidation resistance and creep resistance are good, and the welding performance is also very good.a The titanium alloy can not be hardened by quenching, mainly rely on solid solution strengthening, the heat treatment only annealing search After the stress relief annealing or elimination of work hardening recrystallization degeneration.
A typical grade of titanium alloy is TA7, the composition of Ti-5A1-2.5 Sn. Its use temperature does not exceed 5000C and is mainly used for the manufacture of fuel tanks for missiles, turbines for supersonic aircrafts, etc.
The spunbond process is considered the fastest manufacturing method for nonwoven fabrics. As a result, spunbonding is considered to be more economical than other manufacturing methods such as needle punching staple fiber. During the spunbonding process extruded filaments are spun onto a collecting belt and bonded by applying heated rolls .
1. It reinforce old asphalt concrete road surface and asphalt layer, and prevents damage ;
2. It is used for rebuilding cement concrete road surface into composite road surface and restraining reflection caused by block contraction .
3. It is used in road expansion and improvment project and crack caused by old and new combination position and uneven sedimentation ;
4. It is used in soft soil base reinforcement treatment , is favorable for soft soil water separation and concretion,restrains sedimentation effectivly,distributes stress uniformly and improve overall strength of road base;
5. It is sued for preventing contraction crack caused by new road semi-rigid base layer,and reinforces and prevents road surface crack caused by foundation crack reflection.
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