Faculty: Physical Metallurgy
Speciality: Ferrous metals
Titanium alloys, titanium-based alloys. Lightweight, high strength at temperatures ranging from cryogenic (-250 C) to moderately high (300-600 C) and excellent corrosion resistance of titanium alloys offer good prospects for application as structural materials in many areas, particularly in aviation and other transport sectors engineering.
Titan has a considerable hardness: it is 12 times harder than aluminum, a factor of 4-iron and copper. Another important characteristic of the metal - the yield stress. The higher it is the better part of the metal resist operational loads. Yield strength of titanium is almost 18 times higher than that of aluminum. Specific strength of titanium alloys can be increased by 1,5-2 times.
Its high mechanical properties are well preserved at temperatures of up to several hundred degrees. Pure titanium is suitable for any kind of treatment in the hot and cold: it can be forged, such as iron, pulling and even make him the wire, rolled in sheets, strips, foil in thicknesses up to 0,01 mm. Although "technically pure " titanium has acceptable mechanical properties and has been used for orthopedic and dental implants, for most applications using titanium alloys.
Titanium alloys are prepared by doping titanium following elements (numbers in brackets - the highest for industrial alloys dopant concentrations in wt%): Al (8), V (1916), Mo (1930), Mn (8), Sn (13) , Zr (10), Cr (10), Cu (3), Fe (5), W (5), Ni (32), Si (0,5); rarely used doping Nb (2) and Ta (5) . One of the most commonly alloyed with small amounts of aluminum and vanadium, as a rule, 6% and 4% respectively by weight.
Ti-6Al-4V or Ti 6-4, is one of the most commonly used alloys. It has a chemical composition of 6% aluminum, 4% vanadium, 0.25% (maximum) of iron, 0.2% (max.) of oxygen and the remainder titanium. Widely used in aerospace, aviation, missile and cryogenic technology, shipbuilding, for the manufacture of chemical and metallurgical equipment, as a prosthesis in the surgery and the like, characterized by high technological ductility, good weldability, is used for making silnonagruzhaemyh parts and structures in aeronautical engineering .
Alloy VT6-4 is used: for the manufacture of semi-finished products (sheets, strips, foils, sheets, plates, rods, profiles, pipes, forgings and forged blanks) by the strain as well as bars, welding wire diameter 1,6-7,0 mm; stamped parts, continuously operating at temperatures up to +400-450 ° C, large welded and modular designs of aircraft, tanks, working under internal pressure over a wide temperature range from -196 ° C to +450 ° C, and a number of other structural elements .
Alloy (a + b)-class. Aluminium in alloys of Ti-Al-V increases the strength and heat resistance properties, and vanadium is one of the few alloying elements in titanium, which not only improves the strength properties, but also flexibility.
Along with high specific strength alloys of this type have a lower sensitivity to hydrogen as compared with alloys OT4 and OT4-1, a low propensity to salt corrosion and good processability.
Alloys are well deformed in hot conditions. Alloy welded by all conventional types of welding, including diffusion. When welding EBW weld strength almost equal to the strength of the base material, which distinguishes it from the VT22 alloy.
The process of melting of titanium and its alloys at KESHP is a secondary process of refining metals. It is used for further purification after completion of primary surgery for removing impurities and refining.
The starting material is usually used continuous consumable electrode from the primary metal, which can be cast, received treatment with blood pressure or consisting of scrap. Slag bath contained in a cooled mold, heated and cooled by electric shock (electrical) current between the electrode and a cooled tray. When the temperature of the slag bath temperature exceeds the melting of the metal electrode starts melted, drop, flowing from the electrode tip, fall into the slag bath, forming a pallet metal bath, which gradually hardens. The electrode is fed into the slag bath, and the bar that serves as the second electrode is gradually increasing. Liquid slag thus continuously moves upwards. Where the rising slag meets the walls of the mold, it solidifies that ensures that the solid crust of solid slag between the mold and the solidifying ingot.
Electroslag melting of titanium and its alloys has several advantages. The heating of the molten slag (usually calcium fluoride), an electric current over the surface of the metal in the mold can overheat the metal above its melting temperature. In this case the thermal field is aligned on the metal surface, deeper bath of molten metal, which improves the homogeneity of the ingot. More uniform heating of the ingot over its cross section for the electroslag melting allows ingots of rectangular cross section, which is convenient for further rolling. The same applies to the merits of the exclusion of the metal contact with the outer atmosphere.
Titanium is not only durable, but light metal. She is so strong as steel, but 45% lighter. In addition, two times stronger than aluminum, but 60% heavier. Titan slightly corrosive sea water, and is used in the propeller shafts, equipment and other parts of the ships, which are exposed to sea water. Titanium and its alloys used in aircraft, rockets, where strength, low weight and high temperature stability are important. Further, since titanium does not react in the human body, it and its alloys are used to create artificial hips, pins for setting bones and for other biological implants.
Also used for the manufacture of heat transfer equipment: pipes for heat transfer equipment for various purposes, turbine condensers, as elements lining the inner surface of the chimney. It should be noted that the high capital costs offset by increased longevity, higher reliability, lower maintenance costs and repairs. The existing experience shows that the titanium alloys for resistance to general corrosion surpass the most resistant copper alloys, copper-nickel alloy and stainless steel 10 ... 20 times. Recently, titanium has been widely used for the manufacture of supports offshore oil platforms (titanium platform twice flexible steel), deepwater drilling risers, pipelines, filters, pumps and water intake, pressure vessels, high-stretch flexible mounting platforms.
Used in actively developing nuclear power plants. As an alloying element in steel and nonferrous and ferrous. In the automotive industry for responsible and the most loaded parts as springs, motors and other powerful machines Medicine also can not do without titanium: surgical instruments, implants and even heart valves made from titanium. The advantages of titanium - strength, corrosion resistance, and most importantly the fact that some people have allergies to nickel (a required element of stainless steel). Cells can regenerate on the titanium and bone may continue to grow after implantation of the metal. However revealed that the use of titanium alloy with additions of vanadium is limited because the alloy Ti 6Al-4V is toxic.
Manufacture of golf clubs, knives with Ti 6Al-4V, in construction (as safe for human metal). Of particular note is the use in plastics with excellent durability, this sector accounts for about 20 percent of global consumption. Watch case made of titanium operated perfectly.