Titanium

The different types of titanium alloys are organized into titanium grades, which define its properties and uses and allow manufacturers to determine the most suitable grade for their applications. Titanium has a few unusual qualities which make it a highly desirable metal in a broad range of industries. It has excellent corrosion resistance, high heat resistance, low conductivity and elasticity and high strength to weight ratios. It is used widely for products which require ductility, strength and a high melting point. The navy, marine industries, aquariums, automotive manufacturers, racing sports, jewelers and the aerospace industry all buy titanium to manufacture their products and materials. It is fabricated into many different shapes, including titanium tubing, titanium pipes, titanium wire, titanium bars, titanium plate, titanium foil, titanium rods and titanium sheet, by hot or cold forming, flat rolling, extrusion or welding. These titanium materials are either used as parts, sold as products or sold as stock items in order to be further processed.

Although titanium is a naturally and abundantly occurring element (it is the ninth most abundant element on Earth), it does not occur in pure form and is usually found in mineral deposits in the form of ilmenite. Titanium is extracted most often using the Kroll or Hunter methods, which involve reducing titanium tetrachloride with magnesium. This reduction yields a raw and highly porous ore, which is called a sponge and pressed or melted into blocks for fabrication. When titanium is heated above a certain temperature it reacts with oxygen and either absorbs the oxide and changes its chemistry or becomes explosive, therefore forging and forming titanium can also be difficult and costly. Titanium's natural qualities of strength, low density, ductility and heat transference are often alloyed with various metals to create a hybrid of properties that better suit it to machining. Titanium steel is lighter and far more resistant to corrosion than regular steels; aluminum titanium alloys are finer and stronger; iron, copper and manganese titanium alloys also benefit from combining their strengths with titanium's properties.

There are 38 grades of titanium classified by the American Society for Testing and Materials (ASTM). The first 5 grades are unalloyed, and the rest contain different ratios of elements such as aluminum, vanadium, tin, molybdenum, palladium, zirconium, niobium, nickel, ruthenium, silicon and iron. Titanium is also classified into 3 groups of structural alloys. Alpha titanium is usually alloyed with aluminum and tin, and is low to medium strength, non heat treatable and wieldable. It is ductile, has high notch toughness, and good mechanical properties at cryogenic temperatures. It also has the highest corrosion resistance and is used in the manufacturing of airplane parts and chemical processing equipment. Alpha Beta titanium is medium to high strength, heat treatable and wieldable. It is often hot formed and has limited cold forming abilities. Alpha Beta titanium is used to make marine hardware, aircrafts and prosthetic devices. Finally, Beta titanium, the smallest group, is the highest in strength, most dense, fully heat treatable and wieldable. It exhibits high formability and is often extruded to make heavy duty aircraft parts which are required to maintain structure and shape even under extreme pressure.

The extraction process of titanium is fairly costly and tim consuming, but the parts and products it produces have many different uses and can be used in a wide range of applications. Once processed into an ore in the form of foil, sheet, wire, granules, sponge, powder, mesh and rod, titanium is relatively easy to fabricate into products and is extremely useful. This usefulness is why many industries choose titanium even at a higher cost and research is continually being done on more possible uses for titanium. Aquarium, naval, marine and other saltwater industries often use titanium tubing and titanium sheet for underwater parts due to its resistance to salt erosion, stress, microbiological corrosion and pitting. Because it is such a lightweight material with high strength, parts are manufactured from titanium plates by the automotive industry for valve springs, rocker arms, connecting rods, exhaust systems, drive shafts and steering gears. The biomedical industry uses titanium wire and bars in the production of orthopedic devices and catheters. Racing sports specifically use titanium to increase vehicular speed as it has high heat resistance and strength. Surgical and dental industries use titanium wire and titanium instruments to decrease the chance of allergic reactions and many kinds of prosthesis are manufactured from pure titanium because it does not contaminate or corrode in the body. The aerospace industry uses titanium quite extensively for jet engines, missiles and spacecrafts. Further specialized applications for titanium, titanium oxide and titanium alloys include semiconductor and battery titanium wires, chemical and petroleum handling, agri-food titanium tubing, orthopedics, sporting goods equipment, paint, toothpaste, paper, plastics, cement, jewelry and gem fabrication.

Types of Titanium

• 6Al-4V, the most common titanium alloy, is composed of 90% titanium, six percent aluminum and four percent vanadium.
  
• Aerospace metals, including aluminum beryllium, nickel-based superalloys and titanium, have basic metal properties that are enhanced by key elemental alloying additions.
  
• Bought titanium can be found in various stages of fabrication such as mill products or completed parts. Distributors, retailers, manufacturers and metal finishing industries buy titanium.
  
• Ferro-titanium is a mixture of titanium sponge and titanium scrap with iron. After being mixed, the titanium and iron are melted together, forming a single alloyed metal.
  
• High temperature alloys are materials that have unique strength and/or corrosion properties at temperatures exceeding 1,000ºF (537°C), as well as high creep resistance and resistance to softening and metal loss from oxidation, sulfidation or carburization. High temperature alloys contain a large amount of nickel (from 25 to 60%) and critical amounts of molybdenum, columbium, chromium and titanium.
  
• Super alloys have superior strength and corrosion resistance under high temperatures. Superalloys are used in applications such as jet engine components, valves and gas turbines.
  
• Titanium alloys are composite materials that combines several metal components, with titanium being the predominant element, to create a hybrid metal.
  
• Titanium bars are sections of titanium that have been machined down to a solid bar. The titanium bars are frequently shipped out and used by companies that manufacture titanium products.
  
• Titanium billets are milled products that have been hot-worked by either the forging, extruding or roll processes, forming the material into round or round-corner squared products. Titanium billets, which have diameters starting at four inches, are mostly used as starting stock for subsequent forging or extrusion processes.
  
• Titanium bolts like other bolts, consist of a threaded pin or rod and a head at the opposite end. Titanium bolts are preferred over other materials for their superior strength and corrosion resistance.
  
• Titanium castings are formed by pouring molten material into a mold in which it solidifies into the shape of the mold. The reactive properties of titanium makes the forming of titanium castings complex, though these products have been successfully used in a wide variety of applications.
  
• Titanium foil is a very thin flat mill product of varying size and thickness that is produced during titanium extraction, formed and sold to titanium parts and product manufacturers for secondary fabrication.
• Titanium grades are used to distinguish the between the different types of titanium and titanium alloys based on their different qualities and purities to ensure proper material selection.
• Titanium ingots are large (sometimes more than 10 tons) masses, consisting of primarily titanium but including other alloying elements. Titanium ingots are large and mostly barrel shaped and are used primarily for heat exchangers and piping in such industries as petrochemical plants, nuclear power plants and seawater desalination plants.
  
• Titanium manufacturers provide various titanium products to many industries.
• Titanium metal is an extremely strong, low density and highly corrosion resistant substance used in a wide variety of industrial applications for which these traits and others, such as heat resistance, are desirable.
• Titanium pipes are long hollow tube-like pieces of hardware used for the transport of fluid and gaseous materials in a wide range of industrial, commercial and domestic applications.
  
• Titanium plates are widely used in the medical industry to correct skull defects or repair fracturing of the skull.
  
• Titanium rods have a superior strength-to-mass ratio. Titanium rods, if well-designed, are about 20% lighter than comparable steel rods.
  
• Titanium sheet is a thin, flat piece of titanium.
• Titanium sponge is pure titanium, which has a porous cellular form.
  
• Titanium tubing offers superior strength, rigidity and lightness. Titanium tubing, largely formed from an alloy consisting of 3% aluminum and 2.5% of vanadium (3-2.5), is costly, due to the refinery, tooling and processing costs of the material.
  
• Titanium wire is a fine wire or braided cable that is becoming more popular in the biomedical and industrial fields for its small diameter and admirable strength. Common diameters range from 0.0015" with fine wire to over 0.2" with weld wire.

Titanium Grades

*These figures are guidelines based on industry research; they should not be presumed accurate under all circumstances and are not a substitute for certified measurements. The information is not to be interpreted as absolute material properties nor does it constitute a representation or warranty for which we assume legal liability. User shall determine suitability of the material for the intended use and assumes all risk and liability whatsoever in connection therewith.

Titanium Terms

Alloy - A uniform mixture or solid solution of at least two metals. Titanium is most often acquired as an alloy.

Alpha Case - A brittle, oxygen-enriched surface layer that is caused by the heat treatment of titanium at high temperatures in an oxygen atmosphere. Alpha case should be removed prior to any subsequent processing or finishing, as it can result in the embrittlement of the titanium material, making it susceptible to stress corrosion.

Anodize - To coat or cover a metallic surface with a protective or decorative oxide using electricity. The colors produced by anodizing do not fade, as they are not a dye or a pigment.

Blasting - A mechanical grit or abrasive blasting process used to remove scale from larger titanium products, such as ingots and billets. The grit, composed of silica, zircon and aluminum, leaves a fine dust that is removed from the titanium by a pickling process.

Chromium - An alloying element that is used in several titanium alloys. Chromium typically has an alloying weight percentage range of 2-12%.

Density - The amount of mass contained within a specific volume under standardized conditions. The density of titanium is 4,507 kg m-3, while the density of silver is 10,490 kg m-3.

ELI (Extra Low Interstitials) - The elements oxygen, nitrogen and carbon, referred to as interstitials, which have been reduced beyond the standard titanium alloy requirements in order to improve the ductility and fracture toughness of the alloys.

Embrittlement - A condition of metal that results in the metal's losing a large quantity of ductility and/or toughness. Several sources-such as hydrogen pickup from water vapor, pickling acids and hydrocarbons and liquid metal embrittlement from liquid cadmium, mercury and silver-cause embrittlement in the susceptible titanium alloys.

Grade - The number given to the variety of types of titanium that distinguishes the different qualities and purities of that titanium and its alloys from those of other types. Grade 2 is the most common form of pure titanium, while Grade 4 is the strongest.

Grains - Microstructures that connect to form titanium. The changing of the size and shape of the grains through controlled processes results in the enhancement of the mechanical properties of titanium alloys.

Inclusion - A particle of foreign material, such as oxide, sulfide or silicate compounds, embedded within titanium products. If left unattended, inclusions may cause failure of the material.

Laser Cutting - A widely-used procedure for cutting thin gauge titanium products to close tolerances.

Melting Point - The temperature at which a solid liquefies at standard atmospheric pressure (SAP). The melting point of titanium is 3,034°F (1667.8°C).

Pickling - A process that removes oxide film from the surface of titanium products through chemical bathing.