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Chemical Composition of unalloyed Titanium Grades

Titanium-rich end of Ti-based binary phase diagram different types encountered depending on the type of solute

Production of IngotTitanium sponge, fragmented master alloy, TiO2 and conditioned scrap being recycled are mixed homogeneously, cold pressed into compacts with 65-70% density. Compacts plasma welded into a cylindrical electrode Electrode remelted in a vacuum arc furnace in a water cooled crucible.Due to heat caused by electic arc, titanium at electrode bottom melts and drops fall into underlying melting bath.Ingot formation progresses with electrode getting consumed progressively.SCRAP RECYCLINGRaw materials (Ti sponge, masteralloys etc.) being very expensive, recycling of scrap generated during manufacture is of immense commercial importance.Both solid and turning scrap is recycled.Strict quality control necessary while recycling scrap to ensure product quality.While recycling turnings generated using WC tooling, care should be taken to ensure that tungsten particles do not get into ingot.

Effect of forging temperature on forging pressure for three titanium alloys and 4340 alloy steel

Effect of strain rate on flow stress of titanium alloy Ti-8Al-1Mo-1V at 955C

Effect of strain rate on flow stress of - titanium alloy Ti-6Al-4V at 900C

Effect of strain rate on flow stress of metastable titanium alloy Ti-10V-2Fe-3Al at 815CClosed Die ForgingClosed die forgings are made of titanium alloys with weight ranging from a few grams to over 1 TonneForge hammers as well as mechanical and hydraulic presses used for manufactureChallenge lies in obtaining uniform microstructure and mechanical properties all over the volume of forging, considering that large variations in cross section can occur Critical parts like rotating compressor blades of aero-engine are manufactured using closed die forging

Shear bands in forged blades of Ti 6-2-6-2 S and processing map of alloy 6-2-4-2 STUBE MANUFACTURETube manufacture is largely confined to commercially pure titaniumSeamless tubes are manufactured by hot extrusion followed by cold pilgeringSeam welded tubes are used extensively in heat exchangers in power plants, desalination of sea water, ship building etc.The starting material is cold rolled and slit to width strip, 0.4-0.9mm in thickness depending on application. High demands are placed on dimensional and surface quality aspects of the stripThe tubes are manufactured in 15-30mm rangeHeat Treatment of Ti, its alloysStrss relieving treatment given to relieve residual stresses developed during hot working / fabricationAnnealing carried out to produce an optimum combination of mechanical properties, machinability, dimensional and structural stabilitySolution treatment and aging done to increase strengthOxidising atmosphere is used to reduce hydrogen pick-up. If inspite of it, unacceptable hydrogen pick-up occurs, vacuum annealing is resorted to for removal of hydrogenPoor correlation between strength and hardness. Hence hardness cant be used to monitor Heat Treatment Pickling of Titanium, its AlloysPickling has 2 functions to serve: Removing the oxide scale Removing the case layerMolten salt descaling is an effective method of removing oxide scale. Grit blasting is also effective in removing scaleHF-HNO3 acid pickling used to remove underlying case, once oxide scale is removed. Bath conditions to be closely controlled to prevent hydrogen pick-up Problems in machining titanium Compared to high strength steels, titanium, due to its unique physical and chemical properties, poses the following problems: Lower thermal conductivity of Ti hinders quick dissipation of the heat caused by machining, leading to increased wear of cutting tools. Lower modulus of elasticity leads to high spring back, causing Ti parts to move away from the cutting tool Lower hardness and high chemical reactivity of Ti lead to galling with the cutting tool.WELDING OF TITANIUMFor fabrication of chemical engg. plant & Eqpt., commercially pure titanium is used. TIG & MIG welding methods are used.Welding of alloy titanium is difficult compared to welding pure titanium: alloys are weldable Among + alloys Ti-6Al-4V has good weldability alloys are not weldable Titanium being a reactive metal, entry of air to the weldzone is to be strictly prevented through protection with an inert gas cover to prevent access to air ELECTRON BEAM WELDINGIn aircraft industry alloy grade Ti is used. Electron Beam Welding (EBW) is extensively employed. TIG welding is adopted only in a few cases.Much better joints can be obtained by EBW of alloy grade Ti. By welding in a vacuum chamber, gas absorption is prevented.The HAZ is very narrow and influence of welding on structure is minimal.Complicated work-pieces can be welded without distortion.Components with large wall thickness as well as thin walled components can also be successfully welded.

Comparison of Ti-6Al-4V TIG and EB welds

Microstructures of the alloy Ti-6Al-4V

Typical microstructure of elevated temperature titanium alloys: bimodal (TIMETAL 834) and lamellar (TIMETAL 1100)

Influence of microstructure on creep of TIMETAL 1100

Influence of microstructure on fracture toughness of Ti-6Al-4V (J-integral measurements).

Fatigue crack growth behavior of two extreme microstructures of Ti-6Al-4V

Creep resistant alloy development : Larsen Miller Plot showing improvements in last 40 years

Density normalised temperature dependence of the yield strength of several Ti alloys and a Ni base superalloy

Metallic Materials used as biomaterialsStainless steel, e.g. 316LCast CoCr based alloys, e.g. CoCr30Mo6Wrought CoNiCr alloys, e.g. CoNi35Cr20cp-titanium and titanium alloys, e.g. Ti6Al4Vcp-niobiumcp-tantalum

Why titanium is preferred as a biomaterialIn human body fluid Ti, Ta and Nb show good corrosion resistance. Stainless steels, CoCr and CoNiCr alloys behave poorly.Repair of passive layer occurs fast in Ti, Ta and Nb. It is slow in stainless steels, CoCr and CoNiCr alloys.Ti, Ta and Nb are reported to be biocompatible because they form protective surface layer. Titanium shows better bioadhesion (integration of metallic implants by bone ingrowth) compared to 316L stainless steelWhy titanium is preferred as a biomaterial contd.Titanium has youngs modulus closest to that of bone. Biofunctionality (ratio of fatigue strength to youngs modulus) is highest for titanium alloysTitanium can be processed/fabricated to the required product shape , size and qualityTitanium is less expensive than Co-base alloys, niobium and tantalum

Breakdown potential of metallic biomaterials in Hanks solution and repassivation in 0.9% NaCl (pH=7.4)Attractive features of investment casting of TitaniumIntegral structural elements can be manufactured cost-effectively, with little or no machining effortCast parts show excellent dimensional accuracyCastings have an excellent surface qualitySatisfactory levels of mechanical properties can be guaranteed

Melting of titanium in vacuum arc furnace with a consumable electrodeMolding Materials

Should be non-reactive to liquid Ti or at least react in a delayed way - a challenging task, considering that Ti is a reactive metalConventional molding materials (used in non-tianium casting - typical composition Al2O3-SiO2) not suitable; molten Ti will react and dissolve Al, Si as well as oxygenProprietary non-reactive shell systems have been developed and patented, incorporating facing of high melting metals (tungsten) or special ceramic oxide layers with thermodynamic stability > that of titanium oxide.Technological measures adopted to eliminate casting defectsTo overcome the problem of limited fluidity, centrifuge employed to accelerate molten metal into mold cavityChemical milling of the contaminated surface layer, a few tenths of a millimeter in thicknessHipping at ~1000 bar pressure of an inert gas atmosphere and ~900C to eliminate shrinkage cavities, porosity etc.

Examples of cast titanium alloys

Typical mechanical properties of cast titanium alloys

The Ti-Al phase diagramTITANIUM ALUMINIDESBaseBroad composition(At%)Density(g/cm3)Modulus(Gpa)Ductility at Room Temp.Creep Limit(C)Oxdn. Limit(C)Ti3Al23-25% Al11-18% Nb4.1-4.7100-1452-10760650TiAl48-54% Al3.7-3.9160-1761-41000900Ti2AlNb21-25 Al 25-30 NbConventional Ti alloys4.596-10020600600

Titanium heat exchanger plates

A plate heat exchanger being assembled out of unalloyed titanium sheets

a) Plate and b) tube heat exchangers manufactured from titanium

Components of titanium alloys produced by closed die forging

The main landing gear of the Boeing 777 primarily uses forged parts of Ti-10V-2Fe-3Al, among others the truck beam Bogie Beam

Front fans of commercial Rolls-Royce Trent engines made of Ti-6Al-4V

Titanium blisks for compressor applications

Presently the largest forged titanium blade has a length of 1650 mm (a) and is used for L-0 rows of steam turbines (b)

Open-die forged housing rings for the engine RB199: machining in progress

Intermediate casing for large jet engines. Diameter 152 cm, weight 173 kg; (b)diameter 150 cm, weight 240 kg

Electron beam welded wing-box of the aircraft type F14

Electron beam welded helium gas container for the satellite Symphony

Sequence of operations during spin forming of Ti-15-3 half shells

Various investment cast parts for applications in the low temperature section of a gas turbine engine

Investment cast titanium engine components

Investment cast titanium condenser rotors

Components of a hip implant made from cast titanium

Exhaust gas turbocharger rotors made from TiAl

-TiAl turbine blades

Cost comparison for one design of titanium alloy aircraft fitting machined from blocks, forgings and castings

Comparision of weight forged vs. cast intermediate housing for the engine RB 199