Titanium Welding Overview
Titanium and its alloys offer excellent corrosion resistance to acids, chlorides and salt; a wide continuous service temperature range, from liquid nitrogen (-322°F) to 1100°F; and the highest strength-to-weight ratio of any metal.
For example, the most widely used grade of titanium alloy, ASTM Grade 5 (Ti-6Al-4V), has a yield strength of 120,000 psi and a density of 282 lb/ft3. In comparison, ASTM A36 steel has a yield strength of 36,000 psi and a density of 487 lb/ft3, while 6061-T6 aluminum has a yield strength of 39,900 psi and density of 169 lb/ft3.
In short, titanium is about 45 percent lighter than steel, 60 percent heavier than aluminum and more than three times stronger than either of them. While expensive initially, titanium lowers life cycle costs because of its long service life and reduced (or non-existent) maintenance and repair costs. For example, the Navy replaced copper-nickel with titanium for seawater piping systems on its LDP-17 San Antonio Class of ships because it expects titanium to last the entire 40 to 50 year life of the ship.
In addition to military applications, other common uses for this light, strong and corrosion-resistant metal include those for aerospace, marine, chemical plants, process plants, power generation, oil and gas extraction, medical and sports.
Titanium Welding Processes
The following fusion-welding processes are used for joining titanium and titanium alloys:
- Gas-tungsten arc welding (GTAW)
- Gas-metal arc welding (GMAW)
- Plasma arc welding (PAW)
- Electron-beam welding (EBW)
- Laser-beam welding (LBW)
- Friction welding (FRW)
- Resistance welding (RW)
Fluxes cannot be used with these processes because they combine with titanium to cause brittleness and may reduce corrosion resistance. The welding processes that use fluxes are electroslag welding, submerged arc welding, and flux-cored arc welding. These processes have been used on a limited basis. However, they are not considered to be economical because they require high-cost, fluoride-base fluxes.
Gas-tungsten arc welding is the most widely used process for joining titanium and titanium alloys except for parts with thick sections. Square-groove butt joints can be welded without filler metal in base metals up to 2.5 mm thick. For thicker base metals, the joint should be grooved, and filler metal is required. The heated weld metal in the weld zone must be shielded from the atmosphere to prevent contamination with oxygen, nitrogen, and carbon, which will degrade the weldment ductility.
Gas-metal arc welding is used to join titanium and titanium alloys more than 3 mm thick. It is applied using pulsed current or the spray mode and is less costly than GTAW, especially when the base metal thickness is greater than 13 mm.
Plasma arc welding is also applicable to joining titanium and titanium alloys. It is faster than GTAW and can be used on thicker sections, such as one-pass welding of plate up to 13 mm thick, using keyhole techniques.
Laser-beam welding is increasingly being used to join titanium and titanium alloys. Square-butt weld joint configurations can be used, and the welding process does not require the use of vacuum chambers; gas shielding is still required. This process is more limited than electron-beam welding regarding base metal thickness, which cannot usually exceed 13 mm.
Friction welding is useful in joining tube, pipe, or rods, where joint cleanliness can be achieved without shielding.
Resistance welding is used to join titanium and titanium alloy sheet by either spot welds or continuous seam welds. The process is also used for welding titanium sheet to dissimilar metals, that is, cladding titanium to carbon or stainless steel plate.
You only get one shot at welding titanium. Once you screw up, you cant get away with just welding it again like you can with stainless steel. Usually, the entire weld needs to be removed and sometimes that just plain ruins the product.
Titanium Welding Mistakes
There are 3 big mistake people make when tig welding titanium:
- Using the wrong filler metal – Trying to weld titanium with anything other than titanium turns the weld into a hard as glass material. You can hear it cracking before it even cools off.
- Not shielding the weld puddle adequately – When Titanium gets red hot, it loves to suck in all kind of impurities like oxygen and hydrogen. Once this happens, you are screwed, glued, and tattooed. Game over. The weld has to be removed.
- Not cleaning the metal – porosity is a problem when tig welding titanium. Anything on the surface like oil, or dust, will cause porosity. Strict welding codes like American Welding Society D17.1 have very strict limitations on porosity.
Dynamic Fabrication is your total source for welding, fabrication, machining, and assembly. We produce high quality work ranging from precision parts to complete assemblies. DFI is certified to weld all metals. We guarantee superior workmanship and quick turn-around. Founded in 1981, Dynamic Fabrication serves a wide variety of industries.