Titanium grade 7 (ERTi-7) alloy is probably the most corrosion resistant titanium weld metal in industrial applications. Mechanical and physical properties are similar to those of ERTi-2. The 0.12 wt.% palladium addition improves corrosion performance and extends the use of titanium into mildly reducing media, to much higher chloride levels, or where the environment fluctuates between oxidizing and reducing, and where crevice or under deposit corrosion is a problem.
Titanium grade 7 Welding Rods Filler Metal is used for gas-tungsten-arc-welding (GTAW), gas-metal-arc-welding (GMAW) and plasma-arc-welding (PAW).
Typical Chemical Compositions %:
C 0.03 - O 1.0 - N 0.020 - H 0.015 - Fe 0.20 - Pd 0.12/0.25 - Ti rim.
Typical Mechanical Properties:
Tensile strength: 345 MPa (50,000 psi)
Yield strength: 275 MPa (40,000 psi)
Elongation: 20 %
Filler metals available in spools and in cut straight lengths in a variety of sizes and diameters.
The procedures and equipment are generally similar to those used for welding stainless steel or aluminum. Titanium and titanium alloys are extremely reactive and sensitive to embrittlement by oxygen, nitrogen, and hydrogen, above 315°C (600°F). Additional precautions, exceeding those required during the welding of austenitic stainless steel or aluminum alloys, must be taken to shield the weld and hot root side of the joint from air. In welding titanium or titanium alloys, only argon and helium, and occasionally a mixture of these two gases, are used for shielding. The filler metal composition is usually matched to the grade of titanium being welded. The filler metal and the base metal should be meticulously cleaned at the time of welding. Grease and oil accumulated during forming and machining must also be removed before welding to avoid weld contamination. If the hot end of the filler metal is removed from the gas shield prior to cooling and then reused, it contributes to weld contamination. Welding rod should be added by technique that keeps the hot end within the torch gas blanket. If the rod tip becomes contaminated, the discolored end should be cut off before reusing.
Welding can also be done remotely in a chamber or in a glove bag. These chambers can be purged of air and back filled with inert gas, or, if they are rigid gas tight walls, can be evacuated to at least 10-4 torr [0.013 Pa] to remove any air contaminants.