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This specification defines the requirements for
classifying titanium and titanium alloy electrodes and rods for GTAW, GMAW, and
PAW. Titanium and titanium alloy filler metals are classified based on their
chemical composition, which is determined by filler metal analysis or analysis of
the stock from which the filler metal is made.
The chemical symbol for titanium (Ti) follows the
letters “ER” in the classification to identify the filler metal as titanium or
a titanium- base alloy. The numeral portion of the designation identifies the
chemical composition. Therefore, the classification ERTi-9 is a bare wire
electrode or rod (ER) that is titanium based (Ti) and contains a nominal
alloying content of 3% aluminum and 2.5% vanadium (-9). The letters “ELI” may
appear at the end of the classification, indicating that the filler metal is
produced to meet with extra-low content of interstitial elements (i.e., carbon,
oxygen, hydrogen, and nitrogen).
Titanium is a reactive metal and is sensitive to
embrittlement by oxygen, nitrogen, and hydrogen. A good protective atmosphere
is therefore required during welding, which can be provided by high purity
inert gas shielding in air or in a chamber, or by welding in a vacuum. Filler
metal is usually matched to the chemical composition of the base metal to which
it is joined. For increased joint ductility, unalloyed or pure titanium filler
metal may be used.
In 2004, A 5.16 was revised to adjust interstitial
chemistry ranges of the titanium filler metals to ensure the required
mechanical properties were met. This included designating a range for oxygen
for all alloys instead of maximum oxygen content. Additionally, eighteen new
filler metal compositions were classified. In 2007, A 5.16 was again revised to
include five new classifications.
ERTi-9 and ERTi-9ELi were also combined into the
ERTi-9 classification, because ERTi-9 is now classified with lower interstitial
limits. The lower interstitial content filler metal is required to weld grade 9
titanium alloys.
Titanium welding materials are assigned F-Nos. 51,
52, 53, 54, 55 and 56 in QW-432 of Section IX, and titanium and titanium alloy base
metals are grouped as P-Nos. 51, 52, and 53 in QW/QB-422. The ASME Material
Specifications for the various grades are SB-265, SB-338, SB-348, SB-363,
SB-381, SB-861, and SB-862. The text that follows describes some titanium and
titanium alloy electrodes and rods.
The ERTi-1, ERTi-2, ERTi-3, and ERTi-4 filler metals
are commonly referred to as commercially pure (CP) titanium or unalloyed titanium.
Commercially pure Grade 2, UNS R50400 is the most widely used titanium alloy
for industrial applications because of its good balance of strength,
formability, and weld ability. UNS R50400 base metal is grouped as P-No. 51 in
QW/QB422 and can typically be welded with these filler metals.
The ERTi-5 filler metal has a nominal composition
that includes 6% aluminum and 4% vanadium (6–4 titanium). The 6–4 titanium alloys
have both high strength and excellent fatigue strength, and they are
heat-treatable as well as readily weld able. ERTi-5ELI filler metal is the
extra-low interstitial (ELI) version of ERTi-5 that is used in applications
requiring high fracture toughness.
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