Pure tungsten electrodes

CK's April 2024 catalog gives at least 99.95% tungsten for its pure grade. Diamond Ground describes EWP as at least 99.5% tungsten. CK's green T3327G and blue T3327GL2 are the same nominal size but different grades. Match the grade, torch fit and AC power source. CK ordering dimensions and part numbers

Function and identification

A pure tungsten electrode carries the GTAW arc. Specify filler separately and replace an electrode when erosion, overheating or contamination affects its use. Miller, guide to TIG welding basics

Pure tungsten is identified by a green color mark and the designations EWP in AWS terminology and WP in ISO terminology. CK Worldwide lists these designations together in its ordering chart. Do not confuse green pure tungsten with CK's chartreuse LaYZr blend, which has a different composition and designation. Preserve package identification when preparing electrodes or removing a marked end; color alone is a poor purchasing specification once markings have been ground away. CK tungsten ordering chart

“Pure” means an electrode without intentional oxide additions, rather than an assertion that no trace impurities exist. Diamond Ground Products describes EWP as at least 99.5% tungsten. CK's April 2024 catalog lists its pure grade at at least 99.95%. These are different statements of scope: a general classification description and a supplier's published product table. Specify the required classification and obtain the supplied product's documentation instead of treating the higher number as a universal EWP requirement. DGP electrode guidebook; CK catalog, Form 4500, April 2024, p. 62

Where pure tungsten fits

CK recommends its pure grade for low-to-medium-current AC welding of aluminum and magnesium with transformer-based constant-current sources. It notes easy ball formation, a tendency to spit at higher current and a restriction to non-critical welds. That last restriction is CK's product guidance, not a definition of every welding code's permitted electrodes. A procedure naming pure tungsten still needs an electrode suitable for the specific equipment, joint and acceptance requirements. CK tungsten specifications

Modern AC inverter equipment changes the choice. Miller's April 26, 2026 guidance favors ceriated or lanthanated electrodes over pure tungsten for advanced AC inverters. Pure tungsten develops a rounded tip, which produces a broader arc and can wander; an oversized hot ball can split and contaminate the pool. A properly prepared oxide-doped electrode can retain a truncated point and provide a more focused arc. Miller also acknowledges that some procedures still require pure tungsten, so “inverter” is not an absolute prohibition independent of the machine and procedure. Miller, choosing tungsten for AC TIG

The practical selection sequence is therefore equipment first, then operating conditions: identify AC or DC, source model and waveform, current range, electrode diameter and end preparation. AC balance changes electrode heating and cleaning action; it should not be changed merely to make an unsuitable electrode survive. Compare any proposed electrode substitution with the procedure's requirements and the source manufacturer's recommendations. Miller, AC tungsten selection questions and balance discussion

Diameter, torch fit and end preparation

CK lists both examples at 3/32 inch × 7 inches, nominally 2.4 × 175 mm. Check collet, holder and back-cap clearance with the actual stock. CK ordering dimensions and part numbers

Use end preparation for the chosen electrode and power source rather than applying one sharpening rule to all TIG work. CK's technical guide illustrates a rounded pure-tungsten AC tip with a maximum ball diameter equal to the electrode diameter. It separately illustrates pointed/truncated preparations for other conditions. This is manufacturer guidance for the illustrated setup, not permission to keep increasing current until an arbitrary large ball forms. Its current tables also distinguish tungsten type, polarity, waveform and shielding gas; a diameter alone is insufficient to establish a current limit. CK technical guide, Form 116, December 2023, pp. 6–8

Keep preparation equipment clean. DGP recommends a grinding wheel dedicated to tungsten and cutting away a contaminated portion rather than simply redistributing it during sharpening. It warns that grinding a contaminated tip may leave contamination in the electrode and transfer it onto the wheel for later electrodes to pick up. Avoid improvised snapping methods that can damage the remaining rod. Preparation quality matters to arc repeatability as much as the visible end shape. DGP preparation and contaminated-tip removal

Shielding, inspection and replacement

The hot electrode needs shielding during welding and cooling. Argon or an appropriate argon/helium mixture belongs to a TIG setup; an argon/CO₂ MIG mixture can immediately contaminate it. More flow is not automatically better: insufficient delivery, excessive flow and drafts can all impair coverage. Check the gas supply, hose connections, cup and gas lens as a system before blaming electrode chemistry. Miller, common TIG welding problems

These symptoms can share causes. Miller's troubleshooting guidance connects burnback with electrode heating, size, polarity or shielding, and calls for clean base metal and filler. Replacing a rod without correcting the underlying condition may simply repeat the failure. There is no universal electrode lifetime or replacement interval established by these sources. Miller, TIG basics troubleshooting

Grinding also creates particulate exposure. The absence of intentionally added thorium does not eliminate the need to control grinding dust and follow the electrode and grinder instructions. Keep alloy identification with grinding waste, especially where multiple tungsten grades share a preparation area. DGP grinding guidance

Related reference

Welding methods