User talk:Jordacheha

tungsten eletrodes
EWP (100% Tungsten, Green) These electrodes are unalloyed, “pure” tungsten with a 99.5% tungsten minimum. They provide good arc stability when using AC current, with either balanced wave or unbalanced wave and continuous high-frequency stabilization. Pure tungsten electrodes are preferred for AC sine wave welding of aluminum and magnesium because they provide good arc stability with both argon and helium shielding gas. Because of their inability to carry much heat, the pure tungsten electrode forms a balled end.

EWCe-2 (2% Cerium, Orange) Alloyed with about 2% ceria, a non-radioactive material and the most abundant of the rare earth elements, the addition of this small percentage of cerium oxide increases the electron emission qualities of the electrode which gives them a better starting characteristic and a higher current carrying capacity than pure tungsten. These are all-purpose electrodes that will operate successfully with AC or DC electrode negative. Compared with pure tungsten, the ceriated tungsten electrodes provide for greater arc stability. They have excellent arc starting properties at low current for use on orbital tube, pipe, thin sheet and small delicate part applications. If used on higher current applications the cerium oxide may be concentrated to the excessively hot tip of the electrode. This condition and oxide change will remove the benefits of the cerium. The nonradioactive cerium oxide has slightly different electrical properties as compared to the thoriated tungsten electrodes. For automated (orbital tube, etc.) welding these slight changes may require welding parameters and procedures to be adjusted. The cerium electrodes work well with the Advanced Squarewave power sources and should be ground to a modified point.

'''EWLa-1 (1% Lanthanum, Black), EWLa-1.5 (1.5% Lanthanum, Gold) and EWLa-2 (2% Lanthanum, Blue) Alloyed with nonradioactive lanthanum oxide, often referred to as lanthana, another of the rare earth elements. These electrodes have excellent arc starting, low-burn-off rate, arc stability, and excellent re-ignition characteristics. The addition of 1 – 2% lanthana increases the maximum current carrying capacity by approximately 50% for a given size electrode using alternating current compared to pure tungsten. The higher the percentage of lanthana, the more expensive the electrode. Since lanthana electrodes can operate at slightly different arc voltages than thoriated or ceriated tungsten electrodes these slight changes may require welding parameters and procedures to be adjusted. The 1.5% content appears to most closely match the conductivity properties of 2% thoriated tungsten. Compared to cerium and thorium the lanthana electrodes had less tip wear at given current levels. Lanthanum electrodes generally have longer life and provide greater resistance to tungsten contamination of the weld. The lanthana is dispersed evenly throughout the entire length of the electrode and it maintains a sharpened point well, which is an advantage for welding steel and stainless steel on DC or the AC from Advanced Squarewave power sources. Thus the lanthana electrodes work well on AC or DC electrode negative with a pointed end or they can be balled for use with AC sine wave power sources. EWTh-2 (2% Thorium, Red) and EWTh-1

(1% Thorium, Yellow) Commonly referred to as 1 or 2% thoriated tungstens, these are very commonly used electrodes since they were the first to show better arc performance over pure tungsten for DC welding. However, thoria is a low-level radioactive material, thus vapors, grinding dust and disposal of thorium raises health, safety and environmental concerns. The relatively small amount present has not been found to represent a health hazard. But if welding will be done in confined spaces for prolonged periods of time, or if electrode grinding dust might be ingested, special precautions should be taken concerning proper ventilation. The welder should consult informed safety personnel and take the appropriate steps to avoid the thoria. The thoriated electrode does not ball as does the pure tungsten, cerium or lanthana electrodes. Instead, it forms several small projections across the face of the electrode when used on alternating current. When used on AC sine wave machines, the arc wanders between the multiple projections and is often undesirable for proper welding. Should it be absolutely necessary to weld with these type machines, the higher content lanthana or thoria electrodes should be used. The thoriated electrodes work well with the Advanced Squarewave power sources and should be ground to a modified point. These electrodes are usually preferred for direct current applications. In many DC applications, the electrode is ground to a taper or pointed. The thorium electrode will retain the desired shape in those applications where the pure tungsten would melt back and form the ball end. The thoria content in the electrode is responsible for increasing the life of this type over the pure tungsten, EWP.

EWZr-1 (1% Zirconium, Brown) A zirconium oxide (zirconia) alloyed tungsten electrode is preferred for AC welding when the highest quality work is necessary and where even the smallest amounts of weld pool contamination cannot be tolerated. This is accomplished because the zirconium alloyed tungsten produces an extremely stable arc which resists tungsten spitting in the arc. The current carrying capability is equal to or slightly greater than an equal sized cerium, lanthana or thorium alloyed electrode. Zirconium electrodes are typically used only for AC welding with a balled end.

EWG (unspecified alloy, Gray) This classification covers tungsten electrodes containing unspecified additions of rare earth oxides or combinations of oxides. As specified by the manufacturer, the purpose of the additions is to affect the nature or characteristics of the arc. The manufacturer must identify the specific addition or additions and the quantity or quantities added. Some “rare earth” electrodes are in this category and they contain various percentages of the 17 rare earth metals. One mixture is 98% tungsten, 1.5% lanthanum oxide, and a .5% special mixture of other rare earth oxides. Some of these electrodes work on AC and DC, last longer than thoriated tungsten, can use a smaller size diameter tungsten for the same job, can use a higher current than similar sized thoriated tungstens, reduce tungsten spitting, and are not radioactive.