3.4.5
Electrodes
Tungsten Electrodes
Tungsten is a rare metallic element used for manufacturing TIG welding electrodes. The TIG process
relies on tungsten’s hardness and high-temperature resistance to carry the welding current to the arc.
Tungsten has the highest melting point of any metal, 3,410 degrees Celsius. Tungsten electrodes are
non-consumable and come in a variety of sizes, they are made from pure tungsten or an alloy of
tungsten and other rare earth elements. Choosing the correct tungsten depends on the material being
welded, amps required and whether you are using AC or DC welding current. Tungsten electrodes are
colour-coded at the end for easy identification.
Tungsten Preparation
Always use DIAMOND wheels when grinding and cutting. While tungsten is a very hard material, the
surface of a diamond wheel is harder, and this makes for smooth grinding. Grinding without diamond
wheels, such as aluminium oxide wheels, can lead to jagged edges, imperfections, or poor surface
finishes not visible to the eye that will contribute to weld inconsistency and weld defects.
Always ensure to grind the tungsten in a longitudinal direction on the grinding wheel. Tungsten
electrodes are manufactured with the molecular structure of the grain running lengthwise and thus
grinding crosswise is “grinding against the grain.” If electrodes are ground crosswise, the electrons have
to jump across the grinding marks and the arc can start before the tip and wander. Grinding
longitudinally with the grain, the electrons flow steadily and easily to the end of the tungsten tip. The arc
starts straight and remains narrow, concentrated, and stable.
Electrode Tip/Flat
The shape of the tungsten electrode tip is an important process variable in precision arc welding. A
good selection of tip/flat size will balance the need for several advantages. The bigger the flat, the
more likely arc wander will occur and the more difficult it will be to arc start. However, increasing the
flat to the maximum level that still allows arc start and eliminates arc wonder will improve the weld
penetration and increase the electrode life. Some welders still grind electrodes to a sharp point, which
makes arc starting easier. However, they risk decreased welding performance from melting at the tip
and the possibility of the point falling off into the weld pool.
Electrode Included Angle/Taper
Welding Tungsten electrodes for DC welding should be ground longitudinally and concentrically
with diamond wheels to a specific included angle in conjunction with the tip/flat preparation. Different
angles produce different arc shapes and offer different weld penetration capabilities. In general,
blunter electrodes that have a larger included angle provide the following benefits
：
• Last Longer
• Have better weld penetration
• Have a narrower arc shape
• Can handle more amperage without eroding.
Sharper electrodes with smaller included angle provide:
• Offer less arc weld
• Have a wider arc
• Have a more consistent arc
The included angle determines weld bead shape and size. Generally, as the included angle increases,
penetration increases and bead width decreases.
Содержание GRAND TIG 250 DC PULSE
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