Flux cored TIG filler rods may solve back purging problems!!!

Generally, in the TIG welding of stainless steel piping or closure weld seam of any vessel extensive purging is required before welding, and backing gas during welding, to avoid heat tint brought about by oxidation, which if happened, will result in loss of corrosion resistance.

(Heat tint formed is a thicker chromium oxide scale with a mixture of iron, nickel and other oxides. The thin layer beneath this surface is chromium-depleted layer. If heat tint is not removed, corrosion may start from this chromium-depleted region.)

This flux cored TIG rods contains metal powders and slag formers inside the core which produces slag to protect the reverse side of the root pass. This allows root pass welding without the use of purging gas. Thus, it is possible to eliminate gas purging downtime and save the costs of expensive purging gases before and during welding.

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Formation of key-hole during welding is very important in order to supply slag onto reverse side bead.

Watch Video demonstration of this filler rods by Welding alloys here, https://www.youtube.com/watch?v=X4L81c7IdZQ

Reference: Welding Alloys literature, KOBELKO literature

Keep reading, Happy welding

Thank you,

KP Bhatt

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Spatter generating mechanism in CO2 welding

CO2 dissociates to CO and O2 at high temperature and the heat is absorbed during dissociation. Consequently, the arc heat is also absorbed and the arc concentrates at the bottom of the droplet. This phenomenon vibrates the bottom of the droplet and the weld pool strongly and makes the arc reaction force to push up the droplet.

There are two mechanisms that cause spatter for the different current ranges.

One is the “micro-short circuit (between the droplet and the work pieces)” that occurs in all current range. The arc power causes small spatter by vibrating the weld pool and the bottom of the droplet strongly. The other is the “arc reaction force” that occurs at the middle to high current range. The arc reaction force causes big spatter by pushing up the droplet. The “micro-short circuit” and “arc reaction force” are both caused by the property of the CO2 gas described above.

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A high welding current immediately after short-circuit break makes a long arc and reduces the micro-short circuit. In contrast, a low welding current immediately after short-circuit break reduces the influence of the arc reaction force.

For these reasons, proper welding parameter must be optimized such that arc length is optimized which ultimately decreases the amount of spatter in CO2 welding.

Keep reading, Happy welding

Thank you,

Keyur Badami