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Welding pin holes

HI all

I work in a company manufacturing and repairing mold, plunger for TV glass shell. In process we do welding machining and benching. We are doing tig welding on SS 420 forged casting. During polishing of weld material we are facing pin holes problem. Once a pin hole is welded a new pin hole appears on the same point at around 3 mm. After bechching the pin hole sometimes re-appears. Can any one help me to get rid of this problem? My process is as follows.

Vacuum blasting --Deplating (in NaOH solution)--cleaning--WELDING--MACHINING--POLISHING--sand blasting---plating --assembly.

This is polishing time when pin hole appears. After pin hole welding again polishing id done and pin holes re appears at same place at some distance say 3 to 5 mm away from previous one.

THANKS

RAJESH DUBEY
Plating shop employee - KOTA, RAJASTHAN, India
April 10, 2008

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April 10, 2008

It is contamination, Rahesh.
It may come from your welding rod, from the base material (contaminated from previous weldments), from your gas bottle and torch or from your welding procedure. Make sure everything is in order and you will succeed. Good luck,

Guillermo Marrufo
Monterrey, NL, Mexico