I have observed porosity at the HAZ of mild steel side of AISI 304 stainless steel and mild steel dissimilar weld. Welding technique was SMAW and the electrode used was E308L. What may be the reason for the porosity?
Hydrogen diffusion inside haz may be due improper baked electrodes, moist surfaces or improper welding current.
@Lalit Thakur
Sir, but HAZ at the SS side does not exhibit any porosity.
SS has more resistance to hydrogen diffusion than plain carbon steel. Have you performed preheating to remove the moisture contents ?
No sir, i didnt,actually i was doing repair welding on SS-MS repair welding.
Probably some MnS or other type of non metallic inclusion in the BM of mild steel, the peack temperature reach there might dissolved these inclusions or promote the coalesence. Other reason can be moisture or some oxide you must remove before welding
Following can be the probable causes:
- Improper baking of electrode
- You have not specified the groove dimensions, I understand you are making repair weld
- Sometimes higher heat input also can lead to porosity
- What is the base material thickness
With the above clarifications, some fruitful results can be derived
Is it possible to define somehow the shape and size of these pores? Perhaps you can share a metalografic image of the material. Then interpretation may become easier and more useful.
Degar Siva,
Stainless Steel can absorb Hydrogen and Nitrogen gasses upto
50 and 1500 ppm of these gasses respectively with out revealing.
Better check up your electrode section and preparation procedures.
which may solve your problem.
A.V.Sethuraman
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