HB porosity.

[Subash Kuwait]

Dear friends.........

Please explain about hollow bead porosity ,what is the reason for this problem,how we can reduce  & prevent the problem.Welding process GTAW only,below 6"dia pipes.Material Spe A106 Gr.B.

 

THANKS & REGARDS

subash sundharan,kuwait.

[S.Mohammed]

1. install wind shield around welding area.
2.check.cleaniness of filler n fitup area
3.chek root face/gap it should b as per wps.
4.avoid excessive or more current during root pass.
5.do little preheating to remove moisture from fitup area.
6.last but not least do.frequent root inspection to.avoid abd correct the defects.
7. prepare defects area wise welder wise shift wise for preventive actions.

regards
mohd.

[c sridhar]

 

Hollow bead is a term for linear porosity which occurs in the root pass of an open root weld. 

The parameters which affect the formation of hollow bead are,

       a.      High levels of welding current and travel speed were found to have a major influence on

      Hollow bead. It could be also due to  arc gap.

 

       b.     The hydrogen gas rejected by the saturated liquid ahead of the solid liquid interface accumulates in one single gas   

             bubble, which is enclosed by columnar grains growing parallel (linear pore)  to the welding direction.

   

 Hence,  control the hollow bead defect by 

1.   Controlling the welding current and travel speed.

2.   Reduce the arc gap by increasing the tugsten extension from the ceramic cup by 1 to 2 mm.

 

Sridhar.

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From: Subash Kuwait <suba...@yahoo.com>
To: materials-welding <material...@googlegroups.com>
Sent: Saturday, 4 January 2014 9:47 AM
Subject: [MW:19761] HB porosity.

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