Lasor Welding porosity

[EricZhao]

Recently, I am assigned a project to find reason why our lasor welded part has porosity in the welding bead. Under the microscope, gas bubbles are as large as 5/1000''. The porosity usually exists at the boundary between the bead and the substrate.

As I have little experience with welding porosity anslysis. My questions are: Is there any general reasons that porosity formulate during the welding process? Is there any papers, books devoted specifically to welding porosity?

Thanks in advance

 

[TVP]

What are the materials being joined? How were they fabricated? Are the parts cleaned prior to welding?

 

[EricZhao]

The material is stainless steel. The substrate surface is milled and grinded. The bead is cold drown stainless steel wire. Surface are all cleaned before welding.