ANS:A - close the surface porosity.

Shot peening is not typically performed to close surface porosity in welding processes. Shot peening is a surface treatment method used to induce compressive residual stresses and improve the fatigue strength of metal components. It involves bombarding the surface of a material with small metallic or ceramic particles (shots) at high velocity to create small indentations or dimples. In welding processes, particularly in multipass welding, the primary purpose of shot peening is not to close surface porosity but rather to break the continuity of columnar grains and reduce the likelihood of cracking or other defects along the grain boundaries. Shot peening can also help improve the fatigue resistance and mechanical properties of the weld joint by inducing beneficial compressive stresses. To address surface porosity in welding, other techniques such as proper welding parameters, filler material selection, shielding gas control, and post-weld treatments like grinding or re-welding may be employed, depending on the specific circumstances and requirements of the application.