To Create a Welding Symbol, Using the Symbol Library (AutoCAD Mechanical Toolset)

Click the Annotate tab Symbols panel Welding Symbol drop-down.
AutoCAD Mechanical toolset displays the welding symbols saved in the symbol library.
Click the symbol to insert.
Select an object to attach the weld symbol to.
If you attached the symbol to a line, in the drawing area, specify the start point for the leader.
If you attached the object to an arc, circle, ellipse or spline, skip to the next step.
Specify one or more points to define the vertices of the leader and press ENTER.