That lift arm is probably cast steel, not cast iron. 6011 is a pretty good all-purpose rod, but not for cast iron. Nodular iron, like what's used in high-stress applications for rear end housings, etc. is a lot easier to weld than an engine block or a cylinder head. Jasper engine/transmission exchange in Jasper, Indiana has an entire department dedicated to repairing engine blocks, transmission and rear end housings, and they do the preheat/post heat/peen method. Burying the part in sand to do a slow cooling is also helpful in preventing stress cracks.
Jerry
