Before welding, clean both the base metal and the filler metal. Use a stainless steel brush to remove surface debris, and use a degreaser to remove oil, grease, dirt and paint. Contaminants can result in unstable, contaminated welds. Clamp the two work pieces together to best align your welds, and make short tack welds, 1/4 inch in width, before joining the tack welds with a solid weld bead. Tack welding, like clamping, helps you to achieve and retain good material alignment during welding.
Position your TIG torch differently for different kinds of joints. When welding a butt joint, center the arc on the two edges of the joint. To weld a lap joint, dip the filler rod next to the edge, which receives more heat than the joint beneath it. Be sure that you have enough filler material to complete the joint. Weld a T-joint by joining together the edge and the flat surface, angling the torch to direct more heat to the flat surface, and depositing the filler rod where the edge is melting. When welding a corner joint, direct the torch at the joint centerline and melt both edges of the adjoining pieces.
To improve your arc starting, use the smallest diameter electrode possible that is compatible with your amperage. Use DC-straight polarity when welding stainless steel and 2 percent thoriated tungsten. Use 100 percent argon shielding gas, keep the torch and work leads as short as possible, and move the power source as close to the stainless steel being welded as possible. Whenever possible, use the highest quality torch and work leads.
Ceriated tungsten and pure tungsten electrodes are the two kinds of electrodes recommended for stainless steel welding. Ceriated tungsten electrodes can withstand higher temperatures, start well at low amperages, and work at both AC and DC polarities. Ceriated electrodes allow welding amperages to be increased by 25-30 percent, as opposed to pure electrodes which melt at low temperatures and subsequently interfere with your ability to see the weld puddle.