Welding of 309S 1.4833 Stainless Steel

The austenitic grades are generally considered to be the most weldable of the stainless steel. They can be welded using all of the common processes. This is generally true of Alloys 309/309S and 310/310S. When filler metal is required, matching compositions are generally used. The elevated alloy contents of this grade can make the weld pool sluggish. If weld pool fluidity is a problem, filler metal containing silicon can help (e.g., ER309Si, ER309LSi).

Alloys 309/309S and 310/310S exhibit a relatively high coefficient of thermal expansion and low thermal conductivity and form low levels of ferrite in the solidifying weld metal. These factors can lead to hot cracking. The problem can be more severe for restrained and/or wide joints. Filler metal with a lower alloy content (e.g., ER308) will increase the amount of ferrite in the weld deposit and reduce the tendency for hot cracking. The subsequent dilution of the base metal may decrease the corrosion resistance / heat resistance of the weld.

The "S" grades are relatively low in carbon. With proper weld practices, intergranular corrosion of the heat affected zone is unlikely. Heat tint or scale should be removed to ensure complete restoration of corrosion resistance near the weld. Grinding or brushing with a stainless steel brush can be used to remove the heat tint scale. Acid pickling will also remove heat intent. Small pieces can be treated in a bath, and larger pieces can be locally pickled using a special paste consisting of a mixture of nitric acid and HF or hydrochloric acid suspended in an inert filler. A thorough water wash should immediately follow, taking care to completely remove all traces of pickling paste.

SA 213 TP 309S