We at Divine Metal & Alloys Stainless steel 309 can be divided into two types – welded pipes and seamless pipes. Welded pipes are usually made by welding larger pieces of metal together while seamless pipes are formed through a hot rolling process that creates a single piece with no seams or joints. Both types have their own unique advantages and disadvantages, so it’s important to consider which one is best suited for the application before making a decision.