Double channel torch. which allows concentric flow of two different shielding gases. was designed and manufactured in order to pursue double channel torch gas metal arc welding of unalloyed structural steel S235JR (EN 10025-2) with fourteen passes. Tensile and Charpy V-notch tests were realized and the results were compared with those of conventional gas metal arc welding. https://spencertifieders.shop/product-category/preamps/