... finned tubes. 1, finned tube function: heat transfer;2, the fin-tube type: DR (extrusion type), L (winding type), high frequency ... welding;3, the fin-tube material: 1, base tube: carbon steel, stainless steel, copper ... , copper alloy, titanium and so on. 2, fin: aluminum (extruded type or wound type), steel (wound type, high ...