... ), 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 frequency welding), copper (winding type).4, finned tube ... size: 1, base tube: OD16, OD19, OD1 ", ...