CPC Subgroup
B21D 51/14 Flattening hollow objects for transport or storage; Re-forming same (making tubes from doubled flat material B21C37/14)
Full Title
Making hollow objects (from thick-walled or non uniform tubes B21K21/00) > characterised by the structure of the objects > Flattening hollow objects for transport or storage; Re-forming same (making tubes from doubled flat material B21C37/14)