ROLLING METHOD OF PIPE IN SECOND PIERCER

摘要

PURPOSE:To prevent the generation of flaw on the inside surface of a metallic pipe owing to the friction and seizure between a mandrel and the inside surface of the metallic pipe by cooling the inside surface of the metallic pipe then coating a graphite lubricant thereon in the stage of piercing the metallic pipe with the 2nd piercer in producing the metallic pipe by a Mannesmann double piercing system. CONSTITUTION:The thick walled hollow blank pipe P which is formed with the 1st piercer in a pipe making process by Mannesmann plug mill by a double piercing system is finished to a metallic pipe by expanding and rolling with a plug and drum-type rolls in the 2nd piercer. Cooling water is first injected from the nozzle 4a of an injector 4 for high pressure cooling water to the inside surface of the pipe P to cool the pipe near the inlet of the pierced pipe P, thereby descaling the inside surface of the blank pipe. Fine powder of a graphite solid lubricant is then injected from the nozzle 5a of a supply device 5 to the inside surface of the pipe P. The friction and seizure between the plug of the 2nd piercer and the inside surface of the blank pipe are prevented and the metallic pipe having an excellent inside surface shape is produced stably.