THREADED JOINT FOR STEEL PIPES

摘要

A TREADED JOINT FOR STEEL PIPES WHICH IS CAPABLE OF METAL-TO-METAL SEALING AND WHICH CAN BE SUBJECTED TO REPEATED FASTENING AND UNFASTENING WITHOUT THE APPLICATION OF A LIQUID LUBRICANT CONTAINING A HEAVY METAL POWDER COMPRISES A PIN (1) AND A BOX (2) EACH HAVING A CONTACT SURFACE INCLUDING A THREADED PORTION (3A, 3B) AND AN UNTHREADED METAL CONTACT PORTION (4A, 4B). THE CONTACT SURFACE OF AT LEAST ONE OF THE PIN (1) AND THE BOX (2) ARE COATED WITH AN UNDERCOATING LAYER AND A LUBRICATING COATING LAYER A TOP IT. THE UNDERCOATING LAYER IS A POROUS METAL COATING HAVING A POROSITY OF 5-80% AND A THICKNESS OF 1-30 M AND PREFERABLY A HARDNESS OF 50-250 HV. THE LUBRICATING COATING IS A SOLID LUBRICATING COATING OR A LIQUID LUBRICATING COATING, THE LATTER CONTAINING SUBSTANTIALLY NO HEAVY METAL POWDERS. THE TOTAL THICKNESS OF THE UNDERCOATING LAYER AND THE LUBRICATING COATING LAYER IS AT MOST 100 M.