PCT No. PCT / JP95 / 02034 Sec. 371 Date May 23, 1997 Sec. 102(e) Date May 23, 1997 PCT Filed Oct. 4, 1995 PCT Pub. No. WO96 / 10710 PCT Pub. Date Apr. 11, 1996An object of the present invention is to provide
galling resistance to a threaded joint used for an
oil well pipe. On a thread portion and a metallic sealing portion of the joint, there is provided a
manganese phosphate chemical formation
coating layer, or alternatively there are provided a
nitriding layer of 1 to 20 mu m thickness and a
manganese phosphate chemical formation
coating layer of 5 to 30 mu m thickness, and also there is coated a
solid lubricant which contains
powder of
molybdenum disulfide or
tungsten disulfide and also contains one of
epoxy resin,
furan resin and
polyamide resin as an essential component, and a ratio of composition is maintained at a specific value, so that a
solid lubricant coating layer of 10 to 45 mu m thickness can be formed by heating. Due to the above surface treatment, even when the frequency of repetition of fastening and unfastening of the joint is increased, the occurrence of
galling can be prevented over a long period of time.