STEEL PIPE JOINT HAVING HIGH GALLING RESISTANCE AND SURFACE TREATMENT METHOD THEREOF

摘要

A screw joint of an oil-well pipe having a high seizure resistance. The threaded portion and metal seal portion of the pipe has a manganese phosphate chemical conversion treatment coating layer of 5 to 30 mu m thickness or a double-layer of a nitrogen treatment coating layer of 1 to 20 mu m thickness and a manganese phosphate chemical conversion treatment coating layer of 5 to 30 mu m thickness. The portions have also a solid lubricant coating layer of 10 to 45 mu m thickness formed by coating the portions with a solid lubricant having a specific composition and containing molybdenum disulfide powder or tungsten disulfide powder and at least one component selected from an epoxy resin, a furan resin and a polyamide-imide resin as the essential components and by subjecting them to a heat treatment. Due to such surface treatments, a steel pipe joint at which galling does not occur for a long time even when the number of repeated uses of the steel pipe is large can be obtained.