Tubular threaded joint and lubricating coating forming composition for use therein

Abstract

Provided is a composition for forming a lubricating coating to a tubular threaded joint. The composition contains a melamine cyanurate, a basic metal salt of an aromatic organic acid, and one or more kinds selected from the group consisting of a pine resin-based material, a wax, a metal soap, and a lubricating powder.

Description

TECHNICAL FIELD[0001]The present invention relates to a tubular threaded joint for use in connecting steel pipes and particularly oil country tubular goods, and a surface treatment method thereof.[0002]Priority is claimed on Japanese Patent Application No. 2012-174117, filed on Aug. 6, 2012, the content of which is incorporated herein by reference.BACKGROUND ART[0003]Oil country tubular goods such as tubing and casing used in oil well drilling for excavation of crude oil or gas oil are usually connected (jointed) to each other by a tubular threaded joint. In the past, the depth of the oil wells was 2,000 to 3,000 m, but in deep oil wells such as recent offshore oil fields, the depth may reach 8,000 to 10,000 m. The length of the oil country tubular goods is typically several tens of meters, and the periphery of tubing through which a fluid such as crude oil flows is surrounded with a plurality of casings, and thus the number of the oil country tubular goods jointed by the threaded j...

AI Technical Summary

Benefits of technology

[0116]The effects of the invention will be illustrated by the following Examples and Comparative Examples. In the following description, a contact surface including a threaded portion and an unthreaded metal contact portion of the pin is referred to as “pin surface”, and a contact surface including a threaded portion and an unthreaded metal contact portion of the box is referred to as “box surface”. Surface roughness is Rmax. In addition, % represents % by mass unless otherwise stated.

[0117]A surface treatment shown in Table 2 was performed with respect to a pin surface and a box surface of a premium threaded joint VAM TOP (registered trademark) (outer diameter: 17.78 cm (7 inches), thickness: 1.036 cm (0.408 inches) formed from Cr—Mo steel A or 13% Cr steel B shown in Table 1. Then, a lubricating coating was formed on the pin surface and the box surface, which was subjected to the surface treatment, by an illustrated application method using a composition shown in Table 3 (MCA and a basic metal salt of an aromatic organic acid are illustrated as an essential component, and a pine resin-based material, a wax, a metal soap, and a lubricating powder are illustrated as a selective component). Accordingly, the lubricating coating formed on the pin surface and the box surface had the same composition.

Problems solved by technology

Then, when seal portions of the pin and the box come into contact with each other, and a rate of increase in torque increases.

As a result, optimal fastening torque may not be determined depending on tolerance in an amount of thread interference.

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