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Threaded joint for steel pipes

A technology for threaded joints and steel pipes, applied in threaded connections, pipes/pipe joints/fittings, drill pipes, etc., can solve problems such as scratches and difficulty in providing sufficient lubricity

Inactive Publication Date: 2005-08-17
NIPPON STEEL CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

As a result, even with liquid grease expected to perform a self-healing function, it is difficult to provide sufficient lubricity, and galling may occur due to repeated tightening and loosening of joints

Method used

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  • Threaded joint for steel pipes
  • Threaded joint for steel pipes
  • Threaded joint for steel pipes

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0089] This example illustrates a threaded joint made of 13Cr steel according to the first embodiment of the present invention, which has a lubricating coating including a lower liquid layer and an upper solid layer formed on the female thread surface of the joint.

[0090] The male thread surface of the joint is not treated.

[0091] The surface of the female thread was preliminarily treated by shot blasting. From then on, within one hour, the surface of the female thread was coated with a lubricating coating with a lower liquid layer and an upper solid layer in the manner outlined in Table 1.

[0092] In Table 1, the viscosity of the substance used in the liquid layer is a value measured at 40°C. In the case where the liquid layer is made of an alkaline metal salt of an organic acid (barium sulfonate or calcium sulfonate), it is diluted with a volatile solvent (xylene) and then coated. In the case where the solid layer is made of mica powder, the powder is dispersed in a nitroce...

Embodiment 2

[0104] This example illustrates: according to the second embodiment of the present invention, a threaded joint made of 13Cr steel or carbon steel has a lubricating coating containing a mixture of lubricating oil and wax formed on the surface of the female thread.

[0105] Preliminary surface treatment is performed on the male thread surface of the joint without a lubricating coating, in which the male thread made of carbon steel is chemically surface treated with manganese phosphate, or the male thread made of 13Cr steel is copper plating.

[0106] The surface of the female thread was preliminarily treated in the same manner as in Example 1 (by shot blasting), and within 1 hour from then, the method outlined in Table 3 was used to contain lubricating oil, wax and optional solids. Lubricant coating of a mixture of additives. After heating the mixture to a liquefied mixture (liquefied wax) or after diluting the solvent to prepare a mixture liquid, coating of the mixture is performed...

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Abstract

A threaded joint for steel pipes comprising a pin 1 and a box 2 each having a contact surface comprising a threaded portion 3 or 4 and an unthreaded metal contact portion 8 is provided with improved anti-galling propertied by forming a lubricating coating on the contact surface of at least one of the pin and the box, the lubricating coating exhibiting a self-repairing function by liquid lubrication and having a decreased greasiness. The lubricating coating is (1) a coating which comprises a lower lubricant layer which is in liquid form in the temperature range of above 0 DEG C and below 40 DEG C and an upper lubricant layer which is in solid form at 40 DEG C, or (2) a coating which is semi-solid or solid at 40 DEG C and is formed of a mixture comprising a lubricating oil which is in liquid form in the temperature range of above 0 DEG C and below 40 DEG C and a wax which is in solid form at 40 DEG C, the mixture preferably having been heated so as to liquefy the wax and dissolve in each other the wax and lubricant oil.

Description

Technical field [0001] The present invention relates to a threaded joint for steel pipes having a lubricating coating on its surface, and in particular to a threaded joint in which the lubricating coating provides improved galling resistance to the threaded joint so that it can be tightened repeatedly And loosen the joint, in which there is a coating that reduces greasiness to minimize the adhesion of impurities to the coating. Background technique [0002] Oil well steel pipes, such as pipes and casings used in the drilling of oil or gas wells, are typically connected to each other by threaded joints. In the past, the depth of oil wells was usually 2,000 to 3,000 meters, but recently, in offshore oil fields and other deep oil wells, the depth of oil wells is usually 8,000 to 10,000 meters. [0003] Threaded joints for oil well steel pipes bear various forces in its use environment, including loads such as axial tension due to the weight of oil well pipes and joint components (co...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): F16L15/04C10M177/00F16L15/00F16L15/06
CPCC10M2207/281C10M2201/103C10M2201/0623F16L58/182C10M2207/2623C10M2207/2815C10N2240/22F16L15/004C10M2201/062C10M2219/0463C10N2250/14C10M2201/1033C10M177/00E21B17/042C10M2219/046C10M2207/0285C10M2203/10C10M2203/1006C10M2205/16C10N2250/10Y10T428/1393C10N2040/34C10N2050/023C10N2050/10
Inventor 松本圭司后藤邦夫安乐敏朗永作重夫山本秀男
Owner NIPPON STEEL CORP
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