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Screw joint for steel pipe

A threaded joint, contact surface technology, applied in the direction of threaded connection, pipe/pipe joint/pipe fitting, drill pipe, etc., can solve problems such as difficulty in ensuring the performance of heat-resistant threaded joints

Inactive Publication Date: 2007-07-11
NIPPON STEEL CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It is difficult to ensure these properties required for heat-resistant threaded joints using the above-mentioned conventional solid lubricant coatings

Method used

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  • Screw joint for steel pipe
  • Screw joint for steel pipe

Examples

Experimental program
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Effect test

Embodiment 1-7 and comparative Embodiment 1-4

[0082] Made of a material selected from carbon steel A, Cr-Mo steel B, 13% Cr steel C, and high alloy steel D for steel pipes [outer diameter: 7 inches (178 mm), wall thickness: 0.408 inches (10.4 mm)] For threaded joints, the composition of each material is shown in Table 1 (D is the easiest to wear, and C, B, and A are hard to wear in turn), and the bolt surface and box sleeve surface of the joint are labeled as shown in Table 2 A surface treatment combination of 1-5 (surface pretreatment, optionally forming a solid lubricant coating), as described in each of the examples below. Table 2 shows the surface roughness Rmax (R) of the pretreatment and the thickness (t) of the undercoat (pretreatment coating) and the thickness (t) of the lubricant coating and the ratio of the lubricant powder and the resin (bonding agent). Mass ratio (M). In these embodiments, the contact surfaces of each of the pin and the casing are pretreated, but the solid lubricant coating is formed only on ...

Embodiment 1

[0105] Threaded joints were made of carbon steel of type A shown in Table 1, and the following surface treatments were applied to the threaded joints.

[0106] Sand blasting with No. 60 sand is used to pre-treat the surface of the box cover to make the surface roughness 31 μm. Then the box sleeve was preheated to 60° C., and a solid lubricant coating of polyamideimide resin containing molybdenum disulfide lubricant powder was formed on the contact surface with a thickness of 30 μm. In the solid lubricant coating containing molybdenum disulfide, the mass ratio of molybdenum disulfide to polyamide-imide resin is 4:1. The coating was dried with a first heating step at 100°C for 30 minutes, after cooling the coating to ambient temperature, a second heating step at 260°C for 30 minutes was performed.

[0107] The bolt surface is only machined and ground (surface roughness 3 μm).

[0108] The data shown in Table 2 are not indicated in the following examples.

Embodiment 2

[0110] Repeat the procedure of Example 1, except that the temperature of the preheating box sleeve before coating is changed from 60°C to 100°C, and the heating condition after coating is changed to: the first step of heating is to heat at 100°C for 30 minutes without cooling That is, the second step of heating is directly carried out, and the second step of heating is heating at 260° C. for 30 minutes.

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Abstract

This invention relates to a threaded joint for steel pipes which comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion and which can be prevented from galling during repeated fastening and loosening without application of a compound grease. A solid lubricant coating which comprises a lubricating powder such as molybdenum disulfide and a resin binder is formed on the contact surface of at least one of the pin and the box. The coating is formed by applying a coating fluid and drying the applied coating by first stage heating in the temperature range of from 70 DEG C. to 150 DEG C. and second stage heating in the range of from higher than 150 DEG C. to 380 DEG C. The resulting solid lubricant coating has a hardness of 70-140 on the Rockwell M scale and an adhesive strength of at least 500 N / m as determined by the SAICAS (Surface And Interfacial Cutting Analysis System) method, and it exhibits excellent galling resistance even in the environment of high-temperature oil wells. Inclusion of ultraviolet screening fine particles such as titanium oxide fine particles in the solid lubricant coating increases the rust preventing properties of the threaded joint.

Description

[0001] This application is Chinese patent application 02809630.4 (application date is April 11, 2002, title is "threaded joint for steel pipe and surface treatment method thereof", priority date is April 11, 2001 and May 1, 2001 day) divisional application. technical field [0002] The invention relates to a threaded joint for steel pipes for interconnecting oil well pipes. More specifically, the present invention relates to a threaded joint for steel pipes having a solid lubricant coating, which is excellent in galling resistance, airtightness and rust resistance without the need for coating containing The compound grease of heavy metal powder is traditionally coated with compound grease before each fastening in order to prevent joint wear. The present invention also relates to a surface treatment method capable of forming a solid lubricant coating. Background technique [0003] Oil well pipes are steel pipes used in drilling oil wells, and threaded joints for steel pipes ...

Claims

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Application Information

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IPC IPC(8): E21B17/042F16L15/04F16L15/00
CPCY10T428/31529C10M2201/0653C10M2201/0663C10M2201/0623F16L58/182C10N2240/22C23C24/08F16L15/004C10N2270/00F16L15/001C10M111/04C10M2201/0613E21B17/042C10N2250/121C10M2201/0413C10M2209/1003C10N2230/06Y10T428/1393C10M2201/0803C10M2217/0443Y10T428/31678C10N2250/08Y10T428/139C10M2201/084F16L15/00C10M177/00C10M2209/1013C10N2280/00C10N2030/06C10N2040/34C10N2050/08C10N2050/02C10N2080/00C10N2070/00
Inventor 后藤邦夫
Owner NIPPON STEEL CORP
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