RU2284368C1 - Method of forming protective diffusion coat on external and internal surfaces of tube and its threaded parts and oil well tubing - Google Patents

Abstract

FIELD: manufacture and construction of oil tubes used in construction of oil and gas wells, namely oil well tubing, 64-114 mm in diameter, casing pipes, 114-508 mm in diameter and other pipes.

SUBSTANCE: proposed method includes treatment of threaded parts and adjoining area by isothermal holding in diffusion mixture followed by cooling in air. Diffusion mixture contains metal powder consisting of mixture of zinc, copper and aluminum powders at graininess of 0.1-0.5 mm at the following ratio of components, mass-%: zinc, 25-40; copper, 0.045-0.075; aluminum, 0.175-0.225; the remainder being inert filler. Isothermal holding continues for 1.0-3.0 h at temperature of 440±10°C, thus obtaining protective coat, 30-80 mcm thick. Protective coat includes the following components, mass-%: iron, 6-15; zinc, 84.1-93.4; copper, 0.4-0.6; aluminum, 0.2-0.3. Micro-hardness of protective coat ranges from 4500 to 5250 Mpa determined by method of reduced print of tetrahedral pyramid. Proposed oil well tubing has body with at least one section of thread provided with protective coat made by said method.

EFFECT: enhanced corrosion resistance and tightness of threaded sections of tubes.

3 cl, 2 tbl

Description

The invention relates to a method for the manufacture and construction of oil range pipes, used primarily for the arrangement and operation of oil and gas wells, namely tubing pipes with a diameter of 60-114 mm, casing pipes with a diameter of 114-508 mm and others.

Oil pipes in the tubing string must meet the requirements of high resistance to corrosion and the condition of good multiple make-up.

It is known that a multicomponent oil-containing medium consisting of oil, gas, water and various impurities, in the form of suspended solids, under the influence of which intense corrosion and abrasive metal wear of pipes and couplings is transported under high pressure pipes, is transported under high pressure. At the same time, corrosion and erosion wear occur most intensively in the area of pipe threaded joints, which leads to erosion of the thread, violation of the tightness of the threaded pipe-to-coupling connection and, ultimately, to depressurization of pipe columns and shutdown of wells.

It is known to use galvanized pipes in which threaded sections are subjected to special heat treatment. In this case, after heat treatment of the threaded sections, a structurally uniform zinc coating is formed, (see, for example, Proskurkin EV, Gorbunov NS Diffusion zinc coatings. M: Metallurgy, 1972, p. 248).

The disadvantage of such a pipe is the low hardness of the obtained zinc coating, leading to rapid wear of the threaded pipe joint.

The closest analogue to the proposed method is a method of obtaining a protective diffusion coating on the threaded sections of the steel pipe and adjacent surfaces, including processing the threaded sections by isothermal exposure in a diffusion mixture containing a metal powder and an inert filler powder, and subsequent cooling in air (RU 2221898 C2, IPC 8 C 23 C 10/34, 01/20/2004, p.3, paragraph 3, 5 below, formula).

The objective of the invention is to obtain a protective coating on the threaded sections of tubing, drill and other pipes, providing increased corrosion resistance and tightness of the threaded sections of the tubing.

The problem is solved due to the fact that when implementing the proposed method for obtaining a protective diffusion coating on the threaded sections of the steel pipe and adjacent surfaces, including processing the threaded sections by isothermal exposure in a diffusion mixture containing metal powder and an inert filler powder, and subsequent cooling to in the air. According to this invention, a diffusion mixture is used containing a metal powder consisting of a mixture of zinc, copper and aluminum powders with a grain size of 0.1-0.5 mm and an inert filler, with the following components in the diffusion mixture, wt.%: Zinc 25-40, copper 0.045-0.075, aluminum 0.175-0.225, inert filler - the rest. Alumina or quartz sand with a grain size of 0.15-0.7 mm is used as an inert filler. Isothermal exposure is carried out for 1.0-3.0 hours at a temperature of 440 ± 10 ° C to obtain a protective coating with a thickness of 30-80 microns, containing the following components, wt.%: Iron 6-15, zinc 84.1-93, 4, copper 0.4-0.6, aluminum 0.2-0.3. The resulting coating has a microhardness, determined by the method of the reconstructed imprint of the tetrahedral pyramid (according to Vickers), in the range of 4500-5250 MPa.

In addition, the task is solved due to the fact that before filling the container with a diffusion mixture, the mixture is mixed to give its particles a rolled shape. This allows for reliable gas removal during the process of creating a protective diffusion coating.

The task of creating a tubing with a protective coating, comprising a housing with at least one thread portion with a protective coating, obtained by a method comprising treating threaded sections and adjacent surfaces by isothermal exposure in a diffusion mixture containing metal powder and an inert filler powder , and subsequent cooling in air. According to this invention, a diffusion mixture is used containing a metal powder consisting of a mixture of zinc, copper and aluminum powders with a grain size of 0.1-0.5 mm and an inert filler, with the following components in the diffusion mixture, wt.%: Zinc 25-40, copper 0.045-0.075, aluminum 0.175-0.225, inert filler - the rest. Alumina or quartz sand with a grain size of 0.15-0.7 mm is used as an inert filler. Isothermal exposure is carried out for 1.0-3.0 hours at a temperature of 440 ± 10 ° C to obtain a protective coating with a thickness of 30-80 microns, containing the following components, wt.%: Iron 6-15, zinc 84.1-93, 4, copper 0.4-0.6, aluminum 0.2-0.3. The resulting coating has a microhardness, determined by the method of the reconstructed imprint of the tetrahedral pyramid (according to Vickers), in the range of 4500-5250 MPa.

The technical result from the application of the proposed method for applying a protective diffusion coating to threaded sections and adjacent surfaces of tubing and casing pipes, as well as from the use of these pipes with the described protective coating, is to increase the service life of pipes and, as a result, to increase productivity and reducing the cost of gas and oil production.

The protective coating with the above composition is not prone to aging, which is characteristic of protective layers made of polymeric materials, cracking characteristic of glass enamel and silicate materials, and is also less prone to destruction of the layer due to the loss of zinc atoms due to the formation of a Fe-Zn galvanic pair than when creating a protective iron-zinc coating, under operating conditions it plays the role of a solid lubricant for a threaded couple “pipe-to-pipe”.

To obtain a protective coating on the threaded surface of the steel drill pipe, the threaded sections of the steel pipe and adjacent surfaces are placed in containers with a diffusion mixture. The diffusion mixture consists of a mixture of zinc, copper and aluminum powder with a grain size of 0.1-0.5 mm and an inert filler - quartz sand or alumina with a grain size of 0.15-0.70 mm.

Prepare a diffusion mixture containing a mixture of metal powders and an inert filler, in the following ratio of components, wt.%:

Zinc 25-40 Copper 0.045-0.075 Aluminum 0.175-0.225 Inert filler rest.

First, a mixture of metal powders is prepared by stirring in a mixer to obtain a rolled particle shape and sieved through a sieve with a mesh size of 0.5 mm The inert filler is mixed and sieved separately through a sieve with a mesh size of 0.7 mm Then both components of the diffusion mixture are combined and mixed again. A steel pipe with threaded ends and adjacent surfaces placed in containers with a diffusion mixture is loaded into the furnace and coated with a protective layer by isothermal exposure at a temperature of 440 ± 10 ° C for 1.0 to 3.0 hours, followed by cooling on air.

Depending on the temperature, pipe dimensions, holding time and other parameters, the surface of the protective coating will contain the following components, wt.%: Iron 6-15, zinc 84.1-93.4, copper 0.4-0.6, aluminum 0 , 2-0.3. The coating thickness depending on the time of isothermal exposure can be obtained in the range from 30 to 80 microns.

The content of ingredients and the mode of the process are given in table 1.

Table 2 shows the results of microhardness measurements of the surface protective layer for various materials.

The microhardness was measured by indentation of diamond tips according to GOST 9450-76 “Measurement of the standard of microhardness by indentation of diamond tips”. This standard defines the measurement of the microhardness of metals and alloys by the method of reconstructed imprint of a tetrahedral pyramid with a square base (according to Vickers). This method is standard when measuring protective layers, in particular from a zinc-zinc coating. The load on the indenter when measuring the microhardness was 10 g.

Thus, manufactured in accordance with the proposed method, the tubing or drill pipe allows you to get the claimed technical result, which consists in increasing the service life, productivity and reducing the cost of oil and gas production.

Table 1. Diffusion Coating Parameters The resulting protective coating layer Processing Temperature, ° C Will continue. Processing hours. Metal content. ingredients in diff. mixture,% (by weight) Thickness, microns. The content of ingredients in the coating,% (by weight) Hardness, MPa Zn Cu Al Zn Fe Cu Al 440 ± 10 1,0 25-40 0.045-0.075 0.175-0.225 30,0 93,4 6.0 0.4 0.2 4500 440 ± 10 3.0 25-40 0.045-0.075 0.175-0.225 80.0 84.1 15.0 0.6 0.3 5250 Table 2. No. Type (type) of protective layer The microhardness of the protective layer, MPa one. Zinc Iron / Al Alloy Layer 4500-5250 2. Galvanic zinc layer 300-380 3. Zinc Plating 200-280 four. Phosphate protective layer 150-250 5. Steel 5SP 1422-470 6. Steel 20 2265-2540 7. Steel 22A "select" 3138-3187

Claims (3)

1. The method of obtaining a protective diffusion coating on the threaded sections of the steel pipe and adjacent surfaces, comprising treating the threaded sections and adjacent pipe surfaces by isothermal exposure in a diffusion mixture containing metal powder and an inert filler powder, and subsequent cooling in air, characterized the fact that using a diffusion mixture containing a metal powder consisting of a mixture of zinc, copper and aluminum powders with a grain size of 0.1-0.5 mm, the following containing component in the diffusion mixture, wt.%: zinc 25-40, copper 0.045-0.075, aluminum 0.175-0.225, inert filler - the rest, isothermal exposure is carried out for 1.0-3.0 hours at a temperature of 440 ± 10 ° C to obtain a protective coating with a thickness of 30-80 μm, containing the following components, wt.%: iron 6-15, zinc 84.1-93.4, copper 0.4-0.6, aluminum 0.2-0.3, the coating has a microhardness determined by the method of the reconstructed indentation of the tetrahedral pyramid within 4500-5250 MPa. 2. The method according to claim 1, characterized in that before placing the threaded sections of the pipe and adjacent surfaces in a diffusion mixture, the mixture is stirred to give the particles a rolled shape. 3. A tubing containing a housing with at least one thread portion with a protective coating, characterized in that the protective coating is obtained by the method according to claim 1.