RU2244094C1 - Connecting sleeve for oil assortment pipes and method for applying iron-zinc cover at threaded portions - Google Patents

Abstract

FIELD: mining industry.

SUBSTANCE: device has body with two threaded portions, on which protective layer is applied of alloy including iron and zinc. Iron and zinc are present in alloy in relation from 0.0638 to 03330 for thickness of covering layer of 20-100 micrometers. Micro-hardness of cover determined from method of restored print of four-sided pyramid is within limits of 3360-5250 MPa. Such cover may be received on threaded portions of connecting sleeve by method of diffusive zinc-plating. Zinc-plating is performed in container filled with diffusive mixture containing mixture of zinc powder having graininess of 0.1-0.5 mm and quartz powder with graininess of 0.15-0.70 mm. Process of diffusive zinc-plating is performed by isothermal exposure to temperature of 430°-450°C during 1.5-3 hours with following air cooling. Before filling container with diffusive mixture it is stirred for granting smooth form to mixture particles.

EFFECT: higher durability and impermeability.

2 cl, 1 tbl

Description

The invention relates to the design of couplings for joining oil assortment pipes, used mainly for drilling and equipping 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.

The couplings in the pipe string must meet the requirements of high corrosion resistance 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 solid particles, 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. In this case, threaded connections of tubing are subjected to the greatest corrosion and erosion wear, which leads to erosion of the thread, a violation of the tightness of the threaded connection sec; pipe-couplingsec; 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 homogeneous zinc coating is formed (see, for example, Proskurkin EV, Gorbunov NS Diffusion zinc coatings. M: Metallurgy, 1972, p. 248).

The disadvantage of this coupling is the low hardness of the obtained zinc coating, leading to rapid wear of the thread of the coupling.

Closest to the technical result of the claimed coupling is a coupling with a thermo-galvanized threaded section. The specified area is covered with an intermetallic layer of aluminum-iron-zinc alloy, the thickness of which is 1-3 microns (RF patent No. 2049150, published. 27.11.95).

The known coupling has good anti-corrosion properties, but has insufficient microhardness of the threaded sections, which leads to rapid wear of the threaded connection.

The technical problem solved by the claimed invention is to increase the wear resistance and tightness of the coupling sections of oil assortment pipes used in the drilling, construction and operation of oil and gas wells.

The problem is solved in that in the pipe joint, which includes a housing with two thread sections, on which a protective layer of an alloy containing iron and zinc is applied, the protective layer contains iron and zinc in a ratio of 0.0638 to 0.3330 with a thickness a coating layer of 20-100 μm, while the microhardness of the coating, determined by the method of the reconstructed imprint of the tetrahedral pyramid (according to Vickers), is in the range of 3360-5250 MPa.

Obtaining such a coating on the threaded sections of the pipe coupling is achieved by using the diffusion galvanizing method of the steel body with the threads of the coupling, in which diffusion galvanizing is carried out in a container filled with a diffusion mixture containing a mixture of zinc powder with a grain size of 0.1-0.5 mm and quartz sand with a grain size of 0.15-0.70 mm, while the diffusion galvanizing process is carried out by isothermal exposure at a temperature of 430-450 ° C for 1.5 to 3 hours, followed by cooling air Niemi.

Preferably, before filling the container with the diffusion mixture, the mixture is stirred to give the particles of its components a rounded shape.

The technical result from the application of the proposed coupling is to increase its service life and, as a result, to increase productivity and reduce operating costs.

The pipe coupling consists of a body with two thread sections, on which a protective layer of an alloy comprising iron and zinc is applied. The coupling may comprise two sections with an internal thread, or both sections of the connecting thread may be formed on the outer diameter of the coupling. If necessary, one of the sections can be performed with an internal thread, and the second section with an external thread.

The protective layer of iron-zinc alloy contains iron and zinc in a ratio of 0.0638 to 0.3330 with a coating layer thickness of 20 to 100 microns. In this case, the microhardness of the coating, determined by the method of the reconstructed imprint of the tetrahedral pyramid (according to Vickers), is in the range of 3360-5250 MPa.

The protective layer of iron-zinc alloy with the specified technical characteristics is not prone to aging, which is characteristic of protective layers of polymeric materials.

The zinc component of the iron-zinc alloy provides it with sufficient ductility, tread properties and acts as a solid lubricant when screwing the coupling with the pipe.

To obtain a protective layer on the surface of the coupling made of a steel billet by machining, the steel coupling is loaded into a container with a diffusion mixture. The diffusion mixture consists of a mixture of zinc powder with a grain of 0.1-0.5 mm and silica sand with a grain of 0.15-0.70 mm.

To prepare the diffusion mixture, zinc powder with a percentage of zinc of 98.7-99.975, lead 1.0-0.013, iron 0.05-0.005 and aluminum 0.01-0.005 was used. Zinc powder was prepared by spraying from pig zinc.

The diffusion mixture is stirred in a mixer to obtain a rolled particle shape and sieved through a sieve with a mesh size of 0.5 mm A container with a diffusion mixture into which the processed coupling is immersed is loaded into the furnace and diffusion galvanizing is carried out by isothermal holding at a temperature of 430-450 ° C for 1.5 to 3 hours, followed by cooling in air. Depending on the temperature, size of the coupling, holding time and other parameters, the protective layer of iron-zinc alloy will contain iron and zinc in a ratio of 0.0638 to 0.3330. The thickness of the coating layer depending on the time of isothermal exposure can be obtained in the range from 20 to 100 microns.

Table 1 shows the microhardness measurements of the surface protective layer for various materials. The microhardness was measured by indentation of diamond tips according to GOST 9450-76 sec; The microhardness was measured by indentation of diamond tipssec ;. 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-iron alloy. The load on the indenter when measuring the microhardness was 10 g.

Table 1. No. Type (type) of protective layer Microhardness of the protective layer, (MPa) 1. Zinc alloy layer 3360-5250 2. Galvanic zinc layer 300-380 3. Zinc Plating 200-280 4. Phosphate protective layer 150-250 5. Steel 5SP 1422-1470 6. Steel 20 2265-2540 7. Steel 22A sec; selectsec; 3138-3187

From the above table it can be seen that the proposed coupling and the method of its manufacture allow to obtain the claimed technical result, which consists in increasing the service life of the couplings for oil grade pipes, increasing the productivity of oil and gas wells and reducing the cost of oil and gas production.

It is quite obvious that the claimed coupling can be used not only when connecting oil grade pipes, but also in other cases when pumping corrosive and erosive liquids, for example, when pumping pulp in mining and construction, etc.

Claims (3)

1. The coupling of the pipes of the oil assortment, comprising a housing with two thread sections, on which a protective layer of an alloy comprising iron and zinc is applied, characterized in that the protective layer contains iron and zinc in a ratio of 0.0638 to 0.3330 with a thickness a coating layer of 20-100 μm, while the microhardness of the coating, determined by the method of the reconstructed imprint of the tetrahedral pyramid (according to Vickers), is in the range of 3360-5250 MPa. 2. A method of producing an iron-zinc coating on the threaded portions of the pipe coupling, comprising diffusion galvanizing a steel body with thread portions of the coupling, characterized in that the diffusion galvanizing is carried out in a container filled with a diffusion mixture containing a zinc powder mixture with a grain size of 0.1-0 5 mm and silica sand with a grain size of 0.15-0.70 mm, while the diffusion galvanizing process is carried out by isothermal exposure at a temperature of 430-450 ° C for from 1.5 to 3 hours, followed by hlazhdeniem air. 3. The method according to claim 2, characterized in that before filling the container with a diffusion mixture, said mixture is mixed to give its particles a rounded shape.