CN113147150B

CN113147150B - Manufacturing process of thread of oil pipe without sticking

Info

Publication number: CN113147150B
Application number: CN202110411098.XA
Authority: CN
Inventors: 徐海英
Original assignee: DAQING HUAYU PETROLEUM MACHINERY MANUFACTURING CO LTD
Current assignee: DAQING HUAYU PETROLEUM MACHINERY MANUFACTURING CO LTD
Priority date: 2021-04-16
Filing date: 2021-04-16
Publication date: 2021-10-19
Anticipated expiration: 2041-04-16
Also published as: CN113147150A

Abstract

The invention belongs to the field of oilfield pipeline facilities, and particularly relates to a manufacturing process of a thread of a non-sticking oil pipe, which comprises the following steps: taking a carbon steel pipe material, turning an API oil pipe thread, wherein the thread formed by machining is called a rough machining thread, and a machined workpiece is called a carbon steel substrate; step two, additionally processing a coating layer used for coating the outer side of the rough machining thread, wherein the coating layer is a mixture of copper and tungsten carbide; preheating the section of the rough machining thread on the carbon steel substrate, wherein the preheating temperature is 500-600 ℃, maintaining, and then attaching the film coating layer to the outer surface of the rough machining thread by adopting a rolling process; step four, further heating the outer surface of the film coating layer to maintain the temperature within the range of 770-800 ℃, and then continuously rolling the surface of the film coating layer through a rolling process, wherein the temperature maintaining time in the step is 15-20 seconds; and step five, naturally cooling at room temperature. The invention can effectively prevent thread sticking.

Description

Manufacturing process of thread of oil pipe without sticking

Technical Field

The invention belongs to the field of oilfield pipeline facilities, and particularly relates to a manufacturing process of a thread of a non-sticking oil pipe.

Background

An API oil pipe (called oil pipe for short) is the most commonly used equipment in the oil field downhole operation, and a plurality of oil pipes are often connected together for use in the construction process. According to the related art standards, the end of the tubing is provided with standard API tubing threads by which the tubing is connected to the next tubing or downhole tool. In the actual production, because frequently screw up and dismantle, the interference that the screw-thread fit produced easily causes the damage of screw surface, and then produces the thread gluing problem. The thread gluing not only makes the disassembly of the oil pipe difficult, but also causes the scrapping of the oil pipe, seriously influences the construction efficiency and increases the material loss.

In response to the above problems, the prior art has been to apply grease to the threads prior to tightening. The disadvantage of this kind of scheme is that because one construction usually needs to connect hundreds or even hundreds of oil pipes, consequently increase the process of scribbling the screw thread fat and can produce very big influence to construction progress and rhythm, simultaneously, the thread gluing effect also needs to promote. Therefore, there is a need to develop a new anti-adhesive solution.

Disclosure of Invention

The invention provides a manufacturing process of a thread of a non-sticking oil pipe, which aims to solve the problems in the background technology.

The technical problem solved by the invention is realized by adopting the following technical scheme: the invention provides a manufacturing process of a thread of a non-stick oil pipe, which comprises the following steps:

step one, taking a carbon steel pipe material, machining API oil pipe threads at the end part of the pipe material by adopting a turning process, wherein the machined threads are called rough machining threads, and a machined workpiece is called a carbon steel substrate;

step two, additionally processing a coating layer used for coating the outer side of the rough machining thread, wherein the coating layer is a mixture of copper and tungsten carbide;

preheating the section of the rough machining thread on the carbon steel substrate, wherein the preheating temperature is 500-600 ℃, maintaining, and then attaching the film coating layer to the outer surface of the rough machining thread by adopting a rolling process and attaching the film coating layer to the crest, the tooth side and the tooth bottom of the rough machining thread;

step four, further heating the outer surface of the coating layer to maintain the temperature within the range of 770-800 ℃, and then continuously rolling the surface of the coating layer through a rolling process to promote the mutual permeation between the coating layer and the carbon steel substrate, wherein the temperature is maintained for 15-20 seconds in the step;

and step five, naturally cooling at room temperature.

As a further technical scheme, in the step one, when the thread is roughly processed, all thread surfaces are processed by adopting the tool tip of a turning tool.

As a further technical solution, in the second step, the coating layer is composed of a copper film and tungsten carbide powder, and the tungsten carbide powder is attached to one side of the copper film.

As a further technical scheme, in the second step, the tungsten carbide powder is attached to the copper film through a thermal spraying process.

As a further technical scheme, in the second step, the tungsten carbide powder is attached to the copper film through a cold rolling process.

As a further technical scheme, the thickness of the copper film is 20-30 microns, and the particle size grade of the tungsten carbide powder is WC24, namely the particle size range is 2.41-3.00 microns.

As a further technical scheme, in the fourth step, the heating mode is laser heating.

As a further technical solution, the heating manner is circumferential scanning heating.

The invention has the beneficial effects that:

1. in the prior art, most of coatings on the surfaces of threads are obtained through an electroplating process, a process for adding the coatings on the surfaces of the threads in a metal coating mode is not adopted, and the problem of API oil pipe thread sticking is not solved through the process. Therefore, the invention adopting the brand new process has to overcome a plurality of brand new technical problems, such as:

how to ensure the anti-sticking effect?

How to ensure the dimensional accuracy of the finished thread?

How to prevent the coating layer from tearing during rolling?

How to ensure the bonding strength between the coating layer and the carbon steel substrate?

How to ensure uniformity of mechanical properties of the surface of the finished thread product?

How to avoid decarburization of the carbon steel matrix?

How is the thread deformation prevented?

The invention creatively develops a thread surface metal film coating process capable of increasing the thread anti-sticking performance, overcomes a plurality of technical problems and produces at least the following effects:

firstly, the copper-based material utilizes the self-lubricating property of copper, thereby being beneficial to preventing the occurrence of the sticking condition;

secondly, tungsten carbide with higher hardness is added in the coating layer, and can provide enough support when the surface of the thread bears pressure, improve the surface hardness of the thread, and simultaneously can not damage the toughness of the carbon steel substrate, thereby effectively improving the mechanical property of the thread and further preventing thread sticking;

thirdly, copper has a low hardness and tungsten carbide has a high hardness in terms of physical properties, and microscopically, when the threads are tightened, the harder tungsten carbide bears most of the contact pressure and is not deformed, while the relatively softer copper is deformed by the contact pressure. In this case, the oil pipe thread is dipped with the lubricating oil and then tightened during construction, and after the oil pipe thread is tightened, the lubricating oil is easily retained in the deformation, so that the lubricity of the thread contact surface is remarkably improved, and galling is further prevented.

The dipping of the lubricating oil hardly takes additional construction time, so that the construction process is not affected like the smearing of thread grease.

Fourthly, the temperature is controlled and heated to reach the critical phase transition temperature Ac1(745 ℃) to Ac3(823 ℃) 5 of the oil pipe material (namely carbon steel), at the temperature, the metallographic structure in the carbon steel matrix is transformed, namely, ferrite on the surface layer of the carbon steel matrix is gradually transformed into austenite, the austenite is of a face-centered cubic octahedral structure, the octahedral gap is large, copper atoms and silicon carbide molecules can be accommodated, and through the deep combination, the surface compactness of the carbon steel matrix is greatly enhanced, and the surface hardness and the fatigue resistance of the carbon steel matrix are favorably improved. The temperature range lasts for 15-20 seconds, and the full fusion of the film coating layer and the carbon steel substrate is ensured.

From another perspective, under the action of high temperature, the surface tension of the coating layer is reduced, so that the wettability of copper to the base metal is enhanced, and because the atomic radius, the lattice type, the lattice constant, the number of electrons in the atomic outer layer and the like of iron elements in copper and steel are relatively close, the copper and the iron can be in infinite solid solution in a liquid state, although the copper and the iron are in finite solid solution in a solid state, a brittle intermetallic compound cannot be formed, and the copper and the iron exist in a dual-phase structure form of (alpha + epsilon), so that the firmness degree of the coating layer and the carbon steel substrate is fully ensured, and the coating layer is prevented from falling off.

In addition, interdiffusion, infiltration and fusion between the coating layer and the carbon steel can improve the hardness of a micro area without tungsten carbide dispersed in the coating layer, namely, the hardness of the copper film substrate is improved, so that the hardness of the copper substrate is improved, and the thread anti-galling effect is further improved.

Fifthly, in the invention, the mode of coating film firstly and then heating (without preheating) is adopted, the coating film layer is not melted in the heating process (the melting point of copper is 1083.4 ℃), and the close covering of the coating film layer can avoid the contact of the surface of the rough machined thread with oxygen in the air in the heating process, so that the carbon element in the carbon steel matrix is avoided being separated out, therefore, compared with the mode of improving the mechanical property of the surface of the workpiece by a heat treatment mode, the coating process provided by the invention can not reduce the toughness of the thread.

Sixth, when the conventional heat treatment process is applied to flat surfaces such as planes and cylindrical surfaces, the uniformity of the heat treated surfaces can be ensured, but when the conventional heat treatment process is applied to uneven surfaces of threads, the uniformity of flanks, crests and roots of the threads is difficult to ensure. In the invention, the coating layer can uniformly cover all parts of the thread surface, and the problem of insufficient local performance can not occur.

Seventh, compared with the conventional heat treatment mode, the process of the invention does not cause the deformation of the thread, so that the precision of the thread is easier to ensure, and the sealing performance of the API oil pipe thread is ensured.

2. In the present invention, the bond between the copper film and the tungsten carbide powder constituting the coating layer is not a metallurgical bond but a simple physical bond, and the tungsten carbide is provided on the side facing the carbon steel substrate, which is advantageous in that: all the tungsten carbide powder is positioned at the position closest to the carbon steel matrix, and the binding force of the copper film on the tungsten carbide powder is extremely small, so that the tungsten carbide can be better fused with the carbon steel matrix and the copper film simultaneously after being heated, and the expected effect is ensured. In addition, the method can reduce the brittleness of the film coating layer, ensure the toughness of the film coating layer and prevent the film coating layer from being torn in the processing process.

3. In the fourth step, the copper, the tungsten carbide and the iron can be effectively promoted to be mixed while heating and rolling, so that the film coating layer and the carbon steel substrate are better integrated.

Drawings

FIG. 1 is a schematic view of the construction of an oil pipe according to the present invention.

In the figure: 1-carbon steel substrate, 2-coating layer.

Detailed Description

The first embodiment is as follows:

the invention is further described below with reference to the accompanying drawings:

the embodiment provides a manufacturing process of a thread of a non-stick oil pipe, which comprises the following steps:

step one, taking a carbon steel pipe material, machining API oil pipe threads at the end part of the pipe material by adopting a turning process, and machining all thread surfaces by adopting a tool tip of a turning tool. The thread formed by machining is called rough thread, and the machined workpiece is called a carbon steel base body 1. Wherein the carbon steel pipe material is a steel pipe with the steel grade of J55.

In the prior art, a threading tool which is ground into a specific shape is adopted for cutting during thread turning, the contact area between a turning tool and a workpiece is large during the threading of the threading tool, the surface roughness of the turned workpiece is small, and the characteristic is suitable for machining of conventional threads (the smaller the roughness of the conventional threads is, the better the roughness is), but in the invention, the too small roughness is not beneficial to the adhesion of the coating layer 2. Therefore, the invention can not adopt the thread cutter to cut, and needs to adopt the tool point of the turning tool to cut, thereby forming a plurality of fine spiral tool marks on the surface of the thread, as the preferred proposal, the surface roughness of the thread after the turning is between Ra12.5-Ra25, the roughness value in the range is relatively large, and the invention is beneficial to ensuring the bonding strength of the coating layer 2 and the carbon steel substrate 1.

And step two, additionally processing a coating layer 2 used for coating the outer side of the rough machining thread, wherein the coating layer 2 is a mixture of copper and tungsten carbide.

The special coating layer 2 is made by attaching tungsten carbide on the copper film, which provides a material foundation for the thread anti-sticking performance. The copper-based material utilizes the self-lubricating property of copper, thereby being beneficial to preventing the occurrence of thread gluing. The tungsten carbide with higher hardness can provide enough hard support when the surface of the thread bears pressure, so that the hardness of the surface of the thread is improved, and meanwhile, the toughness of the carbon steel matrix 1 cannot be damaged, so that the mechanical property of the thread is effectively improved, and thread sticking is further prevented.

In addition, the hardness of copper is low and that of tungsten carbide is high in terms of physical properties, and microscopically, when the threads are tightened, the hard tungsten carbide bears most of the contact pressure and is not deformed, while the relatively soft copper is deformed under the force of the contact pressure. In this case, the oil pipe thread is dipped with the lubricating oil and then tightened during construction, and after the oil pipe thread is tightened, the lubricating oil is easily retained in the deformation, so that the lubricity of the thread contact surface is remarkably improved, and galling is further prevented. The dipping of the lubricating oil hardly takes additional construction time, so that the construction process is not affected like the smearing of thread grease.

When the conventional heat treatment process is applied to flat surfaces such as planes, cylindrical surfaces and the like, the uniformity of the heat treatment surface can be ensured, but when the conventional heat treatment process is applied to uneven surfaces of threads, the uniformity of the flanks, crests and roots of the threads is difficult to ensure. In the invention, the coating layer 2 can uniformly cover all parts of the thread surface, and the problem of insufficient local performance can not occur. Compared with the conventional heat treatment mode, the process disclosed by the invention cannot cause deformation of the threads, so that the precision of the threads is easier to guarantee, and the sealing performance of the API oil pipe threads is favorably guaranteed.

And step three, preheating the section of the rough machining thread on the carbon steel substrate 1, wherein the preheating temperature is 500-600 ℃, maintaining the preheating temperature to pre-expand the carbon steel substrate 1, and then attaching the film coating layer 2 to the outer surface of the rough machining thread by adopting a rolling process and attaching the film coating layer to the crest, the tooth side and the tooth bottom of the rough machining thread. The rolling process can be realized by adopting a thread rolling wheel. The thread rolling wheel is made of special ceramic.

The carbon steel substrate 1 is pre-expanded by preheating, so that the coating layer 2 can be prevented from falling off from the carbon steel substrate 1 in the subsequent process.

And step four, further heating the outer surface of the coating layer 2 to maintain the temperature within the range of 770-800 ℃, and then continuously rolling the surface of the coating layer 2 through a rolling process to promote the mutual permeation between the coating layer 2 and the carbon steel substrate 1, wherein the temperature is maintained for 15-20 seconds in the step.

The temperature is controlled and heated to reach the critical phase transition temperature Ac1(745 ℃) to Ac3(823 ℃) 5 of the oil pipe material (namely carbon steel), at the temperature, the metallographic structure in the carbon steel matrix 1 is transformed, namely the ferrite on the surface layer of the carbon steel matrix 1 is gradually transformed into austenite, the austenite is of a face-centered cubic octahedral structure, the octahedral gap is large, and copper atoms and silicon carbide molecules can be accommodated. The temperature range lasts for 15-20 seconds, and the full fusion of the film coating layer 2 and the carbon steel substrate 1 is ensured. On the other hand, under the action of high temperature, the surface tension of the coating layer 2 is reduced, so that the wettability of copper to a base metal is enhanced, and because the atomic radius, the lattice type, the lattice constant, the number of electrons in the atomic outer layer and the like of iron elements in copper and steel are relatively close, the copper and the iron can be in infinite solid solution in a liquid state, although the copper and the iron are in finite solid solution in a solid state, a brittle intermetallic compound cannot be formed, and the copper and the iron exist in a dual-phase structure form of (alpha + epsilon), so that the firmness degree of the coating layer 2 and the carbon steel substrate 1 is fully ensured, and the coating layer 2 is prevented from falling off.

In the invention, the mode of firstly coating the film and then heating (without preheating) is adopted, and the close covering of the film coating layer 2 can avoid the contact of the surface of the rough-machined thread with oxygen in the air in the heating process, so that the carbon element in the carbon steel matrix 1 is prevented from being separated, therefore, compared with the mode of improving the mechanical property of the surface of a workpiece by a heat treatment mode, the film coating process provided by the invention can not reduce the toughness of the thread.

It should be noted that the preheating at 500-600 ℃ is not sufficient to decarburize the carbon steel substrate 1, so that carbon in the carbon steel is not removed before the coating.

And step five, naturally cooling at room temperature.

As a further technical solution, in the second step, the coating layer 2 is composed of a copper film and tungsten carbide powder, and the tungsten carbide powder is attached to one side of the copper film. That is, the bond between the copper film and the tungsten carbide powder constituting the coating layer 2 is not a metallurgical bond but a mere physical bond, and the tungsten carbide is provided on the side facing the carbon steel substrate 1, which is advantageous in that: all the tungsten carbide powder is positioned at the position closest to the carbon steel matrix 1, and the binding force of the copper film on the tungsten carbide powder is extremely small, so that the tungsten carbide can be better fused with the carbon steel matrix 1 and the copper film simultaneously after being heated, and the expected effect is ensured. In addition, the brittleness of the tungsten carbide is large, so that the brittleness of the coating layer 2 can be reduced, the toughness of the coating layer 2 is ensured, and the coating layer 2 is prevented from being torn in the processing process.

Here, it should be noted that: after the tungsten carbide is attached to the copper film, the copper is preferably ensured to be still exposed out of the gaps of the tungsten carbide powder, so that the copper can be always attached to the carbon steel matrix 1 after film coating, and the copper which plays a main role in adhesion can enter the tool marks on the surface of the thread under the extrusion action. Thereby contributing to improvement of the adhesive force of the coating layer 2.

In the implementation process, two points need to be noticed:

1. the temperature of the spray coating should not be too high. The tungsten carbide can be stably attached to the copper film only by ensuring that the tungsten carbide can be stably attached to the copper film, and the copper film can be burnt and damaged when the temperature is too high. The temperature of the tungsten carbide reaching the copper film can be controlled by controlling the distance between the lance and the copper film.

2. The tungsten carbide coating should not be too thick. The invention does not improve the hardness of the thread surface by establishing a tungsten carbide coating, but improves the surface hardness by the interpenetration of tungsten carbide with the carbon steel substrate 1 and the copper film, so that the amount of tungsten carbide is small. Too thick a tungsten carbide coating will not only reduce the toughness of the coating layer 2, but also reduce the quality of the bond between the coating layer 2 and the carbon steel substrate 1.

3. The process of the present invention allows for uniform porosity in the coating, i.e., the coating is not required to cover all surfaces of the copper film.

4. The copper film has a thickness of 20-30 microns and the tungsten carbide powder has a particle size grade of WC24, i.e., a particle size range of 2.41-3.00 microns. The heating of the carbon steel substrate 1 is affected by the excessive thickness of the copper film, and the copper film is easy to tear if the copper film is too thin. The smaller the particle size of the tungsten carbide powder, the better, but the smaller the particle size, the higher the cost.

As a further technical solution, in the fourth step, the heating manner is laser circumferential scanning heating. The thread surface is scanned along the circumferential direction by the strip-shaped light beam, which is equivalent to that a light beam superposed with a taper thread generatrix scans and heats around the axis of the carbon steel matrix 1, and compared with conventional heating modes such as flame heating, the heating mode has smaller thermal influence on the surface which is not directly contacted with the laser beam and heats more uniformly. Delamination of the coating layer 2 can be effectively prevented.

Example two:

the present embodiment is different from the first embodiment only in that: in the second step, the tungsten carbide powder is attached to the copper film through a cold rolling process.

The advantage of this process is the simplicity of the process compared to the examples, the disadvantage being that the amount of tungsten carbide that can adhere is small, and if one wants to increase the amount of tungsten carbide, one has to increase the particles of tungsten carbide, which adversely affects the surface quality of the thread.

Example three:

as a third example, in the first example, the material copper in the coating layer 2 is replaced by tin bronze alloy, and the ratio of tin in tin bronze is adjusted to reduce the melting point of tin bronze alloy to the range of 745 ℃ -770 ℃, so that after heating to the range of 770 ℃ -800 ℃, the coating layer 2 starts to melt and infiltrate the surface of the carbon steel substrate 1, and the molten coating layer 2 adheres to the carbon steel substrate 1 under the action of surface tension. In this case, the brazing is equivalent to brazing tungsten carbide powder particles to the carbon steel substrate 1 with tin bronze as a brazing material. The firmness of the coating layer 2 is therefore greater. However, the molten coating layer 2 has a disadvantage that decarburization of the carbon steel substrate 1 cannot be prevented.

Example four:

in this embodiment, the following process is used to replace the fourth step and the fifth step in the first embodiment:

the invar alloy steel (NI 36%, FE 64%) with extremely small thermal expansion coefficient is made into a sleeve-shaped mould which is hooped on the outer side of the thread (two halves are buckled), then the mould and a workpiece are heated by using an induction heating mode or an electric heating mode, and after heating, the thermal deformation amount of the invar alloy steel is smaller than that of the thread, so that a binding force is formed on the thread, and the binding force and high temperature act together to enable the coating layer 2 to be tightly attached to the carbon steel substrate 1.

In order to prevent the invar steel from penetrating into the coating layer 2, a ceramic lining may be provided inside the mold so as to prevent the invar steel from contacting the coating layer 2, but not to prevent the mold from exerting its constraining effect.

Claims

1. A process for manufacturing oil pipe threads without thread gluing is characterized by comprising the following steps:

step one, taking a carbon steel pipe material, machining API oil pipe threads at the end part of the pipe material by adopting a turning process, wherein the machined threads are called rough machining threads, and the machined workpiece is called a carbon steel substrate (1);

step two, additionally processing a coating layer (2) used for coating the outer side of the rough machining thread, wherein the coating layer (2) is a mixture of copper and tungsten carbide;

the film coating layer (2) consists of a copper film and tungsten carbide powder, wherein the tungsten carbide powder is attached to one side of the copper film and arranged on one side facing the carbon steel substrate;

preheating a section where the rough machining threads are located on the carbon steel substrate (1), wherein the preheating temperature is 500-600 ℃, maintaining the preheating temperature, and then attaching the film coating layer (2) to the outer surface of the rough machining threads by adopting a rolling process and attaching the film coating layer to the crests, the flanks and the bottoms of the rough machining threads;

step four, further heating the outer surface of the coating layer (2) to maintain the temperature within the range of 770-800 ℃, and then continuously rolling the surface of the coating layer (2) through a rolling process to promote the mutual permeation between the coating layer (2) and the carbon steel substrate (1), wherein the temperature is maintained for 15-20 seconds in the step;

and step five, naturally cooling at room temperature.

2. The process of manufacturing a non-galling tubing thread of claim 1, wherein: in the first step, when the rough machining of the threads is carried out, all thread surfaces are machined by adopting the tool tips of the turning tool.

3. The process of manufacturing a non-galling tubing thread of claim 1, wherein: in the second step, the tungsten carbide powder is attached to the copper film through a thermal spraying process.

4. The process of manufacturing a non-galling tubing thread of claim 1, wherein: in the second step, the tungsten carbide powder is attached to the copper film through a cold rolling process.

5. The process for manufacturing a thread of a non-galling oil pipe according to any one of claims 3 or 4, characterized in that: the copper film has a thickness of 20-30 microns and the tungsten carbide powder has a particle size grade of WC24, i.e., a particle size range of 2.41-3.00 microns.

6. The process of manufacturing a non-galling tubing thread of claim 1, wherein: in the fourth step, the heating mode is laser heating.

7. The process of manufacturing a non-galling tubing thread of claim 6, wherein: the heating mode is circumferential scanning heating.