JPH06320348A - Titanium-made drill pipe and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a titanium-made drill pipe and a manufacturing method thereof wherein the drill pipe, even when constituted of titanium material, is excellent in strength and wearing resistance further with excellent corrosion resistance as the titanium material having high specific strength. CONSTITUTION:Joint parts 14, 16 are made of steel, and a pipe main unit is made of titanium, by integrally forming these members by shrinkage fitting with suitable surface roughness and shrinkage fitting margin, to connect the steel-made joint parts to a titanium pipe end part. In this way, excellent joint performance, having torque strength of 0.05kg-m/diameter (mm). length (mm) or more and showing tensile load resistance of 360kg/connection part length (mm) or more, is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium pipe or a titanium alloy pipe (hereinafter, also simply referred to as a titanium pipe) made of titanium, which is formed by shrink-fitting a steel joint to the end of the pipe to improve the joint performance. TECHNICAL FIELD The present invention relates to a drill pipe and a manufacturing method thereof.

[0002]

2. Description of the Related Art Titanium pipes or titanium alloy pipes have been used for oil wells in recent years, and due to their high specific strength and excellent corrosion resistance, attempts have been made to apply them as drill pipes.
Here, a drill pipe is a pipe material for turning a bit for excavation such as an oil well or circulating drilling mud, and each length is usually about 9 m, and they are called tool joints. The joint members are screwed together to make the length as long as 10,000 meters, for example. Such a drill pipe is repeatedly attached and detached, and a large torque is applied when it is rotated, so that it is used under extremely severe conditions. Therefore, usually steel pipes,
Aluminum alloy is used, but in recent years,
Titanium drill pipes are receiving attention.

However, the wear resistance of pure titanium and titanium alloys is inferior to that of conventional materials such as carbon steel, and when a drill pipe is made of a titanium pipe, the wear becomes severe when the screw is attached and detached, and it burns. It has been considered difficult to apply titanium pipes as drill pipes because of the problem that they are susceptible to galling.

Therefore, various attempts have been made to solve these problems from the standpoint of improving the wear resistance by subjecting the threaded portion provided at the pipe end to a surface treatment. For example,
Although it is a method of performing atmospheric oxide film formation treatment on the screw surface (example: heating in air, anodizing method, etc.), up to now, it can withstand the harsh operating environment as a drill pipe,
Results that satisfy the required durability have not been obtained.

The titanium material has a Young's modulus of, for example, about 1/2 of that of carbon steel, and when a drill pipe is constructed from the titanium material, the threaded joint portion of the end of the drill pipe loosens with low torque during use. The very serious problems resulting from the physical properties of are also unsolved.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a titanium drill pipe and a method for manufacturing the titanium drill pipe, which solves the above-mentioned problems of the prior art. Further, another object of the present invention is to provide a titanium drill pipe having excellent strength and wear resistance even if it is made of titanium material, excellent corrosion resistance as a titanium material, and high specific strength, and a manufacturing method thereof. That is.

Further, a specific object of the present invention is 0.05 kg-m /
Titanium drill pipe with a composite of dissimilar materials that has a torque strength of diameter (mm) and length (mm) or more, and a tensile load resistance of 360 kg / joint length (mm) or more that satisfies the excellent joint performance. And a method of manufacturing the same.

[0008]

[Means for Solving the Problems] When a titanium material is applied to a drill pipe as described above, seizure is likely to occur in the threaded joint portion. Also, the titanium material has a Young's modulus of about 1 / th that of steel.
Since it is 2, there is a problem that it loosens with a low torque.

Therefore, the present inventors have conceived that the main body of the drill pipe is made of titanium and only the joint is made of steel. Various means such as welding, diffusion bonding, and brazing can be considered for joining such dissimilar materials, but as a result of repeated experiments, the formation of intermetallic compounds is unavoidable, and no satisfactory joint can be obtained. It was Certain brazing methods have shown promise, but have been unsatisfactory in terms of reliability and cost.

Further, there is a shrink fitting method as one of the joining methods. Generally, however, the shrink fitting method cannot increase the gap at the time of insertion because the heating temperature is restricted by the material surface and the processing surface.
It is said that it is difficult to apply the shrink fitting method to long structures (The Japan Welding Society: Welding and Joining Handbook, Maruzen Co., 199)
0, 643.).

In the case of a drill pipe, it is necessary to have a torque strength and a tensile load resistance that can withstand severe rotation and its own weight. When applying this shrink fitting method to such an application, it is necessary to burn it. The fitting margin must be taken large.
However, when trying to make a large shrinkage fitting margin, Ti alloy 10
The Ti alloy must be heated to a high temperature of 00 ° C. or higher, and as a result, the surface of the Ti alloy is oxidized and becomes brittle, so that desired torque strength and tensile load cannot be obtained. Therefore, it was considered difficult to apply the shrink fitting method to join the titanium pipe body and the steel joint.

[0012] However, as a result of the subsequent study by the present inventors, by performing shrink fitting with the surfaces of the titanium material and the steel material to be joined appropriately roughened, the shrink fitting margin is increased and the temperature is raised to a high temperature. The present invention has been completed by knowing that the joining can be performed without using it as a drill pipe.

[0013] Therefore, the gist of the present invention is that the pipe body is made of titanium and the steel joint portion integrally provided on the pipe end portion by shrink fitting is 0.05 kg-m / diameter.
A titanium drill pipe having a torque strength of (mm) / length (mm) or more and a tensile load resistance of 360 kg / joint length (mm) or more.

Further, from another aspect, the present invention sets the surface roughness of the joint surface to Ra: 25 to 0.0035 Dμm (D is the average diameter of the titanium pipe inner diameter and the steel joint outer diameter). Average diameter D
Is a shrinkage fitting margin of 0.15 to 0.55% to join a steel joint to a pipe end of a titanium pipe main body.

[0015]

Next, the operation of the present invention will be described more specifically with reference to the accompanying drawings. FIG. 1 is a schematic explanatory view of a drill pipe 10 in which the box side and the pin side are omitted in the middle. In the figure, a main body 12 is a titanium pipe, and steel screw joints (tool joints) are provided at both pipe ends. That is, the box joint 14 and the pin joint 16 are provided, and they are integrally formed with the main body 12 by, for example, shrink-fitting length L to be joined by shrink-fitting.

The pipe body may be constituted by a so-called seamless pipe, and the steel joint portion may be constituted in the same manner as in a commonly used steel drill pipe. Further description will be given. Omit it.

According to the present invention, the titanium pipe and the steel joint portion are integrally provided to form a drill pipe.
There are many possible means for integrally providing both of them, but a shrink fitting method, which is a typical example thereof, will be described below.

First, in the present invention, the surface roughness of the joint surface, preferably the side of the titanium pipe and the steel joint portion, is adjusted to Ra of 25 to 0.0035 D (μm) prior to shrink fitting. here,
D is the average diameter of the inner diameter of the titanium pipe and the outer diameter of the steel joint. The inner diameter and the outer diameter refer to the diameter at the median of the surface roughness.

Therefore, when the surface roughness becomes large, the diameter when viewed from the surface is small with respect to the inner diameter of the titanium pipe and large with respect to the outer diameter of the steel joint portion, which is the same as increasing the shrink fitting margin. There is no choice but to heat the titanium tube, which is a tube, to a high temperature. Therefore, even if the surface roughness is too large,
The surface is oxidized and becomes brittle, and it becomes impossible to obtain the desired torque strength and tensile load.

When Ra is less than 25 μm, 0.05 kg · m / diameter (mm)
・ Torque strength over length (mm) and 360 kg / joint length (mm)
The above tensile load cannot be achieved. On the other hand, Ra
When the value exceeds 0.0035 D (μm), it is inevitable to heat it to 800 ° C or more during shrink fitting, and scale is generated on the surface of the titanium material, and the torque strength and tensile load resistance of the shrink fitting portion are deteriorated. Ra of about 25 to 150 μm is generally sufficient.

Since the shrinkage fitting allowance is defined by {(outer diameter of inner tube−inner diameter of outer tube) / (outer diameter of inner tube)} × 100 (%), the adjustment is to adjust the heating temperature. Can be done by Here, in the present invention, the shrink fitting diameter of 0.15
Do ~ 0.55%. If the shrink fitting margin is less than 0.15%, the desired torque strength and tensile load cannot be obtained. On the other hand, if it exceeds 0.55%, it is inevitable to heat it to 800 ° C or more during shrink fitting, and scale is generated on the surface of the titanium material, and the torque strength and tensile load resistance of the shrink fitting portion are deteriorated.

According to the present invention, the length L of the shrink-fitting portion 20 is not particularly limited in the figure, but the one connected at the beginning at the time of excavation has a higher tensile load due to its own weight, so L is set to a large value. Is desirable. In a preferred embodiment of the present invention, the shrink fitting length is 100 to 200 mm.

In the present invention, the titanium tube is pure titanium,
That is, it may be composed of industrially pure titanium metal or may be composed of titanium alloy. Here, the titanium alloy, Ti-6Al-4V, Ti-6Al-4V (ELI), Ti-3Al-2.5V,
Ti-6Al-2Sn-4Zr-6Mo, Ti-6Al-6V-2Sn and the like are exemplified, but the present invention is not particularly limited thereto.

The shape of the joint is not limited to a particular shape, and the shape already used for steel drill pipes may be used as it is. Next, the operation of the shrink fitting process will be described.

A box joint 14 and a pin joint 16 constituting a steel joint portion are prepared in advance, and a titanium pipe of an appropriate length is used as a female mold in the illustrated example, and the steel surface is, for example, Ra25 to Roughen up to about 0.0035D (μm). Both ends of the titanium tube are heated to a temperature of 650 ° C by a heating furnace as appropriate, and then the steel tube is fitted into a steel joint and shrink-fitted. As described above, according to the present invention, it is possible to manufacture a joint that does not undergo severe rotation or looseness due to its own weight even if the steel and the titanium material are joined by shrink fitting.

As described above, when only the joint portion is made of steel, for example, welding causes an intermetallic compound to make it brittle, so that it cannot be joined to the titanium pipe of the main body, so that the connection is made by shrink fitting. However, mere shrink fitting does not provide sufficient strength as a drill pipe, and according to the present invention, by adjusting the surface roughness of the joint surface in an appropriate range and defining the shrink fitting allowance as described above, Make up. Next, the present invention will be described more specifically by way of its examples.

[0027]

【Example】

(Example 1) Titanium alloy (Ti-6% Al-4% V) and steel (SCM435)
Was manufactured under the following combination of processing conditions. The dimensions of the titanium tube are 51 mm outer diameter, 43 mm inner diameter, and 4 m wall thickness.
m, steel fittings have outer diameter 43mm, inner diameter 22mm, wall thickness 10.5m
It was m.

[0028]

[Table 1]

<Manufacturing Method> As shown in FIG. 1, a titanium alloy pipe body 12 is provided on the female side, and a steel pipe fitting 14 is provided on the male side.
16 was applied, the titanium alloy tube on the female side was heated by the induction heating method, the steel tube on the male side was inserted at room temperature, and shrink fitting was performed. The surface roughness of both titanium alloy pipes and steel pipe joints is Ra 6 ~
It was adjusted to 180 μm.

<Results of Performance Confirmation Test> For performance evaluation, torque resistance performance and tensile load resistance performance of the shrink-fitting portion were measured and evaluated. The results are also shown in Table 1. In Example No. 2 and Example No. 6, the surface roughness and shrinkage fitting margin were too small, and the target values of torque strength and tensile load resistance could not be satisfied. Example N
In o.5 and Example No. 9, the surface roughness shrinkage fitting margin was too large, so high temperature heating of the outer metal (900 ° C or higher) was required, and the strength was deteriorated due to the adverse effect of scale.

As can be seen from these results, according to the present invention, it is possible to obtain an appropriate surface roughness and a shrink fitting margin of 0.
Has a torque strength of 05kg-m / diameter (mm) and length (mm) or more,
It is clear that a tensile load of 360 kg / joint length (mm) or more can be satisfied, and it can be applied as a joint in practice.

[0032]

According to the present invention, the problems of seizure resistance and low torque, which are the drawbacks of titanium pipe joints, are solved by forming the joint portion from steel and integrally compositing it. As a result, a titanium drill pipe that can exhibit the original corrosion resistance of titanium and high specific strength characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a titanium drill pipe according to the present invention with a part thereof omitted.

Claims (2)

[Claims] 1. A 0.05 kg-m / diameter (mm) / length (mm), characterized by comprising a titanium pipe main body and a steel joint portion integrally provided on the pipe end by shrink fitting. A titanium drill pipe having the above torque strength and a tensile load resistance of 360 kg / joint length (mm) or more. 2. The surface roughness of the joint surface is Ra: 25 to 0.0035 Dμ.
m (D is the average diameter of the titanium pipe inner diameter and the steel joint outer diameter)
Then, the shrink fitting allowance for the average diameter D is 0.15 to 0.55%
A method for manufacturing a titanium drill pipe, comprising joining a steel joint portion to a pipe end portion of a titanium pipe body by shrink fitting.