JPH0674866B2 - Composite pipe with mechanical properties that withstand high temperatures and pressures and excellent corrosion resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a clad pipe for a line pipe laid in a sour environment oil well having a large amount of H ₂ S.

(Prior art and its problems) Line pipe materials used in crude oil and natural gas oil wells are required to have mechanical properties that withstand high temperatures and pressures and excellent corrosion resistance. Recently, the depth of wells has become deeper and the environment for use has become higher in temperature and pressure, and production has shifted from land to the ocean.
Production in oil wells containing chlorine ions, hydrogen sulfide, and carbon dioxide is unavoidable, and further improvement in mechanical properties and corrosion resistance is required.

Since a single-layer pipe cannot satisfy both of these characteristics at the same time, a two-layer clad pipe has been proposed in which the outer side is formed of carbon steel or low alloy steel and the inner side is formed of stainless steel or high alloy steel.

By the way, the pipe size for this kind of use is generally about
100-600mm, length about 4000-6000mm, outer layer thickness about 10-60m
It is a long thin tube with m and inner layer thickness of about 2-4 mm. Conventionally, to make a two-layer pipe for a line pipe such as an oil well, an inner-layer pipe and an outer-layer pipe are made in advance, and after these pipes are fitted together, they are hydraulically, hot-rolled, hot-extruded or explosively bonded. The manufacturing method is adopted.

These two-layer pipes have a problem that the metal-like adhesion strength between the outer layer and the inner layer is not sufficient, the joining strength is insufficient including the mechanical joining portion, and the uneven thickness becomes large, and Since the outer layer component and the inner layer component suddenly fluctuate greatly at the boundary,
There was a problem that the strength of the entire tube was reduced. Further, when used in a sour environment, there is a problem that hydrogen sulfide enters the mechanical joint during use, and hydrogen sulfide-induced cracking occurs at the joint.

If these two-layer pipes are composited by the centrifugal casting method, the outer layer and the inner layer are metallurgically integrated and the joint strength is increased, but the inner layer component and the outer layer component are mutually diffused, and the mechanical strength of the outer layer and the inner layer There is a problem of reduced corrosion resistance.

The present inventor, when producing a pipe by the centrifugal casting method, if casting is performed so that an intermediate layer having a predetermined thickness is formed between the outer layer and the inner layer,
It has been found that it is possible to manufacture a composite pipe having sufficient bonding strength and preventing the outer layer component and the inner layer component from diffusing each other. In the pipe, except for the intermediate layer, the outer layer component and the inner layer component can be metallurgically integrated without being mixed with each other, so that the outer layer can exhibit a predetermined mechanical strength and the inner layer can have a predetermined corrosion resistance.

(Problems to be Solved by the Invention) The present invention is manufactured by a centrifugal casting method for metallurgically integrating an outer layer and an inner layer, and an intermediate layer having a predetermined thickness is formed between the outer layer and the inner layer. It is an object of the present invention to provide a composite pipe having excellent joint strength and preventing the outer layer component and the inner layer component from being mixed with each other except the intermediate layer.

(Means and Actions for Solving the Problems) The composite pipe of the present invention is formed by a centrifugal casting method, and has a boundary between an outer layer having high mechanical strength that withstands high temperature and high pressure and an inner layer having excellent corrosion resistance. As a part, an intermediate layer having a predetermined thickness, which is composed of an approximately intermediate component of the outer layer material and the inner layer material, is metallurgically integrated with the outer layer and the inner layer.

The composite pipe of the present invention, in% by weight (hereinafter, all the same),
C: 0.05 to 0.20%, Si: 1.0% or less, Mn: 2.0% or less, Cr: 1.0
% Or less, Ni: 0.2 to 2.0%, Mo: 1.0% or less, V: 0.05 to 0.15
%, Al: 0.1% or less, the balance consists of inevitable impurities and Fe, An outer layer of material having a carbon equivalent of 0.45 or less represented by, and a total amount of 100%, C: 0.030% or less, Si: 1.0%
Below, Mn: 2.0% or less, Ni: 12.0 to 16.0%, Cr: 16.0 to 18.0
%, Mo: 2.0 to 3.0%, the total amount is 100% as a boundary portion between the inner layer of the material consisting of the balance unavoidable impurities and Fe.
C: 0.03 to 0.07%, Si: 0.3 to 0.7%, Mn: 0.5 to
1.5%, Cr: 6.0-12.0%, Ni: 4.0-11.0%, Mo: 0.9-1.5
%, Fe: 75.0 to 85.0%, Al: 0.01 to 0.05%, and an unavoidable impurity-containing material, and an intermediate layer having a thickness of 10 to 100 μm is metallurgically integrated with the outer layer and the inner layer. There is.

As described above, in the composite pipe of the present invention, the outer layer is made of low alloy steel and the inner layer is made of corrosion resistant alloy. In the composite pipe according to the present invention, in order to improve the mechanical properties of the outer layer, the outer layer contains predetermined components Ni and V.

Ni has the effect of improving low temperature impact resistance and room temperature strength. The content is 0.2-2.0% to fully exhibit this effect.
Prescribed in. Further, V contributes to improvement of hardenability and refinement of crystal grains. The content is specified to be 0.05 to 0.15% in order to sufficiently exert these effects.

The composite pipe of the present invention includes an intermediate layer having a predetermined component and a thickness between the outer layer and the inner layer. The intermediate layer is formed by mixing with the outer layer material when pouring the inner layer material. The outer layer and the inner layer have sufficient bonding strength, and in order to prevent the outer layer component and the inner layer component from mixing with each other, the thickness of the intermediate layer is 10 ~.
Specify to 100 μm. That is, if the thickness is less than 10 μm, sufficient bonding strength cannot be obtained. In the case of a line pipe with an inner layer thickness of approximately 2 to 4 mm, the thickness of the intermediate layer is 100
If it exceeds μm, the components of the outer layer will penetrate into the inner layer, and the corrosion resistance of the inner layer will be impaired, making it unusable.

That is, by defining the thickness of the intermediate layer to be 10 μm to 100 μm, it is possible to manufacture a desired composite pipe without mixing the component compositions of the outer layer and the inner layer as described above. The thickness of the intermediate layer is preferably in the range of about 20-50 μm.

The adhesive strength between the outer layer and the inner layer has a shear stress of about 40 kgf / mm ² or more.

Further, since the outer layer component and the inner layer component do not diffuse into each other, the outer layer can have a predetermined mechanical strength and the inner layer can have a predetermined corrosion resistance.

The outer layer and the inner layer are metallurgically integrated through the intermediate layer, so that hydrogen sulfide enters the joint between the outer layer and the inner layer and causes hydrogen sulfide-induced cracking at the joint like mechanical joining. Problems that may occur are eliminated.

(Example) In the composite pipe of the present invention, the molten metal of the outer layer material shown in Table 1 is poured into the rotary mold, and after the outer layer is solidified, the molten metal of the inner layer material shown in Table 1 is poured, Melt the surface of the solidified layer,
It was manufactured by fusing the outer layer material and the inner layer material to form an intermediate layer, and then continuing pouring the metal to solidify the inner layer.

In order to keep the thickness of the intermediate layer within a predetermined range, the outer layer material and the inner layer material must be cast at appropriate timings. When the inner layer is cast before the outer layer is solidified, the boundary layer of the intermediate composition is not formed, the outer layer component and the inner layer component are mutually diffused, and when the time for casting the inner layer is long after solidifying the outer layer, , Because the inner layer will not be metallurgically bonded to the outer layer.

The composite pipe manufactured in the example has a length of 5600 mm and an outer diameter of 17
0 mm, inner diameter 134 mm, outer layer thickness 15 mm, inner layer thickness 3 mm,
The thickness of the intermediate layer was about 20 μm.

The alloy components of the obtained intermediate layer are shown in Table 1, and the electron micrograph of the vicinity of the intermediate layer is shown in FIG. In addition, the numerical value of the alloy component of the intermediate layer is an analysis result in a substantially central portion in the thickness direction.

The test tube was subjected to a shearing test specified in ASTM A 264, and the shearing stress was examined. As a result, it was 41 kgf / mm ² .

(Effect of the Invention) The composite pipe of the present invention includes an intermediate layer having a predetermined thickness in which the outer layer component and the inner layer component are mixed. The outer layer and the inner layer are metallurgically integrated through the intermediate layer without the outer layer component and the inner layer component being mixed with each other, and are joined with sufficient strength. Thus, the outer layer can exhibit the desired mechanical properties and the inner layer can have the desired corrosion resistance.

In the composite pipe of the present invention, the outer layer and the inner layer are metallurgically integrated through the intermediate layer, and there is no mechanical joint, so that hydrogen sulfide enters the joint between the outer layer and the inner layer during use, There is no risk of hydrogen sulfide-induced cracking at the joint.

The composite pipe of the present invention is suitable as a line pipe for crude oil and natural gas oil wells.

[Brief description of drawings]

FIG. 1 is a drawing-substitute electron micrograph showing a metal structure in the vicinity of the intermediate layer of the composite tube of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C22C 38/46

Claims (1)

[Claims] 1. In wt%, C: 0.05 to 0.20%, Si: 1.0% or less, Mn: 2.0% or less, Cr: 1.0% or less, Ni: 0.2 to 2.0%, Mo:
1.0% or less, V: 0.05 to 0.15%, Al: 0.1% or less, balance unavoidable impurities and Fe, An outer layer of material having a carbon equivalent of 0.45 or less represented by, and a total amount of 100%, C: 0.030% or less, Si: 1.0%
Below, Mn: 2.0% or less, Ni: 12.0 to 16.0%, Cr: 16.0 to 18.0
%, Mo: 2.0 to 3.0%, the total amount is 100% as a boundary portion between the inner layer of the material consisting of the balance unavoidable impurities and Fe.
C: 0.03 to 0.07%, Si: 0.3 to 0.7%, Mn: 0.5 to
1.5%, Cr: 6.0-12.0%, Ni: 4.0-11.0%, Mo: 0.9-1.5
%, Fe: 75.0 to 85.0%, Al: 0.01 to 0.05%, and an unavoidable impurity-containing material, and an intermediate layer having a thickness of 10 to 100 μm is metallurgically integrated with the outer layer and the inner layer. A composite pipe with excellent corrosion resistance and mechanical properties that can withstand high temperature and high pressure.