JPS63270477A - Production of joint member of oil well pipe having superior corrosion resistance and seizing preventiveness - Google Patents

Abstract

PURPOSE:To produce a joint member of an oil well pipe having superior corro sion resistance and seizing preventiveness by forming an Ni layer of a specified thickness on the female screw part of the joint member by electroless plating and by forming a layer of projected and deposited steel shots each coated with a metallic Zn layer on the male screw part of each mother pipe. CONSTITUTION:Mother pipes 1 and a joint 3 are connected with male screws 2 cut at the ends of the pipes 1 and a female screw 4 cut around the joint 3. At this time, an Ni layer of >=5mu thickness is formed on the female screw 4 by electroless plating and layers of projected and deposited steel shots each coated with a metallic Zn layer 7 on an Fe-Zn alloy layer 6 are formed on the male screws 2 engaged with the female screw 4. Thus, a joint member of an oil well pipe having superior resistance to sulfide stress corrosion cracking and erosion corrosion and superior seizing preventiveness during fastening is obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides an oil country tubular joint that has excellent resistance to sulfide stress corrosion cracking or erosion, and has excellent anti-seize properties during fastening. The present invention relates to a method of manufacturing a member.

[Conventional technology and problems]

Recently, oil and gas wells being developed have been trending toward deeper and more sour wells. The oil country tubular goods used for this purpose are subject to sulfide stress corrosion cracking (5ulf 1deStress C
Corrosion cracking (hereinafter abbreviated as SSC) and erosion, including corrosion, have become a problem. 'Fl joint part has internal pressure, external pressure, tensile load,
In addition to the bending load, the SS is exposed to complex and severe stress conditions that include the circumferential stress generated during fastening.
Because of the complexity of the shape, turbulent flow occurs at the joints, making it easy for turbulence to occur. This is explained in the literature, for example by Geoffrey W.
Rowland;”Planning for Dee
p High Pressured Welts 1n
the North Sea”, European
0ffshore PetroleumConfere
nce (1980) K is also described.

In order to overcome such corrosion problems, it is a common practice to coat the relevant parts with a highly corrosion-resistant material. Conventionally, threaded portions of oil country tubular joints have been treated with sinate, zinc plated, copper plated, etc. However, these methods focused only on the anti-seizure effect when tightening screws, and did not take into account the corrosion problem of the joints mentioned above.
A case in which accident C occurred is also described in the above-mentioned literature.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a joint member that effectively prevents corrosion damage caused by SSC and erosion corrugation of an oil well pipe joint, and prevents seizure during screw fastening.

[Means for solving problems]

The present invention has solved the above-mentioned problems, and its gist is that an electroless nickel plating layer with a thickness of 5 μm or more is applied to the female thread of an oil country pipe joint member, and the other male This is a method for producing an oil country tubular joint member having excellent corrosion resistance and anti-seizure effects, characterized in that a threaded portion is coated with a deposited layer of steel particles that coats a metallic zinc layer.

[Effect] Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows a cross section of an oil well pipe joint.
In the figure, 1 is a main pipe, and a male thread 2 is cut at the end of the pipe.

3 is a joint with a female thread 4 cut on its inner surface. Main tube 1
and the joint 3 are connected by fastening screws. Therefore, in the present invention, an electroless nickel plating layer with a thickness of 5 μm or more is applied to the female thread portion 4 of the oil country tubular joint member as shown in FIG.
In addition to protecting the female thread from the corrosive fluid passing through the inside of the pipe, the male thread 2 is coated with a projected deposited layer of steel particles (hereinafter referred to as the zinc coating layer) that coats the male thread with a metal zinc layer to provide a lubricating effect when tightening the screw. be.

First, the basis for applying electroless nickel plating to the female screw 4 will be described.

Table 1 shows the corrosion resistance of pure metals copper, nickel, zinc, and iron in a sour gas environment as a corrosion loss of 1 dm per day in a NACE liquid specified by NACETM-0177.

From Table 1, it is clear that nickel is an excellent material for covering female screws in a sour environment, and the corrosion resistance of nickel plated materials can be expected. However, there are other methods for nickel plating. Using three typical electroplating baths (chloride bath, Watt bath, sulfamine bath) and a hypophosphorous acid-based electroless plating bath, a nickel plating layer with a thickness of 10 μm was applied to a bending specimen of 80 kg class steel. , immersed in NACE solution for 14 days with bending stress applied,
SC occurrence limit stress Sc (S(! is larger, SSC resistance
As shown in Table 2, electroless plating has better SS resistance than electroplating even with the same plating thickness.
Excellent C properties.

Table 2 The reason for this is presumed to be that electroless plating produces fewer pinholes than electroplating. In the present invention, the thickness of the plating layer is set to 5 μm or more, and the reason for this is that, as shown in Figure 2, a plating thickness of 5 μm or less provides good SS resistance.
◇ Electroless nickel plating is also excellent against erosion, erosion, and corrosion. Maximum 5tn/M.

By immersing various plated specimens in the NACE liquid while rotating them with high-velocity waves, we reproduced the corrosion erosion and investigated the corrosion loss, as shown in Table 3.
The electroless nickel plated material exhibited excellent resistance to corrosion.

Table 3 The cause of this is not clear, but the inventors estimate that
Since the electroless nickel plating layer has higher hardness than other plating layers, it is considered to be effective against corrosion damage including mechanical elements.

Next, we will explain the basis for applying a zinc coating layer to male screws.

Since nickel is an element physicochemically similar to iron, as shown in Table 4, seizing occurs when an electroless nickel plated female screw is fastened to an untreated steel male screw.

Table 4 Rice 1) The degree of seizure is severe in the order of ×>Δ.

O does not cause seizure.

To avoid this, it is necessary to provide a layer with excellent lubrication effect on the threaded surface of the male steel thread. Table 4 shows copper plating, zinc plating, which are well-known screw surface treatment methods.
Phosphate treatment and the lead coating according to the present invention are applied to a steel male screw thread part to a thickness of 10 μm, and this is repeatedly fastened 10 times to a female screw that has been applied with an electroless nickel plating layer to a thickness of 10 μm to prevent seizure. The results of examining the presence or absence of

It is clear from this that the Zn coating according to the present invention has an excellent anti-seizing effect.

In the present invention, the zinc coating layer consists of projected particles having a particle size of 1 to 2w18 as shown in FIG. 3 (gI4 is the core 5,
This is obtained by projecting a structure having an iron-zinc alloy layer 6 on the outside thereof and a metal zinc layer 7 on the outside thereof. As shown in FIG. 4, the structure of this coating layer is such that zinc 7 (FIG. 3), which is the outermost layer of the projected particles, is transferred and deposited as granular zinc 8 onto the projecting object by impact energy. What is characteristic here is that there are many gaps 9 in the coating layer, and that the surface of the target material 10 is subjected to the blasting effect and exhibits an uneven shape, which is directly reflected in the uneven shape of the coating layer surface. be. Because of this structure, compound grease is trapped in the gaps 9 in the coating layer and in the recesses on the surface of the coating layer. This is considered to be the main reason why the zinc coating layer of the present invention has a superior anti-seizure effect compared to a galvanized layer.

The oil well pipe joint obtained in this way has excellent SSC resistance 11
fft exhibits anti-corrosion properties and anti-seizing effects.

〔Example〕

Examples of the present invention will be described below.

Outer diameter 178H1 Wall thickness 11.5 ram SUS 42
0 (C: 0.2%, Mn: 0.4%, St:
0.4%, Cr: 13%, Ni: 0.1%, the balance being substantially Fe) and a 10 μm thick zinc coating layer on each of the steel pipe (male thread) and pipe joint (female thread).6.
A 10° x 20 μm electroless nickel mesh Φ layer was poured to prepare a test material. Electroless nickel plating is nickel chloride 30
? /l, sodium oxyacetate 50 f/l, hypochlorite') :y acid fl') uA 10 f/l, pH
4.5. Applied in a hot [90'C] bath. Using this test material, (a) Presence or absence of seizure due to repeated fastening io times ('b) Constant load stress of a real pipe where a tensile load of 50 inches, which is the joint strength, is applied in the axial direction while circulating NACE liquid in the pipe. Presence or absence of SSC occurrence by corrosion cracking test (e) NACE liquid was circulated in the pipe at a high speed of 51 degrees, and the corrosion status of the plating layer on the inner surface of the joint was evaluated.

The comparison material is the same steel type, the same thread shape, and only the thread surface has been treated. Female thread: Nickel strike steel plated (10 μm thick)
, male thread: Untreated was used. The results are shown in Table 5.

Table 5 [Effects of the Invention] As mentioned above, the present invention has higher SSC resistance than conventional comparative materials!
, shows remarkable effects on erosion resistance, corrosion resistance, and anti-seizure properties.

[Brief explanation of drawings]

Figure 1 is the cross-sectional shape of an oil country pipe joint, Figure 2 is a diagram showing the relationship between electroless nickel plating layer thickness and SC value, Figure 3 is a diagram showing the structure of the projected particles, and Figure 4 is a male thread. FIG. 3 is a diagram showing the structure of a zinc coating layer formed on the surface. 1... Main pipe 2... Male thread 3... Joint 4... Female thread 5... Core (steel)
6... Iron-zinc alloy layer 7... Metallic zinc layer 8.
...Granular zinc 9...Gap. Figure 2 7 people thickness 2? (mem)

Claims (1)

[Claims] An electroless nickel plating layer with a thickness of 5 μm or more is applied to the female threaded part of an oil country tubular joint member, and a projected deposited layer of steel particles covering the metal zinc layer is applied to the other male threaded part that fits into the female threaded part. A method for manufacturing an oil country tubular joint member having excellent corrosion resistance and anti-seizure properties.