JPS60220281A - Corrosion-resistant double pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a corrosion-resistant double pipe suitable for use as oil country tubular goods and the like.

Conventional technology and its assembling points Conventionally, metal pipes used for oil country tubular goods etc. are required to withstand corrosive attacks from fluids containing corrosive impurities. Due to the disadvantages of carbonate cracking and ammonia cracking, such oil country tubular goods are, for example, made of all-carbon steel for the outer pipe and stainless steel for the inner pipe.
iOr-? Generally, alloy steel pipes containing Mo 1 and the like were used. However, metal pipes made of such materials still had the problem of being expensive and expensive.

Purpose of the Invention The present invention is capable of efficiently preventing the occurrence of sulfide cracking, carbonate cracking, or ammonia cracking as described above in an environment containing almost no hydrogen sulfide at low cost. □ The purpose of the invention is to propose a corrosion-resistant double-walled pipe that can be used as a strength support. This is a corrosion-resistant double-walled pipe having an MP& structure, in which the inner pipe is made of extremely mild steel with a Vickers hardness of 150 or less.

In the VC of this invention, extremely mild steel is used for the inner tube. .

The reason for this is that such extremely mild steel is not only low-cost, but also resistant to stress corrosion cracking (hereinafter referred to as iPL) such as stress corrosion cracking (hereinafter simply referred to as 5SCC), carbonate cracking, and ammonia cracking. This is because it has particularly strong resistance not only to SOC (abbreviated as SOC) but also to CO□ corrosion, etc. 1. In order to fully exhibit these characteristics, V must be 150 or less on the Vickers hardness.

The typical composition and mechanical properties of extremely mild steel used as such an inner tube are shown in Table 1 below.

Table 1 On the other hand, any material may be used as the outer tube as long as it has a strength sufficient for practical use, and carbon steel is particularly suitable.

Fig. 1 shows a cross section of a preferred embodiment of the present invention, in which 1 is an outer tube made of carbon steel, 2 is (3: an inner tube made of extremely mild steel of 0.09% or less), and 8 is the same metal sealing part as the inner pipe. In manufacturing such a double pipe, (1) E) The method of making the pipe and the inner pipe separately and joining them by shrink fitting, ( 2) A method of thermally spraying extremely mild steel onto the inner periphery of the outer tube to form the entire inner wall; (8) A method of joining or drilling clad plates or bolts made of extremely mild steel and carbon steel can be used.

Next, the results of investigating the corrosion resistance of the double pipe obtained according to the present invention will be described.

1. Constant load tensile 5sca test Carbon steel with a tensile strength of 6 Q kgf/mm is used as the outer tube, and the inner circumference is made of Vickers? 5UHV150 extra mild steel' (zl, sprayed to 2.8 and 4 mm thickness, 4
Different types of double tubes were prepared, and tensile test pieces were taken from each.

Constant load tensile strength of each test piece obtained at room temperature 5soo
The test results are shown in Table 2. Table 2 also shows test results for conventional pipes made of refined general carbon steel for reference.
Fractured within 500 hours 3 First, no cracking on the surface or near the boundary between the two layers, △: No fracture within 500 hours, and blistering occurred at the boundary between the two layers and the mild steel layer.X: Fractured within 500 hours 0 It is clear from the table As such, 1 and 2 obtained according to this invention
Heavy pipes have much better 5soo resistance than conventional pipes.

2. Ammonia cracking test Among the double pipes subjected to the above constant load tensile 5 soc test, extremely mild steel! - Take an arc-shaped test piece from a piece with a thickness of 8 mm, and perform a crack acceleration test on this test piece under the conditions shown in Section 8. What are the results obtained? ! - Shown in different numbers.

Table 8 Table 4 *Equivalent to tensile strength 60 kff/2, m without mild steel layer ○: No cracks △: Slight cracks ×: Cracks As is clear from the results shown in Table 4, the double pipe of the present invention , Conventional pipe ILv has ammonia cracking resistance 2. .

It is also excellent in terms of sex.

Effects of the Invention Thus, according to the present invention, it is possible to effectively prevent cranking caused by sulfide, carbonate cracking, ammonia cracking, etc., without requiring an alloy containing expensive special elements1, and at low cost. A tube material that can be used is obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a preferred embodiment of the present invention. Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] 1 A pipe material having a double wall structure in which an inner t# is closely held on the inner periphery of an outer pipe serving as a strength support, and the inner pipe is made of extremely mild steel with a Vickers hardness of 150 or less. Corrosion-resistant double pipe.