JPH01278339A - Flexural sour fluid transport pipe - Google Patents

Abstract

PURPOSE:To manufacture a flexural sour fluid transport pipe of superior resistance to hydrogen rising cracking properties and resistance to sulfide corrosion cracking properties and with little lowering of strength of welded spots by having a metal reinforced layer of specific component formation and constituting the same of a high strength steel belt of specific tensile strength with a spheroidized structure. CONSTITUTION:A flexural sour fluid transport pipe consists of a plastic or rubber inner pipe, a metal reinforced layer provided on the inner pipe and a plastic outer coating provided on the metal reinforced pipe. The metal reinforced layer contains 0.40-0.70% of C, 0.1-1% of Si, 0.2-1% of Mn, 0.025% or less of P, and 0.01% or less of S, and if necessary, 0.008-0.050% of A, and the rest is composed of Fe and unavoidable impurities, and is constituted of a high strength steel belt of 50-80kg/mm<2> of tensile strength with a spheroidized structure. Harmful damages such as hydrogen rising cracks, sulfide corrosion cracks and others and not generated on the metal reinforced layer of a flexural pipe, and the strength of steady sections and welded sections of the reinforced layer can be increased and designed stress can be provided high to make the flexural pipe light in weight.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a flexible fluid transport pipe used to transport fluids such as gas, oil, and water.

[Prior Art] In recent years, with the trend toward deeper wells for gas and crude oil, sour environments containing hydrogen sulfide (wet hydrogen sulfide environments) have become more common.

In a flexible fluid transport pipe that has a metal reinforcing layer on the plastic inner tube, the metal reinforcing layer does not come into direct contact with the sour fluid inside, but the water and hydrogen sulfide that permeate through the plastic inner tube are , stays between the reinforcing layers, and its action causes hydrogen-induced cracking (HIC), sulfide stress corrosion cracking (SSCC), etc. in metal reinforced steel materials.

Sulfide stress corrosion cracking can generally be prevented from occurring by reducing the hardness of carbon steel to HRC22 (Rockwell C hardness 22) or less. Therefore, conventionally, flexible fluid transport pipes used in sour environments are made of low carbon steel wire with C082% or less as the metal reinforcement material, which is drawn into a predetermined shape by drawing, roller dicing, rolling, etc. It is made into a deformed steel wire with a cross-sectional shape, and is either left as is or annealed at a low temperature of 500℃ or less to have a tensile strength of 80kg/m.
A material with a tensile strength of 80 kg or less was used.
/mm” is approximately equal to HRC22).

However, it has become clear that hydrogen-induced cracking occurs in rolled low-carbon steel materials as the hydrogen sulfide partial pressure increases in the usage environment.

Furthermore, with conventional low carbon steel reinforcements, the strength of the connected (welded) portions is significantly reduced, making it impossible to increase the design stress.

[Problems to be Solved by the Invention] The object of the present invention is to provide a flexible sour fluid having a reinforcing layer made of high-strength steel material that has excellent resistance to hydrogen-induced cracking and sulfide corrosion cracking and has little strength loss at welded parts. It is to provide axial feed pipe.

[Means for solving 11M] G 0.40 to 0.70%, SLo, as a pressure reinforcement material
1-1%, Mn 0.2-1%, P 0.025% or less, S 0.010% or less, and if necessary, A
Contains Q 0.008 to 0.050%, the remainder is Fe and unavoidable impurities, and has a 1-spheroidal structure,
A high-strength steel wire or high-strength steel strip with excellent hydrogen-induced cracking resistance, characterized by a tensile strength of 50 kg/mm" to 80 kg/mm" (in the present invention, high-strength steel wire and high-strength steel The steel strip (abbreviated as high-strength steel strip) is used.

[Action Co. The reasons for limiting the components of the reinforcing material of the present invention will be explained below.

If the C content is less than 0.40%, the target strength cannot be obtained by single-spheroidization annealing, and the strength of the welded portion is greatly reduced, so 0.40% was set as the lower limit. If C exceeds 0.70%, strong cold working becomes difficult, and slight cracks occur inside the steel wire or copper strip during processing, which not only deteriorates the HIC properties but also causes cracks on the end face. Therefore, 0.70%
was set as the upper limit.

Si is required as a deoxidizing agent at least 0.10%,
As the amount increases, the strength improves.

However, if it exceeds 1%, decarburization of the slab and billet in the heating furnace becomes severe, which remains in the steel wire and copper strip, resulting in frequent cracking during cold working, which is not preferable.

0.2% or more of Mn is required to prevent hot brittleness. In addition, since Mn is an inexpensive element that improves strength,
The higher the amount, the better.However, Mn is an element that tends to segregate together with P, and in particular, in the present invention, the frequency of HIC caused by center segregation increases. The smaller the amount, the better.
However, when producing by continuous casting, the melting temperature is increased, which causes re-P to occur, so only the upper limit was set at 0.025%.

In addition to the same disadvantages as P, S is preferable in small amounts in terms of corrosion resistance, but it can be produced economically at present.

% or less. Note that industrial production of S up to 0.001% is possible.

In some cases, Afl is used as a grain refining agent and as a deoxidizing agent, and in other cases, AQ is not added to specify a coarse grain tone and to prevent nonmetallic inclusions in the steel due to AQ. A
In the case of Q addition, for example, 5olA Q required for grain refinement requires at least 0.006% or more, but at this time, the total A
Since the distribution (ratio) of 5olA Q and In5ol in the amount of Q is 8:2, the lower limit was set to o and ooa%.

When AQ exceeds o or oso%, nonmetallic inclusions in the steel increase, resulting in a decrease in product quality and yield.

Considering the melting yield and variation, in the case of AΩ addition, o, ois ~ 0.035% is usually preferable.

On the other hand, the amount of AQ in steel without AQ addition is less than 0.008%.

AQ may be used as necessary depending on the purpose described above.

Reinforced steel wire (shaped steel wire) by processing steel materials with the above composition.
However, if the processed steel wire or copper strip is used as is, hydrogen-induced cracking will occur in areas where strain is relatively concentrated inside the steel wire or steel strip, so the strain must be removed by annealing. The tensile strength after annealing is required to be 50k in order to increase the design stress and reduce the weight of the flexible tube.
g/I is required to be at least 1 m'', and also required to be at most 80 kg/m2 to prevent sulfide stress corrosion cracking.

In order to obtain a preferable tensile strength with the component system of the reinforcing material according to the present invention, spheroidizing annealing is performed at a temperature of around 600°C to remove processing strain and to transform the pearlite structure into a ferrite matrix with fine spherical cementite dispersed. It is necessary to create a spheroidized tissue, that is, a spheroidized tissue. The degree of the spheroidized structure described above is, for example, the classification No. shown in the spheroidized structure photograph of JIS G 3539.

Among No. 1 to 'No.' and No. 6, No. 1 to No. 3 are preferable, that is, No. 4 and above are not preferable because the degree of spheroidization is small and hydrogen-induced cracking is likely to occur.

[Example] Fig. 1 shows an example of a longitudinal cross-sectional view of a flexible sour fluid transport pipe according to the present invention. A reinforcing steel wire 2 (channel steel wire) is spirally wound so that the upper layer 2-1 and the lower layer 2-2 mesh with each other, and an outer reinforcing layer 3 (copper strip) made of the same material is further formed on top of the inner reinforcing layer 2. The upper and lower layers are spirally wound in opposite directions with a large pitch. The metal reinforcing layer may be formed of either the inner or outer reinforcing layer (either 2 or 3). The outermost layer 4 is a plastic jacket, which protects the metal reinforcing layer from damage from the external environment.

Table 1 shows examples of the characteristics of the metal reinforcing layer in comparison with conventional materials.

In the reinforcing material according to the present invention, hydrogen-induced cracking does not occur, and the tensile strength of the steady portion and welded portion is higher than that of conventional products.

[Effects of the Invention] According to the present invention, harmful damage such as hydrogen-induced cracking and sulfide stress corrosion cracking does not occur in the metal reinforcing layer of a flexible pipe for transporting sour fluid, and furthermore, the steady state of the reinforcing layer The strength of the parts and welded parts is high, making it possible to take a high design stress, and making it possible to reduce the weight of the flexible tube.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an example of a flexible sour fluid transport tube according to the present invention. 1...Plastic inner tube. 2 (2-1, 2-2)... Internal reinforcing layer tube 1
The front skewer test method is NACE (American Corrosion Association) standard TM-02
-84 Compliant ψ fist test method complies with NACE standard TM-01-773
...External reinforcing layer 4...Plastic jacket Patent applicant Furukawa Electric Co., Ltd.

Claims (1)

[Claims] A flexible fluid transport tube comprising a rubber or plastic inner tube, a metal reinforcing layer provided on the inner tube, and a plastic outer jacket provided on the metal reinforcing layer. , the metal reinforcing layer contains 0.40 to 0.70% C, 0.1 to 1% Si, and Mn.
0.2-1%, P 0.025% or less, S 0.01
Contains 0% or less, and if necessary Al 0.008-0.050
%, the balance is Fe and unavoidable impurities, and has a spheroidized structure with a tensile strength of 50 kg/mm^2 ~
A flexible sour fluid transport pipe characterized by being made of a high strength steel strip of 80 kg/mm^2.