WO2001044531A1 - Flexible pipe with low-carbon steel armour - Google Patents

Abstract

The invention relates to a flexible tubular pipe having at least one reinforcing metal armour. The inventive pipe is made from low-carbon steel, i.e. steel with less than 0.16 % carbon, having a predominantly bainitic microstructure and mechanical properties resulting from the addition of micro-alloy elements B, V, Ti, Nb and control of quench hardening conditions.

Description

1) Reinforced flexible pipe, characterized in that at least one of the metallic shaped wires constituting a reinforcing armor is made from a steel having one of the following chemical compositions (I), (II) and (III) : the composition (I) comprises by weight: 0.03% <C <0.16% 0.5% <Mn <2%

0.05% <If <0.5% 0% <Cr <1.8% 0% <Mo <0.25% 0.001% <Al <0.05% 0.001% <Ti <0.05%

0% ≤ V <0.15% 0.0005% ≤ B <0.005% 0.004% ≤ N ≤ 0.012% 0.001% <S <0.09% - possibly up to 0.005% calcium, up to 0.01 % tellurium, up to 0.04% selenium, up to 0.3% lead,

- the remainder being iron and impurities resulting from the production, the chemical composition of the steel further satisfying the relationships: Mn + 0.9Cr + 1, 3Mo + 1.6V> 2.2% and Al + Ti > 3.5N the composition (II) comprises by weight: 0.06% <C <0.11%

1% <Mn <1.7%

0.15% <If <0.40%

0.025% <S <0.10% P <0.025%

0% <Ni <0.25%

0.5% ≤ Cr ≤ 1.20%

0.08% <Mo <0.13%

0% <Cu <0.25% 0.003% ≤ Al ≤ 0.035%

0% <Ti <0.035%

0% ≤ V <0.10%

0% ≤ Nb ≤ 0.06%

0.0008% <B ≤ 0.0040% 0.0060% ≤ N ≤ 0.011%

- possibly one or more elements taken from: Te up to 0.010%, Se up to 0.025%, Bi up to 0.13%, Pb up to 0.090%, Ca up to 0.0040%,

- the remainder being iron and impurities resulting from the preparation, the chemical composition also satisfying the relationships:

Mn + Cr + Mo> 2.1% 0.015% ≤ V + Nb + Ti ≤ 0.13% Al + Ti> 0.020% Mn / S> 12 - the composition (III) comprises by weight:

0.05% ≤ C <0.12% 0.1% ≤ If ≤ 0.45% 1.01% ≤ Mn <1.8% 0.15% ≤ Cr ≤ 1.15% 0.06% <Mo <0.12% Cu <0.30% Ni ≤ 0.30% 0.01% <Ti ≤ 0.04%

0.005% ≤ Al ≤ 0.04% 0.006% ≤ N ≤ 0.013% 0.0005% <B ≤ 0.004% P <0.025% 0.02% <S ≤ 0.1%

0% ≤ Pb ≤ 0.1% 0% ≤ Te ≤ 0.07%

- optionally from 0.0002 to 0.002% of calcium, the remainder being iron and impurities resulting from the production, the chemical composition satisfying in addition the relationships: 0.2% ≤ Ni + Mo + Cu ≤ 0.7%

- the content of non-combined boron being not less than 0.0005% above 950 ° C.

2) Flexible pipe according to claim 1, in which the composition (I) is such that:

0.06% ≤ C <0.12%

0.8% ≤ Mn ≤ 1.7%

0.1% <If ≤ 0.35% 0.1% <Cr ≤ 1.5%

0.07% ≤ Mo ≤ 0.15%

0.001% ≤ Al <0.035%

0.001% <Ti ≤ 0.03% 0% ≤ V ≤ 0.1% 0.001% <B <0.004% 0.004% ≤ N ≤ 0.01% 0.001% ≤ S ≤ 0.09% - possibly up to 0.005% calcium, up to 0.01 % tellurium, up to 0.04% selenium, up to 0.3% lead,

- the remainder being iron and impurities resulting from the production.

3) Flexible pipe according to claim 2, in which the composition (I) is such that: Ni <0.25% Cu ≤ 0.25%

4) flexible pipe according to claim 2 or 3, wherein the composition (I) is such that: P ≤ 0.02%

5) Flexible pipe according to claim 1, in which the composition (III) is such that:

0.05% ≤ C ≤ 0.08%

0.15% <If <0.35%

1.01% ≤ Mn <1.35%

0.8% ≤ Cr ≤ 1.15% 0.08% <Mo ≤ 0.11% 6) Method of manufacturing a form wire for the constitution

of a flexible armed pipe, characterized in that the

following steps :

we make a semi-steel product from steel

having one of the compositions (I), (II) or (III), according to one of the

claims 1 to 5,

at least one hot forming operation is carried out

and / or cold to obtain said form wire,

- quenching with controlled cooling to obtain

an essentially bainitic structure.

FLEXIBLE PIPE COMPRISING LOW CARBON STEEL WEAPONS

The present invention belongs to the technical field of

flexible pipes reinforced with metal armor and adapted to

transport of effluents under pressure which may contain corrosive products

or weakeners. The invention may be suitable for hoses of the flow type

line ”, that is to say flexible pipes unwound from a boat

to be placed on the bottom of the sea and connected between heads of

wells and / or underwater collection facilities, or pipelines

“riser” type hoses, ie pipes that cross the

slice of water and are therefore subjected to dynamic forces due to

the environment. The invention relates more particularly to the type of

metallic materials constituting the form wires of the armor of

reinforcements.

We know from documents WO-91/16461, WO-96/28575, WO-

98/10113 steels and their associated heat treatments which

suitable for making armor wires for pipes

flexible, as described in API RP 17B documents

(Recommended Practices) and SPEC 17J (Specification) which have as their object

flexible pipes for the exploitation of oil fields

offshore. However, these documents do not describe the alloys with very low carbon with mechanical characteristics in accordance with the specifications

loads that the reinforcing armor wires of the

flexible lines.

Figure 1 shows an example of a pipe structure

flexible which combines one or more gas-tight sheaths (2, 5) or

liquids transported, with layers of armor intended to resist

radial forces due to internal pressure and / or external pressure

(1, 3), as well as to the longitudinal forces (4) resulting from the weight of the

driving and / or pressure.

In general, a flexible pipe includes,

inside to outside, a carcass (1) consisting for example of a

stapled strip, a polymer sealing sheath (2), at least one

pressure vault (3) consisting of stapled, coiled wires

in a low pitch spiral, at least one layer of armor wire (4) of

traction wound in a long pitch spiral. This configuration is

called "rough bore".

A flexible pipe variant (not shown here, but known

skilled in the art) may include an internal sealing sheath,

a first layer of armor resistant mainly to pressure

developed by the fluid circulating in the internal sheath,

generally called pressure vault, at least a second layer 3

of armor resistant mainly to traction. This variant is

called "smooth bore".

In another variant, certain hoses have a ply

of armor, placed above the sealing sheath, which resists

both to the tensile effects directed longitudinally and to the component

circumferential due to the internal pressure of the fluid. Such a layer of

pressure reinforcement may include two plies of pitch propeller wires

reverse whose winding angles are close to 55 °. The efforts due to the

internal pressure are, in this case, retained by these layers.

In the presence of corrosive gases in the effluent

transported by pipeline, for example from IΗ2S, the quality of steels

used in the manufacture of all armor wires, as well as

mechanical and thermal treatments carried out on these wires (in particular

work hardening, then possibly annealed) must be

chosen and defined so that these threads jointly provide:

mechanical resistance required in service and installation, and resistance to

corrosion in the presence of H ^ S or CO2. For this, we are, so far,

leads to the use of steels with relatively mechanical qualities

weak, or steels of specific composition combined with

adapted heat treatments. In the first case, this leads to

penalizing steel weights, in the other case, often at costs of more important because of heat treatments. We can

cite with reference the documents already cited: WO-91/16461 and WO-

96/28575.

The present invention relates to a flexible pipe of which at least

a metal reinforcement armor is made from a low steel

carbon content, less than 0.16%, having a microstructure

bainitic predominance, and mechanical properties which result

especially :

adding micro-alloying elements: B, V, Ti, Nb, ...,

- and control of the quenching conditions.

Documents EP-0851038A1, EP-0845544A1 and EP-0775756A1

describe such alloys intended mainly for the manufacture of

forged mechanical parts.

According to the present invention, the vault, carcass or

tensile armor plies are advantageously made from

of a steel having the following composition (I):

0.03% ≤ C ≤ 0.16%

0.5% ≤ Mn <2%

0.05% <If ≤ 0.5%

0% ≤ Cr ≤ 1.8%

0% <Mo <0.25% 0.001% <Al <0.05%

0.001% ≤ Ti <0.05%

0% <V <0.15%

0.0005% ≤ B <0.005%

0.004% ≤ N <0.012%

0.001% <S <0.09%

- possibly up to 0.005% calcium, up to 0.01%

tellurium, up to 0.04% selenium, up to 0.3% lead,

- the remainder being iron and impurities resulting from

furthermore, the chemical composition (I) of the steel satisfying

relationships :

Mn + 0.9Cr + l, 3Mo + 1.6V> 2.2%

Al + Ti> 3.5N

The composition (I) can be such that:

0.06% ≤ C ≤ 0.12%

0.8% ≤ Mn <1.7%

0.1% <If ≤ 0.35%

0.1% ≤ Cr ≤ 1.5%

0.07% ≤ Mo ≤ 0.15%

0.001% <Al ≤ 0.035%

0.001% ≤ Ti <0.03% 0% ≤ V <0.1%

0.001% ≤ B ≤ 0.004%

0.004% ≤ N ≤ 0.01%

0.001% <S <0.09%

- possibly up to 0.005% calcium, up to 0.01%

tellurium, up to 0.04% selenium, up to 0.3% lead,

- the remainder being iron and impurities resulting from

development.

The composition (I) can also be such that:

Ni ≤ 0.25%

Cu ≤ 0.25%

Composition (I) may contain: P ≤ 0.02%

The steel wires of composition (I) can be obtained

by hot and / or cold rolling followed by cooling quenching

controlled to obtain an essentially bainitic structure,

say made up of more than 50% bainite. The resistance Rm can be

greater than 650 MPa, and preferably greater than 1200 PMa

According to the invention, the shaped wires are also made from

composition (II) which comprises by weight:

0.06% <C ≤ 0.11% 1% ≤ Mn <1.7%

0.15% ≤ If ≤ 0.40%

0.025% <S <0.10%

P <0.025%

0% ≤ Ni <0.25%

0.5% <Cr ≤ 1.20%

0.08% ≤ Mo <0.13%

0% ≤ Cu ≤ 0.25%

0.003% ≤ Al ≤ 0.035%

0% ≤ Ti <0.035%

0% <V ≤ 0.10%

0% <Nb <0.06%

0.0008% <B ≤ 0.0040%

0.0060% <N ≤ 0.011%

- possibly one or more elements taken from: Te

up to 0.010%, Se up to 0.025%, Bi up to 0.13%, Pb up to 0.090%,

Ca up to 0.0040%,

- the remainder being iron and impurities resulting from

elaboration, the chemical composition satisfying in addition the relationships:

Mn + Cr + Mo> 2.1%

0.015% <V + Nb + Ti ≤ 0.13% Al + Ti> 0.020%

Mn / S ≥ 12

The steel wires of composition (II) can be obtained

by hot rolling followed by controlled cooling to obtain

an essentially bainitic structure, i.e. made up of more

50% bainite. The controlled cooling phase can be

performed in the hot rolling, i.e. without reheating the wire

after rolling, or after reheating above the AC3 temperature.

The resistance Rm can be greater than or equal to 1000 MPa.

According to the invention, the shaped wires are also produced at

starting from composition (III) which comprises by weight:

0.05% ≤ C ≤ 0.12%

0.1% ≤ If <0.45%

1.01% ≤ Mn ≤ 1.8%

0.15% ≤ Cr ≤ 1.15%

0.06% <Mo ≤ 0.12%

Cu <0.30%

Ni ≤ 0.30%

0.01% ≤ Ti ≤ 0.04%

0.005% ≤ Al ≤ 0.04% 0.006% ≤ N ≤ 0.013%

0.0005% ≤ B <0.004%

P <0.025%

0.02% ≤ S <0.1%

0% ≤ Pb ≤ 0.1%

0% ≤ Te <0.07%

- possibly from 0.0002 to 0.002% calcium, the rest

being iron and impurities resulting from the production, the composition

additionally satisfying the relationships:

0.2% ≤ Ni + Mo + Cu ≤ 0.7%

- the content of non-combined boron being not less than

0.0005% above 950 ° C.

The composition (III) can be such that: 0.05% ≤ C <0.08% 0.15% ≤ Si ≤ 0.35%

1.01% ≤ Mn <1.35% 0.8% ≤ Cr ≤ 1.15% 0.08% ≤ Mo ≤ 0.11%

The shaped threads obtained from composition (III) can

be obtained by a hot forming operation, in a

temperature range defined by the boron content not combined with the

end of this operation, directly followed by controlled cooling

up to room temperature (which ensures the formation of a 10

essentially bainitic structure). The resistance Rm can be

greater than 1000 MPa.

It is clear that such steels can be used in

operating conditions known as "sweet service", that is to say in the absence

of H2S in the effluents transported by the flexible pipe according to

the invention.

One of the advantages, however, is that in the cases

operating where there is H2S limited to partial pressure

about 0.005 MPa, the steel armor according to the invention can

sufficiently resist stress cracking. Preferably, the

permissible H2S content is limited to a partial pressure of 0.002

MPa, and in particular limited to 0.001 MPa. Note that the standard

NACE MR 0175-2000 which concerns stress cracking in

presence of H2S gives a partial pressure of 0.0003 MPa above

of which the properties of metallic materials must respect

this standard. The steels according to the invention, which would not be used for

all the “sour service” conditions according to the standards of the profession,

can advantageously be used for flexible pipes

carrying effluents containing 1Η2S in known quantity and

low.