CZ9904552A3 - Distribution manifold systems for transportation of liquefied natural gas - Google Patents

Abstract

Distribution piping systems for the transport of compressed liquefied natural gas at a pressure of 1035 kPa to 7590 kPa and temperatures from - 123 ° C to - 62 ° C, where pipes and more components of distribution piping systems are made of Ultra - high strength low alloy steels containing less than 9 % wt. Nickel and having a tensile strength exceeding 830 MPa; and Toughness to DBTT less than - 73 ° C.

Description

Technical field

The present invention relates to compressed liquefied natural gas (PLNG) distribution piping systems, and in particular to piping systems and other components which are constructed of ultra high strength low alloy steels containing less than 9 wt. and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT (toughness to brittleness) of less than about -73 ° C (100 ° F).

BACKGROUND OF THE INVENTION

Various terms are used in the following specification. For this reason, a glossary of terms is immediately preceding the claims.

Many natural gas sources are located in remote areas very far from any gas outlet. Sometimes, pipelines leading to these outlets are available to transport the gas produced. If pipeline transport to these outlets is impracticable, natural gas must often be liquefied for transport to the outlet. Liquefied natural gas (LNG) is usually transported in specially built ship tankers, then stored and gasified at a convenient import station near the shopping center. Equipment used for liquefaction, transport, storage and gasification of natural gas is generally very costly; a conventional conventional liquefied natural gas project costs between $ 5 and $ 10 billion, including design costs. A typical “greenfield” liquefied natural gas project requires a gas supply of about 280 Gm ³ (10 TCF (trillions of cubic feet)), and customers of liquefied natural gas are generally large plants. Often, the discovered natural gas sources in remote areas are less than 280 Gm ³ (10 TCF). Even those natural gas sources meeting the minimum requirements of 280 Gm ³ (10 TCF) with 20 years or more of long-term use require all, ie supplier, carrier and LNG, economical production process, storage and transportation of liquefied natural gas. Where LNG customers have alternative gas sources such as pipeline gas, the LNG contracted distribution chain is often not competitive.

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- 2 The LNG contracting plant produces LNG at temperatures around -162 ° C (-260 ° F) at atmospheric pressure. Natural gas flows to a contracted LNG plant at a pressure of from about 4830 kPa (700 psia) to about 7600 kPa (1100 psia) and temperatures from about 21 ° C (70 ° F) to about 38 ° C (100 ° F). To reduce the natural gas temperature to a very low outlet temperature of about -162 ° C (260 ° F), up to 350000 horsepower of cooling power is required in a two-stage LNG process. In the normal treatment of natural gas by liquefaction, water, carbon dioxide, sulfur-containing compounds such as hydrogen sulphide, other acid gases, npentane and heavier hydrocarbons, including benzene, must be sufficiently removed up to ppm as these compounds would freeze and cause problems associated with clogging . The LNG contracted gas treatment plant shall have a treatment facility for the removal of carbon dioxide and acid gases. Repair and processing equipment utilizes the characteristic chemical and physical solvent recovery processes and this requires significant capital investment. Compared to other plants in the plant, this comparison also has a high operating cost. Dry fill dehydrators such as molecular sieves are required to remove water vapor. Scrubbing columns and fractionating equipment are used to remove hydrocarbons that tend to clog the apparatus. At LNG contracting plants, mercury is also removed as it causes equipment defects made of aluminum. After the treatment of natural gas, the nitrogen present is removed, which may contain a large amount of natural gas, since it does not remain in the liquid phase during transport of conventional LNG and is not desirable to be present in vapors in the LNG containers at the point of delivery.

Bunkers, pipelines and other equipment used in LNG contracted plants are mostly made of at least partly aluminum or steel containing nickel (eg 9% nickel by weight) and must necessarily withstand brittle fracture at extremely low operating temperatures. In addition to their use in contract plants, costly materials with high resistance to brittle fracture at low temperatures, including aluminum and commercial steel containing nickel (eg 9% by weight), are mostly used on LNG ships and delivery centers.

A typical LNG ship uses large spherical containers known as Moss balls to store LNG during transportation. Such a ship normally costs more than 230 million · · · · lod lod lod «« «lod lod lod lod lod lod lod stojí stojí stojí lod • ·· ·· ·· ··· · · ·· dollars. A typical project to produce LNG in the Middle East and shipping LNG to the Far East may require 7 to 8 such ships at a total cost of about $ 1.6 to 2.0 billion.

As can be deduced from the earlier discussion, a more economical system is needed for processing, storing and transporting LNG to outlets from distant sources that could compete more effectively with alternative energy supplies. Furthermore, a system is required to commercialize small remote natural gas sources that would otherwise be uneconomical. In addition, a more economical gasification and distribution system is needed to make LNG more economically attractive for smaller consumers. Accordingly, the primary object of the present invention is to provide a more economical system for processing, storing and transporting LNG from distant sources to outlets and substantially reducing the threshold size of both reserves and market requirements so that the LNG task is economically feasible. One way to accomplish this is to use an LNG process at higher pressures and temperatures than used in conventional LNG plants, ie pressures above atmospheric pressure and temperatures above -162 ° C (-260 ° F). The general concept of processing, storing and transporting LNG at elevated pressures and temperatures has already been discussed in industry publications, but these publications generally mention shipping containers made of nickel-containing steels (eg 9 wt%) or aluminum; they meet the design requirements, but are made of expensive materials. For example, on pages 162-164 of NATURAL GAS BY SEA, published by Witherby & Co. Ltd., first edition 1979, second edition 1993 discusses Roger Ffooks converting a ship for Sigalph's crew to transport both MLG (gas liquefied under medium pressure) at 1380 kPa (200 psig) and -115 ° C (-175 ° F) and CNG (compressed natural gas) at 7935 kPa (1150 psig) and -60 ° C (-75 ° F). Mr Ffooks shows that, although it is a technical option, 'buyers' will not find any of these two concepts because of their high storage costs. In the Ffooks' communication, the CNG solution was addressed, ie for -60 ° C (-75 ° F), and the design objective was low-alloy weldable, hardened and tempered steel with good strength (760 MPa (110 ksi)) and good resistance against fracture under operating conditions. (See "A new process for the transportation of natural gas" by R. J. Broeker, International LNG Conference, Chicago, 1968).

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- 4 This Communication also points out that aluminum alloys were the cheapest alloys for MLG, ie temperatures below -115 ° C (-175 ° F). Mr. Ffooks also listed 9 pounds of 9% nickel steel or aluminum alloy operating at much lower pressure of 60 psig in Phoenix Phoenix Ocean on page 164; and shows that this concept does not offer sufficient technical or financial advantages to be commercialized. See also: (i) US Patent 3,298,805 which discloses the use of 9% nickel steel or high strength aluminum alloy for the manufacture of compressed natural gas containers; and (ii) US Patent 4,182,254 which discloses steel containers with 9% nickel or similar steel for the transport of LNG at temperatures from -100 ° C (-148 ° F) to -140 ° C (-220 ° F) and pressures from 4 to 10 atmospheres (i.e., from 59 psia to 147 psia); (iii) US Patent 3,232,725, which discloses natural gas transport in a dense, single-phase state at a temperature below -62 ° C (-80 ° F), or in some cases 68 ° C (-90 ° F) and a pressure of at least 345 kPa ( 50 psi) above the gas pressure at the boiling point at operating temperature using containers made of materials such as steel containing 1 to 2 percent nickel which have been hardened and tempered to provide a resulting tensile strength of 120000 psi; and (iv) "Maritime Transportation of LNG at Intermediate Temperature", CME March 1979, by CPBennett, who reported a case study of LNG transport at 3.1 MPa (450 psi) and -100 ° C (-140 ° F) using a storage tank made of 9% Ni steel or hardened and tempered 3.5% Ni steel with a 9 1/2 inch wall thickness.

Despite all these concepts discussed in the publications, to our knowledge, LNG is not normally commercially processed, stored, and transported at pressures substantially above atmospheric pressure and temperatures substantially above -162 ° C (-260 ° F). This is probably because the system for processing, storing and distributing LNG at such pressures and temperatures by both sea and land was not economically and commercially available.

Nickel-containing steels used for structural applications at cryogenic temperatures, i.e. steels with a nickel content greater than about 3 wt. have a low DBTT value • 9 · 9 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

- 5 (toughness value defined herein), but also relatively low tensile strength. Typical commercially available steels with 3.5 wt. % Ni, 5.5 wt. % Ni and 9 wt. Ni have DBTTs around -100 ° C (-155 ° F), -155 ° C (-250 ° F) and 175 ° C (-280 ° F), and tensile strength up to 485 MPa (70 ksi), 620 MPa (90 ksi) and 830 MPa (120 ksi). To achieve these combinations of strength and toughness, steels have to undergo generally costly processing, e.g., double annealing. In the case of cryogenic temperature applications, commercial nickel steels are commonly used industrially for their good toughness at low temperatures, but have relatively low tensile strength limits. For load-bearing structures and cryogenic temperatures, construction generally requires excessive steel thickness. The combination of high cost and steel thickness results in the use of nickel steels for load-bearing structures and cryogenic temperature, leading to an overall high cost.

Five provisional US patent applications ("PLNG Patent Applications") entitled "Improved Liquefied Natural Gas Processing, Storage and Transport System" describe compressed liquefied natural gas (PLNG) containers and tankers at wide pressure ranging from approximately 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and at a temperature in a wide range from about -123 ° C (-190 ° F) to about -62 ° C (80 ° F). The last application of the above-mentioned PLNG patent has a priority date of 14 May 1998 and is assigned to Applicants the file number 97006P4 and US Patent Application No. 60/085467. The first of the aforementioned patents of the Applicants has a priority date of June 20, 1997 and is assigned USPTO Application Number 60/050280. The second of the above-mentioned PLNG patent applications has a priority date of 28 July 1997 and is designated USPTO under application number 60/053966. The third of said patent applications has a priority date of December 19, 1997 and is assigned USPTO application number 60/068226. The fourth patent application has a priority date of March 30, 1998 and is assigned USPTO application number 60/079904. However, patent applications do not disclose distribution piping systems for the transportation of PLNG.

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- 6 LNG and other cryogenic liquids, such as liquid oxygen, liquid hydrogen and liquid helium, are normally transported by freight from central processing plants to end-user needs. Liquid nitrogen, for example, is transported through distribution piping systems in university campuses and in factories. The LNG market has grown especially in recent years because natural gas combustion is a clean process. Although natural gas is distributed through a piping system, to our knowledge there are no conventional commercial piping systems for PLNG. Deliveries of produced natural gas in the form of PLNG may be advantageous to the final consumer compared to LNG, as PLNG is more economical to process, provided that means of transporting and delivering PLNG are available. In addition, when compared to CNG, PLNG is a higher density, which translates into a higher product weight or energy per volume.

For the construction of commercial piping systems for liquids such as natural gas, carbon steels typically used do not have adequate fracture toughness at cryogenic temperatures, ie temperatures below -40 ° C (-40 ° F). Materials other than carbon steels with better fracture toughness at cryogenic temperature, such as the aforementioned commercial steels containing nickel (3.5 wt% Ni to 9 wt% Ni) with a tensile strength up to approximately 830 MPa (120 ksi), aluminum (AI-5083 or AI-5085) or stainless steel are traditionally used in distribution piping systems that are stressed by cryogenic temperature operation. Special materials such as titanium alloys and special composites with epoxy-impregnated woven glass fiber may also be used. However, these materials are expensive and such projects can often be economically unattractive. These drawbacks make commercially available materials economically unattractive for the production of PLNG piping systems. The discovery of containers suitable for the shipping of PLNG, as discussed in PLNG patent applications, combined with conventional PLNG processing options, require a significant need for piping systems for economically attractive land transport of PLNG, as well as LNG and other cryogenic fluids.

The availability of more cost-effective sources of natural gas transported and distributed in liquid form gives a significant advantage to exploitation

natural gas as a fuel source. The following will be a description of existing and emerging applications using natural gas as energy, which significantly contributes to the availability of more economical land transport and natural gas supply systems such as pipeline systems.

LNG is normally shipped as a cargo to meet fuel requirements in remote locations where there is no gas distribution infrastructure. Local conditions make LNG a competitive economic alternative to gas distribution for many large energy projects. The Alaskan gas company proposed a $ 200 million project for LNG long-range refueling systems for seventeen municipalities in southern Alaska. The company also expects to transport LNG 300 miles from the Cook Inlet liquefaction plant to Fairbanks starting in November 1997. In eastern Arizona, a preliminary feasibility study showed that the LNG base station could offer attractive low-cost power solutions to a large number of isolated municipalities without normal access to gas line. This presents new trends for LNG bulk transport and its use, with the possibility of substantial growth and, in particular, the improved transport system economy. Developed PLNG technology can create economically beneficial conditions for the use of PLNG as a fuel in these and other similar land-based applications if more economic means of PLNG land transport such as pipeline systems are available.

Furthermore, the use of 'portable pipelines' - LNG transportable evaporator systems - to maintain a continuous uninterrupted gas supply is increasing. This helps gas companies to prevent outages and continue to supply natural gas to customers even during peak periods that are on cold winter days in emergency deliveries with damaged underground piping, gas system maintenance, etc. Depending on the application, the LNG evaporator can be installed or placed in a strategic location of the natural gas distribution system and to represent the operational delivery if the LNG tanker performs the filling. To our knowledge, there are no commercial piping systems to transport PLNG to such evaporators to supply additional gas during LNG replacement peaks.

Finally, there are plans for mainstream and main LNG suppliers in Asia to offer the largest amount of LNG as fuel for vehicles (up to 20% of imports). Depending on local •

- 8 conditions, the LNG distribution system for transporting LNG to service stations can be the most attractive economic benefit. In particular, in the absence of a gas distribution infrastructure, such an economical PLNG piping system can create a more attractive and economical alternative.

To be able to compete more effectively with alternative energy supplies, there must be an economical PLNG pipeline distribution system. SUMMARY OF THE INVENTION

It is therefore a particular object of the present invention to provide economical LNG distribution piping systems for substantially higher pressures and temperatures than conventional LNG systems. It is a further object of the present invention to provide manifold systems and other components that are made of materials having adequate strength and fracture toughness to contain said pressurized liquefied natural gas.

Summary of the invention

In accordance with the above object of the present invention, piping systems for transporting pressurized liquefied natural gas (PLNG) at pressures in the range from about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and temperatures in the field from about -123 ° C (-190 ° F) to about -62 ° C (80 ° F). The manifold systems of the present invention have pipes and other components made of ultra-high strength low alloy steel containing less than 9 wt. and having adequate strength and fracture toughness to contain compressed liquefied natural gas. The steel has an ultra high strength, e.g., a tensile strength (as defined herein) of greater than 830 MPa (120 ksi) and a DBTT (as defined herein) of less than about -73 ° C (-100 ° F).

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Overview of pictures

For a better understanding of the present invention, reference will be made to the following detailed description and the accompanying drawings in which:

Giant. 1 schematically illustrates a piping system according to the present invention.

Giant. 2A depicts a plot of critical crack depth at a given crack length as a function of CTOD fracture toughness and residual stress; and FIG. 2B shows the geometry (length and depth) of a crack.

The invention will be described in connection with the preferred subject matter of the invention, but it is to be understood that it is not limited thereto. On the other hand, the invention is intended to cover all alternatives, modifications and equivalents, which the invention may, in spirit and scope, include as defined in the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to distribution piping systems for transportation of PLNG. Piping systems are designed to transport compressed liquefied natural gas (PLNG) at a pressure of about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and a temperature of about -123 ° C (190 ° F) to about -62 ° C (80 ° F) and characterized in that the manifold system and other components are made of ultra high strength low alloy steels with a nickel content of less than 9 wt. and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT less than about -73 ° C (100 ° F). The manifold system is further designed to transport compressed liquefied natural gas at pressures from about 1725 kPa (250 psia) to about 4830 kPa (700 psia) and temperatures from about -112 ° C (-170 ° F) to about -79 ° C. (110 ° F) and characterized in that the manifold systems have piping and other components which (i) are made of ultra high strength low alloy steel containing less than 9 wt. and (ii) have adequate strength and fracture toughness to contain compressed liquefied natural gas.

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PLNG transport piping

The key to forming the manifold systems of the present invention are tubes suitable to contain and transport PLNG at pressures from about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and temperatures from about -123 ° C (-190 ° F) to about -62 ° C (-80T). The PLNG is preferably manufactured and transported at pressures from about 1725 kPa (250 psia) to about 7590 kPa (1100 psia) and temperatures from about -112 ° C (-170 ° F) to about -62 ° C (-80 ° F). . More preferably, the PLNG is manufactured and transported at pressures from about 2415 kPa (350 psia) to about 4830 kPa (700 psia) and temperatures from about -101 ° C (-150 ° F) to about 79 ° C (-110 ° C). F). Most preferably, the lowest pressure and temperature value of PLNG is about 2760 kPa (400 psia) and about -96 ° C (-140 ° F). The pipe is equipped to contain and transport PLNG and is characterized by being made of ultra high strength low alloy steel containing less than 9 wt. and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT less than -73 ° C (-100 ° F). Other system components such as fittings are further made to be characterized in that said fittings are made of ultra high strength low alloy steel containing less than 9 wt. and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT less than -73 ° C (-100 ° F). Storage tanks suitable for use in the manifold systems of the present invention are described in more detail in PLNG patent applications.

Steel for pipelines and other components

Any ultra high strength low alloy steel containing less than 9% by weight may be used to make the piping and other components of the present invention. nickel having adequate toughness to contain cryogenic liquids such as PLNG at operating conditions temperatures according to known fracture mechanics principles as described herein. An example of a non-limiting steel is weldable, ultra-high strength low alloy steel containing less than 9 wt. Nickel having a tensile strength greater than 830 MPa (120 ksi) and adequate toughness to prevent fracture, ie, defects that may occur: · 4 · · · · · · · · · · · 44 ♦ · · 4 4 ··

- 11 under cryogenic temperature conditions. Another example of steel for use in the present invention, without limiting this invention, is a weldable ultra-high strength low alloy steel containing less than 3% nickel and having a tensile strength of at least 1000 MPa (145 ksi) and corresponding toughness to prevent fracture , ie, defects that may occur when operating at cryogenic temperatures. These steels exemplified have a DBTT of less than -73 ° C (-100 ° F).

Recent advances in steel technology have made it possible to manufacture new ultra-high strength low alloy steels with excellent toughness at cryogenic temperatures. For example, three US patents granted to Koo, et al., 5,531,842; 5,545,269; and 5,545,270 disclose novel steels and methods of processing these steels into steel sheets having a tensile strength of about 830 MPa (120 ksi), 965 MPa (140 ksi) and higher. The steels described herein and their processing methods have been improved and modified to allow the combination of a suitable composition and processing method to produce ultra high strength low alloy steels with excellent cryogenic temperature resistance in both the base steel and the heat stressed zone (HAZ) in welding. These ultra high strength low alloy steels increased the toughness value above the standard of commercially available ultra high strength low alloy steels. Enhanced steels are described in a pending U.S. provisional patent application entitled "Ultra High Strength Steels with Excellent Cryogenic Toughness", with priority date 19 December 1997 and US Patent Office ("USPTO") registered under provisional application number 60/068194; in a pending U.S. Provisional Patent Application entitled "Ultra High Strength Ausaged Steels with Excellent Cryogenic Temperature Toughness", with a priority date of December 19, 1997 and the US Patent Office ("USPTO") registered under Provisional Application Number 60/068252; in a pending U.S. Provisional Patent Application entitled "Ultra High Strength Two-Phase Steels with Excellent Cryogenic Toughness", with a priority date of December 19, 1997 and the US Patent Office ("USPTO") registered under Provisional Application Number 60/068816 (collectively designated " Patent applications of steels').

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The new steels described in the patent applications and further described by way of example are particularly suitable for making containers for the storage and transportation of PLNGs according to the invention, the steels having the following characteristics, preferably for steel plates with a thickness of 2.5 cm ( 1 inch) and thicker: (i) DBTT less than -73 ° C (100 ° F), preferably less than about -107 ° C (-160 ° F) for base steel and weld zone (HAZ); (ii) a tensile strength greater than 830 MPa (120 ksi), preferably greater than 860 MPa (125 ksi), and preferably greater than 900 MPa (130 ksi); (iii) excellent weldability; (iv) sufficiently homogeneous microstructure and cross-sectional properties; and (v) improved toughness over a commercially available standard value and ultra-high strength low alloy steels. Even better, these steels have a tensile strength greater than about 930 MPa (135 ksi) or greater than 965 MPa (140 ksi) or greater than 1000 MPa (145 ksi).

The first example of steel

As mentioned above, the co-pending US Provisional Patent Application with priority date 19 December 1997 entitled "Ultra High Strength Steels with Excellent Cryogenic Temperature Toughness" and the US Patent Office ("USPTO") registered under Provisional Application Number 60/068194 discloses a description of steels suitable for use in the present invention. The method is intended for the preparation of ultra-high strength microstructured steel sheets containing predominantly tempered fine-grained needle martensite, tempered fine-grained lower bainite, or a mixture thereof, comprising the steps of: (a) heating the steel sheet to a sufficiently high temperature k (i) ) sufficient homogenization of the steel sheet; (ii) substantially dissolve all niobium and vanadium carbides and carbonitrides in the steel sheet; and (iii) form fine austenitic grains in the steel sheet; (b) hot rolling the steel sheet onto the steel sheet through one or more passes through the rolling mill in the first temperature region in which austenite recrystallizes; (c) further hot-rolling the steel sheet through one or more passes through the rolling mill in a second temperature range below the temperature T _nr and above the transformation temperature ^ 4; (d)

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- 13 quenching of the steel sheet at a cooling rate of 10 ° C per second to 40 ° C per second (18 ° F.s- ¹ to 72 ° F.s- ¹ ) up to a quench stop temperature below the transformation temperature M _s plus 200 ° C (360 ° F); (e) quenching the quenching; and (f) tempering the steel sheet at a tempering temperature of about 400 ° C (752 ° F) up to a transformation temperature Aci, preferably up to but not including this transformation temperature Aci, for a time sufficient to precipitate the curing particles, ie one or more modifications of copper ε, M02C or niobium and vanadium carbides and carbonitrides. The time required for precipitation of the curing particles depends primarily on the thickness of the steel sheet, the steel sheet composition and the tempering temperature, and can be determined by one skilled in the art. (See glossary of terms, predominantly for particle curing terms, temperature Τ _ηΓ , transformation temperature Ar ₃ , M _s and Aci and M02C.)

To ensure toughness at ambient and cryogenic temperatures, the steel of this first example preferably has a microstructure consisting mainly of tempered fine-grained lower bainite, fine-grained acicular martensite, or a mixture thereof. Preferably, the formation of brittle components such as upper bainite, twin martensite and MA is minimized. As used herein, the term "predominantly" refers to at least 50% by volume. Better if the structure comprises at least 60% to 80% by volume of a finely divided fine bainite, finely granular acicular martensite or mixtures thereof. Most preferably, the microstructure comprises at least 90% by volume of the finely divided lower bainite, the finely divided acicular martensite, or a mixture thereof. Best of all, the microstructure contains 100% by volume of finely divided acicular martensite.

The steel sheets processed according to this first example are made to order and consist, for example, of iron and other alloying elements within the weight range shown in Table I below:

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- 14 Table I

Alloying element carbon (C) manganese (Mn) nickel (Ni) copper (Cu) molybdenum (Mo) niobium (Nb) titanium (Ti) aluminum (Al) nitrogen (N)

Range (% w / w)

0.04-0.12, preferably 0.04 - 0.07 0.5-2.5, preferably 1.0-1.8 1.0-3.0, preferably 1.5-2.5 0, 1 -1.5, better 0.5 -1.0 0.1 -0.8, better 0.2-0.5 0.02-0.1, better 0.03-0.05 0.008 - 0, 03, better 0.01 - 0.02 0.001 - 0.05, better 0.005 - 0.03 0.002 - 0.005, better 0.002 - 0.003

Vanadium (V) is sometimes added to the steel preferably up to a concentration of about 0.10% by weight. % and preferably from about 0.02 wt.% to about 0.05 wt.

Chromium (Cr) is sometimes added to the steel preferably up to a concentration of about 1.0 wt. % and more preferably from about 0.2 wt.% to about 0.6 wt.

Silicon (Si) is sometimes added to the steel preferably up to a concentration of about 0.5% by weight. and preferably from about 0.01 wt.% to about 0.05 wt.%, but most preferably from about 0.05 wt.%. % to 0.1 wt.

Boron (B) is sometimes added to the steel preferably up to a concentration of about 0.0020% by weight. and preferably from about 0.0006% to about 0.0010% by weight.

The steel preferably contains at least 1 wt. nickel. The nickel content of the steel can be increased above 3% by weight if this improves the parameters after welding. It is expected that the addition of each 1 wt. Nickel reduces DBTT of steel by 10 ° C (18 ° F). It is preferred that the nickel content is less than 9 wt%, more preferably less than 6 wt%. The nickel content is minimized mainly to reduce the cost of steel. If the nickel content increases above about 3 wt%, the manganese content can be reduced below about 0.5 wt%. % to 0.0 wt. Broadly speaking, it is preferred that the manganese content be up to about 2.5% by weight.

As far as possible, the remaining elements are minimized in the steel. The phosphorus (P) content is preferably less than 0.01 wt%. The sulfur content (S) is preferably less than 0.004%

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The oxygen content (O) is preferably less than 0.002% by weight.

The steel treatment process of this first example will be described in somewhat more detail by molding from steel sheets having the composition described herein: the sheets are heated to a temperature of about 955 ° C to about 1065 ° C (1750T - 1950 ° F); the sheets are hot rolled onto the sheet by one or more passes so that in the first temperature region, when austenite recrystallizes, a 30 to 70 percent reduction in thickness is achieved, ie approximately above T _nr, and further the sheets are hot rolled in one or more passes to about 40 to 80% at a second region temperature below about T _nr and about above Ar ₃ transformation temperature. The hot rolled steel plate is then quenched at a rate of about 10 DEG C. per second to about 40 DEG C. per second (18 DEG F./sec ^1-72 ° Fs ¹⁾ to a suitable QST QAK is defined in the Glossary) below about the transformation temperature M _s plus 200 DEG C. (360 ° F) when quenching ends. In one case of this first example, the steel sheet is then allowed to cool to ambient temperature. This procedure is used to form a microstructure consisting mainly of fine-grained acicular martensite, fine-grained lower bainite, or a mixture thereof, but it is better if it contains 100% fine-grained acicular martensite.

The hardened martensite in the steels of the first example has a high strength, but its toughness can be improved by tempering at a suitable temperature of approximately 400 ° C (752 ° F) up to the transformation temperature Aci. Tempering of the steel in this temperature range also leads to a reduction in the hardening stress, which in turn leads to an improvement in toughness. While tempering can improve the toughness of the steel, this normally results in a considerable loss of strength. In the present invention, the usual loss of strength resulting from tempering is compensated by induction of dispersion precipitation hardening. Dispersion hardening caused by fine copper precipitate and mixed carbides and / or carbonitrides is used to optimize strength and toughness during tempering of the martensitic structure. Unique composition of steels according to this

The first example allows tempering over a wide range of from about 400 ° C to about 650 ° C (750 ° F - 1200 ° F) without any significant loss of hardness from quenching. The steel sheets are preferably tempered at a tempering temperature of from above about 400 ° C (752 ° F) to below the transformation temperature Aci for a sufficiently long time to cause precipitation of the curing particles (as defined herein). This procedure facilitates the transformation of the microstructure of the steel sheets into a predominantly tempered fine-grained needle martensite, a tempered fine-grained lower bainite, or a mixture thereof. The time sufficient to cause precipitation of the curing particles again depends mainly on the thickness of the steel sheet, the steel composition and the tempering temperature which can be determined by the skilled person.

The second example of steel

As noted above, the U.S. Provisional Patent Application pending Priority Date 19 December 1997 entitled "Ultra High Strength Steels with Excellent Cryogenic Temperature Toughness" and USPTO registered under Provisional Application Number 60/068252 provide a description of other steels suitable for use in accordance with the present invention. of the present invention. The process provides for the preparation of ultra-high strength microlaminar microstructured steel sheets containing from about 2% to about 10% by volume film austenite layers and from about 90% to about 98% by volume predominantly fine-grained needle martensite and fine-grained lower bainite, and said method comprising the steps of: (a) heating the steel sheet to a sufficiently high temperature to (i) substantially homogenize the steel sheet, (ii) dissolving all of the niobium and vanadium carbide and carbide contained in the steel sheet, and (iii) forming embryonic fine austenitic grains in steel plate; (b) hot rolling the steel sheet onto the steel sheet through one or more passes through the rolling mill in the first temperature region in which austenite recrystallizes; (c) further hot rolling the steel sheet through one or more passes through the rolling mill in a second temperature region below T _nr and above the transformation temperature A _r3 ; (d) quenching the sheet metal at a rate of from about 10 ° C per second to about 40 ° C in a temperature range of about 10 ° C per second to about 40 ° C per second; • re <»re re re re re re re re re re re re re re re

- 17 seconds (18 ° F - 72 ° F) up to a quench stop temperature (QST) that is below the transformation temperature M _s plus 100 ° C (180 ° F) and approximately above the transformation temperature M _s ; and (e) quenching the quenching. In one instance, the method of this second steel example further comprises the step of allowing the steel sheet to cool in air from the QST temperature to the ambient temperature. Alternatively, the method of this second steel example further comprises the step of leaving the steel sheet at an isothermal temperature QST for 5 minutes before it begins to air cool to ambient temperature. In yet another case, the method of this second steel example further comprises the step of slowly cooling the steel sheet with a QST temperature of less than 1.0 ° C per second (1.8 ° F.s ^-1 ) for up to 5 minutes before allowing it to cool. in air to ambient temperature. In yet another case, the method of the invention further comprises the step of slowly cooling the steel sheet with a QST temperature of less than 1.0 ° C per second (1.8 ° Fs ¹ ) for up to 5 minutes before allowing it to cool in air. to ambient temperature. This treatment facilitates the transformation of the microstructure of the steel sheet to about 2 vol% to 10 vol% of the film austenite layer and about 90 vol% to 98 vol% predominantly fine-grained needle martensite and fine-grained lower bainite. (See glossary of terms, mainly related to the terms temperature T _nr , and transformation temperature Ar ₃ and M _s ).

In order to ensure toughness at ambient and cryogenic temperatures, the needles in the microlaminar microstructure must preferably consist of lower bainite or martensite. It is best to minimize the formation of brittle components such as upper bainite, twin martensite and MA. As used in this second example and in the claims, the term "predominantly" means at least 50% by volume. The remaining microstructure may comprise another fine-grained lower bainite, another fine-grained needle martensite or ferrite. Preferably, the structure comprises at least about 60 vol% to about 80 vol% lower bainite or acicular martensite. More preferably, the microstructure contains at least about 90% by volume of lower bainite or acicular martensite.

V * * * * * · · · · · · 9 · * 9 9 · 9 9 9 ** ** ** ** ** ** ** ** ** ** ** · · · * <<<<* <<

The steel sheets processed according to this second example are made to order and are characterized in that, in one example, they contain iron and other alloying elements preferably in the weight range given in Table II below:

Table II

Alloying elements carbon (C) manganese (Mn) nickel (Ni) copper (Cu) molybdenum (Mo) niobium (Nb) titanium (Ti) aluminum (Al) nitrogen (N)

Range (% w / w)

0.04-0.12, preferably 0.04 - 0.07 0.5-2.5, preferably 1.0-1.8 1.0-3.0, preferably 1.5-2.5 0, 1 -1.0, better 0.2-0.5 0.1 -0.8, better 0.2-0.4 0.02-0.1, better 0.02 - 0.05 0.008 - 0, 03, better 0.01 - 0.02 0.001 - 0.05, better 0.005 - 0.03 0.002 - 0.005, better 0.002 - 0.003

Chromium (Cr) is sometimes added to the steel preferably up to a concentration of about 1.0 wt. % and more preferably from about 0.2 wt.% to about 0.6 wt.

Silicon (Si) is sometimes added to the steel preferably up to a concentration of about 0.5% by weight. % and preferably from about 0.01 wt. % to about 0.5 wt.%, but preferably from about 0.05 wt. % to 0.1 wt.

Boron (B) is sometimes added to the steel preferably up to a concentration of about 0.0020% by weight. and preferably from about 0.0006% to about 0.0010% by weight.

The steel preferably contains at least 1 wt. nickel. The nickel content of the steel can be increased above 3% by weight if this improves the parameters after welding. It is expected that the addition of each 1 wt. Nickel reduces DBTT of steel by 10 ° C (18 ° F). It is preferred that the nickel content is less than 9 wt%, more preferably less than 6 wt%. The nickel content is minimized mainly to reduce the cost of the steel. If the nickel content rises above about 3% by weight, the manganese content can be reduced below about 3% by weight. 4 4 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0.5 wt. % to 0.0 wt. More broadly, it is therefore preferred that the manganese content is up to about 2.5% by weight.

As far as possible, the remaining elements are minimized in the steel. The phosphorus (P) content is preferably less than 0.01 wt%. The sulfur content (S) is preferably less than 0.004% by weight.

The oxygen content (O) is preferably less than 0.002% by weight.

The steel treatment process of this second example will be described in more detail by forming steel sheets having the composition described herein: the sheets are heated at a temperature of about 955 ° C to about 1065 ° C (1750 ° F - 1950 ° F); the sheets are hot rolled on the sheet by one or more passes so that in the first temperature range, when austenite recrystallizes, a 30-70 percent reduction in thickness is achieved, ie approximately above T _nr, and further the sheets are rolled in one or more passes heat to about 40 to 80% at a second region temperature below about T _nr and above a transformation temperature of γγ3. The hot rolled steel plate is then quenched at a rate of about 10 DEG C. per second to about 40 DEG C. per second (18 DEG F./sec ^1-72 ° F./sec ¹⁾ to a temperature suitable QST below about the transformation temperature M _s plus 100 DEG C. (180 DEG F. ), and above the transformation temperature M _s when quenching is complete. In one case of this second example, the steel sheet is allowed to cool from QST to ambient temperature after quenching. Alternatively, in the second example of the steel, after quenching, the steel sheet is left for some time at an isothermal temperature at QST, preferably within about 5 minutes, and then allowed to cool in air to ambient temperature. In yet another instance, after quenching, the steel sheet is allowed to cool more slowly than normal air cooling occurs, i.e. at a rate of 1 ° C per second (1.8 ° Fs ^-1 ), preferably for up to about 5 minutes. In yet another case, the steel sheet is allowed to cool from QST at a slower rate than normal air cooling, i.e. a temperature drop of 1 ° C per second (1.8 ° F.s ^-1 ), preferably for up to about 5 minutes. Last but not least, this second example of steel is • ·

- a transformation temperature M _{s of} about 350 ° C (662 ° F) and therefore a transformation temperature M _{s of} plus 100 ° C (180 ° F) is about 450 ° C (842 ° F).

The steel sheet may be held substantially isothermally on the QST by any suitable method known to those skilled in the art, such as placing a thermal mat over the steel sheet. The steel sheet may be cooled slowly after quenching by any suitable method known to those skilled in the art, such as placing an insulating mat over the steel sheet.

The third example of steel

As discussed above, the prior U.S. patent application pending on priority date 19 December 1997 entitled "Ultra High Strength Two-Phase Steels with Excellent Cryogenic Temperature Toughness" and registered USPTO under application number 60/068816 provides a description of steels suitable for use in the present application invention. This method provides the preparation of ultra-high strength two-phase steel sheets with a microstructure containing from about 10 vol% to 40 vol% of the first phase, which is essentially 100 vol% ferrite (i.e., sufficiently pure or "basic") and from about 60% by volume to 90% by volume of the second phase of predominantly fine needle martensite, fine-grained lower bainite, or a mixture thereof, and that the process comprises the steps of: (a) heating the steel sheet to a sufficiently high temperature to (i) sufficiently homogenize the steel sheet (ii) dissolving all niobium and vanadium carbides and carbonitrides in the steel sheet; and (iii) forming fine austenitic seed grains in the steel sheet; (b) hot rolling the steel sheet onto the steel sheet through one or more passes through the rolling mill in the first temperature region in which austenite recrystallizes; (c) further hot rolling the steel sheet through one or more passes through the rolling mill in a second temperature region below T _nr and above the transformation temperature A _r3 ; (d) further hot rolling the steel sheet through one or more passes through the rolling mill in a third temperature region below the transformation temperature Ar ₃ and above the transformation temperature Ar 3; (i.e., the intercritical temperature region); (e) quenching said steel sheet at a rate of from about 10 ° C per second to about 40 ° C per second (18 ° F - 72 ° F) up to a quench stop temperature (QST) that is preferably below the transformation temperature M _s plus 200 ° C (360 ° F); and (e) stopping said quenching. In another case of this third steel example, QST will be best

21 below about the transformation temperature M _s plus 100 ° C (180 ° F) and preferably below about 350 ° C (662 ° F). In one case of this third steel example, the steel sheet may be allowed to cool to ambient temperature after step (f). This treatment will facilitate the transformation of the steel sheet microstructure to about 10 vol% to 40 vol% of the first ferritic phase and from about 60 vol% to 90 vol% of the second phase with predominant fine-grained needle martensite, fine-grained lower bainite or mixtures thereof. (See glossary of definitions for temperature T _nr , and transformation temperature Ar ₃ and Αη.)

To provide toughness at ambient and cryogenic temperatures, the second stage microstructure of the steel of this third example consists predominantly of fine-grained lower bainite, fine-grained acicular martensite or a mixture thereof. Preferably, formation of brittle components such as upper bainite, twinned martensite and MA in the second phase is substantially minimized. As used herein in the third example and claims, at least 50% by volume is meant. The remaining microstructure of the second phase may comprise further fine-grained lower bainite, another fine-grained needle martensite or ferrite. More preferably, the second phase microstructure comprises at least about 60 vol% to about 80 vol% lower bainite, acicular martensite, or a mixture thereof. More preferably, the second phase microstructure comprises at least about 90% by volume of lower bainite, acicular martensite, or a mixture thereof.

The steel sheets processed according to this third example are made to order and are characterized in that, in one possible case, they contain iron and other alloying elements preferably in the weight range given in Table III below:

• ·

- 22 Table III

Alloying element carbon (C) manganese (Mn) nickel (Ni) niobium (Nb) titanium (Ti) aluminum (Al) nitrogen (N)

Range (% w / w)

0.04-0.12, preferably 0.04-0.07 0.5-2.5, preferably 1.0-1.8 1.0-3.0, preferably 1.5-2.5 0, 02-0.1, better 0.02 - 0.05 0.008 - 0.03, better 0.01 - 0.02 0.001 - 0.05, better 0.005 - 0.03 0.002 - 0.005, better 0.002 - 0.003

Chromium (Cr) is sometimes added to the steel preferably up to a concentration of about 1.0 wt. and preferably from about 0.2 wt. % to about 0.6 wt.

Molybdenum (Mo) is sometimes added to the steel preferably up to a concentration of about 0.8% by weight. % and more preferably from about 0.1 wt. % to about 0.3 wt.

Silicon (Si) is sometimes added to the steel preferably up to a concentration of about 0.5% by weight. % and preferably from about 0.01 wt. % to about 0.5 wt.%, but preferably from about 0.05 wt. % to 0.1 wt.

Copper (Cu) is sometimes added to the steel preferably in a concentration range of about 0.1 wt. about 1.0 wt.%, preferably about 0.2 wt. % to about 0.4 wt.%, but preferably from about 0.05 wt. % to 0.1 wt.

Boron (B) is sometimes added to the steel preferably up to a concentration of about 0.0020% by weight. and preferably from about 0.0006% to about 0.0010% by weight.

The steel preferably contains at least 1 wt. nickel. The nickel content of the steel can be increased above 3% by weight if this improves the parameters after welding. It is expected that the addition of each 1 wt. Nickel reduces DBTT of steel by 10 ° C (18 ° F). It is preferred that the nickel content is less than 9 wt%, more preferably less than 6 wt%. The nickel content is best minimized to reduce the cost of the steel. If the nickel content rises above about 3% by weight, the manganese content can be reduced below about 3% by weight

About 23 wt. % to 0.0 wt. Broadly speaking, it is preferred that the manganese content be up to about 2.5% by weight.

The remaining elements in the steel are minimized as far as possible. The phosphorus (P) content is preferably less than 0.01 wt%. The sulfur content (S) is preferably less than 0.004% by weight.

The oxygen content (O) is preferably less than 0.002% by weight.

The steel treatment process of this third example will be described in more detail by forming steel sheets having the composition described herein: the sheets are heated to a temperature of about 955 ° C to about 1065 ° C (1750 ° F - 1950 ° F); the sheets are hot rolled onto the sheet by one or more passes so that in the first temperature region, when austenite recrystallizes, a 30-70% reduction in thickness is achieved, ie approximately above T _nr, and hot sheets are rolled in one or more passes to about 40 to 80% at a second region temperature below about T _nr and above a transformation temperature of Ar3 and rolling is terminated with one or two passes through the mill to about 15% to 50% in the intercritical temperature region about below a transformation temperature of Ar ₃ and above temperature Αη. The hot rolled steel plate is then quenched at a rate of about 10 DEG C. per second to about 40 DEG C. per second (18 DEG F./sec ^1-72 ° F./sec ¹⁾ to a temperature suitable QST is preferably below about the transformation temperature M _s plus 200 DEG C. (360 DEG F), in which quenching ends. In another instance of the present invention, QST is preferably below approximately the transformation temperature M _s plus 100 ° C (180 ° F), and more preferably below approximately 350 ° C (662 ° F). In one case of this third steel example, the steel sheet is allowed to cool to ambient temperature in air after the quenching is completed.

In the above three steel examples, it is preferred that the nickel content is less than about 3.0 wt%, preferably less than about 2.5 wt%, even more preferably less than about 2.0 wt%, but most preferably less than about 1.8 wt% to minimize the cost of steel because nickel is an expensive alloy.

• ·

• »w

Other suitable steels in connection with the present invention are described in other publications describing ultra high strength, low alloy steels containing less than about 1% nickel and having a tensile strength greater than 830 MPa (120 ksi) and excellent low temperature toughness. Such steels are described, for example, in European patent application published February 5, 1997 with International Application Number PCTZJP96 / 00157 and International Patent Publication No. WO 96/23909 (August 8, 1996 Gazette 1996/36) (such steels preferably have a copper content of 0.1 60% and up to 1.2% by weight) and in U.S. patent application still pending at priority date July 28, 1997 and entitled &quot; Ultra High Strength Weldable Steels with Excellent Ultra Low Temperature Toughness &quot; 053915.

For all steels referred to above, as those skilled in the art know, the term &quot; thickness thinning &quot; as used herein means the percent thinning of the steel sheet or sheet in comparison with the condition prior to the thinning referred to. By way of illustration only, without limiting the invention, a steel sheet of approximately 25.4 cm (10 inches) thick may be thinned by approximately 50% (50 percent thinning) in the first temperature region to a thickness of approximately 12.7 cm (5 inches). then thinning approximately 80% (80 percent thinning) in the second temperature region to a thickness of approximately 2.5 cm (1 inch). By way of illustration only, without limiting the invention, a steel sheet of approximately 25.4 cm (10 inches) thick may decrease by approximately 30% (30 percent thinning) in the first temperature region to a thickness of approximately 17.8 cm (7 inches). then thinning approximately 80% (80 percent thinning) in the second temperature range to approximately 3.6 cm (1.4 inches) thick, and then thinning approximately 30% (30 percent thinning) in the third temperature range to 2 .5 cm (1 inch). As used herein, the term "sheet" means a piece of steel of any size.

As will be understood by those skilled in the art, for any steel referred to above, the steel sheet is heated by suitable means to raise the temperature of a substantial portion of the entire sheet, preferably the entire sheet to the desired temperature, e.g. The appropriate heating temperature to be used for any of the above steels of the appropriate composition may be determined

• ·

- 25 by an experienced expert either experimentally or by calculation on a suitable model. In addition, the furnace temperature and the heating time required to raise the temperature of a substantial portion of the entire sheet, preferably the entire sheet to the desired temperature, can be determined by one skilled in the art according to data from standard industry publications.

As will be understood by those skilled in the art, the temperature T _nr defining the boundary between the recrystallization region and the non-recrystallization region for any of the above steels on the chemical composition of the steel, and in particular the reheat temperature before rolling, carbon content, niobium content and rolling attenuation. Those skilled in the art can determine these temperatures for each steel composition either experimentally or by calculation on a model. Similarly, the transformation temperatures Aci, An, Ar 3 and M _{s referred} to herein can be determined by those skilled in the art either experimentally or by calculation on a model.

As will be understood by those skilled in the art, the temperatures to which reference is subsequently made in describing the process of the present invention, except for the reheating temperature to which the entire sheet is heated, are the temperatures measured on the steel surface. For example, the surface temperature of the steel may be measured by an optical pyrometer or other suitable steel temperature measuring device. The cooling rate referred to herein refers to the center or location closest to the center of the sheet thickness; the quench stop temperature (QST) is the highest or substantially the highest temperature reached on the sheet surface after quenching, because heat is transferred from the center of the sheet thickness. During the experimental determination of the heat of the steel composition according to the examples herein, the thermocouple is placed, for example, in the center or sufficiently in the center of the thickness of the steel sheet so that the center temperature can be measured and the surface temperature measured with an optical pyrometer. The correlation between the center temperature and the surface temperature is recorded, and this is used in the subsequent treatment of a material of the same composition or substantially the same composition, so that the center temperature is determined by the surface temperature. The desired temperature and quench liquid flow rate to accomplish the desired cooling acceleration can be determined by one skilled in the art according to standard reference industry publications.

• ·

The skilled artisan has the required knowledge and experience to utilize the information provided herein to produce ultra high strength low alloy steel sheets having suitable tensile strength and toughness for use in making pipes and other components of the present invention. There are other suitable steels or will be developed later. All such steels fit within the scope of the present proposal. The person skilled in the art has the required knowledge and experience to use the information herein to produce ultra-high strength low alloy steel sheets having a modified thickness compared to the examples of thicknesses herein so that the steel sheets so produced still have suitable high strength and cryogenic temperature toughness. for use in the systems of the present invention. One of ordinary skill in the art can utilize the information herein to produce 2.54 cm (1 inch) thick steel sheets and suitable high strength and suitable cryogenic temperature toughness for use in making pipes and other components of the present invention. There are other suitable steels or will be developed later. All such steels fit within the scope of the present proposal.

If biphasic steels are used to make the pipes of the present invention, they are preferably processed in such a way that the time they are allowed to do for this purpose in the region of intercritical temperatures to form the biphasic structure before accelerated cooling or quenching. A preferred process is the formation of a two-phase structure during cooling of the steel between the transformation temperature Ar ₃ and the transformation temperature An. Another advantage of the steels used to make the pipes of the present invention is that they have a tensile strength of greater than 830 MPa (120 ksi) and a BDTT of less than -73 ° (-100 ° C) after accelerated cooling or quenching, ie without any further processing requiring reheating of the steel such as tempering. More preferably, the tensile strength of the finished steels after quenching or cooling is greater than about 860 MPa (125 ksi) and even more preferably greater than about 900 MPa (130 psi). In some applications, steels having a higher tensile strength after quenching or cooling are preferred

- 27 than about 930 MPa (135 ksi) or greater than about 965 MPa (140 ksi) or greater than about 1000 MPa (145 ksi).

Joining methods for making pipes and other components

Suitable methods for joining steel sheets are required to produce pipes and other components of the present invention. It seems that all bonding methods ensuring adequate strength and toughness according to the present invention are suitable. For the fabrication of pipelines and other components of the present invention, welding is preferred to provide adequate strength and fracture toughness to allow the products to contain or be transported. Such welding methods first require a suitable welding wire, a suitable usable gas, a suitable welding process and a suitable welding process. For example, both shielded metal arc welding (GMAW) and tungsten inert gas (TIG) welding, both known in the steel industry, can be used to join the steel sheets, provided that a suitable welding wire is used.

A first example of welding is a shielded metal arc welding (GMAW), which is used to make welds of an iron-containing material and about 0.07 wt. % of carbon, about 2.05 wt. % manganese, about 0.32 wt. % silicon, about 2.20 wt. % nickel, about 0.45 wt. about 0.56 wt. molybdenum, less than about 110 ppm phosphorus and less than 50 ppm sulfur. Welds are performed on steels such as the above steels using argon as a shielding gas containing less than 1 wt. of oxygen. The welding heat input ranges from about 0.3 kJ.mm ^-1 to about 1.5 kJ.mm ^'1 (7.6 kJ.palec' ^1-38 kJ.palec ^1). Welding in this manner produces welds (see glossary) with a tensile strength of greater than about 900 kPa (130 ksi), preferably greater than about 930 MPa (135 ksi), even better than about 965 MPa (140 ksi), and most preferably greater than approximately 1000 MPa (145 ksi). Welding in this way creates welds with BDTTs below about -73 ° C (-100 ° F), preferably below about -96 ° C (-140T), even more preferably below about 106 ° C (-160 ° F), and most preferably below about - 115 ° C (-175 ° F).

In another welding process, the GMAW process is used to create a metal weld.

% Of an iron-containing material and about 0.10 wt. % carbon (preferably less than about 0.10 wt% carbon, more preferably from about 0.07 to about 0.08 wt% carbon), about 1.60 wt% carbon; % manganese, about 0.25 wt. % silicon, about 1.87 wt. % nickel, about 0.87 wt. about 0.51 wt. molybdenum, less than about 75 ppm phosphorus and less than 100 ppm sulfur. The welding heat input ranges from about 0.3 kj.mm ^-1 to about 1.5 kJ.mm ^'1 (7.6 kJ.palec' ^1-38 kJ.palec ^'1) and is preheated to about 100 ° C (212 ° F). Welding of steels by the above process is carried out using a protective atmosphere of argon containing less than 1 wt. of oxygen. Welding in this manner produces welds with a tensile strength greater than about 900 MPa (130 ksi), preferably greater than about 930 MPa (135 ksi), even more preferably greater than about 965 MPa (140 ksi), and most preferably greater than about 1000 MPa ( 145 ksi). Welding in this manner uses a metal having a BDTT below about 73 ° C (-100 ° F), preferably below about -96 ° C (-140 ° F), more preferably below about -106 ° C (160 ° F), and most preferably below about -115 ° C (-175 ° F).

In another example, inert gas (TIG) tungsten electrode welding uses iron-containing materials of about 0.07 wt% to make metal welds. % of carbon (preferably less than about 0.07 wt% carbon), about 1.80 wt% carbon; % manganese, about 0.20 wt. % silicon, about 4.00 wt. % nickel, about 0.5 wt. about 0.40 wt. % molybdenum, about 0.02 wt. % copper, about 0.02 wt. about 0.010 wt. % titanium, about 0.015 wt. zirconium (Zr), less than 50 ppm phosphorus and less than 30 ppm sulfur. The welding heat input ranges from about 0.3 kj.mm ^-1 to about 1.5 kJ.mm ^'1 (7.6 kJ.palec' ^1-38 kJ.palec ^'1) and is preheated to about 100 ° C (212 ° F). The welds of the steel are carried out as described above, using a protective atmosphere of argon containing less than 1 wt. of oxygen. Welding in this manner produces welds with a tensile strength greater than about 900 MPa (130 ksi), preferably greater than about 930 MPa (135 ksi), even more preferably greater than about 965 MPa (140 ksi), and most preferably greater than about 1000 MPa ( 145 ksi). Welding in this way uses welding metal with a BDTT below approximately -73 ° C (-100 ° F), preferably below

- 29 about -96 ° C (-140 ° F), more preferably below about -106 ° C (-160 ° F), and most preferably below about -115 ° C (-175 ° F).

Welding metal compositions similar to those in the examples can be used in both GMAW and TIG welding processes. It should be added, however, that TIG welds have less impurity and finer microstructure than GMAW welds, thereby improving low temperature toughness.

Those skilled in the art have received sufficient information and experience to perform ultra-high strength welds of low alloy steel sheets of suitable high strength and fracture toughness for use in the fabrication of pipes and other components of the present invention. There may be other welding processes or they may be developed later. All such joints or welding processes are within the scope of the present invention.

Production of piping and other components

The present invention, without limiting its scope, relates to pipes and other components (i) made of materials consisting of ultra high strength low alloy steels containing less than 9 wt. and (ii) having adequate strength and fracture toughness at cryogenic temperatures so as to contain cryogenic temperature liquids, and in particular PLNG; it further relates to piping and other components of materials made of ultra high strength low alloy steels containing less than 9 wt. nickel and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT less than about -73 ° C (-100T); it further relates to pipes and other components of materials (i) made of ultra high strength low alloy steels containing less than 3 wt. and (ii) having adequate strength and fracture toughness at cryogenic temperatures so as to contain cryogenic temperature liquids, and in particular PLNG; furthermore, it relates to piping and other components as well as materials made of ultra-high strength low alloy steels containing less than 3 wt. and (ii) having a corresponding tensile strength exceeding 1000 MPa (145 ksi) and a DBTT of less than about -73 ° C (-100 ° F). Such piping and other components described herein are preferably made of ultra-high strength low alloy steels with excellent cryogenic temperature toughness.

The pipes and other components of the present invention are preferably made of:

9

9 ·

- 30 individual sheets of ultra-high strength low alloy steels with excellent toughness at cryogenic temperatures. Where appropriate, the seams of piping and other components preferably have the same strength and toughness as the ultra-high strength, low-alloy steel sheets. In some cases, at places of lesser stress, under-dimensioning of the strength within the order of 5 to 10% is possible. Seams with recommended properties can be made using any joining technology. An exemplary connection technology is described herein in the subtitle "Connection methods for making pipes and other components".

As will be appreciated by those skilled in the art, for the purpose of assessing fracture toughness and fracture control on a manufactured pipeline for transporting compressed liquids at cryogenic temperatures such as PLNG, a Charpy Notched Tensile Test (CVN) can be used, particularly at the transition temperature from tensile to brittle state. DBTT). For structural steels, DBTT displays two fracture modes. At temperatures below DBTT, the Charpy notch impact test shows a low-energy cleavage (brittle) fracture, while at temperatures above DBTT, it indicates a high-energy ductile fracture. The piping, which is made of welded steel for the transport of PLNG and other substances, must have a DBTT (as determined by the Charpy Notched Tensile Test) well below the design working temperature to avoid brittle fracture. Depending on the design, operating conditions and / or requirements of the classification group for which it is used, the corresponding DBTT temperature must be 5 to 30 ° C (9 to 54 ° F), below the working temperature.

As will be appreciated by those skilled in the art, the operating conditions to be taken into consideration when designing welded steel pipelines for the transport of compressed cryogenic liquids such as PLNG must include, inter alia, operating pressure and temperature, as well as additional stresses on the steel and Welds (see glossary) work. Determination of fracture toughness of steels and welds can be used for standardized mechanical fracture measurements such as (i) the critical stress coefficient (KIC), which is a measurement of the plane fracture toughness, and (ii) the crack size change (CTOD) that can be used to measure elastic-plastic • · <

• · · «·· ··

- 31 fracture toughness, which are known to those skilled in the art. Industrial codes generally accepted for describing the structure of steels can be used to determine the permissible crack size in pipelines based on fracture toughness of steels and welds (including HAZ) and the stresses in pipelines, for example, as described in "Guidance on methods for assessing the acceptability of flaws in fusionwelded structures', often referred to as' PD 6493: 1991 '. Experts can develop a fracture control program to alleviate the potential for fracture by (i) appropriate piping design with minimized stresses, (ii) appropriate manufacturing quality control to minimize defects, (iii) proper piping stress cycles, and (iv) appropriate inspection program to reliably detect pipe cracks and defects. The philosophy that is preferred according to the system of the present invention is a "leak detection over failure" known to those skilled in the art. Here, these considerations are generally referred to as the "known principles of fracture mechanics".

The following is an example of a procedure for calculating the critical crack depth for a given crack length for use in creating a fracture control plan to prevent fractures in the pipeline of the present invention but not limiting these known principles of fracture mechanics.

Giant. 2 shows a crack of length 315 and depth 310. The curve 300 of PD 6493 shown in FIG. 2A is used to calculate critical crack size values based on the following piping design values:

Pipe Diameter: 914 mm (36 inches)

Pipe Wall Thickness: 20 mm (0.787 inches)

Operating axial stress: 0.80 (multiplied) SMYS = 662 MPa (96 ksi)

For the purpose of this example, a crack surface length of 100 mm (4 inches), e.g., a circumferential crack located in a circumferential weld, is evaluated. Referring to Fig. 2A, curve 300 shows a value for the critical crack depth as a function of fracture toughness CTOD and internal stress, for the internal stress level of 15, 25, 50, 75, and 100 percent stress at the ultimate deflection. Internal stress may be caused

· * · · · · · · · · · ·

9 * * · · · · ·

- 32 by production or welding; and PD6493 recommends the use of an internal stress value equivalent to 100% of the permanent deformation stress in the weld (including HAZ) unless the weld is relieved by technology such as post-heat treatment (PWHT) or mechanical stress relief.

Based on the fracture toughness of CTOD at the minimum operating temperature, a pipe welding process can be established to reduce internal stresses and a control program (for both initial and in-service inspection) can be established to compare and measure critical size values cracks. In this case, if the steel at a minimum operating temperature (measured on laboratory samples) has a CTOD toughness of 0.030 mm and the internal stress is reduced to 15 percent of the stress strain limit, the critical value of the crack depth is approximately 1 mm (see point 320 in fig). 2A). By following a similar calculation method known to those skilled in the art, it is possible to determine the critical crack depth for different crack lengths as well as for different crack geometries. Using this information, a quality control program and a control program (techniques, measurable crack dimensions, frequency) can be developed to ensure that cracks are detected and removed before the critical depth is reached or before the planned load is applied. Based on published empirical relationships between CVN, K | _C and CTOD of fracture toughness generally corresponds to a CTOD value of 0.030 mm CVN of about 44 J. However, this example does not limit the invention in any way.

For pipelines and other components requiring steel bending, eg, cylindrical container shape or tubular tube shape, the steel is bent to the desired shape at ambient temperature to avoid adversely affecting the excellent toughness of the steel at cryogenic temperatures. If the steel has to be heated to achieve the desired shape after bending, it is preferably heated to a temperature of no more than about 600 ° C (1112 ° F) to maintain the beneficial effect of the steel microstructure as described above.

The unique advantages associated with such piping and other components are described in detail below.

• ·

- 33 Piping systems

Referring to Fig. 1, the present invention preferably comprises a manifold system for a PLNG 10 manifold according to at least one storage reservoir 12, at least one primary manifold 14, and at least one target location 16. The target location for the purposes of this example only without limiting the invention is a gas station for vehicles, a manufacturing plant, or an LNG evaporator station on a natural gas pipeline. The manifold system shown in Fig. 1 also has at least one secondary manifold 18, and at least one tertiary manifold 15.

The manifold system 10 is preferably designed to control the heat loss of the system due to possible control of the evaporation of PLNG. As is known to those skilled in the art, heat leaks can be controlled by appropriate insulation surrounding the conduit, such as a primary manifold 14 and surrounding the accumulation reservoir 12. Steam handling equipment (not shown in Figure 1) including a vaporized gas condenser can be placed in the conduit system 10, or vaporized vapors can be used as fuel in a gas-powered plant.

PLNG is mainly pumped by a cryogen pump (not shown in Fig. 1). In addition, cryogenic pumps are preferably used at various locations in the manifold system 10 to maintain the pressure and hence the temperature at which PLNG is pumped through the desired locations of the system. Appropriate cryogenic pumps can be selected by experts. The check valve (not shown in FIG. 1) between the target site 16 and the piping in the system, e.g., the secondary manifold 18, preferably prevents backflow from the target site back to the pipeline. An advantage of the manifold systems of the present invention is that the PLNG (liquid) can be pumped to the target sites and thereby prevent the associated increase in compression costs typical of natural gas manifold systems.

A typical PLNG receiving station is located on the coast. This station preferably has at least one storage tank 12 and a PLNG evaporation device (not shown in FIG. 1). Piping system 10 for general urban distribution with 100 consumers or distributors at daily consumption ·· · · · · ·

For example, 34,000 gallons of PLNG for each has a 10 inch primary manifold 14, an approximately 3 inch secondary manifold 18, and about one hundred 1.5 inch tertiary manifolds 15.

Pipes and other components of the above-mentioned PLNG distribution piping systems are preferably made of ultra-high strength low alloy steel as described herein, as well as any other steel described above in the subheading "Pipes and other components". Pipes and other components are sized according to the needs of the PLNG project, according to which the piping system is used. In addition to the information provided in this specification, skilled artisans can use conventional technical practices and references available in industry to design and operate the pipeline systems of the present invention to determine the necessary dimensions, wall thicknesses, etc. for pipes and other components.

The systems of the invention can be advantageously used in the distribution and transportation of PLNG. The systems of the invention are preferably used (i) in the distribution and transport of additional compressed cryogenic liquids, (ii) in the distribution and transport of other compressed non-cryogenic liquids, or (iii) in the distribution and transport of cryogenic liquids at atmospheric pressure.

While the present invention has been described as one or more preferred cases, it is to be understood that further modifications may be made without departing from the scope of the invention, which is further claimed in the following claims.

• ·

- 35 Glossary:

Transformation temperature Ac <

Transformation temperature AC3:

Transformation temperature Αη:

Transformation temperature Ar ₃ :

Cryogenic temperatures:

CTOD:

CVN:

DBTT:

basic:

the temperature at which austenite begins to form during heating;

the temperature at which the conversion of ferrite to austenite is complete during heating;

the temperature at which the conversion of austenite to ferrite and cementite is complete during cooling;

the temperature at which austenite becomes ferrite during cooling;

temperatures below about -40 ° C (-40 ° F);

change of crack dimensions;

notched Charpy toughness;

the tensile to brittle transition temperature separates the two fracture characteristics of structural steels; at temperatures below DBTT there is a tendency to low-energy fracture (brittle) fractures, while at temperatures above DBTT there is a tendency to high-energy ductile fractures; substantially 100% v / v;

• ·

Gm ³ :

GMAW:

Curing particles:

HAZ:

intercritical temperature range:

K, _c :

kJ:

kPa:

ksi:

low alloy steel:

MA:

maximum allowed crack size:

- 36 billion cubic meters;

arc welding with metal under protective atmosphere;

one or more ε-Cu, M02C or niobium and vanadium carbides and carbonitrides;

zone affected by heat;

from about transform temperature Aci to about transform temperature Ac ₃ on heating and about from transform temperature Ar ₃ to about transform temperature Αη on cooling;

critical stress intensity coefficient;

kilojoul;

thousand Pascals;

thousand pounds per square inch;

% steel containing iron and less than 10 wt. alloying additives;

martenzite - austenite;

critical crack length and depth;

M02C:

molybdenum carbide form;

MPa:

Transformation temperature M _s :

«·

- 37 million Pascals;

the temperature at which transformation of austenite to martensite occurs during cooling;

PLNG: compressed liquefied natural gas;

predominantly: at least about 50 percent by volume;

ppm: parts per million parts;

psia:

pounds per square inch - absolute;

hardening:

quenching speed accelerated cooling in such a way that the selected liquid increases the cooling rate of the steel over cooling in air;

a cooling rate at or substantially at the center of the sheet thickness;

Temperature at quenching stop:

the highest or substantially the highest temperature reached by the sheet surface when quenching stops because of the transfer of heat from the center of the sheet thickness;

QST:

temperature at quenching stop;

panes: steel piece having any dimensions;

TCF: trillion cubic feet;

• · ·

- 38 - tensile strength: in the strength test, this is the ratio of the load to the original cross-sectional area; TIG welding: Tungsten electrode welding in argon shielding; Temperature T _nr : temperature below which austenite does not recrystallize; USPTO: [United States Patent and Trademark Office] United States Patent Office; svarek: welded joint or seam including: (i) (ii) zones affected heat (HAZ); and (iii) the base metal in the "immediate vicinity" of HAZ. The part of the parent metal located in the 'immediate vicinity' of the HAZ and thus also the component of the weldment varies depending on factors known to those skilled in the art, for example, and without being exhaustive of these items, on the thickness of the weld, dimensions of welded body, number welds to be formed on the object a distance between welds.

.. WWW-ito & L

Claims (15)

Patent claims A pipe suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of from about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and temperatures from about -123 ° C (-190 ° F) to about -62 ° C (-80 ° F) characterized in that said pipe is made of a material that is ultra high strength low alloy steel containing less than 9 wt. and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT less than about -73 ° C (-100 ° F). 2. A pipe suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of from about 1725 kPa (250 psia) to about 7590 kPa (1100 psia) and temperatures of about -112 ° C (-170 ° F) to about -62 ° C (-80 ° F) characterized in that said pipe is made of a material that is ultra high strength low alloy steel containing less than 9 wt. and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT less than about -73 ° C (-100 ° F). 3. A pipe suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of from about 1725 kPa (250 psia) to about 4830 kPa (700 psia) and temperatures of about -112 ° C (-170 ° F) to about -79 ° C (-110 ° F) characterized in that said pipe (i) is made of a material that is ultra high strength low alloy steel containing less than 9 wt. and (ii) has strength and fracture toughness corresponding to the compressed liquefied natural gas contained. • · - 40 4. A pipe suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of from about 1725 kPa (250 psia) to about 7590 kPa (1100 psia) and temperatures of about -112 ° C (-170 ° F) to about -62 ° C (-80 ° F) characterized in that said pipe is made of a material that is ultra high strength low alloy steel containing less than 9 wt. and having a tensile strength of at least 1000 MPa (145 ksi) and a DBTT of less than about -73 ° C (-100 ° F). A pipe according to any one of claims 1, 2, 3 or 4, wherein said ultra high strength low alloy steel comprises less than 5 wt. nickel. 6. A pipe suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of from about 1725 kPa (250 psia) to about 7590 kPa (1100 psia) and temperatures of about -112 ° C (-170 ° F) to about -62 ° C (-80 ° F) characterized in that said pipe is made of a material that is ultra high strength low alloy steel containing less than 6 wt. and having a tensile strength of at least 830 MPa (120 ksi) and a DBTT of less than about -73 ° C (-100 ° F). 7. A pipe suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of from about 1725 kPa (250 psia) to about 7590 kPa (1100 psia) and temperatures of about -112 ° C (-170 ° F) to about -62 ° C (-80 ° F) characterized in that said pipe is made of a material that is ultra high strength low alloy steel containing less than 3 wt. and having a tensile strength of at least 1000 MPa (145 ksi) and a DBTT of less than about -73 ° C (-100 ° F). • 99 · ·· 9 9 · · · * * * * 999 999 999 999 999 999 999 999 999 999 999 999 999 999 A pipe according to any one of claims 1, 2, 3, 4, 5 (claim 5 is a multiple dependent claim), 6 or 7 made by bending and joining at least one separate sheet of said ultra high strength low alloy steel characterized in that the seams said pipes having a tensile strength greater than about 900 MPa (130 ksi) and a DBTT less than about -73 ° C (-100 ° F). 9. A pipe suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of from about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and temperatures of about -123 ° C (-190 ° F) to about -62 ° C (-80 ° F) characterized in that said manifold system consists of at least one pipe made of ultra high strength low alloy steel containing less than 9 wt. and having a tensile strength of at least 830 MPa (120 ksi) and a DBTT of less than about -73 ° C (100 ° F). 10. The manifold system of claim 9 wherein said high strength low alloy steel comprises less than 5 wt. nickel. · · 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 · · · * ··· · - 42 11. A method of transporting compressed liquefied natural gas from a storage location to a destination, wherein said compressed liquefied natural gas has a pressure of about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and a temperature of about -123 ° C. (190 ° F) to about -62 ° C (-80 ° F), and the method comprises the steps of: (a) supplying said compressed liquefied natural gas to an inlet pipe of a distribution piping system at said storage location, wherein said distribution piping system has at least one pipe made of a material that is ultra high strength low alloy steel containing less than 9 wt. Nickel and having a tensile strength of at least 830 MPa (120 ksi) and a DBTT of less than about -73 ° C (-100 ° F); and (b) pumping said compressed liquefied natural gas to an outlet of said piping system at said destination. 12. The method of claim 11, wherein the evaporating device for converting said compressed liquefied natural gas to a gaseous state is connected to said outlet of said piping system. The method of claim 12, further comprising the step of: (c) supplying said gas to a gas line. - 43 14. A pressurized liquefied natural gas distribution system at a pressure of about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and a temperature of about 123 ° C (190 ° F) to about -62 ° C (-80 ° F) said system comprising a manifold having an inlet for filling said pressurized liquefied natural gas, characterized in that said manifold consists of at least one pipe made of a material that is ultra high strength low alloy steel containing less than 9% by weight . and having a tensile strength greater than 830 MPa (120 ksi) and a DBTT less than about 73 ° C (~ 100 ° F). 15. A container for storing compressed liquefied natural gas at a pressure of about 1725 kPa (250 psia) to about 7590 kPa (1100 psia) and temperatures of about -112 ° C (-170 ° F) to about -62 ° C (-80 ° C). ° F), characterized in that it is made of ultra high strength low alloy steel containing less than 2 wt. and having a tensile strength and fracture toughness corresponding to the compressed liquefied natural gas contained. 16. A container suitable for use in a piping system for transporting compressed liquefied natural gas at a pressure of about 1725 kPa (250 psia) to about 7590 kPa (1100 psia) and temperatures of about -112 ° C (-170 ° F) to about -62 ° C (-80 ° F), characterized in that said container is made of ultra high strength low alloy steel containing less than 2 wt. and having a tensile strength and fracture toughness corresponding to the compressed liquefied natural gas contained.