EP3094915B1 - Sealed and thermally insulating tank comprising metal strips - Google Patents

Description

The invention relates to the field of the manufacture of sealed and thermally insulating tanks and their constituent parts. In particular, the present invention relates to tanks for the storage or transport of cold or hot liquids, for example tanks for the storage and / or transport of liquefied gas by sea.

Waterproof and thermally insulating vessels can be used in different industries to store hot or cold products. For example, in the energy field, liquefied natural gas (LNG) is a liquid that can be stored at atmospheric pressure at about -163 ° C in land-based storage tanks or tanks embedded in floating structures.

We know, for example according to FR-A-2968284 , a storage tank integrated in the hull of a ship, whose sealed barrier, in particular a primary sealed barrier in contact with the product contained in the tank, consists of metal strakes which are connected together, in leaktight manner, by raised edges defining deformable bellows on either side of a welding wing. These strakes are connected at their ends to a connecting ring through the furring sheets both welded to the connecting ring and strakes.

• une barrière d'isolation thermique retenue sur la paroi porteuse, la barrière d'isolation thermique présentant une surface de support plane parallèle à la paroi porteuse respective,
• une barrière d'étanchéité supportée par la barrière d'isolation et comportant une structure répétée comportant alternativement une virure métallique allongée et une aile de soudure allongée liée à la surface de support et saillante par rapport à celle-ci, l'aile de soudure s'étendant parallèlement à la virure métallique sur au moins une partie de la longueur de la virure métallique, la virure métallique comportant dans le sens de la largeur une portion centrale plane posée sur la surface de support et des bords latéraux relevés par rapport à la surface de support qui sont disposés contre les ailes de soudure adjacentes et soudés de manière étanche aux ailes de soudure,

dans laquelle la virure métallique s'étend entre deux bords opposés de la paroi de cuve et présente deux portions d'extrémité qui sont chacune assemblées de manière étanche à une structure d'arrêt respective au niveau desdits bords opposés de la paroi de cuve,
caractérisée en ce que la virure métallique est constituée d'au moins une bande métallique continue présentant plusieurs portions longitudinales ayant des épaisseurs différentes, les portions longitudinales comportant une portion intermédiaire et au moins une portion d'extrémité dont l'épaisseur est supérieure à l'épaisseur de la portion intermédiaire de la bande, la portion d'extrémité plus épaisse formant une zone d'assemblage de la bande avec la structure d'arrêt ou avec une autre bande métallique continue assemblée bout à bout avec la première bande métallique continue pour constituer la virure métallique.According to one embodiment, the invention provides a sealed and thermally insulating tank integrated into a supporting structure, the carrying structure comprising a plurality of load-bearing walls, the tank comprising
a plurality of tank walls each fixed to a respective bearing wall, a tank wall comprising:

• a thermal insulation barrier retained on the load-bearing wall, the thermal insulation barrier having a flat support surface parallel to the respective bearing wall,
• a sealing barrier supported by the insulation barrier and having a repeating structure alternately having an elongated metal strake and an elongate weld wing bonded to and protruding from the support surface, the weld wing extending parallel to the metal strake over at least a portion of the length of the metal strake, the metal strake having in the width direction a flat central portion on the support surface and raised side edges with respect to the surface of support which are arranged against the adjacent welding wings and welded sealingly to the welding wings,

wherein the metal strake extends between two opposite edges of the vessel wall and has two end portions which are each sealingly joined to a respective stop structure at said opposite sides of the vessel wall,
characterized in that the metal strake consists of at least one continuous metal strip having a plurality of longitudinal portions having different thicknesses, the longitudinal portions having an intermediate portion and at least one end portion having a thickness greater than the thickness of the intermediate portion of the strip, the thicker end portion forming an assembly zone of the strip with the stop structure or with another continuous metal strip joined end to end with the first continuous metal strip to constitute the metal strake.

According to embodiments, such a tank may comprise one or more of the following characteristics.

According to one embodiment, the metal strake consists of a single metal strip extending in one piece between the two opposite edges of the tank wall, and in which the two end portions of the strip are more thick as the intermediate portion and are each assembled to the respective stop structure at opposite edges of the vessel wall.

According to one embodiment, the metal strake comprises a second continuous metal strip joined end to end with the first continuous metal strip in the extension of the first continuous metal strip, in which each of the two continuous metal strips has, at the level of the zone assembly of the two metal strips, an end portion thicker than the intermediate portion of the strip.

According to one embodiment, at least one of the two continuous metal strips has, at the end opposite the assembly zone of the two metal strips, a second end portion that is thicker than the intermediate portion of the strip, the second end portion being joined to the stop structure at an edge of the vessel wall.

According to one embodiment, at least one of the two continuous metal strips has, at the end opposite the assembly zone of the two metal strips, a second end portion of the same thickness as the intermediate portion of the strip, the second end portion being joined to the stop structure at an edge of the vessel wall.

According to embodiments, each end portion of the strake is sealingly welded to the respective stop structure.

According to embodiments, the strake is welded to the stop structure by a CMT (Cold Metal Transfer) or TIG (Tungsten Inert Gas) process or by welding. Cold.

According to embodiments, the stop structure comprises a plate positioned above the insulation barrier and the end portion comprises a first segment resting on the plate of the stop structure and a second segment in pressing on the thermal insulation barrier, the first segment and the second segment being connected by a folded segment forming a recess in the direction of thickness of the metal strake.

According to embodiments, the welding wings are interrupted before the end of the metal strake, the raised edges of two adjacent metal strips being welded to each other by an edge weld disposed on a portion of their length to the end of the metal strake.

According to embodiments, the edge edge welds are made using a cold metal or TIG with wire transfer method.

According to embodiments, the end portion has a thickness greater than or equal to 0.9 mm.

According to embodiments, the intermediate portion has a thickness of less than 0.9 mm and preferably a thickness of 0.7 mm.

According to embodiments, the stop structure is welded to a supporting wall.

According to embodiments, the metal strake and the stop structure are made of nickel alloy steel with a low coefficient of expansion, in particular known as Invar®.

$$\mathrm{0,15}\%\le \mathrm{Mn}\le \mathrm{1,5}\%$$

$$0\le \mathrm{Si}\le \mathrm{0,35}\%,\mathrm{de\; préférence}\mathrm{0,1}\%\le \mathrm{Si}\le \mathrm{0,35}\%$$

$$0\le \mathrm{C}\le \mathrm{0,07}\%$$

optionnellement : $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le \mathrm{0,5}\%$$

$$\mathrm{0,01}\%\le \mathrm{Cr}\le \mathrm{0,5}\%$$

le reste étant du fer et des impuretés résultant nécessairement de l'élaboration.According to one embodiment, the metal strake is made of iron-based alloy and comprises by weight: $$34.5\%\le \mathrm{Or}\le 53.5\%$$

$$0.15\%\le \mathrm{mn}\le 1.5\%$$

$$0\le \mathrm{Yes}\le 0.35\%,\mathrm{preferably}0.1\%\le \mathrm{Yes}\le 0.35\%$$

$$0\le \mathrm{VS}\le 0.07\%$$

optionally: $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le 0.5\%$$

$$0.01\%\le \mathrm{Cr}\le 0.5\%$$

the rest being iron and impurities necessarily resulting from the elaboration.

• une barrière d'isolation thermique secondaire réalisée similairement à la barrière d'isolation primaire,
• une barrière d'étanchéité secondaire supportée par la barrière d'isolation secondaire et portant la barrière d'isolation primaire,
• La barrière d'étanchéité secondaire étant réalisée similairement à la barrière d'étanchéité primaire.

According to embodiments, the vessel wall further comprises:

• a secondary thermal insulation barrier similar to the primary insulation barrier,
• a secondary sealing barrier supported by the secondary insulation barrier and carrying the primary insulation barrier,
• The secondary sealing barrier being made similar to the primary sealing barrier.

According to embodiments, the thickness varies gradually over a distance of 500mm. According to embodiments, the end portion extends over 400mm.

Such a tank can be part of a land storage facility, for example to store LNG or be installed in a floating structure, coastal or deep water, including a LNG tank, a floating storage and regasification unit (FSRU) , a floating production and remote storage unit (FPSO) and others.

According to one embodiment, a vessel for the transport of a cold liquid product comprises a double hull and a aforementioned tank disposed in the double hull.

According to one embodiment, the invention also provides a method of loading or unloading such a vessel, in which a cold liquid product is conveyed through isolated pipes from or to a floating or land storage facility to or from the vessel vessel.

According to one embodiment, the invention also provides a transfer system for a cold liquid product, the system comprising the abovementioned vessel, insulated pipes arranged to connect the vessel installed in the hull of the vessel to a floating storage facility. or terrestrial and a pump for driving a flow of cold liquid product through the insulated pipelines from or to the floating or land storage facility to or from the vessel vessel.

According to one embodiment, the first reinforced zone has a first average grain size and the second zone has a second average grain size, the difference in absolute value between the first grain size and the second grain size being less than or equal to at 0.5 index according to ASTM E1 12-10.

$$\mathrm{0,15}\%\le \mathrm{Mn}\le \mathrm{0,5}\%$$

$$\mathrm{0,1}\%\le \mathrm{Si}\le \mathrm{0,35}\%$$

$$\mathrm{0,010}\%\le \mathrm{C}\le \mathrm{0,050}\%$$

optionnellement : $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le \mathrm{0,5}\%$$

$$\mathrm{0,01}\%\le \mathrm{Cr}\le \mathrm{0,5}\%$$

le reste étant du fer et des impuretés résultant nécessairement de l'élaboration.According to one embodiment, the iron-based alloy comprises by weight: $$34.5\le \mathrm{Or}\le 42.5\%$$

$$0.15\%\le \mathrm{mn}\le 0.5\%$$

$$0.1\%\le \mathrm{Yes}\le 0.35\%$$

$$\mathrm{0,010}\%\le \mathrm{VS}\le \mathrm{0,050}\%$$

optionally: $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le 0.5\%$$

$$0.01\%\le \mathrm{Cr}\le 0.5\%$$

the rest being iron and impurities necessarily resulting from the elaboration.

The invention starts from the observation that the quantity of material necessary for the manufacture of a bearing structure comprising a sealed and thermally insulated tank depends on the fatigue resistance of the tank. In particular, the fatigue resistance of the tank depends on the fatigue resistance of the welds present on the impervious barriers forming the tank.

Thus, an idea underlying the invention is to provide a sealed and thermally insulated tank which comprises a sealed barrier having good fatigue resistance while limiting the amount of material necessary for producing such a sealed barrier. According to one aspect of the invention, the impervious barrier is made using strakes extending in one piece between two stop structures, and the strakes have a variable thickness so as to be directly connected to the structures. stop at their ends while having a smaller thickness between these ends. According to another aspect of the invention, the waterproof barrier is made using strakes composed of several bands welded end to end to each other at the reinforced portions of these strips, so that the resistance of this welded assembly is high.

Certain aspects of the invention start from the idea of connecting the strakes to the stop structures with the aid of a weld having good resistance to fatigue.

The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent in the following description of several particular embodiments. of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings.

• La figure 1 est une vue partielle en perspective écorchée d'une paroi de cuve étanche et thermiquement isolant dans laquelle des modes de réalisation de l'invention peuvent être employés.
• La figure 2 est une vue partielle en perspective de la zone II de la figure 1 représentant la membrane étanche primaire.
• La figure 3 est une vue en coupe d'un détail d'une membrane étanche de la paroi de cuve de la figure 1 selon la ligne III-III.
• La figure 4 est une représentation schématique écorchée d'une cuve de navire méthanier et d'un terminal de chargement/déchargement de cette cuve.
• La figure 5 est une vue schématique en section longitudinale d'une bande initiale.
• La figure 6 est une vue schématique en section longitudinale d'une bande intermédiaire.
• La figure 7 est une vue schématique en section longitudinale d'une bande d'épaisseur variable.
• La figure 8 est une représentation schématique d'un flan obtenu à partir de la bande d'épaisseur variable.
• La figure 9 est une représentation schématique en section longitudinale d'un premier assemblage d'un flan avec une deuxième pièce.
• La figure 10 est une représentation schématique en section longitudinale de deux flancs assemblés bout à bout.
• La figure 11 est une vue de dessus schématique représentant plusieurs modes de réalisation d'une virure à bords latéraux relevés convenant pour réaliser une membrane étanche.

On these drawings:

• The figure 1 is a cut away perspective view of a sealed and thermally insulating vessel wall in which embodiments of the invention may be employed.
• The figure 2 is a partial perspective view of Zone II of the figure 1 representing the primary waterproof membrane.
• The figure 3 is a sectional view of a detail of a waterproof membrane of the tank wall of the figure 1 along line III-III.
• The figure 4 is a cutaway schematic representation of a tank of LNG tanker and a loading / unloading terminal of this tank.
• The figure 5 is a schematic view in longitudinal section of an initial band.
• The figure 6 is a schematic view in longitudinal section of an intermediate band.
• The figure 7 is a schematic view in longitudinal section of a band of variable thickness.
• The figure 8 is a schematic representation of a blank obtained from the band of varying thickness.
• The figure 9 is a schematic representation in longitudinal section of a first assembly of a blank with a second part.
• The figure 10 is a schematic representation in longitudinal section of two side walls assembled end to end.
• The figure 11 is a schematic top view showing several embodiments of a strake with raised side edges suitable for producing a waterproof membrane.

The figure 1 represents watertight and insulating walls of a tank integrated in a carrying structure of a ship.

The bearing structure of the tank is here constituted by the inner hull of a double-hulled vessel, the bottom wall of which has been represented by the number 1, and by transverse partitions 2, which define compartments in the inner hull of the ship. The walls of the supporting structure are adjacent two by two at edges.

On each wall of the supporting structure, a corresponding wall of the tank is made by superposing, successively, a secondary insulation layer 3, a secondary sealed barrier 4, a primary insulation layer 5 and a primary sealed barrier 6. At the angle between the two walls 1 and 2, the secondary watertight barriers 4 of the two walls 1 and 2 and the primary watertight barriers 6 of the two walls are connected by a connecting ring 10 in the form of a square tube. . The connecting ring 10 forms a structure which makes it possible to take up the tension forces resulting from the thermal contraction, in particular the metallic elements forming the impermeable barriers, the deformation of the hull at sea and the movements of the cargo. A possible structure of the connecting ring 10 is described in more detail in FR-A-2549575 .

The primary insulating layer and the secondary insulating layer consist of heat-insulating element and more particularly parallelepiped heat insulating boxes 20 and 21 juxtaposed in a regular pattern. Each insulating casing 20 and 21 has a bottom panel and a cover panel 23. Side panels 24 and internal webs 25 extend between the bottom panel and the cover panel 23. The panels delimit a space in which is setting up a heat insulating lining which may for example consist of expanded perlite. Each box 20 and 21 is held on the supporting structure by means of anchoring members 26. The boxes 20 and 21 of the primary insulating layer 5 and the secondary insulating layer 3 bear respectively the primary watertight barrier 6 and the secondary watertight barrier 4.

The secondary 4 and primary 6 watertight barriers each consist of a series of parallel Invar® 8 strakes with raised edges, which are alternately arranged with elongate welding supports 9, also in Invar®. The strakes 8 extend from a first square tube at a first transverse partition 2 to a second square tube of a second not shown transverse partition located at an opposite side of the vessel. The raised edges 13 of the strakes are welded to the welding supports 9 in a sealed manner. The soldering supports 9 are retained each time at the underlying insulating layer 3 or 5, for example by being housed in the inverted T-shaped grooves 7 formed in the cover panels 23 of the boxes 20 and 21.

This alternating structure is formed over the entire surface of the walls, which may involve very long lengths of strakes 8. On these long lengths, the sealed welds between the raised edges 13 of the strakes 8 and the welding supports 9 interposed between them can be made in the form of weld beads 17 rectilinear and parallel to the wall.

Strakes with raised edges 8 are connected directly to the connecting ring 10. For this purpose, the straightened edge strakes 8 have an end edge 11 welded continuously to the fins Inva® 27, 28 of the connecting ring. 10 to resume tension efforts. The primary watertight barrier 5 and the secondary watertight barrier 3 are thus welded respectively to a primary fin 27 and a secondary fin 28. Primary heat insulating caissons 20 are positioned between the primary fin 27 and the secondary fin 28. The primary fin 27 is attached to the primary heat insulated casings 20 by screws 30. The secondary vane 28 is fixed in the same way on the secondary heat insulating elements.

The square tube is connected to the walls 1 and 2 by means of plates 31 which extend in the continuity of the sealed membranes 4 and 6 and fins 27, 28. These plates 31 are welded to flat welded perpendicularly to the walls 1 and 2 of the supporting structure.

The figure 2 shows in greater detail the zone of connection of two strakes 8 of the primary watertight barrier 6 on the welding fin 27. It should be noted that the zone of connection of the strakes 8 of the secondary watertight barrier 4 on the welding wing 28 is performed in the same way.

The raised edges 13 of the raised edge strake 8 have a profile including an inclined portion 14 which rises progressively from the edge 11 in the direction of the strakes 8, then a horizontal portion 15. The strakes 8 are welded edge to edge continuous and sealed at their upper edge along a first portion 29 using a CMT automatic process.

The welding support 9 interposed between two strakes 8 ends slightly before the fin 27. Throughout the central portion of the vessel wall, and to the vicinity of the end edge zone 11, the tight connection between the raised edges 13 of the strakes 8 and the weld supports 9 is formed by the straight weld beads 17, which extend approximately halfway up the raised edges 13 on either side of the weld support 9 and parallel to the support surface. The welding beads 17 are made by a welding machine with wheels.

The rectilinear weld bead 17 extends to near the first portion 29, the weld bead then has an upward curvature to join the edge weld edge-to-edge on the first portion 29.

The figure 3 illustrates in greater detail the arrangement of the vessel wall at the seam between the fin 27 of the connecting ring 10 and the raised-edge strake 8 presented in FIG. figure 2 .

The fin 27 is fixed on the heat-insulating elements 20 by means of screws 30 passing through the fin 27 and screwed into the upper panels 23 of the heat-insulating elements 20. The fastening by means of a screw enables the fin 27 to be stabilized.

The strake 8 extends in one piece between its two end edges 11. Between these two end edges the strake 8 is, on a first part of its length, resting on the fins 27 and on a second part of its length, resting on the primary insulating layer 5.

The strake 8 has a folded segment 34, to ensure the support of the strake 8 on both the fin 27 and the primary insulating layer 5, for most of its lower surface. The folded section extends near the edge of the fin 27 parallel to the fin 27 and compensates for the thickness thereof.

The strake 8 further has a variable thickness along its length. Thus, the strake 8 has at its end edges 11 a thick portion 33 fixed to the fins 27. A thin portion 35 extends between the thick portions 33 and has a constant thickness. The thin portion 35 is connected to the thick portions 33 by transition portions 36 in which the thickness gradually decreases from each thick portion 33 to the thin portion 35.

More particularly, according to one embodiment, the thick portion 33 has a thickness of 0.9mm and extends over a length of 400mm and comprises the folded segment 34. The transition portion 36 then extends over a distance of 500mm and has a thickness decreasing from 0.9mm to 0.7mm. Thus, most of the tank wall is covered by the thin portion 35 of the strake 8 which has a thickness of 0.7mm.

The thick portion 33 is connected to the fin 27 by a weld bead 37 made between the edge 11 of the strake 8 and the upper surface of the fin 27, the fin 27 having a thickness of 1.5 mm. Thus, the weld bead making the junction between the strake 8 and the fin 27, namely the welding of a 0.9mm thick strip on a 1.5mm thick strip, has good fatigue resistance.

The use of such a strake 8 of variable thickness makes it possible to avoid or limit the use, in the length of the strake 8, of a set of metal sheets having different thicknesses, interconnected by weld seams that have insufficient fatigue strength. Indeed, a weld made between a sheet of 0.9mm and a sheet of 0.7mm has a lower fatigue resistance than a weld between a sheet of 0.9mm and a sheet of 1.5mm. However, the lower the fatigue resistance of the sealed barrier, the more necessary hull criteria for the vessel in which the tank is integrated are binding, which requires stiffening of the hull important. This stiffening of the hull is reflected in particular by a large amount of steel necessary for the realization of the hull.

The use of a strake 8 whose thickness varies along its length allows for a waterproof membrane 6 having good fatigue resistance, while avoiding the use of thick strakes along their entire length.

Fatigue resistance being more important, the hull criteria are less restrictive and allow in particular a saving of steel for the realization of the hull. A tank as described above can be incorporated into a ship adapted to a dynamic hull criterion of 95 MPa and a static hull criterion of 145 MPa.

The use of a strake 8 made in one piece over the entire length of the wall also makes it possible to reduce the welding time required for the production of the primary watertight barrier 6 and to reduce the control times of the welds in tank.

The secondary watertight barrier 4 has a configuration similar to the configuration of the primary watertight barrier 6.

Strake 8 of variable thickness can be obtained by a method which will be described below. An example of a method of manufacturing a band of varying thickness according to its alloy length mainly based on iron and nickel will first be described.

In a first step of this process, an initial strip 101 obtained by hot rolling is provided.

$$\mathrm{0,15}\%\le \mathrm{Mn}\le \mathrm{1,5}\%$$

$$0\le \mathrm{Si}\le \mathrm{0,35}\%,\mathrm{de\; préférence}\mathrm{0,1}\%\le \mathrm{Si}\le \mathrm{0,35}\%$$

$$0\le \mathrm{C}\le \mathrm{0,07}\%$$

optionnellement : $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le \mathrm{0,5}\%$$

$$\mathrm{0,01}\%\le \mathrm{Cr}\le \mathrm{0,5}\%$$

le reste étant du fer et des impuretés résultant nécessairement de l'élaboration.The initial band 101 is a cryogenic Invar type alloy strip. This alloy comprises by weight: $$34.5\%\le \mathrm{Or}\le 53.5\%$$

$$0.15\%\le \mathrm{mn}\le 1.5\%$$

$$0\le \mathrm{Yes}\le 0.35\%,\mathrm{preferably}0.1\%\le \mathrm{Yes}\le 0.35\%$$

$$0\le \mathrm{VS}\le 0.07\%$$

optionally: $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le 0.5\%$$

$$0.01\%\le \mathrm{Cr}\le 0.5\%$$

the rest being iron and impurities necessarily resulting from the elaboration.

The function of the silicon is notably to allow the deoxidation and to improve the corrosion resistance of the alloy.

• Il est stable vis-à-vis de la transformation martensitique jusqu'au-dessous de la température T_L de liquéfaction d'un fluide cryogénique. Ce fluide cryogénique est par exemple du butane, du propane, du méthane, de l'azote ou de l'oxygène liquide. Les teneurs en éléments gammagènes, nickel (Ni), manganèse (Mn) et carbone (C), de l'alliage sont ajustées de façon à ce que la température de début de la transformation martensitique soit strictement inférieure à la température T_L de liquéfaction du fluide cryogénique.
• Il présente un faible coefficient moyen de dilatation thermique entre la température ambiante et la température T_L de liquéfaction du fluide cryogénique.
• Il ne présente pas de transition de résilience « ductile-fragile ».

A cryogenic Invar type alloy is an alloy that has three main properties:

• It is stable with respect to the martensitic transformation to below the temperature T _L for liquefying a cryogenic fluid. This cryogenic fluid is for example butane, propane, methane, nitrogen or liquid oxygen. The contents of gammagene elements, nickel (Ni), manganese (Mn) and carbon (C), of the alloy are adjusted so that the start temperature of the martensitic transformation is strictly lower than the temperature _{L L} of liquefaction cryogenic fluid.
• It has a low average coefficient of thermal expansion between the ambient temperature and the temperature _{L L} liquefaction of the cryogenic fluid.
• It does not have a "ductile-fragile" resilience transition.

• un coefficient moyen de dilatation thermique entre 20°C et 100°C inférieur ou égal à 10,5x10^-6 K^-1, en particulier inférieur ou égal à 2,5x10^-6 K^-1 ;
• un coefficient moyen de dilatation thermique entre -180°C et 0°C inférieur ou égal à 10x10^-6K^-1, en particulier inférieur ou égal à 2x10^-6K^-1 ; et
• une résilience supérieure ou égale à 100 joule/cm², en particulier supérieure ou égale à 150 joule/cm², à une température supérieure ou égale à -196°C.

The alloy used preferably has:

• an average coefficient of thermal expansion between 20 ° C and 100 ° C less than or equal to 10.5x10 ^-6 K ^-1 , in particular less than or equal to 2.5x10 ^-6 K ^-1 ;
• an average coefficient of thermal expansion between -180 ° C and 0 ° C less than or equal to 10x10 ^-6 K ^-1 , in particular less than or equal to 2x10 ^-6 K ^-1 ; and
• greater than or equal to 100 joule / cm ² resilience, in particular greater than or equal to 150 joule / cm ² at a temperature greater than or equal to -196 ° C.

$$\mathrm{0,15}\%\le \mathrm{Mn}\le \mathrm{0,5}\%$$

$$0\le \mathrm{Si}\le \mathrm{0,35}\%,\mathrm{de\; préférence}\mathrm{0,1}\%\le \mathrm{Si}\le \mathrm{0,35}\%$$

$$\mathrm{0,010}\%\le \mathrm{C}\le \mathrm{0,050}\%$$

optionnellement : $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le \mathrm{0,5}\%$$

$$\mathrm{0,01}\%\le \mathrm{Cr}\le \mathrm{0,5}\%$$

le reste étant du fer et des impuretés résultant nécessairement de l'élaboration.Preferably, the alloy used has the following composition, in% by weight: $$34.5\le \mathrm{Or}\le 42.5\%$$

$$0.15\%\le \mathrm{mn}\le 0.5\%$$

$$0\le \mathrm{Yes}\le 0.35\%,\mathrm{preferably}0.1\%\le \mathrm{Yes}\le 0.35\%$$

$$\mathrm{0,010}\%\le \mathrm{VS}\le \mathrm{0,050}\%$$

optionally: $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le 0.5\%$$

$$0.01\%\le \mathrm{Cr}\le 0.5\%$$

the rest being iron and impurities necessarily resulting from the elaboration.

• un coefficient moyen de dilatation thermique entre 20°C et 100°C inférieur ou égal à 5,5x 10^-6 K^-1 ;
• un coefficient moyen de dilatation thermique entre -180°C et 0°C inférieur ou égal à 5x10^-6 K^-1; et
• une résilience supérieure ou égale à 100 joule/cm², en particulier supérieure ou égale à 150 joule/cm², à une température supérieure ou égale à -196°C.

In this case, the alloy used preferably has:

• an average coefficient of thermal expansion between 20 ° C and 100 ° C less than or equal to 5.5x10 ^-6 K ^-1 ;
• an average coefficient of thermal expansion between -180 ° C and 0 ° C less than or equal to 5x10 ^-6 K ^-1 ; and
• greater than or equal to 100 joule / cm ² resilience, in particular greater than or equal to 150 joule / cm ² at a temperature greater than or equal to -196 ° C.

$$\mathrm{0,2}\%\le \mathrm{Mn}\le \mathrm{0,4}\%$$

$$\mathrm{0,02}\le \mathrm{C}\le \mathrm{0,04}\%$$

$$\mathrm{0,15}\le \mathrm{Si}\le \mathrm{0,25}\%$$

optionnellement $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le \mathrm{0,5}\%$$

$$\mathrm{0,01}\%\le \mathrm{Cr}\le \mathrm{0,5}\%$$

le reste étant du fer et des impuretés résultant nécessairement de l'élaboration.Even more particularly, $$35\%\le \mathrm{Or}\le 36.5\%$$

$$0.2\%\le \mathrm{mn}\le 0.4\%$$

$$0.02\le \mathrm{VS}\le 0.04\%$$

$$0.15\le \mathrm{Yes}\le 0.25\%$$

optionally $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le 0.5\%$$

$$0.01\%\le \mathrm{Cr}\le 0.5\%$$

the rest being iron and impurities necessarily resulting from the elaboration.

• un coefficient moyen de dilatation thermique entre 20°C et 100°C inférieur ou égal à 1,5x10^-6 K^-1 ;
• un coefficient moyen de dilatation thermique entre -180°C et 0°C inférieur ou égal à 2x10^-6 K^-1 ;
• une résilience supérieure ou égale à 200 joule/cm² à une température supérieure ou égale à -196°C.

In this case, the alloy preferably has:

• an average coefficient of thermal expansion between 20 ° C and 100 ° C less than or equal to 1.5x10 ^-6 K ^-1;
• an average coefficient of thermal expansion between -180 ° C and 0 ° C less than or equal to 2x10 ^-6 K ^-1 ;
• a resiliency greater than or equal to 200 joule / cm ² at a temperature greater than or equal to -196 ° C.

Such an alloy is a cryogenic Invar® type alloy. The trade name of this alloy is Invar®-M93.

Conventionally, the alloys used are produced in electric arc furnace or vacuum induction furnace.

After pocket refining operations to adjust residual alloy content, the alloys are cast into semi-finished products, which are heat-treated, in particular by hot rolling, to obtain strips.

These semi-products are for example ingots. Alternatively, it is slabs continuously cast by means of a continuous slab casting plant.

The strip thus obtained is etched and polished in a continuous process in order to limit its defects: calamine, oxidized penetration, straw and inhomogeneity in thickness in the direction of the length and the width of the strip.

The polishing is in particular carried out by means of grinding wheels or abrasive paper. A function of the polishing is to eliminate the residues of the stripping.

At the end of this polishing step, the initial band 1 provided in the first step of the process is obtained.

Optionally, before the homogeneous cold rolling step, the strip is subjected to a homogenization annealing of the microstructure. This homogenization annealing of the microstructure is particularly carried out at run in a heat treatment furnace, called a homogenization annealing furnace of the microstructure in the following description, with a residence time in the homogenization annealing furnace of the microstructure of between 2 minutes and 25 minutes and a temperature of the strip during homogenization annealing of the microstructure between 850 ° C and 1200 ° C.

The initial band 101 has a constant thickness E ₀ between 1.9 mm and 18 mm (see figure 5 ).

The initial web 101 is then rolled during a homogeneous cold rolling step. The homogeneous rolling is carried out along the length of the initial band 101.

By homogeneous rolling is meant a rolling transforming a band of constant thickness into a thinner band of constant thickness.

More particularly, the homogeneous rolling step comprises one or more passes in a rolling mill where the band passes through a rolling gap delimited between working rolls. The thickness of this rolling slot remains constant during each pass of the homogeneous rolling step.

This homogeneous rolling step results in an intermediate strip 103 of constant thickness E _c according to the rolling direction, that is to say along the length of the intermediate strip 103 (cf. figure 6 ).

Optionally, the homogeneous rolling step comprises at least one intermediate recrystallization annealing.

When present, the intermediate recrystallization annealing is carried out between two successive homogeneous rolling passes. Alternatively or optionally, it is performed before the flexible rolling step at the end of the homogeneous rolling step, ie after all the rolling passes made during the homogeneous rolling step.

For example, the intermediate recrystallization annealing is carried out by passing through an intermediate annealing furnace with a temperature of the strip during the intermediate annealing of between 850 ° C. and 1200 ° C. and residence time in the intermediate annealing furnace between 30 seconds and 5 minutes.

The intermediate recrystallization annealing, or if several is carried out, the last recrystallization intermediate annealing of the homogeneous rolling step, is carried out when the strip has a thickness E _i between the thickness E ₀ of the initial strip. 101 and the thickness E _c of the intermediate band 103.

When the intermediate recrystallization annealing is carried out at the end of the homogeneous rolling step, the thickness E _i of the strip during the intermediate recrystallization annealing is equal to the thickness E _c of the intermediate strip 103 at the beginning of the flexible rolling step.

Advantageously, in the embodiment in which at least one intermediate recrystallization annealing is carried out, a single recrystallization intermediate annealing is carried out. In particular, this intermediate recrystallization annealing is carried out between two successive homogeneous rolling passes when the strip has a thickness E _i strictly greater than the thickness E _c of the intermediate strip 103.

Preferably, the homogeneous rolling step does not include intermediate annealing.

The intermediate strip 103 of thickness E _c obtained at the end of the homogeneous rolling step is then subjected to a cold flexible rolling step.

The flexible rolling is carried out in a rolling direction extending along the length of the intermediate strip 103.

Flexible rolling makes it possible to obtain a strip of variable thickness depending on its length.

For this purpose, the thickness of the rolling slot of the rolling mill used is continuously varied. This variation is a function of the desired thickness of the zone of the strip during rolling so as to obtain a strip of variable thickness along its length.

More particularly, and as illustrated on the figure 7 at the end of the flexible rolling step, a strip 104 of variable thickness is obtained comprising first zones 107 having a first thickness e + s and second zones 110 having a second thickness e, smaller than the first thickness e + s. The first thickness e + s and the second thickness e each correspond to a given rolling slot thickness.

The first zones 107 and the second zones 110 each have a substantially constant thickness, respectively e + s and e.

They are interconnected by connecting zones 111 of non-constant thickness along the length of the band 104 of variable thickness. The thickness of the connection areas 111 varies between e and e + s. In one example, it varies linearly between e and e + s.

The homogeneous rolling step and the flexible rolling step generate in the first zones 107, that is to say in the thickest zones of the strip 104, a rate τ ₁ of plastic deformation, after a possible annealing. intermediate recrystallization, greater than or equal to 30%, more particularly between 30% and 98%, more particularly between 30% and 80%. In the abovementioned ranges, the rate τ ₁ of plastic deformation is advantageously greater than or equal to 35%, more particularly greater than or equal to 40%, and even more particularly greater than or equal to 50%.

• Si aucun recuit intermédiaire de recristallisation n'est effectué pendant l'étape de laminage homogène, le taux τ ₁ de déformation plastique est le taux de réduction total engendré dans les premières zones 107 de la bande 104 par l'étape de laminage homogène et l'étape de laminage flexible, c'est-à-dire résultant de la réduction d'épaisseur depuis l'épaisseur initiale E₀ jusqu'à l'épaisseur e+s.

The rate τ ₁ of plastic deformation generated in the first zones 107 is defined as follows:

• If no recrystallization intermediate annealing is performed during the homogeneous rolling step, the plastic strain rate τ ₁ is the total reduction ratio generated in the first zones 107 of the strip 104 by the homogeneous rolling step and the flexible rolling step, that is to say resulting from the reduction in thickness from the initial thickness E ₀ to the thickness e + s.

In this case, the rate τ ₁ of plastic deformation, in percentage, is given by the following formula: $${\tau }_1=\frac{E_0-\left(e+s\right)}{E_0}\times 100$$

• Si au moins un recuit intermédiaire de recristallisation est effectué pendant l'étape de laminage homogène, le taux τ₁ de déformation plastique est le taux de réduction engendré dans les premières zones 107 du fait de la réduction d'épaisseur de la bande de l'épaisseur E_i qu'elle présente lors du dernier recuit intermédiaire de recristallisation effectué pendant l'étape de laminage homogène jusqu'à l'épaisseur e+s.

Thus, in the case where no intermediate recrystallization annealing is performed, the rate τ ₁ of plastic deformation is equal to the total reduction rate generated in the first zones 107 by the homogeneous rolling step and the flexible rolling step .

• If at least one recrystallization intermediate annealing is carried out during the homogeneous rolling step, the rate of plastic deformation τ ₁ is the reduction rate generated in the first zones 107 because of the reduction in thickness of the strip of the thickness E _i that it presents during the last intermediate recrystallization annealing carried out during the homogeneous rolling step up to the thickness e + s.

In this case, the rate τ ₁ of plastic deformation, in percentage, is given by the following formula: $${\tau }_1=\frac{E_i-\left(e+s\right)}{E_i}\times 100$$

Thus, in the case where one or more intermediate annealings are carried out during the homogeneous rolling step, the rate τ ₁ of plastic deformation is strictly less than the total reduction rate generated in the first zones 107 by the homogeneous rolling step and the cold flexible rolling step.

The rate τ ₂ of plastic deformation, after a possible intermediate recrystallization annealing, generated in the second zones 110, is strictly greater than the rate τ ₁ of plastic deformation in the first zones 107. It is calculated analogously, replacing e + s in formulas (1) and (2) above.

The difference Δ τ of plastic strain rate between the second zones 110 and the first zones 107 is given by the relation Δ τ = τ ₂ - τ ₁ .

This difference Δ τ is advantageously less than or equal to 13% if the thickness E ₀ is strictly greater than 2 mm. It is advantageously less than or equal to 10% if the thickness E ₀ is less than or equal to 2 mm.

More particularly, the difference Δ τ is less than or equal to 10% if E ₀ is strictly greater than 2mm, and the difference Δ τ is less than or equal to 8% if E ₀ is less than or equal to 2mm.

Advantageously, the thickness E _c of the intermediate strip 103 before the flexible rolling step is in particular equal to the thickness e of the second zones 110 multiplied by a reduction coefficient k of between 1.05 and 1.5. Advantageously, k is approximately equal to 1.3.

où n est un coefficient constant compris entre 0,05 et 0,5.Advantageously, the thicknesses e + s and e of the first and second zones 107, 110 respect the equation: $$e+s=\left(\mathrm{not}+1\right).e$$

where n is a constant coefficient between 0.05 and 0.5.

In other words, the first thickness e + s is equal to the second thickness e multiplied by a multiplication coefficient of between 1.05 and 1.5.

This equation is rewritten as follows: s = ne, that is to say that the excess s of the first zones 107 with respect to the second zones 110 is equal to the coefficient n multiplied by the thickness e of the second zones 110.

The thickness e of the second zones 110 is between 0.05 mm and 10 mm, more particularly between 0.15 mm and 10 mm, even more particularly between 0.25 mm and 8.5 mm. When making strips, the thickness e is less than or equal to 2 mm, advantageously between 0.25 mm and 2 mm. When making sheets, the thickness e is strictly greater than 2 mm, in particular between 2.1 mm and 10 mm, more particularly between 2.1 mm and 8.5 mm.

The band 104 of variable thickness resulting from the flexible rolling step is then subjected to a final recrystallization annealing.

The final recrystallization annealing is carried out in a final annealing furnace. The temperature of the final annealing furnace is constant during the final recrystallization annealing. The temperature of the web 104 during the final recrystallization anneal is between 850 ° C and 1200 ° C.

The residence time in the final annealing furnace is between 20 seconds and 5 minutes, more particularly between 30 seconds and 3 minutes.

The running speed of the web 104 in the final annealing furnace is constant. It is for example between 2m / min and 20m / min for a final annealing furnace with a heating length equal to 10m.

Advantageously, the temperature of the band 104 during the final annealing is 1025 ° C. In this case, the residence time in the final annealing furnace is for example between 30 seconds and 60 seconds for a band 104 of variable thickness having second zones 110 of thickness e less than or equal to 2 mm. The residence time in the final annealing furnace is for example between 3 minutes and 5 minutes for a band 104 of variable thickness having second zones 110 of thickness e strictly greater than 2 mm.

The residence time in the final annealing furnace, as well as the final annealing temperature, are chosen so as to obtain, after the final recrystallization annealing, a strip 104 having mechanical properties and grain sizes that are almost homogeneous between the first zones 107 and the second zones 110. The remainder of the description specifies the meaning of "almost homogeneous".

Preferably, the final annealing is carried out under a reducing atmosphere, that is to say for example under pure hydrogen or under H ₂ -N ₂ atmosphere. The frost temperature is preferably below -40 ° C. In the case of an H ₂ -N ₂ atmosphere, the N ₂ content can be between 0% and 95%. The H ₂ -N ₂ atmosphere comprises, for example, approximately 70% of H ₂ and 30% of N ₂ .

According to one embodiment, the band 104 of variable thickness passes continuously from the flexible rolling mill to the final annealing furnace, that is to say without intermediate winding of the variable thickness band 104.

Alternatively, at the end of the flexible rolling step, the variable-thickness strip 104 is rolled up for transport to the final annealing furnace, then rolled out and subjected to the final recrystallization anneal.

According to this variant, the wound strip 104 has for example a length of between 100 m and 2500 m, especially if the thickness e of the second zones 110 of the strip 104 is approximately 0.7 mm.

At the end of the final recrystallization annealing, a strip 104 of variable thickness along its length having the following characteristics is obtained.

It comprises first zones 107 of thickness e + s and second zones of thickness e, possibly interconnected by connecting zones 111 of thickness varying between e and e + s.

Preferably, the difference in absolute value between the average grain size of the first zones 107 and the average grain size of the second zones 110 is less than or equal to 0.5 index according to ASTM standard E1 12-10. The average grain size in ASTM index is determined using the standard image comparison method described in ASTM E1 12-10. According to this method, in order to determine the average grain size of a sample, an image of the screen grain structure obtained by means of an optical microscope at a given magnification of the sample having undergone a dye attack is compared ( Contrast etch in English) with typical images illustrating twinned grains of different sizes having undergone a coloring attack (corresponding to plate III of the standard). The average grain size index of the sample is determined as the index corresponding to the magnification used on the standard image most closely resembling the image seen on the microscope screen.

If the image seen on the screen of the microscope is intermediate between two successive standard images of grain sizes, the index of the average grain size of the image seen under the microscope is determined as being the arithmetic mean between the corresponding indices. magnification used worn on each of the two typical images.

More particularly, the G1 _ASTM index of the average grain size of the first zones 107 is at most 0.5 less than the G2 _ASTM index of the average grain size of the second zones 110.

The band 104 of variable thickness may have almost homogeneous mechanical properties.

• la différence en valeur absolue entre la limite d'élasticité à 0,2% des premières zones 107 notée Rp1 et la limite d'élasticité à 0,2% des deuxièmes zones 110 notée Rp2 est inférieure ou égale à 6MPa, et
• la différence en valeur absolue entre la charge à la rupture des premières zones 107 notée Rm1 et la charge à la rupture des deuxièmes zones 110 notée Rm2 est inférieure ou égale à 6MPa.

In particular :

• the difference in absolute value between the elastic limit at 0.2% of the first zones 107 denoted Rp1 and the 0.2% elasticity limit of the second zones 110 denoted Rp2 is less than or equal to 6 MPa, and
• the difference in absolute value between the breaking load of the first zones 107 denoted Rm1 and the breaking load of the second zones 110 denoted Rm2 is less than or equal to 6MPa.

By elastic limit at 0.2% is meant, in a conventional manner, the value of the stress at 0.2% of plastic deformation.

Conventionally, the load at break corresponds to the maximum stress before necking of the test sample.

une zone de liaison 111 de longueur L3, une deuxième zone 110 de longueur L2, une zone de liaison 111 de longueur L3 et une moitié de première zone 107 de longueur $\frac{L_1}{2}.$

In the example illustrated, the band 104 of variable thickness has a repeating pattern periodically along the entire length of the strip 104. This pattern comprises successively a half of the first zone 107 of length $\frac{{\mathrm{The}}_1}{2},$

a linking zone 111 of length L3, a second zone 110 of length L2, a connecting zone 111 of length L3 and a first zone half 107 of length $\frac{{\mathrm{The}}_1}{2}.$

Advantageously, the length L2 of the second zone 110 is very clearly greater than the length L1 of the first zone 107. By way of example, the length L2 is between 20 and 100 times the length L1.

Each sequence formed of a first zone 107 flanked by two connecting zones 111 forms a zone of excess thickness of the band 104 of variable thickness, that is to say a zone of thickness greater than e. Thus, the band 104 of variable thickness comprises second zones 110 of length L2 of thickness e, separated from each other by zones of extra thickness.

After the final recrystallization annealing, the strip 104 of variable thickness is cut in the zones of excess thickness, preferably in the middle of the zones of extra thickness.

Thus blanks 112 illustrated on the figure 8 comprising a second zone of length L2 framed at each of its longitudinal ends by a connecting zone 111 of length L3 and by a half of first zone 107 of length $\frac{\mathrm{The}1}{2}.$

At the end of the cutting step, the blanks 112 are planed according to a known planing method.

The blanks 112 are then wound in coils to the unit.

According to a variant of the manufacturing method described above, the strip 104 of variable thickness is planed after the final recrystallization annealing and before the blanks 112 are cut.

According to this variant, the web 104 of variable thickness, which is planar, is cut in the zones of excess thickness to form the blanks 112. Preferably, the strip 104 is cut in the middle of the excess thickness zones.

The cutting is for example carried out on the leveling machine used for the flattening of the strip 104. As a variant, the flat strip 104 is wound into a coil and then cut on a machine different from the planer.

The blanks 112 are then wound in coils to the unit.

By means of the manufacturing method described above, blanks 112 formed of a workpiece comprising a central zone 113 of thickness e, framed by reinforced ends 114, ie of thickness greater than the thickness e of the zone, are obtained by means of the manufacturing method described above. 113. The ends 114 correspond to zones of excess thickness of the band 104 of variable thickness and the central zone 113 corresponds to a second zone 110 of the band 104 of variable thickness from which the blank 112 has been cut.

These blanks 112, which have a variable thickness along their length while being formed in one piece, do not have the weaknesses of the welded joints of the state of the art. In addition, their reinforced ends 114 allow to assemble them by welding to other parts while minimizing the mechanical weaknesses due to this assembly by welding.

According to variants, the blanks 112 may for example be obtained by cutting the strip 104 at other places than in two zones of successive overthicknesses. For example, they can be obtained by cutting alternately in a zone of extra thickness and in a second zone 110. In this case, blanks 112 having a single reinforced end 114 having a thickness greater than e are obtained. Such a flank makes it possible to obtain the strake 108 of the figure 11

They can also be obtained by cutting in two second successive zones 110.

For example, and as illustrated on the figure 9 it is possible to assemble a blank 112 with a second piece 116 by welding one of the reinforced ends 114 of the blank 112 to an edge of the second piece 16. The thickness of the second piece 116 is preferably greater than the thickness of the blank. the central zone 113 of the blank 112. The weld performed is more particularly a weld clap, also called lap weld.

The piece 116 may be a blank 112 as described above.

So, on the figure 10 two blanks 112 assembled end to end by welding are illustrated. These two blanks 112 are welded together by their reinforced ends 114. The strakes 108 and 208 of the figure 11 can be joined in the same way, as will be described below.

• la longueur de la zone centrale 113 est par exemple comprise entre 40 m et 60 m ; et
• la longueur de chaque extrémité renforcée 114 est par exemple comprise entre 0,5 m et 2 m.

In the examples illustrated on the Figures 9 and 10 :

• the length of the central zone 113 is for example between 40 m and 60 m; and
• the length of each reinforced end 114 is for example between 0.5 m and 2 m.

The second thickness e is in particular approximately equal to 0.7 mm.

The first thickness e + s is approximately equal to 0.9 mm.

Alternatively, a non-planar piece is formed from the blank 112.

The method of manufacturing a strip of variable thickness along its length described above is particularly advantageous. Indeed, it makes it possible to obtain an alloy strip mainly based on iron and nickel having the chemical composition defined above having zones of different thicknesses but quasi-homogeneous mechanical properties. These properties are obtained through the use of a plastic deformation rate after a possible recrystallization intermediate annealing generated by the homogeneous rolling and flexible rolling steps in the thickest zones greater than or equal to 30%.

The following experimental examples illustrate the importance of the claimed plastic deformation rate range for this type of alloy.

In a first series of experiments, strips of variable thickness have been manufactured, that is to say strips 104 of variable thickness whose thickness e of the second zones 10 is less than or equal to 2 mm.

Table 1 below illustrates the manufacturing trials of strips of variable thickness without intermediate recrystallization annealing.

Table 2 below contains characteristics of the strips obtained by the tests in Table 1.

Table 3 below illustrates the manufacturing trials of strips of variable thickness with an intermediate recrystallization annealing at the thickness E _i .

Table 4 below contains characteristics of the strips obtained by the tests in Table 3.

In a second series of experiments, sheets of variable thickness have been manufactured, that is to say strips 104 of variable thickness whose thickness e of the second zones 110 is strictly greater than 2 mm.

Table 5 illustrates tests for manufacturing sheets of variable thickness with or without intermediate annealing.

Table 6 below contains characteristics of the sheets obtained by the tests in Table 5.

$$\mathrm{0,15}\%\le \mathrm{Mn}\le \mathrm{1,5}\%$$

$$0\le \mathrm{Si}\le \mathrm{0,35}\%,\mathrm{de\; préférence}\mathrm{0,1}\%\le \mathrm{Si}\le \mathrm{0,35}\%$$

$$0\le \mathrm{C}\le \mathrm{0,07}\%$$

optionnellement : $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le \mathrm{0,5}\%$$

$$\mathrm{0,01}\%\le \mathrm{Cr}\le \mathrm{0,5}\%$$

le reste étant du fer et des impuretés résultant nécessairement de l'élaboration,
le procédé comprenant successivement les étapes suivantes :

• fourniture d'une bande initiale (101) d'épaisseur constante (Eo) obtenue par laminage à chaud ;
• laminage homogène à froid de la bande initiale (101) selon sa longueur pour obtenir une bande intermédiaire (103) d'épaisseur constante (E_c) selon la direction de laminage ;
• laminage flexible à froid de la bande intermédiaire (103) selon sa longueur pour obtenir une bande (104) d'épaisseur variable selon la direction de laminage, la bande (104) d'épaisseur variable ayant, selon sa longueur, des premières zones (107) ayant une première épaisseur (e+s) et des deuxièmes zones (110) ayant une deuxième épaisseur (e), inférieure à la première épaisseur (e+s),
• recuit final de recristallisation au défilé de la bande (104) d'épaisseur variable dans un four de recuit final,

dans lequel le taux de déformation plastique engendré, après un éventuel recuit intermédiaire de recristallisation, par les étapes de laminage homogène à froid et de laminage flexible à froid dans les premières zones (107) de la bande (104) d'épaisseur variable est supérieur ou égal à 30%.In all the tables, it was pointed out the tests according to a method of manufacturing a strip of thickness varying according to its length, made of iron-based alloy, the iron-based alloy comprising, by weight: $$34.5\%\le \mathrm{Or}\le 53.5\%$$

$$0.15\%\le \mathrm{mn}\le 1.5\%$$

$$0\le \mathrm{Yes}\le 0.35\%,\mathrm{preferably}0.1\%\le \mathrm{Yes}\le 0.35\%$$

$$0\le \mathrm{VS}\le 0.07\%$$

optionally: $$0\le \mathrm{Co}\le 20\%$$

$$0\le \mathrm{Ti}\le 0.5\%$$

$$0.01\%\le \mathrm{Cr}\le 0.5\%$$

the rest being iron and impurities necessarily resulting from the elaboration,
the process successively comprising the following steps:

• providing an initial strip (101) of constant thickness (Eo) obtained by hot rolling;
• homogeneously cold rolling the initial web (101) along its length to obtain an intermediate web (103) of constant thickness (E _c ) according to the rolling direction;
• cold rolling the intermediate strip (103) along its length to obtain a strip (104) of variable thickness in the rolling direction, the strip (104) of variable thickness having, along its length, first zones ( 107) having a first thickness (e + s) and second regions (110) having a second thickness (e), less than the first thickness (e + s),
• final recrystallization annealing of the band (104) of variable thickness in a final annealing furnace,

in which the rate of plastic deformation generated, after any intermediate recrystallization annealing, by the homogeneous cold rolling and cold rolling steps in the first zones (107) of the variable thickness band (104) is greater than or equal to 30%.

It is found that when the rate of plastic deformation τ1 after any intermediate recrystallization annealing is greater than or equal to 30% (tests 1 to 7 of Table 1, 1 to 3 of Table 3 and 1 to 9 of Table 5), the strip 104 of variable thickness obtained has a difference in average grain size between the average grain size of the first zones 107 (thickness e + s) and the grain size of the second zones 110 (thickness e) less than or equal to 0.5 ASTM index in absolute value. This small difference in average grain size between the first zones 107 and the second zones 110 results in quasi-homogeneous mechanical properties, namely a difference of 0.2% elastic limit ΔRp between the first zones 107 and the second zones 110. zones 110 less than or equal to 6 MPa in absolute value, and a difference between the load at break ΔRm of the first zones 107 and the second zones 110 less than or equal to 6 MPa in absolute value.

It is thus possible to obtain a band 104 of variable thickness having mechanical properties and substantially homogeneous grain sizes at the end of a very simple recrystallization annealing, since carried out at constant temperature and speed of scrolling.

The figure 11 is a schematic view from above of the primary waterproof membrane of a wall of a sealed and insulating tank constructed similarly to the tank of the figure 1 . The ends of the tank wall are symbolized by the welding fins 27 partially shown.

For the purposes of illustration, the three metal strakes 8, 108 and 208 shown on the figure 11 are manufactured according to three different embodiments. In practice, a waterproof membrane can be constructed with strakes all corresponding to the same embodiment, or by combining strakes of several embodiments in any appropriate order. The welding supports 9 are also sketched on the figure 11 , in an exploded representation that places the welding supports 9 away from the strakes 8, 108 and 208 to facilitate understanding.

The strakes of the three embodiments have the common point of extending longitudinally from one end to the other of the tank wall to be welded to the two solder fins 27 and have two raised side edges 13. For example , the width of the flat central portion of the strake is between 40 and 60 cm and the height of the raised edge 13 is between 2 and 6 cm.

The raised edges 13 of the variable thickness strake 8 can be obtained from the flat side 112 by means of a folder comprising three rollers on each side of the sidewall 112. The rollers exert a pressure on the sidewall in order to deform the flank to generate the raised edges. Hydraulic jacks are used to change the position of the rollers and the pressure exerted by them depending on the variation of the thickness of the sidewall.

Strake 8 corresponds to the embodiment described above with reference to figures 2 and3: it is a metal strip extending in one piece from one end to the other of the tank wall and having the reinforced portions 114 at both ends of the strip and the central portion of more thin thickness 113 between them. For the purposes of the representation, the boundaries between the thinner portion 113 and the thicker reinforced portions 114 have been drawn in fine dashed lines, but it is understood that this limit may extend over a relatively large transition zone .

The strake 8 is placed in one piece in the tank. Cutting the inclined portion 14 at both ends of the two raised edges of the strake 8, before proceeding to the assembly and sealing welds with the connecting rings.

The strake 108 or 208, on the other hand, consists of several successive longitudinal strips with raised edges which can be placed one after the other, which makes these embodiments particularly suitable for a very long vessel wall, for example approximately 30 to 50m per longitudinal band, ie a total length greater than 50m. Each successive band is continuous, that is to say that it is obtained from a single flank described above, and not by welding several flanks together.

More specifically, the strake 108 comprises two metal strips with raised edges 13 which are assembled end to end in the extension of one another at an assembly area 40, for example by welding. Each metal band is continuous and has a portion thicker reinforced end end 114 adjacent to the joining zone 40 and having a lower uniform thickness over the rest of its length 113, to the edge of the tank wall where it is joined to the welding fin 27.

The strake 208 is constructed similarly to the strake 108, but with strips whose two ends 114 are reinforced by a greater thickness. As a result, the thicker reinforced ends 114 of the strips constituting the strake 208 are present both at the connection zone 40 between the strips and at the edges of the tank wall where the strake 208 is joined to the fins. As a variant, the strake 208 may be constructed with a higher number of continuous strips laid end to end in the same manner.

When a tank wall is covered with a waterproof membrane manufactured with the strakes 108 or 208, the assembly area 40 of each strake 108 or 208 may be placed in the middle of the tank wall or at other locations. Preferably, these locations are offset longitudinally from one strake to another, thereby to avoid forming a continuous weld line in the transverse direction of the wall.

Although there have been described insulating elements in the form of caissons with expanded perlite, other forms of heat insulating elements are possible. In particular, the boxes can be made with other forms of insulating materials. For example, the boxes may include a layer of insulating foam.

The tanks described above can be used in various types of installations such as land installations or in a floating structure such as a LNG tank or other.

With reference to the figure 4 , a cutaway view of a LNG tanker 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealed barrier intended to be in contact with the LNG contained in the tank, a secondary sealed barrier arranged between the primary watertight barrier and the double hull of the ship, and two thermally insulating barriers respectively arranged between the primary watertight barrier and the secondary watertight barrier, and between the secondary watertight barrier and the double hull 72.

In a manner known per se, loading / unloading lines arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a marine or port terminal to transfer a cargo of LNG from or to the tank 71.

The figure 4 represents an example of a marine terminal comprising a loading and unloading station 75, an underwater pipe 76 and an onshore installation 77. The loading and unloading station 75 is an off-shore fixed installation comprising a movable arm 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can connect to the loading / unloading pipes 73. The movable arm 74 can be adapted to all gauges LNG carriers. A connection pipe (not shown) extends inside the tower 78. The loading and unloading station 75 enables the loading and unloading of the LNG tank 70 from or to the shore facility 77. liquefied gas storage tanks 80 and connecting lines 81 connected by the underwater line 76 to the loading or unloading station 75. The underwater line 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a large distance, for example 5 km, which makes it possible to keep the tanker vessel 70 at great distance from the coast during the loading and unloading operations.

In order to generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the shore installation 77 and / or pumps equipping the loading and unloading station 75 are used.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention as defined by the claims. The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim. <u> Table 1 </ u> Trial Wavelength (m) E ₀ (mm) k E _c (mm) e (mm) n = s / e e + s (mm) L1 (m) L2 (m) L3 (m) τ1 (%) τ2 (%) τ2-τ1 (%) Final annealing T ° C; duration 1 50 4.2 1.3 2.0 1.5 0.25 1.88 1.50 1.90 44.7 55 64 9 1025 ° C; 60s 2 50 4.2 1.15 1.7 1.5 0.15 1.73 1.50 1.90 44.7 59 64 5 1025 ° C; 60s 3 50 3.2 1.15 1.2 1.0 0.15 1.15 1.00 1.50 46.0 64 69 5 1025 ° C; 60s 4 50 2.6 1.3 0.9 0.7 0.25 0.88 1.00 1.50 46.0 66 73 7 1025 ° C; 40s 5 50 2, 6 1.15 0.8 0.7 0.15 0.81 1.00 1.50 46.0 69 73 4 1025 ° C; 40s 6 60 2.6 1.3 0.9 0.7 0.15 0.81 1.00 1.50 56.0 69 73 4 1025 ° C; 40s 7 50 2.1 1.3 0.7 0.5 0.15 0.58 1.20 1.50 45.8 73 76 4 1025 ° C; 30s 8 50 2.3 1.3 2.3 1.8 0.25 2.25 1.20 1.50 45.8 2 22 20 1025 ° C; 60s 9 50 2.1 1.3 2.3 1.8 0.15 2.07 1.20 1.50 45.8 1 14 13 1025 ° C; 60s 10 60 2.1 1.3 2.3 1.8 0.15 2.07 1.20 1.50 55.8 1 14 13 1025 ° C; 60s Trial Properties with thickness e + s Properties with thickness e Delta Rp (MPa) Delta Rm (MPa) DeltaG _ASTM G1 _ASTM Rp (MPa) Rm (MPa) G2 _ASTM Rp (MPa) Rm (MPa) 1 8 288 487 8.5 292 491 -4 -4 0.5 2 8.5 293 492 9 296 495 -3 -3 0.5 3 8.5 293 492 9 295 495 -2 -3 0.5 4 8.5 293 490 9 296 496 -3 -6 0.5 5 9 297 496 9 296 496 1 0 0 6 9 297 495 9 296 496 1 -1 0 7 9.5 300 501 9.5 300 501 0 0 0 8 7.5 284 482 8.5 292 490 -8 -8 1 9 7.5 286 481 8.5 293 491 -7 -10 1 10 7.5 285 483 9 296 496 -11 -13 1.5 Trial Wavelength (m) E ₀ (mm) k E _i (mm) Annealed at E _i T ° C; duration E _c (mm) e (mm) n = s / e e + s (mm) L1 (m) L2 (m) L3 (m) τ1 (%) τ2 (%) τ2-τ1 (%) Final annealing T ° C; duration 1 50 2.6 1.3 1.5 1025 ° C; 50s 0.8 0.6 0.25 0.75 1.20 1.50 45.8 50 60 10 1025 ° C; 40s 2 50 2.6 1.3 1.5 1025 ° C; 50s 0.8 0.6 0.15 0.69 1.20 1.50 45.8 54 60 6 1025 ° C; 40s 3 60 26 1.3 15 1025 ° C ; 50s 0.7 0.5 0.15 0.58 1.20 1.50 55.8 62 67 5 1025 ° C; 30s 4 50 4.2 1.30 2.00 1025 ° C ; 80s 1.95 1.5 0.25 1.88 1.50 1.90 44.7 6 25 19 1025 ° C; 60s 5 50 4.2 1.15 2.00 1025 ° C; 80s 1.73 1.5 0.15 1.73 1.50 1.90 44.7 14 25 11 1025 ° C; 60s 6 50 3.2 1.30 1.30 1025 ° C ; 50s 1.30 1.0 0.25 1.25 1.50 1.90 44.7 4 23 19 1025 ° C; 60s 7 50 3.2 1.15 1.50 1025 ° C; 60s 1.15 1.0 0.15 1.15 1.00 1.50 46.0 23 33 10 1025 ° C; 60s 8 50 2.6 1.30 0.90 1000 ° C; 40s 0.91 0.7 0.25 0.88 1.00 1.50 46.0 3 22 19 1025 ° C; 40s 9 60 2.6 1.15 1.00 1000 ° C ; 40s 0.81 0.7 0.15 0.81 1.00 1.50 56.0 20 30 11 1025 ° C; 40s Trial Properties with thickness e + s Properties with thickness e Delta Rp (MPa) Delta Rm (MPa) DeltaG _ASTM G1 _ASTM Rp (MPa) Rm (MPa) G2 _ASTM Rp (MPa) Rm (MPa) 1 8.5 292 491 8.5 293 491 -1 0 0 2 8.5 293 492 8.5 291 492 2 0 0 3 8.5 293 490 9 296 496 -3 -6 0.5 4 7 281 478 8 290 487 -9 -9 1 5 7 281 477 8 288 487 -7 -10 1 6 6.5 277 473 8 288 487 -11 -14 1.5 7 7 282 477 8 289 487 -7 -10 1 8 6.5 277 474 7.5 285 482 -8 -8 1 9 7 282 479 8 289 487 -7 -8 1 Trial Wavelength (m) E ₀ (mm) k E _i (mm) Annealed at E _i T ° C; duration E _c (mm) e (mm) n = s / e e + s (mm) L1 (m) L2 (m) L3 (m) τ1 (%) τ2 (%) τ2-τ1 (%) Final annealing T ° C; duration 1 12 16 1.30 nothingness 10.7 8.2 0.25 10.25 1.00 1.50 8.0 36 49 13 1025 ° C; 5 min 2 6 16 1.15 nothingness 9.4 8.2 0.15 9.43 0.50 0.75 4.0 41 49 8 1025 ° C; 5 min 3 12 8.2 1.30 nothingness 5.5 4.2 0.25 5.25 0.50 0.75 10.0 36 49 13 1025 ° C; 3min 4 12 8.2 1.15 nothingness 4.8 4.2 0.15 4.83 1.50 2.25 6.0 41 49 8 1025 ° C; 3min 5 6 8.2 1.30 nothingness 4.2 3.2 0.25 4.00 0.80 1.20 2,8 51 61 10 1025 ° C; 3min 6 9 8.2 1.15 nothingness 3.7 3.2 0.15 3.68 1.00 1.50 5.0 55 61 6 1025 ° C; 3min 7 12 16 1.30 8.2 1050 ° C; 5 min 4.2 3.2 0.25 4.00 1.00 1.50 8.0 51 61 10 1025 ° C; 3min 8 12 16 1.15 8.2 1050 ° C; 5 min 4.8 4.2 0.15 4.83 0.50 0.75 10.0 41 49 8 1025 ° C; 3min 9 6 16 1.15 8.2 1050 ° C; 5 min 3.7 3.2 0.15 3.68 0.50 0.75 4.0 55 61 6 1025 ° C; 3min Trial Properties with thickness e + s Properties with thickness e Delta Rp (MPa) Delta Rm (MPa) DeltaG _ASTH G1 _ASTM Rp (MPa) Rm (MPa) G2 _ASTM Rp (MPa) Rm (MPa) 1 7 280 479 7.5 285 483 -5 -4 0.5 2 7 281 477 7.5 285 483 -4 -6 0.5 3 7.5 285 482 8 288 487 -3 -5 0.5 4 8 288 487 8 288 487 0 0 0 5 8.5 293 492 8.5 292 492 1 0 0 6 8.5 292 491 9 297 496 -5 -5 0.5 7 8.5 291 490 8.5 293 490 -2 0 0 8 8 289 487 8.5 292 491 -3 -4 0.5 9 8.5 292 491 8.5 292 490 0 1 0

Claims (19)

1. A sealed and thermally insulating tank incorporated into a bearing structure, the bearing structure comprising a plurality of bearing walls (1, 2), the tank comprising
   a plurality of tank walls each fixed to a respective bearing wall (1, 2), a tank wall comprising:

   a thermal insulation barrier (3, 5) held on the bearing wall, the thermal insulation barrier having a planar support surface parallel to the respective bearing wall,

   a sealing barrier (4, 6) supported by the insulation barrier and comprising a repeating structure alternately made up of an elongate metal strake (8, 108, 208) and an elongate welding flange (9) connected to the support surface and projecting with respect to the latter, the welding flange (9) running parallel to the metal strake (8) over at least part of the length of the metal strake, the metal strake comprising in the widthwise direction a planar central portion placed on the support surface and lateral edges (13) that are turned up with respect to the support surface and arranged against the adjacent welding flanges and welded in a sealed manner to the welding flanges (9),

   in which the metal strake extends between two opposite edges of the tank wall and has two end portions which are each assembled in a sealed manner to a respective stopping structure (10, 27, 28) at said opposite edges of the tank wall,
   characterized in that the metal strake (8, 108, 208) is made up of at least one continuous metal strip having several longitudinal portions of different thicknesses, the longitudinal portions comprising an intermediate portion (113, 35) and at least one end portion (114, 33) of which the thickness is greater than the thickness of the intermediate portion of the strip, the thicker end portion (114, 33) forming an assembly zone for assembling the strip with the stopping structure (10) or with another continuous metal strip butt-joined to the first continuous metal strip to constitute the metal strake.
2. The tank as claimed in claim 1, in which the metal strake (8) is made up of a single metal strip extending in one piece between the two opposite edges of the tank wall, and in which the two end portions (33) of the strip are thicker than the intermediate portion (35, 36) and are each assembled with the respective stopping structure (10, 27, 28) at the opposite edges of the tank wall.
3. The tank as claimed in claim 1, in which the metal strake (108, 208) comprises a second continuous metal strip butt-joined to the first continuous metal strip in the continuation of the first continuous metal strip, in which each of the two continuous metal strips has, at the region (40) of connection of the two metal strips, an end portion (114) that is thicker than the intermediate portion (113) of the strip.
4. The tank as claimed in claim 3, in which at least one of the two continuous metal strips has, at the opposite end to the region (40) of connection of the two metal strips, a second end portion (114) which is thicker than the intermediate portion (113) of the strip, the second end portion (114) being connected to the stopping structure (10, 27, 28) at an edge of the tank wall.
5. The tank as claimed in claim 3 or 4, in which at least one of the two continuous metal strips has, at the opposite end to the region (40) of connection of the two metal strips, a second end portion (114) of the same thickness as the intermediate portion (113) of the strip, the second end portion (114) being connected to the stopping structure (10, 27, 28) at an edge of the tank wall.
6. The tank as claimed in one of claims 1 to 5, in which each end portion of the metal strake (8, 108, 208) is welded in a sealed manner to the respective stopping structure (10).
7. The tank as claimed in claim 6, in which the strake (8) is welded to the stopping structure by a cold metal transfer CMT method or by TIG welding using a filler metal or by cold welding.
8. The tank as claimed in one of claims 1 to 7, in which the stopping structure (10) comprises a plate (27, 28) positioned over the insulating barrier and the end portion of the metal strake (8, 108, 208) comprises a first segment bearing against the plate of the stopping structure and a second segment bearing against the thermal insulating barrier, the first segment and the second segment being connected by a folded segment (34) forming a discontinuity in the thickness direction of the metal strake.
9. The tank as claimed in one of claims 1 to 8, in which the welding flanges (9) are interrupted before the end of the metal strake (8, 108, 208), the turned-up edges of two adjacent metal strakes being welded to one another by an edge weld positioned along part of their length as far as the end of the metal strake.
10. The tank as claimed in claim 9, in which the edge weld of the turned-up edges (13) is performed using a cold metal transfer process.
11. The tank as claimed in one of claims 1 to 10, in which the thicker end portion (114, 33) of the metal strip has a thickness greater than or equal to 0.9 mm.
12. The tank as claimed in one of claims 1 to 11, in which the intermediate portion (35) of the metal strip has a thickness less than 0.9 mm and preferably a thickness of 0.7 mm.
13. The tank as claimed in one of claims 1 to 12, in which the stopping structure (10) is welded to a bearing wall.
14. The tank as claimed in one of claims 1 to 13, in which said metal strake and the stopping structure are made of a nickel-steel alloy with a low coefficient of expansion.
15. The tank as claimed in one of claims 1 to 14, in which the metal strip is made of an alloy based on iron and comprises by weight: $$34.5\%\le \mathrm{Ni}\le \mathrm{53.5\%}$$

    

    $$0.15\%\le \mathrm{Mn}\le 1.5\%$$

    

    $$0\le \mathrm{Si}\le \mathrm{0.35\%,\; preferably\; 0.1\%}\le \mathrm{Si}\le 0.35\%$$

    

    $$0\le \mathrm{C}\le 0.07\%$$

    

    optionally: $$0\le \mathrm{Co}\le \mathrm{20\%}$$

    

    $$0\le \mathrm{Ti}\le \mathrm{0.5\%}$$

    

    $$0.01\%\le \mathrm{Cr}\le \mathrm{0.5\%}$$

    

    the rest being iron and unavoidable impurities resulting from the production process.
16. The tank as claimed in one of claims 1 to 15, in which the tank wall further comprises:

    a secondary thermal insulation barrier (3), the thermal insulation barrier having a planar support surface parallel to the respective bearing wall, and a secondary sealing barrier (4) supported by the secondary insulation barrier and bearing the primary insulation barrier (5),

    the secondary sealing barrier comprising a repeating structure alternately made up of an elongate metal strake (8, 108, 208) and an elongate welding flange (9) connected to the support surface and projecting with respect to the latter, the welding flange (9) running parallel to the metal strake (8) over at least part of the length of the metal strake, the metal strake comprising in the widthwise direction a planar central portion placed on the support surface and lateral edges (13) that are turned up with respect to the support surface and arranged against the adjacent welding flanges and welded in a sealed manner to the welding flanges (9), in which the metal strake extends between two opposite edges of the tank wall and has two end portions which are each assembled in a sealed manner to a respective stopping structure (10, 28) at said opposite edges of the tank wall,

    characterized in that the metal strake (8, 108, 208) is made up of at least one continuous metal strip having several longitudinal portions of different thicknesses, the longitudinal portions comprising an intermediate portion (113, 35) and at least one end portion (114, 33) of which the thickness is greater than the thickness of the intermediate portion of the strip, the thicker end portion (114, 33) forming an assembly zone for assembling the strip with the stopping structure (10) or with another continuous metal strip butt-joined to the first continuous metal strip to constitute the metal strake.
17. A ship (70) for transporting a cold liquid product, the ship comprising a double hull (72) and a tank (71) as claimed in one of claims 1 to 16 placed inside the double hull.
18. The use of a ship (70) as claimed in claim 17 for loading or unloading a cold liquid product, in which a cold liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to a floating or on-shore storage facility (77) to or from the tank of the ship (71).
19. A transfer system for a cold liquid product, the system comprising a ship (70) as claimed in claim 17, insulated pipes (73, 79, 76, 81) arranged in such a way as to connect the tank (71) installed in the hull of the ship to a floating or on-shore storage facility (77) and a pump for driving a stream of cold liquid product through the insulated pipes from or to the floating or on-shore storage facility to or from the tank of the ship.

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