EP2483591B1 - Dual-phase or complex-phase gas cylinder - Google Patents

Description

The invention relates to a "Dual Phase" steel or "Complex Phase" steel gas cylinder corresponding to the draft European standard prEN10338 comprising two welded half-shells, the one forming the upper part of said bottle being provided, substantially at its top by welding, a receiving flange of a gas distribution valve.

The present invention is in the field of gas cylinders designed in steel known as "Dual Phase" steel called "two-phase" or "double phase" in French, or steel called "complex phase" that is to say "phase complex "in French. These steels are covered by the draft standard prEN10338.

It will be noted that the draft standard prEN10338 relates to "cold-rolled flat products in multiphase steels for cold forming" in which the so-called "Dual Phase" (DP) steels and the "Complex Phase" (CP) steels are more particularly described. .

More particularly, the "two-phase" steel is a ferritic matrix steel containing a second martensitic phase present in the form of islands and optionally bainite as a complementary phase. Because of their high level of tensile strength, DP steels have a low yield strength ratio and a high coefficient of work hardening.

Regarding the "complex phase" steel, the latter is a ferritic / bainitic matrix steel containing small amounts of martensite, residual austenite and / or perlite. Extreme grain refining is caused by delayed recrystallization or precipitation of the microalloy elements.

In a usual manner, a low pressure steel gas cylinder consists of two half-shells designed by stamping that is assembled by welding. At the top of the half-shell intended to form the part the top of the bottle is formed an opening at which is welded a flange provided for receiving a gas valve. More particularly, in the center of this collar may be provided a thread in which can be screwed this valve. As for the half-shell forming the lower part of the bottle, it can receive, if necessary, a ring intended to form the foot of the bottle and ensure its stability to the ground.

• on découpe dans une plaque en acier deux disques sensiblement identiques ;
• on emboutit ces deux disques au diamètre et à la profondeur nécessaire à l'obtention de la capacité de la bouteille voulue ;
• sur le dôme, sensiblement en position centrale, de l'un de ces emboutis est réalisé un trou et on vient y souder une collerette ;
• les deux emboutis sont ensuite soudés pour former la bouteille, l'embouti équipé de la collerette constituant la partie supérieure de cette dernière, sachant que l'autre embouti peut avoir reçu, préalablement, l'anneau formant le pied de cette bouteille ;
• on soumet la bouteille ainsi finie à un traitement thermique de recuit de normalisation, dont la finalité est d'éliminer les contraintes dans l'acier consécutivement aux déformations mécaniques lors de l'emboutissage et aux échauffements lors des différentes soudures ;
• on procède à des essais, consistant la plupart du temps, à des épreuves hydrauliques, pour vérifier l'intégrité mécanique et l'étanchéité de la bouteille ;
• pour terminer, celle-ci peut subir un traitement de surface de type grenaillage, puis l'application d'une peinture.

In any case, the bottles, made of classic steel, are designed according to the following steps:

• two substantially identical discs are cut from a steel plate;
• these two discs are stamped to the diameter and depth necessary to obtain the capacity of the desired bottle;
• on the dome, substantially in the central position, one of these stampings is made a hole and is welded to a collar;
• the two stampings are then welded to form the bottle, the stamped equipped with the collar constituting the upper part of the latter, knowing that the other stamped may have previously received the ring forming the foot of the bottle;
• the thus-finished bottle is subjected to a normalization annealing heat treatment, the purpose of which is to eliminate the stresses in the steel as a result of the mechanical deformations during stamping and the heating during the various welds;
• tests, usually consisting of hydraulic tests, to check the mechanical integrity and tightness of the cylinder;
• finally, it can undergo a surface treatment type shot blasting, then the application of a paint.

Such cylinders thus designed in conventional steel have mechanical characteristics, more particularly an elastic resistance, called (Re) and a resistance to rupture, said (Rm) substantially identical at all points of the bottle due to the normalization annealing step giving the steel a standardized microstructure.

Also, during the hydraulic pressure rupture tests of such a bottle designed according to these conventional steels, it has been found that the location of the rupture of the bottle depends mainly on its geometry.

Similarly, the fatigue test, which consists of subjecting the bottle to the maximum pressure before plastic deformation a very large number of times, revealed that the performance of these bottles is generally dependent on the quality of the welds and the annealing, while that breaks have no preferential localization.

However, such conventional steel bottles are, on the other hand, very heavy because of the same steel used imposing a minimum thickness of its walls.

Precisely, in order to avoid the users to have to lift too heavy loads, one seeks to design currently bottles more and more light. If it is possible to reduce the volume to achieve this result, this leads, for the user, to a replacement frequency of the higher bottle.

It is more precisely to remedy these drawbacks, that we now design steel gas cylinders called "Dual phase" or "Complex phase" in response to draft prEN10338 standard. The advantage of such a material lies in the fact that its elastic resistance (Re) or its breaking strength (Rm) increases proportionally to the strain-hardening stresses applied to it during the stamping phase.

In other words, the mechanical characteristics of this steel DP or CP increase during the stamping phase to obtain the two half-shells for the design of the bottle.

The advantage that follows is that the thickness The steel constituting the walls of this bottle may be smaller compared to the thickness of the steel bottles conventionally used before. In short, for the same volume and the same resistance, the bottle can be of a lower weight.

It goes without saying that if this improvement in the mechanical characteristics of the steel DP or CP is obtained under the effect of the stamping operation, we can not subject the bottle to a normalization annealing after stamping. Indeed, such a normalization annealing would lose the benefit resulting from shaping operations conducted beforehand leading to a decrease in the elastic resistance (Re) and the breaking strength (Rm) of the bottle.

Finally, being of a lower weight, these "dual phase" or "complex phase" steel bottles could be presented as having only advantages vis-à-vis conventional steel bottles, except that their manufacturing process generates, moreover, localized stresses at this bottle which have been found to cause premature rupture of the latter during burst tests and fatigue.

In particular, if the stamping stress has the effect of increasing the elastic resistance (Re) and the breaking strength (Rm) of the material, these stresses are not uniformly applied to the sheet to obtain the two half - shells brought to design the bottle.

Thus, the dome of these half-shells forming, as the case, the lower part or the upper part of the bottle, is less solicited by this stamping operation and, consequently, has an elastic resistance (Re) and a resistance at break (Rm) weaker. In addition, it is at the level of the dome of the half-shell forming the upper part of the bottle that we just arrange a hole and weld a flange for receiving the gas valve. This welding operation has for therefore subject the material to high temperature stresses. In sum, substantially at the level of this weld of the collar, there is a zone having been thermally affected, knowing that the effects of this weld can not be eliminated by a normalization annealing operation.

The experience of the practice has therefore shown that it is at the level of this thermally affected area of the dome that breaks occurred in these steel cylinders DP or CP, either during burst tests or fatigue tests .

It is within the framework of an inventive step that it has been thought to reduce the stresses that are applied to this thermally affected zone when the bottle is pressurized.

In particular, it was thought to obtain this result by taking advantage of the peculiarities of the material that constitutes the DP steel.

We know, again, by the document WO96 / 12914 , a gas cylinder made of aluminum and having two half-shells welded together. One of these two half- shells forms the upper part of the bottle and comprises at least one deformation in the form of at least one boss or at least one recess encircling the attachment zone of a valve. The document EP 104 13 38 also discloses a steel gas cylinder comprising two half-shells according to the prior art.

The present invention aims to overcome the disadvantages of gas cylinders of the state of the art.

For this purpose, the invention relates to a "Dual Phase" or "Complex Phase" steel gas cylinder comprising two half-shells welded together, the one forming the upper part of said bottle being provided, substantially at its top by welding, of a receiving collar of a gas distribution valve, characterized in that this half-shell forming the upper part of the bottle comprises a deformation in the form of at least one boss and / or at least one recess circling the collar reception of the gas distribution valve.

The advantages deriving from the present invention consist in that, on the periphery of the receiving flange of the gas distribution valve, a deformation to the material, more particularly to the DP steel constituting the half-shell forming the upper part of the bottle, the elastic resistance Re and the breaking strength Rm of the material in the immediate vicinity of the zone thermally affected by the welding of said collar are improved. Also, this deformation, in the form of strapping, better resistant to deformation stresses, has the direct consequence of limiting the stresses to the thermally affected zone when the bottle is pressurized.

• on conçoit, par emboutissage, deux demi-coquilles en vue de leur assemblage par soudure ;
• on découpe au sommet, en forme de dôme, de l'une des demi-coquilles un trou ;
• on soude dans le trou une collerette de réception d'un robinet de distribution de gaz ;
• avant ou après soudure, on réalise dans cette demi-coquille une déformation sous forme d'au moins un bossage et/ou d'au moins un renfoncement.

The invention also relates to a method of manufacturing such a "Dual Phase" or "Complex Phase" steel gas cylinder, characterized in that:

• it is designed, by stamping, two half-shells for assembly by welding;
• at the top, in the form of a dome, one of the half-shells is cut into a hole;
• a receiver flange of a gas distribution valve is welded into the hole;
• before or after welding, in this half-shell is made a deformation in the form of at least one boss and / or at least one recess.

• la figure 1 représente de façon schématisée et en perspective une bouteille de gaz selon l'invention;
• la figure 2 représente de façon schématisée et vue de face une bouteille de gaz selon l'invention;
• la figure 3 représente de façon schématisée et vue de dessus le dôme de la demi-coquille formant la partie supérieure de la bouteille ; et
• la figure 4 représente de façon schématisée et en coupe la partie supérieure de la bouteille.

Other characteristics and advantages of the invention will emerge from the following detailed description of non-limiting embodiments of the invention, with reference to the appended figures in which:

• the figure 1 schematically shows in perspective a gas cylinder according to the invention;
• the figure 2 schematically shows a front view of a gas cylinder according to the invention;
• the figure 3 represents schematically and seen from above the dome of the half-shell forming the upper part bottle; and
• the figure 4 represents schematically and in section the upper part of the bottle.

The present invention is in the field of gas cylinders and more particularly in the gas cylinders designed in steel called "Dual Phase" (DP) or "complex Phase" (CP) meeting the draft standard prEN10338.

In this regard, such a gas cylinder 1 of DP or CP steel is manufactured according to the following method.

To manufacture such a gas cylinder is first cut two identical discs made of steel "Dual Phase" said DP or "complex phase" said CP in a sheet or plate. Once these two disks obtained are stamped, using a stamping press, these two disks to compose two half-shells which are assembled by welding to form said gas cylinder. Following this stamping, one of the two half-shells is selected, which then becomes the upper part of the gas bottle while the other forms the lower part which can comprise base means.

On this half-shell forming the upper part of the bottle is cut at its top, in the form of a dome, a hole on which is welded a receiving flange of a gas valve.

In particular, before or after welding, in this half-shell a deformation is carried out in the form of at least one boss and / or at least one recess.

Advantageously, this deformation is carried out by stamping.

According to an additional step of the process, deformation is carried out during or after stamping of the half-shell intended to form the upper part of the bottle.

According to another additional step of the method, the deformation is carried out during or after the cutting of the hole in this half-shell.

As visible on the figure 1 , the gas bottle 1 is generally having the form of a bottle and comprises two half-shells 2A and 2B, preferably assembled together by a weld 3.

Often, these two half-shells are in the form of a body preferably of cylindrical shape ending in a spherical, ellipsoidal, paraboloidal dome 4 or the like.

Substantially, one of the two half-shells 2 is designed to form the upper part of the gas bottle 1, while the other shaped its lower part.

According to one embodiment of the invention, the half-shell 2B forming the lower part may comprise at its lower end a ring forming the feet of said gas cylinder 1.

Advantageously, the half-shell 2A forming the upper part comprises more precisely at its top, forming a dome 4, a hole 5, of axis A. This hole 5 is preferably made by a punching operation in said half-shell 2A at the drawing end of the latter being specified that the present invention is not limited to this single embodiment. In particular, one could imagine cutting this hole at the very moment of stamping for the design of this half-shell 2A.

In addition, in this hole 5 is welded a flange 6 for receiving a gas distribution valve. It will be observed that there is around the collar 6 a weld seam.

In this regard, to facilitate its welding, this flange 6 can be engaged in this hole 5 from the inside of the half-shell 2A. A recess at its periphery comes to form a stop in cooperation with the surroundings of this hole 5 by ensuring the positioning of this collar 6.

Especially this half-shell 2A forming the upper part of the gas cylinder 1 further comprises at least one deformation 7 in the form of at least one boss and / or at least one recess circling the collar 6 for receiving the valve. gas.

According to a preferred embodiment of the invention, this deformation 7 is formed by a stamping.

Advantageously, this or these bosses and / or this or these recesses, making it possible, by taking advantage of the particular characteristics of the steel DP or CP, to increase the elastic resistance (Re) and the breaking strength (Rm) of the gas bottle 1 at the dome of the upper part of the latter, more particularly near the flange 6 welded in the hole 5.

Indeed, this zone has been thermally weakened by the welding between the flange 6 and the hole 5.

Preferably, the deformation or deformations, that is to say the bosses and / or the or recesses are located in an area between the flange 6 and the cylindrical portion of the half-shell 2A.

More particularly, this deformation 7, which is a boss or recess, is at a distance, relative to the axis A of the hole 5, beyond one millimeter with respect to the outside edge of the weld bead of the collar 6.

Advantageously, this boss creates a stiffening ring around said collar 6 tending to limit the deformation movements between the collar 6 and the half-shell 2A on which the latter is welded.

More particularly, this boss makes it possible, on the one hand, to deport the movements of the stresses undergone by the thermally affected zone to the outside of the latter and, on the other hand, to increase the rigidity of this zone.

Preferably the first boss or first recess is at a distance beyond one millimeter from the outer edge of the weld bead of the flange 6.

Claims (8)

1. « Dual Phase » or « Complex Phase » gas bottle (1) made of steel, comprising two half shells (2A, 2B) assembled through welding, the one forming the upper portion of said bottle (1) being provided, substantially at its top through welding, with a collar (6) for receiving a gas cut-off valve, characterised in that this half shell (2A) forming the upper portion of the bottle (1) includes at least one deformation (7) in the form of at least one projection or at least one recess surrounding the collar (6) for receiving the gas cut-off valve.
2. Gas bottle (1) according to claim 1, characterised in that the deformation or deformations (7) are located in an area between the collar (6) and the cylindrical portion of the half shell (2A).
3. Gas bottle (1) according to claim 1 or 2, characterised in that the deformation (7) is at a distance of more than one millimetre with respect to the outer edge of the welding seam of the collar (6).
4. Gas bottle (1) according to any of the preceding claims, characterised in that said deformation (7) is formed by deep-drawing.
5. Method for manufacturing such a « Dual Phase » or « Complex Phase » gas bottle made of steel, characterised in that :

   - two half shells are made through deep-drawing, which are assembled through welding in order to form the gas bottle ;

   - a hole is cut at the top, in the form of a dome, of one of the half shells ;

   - a collar for receiving a gas cut-off valve is welded in the hole ;

   - before or after welding, a deformation in the form of at least one projection and/or at least one recess is created in this half shell.
6. Method according to the preceding claim, characterised in that said deformation is brought about during or after deep-drawing of the half shell aimed at forming the upper portion of the bottle.
7. Method according to claim 5, characterised in that said deformation is brought about during or after cutting out the hole in this half shell.
8. Method according to any of claims 5 through 7, characterised in that said deformation is brought about through deep-drawing.

Images