MXPA97002795A

MXPA97002795A - Aluminum manufactured pressure container and method for the manufacture of the mi

Info

Publication number: MXPA97002795A
Application number: MXPA/A/1997/002795A
Authority: MX
Inventors: Boe Einar; Carlsen Hanspaul; Sveinung Haugerud Olav; Stigholgersen
Original assignee: Norsk Hydro As
Priority date: 1994-10-19
Filing date: 1997-04-17
Publication date: 1998-02-01

Abstract

A pressure vessel made of aluminum is described for the transport and storage of fluids. The container comprises two forged parts (2), mainly hemispherical, which are joined together along its periphery by means of plasma welding. Each hemispherical part is provided with a shoulder or flange (4) that is formed under the forging operation, one or both of the flanges can be provided with holes (5) from side to side, which have internal threads for coupling a valve / valves aéste. In addition, one or both of the flanges may be equipped with external threads for the coupling of protective caps (8) or a protective cap and a support leg.

Description

PRESSURE CONTAINER MADE OF ALUMINUM AND METHOD FOR THE MANUFACTURE OF THE SAME DESCRIPTION OF THE INVENTION The present invention relates to a pressure vessel made of aluminum, and a method for manufacturing such a vessel. It has been previously known to produce aluminum pressure vessels that involve extruded, substantially circular profiles that have end caps. The covers can be joined to the profiles by means of welds or threaded connections. The extruded profiles may, due to the extrusion process, be overloaded with longitudinal structural defects in the material.

It is therefore necessary that the profiles be examined by extensive and expensive material tests, to detect possible defects. Another disadvantage is that the extended-shaped containers have relatively low strength and little volume for the shape. In addition, spherical high pressure containers made of steel are known in the art. Such containers can be manufactured when REF: 24554 spherical segments are joined by riveting operations (rivet connections) or, as is more common nowadays, by welding operations. Spherical containers effectively have better strength properties, and at the same time have the largest volume for total weight and surface area. As is known to the inventors, such spherical containers have not yet been manufactured from aluminum. The main reasons for this is that aluminum is not very suitable for welding, since heat cracking can easily occur in the weld zone, followed by reduced strength of the material in this area. Since the costs of materials in relation to aluminum are high, it is necessary to apply a low-cost manufacturing method, to offset the total manufacturing costs when manufacturing aluminum pressure vessels. On the other hand, aluminum is a light weight material relative to steel, and is therefore advantageous for manual handling and transport. According to the invention there is provided a pressure vessel, of aluminum and a method for the manufacture of such a vessel, where the previously known problems are solved, and where the aforementioned advantages are achieved. More precisely, a pressure vessel, made of aluminum, having a good strength, which is able to withstand high pressures compared to its weight, is obtained. The container is simple, inexpensive to manufacture and easy to handle. According to the present invention, the container is characterized in that it consists of two forged mainly hemispherical parts, which are joined along their periphery by means of plasma welding, as described by the construction features in the appended independent claim 1 , or as expressed by the measures or actions in the appended independent claim 5. The dependent claims 2-4 and 5-9 describe advantageous features of the invention. In the subsequent, the invention is described in detail with reference to the drawings, which illustrate the same modalities: Figure 1 is a cross section of a container manufactured, according to the invention, Figure 2 is the right half of a pre-forming tool, Figure 3 is the right half of a finishing forming tool.

As mentioned above, Fig. 1 shows a container 1 according to the invention, where manufacturing has been accomplished. The container consists of two parts 2, forged, hemispherical, made of aluminum and welded (in 3) together on its periphery. Each hemispherical part is provided with a projection or flange 4 having internal holes or diameters 5 from side to side. In relation to each hole, a filling valve 6 and a relief valve 7 are accommodated., respectively. To protect the valves, the protection caps 8 are arranged in relation to each projection or flange, being adapted to the caps to be coupled to the ridges or projections 4 by means of fastening. The purpose of using two valves as shown here is that the container can be used in the collection of outside gas samples. The container can be completely filled, when the gas is filled through the filling valve 6, while the air is evacuated through the valve 7.

The invention, as defined in the claims, is not limited to the mode that includes two valves. The container can have two different applications from those mentioned above, for example it can be used to store propane gas, and then have only one valve to fill and evacuate the gas. With such an application, the lower projection can be used to support a support leg or the like, to support the container under storage and transportation. The two hemispheres 2, as mentioned above, are manufactured by forging (die-forged). The blank can be used to advantageously be cut from an aluminum stud. The manufacturing process for the hemispheres is known: The primordia to be forged are heat treated in a heat treatment furnace at 510 ° C (± 5 ° C) for at least 4 hours.

When the heat treatment has been carried out, preforming of the blanks is carried out in a press comprising a pre-forming tool with an upper tool part 9 and a lower part 10, as shown in figure 2. In this step, the tool is at a temperature of 300-325 ° C and is coated with a lubricant. The forming operation can comprise 1-3 slab beats, depending on the size (capacity) of the press and the dimensions of the primordia. The pre-forming operation forms the primordia - in prefabricated semi-finished products, not rounded, with their outer periphery formed to a final thickness, while the inner shoulder section still has to be subjected to additional forming operations.

A leveling / milling operation is then performed on the semi-finished product, followed by a heat treatment in an oven, as mentioned above, at 510 ° C for at least 4 hours.

The final forging step is carried out at 300-325 ° C with a final forming tool, comprising an upper tool part 11 and a lower part as shown in figure 3. In order to obtain a good material flotation ability in the flange area in the final forging step, the semi-product is placed with its projection section pointing downwards in the final forming tool. With this the material is being bent towards the upper part 11 of the tool, said part comprising a cavity receiving the flange or shoulder of the hemisphere. The final forming operation rounds the hemisphere and forms flange 4 in the middle part of the half part. The final forming operation can advantageously comprise two strokes, applying a lubricant at each slab stroke.

When the final forging operation is completed, the hemispheres are rapidly cooled to room temperature in a water bath. The parts are then machined to their correct dimensions before the welding operation.

As previously mentioned, the container according to the invention is manufactured by welding the two hemispheres to one another at their periphery, by means of plasma welding. See figure 1. It was observed that the use of plasma welding, in combination with a correct flow material, for the material in the container, (base material) results in a welded connection with mechanical characteristics as good as the rest of the container . Advantageously, the container can be made of an alloy of the AIMgSil type (AA6082), and an alloy of the type A1Si5 (AA4043) can be used as the flow material in the welding operation. The A1SÍ5 has a melting point that is lower than that of the AIMgSil, and this feature is of substantial importance to avoid heat cracking in the area near the solidification front (the PMZ zone-partial melting zone). More particularly, when the invention was developed, it was discovered that the aluminum alloy used as the base material in the container, should not contain less than 0.95% by weight of Si, and not less than 0.9% by weight of Mg. In addition, it was discovered that the hydrogen content should not exceed 0.1 ppm, either in the base material or in the flow material (the welding wire). When the welding operation is completed, the containers (spheres) are hardened at approximately 540 ° C for about 4 hours, followed by a sudden cooling in a water bath. In addition, the containers are hardened at approximately 130 ° C for approximately 24 hours, followed by the final work and coating operations.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims

1. A pressure vessel made of aluminum, for the transport and storage of fluids, characterized in that it comprises two forged parts, essentially hemispherical, joined together at its periphery by means of plasma welding.

2. The pressure vessel according to claim 1, characterized in that each hemispherical part is provided with a projection or flange formed by the forging operation.

3. The pressure vessel according to claim 2, characterized in that one or both of the flanges are provided with holes from side to side with the holes for coupling a valve / valves being threaded.

4. The pressure vessel according to claim 2, characterized in that one or both of the flanges are provided with external threads for coupling the protective caps, or a protective cap and a support cap.

5. The method for manufacturing an aluminum container, characterized in that the container is manufactured by joining two hemispherical parts that are forged from circular blanks, the joining of said parts comprising plasma welding along the periphery of the two parts .

6. The method according to claim 5, characterized in that the forging operation of each of the parts comprises two steps, a first step of preforming where the periphery of the blank achieves a final thickness, and which also comprises the formation of a part in projection, central, which serves for a base for the flange, and a second step comprising that in which the periphery is formed into a final shape, for the final curvature, and because the central part is forged to have a final thickness and geometry end under the formation of a flange.

7. The method according to claims 5 and 6, characterized in that the container is made of an AIMgSil alloy.

8. The method according to claim 5, characterized in that a flow material having a melting point lower than that of the base material is added when the welding operation is carried out.

9. The method according to claim 8, characterized in that the flow material consists of an alloy of AlMgSi5.