GB2153278A

GB2153278A - Process for making an annular flange on the bottom of a rotationally symmetrical vessel

Info

Publication number: GB2153278A
Application number: GB08427493A
Authority: GB
Inventors: Jacques Daubresse; Gilbert Lhuillery; Michel Pitavy
Original assignee: Luchaire SA Ste; Vallourec SA Ste; Luchaire SA; Vallourec SA
Current assignee: Luchaire SA Ste; Vallourec SA Ste; Luchaire SA; Vallourec SA
Priority date: 1984-02-02
Filing date: 1984-10-31
Publication date: 1985-08-21
Also published as: IT1184860B; JPH0685945B2; IT8519275A0; JPS60187433A; DE3423146C2; ES8607769A1; GB2153278B; ES540095A0; FR2559078A1; GB8427493D0; DE3423146A1; FR2559078B1

Abstract

The process comprises mounting a vessel 1 on a rotationally symmetrical mandrel 2 whose front end 5 is in contact with the bottom of the vessel 4, causing the bottom of the vessel to bear against the mandrel by means of a counteracting member 7, with the side wall of the counteracting member 7 being so dimensioned as to support and profile the inside wall of the flange. A part of the metal forming the side wall of the vessel in the annular region adjacent to the bottom is displaced by being rolled in the direction of the counteracting member 7 so as to form the annular flange 18, by means of rollers 8, 9. The operation may be carried out in one or more successive rolling passes. The vessel produced has excellent mechanical characteristics in its connecting region, and can be used for producing propulsion unit casings. <IMAGE>

Description

SPECIFICATION Process for making an annular flange on the bottom of a rotationally symmetrical vessel The invention concerns a process for making a one-piece rotationally symmetrical metal vessel comprising a thick bottom, the bottom being surrounded by an annular rotationally symmetrical flange which forms an integral part of the vessel and which is disposed substantially in alignment with the side wall thereof. Such a flange generally performs the function of a connecting member and is required to enjoy a very high level of mechanical strength.

That is the case in particular when the process according to the invention is used for producing a propulsion unit casing.

It is known for thick-wall vessels to be produced by forging or pressing, in a hot condition or in a cold condition, wherein the bottom of the vessel may comprise a flange which is formed by forging or pressing.

However, it is difficult to produce such vessels comprising a relatively thick bottom, relatively thin walls and a high ratio of height over diameter.

European application No 51121 describes a method of arriving at such a result, which comprises making use of a forged blank in which the side walls are then elongated by rotary extrusion, using particular means for combatting a tendency to go off-centre. However, performance of the successive operations referred to above is very delicate, as can be clearly seen from the above-identified document, and it is very difficult to produce high-quality products which are of optimum dimensional and mechanical characteristics, under acceptable economic conditions.

The attempt has therefore been made to move away from the usual methods, by making vessels comprising bottoms which are produced in a different way, with the disadvantage that the flange cannot be produced simultaneously.

It is of course known for a flange to be added to the bottom of a metal vessel, by a suitable fixing means such as screwing, welding, brazing, shrink fitting or the like. However, the connecting region between the flange and the vessel remains a weak point and, in order to have a satisfactory strength level, it is then necessary to reinforce the connecting region, which throws fresh doubts on the economy of the whole of the arrangement.

Attempts have therefore been made to find a way of forming a rotationally symmetrical flange which surrounds the bottom of a onepiece vessel and forms an integral part thereof.

More particularly, an attempt has been made to find a way of forming a flange around the bottom of a vessel, said bottom itself having been previously formed by displacing the thick wall of a tube at one of the ends thereof.

The process according to the invention comprises mounting a one-piece rotationally symmetrical metal vessel on a rotationally symmetrical mandrel which is driven in rotation by a drive means, the front end of said mandrel being in contact with the bottom of the vessel over the entire inside surface thereof and the side wall of the mandrel being in contact with the side wall of the vessel over the inside surface thereof, with a slight or substantially zero clearance. A rotationally symmetrical counteracting member which is coaxial with the mandrel comprises a front surface which covers a part of the outside surface of the bottom of the vessel. The counteracting member applies an axial thrust force against the bottom of the vessel in the direction of the mandrel. It is free to rotate and is therefore driven in rotation with the vessel by the mandrel.The side wall of the counteracting member is of a maximum diameter that is smaller than the outside diameter of the vessel and is so dimensioned as to support and guide the inside wall of the flange during the phase of forming same. A part of the metal which forms the side wall of the vessel, in the annular region adjoining the bottom thereof, is displaced by being pushed back towards the counteracting member so as to form a rasied annular portion which, at the counteracting member side, extends the side wall of the vessel and moves into a position of at least partially covering the side wall of the counteracting member.

The metal is preferably displaced by means of at least one rotationally symmetrical wheel or roller, which is free to rotate about its axis, which rolls on the outside surface of the wall of the vessel in the connecting region between the bottom and the side wall, applying a sufficient pressure to displace the metal.

Preferably also, one or more wheels is used, each thereof being mounted on a wheel carrier head which is movable at least with a translatory movement in two perpendicular axes, the movements of each of said heads being produced by means of a numerical actuating apparatus or a controlled numerical actuating apparatus.

When a plurality of wheels is used, they are distributed about the axis of rotation of the vessel.

The operation of displacing the metal may be carried out, as required, in one or more successive passes.

Depending on the mechanical characteristics of the metal or the alloy forming the vessel, the operation of displacing the metal for forming the flange is effected in a cold condition or in a hot condition.

After the flange has been formed, the operation of rotary extrusion of the side wall of the vessel can be carried out, in the hot condition or in the cold condition, for the purpose of elongating the side wall or reducing its thickness.

The invention also concerns the vessels comprising flanges formed by displacement of the metal from the wall thereof; the invention also concerns vessels with a bottom produced by displacement of the material thereof, such vessels being provided with such flanges.

In a particularly advantageous aspect, the invention also concerns use of the process for producing propulsion unit casings.

The following detailed description and drawings permit the features of the process and the product according to the invention to be understood, without limiting the invention.

Figure 1 shows a view in cross-section of a one-piece rotationally symmetrical metal vessel mounted on a mandrel for the operation of forming a flange, Figure 2 shows the beginning of the operation of forming the flange around the bottom of the vessel in Fig. 1, and Figure 3 shows the end of the operation of forming the flange.

Figs. 1 to 3 are diagrammatic views of one method of carrying into effect the process for forming a flange in accordance with the invention.

The thick-walled one-piece rotationally symmetrical metal vessel 1 shown in cross-section is mounted on a mandrel 2 which is driven in rotation about its axis 3 by a means not shown. The bottom 4 of the vessel is applied against the front end 5 of the mandrel 2 over the entire surface thereof. The side wall 6 of the mandrel, which is cylindrical in these drawings, is covered with a slight or substantially zero clearance, by the side wall 14 of the vessel.

A rotationally symmetrical counteracting member 7 which is mounted for free rotary movement about the common axis 3 is applied against the bottom of the vessel. The counteracting member 7 applies a thrust force as indicated by the arrow F which presses the bottom 4 of the vessel against the front end 5 of the mandrel. Two rollers or wheels 8, 9 which are mounted for free rotary movement about axes 10 and 11 are disposed on respective sides of the mandrel. Each wheel is carried by a movable head (not shown) which is displaced with a translatory movement in a plane defined by two perpendicular axes X and Y, which plane is substantially parallel to the axis 3 of the mandrel.The heads may also be movable with a rotary movement about themselves about an axis that is substantially perpendicular to the plane XY, so as to vary the angle between the axes 10 and 11 of the wheels 8 and 9 and the axis 3 of the mandrel.

By means of a known controlled numerical actuating apparatus, the wheels 8 and 9 are displaced by the heads along the outside wall of the vessel in the region for forming the flange and roll against that wall with a rotary movement, applying thereto a given pressure which causes the metal to be displaced along the generatrix of the wall.

The wheels 8 and 9 follow a helicoidal path along the outside wall 12 of the bottom of the vessel, from the region 13 at which the bottom is connected to the side wall 14, in the direction of the side wall 15 of the counteracting member 7. The front surface 16 of the counteracting member 7 is firmly applied against the bottom 4 whose shape it matches.

The side wall 15 of the counteracting member 7 is so designed as to serve as a support for the inside wall of the flange during the formation thereof.

It will be appreciated, that under the aboveindicated conditions, the metal that is entrained by the wheels 8 and 9 gradually forms a bead or rim portion which goes into a position of at least partially covering the side wall 15 of the counteracting member 7.

In the case of hard metals or alloys such as steel, this operation is to be carried out in the hot condition. It is therefore necessary to provide on the one hand, heating means which raise at least the region to be worked by the wheels 8 and 9 to the desired temperature, and on the other hand, means for holding that temperature for the period of time required for the operation of forming the flange. For that purpose, it is possible to use high frequency heating or heating using torches or heating by any other means.

In the case of steels for example of the composition 32 CD4 (French standard), it is possible to heat the steel to temperatures of the order of for example 850 to 900 C.

Fig. 2 shows the beginning of the operation of forming the flange, with the formation of an annular rim portion 17, while Fig. 3 shows the flange 18 in the course of being finished.

In the three drawings, the axes 10 and 11 of the wheels 8 and 9 are shown substantially parallel to the axis 3. In fact, it may be advantageous for them to be at a variable angle of incidence with respect to the axis 3 in the course of the successive passes carried out by the wheels. The position of the wheels along the axis 3 is generally such that they are displaced relative to each other. As stated above, the number of wheels may vary from one to two or three or even more. The controlled numerical actuating apparatus makes it possible to produce the movement of the wheels, in general by means of successive passes in a perfectly controlled fashion, which makes it possible to produce flanges whose dimensional characteristics are perfectly reproducible.

After the flange has been formed, it is possible if necessary to carry out a local or general heat treatment on the vessel. It is also possible to provide for machining of the outside surface and/or the inside surface of the vessel so as to remove any surface defects and increase dimensional accuracy.

It is finally possible to carry out a rotary extrusion operation, in the hot condition or the cold condition, with respect to the lateral wall 14 of the vessel in order to elongate it or to reduce its thickness. It is also possible to form an aperture in the bottom of the vessel, most frequency in the vicinity of the axis.

The process according to the invention is suitable for producing vessels for many uses and more particularly for producing propulsion unit casings. Many alternative embodiments are possible, without departing from the scope of the invention.

Claims

1. A process for forming an annular flange around the bottom of a one-piece rotationally symmetrical metal vessel, characterised: (i) in that said vessel is mounted on a rotationally symmetrical mandrel which is driven in rotation by a drive means, the front end of said mandrel being in contact with the bottom of the vessel over the whole of the inside surface thereof with a small or substantially zero clearance;; (ii) in that the bottom of the vessel is caused to bear against the mandrel by means of a rotationally symmetric counteracting member which is coaxial with the mandrel and the front surface of which covers a part of the outside surface of the bottom of the vessel, said counteracting member applying an axial thrust force in the direction of the mandrel, the side wall of the counteracting member having a maximum diameter which is smaller than the outside diameter of the vessel and being so dimentioned as to support and to shape the inside wall of the flange in the formation thereof; and (iii) in that a part of the metal which constitutes the side wall of the vesssl in the annular region adjoining the bottom is displaced by a pushing operation in the direction of the counteracting member so as to form a raised annular portion which, on the side of the counteracting member, extends the side wall of the vessel and assumes a position at least partially covering the side wall of the counteracting member.

2. A process according to claim 1 characterised in that the metal is displaced by means of at least one rotationally symmetrical wheel, being free to rotate about its axis, which rolls on the outside surface of the wall of the vessel in the connecting region between the bottom and the side wall, applying a sufficient pressure to displace the metal.

3. A process according to claim 2 characterised in that at least one wheel is mounted on a wheel carrier head that is movable at least with a translatory movement along two perpendicular axes, the movements of said head being produced by means of a numerical control apparatus.

4. A process according to claim 2 or claim 3 characterised by using at least two wheels which are each mounted on a wheel carrier head and which are distributed around the axis of rotation of the vessel.

5. A process according to one of claims 1 to 4 characterised in that the metal displacing operation is carried out in the hot condition or in the cold condition.

6. A process according to one of claims 1 to 5 characterised in that the metal displacing operation is carried out in one or more successive passes.

7. A one-piece rotationally symmetrical metal vessel characterised in that it comprises a flange formed by an annular coaxial raised portion which extends the side wall at the bottom end of the vessel and which is formed by metal that is displaced from said wall.

8. A vessel according to claim 7 characterised in that the bottom thereof is a bottom formed by displacement of the metal of the vessel.

9. A vessel according to claim 7 or claim 8 characterised in that it comprises a side wall which has been reduced in thickness by rotary extrusion.

10. Use of the process according to one of claims 1 to 6 for producing a propulsion unit casing.