EP0004240A1 - Apparatus for applying collars to very thick walls - Google Patents

Abstract

1. Installation for making stub tubing in a wall (1) of very great thickness for a pressure vessel, comprising a press and a punch (4) provided at its end with a centering tip (41) and having a cone-shaped widened portion (42) which is connected by a rounded connecting surface in its lower part to the centering tip and in its upper part to a concave portion (43) widening upwards from a diameter practically equal to that of the tubing to be obtained, the installation also containing a tubular anvil (5) having a cylindrical central passage (50) connected to a rounded bearing face of the wall by an annular inner surface (51) with a shape corresponding to that of the tubing to be obtained, characterised in that the surfaces for connecting the cone (42) at its ends have such small radii that these connections practically form a sharp edge, the cone (42) thus being connected directly to the concave portion (43) of the punch (4).

Description

The subject of the invention is improvements to the process and installation for manufacturing standby tubing on a very thick wall, in particular greater than 200 mm.

The invention provides in particular significant improvements to the process and to the installation described in French patent 2,337,600 filed by the same company on January 9, 1976.

Methods have been known for a long time for manufacturing holding tubes on tubes in which the tube is formed by delivery between a punch which is forcefully passed and a tubular matrix against which the tube is applied. In such a process, which is described in particular in French patent 1,033,854 and its addition no. 61,343, the depression of the punch determines a drawing of the metal which causes in the long run the opening of an orifice in the axis of the punch. To promote this opening, an opening is often made in advance, which widens as it is stretched. The metal is compressed between the die and the punch and therefore undergoes a real stamping.

Such processes had been proposed especially for the manufacture of exchanger tubes often made of a metal which is fairly easily deformable and quite thin. It was difficult to imagine that a similar process could be used, without the risk of cracking, for relatively thick steel sheets. In addition, the calculation shows that in this case, it would have been necessary to spend for the insertion of the punch a very large energy which does not make it possible to obtain the presses which one generally has.

Also, when it was imagined to produce tubing by driving a punch on a relatively thick sheet, as described in French patent 1,198,440, it was considered necessary to prepare beforehand by boring a bowl at the location of the tube to be formed so as to reduce the thickness of the metal to be deformed. Such a process was provided for sheets up to a thickness of 100 mm at most. However, the planned bore was relatively expensive to carry out and also presented a risk of weakening of the metal.

The Applicant Company however thought that it could be possible to produce pipes on even thicker sheets without making a prior cavity, thanks to a modification of the sheet deformation process. In fact, in the method described in French patent 2,337,600, the tubing is produced, as in the known methods, by driving a punch into a sheet metal applied against a tubular matrix and in which an opening has been made beforehand. in the axis of the tubing to be produced. However, the punch is provided with a conical surface which, penetrating into the orifice makes it possible to spread downwards, the edges of which have a wider section and / or a reduced thickness. This produces a primer of tubing which has just applied against the internal surface of the anvil. The first conical surface of the punch is then connected by a convex surface to a cylindrical part of diameter substantially equal to that of the tubing to be produced and, when the penetration of the punch is continued, the metal is pinched between the punch and the 'anvil and deformation continues by drawing the metal. Consequently, while in patent 1,033,864, a drawing was essentially carried out of the metal which produced the opening of a central orifice or the enlargement of an orifice made in advance, in the method according to the patent 2,337 .600, first of all, the widening of the orifice is carried out first, and only then the drawing of the metal. As a result, the risk of cracking the edges of the orifice, which is checked, is reduced. although the progressive enlargement and the phase of stretching deformation occurs on a sheet previously thinned by the enlargement of the orifice and therefore requires less effort than that which might be expected.

However, for sheets thicker than 200 mm, the pro _. yielded described in patent 2,337,600, if it makes it possible to obtain a tubing without risk of cracking and weakening of the metal, still requires a very significant driving force which is difficult to obtain with the usable materials habitually. This is why the process according to patent 2,337,600 has been the subject of in-depth studies with the aim of producing pipes in good conditions on very thick sheets without, however, being obliged to use excess powers. sives.

Thus, by studying the metal deformation process better, we have developed an improved process which makes it possible to produce the tubing in better conditions by using a modified punch.

In the present invention, the entire tubing is formed by a progressive and continuous widening of the orifice, caused by the sinking: of the punch whose active part has a substantially conical shape, the metal being only subjected to a circular traction without compression between the punch and the anvil, the part to be deformed of the sheet extending in overhang from the bearing face of the anvil during the entire formation of the tubing and does not being able to come to bear on the internal wall of the anvil only at the end of the insertion of the punch, the tubing being at this time completely formed.

In the installation for implementing the perfected process, according to the invention, the flared part of the punch has a substantially conical shape up to a diameter equal to that of the inside of the tubing to be obtained, said part conical connecting by a rounded edge of small radius of curvature to a concave O-ring part of identical section to the internal section of the tubing obtained by widening the orifice during the insertion of the conical part.

It has already been indicated that an essential originality of patent 2,337. 600 consisted in carrying out the widening of the orifice in a first phase by driving in a conical part of the punch before the stretching phase allowing the desired length of tubing to be obtained whereas, in the methods known previously, the widening of the orifice was a consequence of the stretching phase. During the studies carried out for the development of this process, it was noted that the first phase of ^the enlargement of the orifice required a much lower power than in the second phase where the metal is compressed between the punch and the ori _- fice. To reduce the press power required, we therefore sought to increase the importance of the enlargement phase of the orifice. However, until now, we thought it necessary to make relatively long tubing therefore requiring drawing of the metal. Maison noted that by only carrying out an enlargement of the orifice, by a part of the recess with conical of the punch, / thinning of the sheet produced in the enlarged part alone made it possible to obtain practically a suitable shape. Consequently, instead of producing the tubing by compression between a punch and a die having respectively the internal section and the external section of the tubing to be obtained, it was possible to produce the tubing on a sheet which, during the entire formation process , stretched cantilevered from the bearing face arrording the anvil, 18 internal section thereof and the external section of the punch practically not involved in the formation of the tubing.

It should be noted, however, that after the formation of the tubing by widening the orifice, it is useful to continue the insertion of the punch over a short distance so as to properly apply the walls of the tubing against the internal wall of the 'anvil and a flared part of the punch extending the conical part. But this operation is carried out without any real work of compressing the metal and is more like a template to be sure of the centering of the orifice of the tubing. Consequently, the internal part of the anvil and the concave toric part extending the conical part of the punch have a shape which corresponds to that which is obtained by the widening of the orifice alone and which can be reduced empirically determined in particular by tests on models. On the contrary, in the preceding processes, the shape of the tubing which one desired to obtain was chosen in advance and the metal was given the desired shape by compression between the punch and the die.

• - la figure 1 représente schématiquement une installation pour la mise en oeuvre de l'invention,
• - la figure 2 est une vue de détail, à échelle agrandie, de la tôle et du poinçon mis en place avant la formation de la tubulure,
• - les figures 3 et 4 représentent schématiquement la phase de déformation monodimensionnelle avec enfoncement de la tôle, effectuée à l'aide de la partie conique du poinçon,
• - la figure 5 représente schématiquement la phase de mise en forme finale sans compression, ni amincissement, effectuée à l'aide de la partie du poinçon galbée et s'évasant vers le haut.

The invention will be better understood with the aid of the following description, with reference to the appended drawings in which:

• FIG. 1 diagrammatically represents an installation for implementing the invention,
• FIG. 2 is a detail view, on an enlarged scale, of the sheet and the punch put in place before the formation of the tubing,
• FIGS. 3 and 4 schematically represent the phase of one-dimensional deformation with penetration of the sheet, carried out using the conical part of the punch,
• - Figure 5 shows schematically the final shaping phase without compression or thinning, performed using the part of the curved punch and flares up.

In Figure 1, there is shown schematically the wall 1 on which the tubing must be formed. In the example shown, this wall may be a sheet in the form of a cylindrical sector or a spherical cap.

In the axis xx 'of the tube to be obtained, a hole 2 is first produced by machining, the diameter of which can advantageously be of the order of the thickness of the wall.

The wall 1 thus machined is placed in the axis of a press 3 provided with a vertically movable punch 4 and an enclosure 5.

.Le conduit 50 est suivi d'une portion supérieure 51 s'évasant progressivement vers le haut et dont la section est déterminée de telle sorte que le métal ne vienne s'y appuyer qu'à la fin de la formation de la tubulure par élargissement de l'orifice.The anvil 5 is tubular and is provided with a cylindrical central duct 50 whose diameter corresponds substantially to the outside diameter of the

The duct 50 is followed by an upper portion 51 which widens progressively upwards and whose cross section is determined so that the metal does not come to bear thereon until the end of the formation of the tubing by widening. of the orifice.

The punch 4 has a special shape. It comprises at its lower end a centering point 41 whose diameter is slightly less than that of the orifice 2. This centering point with substantially cylindrical wall is followed by a first conical surface 42 open upwards, itself followed by a concave toroidal part 43 which widens upwards, and whose cross section corresponds to that of the internal part of the tubing obtained at the end of the insertion of the conical part 42. The conical part 42 is connected to the concave part 43 by a rounded edge 44 of small radius of curvature.

According to the invention, the press 3 forcibly penetrates the punch 4 into the orifice 2. Previously, gold has heated the wall 1 on a part 13 surrounding the orifice and of a diameter D greater than the outside diameter of the tubing to obtain, up to a temperature making it possible to exceed the transformation point A ₃ , but remaining below the usual forging temperatures.

Indeed, the heating of a metal, if it is not accompanied by a deformation thereof, causes a magnification of the grains which gives said metal poor ductility. On the other hand, it is necessary to avoid heating the surrounding which is not subjected to deformation, so as not to cause deterioration, by magnification of the grain, of the metal surrounding the protuberance which one wishes to create. The above defined temperature solves this problem. In fact, in the method according to the invention, there is no real forging of the metal since there is no compression between the punch and the die. We can therefore be satisfied with a lower temperature simply allowing the deformation of the metal. The usual forging temperatures being of the order of 1200 to 1300 ° C, and the transformation point A ₃ of the order of 950 ° C, a heating temperature of 1000 to 1100 ° C will prove satisfactory in to prevent damage and tears.

When the punch 4 descends vertically, the point 41 first enters the orifice 2 and ensures the centering of the punch along the axis xx 'of the orifice: this is the position shown diagrammatically in FIG. 2.

As can be seen in FIGS. 3 and 4, the conical surface 42 then comes to bear on the upper edge of the orifice and tends to widen the diameter of the latter and at the same time to spread down the part of the metal surrounding the orifice and driven by the movement of the punch. Indeed, the half-angle at the top of the cone 42 can. be between 30 and. 45 °. The thrust exerted on the punch can therefore result in a simple widening of the orifice, the wall of which decreases in thickness as the diameter increases. During this operation, the metal is subjected, at each point, only to a one-dimensional circular traction, with depression. The radius of the orifice increasing and the mass being constant, the thickness of the sheet decreases and there is therefore, as indicated in the figures, a thinning of the sheet resulting from the circular traction exerted and which promotes the downward spacing of the metal entrained by the movement of the punch.

In previously known methods, the main aim was to draw the compressed metal between the punch and the die, and the widening of the orifice was only a consequence of this action.

On the other hand, in patent 2,337,600, we first sought to achieve an enlargement of the orifice at least in a first phase of the deformation process. However, the essential originality of the process according to the present invention resides in the fact that the entire formation of the tubing is obtained by the sole widening of the orifice and the spacing downwards of the edges thereof following the displacement of the punch. Indeed, the conical part of it is extended practically to the diameter of the tubing to be obtained, and the internal toric face of the anvil has a section which does not correspond to a shape which one would like to impose on the metal. , but on the contrary to the form which the tubing naturally takes following the widening of the orifice and which could be determined empirically for example by tests on models. Therefore, until the end of the tubing formation phase, the metal does not come to bear on the internal wall of the anvil and is therefore not compressed between it and the punch. This results in a very significant reduction in the pushing force required and this explains why it was possible to produce pipes on walls of thickness greater than 200 mm by exerting a relatively small pushing force, of the order of 3,000 to 5,000 tonnes, whereas with the previously known methods and operating by compression of the metal between a punch and a die, it would have been necessary to use a much higher force, of the order of 20,000 tonnes , to achieve the same result.

When the conical part 42 has ceased to act, the tubing is practically formed, but may not be perfectly centered. However, this is important for making the connection with the pipe that extends the tubing without difficulty. This is why the conical part 42 is connected, by means of a rounded edge of small radius of curvature to a false part 40 of the punch which has a concave toroidal shape of identical section to the internal section of the tubing obtained by widening the orifice Fending the depression of the conical part. A small vertical displacement of the punch, without notable effort, makes it possible to give the tubing the exact profile sought and possibly to eliminate localized irregularities. However, this second phase is a simple layout and cannot be confused with unmatriisation because there is no compression of the sheet, the thickness of the tubing no longer varying. This is why, the effort of 3,000 to 5,000 tonnes which has been indicated above is more than sufficient to carry out this setting operation while a much greater effort would have been necessary to effect true compression. Thus, thanks to the improvement according to the invention, it is possible to produce a tubing birth in a very thick sheet, for example greater than 200 mm, by exerting a relatively small press force, of the order of 3,000 to 5,000 tonnes. On the other hand, tests have shown that the process, thanks to the precautions taken, made it possible to obtain tubing under excellent safety conditions.

The embodiment which has just been described is applicable for walls in the form of a cylindrical sector or for spherical caps.

As the installation used differs essentially from that which was described in patent 2,337,600 by the shape given to the punch and the anvil, the means described in the previous patent will also make it possible to produce orifices in various positions, the wall being placed so that the axis of the orifice is vertical and coincides with the axis of the anvil.

The invention finds its use in the field of metallurgy and more particularly in the manufacture of components of tube-holder ferrules for nuclear reactor vessels or for steam generators. However, the invention is obviously not limited to this application and also covers other embodiments which would differ from those which have been described only by variants or by the use of equivalent means.

In particular, it was indicated that the conical part of the punch could have a half-angle at the top between 30 and 45 ° because it is in this case that the best result will be obtained. However, the choice of the opening angle will depend essentially on the desired result, that is to say as gradual widening as possible of the section of the orifice and of the means available, and in particular of the press height which can dispose.

Likewise, the heating temperatures have been indicated as an indication for the usual steels but could obviously be modified as a function of the characteristics of the metal constituting the wall on which the pipe is to be made.

Claims (5)

1.- Method of manufacturing a waiting tube on a very thick wall in which, after having produced an orifice centered on the axis of the tube to be obtained and heated the part of the sheet metal surrounding the orifice, the wall is deformed by means of a press by force penetration into the orifice of a punch, the cross section of which gradually widens from a centering point to a diameter at least equal to the internal diameter of the tubing to be obtained, the sheet being placed during the operation on a tubular anvil provided with a rounded bearing face, characterized in that the formation of the entire tubing is carried out by a progressive and continuous widening of the orifice, caused by the depression of the punch, the active part of which has a substantially conical shape, the metal being only subjected to a circular traction without compression between the punch and the anvil, the part to be deformed of the sheet extending cantilevered from the f ace of support of the anvil during all the formation of the tubing and being able to come to bear on the internal wall of the anvil only at the end of the insertion of the punch, the tubing being at this time completely formed . ₁ 2.- A method of manufacturing tubing according to claim 1, characterized in that after the formation of the tubing by widening the orifice, a re-centering and a finishing of the tubing formed between a flared part of the extending punch is carried out the conical part and the bearing face of the anvil, without metal compression work. 3.- A method of manufacturing tubing according to claim 1, characterized in that before the insertion of the punch, the sheet is heated on a circular surface of radius greater than that of the base of the tubing to be obtained until a temperature higher than that of the transformation point A ₃ and lower than the forging temperature. 4. Installation for manufacturing tubing for implementing the method according to one of the preceding claims, comprising a press, an anvil of tubular shape and a punch provided at its end with a centering point extended by a part whose section widens progressively, characterized in that the flared part 42 of the punch has a substantially conical shape until to a diameter equal to that of the interior of the tubing to be obtained, said conical part 42 connecting by a rounded edge 44 of small radius of curvature to a concave toric part 43 of section identical to the internal section of the tubing obtained by widening of the orifice during the insertion of the conical part. 5. Installation for manufacturing tubing according to claim 4, characterized in that the conical part 42 has a half-angle at the apex between 45 ° and 30 °.

Images