EP0004240B1 - Apparatus for applying collars to very thick walls - Google Patents

Description

The subject of the invention is an 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 1 033 864 and its addition No. 61 343, the depression of the punch determines a drawing of the metal which causes in the long term the opening of an orifice in the axis of the punch. To facilitate this opening, an opening is often made in advance, which widens as the drawing progresses. 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 has been imagined to produce pipes by pressing a punch on a relatively thick sheet, as described in French patent 1 198 440, it was considered that it was necessary to spare beforehand bore a cup at the location of the tubing 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 anvil and in which a prior arrangement has been made. orifice in the axis of the tubing to be produced. However, the punch is provided with a conical surface which, penetrating into the orifice allows the edges of the latter to be drawn down, the cross section of which widens and the thickness of which decreases. This produces a primer of tubing which is applied against the internal surface of the anvil. The first conical surface of the punch is then connected by a convex connection surface to a cylindrical part of diameter substantially equal to that of the tubing to be produced and which is itself followed by a concave part which widens upwards; thus, when one continues the penetration of the punch, the metal is pinched between the punch and the anvil and the deformation continues by drawing the metal. Consequently, while in the 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 opening is carried out first and only then the drawing of the metal, in this way, the risks of cracking of the edges of the opening are reduced, the control of which is well controlled. 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 of thickness greater than 200 mm, the method described in patent 2,337,600, if it allows tubing to be obtained without risk of cracking and weakening of the metal, still requires a driving force. very important that it is difficult to obtain with the materials usually usable. This is why the method 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 excessive powers.

Thus by better studying the metal deformation process, we have developed an improved installation which allows the tubing to be produced in better conditions by the use of 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, 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 in cantilever from the bearing face of the anvil during the entire formation of the tubing and being unable to come to rest on the internal wall of the anvil at the end of the insertion of the punch, the tubing being at this time completely formed.

To this end, in the improved installation according to the invention, the connecting radii of the conical part at its ends are chosen so small that these connections form practically a sharp angle, the cone is rac thus stringing directly to the concave part of the punch.

In addition, the conical part of the punch extends to a diameter practically equal to that of the tubing to be obtained.

According to a preferred characteristic, the concave part of the punch has a concave toroidal section corresponding to the shape naturally taken by the internal surface of the tubing obtained only by the widening of the orifice and the spacing downwards of the edges of it Ci, consecutive to the depression of the conical part of the punch. ,

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 making it possible to obtain the length of tubing sought while in previously known methods, 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 found that the first phase of enlargement of the orifice required a much lower power than in the second phase where the metal is compressed between the punch and the orifice. To reduce the press power required, we therefore sought to increase the importance of the enlargement phase of the orifice. However, until now, it was believed necessary to produce relatively long tubes therefore requiring drawing of the metal. However, it has been found that by making only an enlargement of the orifice, by a conical part of the punch, the depression with 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 , extended in cantilever from the rounded support face to the anvil, the internal section thereof and the external section of the punch practically involved in the formation of the tubing.

It should be noted, however, that after the tubing has been formed by widening the orifice, it is useful to continue pushing 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. However, 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 obtained by the widening of the orifice alone and which can be determined empirically in particular by tests on scale models. On the contrary, in the preceding methods, 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 accompanying drawings in which:

• FIG. 1 schematically represents an installation for implementing the invention,
• FIG. 2 is a detailed 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,
• FIG. 5 schematically represents the final shaping phase without compression or thinning, carried out using the part of the curved punch and widening upwards.

In Figure 1, there is shown schematically the wall 1 on which must be formed the tubing. 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 anvil 5.

The anvil 5 is tubular and is provided with a cylindrical central duct 50 whose diameter corresponds substantially to the outside diameter of the tubing to be obtained. 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, the wall 1 was heated on a part 13 surrounding the orifice and of a diameter D greater than the outside diameter of the tubing to be obtained, 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 of it, pro there is an enlargement 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 it is desired 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 1,200 to 1,300 ° C, and the transformation point A ₃ of the order of 950 ° C, a heating temperature of 1,000 to 1,100 ° C will prove satisfactory. helping 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 hole 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 displacement of the punch.

In the 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 tubes on walls of thickness greater than 200 mm by exerting a relatively small pushing force, of the order of 29,430 to 49,050 kN (3,000 to 5,000 tonnes), whereas with the previously known methods and operating by compressing the metal between a punch and a die, much more effort should have been used high, around 196,200 kN (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 flared part 43 of the punch which has a concave toroidal shape of identical section to the internal section of the tubing obtained by widening of the orifice during the insertion of the conical part. A small vertical displacement of the punch, without notable effort, makes it possible to give the tubing the exact desired profile and possibly to eliminate localized irregularities. However, this second phase is a simple layout and cannot be confused with a stamping because there is no compression of the sheet, the thickness of the tubing no longer varying. This is why, the effort of 29,430 to 49,050 kN (3,000 to 5,000 tonnes) which has been indicated above is more than sufficient to carry out this setting operation while a much higher effort would have been necessary to perform true compression. Thus, thanks to the improvement according to the invention, it is possible to produce a tubing opening in a sheet of very thick, for example greater than 200 mm, by exerting a relatively small press force, of the order of 29,430 to 49050 kN (3000 to 5000 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 in 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 hole 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 essentially depend 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. that we can have.

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

Claims (3)

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).

2. Installation for making stub tubing according to Claim 1, characterised in that the concave portion (43) of the punch (4) has a concave annular cross-section corresponding to the shape assumed naturally by the inner surface of the tubing obtained solely as a result of the widening of the orifice and the downward separation of the edges of the latter following the penetration of the conical portion (42) of the punch (4).

3. Installation for making stub tubing according to one of Claims 1 and 2, characterised in that the conical portion (42) has a half-angle at the vertex of between 45° and 30°.

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