EP1840230B1 - One-piece calibration method for crankcase tempering, device for implementing the method - Google Patents

Description

The present invention relates to the field of metallurgy and aims to calibrate cylindrical parts formed by rolling.

Manufactured in the field of turbomachines cylindrical parts in one piece to form including compressor housings or blade retention casings. This type of piece which can be of large size and weight is made by rolling an alloy billet adapted to its destination. The rolling is followed by a hot heat treatment in order to improve the mechanical properties by relaxing the internal stresses produced by the plastic deformation forces of the material. In addition to this treatment, a calibration operation is required because of the low tolerances on the dimensions especially internal for this type of part.

Currently, it is carried out, before the heat treatment step, by expansion by acting on the inner surface by means of an apparatus, said expander, provided with appropriate pushing means actuated generally hydraulically. However, it is noted that the geometry of the part is likely to change further during the heat treatment, and a new cold calibration is often necessary. It has been proposed to form the part with an excess thickness capable of absorbing the difference in dimension, but such a solution is not satisfactory, especially for an aviation turbomachine because of the increase in the weight of material engaged.

EP 0553154 describes a method according to which the forming tool is extracted when the temperature of the part has dropped beyond a martensitic transformation threshold resulting in an increase in its inside diameter.

The applicant has set himself the objective of developing a new method of calibrating a cylindrical part obtained by plastic deformation of material, more economical, by reducing the number of operations and by developing a tool of less complex structure and less expensive to make.

The invention results from the observation that has been made concerning certain alloys, including ZSCNU17 steel, which have the property of having a maximum structural shrinkage at a temperature between the heat-treating temperature and the ambient temperature. The material during the cooling phase contracts to this temperature and then expands when the room temperature is brought back to room temperature.

• mise en place de la pièce dans un four vertical, l'axe de la pièce étant vertical,
• positionnement d'un outil de calibrage interne de diamètre supérieur à celui du retrait structural maximum de la pièce, au droit de la pièce en dehors du four, l'axe de l'outil de calibrage étant aligné avec celui de la pièce,
• fermeture du four,
• chauffage de la pièce dans le four jusqu'à une première température,
• ouverture du four,
• descente et mise en place, à l'intérieur de la pièce, de l'outil de calibrage,
• transport de l'ensemble formé par la pièce et l'outil de calibrage jusqu'à une cuve de trempe,
• refroidissement de la pièce jusqu'à une température inférieure à ladite deuxième température,
• extraction de l'outil de calibrage interne.

The method of the invention for calibrating a cylindrical part after forming by rolling of a metallic material having a shrinkage maximum structural temperature at a maximum shrinkage temperature between a first temperature, such as a heat-treating temperature and a second temperature such as ambient temperature, is characterized in that it comprises the following successive steps:

• placing the workpiece in a vertical furnace, the axis of the workpiece being vertical,
• positioning an internal calibration tool with a diameter greater than that of the maximum structural shrinkage of the part, to the right of the part outside the furnace, the axis of the calibration tool being aligned with that of the part,
• closing the oven,
• heating the room in the oven to a first temperature,
• oven opening,
• lowering and placing the calibration tool inside the workpiece,
• transporting the assembly formed by the workpiece and the calibration tool to a quenching tank,
• cooling the room to a temperature below said second temperature,
• extraction of the internal calibration tool.

Thus, by the method of the invention, this property of the material is used to perform the calibration of the part during the quenching phase after the heat treatment, which simplifies the workpiece processing operations. In addition the calibration tool can be a simple ring of appropriate outside diameter without articulated or mechanized element.

Practically, the piece is placed in an oven and heated to its first temperature, which advantageously is its heat treatment temperature; then said calibration tool is placed on the workpiece and the assembly is placed in a quenching tank where the workpiece is cooled to said lower temperature which tends to ambient temperature.

However, although the process is advantageously applied by being associated with the heat treatment and quenching of the workpiece after its rolling production, it can be implemented whenever the material has a maximum withdrawal temperature between a first temperature and a second temperature, the first being higher than the second.

The invention also relates to a particular device for an advantageous implementation of the method. This comprises a dummy with a frame provided with articulated radial arms forming the workpiece supports, a coupling means of the dummy, the calibration tool being suspended by cables or other means equivalent to said attachment means. The hooking means of the dummy is removable, between a position where it is secured by a rod to the dummy and a position where the mannequin suspended by means of attachment by cables or other equivalent means.

• les figures 1 à 5 montrent les différentes étapes du procédé de l'invention selon une première mise en oeuvre;
• les figures 6 à 18 montrent les différentes étapes du procédé selon une autre mise en oeuvre particulièrement avantageuse.

A non-limiting embodiment of the method of the invention will now be described with reference to the drawings in which,

• the Figures 1 to 5 show the different steps of the method of the invention according to a first implementation;
• the Figures 6 to 18 show the different steps of the process according to another particularly advantageous embodiment.

The process is described by detailing the different phases. The part to be calibrated may be a turbomachine casing such as an intermediate casing, a compressor casing or a retention casing which comprises a cylindrical portion formed by plastic deformation of a metallic material such as Z5CNU17 steel. The latter has the property of having a maximum structural shrinkage between 200 and 300 ° C.

On the Figures 1 to 5 the unwinding of a first embodiment of the method of the invention is represented. We see the cylindrical part 1, a housing for example, in vertical support by an edge on a support 3 suspended from a cable allowing its movement by a suitable hoist. The figure 2 shows the part 1 transported with its support 3 in a furnace 5 equipped with a table 7 on which the set piece and support. During its stay in the oven, the part is subjected to a heat treatment at a selected temperature, for example in the case of a turbomachine casing of said steel, at 1000 ° C for a predetermined period; the piece is then in the dilated state. On the figure 3 it can be seen that a calibrating tool 8 of cylindrical shape has also been placed inside the part. This tool is cold, its external profile is identical to the internal profile of the part 1, and its external dimensions are slightly greater than those of the inner surface of the part 1, when it is at its maximum structural shrinkage temperature.

The support is then hooked to a cable of a lifting and transporting machine to move the assembly into a quenching tank 9 as seen on FIG. figure 4 . The tank is filled with quenched fluid to bring the temperature, at a controlled rate, to room temperature. During this process, the part undergoes a shrink and its compression on the gauge 8 is maximum when it reaches its maximum structural shrinkage temperature. For the alloy mentioned above, this temperature is between 200 and 300 ° C. As the dimensions of the caliber 8 are higher, the piece comes to be frayed on it and follow its shape. When the temperature continues to drop the piece expands and thus detaches from the crown formed by the caliber 8. A game "e" is formed, it is represented on the figure 5 . When the temperatures are stabilized, the entire quenching tank is removed and the piece is removed from the support.

An implementation of the more elaborate method allowing a precise adjustment of the caliber with respect to the part is now described.

In this case, a support or manikin 30 composed of a lower frame 31 equipped with first articulated radial arms 32 and second articulated radial arms 33 around horizontal axes is used. These radial arms will serve, in turn, supporting the room during handling. The arms 32 are shown raised up on the figure 6 . The arms 33 are provided with a mass so that in the absence of stress they are vertical as seen on the figure 6 . The manikin 30 comprises means 34 for suspending the frame 31. The means 34 themselves comprise a central vertical rod 35 which comes, as will be seen later, in engagement with a hooking means 36 in the form of a clamp. In the configuration of the figure 6 , the frame 31 is held in suspension by cables 37, only one of which has been shown, from the upper part of the gripper 36. The ring of the caliber 8 is also suspended in this preparatory phase at the upper part of the clamp by cables 38 or other equivalent means of which only one has been shown. The piece 1 rests on an annular table 40 and the assembly formed by the rod 35, the gauge 8 and the clamp is coaxial with the workpiece. We go down vertically. As the radial arms 32 and 33 are raised, the frame 31 can be lowered lower than the table 40. The caliber 8 then bears against the upper edge of the part. Dimensions have been adjusted in such a way that the gauge is held at room temperature by the edge of the workpiece 1. When in the position of the figure 8 the radial arms 33 are tilted; the frame 31 is resting on a restoir 50. The gripper 36 is lowered until it comes into engagement with the rod 35 as seen on FIG. figure 9 . Then lift the whole vertically. In this movement, the part with the table 40 is driven by the radial arms 33, figure 10 . The assembly is deposited in the heat treatment furnace 5 on a repository 70, figure 11 . The repository 70 makes it possible to lower the frame 31 below the level of the part 1. It is then possible to put the arms 33 in a vertical position and to reassemble the support assembly 30 with the template 8 suspended by the cables 38, leaving the part 1 only in support on the restoir 70, figure 13 . The oven is closed with its bell 51 and the heat treatment is carried out. It is observed that the manikin 30 was raised vertically without any other manipulation than the lowering of the radial arms 32, and release of the clamp 36 of the rod 35, figure 13 .

Once the heat treatment is completed, the oven is opened and the manikin 30 is lowered, figure 14 . the radial arms slide along the piece 1, figure 14 . Because of the expanded state of the part 1, the gauge 8 is introduced into its bore when the manikin is lowered below the table supporting the workpiece. The arms 32 are then deployed and engage under the part when the manikin 30 is lifted again, figure 15 . The entire part 1 equipped with its caliber 8 is thus driven to the quenching tank, not shown here. After quenching, the assembly is placed on a resting table 50 to remove the template, figure 16 . The manikin 30 is lowered under the resting table 50 to enable the radial arms 32 to be raised, figure 17 . The gripper 36 is detached from the rod 35 and the manikin 30 is lifted. The gripper 36 then drives the caliber 8 through the cables 38 and the frame 31 through the cables 37. Finally, the calibrated piece 1 is taken to other possible treatments.

The arrangement of the manikin according to the latter implementation has the advantage of ensuring correct positioning and centering of the calibration tool 8 with respect to the part 1 during all the phases of the process without having to intervene specifically on the 8. This solution is advantageous compared to the first where we must come to set up the calibration tool while the room is still in the oven and the processing temperature.

Claims (4)

1. Method of sizing a cylindrical part (1) following shaping, by plastic deformation, of a metal material having maximum structural shrinkage at a maximum-shrinkage temperature between a first temperature and a second temperature which is lower than the first, characterised in that it comprises the following successive steps:

   - placing the part (1) in a vertical furnace, the axis of the part (1) being vertical,

   - positioning an internal-sizing tool of a diameter greater than that of the maximum structural shrinkage of the part at the level of the part outside the furnace, the axis of the sizing tool being aligned with that of the part (1),

   - closing the furnace,

   - heating the part (1 ) in the furnace to a first temperature,

   - opening the furnace,

   - lowering and placing the sizing tool (8) inside the part,

   - transporting the assembly formed by the part (1) and the sizing tool to a tempering tub,

   - cooling the part to a temperature below said second temperature,

   - extracting the internal-sizing tool (8).
2. Method according to claim 1, wherein, before the part (1) is placed in the furnace, the part (1) is arranged in the furnace together with the sizing tool, the sizing tool being placed on the part (1), and the sizing tool is vertically displaced outside the furnace in order to position it at the level of the part, the axis of the tool being aligned with that of the part, outside the furnace.
3. Method according to any one of the preceding claims, wherein the metal is a Z5CNU17 alloy.
4. Device for implementing the method according to any one of the preceding claims, comprising a dummy bar (30) having a frame (31) provided with articulated radial arms (32, 33) forming supports for the part (1), and a means (36) for attaching the dummy bar (30), the sizing tool (8) being suspended by cables (38) or other equivalent means from said attachment means, the means (36) for attaching the dummy bar (30) being movable between a position in which said means is connected to the dummy bar by means of a rod (35), and a position in which the dummy bar is suspended from the attachment means by cables (37) or other equivalent means.

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