EP1840230A2 - One-piece calibration method for crankcase tempering, device for implementing the method - Google Patents

Abstract

The method involves arranging a cylindrical part (1) of an aeronautic turbomachine case e.g. compressor casing, in a pot heater (5), and heating the cylindrical part to a hot thermal processing temperature. An inner sizing die (8) is installed inside the cylindrical part during its maximum structural recess, where the sizing die has a diameter higher than a diameter of the cylindrical part. The cylindrical part is cooled to a temperature lower than an ambient temperature of a maximum structural recess. The inner sizing die is extracted. An independent claim is also included for a cylindrical part sizing device comprising a model.

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.

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,
• positionnement d'un outillage de calibrage interne de diamètre supérieur à celui de la pièce lors de son retrait structural maximum, au droit de la pièce en dehors du four,
• chauffage de la pièce jusqu'à une première température,
• descent et mise en place, à l'intérieur de la pièce, d'un outil de calibrage interne de diamètre supérieur à celui du retrait structural maximum de la pièce,
• 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:

• set up the piece in a vertical oven,
• positioning an internal calibration tool of diameter greater than that of the part during its maximum structural removal, to the right of the piece outside the oven,
• heating the room to a first temperature,
• descent and placement, inside the room, of an internal calibration tool of diameter greater than that of the maximum structural removal of the room,
• 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.

According to another characteristic, the coupling 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.

A non-limiting embodiment of the method of the invention will now be described with reference to the drawings in which,
Figures 1 to 5 show the different steps of the method of the invention according to a first implementation;
Figures 6 to 18 show the different steps of the method according to another particularly advantageous implementation.

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.

FIGS. 1 to 5 show the unwinding of a first mode of implementation of the method of the invention. 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. 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. In Figure 3 we see that it has placed inside the room a calibration tool 8 of cylindrical shape also. 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 in FIG. 4. The tank is filled with a quenched fluid to bring the temperature, at a controlled rate, up 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 fall the room expands and thus disengages from the ring formed by the caliber 8. A game "e" is formed, it is shown in Figure 5. When the temperatures are stabilized, we remove all of the quenching tank 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 upwardly in FIG. 6. The arms 33 are provided with a mass such that, in the absence of stress, they are vertical as can be seen in FIG. 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 clamp. In the configuration of FIG. 6, the frame 31 is held in suspension by cables 37, only one of which has been shown, from the upper part of the gripping clamp 36. The ring of the caliber 8 is also suspended in this phase. preparatory to 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, we can lower the frame 31 lower than the table 40. The caliber 8 then bears against the upper edge of the room. Dimensions have been adjusted such that the gauge is held at room temperature by the edge of the workpiece 1. When in the position of FIG. 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 in FIG. 9. The assembly is then raised vertically. In this movement, the part with the table 40 is driven by the radial arms 33, FIG. 10. The assembly is deposited in the heat-treating furnace 5 on a rack 70, FIG. 11. The rack 70 allows the frame 31 to be lowered. below the level of the part 1. We can then put the arms 33 in the vertical position and reassemble the support assembly 30 with the caliber 8 suspended by the cables 38, leaving the single piece 1 resting on the rest 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, FIG. 13.

Once the heat treatment is complete, the oven is opened and the manikin 30 is lowered, FIG. 14. the radial arms slide along the piece 1, FIG. 14. Due to the expanded state of the piece 1, the gauge 8 is introduced into its bore when the manikin is lowered below the table supporting the piece. The arms 32 are then deployed and engage under the part when the manikin 30, FIG. 15 is raised again. FIG. 15 is thus carried out. The whole of the piece 1 equipped with its gauge 8 is thus brought to the quenching tank, not shown here. After quenching, the assembly is placed on a table 50 to remove the template, FIG. 16. The manikin 30 is lowered under the table 50 to allow the radial arms 32, FIG. 17 to be lifted. hooking 36 of the rod 35 and raises the manikin 30. The clamp 36 then drives the gauge 8 by the cables 38 and the frame 31 by the cables 37. Finally takes the calibrated piece 1 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 (5)

A method of calibrating a cylindrical part (1) after shaping by plastic deformation of a metallic material having a maximum structural shrinkage at a maximum shrinkage temperature between a first temperature and a second temperature lower than the first, characterized by the fact that it comprises the following successive steps: - setting up the part (1) in a vertical oven, positioning of an internal calibration tool of diameter greater than that of the part during its maximum structural shrinkage, to the right of the part outside the furnace, - heating the room (1) to a first temperature, - Descent and establishment, inside the room, an internal calibration tool (8) greater in diameter than the maximum structural shrinkage of the room, transport of the assembly formed by the workpiece and the calibration tool to a quenching tank - cooling of the room to a temperature below said second temperature, - extraction of the internal calibration tool (8). The method of claim 1 wherein the part (1) is placed in an oven and heated to a first heat treatment temperature; after treatment, said calibration tool (8) is placed on the part (1) and the assembly is placed in a quenching tank (9); the part (1) is cooled down to said lower temperature. Method according to one of the preceding claims, the metal of which is a Z5CNU17 alloy. Device for carrying out the method according to one of the preceding claims, comprising a manikin (30) with a frame (31) provided with articulated radial arms (32, 33) forming the supports of the part (1), a means for hooking (36) of the manikin (30), the calibration tool (8) being suspended by cables (38) or other means equivalent to said hooking means. Device according to the preceding claim, the attachment means (36) of the manikin (30) is removable between a position where it is secured by a rod (35) to the manikin and a position where the manikin is suspended by the hooking means by cables (37) or other equivalent means.

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