The present invention relates to the field of metallurgy and is aimed at the sizing of cylindrical parts formed by rolling.
In the field of turbomachinery, cylindrical parts are made as a single piece in order in particular to form compressor casings or blade retention casings. This type of part, which may be large in size and heavy in weight, is made by rolling a bloom of alloy suited to its end-use. The rolling is followed by a heat treatment employing heat in order to improve its mechanical properties by relaxing the internal stresses caused by the work involved in the plastic deformation of the material. Aside from this treatment, a sizing operation is required because of the tight tolerances on the dimensions, particularly internal dimensions, of this type of part.
Currently, prior to the heat treatment step a device known as an expander, provided with appropriate push-rods, generally hydraulically operated, is used to expand the interior surface. However, it is found that the geometry of the part is liable to change further during the heat treatment and a further cold-sizing operation is often needed. It has been proposed for the part to be formed with excess thickness capable of absorbing the change in dimension but such a solution is unsatisfactory, particularly in the case of an aeronautical turbomachine, because of the increase in weight of material involved.
The applicant has set itself the objective of developing a new method for sizing a cylindrical part obtained by the plastic deformation of material that is more economical, reducing the number of operations and developing tooling of a structure that is less complicated and less expensive to produce.
The invention stems from the observation made regarding certain alloys, including steel alloy Z5CNU17, which have the property of exhibiting maximum structural shrinkage at a temperature lying between the hot heat treatment temperature and ambient temperature. The material, during the cooling phase, contracts down to this temperature then expands when the temperature of the part is returned to ambient temperature.
The method of the invention for sizing a cylindrical part following the shaping, by rolling, of a metallic material that has maximum structural shrinkage at a maximum-shrinkage temperature lying between a first temperature, such as a hot heat treatment temperature, and a second temperature such as ambient temperature, is a method which comprises the following successive steps:
Thus, through the method of the invention, this property of the material is put to good use for sizing the part during the tempering phase after heat treatment by the application of heat, thus simplifying the operations involved in treating the part. Furthermore, the sizing tool may be a simple annulus of appropriate outside diameter with no articulated or mechanized parts.
In practice, the part is placed in a furnace and heated to its first temperature, which advantageously is its heat treatment temperature; then, said sizing tool is placed on the part and the assembly is positioned in a tempering tub where the part is cooled to said lower temperature, which tends toward ambient temperature.
However, although the method applies advantageously in combination with the heat treatment and tempering of the part after it has been manufactured by rolling, it can be employed each time the material has a maximum-shrinkage temperature lying between a first temperature and a second temperature, the first being higher than the second.
The invention also relates to a special device allowing for advantageous implementation of the method. This device comprises a dummy bar with a frame provided with articulated radial arms forming supports for the part, a catching means for attaching the dummy bar, the sizing tool being suspended by cables or other equivalent means from said catching means.
According to another characteristic, the catching means for attaching the dummy bar can be moved between a position in which it is secured by a rod to the dummy bar and a position in which the dummy bar is suspended from the catching means by cables or other equivalent means.
A nonlimiting embodiment of the method of the invention is now described with reference to the drawings in which:
The method is described by detailing the various phases. The part to be sized may be a turbomachine casing such as an intermediate casing, a compressor casing or a retention casing comprising a cylindrical part formed by plastic deformation of a metallic material such as Z5CNU17 steel. The latter has the property of having maximum structural shrinkage at between 200 and 300° C.
The support is then attached to a cable of lifting and transport gear to move the assembly to a tempering vessel 9 as can be seen in
A more elaborate embodiment of the method allowing precise adjustment of the sizing gage relative to the part is now described.
Here, use is made of a support or dummy bar 30 made up of a lower frame 31 equipped with articulated first radial arms 32 and second radial arms 33 articulated about horizontal axes. These radial arms will, each in turn, serve to support the part during handling operations. The arms 32 are depicted raised upward in
Once the heat treatment has been completed, the furnace is opened and the dummy bar 30 is lowered,
The configuration of the dummy bar according to the latter embodiment offers the advantage of ensuring correct positioning and centering of the sizing tool 8 relative to the part 1 throughout all the phases of the process without having to act specifically on the tool 8. This solution is advantageous by comparison with the first where the sizing tool has to be fitted while the part is still in the furnace and at the heat treatment temperature.
Number | Date | Country | Kind |
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06 51039 | Mar 2006 | FR | national |
This application is a Divisional of and claims the benefit of priority under 35 U.S.C. §120 from U.S. Ser. No. 11/691,122, filed Mar. 26, 2007, the entire contents of which are incorporated by reference and claims the benefit of priority from prior France application patent 06 51039, filed Mar. 27, 2006.
Number | Name | Date | Kind |
---|---|---|---|
4444604 | Martin | Apr 1984 | A |
4504554 | Yoshioka et al. | Mar 1985 | A |
5620298 | Barwise | Apr 1997 | A |
6074601 | Nakamura | Jun 2000 | A |
20010041127 | Cross | Nov 2001 | A1 |
20030231975 | Braillard et al. | Dec 2003 | A1 |
Number | Date | Country |
---|---|---|
0 553 154 | Jul 1994 | EP |
Number | Date | Country | |
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20100019423 A1 | Jan 2010 | US |
Number | Date | Country | |
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Parent | 11691122 | Mar 2007 | US |
Child | 12575296 | US |