FR2864106A1 - Quenching device for quenching components, notably of heat treated steel, with the circulation of a high pressure quenching gas - Google Patents

Abstract

A quenching device (10) comprises: (A) a quenching enclosure (40) containing a working volume (73) for the components to be quenched; (B) an outer enclosure (20) containing the quenching enclosure and separated from it by a storage volume (41) able to contain a quenching gas at high pressure; (C) a system (54, 60) for the continuous circulation of the quenching gas in the working volume and in the storage volume. The circulation system is placed in the storage volume.

Description

TEMPERATURE DEVICE

  The present invention relates to a quenching device for parts, and more particularly to a quenching device for steel parts that have undergone a physicochemical heat treatment, for example a cementation treatment consisting in introducing carbon into the surface of the parts to improve their performance. hardness.

  The quenching corresponds to a sudden cooling of a heated part beyond a temperature of modification of the structure of the part to a specific phase having advantageous physical properties. Quenching makes it possible to maintain at room temperature the specific phase which is normally stable only at high temperature. In the case of steels, the specific hot phase is austenite which is sought in particular for remarkable hardness properties. However, it is generally not possible in this case, as fast as the cooling may be, to maintain a perfect austenite phase at room temperature. In fact, we obtain a metastable phase, called martensite, which nevertheless retains interesting physical properties.

  In the case of ordinary quenching, the previously heated part is, for example, placed in a quenching tank filled with a quenching liquid, for example oil, stirred during cooling.

  The quenching can also be carried out by passing a quenching gas around the part to be cooled. The gas quenching is generally carried out by arranging the parts to be quenched in a quenching enclosure hermetically sealed and circulating in the enclosure quench gas contained in a high pressure tank. Once the quenching has been completed, the quenching gas can be removed from the quench chamber and rejected or recovered for re-injection into the high pressure tank.

  A gas quenching device is bulky since it comprises at least one quenching vessel, a high pressure reservoir and the pipes connecting the high pressure reservoir and the quench enclosure. In addition, the quenching chamber generally has a large volume since it contains, in addition to the parts to be treated, means for mixing the quenching gas in the enclosure. It follows that the volume of quenching gas to be injected into the chamber during a quench cycle is large compared to the useful volume containing the parts to be treated.

  In addition, when recovery of the quenching gas is carried out after each quenching cycle, the volume of quenching gas to be recovered is such that it is necessary to use a low pressure reservoir connected to the quenching chamber to recover rapidly a portion of the quenching gas contained in the quench chamber by communicating the quench enclosure and the low pressure reservoir. The low pressure tank is connected to the high pressure tank via a compressor for later reinjecting the recovered quench gas into the high pressure tank. Indeed, the frequency of the quenching cycles in an industrial operation of the quenching device is too high to allow recovery of the quenching gas contained in the quenching chamber only by means of a compressor connecting the quench enclosure to the high pressure tank.

  The present invention therefore aims to obtain a quenching device having a small footprint.

  Another object of the present invention is to reduce the volume of quenching gas used to perform a quench cycle.

  Another object of the present invention is to allow a recovery of at least a portion of the quenching gas present in the quench chamber without requiring a low pressure reservoir.

  To achieve these objects, the present invention provides a quenching device comprising a quench enclosure containing a useful volume for receiving parts to be quenched; an outer enclosure containing the quench enclosure and separated from the quench enclosure by a storage volume adapted to contain high pressure quenching gas; and means for continuously circulating quenching gas of the storage volume in the useful volume and the working volume in the storage volume, the circulation means being placed in the storage volume.

  According to one embodiment of the present invention, the circulating means comprise an intake means adapted to release at least one opening in the quench chamber for the passage of quenching gas from the storage volume into the useful volume ; and suction means comprising a quench gas suction inlet of the working volume and an expulsion outlet of the gas sucked into the storage volume.

  According to one embodiment of the present invention, the intake means comprises a plurality of valves disposed on the quench enclosure, the device comprising means for selectively opening a valve or plurality of valves from the plurality of valves to orient the valve. quenching gas flow penetrating the quench enclosure in a preferred direction.

  According to one embodiment of the present invention, the device comprises a heat exchanger between the useful volume and the suction inlet of the suction means for cooling the quenching gas before the quenching gas reaches the quenching means. suction.

  According to one embodiment of the present invention, the device comprises a heat exchanger between the outlet of the suction means and the storage volume.

  According to one embodiment of the present invention, the outer enclosure and the quench enclosure have a common wall comprising an opening for communicating the useful volume with the outside of the outer enclosure.

  According to one embodiment of the present invention, the device comprises an acceleration means disposed in the quench chamber for accelerating the quenching gas reaching the parts to be treated.

  According to one embodiment of the present invention, the acceleration means comprises a box comprising walls defining the effective volume and comprising nozzles for accelerating the flow of the quenching gas.

  According to one embodiment of the present invention, the quenching enclosure comprises an opening at the inlet of the suction means, the device comprising means for sealing the opening.

  According to one embodiment of the present invention, the device further comprises means for establishing a partial vacuum in the quench chamber.

  These and other objects, features, and advantages of the present invention will be set forth in detail in the following description of a particular embodiment, given in a non-limiting manner, with reference to the attached figures in which: FIG. a schematic side view, in partial section, of an exemplary embodiment of a quenching device according to the invention; and Fig. 2 is a sectional view of Fig. 1 taken along line II-II.

  Figures 1 and 2 show an embodiment of a quenching device 10 according to the present invention. The quenching device 10 is connected to a physicochemical heat treatment plant 15, for example, a cementation plant of the type described in the patent application No. 922,778 filed in the name of the Applicant to which reference may be made for further details.

  The quenching device 10 comprises a cylindrical outer enclosure 20 of axis D1, for example horizontal, closed at one end by a cover 22 and closed at the opposite end by a flat closing wall 24. The closing wall 24 is fixed to a fastening support 25 that connects with the processing installation 15.

  The closure wall 24 comprises an opening 26 of substantially rectangular shape. The opening 26 can be closed by means of a door 28, sliding in rails 30, 32 fixed to the closure wall 24, and which can move from an open position to which the opening 26 communicates with the treatment plant 15 at a closed position at which the opening 26 is hermetically sealed from the treatment plant 15.

  A quenching chamber 40 of cylindrical axis D2, parallel to D1, is disposed in the outer enclosure 20 and is fixed at one end to the closure wall 24 so that the opening 26 opens into the quench enclosure 40. The volume which separates the outer enclosure 20 from the quenching enclosure 40 corresponds to a storage volume 41 containing a quench gas under a high pressure, for example of the order of 24 bar. A cylindrical housing 42 of axis D2, disposed between the outer enclosure 20 and the quench enclosure 40, is attached to the quench enclosure 40 at the end of the quench enclosure 40 opposite the 26. The housing 42 is closed, at the end opposite the quenching enclosure 40, by a flat wall 43. The lateral wall of the housing 42 is traversed by a plurality of openings 44.

  An opening 46 passes through the end of the quenching chamber 40 opposite the closure wall 24 and allows the communication between the quenching chamber 40 and the housing 42. The opening 46 can be closed again via a door 48, sliding in rails 50, 52 fixed to the quenching chamber 40, and which can move from an open position to which the opening 46 connuniques with the housing 42 to a closed position to which the opening 46 is hermetically isolated from the housing 42.

  A suction turbine 54 is disposed in the housing 42. A hydraulic motor 56 contained in the outer enclosure 20 and fixed to the plate 43 outside the housing 42, drives the suction turbine 54 via a shaft 57 passing through the wall 43. The turbine 54 comprises a convergent suction duct 58 whose inlet is opposite the opening 46, the door 48 sliding between the opening 46 and the suction duct 58. The turbine 54 is adapted to reject the air sucked at the openings 44, radially with respect to the axis D2.

  Valves 60 are distributed over the quenching enclosure 40, between the outer enclosure 20 and the quench enclosure 40. Each valve 60 communicates, in the open position, the interior volume of the quench enclosure 40 with the volume 41. For example, in Figure 1, two valves 60 are shown at the upper part of the quench chamber 40 and a valve is shown at the lower part of the quench chamber 40 By way of example, in FIG. 2, a valve is shown at the upper part of the quench enclosure 40, two valves are shown at the lower part of the quench enclosure 40 and two valves, diametrically opposite, are represented at a horizontal plane of symmetry of the quenching enclosure 20.

  A box 64, of substantially parallelepipedal shape, is disposed in the quench chamber 40. The box 64 comprises an upper planar wall 66, two side plane walls 68, 70, and a bottom wall 72. The walls define an internal useful volume 73 on which open the openings 26, 46. Each wall 66, 68, 70, 72 of the housing 64 is traversed by nozzles 76. The nozzles 76 are uniformly distributed on the upper and lateral walls 66, 68, 70. As this is shown in FIG. 2, the lower wall 72 of the box 64 supports rails 78, 79 allowing the insertion of a trolley (not shown) into the working volume 73 through the opening 26 and the removal of the trolley from the working volume 73 for the transport of soaked or soaked parts (not shown).

  A first heat exchanger 80 is disposed between the opening 46 of the quenching vessel 40 and the caisson 64. By way of example, the first exchanger 80 comprises parallel straight cylindrical tubes 82 whose axes are substantially horizontal. A second exchanger 84 is disposed outside the housing 42 at the openings 44. For example, the second heat exchanger 84 comprises cylindrical tubes 86 which surround the housing 42 at the openings 44. The means necessary for the operation of the heat exchangers 80, 84 are not shown.

  A vacuum pump 88 may be provided outside the outer enclosure 20. The vacuum pump is connected to the quench enclosure 40 via a pipe 90 and allows the partial vacuum of the quench enclosure 40. The vacuum pump can be coupled to a compressor 92 for reinjecting the quenching gas recovered from the quenching chamber 40 into the outer enclosure 20.

  The outer enclosure 20 is connected to means 94 for supplying the storage volume 41 with quenching gas to compensate for quenching gas losses during the use of the device 10.

  The operation of the quenching device 10 according to the invention will now be described in more detail during a quenching cycle.

  At the beginning of the quenching cycle, the valves 60 and the doors 28, 48 are closed. In the present example of operation, the part of the cementation plant 15 to which the quenching device 10 is connected is under partial vacuum. A partial vacuum is thus achieved in the quench chamber 40. The door 28 is then opened for the removal of the parts arranged in the box 64 having undergone quenching and for the introduction into the box 64 of new parts to be quenched. The door 28 is then closed. The valves 60 and the gate 48 are then opened and the turbine 54 is actuated. A continuous flow of quenching gas is then established between the quenching chamber 40 and the storage volume 41. More specifically, quenching gas present in the storage volume 41 enters the working volume 73 in the enclosure of quenching 40 by the open valves 60 and then by the nozzles 76 of the box 64 and cools the parts present in the working volume 73. The quenching gas is then sucked from the box 64 by the turbine 54 and expelled into the storage volume 41 high pressure through the openings 44 of the housing 42. During the circulation of the quenching gas, the pressures in the storage volume 41 and in the quench chamber 40 are substantially equal to and slightly less than the pressure in the storage volume 41 at the beginning of the quenching cycle. For example, during the circulation of quenching gas, the pressures in the storage volume 41 and in the quench chamber 40 are of the order of 20 bars.

  The quenching gas is cooled before reaching the turbine 54 by passing through the first heat exchanger 80 to extract the calories supplied to the quenching gas by the parts to be quenched. The quenching gas is also cooled by the second heat exchanger 84 at the outlet of the turbine 54 to recover the calories supplied to the quenching gas by the turbine 54. The nozzles 76 accelerate the flow of the quenching gas in the casing 64 to increasing the heat exchange coefficient between the quenching gas and the parts present in the casing 64. The cooling of the quenching gas before its admission into the turbine 54 makes it possible to increase the density of the gas reaching the turbine 54, and therefore to increase the massive flow of the gas driven by the turbine 54. The efficiency of the turbine 54 is thus improved.

  Only certain valves 60 may be open to promote the orientation of the quenching gas flow in the useful volume 73 of the box 64. When only the valves 60 disposed at the upper and / or lower portions of the quench enclosure 40 are open, the flow of quenching gas penetrating into the box 64 and reaching at high speed the parts to be quenched is mainly vertical. Such a flow is desirable when the workpieces are, for example, shafts whose axes are arranged vertically. When only the valves 60 disposed at the horizontal plane of symmetry of the quench chamber 40 are open, the flow of the quenching gas arriving in the box 64 and reaching at high speed the parts to be quenched is mainly horizontal. Such a flow is desirable when the pieces to be quenched are, for example, vertical piles of sprockets.

  At the end of the quenching cycle, the valves 60 and the two doors 28, 48 are closed. The quenching chamber 40 is then evacuated via the vacuum pump 88 for removal of the quenched parts. The gas extracted from the quenching chamber 40 during the evacuation can be rejected or can be reinjected into the storage volume 41.

  The quenching device 10 according to the present invention has many advantages: Firstly, the quenching chamber 40 is integrated with the outer enclosure 20, the volume between the outer enclosure 20 and the quench enclosure 40 forming a volume of storage 41 high pressure quenching gas. There is therefore no need to provide a high pressure tank separated from the quench chamber and the pipes connecting the high-pressure tank and the quench chamber 40. The overall size of the quenching device 10 according to the invention is therefore reduced. For example, the volume of the outer enclosure 20 of the quenching device 10 according to the invention is 6.5 m3. By way of example, a conventional equivalent quenching cell would have a cylindrical shape with a volume greater than 3 m 3 and the associated high-pressure reservoir would have a cylindrical shape with a volume greater than 3 m 3, the resulting bulk being therefore greater.

  Secondly, the flow of the quenching gas entering the quench chamber 40 can be oriented in a preferred direction by a selective opening of the valves 60 distributed over the quench enclosure 40.

  Third, the volume of the quench chamber 40 is reduced and is close to the useful volume receiving the parts to be quenched since the most bulky means involved in the circulation of the quenching gas in the quench chamber are arranged between external enclosure 20 and the quenching enclosure 40 and not in the quench enclosure 40. Only the walls 66, 68, 70, 72 of the box 64 are arranged in the quench enclosure 40. By way of example, the internal volume of the quench chamber 40 is 1, 6 m3 and the useful volume of the box 64 is 1.3 m3. By way of comparison, the volume of an equivalent conventional quenching cell containing means for mixing the quenching gas in the quench chamber 40 is generally greater than 3 cubic meters. The volume of the quench chamber 40 being reduced, the amount of quenching gas used during a quench cycle is reduced. In the case where the quenching gas present in the quench chamber 40 is rejected at the end of a quenching cycle, this saves quenching gas. In the case where the quenching gas present in the quench chamber 40 is recovered at the end of a quenching cycle, recovery of the quenching gas can be carried out by a compressor and a vacuum pump without having to provide a reservoir intermediate low pressure. Indeed, given the small volume of quenching gas to be recovered, the time required to recover the quenching gas only through a compressor and a vacuum pump is compatible with the usual duration of a quenching gas. quench cycle.

  Of course, the present invention is susceptible to various variations and modifications which will be apparent in the art. In particular, the turbine 54 can be driven by an electric motor instead of a hydraulic machine. In addition, there may be provided several turbines for circulating the quenching gas in the quench chamber 40 instead of a single turbine 54.

Claims (10)

  A quenching device (10) comprising: a quench enclosure (40) containing a useful volume (73) for receiving parts to be quenched; an outer enclosure (20) containing the quench enclosure and separated from the quench enclosure by a storage space (41) adapted to contain quench gas at high pressure; and means for circulating (54, 60) quench gas continuously from the storage volume to the useful volume and the working volume to the storage volume, the circulation means being placed in the storage volume.   2. Device according to claim 1, wherein the circulation means comprise: an inlet means (60) adapted to release at least one opening in the quench chamber (40) for the passage of quench gas from storage volume (41) in the useful volume {73); and suction means (54) including a quench gas suction inlet of the working volume and an expulsion outlet of the gas sucked into the storage volume.   Apparatus according to claim 2, wherein the intake means comprises a plurality of valves (60) disposed on the quench enclosure (40), the apparatus comprising means for selectively opening one or more plurality of valves valve arrangement for directing the quenching gas flow into the quench enclosure in a preferred direction.   4. Device according to claim 2, comprising a heat exchanger (80) between the useful volume (73) and the suction inlet of the suction means (54) for cooling the quenching gas before the quenching gas reaches the suction means (54).   5. Device according to claim 2, comprising a heat exchanger (84) between the outlet of the suction means (54) and the storage volume (41).   6. Device according to claim 1, wherein the outer enclosure (20) and the quenching enclosure (40) have a common wall (24) comprising an opening (26) for communicating the useful volume (73) with the outside the outer enclosure (20).   7. Device according to claim 1, comprising an acceleration means (64, 76) disposed in the quench chamber (40) for accelerating quenching gas reaching the parts to be treated.   8. Device according to claim 7, wherein the acceleration means (64, 76) comprises a box (64) comprising walls (66, 68, 70, 72) defining the useful volume (73) and comprising nozzles ( 76) to accelerate the flow of the quenching gas.   9. Device according to claim 2, wherein the quenching chamber (40) comprises an opening (46) at the inlet of the suction means (54), the device comprising means (48) for hermetically sealing the opening.   The apparatus of claim 1, further comprising means (88,92) for establishing a partial vacuum in the quench enclosure (40).