Abstract
The invention relates to a device for water spray quenching that includes (i) a quenching chamber designed and set up to receive metallic workpieces, with a batch of volume V.sub.0 of 0.045 to 3.5 m.sup.3 and (ii) at least one atomizer which is configured to atomize water in air or nitrogen and is fluidically connected to the quenching chamber; in which the at least one atomizer and the device are designed and set up to generate a spray mist with a water content of 2.5 to 40 vol. % and a Sauter mean diameter of 20 to 2000 m and also a spray mist flow through the batch volume V.sub.0 of 0.05 to 25 m.sup.3/s.
Claims
1. An apparatus for water spray quenching comprising a quenching chamber which has been designed and set up to accommodate metallic workpieces and has a charge volume (V.sub.0) of 0.045 to 3.5 m.sup.3; and at least one atomizer which is configured for the atomization of water in air or nitrogen and is fluidically connected to the quenching chamber; wherein the at least one atomizer and the apparatus are designed and set up to generate a spray mist having a water content of 2.5% to 40% by volume and a Sauter diameter of 20 to 2000 μm and to convey a spray mist flow through the charge volume V.sub.0 of 0.05 to 25 m.sup.3/s or to recirculate the spray mist in the charge volume V.sub.0 at a spray mist volume flow rate of 0.05 to 25 m.sup.3/s.
2. The apparatus as claimed in claim 1, wherein said apparatus is designed and set up to generate a spray mist throughput between an inlet and an outlet of the quench chamber of 0.05 to 25 m.sup.3/s.
3. The apparatus as claimed in claim 1, wherein said apparatus comprises a first and second atomizer, each having 3 to 60 atomizer nozzles.
4. The apparatus as claimed in claim 3, wherein outlets of the atomizer nozzles of the first atomizer are disposed in a first horizontal plane, outlets of the atomizer nozzles of the second atomizer are disposed in a second horizontal plane, the quench apparatus comprises one or two receptacles for a first and second charge carrier, and the first and second receptacles are disposed in vertical direction between the first and second horizontal planes.
5. The apparatus as claimed in claim 3, wherein the atomizer nozzles of the first and second atomizers are each designed, configured and arranged in space to subject a horizontal area of 0.16 to 2.25 m.sup.2 uniformly to water spray mist.
6. The apparatus as claimed in claim 5, wherein the atomizer nozzles of the first and second atomizers are independently designed, configured and arranged in space to subject a horizontal area of 0.16 to 2.25 m.sup.2 uniformly to water spray mist in such a way that a vertical component v.sub.z of a flow rate of the water spray mist has a value of 0.8×v.sub.z to 1.2×v.sub.z with 0.5 m/s≤v.sub.z≤35 m/s.
7. The apparatus as claimed in claim 1, wherein the quench chamber is equipped with one or more ventilators or fans having a spray mist volume flow rate of 0.05 to 25 m.sup.3/s.
8. The apparatus as claimed in claim 1, wherein said apparatus comprises at least one recirculator which is fluidically connected to the quench chamber and has a recirculation drive, where the recirculation drive is set up to generate a spray mist volume flow rate of 0.05 to 25 m.sup.3/s.
9. The apparatus as claimed in claim 1, wherein said apparatus comprises an electronic controller and at least one infrared sensor, the at least one infrared sensor is designed and set up to measure the temperature of workpieces disposed on a charge carrier when the charge carrier is being held in a charge carrier receptacle of the apparatus, and an electrical output from the at least one infrared sensor is connected to an electrical input of the electronic controller.
10. The apparatus as claimed in claim 1, wherein the quench chamber comprises a tank for condensed water.
11. A system for thermal or thermochemical treatment of metallic workpieces with subsequent water spray quenching, comprising one or more charge carriers for the storage of workpieces; an oven for the thermal or thermochemical treatment of workpieces disposed on one or more charge carriers, wherein the oven is designed and set up to heat up the workpieces to a temperature of 750 to 1100° C.; an apparatus for water spray quenching as claimed in claim 1; and an automated transfer apparatus designed and set up to transfer workpieces disposed on one or more charge carriers within a period of 10 to 60 s from the oven into a quench chamber of the apparatus.
12. A method of water spray quenching of thermally or thermochemically treated metallic workpieces, comprising the steps of: disposing one or more thermochemically treated workpieces in a charge volume V.sub.0 of an apparatus for water spray quenching; atomizing water in air or nitrogen in order to produce a spray mist; passing spray mist through the charge volume V.sub.0; wherein the charge volume V.sub.0 is in a range of greater than or equal to 0.045 m.sup.3 to less than or equal to 3.5 m.sup.3; the spray mist has a water content of 2.5% to 40% by volume; the spray mist has a Sauter diameter of 20 to 2000 μm; and a spray mist flow through the charge volume V.sub.0 is 0.05 to 25 m.sup.3/s or the spray mist is recirculated in the charge volume V.sub.0 at a spray mist volume flow rate of 0.05 to 25 m.sup.3/s.
13. The method as claimed in claim 12, wherein the one or more workpieces are cooled down from a temperature of 750 to 1100° C. to a temperature of 20° C. to 250° C.
14. The method as claimed in claim 12, wherein the at least one atomizer produces 0.05 to 25 m.sup.3/s of spray mist.
15. The method as claimed in claim 12, wherein a spray mist throughput between an inlet and an outlet of the quench chamber is 0.05 to 25 m.sup.3/s.
Description
[0374] The invention is elucidated in detail hereinafter by figures.
[0375] The figures show:
[0376] FIG. 1 . . . a schematic diagram of a quench apparatus;
[0377] FIG. 2 . . . an atomizer having multiple atomizer nozzles and workpieces disposed beneath;
[0378] FIG. 3 . . . two atomizers disposed above and below workpieces;
[0379] FIG. 4 . . . an apparatus having two nozzle chambers;
[0380] FIG. 5a, 5b a nozzle plate having multiple spray nozzles;
[0381] FIG. 6 . . . an apparatus with recirculator;
[0382] FIG. 7 . . . temperature progression of a workpiece on quenching in a first working example.
[0383] FIG. 1 shows a schematic diagram of an inventive apparatus 1 for water spray quenching, having a quench chamber 2 and an atomizer 30. Disposed within the quench chamber 2 are one or more charge carriers 10 with a multitude of workpieces 11 mounted thereon within a charge volume 5 or V.sub.0. By means of the atomizer 30, a spray mist 300 consisting of water and air or water and nitrogen is generated. As indicated by the spray mist flow arrows 310, the spray mist 300 flows through the charge volume 5/V.sub.0 with the workpieces 11 disposed therein. Preferably, the workpieces 11 are disposed on the charge carriers 11 such that normals (normal vectors) of their proportionally largest surface areas are aligned essentially parallel to a vertical reference axis 20. According to the invention, the flow through the charge volume 5/V.sub.0 is brought about in various ways, as described hereinafter with reference to FIGS. 2 to 6. All embodiments of the inventive apparatus 1 are designed and set up to pass a spray mist 300 through the charge volume 5/V.sub.0, said spray mist 300 being characterized by the following parameters: [0384] 2.5% by volume≤water content≤40% by volume; [0385] 20 μm≤Sauter diameter≤2000 μm; [0386] 0.045 m.sup.3≤charge volume V.sub.0≤3.5 m.sup.3; [0387] 0.05 m.sup.3/s≤spray mist flow rate through the charge volume [0388] V.sub.0≤25 m.sup.3/s;
[0389] The atomizer 30 is connected via a first supply conduit (not shown in FIG. 1) to a pressurized water vessel, and via a second supply conduit (not shown in FIG. 1) to an air- or nitrogen-filled pressurized gas vessel. The pressurized water and pressurized gas vessels (not shown in FIG. 1) are each designed for a pressure of 1 to 20 bar. Disposed in the first and second supply conduits are control valves with which the volume flow rates (1/min) of water and gas that flow to the atomizer 30 from the water and gas pressure vessel respectively are controlled. The atomizer 30 is additionally equipped with one or more atomizer nozzles (not shown in FIG. 1). According to the invention, various concepts known in the prior art are envisaged for the configuration and design of the atomizer nozzles, such as one-phase nozzle for water, one-phase nozzle for gas, externally mixing two-phase nozzle, internally mixing two-phase nozzle (gas on the inside, water on the outside), internally mixing two-phase nozzle (water on the inside, gas on the outside), Venturi nozzles with a main gas flow and secondary water flow, Venturi nozzles with a main water flow and secondary gas flow, orifice nozzles, spiral nozzles, nozzles with and without swirl inserts, and rotary nozzles. The atomizer 30 is designed and set up to assure rapid and uniform flow of spray mist 300 around the workpieces 11.
[0390] The spray mist 300 heats up as it flows around the hot workpieces 11 disposed in the charge volume 5/V.sub.0 and, as indicated by the spray mist flow arrows 320, is removed from the quench chamber 2. In an appropriate embodiment, the apparatus 1 comprises a ventilator 6 or fan 6. The ventilator 6 or fan 6 assists the leading of the spray mist 300 out of the quench chamber 2, and optionally accelerates the flow through the charge volume 5/V.sub.0.
[0391] FIG. 2 shows a perspective detail view of an apparatus of the invention for water spray quenching having atomizers comprising one or more atomizer nozzles 31 and a multitude of workpieces 31 disposed on a charge carrier 10. The atomizer nozzles 31 are arranged in the quench chamber or charge volume of the apparatus in such a way that their longitudinal axes (or center axes or rotational axes) each independently form an angle of 135 to 180 degrees, 150 to 180 degrees or 160 to 180 degrees with a vertical reference axis 20′, or of 0 to 45 degrees, 0 to 30 degrees or, respectively, 0 to 20 degrees with an axis pointing in the opposite direction. Accordingly, a center axis of the spray mist cone 300 generated by each atomizer nozzle 31 is aligned essentially at right angles to a proportionally large surface of each of the workpieces 11. In an appropriate embodiment of the apparatus, the atomizer nozzles 31 are disposed essentially in a two-dimensional hexagonal pattern or a two-dimensional pattern corresponding to a tightest ball packing, in order to achieve maximum uniformity of spray mist distribution in a cross-sectional area of the charge volume at right angles to the reference axis 20′. The primitive basis of a two-dimensional hexagonal pattern is formed/specified by two basis vectors {right arrow over (e)}1=(2d,0) and {right arrow over (e)}.sub.2=(d,√{square root over (3)} d) where d denotes a length of 10 to 50 cm. In a departure from the diagram in FIG. 2, a regular spatial arrangement of the workpieces relative to the spray nozzles is not absolutely necessary in accordance with the invention.
[0392] FIG. 3 shows a perspective detail view of a further apparatus of the invention for water spray quenching with a first and second atomizer 31U and 31L, each of which respectively comprises a multitude of atomizer nozzles 31U and 31L. The atomizer nozzles 31U of the first atomizer 30U are each independently aligned such that their longitudinal axes form an angle of 135 to 180 degrees, 150 to 180 degrees or 160 to 180 degrees with a vertical reference axis 20′. The atomizer nozzles 31L of the second atomizer 30L are each independently aligned such that their longitudinal axes form an angle of 0 to 45 degrees, 0 to 30 degrees or, respectively, 0 to 20 degrees with the vertical reference axis 20′. Accordingly, a center axis of the spray mist cone 300 generated by each atomizer nozzle 31U and 31L is aligned essentially at right angles to a proportionally large surface of each of the workpieces 11. In an appropriate embodiment of the apparatus, the atomizer nozzles 31U and 31L are each independently disposed essentially in a two-dimensional hexagonal pattern or a two-dimensional pattern corresponding to a tightest ball packing, in order to achieve maximum uniformity of spray mist distribution in a cross-sectional area of the charge volume at right angles to the reference axis 20′. In a departure from the diagram in FIG. 3, a regular spatial arrangement of the workpieces relative to the spray nozzles is not absolutely necessary in accordance with the invention.
[0393] FIG. 4 shows a schematic side view of a further inventive apparatus 1 for water spray quenching with a first and second atomizer (30A, 30B), each fluidically connected to a first and second nozzle chamber (40A, 40B). The first and second nozzle chambers 40A and 40B are respectively disposed above and below a charge carrier 11 with metallic workpieces 11 mounted thereon, for example spur gears. Each of the nozzle chambers (40A, 40B) comprises an outlet having 6 to 10 000 spray nozzles (41A, 41B) each having a cross-sectional area of 0.25 π mm.sup.2 to 25 π mm.sup.2. A longitudinal axis of each spray nozzle (41A, 41B) is aligned essentially parallel to a vertical reference axis 20 or at right angles to a surface of the workpiece 11.
[0394] The first and second atomizers (30A, 30B) are each connected via a first supply conduit to a pressurized water vessel and via a second supply conduit to an air- or nitrogen-filled pressurized gas vessel. The pressurized water and pressurized gas vessels (not shown in FIG. 4) are each designed for a pressure of 1 to 20 bar. Control valves 32 and 33 respectively are disposed in the first and second supply conduits. By means of the control valves 32 and 33, the volume flow rates (1/min) of water and gas that flow to the first and second atomizers (30A, 30B) from the water and gas pressure vessels respectively are controlled. In an appropriate embodiment of the apparatus, the first and second atomizers (30A, 30B) are each equipped with an atomizer nozzle 31. According to the invention, various concepts known in the prior art are envisaged for the configuration and design of the atomizer nozzle 31, such as one-phase nozzle for water, one-phase nozzle for gas, externally mixing two-phase nozzle, internally mixing two-phase nozzle (gas on the inside, water on the outside), internally mixing two-phase nozzle (water on the inside, gas on the outside), Venturi nozzles with a main gas flow and secondary water flow, Venturi nozzles with a main water flow and secondary gas flow, orifice nozzles, spiral nozzles, nozzles with and without swirl inserts, and rotary nozzles.
[0395] The atomizers (30A, 30B) each generate, in the nozzle chambers (40A, 40B) connected thereto, a spray mist 300 which exits through the spray nozzles (41A, 41B) and flows over the workpieces 11. The spray nozzles (41A, 41B) have a cross-sectional area of 0.25 π mm.sup.2 to 25 π mm.sup.2 and preferably take the form of simple orifice nozzles. The configuration and dimensions of the spray nozzles (41A, 41B) and the density thereof, i.e. the number of spray nozzles (41A, 41B) per unit area, are chosen such that uniform contact of the workpieces 11 with spray mist is assured.
[0396] In an appropriate configuration of the inventive apparatus 1, the nozzle chambers (40A, 40B) each comprise an outlet or a nozzle plate having two or three mutually superposed perforated plates, wherein a second and optionally a third perforated plate are movable relative to a first perforated plate. FIGS. 5a and 5b show partial top views of such a nozzle plate with three perforated plates, each of which has a multitude of circular holes of the same diameter. The relative arrangement of the holes is the same in each of the three perforated plates, with the position of the centers of the holes corresponding to the lattice points of a hexagonally tightest ball packing in two dimensions. In the position shown in FIG. 5a, all three perforated plates are aligned congruently to one another, such that the holes of the second and third perforated plates coincide with the holes of the first perforated plate. In this case, a nozzle opening formed by three mutually superposed holes in each case has a maximum cross-sectional area. In the position shown in FIG. 5b, the second and third perforated plates are moved relative to the first perforated plate, such that a nozzle opening formed by three mutually superposed holes in each case has a reduced cross-sectional area. The nozzle plate illustrated in FIGS. 5a and 5b comprises a multitude of spray nozzles controllable in parallel, the mode of function of which is based on the principle of an iris.
[0397] FIG. 6 shows a further inventive apparatus 1 for water spray quenching with a quench chamber 2 and a recirculator 7 comprising a recirculation drive 72. In an appropriate embodiment, the recirculator 7 is fluidically connected to the quench chamber 2 via two or more conduits. The quench chamber 2 contains a charge volume 5/V.sub.0 in which there are disposed one or more charge carriers 10 with a multitude of workpieces 11 mounted thereon. An inlet 71 comprises one or more atomizers 30, by means of which a spray mist 300 consisting of water and air or water and nitrogen is generated. The recirculator 7 and the recirculation drive 72 are designed and set up to bring about rapid flow of spray mist 300 through the charge volume 5/V.sub.0. In an appropriate embodiment of the apparatus 1, the recirculation drive 72 takes the form of a ventilator or fan. A portion of the spray mist 300 recirculated in the quench chamber 2 and the recirculator 7 is discharged via an outlet 73. In an appropriate embodiment of the apparatus 1, the outlet 73 is fluidically connected to a water separator (not shown in FIG. 6).
EXAMPLE 1
[0398] 200 steel bolts of diameter 25 mm, length 150 mm and weight 0.56 kg apiece are disposed on a charge carrier in an area having a length and width of 50 cm each. One of the steel bolts has an axial hole at an end face, in which a thermocouple connected to a high-temperature-resistant recorder (Fluke Datapaq® Furnace Tracker) is disposed. The charge carrier is in the form of a grid of carbon fiber-reinforced carbon (CFRC) with a mesh opening of 45 mm×45 mm and a land width of 15 mm. The steel bolts disposed on the charge carrier are heated up in a vacuum furnace equipped with a lock and kept at a temperature of 980° C. over a period of 30 min. Subsequently, the charge carrier together with the steel bolts is removed from the vacuum furnace via the lock and disposed in a quench apparatus of the invention. The quench apparatus comprises an upper and lower nozzle register each having 36 spray nozzles, arranged analogously to the manner shown in FIG. 3 such that the outlets of the spray nozzles in an upper and lower horizontal plane are in a regular pattern within a square having a side length of 40 cm, with a lateral distance between every two adjacent spray nozzles of 8 cm and a vertical distance between the upper and lower horizontal planes of 30 cm. The charge carrier is mounted on two rails such that the steel bolts are disposed virtually in the middle, i.e. at a distance of about 15 cm on each side between the upper lower horizontal planes. The time taken for the transfer from the furnace chamber to the quench apparatus is about 20 s. Immediately after the transfer of the charge carrier to the quench apparatus, each of the spray nozzles in the upper and lower registers is supplied with compressed air and water, respectively with a gauge pressure of 3 and 5 bar and flow rates of 5 m.sup.3/h and 4 l/min. The temperature progression recorded with the thermocouple in the course of quenching is shown in FIG. 7. As apparent from FIG. 7, the steel bolt equipped with the thermocouple has cooled down from 920° C. to 100° C. within about 25 s.
EXAMPLE 2
[0399] 9 of a total of 45 steel gears having external diameter 310 mm, thickness 34 mm and weight 15.1 kg apiece are laid out in a square pattern on each of 5 charge carriers within an area of 1 m×1 m. One of the gears has a horizontal hole at an end face, in which a thermocouple connected to a high-temperature-resistant recorder (Fluke Datapaq® Furnace Tracker) is disposed. Each of the 5 charge carriers is in the form of a grid of carbon fiber-reinforced carbon (CFRC) with a mesh opening of 45 mm×45 mm and a land width of 15 mm. The gear equipped with the thermocouple is disposed in the middle on the third charge carrier, i.e. in the center of the overall batch of 45 gears. The overall batch with the 45 gears is heated up in a vacuum furnace equipped with a lock and kept at a temperature of 980° C. over a period of 60 min. Subsequently, the overall batch is removed from the vacuum furnace via the lock and disposed in a quench chamber of a quench apparatus of the invention. The time taken for the transfer from the furnace chamber to the quench chamber is about 30 s. The quench apparatus is equipped with a recirculator and configured in the manner described in FIG. 6. Immediately after the transfer of the overall batch, with the aid of an atomizer disposed in the circulator and a fan, a water spray mist composed of 97.5% by volume of air and 2.5% by volume of water is generated and directed through the quench chamber, or recirculated in the quench apparatus, at a volume flow rate of 645 m.sup.3/min. The temperature of the water spray mist at the atomizer nozzle is 18° C. Water spray mist is removed with a temperature of 78° C. at a quench chamber outlet. The volume flow rates of the water spray mist generated by the atomizer and that removed at the outlet are of equal size and are each 72 m.sup.3/min. According to the temperature progression recorded by the thermocouple, the gear disposed centrally in the overall batch is cooled down from 940° C. to 100° C. within about 43 s.
LIST OF REFERENCE NUMERALS
[0400] 1 . . . apparatus for water spray quenching [0401] 2 . . . quench chamber [0402] 20 . . . reference axis, positive direction [0403] 20 . . . reference axis, negative direction [0404] 30 . . . atomizer [0405] 30A . . . atomizer [0406] 30B . . . atomizer [0407] 30U . . . atomizer [0408] 30L . . . atomizer [0409] 31 . . . atomizer nozzle [0410] 31U . . . atomizer nozzle [0411] 31L . . . atomizer nozzle [0412] 32 . . . control valve for water [0413] 33 . . . control valve for air or nitrogen [0414] 300 . . . spray mist or water spray mist [0415] 310 . . . spray mist flow arrow [0416] 320 . . . spray mist flow arrow [0417] 40A . . . nozzle chamber [0418] 40B . . . nozzle chamber [0419] 41A . . . spray nozzle [0420] 41B . . . spray nozzle [0421] 5 . . . charge volume V.sub.0 [0422] 6 . . . ventilator or fan for the removal of the spray mist from the quench chamber [0423] 7 . . . recirculator [0424] 71 . . . inlet [0425] 710 . . . inlet flow arrow [0426] 72 . . . recirculation drive (ventilator or fan) [0427] 720 . . . recirculation flow arrow [0428] 73 . . . outlet [0429] 730 . . . outlet flow arrow [0430] 10 . . . charge carrier [0431] 11 . . . workpiece
