DE10038782C1 - Process for cooling, especially quenching and hardening metallic workpieces, especially steel in a cooling chamber comprises circulating parallel cooling gas streams over the workpiece and a heat exchanger - Google Patents

Abstract

Process for cooling, especially quenching and hardening metallic workpieces, especially steel in a cooling chamber (1) comprises circulating at least two parallel cooling gas streams over the workpiece and a heat exchanger (8). The gas is circulated over external circulating lines (22, 23) in which a blower (14, 15) is located. AN Independent claim is also included for a device for carrying out the cooling process. Preferred Features: The cooling gas is nitrogen, helium or hydrogen, or a mixture of at least two of these. The gas is directed coaxially against the suction side of the blower.

Description

The invention relates to a method and a device for cooling, especially for quenching and hardening of metallic work pieces, especially of steel, according to the generic terms of the patent claims 1 and 8.

From DE 28 44 843 A1 it is with a single-chamber furnace Heating and quenching area and with a blower and a cooler known in the quenching phase a part of the heating area relocating thermal insulation to move after the start of the Blown a single circuit of cooling gas over the batch and the To force cooler. One placed in this circuit before the batch Due to its periodic movement, the hinged flap is only used for Cooling gas distribution over the spread batch. This will, however alternating parts of the batch cooled and not cooled, which is the case with a Row of steels harmful by delaying the deterrence affects.  

A similar single-chamber furnace is known from DE 35 36 155 A1 for the purpose of heat treatment of long workpieces on both Each end has a cooler and a blower, both blowers are kept in constant operation. To force a quick turnaround tion of the direction of flow control spools are provided, and the Any cooler that is not required is completely removed from the gas circuit withdrawn while the other cooler is completely in the gas circulation is maintained. As a result, half of the cooling surface is located or the corresponding cooling capacity is not available.

From EP 0 313 888 B2 it is known to work pieces made of steel, in particular especially from hard-hardened, low-alloy steels and / or work heating up pieces with large or complicated shapes and then by gases from the group of helium, hydrogen and stick substance and by gas mixtures of at least two gases from this group quench and harden at pressures between 10 and 40 bar. This is intended to classic water, oil and hardening processes Salt baths with their environmental pollution will be replaced. The hardening happens by means of these gases, which are scarce at high speed below the speed of sound by means of a blower over the Workpieces or workpiece batches and a heat exchanger inside the system are circulated. The hardening can be done in a heated a one-chamber furnace or in a subsequent one belonging to the furnace system switched special quenching chamber to be performed. In the Scripture are also the background for the replacement of the Known hardening process specified.

EP 0 727 498 A1 discloses an unheated cooling chamber to assign a single large-volume circuit line in which one constantly running fan and a heat exchanger are arranged. In the circle Such a cooling gas volume is under pressure and in one Auxiliary circuit kept ready through the heat exchanger that the cooling gas after opening an upper and a lower chamber valve, between where the batch is located, suddenly passed through the batch  becomes.

In the known solutions described, there is still Problem, the cooling and / or quenching effect evenly over all Distribute workpieces in a batch. This succeeds to a sufficient extent neither by moving nor by stationary guidance devices, because quite simply the cross sections of the gas routing devices are smaller than the cross section of the batch, perpendicular to the direction of flow seen.

Another problem is that needed for large batches to circulate large quantities of gas at high speeds. At Try to increase the throughput of fans accordingly one quickly reaches technical limits with regard to diameter and Speed of the gel blower bumped, the problem of quantities distribution over the required cross sections also remained unresolved.

From DE 15 83 424 A it is known to cut individual workpieces To deter gas flows in an oven by reducing the amount of gas is divided within the furnace so that one to the workpiece surface parallel gas flow (primary flow) a variety of for this vertical gas jets (secondary flows) is superimposed on the resulting gas flow to the workpiece surface. The speed of the secondary flows are at least five times the primary flow, and the relationship should be changeable. This can be done either outside the Oven a single blower with an adjustable distribution device can be provided, or two blowers can be inside the furnace be provided both in series and in parallel work and generate different pressures. On the individual The workpiece is therefore only generated a uniform flow pattern. In addition, the known device is an oven in which both the Heating and cooling are carried out so that when Also cool down the heated parts of the oven, especially the heater tion, must be cooled, which delays the cooling process and  the said furnace parts are heavily loaded. However, it is not possible to two or more workpieces arranged in parallel gas streams or a multi-part workpiece batch or workpiece arranged in parallel charge evenly and with the same cooling conditions dosed to cool and solve the invention task.

The invention is therefore based on the object, a method and a Specify device with which even large batches with high Speed cooled or quenched evenly and if necessary can be hardened. In particular, the respective heat transfer from the workpieces or the batch of workpieces to the Cooling gas is equalized to harmful heat stresses and / or to avoid uneven product properties, and further is also the respective heat transfer from the cooling gas to the heat exchangers are evened out because of the processes on the workpiece surfaces and on the surfaces of the heat exchanger itself influence each other.

The solution to the problem is the one specified at the beginning Method according to the invention by the features in the characteristic of Claim 1 and invented in the device specified above appropriately by the Merkmaie in the characterizing part of claim 8.

The object is completely achieved by the invention, in particular, large batches can be processed at high speed cooled or quenched evenly and hardened if necessary. In particular, the respective heat transfer from the factory pieces or the batch of workpieces compared to the cooling gas moderate, and harmful thermal stresses and / or uneven Product properties are avoided. After all, that too Compare the respective heat transfer from the cooling gas to the heat exchanger moderate, because the processes on the workpiece surfaces and on the Surfaces of the heat exchanger in turn influence each other sen. So it is a synergistic effect. Additional advantages are described in the detailed description.  

In the course of further refinements of the method according to the invention, it is particularly advantageous if - either individually or in combination:

• The cooling gas from at least one gas from the group nitrogen, Helium and hydrogen or a mixture of at least there are two of these gases,
• - The cooling gas in the cooling chamber under a pressure of at least 0.5 MPa, preferably of at least 1.0 MPa, is kept,
• - Volume elements of the cooling gas alternately through the circuit lines are passed through,
• - Cooling gas stored under pressure when flooding the cooling chamber directed against at least one of the blowers, around which Speed up,
• - The cooling gas is directed coaxially against the suction side of the fan will, and / or if
• - The cooling gas essentially tangential in the direction of rotation against the The outer circumference of the blower is directed.

In the course of further refinements of the device according to the invention, it is particularly advantageous if - either individually or in combination:

• - The blowers are designed as radial blowers and with vertical ones Rotary axes with their suction openings on the upper ends of the external circuit lines are arranged,
• - the blower with downward intake manifold with the upper side of the cooling chamber,
• - The intake manifolds have rectangular cross sections and immediately  open into the cooling chamber side by side,
• - the intake manifolds are provided with guidance devices,
• - the curved walls of the intake manifold and the guide devices are concentric and arranged,
• - The bottom of the cooling chamber with opposing sideways The outlet manifold is connected to the parts of the circuit lines are,
• - The exhaust manifolds have rectangular cross sections and immediately are connected side by side to the cooling chamber,
• - the exhaust manifolds are provided with guidance devices,
• - the outlet cross-sections of the inlet manifold and the inlet cross-section cuts of the exhaust manifold so laterally offset are that each volume element of the cooling gas is the circulation line flows alternately,
• - The at least one heat exchanger in the lower area of the cooling chamber mer and above the inlet openings of the exhaust manifold is arranged
• - At least one of the blowers is assigned a mouth, by means of which cooling gas stored under pressure when flooding the cooling Chamber against at least one of the blowers is feasible Speed up.
• - The mouth coaxially aligned with the suction side of the blower is, and / or if
• - The mouth essentially tangential in the direction of rotation on the The outer circumference of the fan is aligned.

An embodiment of the subject matter of the invention is explained in more detail below with reference to FIGS. 1 to 7,

Fig. 1 is a "transparent" and partly in vertical section side view of a complete device,

Fig. 2 is a partially sectioned plan view from above of the article of FIG. 1,

Fig. 3 is a partially sectioned front view of the object of FIG. 1 on a reduced scale.

Fig. 4 shows the flow pattern of the cooling gas in a schematic, perspective view,

Fig. 5 shows an enlarged detail of the left part of Fig. 3 with a means for accelerating the speed of the fan by axial actuation of the blower wheel with pressurized cooling gas,

Fig. 6 is an enlarged section of the right part of Fig. 3 with a device for accelerating the speed of the fan by tangential action on the impeller with pressurized cooling gas and

Fig. 7 is a plan view of the subject of Fig. 6.

The central part of the device is a cooling chamber 1 , which is highlighted in FIGS. 1 to 3 by thick lines. The walls of this Kühlkam mer 1 are stiffened by appropriate outer struts so that the cooling chamber 1 can withstand internal pressures up to 5 MPa.

In Fig. 1, a batch 2 is indicated in the cooling chamber 1 with dash-dotted lines, which fills almost the entire upper part of the chamber volume and rests on support supports 3 . On the loading side in a lock chamber 4, a pressure-resistant valve guide 6 guided in horizontal guides 5 is arranged, which can be moved by a drive 7 . In the lower area of the cooling chamber 1 (or in a likewise pressure-resistant extension of this cooling chamber) there is a heat exchanger 8 which also fills the horizontal chamber cross section and which consists of a tube bundle with cooling fins and is circumscribed by a virtual cuboid surface. A refrigerant is supplied and discharged via connections 9 and 10 .

In the illustrated case, the cooling chamber 1 is connected via the lock chamber 4 to a prechamber 11 , which can be a tunnel with a further charging lock, a heat treatment furnace or the like. The cooling chamber 1 can also be designed as a continuous chamber. In this case, a further, analog lock chamber would then be arranged on the side of the lock chamber 4 opposite.

Inside the cooling chamber 1 , two parallel flow paths 12 and 13 for the cooling gas are formed in the manner described in more detail below, which are indicated by arrows. These flow paths, between which there is no partition, continue with essentially the same cross sections in the area of the heat exchanger 8 . (See also Fig. 4).

Laterally above the cooling chamber 1 , two blowers 14 and 15 with fan wheels 14 a and 15 a and drive motors 14 b and 15 b are arranged, which open into the top of the cooling chamber 1 via downward-directed intake manifolds 16 and 17 ( FIG. 3). The horizontal inlet cross-sections at the transition points of manifolds 16 and 17 and cooling chamber 1 are rectangular, are located directly next to each other and at least largely fill the horizontal cross section of the cooling chamber. As a result, the two flow paths 12 and 13 described above are formed.

Fig. 2 shows that the blowers 14 and 15 with their spiral and also pressure-resistant housings and the intake manifolds 16 and 17 are so to speak "nested" in each other to allow the close proximity shaft of the inlet cross-sections.

From Fig. 3 also follows the following: In the intake manifolds 16 and 17 guide devices 18 are arranged, which are shown only for the intake manifold 16 and are concentric with the curved outer walls 16 a and 16 b of the intake manifold. At the bottom of the cooling chamber 1 (or to a corresponding chamber section with the heat exchanger 8 ) two outlet manifolds 19 and 20 are attached below the heat exchanger 8 , in opposite directions as the inlet manifolds 16 and 17 arranged vertically above it. The horizontal manifold cross sections at the transition points from Kühlkam mer 1 and the exhaust manifolds 19 and 20 are also rectangular in shape, lie directly next to each other and at least largely fill the horizontal cross section of the cooling chamber 1 and the heat exchanger 8 . This also forms or supports the two parallel and vertical flow paths 12 and 13 described above. A guide device 21 is only shown for the exhaust manifold 19 .

As shown in FIG. 3, the blowers 14 and 15 designed as radial blowers with vertical rotary axes A1 and A2 are placed with their intake openings 14 c and 15 c on the upper vertical ends of external circuit lines 22 and 23 , which are the outlet manifolds 19 and Connect 20 to blowers 14 and 15 .

The following can be seen from the representations in FIGS. 3 and 4, the description relating to the movement of a volume element of the cooling gas:

The cooling gas flows from the right blower 15 through the inlet manifold 16 into the cooling chamber 1 and there along the (front) flow path 12 through the front region of the batch of workpieces, then through the front region of the heat exchanger 8 , from here through the left-hand outlet manifold 19 into the circuit line 22 and from here to the left blower 14 .

Subsequently, the cooling gas flows from the left blower 14 through the intake manifold 17 into the cooling chamber 1 and there along the (rear) flow path 13 through the rear area of the batch of work, then through the rear area of the heat exchanger 8 , from here through to right-hand outlet manifold 20 in the circuit line 23 and from here to the right blower 15 , whereupon the game is repeated as often as required for each volume element of the cooling gas.

The entire flow path has - in the front view according to FIG. 3 - the shape of a lying figure eight with a "crossing area" within the cooling chamber and heat exchanger. This “intersection area” naturally has a horizontal extent according to the arrows 12 and 13 in FIGS. 1 and 4, local mixing also being possible. Of course, all of these processes take place simultaneously.

A major advantage is thus that inlet manifolds 16 and 17 and outlet manifolds 20 and 19 , which are assigned to the same fan, are connected to different chamber areas, so that the partial flows are permanently mixed. Each volume element of the cooling gas thus alternately passes through the flow paths 12 and 13 , which leads to the cooling process being evened out even with asymmetrically distributed batches.

FIG. 4 shows, in schematic and perspective view of the flow principle described above, in and out of Charge 2 and heat exchanger 8. The two thick arrows represent the flow paths within the batch, it being understood, of course, that these flow paths include an even flow distribution over the cross section of the respective batch part.

The same reference numbers, using - - through 7 with reference to FIG 5 advantageous further possible embodiments of the invention explained.:

FIG. 5 shows - enlarged - the blower 14 arranged on the left in FIG. 3 with the circuit line 22 and the suction opening 14 c. Furthermore, Darge represents a pressure vessel 24 , into which the cooling gas is pumped back after completion of its purpose by means of a compressor, not shown, and compressed to a correspondingly high pressure. This pressure boiler 24 is connected via a shut-off valve 25 to an actuator 26 with an inlet port 27 which penetrates the wall of the circuit line 22 and passes there into a pipe elbow 28 , the mouth 29 of which is arranged coaxially to the axis A1 and on the suction opening 14 c is aimed. So it has the following evidence: When the system is flooded from normal pressure (when charging) to the predetermined quenching pressure, the blower 14 is blown axially and accelerated to its operating speed by the curvature of the impeller blades. As a result, the full cooling capacity can be reached more quickly and the cooling process can be accelerated, and on the other hand the starting current and the starting time of the blower motor 14 b can be significantly reduced. This considerably reduces the peak load on the electrical supply system and expensive control elements for limiting the starting current can be avoided.

Figures 6 and 7 show in vertical section and in plan view -. Ver enlarges -. The right in Figure 3 arranged blower 15 to the circulation line 23 and the suction port 15 c. Furthermore, there is also an analog pressure vessel - not shown - into which the cooling gas is pumped back after the end of its purpose by means of a compressor (not shown) and compressed to a correspondingly high pressure. This pressure vessel is connected via a shut-off valve to an inlet connector 30 which penetrates the housing wall of the fan and merges there into a pipe connector 31 , the mouth 32 of which is aligned with its axis approximately tangentially to the outer circumference of the fan wheel 15 a. This also exerts an additional acceleration effect on the impeller 15 a with the same advantages as described with reference to FIG. 5.

Of course, the systems according to FIG. 5 and according to FIGS. 6 and 7 can also be used symmetrically and / or together. In continuation of the invention, the number of flow paths and fans can also be increased still further.

Embodiments

Hardened by quenching in a system according to FIGS. 1 to 4 batches with the following data:
Batch dimensions:
Width: 600 mm
Height: 600 mm
Length 1000 mm.
Batch weight: 250 kg
Batch surface: max. 7.5 m ²
Deterrence:
Pressure: 2.0 MPa
Medium: helium
Blower output (both blowers):
2.0 MPa He: 132 kW
(Comparison: 2.0 MPa N ₂ : 250 kW)
Temperatures:
Starting temperature: 930 ° C
Uniformity: ± 5 K.
Cooling water: max. 25 ° C
Output: +15 to + 40 ° C
Steels:

• 1.EHT 0.3 + 0.2 (case hardening steel similar to 16MnCr5) Stationary gears, gears, pinions, shafts,
• 2. EHT 0.5 + 0.3 (case hardening steel similar to 16MnCr5) Car gearboxes, gears, pinions, shafts, sliding sleeves,
• 3. EHT 1 , 5 + 0.5 (case hardening steel similar to 16MnCr5) workpieces: transporter gear, sprockets, shafts,
• 4. 42CrMo4 workpieces: injection systems).

In all cases, the times of infiltration and quenching lasted 5 minutes each. The quench gas recovery times  was between 11 and 18 minutes each and for transportation each 10 mins.

Reference list

1

Cooling chamber

2nd

Batch

3rd

Props

4

Lock chamber

5

Horizontal guides

6

Valve spool

7

drive

8th

Heat exchanger

9

Connection

10th

Connection

11

Antechamber

12th

Flow path

13

Flow path

14

fan

14

a fan wheel

14

b drive motor

14

c Intake opening

15

fan

15

a fan wheel

15

b drive motor

15

c Intake opening

16

Intake manifold

16

a outer wall

16

b outer wall

17th

Intake manifold

18th

Control systems

19th

Exhaust manifold

20th

Exhaust manifold

21

Control device

22

Circulation line

23

Circulation line

24th

Pressure vessel

25th

Shut-off valve

26

Actuator

27

Inlet connector

28

Pipe elbow

29

muzzle

30th

Inlet connector

31

Pipe socket

32

muzzle
A1 axis of rotation
A2 axis of rotation

Claims (21)

1. A method for cooling, in particular for quenching and hardening metallic workpieces, in particular steel, in a cooling chamber ( 1 ) by circulating cooling gas in a circuit over the workpieces and at least one heat exchanger ( 8 ), characterized in that at least two at least in substantially parallel cooling gas flows are passed over the workpieces and the at least one heat exchanger ( 8 ) and that the cooling gas is circulated via external circuit lines ( 22 , 23 ), in each of which a blower ( 14 , 15 ) is located. 2. The method according to claim 1, characterized in that the Cooling gas from at least one gas from the group nitrogen, Helium and hydrogen or a mixture of at least two of these gases exist. 3. The method according to claim 1, characterized in that the cooling gas in the cooling chamber ( 1 ) is kept under a pressure of at least 0.5 MPa, preferably of at least 1.0 MPa. 4. The method according to claim 1, characterized in that volume elements of the cooling gas are alternately passed through the circuit lines ( 22 , 23 ). 5. The method according to claim 1, characterized in that pressurized stored cooling gas during the flooding of the cooling chamber ( 1 ) directed against at least one of the blowers ( 14 , 15 ) to flow to accelerate its speed. 6. The method according to claim 5, characterized in that the cooling gas is directed coaxially against the suction side of the fan ( 14 , 15 ). 7. The method according to claim 5, characterized in that the cooling gas is directed substantially tangentially in the direction of rotation against the outer circumference of the fan ( 14 , 15 ). 8. A device for cooling, in particular for quenching and hardening metallic workpieces, especially steels, in a cooling chamber ( 1 ) by circulating cooling gas in the circuit via the workpieces and at least one heat exchanger ( 8 ), characterized in that at least two external circuit lines ( 22 , 23 ) are provided, each with a blower ( 14 , 15 ) through which at least two at least substantially parallel cooling gas flows can be conducted over the workpieces and the at least one heat exchanger ( 8 ). 9. The device according to claim 8, characterized in that the fans ( 14 , 15 ) designed as radial fans and with vertical axes of rotation (A1, A2) with their suction openings ( 14 c, 15 c) on the upper ends of the external circuit lines ( 22 , 23 ) are arranged. 10. The device according to claim 8, characterized in that the fans ( 14 , 15 ) via downward inlet manifold ( 16 , 17 ) with the top of the cooling chamber ( 1 ) are connected. 11. The device according to claim 10, characterized in that the inlet manifold ( 16 , 17 ) have rectangular cross sections and open directly next to each other in the cooling chamber ( 1 ). 12. The apparatus according to claim 11, characterized in that the inlet manifold ( 16 , 17 ) are provided with guide devices ( 18 ). 13. The apparatus according to claim 12, characterized in that the curved walls ( 16 a, 16 b) of the intake manifold ( 16 , 17 ) and the guide devices ( 18 ) are formed and arranged concentrically. 14. The apparatus according to claim 8, characterized in that the underside of the cooling chamber ( 1 ) with opposite side-directed outlet bends ( 19 , 20 ) is connected, which are parts of the circuit lines ( 22 , 23 ). 15. The apparatus according to claim 14, characterized in that the outlet manifolds ( 19 , 20 ) have rectangular cross sections and are connected directly next to one another with the cooling chamber ( 1 ). 16. The apparatus according to claim 15, characterized in that, the outlet manifold ( 19 , 20 ) are provided with guide devices ( 21 ). 17. The apparatus according to claim 8, characterized in that the outlet cross sections of the inlet manifold ( 16 , 17 ) and the inlet cross sections of the outlet manifold ( 19 , 20 ) are arranged laterally offset such that each volume element of the cooling gas, the circuit lines ( 22 , 23 ) alternately flows through. 18. The apparatus according to claim 8, characterized in that the at least one heat exchanger ( 8 ) in the lower region of the cooling chamber ( 1 ) and above the inlet openings of the outlet manifold ( 19 , 20 ) is arranged. 19. The apparatus according to claim 9, characterized in that at least one of the blowers ( 14 , 15 ) is assigned an opening ( 29 , 32 ) by means of which cooling gas stored under pressure when flooding the cooling chamber ( 1 ) against at least one of the blowers ( 14 , 15 ) is feasible to accelerate its speed. 20. The apparatus according to claim 19, characterized in that the mouth ( 29 ) is aligned coaxially on the suction side of the blower ( 14 , 15 ). 21. The apparatus according to claim 19, characterized in that the mouth ( 32 ) is aligned substantially tangentially in the direction of rotation on the outer circumference of the fan ( 14 , 15 ).