Device and method for preheating bar-shaped metallic workpieces

Abstract

The invention relates to a device for preheating rod-shaped metallic workpieces, in particular aluminum rods or bolts, comprising a preheating container (1) for receiving the workpieces, which is supplied with a first fluid heated by a heat source, wherein the preheating container (1) has a supply connection and a return connection which are connected to the heat source via a pump, wherein the first fluid is water. The invention further relates to a method for preheating rod-shaped metallic workpieces, in particular aluminum rods or bolts, with such a device.

Description

[0001] The invention relates to a device and a method for preheating rod-shaped, metallic workpieces, in particular aluminum rods or bolts, with a preheating container for receiving the workpieces, which is supplied with a first fluid heated by a heat source.

[0002] Temperature control during the heating of metal billets is subject to stringent requirements. The billet temperature is of central importance for economical and high-quality extrusion operations. Currently, there are three main alternatives for heating billets: fuel-fired heating with integrated hot shears, billet heating with induction systems, and energy-efficient combined billet heating with rapid gas heating furnaces and induction systems, as described in WO 2010 / 031503 A1.

[0003] To increase energy efficiency, it is known in the prior art to use the exhaust gases generated in the rapid gas heating furnace to heat a preheating zone of the rapid gas heating furnace. Furthermore, it is known from DE 34 34 906 C3 to use exhaust gases from the rapid gas heating furnace to preheat the combustion air of the rapid gas heating furnace. It is also known to direct the exhaust gases from the rapid gas heating furnace into a preheating magazine, in particular a bar preheating magazine, in order to directly preheat the bars stored there.

[0004] DE 20 2018 105 511 U1 proposes passing the exhaust gases from the rapid gas heating furnace through a heat exchanger to transfer its heat to a fluid, particularly water. The heated water is then used in a preheating chamber to wet workpieces, particularly bars, present there. Because the water flows down the workpieces under the influence of gravity, a large-area heat transfer is achieved.

[0005] Further devices for heating rod-shaped metallic workpieces are disclosed in the documents WO 2020 / 064360 A1, WO 2010 / 035016 A1, DE 10 2005 058 812 A1 and DE 20 2018 105 511 U1.

[0006] In practice, the above solution only achieves a limited increase in efficiency. This is due, among other things, to the fact that the wetting process initially cools the heated water before it hits the workpiece and heat transfer can occur.

[0007] This is where the present invention comes in. The invention is based on the object of providing a device for preheating rod-shaped metallic workpieces, in particular aluminum rods or billets, which enables particularly energy-efficient heating of rod-shaped metallic workpieces, in particular aluminum billets. According to the invention, this object is achieved by a device having the features of patent claim 1.

[0008] The invention provides a device for preheating rod-shaped metallic workpieces, in particular aluminum rods or billets, which enables particularly energy-efficient heating of rod-shaped metallic workpieces, in particular aluminum billets. Because the preheating container has a flow connection and a return connection connected to the heat source via a pump, wherein the first fluid is a water-based fluid, flooding of the preheating container with a defined circulating fluid volume is possible. Rod-shaped workpieces arranged in the preheating container are completely surrounded by the fluid in a fluid bath, thereby maximizing the heat transfer from the fluid to the workpieces.

[0009] The term "water-based fluid" refers to water, an aqueous solution, and also water vapor.

[0010] The flow connection and the return connection are connected to a heat exchanger through which a second fluid flows, which is hotter than the first fluid. The second fluid is preferably a process fluid from a production or furnace facility, such as exhaust gases from a gas furnace or coil cooling water. The heat exchanger can also be configured as a heat pump arrangement.

[0011] A heat pump functions like a compression refrigeration system, except that its primary operational focus is not on the evaporator side, which serves as a cooling function, but on the condenser side, which serves as a heating function. The principle of evaporation of refrigerant in the evaporator, the increase in pressure and temperature by the compressor, and the release of heat through condensation in the condenser, with subsequent expansion of the refrigerant via the throttle valve, is the same.

[0012] In one embodiment of the invention, a bar magazine is arranged in the preheating container, wherein the preheating container has a feed opening for loading the bar magazine and a removal opening for unloading the bar magazine. This allows bars to pass through the preheating container. Alternatively, the feed and removal can also be realized through a single opening. In this case, the opening forms both the feed opening and the removal opening.

[0013] In a further embodiment of the invention, the bar magazine is designed as a revolving magazine, with a drive provided by which the revolving magazine can be rotated. This allows preheated bars to be ejected as needed.

[0014] In a further development of the invention, means for drying a workpiece are arranged downstream of the removal device. These drying means can comprise at least one compressed air nozzle connected to a compressed air line, which is arranged in front of the removal opening of the bar magazine and is preferably directed toward it. Alternatively or additionally, the means for drying a workpiece can also comprise pivotably arranged textile strips, such as those known from car washes.

[0015] In one embodiment of the invention, a conveyor device is provided for loading and / or unloading the bar magazine. This enables automated loading and unloading of the bar magazine. In a further embodiment of the invention, a control device is provided, which is connected to the drive of the revolving magazine and is configured such that a defined rotation of the revolving magazine occurs before a bolt is removed by the conveyor device. This enables removal of the maximally heated bar from the magazine.

[0016] In a further development of the invention, the bar magazine is arranged in the preheating tank so that it can be moved vertically via a drive. This enables the bar magazine to automatically immerse itself in the fluid of the preheating tank and also emerge from the fluid.

[0017] The invention is further based on the object of providing a method for preheating rod-shaped metallic workpieces, in particular aluminum rods or billets, which enables particularly energy-efficient heating of rod-shaped metallic workpieces, in particular aluminum billets. According to the invention, this object is achieved by a method having the features of patent claim 12. The workpieces are placed in a preheating container through which water flows. This water is then passed through a heat exchanger, through which a process fluid from a production or furnace facility preferably flows in countercurrent. As a result, the waste heat from the production or furnace facility is used to heat the water used to preheat the aluminum rods or billets.

[0018] In a further development of the invention, a revolver magazine is arranged in the preheating container in such a way that it can rotate so that the uppermost receptacle is aligned with the feed opening and the removal opening above the water surface, wherein the revolver magazine is first rotated during a removal process, after which a workpiece thus conveyed out of the water is conveyed out of the removal opening, after which another workpiece to be heated is conveyed through the feed opening into the space now free in the revolver magazine.

[0019] In an embodiment of the invention, the workpiece conveyed from the removal opening is dried during removal by means of compressed air and / or by means of drying textiles.

[0020] Further developments and refinements of the invention are specified in the remaining subclaims. An embodiment of the invention is illustrated in the drawings and described in detail below. They show: Figure 1: The schematic representation of a device for preheating rod-shaped, metallic workpieces with handling frame a) in a position before workpiece loading; b) in a position during workpiece loading; c) in a position after workpiece loading; Figure 2: The schematic representation of a device from Figure 1 feeding heat pump arrangement.

[0021] The device chosen as an exemplary embodiment for preheating rod-shaped, metallic workpieces comprises a preheating tank 1, in which a revolving magazine 2 is arranged so as to be rotatable via an electric motor (not shown), as well as a loading frame for loading the revolving magazine 2 with metal bolts 3. The preheating tank is filled with water. An inlet line 11 and an outlet line 12 open into the preheating tank 1, via which it is connected to the condenser 41 of a heat pump arrangement 4, the evaporator 42 of which is connected via an inlet line 51 and an outlet line 52 to a heat source, which in the exemplary embodiment is formed by the coil cooling of an induction furnace 5, indicated only schematically.

[0022] The revolver magazine 2 comprises three circular disks 22 arranged concentrically spaced from one another on an axis 21, which in the exemplary embodiment each have six regularly circumferentially arranged circular recesses 23, wherein the recesses 23 of the three circular disks 22 are aligned with one another. A receiving cage 24 for receiving a respective metal bolt 3 is guided through the mutually aligned recesses 23 of the three circular disks 22, which extend almost to the walls of the preheating container 1 arranged parallel to the circular disks 22, which are each provided with two circular recesses, a feed opening 13 and a removal opening 14, the dimensions of which correspond to the dimensions of the recesses 23 of the circular disks 22, with which they can be aligned by rotation of the revolver magazine 2. In such a position, a metal bolt 3 can be inserted into or removed from a receiving cage 24.

[0023] A slide device 6 is arranged, via which a metal bolt 3 can be pushed through the feed opening 13 of the preheating container 1 into a receiving cage 23 of the revolver magazine 2 or pushed out through the removal opening 14. In the Figures 1 a) to 1 c) Such a loading process is shown. The removal of a metal bolt 3 from the revolver magazine is carried out according to Figures 1 c) to 1 a) .

[0024] The slide device 6 and the revolver magazine 2 are connected to a control system (not shown) via which the revolver magazine 2 can be rotated into a defined position within the preheating container 1 and the slide device 6 can subsequently be actuated.

[0025] In the exemplary embodiment, the preheating tank 1 is filled with water down to below the supply opening 13 and the discharge opening 14. Via a first pump (not shown), the water is pumped through the drain line 12 (return line) into the heat pump arrangement 4 and from there through the supply line 11 (supply line) back into the preheating tank 1. The water circulating in this way is guided within the heat pump arrangement 4 around a condenser 41, where it absorbs the heat released by the refrigerant contained therein. The refrigerant is then passed through an expansion valve, where it is expanded. The refrigerant was previously heated in an evaporator 42, which is fed by the coil cooling of the induction furnace 5, and subsequently passed through a compressor 43 (see Figure 2 ).

[0026] To remove a preheated metal bolt 3 from the preheating container 1, the revolver magazine 2 is first rotated via the control system until the metal bolt 3 with the longest residence time is aligned with the removal opening 14. The metal bolt 3 is then moved out of the receiving cage 24 of the revolver magazine 3 through the removal opening 14 via the sliding device 6. Subsequently, a new metal bolt 3 is pushed through the feed opening 13 into the receiving cage 24 of the revolver magazine 2 via the sliding device 6. During the next removal of a metal bolt 3 from the preheating container 1, the revolver magazine 2 is rotated as described above, with the new metal bolt being positioned completely underwater in the preheating container 1 and heated there. The water is continuously heated by the circulation through the heat pump arrangement 4 as described above.

Claims

1. Device for preheating bar-shaped, metallic workpieces, in particular aluminium bars or billets, with a preheating vessel (1) for receiving the workpieces, which is supplied with a first fluid heated by a heat source, characterised in that the preheating vessel (1) has a fluid bath for completely receiving workpieces arranged there as well as a flow connection (11) and a return connection (12), which are connected to the heat source via a pump, wherein the first fluid is water and wherein the flow connection and the return connection are connected to a heat exchanger, through which flows a second fluid which is hotter than the first fluid and which forms the heat source.

2. Device according to claim 1, characterised in that the second fluid is a process fluid of a production or furnace device.

3. Device according to claim 1 or 2, characterised in that the heat exchanger is designed as a heat pump arrangement (4).

4. Device according to claim 1 or 2, characterised in that a bar magazine is arranged in the preheating vessel (1), wherein the preheating vessel has a feed opening (13) for loading the bar magazine and a removal opening (14) for unloading the bar magazine.

5. Device according to claim 4, characterised in that the bar magazine is designed as a revolving magazine (2), wherein a drive is arranged, via which the revolving magazine (2) is rotatable.

6. Device according to claim 4 or 5, characterised in that means for drying a workpiece are arranged downstream of the removal opening (14).

7. Device according to claim 6, characterised in that the means for drying a workpiece comprise at least one compressed air nozzle connected to a compressed air line, which is arranged in front of the removal opening (14) of the bar magazine and is preferably directed towards it.

8. Device according to claim 6 or 7, characterised in that the means for drying a workpiece comprise pivotably arranged textile strips.

9. Device according to one of claims 4 to 8, characterised in that a conveyor device for loading and / or unloading the bar magazine is arranged.

10. Device according to claim 9, characterised in that a control device is arranged, which is connected to the drive of the revolving magazine (2) and which is set up in such a manner that a defined rotation of the revolving magazine (2) takes place before removal of a billet (3) by the conveyor device.

11. Device according to one of claims 4 to 10, characterised in that the bar magazine is arranged in the preheating vessel so as to be vertically movable via an arranged drive.

12. Method for preheating bar-shaped, metallic workpieces, in particular aluminium bars or billets with a device according to one of the previous claims, wherein the workpieces are placed in the fluid bath of a preheating vessel (1), through which water flows, which is passed through a heat exchanger, through which a process fluid of a production or furnace device preferably flows in countercurrent, so that they are completely surrounded by the fluid.

13. Method according to claim 12, characterised in that in the preheating vessel a revolving magazine (2) is arranged to be rotatable in such a manner that the uppermost receptacle is in alignment with the feed opening (13) and the removal opening (14) above the water surface, wherein the revolving magazine is first rotated in the course of a removal process, after which a workpiece conveyed out of the water in this manner is conveyed out of the removal opening (14), after which a further workpiece to be heated is conveyed through the feed opening (13) into the vacated space of the revolving magazine (2).

14. Method according to claim 13, characterised in that the workpiece conveyed out of the removal opening (14) is dried during removal by means of compressed air and / or by means of drying textiles.

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