WO2001020053A1 - Method for heat treatment of metallic slugs - Google Patents

Abstract

The invention relates to a method for the heat treatment of homogenised, cooled cast metallic slugs, which, in relation to a diameter of 200 mm, is reheated to the required temperature for a maximum period of 20 minutes and then subjected to a passive temperature compensation for a maximum period of 3 minutes so that a uniform temperature of less than < 10 K is attained. Heating is carried out by means of gas burner flames and followed by a forced convection effected by spraying jets of hot gas. The reheated metallic slug is thereafter subjected to shock cooling by means of water jets poured to the surface of said billet at a temperature of at least 150K below pressing temperature for a diameter of 200 mm within a maximum jet period of 30 seconds; the required temperature distribution is achieved after a temperature compensation time which is longer than extrusion duration. Also disclosed are devices to carry out said heat treatment.

Description

 Process for the heat treatment of metallic press bolts

description

The invention relates to methods for the heat treatment of metallic press bolts or - when using a pair of warm shears - rod sections prior to being introduced into the extrusion press and devices for carrying out the method.

In the following, such bolts or rod sections are also referred to as "blocks".

Cast, homogenized and then cooled blocks are subjected to a heat treatment immediately before being introduced into the pressing device, in which the blocks are reheated, then cooled and fed to the pressing device.

Such a method is evident, for example, from EP-B1-0 302 623. The press block, which is cast in the usual way, primarily made of an AIMgSi alloy, is first homogenized and cooled after the casting process, in accordance with the prior art. Before pressing, it is heated to a temperature above the solubility temperature of the phases which have been eliminated in the cooling after the homogenization and is kept at this temperature until the phases are dissolved again. After this reheating, during which the block is at a temperature of more than 350 ° C. for a maximum of 20 minutes, the block is rapidly cooled to the pressing temperature, which is lower than the solubility temperature and not more than 510 ° C. With this cooling, the re-excretion of phases is to be prevented. Apart from the fact that it would hardly be technically possible to wait in a production facility with a high throughput until all phases have been resolved, and that the holding time is still limited to a time of less than 20 minutes, which means the dissolution of the eliminated Questioning phases, this method is not suitable for use in a heat treatment process that takes place with a highly productive extrusion press before the actual extrusion process.

The description shows that in the method according to EP-Bl-0 302 623, the cooling process to reach the lowest cooling temperature took up to 20 minutes. It is therefore a process that takes place in the minute range and in which the temperature can even out over long distances due to the heat conduction, i.e. noticeably in the longitudinal direction of the block. This is also the reason why only one temperature is mentioned in the aforementioned document.

Such a moderately fast cooling is disadvantageous, however, if a temperature profile falling against the pressing direction, a so-called temperature taper, is to be achieved in the block by the cooling before pressing, because with a relatively slow cooling there is also considerable temperature compensation in the longitudinal direction , which makes it difficult or impossible to produce the desired temperature taper with the help of controlled cooling. Such a temperature taper is, however, a prerequisite for the advantageous isothermal pressing in direct-working extrusion presses.

The main purpose of the method described in EP-B1-0 302 623 is to improve the quality of the extruded products while increasing the pressing speed. In order to demonstrate this advantage, examples are described in the aforementioned document. This is a method according to the prior art compared with the method according to EP-B1-0 302 623. Regarding the surface quality as well as with regard to the strength values, namely RPO 2, RM and elongation, no noticeably positive effect can be determined when this method is used, taking into account the scatter of technical measurement values. This is not surprising, since experience has shown that the most precise temperature control is very important when extruding, in particular light alloys with high productivity. With regard to this temperature control, however, the aforementioned document does not contain any statements as to which temperature accuracy is required or how this accuracy is to be achieved.

Other publications deal with the heating of such blocks on the one hand and their cooling on the other.

A device for heating press bolts and rods is described in WO 83/02661. Burners or hot gas jets generated by combustion are applied to the surface of the crop. The exhaust gas is collected with an exhaust gas duct above the heating area and fed to a preheating zone with convective heat transfer. The convective heat transfer takes place by blowing the heat material with slot nozzles arranged on the side, the gas flow for feeding these slot nozzles being circulated with fans in a closed circuit. This device is only conditionally suitable for heating with narrow temperature tolerances at high throughput, since the temperature accuracy, which can be achieved with direct flame exposure, leaves something to be desired even with moderate throughputs. This is because the possibility of temperature control is adversely affected by the fact that the exhaust gas collection duct continuously draws off exhaust gas in a certain area of the device, regardless of the heat input and thus the local exhaust gas generation. Another disadvantage is that The convective heating, which is in principle more uniform than the heating with direct flame exposure, takes place at the beginning of the device, where high temperature accuracy is not particularly important because of the low material temperatures there, while at the end of the heating process, where only small temperature differences are tolerated can only be heated with direct flame exposure, which leads to larger local temperature differences due to the process. The device according to WO 83/02661 is therefore unfavorable in terms of heating accuracy, namely the wrong way round.

To the hot exhaust gases from the heating zone, the z. B. works with direct flame exposure to better exploit, a device is described in DE-OS 26 37 646 in which the hot exhaust gas is circulated in convection heating zones before the quick heating part with flame exposure and is inflated with jet jets onto the material before it is blown in the direction of good transport Leaves device through the exhaust stack. The nozzles are slot nozzles arranged on both sides of the material with longitudinal axes of the nozzle openings perpendicular to the product axis. This device also has the arrangement of the convection heating zone in front of the heating zone with direct flame exposure which is unfavorable with regard to the uniformity of the heating.

Other devices with convective heating without any direct flame exposure to the goods are known from DE-OS 35 09 483 AI, DE 34 18 603 Cl and DE 195 38 364 C2. In these devices, the gas stream circulated in the convection zones for the purpose of convective heat transfer is heated with heating devices and the heat is transferred from this gas stream to the material. All of these devices have significant disadvantages. In the case of devices with convective heating without direct exposure to flame, uniform heating with a sufficiently uniform temperature distribution can be achieved, but by limiting the operating temperature to the maximum temperature that is acceptable for the convection system equipped with a hot gas fan, this limits the maximum heat flow density that can be transferred to the good surface and thus a limitation of the heating rate. The result is relatively low throughput rates or long systems with the known disadvantages due to the relatively long column of goods when changing alloys during production, which usually also require a change in the final product temperature. As a result, such devices are inflexible in production and unsuitable for carrying out processes that require high accuracy. Further disadvantages are the higher costs due to the longer length and the higher space requirement.

Devices with heating by direct flame exposure do allow quite high heating rates due to the high furnace chamber temperature - for devices for heating light metal alloys by 1000 ° C - but the temperature distribution in the material is very uneven. Particularly with changing crop surfaces, satisfactory temperature uniformity cannot be achieved due to the changing strong radiation influence, even with complex control and regulation technology. If the production process suddenly stops, e.g. B. because of a press or tool problem, it often even melts the heat. In addition, the energy utilization is low and consequently the heating power and energy requirements related to the material throughput are high.

These disadvantages are also present in the device with convective preheating known from DE-OS 26 37 646. The energy utilization is a bit better, due to the combination of preheating with rapid heating, e.g. B. by direct flame exposure: There is only exhaust gas when the flame exposure is working, but the temperature control is even more difficult and the temperature accuracy in the goods, especially when production is interrupted, e.g. B. when changing tools, unsatisfactory. Therefore, such a device can not be used if special demands must be made on the temperature uniformity, such as. B. when heating aluminum alloys AIMgSi to press temperatures in the homogenization temperature range and close to the melting temperature with subsequent rapid cooling before extrusion to increase productivity and quality.

A number of cooling devices are known for carrying out the cooling process. US-A 5,027,634 describes a cooling device which consists of at least one cooling ring through which the block is pushed during the cooling process by means of an impact device. By changing the impact speed, the cooling caused by the cooling device over the block length can be influenced. The cooling ring itself has numerous bores with a relatively small diameter, through which the water used as cooling fluid is sprayed onto the block. The cooling ring is open at the top for the passage of the impact device. Disadvantages of this device are, in addition to the complicated control of the block movements and the complex transport mechanism, in particular the small cooling nozzles, which tend to clog, and the uneven cooling effect over the circumference, which is caused by the opening at the top of the cooling ring for passage of the impact device, because in there are no cooling nozzles in this area.

The device according to US Pat. No. 5,425,386 attempts to avoid the disadvantage of the small bores in the cooling ring due to an annular slot as the nozzle opening. However, the complicated transport mechanics and the complex control of the block movement are still required. In addition, the annulus supplied with the cooling fluid as a nozzle opening from a prechamber, so that the same pressure is available around the circumference of the entire nozzle slot. There is therefore no way to adapt the cooling to the requirements of the orientation of the block surface. During a significant portion of the cooling process, the block surface temperature is well above the Leidenfrost temperature, so the cooling process is determined by the vapor film immediately on the surface of the block. When the block is horizontal, this vapor film is different on the underside, on the top and on both sides of the block, where the tangent to the surface is vertical. As a result, it should also be possible to adapt the water supply to these different situations in order to achieve uniform cooling.

The device according to US Pat. No. 5,325,694 attempts to simplify the handling of the device and to automate the control by constructing a control loop which links the temperature reduction of the block caused by the cooling with the block feed rate. However, the additional sensors required make the device not only more complex, but also more prone to failure.

US-A 5,337,768 describes a further embodiment of the control of such a device, but which has the same basic disadvantages as the aforementioned US-A 5,325,694.

The invention has for its object to provide methods for the heat treatment of metallic press bolts or rod sections before insertion into the extrusion press, and devices for carrying out the method, in which the above-mentioned disadvantages do not occur. In particular, methods and devices are to be proposed which enable a very fast and at the same time very precise heat treatment from reheating and cooling. This is achieved by the features of the respective main claims, while expedient variants of these methods and devices are defined by the associated subclaims.

In the case of extrusion, in particular of light metal alloys, it is important to achieve high productivity that the entire extrusion is pressed at the highest possible speed while maintaining a specific and optimal extrusion temperature. In order to achieve this goal, different starting temperatures of the block are required, depending on the profile shape and tool - i.e. the degree of forming - and the desired pressing speed, which is as high as possible for productivity reasons - and thus depending on the forming capacity. In the case of direct-working extrusion presses, as are usually used for light metal alloys, it is also important that the block has a temperature profile which drops in the opposite direction to the pressing direction, a so-called "temperature taper". This temperature scanner, as has long been known as the prior art, is required to compensate for the increasing mechanical energy input from the beginning of the block to the end of the block, which is converted into heat during the pressing process, so that the pressing process can nevertheless proceed isothermally. The more precisely this temperature probe is matched to the respective pressing conditions, the higher the pressing speed can be selected and the greater the productivity.

According to the invention, bolts or rods, that is to say blocks, are first heated as quickly as possible to a pressing temperature which is as high as possible and depends on the respective material, the temperature in the block being evenly distributed after this heating with a very low temperature tolerance. Typical is e.g. B. for light metal alloys a temperature tolerance of less than ± 10 K, z. B. ± 5 K for block diameters from 250 mm to 300 mm. After this heating, it is particularly advantageous in highly productive extrusion operation to cool the block as quickly as possible with water in a rugged cooling device, so that after this rugged cooling and the temperature compensation due to the heat conduction dependent on the block material, this with the desired tight tolerance required for the respective press tool - That is, the respective profile shape - and the desired starting temperature, which is as high as possible for productivity reasons, has the optimum starting temperature on the side of the block facing the tool, and the optimum distribution of this temperature over the length of the block. Typical for the fastest possible cooling is an active cooling time of approx. 30 s, which is followed by a time for temperature compensation by heat conduction, which takes place primarily over the cross-section of the block, which is typically somewhat longer than the active cooling time. After the rapid cooling, the block is placed in the extrusion press and pressed. The transfer time required for this is also taken into account when dimensioning the time period for temperature compensation due to heat conduction.

In contrast to the prior art, the method according to the invention allows the block to be provided with exactly the required temperature or temperature distribution, and this with the necessary low temperature tolerance.

When pressing light metal alloys that are difficult to press, e.g. B. Alloys with the numbers 7xxx and 2xxx, for which indirect working extrusion presses are usually used to exclude the influence of friction of the recipient wall, it is advantageous that the block has a defined higher temperature at the beginning than the pressing temperature, which is distributed as evenly as possible in the remaining block. This is also easily possible with the method according to the invention, since in addition to a uniform temperature distribution, local temperature differences, e.g. B. higher temperature can only be generated at the beginning of the block. Another advantage of the method according to the invention is its suitability for press operation with maximum productivity. If the cooling time and temperature compensation time are longer than the pressing sequence, the so-called block sequence time, two cooling devices can be operated in parallel, so that regardless of the block sequence time, each block can individually experience the necessary cooling time and compensation time, even if the two time periods in the addition are longer than the block sequence time.

Even in the event of unintentional interruptions in the pressing operation, the consequences of which are all the more serious the higher the productivity of the extrusion press, the method according to the invention has decisive advantages over the prior art. In fact, according to the invention, rapid heating by means of direct flame exposure during the first part of the heating process is combined with convective heating in the final part. With this convective heating, any material overheating, even if the press is interrupted and consequently the block transport stops, can be prevented by suitable selection of the gas temperature. As soon as the press is operational again, a block with exactly the right press temperature is immediately available.

This essential advantage according to the invention is already achieved in that, according to the invention, a rapid heating device with direct flame exposure in accordance with the known prior art is combined with convective reheating, in which the temperature compensation also takes place. Because of the lower costs of the conventional burners, this solution requires a somewhat lower cost compared to the recuperator burners which can be used particularly advantageously. The main advantage of this simple solution, however, is that it is suitable for retrofitting to carry out the method according to the invention by simply attaching at least one convection heating zone to an existing rapid heating system with direct flame application. A significant advantage, which relates to the production costs, is the extremely low gas consumption compared to systems according to the prior art, which is achieved by the advantageous use of burners with an integrated exhaust gas recuperator for preheating the combustion air. In addition to this cost advantage, the use of recuperative burners with integrated combustion air preheating is also a great advantage in terms of control technology, since combustion air preheating and burner operation are clearly linked. In systems according to the prior art, on the other hand, the exhaust gas from all the burners is collected, withdrawn at one point - usually the beginning of the flame exposure zone - and fed to a central heat exchanger for preheating the combustion air. The central exhaust gas extraction creates a longitudinal flow in the furnace, which adversely affects the temperature control behavior of the individual zones. If the door on the outlet side of the heating device is opened when a block is removed, even cold air can enter the furnace during continuous operation of the exhaust gas extraction system, which in turn adversely affects the temperature distribution in the material column and the temperature control. In the method according to the invention and with the heating device according to the invention, the operation of recuperative burners with an exhaust gas detector ensures that exhaust gas in the same or almost the same amount as the combustion gas generated is only removed when the respective burner is actually switched on.

In addition to this advantage in terms of control technology, there is also an advantage in terms of improving the heat transfer. The recuperator burners are operated at a very high flame exit speed. This creates a jet that flushes the block vigorously and ensures an increase in convective heat transfer even without the use of a special flow drive. In addition, due to the induction effect of the pulsed burner beam, that in the Existing hot exhaust gas is circulated with the heating device, which in turn increases the convective heat transfer.

Furthermore, there is also the possibility, in the method according to the invention, which provides recuperator burners for heating, also to use those recuperator burners which operate in flox mode with flameless oxidation at correspondingly high furnace interior temperatures. Flameless oxidation means that gas, exhaust gas and combustion air are mixed in the burner in such a way that no flame is visible and the thermal energy-releasing oxidation takes place in the burner jet to a certain extent. This has decisive advantages for the equalization of the heat transfer on the block surface.

The aforementioned recuperator burners, some of which are also suitable for Flox operation, are described in DE 34 22 221 4, EP 0 463 218 Bl, EP 0 685 683 Bl and DE 195 41 922 C2.

Finally, the use of recuperative burners according to the invention leads to a shortening of the required system length in comparison with a system of the same power according to the prior art. The reason for this is that the preheating zone, which is required in systems according to the prior art in order to recuperate at least part of the exhaust gas heat, is eliminated. This shorter overall length with greater performance not only means saving space, but is also advantageous in terms of process technology, since the block column contained in the system is shorter, which considerably simplifies the operation of the system with different alloys.

In summary, the method according to the invention has the following advantages with regard to heating: 1. Division of the heating into rapid heating by means of direct flame exposure only in the front part of the heating device, whereas at the end of the heating device the heat transfer takes place convectively. As a result, the high heating rate with direct flame exposure is combined with uniform heating without the risk of local overheating with convective heating.

2. Possibility of retrofitting an existing rapid heating system with direct flame exposure by adding at least one convection zone to the end of the existing heating device.

3. Use of recuprator burners with integrated fresh air preheating. This improves the control behavior of the heating device and also significantly reduces fuel consumption. Reduction of the system length due to the elimination of the preheating zone.

4. Possibility of using burners for operation with flameless oxidation and thereby equalizing the heat transfer with direct burner beam exposure.

The cooling method according to the invention and the device for carrying out this method have further advantages. This is because, as in the prior art, a block is not moved through a cooling ring in the longitudinal direction, but rather the block, held on its end faces, is introduced into a stationary cooling device as a whole. The cooling takes place by means of an annular arrangement of individual nozzles, which are located in a precisely defined, fixed position in relation to the block during the cooling process. The desired cooling effect necessary to achieve the required temperature or temperature distribution is achieved by operating these individual nozzles arranged in rings with different pressures and / or different switch-on times reached. The effort for control and handling is much less than for devices according to the prior art; in addition, the accuracy with regard to the temperature and temperature distribution to be achieved is higher than in known devices and methods.

The invention is explained in more detail below using exemplary embodiments with reference to the accompanying schematic drawing.

Show it

Figure 1 shows the temperature curve for a block over time from the start of rapid heating via the Schroff cooling until it is brought into the press;

Figure 2 shows the arrangement of the individual units for performing the heat treatment according to the invention;

FIG. 3 shows a schematic illustration of a device according to the invention for carrying out the rapid heating with sectional views of the device parts arranged one behind the other, the heating being carried out with direct flame exposure according to the prior art;

FIG. 4 shows a flow diagram of the system for carrying out the rapid heating, shown schematically in FIG. 3;

FIG. 5 shows another embodiment of the zone according to the invention of the device with direct flame exposure using recuperator burners; FIG. 6 advantageous nozzle shapes for high-speed recuperator burners;

FIG. 7 shows a typical temperature profile in the individual parts of the heating device and in the material heated with the device;

Figure8 shows the Schroffabkühlvorrichtung in a schematic, simplified cross section;

FIG. 9 shows a schematically simplified longitudinal view of the rugged cooling device, in which the housing is shown in section;

Figure 10 is a diagram with typical cooling curves for the measuring points in the diagram to be cooled in the block.

The method according to the present invention is illustrated by FIG. 1. FIG. 1 schematically shows the temperature profile for a block over time from the beginning of the heating to the time it is brought into the press. First, the block undergoes rapid heating in a maximum of 20 minutes in the area of the device, which in the example of FIG. 1 works with direct flame exposure through recuperator or recuperator Flox burners, so that there is no preheating zone for exhaust gas cooling. The heating is completed in at least one zone with convective heat transfer at a comparatively low overtemperature. This is also where the tempera compensation takes place for a maximum of 3 minutes. Then the transfer to the cooling station takes place. After the active cooling time of maximum 30 seconds, the block goes through a temperature compensation time. In the end of this compensation time, the block is brought to the press and then shows a temperature difference between the end of the block and the beginning of the block during isothermal pressing. Figure 2 shows schematically how the individual units are arranged for performing the method according to the invention. The press is indicated schematically by reference numerals 2 and 3. 2 denotes the recipient into which the block 1 is inserted and pressed with the press ram 3 during the extrusion process. The extruded profile, or in the case of tools with several outlets, the profiles (not shown) are guided on the press outlet 12. The block 1 is loaded into the press 2, 3 with a block loader 4, which is also only indicated schematically.

The heating takes place in the direction of flow 9, first by direct flame exposure in the front part of the heating device 7 and then, for example, in two convection zones 8a and 8b connected in series, the last convection zone 8b in the direction of flow 9 being operated with a lower gas temperature than the front zone 8a. The block arrives in a transverse transport 5 from the heating device 7. The direction of movement is indicated by the arrow 10. From the transverse transport 5, the block is either introduced into the cooling station 6a or into the cooling station 6b and moves in the direction of the movement arrows 11a and 11b. As already mentioned, more than one cooling station makes sense if a system works with high productivity and short block sequence times.

The good 1, a column of individual bolts or rods which have already been sawn to length (only indicated in the figure for reasons of simplification), is conveyed via a transport device, e.g. B. as shown in Figure 3, a roller conveyor 20 through the Vorrichmng. In the case of non-driven rollers, the transport takes place via impact devices outside the device. Other possibilities, not shown in the figures, are the transport of the goods 1 through the device by means of a walking beam or a transport chain. It can also be powered Rolls or other transport options known from the prior art can be used.

The first part of the device essentially consists of the area of flame exposure. In Figure 3, two flame exposure zones 7a, 7b are shown as an example. In front of the first flame application zone 7 in the direction of transport there is an entry zone 13 and behind the second (last) flame application zone 7b there is a separation zone 14. The separation zone 14 is followed by the first 8a of two convection zones 8a, 8b; the last convection zone 8b in the direction of transport, which primarily applies to temperature compensation, forms the end of the device. In the flame exposure zones 7a, 7b, the material 1 is heated by the flames generated with burner nozzles 15. To a large extent, the heat is transmitted to the material 1 via radiation from the surrounding furnace space. The exhaust gas from the burners is collected in the input zone 13 and the separation zone 14 and is discharged from the apparatus via exhaust gas lines 16.

The convection zones 8a, 8b each have a flow system which contains at least one fan 17, at least one burner 22 for heating the heating gas and nozzles 18 arranged on both sides of the material for blowing, the material for the purpose of convective heat transfer. The nozzles 18 are fed by the fan 17 via a flow channel system 19, see FIG. Fig. 3.

As can be seen from the flow diagram according to FIG. 4, the exhaust gas is passed through a heat exchanger 21, with which the combustion air for the gas burners is preheated. Recuperator burners 22 are expediently used for heating in the convection zones 8a, 8b, so that here the exhaust gas cooled by preheating the combustion air exits to the exhaust port of the burner. A particularly advantageous embodiment of the flame exposure zone is shown schematically in FIG. The heating takes place by means of a smaller number of recuperator burners 22 compared to the flame exposure zone shown in FIG. 3. The external heat exchanger 21 for the combustion air preheating is therefore not required in this embodiment. In addition, the recuperator burners used can be inexpensively designed as high-speed burners and / or high-speed Flox burners, which automatically switch from normal combustion mode to Flox mode when the corresponding furnace chamber temperature is reached.

The high-speed burner jets can act on the material to be heated on a comparatively large area using the Coanda effect with a favorable design of the burner nozzle, as shown in FIG. 5 by the schematic flow arrows 23. The axes of the burners and thus of the flame jets 24 or burner jets during Flox operation can also be inclined against the vertical in order to improve the flow on the surface of the crop. It is also possible to use the burner jets 24 to improve the application of material by means of nozzle mouthpieces made of high-temperature resistant material, e.g. B. affect silicon carbide. FIG. 6 shows such possible, advantageous examples for the nozzles of high-speed burners. FIG. 6a shows a burner nozzle which deforms the round burner jet into a flat jet; FIG. 6b shows a burner nozzle in which the flat jet has a web in the middle and the two partial jets are correspondingly stronger than in FIG. 6a. FIG. 6c shows a burner nozzle with an outlet cross section of the "dog bone"type; FIG. 6d shows the cross section of a burner nozzle with which the burner jet is deflected from the vertical. FIG. 6e shows a burner nozzle which dissolves the burner jet into several — in the figure in three — individual jets which impinge on the surface of the crop in different directions. This way Achieve heat flow densities of 300 kW / m2 and more even over larger parts of the block surface.

The great advantage of the rapid heating device is evident from the schematic temperature profile for the core and the surface of the material 1, which is shown in FIG. In the flame exposure zones, two zones, FI and F2, are assumed in the example in FIG. 7, the furnace chamber temperature is extremely high, as is also the case with the conventional flame exposure zones according to the prior art. Since these zones are now used at the beginning of the device, there is no risk of overheating, and the spreading of the temperature curve for various points of the material shown schematically in FIG. 7 is irrelevant, since the temperature in the following two convection zones K1 and K2 equalize can. Finally, in the second zone K2, the gas temperature (= external room temperature) is in the range of the desired final temperature. As a result, overheating of the goods is prevented even in the event of unscheduled stoppages of the press and consequent interruptions in the transport of goods in the device.

An advantageous exemplary embodiment of a cooling device for carrying out the cooling of the block in accordance with the heat treatment method according to the invention is described with reference to FIGS. 8 to 10.

The block 1 is surrounded by groups of individual nozzles 25 which are arranged in a ring around the block 1 with a division 26 adapted to the spray pattern of the nozzles. The nozzles 25 of a nozzle group are connected to one another by a supply pipe 27. A supply pipe 27 is supplied with the cooling fluid from the supply pipe of a nozzle group 28. Water is used as the cooling fluid, which is specially prepared if necessary, e.g. B. is demineralized. Between the central supply pipe 29, into which the pump (not shown) conveys, there is an actuated by the control Shut-off device 30 and a pressure regulating valve 31, which can either be adjusted by the control or manually. Below the block 1 there is a water basin 32, from which the pump, not shown, conveys the cooling fluid back into the central supply line 29 via a suction line 33. According to the general state of the art, a filter unit and a recooler for removing the heat extracted from the cooling fluid from the block are also installed in this circuit. A drop pipe can also be used instead of the return pump if a water tank with a corresponding height difference can be set up below the cooling device.

Instead of a pump, a pressure accumulator, e.g. B. an elevated water tank can be used.

The block 1 is held by a clamp bracket 34 on both ends, see. Fig. 9. The clamp bracket 34, similar to a screw clamp, consists of a fixed part 34a and a movable part 34b, the movable part z. B. is drawn to the fixed part by means of cylinders 35. Both pneumatic cylinders and hydraulic cylinders can be used. In addition, the clamp bracket 34 is designed so that a nose 34 prevent the block from falling. A linear guide 36 is used to guide the movable part 34b of the clamping bracket 34. This linear guide is firmly connected to guide rails 37, which are displaceable in guide rollers 38 in the longitudinal direction of the block. This displacement causes the block accommodated by the loading and unloading position 39 to be moved in and out with the clamp holder. The displacement can, like the clamping, by means of cylinder 45, pneumatically or hydraulically or with another linear output, e.g. B. by means of chain drive, spindle or rack.

The block arrives in the loading and unloading position 39 with a transverse displacement device 40, which brings the block 1 into the opened clamp holder 34. With the Clamp bracket 34, it is possible to clamp blocks of different lengths. The tool side of the block is always in contact with the fixed clamping bracket 34a, so that there is a clear assignment between the temperature profile and the block. In FIG. 9, the possibility of clamping blocks of different lengths is indicated by the position 34b of the movable clamping bracket, shown in broken lines.

The spray area of the device is enclosed by a housing 41 which can be easily removed. The housing has a door on the loading and unloading side, e.g. B. a lifting door 42. It is advantageous in the housing, for. B. with an appropriately sized fan to generate a vacuum by exhaust air from the housing to the outside, for. B. over the roof. This reliably prevents moisture and steam from entering the installation area of the cooling device and thus the working area of the press. The entire Vorrichmng is carried by a profile steel frame 43, which can be placed on the flat hut floor.

Deviating from this block holder described, it is also possible to use known holders for the block, as are known from block brushing machines.

The angular division 44 of the individual nozzles 25 depends on their spray pattern. In general, an angle of 45 ° is sufficient. This pitch angle permits the problem-free arrangement of the linear guide 36 without impairing the spray pattern of the nozzles on the block surface.

The nozzle groups can be individually activated with the help of the shut-off devices operated by the control. The associated regulating valve 31 allows the individual setting of the desired nozzle pressure for each nozzle group. The adjustment of the regulating valves 31 and the actuation of the shut-off elements 30 take place expediently by means of a process control. For a cooling process before, in which block 1 is both cooled as a whole and is to be given a “temperature taper”, all the nozzle groups are first switched on at the same time. After a time interval sufficient for total cooling, the nozzle groups are switched off one after the other, starting at the tool side of the block, so that the total cooling time increases from the beginning of the block (tool side) to the end of the block (press die side). The greater the time difference between switching off the nozzle group at the beginning and end of the block, the greater the temperature difference over the length of the block and the more pronounced the "temperature taper".

The clamping bracket 34 used according to the invention for the block 1 and engaging on the end faces of the block guarantees a uniform application of the cooling fluid to the block surface, which is not impaired by any deposits. The clamping bracket also shields the end faces of the block, so that the heat flow in block 1 also takes place almost radially at the ends and the temperature distribution caused by the cooling is not disrupted by end effects on the end faces. The uniform application of the cooling fluid, here water, guarantees a uniform cooling in the area of the block surface temperatures of interest, since above the Leiden freezing temperature in the area of stable film evaporation, the heat transfer on a flat surface essentially depends only on the density of water. The influence of the different orientation of the cylindrical block surface on the cooling effect - horizontally when cooling from above on the top of the block, vertically on both sides and horizontally when cooling from below on the underside of the block - can be achieved when using individual nozzles according to the invention by appropriately selected spray nozzles of different sizes , preferably of the same type. Figure 10 shows typical cooling curves for different measuring points in a block. The position of the measuring points 1 to 12 is illustrated in the sketches in the figure. The numbers on the curves refer to the numbers of the temperature measuring points. It can be seen that after a cooling time of approx. 18 s and a compensation time of approx. 60 s following the cooling time, the desired "temperature taper" of approx. 10 K / 100 mm block length is established and the temperature also over the block cross section up to Max. approx. 20 K is balanced. This temperature compensation continues for the period of approx. 25 s that elapses before the start of the press and is required for the movement and positioning of the block, so that both the desired cooling and the desired “temperature taper” are present with good, reproducible accuracy during the pressing process , Since the cooling caused by the cooling device according to the invention serves in particular to increase the pressing speed and thus the production, short block sequence times of 60 s and less can be achieved. For such short block sequence times, it therefore makes sense to operate more than one of the cooling devices according to the invention described in parallel, so that despite the short block sequence time there is still a sufficient time period for the desired temperature compensation over the block cross section.

The cooling according to the invention in a fixed position with different cooling times over the block length uses the known physical property of temperature compensation processes, which take place more slowly with the square with increasing distance between points of the same temperature difference, that is to say take place much faster in the radial direction than in the axial direction.

Claims

claims 1.Procedure for the heat treatment of a cast, homogenized and then cooled metallic press bolt or, when using warm shears, a rod section, preferably made of a light metal alloy, immediately before being introduced into the press device, a) in which the press bolt / rod section (1) is reheated , b) the reheated press stud / rod section (1) is then cooled and c) is fed to the pressing device, characterized in that d) the press stud / rod section (1), based on a diameter of 200 mm, reaches the required temperature in a maximum of 20 minutes is reheated, and that e) the rewarmed press bolt / rod section (1) is subjected to a passive temperature compensation for a maximum of 3 minutes, f) which leads to a temperature uniformity, based on a diameter of 200 mm, of less than ± 10 K. 2.Procedure for the heat treatment of a cast, homogenized and then cooled metallic press bolt or, if a pair of warm scissors is used, a rod section, preferably made of a light metal alloy, immediately before being introduced into the press, a) in which the press bolt / rod section (1) reheats is b) the rewarmed press bolt / rod section (1) is subsequently cooled and c) the press device is fed, in particular according to claim 1, characterized in that d) the rewarmed press bolt / rod section (1) is used for cooling off with water spray nozzles (25) in this manner is subjected to the fact that, based on a diameter of 200 mm, a temperature which is at least 150 K below the pressing temperature is established on the surface of the pressing bolt / rod section (1) within a nozzle spraying time of 30 seconds maximum, and that e) the desired temperature distribution in the press bolt / rod section (1) is established both over the cross section and in the length after a temperature equalization time that is longer than the duration of the nozzle injection. 3. A method for the heat treatment of a press bolt / rod section (1) according to one of claims 1 or 2, characterized in that the press bolt / rod section (1) is heated to the highest optimum temperature for the respective alloy and at a temperature relative to this due to Requirements of the pressing process with a lower pressing temperature following the heating are followed by a rugged cooling, in which the pressing pin / rod section (1) is cooled in such a way that it has the required, lower pressing temperature after an active cooling time and a subsequent temperature equalization time, especially if the Cooling from the highest optimal temperature for the respective alloy to the lower pressing temperature required for the pressing process, a so-called temperature taper is generated. 4. A method for the heat treatment of a press bolt / rod section, in particular according to one of claims 1 to 3, characterized in that in a first part (7) heating by gas burner flames which touch the surface, and in a second part (8) heating by forced convection by means of hot gas nozzle jets blown onto the surface of the good, and that the last sub-area (8b), viewed in the direction of transport of the good, is used for heating by forced convection essentially to equalize the temperature in the good and is operated with only a low upper temperature compared to the final temperature. 5. A method for the heat treatment of a press bolt / rod section, in particular according to one of claims 1 to 4, characterized in that immediately following a previous rapid heating, a rugged cooling with individual water spray nozzles (25) is anticipated, whose axes are directed radially to the horizontal good axis and which can be operated individually or in groups with different pressures and / or different switch-on times. 6. The method according to any one of claims 1 to 5, characterized in that as Cooling fluid demineralized water is used. 7. Device for heat treatment of a cast, homogenized metallic Press bolt or, when using warm shears, a rod section, preferably made of a light metal alloy, immediately before penetrating the press device, a) with a heating device (7, 8) and b) with a cooling device, characterized in that c) the heating device comprises a first part (7) with heating by Gas burner flames which touch the surface and a second part (8) with heating by forced convection by means of hot gas nozzle jets blown onto the material surface, d) the last sub-region (8b) viewed in the material transport direction Heating by forced convection essentially serves to equalize the temperature in the goods and is operated at only a low temperature above the final temperature. 8. Device for heat treatment of a cast, homogenized metallic Press bolt or, when using warm shears, a rod section, preferably made of a light metal alloy, immediately before penetrating the press device, in particular according to claim 7, characterized in that a) the cooling device for the rugged cooling of the reheated press bolt / rod section (1) with individual water spray nozzles (25), b) whose axes are directed radially to the horizontal good axis and c) the individual can be operated in groups with different pressures and / or different switch-on times. 9. Device for the heat treatment of a cast, homogenized metallic Press bolt or, when using warm shears, a rod section, preferably made of a light metal alloy, immediately before entering the pressing device, in particular according to one of claims 7 or 8, characterized in that a) the burners used are recuperative burners, in which the Recuperator for Combustion air preheating is individually integrated in each burner and b) the burner jets emerge from the burner nozzle at high speed, it being possible in particular for at least some recuperator burners to be operated in Flox mode. 10. Vorrichmng according to at least one of claims 7 to 9, characterized in that the nozzles of the recuperator burner (22) are equipped with mouthpieces made of highly heat-resistant material for changing the cross-section of the burner jets (24), in particular the nozzles of the recuperator burner (22) the direction the burner jets (24) change and / or the mouthpieces split the burner jets (24) into at least two individual jets. 11. Vorrichmng according to at least one of claims 7 to 10, characterized in that the pressing bolt or rod section (1) is during the cooling process in a fixed position in the Schroff-cooling device, which consists of annular arrangements of individual nozzles (25), wherein in particular, a nozzle group is formed in each case by the nozzles of an annular nozzle arrangement and / or the nozzles have different sizes depending on the orientation to the lateral surface of the bolt. 12. Vorrichmng according to at least one of claims 7 to 11, characterized in that the bolt is held during the cooling process by a clamping bracket (34) acting on the bolt end faces and adjustable to different bolt lengths, which in particular on the bolt underside lugs (34c) for additional Securing the bolt by positive locking. 13. Vorrichmng according to claim 12, characterized by a loading and unloading position for the clamping device (34) in front of the cooling device. 14. The device according to any one of claims 7 to 13, characterized in that the cooling time for the individual nozzle groups is different, with a period of time for temperature equalization following in particular after the cooling time. 15. Vorrichmng according to at least one of claims 7 to 14, characterized in that at short bolt sequence times at least two cooling devices are operated in parallel. 16. Vorrichmng according to any one of claims 7 to 15, characterized in that the nozzles of the Schroff cooling device are supplied from a pressure accumulator with the cooling fluid.