EP1218562B1 - Method for heat treatment of metallic slugs - Google Patents

Abstract

Heat treating homogenized cooled cast metallic slugs or a rod section made of a lightweight metal alloy comprises: <??>(a) reheating the slugs /rod section for 20 minutes to a required temperature; and <??>(b) subjecting the slugs/rod section to a passive temperature compensation for a maximum of 3 minutes, leading to a temperature uniformity of less than plus or minus 10 K. <??>An Independent claim is also included for a device for heat treating homogenized cooled cast metallic slugs or a rod section made of a lightweight metal alloy comprising a heating device connected to a cooling device.

Description

The invention relates to methods for the heat treatment of metallic Press studs or - if using warm shears - bar sections in front of the Introducing into the extrusion press and devices for performing the Process.

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

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

Such a method is evident, for example, from EP-B 1-0 302 623. there the press block, which is cast in the usual way, primarily from an AIMgSi alloy, First, according to the state of the art, after the casting process homogenized and chilled. Before pressing, it is brought to a temperature the solubility temperature of the cooling after homogenization excreted phases heated and held at this temperature until the phases are dissolved again. After this reheating, at which the block is at a temperature of more than 350 ° C for a maximum of 20 minutes, the block will quickly reach the pressing temperature, which is lower than that Solubility temperature and at most 510 ° C, cooled. At this Cooling should prevent the re-excretion of phases.

Apart from the fact that it should hardly be technically possible, in a high Throughput created production plant to wait until all phases again are resolved, and that the hold time is still less than 20 minutes what is in question is the resolution of the eliminated phases this method is not suitable for being used in a heat treatment process be the one before the actual extrusion process with a highly productive Extrusion takes place.

The description shows that in the process according to EP-B1-0 302 623 the cooling process to reach the lowest cooling temperature up to Took 20 minutes. It is therefore a process that takes place in the Minute range expires and at which the temperature changes through the Heat conduction also over longer distances, so also noticeably in Block longitudinal direction, can compensate. This is also the reason why in the the aforementioned document is only a temperature.

Such an only moderately fast cooling is disadvantageous, however, when the cooling before pressing a falling against the pressing direction Temperature profile, a so-called temperature taper, is to be achieved in the block, because with a relatively slow cooling, there is also considerable temperature compensation takes place in the longitudinal direction, thereby producing the desired temperature tapers with the help of controlled cooling becomes difficult or impossible. On Such a temperature taper is used in direct working extrusion presses Precondition for the advantageous isothermal pressing.

The main purpose of the method described in EP-B1-0 302 623 is one Improve the quality of extruded products while increasing the Press speed. In order to demonstrate this advantage, the aforementioned Scripture examples described. This is a method according to the prior art compared with the method according to EP-B1-0 302 623. Both what the Surface quality as well as regarding the strength values, namely RPO 2, RM and elongation, however, can be taken into account the scatter technical measurements no noticeably positive effect when using this Determine the procedure. This is not surprising since experience has shown that extrusion, in particular of light metal alloys with high Productivity depends on the most precise temperature control. Regarding this However, the temperature control does not contain any statements about what temperature accuracy is required, and how that accuracy should be achieved.

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

So is a device for heating press bolts and rods in the WO 83/02661. The surface of the crop is covered with burners or Hot gas jets generated by combustion are applied. The exhaust gas is collected with an exhaust 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 on the side arranged slot nozzles, the gas flow for feeding these slot nozzles with Fans are circulated in a closed circuit. This device is for Heating with narrow temperature tolerances with high throughput is only limited suitable because the temperature accuracy, which with a direct Flame exposure can be achieved even with moderate throughputs leaves a lot to be desired. The possibility of temperature control is namely adversely affected by the fact that the exhaust manifold is independent of the Heat input and thus the local exhaust gas generation in a certain area the device continuously draws off exhaust gas in the same way. Another disadvantage is that convective heating, which in principle is more uniform than that Direct flame heating at the beginning of the device takes place where there is a high temperature accuracy because of the still low there Material temperatures don't particularly matter while at the end of Heating process, where only slight temperature differences can be tolerated, what is heated only with direct flame exposure leads to larger local temperature differences due to the process. The Device according to WO 83/02661 is therefore in the sense of heating accuracy unfavorable, namely built upside down.

To the hot exhaust gases from the heating zone, the z. B. with direct flame exposure works to better exploit, is in DE-OS 26 37 646 Device described in which in the direction of good transport before Faster heating section with flame exposure to the hot exhaust gas Convection heating zones circulated and blown onto the goods with jet jets before it leaves the device through the exhaust stack. The nozzles are open Slit nozzles arranged on both sides of the good with perpendicular to the good axis standing longitudinal axes of the nozzle openings. This device also has the In view of the uniformity of the heating unfavorable arrangement of the Convection heating zone in front of the heating zone with direct flame exposure.

Other devices with convective heating without any direct Flame exposure to the goods are from DE-OS 35 09 483 A1, DE 34 18 603 C1 and DE 195 38 364 C2 are known. In these devices, the purpose the convective heat transfer in the convection zones circulated gas flow heated with heaters and the heat from this gas stream to the estate transfer.

All of these devices have significant disadvantages. With the devices with convective heating without direct flame exposure can be done uniform heating with a sufficiently uniform temperature distribution achieve by limiting the operating temperature to the maximum for that a convection system equipped with a hot gas fan however, there is a limit to the maximum that can be transferred to the good surface Heat flow density and thus a limitation of the heating rate. The The result is relatively low throughput rates or long systems with the known ones Disadvantages due to the relatively long pillar when changing alloys during the Production, which usually also require a change in the final good temperature. Such devices are inflexible in production and for Performing procedures that require high accuracy is unsuitable. Further Disadvantages are the higher costs due to the longer length and the higher space requirements.

Devices with heating by direct flame exposure do admit due to the high furnace chamber temperature - for devices for heating light metal alloys around 1000 ° C - quite high heating rates, however the temperature distribution in the estate is very uneven. Especially when changing Good surfaces can also be used due to the changing strong radiation influence with elaborate control and regulation technology no satisfactory Achieve temperature uniformity. If the production process suddenly stops, z. B. because of a press or tool problem, it even happens frequently for melting of the heating material. In addition, the energy utilization is low and consequently the heating power and energy requirements related to the material throughput high.

Also in the device known from DE-OS 26 37 646 with convective preheating these disadvantages exist. The energy utilization is a bit better, due to the combination of preheating with rapid heating, e.g. B. through direct flame exposure: Exhaust gas is only generated when the flame is applied works, but the temperature control is even more difficult and Temperature accuracy in the goods, especially during production interruptions, e.g. B. when changing tools, unsatisfactory. Therefore, such a device is not Can be used if special demands are made on temperature uniformity need to be such. B. when heating aluminum alloys AIMgSi Press temperatures in the homogenization temperature range and close to the melting temperature with subsequent rapid cooling before extrusion to increase of productivity and quality.

A number of cooling devices are used to carry out the cooling process known. US-A 5,027,634 describes a cooling device which consists of at least there is a cooling ring through which the block during the cooling process a pushing device is pushed. By changing the The cooling effect brought about by the cooling device can be achieved at an impact speed affect the block length. The cooling ring itself has numerous holes relatively small diameter through which the water used as the cooling fluid is sprayed on the block. The cooling ring is for the passage of the impact device open at the top. A disadvantage of this device, besides the complicated control the block movements and the complex transport mechanics in particular the small cooling nozzles that tend to clog and the uneven cooling effect over the circumference through the opening in the top of the cooling ring for passage of the Shocking device is necessary because there are no cooling nozzles in this area.

The device according to US Pat. No. 5,425,386 attempts to overcome the disadvantage of small holes in the cooling ring through a circular slot as a nozzle opening avoid. The complicated transport mechanics and the complex control of the Block movements are still required. In addition, the annulus supplied as a nozzle opening from a prechamber with the cooling fluid, so that around the Circumference of the entire nozzle slot the same pressure is available. There are therefore no way to meet the needs of orientation of the cooling Adjust block surface. During a significant part of the cooling process the block surface temperature is far above the Suffering frost temperature, so that the cooling process through the vapor film immediately is determined on the surface of the block. When the block is horizontal this vapor film on the bottom, on the top and on both sides of the Blocks where the tangent to the surface is vertical are different. Consequently, water should also be applied to achieve an even level Cooling can be adapted to these different situations.

With the device according to US-A 5,325,694 an attempt is made to build a Control circuit, which reduces the temperature of the block caused by the cooling linked to the block feed rate, the handling of the device to simplify and automate the control. But the Device not only more complex due to the additionally required sensors, but also more prone to failure.

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

The invention has for its object methods for heat treatment of metallic press studs or rod sections before insertion into the Extrusion press, as well as devices to carry out the method to create who do not experience the disadvantages mentioned above. In particular, procedures and devices are proposed that are very fast and at the same time the temperature control very precise heat treatment from reheating and Allow cooling.

This is achieved through the features of the respective main claims 1, 2, 4 and 6 expedient variants of this method and device by the associated Subclaims are defined.

In extrusion, especially of light metal alloys, this is achieved a high level of productivity that the entire strand with as much as possible high speed while maintaining a certain and optimal Strand exit temperature is pressed. To achieve this goal are dependent of profile shape and tool - i.e. the degree of deformation - and the desired for productivity reasons the highest possible press speed - so depending on the forming capacity - different starting temperatures of the block are required. For directly working extrusion presses, as they are usually used for Light metal alloys are used, it is also important that the block at the beginning of the pressing process is falling against the pressing direction Has temperature profile, a so-called "Temperaturtaper". This Temperaturtaper, as has long been known as the prior art, is required by the increasing mechanical input from the beginning of the block to the end of the block Balance energy that is converted into heat during the pressing process, so that nevertheless the pressing process can proceed isothermally. The more precise this Temperature taper is matched to the respective pressing conditions, the higher the press speed can be selected and the greater the productivity.

According to the invention, bolts or rods, i.e. blocks, are initially possible quickly to the highest possible pressing temperature, depending on the respective material heated, after this heating the temperature in the block with very low Temperature tolerance is evenly distributed. Typical is e.g. B. for Light metal alloys have a temperature tolerance of less than ± 10 K, e.g. B. ± 5 K for block diameters from 250 mm to 300 mm.

After this heating, it is particularly important in highly productive extrusion operations advantageous to close the block as quickly as possible with water in a rugged cooling device cool so that after this rugged cooling and temperature compensation as a result the heat conduction depending on the block material with the desired tight Tolerance for the respective pressing tool - i.e. the respective profile shape - and the desired one, as high as possible for productivity reasons Press speed optimal starting temperature at the tool facing Side of the block and the optimal distribution of this temperature over the length of the block. It is typical for cooling as quickly as possible an active cooling time of approx. 30 s, followed by a time for temperature compensation by heat conduction, which mainly takes place over the cross section of the block, that is typically slightly longer than the active cooling time. After the quick After cooling, the block is placed in the extrusion press and pressed. The The transfer time required for this is used in the calculation of the time period for the Temperature compensation due to heat conduction also taken into account.

In contrast to the prior art, the method according to the invention permits Provision of the block with exactly the required temperature or Temperature distribution and this with the necessary low temperature tolerance.

When pressing light alloys that are difficult to press, e.g. B. Alloys with the numbers 7xxx and 2xxx, for which purpose usually indirect extrusion presses are used to exclude the influence of friction on the recipient wall, it is advantageous that the block has a defined higher temperature at the beginning than the pressing temperature distributed as evenly as possible in the rest of the block. This is also easily possible with the method according to the invention, because in addition to a uniform temperature distribution also locally over the block length Temperature differences, e.g. B. higher temperature only at the beginning of the block can be.

Another advantage of the method according to the invention is its suitability for the Press operation with maximum productivity. If cooling time and Temperature compensation time are longer than the press sequence, the so-called Block sequence time, so two cooling devices can be operated in parallel, so that regardless of the block sequence time, each block individually the necessary cooling time as well as compensation time can experience, even if the two periods in the Addition are longer than the block sequence time.

Even in the event of unintentional interruptions in the press operation, the consequences of this are more serious, the higher the productivity of the extrusion press, the invention has Process decisive advantages over the prior art on. This is because, according to the invention, the rapid heating by means of direct flame exposure during the first part of the heating process with a combined convective heating in the final part. With this convective Warming can be done by a suitable choice of gas temperature Material overheating even in the event of a press interruption and consequent standstill of Block transports can be excluded. As soon as the press is operational again, a block with exactly the right pressing 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 a direct Flame exposure according to the known prior art with a convective reheating, in which the temperature compensation also takes place, is combined. This solution requires the usual because of the lower cost Burner compared to the particularly advantageous to use Recuperative burners have a slightly lower cost. The main advantage However, this simple solution is that it is suitable for retrofitting Implementation of the method according to the invention is suitable by adding to an existing one Quick heating system with direct flame exposure simply at least a convection heating zone is being built.

A major advantage, which concerns the production costs, is that in Extremely low compared to systems according to the state of the art Gas consumption due to the advantageous use of burners with integrated Exhaust gas recuperator for preheating the combustion air is reached. Next this cost advantage is the use of recuperative burners with integrated Combustion air preheating is also a great advantage in terms of control technology, because Combustion air preheating and burner operation are clearly linked are. In contrast, in systems according to the prior art, the exhaust gas all burners collected in one place - the beginning of the is common Flame exposure zone - deducted and a central heat exchanger for the combustion air preheating supplied. Through the central exhaust gas extraction there is a longitudinal flow in the furnace which determines the temperature control behavior of the individual zones adversely affected. If the door when removing a block on the outlet side of the heating device can be opened at continuous operation of the exhaust gas extraction even cold air enters the furnace, which in turn the temperature distribution in the material column as well as the Temperature control adversely affected. In the method according to the invention and with the heating device according to the invention is by the operation of Recuperative burners with exhaust gas reducers achieved that only exhaust gas in the same or almost the same amount as the combustion gas generated is withdrawn, if the respective burner is really switched on.

In addition to this control advantage, there is also an advantage with a view to improving heat transfer. The recuperator burners are namely operated at a very high flame exit speed. This creates a jet that flushes the block vigorously and for one Increase in convective heat transfer even without using a special flow drive ensures. On top of that, through the Induction effect of the pulsed burner jet also in the Existing hot exhaust gas is circulated with what in turn increases the convective heat transfer.

Furthermore, there is also the possibility, in the method according to the invention, which provides for recuperator burners, also such recuperator burners to be used, which with so high furnace interior temperatures in the so-called Flox mode work with flameless oxidation. Flameless oxidation means that there is a mixture between gas, exhaust gas and combustion air in the burner in such a way that no flame is visible and the heat energy is released Oxidation takes place to a certain extent in the burner jet. This has crucial Advantages for the equalization of the heat transfer on the block surface.

The aforementioned recuperator burners, partly also suitable for Flox operation, are in EP 0 463 218 B1, EP 0 685 683 B1 and DE 195 41 922 C2.

Finally, the use of recuperative burners leads to the invention a shortening of the required system length in comparison with a system same performance according to the state of the art. The reason for this is that the Preheating zone, which is required in systems according to the state of the art, in order to There is no need to recuperate at least part of the exhaust gas heat. This shorter one Overall length with greater performance not only means saving space, it is also advantageous from a procedural point of view, since the block column contained in the system Shorter is what the operation of the plant with different alloys is essential simplified.

1. Unterteilung der Erwärmung in Schnellerwärmung mittels direkter Flammenbeaufschlagung nur im vorderen Teil der Erwärmungsvorrichtung, wogegen am Ende der Erwärmungsvorrichtung die Wärmeübertragung konvektiv erfolgt. Dadurch wird die hohe Erwärmungsgeschwindigkeit bei direkter Flammenbeaufschlagung mit der gleichmäßigen Erwärmung ohne Gefahr der örtlichen Überhitzung bei konvektiver Erwärmung kombiniert.

2. Möglichkeit der Nachrüstung einer bestehenden Schnellerwärmungsanlage mit direkter Flammenbeaufschlagung durch Anfügen von mindestens einer Konvektionszone am Ende der vorhandenen Erwärmungsvorrichtung.

3. Einsatz von Rekupratorbrennern mit integrierter Frischluftvorwärmung. Dadurch wird das Regelverhalten der Erwärmungsvorrichtung verbessert und zusätzlich der Brennstoffverbrauch erheblich reduziert. Reduzierung der Anlagenlänge durch Fortfall der Vorwärmzone.

4. Möglichkeit des Einsatzes von Brennern zum Betrieb mit flammenloser Oxidation und dadurch Vergleichmäßigung der Wärmeübertragung bei direkter Brennerstrahlbeaufschlagung.

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. This combines the high heating rate with direct flame exposure with even 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 at 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 performing this method. Because it won't be like in the prior art, a block through a cooling ring in the longitudinal direction moved through, but the block, held on its end faces, in total introduced a stationary cooling device. The cooling takes place by means of annular arrangement of individual nozzles, which are in during the cooling process precisely defined, fixed position in relation to the block. The Desired, to achieve the required temperature or temperature distribution necessary cooling effect is arranged by the operation of these in rings Individual nozzles 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 state of the art; in addition, the accuracy in the With regard to the temperature and temperature distribution to be achieved higher than at known facilities and methods.

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

Figur 1

den Temperaturverlauf für einen Block über der Zeit von Beginn der Schnellerwärmung über die Schroffabkühlung bis zum Verbringen in die Presse;

Figur 2

die Anordnung der einzelnen Aggregate zur Durchführung der erfindungsgemäßen Wärmebehandlung;

Figur 3

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung zur Durchführung der Schnellerwärrnung mit Schnittdarstellungen der hintereinander angeordneten Vorrichtungsteile, wobei die Erwärmung mit direkter Flammenbeaufschlagung nach dem Stand der Technik erfolgt;

Figur 4

ein Fließbild der in Figur 3 schematisch dargestellten Anlage zur Durchführung der Schnelleerwärmung;

Figur 5

eine andere erfindungsgemäße Ausführungsform der Zone der Vorrichtung mit direkter Flammenbeaufschlagung mit Verwendung von Rekuperatorbrennern;

Figur 6

vorteilhafte Düsen-Formen für Hochgeschwindigkeits-Rekuperator brenner;

Figur 7

einen typischen Temperaturverlauf in den einzelnen Teilen der Erwärmungsvorrichtung und im mit der Vorrichtung erwärmten Gut;

Figur8

die Schroffabkühlvorrichtung in einem schematisch dargestellten, vereinfachten Querschnitt;

Figur 9

eine schematisch vereinfachte Längsansicht der Schroffabkühlvorrichtung, bei welcher das Gehäuse im Schnitt dargestellt ist;

Figur 10

ein Diagramm mit typischen Abkühlkurven für die im Diagramm bezeichneten Messpunkte im abzukühlenden Block.

Show it

Figure 1

the temperature curve for a block over time from the start of rapid heating through the cooling of the rug to the time it was brought into the press;

Figure 2

the arrangement of the individual units for carrying out the heat treatment according to the invention;

Figure 3

a schematic representation of a device according to the invention for performing 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;

Figure 4

a flow diagram of the plant shown schematically in Figure 3 for performing the rapid heating;

Figure 5

another embodiment according to the invention of the zone of the device with direct flame application using recuperative burners;

F igur 6

advantageous nozzle shapes for high-speed recuperator burners;

Figure 7

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

Figur8

the Schroffabkühlvorrichtung in a schematic, simplified cross section;

Figure 9

a schematically simplified longitudinal view of the Schroffabkühlvorrichtung, in which the housing is shown in section;

Figure 10

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

The method according to the present invention is illustrated by FIG. 1. In Figure 1 is a schematic of the temperature profile for a block over time from Start of heating is shown until it is brought into the press. First the block experiences rapid heating in a maximum of 20 minutes in the area of the Device, which in the example of Figure 1 with direct flame exposure works through recuperator or recuperator Flox burners, so that none Preheating zone for exhaust gas cooling is available. The completion of the warming takes place in at least one zone with convective heat transfer comparatively low overtemperature. The temperature compensation also takes place here 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 runs through one Temperature compensation time. In the end of this equalization period, the block becomes Press spent and then shows a temperature difference in isothermal pressing between the end of the block and the beginning of the block.

Figure 2 shows schematically how the individual units for performing the invention Procedure are arranged. The press is schematic through the Reference numerals 2 and 3 indicated. 2 denotes the recipient in which the Block 1 inserted and during the extrusion process with the press ram 3 is pressed. The extruded profile, or with tools If there are several omissions, the profiles (not shown) are on the press outlet 12 out. The block 1 is loaded into the press 2, 3 with a block loader 4 is also only indicated schematically.

The heating takes place in the direction of flow 9 initially by direct Flame application in the front part of the heating device 7 and then, for example, in two convection zones 8a connected in series and 8b, the last convection zone 8b in the direction of passage 9 being lower Gas temperature is operated as the front zone 8a. Of the Heating device 7, the block enters a transverse transport 5. Die Direction of movement is indicated by arrow 10. From the transverse transport 5 Block placed either in the cooling station 6a or in the cooling station 6b and moves in the direction of the movement arrows 11 a and 11 b. As before mentioned, more than one cooling station makes sense if a system with high Productivity and short block sequence time works.

The Gut 1, a pillar of individual bolts or sawn off to length Rods (only indicated in the figure for the sake of simplicity) via a transport device, e.g. B. as shown in Figure 3, via a roller table 20 passed through the device. The transport takes place with non-driven rollers via impact devices outside the device. Others, not in the figures Possibilities shown are the transport of the goods 1 through the device using a walking beam or a transport chain. It can also be powered Rolls or other transport options known from the prior art are used.

The first part of the device essentially consists of the area where the flame is applied. In Figure 3, two flame exposure zones are exemplary 7a, 7b. Before the first flame exposure zone in the direction of transport 7 there is an entrance zone 13 and behind the second (last) Flame exposure zone 7b a separation zone 14. Closes the separation zone 14 the first 8a of two convection zones 8a, 8b; the in the direction of transport last convection zone 8b, which primarily applies to temperature compensation the completion of the device. In the flame exposure zones 7a, 7b the material 1 is heated by the flames generated with burner nozzles 15. Doing so the heat to a significant extent via radiation from the surrounding Transfer furnace space to good 1. In the entrance zone 13 and the separation zone 14 the exhaust gas from the burner is collected and exhaust gas lines 16 from the Device derived.

The convection zones 8a, 8b each have a flow system that at least a 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 Contains purpose of convective heat transfer. The nozzles 18 are over a Flow channel system 19 fed by the fan 17, s. Fig. 3.

As can be seen from the flow diagram according to FIG. 4, the exhaust gas is generated by a Heat exchanger 21 passed, with which the combustion air for the gas burner is preheated. In the convection zones 8a, 8b are expediently used for Heating recuperative burner 22 used, so here by preheating the flue gas cooled by the combustion air escapes to the exhaust pipe of the burner.

A particularly advantageous embodiment of the flame exposure zone is shown schematically in FIG. The heating is done by a comparison to the smaller number of flame exposure zones shown in FIG Recuperator burners 22. The external one is therefore omitted in this embodiment Heat exchanger 21 for preheating the combustion air. In addition, the recuperator burners used cheaply as high-speed burners and / or High-speed Flox burner that works automatically when the appropriate one is reached Furnace temperature from normal combustion mode to Flox mode change, execute.

The high speed burner beams can be made using the Coanda effect with favorable design of the burner nozzle, the material to be heated on one comparatively large area, as shown in Figure 5 by the schematic Flow arrows 23 is shown. The axes of the burners and thus the Flame beams 24 or burner beams during Flox operation can also be used against the Be inclined vertically to apply the flow to the surface of the crop improve. It is also possible to improve the burner jets 24 Good loading through nozzle mouthpieces made of high temperature resistant Material, e.g. B. affect silicon carbide. FIG. 6 shows such possible advantageous examples of the nozzles of high-speed burners. Figure 6a shows a burner nozzle which converts the round burner jet into a flat jet deformed; Figure 6b shows a burner nozzle in which the flat jet in the middle has a web and the two partial beams are accordingly stronger are formed as in Figure 6a. Figure 6c shows a burner nozzle with a Exit cross-section of the kind of a "dog bone"; Figure 6d shows the Cross section of a burner nozzle with which the burner jet from the vertical is distracted. Figure 6e shows a burner nozzle which in the burner jet several - in the figure in three - resolves individual rays, which with different Impact direction on the good surface. This way Heat flow densities of 300 kW / m2 and more also over larger portions of the Achieve block surface.

The great advantage of the rapid heating device comes from the schematic Temperature profile for the core and the surface of the goods 1, which is shown in FIG 7 is shown. In the flame exposure zones, in the example of Figure 7 are two zones, F1 and F2, assuming the furnace temperature is extremely high, as in the usual flame exposure zones according to the prior art. Since these zones are now used at the beginning of the device, there is no danger of overheating, and that shown schematically in FIG Spreading the temperature curve for different points of the good does not play Role, because in the following two convection zones K1 and K2 the temperature can compensate. Finally, in the second zone K2 Gas temperature (= furnace chamber temperature) in the range of the desired Gutendtemperatur. This means that the goods overheat even in the case of unplanned ones The press comes to a standstill and the resulting interruptions in the transport of goods excluded in the device.

An advantageous embodiment of a cooling device for performing the Cooling of the block according to the heat treatment process according to the invention is described with reference to Figures 8 to 10.

The block 1 is surrounded by groups of individual nozzles 25, which with a Spray pattern of the nozzles adapted pitch 26 in the longitudinal direction of the block 1 these are arranged in a ring. The nozzles 25 of a nozzle group are included connected to each other by a supply pipe 27. A supply pipe 27 is supplied with the cooling fluid from the supply pipe of a nozzle group 28. As Cooling fluid is water that is specially prepared if necessary, e.g. B. is demineralized. Between the central supply pipe 29, in which the Pump, not shown, is operated by the control Shut-off device 30 and a pressure regulating valve 31, either by the control or can be adjusted manually. There is a below block 1 Pool 32, from which the pump, not shown, via an intake line 33 feeds the cooling fluid back into the central supply line 29. In these Circulations are, according to the general state of the art, still one Filter unit and a recooler for removing the block from the cooling fluid extracted heat installed. Instead of the return pump, one can Case line can be used when a water tank with appropriate Height difference can be set up below the cooling device.

Instead of a pump, a pressure accumulator can also be used to supply the spray nozzles 25, z. 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, like 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. It can be both Pneumatic cylinders as well as hydraulic cylinders are used. In addition, the Clamp bracket 34 designed so that a nose 34c prevents the block from falling prevent. Serves to guide the movable part 34b of the clamp bracket 34 a linear guide 36. This linear guide is fixed with guide rails 37 connected, which are displaceable in guide rollers 38 in the longitudinal direction of the block. This Shifting causes the moving in and out of the loading and unloading position 39 blocks received with the clamp bracket. The shift can be like also 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 respectively.

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

The spray area of the device is enclosed by a housing 41 which can be easily removed. The housing has one on the loading and unloading side Door, e.g. B. a lifting door 42. It is advantageous in the housing, for. B. with a appropriately sized fan to create a vacuum by Exhaust air from the housing to the outside, e.g. B. over the roof. This will reliably prevents moisture and steam from entering the installation room Cooling device and thus get into the working area of the press. The whole Device is supported by a steel profile frame 43 which is on the flat Hut floor can be put on.

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

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

With the help of the shut-off devices operated by the control, the nozzle groups can can be activated individually. The associated regulating valve 31 allows individual setting of the nozzle pressure required 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, at which block 1 is both cooled as a whole and one To get "temperature tapers", all nozzle groups are initially at the same time switched on. After a time interval sufficient for total cooling the nozzle groups, starting at the tool side of the block, switched off one after the other so that the total cooling time from the beginning of the block (Tool side) to the end of the block (press ram side) increases. The bigger the Time difference between switching off the nozzle group at the beginning of the block and at Block end, the greater the temperature difference over the block length and the more more pronounced the "temperature tapers".

The one used according to the invention for block 1 and on the end faces of the block attacking clamp bracket 34 guarantees a uniform, not by any deposits affected the block surface the cooling fluid. The clamp 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 does not interfere with end effects is influenced on the end faces. The even exposure to the Cooling fluid, here water, is guaranteed in the interesting area of the block surface temperatures an even cooling, because above the suffering frost 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 the different orientation of the cylindrical block surface on the Cooling effect - horizontal when cooling from the top of the block, vertically on the two sides and horizontally when cooling from below on the underside of the block when using individual nozzles according to the invention by accordingly selected spray nozzles of different sizes, preferably of the same type, be balanced.

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 measurement points. It can be seen that after a cooling time of approx. 18 s and a desired compensation time of approx. 60 s following the cooling time "Temperature taper" of approx. 10 K / 100 mm block length and the temperature also across the block cross-section up to max. approx. 20 K is balanced. This Temperature compensation continues during the time that passes until the start of the press and the time required to move and position the block of approx. 25 s further, so that both the desired Cooling as well as the desired "temperature taper" with good, reproducible Accuracy. Since with the cooling device according to the invention caused cooling in particular the increase in the pressing speed and So that production is used, short block sequence times of 60 s and less can be achieved to reach. For such short block sequence times, it makes sense to use more than one of the to operate described cooling devices according to the invention in parallel, so that despite the short block sequence time, there is still enough time for the desired temperature compensation over the block cross section is available.

The cooling according to the invention in a fixed position with different cooling times over the block length uses the well-known physical property of temperature compensation processes, the same with increasing distance between points The temperature difference with the square is slower, i.e. in the radial direction occur much faster than in the axial direction.

Claims (13)

1. A method for heat treating a cast, homogenised and subsequently cooled metallic extrusion bolt or - when hot shears are used - slug, preferably made of a light metal alloy, immediately before it is fed into the extruder,

   a) wherein the extrusion bolt/slug (1) is reheated,

   b) the reheated extrusion bolt/slug (1) is subsequently cooled, and

   c) is delivered to the extrusion device, characterised in that

   d) the extrusion bolt/slug (1), based on a diameter of 200 mm, is reheated to the desired temperature in 20 minutes at most, and in that

   e) the reheated extrusion bolt/slug (1) is exposed to passive temperature equalisation for 3 minutes at most,

   f) said temperature equalisation resulting in a temperature uniformity, based on a diameter of 200 mm, of less than ± 10 K.
2. A method for heat treating a cast, homogenised and subsequently cooled metallic extrusion bolt or - when hot shears are used - slug, preferably made of a light metal alloy, immediately before it is fed into the extruder,

   a) wherein the extrusion bolt/slug (1) is reheated,

   b) the reheated extrusion bolt/slug (1) is subsequently cooled, and

   c) is delivered to the extrusion device,

   characterised in that

   d) the reheated extrusion bolt/slug (1) is exposed to rapid cooling using water spray nozzles (25), such that - based on a diameter of 200 mm - a temperature at least 150 K below the extrusion temperature is set on the surface of the extrusion bolt/slug (1) within a nozzle spraying period of 30 seconds at most, and in that

   e) the desired temperature distribution is set in the extrusion bolt/slug (1), both over its cross-section and along its length, by the end of a temperature equalisation period which is longer than the nozzle spraying period.
3. The method for heat treating an extrusion bolt/slug (1) as set forth in any one of claims 1 or 2, characterised in that the extrusion bolt/slug (1) is heated to the highest optimal temperature for the respective alloy, and at an extrusion temperature which is lower than this temperature due to the requirements of the extrusion process is rapidly cooled following said heating, wherein the extrusion bolt/slug (1) is cooled such that after an active cooling period and a following temperature equalisation period it exhibits the desired, lower extrusion temperature, in particular when a so-called temperature taper is generated while cooling from the highest optimal temperature for the respective alloy to the lower extrusion temperature required for the extrusion process.
4. A method for heat treating an extrusion bolt/slug, characterised in that: the extrusion bolt/slug is heated in a first part (7) by gas burner flames which contact the surface, and in a second part (8) by forced convection by means of hot gas nozzle jets blown onto the surface of the material; in that the last sub-section (8b) of heating by forced convection, as viewed in the material transport direction, substantially serves to equalise the temperature in the material and is operated with only a low excess temperature as compared to the end temperature; in that - directly following a preceding rapid heating - rapid cooling is anticipated using individual water spray nozzles (25) whose axes are radially directed towards the horizontal axis of the material and which may be operated, individually or in groups, at different pressures and/or with different activation times.
5. The method as set forth in any one of claims 1 to 4, characterised in that de-mineralised water is used as the cooling fluid.
6. A device for heat treating a cast, homogenised metallic extrusion bolt or - when hot shears are used - slug, preferably made of a light metal alloy, immediately before it is fed into the extruder,

   a) comprising a heating device (7, 8) and

   b) comprising a cooling device, characterised in that

   c) the heating device comprises a first part (7) using heating by gas burner flames which contact the surface, and a second part (8) using heating by forced convection by means of hot gas nozzle jets blown onto the surface of the material,

   d) wherein the last sub-section (8b) of heating by forced convection, as viewed in the material transport direction, substantially serves to equalise the temperature in the material and is operated with only a low temperature above the end temperature.
7. The device as set forth in claim 6, characterised in that recuperation burners (22) are used to generate the gas burner flames, and in that the nozzles of the recuperation burners (22) are fitted with dies made of a material with high temperature stability, to alter the cross-section of the burner jets (24), wherein in particular the nozzles of the recuperation burners (22) change the direction of the burner jets (24) and/or the dies divide the burner jets (24) up respectively into at least two individual jets.
8. The device as set forth in at least one of claims 6 or 7, characterised in that the extrusion bolt or slug (1) is in a fixed position in the rapid cooling device during the cooling process, said rapid cooling device consisting of annular arrangements of individual nozzles (25), wherein in particular each group of nozzles is formed by the nozzles of an annular arrangement of nozzles and/or the nozzles exhibit different sizes according to their orientation with respect to the shell surface of the bolt.
9. The device as set forth in any one of claims 6 to 8, characterised in that during the cooling process, the bolt is held by a clamp mounting (34) which grips the facing sides of the bolt and may be set to various bolt lengths, and which in particular comprises catches (34c) on the lower face of the bolt, for additionally securing the bolt through a positive lock.
10. The device as set forth in claim 9, characterised by a loading and unloading position for the clamp mounting (34), before the cooling means.
11. The device as set forth in any one of claims 6 to 10, characterised in that the cooling period is different for the individual groups of nozzles, wherein in particular a period of time for temperature equalisation follows the cooling period.
12. The device as set forth in at least one of claims 6 to 11, characterised in that - for short times per bolt - at least two cooling devices are operated in parallel.
13. The device as set forth in any one of claims 6 to 12, characterised in that the nozzles of the rapid cooling device are supplied with cooling fluid from a pressure accumulator.

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