EP3757496A1 - Continuous roller hearth furnace and method for heating steel plates coated with aluminum, silicon and / or zinc at hardening and pressing temperature - Google Patents

Abstract

The invention relates to a roller hearth continuous furnace system for heating steel blanks coated with aluminum, silicon and / or zinc to hardening and pressing temperature with transport rollers for transporting the steel blanks through a heated oven. In this furnace there is a lifting device with lifting strips with which the steel blanks can be raised or lowered so that a steel plate can be moved through under raised lifting strips. In addition, the steel blanks have no permanent contact with the transport rollers when they pass through the furnace. This means that the coated surface of the steel blanks cannot be adversely affected. In addition, the continuous hearth furnace system enables the steel blanks to pass through very quickly.

Description

The invention initially relates to a roller hearth continuous furnace system for heating steel blanks coated with aluminum, silicon and / or zinc to hardening and pressing temperature with transport rollers for transporting the steel blanks through a heated oven which has a door on its inlet side and its outlet side , which can be opened and closed and thereby enables the feeding and removal of the steel blanks into and out of the furnace, the transport rollers being arranged in the interior of the furnace so that they are all on one level ("roller hearth level") and in parallel spacing to each other and transversely to the transport or passage direction of the steel blanks, and the transport rollers are rotated by means of several drives to move the steel blanks on the transport rollers, and outside of the furnace and at the level of the roller hearth level in front of the entry-side door ( "Infeed door") an infeed roller conveyor and behind the exit-side door ("exit door") is an exit roller conveyor, via whose transport rollers the steel blanks get into and out of the furnace.

Such roller hearth continuous furnace systems have long been known for the so-called “press hardening” of components made from steel materials, which is why the term “steel press hardening” is also used. As a rule, these components, so-called steel blanks, are coated, which may be, for example, a coating based on aluminum or zinc. These coated steel blanks are heated to hardening temperature in the furnace of the continuous roller hearth furnace and then hot-formed in a press. A very rapid cooling of the steel blanks in the press results in not only the deformation but also the quenching speed required for the hardening process, which is why this process is called "press hardening". The aforementioned hardening temperature in the furnace is in a range of approximately 950 ° C., with the roller hearth furnaces, that is to say the ovens of such a roller hearth continuous furnace system, being heated to achieve this press hardening temperature, for example with electrical ones Heating devices or with gas burners, which are usually arranged above and below the roller hearth level. The steel blanks are transported through the furnace by means of the transport rollers, which are rotated according to the transport or flow direction, i.e. there are transport rollers in this furnace over the entire length of the furnace on which the steel blanks are moved or transported forward. This means that the steel blanks are always in contact with the transport rollers during transport through the furnace, which incidentally are usually made of a ceramic material. The coated steel blanks are in permanent contact with the transport rollers when they pass through the furnace. However, this leads to the problem that the coating material on the steel blanks, for example the aluminum coating, melts, namely in the case of aluminum-coated steel blanks at a temperature of around 650 ° C., and this melted, i.e. liquid and aggressive coating material then builds up deposited on the transport rollers (sometimes "pimple formation" occurs) and often even diffuses into these transport rollers. This leads to a limited service life of the transport rollers, which in turn causes considerable operating costs due to the need to replace the transport rollers, business interruptions, etc. Apart from this, the melting or liquefaction of the coating material in the furnace not only leads to damage to the transport rollers, but also frequently to an impairment of the surface of the steel blanks.

The present invention is therefore based on the object of creating a roller-hearth continuous furnace system which avoids the disadvantages associated with the use of the previously known roller-hearth continuous furnace systems and described above, while at the same time the steel blanks are passed through as quickly as possible for economic reasons should.

The object is achieved in a roller hearth continuous furnace of the generic type in that the furnace has a lifting device with at least two lifting strips groups, the lifting strips of which can be raised and lowered to raise or lower the steel blanks positioned in the furnace, the lifting strips -Groups can be controlled with a control device, the lifting bars in the lowered position below are located at the roller hearth level, the width of the lifting bars is less than the distance between two adjacent transport rollers and the lifting bars when they are lifted pass up or above the roller hearth level between two adjacent transport rollers and are arranged in sections in the transport or passage direction of the steel blanks, that in each section of the transport rollers in the furnace there is a lifting strip group with whose lifting strips at least one steel plate fed to the furnace and brought into one of the sections of the transport rollers is raised by means of the control device to the heating or holding position above the roller hearth level for a certain time and that the lift bars of each lift bar group have a design that enables a steel blank to be transported over the transport rollers in the furnace such that a steel blank can be moved through under lifted lift bars.

This roller hearth continuous furnace system according to the invention initially has the decisive advantage that the coated steel blanks have no permanent contact with the transport rollers when they pass through the furnace. For this purpose, a special lifting device with so-called lifting strips, which are integrated in the roller hearth continuous furnace system and arranged in groups in the furnace, is provided. The design and mode of operation of these lift bars is designed in such a way that the, for example, ceramic transport rollers cannot come into contact with the aggressive, molten or liquid coating material of the steel blanks. This is due to the fact that the temperature of the steel blanks, when they have assumed their so-called "heating or holding position" above the roller hearth level by lifting the lift bars, has not yet reached the melting temperature of the coating material, which is around 650 ° C for aluminum coatings Has. The steel blanks are first moved cold into the furnace to the intended place or transported by means of the transport rollers and then lifted into the heating or holding position for a time predetermined by the control device by the lifting bars. It is only there in this heating or holding position that the desired press hardening temperature, for example 950 ° C., of the steel blanks is reached by the heating devices in the furnace. This means that the melting temperature of the coating material is only reached in the raised heating or holding position of the steel blanks, that is to say only there in the heating or holding position Coating melts or becomes liquid. Furthermore, the peculiarity of the roller hearth continuous furnace system according to the invention is that at the relevant place, i.e. the section provided for this steel blanks by the control device (which can also be called "roller conveyor") of the transport rollers, which are inserted into the heating or Holding position raised steel plate remains there until the so-called "oven time", consisting of the heating time and temperature holding time, has ended. The steel plate remains in the raised position until the furnace time has ended, that is, when the coating has a higher melting point than the furnace temperature due to the iron absorption from the metal steel plate and the coating is therefore "heat-resistant". Because the steel plate has a fixed position in the raised heating or holding position, i.e. it is not moved there in the heating or holding position for the predetermined furnace time, the coated surface of the steel plate cannot be adversely affected, such as this is disadvantageously the case with the previously known roller hearth furnaces due to the movement of the steel plates. Only after the end of the furnace time is the steel plate lowered again to the roller hearth level by lowering the lifting bars, at which point the coating material is no longer liquid for the aforementioned reason of iron absorption and therefore no longer leads to damage to the transport rollers. After the steel blank has been lowered to the roller hearth level, this steel blank is then moved out of the furnace for forming in the subsequent press.

Furthermore, the fixed position of the steel blanks or "batches" (this English word means several steel blanks in technical terms) in the furnace chamber ensures exact positioning during the entire process. This is necessary for a partial hardening with narrow transitions between hard and soft. This means that a steel blank should have different degrees of hardness, for example. For example, a square steel plate with a size of 1m x 1m (i.e. 1 meter edge length) can have a (left) half that is supposed to become hard and a (right) half that is supposed to become soft or softer. In order to achieve this, it is important that the steel plate is precisely and firmly positioned during the heating process, otherwise the narrow transition area between the left (afterwards hard) half and the right (afterwards softer) half will not be accurate enough is made. This is important so that only the left half of the steel blank is quenched in the subsequent press when it cools, that is, not its right half. In order to ensure that the right half in the heating or holding position becomes soft or softer than the left half in the oven, i.e. only the left half is brought to the hardening and pressing temperature, the heating devices in the oven are designed or configured accordingly. set, which does not need to be explained here. The same applies to the above-mentioned "batches", that is, if not just a single steel plate but several (for example 2 to 4 steel plates) are moved into a section of the furnace and heated there. The introduction of such "batches" is already known per se and is nowadays carried out very often in such systems.

So that two or more steel blanks can now be heated at the same time in the furnace of the roller hearth continuous furnace system according to the invention for press hardening and the fastest possible passage of the steel blanks through the oven is possible, while at the same time providing sufficient furnace time for the steel blanks in the heating or holding position, the lifting device according to the invention with the lifting strips is designed so that a steel plate can be transported on the transport rollers through the furnace, even under lifting strips on which a steel plate is currently in the raised heating or holding position. In other words, a steel blank can be passed through on the transport rollers in the furnace under other steel blanks that are lifted there and are still in the heating phase. In an embodiment of the roller hearth continuous furnace system according to the invention, which will be described in more detail later, the lifting bars consist of a support structure with a profile, so that steel blanks moving on the transport rollers can pass or be driven through the openings of the lifting bars resulting from this profile shape, if these lift bars are in the raised position. When the lift bars are raised, additional steel plates can therefore be passed underneath the lifted lift bars.

It should also be pointed out that the lifting bars in the roller hearth continuous furnace system according to the invention are designed in such a way that they are in the lowered position below the roller hearth level and when they are lifted between two adjacent transport rollers pass up or above the roller hearth level. The lifting bars, which are located in the furnace along the entire length of the furnace, thus pass between the transport rollers into the furnace space above the roller hearth level. Since the transport rollers are also present continuously over the entire length of the furnace, the lifting bars work along the entire length of the furnace between these transport rollers, and are therefore moved up and down in the vertical direction.

It should also be pointed out that the roller hearth continuous furnace system according to the invention has an inlet door and an outlet door so that unnecessary heat losses or increased protective gas requirements do not occur during operation. However, the presence of these two doors is not an essential prerequisite for the lifting and transport system according to the invention for the steel blanks. In other words, this integrated lifting and transport system would also work with a roller hearth continuous furnace system that has no inlet and / or outlet door (s). The same applies to the infeed roller conveyor and the outfeed roller conveyor, which is already known per se in such continuous hearth furnace systems and ensures the fastest possible process sequence. The roller hearth continuous furnace system according to the invention would, however, in principle also function without an infeed roller conveyor or an outfeed roller conveyor.

In this context, a further significant advantage of the new roller hearth continuous furnace system should be pointed out: Even with the construction according to the invention with the lifting bars, the gas tightness of the furnace is always guaranteed during ongoing operation of the system. The lifting device with the lifting strips does not affect the protective gas tightness of the furnace. This inert gas tightness is very important for the press hardening process.

A more detailed explanation of the drive for the transport rollers is not necessary, since such transport roller drives are known per se in continuous roller hearth furnace systems. Usually the drive takes place electrically in connection with a corresponding control. It is clear that in the case of the continuous roller hearth furnace system according to the invention, a control device is necessary which controls the movements of the Steel blanks and controls the respective components of the system, that means above all the transport rollers, the lift bars and the furnace doors, i.e. the inlet door and the outlet door, which does not require any further explanation here. In any case, the control device must be programmed in such a way that the process runs optimally in the roller hearth continuous furnace system.

In a preferred embodiment of the roller hearth continuous furnace system according to the invention it is provided that the lifting device comprises three lifting strip groups and each lifting strip group is assigned a section of the transport rollers, so that in each of these three sections at least one steel plate positioned there is raised or lowered can be. In such a roller hearth continuous furnace system, there are three sub-sections in which a steel plate or, if necessary, several steel plates are positioned and heated. A relatively high and rapid throughput of steel blanks can be achieved with such a roller hearth continuous furnace system. At this point, it should be pointed out that the size of the roller hearth continuous furnace system or the furnace contained therein is not defined according to the invention, that is, not restricted. It is therefore possible to produce very large and also less large roller hearth continuous furnace systems according to the invention. With a very large roller hearth continuous furnace system, significantly more lifting strip groups (e.g. 10, 20 or 30 lifting strip groups) can be arranged over the entire length of the furnace than with a smaller roller hearth continuous furnace system. The number of subsections (or “roller paths”) of the transport rollers or the lifting strip groups assigned to them are therefore not defined according to the invention. If a large number of partial sections or lifting strip groups are provided, this must be taken into account when programming the control device, but this does not represent any programming difficulty.

In a further embodiment of the roller hearth continuous furnace system according to the invention, a lifting strip is located in each lifting strip group between all adjacent transport rollers. This has the advantage that lift bars can be moved up and down through a section of the transport rollers between all transport rollers, whereby a steel plate on the lift bars has a particularly stable and secure position or position.

Positioning and, in particular, a quasi-extensive storage area, as the steel plate is supported from below by a maximum number of lifting strips. It should be pointed out, however, that according to the invention it is not absolutely necessary that a lifting bar is always located between all adjacent transport rollers. It would therefore also be possible not to arrange eleven lifting bars between all transport rollers in a section that has, for example, twelve transport rollers, but for example only six lifting bars, that is, not to provide a lifting bar between all adjacent transport rollers. The number and geometry of the die lifters must be dimensioned according to the thickness of the steel plates.

As already stated above, the lifting strips of each lifting strip group are designed for the transport of a steel plate over the transport rollers so that a steel plate can be moved under raised lifting strips, and it is proposed in a preferred embodiment of the invention that these lifting strips consist of a Support structure with a profile. In this embodiment, it is provided that the lift bars of each lift bar group sit on a support structure that can be moved up and down, at the upper end of which the individual lift bars are arranged and the height of which is dimensioned so that the steel blanks on the to achieve the heating or holding position above the roller hearth level required height can be raised, the lift bars each consist of a profile lying transversely to the transport or flow direction, which rests only at the ends on the support structure, and the length of the lift bars greater than the width of the continuous Steel blanks are so that moving steel blanks on the transport rollers can pass through the openings of the lifting bars resulting from this support structure when these lifting bars are in the raised position. The profile therefore only rests at the ends, i.e. left and right of the open furnace space. This design enables steel blanks to be passed through in the furnace in a particularly advantageous manner under steel blanks already located there and in the heating or holding position. When the lift bars are raised, additional steel plates can therefore be passed underneath the lifted lift bars. The shape of the aforementioned support structure is not fixed. For example, it can have a rectangular shape.

The roller hearth continuous furnace system according to the invention is particularly advantageously suitable for heating steel blanks with an aluminum-silicon coating or a zinc coating. An aluminum-silicon coating can be an alloy consisting, for example, of 95% aluminum and 5% silicon.

In the roller hearth continuous furnace system according to the invention, transport rollers made of ceramic material are preferably used, because this material is known to be very heat-resistant, so that it is particularly suitable for use here.

With the roller hearth continuous furnace systems according to the invention, a method, which has already been described above, for heating steel blanks coated with aluminum, silicon and / or zinc to the hardening and pressing temperature can advantageously be carried out. Such a method is already known, in which the steel blanks are transported on transport rollers through a heated furnace which has a door on its inlet side and its outlet side that can be opened and closed and thereby the feeding and removal of the steel blanks in and out of the furnace, wherein the transport rollers are arranged in the interior of the furnace so that they all lie on one level ("roller hearth level") and run parallel to one another and transversely to the transport or flow direction of the steel blanks, and the transport rollers are rotated by means of several drives in order to move the steel blanks forward on the transport rollers, and outside the furnace and at the level of the roller hearth level in front of the inlet-side door ("inlet door") there is an inlet roller conveyor and behind the outlet-side door ("outlet door") an outlet roller conveyor are located, so that a steel blanks first over the Transport rollers of the infeed roller conveyor is fed to the oven through the open inlet door and, after the end of the dwell time in the oven ("oven time"), is guided out of the oven through the open outlet door and over the transport rollers of the outlet roller conveyor.

The invention now provides for this method to be designed in such a way that it is carried out with a roller hearth continuous furnace system according to the invention in such a way that the Infeed door steel blanks are gradually fed to the furnace via the transport rollers set in rotation and brought into one of the sections (roller paths) of the transport rollers, these steel blanks with the lift bars of the lift bar group belonging to the respective sections by means of the control device either simultaneously or are raised in a certain order and for a certain time in the heating or holding position above the roller hearth level and then the steel plates are lowered to the end of their furnace time by lowering the lifting bars to the roller hearth level by means of the control device either simultaneously or in a certain order and through the opened exit door can be transported out of the furnace onto the outfeed roller conveyor, where they are gradually removed from the system, whereby the lift bars of each lift bar group enable the transport of a steel blank over the transport rollers in the oven Enabling training have such that a steel plate can be moved through under lifted lift bars. In this way, the heating process upstream of the pressing takes place in an advantageous manner by using the transport and lifting system of the roller hearth continuous furnace system according to the invention, which is already described above and associated with the advantages explained there. In order to avoid repetitions with regard to the design and mode of operation of the individual parts of this integrated transport and lifting system, reference is made to the above statements. With the method according to the invention steel blanks are gradually moved into the furnace, where they are then raised for a certain time, the so-called furnace time, into the heating or holding position with the associated lifting bars. In contrast to the previously known roller hearth furnaces without a lifting device, with this method according to the invention it is possible to realize a continuous flow of the steel blanks through the unimpeded forward movement of the steel blanks on the transport rollers and the simultaneous lifting and lowering of the steel blanks by means of the lifting bars. With the method according to the invention, it is thus possible to move steel blanks into the furnace one by one without interruption, to heat them there and to move them out of the furnace again. In this context, it should be noted that with the method according to the invention a free choice or it is left to the programmer of the control device to which place, i.e. to which section (roller conveyor) a steel blank entering the furnace is brought. So depending on the number of Lifting strip groups provide the most varied of sequences for the infeed, lifting, lowering and removal of the steel blanks. This is essentially due to the design of the lift bars, which enables a steel blank to pass through under lifted lift bars.

In a preferred embodiment of the aforementioned method according to the invention, a particularly advantageous process sequence results. This preferred variant of the method provides that the inlet door is opened and through it the 1st steel blank is fed to the furnace via the transport rollers set in rotation for this purpose and brought into one of the sections of the transport rollers, the inlet door is closed and then the 1st steel blank with it the lift bars of the lift bar group belonging to this section is raised by means of the control device for a certain time in the heating or holding position above the roller hearth level, so that a second steel plate and, if necessary, further steel plates are then gradually moved to other sections of the Transport rollers are brought and raised with the lift bars located there in the heating or holding position above the roller hearth level, so that the 1st steel plate is then lowered to the roller hearth level to end its furnace time by lowering the lift bars in this section, s I open the exit door, the 1st steel blank is transported through this exit door out of the furnace onto the outfeed roller conveyor, where it is removed from the system, and the exit door is closed again so that the inlet door is then opened and through this initially another steel blank is inserted the furnace is transported to the section where the 1st steel blank was previously located, and there this additional steel blank with the lifting bars is lifted into the heating or holding position for a certain time, so that the 2nd steel sheet is then lowered into this section is lowered to the roller hearth level, the outlet door opens, the second steel plate is transported through this outlet door out of the furnace onto the outlet roller conveyor, where it is removed from the system, and the outlet door is closed again, which is then followed in a corresponding manner and after a steel blank is transported out of the furnace and in its place a further steel blank is fed to the furnace, and that this process continues until the last steel blank has been transported out of the furnace. With this process variant A very fast passage of steel blanks in the roller hearth continuous furnace system according to the invention can be realized in a particularly favorable manner.

According to a further development of the aforementioned method variant, another method variant is now specified, specifically for the case that the lifting device comprises three lifting strip groups and each lifting strip group is assigned a section of the transport rollers, so that there is one in each of these three sections in the furnace positioned steel plate can be raised or lowered. In this variant of the method, it is now provided that the inlet door and the outlet door are initially closed, a 1st steel plate is placed on the infeed roller conveyor, then the inlet door is opened and through this the 1st steel plate is fed to the furnace via the transport rollers that are set in rotation for this purpose and is brought into a 1st section of the transport rollers, the inlet door is closed and then the 1st steel plate with the lifting strips of the lifting strips group belonging to this 1st section by means of the control device for a certain time in the heating or holding position above the Roller hearth level is raised that then in a corresponding manner a 2nd steel plate is brought into a 2nd section of the transport rollers and lifted with the lifting bars located there in the heating or holding position above the roller hearth level, that then in a corresponding manner a 3rd steel plate in a 3rd part itt is brought to the transport rollers and raised with the lift bars located there into the heating position above the roller hearth level, so that the 1st steel plate is then lowered to the roller hearth level by lowering the lift bars in the 1st section to end its furnace time, the exit door opens, the 1st The steel blank is transported through this outlet door out of the furnace onto the outlet roller conveyor, where it is removed from the system, and the outlet door is closed again so that the inlet door is then opened and through this first a 4th steel plate into the furnace to the 1st section is transported where the 1st steel plate was previously, and there this 4th steel plate with the lifting bars is raised for a certain time in the heating or holding position, so that the 2nd steel plate is then raised by lowering the lifting bars in the 2nd section the roller hearth level is lowered, the exit door opens, the 2nd steel plate is transported through this exit door from the furnace to the exit roller conveyor, where it is removed from the system, and the outlet door is closed again, that then the inlet door is opened and through this first a 5th steel plate is transported into the furnace to the 2nd section, where the 2nd steel plate was previously, and there this 5th steel plate with the lifting strips for a certain time is raised to the heating or holding position so that the 3rd steel plate is then lowered to the roller hearth level by lowering the lifting strips in the 3rd section, the exit door opens, the 3rd steel plate opens out of the furnace through this exit door The outfeed roller conveyor is transported, where it is removed from the system, and the outfeed door is closed again, so that the infeed door is then opened and through this a 6th steel blank is transported into the furnace to the third section, where the third steel blank was previously , and there this 6th steel plate with the lifting bars for a certain time in the heating or holding position It is necessary that the 4th steel blank is then lowered to the roller hearth level by lowering the lift bars in the 1st section, the exit door opens, the 4th steel blank is transported through this exit door out of the furnace to the exit roller conveyor, where it is removed from the system and the exit door is closed again so that the 5th steel blank is then lowered to the roller hearth level by lowering the lifting bars in the 2nd section, the exit door opens, the 5th steel blank is transported through this exit door from the furnace to the exit roller conveyor , where it is removed from the system and the outlet door is closed again, and that the 6th steel plate is then lowered to the roller hearth level by lowering the lifting strips in the 3rd section, the outlet door opens, the 6th steel plate out of the through this outlet door Oven is transported out onto the outlet roller conveyor, where it is removed from the system, and the outlet door re is closed again, and that the aforementioned process steps are repeated until all other steel sheets to be heated have left the furnace. In this variant, a process with a roller hearth continuous furnace system is carried out in which the steel blanks to be heated can be heated in three sections of the transport rollers, that is, in three lifting strip groups. The process sequence specified in this process variant is particularly fast and effective and is repeated until the first six steel blanks and then all other steel blanks that may still be heated have passed through the furnace and finally left.

For the aforementioned process variant with three sections of the transport rollers or three lifting strip groups, a process variant is finally mentioned in which the 1st section is located in the area directly in front of the exit door, the 3rd section is in the area of the furnace immediately behind the inlet door and the 2nd Section between the 1st section and the 3rd section.

At this point, it should be noted once again that the method according to the invention can also be used in roller hearth continuous furnace systems that not only have two or three lift bar groups, but also significantly more lift bar groups (e.g. 10, 20 or 30 lift bar groups) to have. A roller hearth continuous furnace system with three lifting strip groups is therefore to be regarded as a smaller system.

Fig. 1

eine Längsschnitt-Ansicht einer Ausführungsform der erfindungsge-mäßen Rollenherd-Durchlauf-Ofenanlage mit drei Teilabschnitten der Transportrollen bzw. drei Hubleisten-Gruppen,

Fig. 2

eine Ansicht der in Fig. 1 gezeigten Rollenherd-Durchlauf-Ofenanlage im Querschnitt entlang der Linie A-A von Fig. 1 und

Fig. 3 bis 44

der Ansicht in Fig. 1 entsprechende Prinzip-Darstellungen der Durchführung bzw. des Ablaufs einer erfindungsgemäßen Verfahrensvariante mit einer Rollenherd-Durchlauf-Ofenanlage gemäß den Fig. 1 und 2 mit drei Teilabschnitten der Transportrollen und drei Hubleisten-Gruppen, wobei der Durchlauf von sechs Stahlplatinen Schritt für Schritt dargestellt wird.

The invention will now be explained in more detail below with reference to the schematic drawings. Show it

Fig. 1

a longitudinal sectional view of an embodiment of the roller hearth continuous furnace system according to the invention with three sections of the transport rollers or three lifting strip groups,

Fig. 2

a view of the in Fig. 1 Roller hearth continuous furnace system shown in cross section along line AA of Fig. 1 and

Figures 3 to 44

the view in Fig. 1 corresponding principle representations of the implementation or the sequence of a method variant according to the invention with a roller hearth continuous furnace system according to FIGS Figs. 1 and 2 with three sections of the transport rollers and three lift strip groups, whereby the passage of six steel plates is shown step by step.

The Figs. 1 and 2 show a roller hearth continuous furnace system 1 with a furnace 2, in which the three steel plates 3, 4 and 5 are currently located, in order to be heated to hardening and pressing temperature to become. For this purpose, an upper heating device 6 and a lower heating device 7 are provided in the furnace 2. The steel blanks 3-5 are transported on transport rollers 8. These transport rollers 8 are arranged in the interior 9 of the furnace 2 so that they all lie on one level, the so-called "roller hearth level", and are at a parallel distance from one another and across the transport or The direction of passage of the steel blanks 3 - 5 run. The transport rollers 8 are set in rotation by means of drives that are not shown here but are known per se in order to move the steel blanks 3 - 5 forward on the transport rollers 8. The steel blanks 3 - 5 are fed to one side of the furnace 2 at the level of the roller hearth level, through an inlet-side door, the so-called inlet door 10. On the side of the oven 2 opposite the inlet door 10, also at the level of the roller hearth level, the outlet-side door, i.e. the outlet door 11. With the inlet door 10 or outlet door 11, the openings of the furnace 2 there can be closed and opened, that is, the steel plates 3 - 5 pass through these openings into the furnace 2 and out of it, which will be described in more detail below. The upper heating device 6 is incidentally above the roller hearth level and the lower heating device 7 below the same.

Already at this point it should be pointed out that in front of the inlet door 10 there is no one in the Figs. 1 and 2 , but in the Figures 3 to 44 shown infeed roller conveyor 12 is located. Accordingly, there is an outlet roller conveyor 13 behind the outlet door 11.

Furthermore, a lifting device is provided in the furnace 2 in order to raise and lower the steel blanks 3 - 5. This lifting device, which is thus integrated in the furnace 2, in this embodiment of the continuous roller hearth furnace system 1 comprises three so-called lifting strip groups 14, 15 and 16, to which eleven lifting strips 17 belong. In the present exemplary embodiment, all lifting strips 17 or the three lifting strip groups 14-16 are designed identically, so that their design is described in more detail using only one lifting strip group, namely lifting strip group 14. As in the Figs. 1 and 2 It can be seen that the lifting strips 17 of the lifting strip groups 14-16 are arranged in sections. In the present case, this means that there are three subsections 18, 19 and 20 of the transport rollers 8, each subsection 18-20 comprising twelve transport rollers. In a 1st section 18 is located So the lifting strips group 14, the lifting strips group 15 in the 2nd section 19 and the lifting strips group 16 in the 3rd section 20. Accordingly, the steel plate 3 lies on the lifting strips 17 of the lifting strips group 14, with the Figs. 1 and 2 the state is shown in which this steel blank 3 is in a raised position, the so-called "heating or holding position". After the steel blank 3 had passed through the inlet door 10 on the transport rollers 8 in the 1st section 18, the lifting device for the lifting strip group 14 was activated by means of a control device not shown here, i.e. the lifting strips 17 of the lifting strip group 14 were raised so that the steel blank 3 reaches the heating or holding position above the roller hearth level. In order to achieve this, the lifting bars 17 are designed in such a way that they can reach the area above the roller hearth level between the transport rollers 8, which are spaced apart in parallel, upwards. This is possible because the width of the lifting bars 17 is less than the distance between two adjacent transport rollers 8. The lift bars 17 sit on an up and down support structure 21, which is in the Figs. 1 and 2 is shown and at the upper end of the individual lifting strips 17 are arranged. The lifting strips 17 are designed as profiles. This profile, that is to say a lifting bar 17, rests on the support structure 21 only at the lateral ends. In Fig. 2 this can be seen in the example of the lifting strip group 14 with the steel blank 3 in the heating or holding position. There in Fig. 2 it can be seen that the lifting bar 17, which consists of a profile, is only at its lateral ends, that is to say in this cross-sectional view along line AA from FIG Fig. 1 , is on the support structure 21 at the left or right end. In the present embodiment, the support structure 21 with the lifting bar 17 has a rectangular shape. The length of the lift bar 17 is greater than the width of the steel blank 3. The rectangular support structure 21 with the lift bar 17 is now designed like a frame so that when the lift bars 17 of the lift bar group 14 are raised in the one shown here Heating or holding position are, other steel plates 4 and 5 can be moved under the steel plate 3. The support structure 21 with the lifting bars 17 is designed in such a way that openings 22 arise when the lifting bars 17 are raised, that is to say areas that remain free through which steel blanks can be transported.

It does not require any further explanation that the lifting bars 17 are in the lowered position below the roller hearth level. This is in the in the Figs. 1 and 2 State shown in the lifting strips 17 of the lifting strip groups 15 and 16 is just the case. There the steel blanks 4 and 5 are still on the transport rollers 8. The upward and downward movement of the lifting bars 17 of the three lifting bar groups 14-16 is incidentally in the Figs. 1 and 2 illustrated by small vertical arrows with two arrowheads. For the sake of completeness, it should be noted that in this embodiment there is only one steel plate 3, 4 or 5 in a partial section 18, 19 or 20 or a lifting strip group 14, 15 or 16, but it would also be possible , to transport more than one steel plate, for example 2, 3 or 4 adjacent (possibly smaller) steel plates (the expert speaks of "batches" in this case) in a section and lift them there so that these steel plates can then be heated at the same time For the sake of simplicity, however, this description of the figures describes the case in which there is only one steel plate for lifting or lowering in each lifting strip group 14, 15 and 16.

It has already been explained that the Figs. 1 and 2 the steel blank 3 is in the raised position, ie the so-called heating or holding position. The steel blank 3 remains in this position for a time provided by the control device or programming until the specified press hardening temperature is reached, which is approximately 950 ° C., for example. However, since the melting temperature of the coating material on the steel blanks 3 - 5 is lower than this press hardening temperature, the coating material melts while the steel blank 3 is in the raised heating or holding position. However, because the steel blank 3 no longer has any contact with the transport rollers 8 in the heating or holding position, the disadvantageous effects already explained above do not occur. In this context it should be mentioned that the transport rollers 8 consist of a ceramic material. When the steel blanks 3 - 5 are in the raised position, they have no contact whatsoever with the ceramic transport rollers 8, so that they cannot be damaged either. In the present example, the steel plates 3 - 5 contain an aluminum-silicon coating. Alternatively, there is also a zinc coating possible. However, the basic principle of the present invention is not limited to these coating materials.

For clarification, it should also be pointed out that the above-mentioned arrows with two arrowheads in the Figs. 1 and 2 it is made clear that the lifting bars 17 are moved up and down, that is, they are raised or lowered. In Fig. 1 the lift bars 17 of the lift bar groups 15 and 16 are actually in the lowered position, that is, below the roller hearth level. To illustrate this, in Fig. 1 the upper ends of these lift bars 17 of lift bar groups 15 and 16 are shown again above the transport rollers. As a result, the lifting strips 17 of the lifting strip groups 15 and 16 should be shown once in the lowered and once in the raised position in order to illustrate the principle of the lifting device.

Based on Figures 3 to 44 A possible variant of a method for heating the steel blanks 3, 4 and 5 as well as 23, 24 and 25, that is to say a total of six steel blanks, with the continuous roller hearth furnace system 1 will now be described. For this purpose, the representations according to Figures 3 to 44 for a better understanding carried out simplified, but the basic components of the roller hearth continuous furnace system 1 in the Figures 3 to 44 correspond to the basic components as described in the Figs. 1 and 2 are shown, so that in order to avoid repetition on the above remarks on the Figs. 1 and 2 is referred. The lifting strip groups 14, 15 and 16 are particularly simplified in the Figures 3 to 44 shown.

In the Fig. 3 The first method step is now shown, in which the inlet door 10 and the outlet door 11 are closed and a 1st steel blank 3 is located on the infeed roller conveyor 12. At this point in time, there is still no steel blank in furnace 2, that is, all "places" in furnace 2 are still free. In addition, all three lift bar groups 14, 15 and 16 are in the raised position ("basic position").

Fig. 4 now shows the next step that the inlet door 10 is open and the lifting strip group 14 is in the lowered position, so that the 1st section 18 of FIG Transport rollers 8 the 1st steel plate 3 can be transported. How this happens now shows Fig. 5 . The steel blank 3 is thus transported on the transport rollers 8 and under the lifting strip groups 15 and 16 into the furnace 2 until it has reached its place in the 1st section 18 ( Fig. 6 ). The inlet door 10 is now closed ( Fig. 7 ) and the steel plate 3 is raised into the heating or holding position in which it remains for a certain time in order to reach the necessary press hardening temperature. Meanwhile, the 2nd steel blank 4 is already placed on the infeed roller conveyor 12 ( Fig. 8 ). Then in the next step ( Fig. 9 ) the inlet door 10 is opened and the lifting strip group 15 is lowered into the lower position. Fig. 10 shows how the 2nd steel blank 4 is then transported into the furnace 2 under the lifting strip group 16. By means of the existing drives of the transport rollers 8 forward in the transport or passage direction (in the Fig. 1 as well as the Fig. 3 - 44 if this is from left to right) the steel blank 4 then reaches the 2nd section 19 ( Fig. 11 ). Then the inlet door 10 is closed and the steel blank 4 is raised ( Fig. 12 ). It is in Fig. 12 to see that now both steel plates 3 and 4 remain in the heating or holding position.

As Fig. 13 shows, now follows the 3rd steel blank 5, which is also first placed on the infeed roller conveyor 12 before the infeed door 10 opens ( Fig. 14 ) and the lifting strip group 16 is lowered so that the steel blank 5 can later be lifted. The transport of the steel plate 5 is in the Fig. 15 to see and the Fig. 16 shows the state when the steel blank 5 has reached the free space in the 3rd section 20. Then the inlet door 11 is closed again ( Fig. 17 ) and the steel plate 5 is also raised into the heating or holding position.

In the Fig. 18 it is now shown how the 4th steel blank 23 is already placed on the infeed roller conveyor 12 while the three steel blanks 3 - 5 are still in the furnace 2. Fig. 19 shows the next step that the lifting strip group 14 has been lowered so that the steel blank 3 rests on the transport rollers 8 again and the outlet door 11 is open ( Fig. 19 ) to enable the steel blank 3 to be moved out of the furnace 2 ( Fig. 20 ). Incidentally, this extension takes place at the highest possible speed, so that the process runs as quickly as possible and none during the extension due to the open exit door 11 Heat losses occur and the gas tightness of the furnace 2 remains guaranteed. In Fig. 21 you can then see how the steel blank 3 lies on the outlet roller conveyor 13. There is a lifting frame 26 below the roller hearth level, with which the steel blank 3 can be raised to the height required to reach the removal position above the roller hearth level. The steel blank 3 can then be removed from the outlet roller conveyor 13 after the outlet door 11 has otherwise been closed again (see FIG Fig. 22 ).

Now again the inlet door 10 opens to enable the transport of the 4th steel blank 23 ( Fig. 23 ). This steel blank 23 is now transported into the furnace 2, namely to the 1st section 18 ( Figures 24 and 25 ), where the 1st steel blank 3 was previously. Fig. 26 shows that the inlet door 10 has been closed again and the 4th steel plate 23 is now in the 1st section 18 or there in the heating or holding position, while the steel plates 3 and 4 are also in this position.

In Fig. 27 it can be seen that in the meantime the next, i.e. the 5th steel blank 24 has already been placed on the infeed roller conveyor 12. In the next step, the lift bars 17 of the lift bar group 15 are lowered in the second section 19 and the outlet door 11 is opened ( Fig. 28 ). Now the steel blank 4 is moved out of the furnace 2 ( Fig. 29 ) until it lies on the outfeed roller conveyor 13 ( Fig. 30 ). In Fig. 31 it can be seen that the outlet door 11 is closed again and the steel blank 4 on the outlet roller conveyor 13 has been raised with the lifting frame 26 for the purpose of removing it.

Fig. 32 now shows the next step, that is, the inlet door 10 is open for the next, namely the 5th steel plate 24, for which the space that has become free in the 2nd section 19 of the furnace 2 is provided. In Fig. 33 it is shown how the steel blank 24 is now transported into the furnace until it has reached its position in the 2nd section 19 ( Fig. 34 ). Then the inlet door 10 is closed again ( Fig. 35 ). So there are now the three steel plates 23, 24 and 5 in the furnace 2. At this point it should be noted that from the Figures 3 to 44 the result is that the 1st section 18 is in the area immediately in front of the exit door 11, the 3rd section 20 are located in the area of the furnace 2 directly behind the inlet door 10 and the 2nd section 19 between the 1st section 18 and the 3rd section 20.

While the steel plates 23, 24 and 5 are still in the furnace 2, the next steel plate, namely the 6th steel plate 25, is placed on the infeed roller conveyor 12 ( Fig. 36 ). Then the exit door 11 opens ( Fig. 37 ) and the lifting strip group 16 is lowered so that the steel blank 5 comes back onto the transport rollers 18. Fig. 38 then shows how the steel blank 5 (at the highest speed) is moved out of the furnace 2 until it lies on the outlet roller conveyor 13 ( Fig. 39 ). Then the exit door 11 is closed ( Fig. 40 ) and the steel blank 5 is raised at the outlet for removal ( Fig. 40). Fig. 41 now shows that the steel blank 5 has been removed and the inlet door 10 has opened to enable the steel blank 25 to be transported in ( Fig. 42 ). The steel blank 25 then reaches ( Fig. 43 ) the 3rd section 20. Then the inlet door 10 is closed again ( Fig. 44 ) and the lifting strip group 16 lifts the steel blank 25 into the heating or holding position ( Fig. 44 ). In the in Fig. 44 In the state shown, the three steel plates 23, 24 and 25 are all in the heating or holding position. Analogous to the above-described process sequence for extending or transporting out the steel blanks 3, 4 and 5, the steel blanks 23, 24 and 25 are gradually transported out and further steel blanks are brought in, but this is not further described here. The method steps described above can therefore be continued until all of the steel blanks to be heated have passed their furnace time and have left the furnace.

Finally, it should also be noted that the advantageous sequence described above represents only one possible variant. So there are still countless other process sequences possible in which the desired sequence of feeding, raising or lowering and removing steel blanks is implemented on the basis of a corresponding device or programming of the control device. The basic principle of the roller hearth continuous furnace system according to the invention and the method carried out with it are therefore not based on the above with reference to FIG Fig. 3 - 44 embodiment described limited.

Claims (10)

Roller hearth continuous furnace system for heating steel blanks coated with aluminum, silicon and / or zinc to hardening and pressing temperature with transport rollers for transporting the steel blanks through a heated oven that has a door on its inlet side and one on its outlet side that is opened and closed and thereby enables the steel blanks to be fed into or out of the furnace, the transport rollers being arranged in the interior of the furnace so that they are all on one level ("roller hearth level") and at a parallel distance from one another and across run to the transport or passage direction of the steel blanks, and the transport rollers are rotated by means of several drives to move the steel plates on the transport rollers forward, and outside the furnace and at the level of the roller hearth level in front of the inlet-side door ("inlet door") Infeed roller alley and behind the exit-side door ("Auslauftü re ") there is an outlet roller conveyor, via whose transport rollers the steel blanks get into and out of the furnace,
characterized,
that in the furnace (2) there is a lifting device with at least two lifting strip groups (14 - 16), the lifting strips (17) of which are raised and lowered for raising or lowering the steel plates (3 - 5, 23 - 25) positioned in the furnace (2) can be lowered, whereby the lifting strips groups (14 - 16) can be controlled with a control device, the lifting strips (17) are in the lowered position below the roller hearth level, the width of the lifting strips (17) is less than the distance between two adjacent transport rollers ( 8) is and the lifting strips (17) when lifting between two adjacent transport rollers (8) through upwards or above the Reach the roller hearth level and are arranged in sections in the transport or throughput direction of the steel blanks (3 - 5, 23 - 25) so that a lifting strip group is located in each section (18 - 20) of the transport rollers (8) in the furnace (2) (14-16), with their lifting bars (17) at least one steel plate (3-5, 23-25) fed to the furnace (2) and brought into one of the partial sections (18-20) of the transport rollers (8) by means of the control device is raised for a certain time in the heating or holding position above the roller hearth level, and that the lifting strips (17) of each lifting strip group (14 - 16) enable the transport of a steel plate (3 - 5, 23 - 25) over the transport rollers (8) in the furnace (2) enabling design such that a steel plate (3 - 5, 23 - 25) can be moved through under lifted lift bars (17). Roller hearth continuous furnace system according to claim 1, characterized in that the lifting device comprises three lifting strip groups (14-16) and each lifting strip group (14-16) is assigned a section (18-20) of the transport rollers (8), so that in each of these three subsections (18-20) at least one steel plate (3-5, 23-25) positioned there can be raised or lowered. Roller hearth continuous furnace system according to claim 1 or 2, characterized in that a lifting strip (17) is located in each lifting strip group (14 - 16) between all adjacent transport rollers (8). Roller hearth continuous furnace system according to one of claims 1 to 3, characterized in that the lifting strips (17) of each lifting strip group (14-16) sit on an up and down movable support structure (21), at the upper end of which the individual Lifting bars (17) are arranged and their height is such that the steel plates (3 - 5, 23- 25) can be raised to the height required to reach the heating or holding position above the roller hearth level, the lifting bars (17) each consist of a profile lying transversely to the transport or passage direction, which only rests on the ends of the support structure (21), and the length of the lifting bars (17) is greater than the width of the steel plates (3 - 5, 23 - 25) ) so that on the transport rollers (8) moving steel plates (3 - 5, 23 - 25) can pass through the openings (22) of the lifting bars (17) resulting from this support structure (21) when these lifting bars (17) are in the raised position. Roller hearth continuous furnace system according to one of Claims 1 or 4, characterized in that it is used for heating steel blanks (3 - 5, 23 - 25) with an aluminum-silicon coating or a zinc coating. Roller hearth continuous furnace installation according to one of Claims 1 to 5, characterized in that the transport rollers (8) consist of a ceramic material. Method for heating steel blanks coated with aluminum, silicon and / or zinc to hardening and pressing temperature with a roller hearth continuous furnace system according to one of claims 1 to 6, wherein the steel blanks are transported on transport rollers through a heated oven, which on its inlet side and its outlet side each has a door that can be opened and closed and thereby enables the steel blanks to be fed into or out of the furnace, the transport rollers being arranged in the interior of the furnace so that they are all on one level ( "Roller hearth level") and run parallel to each other and transversely to the transport or flow direction of the steel blanks, and the transport rollers are rotated by means of several drives to move the steel plates on the transport rollers forwards, and being outside the furnace and in height the roller hearth level in front of the inlet-side door ("inlet door") ei n Infeed roller alley and behind the exit door ("outlet door") there is an outlet roller alley, so that a steel blank is first fed to the furnace via the transport rollers of the infeed roller alley through the open inlet door and after the end of the dwell time in the furnace ("furnace time") through the open outlet door and is guided out of the furnace via the transport rollers of the outlet roller conveyor,
characterized,
that steel blanks (3 - 5, 23 - 25) are gradually fed through the inlet door (10) to the furnace (2) via the transport rollers (8), which are set in rotation for this purpose, and into one of the partial sections (18 - 20) of the transport rollers (8) are brought, these steel plates (3-5, 23-25) with the lifting strips (17) of the lifting strips group (14 - 16) belonging to the respective subsections (18-20) by means of the control device either simultaneously or in one specific sequence and for a certain time in the heating or holding position above the roller hearth level and then the steel plates (3 - 5, 23 - 25) to end their furnace time by lowering the lift bars (17) to the roller hearth level by means of the control device either be lowered simultaneously or in a certain sequence and transported through the open discharge door (11) out of the oven (2) onto the discharge roller conveyor (13), where they are gradually removed from the system earth, the lifting strips (17) of each lifting strip group (14-16) have a design that enables a steel blank (3-5, 23-25) to be transported over the transport rollers (8) in the furnace (2) such that a steel blank (3 - 5, 23 - 25) can be moved under the lifted lift bars (17). Method for heating steel blanks coated with aluminum, silicon and / or zinc to hardening and pressing temperature with a roller hearth continuous furnace system according to claim 7,
characterized,
that the inlet door (10) and the outlet door (11) are initially closed, a 1st steel plate (3) is placed on the infeed roller conveyor (12), then the inlet door (10) is opened and through this the 1st steel plate (3) The furnace (2) is fed via the transport rollers (8), which are set in rotation for this purpose, and brought into one of the partial sections (18-20) of the transport rollers (8), the inlet door (10) is closed and then the 1st steel plate (3 ) with the lifting strips (17) of the lifting strips group (14-16) belonging to this section (18-20) by means of the control device in the heating or holding position above the roller hearth level for a certain time is raised so that a second steel plate (4) and, if necessary, further steel plates (5, 23 - 25) are then gradually brought into other sections (18 - 20) of the transport rollers (8) and with the lifting bars located there ( 17) is raised to the heating or holding position above the roller hearth level so that the 1st steel plate (3) is then lowered to the roller hearth level by lowering the lifting bars (17) in this section (18-20) to end its furnace time , the outlet door (11) opens, the 1st steel plate (3) is transported through this outlet door (11) out of the furnace (2) onto the outlet roller conveyor (13), where it is removed from the system (1), and the outlet door (11) is closed again so that the inlet door (10) is then opened and through this first a further steel blank (4-5, 23-25) is transported into the furnace (2) to the section (18-20) , where the 1. Stahlpl atine (3), and there this further steel plate (4 - 5, 23 - 25) with the lifting bars (17) is lifted into the heating or holding position for a certain time so that the 2nd steel plate (4) then passes through Lowering the lift bars (17) in this section (18-20) is lowered to the roller hearth level, the outlet door (11) opens, the second steel plate (4) through this outlet door (11) out of the furnace (2) onto the The outlet roller conveyor (11) is transported, where it is removed from the system (1), and the outlet door (11) is closed again, so that a steel plate (5, 23 - 25) is then gradually removed from the furnace (2) in a corresponding manner. is transported out and in its place a further steel blank is fed to the furnace (2), and that this process continues until the last steel plate has been transported out of the furnace (2) Method for heating steel blanks coated with aluminum, silicon and / or zinc to hardening and pressing temperature with a roller hearth continuous furnace according to claim 8, wherein the lifting device comprises three lifting strip groups and each lifting strip group is assigned a section of the transport rollers, so that a steel plate positioned there can be raised or lowered in each of these three sections in the furnace,
characterized,
that the inlet door (10) and the outlet door (11) are initially closed, a 1st steel plate (3) is placed on the infeed roller conveyor (12), then the inlet door (10) is opened and through this the 1st steel plate (3) The furnace (2) is fed via the transport rollers (8), which are set in rotation for this purpose, and is brought into a 1st section (18) of the transport rollers (8), the inlet door (10) is closed and then the 1st steel plate (3) with the lifting strips (17) of the lifting strips group (14-16) belonging to this 1st section (18) is raised by means of the control device for a certain time in the heating or holding position above the roller hearth level, that then in a corresponding manner 2. Steel plate (4) brought into a 2nd section (19) of the transport rollers (8) and lifted with the lifting bars (17) located there into the heating or holding position above the roller hearth level, that then e A 3rd steel plate (5) is brought into a 3rd section (20) of the transport rollers (8) and lifted with the lifting strips (17) located there into the heating position above the roller hearth level, so that the 1st steel plate (3) is then completed its furnace time is lowered to the roller hearth level by lowering the lifting strips (17) in the 1st section (18), the outlet door (11) opens, the 1st steel plate (3) out of the furnace (2) through this outlet door (11) is transported to the outfeed roller conveyor (13), where it is removed from the system (1), and the outfeed door (11) is closed again so that the infeed door (10) is then opened and through this first a 4th steel plate (23) in the furnace (2) is transported to the 1st section (18), where the 1st steel plate (3) was previously, and there this 4th steel plate (23) with the lifting bars (17) for a certain time in the heating or holding position is raised, that then the 2nd steel plate (4) is lowered to the roller hearth level by lowering the lift bars (17) in the 2nd section (19), the outlet door (11) opens, the second steel plate (4) out of the furnace (2) through this outlet door (11) is transported out onto the outfeed roller conveyor (13), where it is removed from the system (1), and the outfeed door (11) is closed again so that the infeed door (10) is then opened and through this first a 5th steel plate (24) is transported into the furnace (2) to the 2nd section (19), where previously the 2nd steel plate (4) was, and there this 5th steel plate (24) with the lifting bars (17) for a certain time in the heating - or the holding position is raised so that the 3rd steel plate (5) is then lowered by lowering the lifting strips (17) in the 3rd section (20) is lowered to the roller hearth level, the discharge door (11) opens, the 3rd steel plate (5) is transported through this discharge door (11) out of the furnace (2) onto the discharge roller conveyor (13), where it is taken from the system (1), and the outlet door (11) is closed again, so that the inlet door (10) is then opened and through this a 6th steel plate (25) into the furnace (2) to the 3rd section ( 20) is transported where the 3rd steel plate (5) was previously, and there this 6th steel plate (25) with the lifting bars (17) is lifted into the heating or holding position for a certain time, so that the 4th . Steel blank (23) is lowered to the roller hearth level by lowering the lifting strips (17) in the 1st section (18), the outlet door (11) opens, the 4th steel blank (23) through this outlet door (11) out of the furnace ( 2) is transported out onto the outlet roller conveyor (13), where it is removed from the system (1), and the The outlet door (11) is closed again, so that the 5th steel plate (24) is lowered to the roller hearth level by lowering the lifting strips (17) in the 2nd section (19), the outlet door (11) opens, the 5th steel plate ( 24) is transported through this outlet door (11) out of the oven (2) onto the outlet roller conveyor (13), where it is removed from the system (1) and the outlet door (11) is closed again, and then the 6. Steel blank (25) is lowered to the roller hearth level by lowering the lifting strips (17) in the 3rd section (20), the outlet door (11) opens, the 6th steel blank (25) through this outlet door (11) out of the furnace (2nd ) is transported out onto the outlet roller conveyor (13), where it is removed from the system (1), and the outlet door (11) is closed again, and that the aforementioned process steps are repeated until all the other steel blanks to be heated leave the furnace ( 2) have left. Method for heating steel blanks coated with aluminum, silicon and / or zinc to hardening and pressing temperature with a roller hearth continuous furnace system according to claim 9,
characterized,
that in this method the 1st section (18) is in the area immediately in front of the outlet door (11), the 3rd section (20) in the area of the furnace (2) immediately behind the inlet door (10) and the 2nd section (19) are between the 1st section (18) and the 3rd section (20).

Images