EP0499850A1 - Process and continuous furnace for the heat treatment of articles - Google Patents

Abstract

The workpiece charges are transported stepwise through the throughflow furnace lying on movable floor elements (12), and at each step they are individually lifted from below, beginning at the outlet side end (9) of the throughflow furnace, and displaced by one step. In this manner, even extremely heavy workpiece charges, such as coils, can be heat-treated in a throughflow furnace. Transport is effected by a transfer machine (13) which can travel in the longitudinal direction of the furnace, beneath the furnace floor (14) in a space (15) under the furnace, and which can engage through the furnace floor (14) with a lifting device (18). For this purpose the furnace floor has two apertures (20,21) running in the longitudinal direction of the furnace. The movable floor elements (12) form a closed upper floor which covers the apertures (20,21) of the furnace floor. The space (15) under the furnace is thus thermally insulated. <IMAGE>

Description

The invention relates to a method and a continuous furnace for the heat treatment of workpiece batches, which are introduced at the inlet end of the continuous furnace, moved in succession through the continuous furnace and removed from the continuous furnace at the outlet end.

Known continuous processes and furnaces have considerable advantages over stationary furnaces, such as chamber and bell annealers etc., in terms of the degree of automation and, accordingly, the cost-effectiveness as well as the increasing quality requirements for bulk steel heat treatment. However, these advantages have to be bought with certain disadvantages, which relate to the expenditure on equipment and the applicability. Considerable frictional forces occur with push-through furnaces. Although these are avoided in walking beam and step-by-step furnaces as well as in roller hearth furnaces, the outlay on equipment is higher here. Walking beam and step-by-step furnaces require very powerful drive mechanisms, since the entire furnace content has to be transported at the same time. In roller hearth furnaces, the rollers with their drives represent a significant price factor. They also limit the area of application due to their limited load-bearing capacity and temperature resistance.

In particular, the factors of weight and annealing temperature are of crucial importance in the heat treatment of coils made of steel or coil metal. Accordingly, only bell-type annealing furnaces have so far been considered, although these can only be automated to a limited extent and accordingly leave much to be desired in terms of their economy. They also hardly meet the increasing quality requirements for mass steel annealing. In addition, there is less gentle edge treatment of the coils and the risk of tape adhesives.

The invention has for its object to improve the continuous annealing of workpiece batches and in particular to make them applicable to workpiece batches of great weight.

The method according to the invention is used to achieve this object characterized in that the workpiece batches are moved one step at a time, starting at the outlet end of the continuous furnace.

The invention thus improves continuous furnace operation and, in particular, enables its use on extremely heavy batches of workpieces, such as are present, for example, when annealing coils.

In comparison with conventional bell annealers, there are no protective and cooling hoods and thus their sealing problems. The loading and unloading processes are also simplified, while at the same time reducing the space requirement. Above all, there are advantages in connection with the control of temperature and furnace atmosphere. Shielding gas and heating gas consumption are lower, whereby the shielding gas can easily be re-burned. All guiding and convection systems in the ceiling and in the walls, which are possible with continuous ovens and chamber ovens, can be used for heating and cooling, and also in connection with collector hoods for stack covering. The return of the gas circulation takes place from bottom to top, the circulation fans being arranged in the ceiling. You are therefore not endangered by the annealing material and achieve very favorable service lives. Adjustable circulation fans are preferably used which have a spiral with two outlets. In the case of protective gas operation, the protective gas is conducted in countercurrent, which results in optimal surface qualities. It should also be emphasized that the method according to the invention is particularly suitable for high-convection operation, but that high-temperature operation is equally possible.

Advantageously, the batches of workpieces are individually lifted and transported in the direction of passage, preferably being lifted from below through at least one recess in the bottom of the continuous furnace. In this respect, the invention uses the movement sequence of walking beam furnaces, but with the proviso that only one batch of workpieces is moved at a time.

In a further development, the invention proposes that the workpiece batches be carried by mobile floor elements, which together in the lowered position close the recess in the floor of the continuous furnace. The lifting mechanism located underneath the furnace floor is thus optimally shielded, namely during the stationary state by a double floor, which only partially and briefly releases the underbody and its recess during the relocation.

The mobile floor elements are designed so that they connect to each other in the direction of passage and can thereby form a closed floor surface. The batches of workpieces can then be arranged on the mobile floor elements in such a way that doors or separating slides can be retracted to form chambers, i.e. from different heating, cooling, mass transfer or flushing zones and brought to bear on the mobile floor elements. Alternatively, it can be advantageous that the steps by which the workpiece batches are displaced individually are of different lengths. This creates gaps for retracting the gate valve regardless of the mutual spatial assignment of the workpiece batches.

The invention further relates to a continuous furnace for the heat treatment of workpiece batches with an input conveyor, an inlet chamber, at least one treatment chamber, an outlet chamber and an output conveyor and with a transport device for the cyclical transport of the workpiece batches through the continuous furnace, the latter being characterized according to the invention in that it is provided in its base with at least one recess running in the longitudinal direction of the furnace and that the transport device below the base has a converter which can be moved in the longitudinal direction of the furnace and has at least one converter which can be raised through the recess in the base Has lifting device. With each cycle, the converter begins at the outlet end of the continuous furnace and shifts the workpiece batch located there by one step in the direction of passage. It then moves in the opposite direction to move the next batch in each case until it or the input conveyor has loaded the first treatment slot, whereupon the next heat treatment cycle can begin. The continuous furnace according to the invention enables those advantages to be achieved which have already been explained in connection with the method according to the invention.

For extremely heavy workpiece batches, a construction is particularly suitable in which the bottom of the continuous furnace is provided with two parallel recesses which divide it into two edge strips and a central strip, and in which the converter has two lifting devices located next to one another. The material to be treated is not only supported and carried centrally, but in two spaced-apart areas. In terms of manufacturing technology, it is advantageous to connect the edge strips of the base in one piece to the side walls of the continuous furnace.

It has been shown that it is advantageous in terms of design and movement if the converter has two mountings which can be moved synchronously next to each other, each with a lifting device. This also allows the central stripes of the furnace floor to be supported centrally.

In an essential further development of the invention, the input conveyor and preferably also the output conveyor is designed as a roller conveyor extending at least into the inlet chamber, the rollers located at the inner end of which are each divided into at least two spaced sections. The invention therefore makes use of features of conventional roller hearth furnaces, but with two special features. On the one hand, the rollers are only used in areas with low temperatures, which on the one hand means their load capacity and their security against emergency situations and on the other hand allows high treatment temperatures in the middle part of the continuous furnace. For the rest, this results in price advantages and options for implementing defined fall programs. On the other hand, the roller conveyors are provided with transfer areas in which the rollers each form roller sections with spaces for the passage of the lifting device acting from below. This allows a favorable transition from role promotion to the individual implementation according to the invention.

The rollers divided into sections preferably each form three sections, of which the two lateral ones can be driven. This already prevents the workpiece batches from tilting due to the type of funding.

If the continuous furnace according to the invention is used for coil annealing, the input conveyor can easily have corresponding tilting and coil turning devices.

The inlet and outlet chambers will usually be designed as locks, whether as vacuum or flushing locks. The inlet conveyor will usually only extend into the inlet chamber, since this is followed by the heating zones. Different in the outlet area. There, cooling zones, for example rapid cooling devices for residual cooling in high-temperature operation, can be connected upstream of the outlet chamber. Accordingly, it is possible to have the exit conveyor reach these zones in the continuous furnace. For cost reasons, the internal transition areas with the roles divided into sections will only be selected as long as is necessary for the storage space of a batch.

In principle, the workpiece batches can be arranged on any supports or in any containers. This is how conventional grates, baskets and the like come. in question. However, a particularly advantageous and, accordingly, essential further development of the invention is that a mobile floor element is assigned to each workpiece batch, the mobile floor elements when resting on the floor of the continuous furnace, cover the recess in that floor. This also applies to those areas of the roller conveyor in which the rollers are each divided into sections. The entire area or "sub-furnace" located below the floor and integrated into the furnace atmosphere is thus optimally thermally shielded. When stationary, the mobile floor elements form a closed top floor. During the transfer, its stroke is approx. 50 mm, the transfer process taking about one minute. The heating can be switched off during the entire conversion cycle. Even at treatment temperatures of over 1000 ° C, the lower furnace only takes on a temperature slightly above the ambient temperature. The mobile floor elements are reusable and are circulated between the outlet and the inlet of the continuous furnace.

A particularly advantageous construction of the continuous furnace consists in that each floor element has a base plate, supports for the workpiece batches arranged on the base plate and thermal insulation inserted between the supports. The thermal insulation increases the thermal shielding of the sub-oven, whereby the base plate in conjunction with the supports provides the required strength and resilience.

A support and guidance system for the workpiece batch is preferably arranged on the support elements. This support and control system ensures optimal adaptation to the respective workpiece batch, both with regard to the mechanical properties and the desired convection conditions. In this way, optimal heat treatment under the most gentle operations, for example for the belt edges, is ensured. The support and control system can be designed, for example, to accommodate individual coils with a large diameter or a plurality of coils with a smaller diameter. It is preferably detachably connected to the supports and can be made of ceramic if high temperature conditions are required.

Furthermore, the invention is directed to a mobile base element for carrying a batch of workpieces during the cyclical transport through a continuous furnace, this base element being characterized in that it has a base plate, supports for the workpiece batch arranged on the base plate and thermal insulation inserted between the supports. The floor element optimally combines mechanical strength with a high thermal insulation effect and is suitable for forming a closed top floor in the continuous furnace in conjunction with neighboring floor elements of the same type. To adapt to different mechanical and fluidic conditions, a support and guidance system for the workpiece batch is preferably arranged on the support elements, advantageously detachably connected to the supports. In the case of high temperatures, the support and control system is made of ceramic. In any case, the floor element is sandwiched.

Combinations of the features according to the invention that differ from the links discussed above are also considered to be disclosed as essential to the invention.

Fig. 1A

einen Vertikalschnitt durch das einlaßseitige Ende eines erfindungsgemäßen Durchlaufofens, gesehen entlang der Linie I-I in Fig. 2A und Fig. 3;

Fig. 1B

einen Schnitt entsprechend Fig. 1A durch das auslaßseitige Ende des Durchlaufofens, gesehen entlang der Linie I-I in Fig. 2B und Fig. 3;

Fig. 2A

einen Horizontalschnitt durch das einlaßseitige Ende des Durchlaufofens;

Fig. 2B

einen Schnitt entsprechend Fig. 2A durch das auslaßseitige Ende des Durchlaufofens nach Verfahren des Umsetzers;

Fig. 3

einen Schnitt entlang der Linie III-III in Fig. 1A;

Fig. 4

einen Vertikalschnitt durch ein erfindungsmäßes mobiles Bodenelement.

The invention is explained below with reference to a preferred embodiment in connection with the accompanying drawings. The drawing shows in:

Fig. 1A

a vertical section through the inlet end of a continuous furnace according to the invention, seen along the line II in Fig. 2A and Fig. 3;

Figure 1B

a section corresponding to Figure 1A through the outlet end of the continuous furnace, seen along the line II in Fig. 2B and Fig. 3.

Figure 2A

a horizontal section through the inlet end of the continuous furnace;

Figure 2B

a section corresponding to FIG. 2A through the outlet side End of the continuous furnace according to the converter's method;

Fig. 3

a section along the line III-III in Fig. 1A;

Fig. 4

a vertical section through an inventive mobile floor element.

1, the continuous furnace comprises an inlet conveyor 1 in the form of a roller conveyor which extends into an inlet chamber 2 which is designed as a lock chamber. A plurality of treatment chambers adjoins the inlet chamber 2, of which the treatment chambers 3 and 4 are shown in FIG. 1A and the treatment chambers 5, 6 and 7 are shown in FIG. 1B. The treatment chambers can merge. However, separating slides 8 can also be provided in order to optionally seal the treatment chambers from one another. The decisive factor is the respective heating, mass transfer and cooling program. The doors of the lock chamber are to be equated to the separating slide 8.

According to FIG. 1B, the treatment chamber 7 is followed by an outlet chamber 9, which is also designed as a lock. FIG. 1B also shows an exit conveyor 10, also in the form of a roller conveyor, which extends into the treatment chambers. Since the treatment chambers 6 and 7 are cooling chambers, the output conveyor 10 is subjected to thermal loads just as little as the input conveyor 1.

All treatment chambers and also the inlet and outlet chambers are equipped with workpiece batches 11 indicated by dash-dotted lines. The batch of workpieces in the outlet chamber 9 is ready for removal.

Each workpiece batch 11 rests on a mobile floor element 12, as will be explained in more detail in connection with FIG. 4. A converter 13 according to FIGS. 1A and 3, which is also shown in FIG. 1B, takes care of the transport of the mobile floor elements 12, in dash-dotted lines at the end its moving motion.

The converter 13 is arranged below the furnace floor 14 in a lower furnace 15 and has two mountings 16 which can be moved alongside one another in the longitudinal direction. A chain drive 17, indicated schematically in FIG. 1B, is used to drive it. Each carriage 16 carries a lifting device 18 with an upper flat iron 19 (shown in the lowered position in FIG. 1A). The bottom 14 of the continuous furnace is provided with two recesses 20 and 21 which are provided in the direction of the passage and which divide the bottom into two edge strips 22 and a central strip 23 (FIG. 3). The latter is supported separately, while the edge strips 22 are connected in one piece to the associated furnace side walls. Furthermore, the rollers of the roller conveyors 1 and 10 in the inlet chamber 2 and in the treatment chamber 6 are each divided into three sections, namely into the lateral sections 24 and the central sections 25. The spaces between the individual sections, of which only the outer sections 24 are driven, form continuations of the recesses 20 and 21 of the base 14. Through these recesses 20 and 21 and through the spaces between the sections 24 and 25 of the rollers, the flat iron 19 of the converter 13 can reach through when the lifting devices 18 are raised and each have a mobile base element Lift 12 with the workpiece batch 11 on it and move it in the longitudinal direction of the furnace.

If the material to be treated is to be switched one cycle after the end of a heat treatment phase, this is done as follows.

If this has not yet been done, the outlet chamber 9 is emptied, whereupon the cooled batch is transported from the treatment chamber 7 into the outlet chamber 9 by actuating the output conveyor 10. At the same time or thereafter, the batch moves from the treatment chamber 6 into the treatment chamber 7. This takes place in each case with the mobile floor elements 12. The converter 13 is located below the treatment chamber 5. As soon as the treatment chamber 6 is emptied, the lifting devices 17 are actuated so that the flat iron 19 lifts the mobile base element 12 with the workpiece batch 11 located thereon. An actuation of the chain drive 17 allows the converter 13 to move under the treatment chamber 6, the flat irons moving between the roller sections. The load can then be lowered and lowered (position of the converter 13 according to FIG. 1B). This is followed by the transfer of the batch from the adjacent treatment chamber into the treatment chamber 7 which has now been emptied. This process continues step by step until the batch together with the mobile base element has been transferred from the inlet chamber 2 into the first treatment chamber. The inlet chamber 2 can then be filled by actuating the input conveyor 1. However, this can be postponed until it is time to re-populate the treatment chamber 3.

The invention is particularly applicable to heat treatment of particularly difficult workpiece batches, for example coil annealing. As far as heating, cooling and circulation of the atmosphere are concerned, the entire range of variations available can be used. Indications of heating or cooling devices can be found in the treatment chambers 4, 5 and 6. Furthermore, the treatment chambers 4 to 7 show schematic indications of circulating devices arranged in the upper area.

At least in the heating zones, the mobile floor elements 12 are offset by the same stride lengths. In the idle state, they therefore form a closed upper floor which securely closes the recesses 20 and 21 and thereby thermally shields the lower furnace 15. In the inlet and outlet area, the stride length can be adapted to the space available.

4 shows one of the mobile floor elements 12 on an enlarged scale. The base element has a steel base plate 26 which supports 27. Between the supports thermal insulation 28 is inserted. The supports 27 carry a support and guidance system 29, which is detachably attached and in the present case consists of ceramic. The mobile floor element combines great load-bearing capacity with good thermal insulation.

Within the scope of the invention, modification options are readily available. For example, the bottom of the continuous furnace can be provided with a single recess running in the direction of the throughflow. The division of the roles is then adapted to this design. The same applies to the converter, which under these circumstances only requires a single central lifting device. The converter can also work with a single central carriage. The input and output conveyors can be of any design as long as they allow the converter to reach through in the transfer area. However, this can be ensured particularly easily in the case of roller conveyors. Mention should also be made of the possibility of supporting the load in more than two areas transversely to the direction of travel. The support and guidance system can be omitted for the mobile floor elements, provided that the convection control below the workpiece batch is not important. The load then rests directly on the supports. If a support and control system is used, this can also be permanently connected to the supports, provided the workpiece batches do not vary. As a rule, however, specially adapted systems are provided, for example for holding several small coils or for carrying different types of workpieces or workpiece containers.

Claims (12)

Process for the heat treatment of batches of workpieces which are introduced in cycles at the inlet end of a continuous furnace, moved in succession through the continuous furnace and removed from the continuous furnace at the outlet end,
characterized,
that the workpiece batches are shifted one step at a time, starting at the outlet-side end of the continuous furnace, and are preferably lifted individually and transported in the direction of passage. A method according to claim 1, characterized in that the workpiece batches are lifted from below through at least one recess in the bottom of the continuous furnace, wherein they are preferably carried by mobile base elements which together in the lowered position close the recess in the bottom of the continuous furnace. Method according to Claim 1 or 2, characterized in that the steps by which the workpiece batches are displaced individually are of different lengths. Continuous furnace for the heat treatment of workpiece batches with an input conveyor, an inlet chamber, at least one treatment chamber, an outlet chamber and an output conveyor and with a transport device for the cyclical transport of the workpiece batches through the continuous furnace, characterized in that the continuous furnace in its bottom (14) with at least one over the furnace length-extending recess (20, 21) is provided and that the transport device below the bottom has a converter (13) which can be moved over the furnace length and has at least one through the recess in the base has lifting device (18) that can be raised. Continuous furnace according to Claim 4, characterized in that the bottom (14) of the continuous furnace is provided with two parallel recesses (20, 21) which subdivide it into two edge strips (22) and a central strip (23), and in that the converter (13 ) has two adjacent lifting devices (18), the edge strips (22) of the base (14) preferably being connected in one piece to the side walls of the continuous furnace. Continuous furnace according to claim 5, characterized in that the converter (13) has two mountings (16) which can be moved synchronously next to each other, each with a lifting device (18). Continuous furnace according to one of Claims 4 to 6, characterized in that the input conveyor (1) is designed as a roller conveyor which extends at least into the inlet chamber (2), the rollers at the inner end of which are each in at least two spaced sections (24, 25) are divided. Continuous furnace according to one of Claims 6 to 7, characterized in that the exit conveyor (10) is designed as a roller conveyor which extends at least into the outlet chamber (9), the rollers at the inner end of which are each in at least two spaced sections (24, 25) are divided. Continuous furnace according to claim 7 or 8, characterized in that the rollers divided into sections each form three sections (24, 25), of which the two lateral (24) can be driven. Continuous furnace according to one of Claims 4 to 9, characterized in that each workpiece batch (11) is assigned a mobile base element (12), the mobile base elements having the recess (s) (20, 21) when resting on the base (14) of the continuous furnace ) cover in its bottom. Continuous furnace according to claim 10, characterized in that each base element (12) has a base plate (26), supports (27) arranged on the base plate for the workpiece batch and heat insulation (28) inserted between the supports. Continuous furnace according to claim 11, characterized in that a support and guide system (29) for the workpiece batch is arranged on the supports (27), the support and guide system (29) preferably being detachably connected to the supports (27).

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