NO147692B - DEVICE FOR HEAT TREATMENT OF CASTLE GOODS. - Google Patents

Description

The present invention relates to a device for the heat treatment of castings in the form of strings and ingots as well as blocks, rods, tubes and the like, particularly of aluminum or magnesium alloys, during which the castings are preheated using heat carriers such as hot air or hot gas at a higher temperature than a predetermined heat treatment temperature and then kept at said heat treatment temperature.

In a published German patent application (DE-OS 2,349,765)

a method and a device of this kind has previously been proposed, whereby several advantages are achieved over ordinary known methods and devices.

When processing the goods in detail, which means not processing package-like batches of material, but of long strings or groups of consecutive short ingots, uniform quality is ensured to a high degree, as each individual string or ingot is subjected to the same pre-heating

and warm-keeping conditions. The short preheating time enables a better mutual adaptation of the preheating

and the warm-keeping phase. The preheating time for an aluminum alloy ingot to a final temperature of 500 - 600°C

will, depending on the conifer cross-section, be e.g. 10 - 30 minutes by direct exposure to flames and/or hot gas jets. By means of preheating the bars in a special preheating oven, it is possible to achieve a precise individual temperature regulation during the preheating process. This temperature regulation, as well as separate setting of the advance rate of the casting in the preheating furnace and its flow rate through the holding furnace, enables an easier adaptation to a changed flow rate, as such a change may be desirable due to different devices on the output side, alloys that require different treatment, service interruptions and

unused operating capacity.

Due to the preheating furnace's large heat output and the increased throughput rate, the ratio between investment costs and production capacity is quite low with the above-mentioned known device. Finally, it is possible to achieve a continuous material flow. All these factors lead to a considerable rationalization in relation to usual methods and devices.

The invention thus relates to a device for heat treatment of castings in the form of strings or ingots as well as blocks, rods, tubes and the like, in particular of aluminum or magnesium alloys, during which the castings are first passed through a preheating zone and thereby heated at a higher temperature than before determined heat treatment temperature, and is then passed through a warming zone and. including being kept at the aforementioned heat treatment temperature and finally cooled in a cooling station, the goods being moved through the warming station with the help of a transport device which comprises stationary beams provided with sawtooth-like depressions with a gently sloping inclined surface in the direction of transport to accommodate the goods as well as lifting beams which can be driven to move in lifting -directions as well as in the transport direction and lies between, and in rest position below, the stationary beams.

On this background of known technology which is described in previously mentioned DE-OS 2,349,765, it is an object of the invention to improve the above-mentioned known device with regard to a further equalization of the material properties and the geometric shape of the goods as well as an increase of the device's operating efficiency.

This is achieved according to the invention in that the lifting beams have a flat surface for receiving the goods as well as prism-shaped stops arranged on the flat surface with a space between them greater than the transverse dimensions of the goods, whereby the lifting beams can lift the goods out of the depressions and lower them in a controlled manner onto the slightly sloping inclined surfaces in the next-closest recesses, where the goods under the influence of their own weight and at the same time in contact with the lifting beams, which are now regulated to be lowered in the direction opposite to the lifting direction, can roll with a controlled rolling movement down into the bottom of the recesses, as the lifting beams are arranged for movement respectively in the lifting direction and in the transport direction by means of mutually independent drive means.

The regulated turning of the individual pieces of castings about their longitudinal axis, both in the heating furnace and in the cooling station, will to a large extent give the castings a more uniform material quality, in that the heat effect on the goods takes place evenly distributed from all sides and over the entire length of the goods. Above all, however, any deformation and curvature of the ingots is completely avoided at the same time as any existing curvatures are smoothed out, so that exceptionally straight castings with high form quality are obtained. This is also the case when the length of the cast pieces varies.

With the device according to the invention, the handling of the goods is further reduced to a minimum.

The warming oven or the main oven is preferably electric or powered by fuel and exhibits a forced recirculation of the oven atmosphere. The preheating furnace can also be heated in this way, as long as it is ensured that the preheating temperature of the heat carriers is higher than the heat treatment temperature of the castings in the heating furnace.

The invention will now be explained in more detail with the help of design examples and with reference to the attached schematic drawings on which: Fig. 1 shows a schematic sketch of a device according to the invention and equipped with two pre-heating furnaces and a subsequent heat holding furnace; Fig. 2 shows a cross-section through a preheating furnace which is preferably used in a device according to the invention; Fig. 3 shows a section along the line III-III in fig. 2; Fig. 4 shows a longitudinal section through a warming oven which is provided with a transport device and is suitable for use in the device of the invention; Fig. 5 shows a section along the line IV-IV in fig. 4; Fig. 6a - 6e show in chronological order successive transport phases when guiding the castings through the heating furnace, and Fig. 7 and 8 respectively show an interrupted longitudinal section and a cross section along the line VIII-VIII in fig. 7, through a cooling station connected after the warming oven.

In the schematic plan view in fig. 1, the ingots and bolts to be processed are indicated by the reference number 1. From a coating device or a magazine 2, the ingots or bolts 1 are transferred individually to a transport device 8, which is arranged for coating preheating furnaces 3 on the right and left, such as indicated by the horizontal arrows in fig. 1. The bars or bolts 1 are brought individually in a stationary state in the pre-heating furnaces 3 quickly to the desired pre-heating temperature under the influence of hot gases or flames. The individual preheated ingots are then brought back

out of the relevant preheating furnace 3, and are transferred one by one in order from the transport device 8 to a warming furnace 4. This warming furnace 4 is designed as a through-flow furnace and works with moving hot gas,

e.g. cold air. The annealing temperature or holding temperature is maintained constant within a narrow tolerance range over the entire length of the holding furnace, so that the ingots reach the annealing temperature after entering this furnace after a short movement in the furnace, if they have not then reached the desired temperature during preheating.

By changing the preheating time, which means the time period during which the ingots 1 are kept in the preheating furnace 3, as well as by regulating the burners, the preheating temperature can be fine-tuned within a wide range, so that a uniform preheating of the ingots is achieved.

The flow rate and temperature in the holding furnace 4 can be adapted to the casting's alloy composition and the desired crystal structure for the ingot material, e.g. by regulating the temperature of the hot gases.

In the warming furnace 4, there are devices for gradually turning the ingots 1 about their longitudinal axis, so that the ingots are heated completely uniformly and deformation or curvature cannot occur, while already curved ingots are made straight again. This takes place by the bars,

which are made plastic during annealing, straighten themselves under the influence of their own weight.

After exiting the heating furnace 4, the ingots are transferred to a cooling station 6, where the ingots are individually cooled with circulating water and/or air. In the cooling station 6, a device is arranged, particularly shown in fig.

7 and 8, for turning the bars during cooling,

so that curvature or deformation and structural differences in the ingot material are also avoided here due to a uniform cooling effect from all sides.

From the cooling station 6, the bars 1 reach a magazine

7, from where they can be directly or indirectly transferred for further processing at another location.

Separation of pre-heating and keeping warm opens up possibilities for individual regulation of the temperature and, above all, the feed rate or transport speed in both the pre-heating and keeping warm phases. This leads to great adaptability for the device as a whole, which means optimal adaptability to the different operating requirements, such as different desired annealing temperatures for different alloys, interrupted operation or reduced operating capacity when adapting to subsequent equipment, or accumulation in the ingot supply.

In the case of rapid heating by means of direct on-

led flames or hot gas jets in the preheating

oven, the space requirement in the plant as a whole is reduced compared to normal plants of this type. Material flow is significantly improved and material throughput is increased due to the continuous or quasi-continuous process.

Fig. 2 and 3 show in more detail an example of a usable preheating furnace.

This preheating furnace has such a length that the largest ingot length that can occur in practice (7 to 8 metres) fits into the furnace. In the preheating furnace 3, a double guide chain 13 is arranged, on which are attached support devices 12 for the ingots 1 to be heated. The support devices 12 project through a longitudinal slot into a hydraulic curing chamber 15 formed by two curing

bowls 14. At their lower end, these hearth bowls are pivotably stored on each of their carrier rails 16 and are kept at a distance from each other at the top by means of spacers 17. In the lateral direction, the hearth bowls are supported against the oven wall by means of radial support strips 18. removal of the spacers 17 and a small pivoting movement about the storage locations on the support rails 16 inwardly, the hearth bowls 14 can be dismantled without difficulty.

The hearth bowls 14 have four rows of openings 22,

which is directed radially towards the bars 1, and in which likewise radially directed rows of nozzles 21 for the mixing chamber 19, 20 open. The radially directed rows of nozzles extend over the entire length of the hearth bowls 14. Below this, the lower rows of nozzles are arranged close to the support devices 12 and directed upwards, while the two upper rows of nozzles are inclined approximately 90° in relation to each of the lower rows of nozzles and directed obliquely downwards.

The upper rows of nozzles can be adjusted in relation to the lower rows of nozzles.

With the described arrangement of the nozzle rows, by preheating the ingots 1, or 1' (smaller cross-section)

the available overflow areas are used for optimal heat transfer, so that a rotationally symmetrical temperature distribution is achieved over the respective barre cross-section. The nozzles 21 are adjustable with regard to performance in such a way that on the one hand the desired temperature distribution is achieved at the end of the preheating time, and on the other hand the ends of the bars at the beginning of the preheating time can be easily lifted by the support devices 12, so that the heat extension of the bars will not dissipate too much horizontal thrust on the guide chains 13.

The support devices 12 for the bars 1, respectively. 1", is there

where they penetrate through the gap between the two hard-

bowls 14 provided with a support stem of rectangular cross-section, which completes the gap apart from a necessary safety distance to the sides due to thermal expansion.

The flue gases leave the hearth space 15 in an upward direction through the gap formed by the hearth bowls 14 and the spacers 17, and are sucked out together with fresh air from the room outside the hearth bowls through an extraction ventilator 25 above the suction channel 26. The outer lining serves here at the same time as ventilation for the fresh air that is sucked in with the smoke.

For mixing and dosing of the fuel and hot gases, there are pipelines 28 as well as a device 29 for measuring the temperature of the bars 1, respectively. 1\ on the right side of the oven in fig, 2.

For preheating, the bars are pushed by the transport device

8 into the furnace and is received by said carrier devices which are moved by the double guide chain 13. The progress of the double guide chain is controlled by limit switches, not shown, which switch off the driving force when the bars 1 come into contact with a stop 30 at one end of the hearth bowls 14.

Measuring sensors, not shown, which are arranged at evenly distributed distances over the length of the hearth bowls 14, measure the length of the inserted ingots 1. These measuring sensors control the nozzles 21 in the groups in such a way that only a number of nozzles corresponding to the measured ingot length are put into operation during the preheating. The heating is only switched on when the relevant bar 1 has reached the stop 30 in the position shown in fig. 3.

For shorter ingot lengths, it is also possible to cover the preheating furnace 3 with several ingots one after the other in the longitudinal direction.

With the preheating furnace shown, continuous operation is also possible. The bars 1 are then heated in a moving state. The operation is, however, appropriately intermittent, so that the necessary adaptation to the subsequent annealing time in the warming furnace 4

can be achieved.

The warming oven 4, which is shown in longitudinal section in Fig, 4, is arranged for continuous operation and is heated by means of hot gas, e.g. hot air, which is blown through a centrifugal fan 40 towards the ingots 1 or 1' which are to be kept warm, and kept for circulation in the oven.

The bars lie in sawtooth-like depressions 42 with slanted flanks 42a in stationary beams 44 which extend lengthwise of the furnace chamber 4 3. The beams 44 are arranged with certain spaces, of which at least two have a width x (fig. 5). In said spaces of this width, lifting beams 45 are arranged parallel to the beams 44,

which is provided with horizontal plane flat pieces 45'

for receiving the bars 1 or 1\, said flat pieces 45 being bounded by prism-shaped stop pieces in the form of angle profiles 46 which are welded to the plane surfaces of the lifting beams. The angular profiles 46 have a mutual distance that at least approximately corresponds to the distance between neighboring recesses 42 and a small length extension k compared to the length 1 of the flat surface pieces 45' in the transport direction A, so that round bars 1, 1' with a normal cross-sectional dimension can roll along the surface pieces 45 \ i The angle profiles 46 serve exclusively as normally unused safety projections in the event that the bars 1, 1' for one reason or another, e.g. in the raised state, comes into rotation as a result of a torque

produced during the lifting movement. Each lifting beam 45 engages from below with three lifting elements in the form of lifting tubes 50 with a square cross-section and distributed over the length of the lifting beam, said lifting tubes being guided vertically movable, but without turning possibilities, through rectangular longitudinal slits 51 in the floor 52 of the warming oven. One of these longitudinal slits 51

is for better understanding shown dashed in fig. 5, where, however, the floor 52 is omitted.

At the lower end of each lifting tube 50, a nut 5 3 is welded, into which a screw spindle 54 is screwed. Each spindle 5 4 carries at its lower end a bevel gear 55, which engages at an angle of 90° with a another bevel gear 56. All bevel gears 56 are arranged on a common horizontal shaft 57, which is driven by a drive motor 58 for raising the lifting tubes 50 and thus the lifting beams 45.

The shaft 57 is stored in a bearing housing 47, each of which is assigned a spindle 54 with a riser tube 50 and accommodates the associated bevel gear pair 55, 56.

The motor 58 and the bearing housings 57 are carried by a carriage 59, which can be moved on rollers 60. This carriage can be displaced by means of a double-acting drive cylinder 61 in a horizontal direction along the base, possibly on rails 62, with a stroke length y that corresponds to the horizontal length of the inclined surface 42a. The vertical stroke length z for the lifting beam 45, which is produced by the motor 58 by means of the lifting device described, has such a size that the lifting beams 45 with the angle profiles 46 in the lowered position can be moved freely under the bars 1, 1' and in the raised position can lift the bars 1, 1^ which are located on the lifting beams 45 above the inclined surfaces 42a for the sawtooth-like recesses in the fixed beams 44

by horizontal displacement.

In another preferred embodiment (indicated in fig. 4

at the left spindle drive) the nut 53 for each spindle drive is rotatably supported in the bearing housing 47 in fixed connection or in one piece with the bevel gear 55. In this case the screw spindle 54 which is passed through the nut 53 is fixedly connected to the lower end of the lifting tube 50, and not rotatable, but vertically displaceable in the axial direction, arranged in the bearing housing 47.

All parts of the spindle drive are thereby arranged and stored in the bearing housing 47, and the riser tube 50 no longer contains moving parts of the drive. This is an advantage during assembly and maintenance.

In the following, the work function when transporting ingots 1 using the transport device indicated in fig. 4 and 5, be described with reference to fig. 6a - 6e.

In the rest position for the lifting beams 45 (fig. 4 and 6a)

the angle profiles 46 are shifted slightly in front of the recesses 42.

In principle, however, the transport device could also function without the angle profiles 46, namely with a lifting beam 45 with a continuous horizontal flat surface.

As will be seen from fig. 6a, a bar 1 with a larger cross-section is located in the recess 42, with a slightly displaced center point in the transport direction A. This is evident by the weaker rise of the inclined surface 4 2A compared to the opposite side flank without a reference number.

In the resting position indicated in fig. 6a, the bars lie in the recesses 42 in the stationary beams 44. The lifting bars 45 lie in this position under the stationary beams. When the spindle drives are started, the lifting levers are now pushed upwards in the lifting direction B, so that they come to rest on the underside of the bars 1 and raise these out aY the recesses 42 to a height z (fig. 6b).

After completion of this lifting movement, move

each lifting beam 45 by means of the drive cylinder 61 in the transport direction A over a displacement distance y, as indicated in fig. 6c. Hereby, the bars 1 are moved to positions above the inclined surfaces 42a for the nearest following depressions 4 2 in the direction of transport in the stationary

beams 44 (fig. 6c). In this way, it is ensured that even the ingots which may have acquired a curvature during the heat treatment can be transported further through the heating furnace without difficulty.

After the forward displacement of the beams in the transport direction A has been completed, the spindle drives are started again, but now in the opposite direction B' of the lifting direction B. The speed of this movement is controlled so that the bars are placed softly on the inclined surfaces 42a of the stationary beams (fig. 6b). The bars 1 now roll under the influence of their own weight along the inclined surfaces 4 2a down into the recesses 42. An angle ^» is then turned below them (fig. 6e). However, this unrolling is controlled by the lowering of the lifting beams in direction B' in such a way that the bars, which have now been heated to a plastic state, are not exposed to such impact on arrival in the recess 42 that the bars are damaged with regard to shape and surface.

The longitudinal extension and inclination of the inclined surfaces 42 is carried out so that the bars reach the bottom of the recesses 42 after a rotation angle cC, so that in each successive recess they are supported by a different circumferential area, so that all different parts of the circumference of the bars come into contact with the circulating hot gas or hot air. In this way, it becomes possible to keep all areas

of the bars at one and the same very constant temperature.

It regulated the rolling of the bars along the inclined surfaces

42a during the lowering of the lifting beam 45, causes the bars under the influence of their own weight to automatically straighten any curvatures that have previously occurred for one reason or another.

In the described manner, the ingots 1 are transported through the warming furnace so that any force influence on the ingots between the lifting beams 45 and the stationary beams 44 is avoided and the risk of damage to the ingots' surface is practically excluded.

At the same rate as the lifting movement of the lifting beams 45, the furnace tubes 48, 49 are opened and closed respectively. supply and discharge of the bars 1 or 1'. The oven doors 48, 49 are in fig. 4 shown with dashed lines in the open position. Filling and emptying the warming oven 4 can also be carried out in the longitudinal direction of the bars 1 through doors arranged on one side of the oven, so that the doors 48, 49 can be omitted in this case.

The bars 1 can in practice have a weight of an order of magnitude

lt (=lMp). The transport device shown must then, depending on the total number of ingots that can be accommodated in the furnace, be designed for regulated raising, lowering and transport of weights between 25 and 30t. This is not possible with any previously known combined drive device, such as an eccentric drive, and is only possible to implement in practice by mutually separating the lifting and transport movement according to the present invention.

The spray device shown in fig. 7 and 8 show a shower chamber 70, and to the roof 71 of this chamber is attached a closed water channel consisting of several successive sections 72 in the longitudinal direction. Each section 72 of the water channel has its own water inlet 73, and is provided on the underside with spray holes 74, which lie close together in line in the longitudinal direction of the water channel. Beneath the water channel, an axle 75 and several axle pieces 76 are aligned parallel to each other, extending in the same direction,

and a further shaft 77 through the shower chamber.

The shafts 75, 77 as well as the shaft pieces 76 are stored

in bearing brackets 78 firmly connected to the apparatus housing, so that not only the shafts 75, 77, but also the shaft pieces 76 are rotatably arranged in the bearing 79, 80.

The shaft 75, which can be driven by means of a drive motor

81 arranged outside the shower chamber 70, carries at regular intervals rollers 8 2 which are rotatably arranged on the shaft.

The axle pieces 76 are pivotably arranged on a pivoting structure comprising at least two pivot arms 84 and the axle 77. In the normal position shown in fig. 7, the shaft pieces 76 lie in the same horizontal plane as the shaft 75 and at a distance from this which is adapted to the dimensions of the ingots 1 or 1' to be processed.

Loosely rotatable rollers 83 with the same diameter as the rollers 82 on the shaft 75 are arranged for the shaft pieces 76. The rollers 82, 83 are arranged in mutually assigned pairs and form a systematic receiving bed for the bars 1 or 1'. The swing arms that support the axle pieces 76 are fixedly connected to the axle 77. This axle 77 is pivotably arranged with the help of one or two pressure cylinders 85 and an intermediately connected lifting arm 86> which is displaced in relation to the swing arms 84 in the longitudinal direction and connected in a rotationally fixed manner with the axle 77 as well as articulated with the piston rod 87 for the pressure cylinder 85. The swing arms 84 are shown dashed in the swing-out position.

There is also arranged at least one movement arm 88 for

guiding the bars 1 into the shower chamber, the movement arm in question being arranged to swing about the central axis of the shaft 75 by means of a drive cylinder 89 with piston rod 94, between the two positions as in fig. 8

respectively is shown solid and dashed.

In the lower part of the shower chamber 70, a collection vessel 90 is placed, from which a downwardly directed drainage pipe 91 emanates from the vessel's deepest point.

Using the shower device described above

the following work process is carried out:

A hot ingot 1 or 1' that comes out of the warming oven is advanced along a conveyor 92 on the side of the shower device. Below this, the piston rod for the cylinder 89 is retracted, so that the movement arm 88 is located below the movement path of the bars. The cylinder 89 is then brought

to the ejection position so that the movement arm 88 for raising the ingot 1 is brought into the line punctured position, whereby the ingot can easily roll down the inclined even upper side 93 of the movement arm 88 to the rollers 82, 83, for transfer to the aforementioned prismatic receiving bed between the rollers 83, 82. that bar 1 at over-

the guide must not fall abruptly into the roller prism formed by the rollers 82, 83, thereby causing damage,

the cylinder 85 is put into work at the same time as the cylinder 89, or is already in the ejection state after the previous work phase, in which the swing arms 84 assume the raised dashed position.

In this position, the roller 83 catches the ingot 1 which rolls down the movement arm softly and without risk of damage to the surface of the ingot. The cylinder 85 is then brought back to the retracted state, so that the swing arms 84 are controlled to the lowered position which is shown fully drawn, whereby the ingot fits smoothly into the roller prism. Finally, the drive motor 81 initiates a rotation of the shaft 75 and thus the rollers 82 in a clockwise direction of rotation in fig. 8, whereby the bar 1 in the roller prism 82, 83 is brought to continuous anti-clockwise rotation about its longitudinal axis. The swing arms 84 with the axle pieces 76 and the rollers 83 are spring-supported in their lower basic position on the air column which, in a submerged state, is still present in the cylinder 85, so that any impact forces occurring during rotation of the bar 1 are taken up after

yielding and the risk of surface damage or curvature of the bar due to such impacts is reduced. Water is now sprayed onto the ingot 1 or 1<*> through the spray holes 74. As these spray holes 74 are arranged with a small mutual distance along the entire length of the ingot, a very uniform cooling of the ingot is achieved. In order to bring the cooled ingot out of the shower chamber, the piston rod 87 in the cylinder 85 is pushed out after previously retracting the piston rod 94 in the cylinder 89 and thus swinging the movement arm 88 to the intermediate position shown at 93', whereby the swing arms 84 and the shaft pieces 75 are brought from the solid to the dashed position. Under this influence, the ingot is moved out from its prism-shaped receiving bed between the rollers 82, 83, to the surface 93'' of the movement arm which now inclines downwards. From this inclined surface, the bar is transferred to the roller passage 92 for further handling by the piston rod 94 being pulled fully into the cylinder 89 and the movement arm 93 thereby being transferred to its fully extended lowermost position.

Claims (3)

1. Device for the heat treatment of castings in the form of strings or ingots as well as blocks, rods, tubes and the like, especially of aluminum or magnesium alloys, during which the castings are first passed through a preheating zone and thereby heated at a higher temperature than a previously determined heat treatment temperature, and is then passed through a warm-keeping zone and below it is kept at the aforementioned heat treatment temperature and finally cooled in a cooling station, the goods being moved through the warm-keeping station by means of a transport device which comprises stationary beams (44) provided with sawtooth-like recesses (42) with a gently sloping inclined surface (42A) in the transport direction (A) to accommodate the goods (1, 1'), as well as lifting beams (45) which can be driven to move in the lifting direction (B) as well as in the transport direction (A) and lie between, and in a rest position below, the stationary beams (44), characterized in that the lifting beams (45) have a flat surface for receiving the goods (1) as well as prism-shaped stops (46) arranged on the flat surface with spaces between them greater than the transverse dimensions of the goods, whereby the lifting beams can lift the goods out of the recesses and lower it in a controlled manner onto the gently sloping inclined surfaces (42a) in the nearest successive recesses, where the goods, under the influence of their own weight and at the same time in contact with the lifting beams, which are now regulated to be lowered in a direction opposite to the lifting direction (B), can roll with a controlled rolling movement down into the bottom of the recesses, as the lifting beams are arranged for movement respectively. in the lifting direction (B) and in the transport direction (A) by means of mutually independent drive means. 2. Device as specified in claim 1, characterized in that said inclined surface (42a) has a longitudinal extent that deviates from the circumference of the goods. 3. Device as specified in claim 1 or 2, characterized in that said prism-shaped stops are designed as angle profiles (46), whose extent (k) in the direction of transport (A) is small in relation to the intervening spaces (45) on the plane surfaces of the lifting beams , so that the goods can be made to roll a regulated circumferential section on these flat pieces.