DE1765517C3 - Process and system for heating metallic workpieces in induction furnaces - Google Patents

Description

.... »wv ·» «/ do Euuc a predetermined one, the same for all oven levels. Time span is measured.

2. The method according to claim 1, characterized in that the performance of each furnace stage (A or B, C) is regulated to take into account waiting times by switching off and on again in the sense of maintaining the predetermined mean temperature of the workpiece (10).

3. The method according to claim 1 or 2, characterized in that the power supply to the furnace stages (A, B, C) is switched off during the simultaneous Ausarens the workpieces (10) and the simultaneous entry of the next workpieces (10).

4. The method still eär; m of the preceding claims, characterized in that the workpieces (10) are discharged from the last furnace stage (C) at a temperature 'which allows the workpieces (10) to be introduced into a hot rolling mill without intermediate heating.

5. System for the step-by-step, static heating of metallic workpieces in neighboring induction furnaces that sell vertically with their induction coils and can be loaded from locations, in particular according to the method according to one of claims 1 to 3, which includes a horizontal conveyor and a hoist under the furnace steps for entering the edgewise workpieces into the furnace steps and for discharging the workpieces downwards again, characterized in that the conveying device in a known arrangement of the induction furnaces in a row and the stationary arrangement of a lifting mechanism (50) * in each furnace has a carriage (T) with a number of the workpieces (10) at a distance of the furnace pins (A, B, C) on edge holding the compartments (A, B, C) in excess of 1

6. Plant according to claim 5, characterized in that the induction coils of the furnace (A, B, C) have an approximately rectangular cross-section, the long sides of which are one of the longest dimensions of the workpiece (lo matched) forming the slab length and ll & ggett Qusrseiien else the shortest dimension of the slab have matched length, and .that the compartments of the carriage (T) in the sense of up

The invention relates to a method as gradual heating of large, first cold or still warm from a metallic casting forth workpieces, such as slabs, in adjacent induction furnaces in which at the same workpieces. entered in time and from which they are also discharged again at the same time after each static heating, the size of the supplied heating energy decreasing from step to step, as well as to a system for carrying out the process.

In such a known method, described in the German as Auslegeschrift ΐ 019 412, it is assumed that an industrial? The three-current network should be loaded as symmetrically as possible, for example, with a total of three furnace stages, the first furnace stage from phase "or phase II with the power P ₀ and the two further furnace stages from phase III with a total power that is approximately = P" should be. Such a process is however no guarantee for optimal power yield, which has especially with large workpieces, such as slabs, a decisive Einßuß to the economics of the process.

The invention is based on the object of improving the method mentioned at the outset in such a way that not only at the end of the heating up a largely uniform heating of the workpiece to a desired mean temperature is reached, but this step-by-step heating regardless of whether

they to «! S« » kSÜSZ WsfkStÜSk SU ™ SB 6 £ i <äü straight

only started with a cast and still warm workpiece, with minimal effort is achieved.

The set object is achieved erfindungsgsmäö = DA ^e ° by that the power; Each furnace stage is measured in the sense of reaching a predetermined mean temperature for the furnace stage in question and at the same time in accordance with the respective starting temperature in the sense of reaching an assigned difference ⁶ S between surface temperature and temperature in the middle of the workpiece at the end of a predetermined time span that is the same for all furnace stages .

I 765 517
3

With such a dimensioning, each assigned to only one single slab

When the power supplied to the oven is used up, such a car can also be easily moved

The reason for the additional consideration should be used in such a way that when it moves forward by one

existing difference temperature between upper furnace stage at the same time a new slab with under the

surface and center of the workpiece in the hand, the 5 first oven level is brought, while on the other

To control power supply so that in the interest of one end of the car the finished heated slab so

optimal power output during the heating next to the last furnace stage that it arrives from there

Initially considerable differences can easily be taken from the

persturen between the surface and the center of the work- By the German patent specification 1215 187 is

Piece can be allowed, but in the end the arrangement of several induction ovens is already ok

the last furnace stage the desired uniform one row and the stationary arrangement one each

Through heating of the workpiece on its top hoist known on each furnace. Apart from that-

temperature is secured. It is obvious that this is only a one-off

possible, the appropriately programmed, step-by-step heating of several workpieces next to one another

Heating of the Braainien st ' ^{: is} active by a 15 located induction furnace, the conveying

To control computers. sv.Lti you only get out of a taxiway and out of the facility

inductive heating seed, f ~, harvesting from tilting devices assigned to the individual furnaces,

lent reasons of a -veehselstromes suitable Fre- by which the arriving on the taxiway

quenz serve workpieces in an upward sloping position

Since with the ... «the heating swiveled ao and then upwards into the ovens.

Further processing of the workpieces, i.e. which the workpieces are to be pushed, for example

wisely when the slabs are subsequently rolled out again after they have been lowered onto the roller conveyor

to plates or sheets, unforeseen stops have to be swiveled back. Such a foi-

hold can not always be avoided, the inventor is not suitable for the here concerned

The task of heating up large workpieces continues to be the basis for the

to be able to control the workpieces in such a way that the additional swivel devices are also very expensive.

Desired peak temperature at the end of the notice. The now proposed training of the

heating even when waiting times occur with a conveyor with a carriage, including the

minimal additional work required slabs are kept in constant layers,

can be. According to one embodiment, this was also not possible with this prior art

achieved by the dadu.ch method according to the invention.

that the output of each furnace should be taken into account - If necessary, several, for example

Waiting times by dismissing and re-instructing six rows of ovens arranged side by side

switch to a subsequent roller train, which is in

Mean temperature of the workpiece is regulated. 35 in this case, for example, every three minutes eh.e

In the known system mentioned at the beginning, the new slab can be fed in, optimally

Step-by-step heating of metallic workpieces can be used.

the individual furnace stages with each vertical In- Other embodiments of the invention concern ^

duction coils along a horizontal circle- more details of the method according to the invention

arcs are arranged in a distributed manner, while the workpiece « ¹ 40 rens and the one used to carry it out

under the oven steps in each case upright and in ent- system.

In the drawing, the invention is for example

are arranged, which is pneumatically lifted and illustrated at the same time. It shows

can be lowered. While such an arrangement Fig. 1 is a plan view of one of the induction

for smaller, correspondingly light workpieces 45 ovens of a system according to the invention,

is still possible, here it would primarily be F i g. 2 is a side view of the support frame of this

affected large slabs with lengths of at- induction furnace,

for example 6 m and an individual weight of many F i g. 3 shows a section along line 3-3 of FIG. 2, Tons to your practically hardly producible Fig. 4A, 4B and 4C schematically held overweight Guide turntable construction. Dem- 50 tenant views one of several in a row neg, sgenübsr the present invention also includes juxtaposed furnaces, a system for the step-by-step, static calculation of the transport route of slabs through the warming of metallic workpieces in the neighboring system can be seen,

jiüi ίπϊέϋ üüduktiGrsspulcn perpendicularly running <ιηά Fig. 5? '"Show an embodiment of the

induction ovens that can be loaded from below,

in particular according to one of the aforementioned methods, FIG. 6 characteristics of the temperature profile in

which indicate a horizontal conveying stage under the furnace steps, heating a slab, the immediate

equipment and a hoist for entering the bar was delivered from a casting plant,

Workpieces lying on edge in the oven steps Fig. 7 Characteristic curves of the temperature profile for

and for re-ejecting the workpieces downwards 5o> gradual '' heating one to room temperature

has, the conveyor device delivered according to the invention slab.

in a known arrangement of the induction In the system shown, each of the

In one row, the three induction furnaces 15, which are fixed in position, have a slab 10

With one hoist unit on each furnace, one car is installed. Each from a completely surrounding

with an induction that exceeds the number of furnace stages by 1 - 65 stell F

the number of the workpieces in the distance of the tion coil 15 has a rectangular shape and has

Oven step has compartments holding upright. on one side terminals 28 for connecting the

While the lifting devices required here power line on, while on their other side each

an inlet 26 and an outlet 27 for the inductions in the furnaces to be heated is a control circuit

tion coil flowing through cooling liquid provided, whose measuring mechanism consists of a Bram-

is. According to FIG. 3 from I-beam 23 and plate temperature measuring »Proximitye-Thermcele-

24 existing frame F carries laminated magnetic yokes element 102 , which is made by the coil and the

22. who in turn wear straps 30 on which the clothing of the Oienkammer protrudes and the upper

Two turns of the induction coil 15 attached to the surface of the slab when heated

are. The magnet yokes 22 guide the flow of force to measure their temperature. This thermocouple

on the outside of the induction coil 15 and hold is on a compressed air cylinder ' 101 by' a shark

him away from the frame F. terlOl 'attached in such a way that it

Surrounded by the induction coil 15 heating to raising and lowering the slab 10 back in furnaces ί

Chamber is drawn out with a refractory lining 16 and 'before switching on the current to the

Insulating material or another suitable material slab can be pressed. The Thcr'moelc-

provided, which is preferably made of prefabricated, individually element 102 is to a for recording and Regein the

replaceable clay bricks. Temperature serving device 40 (Fig. 5) connected

In the induction coil 15 takes a slab 10 15 sen. that controls the power of the induction coil, during the warming up such a situation. that also a second thermocouple in the workpiece is preferably induced heating current in its element connected to a display device that does not run in a horizontal longitudinal direction, as the arrow X is shown and indicates the uppermost limit temperature (Fig. 1). The direction that points approximately at right angles. This instrument comes into operation when the magnetic thermocouple 102, which runs along the longitudinal axis of the workpiece, or the control device connected to the line of force indicated by the arrow y (FIG. 2) fails. It is best to ^{do 8 e} ° eut f ·,. . . . . ^{Furnace with} two thermocouples equipped, which are arranged in such a way that a warning sign is given, contains three induction furnaces A, B and C which are at the same distance from each other and in a row if the measured by these thermocouples In addition to the temperature difference, a certain size are arranged one above the other (see Fig. 4 A, 4B and 4C). strides. Because that would mean that one of the moreover the system contains a conveyor, which is disturbed by the devices. The two thermocouples independently guide workpieces from one furnace to the next via a compressed air cylinder 101 each and also align them with respect to the furnace. voneir, nder advanced and withdrawn This conveyor consists of a carriage T with corresponding block holders in a row. If the slabs are aligned with the induction furnaces A, B and C , which are arranged opposite one another, then they are lifted vertically by means of lifts, all of which correspond to FIG. Furnace heating chambers introduced. The hoists 60 In them, slabs of different widths can be heated up and down on a common device. The width of a slab will be supported union bar. Each slab 10 before it is inserted into the furnace preferably stands with its lower longitudinal side 11 upright in the manner already mentioned so that a remote control can be used on an insulating plate 51 carried by the hoist to ensure that a slab is in the desired position The height dimension of the coil matches the slab, the height of the coil is to be raised, in this position to be held Facilities may be provided. because yes the slab in each induction coil is on

The plant is supposed to stand for slabs of different length along its length

Size are suitable for this reason is a manual order, connected to each induction coil or automatically operated measuring unit 56 is provided to take advantage of 45 electric power as possible, has the (Fig. 5), which the dimensions of the slabs 10 first induction furnace A, the highest electric nominal measures so also their height before they are advanced into the heating power, the second induction furnace ff, for example, chamber, and the electrical half and the third induction furnace C, for example, control of the induction coils 15 deliver a signal, wise a quarter of this nominal power. It is possible to ensure that the necessary electrical power is supplied to these induction furnaces in different stages.

As shown in Fig. 3, the dimensions of the _{In- There precautions S} taken are proportionate

Induction coils 5 and the slabs 10 slabs that are large on top of one another either from the cold state, i.e. H.

coordinated that the slabs are in a position in- from room temperature, starting or immediately

neren of the heating chamber can be supported, 55 after leaving a casting system, in particular a

in which it is located above the lowest and below the continuous caster, progresses to heat * .. In the first

the top wall of the induction coil induction furnace A can, for example, one before

and at a distance from the windings of the coil, slabs 10 that are cold down to a certain level are passed. Preferably, the heating chamber cutting temperature is heated, the furnace

During the heating through a removable surface, the slab becomes hotter than its interior. Closed in and insulating cover 18, during the second induction furnace B it is heated up to a diameter induction coil 15 at the bottom by a refractory floor cut temperature which is somewhat higher than the plates 19 and 20 are shielded. Everyone is in when they leave the first oven. In the second longitudinal direction of a slab, the winding of the induction furnace B then takes the difference

the induction coil 15 depends on the neighboring 65 surface temperature from the inside

Windingscn, preferably through an epoxy shell, from temperature. In the third induction furnace C

jsohcrl will continue the peak temperature on the surface

To regulate the temperature / u to which the bram- increases, while the difference between denander

7 8

Hcrr- surface and in the interior of the slab 10 of the first furnace is indispensable: For this reason, ¹ sighted temperatures is further reduced. the system will preferably have 'three' ovens per row

The F ί g. 6 and 7 show, for example, temperature-equipped. - '"'" ^J τ / * '■' ν. "■"<· «

Characteristic curves that occur during the gradual heating of the induction furnace Ά in cold slabs in the three induction furnaces A, B and C 5 state, "The temperature curve with the following nominal powers occurred: that of the In- Fig. 7 ergibtj then it is irKder 'ersteirHeizduktionaofcns a was 20 00OkW, the induction period of a' ^ mean temperature of Fetwa tionsofcns B 10 000 kW and that of the furnace 820 C ⁰ C &erwärmt.'Die'vorbestinimjt f Bndtemperatur 5000 kW. the surface " at the end of the first heating season *? '

As FIG. 7 shows, the surface temperature rises ¹ to when the furnace is peeled off ^{f 'eiwai'1150 o;} And in the cold of the middle of the slab entered in the induction furnace A, the 'prevailing''temperature'' about the slab quickly rises, and 480 ° U quickly results in the case of those illustrated in FIGS. 6 and 7' at the end of the first heating stage from the Difference ^; Befcpiel were the ^J E rammen'7800 ϊηπΓ long "and the surface temperature of the inside of the 300 mm thick. They were> n each of the three-Induk Bramrne prevailing temperature an average tem- 15 tio.isöfen A, B and C seventeen minutes laag erperatur that warms about the temperature (860 C) a, and one minute corresponds to transfer the slab selected from the casting slab of the nimt directly an oven to the next and k ". Upon heating of a" cold, "that is, a new for receiving and discharging finished inherits. 1 room temperature in the induction furnace a tinge--heated slabs from the induction furnace C pre-machined slab results in a greater difference 20. The electrical outputs of the individual furnaces / wipers on the surface and inside and the length of the heating periods can vary for each temperature of the slab than is the case with the desired slab size, the respective output -FaII is when the entered slab still needs to be adapted to warming requirements. It comes from the foundry as part of the process (Fig. 6) pull

According to FIG. In the case of the second and third 25, the reference will accordingly be made to a certain case in which the slab's size, its final temperatures and the temperature difference relative to the output were specified in the insulation stages of the slab. If these requirements change slightly until the end of the step-by-step heating, this can result in an increase in the desired maximum peak temperature of the heating output and the duration of the heating compensation. This last-mentioned temperature must be required for 30 periods in order to accelerate or delay the output per furnace time in the illustrated embodiment of a series. The desired rolling temperature for heating. According to FIG. 6 The energy requirement per slab depends on the temperature difference between the surface and its thickness. If the slabs are thicker than in the load and the interior of the slab in the second example described, then a longer heating stage in induction furnace B would be increased and a period would be required.

During the third heating stage in the induction furnace C, the branches are placed in the three furnaces of the plant

decreased. Is the one entered in the first furnace at the same time entered and at the same time from the slab is still about as hot as it was carried out of the foundry. In the case of occurrence unvorhergegckommen, then the furnace is in this overlooked waiting times through the TenHyenrtur-temperature control device as a fixed value under control of v> 40 in each of the 102 ovens the power dsr-heat sensor through turning on and off once an art - and switched off that in .1er slab regulated so that the slab with the desired preset mean temperature reached at the end of the heating period in the second induction mean value of the temperature is maintained furnace B entered. The slabs will remain. The switch-on and switch-off of the electricity for conveyors and hoists and their controls during their heating in the furnaces in the rest area. With the following shown in the characteristic curves for all ovens at the same time or one after the other, each heating period, during which the circuit is heated manually or automatically, the slab is heated in the idle state, is controlled seventeen (see Fig. 5), to ensure that minutes during the time required to transfer them into the slabs with respect to all the furnaces next furnace move one minute 5 ° simultaneously or in sequence,
amounts to. The heating season, however, is extended during the transfer of a slab from the

when the slabs have to wait to be called, first to second and from second to third as a result of delays occurring at the rolling mill, for example, the surface temperature of the furnace, i.e. its surface, drops gen. tip temperature. In the illustrated embodiment

The first induction furnace could evidently continue if the peak temperature of the slab fell if the slabs delivered had a temperature of around 820 ° C when they were transferred from the first furnace, like the 1150 ° C to around 1080 ° C away. In the second furnace case, if it is directly grained from the foundry, the slab temperature on the surface will increase. The in the plant according to the invention again increased to about 1245 ° C, the inside of the slab to be heated and directly from a continuous slab prevailing temperature to about -1000 ° C casting plant usually have rises. This results in an average temperature of a surface temperature of about 705 ° C and about 1120 ° C. During the transfer from the second to the inside a temperature of about 985 °, with the third furnace, the surface temperature drops, the temperature drop runs roughly in a straight line , while the temperature inside the slab gives an average value of the slab temperature, rising somewhat in the third furnace temperature of about 820 ° (cf. FIG. 6). Would the Bram is the peak temperature I29Ö ^L C IMD received in men or in the cold state a transit inside have the slab temperature prevailing average temperature of less than 820 °, then to 1160 ° C, a mean of about 1220 ⁰ C

ίο

is equivalent to. The maximum temperature difference between the interior and the surface of the The slab is usually at around 120 ° C in the third furnace. Flows between the discharge of the slab ^ and the last furnace. and - its alignment with the rolling mill one; Time of about four minutes, then} each other the temperature differences out, and it rird. an even temperature distribution in the slab achieved.

on and off, be it through the temperature control device 40 or by the timer 41.

A computer 32 can be used to monitor, record, display, control and automatically operate the operation of the system. The computer can be arranged at a location remote from the induction furnaces A, B and C. In addition to the measuring units 56 for measuring the dimensions of the slabs and their position in the furnace kö h Übhirih fdi

ret g g de stoves

In Figure 5, a Schallctelle31 is indicated, the ίο can still monitor devices for-the with control devices for the heating periods: and amperage, difi voltage, die, temperatures, die Holding times is given away, including a temperature-demanded output and the phase load temperature controlf by switching the heating on and off, such as any protective devices. Stroms as well as one depending on the width these facilities give the operation of the others Slab adjustable selector switch. By 15 position and signals corresponding to the computer, am these facilities will be the programmed sequence thereby making the required settings and bevel Procedural steps as described above to bring about movements.

was brought about by hand or automatically. If the rolling mill requests a heated slab,

Control takes place either through the temperature, then the operator preferably actuates a temperature control device 40 or by means of a timer 41 or the like, so push-button switch 45. When the slabs have reached their target temperatures as shown in Induction meter is first switched off in each furnace with the aid of a coil and the lifting mechanisms 60 are set in gear setting levers and then set by the control, which lower the slabs and keep them in motion. The control and a roughly speaking slots of the carriage T drop off. The planned recording of the controlled variables 35 is then provided, which can then take place automatically from the last induction furnace C. gene slab is transferred to the rolling mill while the

As the circuit diagram of FIG. 5 shows, B d Idkiöf A d

the induktioasöfsa, which are used for gradual bracing, are connected to a three-phase three-phase network that preferably supplies the induction coils of the three ovens A, B and C each with an emphasis current with a nominal output of 2000 kW or 10 000 kW or 5000 kW. Every induc-

The operation coil is connected to switch £, da- g g p

with the coils either individually or, as indicated by dashed lines in planning and control by means of a computer, at the same time an IMSt can be achieved so that the peak values of the ucd can be switched off. The switches required for production saf a minimum dimension j are preferably Siükongleichrich- sink. A single operator can effortlessly switch. However, other switches, multiple rows of ovens from a single control z. B. Hand switch can be used to control the furnace 40 from the console.

gene slab Erk transferred while the

Slabs move from induction furnaces A and B to furnaces B and C and a new slab is fed to induction furnace A.

You can use several rows of ovens for the gradual Use the heating of the slabs and program that this plant can deliver a larger number of slabs one after the other to the rolling mill capable of being a single row. By corresponding Pl d ie St il i R

In addition 5 sheets of drawings

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Claims (8)

^; Patent claims: ,. ! -., Process for the step-by-step heating of large, initially cold, or from a casting process Her igQch warm metallic workpieces, such as slabs, in neighboring induction furnaces, in -which the workpiece is entered at the same time and from which they are based The amount of heat supplied will also be discharged again at the same time, with the amount of heating energy supplied assuming step by step, because it indicates that the output of each furnace step (A or B, C) is specified in the sense of reaching a furnace step in question ! note the temperature and at the same time according to the respective outlet temperature in the sense of the '-lEÜiT ^emer ^ S ^ Neten difference between Achieving an associated difference between the surface temperature and the temperature in which the surface of the workpiece (iö) at the end of a predetermined for all take one slab are formed on one of their long sides upright. 7. Anlage''nwh ^ claim S or 6, characterized in that measuring mechanisms (thermocouple 102) for measuring the temperature of the workpieces (10) in the furnace calls; (Λ, B, C) are provided and that the energy supply to the various furnace stages can be regulated by these measuring units as a function of the measured workpiece temperature 8. plant according to one of claims 5 to ?, α by the perpendicularity of the solution dimen- ^J entered in a stage furnace (A or B, C) the workpiece (10) be measured and the stroke of the Hubwe / ks (60) Adjusting device that adapts the induction coil in the sense of a complete immersion of the workpiece (10).