WO2013182752A1

WO2013182752A1 - Method and system for providing temperature distribution into an object

Info

Publication number: WO2013182752A1
Application number: PCT/FI2013/050611
Authority: WO
Inventors: Pekka Suominen
Original assignee: EFFMAG Oy
Current assignee: EFFMAG Oy
Priority date: 2012-06-06
Filing date: 2013-06-06
Publication date: 2013-12-12
Anticipated expiration: 2014-12-06

Description

METHOD AND SYSTEM FOR PROVIDING TEMPERATURE DISTRIBUTION INTO AN OBJECT

TECHNICAL FIELD OF THE INVENTION The invention relates to a method and system for providing temperature distribution into an object to be heated.

BACKGROUND OF THE INVENTION

There is a need for example in an extrusion industry for metal or aluminium bars, billets, which have a certain temperature or even certain temperature profile or distribution. For example the metal or aluminium bar to be extruded has to be heated in a longitudinal direction to have a specific changing temperature profile, so that it can be extruded into a homogeneous profile. In other words the head of the billet has to be for example warmer and suitable for starting the extrusion whereas the tail has to be colder, so that it doesn^'t heat too much during the extrusion. Also other kinds of temperature distributions or profiles are also needed depending on the requirements.

According to the known prior art solutions the billets are heated with oven, or gas or electric element heater. Also induction heating is known, where varying magnetic field is used to induce eddy currents inside the object and the object is heated by the eddy currents. Typically the varying magnetic field is implemented by coupling electromagnets around the object to be heated with an alternating current generator of 50Hz or higher frequency. In order to provide a temperature distribution into the object, number of sequential induction heaters ("induction zones") must be used with different power. However, when using sequential induction zones the temperature distribution profile will be quite coarse, rough or gradual.

There are however some disadvantages related to the known systems for providing a temperature distribution profile(s) into the object to be heated, namely the extrusion industry demands the objects with very linear and precise temperature distribution profile(s) (without any gradual step in the temperature distribution curve), which is impossible or at least very hard to achieve by the known systems. SUMMARY OF THE INVENTION

An object of the invention is to alleviate and eliminate the problems relating to the known prior art. Especially the object of the invention is to provide any predetermined shape temperature distribution profile into an object to be heated.

The object of the invention can be achieved by the features of independent claims.

The invention relates to a method for providing a predetermined temperature distribution into an object according to claim 1 . In addition the invention relates to a device according to claim 12 as well as to a computer program product according to claim 26.

According to an embodiment of the invention at least one predetermined temperature distribution is provided to an object to be heated via an electromagnetic induction heating. In the electromagnetic induction varying magnetic field and eddy currents are provided within the object by at least one magnet, advantageously permanent magnet, when said magnet is moved, such as rotated, in the vicinity of the object (and/or when the object is rotated in the vicinity of the magnet) whereupon the object is heated by the power of electromagnetic induction generated by said varying magnetic field and eddy currents. The object is advantageously at least partially electrically conducting so that the varying magnet field may induce eddy currents within said object. Advantageously the object is a metal object, such as elongated (e.g. tubular) aluminium or copper billet to be used in extrusion process. The temperature distribution to be provided by the embodiments of the invention may be nonlinear, curved, or in any shape in axial and/or in radial direction of the object. According to an advantageous embodiment the predetermined temperature distribution is provided by moving the object and the magnetic field relatively in each other, such as moving the object in relation to said magnetic field and manipulating the rate of the induced power (electromagnetic flux) into the object to be heated. According to an advantageous embodiment the object is moved first at least once over said electromagnetic induction heating means and energy or power absorbed by the object is determined in function of length of said object for each portion of the length, when said object is moved over said electromagnetic induction heating means. After this an approximation of the model for feeding the energy or power for each of the portion of the object is determined based on the determined energy or power absorption into each portion of said object and the predetermined temperature for said portion of said object. The embodiment offers clear advantages, namely when the object is moved first at least once over said electromagnetic induction heating means and the approximation of the model is determined, possible effect of the environmental factors effecting to the final result can be overcome. This means that there are no need for separately determining possible undesired and inaccuracy effects, such as changing factors and all kinds of inaccuracies, such as environmental factors, or inaccuracies incurred by the heating device as well as non-identical or symmetrical objects, but these effect are determined at the same when the approximation of the model is determined, which is great advantage. The determination of environmental and other effects is thus very easy, fast and in addition very accurate, because these effects are determined based on the measurements on the actual heating process.

The approximation of the model used comprises advantageously parameters for number of times the object is moved back-and-forth over the electromagnetic induction heating means, as well as for different velocities for different portion of the object so that the portion to be heated higher or absorbing less energy or power portion is driven slower than other to be heated lower or absorbing more energy or power, and/or for different intensities of the induced power or power of the electromagnetic induction heating means so that the portion to be heated in higher temperature or absorbing less energy or power is exposed to greater intensity of the induced power than the portion of the object to be heated in lower temperature or absorbing more energy or power. Thus, since the approximation of the model is determined the object is then moved back-and-forth over the electromagnetic induction heating means based on said determined model so to achieve the predetermined temperature distribution. As an example the power of the electromagnetic induction heating means is kept constant and advantageously at maximum. The maximum power than can be used may be determined based on the material and dimensions of the object, as well as moving velocity of the object. Anyway the maximum power is determined so that the energy absorbed by the object (or portion of the object) rises the surface temperature of the object so that it is below the melting point of the surface of the object at maximum. The calculation of the maximum energy and power to be used avoiding the melting of the surface is kept as a normal task for the skilled person.

In addition according to an embodiment an initial temperature distribution of the object is measured (e.g. by an IR sensors or other known from the prior art) and based on the object details (comprising at least said temperature distribution in function of the length of the object, material, mass and dimensions) a preliminary approximation of the model for total energy to be fed into the object is determined as well as optionally also the energy for each portion of the object, and number of times the object is moved back-and-forth as well as also different velocities and/or intensities for each of the portion. Said preliminary approximation of the model can then be used for determining said actual approximation of the model used for actual heating process. The actual approximation of the model can be achieved from the preliminary approximation by specifying the parameters of the model when the object is moved first at least once over said electromagnetic induction heating means.

For example the preliminary approximation model may have parameters such as total energy required is 100 KJ, number of times for moving the object back and forth is initially 10 times and the total time 100 sec (the power is energy divided by time), whereupon one round takes 10 seconds and should absorb 10 KJ energy (without any melting). However, after the first moving of the object the energy absorbed by the object with one round is determined, and it might be determined for example that only 9 KJ is absorbed (totally, but this can of course be determined in function of length of the object for each portion of the length), whereupon the preliminary approximation model can be modified as to the actual approximation model with parameters so that the total time 100 seconds will be updated to 1 10 seconds (with 10 rounds) in order to compensate the difference. It is to be noted that according to the invention the approximation model may also be adjusted also for other parameters (e.g. velocity and/or intensities for each portion, as well as also for number of times of rounds, but for simplicity only the time needed is described here). It should also be noted that the approximation of the model is determined at least once when the object is moved over said electromagnetic induction heating means, but the determination can naturally be performed also more often, even for every round separately (online adjusting). The applicant has found out that very accurate desired temperature distributions can be achieved already by determining the approximation of the model only once. As an example the number of times the object is moved back-and-forth is determined so that total energy or power to be fed into the object or for a certain portion of the object is divided by the maximum energy or power feedable into the object or for that certain portion of the object so that the surface temperature of the object or that certain portion of the object is kept below the melting point of the object that certain portion of the object.

According to an aspect of the invention the manipulating of the induced power may be achieved e.g. by changing the relative velocity (advantageously the velocity in the elongated object's axial direction) of the object and the magnetic field so that the portion(s) to be heated in higher temperature interacts longer with said magnetic field than the corresponding portion(s) to be heated in lower temperature.

According to an embodiment of the invention the manipulating of the induced power may be achieved e.g. by changing the intensity of the induced power so that the portion(s) to be heated in higher temperature is exposed to greater intensity of the induced power than the corresponding portion(s) of the object to be heated in lower temperature. Changing the intensity of the induced power may be implemented by changing the moving rate, such as rotation rate of the magnet in the vicinity of the object (and/or the rotation rate of the object in the vicinity of the magnet) so that slower the rotation of the magnet (object) for example, less power is absorbed. Changing the intensity of the induced power may also be implemented by changing the distance of the magnet and the object so that greater the distance, less power is absorbed.

The present invention offers clear advantages over the known prior art, such as the possibility to provide any shaped smooth (no separate heating zones) temperature distribution into the object to be heated, which is not possible for example by the systems using oven, gas or electric element heater. In addition also the initial temperature distribution can be taken into account and provide the operational parameters to the heating device so that the desired temperature can be achieved even if the initial temperature distribution of the object was not linear (e.g. the first portion(s) of the object was warmer than another portion(s)). Furthermore the efficiency of the permanent magnet based induction heating (e.g. Effmag heating technology) is already in principle much higher than for example heating the object by e.g. an oven, so when the object is heated from the beginning with the induction heating devices of the invention even more economical savings and very accurate temperature distribution can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

Next the invention will be described in greater detail with reference to exemplary embodiments in accordance with the accompanying drawings, in which: Figure 1 illustrates an exemplary method for providing a predetermined temperature profile to an object to be heated according to an advantageous embodiment of the invention,

Figures 2A-E illustrate exemplary embodiments for providing a predetermined temperature profile to an object to be heated according to an advantageous embodiment of the invention.

Figures 3A-C illustrate principles of an exemplary device for providing a predetermined temperature profile to an object to be heated according to an advantageous embodiment of the invention.

DETAILED DESCRIPTION

Figure 1 illustrates an exemplary method 100 for providing a predetermined temperature profile to an object to be heated according to an advantageous embodiment of the invention, where at first in step 101 the initial temperature of the object can be measured (optional step). This is important for example if the object is stored e.g. different place than where the heating occurs, and because the amount of the induced heating power is depending on the temperature difference between the initial and end temperatures of the object. According to an embodiment the initial temperatures may be measured from number of points of the object, especially if the other end of the object is kept at different temperature than another end of it. Thus the initial temperature profile of the object can be determined before the heating, and thereby also the amount of the induced heating power for each portions of the object can be determined beforehand.

In step 102 the desired temperature distribution profile for the object to be heated is determined for example by inputting temperature for each points of the object. Also the preliminary approximation of the model can be determined in step 102. The desired profile of the object is determined by the needs, such as the needs of the extrusion process, where for example the first portion of the object should have a first temperature, second portion of the object should have a second temperature, third portion of the object should have a third temperature, and so on. Thus it is to be noted that according to embodiments of the invention the temperature distribution profiles may be linear, nonlinear, curved or any shaped (examples are described in Figures 2A-E). In addition it is to be noted that the parameters from an extrusion process may be taken into account via a feedback loop from the extrusion process environment.

In addition in step 102 also at least one of physical and/or material parameters of the object is taken into account, such as e.g. conductivity, resistivity, heat capacity, diameter, length, and mass. Also parameters related to the heating device or process can be taken into account, such as form of the magnetic field induced by the magnet(s) of the device and well as the effect of the distance between the magnet(s) and the object to be heated.

By the parameters provided in step 102 the control parameters may then be provided in step 103 for controlling the heating process. The control parameters may be for example the control parameters for the device described in connection with Figures 3A-C, where the control parameters is configured to control the device to manipulate e.g. the rate of the induced power provided by the varying magnetic field into the object (or different portions of the object) to be heated. According to an embodiment the control parameters are provided for the device in a form of computer program instructions to manipulate said rate of the induced power for each determined portions of the object so that the desired temperature distribution profile is achieved for the whole object.

In step 104 the rate (or amount) of the induced power into the object (or different portions of it) is manipulated based on the parameters determined in step 103 (based on the determined approximation of the model). The rate of the induced power may be manipulated according to embodiment of the invention in many different ways. For example the portion of the object to be heated most may be exposed to greater total power (e.g. longer with said magnetic field) than the portion to be heated less (as is determined by the approximation of the model, for example). In addition the relative velocity of the object and the magnetic field can be changed so that the portion to be heated most is configured to interact longer with said magnetic field than the portion to be heated less. Furthermore also the intensity of the induced power may be changed so that the portion(s) to be heated in higher temperature is exposed to greater intensity of the induced power than the corresponding portion(s) of the object to be heated in lower temperature. Changing the intensity of the induced power may be implemented by changing the moving rate, such as rotation rate of the magnet in the vicinity of the object (and/or the rotation rate of the object) so that slower the rotation of the magnet (object) for example, less power is absorbed. Changing the intensity of the induced power may also be implemented by changing the distance of the magnet and the object so that greater the distance, less power is absorbed.

In step 105 the energy or power absorbed by the object is determined advantageously in function of length of the object for each portion of the length, when said object is moved over said electromagnetic induction heating means at least once (or when said object is moved first time), after which the process may adjust the approximation of the model for feeding the energy or power for each of the portion of the object based on the determined energy or power absorption into each portion of said object and the predetermined temperature for said portion of said object. The adjusting of the approximation of the model is then implemented in step 102 and adjusting the controlling signals controlling the electromagnetic induction heating means is then updated in step 103 to conform the measurements of step 105.

In addition also temperature of at least one portion of the object can be determined also during the heating process e.g. in step 105. According to an embodiment the temperature profile of the object achieved by the process can also be determined. Said temperature (distribution profile) information can then be used as a feedback for adjusting or fine tuning the control parameters. It is to be noted that the object can be moved back and forth (even many times) in relation to magnetic field, whereupon the information gathered in step 105 can be used as feedback information in step 102 (e.g. if the desired temperature is changed) or in step 103. The information gathered in step 105 can also be used as feedback for providing the control parameter(s) for the next object to be heated for example compensating systematic deviations occurred in the process.

It is to be noted that the object to be heated may also be moved back and forth in relation to the magnetic field at least once for example to achieve uniform distribution in the radial direction of the object and in order to prevent melting of the surface of the object. In addition it is to be noted that the induced power within the eddy currents may also be manipulated as a function of time, e.g. introducing higher power at the beginning of the electromagnetic induction heating process for example so that the surface of the object does not have any significant deformations or melting, and again lowering it at least once during the electromagnetic induction heating process in order to fine tune the temperature distribution and deposited power to the object.

Figures 2A-E illustrate exemplary method 200-205 for providing a predetermined temperature profile to an object to be heated according to an advantageous embodiment of the invention. In the examples of Figures 2A and 2B it is assumed that the object is at first transferred over the magnetic field and then at the time instant t the direction is changed opposite, so that the object is in back and forth motion. However it is to be noted that the object can either be passed the magnet(s) only once (one go in one direction or it can be moved back and forth at least once or number of times).

In the method 200 the line 206 represents the control parameters for the object, which is to be heated in uniform temperature, such as 450°C for example. The control parameters of line 206 relate to relative velocity of the object and magnetic field and as it can be seen from Figure 2A, the velocity is constant. Of course there occurs some heat transfer in the object so that the first end of the object introduced with the magnetic field remains little bit cooler than the last end (tail) of the object, because the heat transfers from the end first heated towards the last end and thereby increases the temperature of the last end (tail). Anyhow this can be taken into account in the embodiments of the invention when the (at least one) physical and/or mechanical parameters of the object to be heated are known and/or when the feedback information gathered e.g. in step 105 is used.

The second line 207 represents the control parameters, where the relative velocity of first portion (corresponding the line portion 207a) of the object with the magnetic field is greater than the second portion (corresponding the line portion 207b), whereupon the temperature of the first portion remains cooler than the second portion.

As it can be seen from the method 201 in Figure 2B the temperature distribution profile may also comprise number of portions or its shape can be complex. The line 208 represents the control parameters where the relative velocity of the first portion (corresponding the line portion 208a) is greater than the velocity of second and third portions (corresponding the line portions 208b and 208c), whereupon the relative velocity of the third portion 208c is greater than the velocity of the second one 208b. Even though the line 208 illustrates the control parameters (velocity profile), it also naturally reveals the temperature distribution profile achieved by the embodiment of the invention. Again it is to be noted that the control parameters (effecting e.g. to relative velocity of the object and the magnetic field and thereby the temperature distribution profile) can be different at the first time zone (when the object is transferred into a first direction, so before the instant t) than at the second time zone (when the direction of the object is changed into a second direction, so after the instant t), as can be seen at least in Figure 2B. Thus when backtracking the object in the opposite direction (after t) the third portion (or at least part of it) is introduced before the second and first portions with the magnetic field, and as can be seen from Figure 2B the relative velocity of said third portion (or at least part of it) when backtracking (now corresponding the line portion 208d) is slower than the relative velocity of the rest of said object (now corresponding the line portion 208e).

As can be seen from the method 202 in Figure 2C any kind of temperature profile (in the function of the position of the object) can be achieved by the embodiments described in this document, such as changing the relative velocity of the object and magnetic field, or intensity of the induced power or other manipulating parameters. The solid line in Figure 2C represents linear temperature gradient (e.g. from 400°C to 500°C), dashed line represents uniform temperature (e.g. 425°C all over the object), and dotted line any predetermined shape of the temperature distribution profile. The method 203 in Figure 2D represents the situation where the different portions of the object has different initial temperatures. According to an embodiment of the invention the initial temperature distribution profile can be determined and taken into account as described in this document in order to achieve desired temperature distribution profile to the object after the heating process. The method 204 in Figure 2E represents the situation where the desired temperature distribution profile is achieved by manipulating the intensity of the induced power and especially by changing the rotation rate of the magnet in the vicinity of the object (slower rotation, less power is absorbed).

Especially it is to be noted that when providing or adjusting the control parameters for the heating process, one to all of the above mentioned methods (parameters) for manipulating the rate of the induced power can be used, such as the relative velocity and/or the distance of the object and the interacting magnetic field as well as also rotation rate of the magnetic field (and/or object) inducing the eddy current into the object. Figures 3A illustrates a principle of an exemplary device 300 for providing a predetermined temperature profile to an object to be heated according to an advantageous embodiment of the invention, where the device comprises permanent magnets 301 arranged in a rotor 302, which is rotated in the vicinity of the object 303 to be heated. The object 303 can also be rotated around its longitudinal axis, as well as according to an embodiment its distance from the magnetic field (rotating magnets) can be changed. Especially the relative velocity of the object 303 and the magnetic field induced by the magnets 301 can be changed. Figure 3B illustrated an exemplary device 310 for providing a predetermined temperature distribution into the object 303 via electromagnetic induction heating, where the device comprises at least one permanent magnet 301 arranged to provide varying magnetic field and eddy currents within the object 303 to be heated when said magnet is moved, such as rotated in the proximity of the object, so that said object is heated by the electromagnetic induction generated by said varying magnetic field and eddy currents.

The device comprises introducing means 304, such as a gutter, for moving the object 303 in relation to said magnetic field 302. In addition the device comprises manipulating means 305 for manipulating the rate or amount of the induced power. In addition the device comprises adjusting and control means 306 for controlling the operation of the manipulating means 305.

According to an example the adjusting and control means 306 are configured to move the object first at least once over said electromagnetic induction heating means, and determine energy or power absorbed by the object in function of length of said object for each portion of the length, when said object is moved over said electromagnetic induction heating means. In addition they are advantageously configured to determine an approximation of the model for feeding the energy or power for each of the portion of the object based on the determined energy or power absorption into each portion of said object and the predetermined temperature for said portion of said object. Then the adjusting and control means 306 are, advantageously together with the function of other means of the device, configured to move the object back-and-forth over the electromagnetic induction heating means based on said determined model so to achieve the predetermined temperature distribution. For example, the manipulating means 305 may be configured to change the relative velocity 307 of the object 303 and the magnetic field so that the portion to be heated in higher temperature interacts longer with said magnetic field than the corresponding portion to be heated in lower temperature. In other words the manipulating means 305 may be configured to change the relative velocity of the object and the magnetic field as is illustrated e.g. in connection with Figures 2A and 2B. When chancing the relative velocity the manipulating means 305 advantageously controls the speed (and moving directions) of the introducing means 304 via a driving motor 308. In addition the manipulating means 305 may be configured to change the intensity of the induced power so that the portion to be heated in higher temperature is exposed to greater intensity of the induced power than the corresponding portion of the object to be heated in lower temperature. This can be achieved for example so that the manipulating means 305 controls (and changes) the rotation rate of the magnet 301 in the vicinity of the object (and/or the rotation rate of the object). According to an embodiment a second driving motor 309 may be used for rotating the rotor 302 with the magnet(s) 301 , whereupon the manipulating means 305 may control the rotation rate of the magnets via said second driving motor 309. Furthermore the manipulating means 305 may control (and change) also the relative distance of the object and the magnetic field.

According to an advantageous embodiment the effective varying magnetic field (area of the rotor 302 or magnet(s) 301 ) is configured to be shorter (or smaller) than the length of the object to be heated, whereupon the more accurate or sharp temperature profile can be achieved, because more narrow portion of the object can be heated at a time.

Of course it is to be noted that according to an embodiment of the invention the heating arrangement may comprise plurality of devices 300, 310 coupled (advantageously sequentially) with each other so the object is first transferred over the first device, and after this the second etc., whereupon the each device may provide own temperature distribution to the object for example by different rotation speed or different distance of the magnets.

In addition according to an embodiment the device 310 may comprise temperature measuring means 31 1 configured to measure temperature of at least two portions of the object to be heated before heating, whereupon the desired temperature distribution between these portions is provided by the device by taking into account the initial temperatures of the portions prior to heating. In addition the device may be configured to take into account also at least one physical and/or material property of the object to be heated and thereby configured to change the relative velocity of the object and the magnetic field so that the portion to be heated most interacts longer with said magnetic field than the portion to be heated less (or to control other manipulating parameters so that to change the rate of the induced power).

In addition, according to an embodiment the device 310 may also comprise temperature measuring means 312 configured to measure temperature of a portion of the object also during electromagnetic induction heating in order to use said temperature information as a feedback in the electromagnetic induction heating for manipulating the parameters for the heating, such as changing the relative velocity of the object and the magnetic field.

The device may also comprise means 313 configured to manipulate the induced power within the eddy current as a function of time, e.g. introducing higher power at the beginning of the electromagnetic induction heating process (so that the surface of the object does not have any significant deformations or melting) and lowering it at least once during the electromagnetic induction heating process.

Furthermore the device may comprise means 314 configured to take parameters from an extrusion process into account via feedback loop when changing the manipulating parameters, such as changing the relative velocity of the object and the magnetic field and/or when changing the induced power of the electromagnetic flux.

Again, according to an embodiment the portions of the device, such as the introducing means 304 (a gutter), basement or frame supporting, is grooved to prevent eddy currents on them during heating process and when they are exposed to varying magnetic field. In addition the material of the portions exposed to varying magnetic field, such as introducing means, is chosen to minimize eddy currents, and is advantageously stainless steel, and most advantageously non- magnetic, high electrical resistivity material, and suitable for high temperatures (non-magnetic stainless steel, such as AISI316). An exemplary introducing means, such as the grooved gutter 304, is described in Figure 3C.

Still according to an embodiment the device may also comprise means 315 for removing residues or swarfs protruding from the object 303 to be heated, such as e.g. at least one roller or blade 315, which is configured to bend or cut said residues (e.g. bend along the longitudinal axis of the object to be heated).

It is to be noted that the computer program codes or product may be used for determining the control parameters for the heating process and the device so that both the initial parameters are taken into account (such as the initial temperatures, physical and material properties) as well as the desired temperature information and possible feedback information. The computer codes or program may be run on a data processing means 316, which is advantageously configured to control the device 310 and its sub-means 305-314 and thereby provide a predetermined temperature distribution into an object, such as disclosed in connection with Figures 2A-2C.

The invention has been explained above with reference to the aforementioned embodiments, and several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments, but comprises all possible embodiments within the spirit and scope of the inventive thought and the following patent claims.

Claims

1 . A method for providing a predetermined temperature distribution into an object via an electromagnetic induction heating means, where the electromagnetic induction comprises providing varying magnetic field and eddy currents within the object by at least one permanent magnet when the object and the magnet is moved relatively in each other so that said object is heated by the power of electromagnetic induction generated by said varying magnetic field and eddy currents,

characterized in that the

- the object is moved first at least once over said electromagnetic induction heating means,

- energy or power absorbed by the object is determined in function of length of said object for each portion of the length, when said object is moved over said electromagnetic induction heating means,

- an approximation of the model for feeding the energy or power for each of the portion of the object is determined based on the determined energy or power absorption into each portion of said object and the predetermined temperature for said portion of said object,

wherein

- the approximation of the model comprises parameters for:

o number of times the object is moved back-and-forth over the electromagnetic induction heating means, and

o different velocities for different portion of the object so that the portion to be heated higher or absorbing less energy portion is driven slower than other to be heated lower or absorbing more energy, and/or

o different intensities of the induced power of the electromagnetic induction heating means so that the portion to be heated in higher temperature or absorbing less energy is exposed to greater intensity of the induced power than the portion of the object to be heated in lower temperature or absorbing more energy, and

- the object is moved back-and-forth over the electromagnetic induction heating means based on said determined model so to achieve the predetermined temperature distribution.

2. A method of claim 1 , wherein power of the electromagnetic induction heating means is kept constant and advantageously at least over a predetermined limit but so that the surface of the object is not melt.

3. A method of any previous claims, wherein an initial temperature distribution of the object is measured and based on the object details comprising at least said temperature distribution in function of the length of the object, material, mass and dimensions, a preliminary approximation of the model for total energy or power to be fed into the object is determined as well as optionally also the energy or power for each portion of the object, and number of times the object is moved back-and- forth as well as also different velocities and/or intensities for each of the portion, whereupon said preliminary approximation of the model is used for determining said approximation of the model from said preliminary approximation when the object is moved first at least once over said electromagnetic induction heating means.

4. A method of claim 3, wherein number of times the object is moved back-and- forth is determined so that total energy or power to be fed into the object or for a certain portion of the object is divided by the maximum energy or power feedable into the object or for that certain portion of the object so that the surface temperature of the object or that certain portion of the object is kept below the melting point of the object that certain portion of the object.

5. A method of any previous claims, wherein the approximation of the model is determined at least once when the object is moved over said electromagnetic induction heating means.

6. A method of any previous claims, wherein the changing the intensity of the induced power is implemented by changing the rotation rate of the magnet and/or the object, and/or by changing the distance of the magnet and the object.

7. A method of any previous claims, wherein the effective varying magnetic field is shorter than the object to be heated.

8. A method of any previous claims, wherein temperature of at least two portions of said object to be heated is measured before heating, whereupon the desired temperature distribution between these portions is provided by taking into account the temperatures of the portions, as well as dimensions of the object to be heated and at least one of the material properties of the object to be heated and manipulating the induced power so that the portion to be heated most is exposed to greater total power.

9. A method of any previous claims, wherein temperature of a portion of the object is determined also during electromagnetic induction heating in order to use said temperature information as a feedback in the electromagnetic induction heating for re-determining the approximation of the model.

10. A method of any previous claims, wherein the induced power within the eddy currents is also manipulated as a function of time, e.g. introducing higher power at the beginning of the electromagnetic induction heating process and lowering it at least once during the electromagnetic induction heating process.

1 1 . A method of claims 9 or 10, wherein parameters from an extrusion process is taken into account via feedback loop when changing the relative velocity of the object and the magnetic field and/or when changing the power of the electromagnetic flux.

12. A device for providing a predetermined temperature distribution into an object via an electromagnetic induction heating means comprised by the device, where the electromagnetic induction heating means comprises at least one permanent magnet arranged to provide varying magnetic field and eddy currents within the object to be heated when the object and the magnet is moved relatively in each other so that said object is heated by the power of electromagnetic induction generated by said varying magnetic field and eddy currents, and wherein the device comprises introducing means for moving the object in relation to said magnetic field,

characterized in that the device is configured to

- move the object first at least once over said electromagnetic induction heating means,

- determine energy or power absorbed by the object in function of length of said object for each portion of the length, when said object is moved over said electromagnetic induction heating means,

- determine an approximation of the model for feeding the energy or power for each of the portion of the object based on the determined energy or power absorption into each portion of said object and the predetermined temperature for said portion of said object,

wherein

- the approximation of the model comprises parameters for:

o different velocities for different portion of the object so that the portion to be heated higher or absorbing less energy portion is driven slower than other to be heated lower or absorbing more energy, and/or o different intensities of the induced power of the electromagnetic induction heating means so that the portion to be heated in higher temperature or absorbing less energy is exposed to greater intensity of the induced power than the portion of the object to be heated in lower temperature or absorbing more energy, and

- the device is further configured to move the object back-and-forth over the electromagnetic induction heating means based on said determined model so to achieve the predetermined temperature distribution.

13. A device of claim 12, wherein the device is configured to keep the power of the electromagnetic induction heating means constant and advantageously at least over a predetermined limit but so that the surface of the object is not melt.

14. A device of any of previous claims 12-13, wherein the device is configured to measure an initial temperature distribution of the object and based on the object details comprising at least said temperature distribution in function of the length of the object, material, mass and dimensions, to determine a preliminary approximation of the model for total energy or power to be fed into the object as well as optionally also the energy or power for each portion of the object, and number of times the object is moved back-and-forth as well as also different velocities and/or intensities for each of the portion, whereupon the device is configured to manipulate said preliminary approximation of the model into said approximation of the model when the object is moved first at least once over said electromagnetic induction heating means.

15. A device of claim 14, wherein the device is configured to determine the number of times the object is moved back-and-forth so that total energy or power to be fed into the object or for a certain portion of the object is divided by the maximum energy or power feedable into the object or for that certain portion of the object so that the surface temperature of the object or that certain portion of the object is kept below the melting point of the object that certain portion of the object.

16. A device of any of previous claims 12-15, wherein the device is configured to determine the approximation of the model at least once when the object is moved over said electromagnetic induction heating means.

17. A device of any of previous claims 12-16, wherein the device is configured to change the intensity of the induced power by changing the rotation rate of the magnet and/or the object, and/or by changing the distance of the magnet and the object.

18. A device of any of previous claims 12-17, wherein the effective varying magnetic field is configured to be shorter than the object to be heated.

19. A device of any of previous claims 12-15, wherein the device comprises temperature measuring means configured to measure temperature of at least two portions of said object to be heated before heating, whereupon the desired temperature distribution between these portions is provided by taking into account the initial temperatures of the portions prior to heating, as well as the material properties of the object to be heated and the device is configured to change the relative velocity of the object and the magnetic field so that the portion to be heated most is interacts longer with said magnetic field than the portion to be heated in less.

20. A device of any of previous claims 12-15, wherein the device comprises temperature measuring means configured to measure temperature of a portion of the object also during electromagnetic induction heating in order to use said temperature information as a feedback in the electromagnetic induction heating for changing the relative velocity of the object and the magnetic field.

21 . A device of any of previous claims 12-15, wherein the device is configured to manipulate the induced power of the eddy current as a function of time, e.g. introducing higher power at the beginning of the electromagnetic induction heating process and lowering it at least once during the electromagnetic induction heating process.

22. A device of any of claims 20-21 , wherein the device is configured to take parameters from an extrusion process into account via feedback loop when changing the relative velocity of the object and the magnetic field and/or when changing the power of the electromagnetic flux.

23. A device of any of previous claims 12-22, wherein introducing means, such as a gutter, is grooved to stop eddy currents on the introducing means during the time the object to be heated is situated on the gutter and heated, and wherein the material of the introducing means is chosen to minimize eddy currents and is advantageously non-magnetic, high electrical resistivity material, and suitable for high temperatures.

24. A device of any of previous claims 12-23, wherein the portions of the device, such as a basement or frame supporting said introducing means, influenced by said varying magnetic field, is grooved to prevent said eddy currents.

25. A device of any of previous claims 12-24, wherein device comprises means for removing residues or swarfs protruding from the object to be heated, such as e.g. at least one roller, which is configured to bend or cut said residues.

26. Computer program product adapted to perform at least one step of the any of the method claims 1 -1 1 , when said computer program product is run on a data processing means configured to control the device of any of claims 12-25 for providing a predetermined temperature distribution into an object.