WO2012072771A1 - Method and induction heater for heating billets - Google Patents

Abstract

A method and an induction heater for inductively heating a metal billet by rotating the billet (10.1) about its mid-longitudinal axis in an air gap between the limbs of a ferromagnetic yoke (3) with a coil arrangement (5), which generates a direct magnetic field in the air gap, provide the possibility of different heating in the longitudinal direction of the billet when the yoke (3) is tilted with respect to a substantially horizontal plane containing the mid-longitudinal axis of the billet.

Description

 Method and induction heater for heating billets

The invention relates to a method for inductive heating of a metallic billets by turning the billet about its longitudinal central axis in an air gap between the legs of a ferromagnetic yoke with a coil assembly which generates a DC magnetic field in the air gap, the telachse for the most part the billet orthogonal to its Längsmi interspersed.

The invention further relates to an induction heater for heating billets, having a cross-sectionally M-shaped, ferromagnetic yoke, consisting of an upper transverse leg, down to two outer leg and a center leg to form a shaft between a front end face and connect a rear end face of the yoke, on both sides of each shaft each a jig for rotating a billet is disposed in this shaft and sitting on the center leg of a DC-powered coil assembly which generates a DC magnetic field in both wells.

Such an induction heater is known from EP 2 183 944 B1. The billets or bolts are usually fully cylindrical semi-finished metal products, usually made of aluminum, copper or corresponding alloys. Due to the induced eddy currents, the billets are heated to a large extent uniformly. As a rule, the induction heater is arranged between two parallel production lines, over each of which two billets conveyed, positioned under the corresponding shafts of the induction heater, raised, between the Clamped heads of the two-sided clamping devices and are offset for inductive heating in rotation about its longitudinal central axis. After reaching the Solltempe nature the billets get back in the same way back to the respective production line and are transported to the next processing station, such as an extruder on. The terms "front" and "rear" in connection with the yoke and the billets refer to this direction of transport.

For extruding or for other forming processes, the heated billets are intended to have one from their front to their rear face e.g. from 500 ° C to 400 ° C decreasing temperature. With the known induction heater such a temperature distribution can be achieved only by complex design measures, in particular a change in the air gap between the legs of the M-shaped yoke along the respective billets. The same applies to billets, which have a considerable temperature gradient in the axial direction, ie a temperature difference between their front end face and their rear end face, but should be brought to a uniform final temperature before the induction heating.

Substantial reconstruction work on the known induction heater would also be necessary if two billets of the same material at the same time, but to different final temperatures or two billets of different ma- materials to be heated to the same final temperature. The invention has for its object to provide a method of the type described above to heat billets eg with a predetermined temperature gradient along its axis or two billets in two wells of a ferromagnetic yoke simultaneously, but to heat to different temperatures.

This object is achieved in that the yoke is raised on one side.

For simultaneous but different heating of two billets, the yoke, which may in particular have an M cross-section, is pivoted about an axis which runs parallel to the longitudinal center axes of the billets in the region of one outer limb of the yoke. The other, raised outer leg adjacent billet is then heated less than the billet closer to the pivot axis. Such a one-sided lifting of the yoke also makes it possible to simultaneously heat billets of different materials or different diameters to (approximately) the same temperature.

If, on the other hand, a billet or two billets are to be heated simultaneously with a temperature gradient in the longitudinal direction, the yoke is pivoted about a tilting axis, which is in the region of the front end face of the yoke and parallel to this in a horizontal plane which extends from the longitudinal center axis of the billet below has a distance of a -SD, where D is the diameter of the billet.

The invention has the further object of providing an induction heater of the type described in the introduction, the easy way. the above different conditions of use is customizable.

This object is achieved according to the invention in that the yoke can be tilted relative to a horizontal plane containing the longitudinal central axes of the billets in the shafts in order to influence the temperature of the billets.

By tilting the yoke about an axis parallel to the longitudinal center axes of the billets, e.g. Billets made of different materials in the two shafts to the same temperatures or billets of the same material in the two shafts to be heated to different temperatures.

For the reasons mentioned in the introduction, however, the simple possibility created by the invention of producing a temperature gradient in the axial direction of the billets or of changing an initial temperature gradient is more important. For this purpose, the yoke is tiltable about a tilting axis, which is in the region of the front end face of the yoke and parallel to this. When the yoke is tilted about this tilt axis, e.g. Billets, which have ambient temperature at the beginning of heating, after the completion of the heating, a temperature gradient corresponding to a decreasing from the front end surface to the rear end surface temperature. The amount of the temperature gradient depends on the amount of tilt angle. The latter is easily determined empirically, depending on the desired temperature difference.

Preferably, the tilt axis of the longitudinal center axes of the billet containing, horizontal plane down a distance a ί D, where D is the diameter of the billet or billets. In particular, the yoke for adjusting the position of the tilting axis can be height-adjustable with respect to the horizontal plane containing the longitudinal axes of the bil lets. By adjusting the height of the yoke, both the

The final temperature of the billets at their front end face is influenced and the heating process is adapted to billets of different lengths and / or different diameters.

For this purpose, the yoke may each have a vertical guide in the region of its front end face on both sides of its outer legs, in order to open the yoke, for example. Centrally raise or lower spindle drives or hydraulically. The threaded spindles or the piston rods of hydraulic cylinders can simultaneously have the function of guide rods.

Preferably, the two outer limbs of the yoke are each mounted in a bearing containing the tilt axis.

Suitably, the tilt angle of the yoke is continuously adjustable. A simple construction for tilting the yoke about a tilting axis parallel to the front end face of the yoke is that the center leg of the yoke has at least one cantilevered towards the rear end face of which a lifting device engages.

The lifting device may consist of at least one spindle drive. Alternatively, the lifting device may consist of at least one hydraulic cylinder.

Preferably, the yoke is mounted in a machine frame and tiltable relative thereto.

It is particularly advantageous if it is superconducting at such a ^¬ In duktionsheizer the coil assembly. With a superconducting coil winding, a higher magnetic flux density can be generated in the shafts of the yoke than with a normal conducting winding. When tilted yoke thereby a better linearization of the temperature profile is achieved in accordance with a substantially constant temperature gradient along the billets.

In the drawing, an exemplary embodiment of an induction heater according to the invention by way of example and shown only with the essential components of the invention. It is suitable for heating billets after he ^¬ inventively proposed method. It shows:

1: a side view,

Fig. 2; a section along the line II-II in Figure 1,

Fig. 3 is a side view similar to Figure 1, but partially in section along the line III-III in Fig. 2 and with the yoke and tilted

Fig. 4: a partially sectioned isometry of Indukti ^¬ onsheizers with tilted yoke. Referring particularly to Figures 2, 2 and 4, the induction heater has a machine frame 1 in the form of a solid welded construction comprising four columns connected at their upper ends to double T-beams, which in turn are bolted or welded together. Between the front pillars 1.1 and 1.2 in Figure 2 is a front end plate 2.1. Likewise located between the rear pillars 1.3 and 1.4 corresponding to Figures 1, 3 and 4, a rear end plate 2.2.

The largest part of the space between the pillars 1.1 to 1.4 and the end plates 2.1 and 2.2 assumes an M-shaped egg ^¬ senjoch 3, which according to Figure 2 an upper transverse leg 3.1, two outer legs 3.2 and 3.3 and a central ^{leg ¬} 3.4 comprises. As a result, according to Figure 2 extends between the middle leg 3.4 and the outer ^{leg ¬} 3.2 from the front end face 3.5 to the rear end face 3.6 of the yoke 3 (see Figure 1) a shaft 4.1 and parallel to this another shaft 4.2 between the middle leg 3.4 and the other outer leg 3.3. On the middle leg 3.4 of the yoke 3 sits a coil assembly 5, which is only hinted at here. The coil arrangement 5 may in particular comprise a high-temperature superconducting coil in an approximately annular cryocontainer. Coil arrangements with superconducting, cooled coils are known per se and therefore will not be explained in detail here.

The coil assembly 5 generates in the center leg 3.4 of the yoke, a magnetic flux, which is divided into the transverse leg and 3.1 on the outer legs 3.2, 3.3 and arranged in the wells 4.1 and 4.2 pole shoes back to the center leg 3.4 closes. By means of dashed lines in Figures 1 and 2 indicated transport and lifting devices 20.1 and 20.2 is to be heated in the ^¬ each of the shafts 4.1 and 4.2 Billet 10.1 and 10.2 positioned between the pole shoes, via its two end faces by means of the in Figures 1 and 3 indicated waves 30.1 and 30.2 clamped and offset by means of electric rotary actuators 30.3 and 30.4, in rotation about sei ^¬ ne Mi tellängsachse M until the billet has reached the ge ^¬ desired end temperature and after releasing the voltage again from the feeder 20.1 and 20.2 taken over and, based on its Mi longitudinal axis M, transversely out of the induction heater is transported out. In the position shown in FIG. 1, the respective billet, such as 10.1, is heated substantially evenly between its front end surface and its rear end surface. Frequently, however, the billets in the region of their front end face (near the front end face 3.5 of the yoke 3) to a higher temperature than in the region of their rear

Are heated face, so in the longitudinal direction have a temperature wedge or temperature gradient. For this purpose, the yoke 3 as a whole is tiltably mounted in the machine frame 1 about a tilting axis K (see FIGS. 2 and 4), which extends in the region of the front end face 3.5 of the yoke 3. As illustrated in particular Figures 2 and 4, the yoke 3 has for this purpose on both sides on its Außenschen ^¬ angles 3.2 and 3.3 journals 6.1 and 6.2, which are included in pillow blocks 7.1 and 7.2 and on its transverse yoke 3.1 a cantilever 7, over the rear face 3.6 of the

Jochs 3 also extends and is connected at the end with a lifting device 8, which in the present case comprises a mounted on the machine frame 1 gear motor 8.1 for rotating a threaded spindle 3.2, in a spindle nut 8.3 on End of cantilever 7 is running. Therefore, the yoke 3 can be tilted about the tilting axis K from the position in FIG. 1 by a predetermined angle, for example, into the position according to FIGS. 3 and 4, via the geared motor 8.1.

In an analogous manner, the yoke 3 can also be tiltably mounted in the machine frame 1 about an axis parallel to the central longitudinal axes of the clamped billets, additionally or alternatively by, for example, the billet 10.2 by tilting the

Yoke 3 to heat a ver in the region of the outer leg 3.2 ver ^¬ current less than the billet 10.1. The tilting axis K need not lie exactly in the plane of the front end face 3.5 of the yoke 3. It can be changed, for example, by choosing the attachment points of the bearing journals such as 6.1 supporting tabs such as 3.7 in FIG. The tilting axis K need not lie in the horizontal plane containing the longitudinal central axes of the billets 10.1, 10.2, which is identical to the reference plane which spans the drive shafts 30.1 and 30.2 because the rotary drives 30.3 and 30.4 are connected to the machine frame 1. Depending on the length and / or diameter of the billets better heating results are obtained when the yoke 3 ge ^¬ genüber the machine frame 1 is adjustable in height, in particular from the illustrated vertical position to a position can be lowered, in which the tilt axis K below the Längsmitteiachsen of billets containing lies hori ^¬ zontal reference plane. For this purpose, the pillow block bearing 7.1 and 7.2 along the columns 1.1 and 1.2 are height adjustable, and Although preferably up to an amount which is equal to the maximum paint diameter D to be heated in the induction heater NEN Billets. For this purpose, the pillow block bearings 7.1 and 7.2 arranged in the region of the front face 3.5 of the yoke on carriers 8.1 and 8.2 (see. Fig. 2), which ih ^¬ hand, are vertically adjustable, in the form of threaded despindeln 9.1 and 9.2 with spindle motors 9.3 and 9.4.

To maintain the horizontal position of the yoke 3 as shown in fi gure 1 or the tilted position as shown in Figure 4, simultaneously with a height adjustment of the bearing 7.1 and 7.2, the lifting device 8 in the same direction verstel lt,

Claims

claims A method of inductively heating a metallic billet by rotating the billet (10.1, 10.2) about its longitudinal central axis in an air gap between the billets Legs of a ferromagnetic yoke (3) with a coil arrangement (5) which generates a DC magnetic field in the air gap, which is for the most parts of the billet perpendicular to its longitudinal central axis by ^¬, characterized in that the yoke (3} is raised a ^¬ side , A method according to claim 1, characterized in that the yoke (3) for unilateral lifting about a tilting axis K is pivoted, which is in the region of the front end face (3.5) of the yoke (3) and parallel to this in a horizontal plane, the the longitudinal central axis of the billet has a distance of a ^ D downwards, where D is the diameter of the billet. Method according to claim 1 or 2, characterized in that the angle (θ) about which the yoke is raised on one side is chosen such that the ticket  (10.1, 10.2} is heated over its length with a predetermined temperature gradient. Induction heater for heating billets {10-1, 10.2) with a cross-sectionally M-shaped, ferromagnetic yoke (3), consisting of an upper transverse leg (3.1), down to two outer thighs (3.2, 3.3) and a middle limb (3.4) to form a respective shaft (4.1, 4.2) between a front end face (3.5) and a rear end face (3.6) connect the yoke (3), both sides each  Shaft (4.1, 4.2) each have a jig  (30.1, 30.3, 30.2, 30.4) is arranged for rotation of a billet in this shaft and on the center leg (3.4) a DC-current coil assembly (5) sits, which generates a DC magnetic field in both shafts (4.1, 4.2), characterized in that the yoke (3) can be tilted relative to a horizontal plane containing the longitudinal central axes (M) of the billets (10.1, 10.2) in the shafts (4.1, 4.2) in order to influence the temperature of the billets. Induction heater according to claim 4, characterized in that the yoke (3) about a tilting axis (K) is tiltable, which is in the region of the front end face (3.5) of the yoke (3) and parallel to this. Induction heater according to claim 4 or 5, characterized in that the tilting axis (K) of the The longitudinal center axes (10.1, 10.2) of the billet containing, horizontal plane down a distance a ^ D, where D is the diameter of the billet or billets. Induction heater according to one of claims 4 to 6, characterized in that the yoke (3) for adjusting the position of the tilting axis (K) with respect to the Längsmi telachsen the Billets (10.1, 10.2) containing, horizontal height adjustable. 8. induction heater according to one of claims 4 to 7, characterized in that the yoke (3) in the region of its front end face (3.5) on both sides of its outer ßenschenkel each vertical guide (8.1, 8.2, 9.1 to 9.4). Induction heater according to one of claims 4 to 8, characterized in that the two outer legs (3.2, 3.3) of the yoke (3) in each one the tilting axis (K) containing bearing {7.1, 7.2) are mounted. Induction heater according to one of claims 4 to 9, characterized in that the tilt angle of the yoke (3) is continuously adjustable. Induction heater according to one of claims 4 to 10, characterized in that the center leg (3.4) of the yoke (3) at least one to the rear  End face (3.6) directed cantilever arm (7), on which a lifting device (8) acts. Induction heater according to claim 11, characterized marked ^¬ characterized in that the lifting device of at least one spindle drive (8.1 to 8.3) consists. Induction heater according to claim 11, characterized in that the lifting device (8) consists of at least one hydraulic cylinder. Induction heater according to one of claims 4 to 13, characterized in that the yoke (3) in a machine frame (1) is mounted and tiltable relative to this. 15. Induction heater according to one of claims 1 to 14, characterized in that the coil arrangement is superconducting.