Levitation melting process

Abstract

The invention relates to a method for producing casting bodies in a levitation melting method in which a batch of an electrically conductive material is brought into the sphere of influence of at least one alternating electromagnetic field by means of a starting material having a plurality of pre-separated batches separated by regions of reduced cross-section so that the batch is kept in a state of levitation. The regions are designed in such a way that separation of the pre-separated batches takes place only during melting in an alternating electromagnetic field. The melt is then cast into casting moulds.

Claims

1. A method for producing casting bodies from an electrically conductive material by levitation melting, comprising: introducing of a lowest batch of a starting material for several batches into a sphere of influence of at least one electromagnetic alternating field, wherein the electromagnetic alternating field is created by means of horizontally arranged coils, and wherein the starting material is of an electrically conductive material having several pre-separated batches separated by regions of reduced cross-section and the regions are designed in such a way that separation of the pre-separated batches takes place only during melting in an electromagnetic alternating field, melting the lowest batch, wherein the batch has no contact with a crucible or platform, and wherein the remaining starting material pushes the lowest batch to be melted so far into the alternating electromagnetic field that an induced eddy current is at its maximum, lifting the remaining unmelted starting material from the molten lowest batch in a levitating state, overheating the levitating lowest batch, positioning a mold in a filling area below the levitating lowest batch, casting the entire lowest batch into the mold, removal of a solidified casting body from the mold.

2. The method according to claim 1, wherein the starting material for several batches consists of a cylindrical rod that along its longitudinal axis has regions having reduced cross-sections, wherein the individual regions having the non-reduced cross-section each correspond to the amount of material of a batch.

3. The method according to claim 1, wherein in the starting material for several batches, the cross-section between the batches is reduced to such an extent and/or the regions with reduced cross-section are so long that an eddy current induced in an electromagnetic alternating field in a batch is delimited to such an extent that an adjacent batch is not melted with it.

4. The method according to claim 1, wherein in the starting material for several batches, the regions having a reduced cross-section are dimensioned at least in such a way that they have a mechanical load-bearing capacity that is sufficient for the respective weight of the starting material to be carried.

5. The method according to claim 1, wherein in the starting material for several batches, a heat conduction of the regions having a reduced cross-section is so low that, when a batch is melted, an adjacent batch is not melted with it.

6. The method according to claim 1, wherein the electrically conductive material contains at least one metal from the following group: titanium, zirconium, vanadium, tantalum, tungsten, hafnium, niobium, rhenium, molybdenum, nickel, iron, aluminum.

7. The method according to claim 6, wherein the metal has a proportion of at least 50% by weight of the conductive material.

8. The method according to claim 6, wherein the metal has a proportion of at least 60% by weight of the conductive material.

9. The method according to claim 6, wherein the metal has a proportion of at least 70% by weight of the conductive material.

10. The method according to claim 1, wherein the electrically conductive material is titanium or a titanium alloy.

11. The method according to claim 1, wherein the electrically conductive material is TiAl or TiAlV.

12. The method according to claim 1, wherein the electrically conductive material is used in powder form.

13. The method according to claim 12, wherein the starting material for several batches is produced from the electrically conductive material by pressing with a binding agent and/or sintering.

14. The method according to claim 1, wherein the conductive material is superheated during melting to a temperature that is at least 10° C. above the melting point of the material.

15. The method according to claim 1, wherein the conductive material is superheated during melting to a temperature that is at least 20° C. above the melting point of the material.

16. The method according to claim 1, wherein the conductive material is superheated during melting to a temperature that is at least 30° C. above the melting point of the material.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a side view of three embodiments of a starting material according to the invention.

(2) FIG. 2 is a side view of the structure of a melting region with ferromagnetic element, coils and the lower partial portion of a starting material for several batches.

FIGURE DESCRIPTION

(3) The figures show preferred embodiments. They are for illustration purposes only.

(4) FIG. 1 shows a side view of three embodiments of a starting material according to the invention made of electrically conductive material. All three are vertical circular cylindrical forms. At the upper end, there is a region suitable for mounting in a feeding device. Depending on the method of attachment, this area may be smooth, as shown in the illustration, or provided with holes or a three-dimensional surface structure, in particular an end circumferential widening which allows it to be gripped by a hook or gripper.

(5) The left starting material has six batches, the middle five batches and the right eight batches (1). In the case of the left starting material, the individual batches (1) are separated by notches in a triangular shape. These notches can, for example, be produced by a punch without loss of material. In the middle starting material, the individual batches (1) are separated by wider regions with a reduced cross-section. Such a design can be produced in a simple and cost-effective way by turning a cylindrical rod. The starting material on the right, respectively, has narrow circumferential incisions for the separation of the individual batches (1). In principle, the structure is the same as with the middle starting material, only the distances are reduced and the cross-section of the regions having a reduced cross-section is further reduced. Due to the further reduced cross-section, a better limitation of the induced eddy currents and lower heat conduction can be achieved in order to compensate for the shorter distance.

(6) FIG. 2 shows the section of the lowest three batches (1) of the middle starting material from FIG. 1. The lowest batch (1) is in the sphere of influence of alternating electromagnetic fields (melting region) generated by the coils (2). Below the batch (1) there is an empty casting mould which is held in the filling area by a holder (not shown). A ferromagnetic element (3) is arranged around the sphere of influence of the coils (2). The batch (1) is melted and levitated in the method according to the invention. After the batch (1) has melted, the remaining starting material is drawn upwards and the melt is superheated. The melt is then cast into the casting mould and the solidified casting body is finally removed from the casting mould.

LIST OF REFERENCE SIGNS

(7) 1 batch 2 coil 3 ferromagnetic element