WO2017178109A1

WO2017178109A1 - Ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces

Info

Publication number: WO2017178109A1
Application number: PCT/EP2017/000468
Authority: WO
Inventors: Giovanni FAORO.
Original assignee: Graphite Hi Tech S.R.L.
Priority date: 2016-04-13
Filing date: 2017-04-11
Publication date: 2017-10-19
Also published as: ITUA20162552A1

Abstract

An ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, which comprises a container body that is provided with one or more molding impressions and a lid that is adapted to temporarily close the impressions. The particularity of the present invention resides in that the container body and/or the lid are constituted at least partially by a ceramic compound that comprises at least one from the following refractory materials: clay, Al₂O_3, BN, B₂O₃, BeO, C, CaO, Fe₂O₃, HfO₂, MgO, Na₂O, SiO₂, SiC, Si₃N₄, TiO₂, Y₂O₃, and ZrO₂. According to another embodiment, the container body and/or the lid are at least partially constituted by a refractory alloy that comprises at least one from the following refractory metals: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe. According to a further embodiment, the container body and/or the lid comprise, at least in the stations that can come into contact with the metal, a protective coating that comprises at least one from the following refractory materials: BN, C, H_fO₂, MgO, SiC, Si₃N₄, SiO₂, TiC, Ti0₂, WC, Y₂O₃, and ZrO₃. According to another embodiment, the protective coating comprises at least one from the following refractory metals: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe.

Description

INGOT MOLD, PARTICULARLY FOR THE CONTINUOUS PRODUCTION OF INGOTS AND BARS OF PRECIOUS METAL BY MEANS OF TUNNEL-TYPE FURNACES

The present invention relates to an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces.

As is known, in order to produce ingots and bars of precious metal, there is an increasing frequent use of tunnel-type furnaces, i.e. processing lines wherein the precious metal is melted in graphite ingot molds that, during the molding process, pass along successive work stations.

More particularly, tunnel-type furnaces generally have a loading station, wherein the metal to be melted is loaded into the ingot molds, an induction or resistance heating station, a solidification and cooling station, and an output station.

The process begins with the introduction of the metal to be melted in the form of grains or powder within the graphite ingot molds that, at set times, pass into the melting station and then into the stations assigned to controlled solidification and cooling, and then to the output station, wherein the operator picks up the cold ingot molds and extracts the ingot.

Although they are effective and substantially achieve their purpose, the graphite ingot molds conventionally used in tunnel-type furnaces have some problems that are definitely not negligible.

First of all, while on the one hand graphite is an excellent material in terms of chemical inertia, thermal characteristics (good conductivity, resistance to sudden temperature variations), and mechanical properties at high temperatures, on the other hand the graphite cannot be used in environments in which there is oxygen, in the presence of which the graphite oxidizes and substantially burns.

Graphite ingot molds are therefore generally subject to various types of degradation caused by high-temperature oxidation phenomena.

In addition to this, it should be noted that the use of graphite ingot molds might, during the melting process, compromise the purity of some precious metals, such as for example platinum and palladium.

The aim of the present invention is therefore to solve the problems described above, by providing an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, that eliminates or at least reduces the problem of premature deterioration of the ingot mold itself.

Within the scope of this aim, a particular object of the invention is to provide an ingot mold that is not subject to oxidation-related degradation phenomena even if it is used in the presence of oxygen.

Another object of the invention is to provide an ingot mold that is highly resistant to thermal and mechanical stresses.

Another object of the invention is to provide an ingot mold that is characterized by limited wettability by molten metal and is chemically inert with respect to said metal.

Another object of the invention is to provide an ingot mold that is particularly suitable for use in tunnel-type furnaces.

This aim, as well as the mentioned objects and others that will become better apparent hereinafter, are achieved by an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body provided with one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold being characterized in that said container body and/or said lid are at least partially constituted by a ceramic compound that comprises at least one from the following refractory materials: clay, Al₂0₃, BN, B₂0₃, BeO, C, CaO, Fe₂0₃, Hf0₂, MgO, Na₂0, Si0₂, SiC, Si₃N₄, Ti0₂, Y₂0₃, and Zr0₂.

The aim and objects of the invention are also achieved by an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body provided with one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold being characterized in that said container body and/or said lid are at least partially constituted by a refractory alloy that comprises at least one from the following refractory metals: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe.

The aim and objects of the invention are also achieved by an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body provided with one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold being characterized in that said container body and/or said lid comprise, at least in the stations that can come into contact with said metal, a protective coating that comprises at least one from the following refractory materials: Al₂0₃, BN, C, Hf0_2l MgO, SiC, Si₃N₄, Si0₂, TiC, Ti0₂, WC, Y₂0₃, and Zr0₃.

The aim and objects of the invention are also achieved by an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body provided with one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold being characterized in that said container body and/or said lid comprise, at least in the stations that can come into contact with said metal, a protective coating that comprises at least one from the following refractory metals: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe.

Further characteristics and advantages will become better apparent from the description of preferred but not exclusive embodiments of an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a perspective view of an ingot mold according to the invention;

Figure 2 is a longitudinal sectional view of the ingot mold according to the invention;

Figure 3 is a transverse sectional view of the ingot mold according to the invention;

Figure 4 is a longitudinal sectional view of an ingot mold according to a further aspect of the invention;

Figure 5 is a transverse sectional view of the ingot mold of Figure 4;

Figure 6 is a perspective view of an ingot mold according to a still further aspect of the invention;

Figure 7 is a transverse sectional view of the ingot mold of Figure 6; Figure 8 is a longitudinal sectional view of the ingot mold of Figure 6.

With reference to the cited figures, an ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, is designated generally by the reference numeral 1.

The expression "tunnel-type furnace" here refers to a per se known processing unit, constituted by a melting furnace and other processing stations, controlled by conveyance devices assigned to the movement of the ingot molds from one work station to the next one, by means of a process of continuous conveyance in a tunnel with controlled atmosphere.

These processing stations can comprise, for example, a loading station, wherein the metal to be melted is loaded into the ingot molds and said ingot molds are closed with the corresponding lid, a melting station which comprises the previously mentioned melting furnace, a solidification station, wherein the solidification of the molten metal occurs, a cooling station, wherein the formed ingots or bars are cooled, and an output station.

The ingot mold 1 comprises a container body 2 which is provided with one or more impressions 3, for forming an ingot or a bar, and with a lid 4, which is adapted to close each impression 3 during the forming process.

According to some embodiments, illustrated by way of example in Figures 1 to 5, the lid 4 also has the function of compressing, in a per se known manner, the solid metal that is contained in the impressions 3 during the heating and melting of said metal.

In practice, with the gradual reduction of the volume of the material to be melted that is contained in the impressions 3, which naturally occurs during melting, the lid 4 substantially passes from a first position, in which it rests on the material to be melted but without resting on the container body 2, to a second position, in which it rests on the container body 2, temporarily closing the impressions 3, but without resting on the melted material.

In other cases, instead, the lid 4 only has the function of temporarily closing each impression 3, abutting against the container body 2, as shown by way of example in Figures 6 to 8, wherein the ingot mold according to the invention is designated by the reference numeral 201 and its components have been designated by the same reference numerals used in Figures 1 to 5.

According to a first embodiment of the present invention, the container body 2 and/or the lid 4 are at least partially made of a ceramic compound characterized by a high heat resistance, chemical inertia to the metal to be melted, and low wettability with respect to the molten metal.

Preferably, the ceramic compound according to the present invention is constituted by at least one refractory material chosen from: clay, Al₂0₃, BN, B₂0₃, BeO, C, CaO, Fe₂0₃, Hf0₂, MgO, Na₂0, Si0₂, SiC, Si₃N₄, Ti0_2> Y₂0₃, and Zr0₂.

In a preferred embodiment, the ceramic compound according to the present invention contains from 98.0% to 99.99% by weight of Si0₂.

In this regard, where the present description refers to a percentage by weight of a given material, this is to specify the quantity of said material with respect to the total weight of the composition.

In another preferred embodiment, the ceramic compound according to the present invention contains 20.0% to 90.0% by weight of Al₂0₂ and from 5.0% to 90.0% by weight of Si0₂.

In another preferred embodiment, the ceramic compound according to the present invention contains from 80.0% to 90.0% by weight of SiC, from 6.0% to 8.0% by weight of Si0₂, and from 2.0% to 6.0% by weight of Al₂0₂.

In another preferred embodiment, the ceramic compound according to the present invention contains from 25.0% to 50.0% by weight of C, from 25.0% to 50% by weight of clay, from 10.0% to 25.0% by weight of SiC, and from 2.0% to 5.0% by weight of Fe₂0₂.

In another preferred embodiment, the ceramic compound according to the present invention contains from 98.0% to 99.99% by weight of BN.

In another preferred embodiment, the ceramic compound according to the present invention contains from 98.0% to 99.99% by weight of Si0₂.

In another preferred embodiment, the ceramic compound according to the present invention contains from 85.0% to 95.0% by weight of MgO, from 2.0% to 4.0% by weight of CaO, and from 0.5% to 3.0% by weight of Si0₂.

In another preferred embodiment, the ceramic compound according to the present invention contains from 80.0% to 96.0% by weight of Zr0₂, from 1.0% to 6.0% by weight of Y₂0₃, from 1.0% to 15.0% by weight of Si0₂, from 0.1% to 5.0% by weight of CaO, from 0.1% to 5.0% by weight of MgO, up to 0.5% by weight of Fe₂0₃, up to 1.0% by weight of Al₂0₃, and up to 1.0% by weight of Ti0₂.

In another preferred embodiment, the ceramic compound according to the present invention contains from 90.0% to 99.99% by weight of Y₂0₃.

In another preferred embodiment, the ceramic compound according to the present invention contains from 90.0% to 99.99% by weight of Si₃N₄.

In another preferred embodiment, the ceramic compound according to the present invention contains 20.0% by weight of Si0₂, 0.6% by weight of Al₂0₃, 0.6% by weight of Fe₂0₃, 0.5% by weight of CaO, 0.4% by weight of Na₂0, 3.0% by weight of Si₃N₄, 56.0% by weight of SiC, and 18.9% by weight of C.

In another preferred embodiment, the ceramic compound according to the present invention contains 4.0% by weight of Si0₂, 1.0% by weight of Ti0₂, 5.0% by weight of Al₂0₃, 1.0% by weight of Fe₂0₃, 0.5% by weight of Na₂0, 2.5% by weight of B₂0₃, 3.0% by weight of Si, 45.0% by weight of SiC, and 38.0% by weight of C.

In another preferred embodiment, the ceramic compound according to the present invention contains from 80.0% to 99.99% by weight of Hf0₂.

In another preferred embodiment, the ceramic compound according to the present invention contains from 80.0% to 99.99% by weight of BeO.

According to a further aspect of the present invention, the container body 2 and/or the lid 4 are at least partially made of a refractory alloy that is characterized by high heat resistance, chemical inertia to the metal to be melted, and low wettability with respect to the molten metal.

Preferably, the refractory alloy according to the present invention is constituted by at least one refractory metal selected from: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe.

In a preferred embodiment, the refractory alloy according to the present invention contains from 80.0% to 99.99% by weight of Ta.

In another preferred embodiment, the refractory alloy according to the present invention contains from 99.0% to 99.99% by weight of W.

In another preferred embodiment, the refractory alloy according to the present invention contains from 50.0% to 99.99% by weight of Mo.

In another preferred embodiment, the refractory alloy according to the present invention contains from 40.0% to 99.99% by weight of Ti.

In another preferred embodiment, the refractory alloy according to the present invention contains from 30.0% 99.99% by weight of Pt.

In another preferred embodiment, the refractory alloy according to the present invention contains from 50.0% to 99.99% by weight of Pd.

In another preferred embodiment, the refractory alloy according to the present invention contains from 80.0% to 99.99% by weight of Nb.

In another preferred embodiment, the refractory alloy according to the present invention contains from 90.0% to 99.99% by weight of Rh.

In another preferred embodiment, the refractory alloy according to the present invention contains from 90.0% to 99.99% by weight of Ir.

In another preferred embodiment, the refractory alloy according to the present invention contains from 50.0% to 99.99% by weight of Co.

In another preferred embodiment, the refractory alloy according to the present invention contains from 50.0% to 99.99% by weight of Zr.

In another preferred embodiment, the refractory alloy according to the present invention contains from 90.0% to 99.99% by weight of Fe.

According to a further aspect of the present invention, illustrated by way of example in Figures 4 and 5, in which the ingot mold according to the invention is designated by the reference numeral 101 , a protective coating is applied to the container body 2 and/or to the lid 4.

In the illustrated example, the lid 4 also has the function of compressing the solid metal contained in the impressions 3, during the molding process. However, it will be evident to the person skilled in the art that, in other cases, the lid 4 may only have the function of temporarily closing each impression 3, without thereby abandoning the scope of the invention.

Preferably, said protective coating is applied at least in the stations of the ingot mold 101 that can come into contact with the metal to be melted and/or with the molten metal.

For example, the protective coating may be applied to the inside of the lid 4 and of the impression 3, as shown in Figures 4 and 5, in which it is designated respectively by the reference numerals 5 and 6.

In the case being considered, the ingot mold 101 may be of metal, graphite, or other suitable materials; the protective coating 5 and 6 is used to increase the heat resistance of said ingot mold 101 and to render it chemically inert with respect to the metal to be melted and give it a low wettability to the molten metal.

Preferably, the protective coating according to the present invention is constituted by at least one refractory material selected from: BN, C, Hf0₂, MgO, SiC, Si₃N₄, Si0₂, TiC, Ti0₂, WC, Y₂0₃, and Zr0₃.

In a preferred embodiment, the protective coating according to the present invention contains from 95.0% to 99.99% by weight of BN.

In another preferred embodiment, the protective coating according to the present invention contains from 95.0% to 99.99% by weight of C.

In another preferred embodiment, the protective coating according to the present invention contains from 90.0% to 99.99% by weight of Hf0₂.

In another preferred embodiment, the protective coating according to the present invention contains from 80.0% to 99.99% by weight of MgO.

In another preferred embodiment, the protective coating according to the present invention contains from 80.0% to 99.99% by weight of SiC.

In another preferred embodiment, the protective coating according to the present invention contains from 50.0% to 99.99% by weight of Si0₂.

In another preferred embodiment, the protective coating according to the present invention contains from 90.0% to 99.99% by weight of Zr0₂. In another preferred embodiment, the protective coating according to the present invention contains from 90.0% to 99.99% by weight of Ti0₂.

In another preferred embodiment, the protective coating according to the present invention contains from 99.0% to 99.99% by weight of Si₃N₄.

In another preferred embodiment, the protective coating according to the present invention contains from 90.0% to 99.99% by weight of Y₂0₃.

In another preferred embodiment, the protective coating according to the present invention contains from 99.0% to 99.99% by weight of TiC.

In another preferred embodiment, the protective coating according to the present invention contains 99.0% to 99.99% by weight of WC.

According to a further aspect of the present invention, a protective coating is applied to the container body 2 and/or to the lid 4 in order to increase their heat resistance, render them chemically inert to the metal to be melted and give them low wettability to molten metal; such protective coating is constituted by at least one refractory metal selected from: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe.

In this case also, the container body 2 and the lid 4 may be of metal, graphite, or other suitable materials.

In a preferred embodiment, the protective coating according to the present invention contains from 80.0% to 99.99% by weight of Ta.

In another preferred embodiment, the protective coating according to the present invention contains from 99.0% to 99.99% by weight of W.

In another preferred embodiment, the protective coating according to the present invention contains from 50.0% to 99.99% by weight of Mo.

In another preferred embodiment, the protective coating according to the present invention contains from 40.0% to 99.99% by weight of Ti.

In another preferred embodiment, the protective coating according to the present invention contains from 30.0% to 99.99% by weight of Pt.

In another preferred embodiment, the protective coating according to the present invention contains from 50.0% to 99.99% by weight of Pd.

In another preferred embodiment, the protective coating according to the present invention contains from 80.0% to 99.99% by weight of Nb.

In another preferred embodiment, the protective coating according to the present invention contains from 90.0% to 99.99%) by weight of Rh.

In another preferred embodiment, the protective coating according to the present invention contains from 90.0% to 99.99% by weight of Ir.

In another preferred embodiment, the protective coating according to the present invention contains from 50.0% to 99.99% by weight of Co.

In another preferred embodiment, the protective coating according to the present invention contains from 50.0% to 99.99%) by weight of Zr.

In another preferred embodiment, the protective coating according to the present invention contains from 90.0% to 99.99%) by weight of Fe.

Preferably, the protective coating according to the present invention is provided by means of a process of physical vapor deposition (PVD).

As an alternative, the protective coating may be obtained by means of other per se already known methods, such as for example chemical vapor deposition (CVD) or thermal spray (TS).

In the embodiments shown in Figures 4 and 5, the elements that correspond to the elements that have already been described with reference to the embodiment shown in Figures 1 to 3 and from 6 to 8, have been designated by the same reference numerals.

In practice it has been found that the ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, according to the invention, achieves fully the intended aim.

The ingot mold according to the invention in fact practically eliminates the problem of premature deterioration that characterizes graphite ingot molds.

In particular, the ingot mold according to the invention is not subject to oxidation degradation phenomena, even if it is used in the presence of oxygen.

Also, the ingot mold according to the invention is highly resistant to thermal and mechanical stresses and is also poorly wettable by the molten metal and is chemically inert with respect to it. Advantageously, the ingot mold according to the invention is particularly suitable in tunnel-type furnaces.

Claims

1. An ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body having one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold being characterized in that said container body and/or said lid are at least partially constituted by a ceramic compound that comprises at least one from the following refractory materials: clay, Al₂0₃, BN, B₂0₃, BeO, C, CaO, Fe₂0_3l Hf0₂, MgO, Na₂0, Si0₂, SiC, Si₃N₄, Ti0₂, Y₂0₃, and Zr0₂.

2. The ingot mold according to the preceding claim, wherein the ceramic compound contains from 98.0% to 99.99% by weight of Si0₂.

3. The ingot mold according to claim 1 , wherein the ceramic compound contains from 20.0% to 90.0% by weight of Al₂0₃ and from 5.0% to 90.0% by weight of Si0₂.

4. The ingot mold according to claim 1 , wherein the ceramic compound contains from 80.0% to 90.0% by weight of SiC, from 6.0% to 8.0% by weight of Si0₂, and from 2.0% to 6.0% by weight of Al₂0₃.

5. The ingot mold according to claim 1 , wherein the ceramic compound contains from 25.0% to 50.0% by weight of C, from 25.0% to 50.0% by weight of clay, from 10.0% to 25.0% by weight of SiC, and from 2.0% to 5.0% by weight of Fe₂0₃.

6. The ingot mold according to claim 1 , wherein the ceramic compound contains from 98.0% to 99.99% by weight of BN.

7. The ingot mold according to claim 1 , wherein the ceramic compound contains from 98.0% to 99.99% by weight of Si0₂.

8. The ingot mold according to claim 1 , wherein the ceramic compound contains from 85.0% to 95.0% by weight of MgO, from 2.0% to 4.0% by weight of CaO, and from 0.5% to 3.0% by weight of Si0₂.

9. The ingot mold according to claim 1 , wherein the ceramic compound contains from 80.0% to 96.0% by weight of Zr0₂, from 1.0% to 6.0% by weight of Y₂0₃, from 1.0% to 15.0% by weight of Si0₂, from 0.1 % to 5.0% by weight of CaO, from 0.1% to 5.0% by weight of MgO, from 0.0% to 0.5% by weight of Fe₂0₃, from 0.0% to 1.0% by weight of Al₂0₃, and from 0.0% to .0% by weight of Ti0₂.

10. The ingot mold according to claim 1 , wherein the ceramic compound contains from 90.0% to 99.99% by weight of Y₂0₃.

11. The ingot mold according to claim 1 , wherein the ceramic compound contains from 90.0% to 99.99% by weight of Si₃N₄.

12. The ingot mold according to claim 1 , wherein the ceramic compound contains

20.0% by weight of Si0₂, 0.6% by weight of Al₂0₃, 0.6% by weight of Fe₂0₃, 0.5% by weight of CaO, 0.4% by weight of Na₂0, 3.0% by weight of Si₃N₄, 56.0% by weight of SiC, and 18.9% by weight of C.

13. The ingot mold according to claim 1 , wherein the ceramic compound contains 4.0% by weight of Si0₂, 1.0% by weight of Ti0₂, 5.0% by weight of Al₂0₃, 1.0% by weight of Fe₂0₃, 0.5% by weight of Na₂0, 2.5% by weight of B₂0₃, 3.0% by weight of Si, 45.0% by weight of SiC, and 38.0% by weight of C.

14. The ingot mold according to claim 1 , wherein the ceramic compound contains from 80.0% to 99.99% by weight of Hf0₂.

15. The ingot mold according to claim , wherein the ceramic compound contains from 80.0% to 99.99% by weight of BeO.

16. The ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body provided with one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold is characterized in that said container body and/or said lid are at least partially constituted by a refractory alloy that comprises at least one from the following refractory metals: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe.

17. The ingot mold according to claim 16, wherein the refractory alloy contains from 80.0% to 99.99% by weight of Ta.

18. The ingot mold according to claim 16, wherein the refractory alloy contains from 99.0% to 99.99% by weight of W.

19. The ingot mold according to claim 16, wherein the refractory alloy contains from 50.0% to 99.99% by weight of Mo.

20. The ingot mold according to claim 16, wherein the refractory alloy contains from 40.0% to 99.99% by weight of Ti.

21. The ingot mold according to claim 16, wherein the refractory alloy contains from 30.0% to 99.99% by weight of Pt.

22. The ingot mold according to claim 16, wherein the refractory alloy contains from 50.0% to 99.99% by weight of Pd.

23. The ingot mold according to claim 16, wherein the refractory alloy contains from 80.0% to 99.99% by weight of Nb.

24. The ingot mold according to claim 16, wherein the refractory alloy contains from 90.0% to 99.99% by weight of Rh.

25. The ingot mold according to claim 16, wherein the refractory alloy contains from 90.0% to 99.99% by weight of Ir.

26. The ingot mold according to claim 16, wherein the refractory alloy contains from 50.0% to 99.99% by weight of Co.

27. The ingot mold according to claim 16, wherein the refractory alloy contains from 50.0% to 99.99% by weight of Zr.

28. The ingot mold according to claim 16, wherein the refractory alloy contains from 90.0% to 99.99% by weight of Fe.

29. An ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body provided with one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold is characterized in that said container body and/or said lid comprise, at least in the stations that can come into contact with said metal, a protective coating that comprises at least one from the following refractory materials: BN, C, Hf0₂, MgO, SiC, Si₃N₄, Si0₂, TiC, Ti0₂, WC, Y₂0₃, and ZrO_s.

30. The ingot mold according to claim 29, wherein the protective coating contains from 95.0% to 99.99% by weight of BN.

31. The ingot mold according to claim 29, wherein the protective coating contains from 95.0% to 99.99% by weight of C.

32. The ingot mold according to claim 29, wherein the protective coating contains from 90.0% to 99.99% by weight of Hf0₂.

33. The ingot mold according to claim 29, wherein the protective coating contains from 80.0% to 99.99% by weight of MgO.

34. The ingot mold according to claim 29, wherein the protective coating contains from 80.0% to 99.99% by weight of SiC.

35. The ingot mold according to claim 29, wherein the protective coating contains from 50.0% to 99.99% by weight of Si0₂.

36. The ingot mold according to claim 29, wherein the protective coating contains from 90.0% to 99.99% by weight of Zr0₂.

37. The ingot mold according to claim 29, wherein the protective coating contains from 90.0%> to 99.99% by weight of Ti0₂.

38. The ingot mold according to claim 29, wherein the protective coating contains from 99.0% to 99.99% by weight of Si₃N₄.

39. The ingot mold according to claim 29, wherein the protective coating contains from 90.0% to 99.99% by weight of Y₂0₃.

40. The ingot mold according to claim 29, wherein the protective coating contains from 99.0% to 99.99% by weight of TiC.

41. The ingot mold according to claim 29, wherein the protective coating contains from 99.0% to 99.99% by weight of WC.

42. An ingot mold, particularly for the continuous production of ingots and bars of precious metal by means of tunnel-type furnaces, comprising a container body provided with one or more molding impressions and a lid adapted to temporarily close said molding impressions; said ingot mold is characterized in that said container body and/or said lid comprise, at least in the stations that can come into contact with said metal, a protective coating that comprises at least one from the following refractory metals: Ta, W, Mo, Ti, Pt, Pd, Nb, Rh, Ir, Co, Zr, and Fe.

43. The ingot mold according to claim 42, wherein said protective coating comprises the quantities of refractory metals respectively indicated in claims from 17 to 28.

44. The ingot mold according to claims 29 and 42, wherein said protective coating is obtained by means of physical vapor deposition (PVD).

45. The ingot mold according to claims 29 and 42, wherein said protective coating is obtained by means of chemical vapor deposition (CVD).

46. The ingot mold according to claims 29 and 42, wherein said protective coating is obtained by means of thermal spray (TS).

47. The ingot mold according to one or more of the preceding claims, characterized in that said lid is movable between at least one first position and at least one second position with a gradual reduction, during the melting process, of the volume of the material to be melted that is contained in said molding impressions; in said first position said lid rests on said material to be melted, but without resting on said container body; in said second position said lid rests on said container body, temporarily closing said molding impressions but without resting on the melted material.