Sintered refractory material based on silicon carbide with a silicon nitride binder

Patent metadata

Field	Value
Publication number	US-9321690-B2
Application number	US-86660309-A
Country	US
Kind code	B2
Filing date	Feb 5, 2009
Priority date	Feb 8, 2008
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

A sintered material based on silicon carbide (SiC) reactively sintered between 1,100° C. and 1,700° C. to form a silicon nitride binder (Si 3 N 4 ), intended in particular for fabricating an aluminum electrolysis cell, including 0.05% to 1.5% of boron, the Si 3 N 4 /SiC weight ratio being in the range 0.05 to 0.45. Application, in particular, to an electrolysis cell.

First claim

The invention claimed is:

1. A method comprising:
(A) providing a refractory shaped product based on silicon carbide (SiC) and reactively sintered between 1,100° C. and 1,700° C. to form a silicon nitride binder Si 3 N 4 , including 0.05% to 1.5% of boron as a percentage by weight, the Si 3 N 4 /SiC weight ratio being in the range of 0.05 to 0.45; and
performing in oxidizing conditions a step (B) selected from the group consisting of:
(i) submitting at least one device selected from the group consisting of kiln furniture and other firing supports to a temperature that reaches 1750° C. and to cycling variations of temperature, each of the cycles lasting less than 24 hours and the temperature varying by at least 1000° C. in any of the cycles;
(ii) submitting at least one device selected from the group consisting of a block and a tube of a muffle to a temperature that reaches 1500° C.;
(iii) submitting at least one device selected from the group consisting of a block, a tile and a tube of a domestic incineration furnace to a temperature that reaches 1300° C.;
(iv) submitting at least one device selected from the group consisting of a block, a tile and a tube of a furnace of a glass making factory to a temperature that reaches 1500° C.;
(v) submitting at least one device selected from the group consisting of a block, a tile and a tube of a metallurgical furnace to a temperature that reaches 1500° C.;
(vi) submitting at least one device selected from the group consisting of a block of a skid rail of a metallurgical furnace to a temperature that reaches 1500° C.;
(vii) submitting at least one device selected from the group consisting of a block and a tube of an immersion heater to a temperature that reaches 1500° C.; and
(viii) submitting at least one device selected from the group consisting of a heater tube, a thermocouple protective tube, and a tube for transporting molten metal to a temperature that reaches 1500° C.,
wherein at step (B), the at least one device comprises the refractory shaped product.

2. The method according to claim 1 , wherein at step (B), the at least one device is a kiln furniture chosen from the group consisting of (i) a plate; (ii) a post; (iii) a setter; (iv) a beam; and (v) a roller, or the at least one device is chosen from the group consisting of (i) a block, a tile or a tube of a furnace of a glass making factory in a location where it is not in direct contact with molten glass; (ii) a block, a tile or a tube of a holding furnace; (iii) a block, a tile or a tube of a smelting furnace for non ferrous metals; and (iv) a block of a skid rail of a furnace for the heat treatment of iron or steel bars or of other metallurgical products.

3. The method according to claim 1 , wherein the refractory shaped product has a thickness less than 1/10 of its length and/or of its width.

4. The method according to claim 3 , wherein the refractory shaped product has a thickness less than 2/100 of its length and/or of its width.

5. A firing method in which an item to be fired is supported by a firing support during firing, said firing support comprising a refractory product manufactured by the method of claim 3 and being free of any coating, at least on the surface in contact with said item, and wherein said firing support has not been passivated.

6. A firing method in which an item to be fired is supported by a firing support during firing, said firing support comprising a refractory product manufactured by the method of claim 3 and being free of any coating wherein said firing support has been passivated between 800° C. and 1600° C.

7. The method according to claim 1 , wherein the refractory shaped product has a thickness less than 10 mm.

8. The method according to claim 1 , wherein the percentage by weight of boron in the refractory shaped product is 1.2% or less.

9. The method according to claim 1 , wherein the Si 3 N 4 /SiC weight ratio in the refractory shaped product is in the range 0.1 to 0.2.

10. The method according to claim 9 , wherein silicon nitride Si 3 N 4 in the beta form in the refractory shaped product represents, as a percentage by weight, at least 80% of the whole of silicon nitride Si 3 N 4 in the beta form and in the alpha form.

11. The method according to claim 10 , wherein an amount of Si 2 ON 2 , as a percentage by weight, in the refractory shaped product is less than 5%.

12. The method according to claim 10 , wherein the percentage by weight of boron in the refractory shaped product is 1.2% or less.

13. The method according to claim 10 , wherein the refractory shaped product includes at least 0.3% by weight of boron, as a percentage by weight.

14. A method according to claim 9 , wherein an amount of Si 2 ON 2 , as a percentage by weight, in the refractory shaped product is less than 5%.

15. The method according to claim 14 , wherein the percentage by weight of boron in the refractory shaped product is 1.2% or less.

16. The method according to claim 9 , wherein the percentage by weight of boron in the refractory shaped product is 1.2% or less.

17. The method according to claim 9 , wherein the refractory shaped product includes at least 0.3% by weight of boron, as a percentage by weight.

18. The method according to claim 1 , wherein an amount of Si 2 ON 2 , as a percentage by weight, in the refractory shaped product is less than 5%.

19. The method according to claim 1 , wherein a percentage by weight of calcium in the refractory shaped product is in the range 0.05% to 1.2%.

20. The method according to claim 1 , wherein the refractory shaped product includes at least 0.3% and at most 1.5% by weight of boron, as a percentage by weight.

21. A method according to claim 1 , further comprising applying the refractory shaped product in a refractory lining of an incineration furnace to transfer heat by conduction.

22. The method according to claim 1 , further comprising applying the refractory shaped product in a refractory lining of an incineration furnace, wherein the refractory shaped product has not been submitted to an oxidative post-treatment at a temperature between 1000° C. and 1700° C.

23. The method according to claim 1 , wherein the refractory shaped product is kiln furniture or other firing support on which a coating comprising or made of metal hydrate, alumina, alumina silicate borosilicate, zirconia and mixtures thereof is deposited.

24. The method according to claim 1 , wherein said refractory shaped product is kiln furniture or other firing support free of any coating.

25. The method according to claim 1 , wherein the refractory shaped product is at least partly covered with a coating, to avoid peeling of the coating when the refractory shaped product is used as a support to sinter porcelain pieces.

26. The method according to claim 1 , wherein said refractory shaped product at step (A) is fabricated according to a method comprising the following steps in succession:
a) preparing a charge comprising a particulate mixture comprising a silicon carbide granulate and at least one boron compound;
b) forming said charge in a mold;
c) compacting said charge in the mold to form a preform;
d) unmolding said preform;
e) drying said preform; and
f) firing said preform in a reducing atmosphere of nitrogen at a temperature in the range 1100° C. to 1700° C.

27. The method according to claim 26 , wherein at step (A), the at least one boro

Assignees

• Jorge Eric
• Marguin Olivier
• Moitrier Lionel
• Citti Olivier
• Saint Gobain Ct Recherches

Inventors

• Jorge Eric
• Marguin Olivier
• Moitrier Lionel
• Citti Olivier

Classifications

• C04B2235/5427

  millimeter or submillimeter sized, i.e. larger than 0,1 mm · CPC title

• C04B2235/5436

  micrometer sized, i.e. from 1 to 100 micron · CPC title

• C25C3/085

  characterised by its non electrically conducting heat insulating parts · CPC title

• F27B3/08

  heated electrically, with or without any other source of heat · CPC title

• C04B38/0074

  expressed as porosity percentage · CPC title