Coating compositions for articles of graphite-alumina refractory material

• US 5,840,433 A
• Filed: 03/13/1996
• Issued: 11/24/1998
• Est. Priority Date: 10/27/1993
• Status: Expired due to Fees

• Current Assignee: Foseco International Limited (Vesuvius Plc)
• Original Assignee: Foseco International Limited (Vesuvius Plc)
• Inventors: Juma, Kassum
• Primary Examiner(s): Krynski, William
• Assistant Examiner(s): Bahta, Abraham
• Application Number:
  US08/617,842
• Time in Patent Office: 986 Days
• Field of Search: 428/446, 428/689, 428/699, 428/469, 428/408, 428/403, 428/34.4, 428/34.6, 428/384, 428/323, 428/328, 428/368, 428/432, 428/433, 428/457, 428/472, 428/701, 428/702, 427/443.2, 106/38.35, 106/38.3, 501/133, 501/95, 501/109, 501/94, 501/88, 501/100
• US Class Current: 428/632
• CPC Class Codes: C04B 2111/0087 for metallurgical applications
• CPC Class Codes: C04B 35/103 containing non-oxide refractory materials, e.g. carbon C04B35/106 takes precedence
• CPC Class Codes: C04B 41/009 characterised by the material treated
• CPC Class Codes: C04B 41/5024 Silicates C04B41/5022 takes precedence; silico-fluorides C04B41/5018
• CPC Class Codes: C04B 41/5025 with ceramic materials copper oxide or solid solutions thereof C04B41/5074
• CPC Class Codes: C04B 41/5089 Silica sols, alkyl, ammonium or alkali metal silicate cements
• CPC Class Codes: C04B 41/85 with inorganic materials
• CPC Class Codes: Y10T 428/12611 Oxide-containing component
• CPC Class Codes: Y10T 428/1275 Next to Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/12944 Ni-base component

Abstract

A refractory article of manufacture comprises an article of graphite-alumina refractory material coated with at least one mineral having a sheet structure and a refractory oxide bond. The coating protects the article against thermal shock. A typical mineral having a sheet structure may be talc, a mica, vermiculite, antigorite, kaolinite, montmorillonite, pyrophyllite, or combinations of these materials. A typical refractory oxide bond is formed from alumina gel, silica sol, alumina sol, zirconia sol, or combinations of these materials (such as a combination of alumina gel and cationic silica sol). The coating may also contain a minor proportion of fibrous material and a minor proportion of particulate refractory filler other than the mineral having a sheet structure, and a portion of the mineral content of the mineral forming the sheet structure may include graphite. The coating may be in the form of a fluid having 5-50% by weight of mineral having a street structure, 20-60% by weight of refractory oxide binder for forming the refractory oxide bond, and 20-50% by weight of carrier liquid. The carrier liquid is removed by drying (e.g. in an oven).

Claims

1. A refractory article of manufacture comprising:

an article of graphite-alumina refractory material coated with at least one mineral having a sheet structure and a refractory oxide bond.

2. An article as recited in claim 1 wherein said at least one mineral having a sheet structure comprises talc, a mica, vermiculite, antigorite, kaolinite, montmorillonite, pyrophyllite, or a combination thereof.

3. An article as recited in claim 2 wherein said at least one mineral includes at least some graphite.

4. An article as recited in claim 2 wherein said refractory oxide bond is formed from alumina gel, silica sol, alumina sol, zirconia sol, or a combination thereof.

5. An article as recited in claim 4 wherein said refractory oxide bond is formed from a combination of alumina gel and cationic silica sol.

6. An article as recited in claim 5 wherein said coating also includes a minor proportion of a fibrous material.

7. An article as recited in claim 6 wherein said coating also comprises a minor proportion of a particulate refractory material other than said at least one mineral having a sheet structure.

8. An article as recited in claim 1 wherein said coating comprises a composition that is applied to said article and then dried to remove carrier liquid, said composition comprising, when applied, 5-50% by weight of said at least one mineral having a sheet structure, 20-60% by weight of a refractory oxide binder forming said refractory oxide bond, and 20-50% by weight of carrier liquid.

9. An article as recited in claim 1 wherein said at least one mineral includes at least some graphite.

10. An article as recited in claim 1 wherein said refractory oxide bond is formed from alumina gel, silica sol, alumina sol, zirconia sol, or a combination thereof.

11. An article as recited in claim 1 wherein said refractory oxide bond is formed from a combination of alumina gel and cationic silica sol.

12. An article as recited in claim 1 wherein said coating also includes a minor proportion of a fibrous material.

13. An article as recited in claim 1 wherein said coating also comprises a minor proportion of a particulate refractory material other than said at least one mineral having a sheet structure.

14. An article as recited in claim 3 wherein said refractory oxide bond is formed from alumina gel, silica sol, alumina sol, zirconia sol, or a combination thereof.

15. An article as recited in claim 2 wherein said coating also includes a minor proportion of a fibrous material.

16. An article as recited in claim 2 wherein said coating also comprises a minor proportion of a particulate refractory material other than said at least one mineral having a sheet structure.

17. An article as recited in claim 10 wherein said coating also includes a minor proportion of a fibrous material.

18. An article as recited in claim 10 wherein said coating also comprises a minor proportion of a particulate refractory material other than said at least one mineral having a sheet structure.

19. A method of manufacturing a refractory article comprising the step of:

(a) coating a graphite-alumina refractory material article with at least one mineral having a sheet structure and a refractory oxide bond.

20. A method as recited in claim 19 wherein step (a) is practiced by applying a fluid composition comprising 5-50% by weight of the at least one mineral having a sheet structure, 20-60% by weight of a refractory oxide binder for forming the refractory oxide bond, and 20-50% by weight of carrier liquid;

and drying the coating composition to remove the carrier liquid.