US4567103A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Carbonaceous articles having oxidation prohibitive coatings thereon
Assignee: Graftech Technology LLC
•
Filing: 1984-07-12
•
Granted: 1986-01-28
•
Expires: 2004-07-12
Abstract
Abstract A carbonaceous article, e.g., a carbon or graphite electrode, is provided with an oxidation prohibitive coating comprising a compliant, low strength, porous, sintered, particulate, refractory, ceramic material. A cover layer is preferably applied over this compliant, low strength, ceramic layer, the cover layer comprising a rigid, glassy substance which is plastic and flowable at temperatures above about 750 DEG C.
Inventors
- 👤 Raymond V. Sara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:05
CPC Classifications
C; C04; C04B; C04B41/00; C04B41/009; C04B41/45; C04B41/50; C04B41/5025; C04B41/5076; C04B41/5089; C04B41/52; C04B41/80; C04B41/81; C04B41/85; C04B41/87; C04B41/89; H; H05; H05B; H05B7/00; H05B7/02; H05B7/06; H05B7/08; H05B7/085; Y; Y10; Y10T; Y10T428/00; Y10T428/30
Claims Analysis
Total Claims: 111
Claim 1
Independent Claim
36 words
An article comprising a carbonaceous substrate and an oxidation prohibitive coating overlying and bonded to said substrate, said coating comprising a compliant, low strength, porous, particulate, sintered, ceramic, refractory material containing mullite as a major ingredient.
Claim 2
Dependent Claim
36 words
An article comprising a carbonaceous substrate and an oxidation prohibitive coating overlying and bonded to said substrate, said coating comprising a compliant, low strength, porous, particulate, sintered, ceramic, refractory material containing mullite as a major ingredient.
Claim 3
Dependent Claim
16 words
An article according to claim 1 wherein said coating comprises mullite, aluminum oxide and silicon particles.
Claim 4
Dependent Claim
22 words
An article according to claim 2 wherein said particles are loosely bonded to one another with many void spaces between said particles.
Claim 5
Dependent Claim
13 words
An article according to claim 2 wherein said coating also comprises refractory fibers.
Claim 6
Dependent Claim
16 words
An article according to claim 4 wherein said refractory fibers comprise aluminum, silicon, nitrogen and oxygen.
Claim 7
Dependent Claim
15 words
An article according to claim 5 wherein said refractory fibers comprise a nitrous aluminosilicate compound.
Claim 8
Dependent Claim
21 words
An article according to claim 5 wherein said refractory fibers are arranged in clusters within said void spaces between said particles.
Claim 9
Dependent Claim
19 words
An article according to claim 4 wherein said coating also comprises hollow aluminum oxide shells containing said refractory fibers.
Claim 10
Dependent Claim
27 words
An article according to claim 1 wherein the bond between said coating and said substrate comprises refractory fibers formed in situ within the pores of said substrate.
Claim 11
Dependent Claim
16 words
An article according to claim 9 wherein said refractory fibers comprise aluminum, silicon, nitrogen and oxygen.
Claim 12
Dependent Claim
15 words
An article according to claim 10 wherein said refractory fibers comprise a nitrous aluminosilicate compound.
Claim 13
Dependent Claim
98 words
An article comprising a carbonaceous substrate and an oxidation prohibitive coating thereon, said coating comprising a base layer overlying and bonded to said substrate, said base layer being composed of a compliant, low strength, porous, sintered, particulate, ceramic, refractory material containing mullite as a major ingredient, said material having a tensile strength which is substantially less than the shear strength of the interfacial bond between said base layer and said substrate, and a cover layer overlying and bonded to said base layer comprising a rigid, glassy substance which is plastic and flowable at temperatures above about 750° C.
Claim 14
Dependent Claim
98 words
An article comprising a carbonaceous substrate and an oxidation prohibitive coating thereon, said coating comprising a base layer overlying and bonded to said substrate, said base layer being composed of a compliant, low strength, porous, sintered, particulate, ceramic, refractory material containing mullite as a major ingredient, said material having a tensile strength which is substantially less than the shear strength of the interfacial bond between said base layer and said substrate, and a cover layer overlying and bonded to said base layer comprising a rigid, glassy substance which is plastic and flowable at temperatures above about 750° C.
Claim 15
Dependent Claim
17 words
An article according to claim 12 wherein said base layer comprises mullite, aluminum oxide and silicon particles.
Claim 16
Dependent Claim
22 words
An article according to claim 13 wherein said particles are loosely bonded to one another with many void spaces between said particles.
Claim 17
Dependent Claim
14 words
An article according to claim 14 wherein said base layer also comprises refractory fibers.
Claim 18
Dependent Claim
16 words
An article according to claim 15 wherein said refractory fibers comprise aluminum, silicon, nitrogen and oxygen.
Claim 19
Dependent Claim
15 words
An article according to claim 16 wherein said refractory fibers comprise a nitrous aluminosilicate compound.
Claim 20
Dependent Claim
21 words
An article according to claim 14 wherein said refractory fibers are arranged in clusters within said void spaces between said particles.
Claim 21
Dependent Claim
20 words
An article according to claim 15 wherein said base layer also comprises hollow aluminum oxide shells containing said refractory fibers.
Claim 22
Dependent Claim
24 words
An article according to claim 12 wherein said cover layer comprises oxides of aluminum, sodium and silicon and metallic carbides of silicon or boron.
Claim 23
Dependent Claim
17 words
An article according to claim 20 wherein said cover layer comprises particles of mullite and silicon carbide.
Claim 24
Dependent Claim
17 words
An article according to claim 12 wherein said cover layer comprises oxides of boron, sodium and silicon.
Claim 25
Dependent Claim
28 words
An article according to claim 15 wherein the bond between said base layer and said substrate comprises refractory fibers formed in situ within the pores of said substrate.
Claim 26
Dependent Claim
16 words
An article according to claim 22 wherein said refractory fibers comprise aluminum, silicon, nitrogen and oxygen.
Claim 27
Dependent Claim
15 words
An article according to claim 23 wherein said refractory fibers comprise a nitrous aluminosilicate compound.
Claim 28
Dependent Claim
45 words
An article according to claim 13 wherein said base layer has a modulus of elasticity of about 5.9×10 6 pounds per square inch, a flexural strength of about 2500 pounds per square inch and a coefficient of thermal expansion (CTE) of about 5.5×10 -6 inch/inch/°C.
Claim 29
Dependent Claim
23 words
An article according to claim 13 wherein said cover layer has a modulus of elasticity of about 8×10 6 pounds per square inch.
Claim 30
Dependent Claim
28 words
An article according to claim 13 wherein said carbonaceous substrate comprises electrode grade graphite having a coefficient of thermal expansion (CTE) of less than about 1.5×10 -6 inch/inch/°C.
Claim 31
Dependent Claim
17 words
An electric arc furnace electrode having a coating according to any one of claims 12 to 27.
Claim 32
Dependent Claim
85 words
An article comprising a carbonaceous substrate having an oxidation prohibitive coating thereon which can be rendered resistant to thermal shock upon heating to elevated temperatures above about 1000° C., said coating comprising at least one layer of a dry, particulate composition comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material.
Claim 33
Dependent Claim
85 words
An article comprising a carbonaceous substrate having an oxidation prohibitive coating thereon which can be rendered resistant to thermal shock upon heating to elevated temperatures above about 1000° C., said coating comprising at least one layer of a dry, particulate composition comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material.
Claim 34
Dependent Claim
27 words
An article according to claim 30 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and colloidal silica.
Claim 35
Dependent Claim
38 words
An article according to claim 31 wherein said dry, particulate composition comprises about 52.3 percent by weight mullite, about 10.4 percent by weight silica, about 26.7 percent by weight aluminum and about 9.6 percent by weight sodium silicate.
Claim 36
Dependent Claim
83 words
An article according to claim 30 wherein said coating comprises an additional layer overlying said first layer, said additional layer being composed of a dry, particulate composition comprising 0 to about 70 percent by weight mullite, 0 to about 14 percent by weight silica, from about 5 to about 95 percent by weight of a metallic carbide selected from the group consisting of silicon carbide and boron carbide, and from about 5 to about 14 percent by weight of a silicon-containing binder material.
Claim 37
Dependent Claim
27 words
An article according to claim 33 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and colloidal silica.
Claim 38
Dependent Claim
39 words
An article according to claim 34 wherein said dry, particulate composition comprises about 57.7 percent by weight mullite, about 11.0 percent by weight silica, about 20.3 percent by weight silicon carbide and about 10.6 percent by weight sodium silicate.
Claim 39
Dependent Claim
39 words
An article according to claim 34 wherein said dry, particulate composition comprises about 57.7 percent by weight mullite, about 11 percent by weight silica, about 20.3 percent by weight boron carbide and about 10.6 percent by weight sodium silicate.
Claim 40
Dependent Claim
61 words
An article according to claim 33 wherein said coating comprises an outer layer overlying said additional layer, said outer layer being composed of a dry, particulate composition comprising from about 25 to about 85 percent by weight borosilicate frit, from about 5 to about 15 percent by weight silicon-containing binder material and 0 to about 65 percent by weight filler material.
Claim 41
Dependent Claim
49 words
An article according to claim 37 wherein said borosilicate frit comprises from about 7 to about 52 percent by weight Na 2 O, from about 8 to about 64 percent by weight B 2 O 3 and from about 6 to about 68 percent by weight SiO 2 .
Claim 42
Dependent Claim
27 words
An article according to claim 37 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium, silicate, ethyl silicate and collodial silica.
Claim 43
Dependent Claim
30 words
An article according to claim 37 wherein said filler material is selected from the group consisting of Al 2 O 3 , SiC, mullite, SiO 2 and B 4 C.
Claim 44
Dependent Claim
61 words
An article according to claim 33 wherein said coating comprises an additional layer overlying said first layer, said additional layer being composed of a dry, particulate composition comprising from about 25 to about 85 percent by weight borosilicate frit, from about 5 to about 15 percent by weight silicon-containing binder material and 0 to about 65 percent by weight filler material.
Claim 45
Dependent Claim
49 words
An article according to claim 41 wherein said borosilicate frit comprises from about 7 to about 52 percent by weight Na 2 O, from about 8 to about 64 percent by weight B 2 O 3 and from about 6 to about 68 percent by weight SiO 2 .
Claim 46
Dependent Claim
27 words
An article according to claim 41 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and collodial silica.
Claim 47
Dependent Claim
30 words
An article according to claim 41 wherein said filler material is selected from the group consisting of Al 2 O 3 , SiC, mullite, SiO 2 and B 4 C.
Claim 48
Dependent Claim
31 words
An article according to claim 30 or 33 wherein said carbonaceous substrate is composed of electrode grade graphite having a coefficient of thermal expansion (CTE) less than about 1.5×10 -6 inch/inch/°C.
Claim 49
Dependent Claim
17 words
An electric arc furnace electrode having a coating according to any one of claims 30 to 44.
Claim 50
Dependent Claim
70 words
A coating composition for applying an oxidation prohibitive coating onto a carbonaceous substrate, which comprises from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients.
Claim 51
Dependent Claim
70 words
A coating composition for applying an oxidation prohibitive coating onto a carbonaceous substrate, which comprises from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients.
Claim 52
Dependent Claim
28 words
A coating composition according to claim 47 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and colloidal silica.
Claim 53
Dependent Claim
34 words
A coating composition according to claim 48 comprising about 52.3 percent by weight mullite, about 10.4 percent by weight silica, about 26.7 percent by weight aluminum and about 9.6 percent by weight sodium silicate.
Claim 54
Independent Claim
105 words
A method of protecting a carbonaceous article against oxidation and erosion at elevated temperatures, which comprises: (a) applying to the surfaces of said carbonaceous article a particulate mixture comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum, and from about 5 to about 11 percent by weight of a silicon-containing binder materal, all percentages being based upon the total weight of the dry ingredients; and (b) heating said particulate mixture to temperatures at which silica is reduced by aluminum to produce aluminum oxide and silicon.
Claim 55
Independent Claim
105 words
A method of protecting a carbonaceous article against oxidation and erosion at elevated temperatures, which comprises: (a) applying to the surfaces of said carbonaceous article a particulate mixture comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum, and from about 5 to about 11 percent by weight of a silicon-containing binder materal, all percentages being based upon the total weight of the dry ingredients; and (b) heating said particulate mixture to temperatures at which silica is reduced by aluminum to produce aluminum oxide and silicon.
Claim 56
Dependent Claim
27 words
A method according to claim 41 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and colloidal silica.
Claim 57
Dependent Claim
37 words
A method according to claim 50 wherein said particulate mixture comprises about 52.3 percent by weight mullite, about 10.4 percent by weight silica, about 26.7 percent by weight aluminum and about 9.6 percent by weight sodium silicate.
Claim 58
Dependent Claim
26 words
A method according to claim 50 wherein said particulate mixture is applied to the surfaces of said carbonaceous article in the form of an aqueous slurry.
Claim 59
Dependent Claim
24 words
A method according to claim 53 wherein said slurry is dried under conditions to produce a hard coherent layer adhering to said carbonaceous article.
Claim 60
Dependent Claim
16 words
A method according to claim 54 wherein said slurry is dried in air at ambient temperatures.
Claim 61
Dependent Claim
22 words
A method according to claim 54 wherein said dried coherent layer is heated to a temperature of at least about 1000° C.
Claim 62
Independent Claim
218 words
A method of protecting a carbonaceous article against oxidation and erosion at elevated temperatures, which comprises: (a) applying to the surfaces of said carbonaceous article a first particulate mixture comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients; (b) applying to said first particulate mixture a second particulate mixture comprising 0 to about 70 percent by weight mullite, 0 to about 14 percent by weight silica, from about 5 to about 95 percent by weight of a metallic carbide selected from the group consisting of silicon carbide and boron carbide, and from about 5 to about 15 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients; (c) heating said first particulate mixture either before or after step (b) to a temperature at which silica is reduced by aluminum to produce aluminum oxide and silicon; and (d) heating said second particulate mixture either simultaneously with or after step (c) to a temperature at which a rigid, glassy cover layer is formed.
Claim 63
Independent Claim
218 words
A method of protecting a carbonaceous article against oxidation and erosion at elevated temperatures, which comprises: (a) applying to the surfaces of said carbonaceous article a first particulate mixture comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients; (b) applying to said first particulate mixture a second particulate mixture comprising 0 to about 70 percent by weight mullite, 0 to about 14 percent by weight silica, from about 5 to about 95 percent by weight of a metallic carbide selected from the group consisting of silicon carbide and boron carbide, and from about 5 to about 15 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients; (c) heating said first particulate mixture either before or after step (b) to a temperature at which silica is reduced by aluminum to produce aluminum oxide and silicon; and (d) heating said second particulate mixture either simultaneously with or after step (c) to a temperature at which a rigid, glassy cover layer is formed.
Claim 64
Dependent Claim
32 words
A method according to claim 57 wherein said silicon-containing binder material in said first particulate mixture is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and colloidal silica.
Claim 65
Dependent Claim
38 words
A method according to claim 58 wherein said first particulate mixture comprises about 52.3 percent by weight mullite, about 10.4 percent by weight silica, about 26.7 percent by weight aluminum and about 9.6 percent by weight sodium silicate.
Claim 66
Dependent Claim
32 words
A method according to claim 57 wherein said silicon-containing binder material in said second particulate mixture is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and colloidal silica.
Claim 67
Dependent Claim
40 words
A method according to claim 60 wherein said second particulate mixture comprises about 57.7 percent by weight mullite, about 11.0 percent by weight silica, about 20.3 weight percent by weight silicon carbide and about 10.6 percent by weight sodium silicate.
Claim 68
Dependent Claim
27 words
A method according to claim 57 wherein said first particulate mixture is applied to the surfaces of said carbonaceous article in the form of an aqueous slurry.
Claim 69
Dependent Claim
24 words
A method according to claim 62 wherein said slurry is dried under conditions to produce a hard coherent layer adhering to said carbonaceous article.
Claim 70
Dependent Claim
16 words
A method according to claim 63 wherein said slurry is dried in air at ambient temperature.
Claim 71
Dependent Claim
21 words
A method according to claim 63 wherein said dried coherent layer is heated to temperature of at least about 1000° C.
Claim 72
Dependent Claim
25 words
A method according to claim 63 wherein said second particulate mixture is applied to said first particulate mixture in the form of an aqueous slurry.
Claim 73
Dependent Claim
25 words
A method according to claim 66 wherein said slurry is dried under conditions to produce a hard coherent layer adhering to said first particulate mixture.
Claim 74
Dependent Claim
16 words
A method according to claim 67 wherein said slurry is dried in air at ambient temperature.
Claim 75
Dependent Claim
22 words
A method according to claim 67 wherein said dried coherent layer is heated to a temperature of at least about 1000° C.
Claim 76
Dependent Claim
76 words
A method according to claim 57 wherein a third particulate mixture is applied to said second particulate mixture, said third particulate mixture comprising from about 25 to about 85 percent by weight borosilicate frit, from about 5 to about 15 percent by weight silicon-containing binder material and 0 to about 65 percent by weight filler material, and wherein said third particulate mixture is heated to a temperature at which a rigid, glassy cover layer is formed.
Claim 77
Dependent Claim
49 words
A method according to claim 70 wherein said borosilicate frit comprises from about 7 to about 52 percent by weight Na 2 O, from about 8 to about 64 percent by weight B 2 O 3 and from about 6 to about 68 percent by weight SiO 2 .
Claim 78
Dependent Claim
27 words
A method according to claim 70 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and collodial silica.
Claim 79
Dependent Claim
30 words
A method according to claim 70 wherein said filler material is selected from the group consisting of Al 2 O 3 , SiC, mullite, SiO 2 and B 4 C.
Claim 80
Independent Claim
196 words
A method of protecting a carbonaceous article against oxidation and erosion at elevated temperatures, which comprises: (a) applying to the surfaces of said carbonaceous article a first particulate mixture comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients; (b) applying to said first particulate mixture a second particulate mixture comprising from about 25 to about 85 percent by weight borosilicate frit, from about 5 to about 15 percent by weight silicon-containing binder material and 0 to about 65 percent by weight filler material, all percentages being based upon the total weight of the dry ingredients; (c) heating said first particulate mixture either before or after step (b) to a temperature at which silica is reduced by aluminum to produce aluminum oxide and silicon; and (d) heating said second particulate mixture either simultaneously with or after step (c) to a temperature at which a rigid, glassy cover layer is formed.
Claim 81
Independent Claim
196 words
A method of protecting a carbonaceous article against oxidation and erosion at elevated temperatures, which comprises: (a) applying to the surfaces of said carbonaceous article a first particulate mixture comprising from about 30 to about 75 percent by weight mullite, 0 to about 12 percent by weight silica, from about 15 to about 60 percent by weight aluminum and from about 5 to about 11 percent by weight of a silicon-containing binder material, all percentages being based upon the total weight of the dry ingredients; (b) applying to said first particulate mixture a second particulate mixture comprising from about 25 to about 85 percent by weight borosilicate frit, from about 5 to about 15 percent by weight silicon-containing binder material and 0 to about 65 percent by weight filler material, all percentages being based upon the total weight of the dry ingredients; (c) heating said first particulate mixture either before or after step (b) to a temperature at which silica is reduced by aluminum to produce aluminum oxide and silicon; and (d) heating said second particulate mixture either simultaneously with or after step (c) to a temperature at which a rigid, glassy cover layer is formed.
Claim 82
Dependent Claim
32 words
A method according to claim 74 wherein said silicon-containing binder material in said first particulate mixture is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and collodical silica.
Claim 83
Dependent Claim
38 words
A method according to claim 75 wherein said first particulate mixture comprises about 52.3 percent by weight mullite, about 10.4 percent by weight silica, about 26.7 percent by weight aluminum and about 9.6 percent by weight sodium silicate.
Claim 84
Dependent Claim
49 words
A method according to claim 74 wherein said borosilicate frit comprises from about 7 to about 52 percent by weight Na 2 O, from about 8 to about 64 percent by weight B 2 O 3 and from about 6 to about 68 percent by weight SiO 2 .
Claim 85
Dependent Claim
27 words
A method according to claim 74 wherein said silicon-containing binder material is selected from the group consisting of sodium silicate, potassium silicate, ethyl silicate and collodical silica.
Claim 86
Dependent Claim
30 words
A method according to claim 74 wherein said filler material is selected from the group consisting of Al 2 O 3 , SiC, mullite, SiO 2 and B 4 C.
Claim 87
Dependent Claim
27 words
A method according to claim 74 wherein said first particulate mixture is applied to the surfaces of said carbonaceous article in the form of an aqueous slurry.
Claim 88
Dependent Claim
24 words
A method according to claim 74 wherein said slurry is dried under conditions to produce a hard coherent layer adhering to said carbonaceous article.
Claim 89
Dependent Claim
16 words
A method according to claim 74 wherein said slurry is dried in air at ambient temperature.
Claim 90
Dependent Claim
22 words
A method according to claim 74 wherein said dried coherent layer is heated to a temperature of at least about 1000° C.
Claim 91
Dependent Claim
25 words
A method according to claim 74 wherein said second particulate mixture is applied to said first particulate mixture in the form of an aqueous slurry.
Claim 92
Dependent Claim
25 words
A method according to claim 84 wherein said slurry is dried under conditions to produce a hard coherent layer adherent to said first particulate layer.
Claim 93
Dependent Claim
16 words
A method according to claim 85 wherein said slurry is dried in air at ambient temperature.
Claim 94
Dependent Claim
22 words
A method according to claim 85 wherein said dried coherent layer is heated to a temperature of at least about 1000° C.
Claim 95
Dependent Claim
137 words
In an electric arc furnace for producing steel wherein an electric current is passed through a graphite electrode to establish an electric arc between the tip of said electrode and the molten metal, the improvement which comprises a graphite electrode having an oxidation prohibitive coating thereon, said coating comprising a base layer overlying and bonded to the surfaces of said graphite electrode, said base layer being composed of a compliant, low strength, porous, sintered, particulate, ceramic, refractory material containing mullite as a major ingredient, said material having a tensile strength which is substantially less than the shear strength of the interfacial bond between the base layer and said graphite electrode, and a cover layer overlying and bonded to said base layer comprising a rigid, glassy substance which is plastic and flowable at temperatures above about 750° C.
Claim 96
Dependent Claim
137 words
In an electric arc furnace for producing steel wherein an electric current is passed through a graphite electrode to establish an electric arc between the tip of said electrode and the molten metal, the improvement which comprises a graphite electrode having an oxidation prohibitive coating thereon, said coating comprising a base layer overlying and bonded to the surfaces of said graphite electrode, said base layer being composed of a compliant, low strength, porous, sintered, particulate, ceramic, refractory material containing mullite as a major ingredient, said material having a tensile strength which is substantially less than the shear strength of the interfacial bond between the base layer and said graphite electrode, and a cover layer overlying and bonded to said base layer comprising a rigid, glassy substance which is plastic and flowable at temperatures above about 750° C.
Claim 97
Dependent Claim
17 words
The improvement according to claim 88 wherein said base layer comprises mullite, aluminum oxide and silicon particles.
Claim 98
Dependent Claim
21 words
The improvement according to claim 89 wherein said particles are loosely bonded to one another with many void spaces between particles.
Claim 99
Dependent Claim
14 words
The improvement according to claim 89 wherein said base layer also comprises refractory fibers.
Claim 100
Dependent Claim
16 words
The improvement according to claim 91 wherein said refractory fibers comprise aluminum, silicon, nitrogen and oxygen.
Claim 101
Dependent Claim
15 words
The improvement according to claim 92 wherein said refractory fibers comprise a nitrous aluminosilicate compound.
Claim 102
Dependent Claim
21 words
The improvement according to claim 91 wherein said refractory fibers are arranged in clusters within said void spaces between said particle.
Claim 103
Dependent Claim
20 words
The improvement according to claim 91 wherein said base layer also comprises hollow aluminum oxide shells containing said refractory fibers.
Claim 104
Dependent Claim
25 words
The improvement according to claim 91 wherein said rigid, glassy layer comprises oxides of aluminum, sodium and silicon and metallic carbides of silicon or boron.
Claim 105
Dependent Claim
18 words
The improvement according to claim 88 wherein said rigid, glassy layer contains particles of mullite and silicon carbide.
Claim 106
Dependent Claim
18 words
An article according to claim 88 wherein said rigid, glassy layer comprises oxides of boron, sodium and silicon.
Claim 107
Dependent Claim
29 words
The improvement according to claim 91 wherein the bond between said base layer and said graphite electrode comprises refractory fibers formed in situ within the pores of the graphite.
Claim 108
Dependent Claim
16 words
The improvement according to claim 99 wherein said refractory fibers complete aluminum, silicon, nitrogen and oxygen.
Claim 109
Dependent Claim
15 words
The improvement according to claim 100 wherein said refractory fibers comprise a nitrous aluminosilicate compound.
Claim 110
Dependent Claim
275 words
In the production of steel within an electric arc furnace wherein an electric current is passed through a graphite electrode to establish an electric arc between the tip of said electrode and the molten metal, a process for protecting said electrode against oxidation and erosion at the operating temperatures of said furnace, which comprises: (a) applying to said graphite electrode a protective coating comprising a base layer overlying and bonded to said electrode, said base layer being composed of a compliant, low strength, porous, sintered, particulate, ceramic refractory material containing mullite as a major ingredient, said material having a shear strength which is substantially less than the shear strength of the interfacial bond between said base layer and said graphite electrode and a cover layer overlying and bonded to said base layer comprising a rigid, glassy substance which is plastic and flowable at said operating furnace temperatures, said rigid, glassy cover layer having a co-efficient of thermal expansion which is substantially greater than that of said graphite electrode; (b) heating said furnace and said coated electrode to said operating furnace temperatures; (c) cooling said coated electrode to a temperature which is substantially lower than said operating furnace temperatures whereby said base and cover layers contract at a greater rate than said graphite electrode and produce in said layers a high tensile stress causing microcracks which extend in a direction toward the interface between said base layer and said graphite electrode; and (d) reheating the coated electrode to said operating furnace temperatures whereby said rigid, glassy cover layer is rendered plastic and flowable and seals off said microcracks prohibiting ingress of oxygen toward said graphite electrode.
Claim 111
Dependent Claim
275 words
In the production of steel within an electric arc furnace wherein an electric current is passed through a graphite electrode to establish an electric arc between the tip of said electrode and the molten metal, a process for protecting said electrode against oxidation and erosion at the operating temperatures of said furnace, which comprises: (a) applying to said graphite electrode a protective coating comprising a base layer overlying and bonded to said electrode, said base layer being composed of a compliant, low strength, porous, sintered, particulate, ceramic refractory material containing mullite as a major ingredient, said material having a shear strength which is substantially less than the shear strength of the interfacial bond between said base layer and said graphite electrode and a cover layer overlying and bonded to said base layer comprising a rigid, glassy substance which is plastic and flowable at said operating furnace temperatures, said rigid, glassy cover layer having a co-efficient of thermal expansion which is substantially greater than that of said graphite electrode; (b) heating said furnace and said coated electrode to said operating furnace temperatures; (c) cooling said coated electrode to a temperature which is substantially lower than said operating furnace temperatures whereby said base and cover layers contract at a greater rate than said graphite electrode and produce in said layers a high tensile stress causing microcracks which extend in a direction toward the interface between said base layer and said graphite electrode; and (d) reheating the coated electrode to said operating furnace temperatures whereby said rigid, glassy cover layer is rendered plastic and flowable and seals off said microcracks prohibiting ingress of oxygen toward said graphite electrode.
References Cited (Backward Citations)
DE316450C
Cited
GB894593A
Cited
US3140193A
Cited
GB955629A
Cited
US3348929A
Cited
GB1026055A
Cited
GB1166429A
Cited
JPS4826597A
Cited
US3852107A
Cited
US4301387A
Cited
JPS4926308A
Cited
JPS4929283A
Cited
JPS5248341A
Cited
JPS5318525A
Cited
JPS5447712A
Cited
JPS5527155A
Cited
US4378410A
Cited
US4384046A
Cited
JPS5841782A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-01-27 | 1989-07-29 | 1990-01-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-01-27 | 1993-07-29 | 1994-01-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-01-27 | 1997-07-29 | 1998-01-28 | $7700.00 | Window Closed / Lapsed |