Alumina or alumina-chromia refractories

Claim 2

Method of producing a shaped article of improved refractory material having high flexural strength and high resistence to physical erosion by and chemical attack by molten metals, which method comprises the steps of: (a) heating to fusion Al 2 O 3 powder to form a fused grain material, (b) crushing said fused grain material to a fused grain powder, (c) adding to said fused grain powder a binder comprising unfused Al 2 O 3 powder and chromium metal powder to form a refractory powder mixture, (d) adding water to said refractory powder mixture to make a slurry, (e) forming said slurry in a desired shape, (f) heating said formed slurry only in an oxidizing atmosphere at a sufficiently elevated temperature and for a sufficient time to complete the conversion of the chromium metal to chromium oxide and form a reaction sintered bond, and (g) cooling the thus formed shaped article to ambient temperature.

Claim 3

Method according to claim 1 wherein the crushing in step b) produced a powder at least as fine as 16 Tyler mesh.

Claim 4

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains from 45 to 55 weight percent of fused grain powder from step (b) and the balance binder.

Claim 5

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains about 50 weight percent of fused grain powder from step (b) and the balance binder.

Claim 6

Method according to claim 1 wherein the binder added in step (c) additionally contains calcium aluminate powder.

Claim 7

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains from 18 to 28 weight percent of unfused Al 2 O 3 powder.

Claim 8

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains about 21.5 weight percent of unfused Al 2 O 3 powder.

Claim 9

Method according to claim 1 wherein the unfused Al 2 O 3 powder added in step (c) is at least as fine as 325 Tyler mesh.

Claim 10

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains at least 17 weight percent of chromium metal powder.

Claim 11

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains from 20 to 30 weight percent of chromium metal powder.

Claim 12

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains about 24 weight percent of chromium metal powder.

Claim 13

Method according to claim 1 wherein the chromium metal powder added in step (c) is at least as fine as 15 microns.

Claim 14

Method according to claim 1 wherein the chromium metal powder added in step (c) has an average particle size of 5 microns.

Claim 15

Method according to claim 1 wherein the refractory powder mixture formed in step (c) contains from 3 to 6 weight percent of calcium aluminate powder.

Claim 16

Method according to claim 1 wherein the refractory powder mixture formed in step c) contains about 4 weight percent of calcium aluminate powder.

Claim 17

Method according to claim 1 wherein the temperature in step (f) is between about 1400° C. and 1700° C.

Claim 18

Method according to claim 1 wherein the temperature in step (f) is about 1650° C.

Claim 19

Method of producing a shaped article of improved refractory material having high flexural strength and high resistance to physical erosion by and chemical attack by molten metals, which method comprises the steps of: (a) heating to fusion powders of Al 2 O 3 and Cr 2 O 3 to form a fused grain material, (b) crushing said fused grain material to a fused grain powder, (c) adding to said fused grain powder a binder comprising unfused Al 2 O 3 powder and chromium metal powder to form a refractory powder mixture, (d) adding water to said refractory powder mixture to make a slurry, (e) forming said slurry in a desired shape, (f) heating said formed slurry only in an oxidizing atmosphere at a sufficiently elevated temperature and for a sufficient time to complete the conversion of the chromium metal to chromium oxide and form a reaction sintered bond, and (g) cooling the thus formed shaped article to ambient temperature.

Claim 20

Method of producing a shaped article of improved refractory material having high flexural strength and high resistance to physical erosion by and chemical attack by molten metals, which method comprises the steps of: (a) heating to fusion powders of Al 2 O 3 and Cr 2 O 3 to form a fused grain material, (b) crushing said fused grain material to a fused grain powder, (c) adding to said fused grain powder a binder comprising unfused Al 2 O 3 powder and chromium metal powder to form a refractory powder mixture, (d) adding water to said refractory powder mixture to make a slurry, (e) forming said slurry in a desired shape, (f) heating said formed slurry only in an oxidizing atmosphere at a sufficiently elevated temperature and for a sufficient time to complete the conversion of the chromium metal to chromium oxide and form a reaction sintered bond, and (g) cooling the thus formed shaped article to ambient temperature.

Claim 21

Method according to claim 18 wherein the mixture in step (a) consists of from 60 to 85 weight percent Al 2 O 3 and the balance Cr 2 O 3 .

Claim 22

Method according to claim 18 wherein the mixture in step (a) consists of about 75 weight percent Al 2 O 3 and about 25 weight percent Cr 2 O 3 .

Claim 23

Method according to claim 18 wherein the crushing in step (b) produced a powder at least as fine as 16 Tyler mesh.

Claim 24

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains about 66 weight percent of fused grain powder from step (b) and the balance binder.

Claim 25

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contained from 60 to 71 weight percent of fused grain powder from step (b) and the balance binder.

Claim 26

Method according to claim 18 wherein the binder added in step (c) additionally contains calcium aluminate powder.

Claim 27

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains from 18 to 28 weight percent of unfused Al 2 O 3 powder.

Claim 28

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains about 22.5 weight percent of unfused Al 2 O 3 powder.

Claim 29

Method according to claim 18 wherein the unfused Al 2 O 3 powder added in step (c) is at least as fine as 325 Tyler Mesh.

Claim 30

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains at least 5 weight percent of chromium metal powder.

Claim 31

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains from 7.5 to 9 weight percent of chromium metal powder.

Claim 32

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains about 8 weight percent of chromium metal powder.

Claim 33

Method according to claim 18 wherein the chromium metal powder added in step (c) is at least as fine as 15 microns.

Claim 34

Method according to claim 18 wherein the chromium metal powder added in step (c) has an average particle size of 5 microns.

Claim 35

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains from 3 to 6 weight percent of calcium aluminate powder.

Claim 36

Method according to claim 18 wherein the refractory powder mixture formed in step (c) contains about 4 weight percent of calcium aluminate powder.

Claim 37

Method according to claim 18 wherein the temperature in step (f) is between about 1400° C. and 1700° C.

Claim 38

Method according to claim 18 wherein the temperature in step (f) is about 1650° C.