Process for producing a zirconia refractory body and a product produced by the process

Claim 2

A refractory body made of at least partially stabilized zirconia and having a predetermined shape, produced by a process comprising the steps of: (1) mixing particles consisting of fine particles of zirconia having a monoclinic crystal structure and fine particles of a stabilizer composed of at least one substance selected from the group consisting of MgO, CaO and Y 2 O 3 with a binder, said zirconia particles having an average size of 0.5 to 5 μm comprising 30 to 70% by weight of particles of a diameter of 5 to 10 μm and said stabilizer particles being of a size small enough to pass through a Tyler standard sieve of 325 mesh (44 μm), and an amount of the fine particles of the stabilizer mixed being not less than 2% by weight based on a total weight of the zirconia and stabilizer particles, (2) granulating the resulting mixture to form granulated particles comprising 30 to 70% by weight of particles of a diameter of 1 to 70 μm and 70 to 30% by weight of particles of a diameter of 70 to 170 μm, (3) shaping the granulated mixture into a predetermined form and (4) firing the shaped mass thus formed at a temperature of 1,600° to 1,850° C. to promote sintering and stabilization of the zirconia particles simultaneously.

Claim 3

The refractory body according to claim 1, wherein the firing temperature is 1,700° to 1,850° C.

Claim 4

The refractory body according to claim 1 or 2, wherein the firing is carried out for 5 to 10 hours.

Claim 5

The refractory body according to claim 1, wherein an amount of the fine particles of stabilizer mixed is not more than 6% by weight based on a total weight of the zirconia and stabilizer particles.

Claim 6

The refractory body according to claim 1, wherein the binder is added to the zirconia and stabilizer particles after or at the time of mixing the particles of zirconia and stabilizer.

Claim 7

The refractory body according to claim 1, wherein the binder is an organic binder and/or an inorganic binder.

Claim 8

The refractory body according to claim 6, wherein the organic binder is selected from the group consisting of carboxymethyl cellulose or sodium derivative thereof, polyvinyl alcohol and waste pulp liquor.

Claim 9

The refractory body according to claim 6, wherein the inorganic binder is water.

Claim 10

The refractory body according to claim 1, wherein during the mixing of the fine particles of zirconia and the stabilizer particles, the mixture is ground into a fine particles.

Claim 11

The refractory body according to claim 1, wherein the particles of zirconia are particles of baddeleyite.

Claim 12

The refractory body according to claim 1, wherein the zirconia is obtained by decomposing and refining zircon.

Claim 13

The refractory body according to claim 1, wherein the stabilizer consists of MgO.

Claim 14

The refractory body according to claim 1, wherein the stabilizer consists of CaO.

Claim 15

The refractory body according to claim 1, wherein the stabilizer consists of Y 2 O 3 .

Claim 16

A process for producing a refractory body made of at least partially stabilized zirconia and having a predetermined shape, comprising the steps of: (1) mixing particles consisting of fine particles of zirconia having a monoclinic crystal structure and fine particles of a stabilizer composed of at least one substance selected from the group consisting of MgO, CaO and Y 2 O 3 with a binder, said zirconia particles having an average size of 0.5 to 5 μm comprising 30 to 70% by weight of particles of a diameter of 0.1 to 5 μm and 70 to 30% by weight of particles of a diameter of 5 to 10 μm and said stabilizer particles being of a size small enough to pass through a Tyler standard sieve of 325 mesh (44 μm), and the fine particles of the stabilizer being mixed in an amount of not less than 2% by weight of the zirconia and stabilizer particles, (2) granulating the resulting mixture to form granulated particles comprising 30 to 70% by weight of particles of a diameter of 1 to 70 μm and 70 to 30% by weight of particles of a diameter of 70 to 170 μm, (3) shaping the granulate mixture into a predetermined form and (4) firing the shaped mass thus formed at a temperature of 1,600° to 1,850° C. to promote sintering and stabilization of the zirconia particles simultaneously.

Claim 17

A process for producing a refractory body made of at least partially stabilized zirconia and having a predetermined shape, comprising the steps of: (1) mixing particles consisting of fine particles of zirconia having a monoclinic crystal structure and fine particles of a stabilizer composed of at least one substance selected from the group consisting of MgO, CaO and Y 2 O 3 with a binder, said zirconia particles having an average size of 0.5 to 5 μm comprising 30 to 70% by weight of particles of a diameter of 0.1 to 5 μm and 70 to 30% by weight of particles of a diameter of 5 to 10 μm and said stabilizer particles being of a size small enough to pass through a Tyler standard sieve of 325 mesh (44 μm), and the fine particles of the stabilizer being mixed in an amount of not less than 2% by weight of the zirconia and stabilizer particles, (2) granulating the resulting mixture to form granulated particles comprising 30 to 70% by weight of particles of a diameter of 1 to 70 μm and 70 to 30% by weight of particles of a diameter of 70 to 170 μm, (3) shaping the granulate mixture into a predetermined form and (4) firing the shaped mass thus formed at a temperature of 1,600° to 1,850° C. to promote sintering and stabilization of the zirconia particles simultaneously.

Claim 18

The process according to claim 16, wherein the firing temperature is 1,700° to 1,850° C.

Claim 19

The process according to claim 15 or 16, wherein the firing is carried out for 5 to 10 hours.

Claim 20

The process according to claim 15, wherein the fine particles of stabilizer is mixed in an amount of not more than 6% by weight based on a total weight of the zirconia and stabilizer particles.

Claim 21

The process according to claim 15, wherein the binder is added to the zirconia and stabilizer particles after or at the time of mixing the particles of zirconia and stabilizer.

Claim 22

The process according to claim 15, wherein the binder is an organic binder and/or an inorganic binder.

Claim 23

The process according to claim 20, wherein the organic binder is selected from the group consisting of carboxymethyl cellulose or sodium derivative thereof, polyvinyl alcohol and waste pulp liquor.

Claim 24

The process according to claim 20, wherein the inorganic binder is water.

Claim 25

The process according to claim 15, wherein during the mixing of the fine particles of zirconia and the stabilizer particles, the mixture is ground into a fine particles.

Claim 26

The process according to claim 15, wherein the particles of zirconia are particles of baddeleyite.

Claim 27

The process according to claim 15, wherein the zirconia is obtained by decomposing and refining zircon.

Claim 28

The process according to claim 15, wherein the stabilizer consists of MgO.

Claim 29

The process according to claim 15, wherein the stabilizer consists of CaO.

Claim 30

The process according to claim 15, wherein the stabilizer consists of Y 2 O 3 .