JP2003013195A - Platinum-coated refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a platinum-coated refractory with a long life, having a platinum film on the surface, which does not generate products defects such as bubbles. SOLUTION: A method for manufacturing the objective platinum-coated refractory is characterized in that the surface of a base material for the refractory is ground by 1 mm or more to remove the surface layer, the platinum coating of 300-500 μm thick is formed on the surface of the base material by a spray method, and then baking the base material is fired at temperatures of 1,000-1,400 deg.C in the atmosphere having an oxygen content of 2-12%.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory having a surface coated with platinum, and more particularly to a platinum-coated refractory suitable for manufacturing glass products. [0002] Conventionally, refractory materials used for manufacturing glass products include refractory materials whose surfaces are coated with platinum or a platinum alloy in order to maintain the durability and prevent contamination of molten glass. Is used. [0003] In recent years, a thermal spraying method has been developed in which the surface of a refractory is coated with a small amount of platinum, so that refractory of a complicated shape can be coated. It has been applied. [0004] However, in a fired refractory molded by the slurry casting method, the cast surface serving as the surface of the refractory has a very dense structure and few fine pores. Since the refractory and the sprayed platinum are hard to adhere to each other, the platinum film may be peeled off from the refractory. In addition, since the platinum coating formed by the thermal spraying method is porous and has many fine through-holes, when such a platinum-coated refractory is used for melting glass, a combustion gas or the like in a furnace atmosphere becomes refractory. Through the pores of the object and through holes in the platinum coating,
Since the glass flows out into the molten glass, the number of glass products having many bubble defects increases. [0005] Furthermore, since iron spots made of impurity iron present on the surface and inside of the refractory react with platinum to form a low melting point alloy and cause pinholes in the platinum film, a slurry casting method is used. Even coating the refractories molded and fired with platinum with platinum often did not provide the expected effect and life. An object of the present invention is to provide a platinum-coated refractory having a platinum coating formed on the surface thereof, which solves the above-mentioned problems and has a long life and does not cause product defects such as bubbles. [0007] The platinum-coated refractory of the present invention is obtained by grinding the surface of a refractory substrate by 1 mm or more to remove a surface layer, and spraying the surface of the refractory substrate by thermal spraying. Thickness 300
After forming a platinum film having a thickness of from 500 to 500 μm, the refractory substrate is placed in an atmosphere having an oxygen concentration of 2 to 12% in an atmosphere of 1000 to 140
It is characterized by being fired at a temperature of 0 ° C. The surface of the refractory substrate is removed by grinding in 1 m.
If it is less than m, a surface layer consisting of a cast surface formed by the slurry casting method remains, and such a surface layer has a very dense structure and is necessary for strong bonding with the sprayed platinum. There are few fine pores, and the platinum coating peels off from the refractory substrate surface. It is important that the surface of the refractory substrate be ground by 1 mm or more in order to strengthen the bond between the platinum film and the refractory as the base material of the refractory base material in the present invention. The dense surface layer of the refractory base material is removed by grinding, and pores of several μm to several hundred μm existing inside the refractory are exposed on the surface, and platinum is sprayed so as to penetrate deeply into these pores. It is possible to strengthen the bond between the coating and the refractory. If the thickness of the platinum coating is less than 300 μm, pores are opened in the platinum coating due to shrinkage during the firing treatment.
If the thickness is more than 500 μm, the platinum coating is undesirably separated from the surface of the refractory substrate due to the difference in the coefficient of thermal expansion between platinum and the refractory. The thickness of the platinum film is 300 μm to 5
00 μm is preferred. If the refractory substrate on which the platinum is sprayed is fired in an environment where the oxygen concentration in the atmosphere is lower than 2%,
The iron spots on the surface of the refractory substrate react with the platinum to form a low melting point alloy and generate many pinholes. On the other hand, if the oxygen concentration is higher than 12%, it is not preferable because the loss of platinum due to oxidation and volatilization increases. It is important that the refractory substrate on which platinum is sprayed is fired in an oxidizing atmosphere having an oxygen concentration of 2 to 12%. When the refractory base material on which platinum is sprayed is fired in an oxidizing atmosphere having an oxygen concentration of 2 to 12%, iron spots present on the surface of the refractory base material become completely iron oxide and react with platinum. And a dense platinum film without pinholes or the like can be obtained. In general, a platinum coating formed by a thermal spraying method has a large number of porous and fine through-holes. However, when the firing temperature is lower than 1000 ° C., sintering is insufficient and the pores of the platinum coating are insufficient. It is difficult to obtain a dense platinum coating because it does not block, while if the firing temperature is higher than 1400 ° C,
This is not preferable because not only is the wear of platinum due to oxidation and volatilization increased, but it also causes firing deformation of the refractory substrate. Since the platinum-coated refractory of the present invention has been subjected to a firing treatment at 1000 ° C. to 1400 ° C. for a long time (1 hour to several days),
The platinum coating is densely sintered and has no through holes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the surface of a refractory substrate formed and fired by a slurry casting method is ground by 2 mm to remove a surface layer and expose the inside. Then, the surface of the refractory base material whose inner portion is exposed is sprayed to a thickness of 3 μm.
A platinum coating of 50 μm is formed. Next, the refractory substrate on which the platinum coating is formed is fired at 1350 ° C. for 4 hours in an atmosphere having an oxygen concentration of 8% to obtain a platinum-coated refractory. The platinum-coated refractory obtained in this manner was heated from room temperature at a rate of 200 ° C./hour to a temperature of 200 ° C., and the change in the platinum coating of the platinum-coated refractory was observed. Even when the temperature was raised, the platinum film was firmly bonded without peeling off from the refractory substrate. As a verification test, a platinum-coated refractory was used in a glass melting furnace, and the state of the platinum coating of the platinum-coated refractory and the state of bubbles in the glass product were evaluated. as a result,
No small holes were observed in the platinum coating, and no bubbles were generated from the platinum coating. In addition, there was no bubble in the glass product, and a good glass product could be manufactured. Further, after the verification test, the platinum-coated refractory is taken out, and it is determined whether or not a low melting point alloy of platinum and iron spots causing pinholes is formed at the interface between the refractory substrate and the platinum coating. Examination with an optical microscope showed no observations. On the other hand, as a comparative example, a platinum-coated refractory in which a 350 μm-thick platinum coating was directly formed on the surface of a refractory substrate formed and baked by a slurry casting method by thermal spraying was produced. 20 per hour from room temperature
When the temperature of the platinum coating was increased by heating at a rate of 0 ° C. and the change of the platinum coating was observed, it was found that when the sprayed coating was directly formed on the fired surface, about 90% was obtained.
At 0 ° C., the platinum coating swelled from the refractory and peeled off, making it unusable. As described above, the platinum-coated refractory of the present invention has good adhesion between the platinum coating and the refractory base material, has a long service life, and has a foam or the like from the surface of the platinum coating. When used in a glass melting furnace,
High quality glass products can be stably manufactured over a long period of time. Further, since the platinum-coated refractory of the present invention can be coated on a large-sized or complicated-shaped refractory, a platinum-coated refractory of a large-sized or complicated shape can be easily produced, and is excellent in practical use. It is effective.

Claims (1)

Claims: 1. The surface of a refractory substrate is ground by grinding at least 1 mm to remove a surface layer, and a platinum coating having a thickness of 300 to 500 μm is formed on the surface of the refractory substrate by a thermal spraying method. And then
The refractory substrate is placed in an atmosphere having an oxygen concentration of 2 to 12% for 100 hours.
A platinum-coated refractory obtained by firing at a temperature of 0 to 1400 ° C.