JP4556352B2 - Platinum coated refractory - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refractory having a platinum coating on its surface, and more particularly to a platinum-coated refractory suitable for manufacturing glass products.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, refractories used for the manufacture of glass products have been coated with platinum or a platinum alloy on the surface in order to maintain durability and prevent contamination of molten glass.
[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, which can be applied to a refractory having a complicated shape, and is also applied to a large-scale fired refractory formed by a mud casting method. It has become like this.
[0004]
[Problems to be solved by the invention]
However, the fired refractory molded by the mud casting method has a very dense structure on the casting surface that forms the surface of the refractory, and since there are few microscopic pores, the refractory and the sprayed platinum adhere firmly. Because it is difficult, the platinum film peels off from the refractory. In addition, the platinum coating formed by the thermal spraying method is porous and has many fine through-holes. Therefore, if such a platinum-coated refractory is used for melting glass, the combustion gas in the furnace atmosphere is refractory. Since it flows out into the molten glass through the pores of the object and the through holes of the platinum coating, the number of glass products with many bubble defects increases.
[0005]
In addition, 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, which may cause pinholes in the platinum coating. Coating the fired refractory with platinum often did not provide the expected effect and life.
[0006]
An object of the present invention is to provide a platinum-covered refractory having a platinum film formed on the surface thereof, which solves the above problems and has a long life and does not cause product defects such as bubbles.
[0007]
[Means for Solving the Problems]
The platinum-coated refractory of the present invention grinds the surface of the refractory substrate by 1 mm or more to remove the surface layer, and forms a platinum film having a thickness of 300 to 500 μm on the surface of the refractory substrate by a thermal spraying method. Then, the refractory base material is fired at a temperature of 1000 to 1400 ° C. in an atmosphere having an oxygen concentration of 2 to 12%.
[0008]
If the removal of the surface of the refractory base material by grinding is less than 1 mm, a surface layer composed of a cast surface formed by a slurry casting method remains, and such a surface layer is a very dense structure and is thermally sprayed. There are few minute pores required to bind strongly to the formed platinum, and the platinum coating is peeled off from the surface of the refractory substrate. As the refractory base material used as a base material in the present invention, it is important that the surface of the refractory base material is ground by 1 mm or more in order to strengthen the bonding between the platinum coating and the refractory. The fine 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 by spraying platinum so as to deeply penetrate into the pores. It becomes possible to strengthen the bonding between the coating and the refractory.
[0009]
Further, if the thickness of the platinum coating is less than 300 μm, a hole is opened in the platinum coating due to shrinkage during the firing treatment, and if it is more than 500 μm, the platinum coating is formed of the refractory base material due to the difference in thermal expansion coefficient between platinum and the refractory. Since it peels from the surface, it is not preferable. The thickness of the platinum coating is preferably 300 μm to 500 μm.
[0010]
When the refractory base material sprayed with platinum 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 base material react with platinum to form a low melting point alloy. Many pinholes occur. On the other hand, if the oxygen concentration is higher than 12%, platinum wear due to oxidation volatilization is increased, which is not preferable. It is important that the refractory base material sprayed with platinum is baked in an oxidizing atmosphere having an oxygen concentration of 2 to 12%. When a refractory base material with platinum sprayed in an oxidizing atmosphere with an oxygen concentration of 2 to 12% is fired, the iron spots on the surface of the refractory base material are completely converted to iron oxide, which reacts with platinum. In addition, a dense platinum coating without pinholes can be obtained.
[0011]
In general, platinum coatings formed by thermal spraying have many porous and fine through-holes. However, if the firing temperature is lower than 1000 ° C, sintering is insufficient and the holes in the platinum coating are not sufficiently blocked. On the other hand, it is difficult to obtain a dense platinum film. On the other hand, if the firing temperature is higher than 1400 ° C., not only the wear of platinum due to oxidation volatilization is increased, but also firing deformation of the refractory substrate is not preferable. Since the platinum-coated refractory according to the present invention has been subjected to a baking treatment at 1000 ° C. to 1400 ° C. for a long time (1 hour to several days), the platinum coating is densely sintered and there are no through holes.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
First, the surface of the refractory substrate formed and fired by the mud casting method is ground by 2 mm to remove the surface layer and expose the inside. Thereafter, a platinum film having a thickness of 350 μm is formed on the surface of the refractory base material with the exposed interior by a thermal spraying method.
[0013]
Next, the platinum-coated refractory is obtained by firing the refractory base material on which the platinum coating is formed in an atmosphere having an oxygen concentration of 8% under conditions of 1350 ° C. for 4 hours.
[0014]
Using the platinum-coated refractory thus obtained, the temperature was raised from room temperature at a rate of 200 ° C. per hour, and when the change in the platinum coating of the platinum-coated refractory was observed, the temperature was raised to 1500 ° C. However, the platinum coating was firmly bonded without peeling from the refractory substrate.
[0015]
In addition, as a demonstration 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 film, and no bubbles were generated from the platinum film. Moreover, there were no bubbles in the glass product, and a good glass product could be produced.
[0016]
Furthermore, after the demonstration test, the platinum-covered refractory is taken out, and an optical microscope is used to check whether a low-melting-point alloy of platinum and iron spots that cause pinholes is generated at the interface between the refractory substrate and the platinum coating. I examined it, but it was not observed at all.
[0017]
On the other hand, as a comparative example, a platinum-coated refractory was produced in which a 350 μm thick platinum coating was directly formed on the surface of a refractory substrate formed and fired by the mud casting method. When the temperature of the platinum film was increased by heating at a rate of 200 ° C. per hour from room temperature, and the change in the platinum film was observed, the platinum film swelled from the refractory at about 900 ° C. It peeled off and became unusable.
[0018]
【The invention's effect】
As described above, the platinum-coated refractory of the present invention has good adhesion between the platinum coating and the refractory base material and has a long life, and defects such as bubbles do not occur from the surface of the platinum coating. Therefore, when used in a glass melting furnace, it becomes possible to produce a high-quality glass product stably over a long period of time.
[0019]
In addition, since the platinum-coated refractory of the present invention can be coated on a refractory having a large size or a complicated shape, the platinum-covered refractory having a large size or a complicated shape can be easily produced and has an excellent practical effect. Is.

Claims (1)

The surface of the refractory substrate is ground by 1 mm or more to remove the surface layer, and a platinum film having a thickness of 300 to 500 μm is formed on the surface of the refractory substrate by a thermal spraying method. A platinum-coated refractory obtained by firing at a temperature of 1000 to 1400 ° C. in an atmosphere having a concentration of 2 to 12%.