JPH0238370A - Composite powder for ceramic coating and production thereof - Google Patents

Abstract

PURPOSE:To obtain a composite powder for ceramic coating capable of adhering to the inside of a tube and forming uniform coating layer and further providing structure having excellent thermal shock resistance only by feeding a coating material into a cast iron tube by adding adhering properties to a coating material by a specific constitution. CONSTITUTION:A composite powder for ceramic coating is formed by the following a-e processes: (a) An aggregate such as mica or film-shaped glass or pulverized piece of inorganic hollow particle is blended with a curing agent consisting of powdery burned aluminum phosphate, binder consisting of a liquid alkali metal silicate and water at desired amounts. (b) The above-mentioned blend is irradiated with a microwave to dehydrate and solidify the blend. (c) The solidified blend is crudely crushed. (d) The crushed blend is finely pulverized and (e) further classified. In the obtained composite powder, the aggregate and curing agent are uniformly included in the binder and the curing agent and binder exist in unreacted state and the binder has water absorbing structure because of having pores opened to air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ceramic coating composite powder suitable for forming an antioxidant coating layer that suppresses high-temperature oxidation, and a W1'Zl method thereof.

[Prior Art] Methods of applying ceramic coating to cast iron using dry powder include thermal spraying, or enameling, which involves sprinkling glass frit onto cast iron heated to a high temperature. However, in both methods, the coating powder does not contain a binder (the bonding of the aggregate requires a solid solution phenomenon at high temperatures).

[Problems to be Solved by the Invention] The thermal expansion coefficient of the coating layer thus formed approximates the physical properties of aggregate and is significantly different from the thermal expansion coefficient of cast iron, resulting in a problem of poor thermal shock resistance.

Furthermore, the above method is technically extremely difficult to coat the inner surface of a cast iron pipe with a diameter of approximately 50 mm.

Simply feeding the coating material into the pipe will cause the coating layer on the supply side to grow, making it impossible to achieve uniform coating.

The object of the present invention is to provide a ceramic coating composite that can adhere to the inner surface of a cast iron pipe and form a uniform coat of FnM by simply feeding the coating material into a cast iron pipe, and that the coating layer can have a structure with excellent thermal shock resistance. The present invention provides a powder and a method for producing the same.

[Means for Solving the Problems] The composite powder for ceramic coating of the present invention includes crushed pieces of mica, film glass, or inorganic hollow particles as an aggregate, and calcined aluminum phosphate as a hardening agent.
It is characterized in that it is uniformly included in the alkali metal sphere a salt as a binder, and the curing agent and binder exist in an unreacted state.

In addition, the blending ratio of the aggregate is 40 to 50% by weight, the blending ratio of the curing agent is 11 to 12% by weight, and the blending ratio of the binder is 30 to 5% by weight.
It is desirable that it be 0% by weight.

Furthermore, the method for producing a composite powder for ceramic coating of the present invention includes: (a) an aggregate such as mica, film glass, or crushed pieces of inorganic hollow particles; and a hardening agent made of powdered calcined aluminum phosphate.

Mix desired amounts of a liquid alkali metal silicate binder and water, (b) irradiate the mixture with microwaves to dehydrate and solidify, (c) coarsely pulverize, and (d) finely pulverize. (e) It is characterized by further classification.

Furthermore, as a means for dehydrating and solidifying, a method using a spray dryer or a method of freeze-vacuum drying is also effective.

As a result of repeated creative research, the inventors of the present invention have made it possible to coat the inner surface of cast iron with only the action of feeding by adding bonding properties to the coating material. Furthermore, as a means to improve thermal shock resistance, the aggregates are joined not directly but through a bonding material whose coefficient of thermal expansion is close to that of cast iron. This allows the coefficient of thermal expansion of the entire coating layer to approximate that of cast iron, reducing thermal stress. The structure has been designed to relieve the stress. As a method of adding bonding properties, a binder is coated around the aggregate, and a curing agent that hardens the binder is uniformly dispersed in the binder. When this material is fed into a cast iron pipe, the binder coated on the aggregate adheres to the cast iron, and the aggregates are further laminated together via the binder.

However, in this state, the bonding strength is poor and it easily falls off due to external force7.Therefore, a small amount of water is added to dissolve the soluble binder, causing a chemical reaction with the hardening agent contained in the binder, and silane bonding We decided to maintain the shape retention of the coating layer by increasing the bonding force between the aggregates.

A suitable proportion of the coating material is 40 to 50% aggregate by weight; if it is less than 40%, the strength is insufficient, and if it exceeds 50%, cracks will occur. The curing agent preferably has a weight ratio of 11 to 12%; if it is less than 11%, the binder will swell;
If it exceeds this, cracks will appear. The blending ratio of the binder is 30% by weight.
~50% is suitable; if it is less than 30%, the strength will decrease, and if it exceeds 50%, blistering will tend to occur.

[Example] The present invention will be explained in more detail by the following example.
The present invention is not limited thereto.

Fruit "1" - Pot diameter: 200mm Rotation speed: 60 rpm Magnetic ball diameter:
30mm ball insertion amount: 12kg ball mill with bulk specific gravity: 0.2 g/cm3 grains
The powder, which was pulverized over 3.5 hours by inserting 800 g of Shirasu balloons having a diameter of 44 to 150 μm, was mixed with a sodium silicate solution having a molar ratio of 2.5 and a concentration of 40% in a weight ratio of 1=3.

Next, calcined aluminum phosphate powder (average particle size: 2
0μ) and distilled water at a weight ratio of 17:2.

Next, we created mud by further mixing the 28 types of mixed liquids created above. Next, this mud was transferred to an evaporation dish covered with a heat-resistant sheet and irradiated with microwaves at a frequency of 2450 MHz for 30 minutes.

The thus-obtained lumps were coarsely pulverized using a mechanical crusher, and then milled using a ball mill (bot diameter: 280 mm,
The mixture was ground for 5 hours at a rotation speed of 60 rpm. Next, this powder was classified using a sieve with an aperture ratio of 90 μm to obtain a composite powder for ceramic coating.

Back 0 spot diameter: 200mm Rotation speed: 60rpm Magnetic ball diameter: 30mm Ball insertion amount: 12kg Bulk specific gravity = 0.2 for a ball mill. m3 particle size: 80 Shirasu balloons with a diameter of 44 to 150 μm
Powder inserted for 0g and crushed for 3.5 hours, molar ratio 2
．． 5. Sodium silicate solution with a concentration of 40% in a weight ratio of 1:
They were mixed at a ratio of 3.

Next, calcined aluminum phosphate powder (average particle size: 2
0μ) and distilled water at a weight ratio of 17:2.

Next, we created mud by further mixing the 28 types of mixed liquids created above.

Next, 60 g of distilled water was added to 100 g of this mud and granulated using a spray dryer. The conditions of the spray dryer are as shown below.

Atomizer: 11,000 rpm Hot air population temperature: 240°C Hot air outlet temperature: 110°C Air volume: 10 m”/mi
n Slurry flow ffi 15,000cc/Hr Next, the granular powder was crushed in a ball mill.Crushing conditions: Pot diameter: 200mm Magnetic balls (diameter 30mm): 5.4kg Alumina balls (diameter 5mm): 3.6kg Raw materials: 2kg Number of turns
: 60 rpm time :
The powder was then classified using a sieve with an opening ratio of 90 μm to obtain a composite powder for ceramic coating.

5L Pot diameter: 200mm Rotation speed + 6Orpm Magnetic ball diameter: 30mm Ball insertion amount: 12kg Ball mill with bulk specific gravity: 0.2 g/cm3 grains
800 g of Shirasu balloons having a diameter of 44 to 150 μm were inserted and the powder was pulverized for 3.5 hours, and a sodium silicate solution having a molar ratio of 2.5 and a concentration of 40% was mixed in a weight ratio of 1:3.

Next, calcined aluminum phosphate powder (average particle size: 2
0μ) and distilled water were mixed in a weight ratio of 17=2.

Next, we created mud by further mixing the two types of liquid mixtures created above.

Put this mud in a vat and put it in a freeze-vacuum dryer, -6
It was cooled to 0° C. and reduced to a vacuum pressure of 7×10 −’ Torr. In this state, the temperature was raised and held at 0°C for 1 hour, and then further heated to 40°C over 20 hours.

The thus obtained lumps were coarsely pulverized using a Joe crusher, and then pulverized for 5 hours using a ball mill (pot diameter: φ2801, number of revolutions: 60 rpm). Next, the powder was classified using a sieve with an aperture ratio of 90 μm to obtain a composite powder for ceramic coating.

[Effects of invention

Claims (1)

[Scope of Claims] (1) Pulverized pieces of mica, film glass, or inorganic hollow particles as an aggregate and calcined aluminum phosphate as a hardening agent are uniformly mixed in an alkali metal silicate as a binder. A composite for ceramic coating, characterized in that the curing agent and the binder exist in an unreacted state, and the binder has a structure that has pores that open to the atmosphere and can absorb moisture. powder. (2) The ceramic according to claim 1, wherein the aggregate has a blending ratio of 40 to 50% by weight, the curing agent has a blending ratio of 11 to 12% by weight, and the binder has a blending ratio of 30 to 50% by weight. Composite powder for coating (3) In producing composite powder for ceramic coating, (a) Aggregate such as crushed pieces of mica, membrane glass, or inorganic hollow particles, and a hardening agent consisting of powdered calcined aluminum phosphate. , a binder consisting of a liquid alkali metal silicate, and water are mixed in desired amounts, (b) the above mixture is irradiated with microwaves to dehydrate and solidify, (c) coarsely pulverized, and (d) then finely ground. A method for producing a ceramic coating composite powder, which comprises pulverizing and (e) further classifying. (4) In producing a composite powder for ceramic coating, (a) a curing agent consisting of aggregate such as mica, membrane glass, or crushed pieces of inorganic hollow particles, powdered calcined aluminum phosphate, and liquid alkali; A method for producing a composite powder for ceramic coating, comprising: mixing desired amounts of a binder made of a metal silicate and water, (b) granulating the above mixture using a spray dryer, and (c) pulverizing the mixture into fine particles. . (5) In producing a composite powder for ceramic coating, (a) a curing agent consisting of aggregate such as mica, membrane glass, or crushed pieces of inorganic hollow particles, powdered calcined aluminum phosphate, and liquid alkali; A binder made of a metal silicate and water are mixed in desired amounts, (b) the above mixture is freeze-vacuum dried to dehydrate and solidify, (c) coarsely pulverized, (d) then finely pulverized, (e) A method for producing a composite powder for ceramic coating, which comprises further classification.