Types of Refractory Coatings
1.1 According to Materials:
Aluminosilicate-based: Made with aluminosilicate as the primary raw material, this coating offers excellent high-temperature resistance, typically withstanding temperatures between 1000℃ and 1300℃. It is commonly used for the repair and protection of industrial furnace linings, such as small heating furnaces and annealing furnaces.
Corundum-based: Composed mainly of corundum, this coating excels in high-temperature resistance due to the high hardness and melting point of corundum. It can endure temperatures ranging from 1600℃ to 1800℃, making it ideal for harsh environments such as steel and non-ferrous metal smelting furnaces. It's commonly used in steelmaking converters and electric furnace roofs.
Magnesia-based: Primarily made from magnesite, this coating demonstrates good resistance to alkaline slag erosion and is suitable for use in alkaline environments. It has a refractoriness of 1500℃ to 1700℃ and is widely applied in cement kilns, glass kilns, and other highly alkaline atmospheres.
Silicon Carbide-based: Containing silicon carbide, this coating offers not only high-temperature resistance but also excellent thermal conductivity and wear resistance, withstanding temperatures from 1400℃ to 1600℃. It is commonly used in high-temperature pipelines, circulating fluidized bed boilers, and other applications requiring high wear resistance and heat conductivity.
1.2 According to Binder Types:
Cement Binder: Uses cement as the binder, making it cost-effective and easy to apply. It develops strength during curing, allowing for quick adhesion to the surface. It is suitable for normal and medium-temperature industrial furnace linings, such as those in heat treatment furnaces.
Phosphate Binder: Utilizes phosphate as a binder, offering superior high-temperature performance compared to cement-based binders. It forms a stable bonding phase at high temperatures, improving its refractory properties. It is ideal for high-temperature sections of steel rolling heating furnaces.
Water Glass Binder: Uses water glass as the binder, providing excellent acid resistance and adjustable curing speed. It is widely used in acidic environments, such as in chemical industry furnaces or for the refurbishment of reaction furnaces in sulfuric acid production facilities.
Application Methods for Refractory Coatings
2.1 Pre-application Preparation:
Before applying the refractory coatings, the surface must be thoroughly cleaned to remove impurities such as oil, rust, and dust, ensuring good adhesion. Methods like sandblasting, grinding, and blowing can be used. For example, oil stains on steel furnace walls should be cleaned with chemical cleaning agents before sandblasting.
The spraying equipment, including the spray gun, feed pipes, and air compressor, should be inspected to ensure proper functionality. Spray pressure and air flow should be adjusted according to the coating type and thickness. Typically, the air compressor pressure is adjusted between 0.4 and 0.6 MPa.
Pre-mixing of the spraying material is necessary to ensure an even distribution of raw materials. Powdered materials should be sieved to remove lumps, and liquid binders must be measured and mixed in the correct proportions. Mixing should last at least 15 minutes to guarantee proper consistency.
2.2 Spraying Operation:
The spray gun should be held at an angle of 70° to 90° relative to the surface, with a distance of 0.5 to 1.5 meters. The spraying distance and angle should be adjusted based on the coating material’s rebound. For corundum-based coatings, a distance of around 1 meter and a near-vertical angle is recommended to ensure an even, dense coating.
Spraying should be done in layers, with each layer having a thickness of 20 to 30 mm. Wait for the previous layer to dry slightly before applying the next layer to prevent sagging or cracking. For large industrial furnace linings, the total thickness can reach 100 to 200 mm, depending on the design specifications.
2.3 Post-application Treatment:
After spraying, the coating should be allowed to dry naturally for 24 to 72 hours, depending on the binder type and ambient temperature. During this period, the coating should be protected from impact and vibration.
For high-temperature kilns or furnaces with special requirements, the coating needs to be baked. The temperature should be raised gradually following a predetermined heating curve, removing moisture and further curing the binder. The heating rate during the initial stages is typically 10 to 20℃ per hour, increasing to 30 to 50℃ per hour in the later stages. The final temperature should reach or slightly exceed the intended operating temperature.
Why Choose Rongsheng Refractory?
Henan Rongsheng Xinwei New Materials Research Institute Co., Ltd., headquartered in Zhengzhou City, Henan Province, is part of Henan Rongsheng Technology Group. We have been a leading manufacturer, supplier, and exporter of high-quality refractory materials for over 20 years. Our extensive product range includes high alumina bricks, corundum bricks, AZS bricks, magnesia bricks, fire clay bricks, insulating bricks, and unshaped materials such as refractory castables, refractory cement, refractory mortar, ramming mass, spraying mass, and refractory plastic.
Our products meet the refractory needs of various industries, including Iron & Steel, Cement, Non-ferrous, Power, Petrochemical, and Glass, catering to 90% of the global market. Our products are exported to over 100 countries and regions worldwide, establishing us as one of the top refractory brick and material suppliers in the industry.
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