Enamel reactors are widely used in chemical, pharmaceutical, dye, pesticide, organic synthesis, petroleum, food and defense industry production and scientific research because of their excellent corrosion resistance, good processing performance, and smooth surface. Evaporation, concentration, synthesis, chlorination, nitrification, etc. However, due to its material properties and carelessness during manufacturing, processing, use, transportation, installation, and maintenance, it is easy to cause damage, making it a vulnerable product. An enamel kettle is worth tens of thousands of yuan, and it is a pity to be scrapped due to partial explosion of porcelain. With proper maintenance, the equipment can still be used, which has good practical significance and considerable economic benefits. This paper analyzes the reasons for the damage of enamel kettles, finds preventive methods, and proposes repair measures, which can be used by manufacturers of enamel kettles and users for reference.

The enamel kettle is formed by spraying the enamel frit with high silicon content on the surface of the low carbon steel tire, and calcining at a high temperature of about 900 ℃ to make the enamel adhere to the surface of the metal steel tire. Therefore, the reasons for the damage of the enamel kettle are also various. Generally, there are the following reasons:

1. Mechanical damage

The impact resistance of enamel is very poor, and any metal or hard object hitting it will cause the enamel to break. Therefore, during the use of the enamel kettle, it is strictly necessary to prevent any metal or hard objects from falling into the kettle.

2. Thermal stress damage

The enamel kettle is fired at a high temperature of 900 ℃, and after cooling, the enamel and the steel plate are bonded together. Since the coefficient of linear expansion and elongation of enamel is smaller than that of steel plate, the deformation of glass-lined after cooling is smaller than that of steel plate, and enamel is constrained by steel plate to generate compressive stress. After the enamel kettle is made, the glass lining has pre-compression stress, while the steel plate has pre-tensile stress. Since the prestress is related to the linear expansion coefficient and elongation, and the linear expansion coefficient and elongation are closely related to the temperature, the working temperature of the enamel kettle has a great influence on the use of the enamel kettle. If the stress generated by the enamel exceeds its service stress due to large temperature changes, the enamel will be damaged. Therefore, the enamel layer of the enamel kettle changes rapidly when it is cold and hot, and it is extremely easy to explode the porcelain. Therefore, the enamel kettle has a temperature resistance limit: the temperature is 200 °C, and the temperature resistance changes rapidly: cold shock <110 °C, thermal shock <120 °C. When the material is fed, the temperature difference between the material temperature and the kettle body temperature is too large, and the steam is too violent when heating, and the cooling is too rapid, which can also cause the porcelain to explode. Therefore, the heating and cooling of the enamel kettle should be slow, uniform, and graded cooling during use.

3. Processing stress damage

During the processing of the kettle body, a large amount of internal stress is generated due to rolling, stamping and welding. These stresses should be completely eliminated before enamelling. If the elimination is incomplete, the enamel will burst. This damage tends to occur in the first three months after being put into service. Therefore, heat treatment or aging treatment of the embryo body can prevent the porcelain from bursting.

4. Electrostatic puncture

The liquid with suspended solids is stirred in the enamel kettle. The suspended solids rub strongly against the enamel, and at the same time, the suspended solids also produce friction, which generates a large amount of electrostatic charge. Pitting corrosion, so the stirring speed should not be too fast.

5. Hydrogen evolution corrosion

The jacket of the enamel kettle will scale and rust after a period of use. If an acidic scale remover is used to remove the scale or the coolant in the jacket is acidic, it will cause hydrogen evolution corrosion of the metal (Fe+2HCI=FeC12+H2O) A part of the H atoms diffuse into the holes in the metal and combine into }b. These H atoms can no longer diffuse outward due to the compactness of the enamel. Therefore, when the Hz accumulates to a certain level and forms a certain power, the enamel will rupture. . Therefore, when acid washing is used to clean the scale, a buffer must be added, and the cooling liquid in the jacket must be neutral.

6. The base material is unqualified

 In order to reduce costs, some manufacturers use Q235 steel for the embryo body, which directly leads to the gasification of carbon and sulfur in the steel during the enamelling process, resulting in the formation of a large number of air bubbles between the enamel layer and the substrate and inside the enamel layer, resulting in a decrease in the bonding strength of the enamel. The enamel layer changes rapidly when it encounters cold and heat, and it is very easy to explode the porcelain. Therefore, the enamel kettle uses steel with low carbon content and low sulfur as the embryo body to prevent the porcelain from bursting.

7. Poor quality of enameling

 Some enamel kettle manufacturers have a simple production environment, and the rust and dust removal can not meet the standard, resulting in a poor combination of the bottom glaze and the substrate. Some reduce the number of enamel firing times and increase the thickness of each layer, so that the internal force is too large, which affects the service life of the enamel kettle. Therefore, the quality of the enamel kettle can only be guaranteed by manufacturing in strict accordance with the manufacturing regulations.