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Adhesion between enamel and metal in glass lined mixing kett

Adhesion between enamel and metal in glass lined mixing kettle

كيفية التحقق من ما إذا كان تنظيف الزجاج اصطف مفاعل يتوافق مع المعايير

After the products of glass lined mixing kettle are fired, a porcelain layer firmly close to it is obtained on the metal. The force required for the porcelain layer to fall off the metal surface is called the adhesion between the enamel and the metal. The practice of enamel and a lot of research work have determined that this adhesion is related to many factors.

It is necessary for the metal surface to be well wetted by the enamel melt. The metal surface shall be free from dirt and roughness. The surface tension of the glaze melt should not be too large. As we all know, the completely pure and non oxidizable metal surface cannot be infiltrated by the enamel. In order for the underglaze to flow along the metal surface, there must be a thin layer of oxide on the metal surface. On the steel plate without pre oxidation, the purpose of adhesion cannot be achieved when the underglaze is fired in reducing atmosphere or vacuum. The surface structure of the metal is also affected. The porcelain layer is denser on the loose surface than on the smooth surface.

The composition of the glaze, which determines the surface tension and thermal expansion coefficient of the glaze, is of great significance to enhance the adhesion. The smaller the surface tension of the enamel, the better the infiltration of the metal surface. When the newly fired glass lined mixing kettle products are cooled, its expansion coefficient has a great influence. If the expansion coefficient of the glaze is not large enough, a large compressive stress can be generated in the glaze during cooling, causing the glaze to fall off; When the expansion coefficient of the glaze is too large, cracks can be formed in the ceramic layer.

It is of great significance when there are substances (cobalt and nickel oxides, arsenic and antimony sulfides, copper compounds, etc.) that can increase the adhesion in the composition of the underglaze. Introducing a small amount of such substances (COO about 0.3 ~ 0.5%; NiO about 0.5~1.5%) into the composition of the underglaze can significantly improve the adhesion. When the steel plate coated with the underglaze without dense oxide is impacted or slightly bent, a large piece of porcelain layer will peel off on the surface of the steel plate, which is a silver gray shiny smooth surface. However, the steel plate coated with the same underglaze containing 0.3 ~ 0.5%coo can be bent without the underglaze falling off. However, when it is violently impacted or bent to a considerable extent, the underglaze will fall off in a small needle shape, exposing a dull, rough metal surface with part of the underglaze left.