The well cover process of Shandong nodular cast iron consists of melting, pouring and heat treatment. This paper discusses the influence of each process on the corrosion resistance of nodular cast iron.
1 factors affecting the corrosion resistance of ductile iron manhole cover
The melting process of nodular cast iron is an important factor that affects the corrosion resistance of nodular cast iron manhole cover. Because the smelting process directly determines the purity of the molten steel, which ultimately determines the internal quality and composition of the well cover. In the smelting process, decarburization and chromium retention are more important, followed by the removal of non-metallic inclusions in the molten steel as much as possible.
Chromium is a corrosion-resistant element. The oxide of chromium forms a passive film on the surface of nodular cast iron, which prevents the further oxidation of nodular cast iron, so that nodular cast iron has corrosion-resistant function. When the chromium content in the nodular cast iron is lower than 12, the corrosion resistance of the nodular cast iron will decrease significantly.
The carbon content is directly related to the corrosion resistance of steel。 The existence of carbon makes the nodular cast iron prone to intergranular corrosion when it is welded or heated at about 510-788 ℃。 Therefore, the corrosion resistance of nodular cast iron is strongly affected by the carbon content in the steel。 The development direction of modern nodular cast iron is that low carbon (< 0。08% C) and ultra-low carbon (< 0。03% C) can be regarded as high-purity (< 0。015% C)。
The amount and distribution of nonmetallic inclusions also have an important influence on the corrosion resistance of nodular cast iron. The existence of impurities may make the composition of nodular cast iron uneven, make the electrode potential on the surface of nodular cast iron inconsistent, and lead to electrochemical corrosion. Therefore, reducing the impurities in the manhole cover of nodular cast iron can also add the corrosion resistance function of nodular cast iron.
The above is a detailed introduction to the factors affecting the corrosion resistance of ductile iron manhole covers。 For more information, please click http://www。jnwszy。com