Production process of extra-heavy nodular cast iron manhole cover

Abstract

The invention discloses a production process of an extra-heavy nodular cast iron manhole cover. Pig iron, recirculated iron, steel scraps, ferrosilicon and ferromanganese are adopted as furnace chargeto carry out melting and casting, the processing strength of the nodular cast iron manhole cover is improved, and meanwhile the production requirements for the extra-heavy manhole cover can be met. Molten iron with the proper carbon content and a proper quantity of silicon and manganese are added into the molten furnace charge, shrinkage porosity and cracks can be avoided, appearing of free cementite can be avoided, and nodularizing and the furnace charge is facilitated. Silicon can refine graphite in nodular cast iron, the roundness of graphite nodules can be improved, ferrite can be formedeasily, and cementite is avoided. SiC is utilized as a treatment agent, the carbon equivalent can be improved properly, cost is reduced, meanwhile, the metallurgy conditions of iron liquid are improved, reducibility is enhanced, the adverse effects of rusting furnace charge is relieved, the number of graphite nodules of unit area of the nodular cast iron is increased, and the size of the graphitenodules reaches level 6 or above. The mechanical performance is stable, and the percent of pass of production of the extra-heavy nodular cast iron manhole cover is improved.

Description

technical field [0001] The invention relates to the technical field of ductile iron manhole covers, in particular to a production process for super-heavy nodular cast iron manhole covers. Background technique [0002] The demand for ductile iron manhole covers in the domestic and international markets is increasing day by day, and the market competition is also becoming increasingly fierce. This requires products to be diversified in terms of varieties and functions, and requires light weight, high strength, good surface quality, and long service life. long. In the design of the manhole cover, its epidermis and wall thickness are designed to be thinner and thinner, which provides a greater possibility for the occurrence of cold shut defects. Practice has shown that cold insulation is the first major defect in the production of ductile iron manhole covers. Due to the thin wall thickness and large size range of the two ductile iron manhole covers, the ductile iron has more m...

AI Technical Summary

Problems solved by technology

Although the cold shut phenomenon is a common defect in the foundry industry, the research on the specific product of super heavy ductile iron manhole cover is still of great practical significance

[0003] At present, the manhole covers widely used are cast iron, which has the advantages of compression resistance, wear resistance and high bearing capacity, but it is not corrosion-resistant, especially not suitable for manhole covers with serious corrosion, and because of its high recovery value, so easy to steal

The patent No. is 95228436, and the patent No. 2238265 discloses a composite road manhole cover, which has the advantages of corrosion resistance and low cost, but has the disadvantages of complex structure, troublesome manufacture, and non-wear resistance, especially its bearing capacity of up to If it is less than 360KN stipulated in the national standard, it cannot be used as a super heavy manhole cover

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