Role of RE and Mg on Graphitization of Spheroidal Graphite Malleable Cast Iron

Spheroidal graphite malleable cast iron is a new structural material developed in the recent years. This paper studies the influence of the residual content of rare earth and magnesium on the nodule counts, the time of first stage graphitization and the rate of ferritization of it. Moreover, the role of sulfides of rare earth and magnesium in the process of graphitization has been analyzed. The results show that the residual content of rare earth and magnesium has a notable influence on the graphitic nodule counts and the time of the first stage graphitization of spheroidal graphite, but has unremarkable influence on the time of the second stage graphitization. There are a large number of spherical sulfides of rare earth and magnesium in as-cast structure, which will act as the nucleus of graphite in the process of first stage graphitization.

High-Speed Machining of Malleable Cast Iron by Various Cutting Tools Coated by Physical Vapor Deposition

The coating material of a tool directly affects the efficiency and cost of machining malleable cast iron.However,the machining adaptability of various coating materials to malleable cast iron has been insufficiently researched.In this paper,turning tests were conducted on cemented carbide tools with different coatings(a thick TiN/TiAlN coating,a thin TiN/TiAlN coating,and a nanocomposite(nc)TiAlSiN coating).All coatings were applied by physical vapor deposition.In a comparative study of chip morphology,cutting force,cutting temperature,specific cutting energy,tool wear,and surface roughness,this study analyzed the cutting characteristics of the tools coated with various materials,and established the relationship between the cutting parameters and machining objectives.The results showed that in malleable cast iron machining,the coating material significantly affects the cutting performance of the tool.Among the three tools,the nc-TiAlSiN-coated carbide tool achieved the minimum cutting force,the lowest cutting temperature,least tool wear,longest tool life,and best surface quality.Moreover,in comparisons between cemented-carbide and compacted-graphite cast iron machined under the same conditions,the wear mechanism of the coated tools was found to depend on the cast iron being machined.Therefore,the performance requirements of a tool depend on multiple factors,and selecting an appropriately coated tool for a particular cast iron material is essential.

EFFECT OF STRUCTURE ON GRAPHITIZATION OF WHITE MALLEABLE CAST IRON

The structure of white iron treated with Si-Bi-AI complex inoculant has been observed by SEM and TEM. The results show that, in comparison with the samples treated with ordinary inoculants, disorder, overlapping and inflexion of the pearlitic lamella appear, besides, the dis- location density increases apparently. The graphitization can be quickly realized at the tem- perature lower than that of austenitic transition (720℃).