Process for Production of Compacted Graphite Iron

Abstract

A process for production of compacted graphite iron using in-mould addition of a magnesium alloy is disclosed. The process is characterised by a step of pre-treating the base iron in a ladle or in a furnace with an alloy containing cerium and performing a structure forming treatment in a reaction chamber in the mould using an alloy containing magnesium and lanthanum.

Description

FIELD OF THE INVENTION[0001]The invention relates to a process for production of cast iron with a structure predominantly consisting of compacted graphite shapes. The process is based on a combination of pre-treatment of a base iron and a final treatment in the mould.BACKGROUND ART[0002]Compacted graphite iron is a cast iron alloy with a graphite structure between flake type graphite shapes and spherical shapes. The graphite shape is determined by the conditions in the liquid iron during the solidification. Treatment of a base iron, preferably with a carbon equivalent between 4.0 and 4.4 and with a sulphur content below 0.02%, with a ferrosilicon alloy containing 4-10% magnesium can be used to achieve the compacted graphite structure. The magnesium content must be kept within very narrow limits usually within + / − 0.003% and with a level of about 0.008 to 0.015% depending on conditions of the base iron and the cooling rate in the casting to be produced. As used herein percent refers ...

AI Technical Summary

Benefits of technology

"The present invention relates to a process for producing compacted graphite iron using in-mould addition of a magnesium alloy. The invention solves problems associated with conventional methods of adding magnesium alloy, such as high costs and reduced efficiency. The process involves adjusting the cerium content in the base iron based on the sulphur content, and adding a treatment alloy containing magnesium and lanthanum to reduce defects in the casting. The overall fraction of active metal in the alloys can be 48% Fe, 45% Si, 5% Mg, 1.0% A1, 0.5% La, and a balance of other rare earth elements for the magnesium alloy, and 65% Fe, 25% Ce, 7% La, and a balance of other rare earth elements for the cerium alloy. The process reduces the amount of magnesium needed and minimizes casting defects such as dross and micro-shrinkage."

Problems solved by technology

One problem is that the sulphur level in the base iron often varies.

However, with the in-mould treatment this is practically not possible as the treatment chamber is the same in each mould.

Another problem is that treatment with magnesium makes the structure sensitive to variation in cooling rate.

However high levels of cerium can increase the risk for certain casting defects such as formation of primary carbides and shrinkages.

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