Ce-Bearing FeSi Alloy Inoculation of Electrically Melted, Low Sulphur Grey Cast Irons for Thin Wall Castings

Irina Varvara Balkan,Iulian Riposan

doi:10.3390/met11071122

Abstract

Electrically melted and over-heated (>1500 °C) grey cast iron at less than 0.04%S, as commonly used, solidifies large amounts of carbides and/or undercooled graphite, especially in thin wall castings; this is necessary to achieve a stronger inoculation. The efficiency of Ce-bearing FeSi alloy is tested for lower ladle addition rates (0.15 and 0.25 wt.%), compared to the base and conventional inoculated iron (Ba,Ca-bearing FeSi alloy). The present work explores chill and associated structures in hypoeutectic grey iron (3.6–3.8%CE, 0.02%S, (%Mn) × (%S) = 0.013–0.016, Alres < 0.002%), in wedge castings W1, W2 and W3 (ASTM A 367, furan resin sand mould), at a lower cooling modulus (1.1–3.5 mm) that is typically used to control the quality of thin wall iron castings. Relatively clear and total chill well correlated with the standard thermal (cooling curve) analysis parameters and structural characteristics in wedge castings, at different wall thickness, displayed as the carbides/graphite ratio and presence of undercooled graphite morphologies. The difference in effects of the two inoculants addition is seen as the ability to decrease the amount of carbides and undercooled graphite, with Ce-bearing FeSi alloy outperforming the conventional inoculant, especially as the wall thickness decreased. It appears that Ce-bearing FeSi alloy could be a solution for low sulphur, electric melt, thin wall iron castings production.

Highlights

According to the “Census of World Casting Production” [1], the annual global metalcasting production reached around 110 million metric tons, including both ferrous (78.6%)and non-ferrous (21.4%) alloys
Wedge samples were used for structural analysis, along the central axis and in an as-cast state, to study the effects of casting characteristics and metallurgical treatment applied in the liquid state
The structural characteristics along the central axis of wedge castings, as effects of casting characteristics and metallurgical treatment applied in the liquid state, were correlated with the standard thermal parameters, and the following conclusions could be drawn:

Summary

Introduction

Both of these groups of alloys include representative metallic materials, such as cast irons (69.3%) and cast steel (9.3%), and Al-based (15.8%). Comprising more than two-thirds of production, cast irons are represented by grey (lamellar graphite) (46.9%) cast iron, ductile (nodular graphite) cast iron (21.7%) and malleable (temper carbon graphite) cast iron (0.7%). Grey (lamellar graphite) cast iron continues to be the most produced metallic material in the world foundry industry, despite its rate having decreased due to its replacement by more performant ductile cast iron or by reduced weight Al-based alloys. Important changes are noted in the evolution of grey cast iron production, especially affecting the nomenclature of parts, the size and weight characteristics of castings, as well as its chemical composition and melting procedure [2,3]

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