Effects of Inoculation on Structure Characteristics of High Silicon Ductile Cast Irons in Thin Wall Castings

Iulian Riposan,Eduard Stefan,Stelian Stan,Nicoleta Roxana Pana,Mihai Chisamera

doi:10.3390/met10081091

Abstract

Previous experiments pointed out that the deviation using a sphere as reference of graphite particles is noticeably increased by Si-alloying, with inoculation as a possible beneficial effect. The main objective of the present work is to evaluate the effects of commercial inoculants (Ca/Ca, Ba/Ca, RE-FeSi alloys) on 4.5%Si ductile iron, thin wall castings. FeSiMgRE treated iron (0.032–0.036%Mgres) is in-mold inoculated (a four-work-positions pattern). A complex chemical composition is obtained for each inoculation variant. Wedge casting W3 (ASTM A 367) is used to evaluate structure characteristics at different wall thickness (3–15 mm). Minimum and maximum size, area, nodule count, and representative graphite shape factors are evaluated. Roundness (including AG and Fmax) at 0.6–0.8 level illustrates the common formation of slightly irregular spheroidal graphite (Type V, ISO 945). Ca, RE-FeSi inoculation leads to the highest level of real perimeter and, consequently, to the lowest level of Sphericity. Ca, Ba-FeSi inoculation appears to be better than simple Ca-FeSi for improving graphite parameters, while Ca, RE-FeSi has the lowest beneficial effect, especially as it negatively affects the compactness degree of graphite particles. A two-step liquid treatment using RE-bearing FeSiCaMg master alloy and Ca, Ba-FeSi inoculant appears to be a solution to improve graphite parameters for high-Si ductile irons solidified in thin wall castings.

Highlights

The substitution of cast iron components with Al reduces weight in the automotive industry and it is very attractive for it improves fuel economy and reduces CO2 emissions
In order to remain competitive in the automotive industry, the iron castings must reduce their weight, so thin wall iron castings concept will sustain the survival of cast iron in this industry
It has been shown that thin wall wheel rims made of ductile iron can have the same weight and better mechanical properties than their substitutes made of aluminum alloys [2]

Summary

Introduction

The substitution of cast iron components with Al reduces weight in the automotive industry and it is very attractive for it improves fuel economy and reduces CO2 emissions. The emissions legislation in the automotive industry focuses entirely on tailpipe emissions, with no consideration for the CO2 generated during production of the vehicle, and production, delivery, and consumption of the fuel. If the full life cycle emissions are considered, the use of cast iron in car production has to be reconsidered [1]. It has been shown that thin wall wheel rims made of ductile iron can have the same weight and better mechanical properties than their substitutes made of aluminum alloys [2]

Objectives

Methods

Results