Thermal Analysis of Ca-FeSi inoculated. Ductile Iron [1 (original) (raw)

The Effect of Inoculation on Microstructure and Mechanical Properties of Ductile Iron

The current work proposes thermal analysis system for analysis of ductile iron solidification processing. The system consists of standard pouring cup with built in thermocouple. The thermocouple is connected to data logger system so as to store temperature data of solidification sequence. The ductile iron treatment consists of composition control, melt pre-treatment, magnesium treatment and inoculation processing. Even small change in processing can be monitored by thermal analysis and its effects on final microstructure and mechanical properties were studied. Along with test cups, the tensile test bars were also poured and analyzed for correlating the mechanical properties with solidification sequencing. The melting trials with varying amount of inoculation processing were conducted to study its effect especially on amount of nodule count, nodularity and amount of pearlite and ferrite phase. As the microstructure decides the final mechanical properties in ductile iron castings, the nucleation and proportion of these phases is of paramount importance during solidification. The thermal analysis of base metal and inoculated material can be effectively used for improving mechanical properties of ductile iron castings.

EXPERIMENTAL STUDY ON THE EFFECT OF HEAT TREATMENT ON THE PROPERTIES OF DUCTILE IRON AFTER ALLOYING

Cast Iron, the first man – made composite, is at least 2500 year old. It remains the most important casting material, with over 70 % of the total world tonnage. The man for cast iron longevity are its wide range of mechanical and physical properties coupled with its competitive price. Ductile iron or popularly known as spherodized graphite iron (SGiron) is a special variety of cast iron having carbon content more than 3 % and has graphite present in compact, spherical shapes. These compact spheroid hamper the continuity of the matrix much less than graphite flakes which results in higher strength and toughness with a structure that resembles gray cast iron , thus imparting superior mechanical properties i.e. much higher than all other cast irons and which can be compared to steel .This unique property enables ductile iron to be used for numerous industrial applications .The excellent combination of mechanical properties obtained in S.G. iron can further be improved by the heat treatment. The most recent development in this regard is the production of Austempered Ductile Iron (ADI). It provides an excellent combination of high tensile strength, wear resistance along with good corrosion resistance and quite significant amount of ductility. Due to these factors, S.G. or ductile iron is austempered when a very favouurable combination of various properties is required. But this type of treatment is bit tricky, since it require controlled heating and isothermal holding of the material. So it is necessary to find some attractive methods for property development in S.G. iron.The present work is an attempt to study the properties enhancement of ductile iron by heat treatment. Normalizing, Austenitization, Quenching & Tempering, Austempering methods are applied to study the hardness, tensile strength, and impact strength of the material. The mechanical properties obtain by various technique have been compared to one another using two different grades of S.G. Iron (one with copper and another without copper). The effect of copper has been studied.

Chapter 2 Thermal Analysis of Ductile Iron Casting

2018

Pure metals solidify with a solidification front that is very well defined and a clearly delineated solid-liquid interface. Ductile cast iron solidification is characterised by a very thin solidified skin and appearance of different phases. The outer skin is formed being very thin in ductile iron; the expansion occurs due to graphite nucleation into the casting forces to the mould walls. With proper care taken while designing and during melt processing stage, quality ductile iron castings can be produced with minimal risering. With recent developments in sensing and storing instruments, it is now possible to see and measure structural transformations within the solidification in ductile iron castings very precisely. The shape of a cooling curve measured by a thermocouple mounted on a thermal analysis sample cup reflects the solidification process of the melted cast alloy for the given solidification conditions. By analysing particular cooling curve, the solidification start, eutecti...

The solidification of ductile cast iron

1989

The microsegregation of Mn, Cu, Cr, Mo, Ni and Si has been measured in cast ductile iron and in ductile iron which has been quenched when partially solidified. Effective segregation coefficients have been determined for each of the elements, and used to calculate the segregation on the basis of the Scheil equation. The calculated values agree reasonably well with the values of the solute concentration as a function of the solid fraction measured in quenched samples. The microstructure of the solid phases during the solidification of ductile iron has been observed. Solidification of eutectic ductile iron begins with the independent nucleation of austenite and graphite in the melt. Later the graphite nodules are enveloped by austenite, and further solidification takes place by the thickening of the austenite layers enveloping the graphite. Isolated pockets of interdendritic melt are the last material to solidify. On the basis of the measured segregation of the different alloying eleme...

Quality Improvement of Ductile Iron Casting by Thermal Analysis

Solidification of ductile Iron is complex & often leads to shrinkage. Melt Chemistry of charge prepared is insufficient to explain the way ductile iron shrinkage occurs in castings. The variations in melting, holding, treating and inoculating processes during the manufacturing of ductile iron impacts ductile iron solidification. Experimental results of thermal analysis in the casting where changes in cooling curves explained metallurgical characteristics to quality (shrinkage) of castings. Thermal Analysis of castings reduces quality issues such as shrinkage. Thermal Analysis (TA) is recording, analyzing the data & then interpret on the basis of temperature variation with respect to time of cooling or heated material. In ductile iron castings, the cooling curve gets recorded while solidifying metal in a mold and further analysis of this data is done. Interpretation is done on the basis of belief that during solidification, different events occurring leave their mark on the shape of cooling curves. With the help of this theory, the quality problems especially sinking or shrinkage problems faced for this casting are resolved.

Phase Investigation of Austempered Ductile Iron

In austempering, the microstructural end product of the spheroidal graphite (SG) iron matrix is essentially bainite, a structure formed below the pearlite temperature range but above the martensite range. Ductile cast iron undergoes a remarkable transformation when subjected to the austempering process. Due to isothermal transformation, it produces a microstructure that is stronger and tougher than the structures resulting from conventional heat treatment process. In the present investigation, the SG iron was austempered with three different austempering temperatures (2500 C,3000 C and 3500 C) with varying austempering time. The sample was taken for XRD analysis to study the morphology of the matrix. It was found that both the austenite (111) and ferrite (110) lines are identified nearly in all cases. The maximum intensity of the austenite (111) line is increasing with increasing temperature but ferrite (110) line is increasing with increasing austempering time and decreasing with austempering temoerature. Hence austempering calls for very precise control of process times and temperatures.