Defects and Properties of Cast Metals: Cast Iron & Steel
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Solidification Committee
Program Organizers: Mark Jolly, Cranfield University; Charles Monroe, University of Alabama; Brian Thomas, Colorado School of Mines; Peter Lee, University of Manchester
Wednesday 8:30 AM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Lifeng Zhang, University of Science and Technology Beijing; Peter D. Lee, The University of Manchester
8:30 AM Introductory Comments
8:35 AM Invited
In-situ Observation of Spheroidal Graphite Formation and Measurement of Apparent Volume Expansion in Ductile Cast Iron: Hideyuki Yasuda1; Akira Sugiyama2; Kohei Morishita1; Tomoya Nagira3; Masato Yoshiya3; Kentaro Uesugi4; Akihisa Takeuch4; 1Kyoto University; 2Osaka Sangyo University; 3Osaka University; 4JASRI / Spring-8
In-situ and time-resolved observation of ductile cast iron solidification with 3.6-3.7mass%C and 0.002-0.04mass%Mg) was performed using synchrotron radiation X-ray. Addition of Mg reduced the temperature range that graphite particles grew as a primary phase and promoted spheroidal graphite formation. However, some of the graphite particles tended to deviate from spheroidal shape and the coupled eutectic of austenite and graphite occurred in Al2O3 crucible. On the other hand, the spheroidal shape remained until the end of solidification and the coupled eutectic did not occur in MgO crucible. SEM observation showed that the crucibles modified types of inclusions in the melt. The types significantly influenced nucleation and growth of graphite. The result provides new insights for controlling microstructure of ductile cast iron. In this presentation, we would present in-situ measurement of stress induced during solidification due to the spheroidal graphite growth and discuss shrinkage defects in the cast iron.
X-ray Synchrotron Tomographic Investigation of Graphite Evolution in Near Eutectic Cast Irons: Mohammed Azeem1; Mathias Bjerre2; Niels Tiedje2; Robert Atwood3; Peter Lee1; 1Manchester University; 2Technical University of Denmark; 3Diamond Light Source
Cast irons are a special class of industrial metallic materials with a wide variety of applications ranging from high pressure internal combustion engines through to energy sector where their damping characteristics are used in various housings. This unique blend of properties is closely associated with the morphology and distribution of graphite phase that has been established empirically and through mathematical modeling over past several decades. Here we present a first 4D (3D + temperature) in situ synchrotron X-ray tomographic investigation of various graphite morphologies during conventional solidification in a near eutectic cast iron alloy. The number density and distribution of regular and degenerated graphite nodules will be discussed and correlated with the austenite shell size. The compact graphite was observed to grow from the sample periphery in a complex branching morphology. Some of these branches were observed to nucleate on surface inclusions.
Microstructural Characterization of Graphite Nodules in Fatigue-tested Ductile Cast Iron: Søren Fæster1; Yubin Zhang1; Niels Hansen1; Dorte Juul Jensen1; 1Technical University of Denmark
Thick-walled ductile iron casts have been studied by applying (i) cooling rate calculations by FEM, (ii) microstructural characterization by 2D SEM and 3D X-ray tomography techniques and (iii) fatigue testing of samples drawn from components cast in sand molds and metal molds. An analysis has shown correlations between cooling rate, structure and fatigue strengths demonstrating the benefit of 3D structural characterization to identify possible causes of premature fatigue failure of ductile cast iron. These results are presented and discussed. Also the first results of synchrotron X-ray residual stress measurements at local sites in the matrix near graphite nodules are presented.
Effect of Molybdenum Content, Pouring Temperature and Cooling Rate on the Casting Defects of High Chromium White Cast Iron: Izudin Dugic1; 1Linnaeus University
High chromium white cast are commonly used in application requiring excellent abrasion resistance, as central parts for pumps. The specifications and requirements applied for the white cast iron components are among the most stringent used within the iron foundry branch. One of the biggest problems for the production of these components is hot tearing. Irrespective of the name, this phenomenon represents the formation of an irreversible failure (crack) in the still semisolid casting. This paper aims to investigate the effect of molybdenum content, pouring temperature and cooling rate on the casting defect hot tearing. The procedure to achieve this was to study one casting component, impeller, in a production scale. The experiments showed that molybdenum content and pouring temperature had an important influence on casting defects. It was also observed that the solidification rate has a strong effect on the hot cracking.