METALLURGICAL AND METALLOGRAPHIC METHODOLOGIES
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- Versione italiana
- Academic year
- 2015/2016
- Teacher
- MATTIA MERLIN
- Credits
- 6
- Curriculum
- INDUSTRIALE
- Didactic period
- Primo Semestre
- SSD
- ING-IND/21
Training objectives
- Aim of the course is to give knowledge regarding both the principles of the metallographic laboratory practice and the microstructure of carbon steels and cast irons, according to the production processes and different bulk and surface heat treatments. The student will learn the most important information about some techniques used for the analysis of metallic materials. On the basis of the main acquired knowledge, the student will be able to perform metallographic investigations, to recognize the microstructure of some steels and cast irons under certain heat treatment and supply conditions, and to know how dealing with metallurgical quality control and failure analysis.
Prerequisites
- The student must have the knowledge of the basic topics of metallurgy.
Course programme
- • Elements of metallurgy: phase diagrams, Fe-C phase diagram, TTT and CCT curves, phase and structural constituents. (4 hours)
• Microstructures of steels and cast irons (white, grey, vermicular and spheroidal cast irons). Introduction to the solidification of cast irons. Main etching reagents for metallographic inspection of steels and cast irons (ASTM E407, UNI 3137). Graphite classification in cast irons according to UNI EN ISO 945. (4 hours)
• Main aspects of steel industry. Production of steels, ingot casting and continuous casting. Hot and cold plastic deformation processes for the production of semi-finished steel products. Major and minor segregations in ingots and in continuous casting bars. Microstructural banding in steels (UNI 8449). (4 hours)
• Solidification: thermal and constitutional undercooling. (2 hours)
• Non-metallic inclusions (UNI 3244 and UNI EN 10247): identification of oxides, nitrides, sulphides and methods for reducing the dangers of inclusions. Macro and micrographic methods. (2 hours)
• Analysis of the grain size: methods for both the revealing and the evaluation of the austenitic and/or ferritic grain size (UNI EN ISO 643 and ASTM E112). (2 hours)
• Brinell, Vickers and Rockwell hardness tests. Microhardness tests. (2 hours)
• Description and identification of the most important defects in steels (due to solidification, heat treatments, machining and mechanical deformation). (2 hours)
• Techniques for metallographic inspection (theoretical aspects): visual inspection, optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM). Microanalytical techniques: wavelength dispersive spectroscopy (WDS), energy dispersive spectroscopy (EDS) and electron back-scattered diffraction (EBSD). OES technique in brief. Microstructural analysis with replica technique (UNI 6327, UNI 9993). (8 hours)
• Techniques for metallographic analysis (practical aspects): preparation of samples for metallographic inspection of steels and cast irons. Practical aspects of heat treatments: quenching, annealing and normalizing. Practical aspects of surface hardening treatments and of some coatings. Characterization of metallic materials subjected to thermochemical treatments (carburizing UNI 5381). Hardness tests (Vickers: UNI EN 6507, Brinell: UNI EN 6506, Rockwell: UNI EN 6508) and Vickers hardness profiles. Poldi hardness test. Examples of microstructural investigations by SEM. (18 hours) Didactic methods
- The course is organized as follow:
• Frontal lectures on all the course’s theoretical topics;
• Practical lessons in the Metallurgy lab concerning practical aspects of the course’s topics. In particular, during these lessons it will be possible i) to accurately prepare metallographic samples, ii) to understand the critical issues and suggestions for a good sample preparation, iii) to recognize different metallographic structures of steels and cast irons by means of OM and/or SEM, iv) to perform hardness and microhardness tests. Learning assessment procedures
- The examination is oral and divided in 2 sections.
The first section is performed in order to assess the understanding of the theoretical subjects tackled in the class. In particular, the ability of critically linking the different subjects covered during the course, rather than the capacity to simply repeat the specific topics, is evaluated.
In the second section the student has to demonstrate the understanding of the fundamental skills for the metallographic preparation and for the interpretation of the microstructure of metallic materials (in particular, steels and cast irons), in relation to the production processes and to the heat treatments.
The student must show a sufficient knowledge of the topics in both sections of the examination. The final mark is formulated verifying at which level the learning objectives previously described have been acquired. Reference texts
- • Teacher’s handouts available on the course web page
Specific topics can be further learnt in the following texts:
• G.M. Paolucci, Lezioni di Metallurgia Vol.1 e 2, Ed. Libreria Progetto Padova
• C. Cibaldi, I criteri di scelta e di trattamento degli acciai da costruzione e da utensili, Vol 5.1-5.2-5.3, AQM.
• G. Krauss, Steels: processing, structure and performance, ASM International, 2005
• B.L. Bramfitt, Metallographer’s guide: irons and steels.
