Heat Treatment and Qualitative Metallographic Analysis Lab

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  • Topic: Rockwell scale, Steel, Hardness
  • Pages : 16 (3255 words )
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  • Published : April 27, 2013
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Heat Treatment and Qualitative Metallographic Analysis Lab

ME 3228: Mechanics & Materials Laboratory

Summary
Comparing a material's initial treatment and the microstructures that are formed from different processes, an engineer can accurately understand why certain treated materials of the same family can be stronger than another. In this experiment annealed and cold-worked specimens of AISI 1018 STEEL are used, along with a Hardness tester, a grinding and polishing process, and a micrograph to see the grain structure of the steel. After putting a specimen through a process using each piece of equipment, grain structures of differently treated materials can be compared. The Hardness Tester gives a value of the strength of a material and in this case the annealed steel was 48.6 HRB, untreated steel is usually around 73 HRB, and the cold rolled steel was 90.8 HRB, in the Rockwell scale. These strength values can then be used comparatively with each of the steel's microstructures. The grinding and polishing processes, along with a solution used to etch the surface of the steel, is then used to prepare the material for the micrograph. The steel was first prepared with four types of increasingly fine sandpaper and then polished with four types of increasingly fine polycrystalline diamond suspension fluid and paper. A 2% Nital solution is then used to etch the surface, or to make the grains of the steel more prominent. After this, a micrograph is used to see the grain structures of the differently treated steel and compare the different proportions of ferrite, pearlite, and others such as cementite. The grain structures for each steel varied on these proportions. The annealed steel was made up of 77% ferrite, which is innately soft and roughly 20% pearlite which is much harder. From simply visual interpretations, the cold rolled steel possessed a far higher content of pearlite, despite initial predications that the samples would contain similar composition. Regardless, this test proves the reason why treating a material before it is used can be beneficial in certain situations when hardness is needed.

Table of Contents
Summary…………………………………………………………………………………………………………………………………… 2 List of Equations………………………………………………………………………………………………………………………… 4 List of Tables…………………………………………………………………………………………………………………….…………5 List of Figures…..……………………………………………………………………….………………………………………………...6 Introduction…………………………….…………………………………..……………………………………………………………...7 Theory……………..…………………………………………….…………………………………………………………………………...8 Test Setup & Experimental Procedure………………………………………………………….…………………………….11 Results & Discussion.…………………………………..………………………………………………………………………….…18 Conclusion……….……………………………………………………………………………………………………………………..…23 References……….………………………………………………………………………………………...…………………………..…24 Appendix………….……………………………………………………………………………………………………………………….25

List of Equations

1. Lever rule………………………………………………………………………………………………………………………..9

List of Tables

1. AISI 1018 Steel chemical composition ..........................................................................................................13 2. Theoretical and Experimental compositions of anneal 1018 sample…………………………………………13

List of Figures

1. Phase diagram for steels.……………………………………………….....................................................………...…9

2. Buehler Rockwell hardness tester....................................................................................................................10

3. Grinding wheels image..........................................................................................................................................12

4. Polishing wheels...
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