Experiment (5): Heat Treatment of Plain Carbon Steels

Experiment (5) Heat Treatment of Plain Carbon Steels

Objective (write your own version in the report)

1. Get more acquainted with Fe-Fe₃C phase diagram.
2. Focusing on the plain carbon steel zone in the Fe-Fe₃C system.
3. Studying the effect of the various cooling and heat treatment methods on steel microstructure.
4. Studying the Austenite-to-Martensite transformation and its impact on microstructure.

Key Words

Generate your Abstract and line of thought using (some of) the following keywords (use others if possible):
Phase diagrams: Fe-Fe₃C system, Steel alloys, Phase transformations: heat treatment processes

You should familiarize yourself with all the following heat treatment terms for ferrous and non-ferrous alloys:
Austenizing, Ausforming, Austempering, Martempering, Quenching (Martensite formation), Normalizing, homogenizing, Solution Heat Treatment (SHT-Solutionizing), Precipitation (hardening) Strengthening, Annealing, Aging (natural/artificial), Bainite formation (isothermal transformation), Overtempering, Full annealing/Process annealing, Hardening "of steel" (Martensite formation), Spherodizing, Stress relief, recrystallization Some of them are relevant to this report

Introduction

Discuss the following topics in correct language and organized flow of ideas within your introduction:
1. Need for heat treatment processes (hardening, tempering, softening, recrystallization, stress relief, hot working, diffusion)
2. Differeniate between TMT (Thermo-Mechanical Treatment) and HT (Heat Treatment)
3. Pinpoint the major heat treatment processes, in steps (e.g. martensite formation)
4. Highlight the main controlling parameters in any heat treatment process (temperature, cooling media, time)
5. The effect of carbon content on the microstructure and phase transformation
6. Bonus: Introduce TTT curves (Click here for some useful multimedia about this topic).

** You may find it more convenient to add a separate section (theory) about Martensite transformation, highlighting specific points e.g. types of martensite, microstructure, crystal structure, Martensite formation on the TTT diagram (M_s & M_f)

Procedures

Include full details: magnification power, etching solution (composition/concentration), heat treatment specifications (temperature/time) if any.

Five specimens were used:
        1. X17: 0.8%C, heated for 1 hour at 800 C, then furnace cooled.
        2. X18: Same as X17, but cooled in still air instead (normalized).
        3. OQ: 0.33% C with 3.6% alloying elements, oil quenched and no tempering.
        4. OQ: tempered for 2 hours at 200 C.
        5. OQ: tempered for 2 hours at 600 C.

Common preparation procedures such as grinding and polishing were taken, followed by etching using 3ml of HNO₃ + 100 ml of CH₃OH (methyl alcohol), etched by immersing for 15 seconds.

Results/Discussion

Required: A "neat" sketch for the microstructure

Use (ALL) the following questions to build your discussion in a correct language and organized flow of ideas 1. Define the microstructures formed, parameters, mechanical properties
2. The effect of cooling (media, time) on the formed structures
3. Define the corresponding heat treatment, giving full details

Further References/Images

--Use (some of) the following pictures (make sure to cite) and comment on them in your lab report

[After http://compfab.me.lsu.edu/me3701/experiments/metallography]

--The following sites and books contain useful information and images for several articles that we have encountered in this experiment. Make sure to check them.

Useful page 1

Useful page 2

Kalpakjian, Serope. Manufacturing Process for Engineering Materials. Addison Wesley, 3^rd Ed., 1997.

Smith, William F. . Principles of Materials Science and Engineering. McGraw Hill, 3^rd Ed., 1996. (p. 128-132)

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