Master Thesis: The effect of temperature gradients during intercritical ann

The research institute Swerim provides applied research within mining engineering, process metallurgy and materials and manufacturing engineering, mainly for the mining, steel and metals industry. Swerim has 190 co-workers in two locations in Sweden - Luleå and Stockholm.

Summary

The goal of the study is to determine the effect of temperature gradients in Gleeble specimens on the microstructure and properties of selected steel compositions at a range of intercritical annealing temperatures. Additionally, the effect of starting microstructure on the severity of the phenomenon will be studied, varying from cold rolled, annealed and quenched and annealed and slowly cooled starting structures.
 
Introduction
Intercritical annealing is a steel heat treatment conducted by heating the steel to a temperature between Ac1 and Ac3, soaking for a given length of time and cooling the steel down to room temperature. At the conclusion of soaking, the steel has assumed a microstructure consisting of austenite and ferrite. For advanced high-strength steels (AHSS), the intercritical austenite could consist of equiaxed grains, long banded structures or relatively thin films between lath-shaped ferrite grains, depending on the starting microstructure.
 
The width of the temperature window between Ac1 and Ac3 determines the effect of small temperature changes to the ferrite/austenite ratio at the conclusion of annealing. If the window is small, even a small change in annealing temperature could lead to a large effect on the final properties of the steel.
 
The Gleeble 3800 is a device used to simulate industrial steel processing. In the Gleeble, specimens are held in place by clamps, which also supply direct electrical current for heating the specimen. The clamps are cooled to avoid overheating the device. However, the relatively massive clamps attached to the specimen result in a temperature gradient between the attachment point and the center of the specimen. For sensitive alloying compositions, the gradient may be steep enough to introduce inhomogenuity in the final microstructure, making characterization of the specimen more difficult.
 
The thesis will have a strong emphasis on experimental work. However, the results will be interpreted on the basis of the thermodynamics and kinetics of the relevant phase transformations for the investigated alloying compositions.
 
Goals
The goal of the study is to determine the effect of temperature gradients in Gleeble specimens on the microstructure and properties of selected steel compositions at a range of intercritical annealing temperatures. Additionally, the effect of starting microstructure will be studied, varying from cold rolled, annealed and quenched and annealed and slowly cooled.
 
The study will be conducted on the Gleeble 3800 annealing simulator. The specimens will be characterized on the basis of microstructure, hardness measurements and retained austenite measurements.
 
The results and conclusions of the work will be presented to the research partners of the TMPA research area in one or more of the consortium meetings.
 
Required qualifications
Student in material science, physics, chemistry, or related area. The work should be initiated as soon as possible. The master student performing the work will gain a large industry network. Swerim rewards the student with 50 000 SEK for an approved master thesis (30hp).  
 
Contact
For further information about project, please contact: 
Tuomo Nyyssönen, tuomo.nyyssonen @swerim.se
 
Interested?
Feel free to contact us by completing the form below no later than November 15th, 2022. You will receive a confirmation that Swerim has received your application. Please note that we fill the thesis as soon as we find a suitable applicant, which means we can fill the position before the deadline. We look forward to hearing more about you and what you want to contribute with us.