Thesis defence in the University of Oulu

Doctoral Candidate

Master of Science Vahid Javaheri

Faculty and research unit

University of Oulu Graduate School, Faculty of Technology, Materials and Mechanical Engineering Research Unit

Field of study

Materials Engineering

Date and time of the thesis defence

1.11.2019 12:00

Place of the thesis defence

Linnanmaa, sali L10

Topic of the dissertation

Design, thermomechanical processing and induction hardening of a new medium-carbon steel microalloyed with niobium

Opponent

Professor Hans-Olof Andren, Chalmers University of Technology

Second opponent

Professor Pasi Peura, University of Tampere

Custos

Professor David Porter, University of Oulu

Development of a new slurry pipeline steel with induction hardening

The main aim of this thesis was to develop a steel composition and processing route suitable for making a slurry transportation pipeline with the aid of induction hardening, and to characterize the phase transformations and microstructures involved in the various stages of the processing route.

A novel steel chemistry was designed based on metallurgical principles assisted by computational thermodynamics and kinetics. The designed composition is a medium-carbon, low-alloy steel microalloyed with niobium, in wt.% 0.40 C, 0.20 Si, 0.25 Mn, 0.50 Mo, 0.90 Cr, and 0.012 Nb.

This was subsequently cast, thermomechanically rolled on a laboratory rolling mill to two bainitic microstructures, and finally subjected to the thermal cycles predicted to be encountered with the internal induction hardening of a typical pipe geometry.

The phase transformations and microstructures found at various stages of the simulated production process have been characterized and algorithms developed to enable the optimization of microstructure and hardness through the pipe wall thickness.

The thesis has been made within the European Industrial Doctorate (EID) project called Mathematics and Materials Science for Steel Production and Manufacturing, abbreviated as MIMESIS, which has five partners: EFD Induction in Norway; SSAB, Outokumpu, and the University of Oulu in Finland; and Weierstrass Institute for Applied Analysis and Stochastics (WIAS) in Germany.

This thesis has been made within the European Industrial Doctorate (EID) project called Mathematics and Materials Science for Steel Production and Manufacturing, abbreviated as MIMESIS, which has five partners: EFD Induction in Norway; SSAB, Outokumpu, and the University of Oulu in Finland; and Weierstrass Institute for Applied Analysis and Stochastics (WIAS) in Germany.

Dissertation

Last updated: 25.10.2019