SSAB : Doctoral research provides guidelines for properties of next generation of steels - SSAB

Olli Oja, MSc (Tech), who works as a product development engineer at SSAB Hämeenlinna, investigated the Correlation between the Microstructure and Mechanical Properties of Intercritically Annealed Advanced High-Strength Steels in his doctoral dissertation. Even the smallest structural changes can have major effects on formability. Among many things, this is beneficial in decreasing vehicle weight for improved energy efficiency.

Olli Oja started working in his master's thesis in 2009 in Raahe, where he worked in product development at the mill until 2014, when he switched to the Hämeenlinna Works.

"I did the research for many years in addition to my daily work in the evenings and at weekends. The corona pandemic slightly slowed the project in the final stage, but now I have again time for family and friends," Olli says.

Product development engineer Olli Oja defended his doctoral dissertation at Tampere University, Finland on August 12, 2022.

The research showed that the composition and heat treatment combinations of certain high-strength, cold-formable steels can be used to balance the microstructure and formability properties for different purposes. The results led to a formability map which indicates the link between the formability type and the microstructure.

"For customers, this can be seen by optimized formability and microstructural properties. The customers' products become lighter and complex parts can be more easily formed. Advanced steels help to reduce dependence on fossil fuels," Olli Oja says.

"My research focuses on silicon- and aluminum-alloyed high-strength, cold-formable steels, which are used particularly by the automotive industry. The steels examined in the research are part of the advanced high-strength steels (AHSS) family. The findings provide guidelines for the development of our future products and next generation steels," he adds.

Research and development of aluminum-alloyed steels continues in Hämeenlinna. The first tests were done in 2016 and a couple of years later we announced the first dual-phase high formability (DH steels) in our production program.

"DH steels are an example of products where the heat treatment methods discussed in my work can be used. The steel is made at SSAB's mill in Raahe, from where it comes by rail to Hämeenlinna for pickling, rolling and galvanizing. All SSAB's galvanized products are made in Hämeenlinna," Olli Oja says.

Olli Oja defended his doctoral dissertation Correlation between the Microstructure and Mechanical Properties of Intercritically Annealed Advanced High-Strength Steels in the Faculty of Engineering and Natural Sciences at Tampere University on August 12, 2022.

You can read the doctoral dissertation here https://urn.fi/URN:ISBN:978-952-03-2455-1

Olli Oja in the R&D laboratory in SSAB Hämeenlinna, Finland. The left of the picture shows a field emission scanning electron microscope (FESEM), which was one of the devices Olli Oja used in his research work.