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Henri Järvinen: Successful processing of hot-dip galvanized press-hardening steels requires exceptionally low hot forming temperature and tailoring of steel composition

Tampere University
LocationKorkeakoulunkatu 6, Tampere: Konetalo, auditorium K1702 and remote connection
Date12.11.2021 10.00–14.00
Entrance feeFree of charge
Väitöstutkija yliopiston kampuksella.
Hot-dip galvanized, i.e. zinc-coated press-hardening steels (PHS) are high-strength and corrosion resistant materials that are used in particular in structural safety components of a car body. However, limited understanding of the material behavior and challenges in their processing, such as the risk of crack formation during the hot forming step of the press-hardening process, have delayed their commercial breakthrough. Henri Järvinen's doctoral dissertation highlights novel information on designing new steel grades, which helps to eliminate detrimental cracking and optimize their mechanical behavior.

Car body assemblies combine a wide range of different steel grades. So-called press-hardening (or hot-stamping) technology has enabled producing high-strength complex shaped components out of steel sheet. This has led to a possibility to decrease the car body weight at the same time as reducing CO2 emissions and optimizing the fuel (or battery) economy of cars.

“The development of new PHS grades requires both clever metallurgical design as well as understanding of each detail of the press-hardening process”, explains Henri Järvinen.

Hot-dip galvanized PHS, considered as premium materials on the market, are especially demanding to manufacture without quality issues: low melting point of the zinc and zinc-rich phases of the coating makes also steel susceptible to cracks.

“It was also interesting to observe that coating type may set some limitations for the steel chemistry and vice versa, which essentially guides the research and development of these materials,“ Järvinen continues.

Henri Järvinen studied a group of industrially manufactured press-hardening steels together with novel steels designed during the dissertation  project. A laboratory built press-hardening equipment was used to understand the application related factors controlling the mechanical behavior of steels as well as to increase understanding on the mechanisms occurring on the coating and steel interface.

“Coating and steel merge together during the high-temperature heat treatment stage of the press-hardening process, and thus it is important to realize that in this material group steel and coating must be considered as an entity – not separately as steel and coating”, says Järvinen.

It was noticed that the standard commercial steel grades cannot be manufactured successfully as zinc-coated versions only with traditional process parameter control. In turn, the combination of crack-free parts and excellent corrosion protection properties can be only attained by carrying out the hot forming stage clearly at unconventionally low temperatures. This requires modified steel chemistry.  

Henri Järvinen has worked at Metso Outotec (formerly Metso Minerals) since 2018.

The doctoral dissertation of MSc (Tech) Henri Järvinen in the field of materials engineering titled Processing and Properties of Hot-Dip Galvanized Press-Hardening Steels will be publicly examined in the Faculty of Engineering and Natural Sciences at Tampere University on Friday 12th of November 2021 in the auditorium K1702 of the Konetalo building (Korkeakoulunkatu 6, Tampere). The Opponents will be Prof. (emer.) David Porter from the University of Oulu and Prof. David Penney from the Swansea University. The Custos will be Prof. Pasi Peura from the Faculty of Engineering and Natural Sciences.

The dissertation is available online at:

The dissertation can be followed by remote connection (Panopto).

Photo: Jonne Renvall / Tampere University