Effect of processing temperatures on the properties of a high-strength steel welded by FSW

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2018-11-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
13
1173-1185
Series
Welding in the World, Volume 62, issue 6
Abstract
The need for weight reduction without compromising load-bearing capacity has driven the development of modern high-strength steels (HSS). The ability to take full advantage of these modern HSS is limited by their weldability. Friction stir welding (FSW) can join HSS at low peak temperatures, better preserving the properties of the base material. This work evaluates the influence of different FSW peak temperatures and cooling rates on the properties of a modern HSS. A HSS produced by a thermo-mechanically controlled process was welded by FSW with peak temperatures, measured within the processed zone, ranging from about 900 to 650 °C. Temperatures were measured using thermocouples positioned at the mid-thickness of the workpiece, at 5 to 10 mm from the joint line. The effect of the different peak temperatures was evaluated by mechanical testing, including bending, tensile testing with digital imaging correlation, Charpy impact test, and hardness measurements. Microscopic analyses, including optical microscopy and electron backscatter diffraction, were used to evaluate the microstructure. Results show that FSW enables welding HSS within the intercritical temperature domain. The impact toughness of the best weld condition overmatched the base material by over 37%, at both − 40 and − 60 °C. The yield strength efficiency was about 70%.
Description
Keywords
Friction stir welding, High-strength steels, Mechanical properties, Microstructure, Temperature
Other note
Citation
Sorger, G, Sarikka, T, Vilaça, P & Santos, T G 2018, ' Effect of processing temperatures on the properties of a high-strength steel welded by FSW ', Welding in the World, vol. 62, no. 6, pp. 1173-1185 . https://doi.org/10.1007/s40194-018-0612-8