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 KEYNOTE AND INVITED SPEAKERS |
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| Full name of the lecturer |
Jorge Fernandez dos Santos |
Company |
GKSS Forschungszentrum |
Department |
Joining Technology |
| Summary speaker resume |
1976 - Metallurgic Engineer, Universidade Federal Fluminense
1978 - M.Sc in Welding Metallurgy, COPPE/UFRJ
1982 - PhD in Welding Technology, Cranfield University, UK.
1985 - Welding Engineer, Underwater Engineering. Today - Welding Technology Group
Head, GKSS Forschungszentrum |
Title of the lecture |
Microstructure and Properties of Friction Stir Welded Joints in a S355 Steel Grade |
Summary of the spoken topic |
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In the present work, double pass friction stir welds in a 12 mm-thick S355 steel
grade have been produced and analysed. Microstructure across the weld zone have
been characterised and correlated with hardness and tensile test results obtained.
Additionally, the toughness behaviour of the welds has been evaluated by Charpy
impact and crack tip opening displacement testing. Of particular interest is the
effect of a double-pass weld, by welding halfway through the plate thickness from
one side and then welding from the second side of the joint. The effect of the second
weld is to temper back the hardness of the first weld, and the effect of this on
the toughness of the resultant weld is discussed. The observed microstructures consisted
basically of bainitic colonies in the stir zone and recrystallised acicular structures (double-pass welds) in the HAZ, especially next to the stir zone. In the double-pass
welds a limited effect of the additional thermal cycle, originating from the second
pass, on the microstructure could be observed. The microhardness profiles of the
welds showed an increase of hardness at the welded region. The first pass presents
slightly softened material both in the stir zone and the HAZ caused by the heat
treatment from the second pass. The tensile tests confirmed the indications from
the hardness testing since all specimens failed out of the weld region, in the base
material (overmatching). The results of the Charpy impact tests were in general
inferior to those obtained in the base material. Nevertheless, all the values in
both the stir and heat affected zones exceeded the requirements imposed by codes
and standards. The CTOD values demonstrate in general a good performance of the
joints |
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