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This study deals with the butt welding of mild or structural steel sheets whose thickness ranges between 1 and 5 mm. A few results relate to 5 to 11 mm thick microalloyed steel plates. Welds were carried out using four different CO(2) lasers with 1 to 7 kW power. The weld shape is described according to the welding conditions and the weld penetration is presented in a diagram as a function of the beam power and the welding rate. The welding thermal cycles are analysed (heating rate, peak temperature, cooling rate) and the cooling parameters are presented as a unique function of heat input and thickness. Considering the short cooling times associated with laser welding, mild steel joints display a wide range of microstructures, despite their low hardenability. The welded joint properties, especially ductility, depend on these microstructures. Ductility of laser joints is better assessed with strain controlled tests. Cold rolling of a strip with a laser joint displays a sharp local increase of the force separating the rolls, associated with the particular cold working behaviour of the weld microstructure. After cold rolling and annealing the welded joint microstructure is very similar to that of the base metal. The toughness of laser welded joints of microalloyed C-Mn steel plates appears to be very dependent on the welding conditions and the precise nature of the welded joint microstructure.

Additional information

Authors: INSTITUT DE RECHERCHES DE LA SIDÉRURGIE FRANÇAISE, Institut de Recherches de la Sidérurgie Française, Saint-Germain-en-Laye (FR);INSTITUT DE RECHERCHES DE LA SIDERURGIE FRANCAISE, Institut de Recherches de la Siderurgie Francaise, Saint-Germain-en-Laye (FR)
Bibliographic Reference: EUR 13515 FR (1991) 180 pp., FS, ECU 15
Availability: (2)
ISBN: ISBN 92-826-0585-X
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