Microstructural Characterization of Laser Weld of Hot-Stamped Al-Si Coated 22MnB5 and Modification of Weld Properties by Hybrid Welding

The presence of Al-Si coating on 22MnB5 leads to the formation of large ferritic bands in the dominantly martensitic microstructure of butt laser welds. Rapid cooling of laser weld metal is responsible for insufficient diffusion of coating elements into the steel and incomplete homogenization of wel...

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Bibliographic Details
Published in:Materials Vol. 14; no. 14; p. 3943
Main Authors: Šebestová, Hana, Horník, Petr, Mikmeková, Šárka, Mrňa, Libor, Doležal, Pavel, Novotný, Jan
Format: Journal Article
Language:English
Published: Basel MDPI AG 14.07.2021
MDPI
Subjects:
Aluminum
Arc heating
Arc welding
Base metal
Boron
Cooling rate
Diffusion coating
Gas tungsten arc welding
Heat affected zone
Heat treating
Laser beam welding
Laser cooling
Lasers
Mechanical properties
Metal fatigue
Microhardness
Microstructure
Shear strength
Silicon
Solid solutions
Steel
Tensile strength
Tensile tests
Ultimate tensile strength
Weld metal
Welded joints
ISSN:1996-1944, 1996-1944
Online Access:Get full text
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Summary:The presence of Al-Si coating on 22MnB5 leads to the formation of large ferritic bands in the dominantly martensitic microstructure of butt laser welds. Rapid cooling of laser weld metal is responsible for insufficient diffusion of coating elements into the steel and incomplete homogenization of weld fusion zone. The Al-rich regions promote the formation of ferritic solid solution. Soft ferritic bands cause weld joint weakening. Laser welds reached only 64% of base metal’s ultimate tensile strength, and they always fractured in the fusion zone during the tensile tests. We implemented hybrid laser-TIG welding technology to reduce weld cooling rate by the addition of heat of the arc. The effect of arc current on weld microstructure and mechanical properties was investigated. Thanks to the slower cooling, the large ferritic bands were eliminated. The hybrid welds reached greater ultimate tensile strength compared to laser welds. The location of the fracture moved from the fusion zone to a tempered heat-affected zone characterized by a drop in microhardness. The minimum of microhardness was independent of heat input in this region.
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ISSN:1996-1944
1996-1944
DOI:10.3390/ma14143943