Effects of Phase Transformation on Distortion and Residual Stress Generated by Laser Beam Welding on High-Strength Steel

2012 ◽  
Vol 56 (3-4) ◽  
pp. 64-70 ◽  
Author(s):  
You-Chul Kim ◽  
Mikihito Hirohata ◽  
Koutarou Inse
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Laser Beam ◽  
High Strength Steel ◽  
Laser Beam Welding ◽  
High Strength

scholarly journals Distortion and Residual Stress Generated by Laser Beam Welding of High Strength Steel

2010 ◽  
Vol 28 (3) ◽  
pp. 281-287 ◽  
Author(s):  
You-Chul KIM ◽  
Mikihito HIROHATA ◽  
Yusuke HAGEYAMA ◽  
Koutarou INOSE
Keyword(s):  
Residual Stress ◽  
Laser Beam ◽  
High Strength Steel ◽  
Laser Beam Welding ◽  
High Strength

Distortion and residual stress generated by laser beam welding of high strength steel

2013 ◽  
Vol 28 (9) ◽  
pp. 693-699 ◽  
Author(s):  
You-Chul Kim ◽  
Mikihito Hirohata ◽  
Yusuke Hageyama ◽  
Koutaro Inose
Keyword(s):  
Residual Stress ◽  
Laser Beam ◽  
High Strength Steel ◽  
Laser Beam Welding ◽  
High Strength

Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints

2020 ◽  
Vol 62 (9) ◽  
pp. 891-900
Author(s):  
Jonas Hensel ◽  
Arne Kromm ◽  
Thomas Nitschke-Pagel ◽  
Jonny Dixneit ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Fatigue Strength ◽  
High Strength Steel ◽  
Transformation Temperature ◽  
Fatigue Cracks ◽  
High Strength ◽  
Filler Material ◽  
Phase Transformation Temperature ◽  
Filler Materials

Abstract The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades.

Hydrogen Charging of High Strength Steel Specimens and Physical Simulation of Cold Cracking under Laser Beam Welding Conditions

2012 ◽  
Vol 706-709 ◽  
pp. 1391-1396
Author(s):  
Ossama Dreibati ◽  
R. Ossenbrink ◽  
Vesselin Michailov
Keyword(s):  
Laser Beam ◽  
High Strength Steel ◽  
Physical Simulation ◽  
Laser Beam Welding ◽  
High Strength ◽  
Cold Cracking ◽  
Tension Stress ◽  
Pure Hydrogen ◽  
Diffusible Hydrogen ◽  
Hydrogen Charging

Cold cracks occur during the cooling down of welded joint at low temperatures or later at room temperature after the end of welding. It is associated with the formation of brittle microstructures as martensite in the presence of diffusible hydrogen as well as of tension stresses. By using an enhanced Simulation-und Testing Center Gleeble 3500, a procedure for physical simulation of cold cracking under laser beam welding conditions is suggested. The approach reproduces combinations of the cold crack main parameters, a brittle microstructure, tension stress and high local hydrogen concentration under welding conditions which induce a cold crack. A specimen geometry and technique were developed to enable the gaseous hydrogen charging from pure hydrogen atmosphere. The amount of charged hydrogen can be adjusted through varying the charging parameters like temperature, gas pressure and charging time. The hydrogen charging technique and the cold crack testing procedure were proven with high strength steel specimens.

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