Characteristics of the heat-affected zone in ultra-fine grained steel during ultra-narrow gap GMA welding. Softening zone and microstructures of the heat-affected zone in ultra-fine grained steel

2005 ◽  
Vol 19 (6) ◽  
pp. 447-455 ◽  
Author(s):  
R Ito ◽  
K Hiraoka ◽  
C Shiga
Author(s):  
Michael Santella ◽  
X. Frank Chen ◽  
Philip Maziasz ◽  
Jason Rausch ◽  
Jonathan Salkin

AbstractA 50.8-mm-deep gas tungsten arc weld was made with matching filler metal in cast Haynes 282 alloy. The narrow-gap joint was filled with 104 weld beads. Visual and dye-penetrant inspection of cross-weld specimens indicated that the cast base metal contained numerous casting defects. No visible indications of physical defects were found in the weld deposit. The weld heat-affected zone was characterized by microcracking and localized recrystallization. The cause of the cracking could not be determined. Hardness testing showed that a softened region in the as-welded heat-affected zone was nearly eliminated by post-weld heat treatment. Tensile testing up to 816 °C showed that cross-weld specimen strengths ranged from 57 to 79% of the cast base metal tensile strength. The stress-rupture strengths of cross-weld specimens are within 20% of base metal reference data. Failures of both tensile and stress-rupture specimens occurred in the base metal.


2007 ◽  
Vol 539-543 ◽  
pp. 4063-4068 ◽  
Author(s):  
Hideki Hamatani ◽  
Yasunobu Miyazaki ◽  
Tadayuki Otani ◽  
Shigeru Ohkita

Ultra-fine grained steel (UFGS) with an average grain size of less than 1μm has been developed and is expected to demonstrate superior properties. However, its welded heat-affected zone, HAZ, substantially affecting the strength of a welded joint, will be easily softened after welding. Therefore, minimization of UFGS’s HAZ size during laser welding was carried out using the cooling conductor liquid nitrogen. It was found that a shielding gas with adequate flow rate for the liquid nitrogen depth was used to displace nitrogen on the area of laser beam irradiation to stabilize the weld bead. Also, because YAG laser system was mainly used because it has a lower laser induced plasma or plume temperature, which results in a decreased occurrence of pit and blowhole. HAZ size minimization strongly depends on the initial plate temperature. Reduced initial plate temperature shrinks the specific heated temperature range in which softening occurs. However, due possibly to decreasing thermal conductivity under room temperature, which prevents heat removal, the benefit of reducing the initial plate temperature is limited. The optimal initial temperature to minimize the HAZ size, in the present work, was found to be 123K.


2011 ◽  
Vol 299-300 ◽  
pp. 372-375
Author(s):  
Jin Gang Qi ◽  
Dong Jun Zhang ◽  
Zuo Fu Zhao ◽  
Shan Dai ◽  
Xiao Chen Liu

In order to improve toughness of the weld heat affected zone (HAZ) of ultra-fine grained (UFG) steel, a thermal simulation procedure of Fe-Mn-Si UFG steels with different Al addition was conducted and the corresponding microstructure was characterized and investigated. The results indicate that the maximum value on driving force of nucleation is ultra-fine grain steel with wtAl=0.6%, it has been explained in Nucleation kinetics that the grains are fine in UFG2. On the other hand, the bainite ferrite growth orientation has been increased. The toughness was remarkably enhanced in the steel welded heat affected zone. The formation of strie retained austenite and grain refinement of bainite ferrite in Fe-Mn-Si UFG steels with Al additions results in the increasing toughness of weld HAZ.


2019 ◽  
Vol 50 (7) ◽  
pp. 3080-3090 ◽  
Author(s):  
Y. Liu ◽  
S. Tsukamoto ◽  
H. Hongo ◽  
F. Yin ◽  
M. Tabuchi ◽  
...  

2017 ◽  
Vol 61 (2) ◽  
pp. 241-248 ◽  
Author(s):  
W. H. Xu ◽  
C. L. Dong ◽  
Y. P. Zhang ◽  
Y. Y. Yi

2016 ◽  
Vol 258 ◽  
pp. 635-638 ◽  
Author(s):  
Michal Junek ◽  
Marie Svobodová ◽  
Jiří Janovec ◽  
Jakub Horváth

This article deals with the results of mechanical testing and structural analysis of sections of narrow gap orbital welded P91 steel on tube OD 355.6 x 40 mm. The evaluation of mechanical properties was based on tensile test at room temperature on mini-tensile specimens and on measurement of modulus of elasticity. Weld was cut longitudinally into 9 narrow slices by using waterjet. From these slices 108 flat mini-tensile specimens (dimensions of gauge is 2 x 2 mm) were prepared. In experimental part microstructure evaluation and documentation of fracture surface of each mini-tensile specimen were carried out. The aim of these experiments was to assess the mechanical properties of the individual sections of the weld (base metal, heat affected zone and weld metal). These data can be used for new approaches of FEM modelling of welds considering heat affected zone like a combination of different materials with different mechanical properties, which connect the thermally unaffected base metal and weld metal.


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