Ultra-narrow gap laser welding (ultra-NGLW) is an advanced welding technology for thick bainite steel with a welding gap of only 4 mm. We studied the failure mechanism of the tensile fracture of ultra-NGLW joints of bainitic steel via in situ tensile tests. The tests show that cracks for all micro-zone specimens propagated along the tensile direction at 42°∼45°. Further analysis of the crack tips by Electron Back Scatter Diffraction showed main cracks along directions with high Schmid Factors (SF >0.44), and micro-cracks were found on the grain boundaries of (111) and (101) grains. It was revealed that the wire-filling zone and heat-affected zone were mainly intergranular expansion, whereas in the no filling zone, the crack propagation was transgranular.
LiRWangTWangCA study of narrow gap laser welding for thick plates using the multi-layer and multi-pass method. Optics Laser Technol. 2014; 64(4):172–183. doi: 10.1016/j.optlastec.2014.04.015
2.
YiwenZMaolongZZhiyuanSMicrostructures and properties of 50 mm thick SA508Gr.3Cl.2 steel welding joints by ultra-narrow-gap laser welding with filler wire. Chin J Lasers. 2017; 44(11):1102006. doi: 10.3788/CJL201744.1102006
3.
ZhangXAshidaETarasawaSWelding of thick stainless steel plates up to 50 mm with high brightness lasers. J Laser Appl. 2011; 23(2):807–819. doi: 10.1007/s00340-011-4577-1
4.
ElmesalamyAFrancisJALiL.A comparison of residual stresses in multi pass narrow gap laser welds and gas-tungsten arc welds in AISI 316L stainless steel. Int J Pressure Vessels Piping. 2014; 113(113):49–59. doi: 10.1016/j.ijpvp.2013.11.002
5.
LiqunL.Numerical simulation of temperature and stress fields in wire filling laser multilayer welding. Chin J Lasers. 2011; 38(10):1003002-1–1003002-5. doi: 10.3788/CJL201138.1003002
6.
AtabakiMYazdianNMaJHigh power laser welding of thick steel plates in a horizontal butt joint configuration. Opt Laser Technol. 2016; 83:1–12. doi: 10.1016/j.optlastec.2016.03.016
7.
FengJGuoWIrvineNUnderstanding and elimination of process defects in narrow gap multi-pass fiber laser welding of ferritic steel sheets of 30 mm thickness. Int J Adv Manuf Technol. 2016; 88:1821–1830. doi: 10.1007/s00170-016-8929-1
8.
HaddadMIvanisenkoYCourtois-ManaraEIn-situ tensile test of high strength nanocrystalline bainitic steel. Mater Sci Eng A. 2015; 620:30–35. doi: 10.1016/j.msea.2014.09.088
9.
GuoWLiLDongSComparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel. Opt Lasers Eng. 2017; 91:1–15. doi: 10.1016/j.optlaseng.2016.11.011
10.
Xin-PingLFu-ZhenX.Heterogeneous mechanical property and microstructure of welded joints of CrMoV steel. Pressure Vessel Technology, 2014.
11.
DandanKTianmingWGaojianWEffect of heat input on microstructure and mechanical properties of welded joint of 1000MPa high-strength steel B950CF for hydropower engineering. Hot Work Technol. 2018; 47(17):221–224.
12.
Zhang XPDornL.Investigation on the possibility of using the microshear test as a surveillance method to estimate the mechanical properties and fracture toughness of nuclear pressure vessel steel, A508CL3, and its joints welded by narrow-gap submerged-arc welding. Int J Pressure Vessels Piping. 1999; 76(1):35–41. doi: 10.1016/S0308-0161(98)00097-0
13.
MarkushovYEvtihievNGrezevNMultipass narrow gap of heavy gauge steel with filler wire. Phys Procedia. 2015; 71:267–271. doi: 10.1016/j.phpro.2015.08.299
14.
WenzhengWYongkangZFuyinJStudy on fiber laser wire filling welding process and weld microstructure of 20 steel. Hot Working Technology, 2013.
15.
YanbinCJiecaiFLiqunLI.Research on the characteristics of Double-Sided Hybrid laser-GMAW Synchronous Horizontal welding of high-strength thick steel plates. J Mech Eng. 2016; 52(2):47. doi: 10.3901/JME.2016.02.047
16.
JieYLiqunLWangTWeld microstructure characteristics of dual laser beam multi-layer welded high strength steel with filler wire. Chin J Lasers. 2010; 37(5):1361–1367. doi: 10.3788/CJL20103705.1361
17.
XiaoboZRuiCWeiFFracture mechanism of In-situ tensile of TIG welding joints for 980MPa high strength Steels. China Mech Eng. 2010; 21(22):2746–2750.
18.
Li-HuaQIWei-WeiZXiao-FengLAnalysis of Plasticity deformation by In-situ Means of high strength Pipeline. J Shanghai Jiaotong Univ. 2012; 46(9):1455–1460.
19.
GuibinCXinhuaJULixinYEBSD characterization on the grain size of ferrite of ultra low-carbon IF steel. Materials Rev. 2018.
20.
HuaYPeileiZZhishuiYU.In-situ tensile research on microstructure of modified high manganese steel. Hot Work Technol. 2014; 43(2):64–66.
21.
NingXUFenghuiWJinhengLIn-situ TEM observation of micro-fracture behavior of X80 pipeline steel welding joint. Mater Sci Technol, 2015.
