Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5007872 | Optics and Lasers in Engineering | 2017 | 11 Pages |
Abstract
Hybrid fiber laser-arc welding (HLAW) process was applied to a novel hot-rolled Nb-Ti-Mo microalloyed steels of 8Â mm thickness. The steel is primarily used to manufacture automotive and construction machinery components, etc. To elucidate the effect of heat input on geometry, microstructure and mechanical properties, different heat inputs (3.90, 5.20 and 7.75Â kJ/cm) were used by changing the welding speeds. With increased heat input, the depth/width of penetration was decreased, and the geometry of fusion zone (FZ) changed to “wine cup-like” shape. In regard to the microstructural constituents, the martensite content was decreased, but granular bainite (GB) content was increased. The main microstructural difference was in the FZ cross-section at 7.75Â kJ/cm because of the effect of thermal source on the top and bottom. The microstructure of the top part consisted of GB, grain boundary ferrite, and acicular ferrite, while the bottom part was primarily lath martensite. The hardness distribution was similar for different heat inputs. Hardness in FZ, coarse-grained HAZ and mixed-grained HAZ was higher than the base metal (BM), but for the fine-grained HAZ was similar or marginally less than the base metal (BM). Tensile strain was concentrated in the BM such that the fracture occurred in this region. In summary, the geometry, microstructure, and mechanical properties of weld joints were superior at heat input of 5.20Â kJ/cm.
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Authors
X.-N. Wang, S.-H. Zhang, J. Zhou, M. Zhang, C.-J. Chen, R.D.K. Misra,