期刊
JOURNAL OF MATERIALS PROCESSING TECHNOLOGY
卷 226, 期 -, 页码 106-114出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jmatprotec.2015.07.010
关键词
Laser welding; Steel; Precipitation; Phase transformation; Hardness measurement; Martensite
资金
- National Nature Science Foundation of China [51305285]
- Basic Research Program of Jiangsu Province [BK20130315, BK20140334]
- Natural Science Foundation of the Jiangsu Higher Education Institutions of China [14KJB460024]
- China Postdoctoral Science Foundation [2014M561707]
A 4-kW fiber laser was adopted to weld nano-scale precipitate-strengthened C-Mn steel (NPS steel). Only martensite was found in the fusion zone (FZ), fusion line and coarse-grained heat-affected zone (CGHAZ). The heat-affected zone (HAZ) consisted of both ferrite and martenite/austenite island (M/A island), which were found in both the fine-grained heat-affected zone (FGHAZ) and the mix-grained heat-affected zone (MGHAZ). In the FZ, original niobium titanium carbonitride and niobium titanium carbide precipitates were completely re-dissolved in the re-heating process, and only niobium titanium carbonitride re-precipitated in the subsequent cooling process. The original precipitates coarsened in heat-affected zone (HAZ) like Ostwald ripening phenomenon. Micro-hardness and yield strength of the FZ and the HAZ were higher than those in the base material (BM). Compared with the BM, the strengthening mechanism of the FZ and the CGHAZ were transformation strengthening and grain-refinement strengthening; precipitate strengthening. Transformation strengthening was the primary and important strengthening mechanism in the FGHAZ and the MGHAZ. (C) 2015 Elsevier B.V. All rights reserved.
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