Characterization of bainite-ferrite structures formed on the heat-affected zone of a dissimilar welds of high-strength steel (S700MC/S960QC) and their dependency on cooling time
| Autor: | Belinga Mvola, Pavel Layus, Paul Kah, Xiaoyu Cai, Bayock Njock Francois |
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| Rok vydání: | 2020 |
| Předmět: |
010302 applied physics
Heat-affected zone Dependency (UML) Materials science Bainite Metallurgy High strength steel 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Cooling time Characterization (materials science) Ferrite (iron) 0103 physical sciences 0210 nano-technology |
| Zdroj: | Zavarivanje i zavarene konstrukcije. 65:159-172 |
| ISSN: | 0354-7965 |
| Popis: | Modern steel structures and joints must satisfy various increasingly demanding requirements such as high yield strength, improved cross section to mass ratio, and desirable ductile-to-brittle transition properties. Consequently, joining different types of high-strength steels has become an attractive option from the cost perspective and for weight and corrosion reduction. In dissimilar welding, however, there remains a need for better understanding of discrepancies in microstructure formation resulting from asymmetric heat distribution. In this study, a characterization of the transformation of bainite, ferrite, and martensite in the microstructure of the heat affected zone (HAZ) formed by a cooling time of 10 kJ/cm of heat input was carried out for dissimilar high-strength joint steels (S700MC/S960QC). The characterization was performed by scan electron microscopy (SEM) sampling, the images of which were analyzed by ImageJ Pro and evaluated by volume fraction of block - like granular bainite (GB). The alloy elements composition close to the fusion line of both materials was then assessed using energy dispersive X-ray spectroscopy (EDS). The results showed a strong presence of GB, which had about 70% volume fraction in S700MC at 615 °C, and which comprised formations of lower bainite and retained austenite (RA) at 420 °C. The presence of 55% block GB was observed at 470 °C in S960QC, which was caused by the formation of tempered martensite (TMA) at 400 °C. Presence of 1.3Ni, 0.4Mo, and 1.6Mn in the coarse grain heat affected zone (CGHAZ) of S700MC confirmed the risk of brittle failure on the S700MC side due to the high presence of carbide and ferrite in the GB. |
| Databáze: | OpenAIRE |
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