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Metals 2019, 9(2), 150; https://doi.org/10.3390/met9020150

Comparative Investigation on the Ablation of Uncoated and Coated Mild Steel Inflicted by the 2 ms 2 kA Rectangular Current

1
Key Laboratory of Control of Power Transmission and Conversion, Ministry of Education, Department of Electrical and Engineering, Shanghai Jiao Tong University, Shanghai 200030, China
2
SINOPEC Researching Institute of Safety Engineering, No. 339 Songling Road, Licang District, Qingdao 266000, China
*
Author to whom correspondence should be addressed.
Received: 7 December 2018 / Revised: 16 January 2019 / Accepted: 25 January 2019 / Published: 29 January 2019
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Abstract

The micro ablation characteristics of steel inflicted by the lightning currents and the influence of anti-corrosion coating on these characteristics are seldom investigated, even though fundamental to applications of steel. In this work, ablation tests on uncoated and coated mild steel plates were conducted with the 2 ms rectangular current simulating the component B of lightning currents. The macro-morphology, microstructure, and Vickers hardness of ablation zones were investigated systematically. The ablation characteristics and mechanisms of coated and uncoated steel were analyzed comparatively. It was found that the energy density of the 2 kA 2 ms rectangular current arc exceeded 106 W/cm2 causing the steel near the arc root melted within 2 ms and ablation formed. The width-depth-ratio of the ablated zone was 43.7 for uncoated plate, and only 7.5 for coated plate, since coating constricted the splashing effect of steel melt occurring on uncoated plate and confined the arc root. The metallographic microstructure and EBSD results showed the ablated zones of uncoated and coated steel both consisted of quenched martensite mixed with a handful of ferrite. There were fined equiaxed grains both in the fusion zone (FZ) and heat affected zone (HAZ) of uncoated plates whereas coarser columnar grains and fined equiaxed grains in the FZ and HAZ of coated plates, respectively. In the HAZ of uncoated plate, the average Vickers hardness of steel increased by 113%, while, in the HAZ and FZ of the coated plate, it increased by 209% and 136%, respectively. View Full-Text
Keywords: ablation; mild steel; lightning current; anti-corrosion coating; microstructure; EBSD; Vickers hardness ablation; mild steel; lightning current; anti-corrosion coating; microstructure; EBSD; Vickers hardness
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Dai, M.; Liu, Y.; Fu, Z.; Liu, J.; Bi, X. Comparative Investigation on the Ablation of Uncoated and Coated Mild Steel Inflicted by the 2 ms 2 kA Rectangular Current. Metals 2019, 9, 150.

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