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To decrease the turning-induced pitting susceptibility of laser-cladded Fe–Cr–Ni layer by low plasticity burnishing

Zhang Peirong, Hu Shunrui, Lv Tao, Du Jin, Su Guosheng, Liu Zhanqiang, Xu Chonghai

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 4

art. no. e179, 2022

Corrosion resistance of machined surface and its correlation with surface roughness have been the important concerns for sustainability of the final products. However, the pitting corrosion of laser-cladded Fe–Cr–Ni layers by turning exhibits susceptibility to surface roughness characteristics. In present study, the generation mechanism of pitting susceptibility by turning and the effect of burnishing on decreasing the pitting susceptibility were explored. To this end, a theoretical model of the potential difference between roughness peaks and valleys was established with considering the functional parameters of the surface roughness. Then, the correlations between the potential difference and pitting characteristics including pitting depth, width and area were analyzed in order to reveal the generation mechanism of pitting susceptibility. The occurrence of pitting corrosion could be predicted by the local potential difference, which was higher at the location where pitting corrosion would occur while lower where pitting corrosion did not occur. Finally, the influence of each functional parameter of surface roughness on the potential difference was analyzed using the proposed model, with which the machining schematics were discussed. On the basis of this research, it was expected to improve the corrosion resistance of the claddings by turning and subsequent burnishing process chain.

Investigation of electric potential difference during the top oxygen blowing in converter

Semykin S. I., Golub T. S.

Journal of Achievements in Materials and Manufacturing Engineering

2018

Vol. 88, nr 1

35--40

Purpose: of this paper is to investigate the method of monitoring the course of the main oxidation-reduction processes and dust depression during the top oxygen blowing, based on the registration of natural electric potential difference on the lance-metal melt site during the blowing. Design/methodology/approach: Exchange processes in the converter bath take place with exchange of electrons and ions between metal and slag melts and gas phase. Since the processes are far from equilibrium, if to complete the circuit it will be possible to register the potential difference. Investigation was conducted in industrial converters of 60-t capacity at medium-carbon steel smelting. During the blowing the potential difference in the lancemetal bath site, the position of the lance and the dust level after gas cleaning were recorded. Findings: It was revealed that the level and sign of variation of the potential difference in the lance-metal bath site reflects the course of the main oxidation-reduction processes in the sub lance area during melting periods: oxidation of silicon, carbon and iron. The probable course of gaseous oxygen interaction with the metal fusion was discussed. Practical implications: In order to reduce the dust level without slowing down the carbon oxidation process, it was recommended to place the lance at a level corresponded to the potential difference during the active carbon oxidation period 30 % lower than 200-210 mV. The results of heats, conducted with the proposed mode of lance position, showed that the level of dust emission was 16% lower than on the comparative melting. Originality/value: The level and sign of the potential difference is possible to use to select the lance position during the blowing for longer slag foamed state without overflow that ensures a lower level of dust emission.