Evolution of plasticized MnO–Al2O3–SiO2-based nonmetallic inclusion in 18wt%Cr-8wt% Ni stainless steel and its properties during soaking process

The properties of MnO–Al2O3–SiO2-based plasticized inclusion are likely to change during soaking process due to its low melting point. In this study, the evolution of the MnO–Al2O3–SiO2-based inclusion of 18 wt%Cr-8 wt%Ni stainless steel under isothermal soaking process at 1250°C for different times was investigated by laboratory-scale experiments and thermodynamic analysis. The results showed that the inclusion population density increased at the first stage and then decreased while their average size first decreased and then increased. In addition, almost no Cr2O3-concentrated regions existed within the inclusion before soaking, but more and more Cr2O3 precipitates were formed during soaking. Furthermore, the plasticity of the inclusion deteriorated due to a decrease in the amount of liquid phase and an increase in the high-melting-pointphase MnO–Cr2O3 spinel after the soaking process. In-situ observations by high-temperature confocal laser scanning microscopy(CLSM) confirmed that liquid phases were produced in the inclusions and the inclusions grew rather quickly during the soaking process. Both the experimental results and thermodynamic analysis conclude that there are three routes for inclusion evolution during the soaking process. In particular, Ostwald ripening plays an important role in the inclusion evolution, i.e., MnO–Al2O3–SiO2-based inclusions grow by absorbing the newly precipitated smaller-size MnO–Cr2O3 inclusions.

Analysis of the First Soaking Rain Process in Lanzhou City in 2011

[Objective]The research aimed to analyze the first soaking rain process in Lanzhou in 2011.[Method]By diagnostic analyses on weather scale,meso-scale system and physical quantity when the first soaking rain weather happened in Lanzhou City in 2011,formation reason and physical quantity characteristics of the soaking rain weather were discussed.[Result]Combination of the plateau low vortex and westerly cold trough was influence system of the first soaking rain.There was a southwest-southeast airflow from Sichuan Basin to Hexi in front of the trough at 700 hPa.It was commonly referred to as ＂ inverted-buckle wind＂,and provided sufficient water vapour for occurrence and maintaining of the precipitation.Convergence at the low layer and divergence at the high layer were favourable for vertical motion.Analyses on physical quantity and meso-scale system also proved important role of the ＂ inverted-buckle wind＂ at the low layer.[Conclusion]The research provided reference for real-time forecast business of the long drought turning rain in spring.