Effect of Cooling Rate on the Formation of Nonmetallic Inclusions in X80 Pipeline Steel

Abstract

Nonmetallic inclusions have a strong influence on the hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) in pipeline steels, which should be well controlled to improve the steel resistance to HIC and SSC. The effects of cooling rate on the formation of nonmetallic inclusions have been studied both experimentally and thermodynamically. It was found that the increasing cooling rate increased the number density and decreased the size of the inclusions, while the inverse results were obtained by decreasing the cooling rate. Furthermore, as the cooling rate decreased from 10 to 0.035 K/s, the inclusions were changed from Al2O3-CaO to Al2O3-CaO-MgO-CaS. At a high cooling rate, the reaction time is short and the inclusions cannot be completely transformed which should be mainly formed at high temperatures. While, at low cooling rate, the inclusions can be gradually transformed and tend to follow the equilibrium compositions.

Evolution Mechanism of MgO–Al2O3–SiO2–CaO Inclusions During Continuous Casting of Si‐Killed Spring Steel

“…[12,17,21] Because the evolution trend of inclusions in CC is consistent with the thermodynamic evolution, different dynamic conditions may cause differences in the evolution degree of inclusions. [25] Therefore, the casting parameters in this study were adopted to minimize the differences in the dynamic conditions between the two heat conditions in the CC process, as shown in Table 1. Two trails were conducted, marked as Heats A and B, respectively.…”

Refining and Casting of Steel

“…Three papers are based on the studies, regarding the processes taking place in the mold from the viewpoint of heat transfer and multiphase flow influenced by deep submerged entry nozzle (SEN) immersion [9], nozzle clogging [10], and mold flux interaction with steel [11]. Finally, the authors contributed to this Special Issue by also focusing their attention on the complex phenomenon connected to steel cooling, its solidification and quality [12][13][14][15]. All published contributions and their briefly commented upon abstracts are organized based on the technological flow valid for modern steel production in the next subchapters.…”

“…Cooling rate effect on formation of non-metallic inclusions in X80 pipeline steel is the topic of the research presented by Zhang et al [13]. Non-metallic inclusions have a strong influence on the hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) in pipeline steels, which should be well controlled to improve the steel resistance to HIC and SSC.…”

“…At a high cooling rate, the reaction time is short and the inclusions cannot be completely transformed, which should be mainly formed at high temperatures. Meanwhile, at a low cooling rate, the inclusions can be gradually transformed and tend to follow the equilibrium compositions [13].…”

Thermodynamic study on gas hydrates: experimental determination of equilibrium data by high-pressure microcalorimetry and modeling up to 100 MPa.

“…This assumption is consistent since the gas hydrate is formed from distinct phases in absence of mixing. Several works in the literature point out that the cooling / heating rate interferes on the formation of several materials, including hydrates and inclusion compounds (CHROSTEK, 2016;SVARTAAS, 2011;ZHANG et al, 2019;WELLEN et al, 2015). Therefore, a higher heterogeneity of the hydrate lattice could explain the slightly lower dissociation temperature by cooling / heating the system faster.…”