Mg-Al spinel in the liquid steel of casing pipe
begins to change into the liquid calcium aluminate; the magnesia-alumina spinel is more easily modified into the liquid inclusion than the alumina; the inclusions in the molten steel refining process are affected by the slag reaction and the influence of calcium treatment on the evolution of inclusions in the liquid state according to the Al2O3 → MgO-Al2O3 system inclusions → Ca O-Al2O3-MgO or Ca O-Al2O3 systems.
The results show that under this parameter, the martensitic transformation is basically completed in the casing, and the lower bainite is contained in the microstructure, and the lower bainite has a high strength and toughness. The casing will stop producing microcracks and inhibit the micro crack expansion. The hardness of the casing can still reach 48HRC left right, which effectively ensures the quenching quality.
The alternative quenching method provided by this study can not only reduce the internal stress produced in the quenching process, but also guarantee the occurrence of martensitic transformation inside and outside the casing, which is beneficial to restrain the occurrence of quenching or to expand the crack.
The modeling method and simulation method provide the theoretical basis for the analysis of the casing temperature and stress field under different working conditions and different actual conditions. It provides a theoretical basis for the further analysis of different specifications, different uses of the casing, and the treatment process has great reference value