Magnesium aluminum microstructure of Casing pipe

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 martensite transformation is basically completed in casing pipe, and the lower bainite is also contained in the microstructure, while the lower bainite has higher strength and toughness, and the casing pipe will stop producing microcracks and inhibit its expansion, and the quenching hardness of the casing pipe can still reach about 48 HRC, effectively ensuring the quenching quality.

The oil-water alternating-quenching method provided by this study can not only reduce the internal stress generated during quenching, but also ensure the simultaneity of the martensitic transformation both inside and outside the casing, which is beneficial to suppress the occurrence or expansion of quenching cracks.

The modeling method and simulation method of casing pipe provide some theoretical basis for analyzing casing temperature and stress field under different working conditions and different practical operating parameters, and provide a theoretical basis for further analysis of casing pipe with different specifications and different uses, tube heat treatment process has a greater reference value.