Experimental Research on BG110T Anti-collapse Casing(PartⅡ)——Influence by residual stress, average wall thickness and yield strength on critical anti-collapse strength

Based on the R & D of the BG110T and BG110TT casings, a systematic research concerning the influence by the heat treatment processes adopted during pipe rolling on the residual stress, wall thickness tolerance, yield strength and critical anti-collapse strength of the casing is conducted. The result demonstrates that the casing yield strength can be enhanced, while the residual stress thereof can be reduced by means of the minus tolerance being used for the groove design, multi-stand reeling and properly controlling of the tempering temperature and the temperature for straightening, so as to considerably increase anti-collapse performance of the casing, and that critical anti-collapse strength of the casing will be up to 1.6 times as great as the API specified value in case the residual stress is within 100 MPa, and the wall thickness tolerance is about +8% owing to properly controlling.