Technology of Seamless Casing Pipe Production

　　Seamless Oil Casing Pipe is produced by hot rolling of medium carbon-manganese V-containing steel and normalizing treatment of finishing rolling temperature > phase transformation point Ar3. The existing production methods of API-5CT Seamless Oil Casing Pipe have the advantages of low cost, saving heat treatment resources and shortening delivery period. However, the process control of  Seamless Oil Casing Pipe is very complex (such as deformation, deformation rate, cooling rate and other performance factors can not be controlled artificially). In addition, the lack of effective process control technology has made the product performance control unstable. The specific performance is that the yield strength can not be stabilized in the range of 552 758 MPa, and the impact toughness is often lower than that of longitudinal 27J or transverse 14J (API 5). The requirement of CT standard seriously affects the yield and safety of the material.

　　The development of Seamless Oil Casing Pipe originated in the mid-1990s, and experienced the development process of medium carbon-manganese Cr-Mo bainitic non-quenched and tempered steel to medium carbon-manganese microalloyed ferrite+pearlite fine grain steel. During this period, due to the instability of performance, especially the abnormal low impact toughness, many major accidents occurred during the use of users. At present, medium carbon-manganese V-containing steel is widely used, such as 27Mn2V, 34Mn2V, 36Mn2V, 36Mn2VN, 35Mn2V and 40Mn2V, which are common in China. Although the development of steel grades is more comprehensive, steel grades are only one of the factors affecting performance, and the control of performance depends more on the control of process parameters.