N80-1 non-tempered seamless sleeve is produced by V-rolling of medium carbon manganese steel. The control of finishing rolling temperature > transformation point Ar3 is equivalent to normalizing treatment. The production method of N80-1 non-tempered seamless casing has the advantages of low cost, saving heat treatment resources and shortening delivery time. However, the process control of N80-1 non-tempered seamless casing is very complex (such as deformation, deformation rate, cooling rate and other performance factors that can not be controlled artificially), coupled with the lack of effective process control technology, which makes the performance control of the product unstable, unstable in the range of 552-758 MPa, and impact toughness often. Lower than the longitudinal 27J or transverse 14J (API 5CT standard requirements), seriously affecting material production and use safety. N80-1 non-tempered seamless casing was developed in the mid-1990s. It has experienced medium carbon manganese Cr-Mo bainite non-tempered steel and medium carbon manganese micro-alloyed ferrite.  During the development of human body and pearlite fine grain steels, many serious accidents have been caused by the users because of the unstable properties, especially the abnormal impact toughness.


At present, commonly used medium carbon manganese V steel, such as domestic 27Mn2V, 34Mn2V, 36Mn2V, 36Mn2VN, 35Mn2V and 40Mn2V. Although the development of steel grades is more comprehensive, steel grades are only one of the factors affecting performance, and performance control is more controlled by process parameters. At present, the research on the control method of N80-1 non-tempered seamless sleeve is less and scattered. The mature or controlled steel and cold control technology as well as the theory of sheet and bar are adopted.  This controlled rolling and controlled cooling technology is mainly controlled by the deformation amount, deformation temperature and deformation rate of each pass in the rolling process to achieve the purpose of austenite recrystallization and grain refinement, and then controlled cooling to change the structure. In the process of transformation, the termination temperature should be controlled to uniformly organize and eliminate the residual stress so as to achieve the ideal structure and ultimately achieve the purpose of performance control. However, the N80-1 non-tempered seamless casing can not be controlled artificially except the deformation temperature, the deformation temperature, the deformation rate and the cooling rate. Therefore, the traditional control rolling and cooling technology can not be applied to the process control of N80-1 non-tempered seamless sleeve, but can only qualitatively explain some phenomena or optimize its performance. Traditional rolling and controlled cooling technology control is usually based on Gleeble compressive stress thermal simulation test. Through hardness test and microstructure observation, the process control of deformation, deformation temperature, deformation rate, cooling rate and termination temperature of each pass can be obtained. Parameters.


The application of this controlled rolling and controlled cooling technology and research method in N80-1 non-tempered seamless casing mainly has the following problems and shortcomings: 1. Traditional rolling and cooling technologies require deformation, deformation temperature, deformation rate and cooling rate to be controlled. However, for N80-1 non-tempered seamless casing, the parameters of deformation, deformation temperature, deformation rate and cooling rate are not controlled artificially, so it loses operability and practical significance. 2. Traditional rolling and cooling technology control is based on the study of hardness and microstructure, lacking quantitative relationship data of tensile properties and impact properties, while the two main performance indexes of N80-1 non-tempered seamless sleeve are tensile properties. Performance and impact toughness.