Fea Analysis Of Residual Stress For Heat Treatment Of Oil Casing

Oil casing is an important guarantee for duration and the safety of the oil wells. Owing to the work environment is very disgusting, the requirements for the quality and performance of Oil Casing is very strict. It will generate residual stress during the process of heat treatment,the residual stress would seriously reduce the performance of casing seriously. Consequently,controlling the residual stress is a important measure of Improving the performance of the oil casing.This article is based on the principles of Heat Transfer and FEM firstly,use the nonlinear finite element analysis software ABAQUS,constructs the finite element model,the model accounted for the phase transition of the material and thermal boundary condition during the process of heat treatment. With this model, firstly, simulated the whole process of the heat treatment of the oil casing(quenching, tempering and cooling). Secondly, simulated the residual stress of the heat treatment process in terms of different technological parameter, through comparative analysis, fixed the principal factor which can influence the residual stress, obtain the best process program.The conclusion drawn from the calculations was that, the cooling rate had effect on residual stress during the process of quenching, when the cooling rate increased, the residual stress reduced. The conductivity of the material would affect the residual stress to some extent. Through the compare between N80 grade oil casing and BT100H grade oil casing, the bigger the conductivity of the material is, the smaller the residual stress is. During the process of tempering, the tempering temperature had strong effect on reducing the residual stress, however, the soaking time didn't. The cooling process can reduce the residual stress further. Optimum program can be obtained through the comparison between N80 grade oil casing and BT100H grade oil casing that, for N80 grade oil casing, the quenching temperature is 870℃, the spray flow inside is 700 m3 h, the spray flow outside is 2 300 m3 h,the cooling rate is 56℃/s, the temperature of the water is 40℃. The tempering temperature is 660℃, the soaking time was 3 600s.The oil casing pipe would be cooled in the air after tempering. For BT100H grade oil casing, the process plan was proposed to bi similer as N80 grade oil casing.The simulation use Multi-step analysis, make the result of quenching as the initial state of tempering, and make the result of tempering as the initial state of cooling, link the three processes together, make them a whole process, increase the authenticity and accuracy of the calculation. This article can provide reference for heat treatment of oil casing.