The Temperature And Stress Field Numerical Simulation Of AP1000Nuclear Power Main Piping In The Heat Treatment

In this paper the numerical simulation of correlative technology was provided,which has a certain guiding significance for the actual production. Three-dimensionalfinite element model of main piping was constructed. and the temperature field andstress field in the heating process was calculated by the use of ANSYS software andthe element types of solid5,solid70and solid45. The main piping was heated bystepwise heating. The initial temperature of the first stage was20℃and then heated to600℃by the heating speed range form1.5℃/min to24℃/min,and then keeping thetime of heat preservation for0to5h;In the second stage the heating speed range wasform2.5℃/min to24℃/min, and then was heated to1100℃and keeping thetemperature of heat preservation at1100℃and the time of heat preservation for0to3h.The influence of the temperature field and stress field under different heating rate andholding time was discussed. In the quenching stage, the initial temperature is1050℃and medium temperature is20℃. Water and salt water as the quenching medium waschosen. The flow rate of medium was0.3m/s,0.5m/s,0.7m/s and1m/s.The temperaturefield,stress field and plastic field of main piping under different flow rate and differentmedium in the quenching stage was discussed. In addition, The pipe joint of mainpiping was clamped with the chuck clamp and the simulation of quenching stageunder the clamping state was discussed.The results show that in the heating stage,the temperature of main piping in thedifferent part is nonuniform by the growth of the heating time. As the nonuniformtemperature continues to increase,the stress increase. In the preservation stage, thetemperature of main piping tend to be uniform by the growth of holding time, thestress reduce. If the speed of heating was increased that the temperature of mainpiping will be more nonuniform. By comparing the stress field data under differentheating process with the yield strength of316LN steel under different temperature, thehot working process was adjusted. The main piping was heated to600℃at heatingrate of1.5°C/min and keeping the time of heat preservation for5h first, and thenheated to1100℃at heating rate of2.5°C/min and keeping the time of heatpreservation for3h.Under the craft, the main piping won’t produce plastic deformationprocess, and compared with the actual hot working process it takes less time.Thetechnology could be used to provide reference for main piping heating technology in the future.In the quenching stage, different medium make little influence on the mainpiping in the quenching process, and the faster flow rate will make the main pipingfaster cooling rate. At the same time, the stress and strain will be increased too. Yet, inthe presnt research work, we couldn’t make the core of main piping cooled totemperature427℃in3minutes. Besides that, the plastic deformation of the pipe jointwas hindered under clamping state, the simulation show that the local stress willpreoduce crack. So the technology should be considered carefully in the actualproduction.