The Quality Control Technology Research For Hot Bending Process Of The Hot Section In AP000Main Pipe System

AP1000is the third generation of nuclear power technology developed by theWestinghouse Company in USA. The main pipe system of AP1000includes two loops,each loop consists of two hot section tube and four pillars of cold section tube.This paper put the hot section tube of the main pipe system in AP1000as researchobject. In the hot bending process, when the mould is removed, the hot section tube is easyto rebound due to the work of internal residual stress in the tube. What’s more, during thehot bending process, the cross section of the pipe is easy to distort and the thickness of thewall will change, the inside wall of the bending section will be thicker and the outside wallwill be thinner. According to these problems, this paper uses finite element software Marcto analyze the hot bending process of the pipe, and this analysis is a thermal-mechanicalcoupled analysis. Through the calculation and analysis, this paper gives out the internaltemperature field and stress strain field of the pipe in the hot bending process. This paperuses the function pre-state of Marc to simulate the rebound process after the hot bendingof the pipe. By changing the parameters value in the hot bending process, this paperobtained the rebound angles of the hot section tube under different craft parameters andthe law of different craft parameters’ influence on the rebound angles of the hot sectiontube. This paper analyzed what influence the clearance of the core mould and the wall ofthe pipe have on the forming quality. The research indicates that, if the technique allows,the clearance of the core mold and pipe should be as small as possible, because this isadvantageous to transfer the internal forming pressure uniformly and improve the qualityof the bending pipe.In order to verify the correctness of the analysis results, this paper established thephysical model of the hot bending process of the pipe by using geometric similarityprinciple and realized the simulative bending of the hot section tube in AP1000main pipesystem. Through the experiment, we obtained the value of the rebound angle and thevariation of the wall thickness for the steel pipe. Through the contrast between the finiteelement analysis and the experiment, we can know that their results fit well. The research results of this paper can provide some valuable data for the production of the hot sectiontube in AP1000main pipe system.