| With the progress of society and science,HDPE pipe replaced the traditional metal pipes gradually,it has been widely used in the field of water supply and gas transportation.In the process of servicing,the most vulnerable and leakage parts of the pipeline is the connector,so the quality of HDPE pipe hot melt welding joints on the safety of the pipeline system is particularly important.During the welding process,the selection and setting of welding parameters are important factors to determine the performance of the welded joint and the important part of the pressure pipeline security applications.Based on thermal fusion welding of HDPE pipe,a welding joint of one dimensional unsteady heat transfer model of the HDPE pipe was established by MARC to study the field of welding temperature and stress of HDPE pipe weld under the fast cooling and simulate the temperature field and stress field of the weld at different cooling rates.In order to verify the simulation results,the PE100 water supply pipe with a diameter of 110 mm,SDR=17 and wall thickness of 6.47 mm was used as the test material,and welding was carried out under different conditions.Under the condition of the optimum welding temperature of 210 ?,the HDPE tube was welded by the welding pressure of 0.2 MPa,and the welding joint was put into the cold and hot circulation box rapidly after the pressure process was completed.The temperature of the cold and hot circulation box was set to be-15 ?,-10 ?,0 ?,10 ? and 15 ?,after the welding joint cooled to room temperature at25 ?,the welding joints under different cooling conditions was obtained.In the process of welding and cooling,the temperature of welded joint was collected in real time by thermocouple and temperature inspection instrument.By comparing the measured temperature field with the simulation results,the simulation results are consistent with the experimental data,and the basic trend was consistent.In order to solving the HDPE pipe quality evaluation of the welding joint in a long cycle,high cost,process by experience and analysis of problems such as inaccurate.Researching and developing the welding process database of HDPE pipe on thermal fusion welding,which include material type table,weldingparameter table,fast cooling down weld fracture data table,test data of weld fracture under annealing conditions and so on.And the required parameters measured data recorded,stored records and experiments,provide the basis for the query part,allow the operator to quickly find specific data in a group,improving efficiency,analysis of data provides the convenience.To optimize thermal fusion welding process,welding temperature 210 ?,welding pressure 0.2 MPa under the condition of natural cooling to room temperature of welded joint,in holding furnace at 70 ?,80 ?,90 ?,80 ?for 24 hours after the heat preservation cool to room temperature.The natural cooling after welding,heat preservation heat treatment after welding,fast cooling after welding three welding post-treatment process conditions for welding joints,bending test,scanning electron microscopy test and XRD test,get the different cooling rate by analyzing test data,the impact on the weld crystallinity.Concluded that the cooling rate of 18.6 ?/min for HDPE welding joint cooling rate.80 ? is the best heat treatment temperature for HDPE pipe welding joint. |
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