聚乙烯管材热熔对接接头抵抗慢速裂纹扩展性能评价

Evaluation of Slow Crack Growth Resistance for Polyethylene Pipe Butt⁃Fusion Welded Joint

采用应变硬化试验(SH)对不同焊接工艺下的聚乙烯管材热熔对接接头抵抗慢速裂纹扩展(SCG)性能进行评价。通过建立焊接温度梯度(190~250℃)、焊接压力梯度(0.6~1.4 MPa)和吸热时间梯度(40~140 s)试验,分析在不同焊接工艺参数条件下,不同聚乙烯管材热熔对接接头耐SCG性能的变化规律,探索冷焊及过焊2种典型缺陷对管材接头耐SCG性能的影响。结果表明,焊接温度、焊接压力和吸热时间都是影响管材热熔对接接头耐SCG性能的重要工艺参数,试验测得PE100,dn110,SDR11型管材的最佳焊接参数为焊接温度230℃,焊接压力1 MPa及吸热时间100 s,当焊接参数选取过高或过低时,会造成管材接头出现过焊或冷焊缺陷,降低管材接头的耐SCG性能。

The strain-hardening test was adopted to evaluate the slow crack growth(SCG)resistance of polyethylene(PE)pipe butt-fusion welded joint under different welding processes.The variation rule for the SCG resistance of PE pipe butt-fusion welded joint was analyzed under different welding process parameters by establishing a welding temperature gradient between 190 and 250 ℃,a welding stress gradient between 0.6 and 1.4 MPa,and an endothermic time gradient between 40 and 140 s.The effects of cold-welding and over-welding defects on the SCG resistance of PE pipe joint were investigated.The results indicated that the welding temperature,welding pressure and the endothermic time were all the important process parameters that influenced the SCG resistance of the PE pipe butt-fusion welded joints,and the optimum welding parameters could be determined as 220 ℃,1 MPa and 100 s for the PE 100 pipe(dn110,SDR11).The selection of lower or higher welding parameters could result in the formation of cold-welding or over-welding defects in the pipe joint,thus reducing the SCG resistance.