Abstract: In this study， the polyethylene/carbon black composites for pipelines were prepared through melt blending carbon black with polyethylene. The resultant welding composites were further used to weld pipelines under different welding conditions including single-program welding and multi-program welding， and the welding properties， mechanical properties， crystallization properties， and microscopic morphology of the welded pipes were studied. The results indicated that the processing temperature of the extruder should not exceed 240 oC， and the screw speed should not exceed 40 rpm. This can effectively avoid the defects of uneven dispersion of carbon black and bubble in the preparation process of pipeline. In the single-stage welding process， the temperature was found to rise sharply at the end of the experiment. However， the temperature of the melting zone could keep in a relatively stable range in the multi-stage welding procedure. The tensile stripping test results indicated that the welding performance of welded samples obtained from the multi-stage welding process was better than that from the single-stage welding process.

Key words: polyethylene, electrofusion welding, welding performance