Influence of temperature-time conditions of polymer pipes welding at low temperatures on the structure and properties of materials of joints part ii. Experimental studies

Subject of research: the process of a supramolecular structure formation in the heat-affected zone (HAZ) depending on the temperature-time conditions implemented in the welding process at various air temperatures. Purpose of research: establishing the effectiveness of the proposed technology for welding saddles to polyethylene pipes of gas pipelines at ambient temperatures below those established by regulatory documents for welding work based on a study of the relationship between temperature and time conditions, the structure and properties of materials of welded joints. Methods and objects of research: in the second part of the work, the object of study is the process of obtaining a strong welded joint by welding a saddle branch to a polyethylene pipe of an existing gas pipeline at low temperatures. The strength of the connection is established by tensile pull tests of the welded saddles. The formation of supramolecular structures is studied by analyzing the kinetics of crystallization of melts based on the data of a differential scanning calorimeter and visualizing the formations with a scanning electron microscope. Main results of research: it has been established that when welding saddles to polyethylene pipes of existing gas pipelines at low temperatures by preheating, equalizing temperatures with design parameters, heating in a regulated mode, and cooling under a layer of heat-insulating material of calculated thickness, a temperature-time regime is implemented that determines the structure formation of the material of the welded joint, providing the strength of the connection corresponding to welding at acceptable temperatures.