The author analyses the changes of heat distribution in welded joints of 30HGSA steel depending on different types of gas shielding. It is determined that thermal cycles in the weld metal and in the heat-affected zone differ depending on the type of gas shielding. In the range of 760...790°С the temperatures level and a hotter metal of the weld becomes less hot in comparison with the metal of the heat-affected zone with any type of gas shielding. The rate of temperature saturation in the welded parts is a little higher with double-jet gas shielding, levelling of the temperatures between the weld metal and the heat-affected metal occurs 1...1.4 seconds earlier than with conventional single-jet gas shielding.
In the given paper we consider the impact of wind velocity upon the active shielding gas flow and changes of thermal processes in the MAG welding area. The authors completed numerical simulation of consumable electrode welding under traditional and two-jet gas shielding. It was established that application of two-jet gas shielding for MAG welding increases the hardness of the shielding gas jet and reduces wind-related displacement of thermal fields in the welded item. This ensures more qualitative shielding of the welding area under the windy conditions and uniform heat distribution in the welded item which leads to more homogeneous structure of weld and HAZ metal in comparison to the traditional (one-jet) gas shielding.
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