Influence of Gas Shielding Method in Welding with Consumable Electrode on Heat Distribution in a Welded Product

Abstract

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.

The Influence of Two-Jet Gas Shielding Parameters on the Structure and Microhardness of Steel 45 Joints during Consumable Electrode Welding

“…The shielding properties of the gas jet mainly depend on the properties of the gas used [26] and the gas-dynamic parameters of its outflow from the nozzle of the welding torch [25][26][27].…”

“…Two-jet gas shielding during consumable electrode welding [4,25,28] ensures the stability of the internal jet of the supplied gas, reliable welding zone shielding, and reduces eddies in the HAZ. Controlling the dynamic impact of the internal shielding gas jet on the processes in the welding zone changes the heat and mass transfer processes in the welding zone and results in the intensive mixing of the molten electrode metal with the base metal in the weld pool.…”

“…The authors of works [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] researched the effect of changing shielding gas flows on the consumable electrode welding process and noted that an increase in the gas outflow rate improves the quality of the welding zone shielding, the formation of the weld, and the stability of the welding process.…”

“…The authors of [18,19] suggest that the control of shielding gas dynamics is a promising method for improving the technology of consumable electrode welding in shielding gases. Some studies offer using small diameter nozzles for narrow gap welding while maintaining the recommended gas flow rate for standard torches [14][15][16][17] with two-layer shielding using two different gases (Ar, CO 2 ) [12,24] or two-jet gas shielding, which requires two coaxial jets of one gas and one common chamber [4,25]. These parameters provide reliable shielding of the weld pool compared with the single-jet (traditional) method, increase the stability and frequency of droplet transfer from the electrode to the weld pool, refine the weld metal structure, smooth transition from the weld metal to the base metal, improve the mechanical properties of welded joints, and reduce the chemical heterogeneity of the weld metal due to a positive gas-dynamic effect on the processes in the welding zone and more intensive mixing of the molten metal in the weld pool.…”

“…The authors of works [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] investigated how shielding gas flow dynamics affected consumable electrode welding processes and discovered that an increase in the gas flow rate from the welding nozzle improves the quality of the welding zone shielding and the formation of the weld seam, as well as increases the stability of the welding process. A decrease in the electrode wire stick-out increases the microhardness because the density and flow rate of the shielding gas also increase (at a constant flow rate), which in turn increases the cooling rate of the metal under the welding nozzle and thus the microhardness in the HAZ.…”