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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 results of investigations carried out to study the effect of the dynamic characteristics of power sources on the stability of melting and electrode metal transfer to the weld pool in consumable...

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.

The influence of the welding current and method of gas shielding in MAG welding on the content of silicon and manganese is considered. Results of study of the welded specimens of steels 45 and 30HGSA when applying welding wire of different formulas and different types of gas shielding (traditional shielding and two-jet shielding) are given. It is established that in MAG welding the value of the welding current and the speed of the gas flow from the welding nozzle have a considerable impact on the chemical composition of the weld metal. The consumable electrode welding under double-jet gas shielding provides the directed gas-dynamics in the welding area and enables controlling the electrode metal transfer and the chemical composition of a weld.

A set of various factors and phenomena defines the quality of welded joints. This is especially noticeable for outdoor welding. A numerical simulation of welding processes with consumable electrode with traditional and two-jet gas shielding was carried out to study the influence of wind speed on the movement of the shielding gas (CO2) and the change of thermal processes in the heat affected zone. It is established that the use of two-jet shielding in welding with a consumable electrode leads to an increase in hardness of the shielding gas stream and lower offset of thermal fields in the welded product in the wind direction. It testifies to a better quality of shielding and smaller probable changes in symmetry of structure formation and mechanical properties of the heat affected zone.

The processes taking place in a drop of a molten electrode metal and in a metal of a weld pool play the dominant role in formation of joint welds properties. In consumable electrode welding with jet gas shielding under certain conditions a drop of an electrode metal is influenced by the main forces as well as by the force of a shielding gas jet impact which depends upon the method and composition of a gas shielding in a welding area. The results of research have stated that the force of a shielding gas jet impact on a drop of an electrode metal in double-jet gas shielding is twelvefold as in one-jet one; it is directed along the electrode to a workpiece and stimulates stability of the electrode metal drops transfer into a weld pool.

A combination of various factors and phenomena determines the quality of the welded joints. The basic role in setting the properties of the welded joints belongs to the processes taking place in the drop of the melted electrode metal. The paper considers the influence and vector components of the basic forces on the melted metal drop in gas jet shielded welding a moment before the drop transfers from the electrode to the weld pool. Methods of calculating the force exerted by a shielding gas jet on the drop of the electrode metal and subject to its dissociation are offered. The frequency and stability of drop transfer to the weld pool increase with the growth of the shielding gas impact force on the electrode metal drop in double jet gas shielding.

Controlling the processes, which take place during consumable-electrode shield-gas welding, is one of the main problems of the welding industry. The paper shows that under the certain conditions the electrode-metal drop and heat distribution in the weld area are influenced by the active shielding gas jet. The paper provides the results of modeling heat distribution in the weld area and active shielding gas outflow from the traditional and double-jet welding torch nozzles.

The paper considers the ways of weld geometry controlling when consumable electrode welding under single-jet and double-jet gas shielding. The authors provide comparative results of experimental studies on the effects of shielding gas supply upon the weld geometry in weld joints produced from construction carbon steel 45. It has been established that gas-dynamic effect of the shielding gas has a significant impact upon shaping and weld geometry when consumable electrode welding under double-jet gas shielding.

In the paper we present the results of the study of the power supply characteristics effect upon the stability of electrode metal melting and transfer into the weld pool in the process of consumable electrode welding. It was shown that application of inverter type welding power supplies of the new generation results in changing the characteristics of the heat and mass transfer which has a decisive impact upon the heat content of the weld pool, reduction of residual stresses in the heat-affected zone (HAZ). The authors also substantiate the tendency to the reduction of the structural constituents in the area of the permanent joint.

The article presents the results of experimental studies showing that the use of an inverter power supply instead of a diode rectifier provides:: fine-droplet electrode metal transfer which reduces generation time by 46% and transfer time by 28%; transfer of alloying elements from welding materials into the weld metal which reduces its loss from the welding line by 6% and the heat affected area by 3%; reducing the emission rate of welding fumes and their components by 23%; reducing specific emission of welding fumes and their components by 23%.

In the context of a significant increase in production output and use of welding technologies in the manufacturing of engineering products the problem of hygienic characteristics of working conditions in arc fusion welding is becoming increasingly important. The work represents how the dynamic characteristics of a power supply affect the transfer of alloying elements from a coated electrode into a base metal, a slag phase and a solid component of welding fumes. Short-circuit current limiting in inverters reduces overheating of electrode metal drops by 15%; welding fumes quantitative component - to 38%; manganese - to 30%; thermal radiation intensity - by 37%.

Chemical composition of weld metal and properties of a joint weld are dominated by the processes occurring in the drop of molten electrode metal and in metal of the weld pool. Under certain conditions in consumable electrode welding with jet gas shielding the drop of electrode metal is influenced significantly both by main forces and the force of gas-dynamic impact of the shielding gas jet. The results of research have revealed that changing rate of shielding gas flow on the nozzle section influences the processes taking place in the welding area. There are changes in the transfer frequency of electrode metal drops and chemical composition of weld metal.

The influence of the welding current and method of gas shielding in MAG welding on the content of manganese is considered in the paper. Results of study of the welded specimens of steels 45 when applying welding wire of different formulas and different types of gas shielding (traditional shielding and double-jet shielding) are given. It is found that in MAG welding the value of the welding current and the speed of the gas flow from the welding nozzle have a considerable impact on the chemical composition of the weld metal. The consumable electrode welding under double-jet gas shielding provides the directed gas-dynamics in the welding area and enables controlling the electrode metal transfer and the chemical composition of a weld.

The author considers gas-dynamic influence upon microhardness and weld configuration of single-pass welds from steel 30HGSA when welding with consumable electrode under double-jet shielding. The relations to the chosen controlled welding parameters (Q, L, I) are developed and the controlling influence of the gas-dynamic affect of dynamic shield gas jet over formation of welds from alloy-treated steel 30HGSA is determined.

The characteristics of heating processes determine fusion efficiency for base metal and filler material, direction and completeness of metallurgical processes in a welding pool, formation of weld metal structure and heat-affected zone, service properties of welded joints. Under certain conditions in consumable electrode welding with jet gas shield an electrode metal droplet and processes in the weld zone are influenced by the force of shielding gas jet besides the main forces. Significant influence of this force is noted in CO 2 double-jet gas shield. Basing on the research results it was determined that distribution of heat in the electrode, fused metal droplet, arc space, welding pool and parts being welded depends on the shape and velocity of active shielding gas flow.

This work presents peculiarities of forming a structure, phase and chemical composition while welding medium-carbon steels (Steel 45) depending on a heat content of molten electrode metal droplets when using welding power sources having different power parameters. It was experimentally established that the power inverter provides the decreased heat input into droplets of electrode metal during the welding process. This stimulates obtaining a fine-grained structure of the deposited metal and heat affected zone, reduces the extent of the HAZ that enhances working properties of welded joints.