翻译

Research on Welding with Active Flux

Abstract The welding with active agent has developed as a new joint technology in last decade because activate agent supplies a means of significantly improving weld penetration, performance and increasing the productivity of the welding process. The agent was employed mainly in TIG firstly, and has been applied successfully in welding of carbon steel, stainless steel, nickel based alloy and titanium alloy. Now the research on welding of aluminum and magnesium alloy with agent is ongoing. About the mechanism that activate agent can increase weld penetration, it was thought that arc visibly constricts in the presence of an activating agent, which improve arc energy density and arc force to pool, or that agent makes the pool to form a positive gradient and deeper weld penetration. Or both of them are playing role in increasing of weld penetration. With the development of ATIG, it will become a tendency that active agent will be used in other welding methods, such as MIG/MAG, PAW, and laser welding. There are some elementary research results for penetration increasement and weld shape modification.

Keywords: active flux welding; A-TIG；PAW; Laser welding,

In order to improve the forming and control of stomatal defects in welding, Parton Welding Institute (PWI) in twentieth Century 's proposed active agent welding, welding in the welding area before activating flux coated with a layer of oxide by halide and composition Fig 1.

Active agent of titanium alloy TIG

welding A-TIG study shows that, I Active flux

surfactant active agent can inhibit the Welding torch molten pool weld bead hydrogen welding process schematic workpiece

diagram of suction effect, reduce the

bubble liquid titanium alloy produced in

probability, while increasing the heat Page 1

penetration ability and improve welding penetration. Since, PWI successfully developed first multi titanium alloy TIG welding flux activity, has formed a titanium alloy active agent ANT series, as well as low alloy steel, stainless steel, aluminum

alloy and super alloy active agent series. In twentieth Century in Britain, Japan, the United States and other countries also pay attention to study on active agent welding, A-TIG welding to develop their active agents, the application of A-TIG welding, butt joint angle, T joint, lap, plug welding structure. Study on A-TIG welding technology in China this year to have a great development. A-TIG welding technology has been applied in aviation, rocket manufacturing and atomic energy industry, the mechanism of A-TIG welding has deep research, the development of an active agent is for different materials, the two is towards efficient development, in addition to active agent applications based on A-TIG welding is also extended to other welding method. This paper mainly introduces the current situation and development trend of surfactant welding research.

1、Research and development of active agent

The active agent of different materials for development, is the key to active welding application development. At present, PWI America Edison Welding Research Institute (EWI) center is connected with the Navy NJC, as well as Britain and Japan have agents for products, stainless steel, carbon steel and nickel based alloy materials such as titanium alloy A-TIG welding. The development of low carbon steel, stainless steel and titanium alloy active agent in China has also been progress. The use of multiple compound welding active agent, the main ingredients are oxides, chlorides and fluorides, its composition and work piece material is closely related. The carbon oxide activity based welding effect is good, research shows that when the content of SiO2 is 40% of the weld penetration depth is the most significant; TiO2 and Cr2O3 significant effect on content is lower than 30%, and only the halide content helps to increase the weld penetration. Welding compared with TIG, CaF, SiO2, Ti, Cr2O3. Low carbon steel welding active agent composition, the weld penetration increased by 3times, 12mm thick plate groove of a welding surface, forming good, but the penetration depth increases with the arc length.

Single component surfactant CaF2, SiO2, NaF, Cr2O3 and TiO2 can effectively increase the stainless steel weld penetration, which Si: works best, CaF: is not conducive to the formation of weld. By B2O3, MnO, Fe2O3, Al2O3, SiO2, TiO2, Cr2O3,

NaF and other components of the stainless steel active agent, welding penetration increases more than times, times mm thick butt welding, chemical composition, microstructure of weld metal, and the mechanical properties of the welding joints and intergranular corrosion resistance can meet the relevant requirements. Dinechin's study also showed that surfactants can relax the joint clearance requirements of assembly automation, reduce the sensitivity of weld quality on the arc length fluctuation.

The surfactant can improve the composition of commonly used titanium alloy welding penetration, but the fluoride on titanium alloy welding penetration effect. With fluoride as active agent PWI developed the titanium alloy A-TIG welding mm thick welded seam, narrow, small heat affected zone. Beijing Research Institute of Aviation Engineering developed a different thickness of titanium alloy FT-01 and FT- 02 surfactant, in improving weld quality, improve the weld depth to width ratio, reduce the welding heat input, reduce welding deformation, showed the excellent performance, for BT20 titanium alloy (2.5mm), which can realize one side welding seam, grain refinement analysis shows that, the porosity decreases, the static strength has little effect of surfactants on the joint properties of TC titanium alloy, can improve the elongation.

Recently, research on active agent of aluminum magnesium alloy has become a key active agent welding. Sire of the active agent TiO2, Al2O3, LiF, SiO2 and AlF on the influence of aluminum alloy TIG welding, FBTIG test results by the method of intermediate surfactant coating clearance ^- of the MM display, AC welding SiO, AlF can increase the penetration depth and weld area, the smaller the gap the greater the role, and LiF had no effect, TiO2, Al2O3 decreased the penetration depth, no effect on the weld area; DC welding only Si significantly increased the weld penetration and forming coefficient, the smaller the gap the greater the role of the same. Study, Marya activity of magnesium alloy agent found in LiCl, CaCl2, CdCl2, PbCl2, CeCl3 chloride can improve the penetration depth, the depth to width ratio.

The role of active agent and welding process, coating amount and other factors, studies have suggested that the coating amount increase, increase the weld penetration, weld width, but the amount of active agent coating has a saturation point increase

penetration ability.

2、Active agent arc constrained function

On the active agent to enhance penetration, improve the weld welding mechanism, there is no unified view, the existing view mainly involves the influence of surfactants on the flow of arc and weld pool.

2.1 active agents arc constrained function

Many studies suggest that the active agent is the main reason for constrained arc penetration increased. In the arc evaporation under high temperature active agent, to form atoms surrounded in the arc around the periphery of the arc, low temperature, electron capture of the active agent evaporation region in the formation of negative ions, so that the number of electrons in the arc arc contraction, reduce, thus, improve the arc force arc current density and the effect on the weld pool, thus increasing the weld penetration. The analysis of PWI, has the function of shielding around the compound surfactant decomposition of molten pool, the electronic capture electronegative arc promoting anode spot near the arc, compound influence degree of compression of the arc, and the ratio of depth to width is directly related to the arc compression coefficient.

Lucas study confirmed that the anode region arc by active element active agent vapor molecules and charged particles surrounded and compressed, anode spot current density can increase 1.5～2 times (Fig. 2), which makes the weld penetration of 1.5～2. increased 5 times. Lucas analysis shows that the central region of the arc temperature is higher than the ionization temperature of gas and surfactant molecules, atoms will be ionized into electrons and positive ions, and in the low temperature region of arc column edge, surfactant vapor still exist in the molecular dissociation and atomic form, the cross-sectional area of the surfactant effective collision than atom, electron to capture the edge of the arc column, the formation of negative ions, the arc column edge area as the carrier to reduce the number of electrons current forced arc contraction. Study on the activity of aluminum alloy welding agent also found the binding effect of surfactant on the arc, and the penetration depth increases with the increase of arc voltage, but did not find the active agent has an effect on the

surface tension.

Study on A-TIG welding of magnesium alloy Marya were not found in the arc contraction penetration increases, but is always accompanied by the increase of the voltage of J, that live agent to increase the penetration depth is mainly affected by the arc characteristic, improve the effect of arc heat and force effect on the weld pool, the change of surface tension is a secondary factor.

Figure 2 stainless steel TIG welding and A-TIG welding characteristics

2.2、The surface tension of active agent change of molten pool

The arc contraction phenomenon only in the observation of the arc shape, the existence of negative ions has not been confirmed, so some researchers believe that the change of surface tension plays a major role in the active agent in welding. Active agent can make the molten metal is formed from the periphery to the center of the surface tension of flow, cause the arc more energy transfer to the bottom of molten pool through the liquid metal flow, heating efficiency of the molten pool at the bottom of the increase so as to form a deeper penetration. Yang Chunli and other researchers believe, whether the arc contraction and the use of active agent, even if the arc does not shrink, the surfactant still makes the weld penetration increases, a small amount of surfactant on the welding penetration effect, active dose increased to a certain degree of penetration is basically saturated, is due to changes the surface tension of the saturated. Studies have also recognized, is the common effect of the changes

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