Last changes date: November 12, 2003

11.1.3. Influencing an chemical composition of welded metal, welding materials (welding compounds, shielding gases and their mixtures) on penetration of metal at welding 

It is known that the chemical composition of the basic and electrode metal exercises influence over depth of penetration; for example, usage of a welding rod from copper at welding steel decreases the depth of penetration. The carbon content also exercises influence over penetration: the depth of penetration is minimum at low carbon content, and at its contents within the limits of 0.10... 0.13 % the depth of penetration Hp remains invariable, but then is augmented with growth of carbon content [1471].

In investigation [1505] they studied influencing six impurity elements S, P, Si, Mn, Ti and Al on the weld sizes for alloy Inconel 600. With this purpose authors have utillized alloy sucelted by a laboratory way. Update of a weld material S, P, Si, Mn, Ti and Al conducted by pressing and caking of dusts from these elements. The obtained rods treated mechanically up to the size 76.2x5.1x1.27 mm and located in a gap between welded edges of plates. Arc welding with tungsten electrode in argon run with conditions as follows: arc current — constant reverse polarities (100 A), arc voltage — 10 V, length of an arc — 2.4 mm, welding rate — 22.9 mm/min, amplitude of cross oscillations of the electrode — 12.7 mm with an oscillation frequency 26 min-1 at number of layers 3 and expenditure of argon of 18.9 liters per min.

In the held studies the full factor experiment from 64 expertises was constructed, in which one instituted cross sectional area of a joint, and also its width and depth of penetration. 64 welded samples in total are learnt, in which one impurity are in different combinations. It was established that Si and Ti essentially augment both sectional area of a joint and depth of penetration (Fig.11.28). The authors [1505] link it to voltage variations on an anode. The operating of Si increases in presence S, and the operating of Ti is moderated in presence Al. The phosphorum promotes magnification of a sectional area of a joint. The aluminum moderates simultaneously sectional area and depth of penetration. It explain by formation of a high-melting film of oxides Al on a surface of a weld pool.  

Fig.11.28 [1505]
Summary of effects on cross-sectional Fp area and depth of penetration Hp: a - cross sectional area Fp, b - depth of penetration Hp

The considerable influencing of the contents of sulfur on depth of penetration of metal at arc welding was noted also in works [683, 1506 etc.]. By results of studies [1507] impurity elements do not render the influencings on the configuration of an arc, but inflect depth of penetration and undercuts is interquartile, owing to variation of surface tension forces.

The authors [1508] investigated the influencing oxide FeO on behavior of welding welding compounds of a system SiO2-MnO-FeO and system SiO2-MnO-CaO-MnO2. In expertises, which one conducted on samples from steel 1020 and steel 4340, instituted influencing FeO on repeatability of combustion of an arc, geometrical arguments of a weld (deposited bead), surface tension and viscosity of molten metal of a weld pool. More deep penetration of base metal is supervised at magnification of viscosity of molten metal of a pool, repeatability of an arc, abatement of interfacial energy between welding compound and base metal, which one, in turn, depend on the contents FeO in welding welding compound. In a Fig. 11.29 influencing the contents FeO on depth of penetration Hp and weld shape factor of a joint for the studied steels is rotined.  

Fig.11.29 a,b - Penetration Hp as a function of wt-% FeO for 1020 steel (a) and 4340 one (b); SiO2  concentration was fixed at 40 wt-%;

c,d - Width-to-depth ratio (B/ Hp) as a function of wt-% FeO for 1020 steel (c) and 4340 one (d) [1508]


The systematic studies of influencing of different chemical elements on penetration of stainless steel 304 are held by the author [1509]. Is established, that the influencing of such surfactant member as sulfur, can be explained within the framework of the known theory of flows of liquid metal in a pool aroused by their influencing on a temperature coefficient of surface tension of molten metal. The sulfur as a strong surfactant member renders essential influencing on depth of penetration (Fig. 11.30,a), but at the presence of oxygen its influencing is loosened.  

Fig.11.30 Effect of manganese (a), silicon (b) and sulphur (c) content on relative penetration Hp/B [1509]

Such elements as Si and Mn render more composite influencing (Fig. 11.30) which is not depicted within the framework of the given theory, that testifies to influencing the padding factors. The author [1509] considers that the influencing, for example, silicon is connected with its affecting on viscosity of molten metal. Besides is established, that such elements, as phosphorum, molybdenum and copper not being in relation to Ferri lactas, the affectings on depth of penetration of metal, at least in that percentage do not render surfactant, in which one they are in stainless steels (Fig. 11.31).  

Fig.11.31 Effect of aluminium (a) and phosphorus (b) content on relative penetration Hp/B [1509]

Thus study [1509] have affirmed effect of influencing of small amounts of sulfur, oxygen and aluminum on penetration of stainless steel at welding with tungsten electrode  in an inert atmosphere. This influencing is aroused by straight or oblique affecting on a temperature coefficient of surface tension for liquid steel and, as result, on a flow pattern of metal inside a weld pool.

At the small contents be sulphur (less than 0.005%) sufficient penetration can is obtained if there is oxygen. It is necessary to count the optimal contents of sulfur as such, that it fited workabilities, weldability and formability; for stainless steel such as 304 as the reasonable compromise it is possible to count the contents of sulfur within the limits of 0.01...0.015%. The influencing of aluminum most is hardly exhibited at its contents 0.010% [1509].

In the work [1510] they investigated the shape of penetration, applying the CO2-laser by power of 5 kW for implementation of axles on seven cast irons with the contents S in a spacing 0.011...0.096% and equipment for EBW by power of 35 kW for implementation of beads on five stainless steels with the contents of sulfur 0.001...0.008%, and also flow of liquid metal in a weld pool, depositing beads on three carbon steels with the contents S in range 0.0005...0.007%. The influencing of speed of movement of the beam and contents of sulfur on depth of penetration is shown in a Fig.11.32.  

Fig.11.32 Dependence of penetration depth (a) and bead width (b) on sulphur content and welding speed using a focussed laser beam [1510]

In experiments [1510] is obtained that on cast iron the shape of a zone of penetration with magnification of the contents S crossed from goblet to conical and further to cylindrical with roundoff on the bottom. The surface of an bead obtained on steel, at the small contents S is obtained smooth, but with growth of the contents S occur and the ripples on a surface grow. The pool has the elongated shape and with growth of the contents S its elongation grows.

At the low contents S flows of molten metal are hoisted to a surface of the pool, flow on its edges to the back end and are reverted to center of a pool, derivating a dark zone of cold metal. At the high contents S in acclinal bottom of a pool the bench will be derivated, and the melt with all surface of bottom flows to the back end of a pool, whence is reverted to center, derivating more lengthy dark zone of cold metal.

In work [790] they investigated electron-beam welding (EBW) and TIG welding in inert gas for two fusing of stainless steel 304L, penetration, distinguishing in the performances, in connection with the different contents of sulfur.

At both methods of welding the noticeable influencing thermal capillry flows in a weld pool on relative depth of penetration of metal was supervised, and thermalcapillarity in both cases had the close performances, that testifies to its large role in oscillatings the shape and sizes of a joint between the different fusings of the same steel. In a Fig.11.33 the dependences of relative depth of penetration on length of an arc and size of an electron beam, and also from power of these heat sources are shown.  

Fig.11.33 Weld Hp/B ratios for GTA and similar welds made on low- and high sulphur material; a - fixed arc power, b - fixed beam power, c - fixed arc length, d - fixed beam size [790]

The joint welds at EB-welding and TIG welding (TIGW) are quantitatively look-alike, however full concurrence between joints at these different aspects of welding misses — at TIGW higher is supervised thermalcapillar convection. In opinion of the authors [790] by one of the factors confining thermalcapillar flows at TIG, is the magnification of length of an arc with growth of arc current. Besides the current of fluid at TIGW is confined to non-Gaussian allocation of power in an arc — in this case it closer to rectangular.

Influencing of shielding gas. The feeding in an arc zone of different shielding gases renders all-up influencing on process of welding, inflecting both power and response curves of a welding arc, and passing of different processes in a weld pool.

For example, study of penetrating capacity of a welding arc of a straight polarity with nonconsumable electrode in different shielding gases and their mixtures executed in the work [1511], has shown, that depth of penetration Hp of base metal (aluminium alloy) and width of a joint in much depend on a type of shielding gas (Fig.11.34). The greatest depth of penetration takes place at welding in helium, least — at welding in argon. Usage as a shielding medium of a neon receivable usually at the maiden stage of a manufacturing process of separation of helium from air, gives intermediate values of depth of penetration as contrasted to Ar and He.  

Fig.11.34 Effect of shielding medium composition on penetrarion depth Hp (a) and weld width (b)  for aluminium alloy 1201 with straight polarity current [1511]: 1 - current 150 A, arc length 2 mm; 2 - current 200 A, arc length 1.2 mm; 3 - current 200 A, arc length 0.3 mm 

The welding in an argon is characterized by minimum bulk of a weld pool, whereas at usage of helium it has the maximal sizes.   

11.2. Methods of control by the shape and sizes of a zone of

penetration at arc welding

11.2.1. Applying the activating welding fluxes 

At usage of some methods of welding in environment of inert gases many explorers marked heightened instability of a welding arc, its dimensional instability aroused by a wandering of a arc active spot, disposed on a welded workpiece and, as a consequent, irregularity of forming of a joint weld [1512—1514 etc.].

In the work [1513] it is established that for the preventing of a wandering of an arc are indispensable a careful square-wave stripping of a surface or even oxidizing, and also similarity of an elemental composition of base metal and filler wires. At welding of medium-alloyed steels and heterogeneous metals it is recommended to increase potential gradient of arc column at the expense of applying shielding gases with a heightened potential of ionization and stimulation, and also at the expense of constriction of an arc by the chilled channel or longitudinal magnetic field.

By the authors of the work [1514] is shown that the preliminary acidification of a surface at welding stainless steel such as 18-8 allows essentially to reduce linear energy indispensable for end-to-end penetration of metal. Thus width and length of a pool is considerably moderated on the part of an arc and total weight of a pool. Corrosive and the mechanical tests of joints welded on an oxidated surface, have shown identity with quality of joints obtained by a customary method.

The applying of special activating fluxes (AF) at TIG welding allows to inflect and to stabilize penetrating capacity of a welding arc in a broad range of welding conditions. Thus as the basic activating reductant of welding flux the oxygen having high surface and reactivity will be utillized [686].

In the work [1515] for the first time was shown that applying welding fluxes of definite composition at TIG welding it is possible sharply to augment the penetrating capacity of an arc. Thus is inflected not only depth of penetration, but also its shape. The features of melting of titanium alloys were investigated at TIG welding with the padding introducing in an arc zone of oxygen-free welding fluxes containing such reductants, as fluorides both chlorides alcalinous and earth metals. In the experiments the arc current did not exceed 350 A, and welding travel speed varied in limits Vc=10...20 m/h. Welding flux in an arc zone inputed by deposition it on a welded plate directly ahead of welding.

By studies [1515] was established that at thickness of a stratum of welding flux not less than 0.20...0.25 mms in series of cases is possible in enough broad limits to regulate width of a joint and depth of penetration Hp at practically invariable electric arguments of process. Simultaneously to variation of arguments of a joint there was a magnification of the cross area section of the zone of penetration Fn.

The considerable effect was obtained at usage of composite systems of welding fluxes on the basis of salts of alcali metals (Fig.11.35). The physicochemical properties of fluorides and chlorides of these metals, in particularly, rather low melting points Tm and boiling Tb do not allow to apply their salts by the way of single-component welding flux.  

Fig.11.35 Dependence of bead width B (a) and  penetration depth Hp (b) for titanium alloy VT15 on alkaline salts content in flux with welding current 100 A, arc voltage 9 V, travel speed 15 m/h [1551]

Held in [1515] the studies have shown that the existing of welding flux in an arc zone allows sharply to diminish a form factor of a weld (B/H ratio). The concentration of a thermal energy of an arc on a reduced lease of base metal increases performance of penetration of titanium and slashes expenditures of linear welding energy. This effect has appeared characteristic and for other metals — Mb, Mo and austenite steels. Because of performance of the given method of process control of penetration of metal for welding alloys of titanium the special welding flux of the mark AN-T9A was designed, the applying considerably augments which one depth of penetration and moderates width of a weld pool and joint.

In the work [1516] the studies which were had for an object to clarify a reasons of such resizing of joints if there is welding flux on a surface of welded metal were held. Oscillographic testing of electric arguments of process has shown that the moment of transferring of an arc on a stratum of welding flux is tracked by spontaneous magnification of an arc drop voltage at magnitude DUa and applicable abatement of arc current (at constant power of an arc). The magnitude DUa depending on composition of welding flux fluxed was 1.0... 4.7 V, and greater magnitude DUa corresponded more deep and narrow penetration.

Held in [1516] the studies and analysis of their results have shown that the applying of welding flux results in a heightening of concentration of a thermal output of an arc in connection with an abatement of the sizes of a spot of heating and limitation of width of penetration of metal by a pool film of welding flux. Thus the contraction ratio of welds depends on physicochemical properties of welding flux, especially from its capacity to wet solid titanium in liquid state at heats. More high voltage on an arc and the heightening of the floor space of a zone of penetration at welding with welding flux is explained by magnification of concealed component length of an arc and heightening of an anode voltage drop.

Many explorers count that all developments of operating of activating welding fluxes by the way waists and recesses of a weld and also magnification of the area of the penetration zone are a consequent contraction of an arc which one usually understand an extent of concentration of a thermal energy in an arc. The contraction coefficient Ka takes a part in a distribution function of a current density in a column of an arc recorded by the way of a gaussian law and a coupling equation between its arguments:

             j(R)=j0*exp(-Ka*R2), Ia=pj0/(Ka)2,                    (11.5)

where j0 — the current density on a axis of an arc through which current Ia pass.

The physical essence of contraction is encompass byed volume that the energy consumable by a column of an arc in equilibrium state is lost by means of radiating and thermal conductivity, and speed of losses the above, than more heat conductivity of plasma of an arc and gradient of temperature in it1. Variation of any arguments of an arc, for example, the magnification of an electric field strength results in growth of a gradient of temperature, electrical and thermal conductivity of arc plasma and also current density j0 on the axis of an arc. As a result of it at an invariable current of an arc Ia effective diameter of its current-carrying zone is moderated that is contraction coefficient Ka pursuant to the second formula (11.5) increases.

The heightening of arc contraction at availability in a welding zone of activating welding fluxes is connected to such factors as wettability by welding flux of solid metal, discrepancy of electrical conductivity of salts of welding flux and pool titanium, decrease of electrical conductivity of peripheral zones of the arc column, heightening of thermal conductivity of arc gas, screening by welding flux of metal around of a weld pool [1517—1519 etc.].

The author of the work [1518] investigated the influencing of different halogenides plotted on front face of a weld material (the titanium alloy VT14), on effect of magnification of depth of penetration with the purpose of usage of obtained data for developing new welding fluxes. As a result of experiments is established that the effect of penetration the above than is more than atoms of halogen contains welding flux, that is than its basicity and less combining weight more. Effect of penetration magnification the above than above potential of ionization of metal which is included in chemical combination with halogen. On performance of a heightening the penetrating capacity of an arc the halogens are laied out in the following order: fluorine, bromine, chlorine.

In the publication [1520] the results of study of influencing of activating welding fluxes on forming of a joint weld, composition of plasma of an arc, allocation of a current density and stress in an anode spot are shown. The experiments conducted at a current 150A and customizing length of an arc of 1 mm; as a welding electrode have utillized a tungsten bar of the mark VL a dia of 3 mm with an angle of sharpening 55 degrees. Welding flux by the way of finely divided dust plotted on a surface of welded plates with the help of the special device; the width of fluxe track was 8 mm.

Influencing of activating welding flux on main dimensions of a weld studied on plates from steel H18N9T by thickness of 8 mm without their full penetration at welding rate 5 m/h. As a result of the executed experiments was established that at the introducing in a weld pool of activating welding flux the depth of penetration Hp increases with a simultaneous abatement of width of a weld B (Fig.11.36) sharply. The maximal depth of penetration was obtained at the putting in a welding zone 4 mG/cm of activating flux.  

Fig.11.36 Dependence of bead width B and  penetration depth Hp  on flux amount having been put into welding zone [1520]

Distribution of current density in an anode spot of an arc instituted under the method of application split copper water-cooled anode2, and pressure distribution of an arc — with the help of a manometric method [1521]; diameter of a receptor opening fluxed was 0.5 mm. The observed data are presented in the Fig.11.37, from which it’s seen that at availability in a weld pool of activating welding flux the current density in a active spot of a welding arc increases sharply. The maximal current density was obtained at concentration of activating welding flux equal 4 mG/cm.  

Fig.11.37 Distribution of current density (a) and arc pressure in anode spot (b): 
a) 1 - with flux FS-71; 2 - flux free; b) 1 - with flux FS-71; 2 - flux free; 3 - data of [1642]


From the held experiments it is followed that putting in a welding zone of activating welding flux slashes both axial pressure of the arc p0 and full force of an arc Fa. In opinion of the authors of work [1520] this decrease is connected to originating of a counter current of vapors of metal of an anode and reductants of activating welding flux originating because of large concentration of energy stream in a central zone of a active spot of the welding arc.

In the work [1522] the mathematical model depicting contraction an arcs by welding flux at welding by a tungsten welding electrode in an argon is proposed. This model takes into account the processes on an anode, variation of a heat conductivity of arc gas, phenomena on peripherals of a column of an arcs conditioned by negatively ionized atoms, and mounts their analytical intercoupling dimensioned of conducting column of plasma of an arc and anode spot. The allocation of a current density in an anode spot obtained by analytical account with usage of the designed pattern, is close to results of experimental measurings.

With the help of the given model is affirmed that the influencing of activating welding flux on an arc is encompass contraction of its positive column and active spot. This phenomenon is conditioned by operating of a series of the factors: by screening of metal around of a weld pool by liquid welding flux and stabilizing within the limits of a weld pool of an anode spot; by a heightening of thermal conductivity of arc gas in connection with appearance in an arc of impurities of molecular vapors of welding flux; by deionization of peripheral parts of an arc as a result of gripping conduction electrons by electronegative fragments of vapors of welding flux and products of its interplay with welded metal.

At practical usage of activating welding flux for TIG welding of titanium alloys due to interplay of metal and welding flux the porosity of joints is eliminated updating cast weld structure also is ensured. The decrease of linear energy of welding with welding flux abbreviates an expansion HAZ, improves shielding reliability of an arc and weld pool by inert gas. All this promotes meliorating of mechanical characteristics of weld joints and enables to weld for one pass without edge preparing of metal by thickness up to 12 mm.

However at welding with activating welding flux there are some impediments. In particularly, thickness and uniformity of a stratum of welding flux render noticeable influencing on repeatability of process and the deposition of a stratum of welding flux with the given sizes has definite complications. Besides at manual welding ahead of front of a pool the film will be appeared that degrades visibility of the butt between edges welded.

One of the best alternatives removing these deficiencies is the feeding in a welding zone of a powdered wire as filler metal; like filling agent of the wire have utillized welding flux ANT-17A [1523]. Nevertheless, as it is marked in the work [1524], the welding flux ANT-17A has the series of deficiencies, among which one a heightened wandering of an arc with a drift on one of edges of a butt at thickness of welded metal 0.8... 1.5 mms, and also considerable adhesion of molten welding flux and solid titanium handicapping welding with a filler wire. These deficiencies the welding flux ANT-23A, having a low adhesion to titanium and easily eliminated if necessary implementations of the second pass is dispossessed.

On data of work [1525] activating welding fluxes on the basis of halogenides increase penetrating capacity of an arc at TIG welding of parts by thickness up to 6 mm; at thicknesses 7...8 mms these welding fluxes have small effectiveness and at thickness more than 8 mms — do not influence penetration of welded metal. The accounts, held by the authors, and the experiments have shown that the limiting thickness of metal, at which one is still exhibited acting of activating welding fluxes is 20... 22 mm (Fig.11.38).  

Fig.11.38 Dependence of penetration depth Hp on metal thickness at welding with activating fluxes FS-300 and FS-71 and DC straight polarity current 250 A, arc length 
1 mm, travel speed 10 m/h  [1525]

In their judgement, at high values of arc current the vapors of welding flux do not fall in an arc and cease to influence its properties. The deduction from here flows out, that the heightening of performance of activating fluxes is possible by immersing of an arc into the weld pool.

TIG welding with usage of activating fluxes was successfully applied at fabrication of welded structures from alloys of molybdenum. The special properties of these alloys require the applying methods of welding with maximal concentration of a thermal energy, in this connection the greatest propagation was received with electron-beam welding of constructions from materials on the basis of molybdenum. Held in the work [1526] studies have shown that usage of activating welding fluxes at TIG welding of molybdenic alloys allows to increase penetrating capacity of an arc, to diminish width of joints and HAZ sizes. The weldings, obtained by this method, joints have sufficient microhomogeneity.

At welding the special steels the applying of activating fluxes augments range of thicknesses of metal welded with full penetration without edges preparing and also it is essential to facilitate deriving of weld joint with groove in edges at the expense of magnification of an obtusion and abatement of an amount of metal for infill of groove [1527].

The applying of activating welding flux at TIG welding of high-strength steels meliorates conditions of a crystallization of a welded material, increases its mechanical characteristics and stability against formation of crystallizational cracks. It takes place because at usage of activating welding flux the front of a crystallization of molten metal acquires composite dimensional pattern, stipulating different attitude of primary crystallites in miscellaneous leases of a weld pool and subsequently — a laminated constitution of metal in a cross-section of a joint. The most legiblly laminated constitution of a joint weld is exhibited at length of an arc 1.0...1.5 mm; at length of an arc outside this range the lamination in joints is exhibited is more gentle [1528].

In the work [1529] the dependence of width of a joint and revertive bead from arc current is established at single-pass welding of titanium alloy OT4 by thickness of 5 mm. The current increase calls magnification of both indicated arguments of a joint, and width of a revertive bead increases much more intensively (Fig.11.39). At a current 125... 130 A the shape of penetration becomes close to rectangular — with identical width of a joint and revertive bead. The current increase on 25 A results in magnification of width of a revertive bead in 1.5 times, whereas the weld becomes wider only on 1 mm. This phenomenon the authors explain by the greater uniformity of a specific heat flow and pressure of an arc at a submerged-arc welding and screening of a surface of joined edges by boiling welding flux.  

Fig.11.39 Dependence of weld width B1 and reverse bead width B2 on welding current: 1 - weld width, with a flux; 
2 - reverse bead width; with a flux; 3 - weld width, flux free [1525]


On the basis of obtained result ins [1529] the feasibility TIG welding with flux for fabrication of a multilayer construction, T joints, and also for an electric riveting is investigated. In all cases the indispensable arguments of a welding conditions have appeared much below, than at deriving these joints by other methods; for example, without usage of flux the welding of T joints did not manage to be executed for one pass.

In connection with established regularities of a heightening of  penetration depth at TIG welding by feeding in an arc zone of different matters, they have offered to input by the way of welding fluxes-pastas or gaseous components to shielding gases [1530], and also flux filling agent of powdered wires [1531]. As gaseous of the components to an argon or helium apply gaseous fluorides BF3, WF6, SF6 in amounts 0.01...2.5%. At usage of such components the arc voltage drop increases, also the temperature of a tungsten is increased, the column of an arc is constricted, thermal efficiency is augmented and coefficient of concentration of its heat flow. All this results in magnification of  penetration depth of welded metal [1532], however slashes impact elasticity of weld joints and degrades sanitary-hygienic conditions in a welding zone [1533].

According to studies of process of welding of copper M1 the with melting electrode by an immersed arc [1534] composition of a shielding gaseous mixture influences on  penetration depth for welded metal only at rather small currents not superior noticeably 230...250A (Fig.11.40). At full submergence of the arc in a weld pool having place at the current more 300A, the composition of shielding atmosphere ceases to exercise influence over the power performances of process and nature of electrode metal transfer.  

Fig. 11.40 Effect of shielding  gas composition on the penetration zone area of welded metal [1534]

In the work [1535] the influencing fluorides on penetration is learnt at MIG welding of copper. As welding fluxes have utillized such matters as NaF, BaF2, CaF2, MgF2, MnF2, AlF3. Welding flux plotted by a thin layer on a surface of plates welded by the size 160x45x5 mm from copper mark M1. Welding was executed by a welding elecrode a dia of 3 mm at arc current 300 A, welding rate 5 mm/s with and length 2 mm. For determination the thermal efficiency during welding at experiments conducted a calorimetric of samples and performance of process of penetration valued on welds cross sections.

The influencing of different fluorides on  penetration depth Hp and its penetration zone area Fn is shown in a Fig.11.41, from which one follows that the applying of these matters allows to inflect geometrical arguments of penetration zone of in sufficiently broad limits. Thus NaF and BaF2 moderate, and MgF2, MnF2, CaF2 and AlF3 augment  penetration depth of metal.

Fig. 11.41 Effect of fluorides on depth (a) and zone area (b) of penetration [1535]

Held in [1535] the studies established sufficiently strong correlation between magnitude of thermal efficiency and work function of conduction electron from metal (Fig.11.42). The similar dependence was established earlier for fluorides BaF2, SrF2, CaF2 and MgF2 in work [1536] at welding low-carbon steel. Such correlation link can form the basis a choice of reductants of welding fluxes-pastas for TIG welding of metals.

Fig. 11.42 Correlation dependence between thermal efficiency and work function of a conduction electron We from metal entered into fluoride [1535]

On the foundation of the held studies in work [1535] the welding flux-pasta AN-M15A with the high power and metallurgical performances is designed. The TIG welding of copper on this welding flux has received technical application at welding the ribbons and bands from copper and its alloys.

The acting of welding fluxes composed of fluorides on penetration of metal was studied by the authors of the work [1537]. In experiments on welding the plates by thickness of 8 mm have utillized welding flux BMK-1 having composition 35%CaF2, 35% MgF2 and 30% BaF, which was plotted on a welded surface by the way of alcoholic solution directly ahead of welding arc. The tungsten electrode with dia 2 mm had an angle of sharpening 15 degrees and diameter of an obtusion 0.3 mm. Welding was executed with jet shielding of a surface by argon of the mark I (GOST 10157-79) or in the camera charged with an argon. The jet shielding of a joint weld realized by a nozzle having diameter 19 mm, at discharge velocity of an argon 15... 20 l\min. At an arc voltage drop 10 V main specifications of a welding conditions varied in following ranges: arc current — 100...200A, welding rate — 1.25... 2.78 mm/s. Samples welded was obtained at first in the flat position and, secondly, with implementation of horizontal welds on a vertical plain.

As a result of the held experiments the sufficiently strong influencing of flux reagent on metal penetration was established: at the introducing of welding flux the  penetration depth increased and width of a joint was moderated in 1.5 times. The attitude of welding practically does not exercise influence over width of a weld, but the  penetration depth at welding on a vertical plain is a little bit higher, than in the a flat position at the expense of running-off of metal from under an arc. At usage of welding flux a form factor of penetration in 1.5... 2.0 times are higher than at customary TIG welding.

In the work [1538] the influencing of activating fluxes FAST-1 and US-27A on  penetration depth Hp and width of a weld B on steels applied in power energy system was investigated. The results of experiments on influencing arc current and angle of lean of a welding electrode are shown in a Fig.11.43 and 11.44. From obtained data follows that the incremental of  penetration depth fluxes from 10 up to 75% for welding flux a US-27A and 64...130% — for flux FAST-1. At deflection of a welding electrode from a vertical position on 10... 20 degrees oscillatings of arc length and the performance of activating fluxes remains to welding rate high, that allows to apply them at manual TIG welding.

Fig. 11.43 [1538] Effect of arc current Iw on penetration depth Hp (a) and bead width B (b) at welding with activating welding fluxes with Vc=2 mm/s, La=1 mm

At magnification of lean angle for welding electrode from 70 up to 90 degrees the influencing of activating welding flux FAST-1on an abatement of width of a weld is boosted. The acting of flux a US-27A at ascending the lean angle of electrode is exhibited only in minor magnification of width of a weld. As a whole applying of activating fluxes FAST-1 and US-27A promotes an abatement of porosity of metal and meliorating of forming of a joint weld and it quality.

Fig. 11.44 Effect of arc length on penetration depth Hp at welding with activating welding fluxes with lean angle of electrode 80o by an angle forward (a) and 80 o  by an angle back (b): Ic=150 A, Vc=3.5 mm/s [1538]

In the work [1539] the results of studies the mechanized TIG welding of constructions from stainless steel with usage of activating fluxes are investigated. The penetrating capacity of the arc studied by a building-up welding 3...5 beads with length 100...150 mm on the flat or tubular samples. Experimentally was established that at development and choice of composition of activating flux it is necessary to take into account not only mark of metal welded but also the applied method of welding.

In the Fig.11.45 the dependences of  penetration depth and form factor of a joint from arc current for steel H18N9T are shown. It is obtained that the effectiveness of activating flux (AF) increases at magnification of arc current and decreasing the travel speed of welding. Most essentially  penetration depth is inflected at usage AF. If the flux will not be utillized, the  penetration depth practically does not range of currents up to 180...190A. The AF applying essentially slashes influencing arguments of a welding conditions at a rather broad range of welding rate variation.

Fig. 11.45 Effect of arc current and travel speed on penetration depth (a) and weld shape coefficient (b) at welding with activating welding flux and without it: 1,2 — travel speed accordingly 4 and 12 m/h [1539]

During the single-pass orbital welding of pipes were detected repeatability of  penetration depth and particular shape of a penetration zone approaching to X-preparing of edges in the all positions irrespective of the shape of edge preparation  (in experiments have utillized butts without groove, with V-shape and special groove on edges).

Analysis of results of practical using of the series of activating fluxes executed in work [692] has shown technological and economical advantages of manual and machine welding of thin and thick metal with usage of such fluxes at implementation butt, angular and T joints in different welded structures.

Thus the advantages of activating fluxes (AF) are as follows [690, 1540]:

1) The  penetration depth Hp is augmented; for example, at welding stainless steels the depth Hp increases from 3 mm at welding by a customary method and up to 12 mm at usage of a method ATIG;

2) The considerable variations of  penetration depth are prevented at oscillatings some chemical elements within the limits of an elemental composition for the given mark of base metal (cast-to-cast variation);

3) The shrinkage of joint after welding and its welding strains is slashed at the expense of deriving more deep joint as contrasted to by multipass welding with usage of V-figurative edge preparation.

As the given method requires the usage of more short arc, its applying is more preferential at the machine methods of welding. To deficiencies of a method are referred the inferior aspect of a surface of a joint as contrasted to by welding without flux and necessity of clearing of this surface after welding.

To deficiencies of applying of activating welding fluxes the instability of forming of a joint aroused by irregularity of deposition of a stratum of welding flux along a welded butt is referred. By results of studies executed in the work [1541] reasons of irregular inflow of welding flux in an arc are the deflections of arc length and lean angle of a welding electrode and also the low bond strength of a dust of welding flux with a surface of a part, as a result of which part of welding flux before an arc is blown by a flow of shielding gas.

In the work [1542] the basic technological process is described on which one the longitudinal butts of cowlings with thickness of edges of 14 mm was welded without edge preparation for one pass by an immersed arc by the tungsten welding rod in an argon. The penetration of metal was full at a current 750A and welding rate 2.5 m/h. However width of a weld bead and its width lengthwise of butt were unstable and their deflections on separate leases of a joint reached 50% from maximum ratings. At the same time as a result of heat input surplus the width of penetration reached 1.8 thickness of edges.

For meliorating the joint shape in [1542] they have tested a method of TIG welding on a stratum of activating flux. The bottom penetration of an arc in a weld pool ensures effective affecting of activating welding flux on penetrating capacity of an arc at thickness of welded edges of 14 mm without their edge preparation. It allows as contrasted to by welding by an immersed arc twice to diminish the linear energy and to improve forming the joint. By studies was established that the welding by the immersed arc with the components of activating flux does not degrade pattern and mechanical characteristics of weld joint.

The activating fluxes were widely utillized in mounting conditions at building the generating energy sets of Kursk and Smolensk atomic power plants [1543]. With the help of activating fluxes the orbital welding of pipes from stainless steel a diameter 57...160 mm with wall thickness 3.5...10.0 mm was executed.

The activating fluxes and designed on their basis of a weld procedures are widely applied in different industries and allow to reduce in 2.5... 3.5 times arc current at welding steels of different methods of melt in an argon and up to 3 times — at welding in helium (Fig. 11.46).

Fig. 11.46 Effect of activating welding flux on penetration of steel at welding in Ar and He: AF — activating welding flux, ESM — steel after electroslag melting, UAM — steel after unshielding arc melting [686]

The studies executed by the authors of the work [689] have shown that the applying of activating fluxes at welding by a melting electrode in CO2 does not render essential influencing on  penetration depth of base metal and nature of electrode metal transfer that probably is connected to presence at a shielding medium of such active gas as oxygen. The experiments have shown that the acting of catalysts on penetration depth more is hardly exhibited at welding in an argon or its mixtures with carbon dioxide. In these cases the magnification of  penetration depth in 1.2...1.6 times taken a place as contrasted to by welding method in carbon dioxide which one for want of catalysts usually ensured deriving a no-bottom of penetration.

The effect of magnification of penetration depth in the greater measure is exhibited at welding in a pure argon: the applying of catalysts allows to augment the penetration depth in 1.6 times as contrasted to by welding in CO2 or mixture 85%Ar+15%CO2 and in 1.8 times — as contrasted to by welding in an argon without a catalyst. Thus there is a variation of the shape of a penetration zone: the fingerlike shape of penetration, characteristic for welding in a clean argon, tends to the wedge shape. Matching of technological possibilities of welding in an argon with a catalyst and welding in CO2 without a catalyst has shown that at single-pass welding with full penetration of metal of identical thickness the in case of the former linear energy approximately in 2.6 times is higher than in second. Thus the properties of weld joints are meliorated especially impact elasticity of a weld material at low temperatures [689].


11.2.2. Usage of gas mixtures with the activating components


Proceeding from essential influencing of different elements on penetration depth of metal welded many explorers had input different gaseous matters into a welding zone. For example, in the work [1544] was established that at magnification of the contents in an argon the sulfur hecsofluoride SF6 (elegas) for steel VP25 the penetration depth increases on 60% (from 1.1 mm up to 1.8 mm); thus the arc voltage drop is augmented on 6... 7 V at constant arc length. For titanium alloy OT4 the penetration depth has increased almost in 3 times (from 1.0 mm up to 2.8 mm). The authors [1545] had marked that thus the impact elasticity of weld joints from steel and titanium alloys is slashed.

In the work [1544] they investigated a possibility of a heightening of penetration depth of metal at the expense of the components gaseous of fluorides in shielding gas mixture. The studies have shown that such a component as sulfur hecsofluoride in shielding gas increases power of an arc on 30...50% that results in variation of geometrical arguments of a penetration zone (Fig.11.47).

Fig. 11.47 Dependence of weld bead geometrical parameters from SF2 content in shielding gas [1544]

The penetration depth and the form factor of a joint at first grow at magnification of the contents SF6 in noticeably to argon and then are stabilized at a definite level. Thus for steel VP25 the penetration depth increases approximately on 60% and for titanium alloy OT4 — in 3 times. On data [1546] the component of halogenides in shielding gas results in contraction of an arc, essentially moderating the sizes of a zone of its electrical conductivity and increasing it penetrating capacity.

By the authors [1547] was established that at welding the titanium alloys in a mixture of an argon with 2% of hecsofluoride the  penetration depth increases on 170...180% at invariable arc current.

As one of elements the introducing which one allows to diminish variations of  penetration depth at welding the steels with variations of an elemental composition, the nitric oxide NO has being utillized. Falling in an arc zone NO dissociates on ions of oxygen and nitrogen which one are absorbed by liquid metal of a weld pool. Studies executed in the work [1548] have shown that the component 0.03% NO to an argon inflects on the picture of flows of liquid metal in a weld pool, and in a minor measure slashing its width, essentially augments its depth, especially at the low contents of sulfur in steel. For example, at arc current 150A the attachment 0.003% NO allows to receive the favourable shape of a joint. Though the input NO does not give a full solution of a problem, bound with discrepancies in  penetration depth for steels from different fusings, nevertheless applying of the mixture Ar+NO at the low contents of sulfur (up to 0.003%) allows considerably to improve the shape of a weld.

In the work [1549] influencing of shielding gas composition on depth and shape of a penetration zone was investigated at welding by the composite wire of bronze BrANMc 8,5-4-4-1,5. In a Fig. 11.48 the experimental data about nature of this influencing are shown.

Fig. 11.48 Dependence of penetration depth from composition and shielding gas expenditure [1549]

Is was established that the shape of the penetration zone at shielding by helium and mixtures Ar+He differs from welding in an argon by more even penetration and its smaller sizes. The magnification of expenditure does not result in a heightening of an arc voltage drop up to 28...32 V and abatement of arc current with 240...300A at Q=0.28 l/s up to 190...250A at Q=1.0 l/s.

By the most significant factors influential in variation of the shape and the sizes of a penetration zone author [1549] counts thermal properties of arc plasma (thermal conductivity) and degree of dissociation of a shielding medium. In particularly, at welding in CO2 the  penetration depth is less than at welding in an argon, that is explained by energy consumptions on dissociation of carbon dioxide.

By the authors of the publication [1550] the basic results of works dedicated variation of properties of a welding arc and basic performances of welding process depending on composition of a gaseous fluid are reviewed. Influencing different shielding gases and their mixtures, wires with a different elemental composition, welding rods with coatings of a different type was reviewed and coatings for protection of surfaces of welded metals from sparks of molten metal on variation of composition of a gaseous fluid in a welding zone.


11.2.3. Analysis of reasons for penetration depth increase with

usage the activating welding materials 

To the present time there is not a uniform judgement on the physical causes of operating of catalysts entered into a welding zone with the purpose of a heightening of  penetration depth and stabilizing of geometrical sizes of a joint weld. Therefore there are some hypotheses which are accounting for the physical causes of increasing the  penetration depth of metal at usage of activating fluxes or the activating gaseous components to shielding mixtures (Fig.11.49).

Fig. 11.49 The mechanism of activating welding flux influencing on metal penetration: a — welding with convenient technology, b — welding with activating flux (ATIG welding) [692]

Hypothesis I: "Contraction of the arc column and anode spot". The abatement of the sizes of the arc column which one is supervised visually and is affirmed by the applicable measurings [1546] is aroused, in opinion of the authors [1551], gripping of low-velocity electrons on peripherals of the arc column by molecules of halogens having a high electron attachment at plasma temperatures in the arc. The authors of the work [1546] count that the arc contraction first of all is aroused by a heightening of thermal conductivity of arc gas and chilling of peripheral leases of an arc. In the work [1515] the judgement is pronounced, that the contraction of a column of an arc and anode spot is aroused by screening by solid halogens of metal around of a weld pool, and also heightening of thermal conductivity of gas in the near arc room and deionization of peripherals of the arc column tracking by gripping of conduction electrons molecular byfluorid preparation products of interplay of metal and welding flux.

In opinion of the authors of the work [1552] increasing the penetrating capacity of an arc at availability in its bulk of electronegative elements (EE) are stipulated by composite processes of interplay of plasma streams in the arc and also physicochemical processes in a weld pool and on its surface. These processes preclude with infiltration EE in cathodic area of an arc and safeguard a tungsten welding rod from flash-off that ensures repeatability of welding process.

Hypothesis II: «Originating thermal-capillary and concentration-capillary convection of Marangoni». According to this hypothesis pushed by the authors of the works [535, 685] availability in a weld pool of some surfactant elements, results in a veering of of a thermal-capillary convection aroused by a nonuniform distribution of temperature in a weld pool. Thus there is such an aspect of a convection at which one the vertical stream of molten metal is intensified, directional to bottom of a weld pool [1520]. Under certain conditions nonuniform distribution of surfactant elements on a surface of a crater of a weld pool calls a concentration-capillary convection, as a result of which one the overheated strata of metal from under an arc are transferred to bottom of a weld pool, augmenting its depth and, therefore,  penetration depth of welded metal.

Hypothesis III: «Magnification of crater depth in the weld pool». The given hypothesis is grounded on analysis of balance of forces in a weld pool crater in which main forces are surface tension one and pressure force of the welding arc [686]. For the benefit of the given hypothesis the results of experiments executed in the work testify [1516] according to which one at transferring an arc to welding flux there is a spontaneous heightening an arc voltage drop component in investigated range of welding conditions DUa=1.0...4.7 V and greater magnitude DUa more deep corresponded and narrow penetration. As spacing interval from a welding rod up to a part was maintained invariable and the sum of a cathodic and anode voltage drop is stable enough it testified to magnification of concealed component arc length that is about ascending depth of a crater of a weld pool.    


If to accept the data of studies [1553] that the electric field strength in the arc column  with halogenides fluxes is 1.85 V/mm, the jump of arc voltage DUa in range 1.0...4.7 V corresponds the increasing of hidden component of arc length on DUa =0.5...2.5 mm. At sufficiently small thickness of welded metal S such an increasing of weld pool crater depth can essentially approximate the anode spot of the arc to a lower surface of a plate welded, therefore because of the reflex of thermal flow will be warm the workpiece and increasing the  penetration depth DHp by even more considerable than DLa down to full penetration on all thickness of metal welded.

Unfortunately, in the literature there are data shortage for influencing the thickness of an interlayer under the arc on weld pool crater depth at welding with activating flux and without it, that does not give a possibility quantitatively to evaluate the contribution of increasing the crater depth to a total increasing of penetration depth of metal welded.

It is necessary to mark that it is sufficiently important to determine the relative quantitative influencing of physical phenomena depicted by hypotheses I, II, III, in a increasing of  penetration depth at welding with activating welding materials. If the greatest contribution gives the phenomena on the hypothesis I, it is necessary to strive to obtain the greater constriction of the arc column and the anode spot. At prevalence of the physical phenomena on the hypothesis II it is necessary to input into activating fluxes such reductants which promote the progressing of a vertical axial stream of liquid metal, heated by the arc. At the greater contribution the physical phenomena of the hypothesis III it is necessary to input into the activating fluxes such matters as much as possible reducing the surface tension of molten metal in the weld pool crater and augmenting the force of the arc pressure.


11.2.4. The technological methods of increasing the penetrating capacity of the arc and control of the penetration shape at arc welding


1. Welding by an immersed arc. This method of welding grounded on forced submergence of an arc into the weld pool crater for the first time is proposed in the work [1554]. By the authors [1555] the weld procedure permitting to gain weld joints from titanium alloy VT6C by thickness up to 10 mm in environment of an argon and helium is designed.

The essence of the process is to encompass  the submergence of the welding arc with a tungsten welding rod more lower than the upper surfaces of welded parts are located. After ignition of the arc the welding electrodd is step-by-step sunk between welded edges before their full penetration (Fig.11.50,a). As at an abatement of arc length pursuant to the formula (3.3) its forces are augmented, the molten metal is displaced from crater part of  weld pool in its tail region.

Fig. 11.50 The technological scheme of welding by an immersed arc (a), influencing of linear energy (b) and welding current (c) on penetration depth Hp and weld width B: b,c — Vc=12 m/h; 1,3 — in argon, 2,4 — in helium [1555]

The increasing the arc pressure allows to setup the welding electrode below than surface of welded plates until installation of dynamic balance between force of the arc and oppositioning to it forces of surface tension and hydrostatic pressure of molten metal in the weld pool. In such a position of welding electrode displace lengthwise axis of joint, executing welding with deep penetration.

At the given welding method the arc length is within the range 1...2 mm at an arc voltage drop 9...10 V [1555]. At welding the titanium alloy VT6S with thickness of 7 mm with a surfaced arc the width of a weld is within the range 18...21 mm and at an immersed arc — from 10 up to 12 mm (Fig.11.50,a). In the given technology the tungsten welding electrode with dia 6...7 mm is applied that is a little bit greater than at customary TIG welding. The angle of sharpening of a tungsten electrode is recommended in range 70... 90 degrees. The welding rate at the given technological schema varies within the limits 10...14 m/h.

The method of welding by an immersed arc allows to weld the sheets of titanium alloys by thickness up to 10 mm without groove edges and without the applying of filler material and specialized machinery. Thus the efficiency of heating the workpiece and output of process is augmented. By the held studies is established that the welding in a shielding helium ensures more deep penetration than at usage of argon [1555].

This method of increasing the penetrating capacity of an arc was utilised at TIG welding of different materials [672, 1534, 1554, 1556, 1557]. The  penetration depth of metal at usage of the given technological schema depends predominantly on linear energy of a welding arc (Fig. 11.51). 

Fig. 11.51 Dependence of penetration depth from linear energy at welding by an immersed welding electrode: 1 — data of [1556], 2 — data of [672]

The method of welding by an immersed arc is recommended for butts of titanium alloys by thickness up to 70 mm. Thus the immersing depth of a welding electrode should not exceed 50% of welded metal thickness [672].

2. Usage the multiarc and multielectrode welding. To effective methods of a heightening the penetrating capacity of arc welding is related the feeding into an arc zone of two or more filler wires (multielectrode welding) or usage of multiarc process at which one of two or more arcs are applied simultaneously being laied out on some spacing interval from each other and following lengthwise axis of welded butt.

The method of arc welding by the splited welding electrode has considerable technological possibilities. At this techniques in the common melting room two or more electrode wires (bundle of welding rods) move having the common current lead (Fig. 11.52). In this case to main specifications of a welding conditions (arc current, arc voltage and welding rate) two arguments are added: a location of welding rods concerning a fulcrum of a joint and spacing interval between welding rods Le.

Fig. 11.52 The scheme of automatic welding by the splited electrode at transverse (a), longitudinal (b) and oblique (c) location of welding electrodes [1558]

In a Fig.11.53 the outlines of a cross-section of beads executed by welding electrodes with a different location concerning of joint axis with electrode separation Le=10 mm are shown. For matching delineations of an bead deposited on a surface by one welding electrode here are plotted. From these data it is followed that at a longitudinal location of welding electrodes the shape of a joint is inflected poorly as contrasted to by customary one-electrode welding. However at a cross-cut location of welding electrrodes this variation is essential: the  penetration depth is moderated also bead becomes much wider.

Fig. 11.53 Cross-sections of the beads fulfilled by one-electrode welding and by a splited welding electrode [1200]

Rather characteristic there is an appearance of an almost flat part in the root of the weld that is the penetration zone acquires close to an orthogon of a delineation. The weld pool thus becomes much wider and more shortly and the process differs by considerably higher stability. At welding by the splited welding electrode coefficient of fusion of a wire on the average on 20% is higher than at one-electrode welding.

In a Fig. 11.54,a the outlines of a cross-section of the bead executed at variation of spacing interval Le between wires of a splited welding electrrode from 0 up to 20 mm are figured. From these data it is followed that at increasing of spacing interval Le results in an abatement of  penetration depth, ascending of width of an bead and form factor of the weldt. The nature of variation of the basic geometrical arguments of an bead is rotined in a Fig.11.54,b. The similar results are obtained at usage of the splited welding electrode at welding the aluminum alloys plates[1204].

Fig. 11.54 Variation of the bead shape at different spacing interval Le between

wires of the splited welding electrode (a), influencing of polarity and welding current magnitude on a fraction of base metal involvement in the joint (b), on penetration depth (c), weld shape coefficient (d) and weld width (e) at Ua=30...32 V, Vc=30 m/h [1558]


At welding conditions utilised in held experiments the bead acquires the flat shape in bottom of a penetration zone at Le=9...12 mm. The further increasing of distance Le results in formation of the saddle and at a some more large bead is reshaped poor and at reaching Le of a defined value is partitioned on two separate beads from each wire of the splited welding electrode.

By the held studies is established that as contrasted to arc welding at welding by the splited welding electrode ensures a considerable abatement of a fraction of base metal in a weld. At welding by a current of a straight polarity of customary low-carbon steel by a wire the fraction of base metal is slashed up to 35...40% that it is impossible to achieve at arc welding. At usage of the splited welding electrode from austenite wire a dia of 2 mm the fraction of base metal can be reduced up to 20...25% and at diameter of 1.6 mm — up to 15...20% [1558].

Applying of the belt splited welding electrode (the Fig.11.55) enlarges the technological possibilities of the given method of welding as allows even more flexibly to regulate the shape of a weld at increasing of rate fusion of a welding electrode [1559]. Due to an essential dispersion of arc heat there is possibility of a considerable current increase in welding electrodes without impairment of repeatability of welding process.

Fig. 11.55 The scheme of welding by the decomposed belt welding rod: 1,2 — belt welding rods, 3 — the maiden stratum, 4 — a facing stratum [1559]

In the work [1560] the possibility of obtaining the quality joints with a small form factor is established at arc welding in CO2  for heavy plates of low-carbon steel. It allows to reduce expenditure of filler material, electrical power, welding strains, and also to increase the mechanical characteristics of welded joint. In a Fig.11.56 the possible schemas of groove edges under arc welding are shown. At a rather low speed of welding more preferential are the schemas of a Fig.11.56,b,c as at welding under the schema of a Fig.11.56,a it is possible flowing of molten metal in a gap before the arc. The data by a method can gain quality weld joints at welding metal by thickness of 18 mm by an one-pass joint and 36 mm — by a two-sided joint. Recommended arguments of a condition of arc welding: arc current — 380...400 A, arc voltage — 28... 32 V, welding rate — 18...20 m/h.

Fig. 11.56 The schemes of edges preparation for arc welding: U-shape (a), V-shape (b) and double-sided (c) [1560]

Applying features of multiarc welding for raising the productivity of a manufacturing process, meliorating of forming of a weld and removal such defects of its shaping as undercuts, explicitly are reviewed in the Chapter 13 of this monograph (look the volume III).

3. Usage of lateral vibrations of a welding electrode and the arc. In the work [1199] was established that the shape of a penetration zone and its depth are moderated with increasing of amplitude and oscillation frequency of a welding electrode that allows to provide satisfactory weld forming at welding on enlarged gaps between joined parts.

As a result of the executed studies by the authors of the publication [1561] the welding method of rotary butts of tubes is proposed at which the penetrating capacity of a welding arc is regulated at the expense of variation of amplitude and frequency of lateral vibrations of a welding electrode. The method ensures a possibility of implementation of automatic welding of butts with a variable gap. It has large value at fabrication steel constructions with long-sized butt welds described by considerable irregularity of a gap between welded plates [1562].

The author of the work [1563] recommends with the purpose of stabilizing  penetration depth and obtaining of the favourable shape to joints at welding in shielding gases to communicate to a welding electrode of lateral vibrations, due to what there is a pressure relieve of a gas stream and heat, selected by an arc, on a surface of a welded workpiece. The oscillatings of a welding electrode not only moderate the size of drips and extent of overheat of metal, but also meliorate forming welds and stabilizings the combustion of an arc.

In the work [870] was shown that the lateral vibrations of a welding electrodr (ELV) allow follow-up to affect conditions of input of heat in different parts of a welded joint, that is specially important at one-sided welding on a weight of a root welds of butts (tubes, shells) with a changed gap. The ELV allow to regulate the sizes and shape of a weld, condition of a crystallization of weld pool that is specially important at welding in different positions. The ELV practically do not render the influencings on repeatability of an arc and output of welding process.

At welding in carbon dioxide applying of lateral vibrations of a welding electrods with amplitude Ae=8...14 mm and frequency fe=100...150 1/min are ensured with effective regulation of length and width of the weld pool without variation of a welding conditions that has the relevant value at welding in different positions [1202].

By studies [1564] was established that cross-cut movements of an arc with frequency 0...8 Hz and amplitude 0...8 mm influence pattern and properties of weld joints thin-sheet high-strength steels 42H2GSNM and H18N9 at TIG welding noticeably. It was established that there is a frequency range and oscillation frequencies of a welding electrode (3 Hz and 3 mm) in which one at satisfactory forming of beads the column texture of a joint is loosened, the crystallites acquire the curved shape and become short, with blurred boundaries; the eased plain in an bead part of bead fades. The repeated reheats promote slackening of a chemical microinhomogeneity of a weld material and grinding of a microstructure of metal in HAZ. As a result of it the mechanical characteristics of weld joint, specially plasticity, are increased.

In the series of cases cross-cut concerning a axis of a joint of oscillating of a welding arc are called by laying of a cross-cut variable magnetic field [1203].

By the authors of the work [524] was established that as a result of welding with oscillatings of an arc the magnetic field moderates a grain sizes of a weld metal and the tendency to progressing a liquation is slashed. At definite combination of frequency of amplitude the tendency of a weld metal to hot cracking is slashed, that was revealed in an abatement of mean length of fractures on 40%.

At a welding electrode migrating lengthwise joint axis the arc oscillating can fulfill only with the help of a cross-cut magnetic field [524, 1565, 1566 etc.]. For example, in the work [1565] the optimal nature of lateral vibrations supplying even penetration of sheets on all width of a joint is determined the machinery for welding and building-up welding by an arc controlled by a magnetic field and is designed.

By the authors [1566] influencing the arc oscillatings resulting passage alternating-current through a part of filler material (Fig.11.57), on the shape of penetration, hardness, pattern and mechanical characteristics of joints was investigated at TIG welding the aluminium alloys 1201, AMg6, 1420 and 1460.

Fig. 11.57 The technological scheme of TIG welding with current-carrying filler metal: 1 — welding torch; 2 — the filler wire; 3 — the workpiece; Ia, If — currents in the arc and filler wire [1566]

It was established that the sizes of penetration of joints depend on values of currents driving through an arc gap and a part of a filler wire, and frequency of gang of their polarities. At identical  penetration depth width of joints and the extent weakness of weld joints obtained by welding by an arc with oscillatings, is less, than at welding by a stationary arc. Intensive stirring of molten metal and variation of conditions of its crystallization promote forming of shallow equilibrium dendrites that ensures a heightening of hardness of a weld material.

4. Applying the hollow electrodes. As shown by numerous studies of the different authors the pressure distribution of an arc has bell-shaped nature and can be depicted more precisely by Gaussian low of allocation or simplistically — by parabolical dependence (look Chapter 12 in the volume III). Such a nature of pressure distribution of an arc results at usage of customary welding electrodes as to the unfavorable shape of penetration and to originating the different kind of defects, especially at augmented welding conditions (the current or travel speed of the arc).

According to studies of the authors of the work [1567] by one of methods of a heightening of properties of weld joints at the expense of meliorating their geometry is the welding in inert gas with hollow tungsten welding electrode. They had shown that for deriving joints of the favourable shape it is necessary not only to flash down arcs, but also to change pressure distribution in it that is to pass from parabolical allocation to rectangular one. It allows to increase values of arc current without a sharp pressure buildup of an arc at its center that takes place at welding by a customary welding electrode. As a result of the held studies the possibility of welding with hollow welding electrode on a current 800 is shown and at deriving good geometry of a welded joint.

5. Imposition the longitudinal magnetic field on the arc. The authors of the works [1494, 1568] the pattern permitting to explain behavior of an arc with imposition on it the  longitudinal magnetic field had proposed. The radial movements of conduction electrons in an arc are conditioned by acting forces of an electrical field of an arc, and radial movements of ions — heat-dynamics nature of directional streams, originating in an arc plasma. On the proposed method of influencing of a magnetic field the cross-section of the arc column is moderated by a arc column at an induction of a longitudinal magnetic field more than 0.1 T that is exhibited in increasing it penetrating capacity in 1.5...2 times (look the Fig.11.16).

At arc welding by electric rivets with usage of the modified keeper with a built-in electromagnet (Fig.11.58, a) the imposing of the longitudinal magnetic field augments  penetration depth of metal and this increasing depends on time of affecting of a magnetic field which one is customary less time of welding (Fig.11.58,a).

Fig. 11.58 The modernization scheme for electrode holder at electric riveting welding (a) and influencing of time of affecting of a magnetic field tm on penetration depth Hp at Ua=36 V, tc=4 sec, de=1.6 mm (b); a) 1,3 — the bushing; 2 — the electromagnet; 4 — the guide bushing; 5 — the mouthpiece; 6 — the abutment cooled nozzle [1495]

6. Usage of pulsing-arc welding. At imposing on the arc of impulses of welding current the deriving both deep and surface type of penetration of welded metal is possible. The surface penetration takes place at such welding conditions when there is a strong anode stream and there are surface oscillatings of molten metal in the weld pool [1569].

7. Usage the high-frequency arc. The positive results were obtained in applying of the high-frequency  current at welding the aluminium alloys in the work [1570]. The welding arc through which high-frequency current past differs by heightened stability, which one sometimes value on a fracture arc length. The results of experiments have shown that the fracture arc length with a power current of 50 Hz and applying of an oscillator fluxes 13.6 mm and at power supply by a current by frequency of 600 Hz — 54 mm.

The penetrating capacity of the high-frequency arc approximately in 3 times is higher than arc with an usual current (Fig.11.59); thus penetration width essentially is not inflected that testifies to increasing of the penetration zone area. It was obtained also that the current magnitude and  penetration depth is rather gentle depend on length of an arc that is the relevant advantage of the given method of welding.

Fig. 11.59 Dependence of penetration depth (a) and weld shape coefficient (b) from arc current at its different frequency [1570]

Many processing behavior of a method of welding is with an arc of high-frequency on sufficiently high level. The arc burning is stable and is easily excited without applying any devices for ionization of an arc gap and supply of repeatability of arc combustion. The mechanical characteristics of weld joints correspond to given requests, the amount of pores and slag inclusions is moderated, a joint weld and HAZ have the favourable microstructure [1570].

On data of the authors [1333] applying of welding by a current of high-frequency for pipelines with diameter 6.8 and 12 mm from steel H18N9T have allowed to diminish magnitude of a sag of the radical of a joint inside of a tube in 2 times, and width of a joint — in 1.5 times as contrasted to by impulsive low-frequency welding.

In study [1571] they had been learnt the penetrating capacity of an high-frequency arc at TIG welding in argon of steel H18N9T by thickness of 2 mm. The parameters of welding conditions were: current 50...70 A, arc gap length — 1... 3 mm, sharpening angle of tungsten electrode — 30...90 degrees, the electrode blunting — 0...1.5 mm. Experimentally it was demonstrated that if in customary process of welding by a direct current of perturbation lengthwise of arc gap, angle of sharpening and blunting of a welding electrode essentially influence penetration, transferring to welding by the modulated current in the learnt frequency range 3...3000 Hz considerably is slashed with affecting the indicated arguments.

8. Applying the activating welding electrodes. By the authors of the work [1572] the possibility of welding the steel such as X18N10T by surfaced-activated electrode in carbon dioxide by a direct current with normal polarity was established. It was established that there is a dependence of extreme arc current on an amount of the coating having put on the welding electrode and stick-out of the welding electrode.

The least losses of electrode metal are reached at length interval from the current-carrying mouthpiece up to an workpiece 14...15 mm. The applying of surfaced-activated electrodes allows to diminish the sizes of groove preparation. On data of the publication [715] applying the activated wires allows to increase welding rate up to 120...130 m/h.

9. Applying the combined processes of arc welding. In the work [1573] the combined process of arc TIG and MIG welding was proposed. The given method has rational range of applications for welding both buildng-up welding of non-ferrous metals and alloy steels.

     10. Usage the edge preparation with special shape. In the work [1574] they proposed the butt joint with a cavity formed by two grooves, executed up to assembly on the sizes depending on thickness of a welded sheets in definite limits the supplying maximal increasing of  penetration depth at the expense of forming the radical of a joint is lower than this cavity on an blunting. The sizes of grooves in samples in the indicated limits influences the sizes and quality of a joint. The held studies have allowed to select an optimum alternative for industrial usage. By the authors [1575] the variation of  penetration depth was investigated at welding aluminum and its alloys depending on the shape of butts, including if there is a cavity in groove preparation.