CC BY
128
УДК 621.791
DETAILED MIG/MAG WELDING METAL TRANSFER CLASSIFICATION. PART 1: GENERAL CONSIDERATIONS
Vladimir Ponomarov, Americo Scotti, William Lucas
Metal transfer modes in arc welding processes have previously been classified as Natural or Controlled Metal Transfer. Modern laboratory techniques have helped to establish a new transfer classification mode in MIG/MAG welding of carbon steels, which has been termed Interchangeable Metal Transfer. Several experiments with different combinations of gas-wire-parameters were carried out to observe metal transfer and to characterize the various transfer modes. Laser backlighting techniques and high speed filming were employed to study metal transfer. The video was synchronized with the welding current and arc voltage signals to aid the understanding of the transfer behaviour. Phenomenological explanations based on arc physics are given to justify the main governing factors for the particular metal transfer characteristics. A classification for metal transfer modes is proposed, in which the modes are independent of the type of shielding gas or welding power source.
Key words: MIG/MAG Welding; Metal Transfer Classification.
Gas Metal Arc Welding (GMAW or MIG/MAG) is a widely used process in the metal fabrication industry. Welds are produced by using an arc to melt a wire electrode. Metal from the melting wire is transferred to the joint in the form of droplets that detach from the electrode tip. The performance of this process is governed by the metal transfer mode that is the way in which the metal droplets are detached from the wire electrode and transferred to the weld pool.
Several characteristic transfer modes have been described in current literature. The first classification, established more than 30 years ago by the International Institute of Welding (IIW), as seen in the IIW Doc. XII-636-76 [1], is still used by several researchers. Despite its merit, this classification is applicable to natural transfer modes only and neither encompasses recent controlled transfer types nor the metal transfer modes recognizable only when using sophisticated measurement techniques. Natural modes are defined here as a mode with transfers not forced by additional electrical parameter or wire feeding control, in contrast to controlled transfer modes.
During the last decade, some leading researchers have contributed to the elaboration of a more comprehensive classification. Norrish [2] proposed to extend the above mentioned classification adding two more groups of modes namely Controlled Transfer Modes and Extended Operating Modes. He also proposed to consider the transfer modes mentioned in the former classification as the Natural Transfer Modes. Norrish's intention was to encompass transfers modes that happen in novel processes. However Lucas et al. [3] suggested restraining the classification to Natural and Controlled Transfer Modes. In addi-
tion, these authors proposed an extra fixed alphabetic label for each "fundamental" metal transfer mode (A - short-circuiting, B - globular, C - pulsed, D -
N C
spray and E - Rotating), furnishing those labels with superscripts and , depending whether the metal transfer is natural or it is generated by a control system (e.g. Ac is a controlled short-circuiting transfer). Iordachescu and Quintino [4] proposed a similar approach using alphanumeric labels (A, B1, B2, C1, C2 and C3). In spite of a good intention, both labeling approaches look somewhat confusing. Izutani et al. [5] presented a rich description of the metal transfer modes, yet partially polemic, and suggested some improvements for the classification in force. Despite the above mentioned works, there is little published information on multi-mode metal transfer, hereafter referred as "Interchangeable metal transfer", observed and studied by some researchers including the present paper authors.
From those works, it is clear to have in the welding community two tendencies. Some authors look after simplifying the classification, while the others strive for a more comprehensive and detailed, i.e., towards a more detailed one. The first approach is focused on allowing the broadest welding community to apply the classification for practical situations, aiming mainly to meet industrial needs, whilst not covering the entire range of metal transfer modes. The latter approach strives to cover the intricate physical aspects of metal transfer.
Thus, the initial objective of this work was to carry out a detailed study of metal transfer in MIG/MAG welding with the intention of identifying all types of metal transfer, including the novel controlled transfer modes produced by the new power sources, as well as the above mentioned "Interchangeable metal transfer". The final intention is a more detailed classification in order that all types of metal transfer can be classified.
Experimental procedures. A series of experiments was carried out with the aim of reproducing parameters that would lead to differing types of metal transfer in MIG/MAG welding including interchangeable metal transfer. Bead-on-plate welds were carried out on carbon steel plates using a 1.0-mm-diameter wire of the AWS ER70S-6 class with DCEP. The approach was to select a different shielding gas (Ar + 2% or 5%O2) and then set a combination of inductance, welding current and arc voltage to produce the desired droplet transfer mode. An electronic constant voltage output characteristic power source was used in these experiments.
The main methodological approach applied was based on a system for metal transfer visualization as used by Lin et al. [6] and Bálsamo et al. [7], among others. The experimental rig was set up as shown in fig. 1. A shadow of the non-transparent components (contact tube, electrode, metal drops, weld pool and plate) of the arc region was projected onto the lens of a camera, a technique
known as backlighting. A high-speed digital camera working at 2,000 fps and a 632.2 nm He-Ne laser were used. To enable the arc to be seen also, optical filters of different intensity were employed. The electric signals were synchronised with the film frames to correlate the variations in arc voltage and welding current with the formation and detachment of the droplets. Synchronization was carried out using a dedicated program built in a Lab View® platform.
Fig. 1. Details of the optical laser system used for metal transfer visualization: 1 - light source (laser); 2 - neutral filters; 3 - divergent lens; 4 - convergent lens; 5 - protection glass; 6 - band-pass and neutral filters; 7 - high-speed video camera; 8 - monitor; 9 - image recording unit; 10 - computer;
11 - current hall probe
The natural metal transfer modes. Modes such as "short-circuit", "globular" and "spray", occur as a function of the set electrical parameters, i.e. current and voltage. The modes and variations of these modes, e.g. contact and free flight transfer, are listed in table below. The physical forces affecting natural MIG/MAG welding droplet transfer are not to be dealt with in detail in this work, but, for the sake of completeness to define their physical character, they are also listed in the table. It is common to all modes in table to occur "naturally", that is, they are not forced by additional electrical parameter or wire feeding control. However, more than one single transfer mode may be referred to either as "contact" or "free flight" category.
Heald et al. [8] showed that the groups of modes, and respective transfer modes, are related to welding process parameters and shielding gas types, usually represented through diagrams, which are often referred to as "transfer mode
maps". Scotti [9] presented different versions for them, having similar content, yet using different approaches, as illustrated in fig. 2. Arc voltage (Ua) plotted against welding current (Iw) is the most conventional way of representing a transfer map. A second version would use "arc length" (La), or, more precisely, the "arc gap extension", instead of arc voltage, since arc gap is considered to describe the influence on transfer behaviour more realistically. It is important to point out that the arc voltage and the arc length are in some cases incorrectly used as synonyms. A direct relationship between the arc length and the arc voltage is widely known (the higher the arc length, the higher the arc voltage), but it is valid only for a given current. When the correlations are established as a function of the current, as the present case, the arc length can be maintained constant for different current values, because they are independent of each other. On the other hand, the voltage will increase as the current is augmented for any arc length, since the voltage is dependent of the current for a given arc length (static characteristics of arcs). As a result, the two drawings can take slight differences in shape.
To be classified as a pure Short-circuiting mode, there must be a short-circuit between the droplet under formation and the pool before drop detachment. During the short-circuit periods, the arc extinguishes. As shown in fig. 3, a liquid metal bridge is formed and then grows as the droplet is sucked into the molten pool (by surface tension). As the short-circuit current at this stage is not very pronounced, there is insufficient electromagnetic force to constrict (pinch effect) the metal bridge. Then, owing to a reduced electrical resistance in the bridging, the current increases progressively, heating the wire by Joule effect. The bridge is necked out by the combined effect of the surface tension and the progressive electromagnetic forces, the latter as a consequence of the increased current at the final stage.
Although there is an equilibrium between the wire melting rate and its feeding speed during the short-circuiting mode, just after the end of the short-circuit, the first parameter becomes higher than the latter one (due to the still elevated post short-circuit current), leading to a limited increase of the arc length. At this point, there is also an accelerated formation of a new droplet at the tip of the electrode wire. As the current subsequently falls, the rate of the wire melting matches the wire feed speed during the following few milliseconds. Afterwards, as the current intensity becomes smaller, the wire feeding rate exceeds the wire melting rate, causing the wire to gradually approach the weld pool.
As a characteristic of metal transfer, it is important to point out that, during the end of the "open arc period", there is a continuous, yet slow, droplet approach towards the weld pool (the melting rate at this period is low and so is the droplet formation speed). Another inherent phenomenon is an oscillation of both the droplet and the weld pool, leading to arc length variations (from 1 to 2 mm).
If this droplet-pool oscillation (each at its own frequencies, according to different molten masses, viscosity, etc) is towards each other, consistent short-circuit conditions take place. On the other hand, if the oscillations are chaotically out of phase, slight contacts between the wire electrode and the weld pool may occur, a phenomenon called "incidental short-circuiting". No metal transfer, but spatter generation may result.
MIG/MAG welding natural metal transfer modes
Transfer mode
Short-circuiting (с короткими замыканиями)
Bridging (посредством перемычек)
Forced short-circuiting (погруженной дугой)
Appearance
Main governing force (effect)
Surface tension and electromagnetic pinch effect
Surface tension
Strongly pronounced electromagnetic pinch effect
Globular (крупно-капельный)
Repelled Globular (крупно-капельный с отклоненной каплей)
Projected Spray (cmpyuHbiü)
Streaming Spray (струйный с утонением торца электрода)
Rotating Spray
(струйно-
вращательный)
Explosive (взры воооразны й)
Gravitational force
Gravitational force and repelling forces
Electromagnetic force
Electromagnetic force and chemical reactions
(*) this sequence of photographs was kindly provided by Frornus, through Mr. Stephan Egerland and Mr. Josef Artelsmair
Group of modes
Contact Transfer (перенос через контакт)
Free-flight Transfer (перенос оез коротких замыканий)
Fig. 2. Schematic maps of the main natural metal transfer modes occurring in MIG/MAG welding as a function of the welding current (Iw), represented by either the welding voltage setting, on the left, or the arc length, on the right
Fig. 3. Typical traces of arc length (La), arc voltage (Ua) and welding current (Iw) during MIG/MAG welding short-circuiting transfer
Bridging transfer, also belonging to the "contact transfer group", happens when the wire is subject to only low short-circuit current during the contact drop-pool. The surface tension becomes the driving force for metal transfer, reducing the importance of the pinch effect on droplet detachment. Neither droplet repulsion (low pool and droplet oscillation) nor spatter generation is observed with bridging transfer and smooth weld pool behavior leads to a uniform bead appearance. Usually generated with a constant current power source characteristic and/or very high inductance levels, this transfer mode has a restricted range of parameters (arc voltage, welding current and welding speed). However, once set, the transfer mode can be properly used for, e.g., joining thin sheet metals.
99
The forced short-circuiting transfer mode, is characterized by parameter settings for a short arc with a very high wire feed speed (over 10-12 m/min), to produce a welding current as high as 250 to 350 A. As the transfer is governed by a strong electromagnetic (pinch) force, the droplets are of small size (no time to reach bigger volume) with a high transfer rate minimizing the surface tension effect. There is a high level of spatter.
Globular metal transfer is encountered when operating the welding process with low to moderate current and moderate to high voltage (i.e., extended arc lengths), thereby avoiding short-circuits. Large droplets, reaching diameters of 1.5 to 3 times the wire diameter, and very low droplet transfer rates, in the order of 1 to 10 droplets per second, characterize this transfer mode. Being retained at the wire tip during its growth by surface tension and vapor jet reaction force, the droplet is detached finally when gravity and aerodynamic forces exceed the former (a critical droplet diameter is reached). Electromagnetic forces are negligible due to the lower current. When the droplet starts growing, the neck formed at the interface between the wire end and the droplet presents a larger area than the arc coupling area (due to the low current), which also makes the pinch effect act backwards. As the droplet grows, the neck elongates up to a point in which the arc coupling area overcomes the neck area, when the pinch effect now helps the transfer. Thus, the electromagnetic force, even on a small scale, contributes to droplet growth. This helps to explain why the droplet size and transfer frequency do not change very much inside the operational current envelope for globular transfer. Droplet size, shape and behavior depend on the shielding gas type, filler material diameter and composition and the welding current level.
"Repelled Globular"' droplet detachment may arise from globular transfer when applying certain welding conditions (some types of shielding gas, DCEN polarity, etc.). The arc spots become constricted and concentrated underneath the droplet, creating repulsive forces (the pinch effect acting backwards and the metal vaporization reaction). It is believed that excessive vapor can also be formed in the pool by some shielding gases (especially CO2 rich gases). The large droplet formed just over the weld pool results in a high pressure acting on the droplet due to a small escape area. The forces repel the droplet from the wire axis, causing it to grow further and towards one side. Droplet transfer occurs when gravity and aerodynamic forces exceed the repelling arc forces.
Based on the dominant nature of gravitational forces, the globular transfer modes, both pure and repelled, are known to have very limited suitability for welding in positions other than the flat. When welding, e.g., in the vertical position, some droplets are simply lost, since their mass and volume impede a proper transfer from the wire to the weld pool. As in short-circuit transfer, the wire feed and fusion rate are approximately the same. But, during the droplet growing phase, the arc length becomes progressively smaller and (when using constant voltage power source and most shielding gases) the current increases propor-
tionally. The fusion rate increases more than the wire feed speed (not as much as in short-circuit, since, in this case, the current rise is less) and the drop grows in all directions, including up the wire. It means that at first the electrode does not approach the welding pool but the droplet does. When detachment starts (necking due to gravity force, the current gradually reduces (in response to the higher electrical resistance), making the fusion rate smaller than the wire feed rate. With necking, the slight pinch effect assists the gravity force to overcome the surface tension retaining action and to detach the droplet.
Projected Spray is characterized by small droplets (close to the electrode diameter) transferring from the electrode tip to the weld pool at a rate of hundreds per second, without short-circuiting the pool. Very regular, yet high, heat transfer to the pool is obtained and no significant amounts of spatter are observed. However, projected spray transfer can only be used in the flat position, because of the large volume of the molten metal in the weld pool. A prerequisite for projected spray is both high voltage (long arc) and moderate to high current, the latter to exceed the so-called "transition current". This threshold is dependent on a great number of parameters, such as filler material, shielding gas composition and electrode extension/diameter. Below the "transition current" and with moderate to high voltage, the transfer is globular. If the current is set above the transition current, the spherical droplets become progressively smaller, correspondingly increasing the transfer rate. The wire electrode tip becomes a little bit pointed. The radial, compressing, fraction of the electromagnetic force increases dramatically, subjecting the droplet to a strong pinch effect, limiting its volume and size and allowing only a small droplet to be formed. There is very little oscillation of current and the equilibrium of wire feed rate and fusion rate is acceptable. At this level of current, the balance of forces acting in the metal transfer is not only based on the static equilibrium theory, but upon a combination of forces explained by the pinch instability, as proposed by Allum [1]. Kim and Eager [10] found that the static force balance theory would give more realistic representation of the globular metal transfer phenomenon if the effect of dynamics of droplet motion at the electrode tip is taken into consideration. In addition, they state that the pinch instability theory is unable to explain the metal transfer at globular and spray projected transfer mode, but the droplet size at the streaming transfer is thought to be determined by the pinch instability.
With a further increase of the welding current, projected spray transforms into "Streaming Spray" transfer. In addition to higher heat produced in the electrode tip, the anodic area needs, to some extent, to increase due to higher current arriving the wire end (the arc climbs the wire surface). As a result, a wire volume above the arc-wire coupling is heated enough to become plastic, resulting in the "tapered" shape of the electrode end. Hence, the wire end changes into an almost molten stream towards the weld pool, forming a conic shaped metal column. At the tip, very fine droplets are formed and detached. Electromagnetic
forces (acting predominantly in accordance with the pinch instability phenomenon), mentioned in the "projected spray" section, are taken as the governing phenomenon in the metal transfer, leading to smaller droplet diameters and higher transfer frequency than with projected spray. As long as this tapered end does not touch the pool, there is no spatter. Welding in positions other than the flat one becomes even more difficult.
Beyond "Streaming Spray", the "Rotating Spray" transfer mode takes place, attainable by further raising of the current. The wire electrode tapering effect is more pronounced with overheating, resulting in an extended metal filament. Strong electromagnetic forces, caused by the highest welding current applied, move the column away from its straight line of flow. The combination of asymmetric radial forces and azimuthal forces results in a spiral motion of the column. The droplets (extremely fine) are detached from the tip of the rotational filament in tangential direction, producing a lot of spatter.
It has been observed that, under some circumstances (certain gas and wire compositions), droplets attached to the electrode tip can eject material in an explosive manner in which small droplets are expelled from the molten part of the electrode tip and transferred to the weld pool. This is thought to be due to chemical reactions (gas-metal) inside the droplet. This transfer mode is named Explosive Transfer and is usually accompanied by considerable amount of fine spatter.
Modes resulting from controlling the transfer. Special welding applications (e.g. joining thin sheet metals, welding in the vertical position or required low spatter) highlight the physical limitations of "natural" transfer modes. These limitations can be overcome by using advanced welding equipment, which allows automatic adjustments and control of the transfer. The resulting transfers can be categorized as "controlled metal transfer", but they are in effect natural modes obtained deliberately, either through programming parameter alterations or through adaptive control as a response to a parameter variation. The most common examples of controlled metal transfer modes are the "pulsed transfer" and the "controlled contact transfer".
Commercially applied since the 1960's, the "pulsed transfer mode" is a very well-known approach to control the droplets. In pulsed transfer a long arc length is used and the welding current is cyclically pulsed from a low value (base current), sufficient, however, to maintain the arc, to a high value (pulse current) and sufficient to form and detach a droplet (a spray-like transfer). For a given pulse current, pulse time is precisely required to lead to one drop detached per pulse, as explained by Kim and Eagar [11] amongst others. Ueyama et al. [12] describe a special pulse mode variant, denominated AC (Alternating Current) or VP (Variable Polarity) MIG/MAG welding. During DCEN polarity, a droplet forms on the end of the wire. The droplet is forced across the arc when the current switches to DCEP polarity. Nascimento et al [13] explain that the transfer is controlled by the parameter settings at both polarities. Another special
controlled pulse mode is double pulsed MIG/MAG welding, in which the high frequency pulsing current controls metal transfer but superimposed low frequency or thermal pulsation is used to control the weld pool (similar to pulsed TIG).
Controlled contact transfer modes may be considered as a means of improving the regularity of the droplet to weld pool contacts which occur under natural short-circuiting transfer. By reducing the randomness of natural transfer, a "softer" droplet detachment (no spatter and improved weld pool controllability, due to higher thermal regularity), is achieved. To achieve this aim, many researchers, like for instance Stava [14], suggest to use adaptive control systems for modulating current (control of the voltage signal level throughout each contact stage), while Pickin and Young [15], alike other specialists, added wire feeding variations to assist molten metal bridge breaking. Branded commercial names, such as STT™, CMT™, RMD™, FastRoot™, etc. are related to controlled metal transfer techniques.
The controlled metal transfer modes might be sub-classified in accordance with the main parameter (parameters) subjected to adaptive control, as follows: spray Transfer Controlled by Pulsed Current (DC and AC) (the current is automatically adjusted by the machine using an algorithm to form the appropriate pulse and base periods); contact Transfer Controlled by Current (the current is controlled during and/or before the short-circuit stage); contact Transfer Controlled by Current and Wire Feeding (not only current, but also the feeding of the wire, forward and backwardly, is controlled during and/or before the short-circuit stage).
Modes that happen in an interchangeable way. Scotti [9] and Ponoma-rev et al. [16], showed that there is a pattern of transfer which is not widely commented on in the current literature, most likely because the related transfers are difficult to be identified using ordinary laboratory techniques. Moreover, they are easily confused with temporary transfer instability during a setting at a transition operational envelope between two adjacent natural modes. To certain welding conditions, two or more transfer natural-like modes happen in a periodic sequence (without any interference of the operator and/or a control system), such as interchanging of modes. One important characteristic of this transfer is that the following mode is a consequence of the previous one (the variation of current, electrode temperature and/or plasma status due to a transfer mode gives rise to conditions for the following mode to take place). For instance: short-circuiting-Projected Spray; short-circuiting-Streaming Spray; globular-Projected Spray; globular-Streaming Spray; globular-Short-circuiting-Streaming Spray-Globular; others.
These modes are described in more details in the second part of this work: Detailed MIG/MAG welding metal transfer classification. Part 2: Interchangeable metal transfer phenomenon.
Detailed Classification of Metal Transfer Modes. First of all, it is important to state the terminology used in this work for this classification:
- Mode (metal transfer mode) defines a characteristic behavior of a drop under transference in MIG/MAG welding, e.g. "globular" mode (large drops travelling from the wire tip to the weld pool) or the so-called "spray" mode (small droplets travelling consecutively from the wire tip to the weld pool).
- Group (group of modes) stands for a number of modes that have similar characteristics.
- Class (classes of modes) is the highest hierarchical (parental) grouping of modes. A class of mode can be formed by one or more groups.
Members of the IIW have reached a consensus on a simple metal transfer classification which has two classes, namely "Natural Metal Transfer" and the "Controlled Metal Transfer In the proposed detailed classification, a third "Interchangeable Metal Transfer" class is included to cover those modes which have periodical changes in the transfer mode provoked by changes in welding parameters (an "autophagic" behavior).
The Interchangeable Transfer Mode cannot be attributed to either Natural Transfer Modes because its characteristic sequential periodic changing between two or even more natural transfer modes or to Controlled Transfer Modes because there is no in-line or off-line control. These types of transfer mode possess all characteristics of an individual class of modes which has been called Class of Interchangeable Transfer Modes, as summarized in fig. 4.
MIG/MAG Welding Metal Transfer Modes
Natural Metal Transfer Class
Contact Transfer Group
s Bridging transfer s Short-circuiting transfer s Forced short-circuiting transfer
Free-Flight Transfer Group
s Globulor transfer s Globular repelled transfer s Projected spray trans far s Streaming spray transfer s Rotating spray transfer s Explosive transfer
Controlled M CU etal Transfer 1SS
s Spray transfer controlled by pulsed current
s spray transfer controlled by pulsed
current in AC s Contact transfer controlled by current
S Contact transfer controlled by
current and wire feeding sOthers
\_/
Interchangeable Metal Transfer j Class J
s Short-circuiting - projected spray transfer
s Short-circuiting - streaming spray transfer
s Globular - projected spray transfer s Globular - streaming spray transfer s Globular - short-circuiting -streaming spray transfer Others y
Fig. 4. MIG/MAG Welding Metal Transfer Classification based on hierarchical order: classes, groups and modes
The characteristics of the three classes of metal transfer modes are as follows:
- the 'Natural Metal Transfer' class contains those modes that occur without any further adaptive welding parameter control (e.g. arc voltage, welding current, wire feed speed, inductance). Hence, droplet transfer is primarily affected by a resultant physical balance of forces acting upon the droplet. Two different groups can be found within the natural metal transfer class. The first is governed by "contact' droplet transfer, while the second shows a "free-flight" droplet transfer to the weld pool.
- the "ControlledMetal Transfer" class consists of "improved" natural modes, for getting better process characteristics, such as spatter minimization, weld geometry control, heat input stabilization and so forth. Hence, the balance of transfer governing forces still prevails but the forces are controlled and/or modified deliberately.
- the "Interchangeable Metal Transfer" describes a class of modes that occur with two or more natural transfer modes happening in a periodic repetitive sequence, one following the other, as a consequence of the previous one. There is no operator or adaptive control system interference.
Conclusion. The proposed detailed Classification for metal transfer modes satisfies the demand for having a systematic method to describe all metal transfer types in MIG/MAG welding, including the novel or not easily observed ones.
The categorization in Metal Transfer Mode, Group of Modes and Classes of Modes avoids specific applications or commercial names since it is based on global characteristics of the metal transfer and on the phenomena taking place.
There is no one best mode covering all applications as there is a preferred mode for a specific application.
Acknowledgements. The authors would like to thank the Brazilian agencies for research and development (CNPq and Fapemig), which have provided the financial backing for the specialized equipment used in this work (highspeed camera, laser back-light system, synchronized frames-electrical signal data loggers).
References
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9. Scotti A., Mapping the Transfer Modes for Stainless Steel GMAW, J. of Science and Technology of Welding and Joining, 2000, 5 (4), 227-234 (ISSN 1362-1718).
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11. Kim Y.S., Eagar T.W., Metal Transfer in Pulsed Current Gas Metal Arc Welding, Welding Journal, 1993, 72 (7), 279s-287s.
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Ponomarov Vladimir, candidate of technical science, [email protected], Brazil, Uberlandia, Federal University of Uberlandia,
Scotti Americo, candidate of technical science, ascotti@,ufu.br, Brazil, Uberlandia, Federal University of Uberlandia,
Lucas William, candidate of technical science, ponomarev@mecanica,ufu.br, UK, Cambridge, The Welding Institute, TWI Ltd, CB21 6AL
ДЕТАЛИЗИРОВАННАЯ КЛАССИФИКАЦИЯ СПОСОБОВ ПЕРЕНОСА ЭЛЕКТРОДНОГО МЕТАЛЛА ПРИ СВАРКЕ В ЗАЩИТНЫХ ГАЗАХ. ЧАСТЬ 1: ОБЩИЕ ПОЛОЖЕНИЯ
Владимир Пономарев, Америко Скотти, Уильям Лукас
Выполнены многочисленные эксперименты с различными сочетаниями защитных сред, сварочных проволок и параметров сварки для более детального изучения различных способов переноса электродного металла. Для регистрации переноса металла использовалась скоростная видеосъемка с лазерной подсветкой и синхронизацией с электрическими параметрами дуги. Для каждого способа переноса металла указаны основополагающие факторы его существования исходя из физики дуги. В предложенной классификации способы переноса электродного металла даны вне зависимости от типа защитной среды и характеристик сварочного источника питания.
Ключевые слова: сварка в защитных газах, классификация переноса электродного металла.
Владимир Пономарев, канд. техн. наук, [email protected], Бразилия, Уберландия, Федеральный Унивеситет города Уберландия,
Америко Скотти, канд. техн. наук, ascotti@,ufu.br, Бразилия, Уберландия, Федеральный Унивеситет города Уберландия,
Уильям Лукас, канд. техн. наук, ponomarevamecanicajifu.hr, Англия, Кембридж, Институт Сварки (TWI Ltd), CB21 6AL
