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WELDING                                                                                                  WELDING
 Methodology for studying the characteristics of   video cameras. A source of intense radiation is needed that provides the arc "overexposure"

    mode and contributes to improved visualization of the heat and mass transfer characteristics.
 heat and mass transfer   Initially, during the experiments, a CuBr laser was used [6]. High pulse power and short pulse
    duration (40 nanoseconds), which made it possible to carry out temporal filtering of the image,

    Introduction  in consumable-electrode   were  its obvious advantages.  A  high pulse repetition  rate  (up to 700  kHz) provided a  time
    Analysis of the causes and nature of   resolution of up to a few microseconds. The combination of these properties made it possible to
 the  destruction  of  many  metal  structures   arc welding with video   get rid of the background illumination completely, Figure 2.
 shows that their destruction often occurs in      Analysis of the images presented in Figure 2 shows that their quality is significantly inferior
 the zones of welded joints. This inevitably   recording of images   to the quality of images obtained earlier using high-speed film cameras [7]. Apparently, this
 leads to a decrease in the level of permissible   is due to the technical characteristics of the video camera used and the insufficient backlight
 operating loads in extreme conditions and   under conditions of   available.
 low ambient temperatures [1]. It is known      Modernization of the research complex for solving problems of the above stated
 that  the  manufacture  of  metal  structures  laser coherent radiation  goal

 with  high  strength  is  very  difficult  due  to
 the action of a number of specific factors:
 ambient  temperature,  types  and  technical
 characteristics  of  equipment  used  for
 welding, quality  and  technological  properties  of  welding materials,  and  a  number  of  other
 indicators [2]. This circumstance has a significant effect on the stability of melting and transfer
 of  electrode  metal  into  the  weld  pool,  which  requires  additional  efforts  to  control  the  fast
 processes of formation of permanent joints, and, first of all, the change in the characteristics
 of heat and mass transfer during welding [3]. The instability of the characteristics of heat and
 mass transfer during welding or surfacing leads to a deterioration in the formation of the weld
 metal, which negatively affects the reliability of metal structures as a whole [4].
    The  purpose  of  the  work  is  to  study  the  characteristics  of  heat  and  mass  transfer  in
 consumable-electrode arc welding using high-speed video recording methods for the stages of
 melting and transfer of electrode metal into the weld pool.
    The structure of the experimental research complex.  Fig. 2. Video frames of the welding microcycle (period of melting and transfer of one drop of electrode metal), sequence of
    frames: 1 - 2 - 3 (interval of arc burning), 4 - 5 - 6 (interval of short circuit)..


            For a comprehensive study of the processes of melting and transfer of electrode metal
    into the weld pool, synchronization of all blocks and components is required - a laser, a high-
    speed camera, an oscilloscope, and welding equipment. Taking into account the listed features,
    a modified CuBr laser was used in the complex, with the following parameters: the average
    output power is regulated in the range from 1 to 3 W; repetition rate of radiation pulses from
    10 to 25 kHz. The laser is made in the form of two blocks - an active element (AE) and a power
    source (IP). The active element includes a gas-discharge tube with an active zone length of
    40 cm and a diameter of 2 cm, a high-voltage switch (thyratron TGI1-270 / 12), a thyratron
    triggering circuit with optical isolation, and thermal stabilization units. The design of the laser
    provides  for  various  operating  modes:  generator  and  amplifier  modes.  This  is  achieved  by
    using removable resonators. This active element can be used to implement a laser monitor
    circuit for diagnosing processes in a molten pool with complete suppression of the effect of the
    welding arc radiation.

 Fig.1. Research complex: 1 - suspended welding head; 2 - the studied object of heat and mass transfer; 3 - high-speed      Figure 3 shows video frames of the process of melting and transfer of electrode metal
 video camera; 4 - welding power source; 5 - source of coherent radiation; 6 - process control unit; 7 - unit for measuring the   into the weld pool, obtained by research using a modernized source of coherent radiation.
 energy parameters of the mode; 8 - personal computer with special software  Equipment, welding materials and modes are similar to the case, video frames of which are
    shown in Figure 2 (welding with solid wire SV-08G2S, diameter 1.2 mm, FEB power source -

    To register  the  kinetics of  melting and  transfer  of  electrode  metal  to the  weld pool,   315 "Magma", FEB-09 feed mechanism, protective medium - carbon dioxide ; arc voltage 22.3
 various visualization methods are used, carried out synchronously with the registration of the   V; electrode wire feed rate 2.3 m / min; image registration was carried out with a Baumer
 main energy parameters: arc current and voltage across the arc gap. To solve the problems   camera, shooting speed 1500 frames / sec, exposure 5 μs). For visual analysis of heat and
 formulated above, a diagnostic complex was developed that allows visual-optical control of the   mass transfer processes, shadow shooting was carried out under laser illumination and the use
 welding process, as well as recording electrical and energy parameters [5], the block diagram   of simultaneous spectral and time filtration for a detailed study of the processes occurring in
 of which is shown in Figure 1.  the melt bath.
    Analysis of the features of registration of fast processes in electric arc welding with a      To completely suppress the background radiation and obtain images with a minimum
 consumable electrode.  exposure, filtering was used, which was provided directly by the medium of the developed
    The  experience  of  using  diagnostic systems  of  the  presented  type  shows  that  the   laser - the implementation of an active optical system (laser monitor).
 registration  of  heat  and  mass  transfer  characteristics  has  a  number  of  specific  features.  In   An important component of the obtained results of the heat and mass transfer process is the
 particular, the quality of video images is highly dependent on the technical characteristics of   possibility of simultaneous synchronous registration of the energy parameters of the welding
    arc.

 24  Stanochniy park                                                                            Stanochniy park      25
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