Page 24 - ST Sept

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.

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