PSI - Issue 36

Olexandr Ivanov et al. / Procedia Structural Integrity 36 (2022) 223–230 Olexandr Ivanov et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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the affection of phase transformations in the surfacing zone, the thermal cycle also causes an effect on the work surface outside the surfacing zone, partially it can work as a type of heat treatment. Therefore, the aim of this work is researching of the structure and properties of hardfacing by flux-cored electrodes based on the Fe-Ti-Mo-B-C system, hardfaced under low current, as well as a theoretical calculation and experimental determination of thermal cycle while harfacing. 2. Methods and materials The FCAW material was manufactured as powder electrodes (width is 8 mm, height is 2.5 mm, length is 420 mm), where mixture of fine sized (~ 5 μm) powders of initial components was placed into sh eath of electrode, which is a low carbon 08 kp steel (DSTU EN 10139:2018 ) with size 0.5 × 20 mm. Chemical composition of electrode shown in Table 1. Table 1. Chemical composition of experimental electrode. Ti, % Mo, % B, % C, % Fe, % 8.24 8.28 22.01 5.50 55.96 The hardfacing was carried out on a plate made of steel 40 (DSTU 7809:2015), where thermocouples were installed at 0.5 cm distance from surfaced area for fixing the temperature. Measured data were processed via an analog-to-digital converter based on Arduino with subsequent processing on a PC (Fig. 1). VDU-506 rectifier was used for hardfacing. Welding parameters were as follows: direct current 150 A with a reverse polarity, arc-voltage 30- 32 V. Cooling was carried out on an air at 20 ° C .

Fig. 1. Equipment for experimental determination of the thermal cycle during hardfacing: 1 - PC; 2 - analog-to-digital converter based on Arduino; 3 - thermocouples; 4 - steel substrate.

In order to analytical solving of the Fourier heat equation for the process of surfacing of experimental sample, the heat transfer process was modeled as the motion of a continuous point heat source of power q with velocity v on the surface of the half-infinite body (Fig. 2) at a distance l from its edge. Such scheme simulates the process of FCAW of the surfaces that require restoration or increasing of durability. While simulation, the boundary surfaces of the working body (y = l and z = 0) were assumed to be heat impermeable (adiabatic condition). In such case, the reflection of the heat flux from the surface (y = l) was modeled using a fictitious heat source of similar power, which was located symmetrically according to the main one. Thus, the temperature at any point A was determined by the total influence of the main and fictitious heat sources.