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  • Experimental trials were created using full factorial

    2018-10-25

    Experimental trials were created using full factorial experiments by Design of Experiments (DoE) as per Table 2. Low alloy steel (T11) tube with 48 mm outer diameter and 6 mm thickness was chosen for study. Different dimensions of piping could be accommodated by changing the MIAB weld head. The chemical composition and mechanical properties of the steel tube are given in Table 3. For all welding trials the arc gap and upset pressure are maintained as 2 mm and 16 MPa, respectively. MIAB welded T11 tubes are shown in Fig. 5. The tubes are provided with thermocouples for measuring temperature gradient across the tubes. The welded tube was sectioned transverse to the weld line (Fig. 6) and prepared for metallographic study. The prepared surface is etched with 4% Nital. Various zones like TMAZ (thermo-mechanically affected zone), and the gsk-3 metal was characterized using optical microscope and SEM. Transverse hardness survey of welded tubes was carried out using Vickers microhardness tester under 100 g load. The hardness readings are taken at 0.5 mm distance interval for all the samples. Transverse tension test was done with the weld line at the centre to assess the tensile strength of welded tubes. Root bend test was carried out for the welded tubes to evaluate the weld ductility. Tension test, hardness test and bend test were carried out in accordance with ASTM E370.
    Results
    Discussion
    Conclusion In all MIAB welded samples, four distinct TMAZs were present from weld interface to base metal:
    Acknowledgements The authors acknowledge and thank Welding Research Institute, Bharat Heavy Electricals Limited, Tiruchirappalli for MIAB welding trials and PSG College of Technology, Coimbatore for providing testing facilities for this work.
    Introduction Ultrasonic wave velocity can be correlated with the measurements of an accepted hardness test technique for the materials with different hardness values. For this purpose, heat treatment techniques, such as annealing, should be used to obtain the samples of a material. Time and temperature are the main variables of annealing process, which should be determined carefully in order to obtain the materials with desired hardness. Some studies have been conducted to investigate the behaviors of materials under different annealing conditions. During overkill studies, the annealing treatments were performed with different parameters to investigate their effect on hardness. Li et al. [1] investigated the annealing softening behavior of cold-rolled low-carbon steel. The annealing behavior and mechanical properties of severely deformed interstitial-free steel were studied by Gazder et al. [2]. The annealing behavior of martensitic steel was investigated by Kimura et al. [3]. Fargas et al. [4] investigated the effect of annealing temperature on the mechanical properties of hot-rolled duplex stainless steel. Euh et al. [5] studied the effect of temperature on hardness improvement in vanadium carbide coated steels. Irani et al. [6] studied the effect of forging temperature on the hardness of low carbon steel gears. The effect of annealing temperature on properties of stainless steels was investigated by Negm [7]. Kang et al. [8] investigated the effects of recrystallization annealing temperature on the mechanical properties of twinning induced plasticity steels. The effect of annealing temperature on microstructure, phase composition and mechanical properties of thixo-cast 100Cr6 steel was studied by Rogal et al. [9]. Liu et al. [10] investigated the decrease in hardness during the isothermal process at 700 °C for Fe–24Mn-0.7Si-1.0Al TWIP steel. Various correlations between ultrasonic parameters and material properties have been proposed. Bibliographies and detailed explanations of previous studies were discussed in the handbook of the American Society of Nondestructive Testing [11]. Effect of hardness on ultrasonic waves was investigated by various authors. Kleesattel et al. [12] developed a correlation for measurement of surface hardness and proposed the ultrasonic contact impedance hardness test method in 1961. Rosen et al. [13] presented a relation between ultrasonic attenuation and hardness of aluminum–copper alloys by varying the age hardening processes. Another correlation between ultrasonic wave velocity and hardness was developed by Rosen et al. [14], for hardness prediction of aged aluminum alloy 2024.