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Specifications for Underwater Welding have not yet addressed the effect of water temperature on weldment microstructure. The environmental effects on Underwater Wet Welding using a shielded metal arc welding (SMAW) process are severe with higher quenching rates, porosity, slag inclusions and diffusible hydrogen levels. One of the problems associated with these high quenching rates and high diffusible hydrogen levels is the increased likelihood of underbead cracking in the heat affected zone (HAZ), particularly with steel weldment which have a higher carbon equivalent (approximately greater than 0.3). In this work, the underbead cracking resulting in three underwater test welds made on ASTM 516 grade 70 steel three different water temperatures (2.8 deg C, 10 deg C and 31 deg C) was investigated. This was done by optical and scanning electron microscopy (SEM) and by making microhardness measurements. HAZ underbead cracking was observed in all three weldments, but was much less prevalent in the 31 deg C sample and could only be seen at high magnifications in the optical microscope. The cracking in this weldment only appeared to occur in isolated regions where head tempering had been ineffective for some reason. The weldments made at 10 deg C and 2.8 deg C both showed extensive evidence of underbead HAZ cracking typical of that associated with rapid cooling rates, high diffusible hydrogen levels and hard microstructures. SEM studies of the surfaces of these cracks showed evidence for transgranular failure with secondary cracking, both of which are typical of hydrogen induced cracking. This work highlights the importance of water temperature, quenching and diffusible hydrogen levels in underwater wet welding. This is an issue of critical importance in the future wet welding structural repair of Naval ships.
This book covers various aspects of characterization of materials in the areas of metals, alloys, steels, welding, nanomaterials, intermetallic, and surface coatings. These materials are obtained by different methods and techniques like spray, mechanical milling, sol-gel, casting, biosynthesis, and chemical reduction among others. Some of these materials are classified according to application such as materials for medical application, materials for industrial applications, materials used in the oil industry and materials used like coatings. The authors provide a comprehensive overview of structural characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, image analysis, finite element method (FEM), optical microscopy (OM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), differential scanning calorimetry (DSC), ultraviolet–visible spectroscopy (UV-Vis), infrared photo-thermal radiometry (IPTR), electrochemical impedance spectroscopy (EIS), thermogravimetry analysis (TGA), thermo luminescence (TL), photoluminescence (PL), high resolution transmission electron microscopy (HRTEM), and radio frequency (RF). The book includes theoretical models and illustrations of characterization properties—both structural and chemical.
The proceedings of an international seminar organised by TWI in conjunction with the Paton Welding Institute, Ukraine and held at TWI Middlesbrough in April 1997. The delegates examined recent theoretical and practical developments of the materials, equipment and processes involved.
A comprehensive guide to avoiding hydrogen cracking which serves as an essential problem-solver for anyone involved in the welding of ferritic steels. The authors provide a lucid and thorough explanation of the theoretical background to the subject but the main emphasis throughout is firmly on practice.
Versatility, speed and low cost make wet-stick welding an attractive method for use in underwater repair and construction. This training manual and reference book contains step-by-step procedures for performing basic manual metal arc welding operations together with information on welding equipment, consumables and safety. Exercises are included.