Abdulkareem S. Aloraier

Role of Welding Parameters Using the Flux Cored Arc Welding Process of Low Alloy Steels on Bead Geometry and Mechanical Properties

Welding parameters have direct effects on the bead geometry, microstructure, and mechanical properties of low alloy steels. A series of experiments have been carried out to examine some of these parameters using the flux cored arc welding process (FCAW). In this article, an experimental study was conducted to investigate the influence of welding parameters in FCAW process particularly welding voltage and travel speed on weld bead dimensions. The study also includes the effects of bead overlap and deposition sequence on the parent material and the heat-affected zone (HAZ) properties. It was found that an increase in the welding voltage leads to an increase in the weld bead width, and the increase in the welding traverse speed leads to a decrease in the weld bead width. When studying the bead overlap percentages, it was found that the 50% bead overlap can be considered to be practically a better option than the higher percentages of bead overlap (i.e., 70-90%). The experimental investigation of studying the deposition sequence showed that there were no significant differences in the microstructure, hardness, and the size of the refined HAZ between the two proposed deposition sequences. However, a significant improvement in the microstructure and the size of the refined HAZ, and a reduction in the hardness were achieved after depositing the second welding bead, irrespective of the depositing sequence.

Hardness, Microstructure, and Residual Stresses in Low Carbon Steel Welding with Post-weld Heat Treatment and Temper Bead Welding

This paper investigates the effects of post-weld heat treatment (PWHT) and temper bead welding (TBW) on hardness, microstructure and residual stresses in multi-layer welding on low carbon steel specimens made with two different weld geometries, viz. (1) smooth-contoured and (2) U-shaped. It was found that the PWHT technique gave overall lower hardness than the TBW technique, but the hardness values in both techniques were acceptable. Microscopy analysis showed that the TBW technique was more effective in tempering the heat affected zone as the grain size decreased slightly at the fusion line in spite of the higher temperature at the fusion line. Residual stresses measured using the hole-drilling method showed that the residual stress is not reduced below yield stress near the last bead solidified in TBW. Only PWHT gives low residual stress results in this area. High tensile residual stresses may result in sensitivity to fatigue loading.

Investigation on Preferential Corrosion of Welded Carbon Steel Under Flowing Conditions by EIS

Carbon steels are used extensively in construction of oil and gas pipes but they exhibit poor corrosion-resistance properties because of internal corrosion. In this research, a rotating cylinder electrode apparatus was designed so that electrodes machined from the weld metal, heat-affected zone, and parent material of a welded X65 pipeline steel could be tested in high shear stress conditions using electromechanical impedance spectroscopy. The aim was to investigate the cause of the severe localized corrosion that sometimes occurs at welds in carbon steel pipelines carrying hydrocarbons and inhibited brine solutions saturated with carbon dioxide. It was concluded that the surface films play an important role in effective inhibition, and this inhibition is more effective on a clean surface rather than on a precorroded one.

Effect of inhibitors on preferential weld corrosion under sweet conditions

Purpose – The aim of this investigation was to compare the performance of three typical oil field carbon dioxide corrosion inhibitors in controlling preferential weld corrosion (PWC) of X65 pipeline steel in artificial seawater (3.5 weight per cent) saturated with carbon dioxide at one bar pressure. Design/methodology/approach – A novel rotating cylinder electrode (RCE) apparatus was used to evaluate the effect of flow on the inhibition for the weld metal (WM), heat-affected zone (HAZ) and parent material. To fulfill this objective, the galvanic currents flowing between the weld regions were recorded using parallel zero-resistance ammeters, and the self-corrosion rates of the couples were obtained by linear polarization resistance measurements. Findings – The results showed that when 30 ppm of green oil field inhibitors were present in the service environment, a current reversal took place, resulting in accelerated weld corrosion. At high shear stress, the currents increased and further reversals occurred...

Weld repair procedures of aged components in the refineries and power plants: Kuwait and Australia

Abstract Petroleum refineries and power plants seek to extend the life of their aging components through weld repairs. Some of the repairs require stress relieving using post weld heat treatment (PWHT). However, PWHT is a cost and time consuming process. This paper provides a brief description of different alternative techniques for PWHT: half-bead welding, temper-bead welding and cold repairs. It presents a short survey about the different repairs techniques with or without the PWHT and their use in refineries and power plants in Kuwait and Australia. Some of these repairs now have had a successful life of over a decade; the oldest is nearly 20 years old. Details of the methods used are described and recommendations made concerning the alternative techniques. The availability of skilled labour turns out to be a decisive issue.