Investigation of Effects of Mig Welding on Corrosion Behaviour of AISI 1010 Carbon Steel
This paper presents the corrosion behaviour of welded low carbon steel at different welding voltages and filler materials. The welding process was conducted on butt joint 
specimens using the metal inert gas (MIG) technique at a welding voltage range of 19 to 21 V with 1 V interval, and the filler materials used were ER 308L and ER 70S-6 with 
1.2 mm diameter. Heat treatment through full annealing was done to the welded low carbon steel, and the corrosion behaviour was tested using a synthetic seawater 
environment with 3.5 wt% NaCl. Microstructure changes were observed using a scanning electron microscope (SEM). The results showed that the corrosion rate decreased when the welding voltage increased, as it directly affected the welding heat input. The welding heat input was found to have a significant effect on the corrosion rate as it changed the ferrite content in the microstructure of the specimens. Decrease in the corrosion rate was also found when the full annealing process was done to the 
specimens and ER 308L filler material was used. From a metallographic study, iron oxides and pitting were found on the surface of the exposed area after the corrosion test. 
It is apparent that the combination of higher welding voltage, heat treatment and the use of ER 308L filler material can reduce the corrosion rate of AISI 1010 carbon steel.
Detection Of Defects On Weld Bead Through The Wavelet Analysis Of The Acquired Arc Sound Signal
Recently, the development of online quality monitoring system based on the arc sound signal has become one of the main interests due its ability to provide the non-contact 
measurement. Notwithstanding, numerous unrelated-to-defect sources which influence the sound generation are one of the aspects that increase the difficulties of applying this 
method to detect the defect during welding process. This work aims to reveal the hidden information that associates with the existence of irregularities and porosity on the weld bead from the acquired arc sound by applying the discrete wavelet transform. To achieve the aim, the arc sound signal was captured during the metal inert gas (MIG) 
welding process of three API 5L X70 steel specimens. Prior to the signal acquisition process, the frequency range was set from 20 Hz to 10 000 Hz which is in audible 
range. In the next stage, a discrete wavelet transform was applied to the acquired sound in order to reveal the hidden information associated with the occurrence of discontinuity 
and porosity. According to the results, it was clear that the acquired arc sound was not giving an obvious indication of the presence of defect as well as its location due to the high noise level. More interesting findings have been obtained when the discrete wavelet transform (DWT) analysis was applied. The analysis results indicate that the 
level 8 of the approximate and detail wavelet coefficient have given a significant sign associated with the presence of irregularities and porosity respectively. Moreover, 
despite giving the information on the surfaces pores, the detail wavelet coefficient was found to give a clear indication of the sub-surface porosity formation during welding process. Hence, it could be concluded that the hidden information with respect to the occurrence of discontinuity and porosity on the weld bead could be obtained by applying the discrete wavelet transform
Optimization of filtration conditions for CIP wastewater treatment by nanofiltration process using Taguchi approach
Abstract In this study, the nanofiltration of cleaning-in-place (CIP) wastewater was studied using a two-step nanofiltration (NF) process. In the first step, the effects of operating parameters including pH, temperature, and transmembrane pressure on the membrane fouling were investigated using a loose NF membrane. Also, Taguchi method was applied in order to design the experiments and optimize the experimental results. The optimum conditions providing the lowest flux decline were estimated. L9 (34) orthogonal array for experimental planning and the smaller-the-better response category was selected to obtain optimum conditions. Analysis of variance (ANOVA) was used to determine the most significant parameters affecting the flux decline caused by membrane fouling. The optimum conditions were found as the second level of pH (7), first level of temperature (25 °C) and first level of transmembrane pressure (12 bar). Under these conditions, flux decline caused by membrane fouling was predicted as 24% that was within the range of confidence limit of the observed value of 20%. Transmembrane pressure was found to be the most important factor on the flux decline. The effect of pH on the membrane fouling was also investigated with scanning electron microscopy (SEM) and contact angle measurements. It was found that pore plugging was dominant at pH 4. In the first step of the treatment; 97% chemical oxygen demand (COD), 100% sulphate, 50% chloride and 38% conductivity removal was obtained under the optimized conditions. In the second step, the quality of permeate obtained from the first step was improved using a tight membrane at 20 and 30 bar. Even better rejections were achieved especially for chloride and conductivity in the second step at 30 bar.