جستجوی مقالات مرتبط با کلیدواژه « فلز جوش » در نشریات گروه « مواد و متالورژی »

In this research, the corrosion resistance of weld metal in API-5L X90 micro-alloy steel joints was investigated. Welding was performed using filler metals ER120S-G, ER100S-G and ER90S-B3 by GTAW process. Microstructural studies were performed using light microscope and SEM scanning electron microscope. Microstructural studies showed that the base metal microstructure consists of ferrite and granular bentite. It was found that different weld metals all contain different amounts of accular Ferrite, polygonal ferrites and martensite / austenite (MA) islands. The highest amount of accular Ferrite was observed in ER 120 SG welding metal. The results of corrosion test showed that ER120SG welding metal and base metal had the lowest flow density and corrosion rate. And the highest corrosion rate was obtained for ER100SG welding metal.

In this study, DIN 34CrAlNi7 Nitriding steel in two states before and after nitriding, were welded by tungsten-gas arc welding process using two types of fillers (ER309L and ER312). The aim of this research was to investigate the best conditions for welding (before or after nitriding) and also to choose the best filler metal. The microstructure of the joint was examined using an optical microscope. A tensile strength test was also used to evaluate the mechanical properties. Fracture surfaces were also studied using a scanning electron microscope (SEM). According to the results Welding of these steels with ER309L filler is allowed only in the pre-nitriding state. If the base metal is nitriding, due to microstructural changes in the weld metal, filler metal ER309L cannot be used. However, the results of samples welded with ER312 filler metal show that if the base metal mixing percentage is less than 30%, this filler can be used for welding base metals in both before and after nitriding.

The microstructure and mechanical properties of HSLA-100 steel weld joints was investigated. Welding with three heat input of 0.820, 1.176 and 1.392 kJ / mm was performed using E12018 electrode. Microstructural studies were performed using scanning electron and optical microscopes. The mechanical properties of welded joints were evaluated by impact and microhardness tests. Microstructural studies showed that with increasing the heat input, the amount of acicular ferrite in the weld metal decreased and the amount of polyhedral and quasi-polygonal ferrite increased. It was found that with increasing the heat input, the amount of layered bainite in the heat affected zone increased and the amount of granular bainite decreased. Due to the decrease in the amount of acicular ferrite in the weld metal microstructure with increasing inlet temperature, the amount of hardness and impact energy decreased. The results showed that the increase in heat input due to the reduction of the acicular ferrite of the weld metal and the dissolution of precipitates in the coarse grain heat affected zone has caused a decrease in hardness in these zones. It was found that with increasing the heat input due to decreasing the acicular ferrite, the impact energy of the weld metal decreased by 29% (from 45 joules at an heat input of 0.82 to 32 joules at an heat input of 1.392 kJ / mm). It was found that at all heat inputs, the impact energy of the base metal is greater than the impact energy of the weld metal.

In this research, microstructure and mechanical properties of AISI316 to AISI430 dissimilar joint were investigated. For this purpose, GTAW process using ER316L and ER2209 filler metals with diameter of 2.4 mm was used. The microstructure and fracture surface of the welded samples were characterized by optical microscopy and scanning electron microscopy. Also the mechanical properties of the welded samples were evaluated by tension, impact and microhardness tests. It was found that the microstructure of the welded sample with ER316L filler metal contained Widmanstatten austenite with inter-dendritic and lathy ferrites. Also, in the welded sample with ER2209 filler metal, Austenite phase in ferrite matrix was seen. In tension test, all samples were fractured from AISI430 side of the joint in a ductile manner. ER2209 weld metal indicated low impact energy of about 27 J, while ER316L weld metal indicated higher impact energy of about 43 J. The fracture surface in both welded samples indicated brittle fracture mode. The microhardness of the weld metal of the welded sample with ER316L filler metal was higher than the welded sample with ER2209 filler metal due to the presence of alloying elements, proper distribution of delta ferrite and finer microstructure.

The effect of heat input of submerged arc welding process on the corrosion bahavior of weld metal of API X42 gas pipeline steel weld joint was investigated. For this purpose, 6 annealed sheets of 15mm thickness were prepared from the X42 microalloyed steel. Submerged arc welding process with varying heat input of 37.8, 18.9 and 12.6 kJ/mm was used for joint welding. Then potentiodynamic polarization and electrochemical impedance spectroscopy methods were used to evaluate the corrosion behavior of the welded joints (in 3.5% NaCl solution). The evaluation of the microstructures of the welded metals in the weld joints were conducted using the scanning electron microscopy. X-ray diffraction was used for the analysis of the phases formed in the weld metal microstructure. Scanning electron microscopy observations and patterns obtained from the X-ray diffraction showed that the increase in heat input resulted in the increase in the amount of ferrite. The grain size also increased. Corrosion test results showed that by increasing the heat input of the weld process, the corrosion resistance increased.

In this study, the effects of welding process interpass temperatures on the weld metal corrosion behavior of Hadfield high carbon steel welding joints was investigated. For this purpose, initially 6 austenitized sheets with 2mm thickness prepared from Hadfield steel. Then shielded metal arc welding process with interpass temperature of 700, 850 and 1000°C was used for welding. Then potentiodynamic polarization and electrochemical impedance spectroscopy methods were used to evaluate corrosion behavior of welded joints’ weld metal in the 3.5wt. %NaCl solution. Also, the evaluation of the microstructures of weld metal in welded joints were conducted by optical microscopy. X-ray diffraction was used for the analysis of phases formed in the weld metal microstructure and the weld metal corrosion mechanism was determined by scanning electron microscopy examination. Optical microscopy observations and patterns obtained from X-ray diffraction showed that increasing in interpass temperature resulted in increase in carbide precipitates and decrease in austenite grain size in the weld metal microstructures of Hadfield steel welding joints. Corrosion test results showed that by increasing the interpass temperature in the welding process, weld metal of Hadfield steel welding joints showed decreese in corrosion resistance. Also, scanning electron microscopy images from corrosion morphology of weld metals indicated that increasing in interpass temperature in the welding process of Hadfield steel, led to occurrence of micro-galvanic localized corrosion.

In this investigation effect of preheating temperature of the GTAW process on weldability of the ferritic ductile cast iron has been studied. The ductile cast iron plates were welded in butt joint design by GTAW with ERNiCu-B wire in different preheats (100-600) temperature. The XRF was used for determining of the chemical analysis of the weld metals. The OM and SEM were used for study of the microstructure characteristics of weld metal, fusion line and HAZ at different samples. In addition tensile, hardness and impact test were used for determining of mechanical properties of the weld metal and HAZ of different samples. The OM and chemical analysis of different samples weld metals result shows, that by increasing of the preheat temperature, the solidification time, percent of dilution, percent of the Fe, Si, Mn, C elements in the weld metals were increased while the tensile strength and hardness of the weld metals were increased. The hardness of UMZ and PMZ were reduced when the preheating temperature increased. The SEM and OM of the HAZ result shows, that the HAZ width increased and the graphite nodule size and volume fraction of the ferrite phase in the microstructure were changed when the preheating temperature increased, also the hardness of the HAZ decreased and impact energy increased. In a general summary, the 400 is the appropriate temperature for preheating of the welding of the ferritic cast iron by GTAW.