Welding Metallurgy of

Obtaining fine microstructure and unsupported overhangs by low heat input pulse arc additive manufacturing

Coarse grains and gas pores are two main problems that limit the application of additive manufacturing aluminum alloys. To reduce porosity and refine grains, this paper presents a quantitative investigation into the effect of pulse frequency and arc current on the porosity and grains of arc additive manufacturing Al–5Si alloy. The experiment results show that pulse frequency and arc current have a significant impact on the macrostructure, microstructure, porosity, and tensile properties of the samples. Fine grains and a uniform microstructure can be obtained with low pulse frequency and low arc current as a result of the rapid cooling of the molten pool. With the increase of pulse frequency, density shows a trend that firstly escalates and attains the maximum value at 50 Hz, but later declines as a result of the relation between pores formation and gas escape. Moreover, better tensile properties can be obtained at low pulse frequency and low arc current because of the finer grains.

Reducing Porosity and Refining Grains for Arc Additive Manufacturing Aluminum Alloy by Adjusting Arc Pulse Frequency and Current.

A numerical procedure is provided to analyze temperature and residual stress fields in multi-pass TIG welds with different pipe and electrode material. Based on the ABAQUS software and FORTRAN codes, to appraise the temperature fields and the residual stresses over the TIG process, an uncoupled thermo-mechanical, finite element model (FEM) is developed. For considering volumetric thermal flux on the workpiece, the “GOLDACK” method is used. The silent element method is utilized to model the weld deposit. To validate the presented simulation model, the TIG process is performed in two passes on SUS304 stainless steel pipe. Then, the process is modeled for three and four passes to consider the effect of pass number on axial and hoop residual stresses in the outer and inner surfaces of the welded pipes. Additionally, the effects of base material and preheating temperature on the internal and external surface stresses of pipe are investigated. Results show that, the base material type has a greater effect on the tensile axial residual stress of the outer surface rather than that of the inner surface. However, the welding pass number shows no significant influence on the peak of the tensile axial residual stress on the inner surface of the pipe. In terms of preheating, the stress magnitude is reduced by raising the preheating temperature but with more intense in the inner surface of the pipe. Additionally, to keep the tensile axial residual stress below the base metal yield strength, the preheating at least up to 325 °C is essential.

Effects of material type, preheating and weld pass number on residual stress of welded steel pipes by multi-pass TIG welding (C-Mn, SUS304, SUS316)

The weldability of carbon steel is determined by carbon equivalent (CE) for predicting/estimating preheat temperatures necessary for weld integrity of the weldment. The microstructure of the welded...

A review of weldability of carbon steel in arc-based welding processes

The effect of heat input in MMAW arc welding on cooling rate and hardness of weld joint is investigated in this paper. The parameter affects the heat input are welding current, arc voltage and welding speed. Mild steel weldments were welded under varying current 80, 90 and 100 ampere and keeping arc voltage and travel speed constant. Other mild steel specimens were welded under varying arc voltage 21V, 23V and 25V and keeping welding current and welding speed constant. Other mild steel specimens were welded by varying welding travel speed 1.52 mm/sec, 1.67 mm/sec and 1.82 mm/sec and keeping arc voltage and welding current constant. Heat input was calculated for each weldment. Rockwell hardness testing of all specimens was done. It was observed that with increase in arc current hardness of mild steel weld joint was increased up to optimum level and then decreased. Cooling rate was decreased with increased in arc current. With increase in welding arc voltage hardness of weld joint decreased and cooling rate was decreased also. With increase in welding travel speed hardness of weld joint increased and cooling rate was increased also. Keywords - MMAW, welding current, arc voltage, welding speed, cooling rate

Investigation on Effect of Heat Input on Cooling Rate and Mechanical Property (Hardness) Of Mild Steel Weld Joint by MMAW Process

The six upper front teeth determine the appearance of Aesthetic dentistry. The study will define lateral incisors based on their lower angles as round, square, or square/round. LORIN molds to shape teeth were utilized. It extracted 144 teeth images from him and used 36 photographs of denture lateral incisors. The aim of the proposed work is to develop a model capable of determining the most likely form the teeth will take. Intelligent systems first distinguish denture picture edges and separate gums from teeth. After early processing teeth were extracted. and use morphological methods performed to remove the hump, and The Savitzky-Golay filter then softens the corners. Images were tested to determine their type. Fuzzy logic determines the filter's mask size by finding the most matching teeth. we were cropped 50%, 66%, and 75% of the teeth and compared the rest lower parts of the teeth. Then, each type of tooth is matched using Pearson's correlation coefficient and LORIN-certified dental molds. When evaluating pictures of lateral incisor teeth, researchers found 36.1% accuracy when using the entire tooth, and 66.1% accuracy when cropping 75% of the tooth. The best match and discrimination of the lateral incisor were at cropping 50% and 66%, his accuracy was 86.1%. This study's results were compared to previous research on this subject, demonstrating their reliability and precision. 

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Classification of Lateral Incisor Teeth for Aesthetic Dentistry Using Intelligent Techniques

Makishima and Mackenzie model was used to simulation of acoustic properties (longitudinal and shear ultrasonic wave velocities, elastic moduli theoretically for many tellurite and borate glasses. The model was proposed mainly depending on the values of the experimentally measured density, which are obtained before. In this search work, we are trying to obtain the values of densities of amorphous glasses (as the density depends on the geometry of the network structure of these glasses). In addition, the problem of simulating the slope of linear regression between the experimentally determined bulk modulus and the product of packing density and experimental Young's modulus, were solved in this search work. The results showed good agreement between the experimentally measured values of densities and both ultrasonic wave velocities, and those theoretically determined.

Y Merchant Samir

Papers

Investigation on Effect of Heat Input on Cooling Rate and Mechanical Property (Hardness) Of Mild Steel Weld Joint by MMAW Process

Classification of Lateral Incisor Teeth for Aesthetic Dentistry Using Intelligent Techniques

Simulation of acoustic properties of borate and tellurite glasses