Advances in Plasma Arc Welding: A Review

The nature of welding in the aeronautical industry is characterized by low unit production, high unit cost, extreme reliability and severe service conditions. These characteristics point towards more expensive and more concentrated heat sources such as plasma arc, laser beam and electron beam welding as the processes of choice for welding of critical components. Among various precision welding processes, Plasma Arc welding has gained importance in small and medium scale industries manufacturing bellows , diaphragms etc because of less expensive and easy to operate. This paper reviews the works on Plasma Arc welding and associated phenomena such as Micro Plasma Arc Welding, Variable Polarity Plasma Arc welding and Keyhole Plasma Arc Welding. The review covers works carried out by various researchers on various metals using different modes of plasma arc

Effect of Pulse Current Micro Plasma Arc Welding Parameters on Pitting Corrosion Rate of AISI 321 Sheets in 3.5 N NaCl Medium

Austenitic stainless steel sheets are used for fabrication of components, which require high temperature resistance and corrosion resistance such as metal bellows used in expansion joints in aircraft, aerospace and petroleum industries. When they are exposed to sea water after welding they are subjected to corrosion as there are changes in properties of the base metal after welding. The corrosion rate depends on the chemical composition of the base metal and the nature of welding process adopted. Corrosion resistance of welded joints can be improved by controlling the process parameters of the welding process. In the present work Pulsed Current Micro Plasma Arc Welding (MPAW) is carried out on AISI 321 austenitic stainless steel of 0.3 mm thick. Peak current, Base current, Pulse rate and Pulse width are chosen as the input parameters and pitting corrosion rate of weldment in 3.5N NaCl solution is considered as output response. Pitting corrosion rate is computed using Linear Polarization method from Tafel plots. Response Surface Method (RSM) is adopted by using Box-Behnken Design and total 27 experiments are performed. Empirical relation between input and output response is developed using statistical software and its adequacy is checked using Analysis of Variance (ANOVA) at 95% confidence level. The main effect and interaction effect of input parameters on output response are also studied

Optimum combination of machining parameters during drilling of aluminium 7075 alloys using Grey based Taguchi approach

From ancient days to till today manufacturing industries, especially making of holes on the parts during drilling process for precision assembling of parts facing problems with burr formation. Drilling operation is one of the finishing operation in the production cycle, removing of burrs during drilling process is a time consuming and non-value added process to the manufacturing sector. So reducing the size of burrs is the main aim of the present study. In the present work, optimization of burr size is considered during drilling of aluminium 7075 alloy. In this connection, experiments are conducted based on Grey based Taguchi. From Grey relational grades of responses selected optimal combination of parameters to attain multiple performance characteristics of responses with a corresponding higher grey relational grade. For identifying the most significant input parameters that influence the output responses ANOVA is conducted. Based on interaction effect plots of data means of responses from results of ANOVA, confirmation tests are conducted by choosing most significant parameters. Finally, observations reveals that feed rate, point and clearance angles are the most influential factors on burr size and also experimental results divulge that the lower the thrust force causes to decrease the burr height. The proposed approach is helpful to the budding entrepreneurs in the related areas to select optimal combination of drilling parameters to attain multiple performance characteristics of responses especially in burr size to prevent the post finishing operations up to certain extent

Optimization of machining parameters during end milling of super alloys using grey based taguchi method coupled with entropy measurement technique

High-quality products include those with better surface quality and texture, close dimensional tolerances and form accuracies at precise level, increase fatigue life and burr-free. Burr formation is one of the most common inevitable facts occurring in all material removal processes, reduces assembly and machined part quality. But, burr formation during milling is a more complex mechanism compare to remaining machining burrs and leads to numerous difficulties during the deburring process. To prevent this, one should optimize the combination of cutting parameters during machining itself. In order to build up a link between quality and productivity and to attain the same in the cost-effective way, the present work concentrate on multi objective optimization of CNC end milling process parameters. Multiple performance characteristics with respect to surface quality and performance index like assembly work have been put up, to assess an equivalent single quality index (called grey relational grade) has been optimized finally by Grey based Taguchi method. After that priority weight of individual quality and performance attributes has been estimated by entropy measurement technique on the basis of relative significance and check the feasibility of the proposed technique has been demonstrated in this context

Study on Weld Quality Characteristics of Micro Plasma Arc Welded Austenitic Stainless Steels

AbstractMicro Plasma Arc Welding (MPAW) is one of the important arc welding process commonly using in sheet metal industry for manufacturing metal bellows, metal diaphragms etc. The paper focuses on weld quality characteristics like weld bead geometry, grain size, hardness and ultimate tensile strength of MPAW welded joints of various austenitic stainless steels namely AISI 316L, AISI 316Ti, and AISI 321. From the analysis carried out it is noticed that for the same thickness of work piece material and same welding conditions, AISI 304L has achieved sound weld bead geometry, highest tensile strength and hardness. However it is noticed that AISI 316L has attained lowest tensile strength, AISI 321 has lowest hardness and grain size