Manufacturing Technology Today

S. Ragu Nathan ¹, S. Malarvizhi ¹, V. Balasubramanian ¹, A. G. Rao ²

Affiliations
1 Centre for Materials Joining & Research (CEMAJOR), Dept., of Manufacturing Engg, Annamalai University, Annamalainagar, Tamilnadu, IN
2 Marine Metallurgy Dept., Naval Materials Research Laboratory (NMRL), Ambernath, Mumbai, Maharastra, IN

Abstract

Friction Stir Welding (FSW) of high strength low alloy (HSLA) steel has drawn attention of researchers worldwide owing to its many benefits in construction of warships. In order to improve the weld quality and tool life, it is important to optimize the welding speed with the objective of producing defect free friction stir welded HSLA steel joints with excellent combination of strength and toughness. Hence, in this investigation an attempt has been made to understand the influence of welding speed on tensile and impact toughness properties of friction stir welded high strength low alloy (HSLA) steel joints. Five different welding speeds (20, 25, 30, 35 and 40 mm/min respectively) and constant tool rotational speed (600 rpm) are used to fabricate the HSLA steel joints. Due to the formation of lath upper bainite and acicular ferrite microstructure in the stir zone under optimum heat input condition could be the reason for superior mechanical properties of the joint fabricated using welding speed of 30 mm/min compared to other joints.

Keywords

Friction Stir Welding, Welding Speed, HSLA Steel, Tensile Properties.

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R. Kamal Jayaraj ¹, S. Malarvizhi ¹, V. Balasubramanian ²

Affiliations
1 Dept of Manufacturing Engineering, Annamalai University, Annamalai Nagar, Tamil Nadu, IN
2 Centre for Materials Joining and Research (CEMAJOR), Dept of Manufacturing Engineering, Annamalai University, Annamalai Nagar, Tamil Nadu, IN

Abstract

Joining of dissimilar alloys such as Aluminium (Al) and Magnesium (Mg) by fusion welding processes was very difficult due to formation of Al12Mg17 intermetallic compounds in fusion zone. However, friction stir welding (FSW) is expected to join dissimilar alloys with adequate joint strength because it is a solid-state process. But the Al/Mg FSW dissimilar joints are more prone to corrosion attack due to intercalated microstructure present in weld nugget (stir zone). The limitation of low corrosion resistance restricts practical applications of these types of joints. In this investigation, an attempt has been made to develop an empirical relationship to predict the corrosion rate of nugget region of friction stir welded dissimilar joints of AA6061 Al - AZ31B Mg alloys. Three important immersion corrosion test parameters, namely, chloride ion concentration, pH value and immersion time are chosen as input parameters. Three factors, five level, central composite rotatable design matrix is used to minimize the number of experimental conditions. Response surface methodology is used to develop an empirical relationship. The developed relationship can be effectively used to predict the corrosion rate of friction stir welded dissimilar joints of AA6061 Al - AZ31B Mg alloys at 95 % confidence level. The methodology adopted to develop the relationship is presented in this paper.

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S. Sree Sabari ¹, V. Balasubramanian ², S. Malarvizhi ²

Affiliations
1 Dept of Manufacturing Engg, Annamalai University, Annamalai Nagar, Tamil Nadu, IN
2 Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar, Tamil Nadu, IN

Abstract

AA2519-T87 is an age hardenable aluminium alloy used in the fabrication of light combat vehicles in the military application. Fusion welding of this aluminium alloy results in solidification related problems like porosity, hot cracking, etc. In order to overcome such problems, friction stir welding (FSW) process is used to join this material. The thermal cycle experienced by the thermo mechanical affected zone (TMAZ) and heat affected zone (HAZ) is causing grain coarsening and precipitates dissolution and resulting in poor joint properties. To get rid of this problem, under water friction stir welding (UWFSW) process can be adopted. However, the material flow during friction stirring will be entirely different in FSW and UWFSW. Hence an investigation is undertaken to study the effect of tool pin profiles on stir zone characteristics and the resultant tensile properties of the joints fabricated by UWFSW. Four different pin profiles, namely, straight cylindrical (STC), taper cylindrical (TAC), straight threaded cylindrical (STC), and taper threaded cylindrical (TTC) were used to fabricate the joints. From this investigation, it is found that the joint made by taper threaded pin profiled tool exhibited higher tensile properties and this may be attributed to the grain boundary strengthening and narrowing of lower hardness distribution region (LHDR).

Keywords

Underwater Friction Stir Welding, Pin Profiles, Microstructure, Tensile Properties, Microhardness.

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R. Kamal Jayaraj ¹, S. Malarvizhi ¹, V. Balasubramanian ¹

Affiliations
1 Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar, Tamil Nadu, IN

Abstract

Joining of magnesium alloys is increased because of its superior properties like light weight and high specific strength. Compared to fusion welding process, friction stir welding (FSW) is widely adaptable to join magnesium and its alloy. In the FSW joint, grains are very fine in stir zone (SZ) compared to the other zones. This leads to severe corrosion attack at the stir zone. The chloride ion concentration, pH value and immersion time are reported to be the more influencing parameters on corrosion attack. The present work aims to identify the minimum corrosion conditions in the SZ of friction stir welded AZ31B magnesium alloys by statistical tools such as design of experiments (DoE), analysis of variance and response surface methodology (RSM). From the results, it is found that the chloride ion concentration has a greater influence on corrosion rate than the other two parameters.

Keywords

Friction Stir Welding, AZ31B Magnesium Alloy, Response Surface Methodology, Corrosion Rate.

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K. Karthick ¹, S. Malarvizhi ¹, V. Balasubramanian ¹, S. A. Krishnan ², Shaju K. Albert ²

Affiliations
1 Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar, IN
2 Materials Mechanics Section, Materials Technology Division,Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, IN

Abstract

In sodium cooled fast breeder reactor at Kalpakkam, the steam generators are constructed using modified 9Cr-1Mo (also called as Grade 91 or P91) ferritic steel because of its high temperature strength and resistance to stress corrosion cracking. The interconnecting sodium piping between reactor and steam generator is made up of AISI 316LN because of its high creep strength and corrosion resistance. Nickel based fillers (Inconel 82/182) are commonly used to weld the 316LN piping with steam generator. For a better structural integrity assessment of this dissimilar joint, the tensile properties of each region need to be evaluated. Evaluating the tensile properties of various regions by smooth tensile specimens is quite complex and time consuming. In the present investigation, the notch tensile properties of various regions were evaluated by placing a notch at the desired locations of the dissimilar metal weld joint (DMWJ). The dissimilar joint between P91 and 316LN is fabricated by manual metal arc welding (MMAW) process using Inconel 182 electrodes. Notch tensile properties of each region were evaluated by placing a notch at different locations (viz. weld metal, buttering, HAZ of P91 and HAZ of 316LN). Microhardness variation across the DMWJ was recorded. Microstructural features of various regions were characterized by optical and scanning electron microscope. From this investigation, it is found that the notch placed in the HAZ of P91 exhibited highest notch tensile strength than other regions. A non-uniform hardness distribution is observed across the DMWJ and the maximum hardness is recorded at the interface between P91 HAZ to Inconel 182 buttering. The hardness is minimum at the outer edge of HAZ of P91 side. Evolution of carbon enriched hard zone at the interface between P91 and Inconel 182 buttering could be the reason for highest notch tensile strength.

Keywords

Dissimilar Metal Weld Joint, Notch Tensile Test, Microhardness, Microstructure.

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Addanki Ramaswamy ¹, S. Malarvizhi ¹, V. Balasubramanian ¹

Affiliations
1 Centre for Materials Joining and Research (CEMAJOR) Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar- 608 002, IN

Abstract

Heat treatable aluminium alloy such as AA6061 finding wide applications especially in the fabrication of door, hood and trunk components in automobile sector. These components are made up of thin sheets of aluminium alloys due to the low density, high strength to weight ratio, excellent weld ability and better corrosion resistance characteristics. Gas metal arc welding (GMAW) process is one of the most widely used welding technologies in the automobile industry, because of its higher productivity. Cold metal transfer (CMT) welding technique, the most advanced variant of GMAW process attracts the automobile manufacturers because of its capabilities such as stable arc, higher welding speed, less spatter and minimum distortion. This paper focuses on the welding of thin sheets of AA6061-T6 aluminium alloys by constant current-gas metal arc welding (CC-GMAW) and cold metal transfer-gas metal arc welding (CMT-GMAW) processes and highlights its tensile properties. The micro hardness variation across the weld joint was recorded by Vickers micro hardness tester. A soft zone is observed in the HAZ region in both the cases, but the relative softening with respect to the base material is less in case of CMT-GMAW joint compared with the CC-GMAW joint. It is also observed that the width of the soft zone in CMT-GMAW joint is less compared with the CC-GMAW joint. It is concluded that the mechanical properties of CMT-GMAW joint are improved compared with the CC-GMAW joint due to the better refinement of grain structure with narrow soft zone formation.

Keywords

Aluminium Alloy, Gas Metal Arc Welding, Cold Metal Transfer Arc Welding, Tensile Properties, Micro Hardness

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V. Vaithiyanathan ¹, V. Balasubramanian ¹, S. Malarvizhi ¹, Vijay Petley ², Shweta Verma ²

Affiliations
1 Centre for Materials Joining & Research (CEMAJOR), Dept. of Mfg. Engg., Annamalai University, Annamalai Nagar, Tamilnadu, IN
2 Materials Group (MTG) Gas Turbine Research Establishment (GTRE), Bengaluru, IN

Abstract

Titanium and its alloys have been considered as one of the best engineering materials for aero-engine applications, because they possess many good characteristics such as high specific strength, superior corrosion resistance and good high temperature strength. Gas tungsten arc welding (GTAW) welding process is generally preferred because to repair aero-engine blades of its high versatility and easy applicability. Gas Tungsten Constricted Arc welding (GTCAW) is a new variant of GTAW process. It generates very high frequency (20 kHz) and alters the magnetic field of the arc, thus enabling the control of constriction of arc and leading to less heat input, narrow heat affected zone (HAZ), reduced residual stresses and distortion compared to conventional GTAW process. This paper reports the tensile properties of GTA and GTCA welded thin sheets (1.2 mm) of Ti-6Al-4V alloy used in aero-engine applications. The joints were characterized using optical microscopy, scanning electron microscopy and microhardness survey. From this investigation, it is found that GTCAW joints exhibited superior tensile properties compared to GTAW joints due to reduction of prior beta grain boundary, higher fusion zone hardness and narrow heat affected zone. Hence, it is preferred that GTCAW process can be employed to repair aero-engine components over GTAW process.

Keywords

Titanium Alloy, Gas Tungsten Arc Welding, Gas Tungsten Constricted Arc Welding, Tensile Properties, Microstructure.

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Tushar Sonar ¹, V. Balasubramanian ¹, S. Malarvizhi ¹, T. Venkateswaran ², D. Sivakumar ²

Affiliations
1 Centre for Material Joining and Research (CEMAJOR), Dept. of Mfg. Engg., Annamalai University, Annamalai Nagar, Tamilnadu, IN
2 Vikram Sarabhai Space Centre (VSSC), ISRO, Thiruvananthapuram, IN

Abstract

Inconel 718 is a nickel-based superalloy which is of potential interest in high temperature applications in rocket and gas turbines. This alloy is mostly joined by Gas Tungsten Arc Welding (GTAW) process for clean and precise welds and it is economical and shop friendly. However, due to the high heat input associated with this process, the joints are more prone for metallurgical problems such as coarse dendritic structure and segregation in weld metal region and liquation cracking in heat affected zone (HAZ) which significantly reduces the mechanical properties of the welded joints. To overcome these shortcomings, a recently developed Gas Tungsten Constricted Arc Welding (GTCAW) process is used for joining Inconel 718 alloy. It is the advanced variant of GTAW process with magnetic arc constriction achieved by introducing high frequency pulsing Current (known as Delta Current). Delta Current pulsing at a very high frequency is controlling factor for the rise and fall of magnetic arc constriction during welding. The main objective of this investigation is to make the potential use of Magnetic Arc Constriction to reduce the heat input for minimizing metallurgical problems and enhancing the mechanical properties of the joints. To achieve this, main effect of Delta Current on tensile properties and microstructural characteristics of Inconel 718 alloy is investigated.

Keywords

Gas Tungsten Constricted Arc Welding (GTCAW), Delta Current, Tensile Properties, Microstructural Characteristics.

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N. Sankar ¹, S. Malarvizhi ¹, V. Balasubramanian ¹

Affiliations
1 Annamalai University, Annamalainagar (P.O), Tamilnadu, IN

Abstract

Low carbon steels are widely used in the manufacturing sectors due to their easy weldability than other carbon steels. Usually, the welding processes like shielded metal arc welding (SMAW), and gas metal arc welding (GMAW) are used for welding thick low carbon steel plates. Recently, a novel “rotary arc” or “spin arc” technique is developed with a rotary motion of filler wire that can change the flow of the weld puddle. In this investigation, an attempt has been made to join 12mm thick carbon steel plates made by stationary arc gas metal arc welding (SA-GMAW) and rotating arc gas metal arc welding (RA-GMAW) processes. The objective of present paper is to study the influence of rotating arc on mechanical properties and microstructural characteristics of GMA welded carbon steel joints. The results indicated that the arc rotation of GMAW process yielded 15% improvement in joint efficiency than the conventional stationary arc process.

Keywords

Carbon Steel, Rotating Arc Welding, Tensile Properties, Impact Toughness and Microstructural Characteristics.

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Tushar Sonar ¹, V. Balasubramanian ², S. Malarvizhi ², Namita Dusane ³, V. Sivamaran ⁴, C. Rajendran ⁵

Affiliations
1 G. S. Mandal's Maharashtra Institute of Technology, Aurangabad, Maharashtra, IN
2 Annamalai University, Annamalai Nagar, Tamil Nadu, IN
3 Hinduja College of Commerce, Mumbai, Maharashtra, IN
4 Audisankara College of Engineering & Technology (Autonomous), Gudur, Andhra Pradesh, IN
5 Sri Krishna College of Engineering and Technology, Coimbatore, Tamil Nadu, IN

Abstract

The objective of this paper is to explain about application of Internet of Things (IoT) and Artificial Intelligence (AI) in welding of Indian Railways. The introduction of welding technology has also been followed by the country’s economic growth. Indian Railways has long been the single most significant infrastructure entity in India, with the railway track network expanding for many years. The new manufacturing sector is speeding the transition to digital and intelligent manufacturing, with the ongoing growth and maturity of cloud computing, big data, IoT and other innovations. Welding methods are also one of the fields where AI is tested and used early, with the help of information technology. Train maintenance and repair is usually carried out in demanding working conditions and frequently under demand from time. In such high demand and dynamic activities, it helps to decrease human error. In the welding of rail tracks and machine parts, IoT and AI will certainly offer many advantages in less time and with greater accuracy and precision. It will allow the Indian Railways to become more profitable and effective.

Keywords

Indian Railways, Internet of Things, Artificial Intelligence, Welding 4.0.

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B. Prasanna Nagasai ¹, S. Malarvizhi ¹, V. Balasubramanian ¹

Affiliations
1 Centre for Materials Joining & Research (CEMAJOR), Annamalai University, Annamalainagar, Tamilnadu, India, IN

Abstract

AA5356 (Al-Mg) alloys can reach medium strength without a solid solution and quenching treatment, thereby avoiding product distortion caused by quenching, which has attracted the attention of wire arc additive manufacturing (WAAM) researchers. However, challenges during the additive manufacturing of aluminum alloys, such as porosity or poor mechanical properties, can be overcome by using arc technologies with low heat input. This paper presents metallurgical characteristics and mechanical properties of wire arc additive manufactured AA5356 alloy cylindrical components fabricated by Gas Metal Arc Welding (GMAW) and Cold Metal Transferred (CMT) arc welding processes. Herein, comparison between the welding processes and the resulting heat input show the effect on resulting microstructural characteristics of additively manufactured AA5356 parts. Firstly, the influence of heat input on the porosity was analyzed. Subsequently, the effect of heat input on the microstructural characteristics of the components was studied. The component produced by CMT process exhibits fewer and smaller pores with finer grains and reduced segregation of β-(Al3Mg2) phases than the GMAW process.

Keywords

Wire Arc Additive Manufacturing, Al-Mg Alloy, Porosity, Metallurgical Characteristics.

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