Indian Welding Journal

Rakesh Kaul ¹, N. G. Muralidharan ¹, K. V. Kashiviswanathan ¹, Baldev Raj ¹

Affiliations
1 PIE & NDT Development, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603 102, IN

Abstract

It is well known that fusion welding process cannot be used for welding austenitic stainless steel with copper and if by any chance, copper comes into contact with stainless steel during welding operation and stresses of sufficient magnitude are present in the material, it results in the cracking of stainless steel. The reason for this cracking is attributed to the phenomenon of Liquid Metal Embrittlement (LME) which refers to the degradation in mechanical properties of some metal/alloys when they are stressed in contact with certain liquid metal environments.

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Baldev Raj ¹, C. V. Subramanian ¹

Affiliations
1 Division for PIE & NDT Development, Indira Gandhi Centre for Atomic Research, Kalpakkam, IN

Abstract

Non-destructive Testing (NDT) is an integral and the most important constituent of the Quality Assurance (QA) programme of any industry. The objectives of the QA programmes are safety, reliability and economy. Non-destructive evaluation (NDE) places due emphasis on characterisation of material including quantitative determination of the size, shape and location of a defect or anomaly thus enabling evaluation of structural integrity of a component.

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P. Palanichamy ¹, A. Joseph ¹, K. V. Kasiviswanathan ¹, D. K. Bhattacharya ¹, Baldev Raj ¹

Affiliations
1 Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, IN

Abstract

This paper discusses the results of measurement of residual stress pattern across butt weld joints by ultrasonic velocity measurements in 15 mm and 47 mm thick AISI type 304 stainless steel plates. These are supplemented by results obtained from hole drilling strain gauge measurements. Pulse echo overlap technique was used to measure the through thickness longitudinal ultrasonic velocities. Acoustoelastic constant was determined to convert the change in ultrasonic velocities to residual stress values. The residual stress pattren obtained by the two techniques showed similar trends. Brief overview of various other residual stress measurement methods, and various techniques for ultrasonic velocity measurements are included in the paper.

Keywords

Residual Stress, Austenitic Stainless Steel, Weld Joint, Ultrasonic Velocity, Acoustoelastic Constant, Strain Guage Technique.

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Baldev Raj ¹, C. V. Subramanian ¹

Affiliations
1 Division for Post-Irradiation Examination and NDT Development, IN

Abstract

Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, India, is engaged in multidisciplinary R&D efforts in welding technology relevant to Fast Breeder Reactor Programme of the Country. R&D efforts initiated in the year 1974 have matured into groups with strong scientific and technological base in areas of design, processes and characterisation through complementary use of destructive and nondestructive test techniques.

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C. V. Subramanian ¹, Baldev Raj ¹

Affiliations
1 Indian Institute of Welding, IN

Abstract

Welding is an important means to fabricate structures and components from a wide spectrum of materials, of varied complexity and thickness ranges. Welds can be made with properties appropriate for service conditions. The requisite quality can be achieved based on adequate and appropriate testing, measurement and control of welds.

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P. Kalyanasundaram ¹, Baldev Raj ¹, P. Barat ¹, T. Jayakurnar ¹

Affiliations
1 Division for PIE & NDT Development, Indira Gandhi Centre for Atomic Research, Kalpakkam 630 102, IN

Abstract

Load bearing capacity of any structure for a given dimension can be increased by improving the reliability of detection of smaller defects in weldments. This is highly desirable in aeronautical and space industries where the overall weight of the structure is a major constraint as it decides the pay load capacity.

Maraging steels are widely used in space industries for fabrication of rocket motor casings. Conventional ultrasonic pulse echo technique is applied for defect detection in weldments. However, inspection by ultrasonic testing of top midsection of maraging steel weldments, which is acoustically noisy, poses problems for reliable detection of defects of size 3 mm long x 1 mm deep or less (a design requirement). This is because of small amplitude difference of echo signal (2dB) between the noise and defect signals. Reliability of detection of such defects is improved by adopting advanced signal processing and pattern recognition techniques, which in turn increases the load bearing capacity of the structures.

A developmental work was undertaken for reliable detection of small defects in maraging steel weldments. For this purpose, a fatigue crack of 3 mm x 1 mm size was created in top midsection of the maraging steel weldments representing expected weld defects formed during fabrication. This paper discusses the application of advanced techniques like, autocorrelation, cross power spectral analysis, demodulation and cluster analysis for detection of the simulated fatigue crack. By adopting these techniques 95% reliability has been achieved for the detection of the fatigue crack. The approach has been assessed for shop floor adaptability. The approach would yield considerable enhancement in the pay lead of space vehicle thus resulting in enhanced capability and effective utilization.

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V. C. Padaki ¹, P. Barat ¹, Baldev Raj ¹, D. K. Bhattacharya ¹

Affiliations
1 Radiometallurgy Laboratory, Reactor Research Centre, Kalpakkam—603 102, IN

Abstract

Austenitic steel welded structures are widely used in power stations, petrochemical industries and nuclear industries. These welded structures pose unique problems for ultrasonic testing not experienced with ferritic steel welds. Since X radiography cannot be used in many cases (like inservice inspection, thick welds, planar defects, etc.), it becomes imperative that ultrasonic testing be used. To do this, the problems encountered during examination of austenitic steel weldments must be understood and solved.

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Baldev Raj ¹

Affiliations
1 Elect, International Institute of Welding

Abstract

India is racing at high pace to be among the frontier economies of the world by 2020. The track record in the last ten years and a way forward from $1.4 trillion economy to $3 trillion by 2017 translates into rapid growth in energy, infrastructure and strategic sectors, in addition to enhance contributions by services, consumables, tourism and agriculture domains. Among the policies, science and technology, finance and demographic issues, materials manufacturing and the welding are crucial to achieve the spectacular growth with competitiveness and in robust (minimum risk and high performance) manners.

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Baldev Raj

Abstract

My dear colleagues,

The Indian Institute of Welding has done extremely well in bringing academia, research and industry together in a friendly and productive environment to discus various facets of Welding Science and Technology. The welding professionals in India have met the challenges of atomic energy, space, defence, heavy industries and precision engineering in an admirable way to attract the attention of leading technocrats in India and abroad. However, there is no room for complacency, as in today’s world of global competitiveness, continued quality, reliability improvement, cost-effectiveness, timely deliveries, brand name, strategies, etc. are the key drivers for success. The Indian Institute of Welding needs the involvement of all welding professionals, who have the commitment to the Institute’s objectives to obtain success in these key drivers. Todays scenario of newer materials and advances in welding processes, have been continuously posing fresh challenges and opportunities to welding professionals. The firm and robust knowledge - base in Welding Science and Technology, available in abundance in our country, is an asset that has to be enhanced and leveraged for achieving our end objectives of being a leading nation in our chosen field of experties. Advances in materials science and engineering, robotics, intelligent welding, modeling, etc. need to be utilized judiciously to enable us to do welding with quality and in a cost-effective manner. To ensure this, education at all levels and continuing education of professionals in industry emerges as a major area of focus. Fortunately, India being an international leader in software provides us with the possibility of spreading the knowledge and information-base in Welding Science and Technology to a large number of students and professionals expeditiously and with the highest standards of quality. I am confident that we can achieve all these and bring laurels to our profession, our organisation and our country.

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Baldev Raj ¹, A. K. Bhaduri ¹

Affiliations
1 Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603102, Tamilnadu, IN

Abstract

As welding technology improves, industry is incorporating more types of automatic welding equipment. One of the most important approaches being used is called intelligent automation for welding technology. This approach combines automatic welding equipment, the knowledge of human experts , and Artificial Intelligence (AI). An intelligent welding machine is the one equipped with sensors, artificial intelligence and actuators to sense and control welding operations in real time. Developing smart or intelligent welding machines can reduce the occurrence of defects in welds. Intelligent welder is differentiated from a mere mechanised or pre-programmed welder in that it controls the quality of the weld directly rather than simply maintaining the welding parameters within specified limits of the values based on experience and/or trial welds.

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V. Anandkumar ¹, E. Venkatesan ¹, Baldev Raj ¹, C. Karthikeyan ², R. S. Babu ²

Affiliations
1 Indira Gandhi Centre for Atomic Research, Kalpakkam, IN
2 The Welding Research Institute, BHEL, Tiruchirapalli, IN

Abstract

Steam generators are critical components for the Prototype fast Breeder Reactor being designed at the Indira Gandhi Centre for Atomic Research, Kalpakkam. A leak in the steam generators can have serious consequences leading to rupture of steam generator tubes. Consequently, by introducing a known leak in the experimental loop, data is required to be generated which can predict the response of the material to the leak as a function of leak rate, time, temperature, steam pressure and the size of the microhole as a result of sodium water reaction.

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S. Murugan ¹, P. V. Kumar ¹, Baldev Raj ¹, M. S. C. Bose ²

Affiliations
1 Metallurgy and Materials Group Indira Gandhi Centre for Atomic Research, Kalpakkam, IN
2 Department of Mechanical Engineering Indian Institute of Technology, Powai, Bombay, IN

Abstract

Residual stresses are self equilibrating stresses existing in materials or components under uniform temperature conditions. When two pieces of plates/pipes are joined together by welding, localised residual stresses coupled with shrinkage are generated in the vicinity of the weld. The presence of these residual stresses can be detrimental to the strength of the joint. Tensile residual stresses are generally detrimental, increasing the susceptibility of a weld to fatigue damage, stress corrosion and fracture. During welding, temperature conditions range from melting point of the material to room temperature. Mechanical and thermal properties of the material are temperature dependent and this change with temperature during the welding process. The material stress-strain behaviour is elastic-plastic and temperature dependent. Thermal stresses are produced in the material during the process of heating and cooling. When the material is cooled to room temperature, the locked up stresses present in the material are retained residual tresses.

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S. Murugan ¹, Baldev Raj ¹

Affiliations
1 Metallurgy and Materials Group Indira Gandhi Centre for Atomic Research. Kalpakkam, IN

Abstract

During the process of welding, the intense heat source leads to rapid heating, melting of the material and vigorous circulation of the molten metal. The circulation in the molten metal is driven by the forces of buoyancy, surface tension and in addition, by electromagnetic forces (if electric current is utilised for welding). In fusion welding process, the temperature of molten weld pool ranges from near the boiling point on the top surface to liquidus- solidus transformation temperature at the edge of fusion boundary. The resulting heat transfer and the fluid flow determine the microstructure, size and shape of the weld region, the properties of weld metal and the base metal, and the residual stress distribution, The evolving microstructure and the residual stress distribution can significantly affect the strength and performance of the welded component. Experimental determination of the temperature distribution, microstructure and the residual stress distribution is not always feasible, and is expensive even if it is feasible. Theoretical models taking into account the various parameters involved in the welding processes are developed to predict the temperature distribution, evolution of microstructure and the residual stresses in the welded joint. Using validated computer models, allowable design loads and consequent inservice behaviour of the welded joint under different environmental conditions can be predicted.

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Baldev Raj ¹

Affiliations
1 Indira Gandhi Centre for Atomic Research, Kalpakkam - 603 102, IN

Abstract

Welding Technology is an essential ingredient of the industrial world. It is impossible to imagine the industrial scenario without this technology. While it is necessary to use the already established welding technology in the conventional materials and components with more and more stringent control on quality and reliability, it is also necessary that conventional and newer welding technologies are used in newer materials and in newer component designs that are undertaken tor newer applications, and for improving the economy. A good welding technology and practice must ensure that, whatever may be the innovations introduced, there must not be any sacrifice on safety and reliability that are expected from the components. All the efforts made to design a good weld and to fabricate one may simply be wasted If It Is not ascertained and known beforehand that the joint is indeed fit for the purpose. Management of weld quality should be comprehensive, covering design, fabrication, use and discard.

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