A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Gopal, K. A.
- Laser Welding of Precision Engineering Components
Authors
1 Group for Remote Handling, Robotics, Irradiation Experiments and Post Irradiation Examination (GRIP), Metallurgy and Materials Group (MMG), Indira Gandhi Centre for Atomic Research (IGCAR) Kalpakkam- 603 102, IN
Source
Indian Welding Journal, Vol 44, No 2 (2011), Pagination: 54-59Abstract
Laser beam welding (LBW) with its high power density produces narrow and deep welds with a small heat-affected zone. Nd-YAG laser has been used extensively in the fabrication of small precision components at Indira Gandhi Centre for Atomic Research (IGCAR). Some important laser welding works carried out are related to Eddy Current based Position Sensor (ECPS) and Sodium Leak Detector (SLD) in Diverse Safety Rod Drive Mechanism (DSRDM) of Prototype Fast Breeder Reactor (PFBR), and components for Ir-192 High Dose Rate (HDR) source for Board o f Radiation and Isotope Technology (BRIT). ECPS is being designed to incorporate in the DSRDM to provide a measurement on signal which indicates that all the safety rods are dropped in case of a reactor scram signal. Mineral insulated (MI) cable of 1 mm diameter used as the eddy current coil in the ECPS has been terminated with suitable end configuration using laser welding. SLD is housed inside the electromagnet assembly of DSRDM to indicate if there is any leakage of sodium into the electromagnet. The fabrication of SLD requires precision laser welding of a few of its components. For the indigenous development of Ir-192 source assembly for use in HDR Branchy therapy, the feasibility study has been carried out for the fabrication of the miniature source holder by laser welding process. This paper discusses the techniques followed in the successful fabrication of above mentioned variety of intricate components used in critical applications.
Keywords
Nd-YAG Laser Welding, Precision Components, PFBR, ECPS, DSRDM, Sodium Leak Detector, HDR Source.
- Prediction of Weld Penetration in Circular Laser Welds of Ferritic Steel (P91) Material
Authors
1 Water & Steam Chemistry Division, Chemistry Group, Bhabha Atomic Research Centre, Kalpakkam, IN
2 IDEAS
3 Materials Technology Division, Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, IN
Source
Indian Welding Journal, Vol 46, No 2 (2013), Pagination: 54-66Abstract
Any weld designer will always try to design a weld joint with as much low heat input as possible, at the same time obtain a good depth of penetration and in the process maintain minimum heat affected zone. When a tube or a rod has to be welded using a process and if a design analysis can be done, prior to freezing of the design, to find the depth of penetration, then it may raise the confidence level of the weld design. By this way we can avoid wasting time in carrying out random trials. In the present work an approximate method of predicting the depth of penetration during welding over the peripheral of a circular rod has been formulated under Laser Welding Process. This method will be helpful to design the joint with enhanced efficiency and with lesser probability of defects like lack of penetration and excess penetration. In the analysis ‘Thermal Explosion” theory has been used to predict the depth of penetration to map the fusion zone of a circular weld joint on P91 rod. The calculated depth of penetration has been compared with the measured depth of penetration on the weld carried out on a rod using Laser Welding process and the results were found to be nearly matching. It has been found that the depth of penetration increases as the welding progresses over the rod and the difference between the depth of penetration between starting & ending points is around a few microns. This is due to the buildup of heat in the cross section of the rod as the weld progresses.