Indian Welding Journal (Official Journal of the Indian Institute of

Indian Welding Journal
(Official Journal of the Indian Institute of Welding)
Volume 45 No.2 April 2012
LASER-MIG Hybrid Welding of Thick Plates of Mild Steel in Single Pass
G. Padmanabham, B.Shanmugarajan and K. V. Phani Prabhakar
pp. 29-39.
Laser hybrid welding combines the deep penetration capability of laser beam and edge gap bridging capability
of an arc welding process such as MIG/MAG. In the present work, a 3.5 kW slab CO LASER -MIG hybrid welding
system was used to carry our laser hybrid welding studies with an aim to achieve butt welds of 12mm thick mild
steel plates in single pass. Bead-on-plate studies were carried out to first understand the effect of parameters
such as laser power, focal plane position of the laser, MIG wire feed rate, composition of shielding gas, distance
between laser and MIG arc on the weld penetration. The optimized parameters were then applied on butt welds
with Y-groove edge preparation with varying root face height and groove angle to identify suitable joint design.
Combining the results of bead-on-plate experiments and butt welding experiments, welding of 12 mm thick
mild steel plates in single pass could be achieved. The LASER-MIG hybrid butt welds so fabricated showed
100% joint efficiency and high bend ductility.
Corrosion Fatigue behavior of Submerged Arc Welded high strength steel used in
Naval Structures
H. Das and T. K. Pal
pp. 40-51.
Corrosion prevention is a major concern for naval structures particularly for welded joint of high strength steel.
Although cathodic protection (CP) is still widely used to prevent corrosion of structural steels in marine
environment, effectiveness of CP has not been proven for structural steels with a yield stress above 400 MPa. In
the present investigation, high strength steel plate of DMR 249A was welded by Submerged Arc Welding (SAW)
process and the corrosion fatigue tests were performed on weld metal in air and 3.5% NaCl solution at room
temperature with R ratio of 0.1 and a cyclic frequency of 0.01 Hz with and without cathodic potential. Optimum
cathodic potential for weld metal was also evaluated in unstressed condition from the minimum corrosion
coefficient among four potentials (under at -800, -875, -950, -1025) mV based on potentiostatic polarization
curves (E value) of weld metal. Corrosion fatigue results suggest that optimum cathodic potential data corr
(-875 mV) determined in unstressed condition could be used to improve the corrosion fatigue life of weld metal
used in naval structure.
In-situ repair of multiple cracks present in the RTJ groove of high pressure
hydrogen bearing DHDS reactor by welding
Swapan Kumar Bagchi, Kaushik Boral and Amit Kumar Mishra
pp. 52-54.
This article describes a detailed repair procedure with necessary heat treatment involving the repair of multiple
cracks in the Ring type joint (RTJ) groove of top man-way flange observed during the first internal inspection of
the Reactor (25-R-01). Detailed site inspection and laboratory investigations, including visual inspection,
thickness measurements, metallographic analysis, hardness testing of RTJ groove and RTJ gasket, Dye
Penetrant testing, cladding disbonding testing by ultrasonic method, ferrite number measurement etc., were
performed to identify the cause and mechanism of damage. Various factors like Stress corrosion cracking,
Hydrogen induced cracking, sigma phase formation, have been involved with respect to the operating
conditions of the equipment. In view of the above observations and ascertaining the severity of the overall
damage of the Reactor, the in-situ repair methodology by welding was developed & repair jobs were
successfully undertaken.
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