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Research & Development
 
Welding of AA2219 Aluminium Alloy
WRI was entrusted with the task of developing welding procedure for the high strength aluminum alloy AA2219. 

The scope involved establishment of welding procedure for the aluminium alloy AA2219 (Al-Cu Alloy) in heat-treated (T87 temper) condition using the TIG welding process in Direct Current Straight Polarity (TIG, DCSP) mode in place of the AC TIG process which is usually used to weld aluminum. The welding process was successfully established using a mechanized welding

set-up for different welding speeds and heat input levels while meeting the special requirements of TIG welding of aluminium alloys in DCSP mode. 7mm thick AA2219 aluminum alloy plates were successfully welded using square butt joint geometry in single pass with feeding of 1.6mm dia filler wire and at d by the customer and the report was accepted. 

welding speeds of 350mm/min and 450mm/min. A narrow weld-bead width of about 10mm as shown in the photo-macro-graph, with very good joint strength could be achieved. This is the first

time that this technology of DCSP TIG welding of AA2219 aluminum alloy has been established in India. The work was appreciate

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Resistance Seam Welding Controller 

A special purpose cladding system has been developed for internal stelliting of tubes and valves having small diameter bores using MIG welding Process. Salient features of the machine include a special purpose welding torch, a column mounted X-Y slides, a motorized torch holder and synergic MIG welding power source. This system enables mechanised cladding of deep bores with restricted axis in cylindrical sections resulting in excellent weld quality.

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Metal Powder addition in Tandem Submerged Arc

In Tandem Submerged Arc Welding the arc cavity has excess heat energy which can be advantageously utilized. The introduction of additional filler material in the form of metal powder can lead to sustained increase in the
deposition rate resulting in reduced joint completion time. Further metal powder addition to Tandem submerged arc welding reduces the depth of penetration and dilution by 20-30 % which results in improved mechanical properties. A 60 % increase in productivity can be achieved for the same energy input. Procedures have been established for addition of iron powder for welding of mild steel. With the addition of metal powder having chemical composition matching with that of the filler wires, this technique can be applied in welding of offshore structures, shipbuilding and pipe welding. 

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Mechanised Stelliting of OFE Seat Ring

Stelliting of OFE seat ring is done manually employing gas stelliting and partly by plasma stelliting process. The manual stelliting is a slow process and gives very low productivity and also quality problems. The plasma stelliting though relatively fast, involves loss of stellite powder and over heating of the components particularly the smaller diameter seat rings. The flux cored stelliting process has been found to be good an alternative for this application. A mechanised system consisting of welding positioner, oscillation unit and GMAW power source has been developed. The mechanised flux cored stelliting process is found to provide consistent quality and improved productivity of 5 to 10 times in OFE seat ring stelliting application. 

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Repair of Inconel Muffle of FHD Furnace

WRI was approached for repair of muffle of FHD furnace. The muffle was fabricated out of inconel material (thickness 5 mm) and of size 100 X 450 X 3300mm long. Some portion of the muffle (about one meter length) got deformed during usage and is to be replaced by welding good portion from another damaged muffle. The repaired muffle should be with minimum distortion and should be gas leak tight for 2kg/cm2 pressure. The inner surface ofbottom portion and sides should be flush ground.The bottom portion and sides of the muffle were welded by manual TIG process with filler wire while top curved portion was welded by TIG / SMAW process at WRI meeting the requirements on distortion and leak tightness

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Repair of a cooler for FHD sintering furnace

WRI was referred for repair of a cooler for FHD sintering furnace, which had leakages at several locations. This Cooler was used for cooling the sintered rods coming out of the furnace. The cooling tank was made up of 5mm thick 316 type stainless steel. In-situ metallography was done on the material and the cause of failure was assigned to thermal fatigue. 

The Liquid Penetrant test was conducted to identify the defects. The cooler was subjected to hydraulic test and leakage was found in many places. The defective areas had limited access to repair welding. The repair welding was carried out successfully using MMAW and TIG welding. 

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Low Cycle Fatigue Test 

Low Cycle load tests on butt joints were carried out to qualify welding consumables. The tests were carried out at as low a frequency of 0.5 Hz at specified stress range on full scale weld specimens up to fracture or up to specified load cycles whichever was earlier both in air and saline water medium using Instron 1276. The objective of the tests is to evaluate the fatigue performance of the joints welded with different welding consumables supplied by different vendors.

To carry out fatigue tests in saline water medium, a suitable chamber was designed and fabricated at WRI which is to be leak-proof through out the test.

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