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| Welding Research Institute (WRI) has developed seam-tracking systems which can be
effectively employed for welding automation. Two different types of weld seam trackers
have been developed at WRI. The first type of seam tracker is based on non-contact
inductive type position sensor and the second type is based on through-the arc sensing.
Ministry of Information Technology (MIT) has sponsored this development. |
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The inductive sensor based seam tracker can be applied for
fillet welds in large beams, circular fillets of flanges etc.
Through the arc sensing based seam tracker can be employed with oscillating torch GMAW as the process for
butt welded joints The major benefits of employing seam
trackers are Improved quality and increased productivity of
welded joints by avoiding defects due to mis-alignment of
seams. Precise control over the job conditions during
welding and less dependency on the operator are additional
benefits. |
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Over
the years a number of special purpose in-situ
polishing devices such as Controlled Electro
Polisher In-situ (CEPIN), All Position In-situ
Electro polisher (APINE) and Versatile All position
In-situ Electro polisher (VAPINE) have been
developed to enable metallographic polishing in
difficult location. With these techniques it is also
possible to carry out high quality replication even
on warm components. |
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Conventional
arc welding techniques make use of wider weld grooves with
included angles of 60-90º for plate thickness upto 50 mm
in general. For higher thickness, the edge preparation
comprises of a relatively wider root preparation with 10
to 20º included angle. The edge preparations call for
considerable deposition of weld metal and consumption of
flux. Modern fabrication techniques aim at maximising
productivity and cost savings. Narrow Gap Welding
Technique applied to conventional arc welding processes is
a potential tool for welding fabrication industry for
achieving this goal especially for welding of thick
section joints using submerged arc welding. WRI has
developed modular type narrow gap welding head, which can
be interfaced with conventional Submerged Arc Welding
system having suitable rigidity. Narrow Gap technology has
been established for butt welding steel plates upto 180 mm
thickness.
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| Applications
of high energy density Electron Beam Welding
Technology |
Electron
Beam Welding (EBW) facility available at WRI was
retrofitted with CNC controlled positioning tables and
control systems. With this facility, welding of stainless
steel, aluminium and copper alloys have been successfully
established and applied to industrial products.
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WRI
has carried out number of repair jobs for critical
applications involving various types of cast iron, alloy
steels and non-ferrous alloys. These include
- Severely
damaged hydro turbine runners weighing 13 tonnes
made of martensitic stainless steel.
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- Extensively
cracked Nickel valve casting of chemical plants.
- Circumferentially
cracked Carbon Manganese hydraulic steel
cylinders of paper mill.
- As a part of the continuing community service, temple bells of Brahadeeswar temple, Thanjavur and
Swaminathaswamy temple, Swamimalai were repaired and handed over to the
temple authorities.
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- Worn
out forged dies, steel roll mills, bowl mill coal
crusher rolls and crane wheels.
- Severely
cracked ancient church and temple bells made of
bronze.
- Fabrication
of components for Aluminium bridges, foundation bolts,
damper flappers, MgO filled thin sheet thermocouples
- Surfacing
of pulverising rolls, valve wedges, seat rings
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| Development
of Electrodes & Fluxes |
Following stick electrodes
and Submerged Arc Welding fluxes have been developed.
- General purpose
all position welding electrodes conforming to
AWS E 6012, E 6013, E 7018.
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- Low
Alloy Steel Electrode conforming to E7018A1,
E8018 B2 & E9018 B3.
- Austenitic
stainless steel electrode conforming to AWS E308
with controlled ferrite, E410 & E430.
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- Special
purpose hardfacing electrode for sugar cane crusher
rolls and worn out components of cement industry.
- Fused
flux for high speed and Narrow Gap welding techniques.
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Extensive
weldability evaluation of indigenously developed high
strength low alloy steel and quenched & tempered
steels for structural and pressure vessel applications
have been done. The susceptibility of the materials for
hot cracking, hydrogen induced cold cracking and lamellar
tearing was thoroughly examined using different types of
weldability tests. Welding parameters have been optimized
and safe welding procedures have been recommended. Welding
procedures have also been established for a variety of
industrial components such as heat exchangers, pressure
vessels, pen stocks, steam turbines and number of critical
applications to enable arriving at appropriate Welding
Procedure Specifications.
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Remaining
Life and Condition Assessment studies of several
Power, Chemical, Process and Fertilizer plants have
been conducted through elaborate Non Destructive
Examination and In-situ metallography. |
The
extent, nature and type of damage have been thoroughly
analysed and recommendations on appropriate
Run-Retire-Repair and periodicity of inspection have been
made.
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Following engineering
services have been offered to a number of fabricators and
user – industries:
- Prediction and control
of longitudinal distortion to within +/- 5 mm over 14
m length and whole axis within +/- 1.5 mm in wind box
assemblies of Power plants using Weld sequencing
techniques
- Control of twist
distortion within 3 mm with stringent requirements to
restrict camber in box section column of tower type
boiler structures
- Control of axis shift
distortion in cylindrical and spherical shells by
analyzing deformation kinetics using in-process
multi-channel programmable strain data acquisition
system to decide weld sequence.
- Residual stress
measurements in
- CO2
absorber vessels to decide on the inter
stage stress relieving heat treatment,
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- Welded
line pipes to device methods to minimize residual
stresses,
- Bogie
frames & torroidal rings to decide on the
necessity for post weld heat treatment and
- Large
welded structures to assess the stress level in as
welded condition.
- Fatigue analysis of
railway bridges, crane girders, locomotive bogie
frames, repair welded hydro turbines, landing gear
lugs, triplex chains and ball mill shafts.
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WRI has offered testing
services for a wide variety of customers in the following
areas:
- Electrode testing for
initial qualification and periodic surveillance as per
AWS and BIS.
- Welding Power Source
testing for static & dynamic characteristics
- Conventional mechanical,
chemical, metallurgical and NDT tests on weld samples
for qualification of welding consumables, welding
procedures and welders.
Resistance Seam Welding Controller
Resistance seam welding controller was developed by WRI. This controller can programme the current and
sequence of AC type resistance seam welding machine. It provides the feedback capability to control the welding
current on line. The controller can be easily retrofitted to any AC type resistance seam welding machine. The
developed controller was tested successfully with the radiator flute assembly seam welding machine available in
BHEL, Bhopal. Leak test conducted on the radiator flute assembly using the above controller indicated satisfactory
performance.
Metal Powder addition in Tandem Submerged Arc
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In Tandem Submerged Arc Welding the arc cavity has excess heat energy which can be advantageously utilized.
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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
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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
of
bottom 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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Welding of AA2219 Aluminium
Alloy
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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 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
appreciated by the customer and the report was accepted.
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Repair of a cooler for FHD sintering furnace
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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
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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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