2. CONTENTS
Introduction to Weld ability
Weld ability Tests and its Classification
Importance of Actual Welding Tests
Fabrication Weld ability Test
Service Weld ability Test
References
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3. INTRODUCTION TO
WELDABILITY
Weld ability of a material or a combination of materials
to be welded under fabrication conditions into a
specific, suitably designed structure and to perform
satisfactorily in intended service.
Weld ability compasses the following aspects:-
1. Metallurgical compatibility of materials being welded
2. Mechanical soundness
3. Good serviceability of the welded joint.
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4. Weld ability Assessment
Prior to define weld ability three things need to be
decided and they are:-
1) The degree of tolerance that can be allowed for purely
metallurgical defects
2) The degree of tolerance that can be allowed for
operational defects
3) The type of test that would be suitable in circumstances
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6. Importance of Actual Welding
Test
It overcomes the limitation of theoretical tests as theoretical tests do
not take into account all welding variables while calculating weld
ability. Also it doesn’t take into account effect of preheat, electrode
composition, etc.
It also overcomes the limitation of simulated test as simulated test
does not accounts for residual and reaction stresses, HIC and other
conditions that may be imposed on production welds
Visual test can’t be used as weld ability defects are often difficult to
see.
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7. Purposes of Actual Welding Test
They are used to calibrate the weld ability of
particular grades of individual heats of metals and
alloys. For this purpose the specimen dimensions
and welding conditions are prescribed and fixed to
make the material sample the only variable
They are used to establish a compatible
combination of base material, filler metal &
welding conditions that will produce welded joints
satisfactory for the application
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8. Fabrication Welding Test
The test in this category determines the
susceptibility of the welded joint to cracking and
can be grouped under three headings according
to type of cracking that they produce:-
1)Hot cracking test
2)Cold cracking test
3)Test related to cracks associated with
specific fabrication conditions or structures
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9. HOT CRACKING TEST (MUREX
TEST)
1) Size of plate is 10-15mm thick
and 50 x 70mm
2) Speed of rotation is 10 per
second
3) Initial angle is 900 and maximum
obtained angle is 1200
4) One clamp is fixed and other
rotating
5) This test has been mainly used
for accessing cracking sensitivity of
C and low alloy steels weld deposits
made with coated electrodes.
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10. COLD CRACKING TEST
(LEHIGH RESTRAINT TEST
1) U- groove is made in a plate
about 300mm x 200mm.
2) For 25mm plate thickness
length of groove is 90mm with
single U and for above it is
140mm with double U.
3) Thickness of plate is around
12-50mm
4) Root gap of groove is 1.6-
2mm.
5) VT, MPT & RT is carried out
after welding
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11. Lehigh Restraint Test
Steels with 0.3% C cracks occur practically
exclusively in the weld metal but may be
initiated in the root or upper part whereas the
crack sensitive higher C and alloy steels show
cracking in HAZ.
This test is recommended for selection of
electrodes for use with Arc welding Processes
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12. Test for Specific Types of
Cracking
Various types of cracks categorised have distinct
characteristics and thus specially designed cracks are there
for them and they are as follows:-
Lamellar Tearing and
Reheat Cracking
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13. Lamellar Tearing
Through thickness Ductility test,
The cranfield test,
Lehigh cantilever lamellar tearing test,
The window test,
The H test,
The Brodeau test,
The notched tensile strength test.
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16. References
R.S.Parmar, Welding Engineering and
Technology, Page no:431-499.
Joint Design, Testing and Inspection by
Edward R. Bohnart.
Other Internet papers.
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