282
Gas Tungsten Arc Welding Handbook
Summary
Inspections are made during and after
the manufacturing cycle to ensure that parts
meet specifi cations. Types of inspection include
nondestructive examination (NDE), in which no
portion of the completed weld is destroyed, and
destructive tests, in which the weld is destroyed.
Weld integrity inspections may also be required in
addition to the nondestructive test requirements to
verify the weld quality. NDE includes visual tests,
penetrant tests, magnetic particle tests, ultrasonic
tests, and radiographic tests. Destructive tests include
bend tests, tensile tests, notch-toughness tests, cross
section tests, and nick-break tests. Weld integrity
inspections include pressure tests, hardness tests,
corrosion tests, and ferrite tests.
Intended weld repairs must be evaluated as
to whether the discontinuity should be removed.
Repairing a completed weld could cause buckling,
distortion, or misalignment of the reworked area.
In some cases, a discontinuity can be left in a weld
without affecting the weld’s function.
Repairs can be made to correct dimensional
problems, surface defects, and internal defects.
Common surface defects include longitudinal,
transverse, or crater cracks; undercut at the edges
of the weld; porosity; cold laps; and incomplete
penetration. Internal defects are generally found by
radiographic and ultrasonic testing.
Stringer beads should be used for welding
repairs in order to minimize shrinkage of the joint.
If the weld repair is deep, an X-ray should be made
after two or three completed passes to confi rm that
the original crack has been fully repaired and new
cracks have not formed. Where the grain size must
be controlled throughout the repair, temper beads
should be used to reduce the surface grain size.
All nondestructive testing required for fi nal
acceptance of the weld must be completed after the
weld repair is done. Repairs can cause new problems
in a weld.
Review Questions
Write your answers on a separate sheet of paper. Do not
write in this book.
1. Inspections and tests made on a weld that do not
destroy any portion of the completed weld are
called _____.
2. A(n) _____ test is used to identify bad welds
before other more expensive and time-
consuming types of inspection are performed.
3. What is the difference between a fl aw and a
defect?
4. A penetrant test (PT) will only reveal disconti-
nuities that are located _____.
5. In a magnetic particle test, _____ particles form
a pattern on the surface of the material where a
defect is located.
6. What does an ultrasonic test of a weld reveal?
7. List four factors that can cause misinterpretation
of an ultrasonic test.
8. Radiographic tests use the ability of short wave-
length radiations, such as _____ or _____, to
penetrate opaque material.
9. What is the purpose of a penetrameter?
10. List the three types of bend tests.
11. List the three mechanical values of a weld deter-
mined by tensile tests.
12. _____ tests are used to defi ne the ability of welds
to resist cracking or crack propagation at low
temperatures under loads.
13. A pressure test that uses fl uid is called a(n) _____
test.
14. In a corrosion test, test weldments are sprayed
with a(n) _____ mixture and allowed to corrode.
15. Why should all rejected welds be thoroughly
reviewed before attempting a repair?
16. List three conditions that require dimensional
repair.
17. What should be avoided when grinding out
undercut defects?
18. What type of defects located in the body of a
weld are very hard to locate using grinding or
routing?
19. What should be done when making a deep
weld repair to confi rm that new cracks have not
formed?
20. _____ beads reduce the surface grain size and are
removed after welding.