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2A2-5: Testing of Metals > Objective 03: Welding Discontinuities > Flashcards

Objective 03: Welding Discontinuities Flashcards

1
Q

What is the objective of good welding practice?

A

To produce weldments with the integrity to ensure they perform adequately for the service intended

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2
Q

What does good welding practice try to avoid?

A

Weld discontinuities that may lead to defects

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3
Q

What are 4 causes of Weld Discontinuities?

A
  1. Departures from qualified procedures
  2. Altering weld designs
  3. Substituting or using defective materials
  4. Substituting or using defective electrodes
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4
Q

Why can weld discontinuities be problematic?

A

They can cause a structure to fail in service which can be costly and jeopardize safety

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5
Q

What does the existence of Weld Discontinuities necessitate?

A

The identification, evaluation, and disposition of Weld Discontinuities

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6
Q

What is the first step in welding inspection?

A

Visual identification of imperfections in welds

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7
Q

How effective is visual indentification of weld imperfecions?

A

It can usually reveal 80% of weld imperfections

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8
Q

How can weld imperfections not detectable visually be uncovered?

A

NDE can reveal their location and size

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9
Q

How are weld imperfections evaluated?

A

The Inspector judges whether or not the discontinuity is likely to become a defect leading to failure based on the use of specifications, standards, and codes which provide acceptance and rejection criteria for types of weld discontinuities

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10
Q

What does an Inspector require to know and have experince with to properly evaluate weld imperfections?

A
  1. The flaws associated with a particular welding process and procedure
  2. The metallurgy of the base metals and filler metals used
  3. The design of the weld joint
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11
Q

What possible decisions (disposition) can the evaluation of weld discontinuities lead to?

A
  1. The weldment is acceptable
  2. Requires rework
  3. Unsuitable for the service intended and must be removed
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12
Q

Can personnel involved in the inspection be involved in the final disposition decisions?

A

No, especially when the decisions are of a critical nature requiring an engineering assessment

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13
Q

Is there a standard welding terminology?

A

Yes

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14
Q

Weld Defect

A

A discontinuity or flaw whose size, shape, type, location, or orientation creates a substantial chance of material failure and is therefore detrimental to the integrety of the pressure equipment

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15
Q

Weld Discontinuity

A

Any local variation in material continuity; including changes in geometry, properties of composition or structures, holes, cavities, or cracks

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16
Q

Weld Fault

A

Defect, imperfection or flaw

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17
Q

Why shouldn’t the term Fault be using for welding?

A

It is imprecise and there are other precise terms that can be used

18
Q

Weld Flaw

A

An imperfection in the material that may or may not be harmful

19
Q

What is another term for Flaw in Welding?

A

Imperfection

20
Q

What are 3 categories by Cause of Weld Discontinuities?

A
  1. Weld Procedure
  2. Weld Design
  3. Metallurgical Causes
21
Q

What are classes by Description of Weld Discontinuities?

A
  1. Dimensional
  2. Structural
  3. Base Metal Properties
22
Q

Dimensional Discontinuities

A

Any inconsistencies or departures from specified dimensions in the weld, weld joint, or parent metal and includes welds with imperfect shapes or unacceptable contours, incl. undercut, underfill, and overlap

23
Q

Structural Discontinuities

A

Flaws in the weld deposit or heat affected zone where the flaw’s potential for failure is directly related to its shape and location in the weld

24
Q

How severe are planar defects, e.g. cracks and lack of fusion?

A

They are sharp and pointed and create severe notching and high potential for failure

25
Q

How severe are pores and non-metallic inclusions in welds?

A

They are usually rounded and pose less potential for failure

26
Q

Base Metal Discontinuities

A

Deficiencies in the chemical, physical, or mechanical properties of the base metals which may contribute to a defect in rg weldment

27
Q

How do Base Metal Discontinuities mainly arise?

A

From the production of the metal and its subsequent processing and manufacturing

28
Q

What is the property most affected by weld defects?

A

Weld Strength

29
Q

What is particularly problematic about planar-type defects?

A

They can cause rapid propagation of cracking through a weldment

30
Q

Weld Discontinuity Notching

A

Abrupt changes in the contour of the weld where it fuses to the base metal

31
Q

What is problematic about Weld Discontinuity Notching?

A

They can reduce the fatigue resistance of welded joints and cause failure even though the yield strength of the original base metal was never exceeded

32
Q

What is Fatigue Failure in welded joints associated with?

A

Cyclical loading of the joint

33
Q

What is problematic about Spherical Type Weld Defects?

A
  1. Create voids
  2. Displace weld metal
  3. Reduce intended volume of deposited weld metal
34
Q

What is the result of failure to fill a joint or melting away of the base metal?

A

Reduction of the through thickness of the base metal

35
Q

What is problematic about inappropriate chemical properties when welding?

A

It can cause a weldment to lose impact and tensile strength in a very hot or cold environment

36
Q

What is problematic about failing to match base metal to electrodes correctly?

A

It can cause a loss of resistance to corrosion at the surface of a metal

37
Q

What are the 5 basic weld joints?

A
  1. Butt
  2. Tee
  3. Lap
  4. Edge
  5. Corner
38
Q

How can a weld failure occur if the weld deposit forming the joint is sound?

A

The joint has some undesireable features

39
Q

What are some undesireable weld joint features?

A
  1. Highly restrained tee and corner joints, unless properly designed, are sites of weld failure
  2. Misaligned butt joints can be areas of high stress
  3. Steep transitions between thick and thin lapped material can create areas of high stress
40
Q

Is the degree of weld quality possible, the same as the degree of weld quality necessary?

A

No

41
Q

What determines the required degree of weld quality necessary?

A

The function imposed on the weldment

2A2-5: Testing of Metals (12 decks)

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