Weld Discontinuities and Defects Quiz_CWB_Part 2/4
78 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is convexity defined as?

  • The minimum distance from the face of a convex fillet weld parallel to a line joining the weld toes
  • The minimum distance from the face of a concave fillet weld parallel to a line joining the weld toes
  • The maximum distance from the face of a convex fillet weld perpendicular to a line joining the weld toes (correct)
  • The maximum distance from the face of a concave fillet weld perpendicular to a line joining the weld toes

    • What can excessive convexity lead to in multipass welds?

  • Improved weld fluidity
  • Notch effects and other weld discontinuities (correct)
  • Smooth weld profile
  • Reduced stress risers

    • What are some probable causes of convexity?

  • Operator certification, welding machine brand, ambient temperature, and joint type
  • Operator technique, electrode, welding parameters, and surface contaminants (correct)
  • Welding current, weld time, electrode angle, and weld position
  • Welding position, base metal type, filler metal diameter, and shielding gas flow rate

    • How can excessive convexity be corrected on fillet welds?

    <p>Grinding to achieve a flat weld profile</p> Signup and view all the answers

    What is the recommended action for correcting convexity caused by insufficient heat input in a weld?

    <p>Complete removal of the weld and deposition of a new weld</p> Signup and view all the answers

    What action is recommended for grooving the toes of multipass welds before depositing the next pass?

    <p>Groove the toes before depositing the next pass</p> Signup and view all the answers

    What are the effects of excessive weld reinforcement?

    <p>Stiffens the section, establishes notches, and increases weight</p> Signup and view all the answers

    What is the maximum reinforcement permitted for groove welds according to CSA Standard W59?

    <p>3mm</p> Signup and view all the answers

    What is a probable cause of underfill in welds?

    <p>Fast travel speed and incorrect weave techniques</p> Signup and view all the answers

    How can insufficient throat in fillet welds be corrected?

    <p>By adding more weld metal</p> Signup and view all the answers

    What is the recommended action for correcting insufficient leg size in fillet welds?

    <p>Deposit additional passes</p> Signup and view all the answers

    What is undercutting in welding?

    <p>The melting away of parent metal during welding, left unfilled with weld metal</p> Signup and view all the answers

    At what stage of the welding process can undercut occur?

    <p>Any stage</p> Signup and view all the answers

    What are the probable causes of undercut discontinuities?

    <p>Operator technique, electrode type or size, welding parameters, joint accessibility and position, and joint preparation</p> Signup and view all the answers

    How can surface undercut discontinuities be corrected?

    <p>By cleaning and adding an additional pass</p> Signup and view all the answers

    What is the potential difficulty in fixing root undercut on small diameter pipe?

    <p>It may be more difficult to fix</p> Signup and view all the answers

    What is the definition of concavity in welds?

    <p>The maximum distance from the face of a concave fillet weld to a line joining the weld toes</p> Signup and view all the answers

    What can cause excessive concavity in welds?

    <p>Operator technique, welding parameters, and position of welding</p> Signup and view all the answers

    How can the leg and throat size of concave fillet welds be measured?

    <p>With fillet weld gauges</p> Signup and view all the answers

    What can lead to out-of-line weld beads?

    <p>Misalignment of the weld due to insufficient care in positioning automatic welding machines</p> Signup and view all the answers

    What is the result of incomplete joint penetration when complete joint penetration is required?

    <p>The need to remove the weld from one side and deposit a new weld</p> Signup and view all the answers

    What is incomplete fusion in welding?

    <p>The failure to fuse between weld metal and fusion faces or adjoining weld beads</p> Signup and view all the answers

    What can inhibit electrode manipulation and affect the welding process?

    <p>Improper joint design, poor joint preparation, and fit-up</p> Signup and view all the answers

    How are large diameter pipes with undercut defects repaired?

    <p>Using the same method as external undercut</p> Signup and view all the answers

    What are the causes of concavity in welds?

    <p>Operator technique, welding parameters, and position of welding</p> Signup and view all the answers

    How can weld deficiencies due to insufficient or excessive size be detected?

    <p>By visual examination or using suitable gauges</p> Signup and view all the answers

    What can cause incomplete fusion in welding?

    <p>Improper electrode selection, welding parameters, and cleaning of material</p> Signup and view all the answers

    What is the effect of misalignment of the weld due to insufficient care in positioning automatic welding machines?

    <p>Out-of-line weld beads</p> Signup and view all the answers

    What are the primary causes of welding distortion?

    <p>Thermal expansions and contractions</p> Signup and view all the answers

    Which of the following is a common type of welding distortion?

    <p>Bending or angular distortion</p> Signup and view all the answers

    What is the primary cause of slag inclusions in welding?

    <p>Incomplete removal of slag during welding</p> Signup and view all the answers

    What is the most likely cause of porosity in welding?

    <p>Presence of gas pockets in the weld metal</p> Signup and view all the answers

    What is the primary cause of solidification cracking in welds?

    <p>Contraction strains during solidification</p> Signup and view all the answers

    When does hydrogen-induced cold cracking typically occur after welding?

    <p>Hours, days, weeks, or even months after welding</p> Signup and view all the answers

    What factor is NOT necessary for hydrogen-induced cold cracking to occur?

    <p>Low hydrogen content</p> Signup and view all the answers

    Which type of cracks are located in the weld metal and may be either longitudinal or transverse?

    <p>Hot cracks</p> Signup and view all the answers

    What increases the risk of solidification cracking?

    <p>Greater depth of the weld deposit than the width</p> Signup and view all the answers

    What is the most economical method of preventing hydrogen-induced cold cracking?

    <p>Using a low-hydrogen process</p> Signup and view all the answers

    Where do solidification cracks typically occur?

    <p>In the weld metal</p> Signup and view all the answers

    What causes the rejection of alloying elements and impurities ahead of the growing crystals during solidification?

    <p>Grains beginning to grow from the fusion boundary</p> Signup and view all the answers

    What is the temperature range at which hydrogen-induced cold cracking usually occurs?

    <p>Below 150 °C</p> Signup and view all the answers

    What is the primary cause of hot cracks in welds?

    <p>Combined effects of metallurgical and mechanical factors at the grain boundaries</p> Signup and view all the answers

    What is the effect of the rejection of hydrogen from the solution and its collection at grain discontinuities during welding?

    <p>Creation of pressure and stress levels, leading to cracks</p> Signup and view all the answers

    What is the risk of solidification cracking increased by?

    <p>Greater depth of the weld deposit than the width</p> Signup and view all the answers

    What can cause slag inclusions in welding?

    <p>Insufficient cleaning between weld passes</p> Signup and view all the answers

    Which factor is crucial in preventing tungsten inclusions in welding?

    <p>Proper sharpening of the tungsten electrode</p> Signup and view all the answers

    How can copper inclusions occur in welding?

    <p>Pieces of the copper sheath of a carbon arc-air electrode falling into the groove</p> Signup and view all the answers

    What can prevent the presence of oxides on the internal surface of welds in pipe and tube welding?

    <p>Purging with inert gas</p> Signup and view all the answers

    What can cause porosity in welding?

    <p>Gases dissolving into the liquid metal from impurities in the base metal</p> Signup and view all the answers

    What is characteristic of tungsten inert gas welding process?

    <p>Tungsten inclusions</p> Signup and view all the answers

    What requires non-destructive testing methods for detection in welding?

    <p>Sub-surface porosity</p> Signup and view all the answers

    What is accumulative in multipass welding?

    <p>Porosity</p> Signup and view all the answers

    What can lead to sub-surface porosity in welding?

    <p>Incomplete shielding</p> Signup and view all the answers

    What can assist in determining the probable cause of porosity in welding?

    <p>The location of porosity in relation to the depth on the cross-section of the weld</p> Signup and view all the answers

    What is crucial for preventing slag inclusions in high-speed welding applications?

    <p>Choosing the right welding electrode</p> Signup and view all the answers

    What can result in slag inclusions due to the arc failing to heat the root area sufficiently?

    <p>Using the wrong size of electrode</p> Signup and view all the answers

    What can cause surface irregularities in welding such as spatter, inadequately filled craters, and arc strikes?

    <p>Incorrect welding parameters or technique</p> Signup and view all the answers

    What may result in cracks due to rapid cooling in the completed weld?

    <p>Tack welds left for inclusion</p> Signup and view all the answers

    What may lead to quenched and embrittled conditions in the weld zone, particularly in alloy steels?

    <p>Stray arc strikes</p> Signup and view all the answers

    What are slag inclusions in welds typically composed of?

    <p>Oxides and nonmetallic solids</p> Signup and view all the answers

    What is the primary function of slag during welding with covered electrodes, tubular flux cored electrodes, and submerged arc electrodes/flux?

    <p>Serving as scavengers of impurities in the molten metal pool</p> Signup and view all the answers

    What factors can affect the ability of slag to rise to the surface of the weld?

    <p>High viscosity weld metal, rapid solidification, improper electrode manipulation, improper interpass cleaning</p> Signup and view all the answers

    What can prevent slag from rising to the surface of the weld, usually due to incorrect welding parameters in high-speed applications?

    <p>Rapid solidification of the weld metal</p> Signup and view all the answers

    What is the typical reason for slag to have time to float to the surface of the weld?

    <p>Lower density compared to the weld metal</p> Signup and view all the answers

    What can inhibit the ability of slag to rise to the surface of the weld?

    <p>Improper electrode manipulation and rapid solidification of the weld metal</p> Signup and view all the answers

    What do high-speed welding applications require to ensure that slag has adequate time to escape?

    <p>Procedures to ensure proper slag management</p> Signup and view all the answers

    What can cause porosity in welding?

    <p>Moisture pick-up on flux-coated electrodes</p> Signup and view all the answers

    How should consumables be stored to avoid moisture?

    <p>At temperatures above 120°C (250°F)</p> Signup and view all the answers

    What is important to prevent porosity in welding?

    <p>Selecting the proper filler metal to match the chemistry and properties of the material</p> Signup and view all the answers

    What can cause porosity associated with shielding gases?

    <p>Poor distribution and impurities collected in the gas</p> Signup and view all the answers

    What can cause porosity in manual welding applications?

    <p>Faulty manipulation of the electrode and incorrect arc voltages</p> Signup and view all the answers

    What can cause scattered surface porosity in submerged arc welding?

    <p>Insufficient flux coverage</p> Signup and view all the answers

    What may cause porosity due to tack welds?

    <p>Slag residue left on the surface</p> Signup and view all the answers

    How can porosity be detected?

    <p>By visual examination or NDT methods</p> Signup and view all the answers

    What is the recommended action for repairing a weld with porosity?

    <p>Grinding or gouging to remove the porosity and re-welding</p> Signup and view all the answers

    What is crucial to ensure before depositing the next pass in welding?

    <p>All slag is removed from the surface</p> Signup and view all the answers

    What should be referenced to determine acceptance limits for porosity?

    <p>Relevant codes and standards</p> Signup and view all the answers

    What is important to prevent porosity associated with surface contaminants?

    <p>Proper preparation of materials for welding</p> Signup and view all the answers

    Study Notes

    Weld Discontinuities and Defects in Welding Processes

    • Large diameter pipes can be repaired using the same method as external undercut, while small diameter pipes with undercut defects require cutting out the section and preparing a new joint.
    • Acceptable and unacceptable groove weld profiles are shown in Figure 19, with specific criteria for reinforcement, underfill, excessive weld reinforcement, undercut, and overlap.
    • Concavity in welds is defined as the maximum distance from the face of a concave fillet weld to a line joining the weld toes, and excessive concavity can occur with fillet welds.
    • Causes of concavity in welds include operator technique, welding parameters, and position of welding, and excessively concave welds can give a deceptive appearance of the actual weld size.
    • Desirable, acceptable, and unacceptable fillet weld profiles are shown in Figure 23, with specific criteria for convexity, excessive undercut, overlap, and insufficient leg.
    • Weld deficiencies due to insufficient or excessive size and poor profile may be detected by visual examination or by using suitable gauges.
    • The leg and throat size of concave fillet welds can be measured with fillet weld gauges, and only the leg size of convex fillet welds can be measured with fillet weld gauges.
    • Misalignment of the weld due to insufficient care in positioning automatic welding machines, incorrect bead placement, incorrect edge preparation, or inaccurate backgouging can lead to out-of-line weld beads.
    • Out-of-line weld beads can result in incomplete joint penetration when complete joint penetration is required, and correction requires the removal of the weld from one side by grinding or gouging and the depositing of a new weld.
    • Incomplete fusion is the failure to fuse between weld metal and fusion faces or adjoining weld beads, and it may occur at any point in the welding groove or fillet weld.
    • Incomplete fusion may be caused by factors such as improper electrode selection, welding parameters, manipulation of the electrode, cleaning of material, joint design, and poor joint preparation and fit-up.
    • Improper joint design, poor joint preparation, and fit-up can inhibit electrode manipulation and affect the welding process.

    Weld Discontinuities and Their Causes

    • Distortion in welding can be caused by factors such as improper welding parameters, weld pass sequencing, joint preparation, fit-up, and design
    • Surface irregularities in welding, such as spatter, inadequately filled craters, and arc strikes, are typically the result of incorrect welding parameters or technique
    • Excessive spatter poses challenges for subsequent painting operations and is labor-intensive to remove
    • Tack welds left for inclusion in the completed weld may result in cracks due to rapid cooling
    • Stray arc strikes may lead to quenched and embrittled conditions in the weld zone, particularly in alloy steels
    • Slag inclusions, which are oxides and nonmetallic solids, can be found as elongated or multifaceted inclusions in welds
    • Slag is produced during welding with covered electrodes, tubular flux cored electrodes, and submerged arc electrodes/flux, serving as scavengers of impurities in the molten metal pool
    • Factors affecting the ability of slag to rise to the surface of the weld include high viscosity weld metal, rapid solidification, improper electrode manipulation, improper interpass cleaning, and weld discontinuities from a previous pass
    • Rapid solidification of the weld metal can prevent slag from rising to the surface, usually due to incorrect welding parameters in high-speed applications
    • Slag generally has time to float to the surface of the weld due to its lower density
    • The ability of slag to rise to the surface of the weld may be affected by factors such as improper manipulation of the electrode and rapid solidification of the weld metal
    • High-speed welding applications require procedures to ensure that slag has adequate time to escape

    Recognizing and Preventing Porosity in Welding Processes

    • Porosity in welding can be caused by moisture, chemistry and structure of the parent material, surface contaminants, shielding gas, welder technique, air contaminants, insufficient flux coverage, and slag residue.
    • Moisture pick-up on flux-coated electrodes or on the surface of flux-cored wire exposed to humid conditions causes porosity.
    • Proper storage of consumables is crucial to avoid moisture, with storage temperatures for SMAW above 120°C (250°F) to maintain acceptable moisture levels.
    • Selecting the proper filler metal to match the chemistry and properties of the material to be welded is important to prevent porosity.
    • Surface contaminants like oil, grease, paint, oxides, and rust can cause porosity, and methods of preparing materials for welding can introduce contaminants.
    • Porosity associated with shielding gases can result from poor distribution, insufficient or excessive flow rates, or impurities collected in the gas through hoses and connections.
    • In manual welding applications, porosity can be caused by faulty manipulation of the electrode, excessive arc voltages, incorrect electrode angle, and incorrect weave techniques.
    • Welding operations in close proximity to painting operations may result in porosity problems due to air contaminants.
    • Insufficient flux coverage in submerged arc welding can cause scattered surface porosity.
    • Slag left on the surface of tack welds may cause porosity, and interpass cleaning operations should ensure all slag is removed before depositing the next pass.
    • Porosity may be detected by visual examination or NDT methods, and relevant codes and standards should be referenced to determine acceptance limits.
    • Repairing a weld with porosity that is determined to be a defect requires grinding or gouging to remove the porosity and re-welding, ensuring a desirable groove profile is achieved for the repair weld passes.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    WSS Study Guide WD2.1 Intermediate Weld Discontinuities PDF
    WSS Study Guide WD2.1 Intermediate Weld Discontinuities PDF

    Description

    Test your knowledge of weld discontinuities and defects in welding processes with this quiz. Explore topics such as groove weld profiles, concave and fillet weld profiles, weld deficiencies, misalignment, out-of-line weld beads, incomplete fusion, and factors causing weld defects.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser