Welding Discontinuities Quiz-Easy-12Questions CWB

Welding Defects and Corrective Measures

• Prior knowledge of code and procedure requirements is crucial for informed decisions on cutting and preparation methods.
• Material inspection upon receipt is essential to ensure proper type, grade, and acceptable condition.
• Requesting Mill Certificates for ordered material helps in verifying the type and grade received.
• Machinists aware of required tolerances are more likely to adhere to requirements and identify problems early in material preparation.
• Overlap is an excess of weld metal at the toe of a weld, causing stress concentration and masking incomplete fusion.
• Probable causes of overlap include operator technique, electrode size, welding parameters, and surface contaminants.
• Proper welding procedures and techniques should prevent overlap, and if it occurs, grinding and blending can correct it.
• Magnetic particle testing (MT) is recommended after overlap repair to ensure complete removal and detect hidden overlap.
• Convexity is the maximum distance from the face of a convex fillet weld perpendicular to a line joining the weld toes.
• Excessive convexity in single pass fillet welds adds stress risers, while in multipass welds, it may lead to other discontinuities.
• Probable causes of convexity are operator technique, electrode size, welding parameters, and surface contaminants.
• Excessive weld reinforcement stiffens the section, establishes notches, and increases weight in groove welds. Proper welding procedures and techniques should prevent excessive weld reinforcement.

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.