Abstract
Corrosion fatigue cracking of a circumferential weld due to the welds lack of ductility is often referred to as a lack of a set ring defect. Such defects can be difficult to detect as they are often only visible during a microscopic analysis. With the right prevention methods and pre-inspection activities, the failure of a circumferential weld due to a lack of a setting ring can be avoided. This article provides a comprehensive overview of the characteristics, causes and prevention of circumferential weld lack of a setting ring defects.
Introduction
Circumferential welds are the most common type of welds found in a variety of applications, including pipelines, ships, nuclear reactors and boilers. All these applications take advantage of the strength and integrity of the welds to withstand intense forces and temperatures.
However, a circumferential weld can also be prone to corrosion fatigue cracking if it does not have sufficient ductility. This defect is often referred to as a lack of a setting ring, and it is characterized by a crack that forms in the vicinity of the weld.
Corrosion fatigue cracking of a circumferential weld due to the welds lack of ductility is often referred to as a lack of a set ring defect. Such defects can occur when the metal of the weld exhibits a high concentration of hydrogen, which causes the metal to crack at smaller values of applied applied stress than normal.
Because the lack of a setting ring is only visible under microscopic analysis, it can be difficult to detect unless the weld is inspected for such defects. This makes it important to use the appropriate prevention methods and pre-inspection activities to avoid the failure of the circumferential weld due to a lack of a setting ring.
Characteristics
The lack of a setting ring often exhibits a continuous radiating cracking pattern on the surface of the circumferential weld. This pattern can be seen due to the micro-fissures formed in the welds metal which gradually accelerate and form a cohesive crack.
The depth of the defect is usually shallow and only visible under a microscope. However, it can become deeper over time if the cracking is allowed to progress unchecked.
The defect is usually located close to the weld joint, however its exact location can vary depending on the welds orientation.
Causes
The main cause of a lack of a setting ring is a welds lack of ductility. Specifically, the metal of the weld should have a sufficient amount of hydrogen content to be able to withstand the stress created by the weld.
However, if the weld contains a higher concentration of hydrogen than is optimal, the metal will become more brittle and susceptible to cracking. Additionally, environmental factors such as exposure to moisture, temperature and other corrosive materials, can further weaken the weld and make it more prone to cracking.
Finally, improper weld preparation and technique can also lead to the lack of a setting ring. Specifically, incorrect weld pass size and poor penetration can create shallow welds that are more prone to cracking.
Prevention
The key to preventing a lack of a setting ring is to ensure that the weld is properly prepared and has the necessary amount of ductility to withstand the stresses of its application.
This includes performing a “wet-hole” test to check the welds hydrogen content and performing a metallurgical analysis to determine if the weld material meets the required standards.
Additionally, the weld should be inspected regularly and the environment in which the weld is located should be monitored to ensure that the weld is not exposed to excessive temperature, moisture or corrosive materials.
Finally, proper weld preparation and technique should be used to ensure that the weld is properly made and that the pass size is correct.
Conclusion
Lack of a setting ring is a common defect found in circumferential welds. Such defects can be difficult to detect as they are often only visible during a microscopic analysis. With the right prevention methods and pre-inspection activities, the failure of a circumferential weld due to a lack of a setting ring can be avoided.
