[Discussion Thread 12] In what aspect does the weld bead height mainly affect the operational safety of containers? ()

Baidu’s content: Weld reinforcement; English name: reinforcement； Definition of excess weld metal: The height of the metal portion located on the line connecting the two weld toes on the surface of the weld. 1. The role of weld height: There should be a weld height during the welding process. Because the outermost layer serves to insulate and slow down cooling, it plays a significant role in refining the grain structure and reducing welding stress. It is also a collection area for impurities such as pores. 2. Disadvantages of excessive height: Pressure vessels should avoid sudden changes that could lead to local stress concentration. Furthermore, the residual height must have defects, and such defects are likely to be the nuclei for the formation of fatigue cracks. Crack source → fatigue propagation → fracture. China and Japan once conducted joint experiments and found that equipment with residual height had a service life 2.0 to 2.5 times shorter than that of equipment without residual height after grinding.

bg14.jpg After checking some information: see the figures below to determine which of A and B is primary and which is secondary; choose the one that should be selected first in a single-choice scenario.

It’s similar to the source I found on the third floor. :handshake, but the answer has still not been finalized.

3. Requirements of the standard regarding residual height: 1) JB4732 requires grinding for fatigue-prone equipment, while there are specific limits for other types of equipment. Basically, it doesn’t affect the soldering; polishing is not required. For fatigue, Ha

Answer A is undoubtedly correct; the excess height of the weld causes a sudden change in shape, leading to stress concentration, which in turn facilitates stress corrosion. Therefore, answer B is also correct.

The weld bead excess on fatigued components needs to be removed, while for stress-corrosion-resistant components, a smooth transition of the weld is generally required.

The weld bead excess height, by causing discontinuity in the structure, is susceptible to failure under fatigue loads. Many pressure vessels in Japan have their weld bead heights ground flat.

Clause 11.3.3.1a of the JB4732-95 Standard for Analysis and Design of Pressure Vessels requires that no residual height be allowed for vessels that are to be designed for fatigue analysis in accordance with Appendix C.

This fatigue life mainly arises in devices subjected to fatigue analysis, while stress concentration can exist in all types of devices. Looking at it this way, does the answer focus on B?

Stress corrosion refers to a specific form of fracture that occurs in sensitive metals or alloys under the combined effect of certain tensile stresses (external forces or residual stresses) and a particular corrosive environment. This is not a phenomenon that occurs in all pressure vessels.