1. Q: Why is wall thickness consistency important, and how do seamless pipes perform?
A: Consistent wall thickness ensures uniform strength and pressure containment. While seamless pipes generally have good consistency, they can have more eccentricity (variation in wall thickness around the circumference) compared to high-quality welded pipes, which is a key inspection point.
2. Q: What is the difference between "Hot Finished" and "Cold Drawn" seamless pipe?
A: Hot Finished pipes are formed at high temperatures and have improved ductility and a uniform microstructure. Cold Drawn pipes are further processed at room temperature, resulting in tighter dimensional tolerances, a smoother surface finish, and increased strength through strain hardening.
3. Q: What are the typical carbon steel grades used for seamless pipes?
A: Common grades include ASTM A106 Grade B (for high temp), API 5L Grade B (for pipelines), ASTM A53 Grade B (general use), and carbon steel grades like 1020, 1045, which indicate carbon content (e.g., 1045 has ~0.45% carbon).
4. Q: What are the primary failure modes for carbon seamless pipes in service?
A: Common failure modes include internal/external corrosion, erosion (especially from sand in oil & gas), pitting, and cracking due to hydrogen embrittlement or stress corrosion cracking in harsh environments.
5. Q: How does carbon content affect the pipe's properties?
A: Higher carbon content increases tensile strength and hardness but decreases ductility and weldability. Low-carbon steels (e.g., 1020) are more ductile and easier to weld, while medium-carbon steels (e.g., 1045) are stronger but harder to weld.
