1. Q: What is the main characteristic of ASTM A335 P11, P22, P91 pipes?
A: These are chrome-molybdenum (Cr-Mo) alloy steel seamless pipes (P11: 1.25Cr-0.5Mo, P22: 2.25Cr-1Mo, P91: 9Cr-1Mo-V) designed for high-temperature service in power generation and refining, offering creep strength and oxidation resistance.
2. Q: What is "HIC Test" and where is it required?
A: Hydrogen Induced Cracking (HIC) Test evaluates resistance to stepwise cracking in wet H₂S service. It's required for pipes used in sour oil and gas applications, typically specified for API 5L PSL 2 and certain ASTM grades.
3. Q: Define "Carbon Equivalent (C.E.)" and its importance.
A: C.E. (e.g., IIW formula: C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) is a calculated value that predicts the hardenability and weldability of steel. Lower C.E. generally indicates better weldability (less risk of cold cracking). It is often specified for PSL 2 pipes and offshore grades.
4. Q: What is the purpose of "Normalizing Heat Treatment"?
A: Normalizing involves heating the pipe above its critical temperature and air-cooling. It refines the grain structure, improves uniformity, enhances mechanical properties (toughness, strength), and is common for grades like API 5L PSL 2 X52 and above.
5. Q: What does "SS" stand for in ASTM A312 TP304/304L SS?
A: "SS" stands for Stainless Steel. ASTM A312 covers seamless (and welded) stainless steel pipes. TP304/304L are common austenitic grades for corrosion resistance.
