1. Q: Does the grade determine the allowable pressure of a pipe?
A: Indirectly, yes. The pressure rating (like PN or Class) is calculated based on the material's allowable stress (derived from the grade's yield/tensile strength), the wall thickness (Schedule), and the diameter.
2. Q: What is "Carbon Equivalent" (CE) and why is it important for pipe grades?
A: Carbon Equivalent is a calculated value that sums the effects of carbon and other alloying elements on hardness and weldability. Standards like API 5L PSL2 set maximum CE limits to ensure good weldability, especially for high-strength grades.
3. Q: What is normalized heat treatment?
A: It's a process where the steel is heated above its critical temperature and then cooled in still air. It refines the grain structure and improves mechanical properties. Many grades, like API 5L PSL2 grades above X60, often require normalization.
4. Q: Can seamless pipe grades be used for corrosive services?
A: Carbon steel seamless pipes have limited corrosion resistance. For corrosive environments, grades with added corrosion-resistant elements (like chromium in alloy steels ASTM A335) or completely different materials (stainless steel, e.g., ASTM A312) are used.
5. Q: What key factors should be considered when selecting a seamless pipe grade?
A: Key factors include: Design pressure and temperature, service environment (corrosivity, low temperature), required mechanical strength, weldability, compliance with industry or project specifications (e.g., ASTM, API, EN), and cost.
