Q: What is the primary function of adding Molybdenum (Mo) to steel grades like 15CrMoG or 1Cr5Mo?
A: Molybdenum enhances creep strength at high temperatures and improves corrosion resistance, especially against pitting in certain environments.
Q: Why is the element Niobium (Nb/Cb) added to some micro-alloyed pipeline steels like those in API 5L?
A: Niobium is a potent grain refiner. It increases strength and toughness by inhibiting grain growth during thermo-mechanical controlled processing (TMCP).
Q: What is the key advantage of using "fine-grain" steel (e.g., HRBF400) in manufacturing?
A: It allows for achieving higher strength without extensive use of costly alloying elements, aligning with energy-saving policies. This principle also applies to high-strength, low-alloy (HSLA) pipe steels-2.
Q: For a seamless pipe made of grade 42CrMo (GB/T 8162), what is its most likely final heat treatment state?
A: It is often supplied in a quenched and tempered (+QT) condition to achieve an optimal combination of high strength and good toughness.
Q: What does the "G" suffix indicate in boiler tube grades like 20G?
A: The "G" stands for "Gao Ya Guo Lu" (High-Pressure Boiler) in Chinese. It signifies that the steel is manufactured with more stringent controls on purity, homogeneity, and properties suitable for high-pressure service.
