1. Q: What are the primary material standards for 20MnV6 and 20MnV steel pipes?
A: 20MnV6 is typically specified under European/DIN standards (e.g., DIN 17200, EN 10273 for pressure purposes). 20MnV is a Chinese GB standard steel grade (e.g., GB/T 3077 for alloy structural steel).
2. Q: What is the key chemical composition difference between 20MnV6 and 20MnV?
A: Both are Mn-V (Manganese-Vanadium) low-alloy steels. The exact composition ranges differ per standard, but 20MnV6 generally has slightly higher specified limits for Mn and a defined Boron (B) content for hardenability, while 20MnV (GB) focuses on Mn, V, and carbon ranges without mandatory Boron.
3. Q: What are the main mechanical properties achieved after heat treatment?
A: After quenching and tempering, both offer high tensile strength (>700 MPa for 20MnV6, similar for 20MnV) and good toughness. Yield strength typically exceeds 550 MPa.
4. Q: For what primary applications are these steel pipes used?
A: They are commonly used for high-pressure hydraulic cylinders, pneumatic cylinders, high-stress mechanical structures, and certain pressure vessel components (where standards permit).
5. Q: Why is vanadium (V) added to these steels?
A: Vanadium forms fine carbides, which inhibit grain growth during heating, providing grain refinement. This increases strength, toughness, and fatigue resistance.
