1. Q: What are the material properties of 5155 steel pipe?
A: 5155 is an AISI standard medium-carbon chromium alloy steel with a carbon content of 0.51% to 0.59% and a chromium content of 0.70% to 0.90%. It features high hardness, excellent wear resistance, and good hardenability, making it particularly suitable for mechanical components subject to heavy loads and wear.
2. Q: What are the typical mechanical properties of 5155 steel pipe?
A: After quenching and tempering, the tensile strength can reach 980 to 1200 MPa, the yield strength 850 to 1000 MPa, and the elongation ≥12%. The impact energy at room temperature is ≥24 J, and the hardness is HRC 28 to 35 (depending on the tempering temperature).
3. Q: What are the key points of the heat treatment process for 5155?
A: Preheat to 650°C to prevent cracking. Austenitize at 840-870°C followed by oil quenching. The recommended tempering temperature is 450-600°C. Avoid slow cooling from 250-400°C to prevent temper brittleness. Large-cross-section parts require a longer holding time.
4. Q: What are the advantages of 5155 compared to 5140 steel pipe?
A: 5155 has a higher carbon content (0.51% vs. 0.40%), significantly improving wear resistance and strength. However, its weldability is poor, requiring rigorous preheating and post-weld heat treatment.
5. Q: What are the main applications for 5155 steel pipe?
A: It is commonly used in high-stress, wear-resistant environments such as heavy gears, mining machinery shafts, hydraulic piston rods, and military armor components. It is not recommended for high-temperature conditions above 400°C.
