1. Material Definition and Core Properties
Q: What is ASTM A519 4620 steel pipe made of?
A:
4620 steel pipe is a low-carbon nickel-molybdenum alloy steel seamless pipe (UNS G46200) specified in the ASTM A519 standard. Its core composition is: 0.17%-0.22% carbon, 1.65%-2.00% nickel, and 0.20%-0.30% molybdenum. This material, reinforced with nickel and molybdenum, combines high hardenability (oil quenching critical diameter 70mm) with excellent carburizing properties (case hardness HRC 58-62). It features outstanding core toughness (core impact energy ≥60J), and a controlled retained austenite content of 12%-18% after carburizing, making it particularly suitable for highly loaded gears and transmission components.
2. Mechanical Properties and Technical Parameters
Q: What are the performance specifications of 4620 steel pipe? A:
In the carburized, quenched, and low-temperature tempered state:
Surface properties: Hardness HRC 58-62, contact fatigue limit ≥ 1900 MPa
Core properties: Tensile strength ≥ 950 MPa, yield strength ≥ 800 MPa, impact energy at -30°C ≥ 55J
Special properties: Bending fatigue strength (10⁷ cycles) is 58%-62% of tensile strength, and grain size after high-temperature carburizing remains at ASTM grade 7-9.
The optimized carburizing process allows for a smoother carburized layer gradient (hardness slope ≤ 30 HV/0.1mm).
3. Typical Application Scenarios
Q: What are the main applications of 4620 steel pipe?
A:
Automotive Transmission: New Energy Vehicle Reducer Gears, Heavy Truck Transmission Synchronizer Rings
Energy Equipment: Planetary Gears in Wind Turbine Gearboxes 5MW and Above, Nuclear Power Circulation Pump Drive Shafts
Engineering Machinery: Main Drive Gears for Shield Machines, Slewing Bearings for Mining Equipment
Military Specialty: Armored Vehicle Transmission Gears (Requires MIL-S-6050 Testing)
4. Key Points for Heat Treatment and Processing
Q: How to optimize the heat treatment and processing of 4620 steel pipe? A:
The cutting-edge "low-pressure carburizing + high-pressure gas quenching" process must be used:
Carburize at 930°C, 0.2 MPa propane atmosphere for 6-8 hours, with a carbon potential control accuracy of ±0.03%
Quench with 15 bar nitrogen, cooling rate >100°C/s
Cryogenic treatment (-120°C x 6 hours) + low-temperature tempering (180°C x 4 hours)
Processing Key Points:
Welding requires ERNiCrMo-3 wire, preheated to 250°C
For turning, CBN tools are recommended (cutting speed 90-110 m/min)
Slow cooling between 600-800°C is prohibited to prevent grain boundary oxidation.
5. Comparison with Similar Materials
Q: What is the difference between 4620, 4320, and 9310 steel pipes? A:
vs. 4320: 4620 contains no chromium, resulting in a 15% lower cost and 20% higher toughness in the weld heat-affected zone.
vs. 9310: 4620 has a lower nickel content (1.65%-2.00% vs. 3.0%-3.5%), resulting in a 25% reduction in carburizing deformation.
No Substitution Principle:
▶ Strictly prohibited as a substitute for CSS-42L in ultra-high-speed (>30,000 rpm) aviation gears.
▶ Strictly prohibited as a substitute for Pyrowear 53 in high-temperature (>400°C) wear-resistant parts.
