1. What is the basic definition and core properties of EH500 steel pipe?
EH500 is an E-grade ultra-high-strength hull structural steel in the GB/T 712-2023 standard, representing the cutting-edge technology of Chinese shipbuilding steel. Its core properties include:
Yield strength ≥ 500 MPa, tensile strength 610-770 MPa, designed specifically for ultra-large polar vessels and deep-sea equipment;
-40°C ultra-low-temperature impact toughness (KV2 ≥ 42 J), meeting the requirements of extreme polar environments;
A high-Ni-Mo-Cu alloy system (Ni 1.5%-2.0%, Mo 0.2%-0.4%) and direct quenching and tempering (DQ+T) process achieve a perfect combination of ultra-high strength and low-temperature toughness.
2. What are the main applications of EH500 steel pipe? Polar heavy icebreakers: Key load-bearing structures for polar regions with ice thicknesses greater than 2 meters;
Ultra-deepwater drilling platforms: Jackets and cantilever beams supporting vessels in depths of 4,000 meters;
Military polar vessels: Armor and pressure hulls for ice-based combat vessels.
3. What are the major technological breakthroughs of EH500 compared to DH500?
Improved low-temperature toughness: Impact energy at -40°C is increased from 34 J in DH500 to 42 J, with an NDT temperature ≤ -60°C;
Alloy system upgrade: Ni content is increased to 1.5%-2.0%, and 0.1%-0.2% rare earth elements are added to optimize grain boundaries;
Process innovation: Ultra-rapid cooling (UFC) combined with two-phase quenching is used to achieve a prior austenite grain size of ASTM Grade 12.
4. What special process controls are required for processing EH500? Welding Technology:
E-grade special welding consumables (such as AWS E13018-G) must be used, with a preheat temperature ≥ 180°C.
Narrow-gap laser-arc hybrid welding is used with controlled heat input (15-30 kJ/cm2).
Forming Process: Cold bending is prohibited; intermediate-temperature forming (400-600°C) or hydraulic hot bending is required.
Post-weld Treatment: All welds must undergo a stress relief annealing at 600°C for 4 hours, accompanied by neutron diffraction residual stress testing.
5. How is the extreme performance of the EH500 verified? What are the key test items? Full Lifecycle Testing System:
Chemical Composition: C ≤ 0.10%, P ≤ 0.010%, S ≤ 0.005%, O ≤ 10ppm;
-40°C Test Series: Including impact, CTOD (δ ≥ 0.25mm), and DWTT (SA ≥ 80%);
Non-destructive Testing:
100% full-section industrial CT scanning for microscopic defects;
3D residual stress mapping analysis (synchrotron radiation method).
