1. What is the basic definition and core properties of AH620 steel pipe?
AH620 is a Class A ultra-high-strength hull structural steel in the GB/T 712-2023 standard. Its core properties include:
Yield strength ≥ 620 MPa and tensile strength 720-890 MPa, making it suitable for ultra-high stress structures in ultra-large ships and offshore engineering;
-20°C low-temperature impact toughness (KV2 ≥ 34 J), meeting the requirements of conventional low-temperature environments;
A balance of high strength and weldability is achieved through Nb-V-Ti-Mo composite microalloying and the controlled rolling and controlled cooling (TMCP) process.
2. What are the main applications of AH620 steel pipe?
Ultra-large container ships: For example, the decks and side plating of 40,000 TEU vessels, along with other critical load-bearing areas;
Deepwater oil and gas equipment: For ultra-high-load structures such as pile legs and cantilever beams on semi-submersible drilling platforms;
Conventional waters: For example, the hull frames of FPSOs (Floating Production Storage and Offloading) vessels, adapting to most shipping environments.
3. What technical improvements does the AH620 offer compared to the AH550?
Strength upgrade: Yield strength increased from 550 MPa to 620 MPa, resulting in significant weight reduction;
Welding optimization: Low carbon equivalent design (CEV ≤ 0.52%) reduces the risk of cold cracking in high-strength steel welds;
Economic efficiency: Under the same load, material usage can be reduced by approximately 12% compared to the AH550, reducing costs.
4. What key points should be considered when processing and welding AH620 steel pipe? Welding Process: Low-hydrogen electrodes (such as AWS E14018-G) are recommended, with a preheat temperature of 160-200°C (higher for plate thickness > 30mm).
Cold Forming Control: A bend radius of ≥ 5 times the wall thickness is recommended to avoid cold deformation and microcracks.
Post-weld Inspection: 100% ultrasonic testing (UT) and magnetic particle testing (MT) are required for critical welds.
5. How is AH620 steel pipe inspected? What are the key inspection indicators? Marking Verification: The steel pipe surface must be marked with "AH620," the GB/T 712 standard number, the batch number, and the manufacturer's information.
Performance Testing: The Material Certificate (MTC) must include:
Chemical composition (e.g., C ≤ 0.16%, Mn ≤ 1.80%);
Mechanical properties (yield strength ≥ 620 MPa, tensile strength 720-890 MPa);
-20°C impact test data (average of three specimens ≥ 34 J, single specimen ≥ 24 J);
Non-destructive Testing: UT/MT/RT sampling or full inspection will be conducted based on project requirements.
