Introduction to ABS Grade AQ70 Steel Plate
In the competitive shipbuilding industry, achieving the perfect balance of strength, weight, and fabrication cost is a constant challenge. ABS Grade AQ70 Steel Plate emerges as a superior solution, offering the high tensile strength of 70 ksi (690 MPa) through the advanced Thermo-Mechanical Control Process (TMCP). Unlike its quenched and tempered counterpart (EQ70), AQ70 achieves its remarkable properties during the rolling and controlled cooling phases, resulting in a steel that is not only strong and tough but also boasts exceptional weldability.
At IBC Group, we specialize in supplying certified ABS AQ70 plates to shipyards globally, enabling the construction of lighter, stronger, and more fuel-efficient vessels without compromising on safety or significantly increasing fabrication costs.
ABS Grade AQ70 Chemical Composition
The chemical composition of AQ70 is designed to be “lean” and weld-friendly. The TMCP process relies less on high levels of carbon and alloying elements for strength, and more on the microstructural refinement achieved through controlled deformation and cooling. This results in a lower Carbon Equivalent (Ceq), which is a critical advantage.
A typical chemical composition range for AQ70 is as follows:
| C max | Si max | Mn | P max | S max | N max. |
| 0.21 | 0.55 | 1.70 | 0.030 | 0.030 | 0.020 |
ABS Grade AQ70 Mechanical Property
AQ70 is required to meet the same stringent room-temperature mechanical properties as EQ70, ensuring structural performance in marine environments.
| Yield Strength (MPa) min. | Tensile Strength (MPa) | Elongation min. % |
| 690 | 770-940 | 14 |
Key Characteristics Explained:
High Strength from TMCP: The Thermo-Mechanical Control Process refines the steel’s grain structure to an ultra-fine level. This grain refinement is the key mechanism that simultaneously increases both strength and toughness.
Excellent Low-Temperature Toughness: Like EQ70, AQ70 is mandated to possess high impact energy at -40°C, making it suitable for vessels operating in cold climates and ice-free zones of Arctic waters.
AQ70 vs. EQ70: The Core Distinction
While both grades share the same mechanical property targets, their production process defines their key differences:
| Feature | AQ70 (TMCP) | EQ70 (Quenched & Tempered) |
| Production Process | Thermo-Mechanical Control Process | Quenching + Tempering |
| Weldability | Excellent (Lower Ceq/Pcm) | Good (Higher Ceq/Pcm) |
| Primary Advantage | Ease of fabrication, cost-effective welding | Superior through-thickness performance (Z-quality), better for highly constrained structures |
| Best For | Large panel structures, hull plating, where welding efficiency is key | Critical, highly stressed components, areas requiring high Z-direction properties |
ABS Grade AQ70 Application
The combination of high strength, good toughness, and excellent weldability makes AQ70 ideally suited for a wide range of marine structures where weight reduction and fabrication efficiency are priorities.
Primary Applications Include:
Hull Plating for Large Vessels: Used in the deck and bottom plating of large container ships, bulk carriers, and tankers. The use of AQ70 allows for thinner plates, reducing overall steel weight and improving cargo capacity and fuel efficiency.
Longitudinal and Transverse Strengthening Members: Such as girders and stringers, where its high strength is effectively utilized.
Offshore Module Support Structures: Used in non-critical areas of offshore platforms where high strength and easy weldability are beneficial.
General High-Strength Applications: In any ship structure where the specification calls for 70 ksi yield strength and the superior weldability of TMCP steel offers a fabrication advantage over Q&T steel.
Why Source ABS AQ70 from IBC Group?
Choosing IBC Group as your ABS AQ70 supplier means partnering with a team that understands both the material science and the practical demands of shipbuilding.
Expertise in TMCP Steels: We provide expert guidance on the benefits and optimal applications of AQ70, helping you maximize its cost and performance advantages in your projects.
Certified Quality Assurance: Every plate we supply comes with full traceability and the necessary ABS certification and Mill Test Certificates (MTC 3.1), guaranteeing compliance with all mechanical and chemical requirements.
Optimized Supply for Shipyards: We understand the critical importance of welding in shipbuilding schedules. By supplying AQ70, we help you reduce pre-heat costs and increase welding speed, directly impacting your project’s bottom line.
Global Logistics Network: We ensure reliable and timely delivery to shipyards across the globe, supporting your just-in-time production needs.
Conclusion
ABS Grade AQ70 Shipbuilding Steel Plate represents the modern evolution of high-strength steel, where advanced manufacturing processes like TMCP deliver exceptional performance while simplifying fabrication. It is the intelligent choice for shipbuilders aiming to enhance vessel efficiency without incurring the high welding costs associated with traditional Q&T grades.
For a reliable supply of fully certified ABS Grade AQ70 steel plate and expert advice on its application, contact IBC Group today. Let us help you build stronger, lighter, and more efficient vessels with the power of Thermo-Mechanical Control Process steel.