In the world of modern engineering and fabrication, the demand for high-strength, weldable, and durable steels has never been greater. Among these advanced materials, P690 grade steel stands out as one of the most reliable options for heavy-duty structural applications. This article by SAKYSTEEL explores the definition, composition, properties, and applications of P690 steel, helping engineers, fabricators, and project managers understand why this grade has become a preferred choice in pressure vessels, offshore platforms, and high-strength structures.
P690 is a high-strength quenched and tempered steel primarily used in the fabrication of pressure vessels, boilers, and heavy structural components. The “P” in its name denotes pressure vessel steel, while the number “690” refers to its minimum yield strength of 690 MPa, which is exceptionally high compared to conventional structural steels.
This material is part of the EN 10028-6 standard, which defines steels for pressure purposes that undergo quenched and tempered (QT) heat treatment. Due to its superior mechanical performance and consistent weldability, P690 is widely adopted in energy, petrochemical, offshore, and defense sectors.
Key Characteristics:
Minimum yield strength: 690 MPa
Tensile strength range: 770–940 MPa
Heat treatment: Quenched and tempered
Excellent toughness at low temperatures
Good weldability with controlled preheating and post-weld treatment
At SAKYSTEEL, we supply P690Q, P690QL, and P690QL2 variants, offering different impact toughness grades suited for a variety of service environments.
P690 is classified into three sub-grades based on impact testing temperature requirements:
| Grade | Designation | Minimum Impact Test Temperature | Typical Application |
|---|---|---|---|
| P690Q | Quenched & Tempered | 0°C | General pressure vessels |
| P690QL | Quenched & Tempered (Low temperature) | -40°C | Offshore & cryogenic |
| P690QL2 | Quenched & Tempered (Extra low temperature) | -60°C | Arctic & sub-zero environments |
All these grades conform to EN 10028-6 and may also be supplied to ASME/ASTM equivalents on request. Each plate or component from SAKYSTEEL is fully traceable, supplied with a 3.1 or 3.2 EN 10204 certificate, and tested according to international standards.
The chemical composition of P690 steel is carefully balanced to achieve high strength without sacrificing weldability or toughness. A typical range is shown below:
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.18 max |
| Silicon (Si) | 0.50 max |
| Manganese (Mn) | 0.60–1.70 |
| Phosphorus (P) | 0.025 max |
| Sulfur (S) | 0.015 max |
| Chromium (Cr) | 1.00–2.00 |
| Nickel (Ni) | 1.00–2.00 |
| Molybdenum (Mo) | 0.30–0.70 |
| Vanadium (V) | 0.08–0.20 |
The alloying combination of Ni, Cr, and Mo provides excellent hardenability and corrosion resistance, while low carbon content ensures good weldability.
The key feature of P690 grade steel is its exceptional mechanical performance. After quenching and tempering, the material delivers a balance of high yield strength, tensile strength, and toughness that make it ideal for extreme service conditions.
| Property | Typical Value |
|---|---|
| Yield Strength (MPa) | ≥690 |
| Tensile Strength (MPa) | 770–940 |
| Elongation (%) | 14–16 |
| Impact Energy (Charpy V-notch) | ≥60 J at specified temperature |
| Hardness (HBW) | ≤ 300 |
Even under low-temperature conditions, P690 maintains impact toughness and ductility, preventing brittle failure and ensuring long-term reliability.
Producing P690 grade steel requires advanced metallurgy and controlled heat treatment to achieve its fine-grained microstructure. The general process includes:
Primary Melting – Using Electric Arc Furnace (EAF) or Basic Oxygen Furnace (BOF).
Refining – Ladle Furnace (LF) and Vacuum Degassing (VD) to remove impurities.
Continuous Casting – Forming billets or slabs with uniform composition.
Hot Rolling – Plates are rolled to the desired thickness range (typically 6–120 mm).
Quenching – Rapid cooling to achieve martensitic structure.
Tempering – Controlled reheating to restore ductility and toughness.
Ultrasonic & Surface Testing – Ensuring flawless plates before dispatch.
SAKYSTEEL utilizes modern production lines to guarantee dimensional accuracy, surface finish, and mechanical consistency across every P690 batch.
Although P690 steel has high strength, it remains weldable using conventional processes such as SMAW, SAW, GTAW, or GMAW — provided that proper preheating and post-weld heat treatment (PWHT) procedures are followed.
Key Welding Recommendations:
Preheat to 150–200°C to reduce hydrogen cracking risk
Maintain interpass temperature below 250°C
Use low-hydrogen electrodes (e.g., E11018-G)
Conduct PWHT at 580–620°C for stress relief
Ensure slow cooling after welding to prevent hardness increase
Proper control during welding ensures sound joints with minimal risk of brittleness or loss of toughness.
The combination of high strength, excellent weldability, and impact toughness makes P690 ideal for demanding engineering environments. Common applications include:
Used in the oil, gas, and chemical industries for vessels that handle high internal pressures and corrosive media. Its superior yield strength allows for thinner walls, reducing weight and cost.
P690QL and P690QL2 grades are frequently used in offshore structural components, such as legs, braces, and jackets, where high toughness and low-temperature performance are critical.
High-temperature strength and stability make P690 suitable for boiler drums and heat exchanger shells operating under cyclic stress.
Used in load-bearing frames, lifting booms, and mechanical arms, P690 provides both high load capacity and resistance to fatigue failure.
In naval structures or defense vehicles, the strength-to-weight advantage of P690 improves protection while minimizing total mass.
Choosing P690 offers numerous performance and economic benefits compared with conventional steels such as P355 or P460.
Main Advantages:
High Strength: Allows thinner designs for the same load, reducing overall weight.
Excellent Weldability: Maintains joint integrity when properly treated.
Superior Toughness: Withstands dynamic and low-temperature impacts.
Enhanced Durability: Resists fatigue and stress corrosion cracking.
Cost Efficiency: Reduced material thickness leads to lower fabrication and transport costs.
Extended Service Life: Reliable performance under severe operating environments.
SAKYSTEEL provides customized P690 products that meet project-specific requirements — from plate thickness and surface finish to impact toughness and certification level.
| Property | P355 | P460 | P690 |
|---|---|---|---|
| Yield Strength (MPa) | 355 | 460 | 690 |
| Heat Treatment | Normalized | Normalized | Quenched & Tempered |
| Weldability | Excellent | Good | Controlled Preheat Required |
| Application | General vessels | Medium-pressure | High-pressure, offshore |
| Weight Efficiency | Moderate | Good | Excellent |
As shown, P690 provides almost double the yield strength of P355, allowing designers to create lighter yet stronger pressure vessels and offshore components.
Each plate and product supplied by SAKYSTEEL undergoes rigorous testing and inspection before delivery:
Ultrasonic testing (UT) and surface defect check
Tensile, impact, and hardness tests per EN 10028-6
Heat treatment verification (Q&T cycle records)
Dimensional inspection and flatness test
EN 10204 3.1 / 3.2 Certification
Third-party inspection (Lloyd’s, DNV, SGS, TUV) on request
SAKYSTEEL maintains full traceability from raw material to finished product, ensuring total confidence for every client.
P690 grade steel can be supplied in a range of product forms depending on project requirements:
Plates: 6–120 mm thickness
Forged blocks
Flanges and fittings
Rolled bars
Cut profiles and prefabricated shapes
Custom-machined components
Each is available with mill certificates, export packaging, and inspection reports ready for international shipment.
To preserve the mechanical integrity of P690 steel before fabrication, attention must be given to proper handling and storage:
Store plates in dry, covered areas to prevent corrosion.
Avoid stacking with dissimilar metals to prevent galvanic reactions.
Use soft lifting tools to prevent surface marks or dents.
Apply temporary protective oil film for long-term storage.
These practices help maintain surface quality and mechanical reliability until processing begins.
With decades of export experience, SAKYSTEEL serves clients in Europe, the Middle East, Southeast Asia, and South America. Our logistics team provides door-to-door delivery, supporting Incoterms such as FOB, CFR, CIF, and DAP.
We can also arrange:
Cut-to-size services
Custom export packaging
Express mill test certificate transmission
Flexible production schedules for urgent projects
SAKYSTEEL is committed to providing reliable materials and on-time delivery, helping our partners complete projects efficiently and confidently.
Q1: What is P690 used for?
A1: P690 is mainly used in pressure vessels, offshore structures, and high-strength load-bearing components requiring superior yield strength and toughness.
Q2: Is P690 weldable?
A2: Yes, it can be welded using conventional methods, but preheating and PWHT are necessary to prevent cracking.
Q3: What’s the difference between P690Q and P690QL2?
A3: The difference lies in impact test temperature — Q is tested at 0°C, QL at -40°C, and QL2 at -60°C.
Q4: Does SAKYSTEEL provide certification?
A4: Absolutely. All materials are delivered with EN 10204 3.1 or 3.2 certificates, and third-party inspection can be arranged on request.
Q5: Can P690 replace Inconel or Duplex steels?
A5: Not directly — P690 offers strength similar to some duplex grades but lacks their corrosion resistance. It is best for structural strength, not for aggressive chemical environments.
P690 grade steel represents the new generation of high-strength quenched and tempered materials designed for critical engineering applications. Its blend of 690 MPa yield strength, excellent toughness, and controlled weldability make it indispensable for pressure vessels, offshore platforms, and heavy structural components worldwide.
By choosing SAKYSTEEL, you gain access to:
Consistent quality certified to international standards
Customized production and inspection options
Global shipping and technical support
With continuous innovation and commitment to excellence, SAKYSTEEL remains your trusted partner in high-strength steel solutions.