P690QL1 is a high-strength quenched and tempered structural steel plate specified in the European standard EN 10025-6. It is primarily used in applications requiring high yield strength combined with good toughness and weldability, such as heavy machinery, offshore structures, pressure vessels, and large engineering components.
Executive Standard
P690QL1 is governed by the European standard EN 10025-6:2004, which covers high-strength structural steels in quenched and tempered conditions.
Grade Designation
The designation "P690QL1" can be interpreted as follows:
P – Mechanical properties apply to plates
690 – Minimum yield strength of 690 MPa
Q – Quenched and tempered (QT)
L1 – Impact toughness level (Charpy V-notch impact energy ≥ 27 J at -40°C)
Chemical composition % of steel P690QL1
| According EN 10216-3:2014: 1.2=< Mn=<1.7; P=<0.025; S=<0.015; Al=<0.02; |
| C | Si | Mn | Ni | P | S | Cr | Mo | V | N | Nb | Ti | Cu | Zr | B |
| max 0.2 | max 0.8 | max 1.7 | max 2.5 | max 0.02 | max 0.008 | max 1.5 | max 0.7 | max 0.12 | max 0.015 | max 0.06 | max 0.05 | max 0.3 | max 0.15 | max 0.005 |
Mechanical properties of steel P690QL1
| Nominal thickness (mm): | to 100 | 100 - 150 |
| Rm - Tensile strength (MPa) (+QT) | 770-940 | 720-900 |
| Nominal thickness (mm): | to 50 | 50 - 100 | 100 - 150 |
| ReH - Minimum yield strength (MPa) (+QT) | 690 | 670 | 630 |
| Nominal thickness(mm): | to 20 | 20 - 40 | 40 - 50 | 50 - 65 | 65 - 80 | 80 - 100 |
| Rp0.2 0.2% proof strength (MPa) (+QT) | 690 | 650 | 615 | 580 | 540 | 500 |
| KV - Impact energy (J) transverse, (+QT) | -40° 27 |
-20° 31-40 |
0° 39-60 |
+20° 43 |
| KV - Impact energy (J) longitud., (+QT) | -30° 40 |
-20° 47 |
-10° 53 |
0° 60 |
+20° 65 |
| A - Min. elongation at fracture (%) (+QT) | 14-16 |
process characteristics
1. Quenching and Tempering Process
P690QL1 steel is produced by a standard quenching and tempering (Q&T) process, which involves heating to the austenitization temperature, rapid cooling in water or oil, and subsequent tempering at a controlled temperature.
This process ensures a high-strength, fine-grained microstructure with good toughness and ductility.
2. Chemical Composition Control
The steel is smelted with strict control of chemical composition, including low carbon content and optimized amounts of chromium, nickel, and molybdenum.
These elements help reduce the carbon equivalent and improve weldability while maintaining high strength.
3. Controlled Rolling and Microstructure Refinement
Controlled rolling and accelerated cooling are applied to refine the grain size, resulting in excellent low-temperature toughness, especially at -40°C.
A fine-grained structure also contributes to higher strength and better resistance to brittle fracture.
4. Welding and Heat Treatment Requirements
Although P690QL1 has good weldability, preheating and interpass temperature control are usually necessary to prevent cold cracking.
Post-weld heat treatment is often recommended to restore toughness in the heat-affected zone and ensure structural integrity.
5. Quality Inspection
The manufacturing process includes ultrasonic testing, mechanical property testing, and strict dimensional control to meet EN 10028-6 standards.
These inspections ensure consistent quality and reliability for pressure vessel applications.
applications
Petrochemical and Chemical Industry
P690QL1 is widely used in the fabrication of pressure vessels, reactors, and storage tanks. These components operate under high pressure, high temperature, and corrosive conditions, and the steel's high yield strength, good toughness, and resistance to hydrogen-induced cracking ensure reliable performance and long service life.
Power Generation Sector
The steel is commonly applied in power plant boilers, including boiler drums, headers, and heat exchanger components. Its ability to withstand elevated pressures and temperatures, combined with excellent weldability, makes it suitable for critical power equipment that requires high structural integrity.
Cryogenic Applications
Due to its good low-temperature toughness (down to -40°C), P690QL1 is used in LNG storage tanks, cryogenic separators, and other equipment operating at extremely low temperatures. Its fine-grained microstructure ensures resistance to brittle fracture under cold conditions.
Offshore and Marine Engineering
P690QL1 is extensively employed in offshore platforms, subsea pipelines, and ship structures. These applications demand high strength, fatigue resistance, and corrosion resistance, all of which are provided by the steel's quenched and tempered microstructure and controlled chemical composition.
Nuclear Power Industry
The steel is used for key components in nuclear power plants where safety and reliability are paramount. Its consistent mechanical properties, excellent weldability, and ability to maintain performance under high stress make it suitable for reactor pressure vessels and related structures.
Heavy Machinery and Construction
P690QL1 is also utilized in heavy machinery, such as crane booms, hydraulic supports, and large structural components, where high strength and good formability are required to reduce weight while maintaining structural stability.
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What is P690QL1?
P690QL1 is a high-strength quenched and tempered alloy structural steel. It has excellent toughness, weldability and corrosion resistance, widely used in heavy machinery, construction and offshore engineering fields requiring high load-bearing capacity.
What are the main chemical components of P690QL1?
The main chemical components of P690QL1 include C, Si, Mn, P, S, Cr, Mo, Ni, etc. Strict control of impurity content (especially P and S) ensures its mechanical properties and processing performance.
What is the minimum yield strength of P690QL1?
The minimum yield strength of P690QL1 is 690 MPa, which is the key index that distinguishes it from ordinary structural steel. This high yield strength enables it to bear large loads in engineering applications.
What is the tensile strength range of P690QL1?
The tensile strength of P690QL1 generally ranges from 770 MPa to 940 MPa. This strength range ensures good ductility while maintaining high hardness, meeting the requirements of complex engineering environments.
What heat treatment process does P690QL1 undergo?
P690QL1 undergoes quenching and tempering heat treatment. Quenching improves hardness and strength, while tempering reduces brittleness and improves toughness, making the steel have balanced mechanical properties.
Is P690QL1 easy to weld?
Yes, P690QL1 has good weldability. Proper preheating (usually 80-150℃) and post-weld heat treatment can avoid weld cracks and ensure the strength and toughness of the weld joint.
What are the common applications of P690QL1?
P690QL1 is commonly used in manufacturing heavy machinery parts, construction machinery (such as excavator arms), offshore platforms, bridge supports and other structures that require high strength and durability.
What is the impact toughness of P690QL1?
P690QL1 has excellent impact toughness, especially at low temperatures. The impact energy at -20℃ is usually not less than 30 J, which can resist sudden impact loads in cold environments.
Can P690QL1 be used in low-temperature environments?
Yes, P690QL1 is suitable for low-temperature environments. Its good low-temperature toughness ensures that it will not become brittle or crack when working at temperatures as low as -20℃, adapting to cold area projects.
What is the hardness of P690QL1?
The hardness of P690QL1 (HB) is generally between 220 and 280. This hardness range balances wear resistance and machinability, making it easy to cut, drill and other processing operations.