Q345R is a low-alloy high-strength boiler and pressure vessel steel. It is mainly used to manufacture pressure-bearing equipment such as boilers, storage tanks, and pressure vessels, suitable for high-temperature and high-pressure working environments.
Nomenclature and Standards
"Q" (Qu): Represents the yield strength.
"345": Indicates a minimum yield strength of 345 MPa (for plate thickness ≤16mm).
"R" (Rong): Signifies its designation for pressure vessels (Rongqi).
Historical Context: This grade was established by merging several older grades, including 16MnR, 16Mng, and 19Mng, to unify the standards for boiler and pressure vessel steel.
Q345R Steel Plate Chemical Composition:
| Steel Grade | C % | Si % | Mn % | Cu % | Ni % | Cr% | Mo % | V % | Ti % | Alt % | P % | S % | Nb |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Q345R | 0.20 | 0.55 | 1.2-1.7 | 0.30 | 0.30 | 0.30 | 0.08 | 0.050 | 0.030 | 0.020 | 0.025 | 0.010 | 0.050 |
Q345R Steel Plate Mechanical Property:
| Steel Grade | Thickness(mm) | Min Yield | Tensile | Elongation | Min Impact Energy | |
|---|---|---|---|---|---|---|
| Degree | Min J | |||||
| Q345R | 3-16 | 345Mpa | 510-640 Mpa | 21% | 0 | 41J |
| 16-36 | 325Mpa | 500-630 Mpa | 21% | 0 | 41J | |
| 36-60 | 315 Mpa | 490-620 Mpa | 21% | 0 | 41J | |
| 60-100 | 305 Mpa | 490-620 Mpa | 20% | 0 | 41J | |
| 100-150 | 285 Mpa | 480-610 Mpa | 20% | 0 | 41J | |
| 150-250 | 265 Mpa | 470-600 Mpa | 20% | 0 | 41J | |
Q345R Processing Flow
Raw Material Preparation:
Select Q345R steel plates that meet GB 713 standards, check dimensions (thickness, width, length) and quality certificates to ensure compliance with processing requirements.
Cutting and Blanking:
Adopt flame cutting, plasma cutting or shearing to cut the steel plates into the required shape and size according to the design drawings, and remove burrs and sharp edges after cutting.
Forming Processing:
Use bending, rolling or pressing equipment to shape the blank into the desired structure (e.g., cylinder, header, curved plate) for pressure vessel and boiler components.
Welding Operation:
Perform welding via SMAW, GMAW or SAW. Conduct pre-welding preheating (60-150℃) and post-weld heat treatment (PWHT) for thick plates to eliminate stress and ensure weld quality.
Surface Treatment:
Remove welding spatter, rust and oil stains through grinding, pickling or shot blasting to improve surface cleanliness and corrosion resistance.
Inspection and Testing: Carry out non-destructive testing (UT, RT, MT) on welds and base metal, and verify dimensional accuracy and appearance quality to confirm compliance with application standards.
Final Finishing and Delivery:
Perform final trimming, coating (if required) and packaging, then deliver qualified products after passing comprehensive inspection.
applications
Boiler and pressure vessel fabrication:
Q345R is widely used for key pressure-bearing components such as boiler drums, headers, water walls, and economizers, as well as for general pressure vessels requiring reliable strength, toughness, and weldability under medium-temperature and medium-pressure conditions.
Petrochemical and chemical industry equipment:
It is commonly applied in storage tanks, reaction vessels, heat exchangers, and separators that handle oil, gas, and various chemical media, providing good structural integrity and process compatibility.
Power generation systems:
Q345R is used in thermal power plants and nuclear power auxiliary equipment (non-core pressure parts) for components that operate under elevated temperatures and cyclic loading, where stable mechanical properties are essential.
Pipeline and process plant infrastructure:
It serves in low- to medium-pressure pipelines, pipe supports, and pressure-containing structures in refineries, gas processing plants, and industrial facilities, often combined with welding-intensive fabrication.
Marine and heavy machinery:
Q345R is suitable for marine pressure vessels, offshore auxiliary equipment, and hydraulic tanks in heavy machinery, leveraging its good formability and weldability to meet complex structural and safety requirements.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
Can Q345R steel be used in hydrogen-containing environments?
Q345R can be used in low-pressure hydrogen-containing environments, but it needs to avoid hydrogen embrittlement. It is necessary to control the hydrogen partial pressure, temperature and stress, and conduct hydrogen embrittlement testing if necessary to ensure safe operation.
What is the coefficient of thermal expansion of Q345R steel?
The coefficient of thermal expansion of Q345R is about 12×10^-6 /℃ (20℃ to 100℃). This parameter is crucial for thermal stress calculation in equipment design, avoiding structural damage due to thermal expansion and contraction.
What are the delivery states of Q345R steel plates?
The common delivery states of Q345R are normalizing (N), annealing (A) or hot rolling (AR). Normalizing is the most common state, which ensures uniform structure and stable mechanical properties, meeting pressure vessel requirements.
How to judge the quality of Q345R steel plates?
Judge Q345R quality by checking chemical composition (via spectrum analysis), mechanical properties (tensile, impact tests), surface quality, internal defects (ultrasonic testing), and verifying compliance with GB/T 713-2014 standard.
Can Q345R steel be welded with stainless steel?
Yes, Q345R can be welded with stainless steel, but it is necessary to use transition electrodes or fillers to avoid carbon migration and brittle phases. Control welding parameters strictly to ensure weld strength and corrosion resistance.
What is the service life of Q345R pressure vessels under normal working conditions?
Under normal working conditions (compliant with design, installation and maintenance requirements), the service life of Q345R pressure vessels is usually 10-15 years. Regular inspection and maintenance can extend its service life appropriately.
What is the density of Q345R steel?
The density of Q345R steel is about 7.85 g/cm³, the same as ordinary carbon steel and most low-alloy steels. This density value is used for weight calculation in equipment design, transportation and installation.
What are the precautions for storing Q345R steel plates?
Store Q345R plates in a dry, well-ventilated warehouse to avoid moisture and corrosion. Stack them neatly with padding between layers, away from chemicals. Avoid mechanical damage to the surface and mark clearly for easy identification.
Can Q345R steel be used in high-temperature pressure vessels? What is the maximum temperature limit?
Q345R can be used in high-temperature pressure vessels, with a general maximum temperature limit of 450℃. Beyond this temperature, its strength will decrease significantly, and high-temperature alloy steel should be used instead to ensure safety.
What is the role of manganese (Mn) in Q345R steel?
Manganese is a key alloying element in Q345R. It improves the steel's strength and toughness by solid solution strengthening, refines grains, and reduces the harmful effects of sulfur. The Mn content is usually controlled between 1.20% and 1.60%.