Q345R is a specialized Chinese low-alloy high-strength steel designed for boilers and pressure vessels per the GB/T 713 standard.
Key Specifications
"Q": Stands for Qu (Yield point).
"345": Represents the minimum yield strength of 345 MPa for thin plates.
"R": Stands for Rong (Pressure vessel).
Q345R Chemical composition
|
Grade |
C % |
Si % |
Mn % |
Cu % |
Ni % |
Cr% |
Mo % |
V % |
|
Q345R |
0.20 |
0.55 |
1.2-1.7 |
0.30 |
0.30 |
0.30 |
0.08 |
0.050 |
|
Ti % |
Alt % |
P % |
S % |
Nb |
|
|
|
|
|
0.030 |
0.020 |
0.025 |
0.010 |
0.050 |
|
|
|
Q345R Mechanical Property
|
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 |
|
Mechanical Property Advantages
High Strength:
With a minimum yield strength of 345 MPa (for thin plates)-significantly higher than ordinary carbon steel like Q245R (235 MPa)-Q345R can withstand higher pressures. This allows for the design of safer and potentially thinner pressure vessel walls.
Excellent Comprehensive Toughness and Plasticity:
Q345R exhibits high elongation and impact toughness. It guarantees specific impact energy values at 0°C or lower (depending on the grade), ensuring reliability and resistance to brittle fracture across various operating conditions.
Stable Performance:
This steel maintains stable mechanical properties at both room temperature and medium-to-high temperatures, making it suitable for long-term operation within a temperature range typically below 450°C.
Process and Application Advantages
Superior Welding Performance:
Due to its low carbon content and strictly controlled impurities-such as Phosphorus (P) and Sulfur (S)-Q345R offers excellent weldability. This minimizes the risk of weld cracking and facilitates the fabrication of large, complex welded structures.
Cost-Effectiveness:
Compared to traditional steels, equipment manufactured with Q345R can achieve a weight reduction of 15-20%, thereby improving material utilization and overall economic efficiency.
Corrosion Resistance:
Through optimized alloy composition and manufacturing processes, Q345R can form a dense oxide film on its surface, providing resistance against general corrosion, pitting, and oxidation.
Resistance to Hydrogen-Induced Cracking (HIC):
Specific grades, such as Q345R(HIC), are specially designed and tested to effectively resist hydrogen-induced cracking, making them ideal for environments containing corrosive media like hydrogen sulfide (H₂S).
Standardization and Wide Availability:
As the most widely used pressure vessel steel plate in China, it complies with the rigorous GB/T 713 standard. Its mature production and application history ensure easy procurement and reliable quality control.
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What is the delivery state of Q345R?
The standard delivery state of Q345R is normalizing (N). For special needs, it can also be delivered in hot-rolled (AR) state, but normalizing is preferred to ensure stable mechanical properties.
Can Q345R be bent or formed?
Q345R has good formability and can be bent, rolled and formed by cold or hot processing. The forming process should avoid excessive deformation to prevent cracks and ensure the dimensional accuracy of components.
What is the difference between Q345R and Q245R?
The main difference is yield strength: Q345R is 345 MPa, Q245R is 245 MPa. Q345R has higher strength, suitable for higher pressure vessels; Q245R is for low-pressure conditions, with lower cost.
How to store Q345R steel plates?
Q345R steel plates should be stored in a dry, ventilated warehouse to avoid moisture and rust. They should be placed on wooden pallets, away from corrosive substances, and covered with waterproof cloth if stored outdoors.
Can Q345R be used for high-pressure vessels?
Yes, Q345R is suitable for manufacturing medium and high-pressure vessels. Its high yield strength and good toughness can withstand the pressure load of high-pressure working conditions, but it needs to be designed and inspected in accordance with standards.
What is the grain size requirement of Q345R?
Q345R requires uniform grain size, usually not coarser than grade 5 (according to GB/T 6394). Fine grains can improve the steel's toughness and strength, reducing the risk of brittle fracture.
Is Q345R resistant to corrosion?
Q345R has general corrosion resistance in atmospheric and mild environments. For corrosive media (like acid, alkali), it needs anti-corrosion treatment (such as painting, galvanizing, lining) to extend service life.
What is the welding material matching Q345R?
Welding materials matching Q345R include E50 series electrodes (for manual arc welding), ER50-6 welding wire (for gas metal arc welding), etc. The welding material should have similar strength and toughness to the base metal.
Can Q345R be used at high temperatures?
Q345R can be used at medium and low temperatures, generally up to 450℃. At higher temperatures, its strength will decrease, so it is not suitable for long-term use in high-temperature environments above 450℃.
What certificates are required for Q345R supply?
Q345R supply requires a quality certificate (including chemical composition, mechanical properties, inspection results), and ultrasonic flaw detection report if needed. The certificate must comply with GB/T 713-2014 standard.