Chemical Composition and Mechanical Properties of Q345R Pressure Vessel Steel
Q345R is a Chinese pressure vessel steel grade specified in GB/T 713, widely used for boilers and pressure vessels. This page provides the chemical composition, mechanical properties, and high-temperature performance of Q345R steel plates.
Grade designation method:The grades of carbon steel and low-alloy high-strength steel are indicated by the yield strength value and the first letter of the Chinese pinyin for "yield" and the first letter of the Chinese pinyin for "pressure vessel," for example: Q345R.
Q345R Approximate Grade Lookup Table
Q345R Chemical Composition
| Grade | Chemical Composition (%) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| C | Si | Mn | Cu | Ni | Cr | Mo | Nb | V | Ti | Alt | P | S | Others | ||
| Q345R | ≤0.20 | ≤0.55 | 1.20–1.70 | ≤0.30 | ≤0.30 | ≤0.30 | ≤0.08 | ≤0.050 | ≤0.050 | ≤0.030 | - | ≤0.025 | ≤0.010 | Cu+Ni+Cr+Mo ≤0.70 | |
Notes:
a) The lower limit of carbon content may be waived by agreement between supplier and buyer.
b) Aluminum content is not required unless otherwise specified.
7.1.2 For Q345R and Q370R steel plates with a thickness greater than 60 mm, the upper limit of carbon content can be increased to 0.22% and 0.20% respectively; for Q245R steel plates with a thickness greater than 60 mm, the upper limit of manganese content can be increased to 1.20%.
7.1.3 Trace amounts of niobium, vanadium, and titanium may be added to Q245R steel. The content of these elements should be specified in the quality certificate. The total content of these three elements should not exceed 0.050%, 0.120%, and 0.150%, respectively.
7.1.4 As required by the buyer, the nitrogen content of Q420R and Q460R steel plates shall not exceed 0.020% and 0.025%, respectively.
7.1.5 According to the buyer's requirements, an appropriate amount of rare earth elements may be added to 07Cr2AlMoR steel.
7.1.6 The content of residual elements chromium, nickel, and copper should not exceed 0.30% each, and molybdenum should not exceed 0.080%, with the total content of these elements not exceeding 0.70%. Analysis is not required if the supplier can guarantee this.
7.1.7 According to the buyer's requirements, the carbon equivalent of the Q245R grade can be specified, and the value shall be determined through negotiation between the supplier and the buyer.
7.1.8 The permissible deviation of the chemical composition of finished steel products shall comply with the provisions of CB/T 713.1.
7.1.9 For a comparison of similar grades with relevant international standards, please refer to Appendix A.
7.3Delivery status
7.3.1 The delivery condition of steel plates and strips shall be as specified in Table 2.
7.3.2 The tempering temperature of 18MnMoNbR and 13MnNiMoR steel plates shall not be lower than 620℃, the tempering temperature of 15CrMoR and 14Cr1MoR steel plates shall not be lower than 650℃, and the tempering temperature of 12Cr2Mo1R, 12Cr1MoVR, 12Cr2Me1VR and 0.7Cr2AlMoR steel plates shall not be lower than 680℃.
7.3.3 With the consent of the purchaser, steel plates with a thickness greater than 50 mm that have been normalized and tempered may be delivered after normalizing (accelerated cooling is permitted) and tempering.
Q345R Mechanical Properties
| Thickness (mm) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Impact Test (0°C, J) | Bending Test |
|---|---|---|---|---|---|
| 3–16 | 510–640 | 345 | 21 | 41 | D = 2a |
| >16–36 | 500–630 | 325 | 21 | 41 | D = 3a |
| >36–60 | 490–620 | 315 | 21 | 41 | D = 3a |
D = bending indenter diameter; a = specimen thickness. When yield point is not obvious, Rp0.2 may be used instead.
7.4.1 The general requirements for the mechanical and technological properties of steel plates shall comply with the provisions of GB/T 713.1.
7.4.2 The results of the tensile test, Charpy (V-notch) impact test and bending test of the steel plate shall conform to the provisions of Table 2.
7.4.3 For steel plates with a thickness greater than 60 mm, bending tests may be waived upon agreement between the supplier and the buyer and as specified in the contract.
7.4.4 For chromium-molybdenum alloy steel plates used in hydrogen production equipment, the mechanical properties shall comply with the provisions of Appendix B.
7.4.5 According to the buyer's requirements, Q245R, Q345R and 13MnNiMoR grade steels can be subjected to an impact test at -20℃ instead of the 0℃ impact test in Table 2, and their impact absorption energy values shall meet the requirements of Table 2.
7.4.6 Upon the buyer's request, high-temperature tensile tests may be conducted on steel plates with a thickness greater than 20 mm. The test temperature shall be specified in the contract. The specified plastic elongation strength (Rpo.2) or lower yield strength (RL) at high temperature shall conform to the provisions of Table 3.
7.4.7 A thickness direction tensile test may be conducted upon the buyer's request, and the technical requirements shall be specified in the contract.
7.4.8 Drop hammer test may be conducted upon the buyer's request, and the technical requirements shall be specified in the contract.
Q345R High-Temperature Mechanical Properties
| Thickness (mm) | 100°C | 200°C | 300°C | 400°C | 500°C |
|---|---|---|---|---|---|
| 20–36 | 295 | 255 | 215 | 190 | 180 |
| 60–100 | 275 | 225 | 185 | 165 | 155 |
ᵃ When the yielding phenomenon is not obvious, the specified plastic elongation strength Rp0.2 can be used instead.
7.5 Hydrogen-induced cracking resistance test
Additional technical requirements for non-alloy steels and alloy steels for hydrogen-induced cracking (HIC) applications may be specified as required by the buyer. The specific requirements shall comply with the provisions of Appendix C, and the qualification level shall be indicated in the contract.
7.6 Non-destructive testing
As required by the buyer, each steel plate and strip shall be subjected to ultrasonic testing, and the testing method shall be in accordance with the provisions of NB/T 47013.3. The qualification level shall be specified in the contract.
7.7 Surface Quality
The surface quality of steel plates and strips shall conform to the requirements of GB/T 713.1.
7.8 Other Additional Requirements
Additional technical requirements for chromium-molybdenum steel plates used in hydrogen-contaminated equipment may be specified upon the request of the buyer and as agreed upon by both parties and noted in the contract. For chromium-molybdenum alloy steel plates used in hydrogen-contaminated equipment, the chemical composition should meet the requirements of Table 1 and Appendix B.