Chemical composition and mechanical properties of Q345R, a Chinese grade of  pressure vessel steel.
Q345R Approximate Grade Lookup Table

Table 1  Chemical Composition

Grade Chemical Composition(Quality Fraction)/%
C Si Mn Cu Ni Cr Mo Nb V Ti Altb 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
≤0.7c

7.1.2    For Q345R 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 Q345R 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.                
7.1.6 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 Q345R 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 GB/T 713.1.                
7.1.9  For a comparison of similar grades with relevant international standards, please refer to Appendix A.

Table 2  Mechanical properties and processing properties

Grade delivery status Thickness mm Tensile test Impact test 180°Bending testb=2a
Tensile strengthRm/MPa Lower yield strengthReL/MPa Elongation after fractureA/% Temperature/℃ Impact absorption energy KV2/J
≥ 　 ≥
Q345R Hot rolled 、
Normalizing rolling、
Normalizing or
Normalizing + Tempering		 3～16 510～640 345 21 0 41 D=2a
>16～36 500～630 325 D=3a
>36～60 490～620 315
>60～100 490～620 305 20
>100～150 480～610 285
>150～250 470～600 265

Note: D is the diameter of the bending indenter; b is the width of the specimen; a is the thickness of the specimen. When the yielding phenomenon is not obvious, the specified plastic elongation strength Rp0.2 can be used instead.

Table 3  High temperature mechanical properties

Grade Thickness/mm Test temperature/℃
100 150 200 250 300 350 400 450 500
ReLᵃ(orRp0.2)/MPa,≥
Q345R >20～36 295 275 255 235 215 200 190 180 　
>36～60 285 260 240 220 200 185 175 165 —
>60～100 275 250 225 205 185 175 165 155 　
>100～150 260 240 220 200 180 170 160 150 一
>150～250 245 230 215 195 175 165 155 145  

ᵃ When the yielding phenomenon is not obvious, the specified plastic elongation strength Rp0.2 can be used instead.