Chemical composition and mechanical properties of 18MnMoNbR, a pressure vessel steel grade in China.
18MnMoNbR Closer 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
18MnMoNbR ≤0.21 0.15~0.50 1.20~1.60 ≤0.30 ≤0.30 ≤0.30 0.45~0.65 0.025~0.050 　 　 　 ≤0.020 ≤0.010 　

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.
7.1.8  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.

Table 2  Mechanical properties and processing properties

Grade Delivery status Thickness mm Tensile test Impact test 180°Bending test b=2a
Tensile strengthRm/MPa Lower yield strengthReL/MPa Elongation after fractureA/% Temperature/℃ Impact absorption energy KV2/J
≥ 　 ≥
18MnMoNbR Normalizing+
Tempering		 30～60 570～720 400 18 0 47 D=3a
>60～100 390

Note: D is the diameter of the bending indenter; b is the width of the sample; a is the thickness of the sample.
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(or Rp0.2)/MPa,≥
18MnMoNbR 30～60 375 365 360 355 350 340 310 275 　
>60～100 370 360 355 350 345 335 305 270 　

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