Chemical element composition of Chinese grade Q420NC low alloy high strength structural steel
Q420NC Approximate Grade Lookup Table

Grade Chemical Composition（Quality Fraction）/ %
Steel grade Quality grade C Si Mn Pᵃ Sᵃ Nb V Tiᶜ Cr Ni Cu Mo N Alsᵈ≥
≤ ≤ ≤
Q420N C 0.2 0.6 1~1.7 0.03 0.03 0.01~0.05 0.01~0.2 0.006~0.05 0.3 0.8 0.4 0.1 0.015 0.015
The steel should contain at least one of the grain-refining elements such as aluminum, niobium, vanadium, and titanium. When added alone or in combination, the content of at least one alloying element should not be less than the lower limit specified in the table.
a.For structural steel and bar stock, the upper limit for phosphorus and sulfur content can be increased by 0.005%.
b.V+Nb+Ti≤0.22%,Mo+Cr≤0.30%。
c.It can be as high as 0.20%.
d.All-aluminum (Alt) can be used as a substitute, in which case the minimum content of all-aluminum is 0.020%. When grain-refining elements such as niobium, vanadium, and titanium are added to the steel and their content is not less than the lower limit specified in the table, there is no limit to the lower limit of aluminum content.

Table 2  Tensile properties

Grade Upper yield strength ReHᵃ/MPA≥ Tensile strength Rｍ/MPA Elongation after fracture A/％≥ KV2(J)
Steel grade Quality grade Nominal thickness or diameter/ｍｍ 0℃
≤16 ＞16~40 ＞40~63 ＞63~80 ＞80~100 ＞100~150 ＞150~200 ＞200~250 ≤100 ＞100~200 ＞200~250 ≤16 ＞16~40 ＞40~63 ＞63~80 ＞80~200 ＞200~250 Vertical Horizontal
Q420N C 420 400 390 370 360 340 330 320 520~680 500~650 500~650 19 19 19 18 18 18 34 27
Note: Normalized condition includes normalized + tempered condition. a. When yield strength is not obvious, the specified plastic elongation strength Rp0.2 can be used instead of the upper yield strength ReH.