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What is Q420GJD construction steel

1. In terms of the material Q420GJD, it is obvious that it is high-grade steel, executing the Chinese national standard GB/T 19879.

2. Q420GJD construction steel heat treatment process includes: hot rolling, normalizing, normalizing and tempering, TMCP, TMCP+tempering, quenching and tempering. The heat treatment state can be selected according to the design.

3. The grades of Q420GJD tear resistance in the thickness direction indicate: Q420GJD-Z15, Q420GJD-Z25, Q420GJD-Z35.

4. Q420GJD construction steel smelting composition:

C Si Mn P S Vb NBb Tib ALsa Cr Cu Ni Mo
                   
0.2 0.55 ≤1.70 0.025 0.015 0.2 0.07 0.03 0.015 0.8 0.3 1 0.5

5. Q420GJD steel carbon equivalent and crack sensitivity index

Heat treatment state Carbon equivalent under specified thickness CE/% Weld crack sensitivity index under specified thickness Pcm/%
≤50mm >50-100mm ≤50mm >50-100mm
AR\N\NR\N+T ≤0.48 ≤0.50 ≤0.31 ≤0.33
TMCP ≤0.43 - ≤0.29 -

6. Q420GJD steel mechanical properties:

Yield strength ReL(N/mm2) Tensile strength Rm/(N/mm2) Elongation A/% Impact energy (longitudinal) Akv/J 180○ bending test
d=Bend center diameter
a=The thickness of the sample
the yield ratio is not greater than
Steel plate thickness/mm
6-16 >16-35 >35-50 >50-100 Temperature ℃ not less than Steel plate thickness/mm
≤16 >16
≥420 420-550 410-540 400-530 520-680 ≥19   34 d=2a d=3a 0.85
-20
 

7. Sulfur content (mass fraction) corresponding to different thickness direction performance levels of Q420GJD construction steel:
Z15: ≤0.010; Z25: ≤0.007; Z35: ≤0.005; Unit: %.

8. Generally speaking, in high-rise buildings, Q420GJD steel plates have complex forces, and different thicknesses have relatively different corresponding technical processes.

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