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/%
Heat treatment state	≤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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