Grade	C	Si	Mn	P	S	Nb	V	Ti	Cr	Ni	Cu
20	0.17-0.23	0.17-0.37	0.35-0.65	≤0.035	≤0.030	/	/	/	≤0.25	≤0.30	≤0.25
45	0.42-0.50	0.17-0.37	0.50-0.80	≤0.035	≤0.030	/	/	/	≤0.25	≤0.30	≤0.25
20Mn	0.17-0.23	0.07-0.37	0.70-1.00	≤0.035	≤0.030	/	/	/	≤0.25	≤0.30	≤0.25
Q345B	≤0.20	≤0.50	≤1.70	≤0.035	≤0.035	≤0.07	≤0.15	≤0.20	≤0.30	≤0.50	≤0.30
Q345C	≤0.20	≤0.50	≤1.70	≤0.035	≤0.030	≤0.07	≤0.15	≤0.20	≤0.30	≤0.50	≤0.30
Q345D	≤0.18	≤0.50	≤1.70	≤0.035	≤0.025	≤0.025	≤0.15	≤0.20	≤0.30	≤0.50	≤0.30
45Mn2	0.42-0.49	0.17-0.37	1.40-1.80	≤0.035	≤0.035	/	/	/	≤0.25	/	≤0.25
27SiMn	0.24-0.32	1.10-1.40	1.10-1.40	≤0.035	≤0.035	/	/	/	≤0.30	/	≤0.20

Grade	Chemical Composition				Yeild Strength    min Mpa			Tensile Strength	Elongation	Impact Test
					T in mm			Mpa
					≤16	＞16 ≤30	＞30			℃	Impact/J
											≥
20	/	/	/	/	245	235	225	≥410	≥20	-	-
45	/	/	/	/	335	325	315	≥590	≥14	-	-
20Mn	/	/	/	/	275	265	255	≥450	≥20	-	-
Q345B	≤0.012	≤0.10	/	/	345	325	295	470-630	≥20	20	34
Q345C	≤0.012	≤0.10	/	≥0.015	345	325	295	470-630	≥21	0	34
Q345D	≤0.012	≤0.10	/	≥0.015	345	325	295	470-630	≥21	-20	34
45Mn2	/	≤0.25	/	/	885			≥735	≥10	-	-
27SiMn	/	≤0.30	/	/	980			≥835	≥12	-	-

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