What is difference between ASTM A514 Grade A and B ?

In u.s. specification ASTM A514/A514M,there are steel materials A514 grade A,A514 grade B,A514 grade C,A514 grade E,A514 grade F,A514 grade H,A514 grade J,A514 grade K,A514 grade M,A514 grade P,A514 grade Q,A514 grade R,A514 grade S,A514 grade T.These A514 high strength steel materials normally rolled as steel plates,steel sheets,steel pipes shapes.Hot rolled steel plates rolling range as thickness from 0.197 Inches to 11.8 Inches,width up to 165 Inches and length up to 709 Inches.

What is difference between steel materials ASTM A514 Grade A and B ? The main gap is in ASTM A514GRA chemical composition and A514GRB chemical composition.Steel materials A514GRA added Zirconium element,and steel materials A514GRB added Vanadium and Titanium elements when rolling.
 

High strength steel grades A514GrA vs A514GrB		Chemical composition: Heat Analysis  Max%
Standard	Grade	C	Mn	P	S	Si	Cr	Mo	V	Ti	Zr	B
ASTM A514/A514M	A514GrA	0.15-0.21	0.8-1.1	0.035	0.035	0.4-0.8	0.5-0.8	0.18-0.28	/	/	0.15-0.5	0.0025
ASTM A514/A514M	A514GrB	0.12-0.21	0.7-1.0	0.035	0.035	0.2-0.35	0.4-0.65	0.15-0.25	0.03-0.08	0.01-0.03	/	0.0005- 0.005
Mechanical Properties:		Thickness		Yield strength			Tensile strength
				Mpa  Min.			Mpa
ASTM A514/A514M	A514GrA	T≤65		690			760-895
ASTM A514/A514M	A514GrB	T≤65		690			760-895