Looking at the worldwide guide to equivalent irons and steels, I do not see a 1528 grade. I see a 1527, and then a 1533. Grade series 1500 is filed under Carbon Steel, High Manganese. AISI 1527 for bar specifies C = .22/.29, Mn = 1.20/1.50, P = .040 max and S = .050 max. AISI 1533 for bar, bloom, billet, or slab specifies C = 0.30/0.37, Mn = 1.10/1.40, P = .040 max and S = .050 max.
Kevin