Y-fb gfb40 gfb42 gfb45 Al2o3(%)min. 40 40 42 45 Fe2o3(%)max. 2.5 Refractoriness()min. 1710 1730 1750 1750 Refractoriness under load 0.2mpa()min. 1300 1350 1400 1400 Apparent porosity(%)max. 22 20 20 20 Cold crushing strength (mpa)min. 30 30 35 40 Linear change after reheating(%)max. At 1350 2h +0.1 -0.4 At1400x3h +0.1 +0.1 +0.2 - 0.5 -0.4 -0.2.