HIGH STRENGTH STEEL PLATE - STEEL PLATE AND HIGH STRENGTH GALVANISED STEEL PLATE HAVING EXCELLENT STABILITY OF SHAPE AND METHOD OF THEIR MANUFACTURING Russian patent published in 2016 - IPC C22C38/06 C22C38/04 C21D8/02 C23C2/06 C23C2/26 

FIELD: metallurgy.

SUBSTANCE: invention relates to high strength steel plate used in automotive industry. Plate is made of steel containing in wt %: C from 0.075 to 0.30, Si from 0.30 to 2.5, Mn from 1.3 to 3.5, P from 0.001 to 0.03, S from 0.0001 to 0.01, Al from 0.080 to 1.50, N from 0.0001 to 0.01, O from 0.0001 to 0.01, and rest is for Fe and inevitable admixtures. In range from 1/8 to 3/8 of thickness the plate structure contains residual austenite from 5 vol % to 20 vol %, and carbon content in solid solution contained in phase of residual austenite is from 0.80 to 1.00 wt %. Values W_Siγ and W_Mnγ determined as quantity if silicium and manganese in solid solution, contained in phase of residual austenite, by 1.10 times or more exceed values W_Si* and W_Mn*, determined as average amount of silicium and manganese in range from 1/8 of thickness to 3/8 of thickness of steel plate. Mode of frequency distribution F(W_Si, W_Al) measured in measuring areas with diameter 1 mcm or below, and being sum of ratio between W_Si determined as measured quantity of silicon in each of multiple measuring areas, and W_Si* being average quantity of silicon, and ratio between W_Al determined as measured quantity of aluminium in each of multiple measuring areas, and W_Al* being average quantity of aluminium, is from 1.95 to 2.05. Coefficient of kurtosis of frequency distribution F(W_Si, W_Al) is 2.00 or more.

EFFECT: manufactured plates have high machinability and stability of shape providing high strength.

14 cl, 17 tbl, 1 ex