Abstract
Planar anisotropy of γ value (Δγ=|γ0+γ90/2-γ45|) of Nb-treated high strength hot-rolled steel sheet is usually high. The way for decreasing Δγ was studied with laboratory melted materials and experimental rolling mill.
Mechanism which leads to the increase of Δγ can probably be explained as follows: The rolling conditions such as rolling sequence or lubrication may affect the development of austenite texture in a temperature range where recrystallization does not take place. This texture is inherited by ferrite through the γ-α transformation.
Unidirectional rolling makes Δγ higher than reverse rolling and water-lubrication or no-lubrication makes Δγ higher than oil-lubrication.
Ti, V, Mo do not have such a strong effect of increasing the lowest temperature of γ recrystallization (Tc) as Nb does.
So these elements are suitable to the additions for decreasing Δγ of high strength hot-rolled steel sheet for deep drawing.
