Effect of Carbon Content on Deep Drawability of Rimmed Steel Sheet

Abstract

The deep drawability (R-value) was studied in rimmed steel sheets melted in air. The variables examined were the carbon content, the cold rolling reduction (50-90%) and annealing conditions (700° and 800°×5hr in non-decarburizing atmosphere and 750°×10hr in decarburizing atmosphere).
The following results have been obtained:
1. The R-value not only has the well-known dependence upon the texture but also the dependence upon the grain size d, which can be expressed by the formula.
R=R₀+k (d^-1/2-d₀^-1/2)
In this formula,
(1) the R₀-value at the completion of recrystallization is mainly determined by cold rolling reduction and carbon content;
(2) |k| is almost constant at 50-80% cold reduction, and decreases over 85%;
(3)(d^-1/2d₀^-1/2)(the term expressing the effect of grain growth after the completion of recrystallization) is affected by the factors such as carbon and oxygen contents and annealing conditions;
(4) the high R-value can be obtained in the low-carbon material in non-decarburizing annealing condition, and in the high carbon (that is low oxygen) material in the decarburizing condition; and
(5) the R-value of the low carbon material can be raised through the increase in R₀ and that of the high carbon material through the increase in |d^-1/2-d₀^-1/2|.
2. When carbon content is low or annealing temperature is high, the cold rolling reduction for getting maximum R-value is high.