Deep drawable steels

Abstract Deep drawable steels are widely used in the automobile industry for their ability to be formed into intricate shapes. These steels are essentially low carbon steels that are characterized by excellent r m (average Lankford Parameters) value. These steels can be broadly classified into three different categories, such as Al-killed (AK), Interstitial Free (IF), and Bake Hardenable (BH) grades. IF steels possess higher r m value and lower strength than AK steels. IF steels are generally processed through continuous annealing whereas AK- steels are produced preferably through the batch annealing route. Substitutional alloying elements (such as Mn, P, etc.) are often added to IF steels to produce the interstitial free high strength grade, the higher strength version of IF steels. In the BH grade of low carbon steels, yield strength can be further increased by high temperature strain aging of the steel, caused by the presence of low amounts of free carbon. In these grades, a very small amount of carbon (10–20 ppm) is deliberately kept free in the Fe matrix after the final annealing treatment. The final properties of deep drawing steels are essentially dependent upon the cleanliness, grain size, texture, and precipitation behavior of these steels. Very often these parameters have a synergistic effect on each other. Thus close control over every step in the production process is of utmost importance in order to achieve the desired properties in these grades of steel.