Effect of Crystallographic Texture on Presss Froming of Extra-Low Carbon Rimmed Steel Sheet

Abstract

Effects of crystallographic texture on the plastic deformation of solid state decarburized rimmed steel sheets have been studied. Three typical textures composed of a main preferred orientation, (111)[110], (110)[001] and (100)±10° to the rolling plane, [011]±25° to the rolling direction, were obtained from the same mother hot coil. Tensile tests, cupping tests and Erichsen tests were carried out in the dead soft condition and effects of crystallographic texture on the press formability were investigated with specimens of the same chemical composition, the same second phase particles and almost the same grain size. Moreover, effects of interaction between crystallographic texture and mechanical fiber on the elongation and effects of interactions between texture, mechanical fiber, grain size and the dimensinal effect of testing tool on the stretchability were examined.
The results obtained are summarized as follows:
1) The plastic anisotropy ratio “r” can be related to crystallographic texture and the deepdrawability is predominatly influenced by the preferred orientation and the sharpness of texture.
2) Texture is a basic factor for the earing behaviour in deep-drawing test, but a more thoroughgoing study is necessary to get a clearer picture on the interrelation between the plane anisotropy of “r” and the earing.
3) Young's modulus and poisson's ratio are considerably influenced by texture, and the results of testing agree with the estimates made by theoretical calculations.
4) Plane anisotropies of yield strength, tensile strength and strain hardening exponet are slightly influenced by texture, whereas plane anisotropy of elongation is remarkably influenced. The fact can be interpreted by considering the influence of “r” on the dimensional effect of local elongation and the interaction between “r” and mechanical fiber on uniform elongation.
5) As a result of stretching cup test, it was made clear that strain distribution is influenced by plastic anisotropy.
6) Stretchability is also remarkably influenced by texture. In this regard, interactions among the dimensional effect of testing tool, grain size and mechanical fiber shold always be taken tnto cosideration as important factors.