Study of the role played by nitrogen on the deep-drawing properties of aluminium killed steel sheets obtained after a continuous annealing

摘要

The aim of this paper is to discuss the role played by nitrogen on the deep-drawability of low carbon aluminium-killed steel sheets produced by continuous annealing. The different precipitation states of nitrogen in these sheets were thus studied by Transmission Electron Microscopy (TEM) observations. They showed that two types of nitrides may form: (Al,Cr)N nitrides with a cubic NaCl structure and AlN nitrides with a hexagonal wurtzite structure. It was then possible to investigate, for different precipitation states of carbon, the effect of these two types of nitride on the deep-drawing properties. The results showed that carbon has a primordial role on the drawability, while nitrogen has a secondary one except if it is engaged in (Al,Cr)N nitrides and the carbon content is low.