Boron effect on processing properties of middle-carbon structural steels of the common product range

Abstract

The object of study is low-alloyed boron-containing structural steels. The research method is analysis of the deoxidation effect on the boron uptake degree and the quality of the metal according to the statistical processing of current production meltings. The objective is to determine the optimum degree of steel deoxidation in order to obtain stable mechanical properties of the finished metal. The distinguishing features of boron steels production have been analyzed. It has been shown that the efficiency of microalloying with boron depends on the deoxidation technology and heat treatment in the production cycle. Under Ilyich Iron and Steel Works of Mariupol (MMKI) conditions, the absence of heat treatment departments for thin rolled products and the limited variability of operations for thick rolled products restricts the possibility of producing boron-containing steels. The structure of boron-containing steels production over the period from 2016 till 2018 has been analyzed. It has been shown that these are mainly medium-carbon structural steels of the common product range, alloyed with manganese and aluminum. In the absence of modern means of secondary treatment, boron microalloying (PB 20, lumps of 10-50 mm in size) is carried out after complete deoxidation of the metal, while the degree of boron absorption is quite substantial and amounts to 77-92%. Using A36 steel as an example, the basic mechanical properties of finished rolled products have been analyzed. The stabilization of mechanical properties within narrower limits and the possibility to reduce the aluminum consumption by 8-10% are considered to be the result of boron positive effect on the steel quality. The optimal content of acid-soluble aluminum in metal should be 0,028-0,032%. Saving aluminum will make it possible to use stronger nitride-forming elements such as titanium to stabilize the quality indicators of the finished metal