Surface hot shortness of copper containing steel in a compact strip production process

Abstract

The compact strip production (CSP) process has received much attention because it is environment friendly and can be used for recycling resources. However, steel scrap, the main material used in the CSP process, causes surface cracks in the hot strip being manufactured as a result of surface hot shortness by Cu and Sn in the steel scrap. This study investigates the influence of heat pattern on the brittleness of Cu-containing steels prior to treatment in a reheating tunnel furnace at 1100°C. The prior austenite grain size of a sample that was reheated from room temperature before being transferred to a tunnel furnace was finer than that obtained by the direct transfer process, and the crack depth was inhibited by 50%. In contrast, the prior austenite grain size of a sample obtained by a process in which austenite is reheated from a cooling stop temperature of 650°C-850°C was almost the same as that obtained by direct transfer to the tunnel furnace. However, the crack depth in the case of reheating from the cooling stop temperature of 650°C-850°C was greater than in the case of direct transfer. This deep cracking was caused by a noninternal oxidation area at the scale/steel interface. © 2011 The Japan Institute of Metals.