Experimental Investigation of Surface Hot Shortness inScrap-Based Steels : Effects of Copper Behaviour Under Various Heat Exposure Conditions in Different Steel Grades

Sammanfattning

SSAB aims to redefine their future of steel production by replacing iron ore–based raw materialswith recycled steel scrap. However, the use of steel scrap introduces challenges associated withtramp elements, particularly copper and tin, which cannot be removed during processing andmay lead to a phenomenon known as surface hot shortness. To improve the understanding of surface hot shortness, including the conditions under which itis most severe and how it may be mitigated, different steel samples were exposed for 8 to 64minutes at the temperature range 950 ◦C to 1250 ◦C. The behaviour of copper in the sampleswas investigated using light optical microscopy (LOM) and scanning electron microscopy (SEM),combined with energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction(EBSD). The results demonstrated that copper behaviour is strongly influenced by both alloy composi-tion and exposure conditions, including temperature and time. The most pronounced effects ofsurface hot shortness were observed at lower temperatures, as well as at higher temperatureswhen the exposure time was short. These findings contribute to a better understanding of themechanisms governing surface hot shortness and may support the development of strategies toreduce its impact in scrap-based steel production.