Tomoki Fukagawa

Effect of Small Amounts of Ni on Liquid-Cu Embrittlement in Hot-Rolled Mild Steel After High-Temperature Oxidation

The effects of additions of as little as 0.02%Nito mild steel on the morphology of the scale-steelinterface and surface cracking were studied duringhigh-temperature oxidation and subsequent hot-ductility tests of 0.5%Cu-bearing steel. Liquid-Cuembrittlement occurs in a steel containing0.5%Cu-0.001%Ni because of concentrated liquid-Cu layerat the scale-steel interface over the temperature rangeof 1100-1300°C. The addition of as little as0.023%Ni to 0.50%Cu-containing steel recovers theductility in the oxidation temperature range of1250-1300°C. This is because liquid-Cu particles areoccluded into the scale. Thus, the amount of enriched Cuper unit surface area decreases at the scale-steelinterface. It is suggested that liquid-Cu particleocclusion, which has not yet been elucidated, results from heterogeneous enrichment of Ni andheterogeneous oxidation at the scale-steelinterface.