A mechanism responsible for the degradation of steels during casting is reported this week in Nature Communications. The discovery may lead to changes in steel manufacture that could result in practical improvements to the 50 million tons of ingots, heavy plates and castings produced annually.
Steels are alloys made from a range of different elements. A major fabrication issue causing early failure is the nonuniform distribution, or segregation, of these elements in the material during solidification. Whilst some causes for segregation are known, for example convection during the casting process, it remains an issue for steel manufacturing and the full explanation behind its occurrence is unclear.
Dianzhong Li and colleagues have now uncovered a mechanism where impurities based on compounds formed by oxygen and lighter metals create a material flow that drives compositional variation during casting. In experiments using large steel casts of up to 650 tons in weight, segregation could be avoided by reducing the amount of oxygen in the steel. Controlling oxygen concentration could therefore be a promising method to improve the quality of steels produced in the future.