Mechanical properties of the industrial HK40 reforming tubes produced by an improved centrifugal processing

The structures and the mechanical properties of industrially electromagneti c centrifugal cast HK40 reforming tubes were investigated and compared with the traditional commercial HK30 tubes. It is found that the structure chan ges caused by the electromagnetic field primarily consist of grain refining and increase of the eutectic carbides. Both the tensile properties at room temperature and the stress rupture strength at elevated temperature are no ticeably improved by the introduction of the electromagnetic field. A furth er increase of the exciting current has no evident influence on the tensile properties, but markedly improves the stress rupture strength of the cast tubes. The relationships between the mechanical properties and the structur e changes of the cast tubes induced by the electromagnetic field are discus sed in detail.