1982 Volume 68 Issue 3 Pages 444-450
A study has been made on the high-temperature properties after long-term high-temperature heating of HK40 (25Cr-20Ni) and HP (25Cr-35Ni) centrifugal casting tubes which are widely used as reformer tubes in the steam reforming process or cracking tubes in the ethylene producing equipments.
In the short time tensile testing at 700°C or below, there is a marked deterioration in the ductility of HK40 and HP after long-term heating between 800° and 982°C. At testing temperature above 700 °C, the ductility of HK40 is incressed by long-term heating, whereas that of HP is not affected by long-term heating.
In the creep rupture testing, HK40 after long-term heating shows lower gradient in the log σ vs. log t curve than that of the as cast alloy and, hence, its long time rupture strength is markedly superior to that of as cast alloy. However, HP after long-term heating shows lower strength and higher ductility in creep rupture testing as compared with the as cast alloy.