采用在没有外力作用下进行的反复加热和冷却的热疲劳试验方法,在试样加热温度为500±8℃的条件下,研究了球铁和蠕铁的热疲劳裂纹的扩展过程。所用试样尺寸为30×24×15毫米。在试样30×15毫米一侧,开有宽0.2毫米、深0.5～1毫米的缺口。研究表明,球铁和蠕铁的热疲劳裂纹都是沿石墨扩展的;当进入屈服强度较低的高温区时,裂纹就显著地发生分 The thermal fatigue test method of repeated heating and cooling without external force was used to study the thermal fatigue crack growth of ductile iron and vermicular iron at the heating temperature of 500 ± 8 ℃. The sample size used is 30 × 24 × 15 mm. On the 30 × 15 mm side of the specimen, a notch of 0.2 mm in width and 0.5-1 mm in depth was opened. It has been shown that the thermal fatigue cracks of ductile iron and vermicular iron all extend along the graphite. When entering into the high temperature zone with lower yield strength, the crack is obviously divided