Effect of Water Vapor Pressure on Environment Embrittlement of Spheroidal Graphite Cast Iron.

研究了高强度球墨铸铁在蒸汽环境下的“水围护”现象。得到了以下结果：高强度球墨铸铁（珠光体、马氏体、等温球墨铸铁）受水围护现象显著。在水附着条件下进行塑性变形后，经氢分析确认氢体积增加，认为这种围合是由于氢脆性造成的。(1)真空条件下的拉伸特性值高于干燥条件下（湿度为0%）的气氛。(2)拉伸特性随蒸汽压力的升高而下降。但与水附着条件相比，下降量较小。(3)不存在与水附着条件评价一致的等级护堤临界蒸汽压力。测试了干燥和湿（湿度大于95%）氢气气氛下的拉伸强度。得到了以下结果：(1)湿氢气气氛比干氢气气氛更明显。(2)应变速率对围护效果的影响较小。(3)在大气内部存在一个临界暴露时间，这一暴露时间演变为围城。(4)铸铁中的石墨对湿氢气中显著的钢化现象有影响。

"Water embattlement" phenomenon under the steam circumstance in the high strength nodular graphite cast iron was examined. The following results were obtained.The embattlement phenomenon by the water was remarkable with the high strength nodular graphite cast iron (pearlite, martensite, austempering nodular graphite cast iron).After plastic deformation is done in the water adhesion condition, increase in hydrogen volume is confirmed as a result of doing hydrogen analysis, and it is considered that this embattlement is attributable to the hydrogen brittleness.(1) Tensile characteristics in the vacuum are higher value than the atmosphere inside of the drying condition (humidity of 0%).(2) Tensile characteristics decline in accordance with the rise in the steam pressure. But, that decline volume is small in comparison with the water adhesion condition.(3) The critical steam pressure which the embattlement of the grade which was the same as the water adhesion condition evaluated didn't exist.Tensile strength in the drying and wet (more than humidity of 95%) hydrogen gas atmosphere was examined. The following results were obtained.(1) Wet hydrogen gas atmosphere embattles more remarkably than dry hydrogen gas.(2) The effect to the embattlement of the strain rate is small.(3) There is critical exposure time in the inside of the atmosphere which evolutes embattlement.(4) Graphite in the cast iron affects in the remarkable embattlement phenomenon in wet hydrogen gas.