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

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"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.