Casting Technology Optimization of High-Ni Austenite Nodular Iron Volute Housing
The structure and production technology of a high-Ni nodular iron volute housing casting were introduced.In order to eliminate the defects including surface shrinkage cavities,shrinkage porosities,micro-shrinkage porosities and chunky graphite,surface worsening layer,carbide,the casting technology optimization was conducted.Finally,pointed out:(1)Since the liquid contraction rate of the high-Ni austenite nodular iron was high,its graphite expansion volume was less,to design the riser according the directional solidification principle was the effective measure to prevent shrinkage cavities and porosities of volute housing.(2)Since chunky graphite was easy to occur in the thick place and the tongue tip of the volute housing,intensifying inoculation could prevent such type defect.(3)Surface worsening layer exceeding standard could be avoided by relatively higher residual Mg content and brushing the sand cores with coating.(4)Since cooling rate being slower,more amount carbide precipitated in the tongue tip place,good inoculation could reduce carbide precipitating amount,and heat treatment could also change the volume fraction and morphology of the carbide.