An introduction was made on the structure of high Ni austenite nodular iron exhaust manifold,and the fracture problem occurring during test of the first-delivered sample.Through production test,it was validated that the fracture reason of the exhaust manifold was that since stream inoculation being not conducted during the pouring process and thereby caused chunky graphite and caused mechanical properties decreasing and accelerating risk of casting cracking and failure.Finally pointed out:(1)Beside strictly complying with the process requirements during production process of high Ni austenite nodular iron,it was also needed to conduct stream inoculation.(2)Under the precondition to ensure the nodularizing process meeting requirements,stream inoculation could further increase graphite crystallizing nucleus,increase eutectic cell number,avoid chunky graphite formation.
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