Effect Of Silicon On Microstructure And Mechanical Properties Of Heavy Section Ductile Iron

As the basic research of the container for storage and transportation of the spent fuel,two groups heavy section ductile of 400×400×400mm with Si content of 1.8%and 2.4%were cast and the impact of Si content on the performance and microstructure of high toughness ductile iron were discussedIt can be found from the test cube cooling curve that the overall of the heavy section sphere pieces cooling slowly and the heart ministry of the casting coagulation time lasted 270min.The eutectic solidification time is the shortest for 100 min on the apex angle from the sand mold castings surface 50 mm.Eutectic solidification time length of the main differences is the platform time the eutectic,Eutectic platform in 1145?,The center position eutectic platform time up to 180min,The casting top corner from the sand surface 50mm at almost no eutectic platform.With the Si content from 1.8%to 2.4%,the major graphite morphology of the test block deteriorates from spherical into clumps like,group flocculent in the center section axis direction 20mm from the bottom(near the edge).Tensile strength increases from 350MPa to 384MPa,the extending rate is reduced from 18%to 7%,percentage reduction of area from 17.5%down to 11%,impact toughness is reduced from 33J/cm 2 to 28J/cm 2 at room temperature and from 12J/cm 2 to 3J/cm 2 at-60?.With the Si content from 1.8%to 2.4%,the major graphite morphology of the test block deteriorates from spherical,group flocculent into clumps,worms and flaky like,group flocculent in the center section axis direction 100mm from the bottom.Tensile strength increases from 285MPa to 311MPa,the extending rate is reduced from 4%to 3.5%,percentage reduction of area from 6%up to 7%,impact toughness is reduced from 23J/cm 2 to 16J/cm 2 at room temperature and from 5J/cm 2 to 2J/cm 2 at-60?.With the Si content from 1.8%to 2.4%,the major graphite morphology of the test block deteriorates from group flocculent and chunky into chunky in the geometric center 200mm from the bottom(final solidification position).Tensile strength increases from 235MPa to 279MPa,impact toughness is reduced from 14J/cm 2 to 9J/cm 2 at room temperature and from 2J/cm 2 to 1 J/cm 2 at-60?.The casting which contains 1.8%Si with an elongation of 1%and cross section contraction rate of 2.5%,however,casting which Si content of 2.4%is shown brittle fracture.It will promote the formation of chunky graphite and reduce the graphite roundness when Si element content from 1.8%to 2.4%.Under this condition,the castings are more likely to brittle fracture with the reduction of the impact toughness and the improvement of the ductile-brittle transition temperature.At the same time,increasing the Si content can also increases the hardness and tensile strength of the casting.