Fabrication And Extrusion Of Semi-solid Slurry Of Hypereutectic High Cr Cast Iron

In this research, the semisolid slurry of hypereutectic high Cr cast iron has been fabricated by the slope plate, and shaped by semisolid extrusion molding.During slurry fabrication, the forming of thinner primary carbide was considered, the influence of technical parameters from the angle of single-factor, such as pouring temperature, length of slope plate, radius of groove, temperature and so on, to the pattern and dimension of primary carbide were researched. The results indicate that: comparing to the conventional microstructure, the primary carbide of hypereutectic high Cr cast iron has been refined obviously after treated by slope plate. It is because the melt on the plate was chilled, primary carbide continually nucleating and growing, simultaneity under the actions of cutting, rolling, friction, impacting and so on, the primary carbide is broken up and crashed, then finally be refined.Because of the chilling of slope plate, there are a mass of small carbide occurred in the melt. When the temperature is lower, the growing tendency of primary carbide should be smaller. Along with the rise of pouring temperature, the growing tendence increases, the primary carbide becomes larger. If the pouring temperature continually to rise, the viscosity of melt will debase, then flowing velocity increasing, shearing increasing, and finally the primary carbide become smaller.If the length of the slope plate is shorter, the time of chilling shearing will be also shorter, the carbide is crassitude. If the length of slope plate is longer, the temperature decreasing of melt will be larger, the viscosity increasing, flowing velocity slowing, then the action to primary carbide is weaken, effect of refinement is not obvious. If the inclining angle is smaller, the flowing velocity will be slower, shearing force is smaller, and as a result, the primary carbide will be crassitude. If the inclining angle is larger, the time of shearing force to the melt will be shorter, effect of refinement is not obvious. If the radius of groove is larger, the contact area between melt and slopeplate will be larger, the thickness of melt is thinner, chilling effect is nice, as a result, the structure is more satisfying. If the temperature of plate is higher, the temperature gradient in the melt will be smaller, then the growing velocity of primary carbide decreased, and the dimension of it will become smaller. The research result indicates that: when the pouring temperature is 1390°C, length of slope plate is 500mm, inclining angle is 30°, radius of groove section is 400mm, temperature is 150°C, the primary carbide in the slurry is smallest and uniform distribution.Use these technical parameters, carry the semisolid extrusion shaping to the slurry, then test the impact ductility, rigidity and impacting grinding abrasion. Because primary carbide is small and uniform distribution, the casting part is compact. As a result, when the rigidity is un-fluky, the ductility and abradability is much more advanced comparing to the regular sand casting.