CONTROL OF CAST GRAIN SIZE OF STEEL CASTINGS-EFFECT OF STRUCTURE AND NONMETALLICS ON PROPERTIES.
Final rept. 1 Oct 65-30 Sep 66,
CASE INST OF TECH CLEVELAND OHIO DEPT OF METALLURGY
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The relation of dendrite structure, nonmetallics and microporosity to solidification time and refinement by inoculation was investigated and correlated to mechanical properties of AISI 4335 steel castings. The dendrite spacing is determined by solidification time and significantly influenced by solute content. Titanium and boron effectively refine the secondary dendrite spacing selenium tellurium and sulfur have the opposite effect. Titanium inoculation also nucleates equiaxed dendrites thereby reducing or eliminating the columnar dendritic structure. Increasing solidification time and amount or size of nonmetallics decrease the ductility. Improvements in ductility from grain refinement by either inoculation or shorter solidification time are caused by improved distribution or reduction of the size of nonmetallics. Microprobe analysis indicates no significant differences in the segregation behavior of the elements manganese and chromium from inoculation. A hypothesis concerning the formation of dendrite arms was postulated based upon measurements of solute distribution and existing theories of dendrite arm formation. Author
- Properties of Metals and Alloys