Effects o grain refinement on hot tear resistance and shrinkage characteristics of permanent mold cast yellow brass (C85800)

摘要

Grain refinement of yellow brass has been studied by adding boron, zirconium, a combination of zirconium and boron, and a proprietary grain refiner (FKM 2000), and compared with alloys prepared from commercially-available, grain-refined ingots. Of these, boron was found to be most effective in producing grain refinement. The effectiveness of zirconium was increased in the presence of boron. Although FKM 2000 is used commercially for grain refinement, the present study shows that its effectivenessas a grain refiner is less than that of boron.It is shown that grain refinement can prevent the formation of hot tear cracks in yellow brass with relatively high tin (~1 %) and lead (~1.4%) contents.The shrinkage characteristics of the alloys were established in both the refined and unrefined conditions, using a Tatur mold. This mold yields information on macroporosity in the form of pipe volume, slumping and contraction volume, as well asmicroporosity in permanent mold (PM) casting operations. The pipe profile seemed to distinguish between refined (shiny interior, conical and narrow profile with pointed end) and the unrefined (rough interior, cylindrical and wide profile with rounded end).Mechanical properties of yellow brass did not improve significantly, following grain refinement.