Properties of a gypsum-bonded magnesia investment using a K2SO4 solution for titanium casting.

The purpose of the study was to investigate the effects of a K2SO4 solution on the improvement of the properties of an experimental magnesia-based gypsum-bonded investment. The characteristics of the experimental investment with different ratios of a K2SO4 solution were as follows: setting time ranged from 34 to 152 minutes, green and fired compressive strengths were approximately 2.15 to 5.81 MPa and 1.63 to 2.45 MPa, respectively; thermal expansion was 0.38 to 0.47% at 700 degrees C, which did not show any significant differences due to the concentration of the K2SO4 solution. Titanium casting could be obtained using the experimental investment mixed with a 1% K2SO4 solution, and the reaction layer thickness of the casting was less than 200 microm. The results suggest that the experimental investment mixed with 1% K2SO4 showed acceptable physical properties and casting characteristics for titanium casting.