Fast And Slow Investment Methods Of Casting The Highest Accuracy And Physical Properties Of A Comparative Study

Objective:To investigate the effect on cast accuracy and physical properties of quick-heating investing method and slow-heating investing method.Methods:A 26mm height cylindrical mode was made by stainless steel. The taper of the axial plane of the mode was 4°and the shoulder preparation margin was 1mm. A stainless steel pipe should be made to control the thickness of wax pattern. According to the manufacture's instructions of powder-hydraulic proportion,36 crown-type wax patterns were prepared using pattern resin. The pattern resin crowns were completed on the same standard mold. Then they were randomly divided into 6 groups. Each group was invested with 3 different phosphate-bonded investments. According to the different time from setting to heating, castings were designed for quick-heating method groups and slow-heating method groups. Then the marginal precision of the crowns, surface roughness and hardness were measured.Results:①Cast accuracy The average marginal precision of quick-heating method groups was (96.63±7.46)μm; The average marginal precision of slow-heating method groups was (41.67±3.94)μm. There is significance statistical difference between the two groups (P<0.05);②Surface roughness The average surface roughness Ra and Rz of quick-heating method groups was (3.44±0.65)μm and (25.03±5.42) um respectively; The average surface roughness Ra and Rz of slow-heating method groups was (5.79±1.26)μm and (31.46±5.66)μm respectively. There is significance statistical difference between the two groups (P<0.05);③Hardness The average hardness of quick-heating method groups and slow-heating method was (59.33±1.21)HRB and (59.67±0.81) HRB respectively. There is no significance statistical difference between the two groups (P>0.05). Conclusions:①Cast accuracy The marginal precision of slow-heating methods groups was smaller than the quick-heating method, the slow-heating method was more accuracy;②Surface roughness The surface roughness of quick-heating methods groups was smaller than the slow-heating method;③Hardness The hardness of quick-heating methods groups and slow-heating method groups show no significance statistical difference.