【正文】 The research on lost foam casting are mainly on aluminum alloys, such A356 [1, 2, 3, 4], [5], A319 [6]. The research of lostfoam casting on other materials is also reported, AZ91 [7], AM60B [8] and gray cast iron [9]. The fluidity of melts during lostfoam casting increases with melt temperature [1, 8]. The fluidity also increases with sand temperature [7]. Coating of pattern with ceramic improves the fluidity [7]. The thickness of mold patterns influences the fluidity [1].The foam density is also influences fluidity [8] in which the ability of the molten metal fills the mold patterns with a density of lb/ft3 better than polystyrene foam with a density of and lb/ft3. Patterns with low density polystyrene foam show a sound casting. The ability of the molten metal fills the mold pattern with a density of 26 kg/m3 is faster than that of the pattern density 21 kg/m3. Filling speed of molten metal reaches to cm/sec for the mold pattern with a density of 26 kg/m3, and reached to cm/sec in the mold pattern with a density of 21 kg/m3 [7]. The liquid metal filling rate increases with permeability of sand mold [6]. Liquid metal reached a length of 150 mm for secs for the mold sand with AFS type 20 and seconds the mold sand with AFS 55 [7]. A fluidity is obtained by coating the mold pattern 45 Bc (high density) than the pattern of the mold with coating 35 Bc (low density). The porosity in casting products increases with density of polystiren foam [5] and melts temperature [4,7]. Surface roughness is also an important issue which must be optimized in materials processing. The rough surfaces are often hindered in many structural applications. The rough surface reduces corrosion resistance and fatigue strength. The aim of this research is to investigate the effect of pouring temperature, EPS foam density and sand mesh size on fluidity and surface roughness during lostfoam casting of .2. ExperimentThe material used was aluminum alloy , with chemical positions (wt%) Si, Fe, Mg, Zn, Ti and bal Al. The pattern was prepared by a hot wire cutter from an EPS (expanded polystyrene) foam block. In order to study the effects of pouring temperature, EPS foam density, sand mesh size and pattern thickness, experiments were conducted with various pouring temperatures, EPS foam density, sand mesh size and pattern thickness. The density of pattern of the EPS was 7, 18 and 20 kg/m3. Silica sand was used with mesh 70 ( 70 mesh), mesh 35 (35 mesh up to 70 mesh) and 20 mesh (20 mesh to 35 mesh). Aluminum alloy was melted in the crucible furnace at temperature 750 ℃, and then poured at 680, 710 and 740℃. Figure 1. Patern of EPS (expandable polystyrene) foam.An engineering drawing of the test pattern used to study the fluidity characteristics is shown in Fig. 1. A strip, 180 mm long, 15 mm width and 3, 5, 7 and 11 mm thick was attached to a gating system consisting of a rectangular downsprue and apouring 25 mm in cross section. The gating system and the strip were cut from EPS foam boards. The patterns were not coated with a mercial coating. Pattern was put on the base of the flask, and the flask was filled with mold packing sand in vibration. Molten aluminum was poured into EPS foam pattern. The fluidity was determined by measuring the length of cast products at every thickness of sample. The samples surface roughness was measured using Surf 120A contact stylus profilometer (Advanced Metrology System, UK). The roughness was measured at five different locations on the surface to obtain the average of arithmetic medium values (Ra) of the distance travelled by the stylus.3. Results and DiscussionThe effect of EPS density on the fluidity was investigated with density of 7, 18 and 20 kg/m3, the EPS thickness of 3, 5, 7 and 11 mm, and the pouring temperature of 680, 710 and 740 ℃, and sand mold with a mesh size of 70. Figure 2 shows the fluidity along the density of the EPS foam for four pattern thickness (3, 5, 7, and 11) and pouring temperature of 680, 710 and 740 ℃. The fluidity decreases with increasing density of EPS foam at every EPS thickness. The increase of EPS foam density cause the pressure difference on the contact surface to the EPS polystirene foam. The gas on the melt and penguapan EPS polystirene foam cause the decrease of fluidity. A higher EPS density will cause a higher backpressure that influence the fluidity during lostfoam casting. This finding is also confirmed in ref. [8]. Effect of mesh sizes on the fluidity was investigated on the mesh size of 20, 35 and 70, the pattern of EPS foam with density of 7, 18 and 20 kg/m3, and the pouring temperature of 710 ℃. Figure 3 shows the fluidity with mesh size 20, 35 and 70 and the mold pattern of polystyrene foam with density of 7, 18 and 20 kg/m3. Fluidity is relatively constant with increasing sand mesh size. Mesh size of the molding sands affect the permeability properties of sand in the absorbing gas formed by the evaporation of polystyrene foam. However it does not increase fluidity.a. b.c.Figure 2. Fluidity along the density of the EPS foam for four patern thickness, pouring temperature: a. 680 ℃, b. 710℃ and c. 740 ℃Effect of pouring temperature on the fluidity was observed at the pouring temperatures of 680, 710 and 740 ℃, the EPS foam density of 7, 18 and 20 kg/m3, the EPS foam thickness of 3, 5, 7 and 11 mm, and sand mesh size of 70.a. b. c.Figure 3. Fluidity along the mesh size of the silica sand for four patern thickness and EPS foam density of: a. 7, b. 18, and c. 20 kg/m3 Figure 4 shows the fluidity at pouring temperatures of 680, 710 and 740 ℃, and EPS foam density of 7, 18 and 20 kg/m 3, and the EPS foam thickness of 3, 5, 7 and 11 mm, and sand mesh size of 70. The fluidity increases with increasing thickness of the EPS foam, increasing pouring temperature for all EPS density. The fluidity increases with increasi