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Page 22

PŘESNÉ LITÍ

S. Roy – U. K. Maity – A. K. Pramanick – P. K. Datta

Kinetics of liquid metal flow in gating design of investment casting production

Tab. III. Casting parameters (Fig. 4)

Tab. V. Casting product parameters (Fig. 5)

Volume (× 10 6 m3)

Heat Dissipating Area (× 103 m2)

Weight (× 103 kg)

Volume (× 10 6 m3)

Heat Dissipating Area (× 103 m2)

Weight (× 103 kg)

12.7

8.125

0.119

13.0

6.5

0.12

Tab. IV. Comparison of design and actual gating (Fig. 4) Cup (× 103 m)

Sprue Pipe (× 103 m)

Dam (× 103 m)

Sprue Gate (× 103 m)

dc

Zc

ds

Zs

dD

ZD

dg

Zg

Cal.

7.3

10

5

45

2.7

10

2

25

Design

8.5

10

5

45

4

10

2

25

Tab. VI. Calculated and design summary (Fig. 5) Cup (× 103 m)

Sprue Pipe (× 103 m)

Dam (× 103 m)

Sprue Gate (× 103 m)

dc

Zc

ds

Zs

dD

ZD

dg

Zg

Cal.

7.5

10

5

40

2.7

10

2

25

Design

9.5

10

5

40

4

10

2

25

Tortoise with dam sprue at the tail A wax pattern model of a tortoise (Fig. 7) was cast using a dam sprue. Details of casting produced has been shown in Tab. V with calculated and designed gating parameters in Tab. VI. Experimental results of actual casting Calculated and experimental filling times have been plotted for two casting in Fig. 8 and 9. Yield of castings has been shown in Tab. VII. Calculated Filling Time D i s c6u s s i o nExperimented o f r e s uFilling l t s Time 5

7

7

6

6

5

5

7

7

6

6

5

5

4

4

6

Calculated Calculated FillingFilling Time Time 5 Experimented Experimented FillingFilling Time Time Filling Time (s)

7

Fig. 7. Gated casting (top), schematic diagram of casting (bottom 7 Calculated Filling Time left), sectional view of the dam sprue (bottom right) Experimented Filling Time

7 4

Calculated Filling Time

3

5

4

4

3

3

2

2

1

1 0.2 0.4

0.4 0.6

0.60.8

0.81.0

Filling Time (s)

Filling Time (s)

Filling Time (s)

0 0 0.0 0.0 0.2

3

3

2

2

1

1

0 0 1.0 0.0 0.0 0.2

Percentage of Volume Percentage of Volume

Filling Time (s)

5

Calculated Filling Time Calculated Filling Time Experimented Experimented FillingFilling Time Time

4 3

Calculated Calculated FillingFilling Time Time 7 Experimented Experimented FillingFilling Time2 Time

5 0

0.0

0.2

4 3 2 1

0.2 0.4

0.4 0.6

0.600.8 0.0

Percentage Percentage of Volume of Volume

Artisans are using satisfactory design of casting as checked by Reynold’s No. Foundry engineer should be able to better gating 0.4 0.6 0.8 1.0 design by optimizing channel height and Percentage of Volume diameter for quality casting production. The following conclusion can be drawn on the proposed model of the gating system.

Calculated Filling Time dimensions for production Experimented Filling Time

6 1

Filling Time (s)

6

6

Filling Time (s)

7

7

Filling Time (s)

Filling Time (s) Filling Time (s)

Filling Time (s)

Experimented Filling Time 6 metal as The liquid per Stefanescu [10] within capillary mold The mathematical model for kinetics in liquid metal flow within 2 4 4 4 gets further restricted or assisted due to the surface tension investment mold has been based on Bernoulli’s equation as 5 1 effect of4 the fluids. However, in case of ordinary liquid like usual.3 The kinetic energy correction factor [8] (α) 3 3 has been 0 water or kerosene due0.4to lower wetting angle (θ < 90°) the added2 for real metal flow. 0.0 0.2 0.6 0.8 1.0 2 2 3 flow accelerates. ButPercentage in caseof of liquid metal within the capillary Further to this differential pressure of air in ambient condition Volume 1 air pressure in investment mold has been 1 1 taken care sections2 of investment molds the higher wetting angle and hot (θ > 90°)1 restricts the flow, thereby increasing the filling time of due0 to huge difference of densities in two 0 temperatures. 0 0.2 0.6 0.8 1.0 0.0 0.0 0.2 0.2 0.4 0.4 0.6 0.6 0.8 0.8 1.0 1.0 of the mold. This surface tension effect naturally comes in Unlike 0.0 sand mold in 0.4 investment mold lighter hot air easily get 0 Percentage of Volume Percentage Percentage of Volume of Volume controlling which0.6is to be 0.07the kinetics 0.2 0.4 0.8 taken 1.0 care of further for dispatched initiating a suction within the mold effected by Calculated Filling Time Percentage of Volume actual gating system in investment molds. normal atmospheric pressure pushed on the liquid metal in Experimented Filling Time 6 the sprue. 5 Conclusion

0.8 1.0 0.2

1.0

0.4

0.6

0.8

Tab. VII. Yield Percentage of Volume

1.0

and Reynold’s Nos. of cast-

ings

Fig. 8. Comparison of experimental and calculated filling time with respect to percentage of volume filled for casting: dancing doll 7 6

152 me (s)

5 4

Fig. 9. Comparison of experimental and calculated filling time with respect to percentage of volume for casting: tortoise

Calculated Filling Time Experimented Filling Time

S l é vá re ns t v í . L X V . k v ě te n – č e r v e n 2017 . 5 – 6

Model

Yield of casting

Reynold’s No

Doll

74 %

2814

Tortoise

72 %

2940

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