Most investment casting foundries use Zircon Flour for making the primary slurry. Zircon continues to be in short supply and the prices are rising. Many customers began to adopt Fused Silica flour in the dipping and coasting process to make primary slurry, while to use fused silica grains rainfall sander to form a hard ceramic shell. 

 

Some new customers might have main questions as follows:

 

Question 1.

Can fused silica flour and grains be used to replace Zircon flour and grains?Yes,It's ture.

Question 2.How many percentage of Zircon powder can be replaced by fused silica powder?It is usually 25% and 50% max.

Question 3.How to use fused silica sand? It is same as to use Zircon sand.

Question 4.Why fused silica can instead Zircon?

 

Fused silica has the following advantages:

1) Fused silica decrease in material consumption
Fused Silica's density is 2.21g/cm3,just roughly half of Zircon's density. If Zircon flour is replace 20% in primary slurry batch with Fused Silica, it needs lesser material by weight. For example if  slurry mix had 50 kgs of Zircon and try and replace 10 kgs then it would need to add around 6 kgs of Fused Silica flour to achieve the existing viscosities and flow properties.

2) Fused silica increase permeability and porosity
Zircon is very dense. Fused Silica is lighter and does not pack as tightly as Zircon which is why it helps in improving the permeability of your shell. It is also more porous.

3) fused slica ceramic shell is Easier knock-out
Fused Silica knocks out much easier than Zircon or Alumino-Silicates. This is because of the Cristobalite formation while pouring which easily breaks down upon cooling.

4) Faster leaching and shell removal
The moment to add fused silica in the shell it helps in the leaching process and it is much easier to remove shell materials off cavities and holes.

5) Fused Silica price is cheaper
The typical specification sheet of Chem&Size minerals Fused Silica sand,fused silica grains and fused silica powder and fused silica flours for your perusal.
 

1．	Physical Properties
1.1	Composition		SiO2
1.2	Structure		Amorphous
1.3	Colour		Transparent or white
1.4	Melting Temperature		approx.1750℃
1.5	Specific Gravity		2.21g/cm3
1.6	Hardness		7 Mohs
1.7	Thermal Expansion		0.5*10-6
2．	Chemical Properties
		Investment Casting Grade
2.1	SiO2	>99.90%
2.2	Al2O3	<200ppm
	The finer the power,the higher the Al2O3,as powder is produced by ball mill with Alumina ball.
2.3	Fe2O3	<50ppm
2.4	TiO2	<20ppm
2.5	MgO	<40ppm
2.6	CaO	<40ppm
2.7	AlkaliesNa2O+K2O	<100ppm
3.	Particle Size	Distribution

     

		10/20mesh	20/50mesh	30/50mesh	50/100mesh	-100mesh	-200mesh	-325mesh
Mesh	Microns
8	2360	<2
12	1700	6-25
16	1180	33-50
20	850	25-45	<1	<1
30	600	13	25-40	15-30
40	425		32-45	38-50
50	300		15-30	20-35	<13
70	212				30-60
80	180		0-11	<10			<1
100	150				28-51	<15	<1
140	106				4-16	17-40	<10
200	75				<2	19-34	<10	<3
325	45					14-30	15-30	4-11
Pan		<3	<2	<2	<1	4-20	70-80	86-97

 

*Pan designates the percentage of fused silica passing the last reported screen for each size.

4.    Dust Removal

Investment casting grade fused silica is treated by dust removal equipment, so that this grade fused silica dust is in the lowest level.

The difference between common grade fused silica and investment grade fused silica.

4.1 Non Dust Removal fused silica

4.2.Dust Removed fused silica for Investment Casting