Green sand formula for casting

Reference materials for sand properties

1. Raw materials

1) The original sand is mostly made of silica sand with a particle size equivalent to No. 6. For situations where surface quality of castings is highly valued, sometimes a mixture of No. 7 silica sand is also used.

2) Additives

① Both Ca and Na based bentonite are used in practical applications. When selecting additives, in addition to considering machine characteristics, the ability of the target product (pouring weight and shape, etc.) and the sand box dismantling equipment should also be considered.


② Coal powder often uses marine coal with an ash content of around 8%


2. Recommended values for properties of mixed molding sand

1) Moisture: 3-4% (ensure appropriate moisture value for CB, prioritize management of CB value)

2) CB value: 33-39% (during the stage of supplying sand to the molding machine, the CB value excluded by the sand mixer should be adjusted reasonably)

3) Compression strength (compressive): 10-14N/cm2 (1.0-1.4K)

G/cm2)

4) Total clay composition: 10-12% (this is to ensure water retention and reduce changes in CB value)

Reference value:

5) Breathability: above 120


6) Lg Loss: 3-4%


7) Active clay composition: 6-8%


8) Surface stability: above 85%


3. Reference value for the addition rate of additives (the ratio added to the sand mixer)


① Bentonite 0.3-0.6%


② Coal powder 0.05-0.15%


4. Reference materials for raw sand materials


1) Silica sand


① SiO2 purity: above 95%


② Particle size index: equivalent to AFS62


③ In terms of particle size distribution, the sum of 200mesh, 280mesh, and PAN is below 0.1%


2) Bentonite


① Montmorillonite content: Na based bentonite with over 90% content


② Moisture: 8-10%


③ Particle size: 200mesh, passing 75-85%


④ PH: 8.5-10.5


3) Coal powder


5. Ash content: below 8%


① Volatile components: 42 ± 3%


② Fixed carbon: 48 ± 3%


③ Particle size: 200mesh, passing through more than 50%, passing through less than 5% at 35mesh.

a) New sand raw material reference

When using new sand to make sand molds, mix thoroughly in the ratio of 100 parts of new sand, 7.5 parts of bentonite, 2 parts of coal powder, and 0.5 parts of starch, and prepare the mixed molding sand.