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After the sodium water glass sand is blown hardened by CO2 and left for a period of time, sometimes a substance like white frost will appear on the surface of the lower mold (core), which seriously reduces the surface strength at that place, and is prone to sand flushing defects during pouring. According to the analysis, the main component of this white substance is NaHCO3, which may be caused by too much water content or CO2 in the sodium water glass sand.
The reaction is as follows: Na2CO3+H2O→NaHCO3+NaOH Na2O+2CO2+H2O→ 2NaHCO3 NaHCO3 is easy to migrate outward with moisture, so that frost-like powder appears on the surface of the mold and core. The solution is as follows: 1. Control the moisture of sodium water glass sand not to be too high (especially during steel shaft factory the rainy season and winter). 2. The CO2 blowing time should not be too long. 3. The hardened type and core should not be left for a long time. 4. Add syrup with a density of 1.3g/cm3, which accounts for about 1% (mass fraction) of the sand, to effectively prevent powdering on the surface.
After the sodium water glass sand is blown hardened by CO2 and left for a period of time, sometimes a substance like white frost will appear on the surface of the lower mold (core), which seriously reduces the surface strength at that place, and is prone to sand flushing defects during pouring. According to the analysis, the main component of this white substance is NaHCO3, which may be caused by too much water content or CO2 in the sodium water glass sand.
The reaction is as follows: Na2CO3+H2O→NaHCO3+NaOH Na2O+2CO2+H2O→ 2NaHCO3 NaHCO3 is easy to migrate outward with moisture, so that frost-like powder appears on the surface of the mold and core. The solution is as follows: 1. Control the moisture of sodium water glass sand not to be too high (especially during steel shaft factory the rainy season and winter). 2. The CO2 blowing time should not be too long. 3. The hardened type and core should not be left for a long time. 4. Add syrup with a density of 1.3g/cm3, which accounts for about 1% (mass fraction) of the sand, to effectively prevent powdering on the surface.
