In the process of sand casting, especially the process of casting by adding CO2 gas to the mold (CO2 process) is often found defects caused by sand that incorporated into the casting product or sand that is molten to the metal liquid. This may be due to an unsuitable composition between sand, binder and CO2 gas serving as hardener.
In this research we will look for the most appropriate composition of a mixture of silica sand, a sand binder called a sodium silicate / waterglass and the amount of CO2 gas that needs to be added to the mold by varying the waterglass and CO2 levels. After that the molding sands will be tested for strength, hardness and toughness by conducting tensile testing, hard testing, and broken testing. The test variable is given based on the hardening reaction of the mold by CO2, that is Na2O. mSiO2. H2O + CO2 ? NaCO3. H2O + SiO2. Meanwhile, to support the research, casting products will be tested by radiography method. From the sand testing result, it was found that 6% waterglass and CO2 at 150 kPa pressure had the highest tensile strength and hardness of 5 N/cm and the sand hardness surface value of 2,1 mm, but had the lowest toughness value of 32 N/cm2. In the test of castings with radiographic method, it was found that castings with waterglass composition of 4.5% were seen to have the least defect of castings. |