Study On The Sodium Silicate Sand Used In Iron Castings

?The sodium silicate sands process has many advantages including being odor free,non-toxic and environme.tally friendly,hence it is considered as one of the most promising casting mould sands to allow low environmental impact.However,sodium silicate sands were poor in collapsibility after pouring and the bum-on defects were often found in the production of steel casting.Both problems limited the popularization and application of sodium silicate sand.Therefore,the subject of this research was the study on the collapsibility of sodium silicate sand and the penetration defect of iron castings.Firstly,in order to determine the hardening process of CO₂ sodium silicate sand under laboratory conditions,the hardening mechanism of CO₂ sodium silicate sand was analyzed.The test sample preparation equipment and the blowing hardening device were redesigned and invented the hot air-CO₂ mixed gas blowing hardening device.The pressure and temperature of blown mixed gas were well chosen.Besides,the effects of the blowing time and the flow rate of mixed gas on the room temperature strength of sodium silicate sand were studied.The results showed that when the blowing time is 50s to 60s and the flow rate is 30 L/min,the initial strength could ensiure the need of drawing,meanwhile the final strength was high enough.Secondly,our Research Group has invented the additives and studied the influence of DH additives on the collapsibility of sodium silicate sand.Besides,orthogonal test was used to optimize the amount of additives,the amount of sodium silicate and blowing process.The results showed that after adding the additive,the "double peak" phenomenon of retained strength curve disappeared.Retained strength entered in a downtrend,thus improving the collapsibility of sodium silicate sand significantly.When the amount of additive ? was 0.6 percent;the amount of additive? was 5 percent;the amount of sodium silicate was 5 percent;the proportion of CO₂ in the mixed gas was 40%,the initial strength and final strength and the residual strength at 800 and 1000 degrees were more reasonable.Eventually,the penetration defects produced in the production of iron has been studied and analyzed.The interface of sodium silicate sand mould and iron casting were simulated and the sintering of the simulative interface with additives was carried out.The effects of additives on the sintaing properties of the sintered interfaces were investigated.At last,the molding sand,composed of sodiun silicate sand and the additives,was used in dhe pouring experiment of iron casting sample.The results showed that,in the process of casting,adding the additive can reduce mold's surface pore,prevent metal penetration,and thus improving the penetration defect of iron casting substantially.The pouring experiment results showed that the sintered layer at the interface of casting and sodium silicate sand mold had obvious brittleness when cooling to room temperature and could be cleaned easily.