Adhesion Research In The Reclaimed Process Of Foundry Returned Clay (Mixed) Sand

Our country is the largest producer of castings, casting output has ranked first in the world, the emissions of the used sand is very large. If the used foundry sand doesn’t been regeneration, this is an enormous waste for the limited resources, and will also cause serious environmental pollution. Through adhesion research in the reclaimed process of foundry returned clay (mixed) sand, can obtain the quite explicit regeneration technology mechanism of foundry used sand, and provide a solid theoretical basis for solving the problem of mixed used sand reclamation.In this paper, has designed a test device of foundry sand binder adhesion.This device use quartz chip to simulate the ideal sand surface, through the shear stress and drawing force to detect adhesion between quartz chip and the adhesive, accordingly,as adhesion between sand and the adhesive test results. The test device is fabricated in the sand strength machine used, with the characteristics of accurate measurements、reasonably simple structure、low price、easy to use.Through researching adhesion of several commonly used bentonite with temperature changes, the results show that:from room temperature to 300℃, between bentonite and quartz’s shear stress is gradually increasing; From 300℃1100℃, shear stress is gradually decreasing; When heated to 800℃, a small amount of bentonite automatic abscission from quartz chip, when heated to 1100℃, this phenomenon is more obvious, large pieces of bentonite abscission from the quartz-chip. Between bentonite and quartz’s drawing force changes is more complex, after air-dried at room temperature for 24 hours, between bentonite and quartz chip have a greater drawing force; Around at 600℃, drawing force is the smallest; From about 700℃to 1000℃, the drawing force began to increase.The results from the X-ray diffraction can be seen:after air-dried at room temperature for 24 hours, the mineral composition of bentonite contain a large number of crystal water and structural water; When heated to 900℃in the material composition, there is no crystal water or structural water, comparison air-dried at room temperature for 24 hours, mineral composition of bentonite has become a great changes. From scanning electron microscope images can be seen, after air-dried at room temperature for 24 hours, between bentonite and quartz chip’s bonding interface, bentonite is a layer sheet, attached to the quartz chip, but at 900℃,the bonding interface is the honeycomb.In the study of water vapor method、low-temperature method、hot method and microwave,in addition to water vapor method has significantly reduced for bentonite adhesion, the use of other methods does not significantly reduce for adhesion. In the study of bentonite thickness change, with the increase in thickness of bentonite, bentonite film crack increasing, adhesion reducing.In the study adhesion of resin-bonded sand, the results show that:furan resin film appear coking phenomenon at 300℃, resin film become dark.At 400℃, resin film is burned off a large portion. At 500℃,resin film was completely burned out, sand surface and with the same new sand surface have the same microscopic characteristics. After hardening, furan resin film adhesion is largest. After hardening, the heating temperature from 100℃to 500℃,as the temperature increasing, adhesion decreases, especially when heated to 300℃, adhesion began to sharply reduce, when heated to 500℃, adhesion to OMPa.In the study adhesion of clay and resin compound adhesive film, the results show that:Under the same conditions, mixed adhesive film adhesion is obviously smaller than the single resin adhesion.Through researching several chemical on the effects of bentonite adhesion, the results show that:bentonite at room temperature, methanol and ethanol have the greatest impact on the adhesion, the two chemical reduce adhesion to OMPa. bentonite at 900℃, the impact of chemical on adhesion is not very clear, Only butyric acid reduce adhesion more obvious.Through researching several chemical on the effects of foundry returned clay (mixed) sand:through testing the sediment percentage found that, in the speed of 2600 r/min,round-barrels spacing 3mm, compared to do not add any chemical to increase the mill for half an hour, add ethanol、water solution and ethanol、butyric acid、water solution, percentage reduction is obvious.But in the speed of 3000 r/min,round-barrels spacing 3mm, add ethanol、water solution and ethanol、butyric acid、water solution,the effect is not very clear. through testing the alexa reduction、grain size distribution、acid consumption value found that, compared to do not add any chemical to increase the mill for half an hour,add ethanol、water solution and ethanol、butyric acid、water solution, the impact on the properties of reclaimed sand is not great, numerical tests are very close to.