Research On The Preparation Technique Of A Phosphate Bake Binder For Foundry

Inorganic Phosphate binder is a new type of foundry binder and has very application value for its low gas evolution, good collapsibility, non-toxic and environmental protection,as compared with the organic resin binder. But its poor stability, poor humidity resistance and low sticking power are still existed that limited its applacation in practice. In this paper,an Al-Zn compound phosphate binder was prepared, with high strength and good humidity resistance, can be used in casting production.Firstly, the theory of phosphate binder preparation process was analyzed, and aluminum dihydrogen phosphate and zinc dihydrogen phosphate were identified as the main ingredient of compound phosphate binder. Testing showed that Al-Zn compound phosphate binder has a great advantage in terms of strength and stability, but its humidity resistance remains to be improved.Next, the influence of modifier species and amount for phosphate properties was explored. It was found that the effection of magnesium oxide and M agent simultaneously adding to the binder much better than singly adding is more stable. On the basis of the adding amount of phosphoric acid and water is 265: 70, The tensile strength of sand was used as main index and the proportion of the components was decided by an orthogonal test as followed: phosphoric acid: aluminum hydroxide: Zinc Oxide: M agent =265: 35: 26: 9:10, the modified binder has a good storage stability.Then, hardening process was studied, which illustrated that the humidity resistancer,tensile strength and other properties of the binde had close realationship with hardening processes, When the heating temperature is too high or too low and the heating time is unduly long or too short, it will affect the binder strength. Finally, the best combination of drying temperatures and drying time was 200℃×20min.Ultimately, the properties of the phosphate binder was tested, performance indicators are as follows: viscosity was 475mpa·s; hardening process was 200℃×20min, when the binder was added 3%, initial tensile strength was 3.05 MPa, 24 h tensile strength was2.47MPa;gas evolution was 10ml/g, high temperature residual strength is 0MPa; through the production verification test, the castings had a good surface quality, the sand had a good collapsibility.