Research On Hardeners For No-Bake Phosphate Binder Sand

Magnesia often used as hardener for no-bake phosphate binder sand. On the basis of study on it, properties of powder composite hardeners, suspended liquid hardeners, and pure liquid hardeners for no-bake phosphate binder sand were studied. When the addition of phosphate binder is 2%, conclusions are as follows.Firstly, when the addition of magnesia increases from 5% to 10%, scrip time reduces from 80 minutes to 40 minutes. Moderate addition of magnesia makes no-bake phosphate binder sand get highest 24h compressive strength. When the addition of magnesia is 15%, the 24h compressive strength is 0.63MPa. With the addition of magnesia increases, residual strength reduces, but anti-wettability increases.Secondly, powder composite hardeners which contain copper oxide can improve 24h compressive strength and extend scrip time. Powder composite hardeners that contain alumina or PVB can improve 24h compressive strength but have no effect on scrip time. In all powder composite hardeners, the one contains 30% copper oxide is the best one in improving 24h compressive strength. It can improve the 24h compressive strength to 0.97MPa. Though the scrip time extended from 20 minutes to 30 minutes, it still meet the requirement.Thirdly, the best scheme of suspended liquid hardeners was determined by orthogonal test, it is the one industrial alcohol vector and 4% SN suspension agent added by weight based on magnesia powder. At significant level a=0.05, the addition of suspension agent and interaction between vector and suspension agent are significant factors. An acidic material was introduced to improve storage stability of suspended liquid hardeners. Suspended liquid hardeners which contain acidic material never coagulate in long-term storage.Finally, the addition are large when sodium silicate and ethanolamine used as pure liquid hardeners. When sodium silicate used as pure liquid hardener, the highest 24h compressive strength is 0.25MPa when the addition is 80%. When ethanolamine used as pure liquid hardener, the highest 24h compressive strength is 0.02MPa when the addition is 80%, and it can reach 0.25MPa by adjusting the composition of phosphate binder.