Research On The Materials And Preparation Technique Of An Inorganic Binder For Warm Box Core-making Process

The focus of research on binder has begun to environmentally friendly direction.Although resin sand was widely used,to some extent,improved the casting quality and production efficiency.But resin sand would send out pungent odor and harmful gas in use process,polluted the environment.The inorganic binder has the characteristics of low gas evolution and avirulent environmental protection,it was the developing direction of the green binder.In this thesis,an inorganic binder was prepared,with low addition,high strength,good collapsibility,it can be used in casting production.Firstly,with the ordinary sodium silicate as the main part of binder,the binder was cured by a warm-box process in which a powder hardening accelerator was added and a hot air was blown.But the strength and collapsibility of sand was not good.Therefore,potassium hydroxide,sodium pyrophosphate,B agent and silane were used as compound modifiers,and a good result was achieved.The tensile strength and collapsibility of core were used as main index and the proportion of the components was decided by an orthogonal test as followed: water glass: potassium hydroxide: B agent: sodium pyrophosphate:silane=1000: 45: 8: 4: 2.Then,the hardening accelerator was introduced into the mixing sand,and the proportion of the components was decided by an orthogonal test as followed: crystalline silica: silica fume: D agent: starch=15:10:1:1.The technological parameter of the warm box core-making process was decided by an orthogonal test as followed: the core box temperature was 175?,heating air temperature was 120? and the blowing time of hot air was 40 s.The properties of modified binder are as followed: the viscosity is 78mPa·s,modulus is2.33,density is 1.45g/cm3.With the binder addition 2%,curing-promoter addition 0.6% and surfactant addition 0.5% to the sand,the thermal strength of sand was 0.63 MPa,the atmospheric temperature strength can be 2.60 MPa,the strength after 4 hours can be 2.64 MPa.The strength after 24 hours can be 2.54 MPa.The gas evolution was 8.5ml/g in the850?×3min condition,high temperature residual strength was 0MPa in the 750?×5min condition.The binder can meet the requirements of casting production.Finally,a core-making and proving casting experiment were done successfully with theprepared inorganic binder,a qualified casting was produced,and the production process was evaluated.