The performance of sand core was improved by using the modified water glass as a binder and adding powder additives in the sand hardening process. The optimal proportion of the compound additives was determined by an ...The performance of sand core was improved by using the modified water glass as a binder and adding powder additives in the sand hardening process. The optimal proportion of the compound additives was determined by an orthogonal test, with a ratio of microsilica: polyvinyl alcohol solution: borax: B agent = 25: 20: 2: 1. The binder accounted for 2% of the sand by weight, and the compound additives accounted for 0.96%. The core box was heated to 175 °C, and the compressed hot air of 120 °C kept blowing for 40 s. Tensile strength was used as the main indicator to evaluate the humidity-resistance of the sand core. For the sand core, the instant tensile strength reached 0.73 MPa, the tensile strength at room temperature was 1.81 MPa, and that of sand core holding at the condition of 35 °C and 90% RH for 2 h and for 4 h reached 1.61 MPa and 1.19 MPa, respectively. The gas evolution was 7.5 mL·g-1 at 850 °C for 3 min. The residual tensile strength was 0 MPa at 750 °C for 5 min. Fourier-transform infrared spectroscopy analysis showed that the humidity-resistance of the core was greatly improved by the powder additives.展开更多
In order to improve the sintering activity of TiC which was usually added into the binder of polycrystalline diamond(PCD) and polycrystalline cubic boron nitride(PCBN),the powders of TiC and Ti mixed as molar ratio of...In order to improve the sintering activity of TiC which was usually added into the binder of polycrystalline diamond(PCD) and polycrystalline cubic boron nitride(PCBN),the powders of TiC and Ti mixed as molar ratio of TiC:Ti = 1:0.3 were treated by mechanical alloying.The structure and the morphology of the milled powders were analyzed by X-ray diffraction(XRD) and scan electron microscope(SEM), respectively.The milled powders were sintered by cubic hinge press.The structure of the sintered sample was analyzed by X-ray diffraction and the hardness was tested.The results showed that the grain size of the TiC and the Ti powders were decreased,as the milling time increased,and the nonstoichiometric compound of TiC_x was formed.The sintering activity of the TiC/Ti powders treated by mechanical alloying increased greatly.The hardness of the sintered sample improved from 829.2 HV for the raw powders to 2587.37 HV for the powders mechanical alloyed 20 hours.展开更多
文摘The performance of sand core was improved by using the modified water glass as a binder and adding powder additives in the sand hardening process. The optimal proportion of the compound additives was determined by an orthogonal test, with a ratio of microsilica: polyvinyl alcohol solution: borax: B agent = 25: 20: 2: 1. The binder accounted for 2% of the sand by weight, and the compound additives accounted for 0.96%. The core box was heated to 175 °C, and the compressed hot air of 120 °C kept blowing for 40 s. Tensile strength was used as the main indicator to evaluate the humidity-resistance of the sand core. For the sand core, the instant tensile strength reached 0.73 MPa, the tensile strength at room temperature was 1.81 MPa, and that of sand core holding at the condition of 35 °C and 90% RH for 2 h and for 4 h reached 1.61 MPa and 1.19 MPa, respectively. The gas evolution was 7.5 mL·g-1 at 850 °C for 3 min. The residual tensile strength was 0 MPa at 750 °C for 5 min. Fourier-transform infrared spectroscopy analysis showed that the humidity-resistance of the core was greatly improved by the powder additives.
文摘In order to improve the sintering activity of TiC which was usually added into the binder of polycrystalline diamond(PCD) and polycrystalline cubic boron nitride(PCBN),the powders of TiC and Ti mixed as molar ratio of TiC:Ti = 1:0.3 were treated by mechanical alloying.The structure and the morphology of the milled powders were analyzed by X-ray diffraction(XRD) and scan electron microscope(SEM), respectively.The milled powders were sintered by cubic hinge press.The structure of the sintered sample was analyzed by X-ray diffraction and the hardness was tested.The results showed that the grain size of the TiC and the Ti powders were decreased,as the milling time increased,and the nonstoichiometric compound of TiC_x was formed.The sintering activity of the TiC/Ti powders treated by mechanical alloying increased greatly.The hardness of the sintered sample improved from 829.2 HV for the raw powders to 2587.37 HV for the powders mechanical alloyed 20 hours.
