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作者利用扫描电镜对普通水玻璃砂和SGD型改性水玻璃砂用加热法硬化后的粘结剂分布状况和经历不同温度加热冷却后粘结剂的变化进行考察,以揭示两种水玻璃砂残留强度变化的机理。扫描电镜观察表明:在200～600℃进一步加热后,热硬法普通水玻璃砂的热强度和残留强度剧烈下降的原因是在于加热过程中水份大量脱失而形成带褶皱的薄壁粘结膜空泡的缘故。加热至800℃左右的高温时,由于水玻璃熔融,加大了砂粒与粘结膜之间的结合面,致使残留强度有较大幅度的回升;而在SGD型改性水玻璃砂中则借其中几种改性剂组成分别以残炭、弥散质点和大小不等的气泡形式对粘结膜作不同程度的破环,使其残留的粘结强度大大削弱。文中并指出:无论改性与否,水玻璃砂加热至1200℃时砂粒表面有较大程度的熔化,砂粒与粘结膜之间的界限消失,从而使残留强度再次回升。
Using scanning electron microscopy, the distribution of ordinary sodium silicate sand and SGD modified sodium silicate sand cured by heating method and the changes of binders after heating and cooling under different temperatures were investigated to reveal that the two types of sodium silicate sand Residual strength changes in the mechanism. Scanning electron microscopy observation shows that the reason for the sharp decrease of the hot strength and the residual strength of the hot sapphire ordinary sodium silicate sand after further heating at 200-600 ° C is that a large amount of water is lost during heating to form the thin-walled bonded with wrinkles Membrane bubble reason. Heated to about 800 ℃ high temperature, due to the melting of water glass, increased the bonding surface between the sand and the adhesive film, resulting in a substantial increase in the residual strength; and in SGD modified sodium silicate sand by Several of the modifiers, respectively, to the residual carbon, the size of the dispersed particles and the size of the bubbles in different forms of the adhesive film broken ring to the extent that its residual bond strength is greatly weakened. It is pointed out in the paper that regardless of the modification or not, the surface of grit is melted when the sodium silicate sand is heated to 1200 ℃, the boundary between grit and the adhesive film disappears, and the residual strength rises again.