铂金首饰铸造用石英坩埚的使用效果

Service Effect of Quartz Crucible for Platinum Jewelry Casting

采用电感耦合等离子体发射光谱仪、X射线荧光光谱仪、热膨胀仪、体视显微镜、扫描电镜、X射线衍射仪等手段对铂金首饰铸造用石英坩埚的使用效果进行了研究。结果表明,石英坩埚的抗热震性较好,但是耐热度不足,在铂金熔化的高温作用下,坩埚内壁呈现熔融状态,并伴随大量气泡,浇注时容易有部分熔融石英和气泡被带入铸型。金属液浇注后在坩埚内壁熔融态石英形成透明玻璃层,并产生了明显的气泡带及少量的金属珠滞留,在坩埚外层则出现了少部分的方石英转变,坩埚容积随着熔炼次数的增多而不断扩大,增加了开裂倾向。

The service effect of the quartz crucible commonly used for platinum jewelry casting was analyzed with ICP-AES, XRF, thermal dilatometer, stereomicroscope, SEM and XRD. The results indicate that the quartz crucible has good thermal shocking resistance, however, its heat resistance is low, so under the high temperature effect of the molten platinum alloy, the crucible inner wall presents as the fused state with amounts of bubbles, thus it is inevitable that part of fused quartz and bubbles are drawn into the mold cavity during pouring. After pouring, the fused quartz in the inner wall of the crucible is formed into translucent glass layer with an obvious bubble band and some metal beads embedded, while there exists a little of cristobalite transformation in the outside wall, and the crucible volume will enlarge continuously with the increase of melting times, increasing the cracking tendency.