首饰石膏铸型焙烧工艺试验

Baking Process Experiment of Gypsum Investment Mould in Jewelry Casting

从铸粉的热膨胀收缩曲线出发,拟定铸型的焙烧制度,测量了铸型内部温度与炉膛温度的同步情况,并试验了炉膛内气氛对焙烧效果的影响。结果表明,石膏铸型内部温度相对炉膛温度有较大的滞后,焙烧制度应采用控制升温速度和多平台保温的方式。焙烧过程中向炉膛内充入空气,有利于清除残留碳,提高铸型质量。对试验铸粉材料,适合的焙烧制度为:室温至180℃(125℃/h);180℃保温1 h;180℃至350℃(135℃/h),350℃保温1.5 h;350℃至730℃(175℃/h),730℃保温3 h;铸造温度下保温1.5 h。

The burnout process of gypsum investment mould determine the ultimate performance to a large extent. In this paper, based on the thermal expansion curve of the tested powder for investment mould, the baking cycle was put forward and the synchronization between the hearth temperature and the mold temperature was measured, and the effect of the hearth atmosphere on baking effect was tested. The experiment results showed that the internal gypsum mould temperature had a large lag relative to the hearth, therefore, the baking cycle should take the style of controlledjheating speed and multi-platformed heat preservation. Besides, introducing dry fresh air into the hearth during the baking is conducive to removal of residual carbon and improving the quality of the mold. For the tested investment mould powder, the suitable baking schedule was as below： heating from room temperature to 180 ℃ （125 ℃/h） ＋ 180 ℃ （holding for 1 h） ＋ heating from 180 ℃ to 350 ℃ （135 ℃/h） ＋ 350 ℃ （holding for 1.5 h） ＋ heating from 350 ℃ to 730 ℃ （175 ℃/h） ＋ 730 ℃ （holding for 3 h） ＋ casting temperature （holding for 1.5 h）.