Fig. 6. SEM images were taken of the sample cross-section.
图6. 样品截面的 SEM图。
In addition to detailed SEM analyses, the casting defect
also underwent x-ray diffraction analysis (XRD). Tis process confirmed that the sample consist of amorphous SiO2
and colloidal carbon. Detailed analysis of the casting defect shows that the white film comprises three phases: silicon, oxygen and colloidal carbon. Te casting defect spreads from the mold side in the direction of the iron.
Theory According to literature on the subject, solid, amorphous
SiO can form following the simultaneous vaporiza- tion of silicon and silicon dioxide in a vacuum at around 1,400C and condensate on the surface. SiO gas consists of diatomic molecules with a silicon-oxygen double bond. According to the literature, five modifications of solid SiO exist depending on the cooling speed or condensa- tion temperature following vaporization. At temperatures in excess of 800C, a yellow-brown powder is formed; at temperatures in excess of 1,000C, yellow-colored glass is formed. Both substances contain Si and SiO2
. Below
800C, a black, glassy substance is formed; at even lower temperatures, the black, coke-like character of solid SiO is formed. During quenching with a water-cooled device, a black, fibrous modification is formed. According to theory, the SiO molecules bond possibly as early as the vaporiza- tion phase before separating into (SiO) chains or rings. In its gaseous state (SiOg
K-1
temperatures in excess of 1,000С. Te following parameters , SC298 = 211.489 J mol-1
), silicon oxide is stable at
have already been calculated for the gas: C �po = 29.901 J mol-1
K-1 , ∆HBil. = 100.000 kJ mol-1 . During rapid cooling, SiOg condenses into a light- 64 |
FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION December 2014
氧和胶体碳。铸件缺陷从砂型侧沿铸铁的方向扩散。 原理
根据有关文献，在真空中约1400℃时，硅和二氧 化硅同时蒸发会形成固态的非晶SiO，并在铸件表面 冷凝。SiO气体由具有硅氧双键的双原子分子组成。 根据文献，视蒸发后的冷却速度或冷凝温度不同，固 态SiO存在5种形式。在温度超过800℃时，形成的是 黄棕色粉末；超过1000C时，产生黄色的玻璃状固 体。两种固体都包含Si和SiO2
。温度低于800℃时，
产生黑色的玻璃状物质；温度更低时，形成黑色的 焦炭状SiO固体。使用水冷设备淬火时，产生的是黑 色的纤维状固体。结合理论，SiO分子可能在分离至 （SiO）链或环之前便已在蒸发阶段结合。 气态的硅氧化物（SiOg
）在温度超过1000℃时
保持稳定。已经计算出该气体的如下参数：Cp^o = 29.901 J mol-1
K-1 S298^0= 211.489 J mol-1
中，SiOg冷凝为淡棕色非晶产物SiOx-1 g/cm3
非晶SiOx (0 < x < 1)，SiOx
, ∆H(Bil.)= 100.000 kJ mol-1 K-1
,
。在快速冷却的过程 （密度：2.15
）。真空条件下，它将继续蒸发，冷凝产生 的性质可以根据蒸发条
件确定。在时效和退火过程中，SiOx退化为Si和SiO2
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