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1 现代微孔密封技术概述 在目前国内的生产技术条件下,常可见到灰口铸铁或铜、铝和镁等合金浇铸的铸件存在很多孔隙。以铝合金铸件为例,铝合金溶液在冷却和凝固的时候,仅由于其液体状态向固体状态的变化,随着大约有5％的体积变化而产生收缩孔。随着进一步的凝固,混杂在溶液中的氢气释放出而产生气泡,从而形成气孔。凝固时的收缩和气体释放相关连,从而产生出管状、大型球状孔、针孔、粒界龟裂和收缩性多孔质等各种缺陷,这种缺陷的结晶
1 Overview of modern micro-porous sealing technology In the current domestic production technology, often seen in gray cast iron or copper, aluminum and magnesium alloy casting castings, there are many pores. Taking aluminum alloy castings as an example, when the aluminum alloy solution is cooled and solidified, the shrinkage pores are generated with a volume change of about 5% only due to the change of the liquid state to the solid state. With further solidification, the hydrogen mixed with the solution is released to generate bubbles, thereby forming pores. The shrinkage during solidification is related to gas release, resulting in various defects such as tubular, large spherical pores, pinholes, grain boundaries and shrinkage porosity, and the like