It is often assumed that hydrogen may be desirable or tolerable in pressure-tight applications. The assumption is that hydrogen porosity is always present in the cast structure as integrally enclosed rounded voids. In fact, hydrogen porosity may occur as rounded or elongated voids and in the presence of shrinkage may decrease rather than increase resistance to pressure leakage.
Hydrogen Removal
Dissolved hydrogen levels can be reduced by a number of methods, the most important of which is fluxing with dry, chemically pure nitrogen, argon, chlorine, and freon. Compounds such as hexachloroethane are in common use; these compounds dissociate at molten metal temperatures to provide the generation of fluxing gas. Gas fluxing reduces the dissolved hydrogen content of molten aluminum by partial pressure diffusion. The use of reactive gases such as chlorine improves the rate of degassing by altering the gas/metal interface to improve diffusion kinetics. Holding the melt undisturbed for long periods of time at or near the liquidus also reduces hydrogen content to a level no greater than that defined for the alloy as the temperature-dependent liquid solubility.
ezgi çevrilecek kısım hangisiyse ben de çevirip gönderebilirim
nihan taşkın 05054060
tamam ezgi çevireyim bu arada elif ezginin nosu 05054059
Bu canım :)
zaten cok bişi yok :D
herkese versek gönderdiğimden de az tutar aslında :D
05 Kasım 2009 18:06 tarihinde deniz bilen <bilen...@gmail.com> yazdı:
hepsi bu mu bu paragrafı yani sadece peki cevirip yollarım
virdim ama
05 Kasım 2009 17:47 tarihinde ezgi kapan <ezgi...@gmail.com> yazdı:
deniz canım sen üçüncü sayfadaki şu kısmı çevir canım. en iyisi ben bölüştüreyim de hallolsun :)
It is often assumed that hydrogen may be desirable or tolerable in pressure-tight applications. The assumption is that hydrogen porosity is always present in the cast structure as integrally enclosed rounded voids. In fact, hydrogen porosity may occur as rounded or elongated voids and in the presence of shrinkage may decrease rather than increase resistance to pressure leakage.
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Ezgi Kapan
Yıldız Teknik Üniversitesi
Kimya Metalurji Fakültesi
Metalurji ve Malzeme Mühendisliği
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deniz :)
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Ezgi Kapan
Yıldız Teknik Üniversitesi
Kimya Metalurji Fakültesi
Metalurji ve Malzeme Mühendisliği
Hydrogen in Solid Solution
The disposition of hydrogen in a solidified structure depends on the dissolved hydrogen level and the conditions under which solidification occurs. Because the presence of hydrogen porosity is a result of diffusion-controlled nucleation and growth, decreasing the hydrogen concentration and increasing the rate of solidification act to suppress void formation and growth. For this reason, castings made in expendable mold processes are more susceptible to hydrogen-related defects than parts produced by permanent mold or pressure die casting.