A virtual leak is a pocket of gas physically trapped within the weld with only a small, very low conductance, path from which to evacuate. Learn about common examples of virtual leaks and what causes them.
The most basic difference between grade 304 and grade 316 stainless steels is that 316 tends to have more nickel and a bit of molybdenum in the mix. Though the stainless steel 304 alloy has a higher melting point, grade 316 has a better resistance to chemicals and chlorides (like salt) than grade 304 stainless steel. 316 has better resistance to acids, alkalis, and chloride pitting. 316 has a maximum use temperature of 800 degrees C.
Across various industries, vacuum purging is used to remove volatile substances/chemicals from the test item at low temperatures first before heating. Under vacuum, butane, propane, and other solvents convert into a gaseous form and evaporate, also known as “outgassing.” Vacuum purging works by lowering the atmospheric pressure in a vacuum oven chamber. Atmospheric pressure prevents “outgassing” from the surface area of the test specimen.
Metals the most prevalent choice of vacuum chamber materials, with stainless steel (SS) far ahead of other metals such as mild steel. For example, deciding to use SS doesn’t mean any and all SS alloys. Free-machining alloys such as 303 SS contain sulfur (S), but the vapor pressure of the sulfur (S) is too high for high vacuum systems. 304 SS, though, is the most common choice. This helps narrow things down, but for ultrahigh vacuum (UHV) the low-carbon 304L alloy is recommended.
Historically, the following three factors have made stainless steel the preferred material for the manufacture of vacuum chambers.
Published by Oerlikon Leybold Vacuum. Oerlikon Leybold Vacuum, a member of the globally active industrial Oerlikon Group of companies has developed into the world market leader in the area of vacuum technology.
