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AWS A4.3-93 pdf free download
AWS A4.3-93 pdf free download.Standard Methods for Determination of the Diffusible Hydrogen Content of Martensitic, Bainitic, and Ferritic Steel Weld Metal Produced by Arc Welding.
displacement of glycerin, paraffin, or silicone oil because of the degree of hydrogen solubility in these fluids. The degassing must take place in an inert atmosphere or environment in order to prevent loss or gain of hydrogen through reaction.
Two types of analytical apparatus are known which meet the above requirement. One is a mercury-filled eudiometer, and the other is a gas chromatograph. Both types of apparatus require loading of the test specimen into an isolation chamber and allowing the hydrogen to diffuse out of the specimen, usually at a temperature somewhat above room temperature, into the isolation chamber where it recombines into molecular hydrogen. After evolution of diffusible hydrogen is virtually complete, the volume of hydrogen collected is measured. Whichever analytical apparatus is employed, it shall be accurately readable to 0.02 ml of hydrogen gas or less.
In general, the isolation chamber used for collection must be gas-tight and fabricated of materials which preclude loss of hydrogen collected via diffusion during the time at test temperature.
6.2 Loading the Test Specimen Into the Analytical Apparatus. If the hydrogen analysis results are not affected by moisture or liquid from the low-temperature bath adhering to the test specimen, the test specimen may be loaded directly from the bath into the analytical apparatus. Some gas chromatographs can be used in this way. It is the responsibility of the user to determine from the instrument manufacturer if contaminants on the test specimen at this point affect the results. Specimens shall not be loaded if covered with heavy frost.
For mercury displacement and other apparatus from which results could be affected by moisture or contamination from the low-temperature liquid bath, the specimen shall be cleaned of moisture and other contaminants by agitating in cool water until the resulting ice skin melts. This raises the test specimen temperature to slightly above 0°C (32°F). A quick rinse in a residue-free solvent shall be employed if the low-temperature bath liquid is not water soluble, and may be employed if it is water soluble. In either case, the specimen shall then be wiped dry or blown dry with cool air and immediately loaded into the isolation chamber.
If the analytical apparatus is a gas chromatograph, the required purge gas shall then be vented into the isolation chamber. If the analytical apparatus is a mercury eudiometer, the mercury shall then be drawn up into the eudiometer over the test specimen so that mercury entirely fills the eudiometer to the valve at the top, which is then closed, as described in 7.2. The time from the test specimen reaching 0°C (32°F) to sealing of the purged isolation chamber or eudiometer shall not exceed 150 seconds. See Figure 4 for a sketch of a suitable cud iometer for mercury displacement measurements.AWS A4.3-93 pdf free download.
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