ISO 4491-4-2019 pdf download.Metallic powders一Determination of oxygen content by reduction methods一 Part 4: Total oxygen by reduction-extraction.
The materials needed wiLl depend on the type of equipment used, for example high purity inert gas (helium or argon).
Calibration of the measunng device, when necessary, requires high punty gas, CO. CO2. or certified metallic reference materials.
6 Test portion
The analysis shalt be carried out un one or several test port ions The number ul teat portions required to reach the required precision can be determined by a gauge repeatability and reproducibility study II a gauge repeatability and reproducibility study is not made, the analysis shall be carried out on two test portions. Several methods can be used to prepare the test portion prior to its introduction into the apparatus.
a) The teci portion Is weighed directly Into the degacced crucible
b) A quantity of the powder sample is uniaxially compacted in a small cylindrical die, without any luiwicant or binder, under a pressure of 100 MN/mm2 to 200 MN/mm2. The mass of the compact Is determined.
c) A quantity of the powder sample is enclosed in a smaLl capsule of known weight made of platinum. tin, nickel, or Iron-nickel foil of high purity. The whole capsule Is weighed. The oxygen content o( the foil shall be known or determined previously.
d) I tithe case of a compact, a suitable fragment of the sample is weighed as the test portion. All weighings shall be to the nearest 0.000 1 g.
A metal foil capsule maybe used solely to facilitate th introduction of the sample Into the apparatus. In this case, the weight of the capsule shall be kept to a minimum.
Alternatively, the metal of the capsule can constitute the metal bath needed for convenient extraction; in this case, the m,,ss of the capsule is chusen to give the bash/test-portion mass ratio recnmnwndc’cl for the particular analysis.
When the graphite crucible is used with a metal bath for several consecutive analyses, it Is necessary to degas the bath prior to the beginning of each extraction operation.
The bath/test-portion mass ratio is maintained larger than the recommended minimum value. if necessary. by the periodic introduction of fragments of metal followed by degassmg of the bath.
The mass of the test portion shall be selected depending on the sensitivity of the apparattis used and the expected oxygen content. Frequently, a mass between 0,1 g and I g is chosen.
7 Procedure
7.1 General
For the reason given in the Introduction. it is nut poisible to specify the conditions of oxygen determination far each of the various metals, alloys, and carbldes to be analysed, and for each of the types of apparatus avaibble, It should be noted that, especially when the reduction is carried out in the solid state and with continuous heating, the reaction may be slow and the time for complete reduction of the oxides will depend on the oxygen content.ISO 4491-4 pdf download.