ISO 4491-3:1997 pdf download – Metallic powders – Determination of oxygen content by reduction methods
1 Scope
This part of IS0 4491 specifies a method for the determination of the hydrogen-reducible oxygen content of metallic powders containing 0,05 % (m/m) to 3 % (m/m) oxygen.
The method is applicable to unalloyed, partially alloyed or completely alloyed metal powders and also to mixtures of carbides and binder metal. It is not applicable to powders containing lubricants or organic binders.
The method may be extended to powders containing carbon by the use of a special catalytic device.
This part of IS0 4491 shall be read in conjunction with ISO 760 and IS0 4491-I.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO 4491. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of IS0 4491 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 760:1978, Determination of water – Karl Fischer method (General method).
ISO 4491-I :I 989, Metallic powders – Determination of oxygen content by reduction methods guidelines.
42 . Karl Fischer reagent, equivalent to 1 mg of oxygen per millilitre.
Determine the titre of the Karl Fischer reagent by one of the following methods:
a) Add to the titration flask 20 mg to 30 mg of water, weighed to the nearest 0,l mg.
b) Add 100 mg to 200 mg, weighed to the nearest 0,l mg, of sodium tartrate dihydrate [certified material containing theoretically 1566 % (m/m) of water, corresponding to 13,92 % (m/m) of oxygen], previously ground to fine powder and dried at 105 ℃ + 5 ℃ to constant mass.
c) Use the method described in clause 7, taking 100 mg to 200 mg of pure sodium tartrate dihydrate, weighed to the nearest 0,l mg, as the test portion, but limiting the procedure to the drying step at 170 OC and the subsequent titration.
See IS0 760 for detailed procedures of standardization.
4.3 Hydrogen, having a maximum oxygen content of 0,005 % (m/m) and a dew point not exceeding – 45 ℃. 44 . Nitrogen or argon, having a maximum oxygen content of 0,005 % (m/m) and a dew point not exceeding – 45 ℃.
5.6 Reduction tube (F), gas-tight, made of quartz or refractory material (for example dense alumina), meeting one of the following sets of specifications:
a) A tube closed at one end with an internal diameter of 27 mm to 30 mm and a length of about 400 mm with two smaller quartz tubes of diameter 5 mm to 6 mm and lengths 60 mm to 80 mm and 200 mm to 240 mm, respectively, arranged as shown in figure 3. This arrangement is inserted into the first drying furnace and then into the reduction furnace.
b) An open-ended tube with an internal diameter of about 20 mm, a length of 1 m, and a gas inlet and outlet. This tube is permanently inserted in the two furnaces
5.7 Two furnaces (G), one for drying the test portion and the other for oxide reduction, with temperature control systems capable of maintaining the temperature in the part of the tube containing the boat (5.8) within the specified temperature tolerances.
NOTE – If available, one furnace combining both these functions may be used.