A simple and accurate method has been developed for the metallographic analysis of vanadium in high strength steel.
1. Separation of vanadium compound from steel.
(a) The steel sample covered with close-texture filter paper as a diaphragm and connected as an anode, is dissolved into 100 to 130m
l of 1% NaCl-5% EDTA electrolyte (pH 6-7) with current density of 50 mA/cm
2 for 1 to 2 hr. Remove the anode, and residue is collected into the filter paper. To the residue and filter paper add 50ml of HCl (1: 4), and pass in a stream of air for 30 min at room temperature.
(b) Filter and wash with water. Add 5m
l of HNO
3 and 10m
l of HClO
4 to the filterate and evaporate to dense white fumes, cool, dilute to 50ml and determine vanadium as (Fe, V)
3C in accordance with section 2.
(c) Add 30m
l of HNO
3 and 20m
l of HClO
4 to the electroyte and evaporate to dense white fumes, cool, dilute to 100m
l, and determine vanadium as solid solution in accordance with section 2.
(d) Transfer the paper and residue (paragraph (b)) to a beaker, add 30m
l of HCl (1:1) and boil for 5 min.
(e) Filter and wash with water. Add 5m
l of HNO
3 and 10m
l of HClO
4 to the filterate and evaporate to dense white fumes, cool, dilute to 50ml, and determine vanadium as V
2O
3 in accordance with section 2.
(f) Transfer the paper and residue (paragraph (e)) to a beaker, add 40m
l of HNO
3 (1:3), and boil for 5 min.
(g) Filter and wash with water. Add 10m
l of HClO
4 to the filterate and evaporate to dense white fumes, cool, dilute to 50m
l, and determine vanadium as V
4C
3 in accordance with section 2.
(h) Transfer the paper and residue (paragraph (g)) to a beaker, add 30m
l of HNO
3 (1:1) and 5ml of H
2O
2 and boil for 10 min.
(i) Filter and wash with water. Add 10m
l of HClO
4 to the filterate and evaporate to dense white fumes, cool, dilute to 50m
l, and determine vanadium as VN in accordance with section 2. Discard the residue.
2. Photometric determination of vanadium.
Transfer 20m
l of each of solutions (section 1.(b), (c), (e), (g) and (i)) to separatory funnels, add 2m
l of copper solution (0.5%) and 1 drop of KMnO
4 solution (1%), and let stand for 5min. Add 15m
l of N-benzoylphenylhydroyxylamine chloroform solution (0.067%) and 10m
l of HCl (2:1), and shake for 30 sec. Measure the absorbance of organic phase against chloroform at 530mμ.
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