Abstract
This work, a part of a general program of research on the state analysis of steel, was carried out to develop a simple method for extraction and determination of molybdenum carbides [(Fe, Mo) 3C and Mo2C] in low alloy steel. The procedure is as follows:
1. Extraction of molybdenum carbides from steel.
(a) Cover the steel sample with close-texture filter paper as a diaphragm, connected as an anode, is dissolved into 100 to 130ml of 1% NaCl-5% EDTA electrolyte (H 6 to 7) at a current density of 50mA/ cm2 for 1 to 2 hr. Remove the anode and the residue is collected into an Erlenmeyer flask. To the residue add 20ml of 6N HCl and pass in a stream of argon gas for 10 min at room temperature.
(b) Filter and wash with water. Add 5 ml of HNO3 and 10ml of HC1O4 to the filtrate and evaporate to dense white fumes. Cool dilute to 100 ml and determine Mo as (Fe, Mo) 3C in accordance with section 2.
(c) Transfer a quarter of the electrolyte to a beaker. Add 20ml of HNO3 and 10ml of HC1O4 and evaporate to dense white fumes. Cool, dilute to 100 ml and determine Mo as solid solution in accordance with section 2.
(d) Transfer the paper and residue (paragraph (b)) to a beaker, and 30 ml of HNO3 and 10 ml of HC1-O4 and evaporate to dense white fumes. Cool, dilute to 100 ml and determine Mo as Mo2C in accordance with section 2.
2) Photometric determination of molybdenum.
Transfer 10 to 20 ml of each of solutions (section 1 (b), (c) and (d)) to 50ml volumetric flasks. If the iron contents is less than 40 mg, add iron solution (0.02g Fe/m/) until a total of40 to 50 mg of iron. To each flask add 5 ml of thiourea solution (10%), 8 ml of HC1O4, 2 ml of NaCNS solution (30%) and 10 ml of ascorbic acid solution (5%), dilute to 50 ml and let stand for 10 min. Measure the absorbance of solution against water at 460 mu.
A complete analysis can be carried out in 3 to 4 hr.
