Metallographic Analysis of Microarnount of Boron in Boron Treated Steel

Abstract

This paper is a part of the general investigation of new mefallographic analyses for steel. A simple and reliable method is described for the metallographic analysis of microamount of boron in boron treated steel, by a new electrolytic extraction method using NaCl-EDTA solution as an electrolyte.
The procedure is as follows:
1. Separation of boron compound from steel.
(a) Cover the steel sample with close-texture filter paper as a diaphragm, connected as an anode, is dissolved into 100 to 150ml of 1% NaCl-5% EDTA electrolyte (pH 6-7) at a current density of 50mA/cm² for 2 to 4 hr. Remove the anode, and residue is collected into the filter paper. Transfer the paper and residue to a quartz beaker, and 20ml of HNO₃ (1: 2) and boil for 5min.
(b) Filter and wash with hot water. Add 12ml of H₂SO₄ (1: 1) and 6ml of H₃PO₄ (1: 1) to the filterate and evaporate to copious fumes. Dissolve the salt with 50ml of water, cool, dilute to 250ml, and determine boron as carbide continue in accordance with section 2.
(c) Add 12ml of H₂SO₄ (1: 1) and 10ml of H₂O₂ to the electrolyte and boil for 30min, cool, dilute to 250ml, and determine boron as solid solution continue in accordance with section 2.(d) Transfer the paper and residue (Paragraph (b)) to a quartz beaker, add 20ml of HCI (1: 1) and boil for 10min.
(e) Filter and wash with hot water. Add 1 ml of HNO₃ (conc.), 6ml of H₂SO₄ (1: 1) and 4 ml of H₈FO₄ (1: 1) to the filterate and evaporate to copious fumes. Dissolve the salt with 10ml of water, cool, dilute to 100ml, and determine boron as oxide continue in accordance with section 2.
(f) Transfer the paper and residue (Paragraph (e)) to a platinum crucible, and ingnite. at 500°C. Add 1g of Na₂CO₂ and heat gradually until fusion is complete. Cool, take up the melt in 6 ml of H₂SO₄ (1: 1), and dilute to 100ml, and determine boron as nitride continue in accordance with section 2.
2. Determination of boron compound. Transfer 25 in/ of each of the solution of section 1.(b), (c), (e), and (f) to.separatory funnel. Add 10ml of water and 5ml of HF (5%) and let stand for 1hr. Add 20ml of water, 2ml of methylene blue solution (0.001M) and 25ml of dichlorocthane, and shake for 1min. Let stand for 5 min to allow the layers to separate. Filter the dichlorosthane solution through a dry filter paper into a dry absorption cell. Measure the absorbance against blank solution at 660μ.