Determination of Nitrogen in High Carbon Ferrochromium by Graphite Capsule Method

Abstract

A vacuum fusion method was used for determination of nitrogen in high carbon ferrochromium by means of a graphite capsule method. Comparisons of metal baths, grain size and grain states of colors were investigated. Nickel, Platinum and Cerium alloys of these metals were used as metal baths for promoting complete extraction of nitrogen from the sample. Best results were obtained when 0.4g of sample and 0.8g of Platinum-Cerium (6%) alloy were enveloped in a degassed graphite capsule and were extracted nitrogen at 1850°C for 20min in the apparatus used. Sample grains were manually fractionated by their surface color and were determined nitrogen with both conventional and the capsule method using PlatinumCerium alloy as bath metal. Black fraction gave nitrogen values as high as 0.038%, while white one gave 0.024%. Dependence of nitrogen value on grain size was detected. Compalative determination were made for nitrogen in the sample of 200-280 mesh size with this method, two chemical methods (Maekawa method and SnCl₂-polyphosphoric acid method), an oxidizing fusion method and an inert gas fusion method. The nitrogen values obtained by these methods were 0.036%, 0.029%, 0.031%, 0.024%, 0.027%, respectively. The best result was assumed to be the highest one, because all of these methods were suffered from negative inclinations.