Review of Methods for the Determination of Carbon and Sulfur (1)

Determination of carbon and sulfur in steel, first of all, the sample in a high-temperature furnace (such as resistance furnace, high-frequency furnace, electric arc furnace, etc.) through the oxygen combustion, the generation and escape CO₂ and SO₂ gas, with this method to realize the carbon and sulfur and the separation of metal elements and their compounds, and then determine the content of CO₂ and SO₂, and then converted to the carbon and sulfur content in steel. This article summarizes the methods of carbon and sulfur determination.

1.1 Weight Method for Carbon and Sulfur Measurement

The principle of carbon measurement by weight method is to burn the specimen with oxygen, so that the carbon oxidized into CO2. gas mixture by removing sulfur, commonly used alkali asbestos absorption of CO2, from the increment to find out the carbon content.

Sulfur is determined gravimetrically, mostly by the wet method. The sample is oxidized by acid decomposition and transformed into sulfate, then BaCl₂ is added in hydrochloric acid medium to generate BaSO4, and the sulfur content is finally calculated by precipitation, filtration, washing, cauterization and weighing.

The disadvantage of the gravimetric method is that it is slow to analyze, but the advantage is that it has a high degree of accuracy, based on which the gravimetric method has been recommended as a standard method at home and abroad.

1.2 Volumetric Gas Method for Carbon Measurement

The classical isobaric gas volumetric method for carbon determination (absolute values can be determined) has been recommended as a standard method at home and abroad. The specimen is placed in a tube furnace, heated and burned with oxygen to oxidize the carbon to CO₂, and after removing SO₂, the gas mixture is collected in a gas measuring tube and its volume is measured. The CO2 is then absorbed with KOH solution and the volume of the remaining gas is measured. The difference in the volume of the gas before and after absorption is the volume of CO₂, from which the carbon content is calculated, and the measurement range of this method is 0.05%~4.0%.

The measurement range of this method is 0.05%~4.0%. This method is accurate, but it is slow, manual operation is cumbersome and time-consuming. In order to improve the above problems, China's analysts put forward the “differential pressure” gas volumetric method of carbon, the study of the theory of differential pressure carbon determination, the establishment of the equation of differential pressure carbon determination, the development of differential pressure carbon determination of the instrument, the development of the process of differential pressure carbon determination, carbon analysis can be completed within 60s, high accuracy, and comprehensively enhance the gas volumetric method of carbon determination. The method of carbon determination by gas volumetric method has been improved in all aspects.