The Acknowledgement of Carbon & Sulfur Analyzer

About Carbon & Sulfur Analyzer, in simple terms, it is to determine the content of carbon and sulfur in the sample. Take our CS-8820S Carbon & Sulfur Analyzer as an example, it is a type of All-in-one.

What is the principle of Carbon & Sulfur Analyzer? As we all known, carbon and sulfur elements are all non-metallic elements, corresponding carbides or sulfides can be formed in metals or alloys, it can be oxidized into CO2 and SO2 under high temperature and oxygen-rich conditions.

C+O2=CO2 ↑

4Fe3C+13O2=6Fe2O3+4CO2↑

Mn3C+3O2=Mn3O4+CO2↑

S+O2=SO2↑

3MnS+5O2=Mn3O4+3SO2↑

3FeS+5O2=Fe3O4+3SO2↑

CO2 and SO2 are polar molecule, they have a permanent dipole moment, so that they all have structures such as vibration and rotation. They divided into split energy levels according to quantum mechanics, and they are coupled with incident characteristic wavelength infrared radiation to produce absorption. The concentration of the corresponding gas can be calculated by measuring the intensity of the absorbed thick infrared light, which is the theoretical basis for infrared gas analysis. The Infrared Carbon & Sulfur Analyzer uses the characteristics of CO2 and SO2 at 4.26µm and 7.4µm respectively, which have strong characteristic absorption bands, by measuring the gas absorption light intensity and analyzing the content of CO2 and SO2, the percentage content of carbon and sulfur in the tested sample is indirectly determined.

Carbon exists in two main forms in steel: one is compound carbon, which is carbon exists in compound form, mainly in the form of carbides of iron and carbides of alloying elements, such as Fe3C, Mn3C, Cr3C2, WC, W2C, VC, TiC and etc. The other is free carbon. For example, the carbon in iron-carbon solid solution, amorphous carbon, graphitic carbon, and annealing carbon are collectively referred to as free carbon.

In steel, compound carbon is generally the main component, and free carbon only exists in iron and high carbon steel after annealing. Combined carbon and free carbon, called total carbon.

Combined carbon and free carbon, called total carbon. Carbon is an important element in steel, when the carbon content increases, its strength and hardness increase, while plasticity and ductility decrease, making the steel brittle and difficult to process. on the contrary, as the carbon content decreases, the toughness of steel is enhanced and chip processing is easier, sulfur is a harmful element in steel, it exists in steel in the form of sulfide, mainly Mns, if the manganese content is very low, the excess sulfur and iron will synthesize FeS, FeS and MnS are the causes of cracks during thermal deformation. This poor performance is called hot brittleness. In addition, the presence of sulfur in the steel can reduce the mechanical properties of the steel(mainly fatigue limit, plasticity and wear resistance). The presence of sulfur is also detrimental to the corrosion resistance and weldability of steel, therefore, the lower the sulfur content in steel, the better. Generally the content of sulfur in steel is at least an order of magnitude less than carbon.