Material Characteristics of Low Carbon Steel Sheets Treated by Nitro-Oxidation in Fluid Environment

Abstract

The paper deals with a detailed analysis of deep drawing DC 01/DIN EN 10130-9 steel sheets of 1 mm in thickness treated by nitro-oxidation in fluid environment. The nitridation at 580°C/45 min and oxidation at 350°C/5 min was used. The surface Fe3O4 and Fe2O3 oxide layer, as well as the presence of Fe2-3N, γ'- Fe4N nitrides and ferritic matrix, was proved by X-ray diffraction. The Fe2-3N nitrides formed a continuous ε-phase of 7,1 μm in thickness with the microhardness 6,5 times higher than the base material. Corrosion resistance test revealed the highest level according to STN EN ISO 10286/C standard in comparison to the non-treated material. Analysis of mechanical properties showed a significant increase of tensile strength. Ductility decreased approximately by 7,5 %. Erichsen cupping test showed a 15 % decrease of Erichsen cupping index. Fukui deep-drawing test of nitro-oxidised steel exhibited 1,5 % increase of "m" deep-drawing coefficient.

Keywords

• corrosion
• low carbon steel
• mechanical properties
• nitro-oxidation