Abstract: Measures had been taken which decreased the content of nitrogen and oxygen, increased the production ration of welding wire and improved the welding metallurgy performance during the producing process of ER70S-6 steel in domestic steel-making plant. The results showed that nitrogen content falled 3×10^-6, 4×10^-6 and 2×10^-6 during converter, refining and continuous casting respectively. Nitrogen content decreased 11×10^-6 in whole process and total oxygen content decreased 27×10^-6 in roll product. Macro metallographic picture showed that the quantities of inclusions got lower, the diameters of particles becomed smaller, and distribution morphology changed from chain to disperse. Meanwhile the micro metallographic photo showed that the granularity augmented slightly and the inclusions precipitated along the boundary were improved.

Key words: ER70S-6 steel, nitrogen content, oxygen content, inclusions, structure