Abstract: The complete comparison and analysis of quality between domestic high quality 55SiCrA spring steel, SAE9254V spring steel of POSCO and 65Si2CrV spring steel of Nippon Steel for valve spring were studied. Results show the main differences between domestic spring steel and overseas spring steel: the Als mass fraction of domestic spring steel is up to 40×10-6 and the Al2O3 mass fraction of inclusions in domestic spring steel is up to 42 %, so the aspect ratios of inclusions are all less than 3 and the width size of inclusions is large. In addition, the large and negative inclusions with high content of MgO or Al2O3 were found in domestic spring steel by nonaqueous solution electrolysis. In order to solve this problem, the Als mass fraction of steel must be reduced to less than 20×10-6, so the alloy with low content of aluminum should be used and the steel should be refined by the slag of low basicity and low Al2O3 content, moreover, the magnesia refractory containing Al2O3 should be avoided using during the smelting process, the Al2O3 mass fraction of inclusions should be reduced to 10 %-20 %, thus the plasticity of inclusions can be improved. Besides, there are much proeutectoid ferrite in microstructure and bad decarburized layer in domestic spring steel.

Key words: spring steel, inclusions, microstructure, mechanical properties, T.O；nitrogen content, nonaqueous solution electrolysis