Study On Behaviors And Influence On Fatigue Property Of Inclusions In 60si2cra Spring Steel

Spring steel is the main material which manufactures kinds of spring and similar accessories. Spring steel, as an independent category of special steel plays a vital role in the national economy. High strength and light weight are trends in production and application of spring steel. The fatigue failure problem of spring is more obvious with the enhancement of spring design stress. So how to improve fatigue property in high stress condition becomes an important subject in spring steel's research and development.According to the condition that the 60Si2CrA spring steel which is produced by Shijiazhuang Steel Cooperation and whose quantity of inclusions exceeds the allowed figure is partly not able to satisfy the operation requirements, conventional mechanics property and fatigue property of this steel are examined and fatigue failure behavior is researched. The inclusions which become the weary source on the fatigue section are objectively reflected by the detection. The influences of type, feature, grade and distribution of non-metallic inclusions on microstructure, intensity, tough and fatigue life of 60Si2CrA spring steel are researched. The experiment discovered that the Al2O3 inclusions which have edges and corners cause the belt-shaped non-uniform microstructure, the aeolotropism of the material and reduction of toughness. It is proved that the polygonal silicon-aluminous duplex impurity, the belt edges and corners Al2O3 and the spherical calcium aluminates inclusions are most harmful to the fatigue life of materials. When B and D typical non-metallic inclusions grade is above 2.5 levels and inclusion total grade is above 4 levels in the steel, the fatigue life of the samples can reduce greatly. In addition, the big grain inclusions whose size are between 20 and 30μm would be the weary source and make the S ? N curve move down wholly and have big relative dispersion, make the fatigue limit reduce greatly. According to the origin of inclusions in the steel, modification of inclusions and optimization of molten steel are researched.