The Experiment Research Of SUP6 Spring Steel Decarburization And Billet Segregation

Spring steel is an important part of manufacturing materials of mechanical equipment base parts and its performance requirements, especially fatigue properties, are very strict. Decarburization and segregation are two crucial factorsinfluencing the fatigue performance of spring steel. Therefore, in this paper, take automotive coil spring steel SUP6 asresearch object to detect its inclusion's morphology, size and compositionstructure and test its surface decarburization and segregation before and after heating on the spot. Then compare and analyze the detection condition, evaluate the heating process.Laboratory studies on evolution rules of decarburization layer show that: when the heat preservation time is 20 min and 30 min, decarburization layer depth increases from 45.8?m and 64.1?m by 950? to 160.1?m and 211.0?m by 1150? along with the rise of temperature, and decarburization layer depth decreases to 95.4?m and 136.4?m when temperature rise to 1250?. But when the heat preservation time rise to 60 min and 90 min, decarburized layer depth is a monotonically increasing trend from 113.4?m and 175.1?mto 320.5?mand 505?m by 950?when temperature rises. Establish the decarburizedlayer depth calculation model with the temperature change:? ?K(T) exp(M(T) ?t).Laboratory studies on segregation characteristics show that: when the temperature increases from 950? to 1250? and the heat preservation time is 20 min and 60 min, segregation band spacing decreases form 28.6?m and 20.4?m to 20.9?m and 8.2?m and the degree of segregation is gradually reduced, which means elements are more likely to spread evenly. When the heat preservation time is 30 min, segregation band spacing increases from 17.4?m by 950? to 24.6?m by 1050?, then decreases to 21.5?m when the temperature increases to 1250?. Banded black line is extremely thick when temperature is 950?, and the segregation degree decreases when temperature increases. Casting billet segregation's hereditary is resulted in horizontal and vertical center of hot rolled strip is banded structure. The main reason is caused by the segregation of C, and C, Si segregation in continuous casting billet will be left to the hot strip. Research on segregation and decarburization of casting SUP6 spring steel billetshow that, when temperature is 1100? and the heat preservation time is 30 min, this casting billet is expected to meet the requirement of fatigue performance under such decarburized layer depth and degree ofsegregation.