The influences of specimen diameter on continuous cooling transformation curves measured with dilatation method

摘要

The continuous cooling transformation (CCT) curves of C45 steel were measured by the dilatation method with the different diameters of specimens in Gleeble 1500D. The microstructures were analyzed by optical microscope OLYMPUS-PMG3. The experimental results show that: the effects of the specimen diameter on CCT curves are significant; increasing the specimen diameter, both temperature in the specimen core and austenitizing temperature would be increased significantly, so that the CCT curves move down; but there is no influence of the specimen diameter on the microstructures of the steel significantly. In order to obtain precise CCT curves, the specimen diameter should be machined into small size, such as 6 mm or less than 6 mm in diameter.