Study of controlled rolling and cooling of 490 MPa grade low carbon cold heading steel

Effects of technological parameters of controlled rolling and controlled cooling on the mechanical properties of ML15 steel were investigated. The results showed that good mechanical properties could be obtained by low temperature rolling compared with conventional methods (rapid cooling after rolling), because the deformation induced ferrite transformation is occurred during deformation and the ferrite grains are refined. The mechanical properties of the specimens (rapid cooled after conventional rolling) are better than that of slow cooled after low temperature rolling. The lower finish cooling temperature, the shorter interlamellar spacing in pearlite colonies and the higher tensile strength and ductility are. The mechanical properties of the low carbon ML15 bars produced by controlled rolling and controlled cooling without heat treatment of which tensile strength reaches 490 MPa are superior than that produced by conventional rolling without controlled cooling.