The fracture behavior of bainitic steel is closely related to its microstructure. The microstructure of bainitic steel is mainly composed of tempered martensite and ferrite, accompanied by the distribution of carbides. This organizational structure makes bainitic steel show a lower crack rate during crack propagation, thereby improving its fatigue resistance. In addition, the fracture behavior of bainitic steel is also affected by the heat treatment process. For example, adding 0.05% molybdenum and boron to low-carbon steel with a carbon content of 0.10% can optimize the austenite-ferrite transformation, thereby affecting the formation and distribution of bainite. The reduction of the transformation temperature will refine the size of the bainitic ferrite sheet, thereby improving the tensile strength.
Fracture mechanism of bainitic steel
The fracture mechanism of bainitic steel mainly includes cleavage fracture and quasi-cleavage fracture. In the upper bainite, the cleavage facets in the spherulite cut a number of bainite grains, and the main size that determines the fracture is the austenite grain size. In the lower bainite, the cleavage planes in the acicular ferrite are not aligned in a straight line, and the main feature that determines the fracture is the acicular ferrite grain size. The acicular ferrite grain size of the lower bainite is only 1/2 of the austenite grain size in the upper bainite, so the fracture performance of the lower bainite is better than that of the upper bainite.
stainless steel cold drawn tube
