The Structure and the Magnetic and Mechanical Properties of Steel M74 and the Possibility of Nondestructive Testing of Heat-Treatment-Hardened Rails

摘要

Dependences of the coercive force, the relaxation magnetization, the hardness, and the strength and plastic properties of steel M74, intended for manufacturing railroad rails, on its tempering temperature were studied. Hardened specimens have the martensite structure as well as the sorbite structure of different dispersity. Analogous dependences of critical fields, which correspond to the displacement of 180 deg and 90 deg domain walls during the magnetization reversal, and of the induced magnetic-anisotropy field were also analyzed. An MC-2 ИФМ magnetic structure analyzer was shown to be suitable for the nondestructive testing of the mechanical properties of finished rails. The correlation model is two-parameter; i.e., analyzer readings are used that were recorded after successive magnetization reversals of inspected sections of rails to magnetic fields corresponding to two different currents in the electromagnetic coils.