Estimation of residual stresses in plastically deformed eutectoid steel with different perlite morphology via magnetic parameters

Measurements of magnetic properties, as well as microscopic and X-ray diffraction investigations, of eutectoid steels with the structure of spheroidized and of coarse lamellar pearlite after cold plastic deformation by tension have been carried out. The steel with the coarse lamellar pearlite was unexpectedly found to have a lower coercivity than the steel with the spheroidized pearlite. With growing elongation, the coercivity of the steels with various pearlite morphologies grows, whereas the remanence and maximal magnetic permeability decrease. At an elongation more than 0.7%, the remanence and maximum magnetic permeability become almost equal. The difference in the coercivity of eutectoid steel with various pearlite morphology raises with elongation growth. The main changes in magnetic properties occur prior to elongations of 2-4%. The magnetoelastic fields H sigma were calculated from the field dependences of the magnetic incremental permeability and the residual compressive stresses, estimated. It is found that the average residual stresses are -222 MPa for steel with the spheroidized pearlite and -349 MPa for steel with the lamellar pearlite. According to the results of X-ray diffraction analysis, the values of residual stresses are -251 MPa and -342 MPa for steels with the spheroidized and lamellar pearlite, respectively.