Effect of cooling rate on microstructure and crystallographic characters for Fe3O4 seam-free on J82B steel from 650 ​°C

Abstract

Surface quality and tensile strength are required for the deep processing yield of high-carbon steel wires, particularly those with a cumulative reduction rate above 60 ​%. A systematic investigation was conducted to discern the influence mechanism of cooling rate on microstructure and crystallographic characteristics for the matrix from 650 ​°C. The results show that the microstructure of the sample cooled at 1.5 ​°C/s consists of a single pearlite, and the grain orientation is mainly the easy sliding crystal plane {101}. The retained austenite/martensite microstructure appears and grows with the cooling rate increasing to 4.5 and 7.5 ​°C/s. The grain orientation shifts from an easy slip {101} plane orientation to hard slip {001} and {111} plane orientations. The number of high-angle grain boundaries that inhibit crack expansion decreased. In addition, the number of twin boundaries in the austenite/martensite grains increased. An increase in the cooling rate increased the material hardness and decreased the plastic toughness. Therefore, the cooling rate of 1.5 ​°C/s from 650 ​°C might concurrently yield the optimal surface quality and the microstructure of the matrix during steel production.