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

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 degrees C. The results show that the microstructure of the sample cooled at 1.5 degrees 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 degrees 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 degrees C/s from 650 degrees C might concurrently yield the optimal surface quality and the microstructure of the matrix during steel production.